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Sample records for diblock copolymer self-assembly

  1. Self-Assembly of Globular Protein-Polymer Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Thomas, C. S.; Olsen, B. D.

    2011-03-01

    The self-assembly of globular protein-polymer diblock copolymers into nanostructured phases is demonstrated as an elegant and simple method for structural control in biocatalysis or bioelectronics. In order to fundamentally investigate self-assembly in these complex block copolymer systems, a red fluorescent protein was expressed in E. coli and site-specifically conjugated to a low polydispersity poly(N-isopropyl acrylamide) (PNIPAM) block using thiol-maleimide coupling to form a well-defined model globular protein-polymer diblock. Functional protein materials are obtained by solvent evaporation and solvent annealing above and below the lower critical solution temperature of PNIPAM in order to access different pathways toward self-assembly. Small angle x-ray scattering and microscopy are used to show that the diblock forms lamellar nanostructures and to explore dependence of nanostructure formation on processing conditions. Circular dichroism and UV-vis show that a large fraction of the protein remains in its folded state after conjugation, and wide angle x-ray scattering demonstrates that diblock copolymer self-assembly changes the protein packing symmetry.

  2. Self-assembly of cyclic rod-coil diblock copolymers.

    PubMed

    He, Linli; Chen, Zenglei; Zhang, Ruifen; Zhang, Linxi; Jiang, Zhouting

    2013-03-07

    The phase behavior of cyclic rod-coil diblock copolymer melts is investigated by the dissipative particle dynamics simulation. In order to understand the effect of chain topological architecture better, we also study the linear rod-coil system. The comparison of the calculated phase diagrams between the two rod-coil copolymers reveals that the order-disorder transition point (χN)ODT for cyclic rod-coil diblock copolymers is always higher than that of equivalent linear rod-coil diblocks. In addition, the phase diagram for cyclic system is more "symmetrical," due to the topological constraint. Moreover, there are significant differences in the self-assembled overall morphologies and the local molecular arrangements. For example, frod = 0.5, both lamellar structures are formed while rod packing is different greatly in cyclic and linear cases. The lamellae with rods arranged coplanarly into bilayers occurs in cyclic rod-coil diblocks, while the lamellar structure with rods arranged end by end into interdigitated bilayers appears in linear counterpart. In both the lamellar phases, the domain size ratio of cyclic to linear diblocks is ranged from 0.63 to 0.70. This is attributed to that the cyclic architecture with the additional junction increases the contacts between incompatible blocks and prevents the coil chains from expanding as much as the linear cases. As frod = 0.7, the hexagonally packed cylinder is observed for cyclic rod-coil diblocks, while liquid-crystalline smectic A lamellar phase is formed in linear system. As a result, the cyclization of a linear rod-coil block copolymer can induce remarkable differences in the self-assembly behavior and also diversify its physical properties and applications greatly.

  3. Nanoscale protein patterning using self-assembled diblock copolymers.

    PubMed

    Kumar, Nitin; Hahm, Jong-in

    2005-07-19

    Novel methods for immobilizing proteins on surfaces have the potential to impact basic biological research as well as various biochip applications. Here, we demonstrate a unique method to pattern proteins with a nanometer periodicity on silicon oxide substrates using microphase-separated diblock copolymer thin films. We developed a straightforward and effective protein immobilization technique using the microphase-separated domains of polystyrene-block-poly(methyl methacrylate) to localize various model protein molecules such as bovine immunoglobulin G, fluorescein isothiocyanate conjugated anti-bovine immunoglobulin G, and protein G. The self-organizing nature of the diblock copolymer was exploited to produce periodically alternating, nanometer-spaced polymeric domains exposing the two chemical compositions of the diblock to surface. We demonstrate that the model proteins selectively self-organize themselves on the microdomain regions of specific polymer components due to their preferential interactions with one of the two polymer segments. This diblock copolymer-based, self-assembly approach represents a step forward for facile, nanometer-spaced protein immobilization with high areal density and could provide a pathway to high-throughput proteomic arrays and biosensors.

  4. Crafting threads of diblock copolymer micelles via flow-enabled self-assembly.

    PubMed

    Li, Bo; Han, Wei; Jiang, Beibei; Lin, Zhiqun

    2014-03-25

    Hierarchically assembled amphiphilic diblock copolymer micelles were exquisitely crafted over large areas by capitalizing on two concurrent self-assembling processes at different length scales, namely, the periodic threads composed of a monolayer or a bilayer of diblock copolymer micelles precisely positioned by flow-enabled self-assembly (FESA) on the microscopic scale and the self-assembly of amphiphilic diblock copolymer micelles into ordered arrays within an individual thread on the nanometer scale. A minimum spacing between two adjacent threads λmin was observed. A model was proposed to rationalize the relationship between the thread width and λmin. Such FESA of diblock copolymer micelles is remarkably controllable and easy to implement. It opens up possibilities for lithography-free positioning and patterning of diblock copolymer micelles for various applications in template fabrication of periodic inorganic nanostructures, nanoelectronics, optoelectronics, magnetic devices, and biotechnology.

  5. Controlled self-assembly in homopolymer and diblock copolymer

    NASA Astrophysics Data System (ADS)

    Zhuang, Lei

    This thesis work studies the process, mechanism and control of self-assembly in homopolymers and diblock copolymers. These studies are aimed at finding novel patterning methods that can lead to low cost lithography technologies capable of creating micrometer to nanometer patterns over a large area. We first present a new phenomenon called Lithographically-Induced Self-Assembly (LISA) that can create ordered arrays of pillars in a homopolymer film with a mask placed close to its surface. We demonstrate that the shape, size and morphology of the ordered pillar arrays can be controlled with a patterned mask. A model is developed based on the instability in a fluidic film induced by the Coulomb force from charge accumulation in the polymer film and the mask. Experimental results are shown to support the model. We also investigate the behavior of defects that destroy the ordering of the LISA array and propose ways to prevent them. This self-assembly phenomenon is used as a patterning technique to define the active area of an organic light emitting diode (OLED). The device shows significantly improved lifetime due to the restriction of defect growth. Another patterning technology that is closely related to LISA, Lithographically-Induced Self-Construction (LISC), is also introduced. LISC can form mesas of polymer from the initial thin film and they inherit the shape and size of the mask patterns. A model based on the dynamics of LISA pillar formation and mass conservation is presented and provides a guideline for choosing LISC process parameters. In the final part of the thesis, we study a technique to control the orientation of diblock copolymer phase separation in a thin film by applying a pressure on the film through a flat mask. The result is a well-ordered grating pattern of the phase separation with a period of tens of nanometers. The effect of pressure and film thickness on the final pattern is investigated by experiments. We suggest that the increased ordering is

  6. Supramolecular self-assembly of conjugated diblock copolymers.

    SciTech Connect

    Wang, H.; You, W.; Jiang, P.; Yu, L.; Wang, H. H.; Univ. of Chicago

    2004-02-20

    This paper describes the synthesis and characterization of a novel series of copolymers with different lengths of oligo(phenylene vinylene) (OPV) as the rod block, and poly(propylene oxide) as the coil block. Detailed characterization by means of transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle neutron scattering (SANS) revealed the strong tendency of these copolymers to self-assemble into cylindrical micelles in solution and as-casted films on a nanometer scale. These micelles have a cylindrical OPV core surrounded by a poly(propylene glycol) (PPG) corona and readily align with each other to form parallel packed structures when mica is used as the substrate. A packing model has been proposed for these cylindrical micelles.

  7. Tunable Self-Assembly of Diblock Copolymers into Colloidal Particles with Triply Periodic Minimal Surfaces.

    PubMed

    Lin, Zhixing; Liu, Shaohua; Mao, Wenting; Tian, Hao; Wang, Nan; Zhang, Ninghe; Tian, Feng; Han, Lu; Feng, Xinliang; Mai, Yiyong

    2017-06-12

    We herein report the tunable self-assembly of simple block copolymers, namely polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymers, into porous cubosomes with inverse Im3‾m or Pn3‾m mesophases of controlled unit cell parameters as well as hexasomes with an inverse hexagonal (p6mm) structure, which have been rarely observed in polymer self-assembly. A new morphological phase diagram was constructed for the solution self-assembly of PS-b-PEO based on the volume fraction of the PS block against the initial copolymer concentration. The formation mechanisms of the cubosomes and hexasomes have also been revealed. This study not only affords a simple system for the controllable preparation and fundamental studies of ordered bicontinuous structures, but also opens up a new avenue towards porous architectures with highly ordered pores. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Nanoscale protein arrays of rich morphologies via self-assembly on chemically treated diblock copolymer surfaces

    NASA Astrophysics Data System (ADS)

    Song, Sheng; Milchak, Marissa; Zhou, Hebing; Lee, Thomas; Hanscom, Mark; Hahm, Jong-in

    2013-03-01

    Well-controlled assembly of proteins on supramolecular templates of block copolymers can be extremely useful for high-throughput biodetection. We report the adsorption and assembly characteristics of a model antibody protein to various polystyrene-block-poly(4-vinylpyridine) templates whose distinctive nanoscale structures are obtained through time-regulated exposure to chloroform vapor. The strong adsorption preference of the protein to the polystyrene segment in the diblock copolymer templates leads to an easily predictable, controllable, rich set of nanoscale protein morphologies through self-assembly. We also demonstrate that the chemical identities of various subareas within individual nanostructures can be readily elucidated by investigating the corresponding protein adsorption behavior on each chemically distinct area of the template. In our approach, a rich set of intricate nanoscale morphologies of protein arrays that cannot be easily attained through other means can be generated straightforwardly via self-assembly of proteins on chemically treated diblock copolymer surfaces, without the use of clean-room-based fabrication tools. Our approach provides much-needed flexibility and versatility for the use of block copolymer-based protein arrays in biodetection. The ease of fabrication in producing well-defined and self-assembled templates can contribute to a high degree of versatility and simplicity in acquiring an intricate nanoscale geometry and spatial distribution of proteins in arrays. These advantages can be extremely beneficial both for fundamental research and biomedical detection, especially in the areas of solid-state-based, high-throughput protein sensing.

  9. Nanoscale Protein Arrays of Rich Morphologies via Self-assembly on Chemically Treated Diblock Copolymer Surfaces

    PubMed Central

    Song, Sheng; Milchak, Marissa; Zhou, Hebing; Lee, Thomas; Hanscom, Mark

    2013-01-01

    Well-controlled assembly of proteins on supramolecular templates of block copolymers can be extremely useful for high-throughput biodetection. We report the adsorption and assembly characteristics of a model antibody protein to various polystyrene-block-poly(4-vinylpyridine) templates whose distinctive nanoscale structures are obtained through time-regulated exposure to chloroform vapor. Strong adsorption preference of the protein to the polystyrene segment in the diblock copolymer templates leads to an easily predictable, controllable, rich set of nanoscale protein morphologies through self-assembly. We also demonstrate that the chemical identities of various subareas within individual nanostructures can be readily elucidated by investigating the corresponding protein adsorption behavior to each chemically distinct area of the template. In our approach, a rich set of intricate nanoscale morphologies of protein arrays that cannot be easily attained through other means can be generated straightforwardly via self-assembly of proteins on chemically treated diblock copolymer surfaces, without the use of clean room-based fabrication tools. Our approach provides much-needed flexibility and versatility for the use of block copolymer-based protein arrays in biodetection. The ease of fabrication in producing well-defined and self-assembled templates can contribute to a high degree of versatility and simplicity in acquiring intricate nanoscale geometry and spatial distribution of proteins in arrays. These advantages can be extremely beneficial both for fundamental research and biomedical detection, especially in the areas of solid-state based, high-throughput protein sensing. PMID:23395956

  10. Kinetically Controlled Nanostructure Formation in Self-Assembled Globular Protein-Polymer Diblock Copolymers

    PubMed Central

    Thomas, Carla S.; Xu, Liza; Olsen, Bradley D.

    2014-01-01

    Aqueous processing of globular protein-polymer diblock copolymers into solid-state materials and subsequent solvent annealing enables kinetic and thermodynamic control of nanostructure formation to produce block copolymer morphologies that maintain a high degree of protein fold and function. Using model diblock copolymers composed of mCherry-b-poly(N-isopropylacrylamide), orthogonal control over solubility of the protein block through changes in pH and the polymer block through changes in temperature is demonstrated during casting and solvent annealing. Hexagonal cylinders, perforated lamellae, lamellae, or hexagonal and disordered micellar phases are observed depending upon the coil fraction of the block copolymer and the kinetic pathway used for self-assembly. Good solvents for the polymer block produce ordered structures reminiscent of coil-coil diblock copolymers, while an unfavorable solvent results in kinetically trapped micellar structures. Decreasing solvent quality for the protein improves long-range ordering, suggesting that the strength of protein interactions influences nanostructure formation. Subsequent solvent annealing results in evolution of the nanostructures, with the best ordering and the highest protein function observed when annealing in a good solvent for both blocks. While protein secondary structure was found to be almost entirely preserved for all processing pathways, UV-vis spectroscopy of solid-state films indicates that using a good solvent for the protein block enables up to 70% of the protein to be retained in its functional form. PMID:22924842

  11. Kinetically controlled nanostructure formation in self-assembled globular protein-polymer diblock copolymers.

    PubMed

    Thomas, Carla S; Xu, Liza; Olsen, Bradley D

    2012-09-10

    Aqueous processing of globular protein-polymer diblock copolymers into solid-state materials and subsequent solvent annealing enables kinetic and thermodynamic control of nanostructure formation to produce block copolymer morphologies that maintain a high degree of protein fold and function. When model diblock copolymers composed of mCherry-b-poly(N-isopropylacrylamide) are used, orthogonal control over solubility of the protein block through changes in pH and the polymer block through changes in temperature is demonstrated during casting and solvent annealing. Hexagonal cylinders, perforated lamellae, lamellae, or hexagonal and disordered micellar phases are observed, depending on the coil fraction of the block copolymer and the kinetic pathway used for self-assembly. Good solvents for the polymer block produce ordered structures reminiscent of coil-coil diblock copolymers, while an unfavorable solvent results in kinetically trapped micellar structures. Decreasing solvent quality for the protein improves long-range ordering, suggesting that the strength of protein interactions influences nanostructure formation. Subsequent solvent annealing results in evolution of the nanostructures, with the best ordering and the highest protein function observed when annealing in a good solvent for both blocks. While protein secondary structure was found to be almost entirely preserved for all processing pathways, UV-vis spectroscopy of solid-state films indicates that using a good solvent for the protein block enables up to 70% of the protein to be retained in its functional form.

  12. Polymerization-Induced Self-Assembly of Galactose-Functionalized Biocompatible Diblock Copolymers for Intracellular Delivery

    PubMed Central

    2013-01-01

    Recent advances in polymer science are enabling substantial progress in nanobiotechnology, particularly in the design of new tools for enhanced understanding of cell biology and for smart drug delivery formulations. Herein, a range of novel galactosylated diblock copolymer nano-objects is prepared directly in concentrated aqueous solution via reversible addition–fragmentation chain transfer polymerization using polymerization-induced self-assembly. The resulting nanospheres, worm-like micelles, or vesicles interact in vitro with galectins as judged by a turbidity assay. In addition, galactosylated vesicles are highly biocompatible and allow intracellular delivery of an encapsulated molecular cargo. PMID:23941545

  13. Self-assembly behavior of AB/AC diblock copolymer mixtures in dilute solution.

    PubMed

    Zhuang, Ying; Lin, Jiaping; Wang, Liquan; Zhang, Liangshun

    2009-02-19

    The self-assembly behavior of AB/AC amphiphilic diblock copolymer mixtures in dilute solution was studied by a real-space-implemented self-consistent field theory in three dimensions. The AB and AC copolymers have a common hydrophobic block A but different hydrophilic blocks B and C. Two cases were studied: one in which copolymers AB and AC have same hydrophobic and hydrophilic block lengths and one in which copolymers AB and AC have different hydrophobic and hydrophilic block lengths. It was found that the two copolymers can cooperatively self-assemble into hybrid aggregates. The morphologies of the formed aggregates were found to be dependent on the mixture ratio and the interaction between the B and C blocks. For the AB/AC copolymers with different hydrophobic and hydrophilic lengths, chain segregation was found in the formed hybrid aggregates. Based on the obtained calculation results, phase diagrams as functions of the mixture ratio and interaction between the B and C blocks were constructed.

  14. Guided self-assembly of diblock copolymer thin films on chemically patterned substrates.

    PubMed

    Wu, Xiang-Fa; Dzenis, Yuris A

    2006-11-07

    We study the guided self-assembly of symmetric/asymmetric diblock copolymer (BCP) films on heterogeneous substrates with chemically patterned surface by using a coarse-grained phase-separation model. During the procedure, the free energy employed for the BCP films was modeled by the Ginzburg-Landau free energy with nonlocal interaction, and the flat, chemically patterned surface was considered as a heterogeneous surface with short-range interaction with the BCP molecules. The resulting Cahn-Hilliard equation was solved by means of an efficient semi-implicit Fourier-spectral algorithm. Effects of pattern scale, surface chemical potential, and BCP asymmetry on the self-assembly process were explored in detail and compared with those without chemically patterned substrate surfaces. It was found that the morphology of both symmetric and asymmetric BCP films is strongly influenced by the commensurability between the unconstrained natural period lambda* of the bulk BCP and the artificial pattern period. Simulation shows that patterned surface with period close to lambda* leads to highly ordered morphology after self-assembly for both symmetric and asymmetric BCP films, and it also dramatically accelerates the guided self-assembly process. The present simulation is in a very good agreement with the recent experimental observation in BCP nanolithography. Finally, the present study also expects an innovative nanomanufacturing method to produce highly ordered nanodots based on the guided self-assembly of asymmetric BCP films on chemically patterned substrates.

  15. Stimulus-responsive self-assembly: reversible, redox-controlled micellization of polyferrocenylsilane diblock copolymers.

    PubMed

    Eloi, Jean-Charles; Rider, David A; Cambridge, Graeme; Whittell, George R; Winnik, Mitchell A; Manners, Ian

    2011-06-15

    In depth studies of the use of electron transfer reactions as a means to control the self-assembly of diblock copolymers with an electroactive metalloblock are reported. Specifically, the redox-triggered self-assembly of a series of polystyrene-block-polyferrocenylsilane (PS-b-PFS) diblock copolymers in dichloromethane solution is described. In the case of the amorphous polystyrene(n)-b-poly(ferrocenylphenylmethylsilane)(m) diblock copolymers (PS(n)-b-PFMPS(m): n = 548, m = 73; n = 71, m = 165; where n and m are the number-averaged degrees of polymerization), spherical micelles with an oxidized PFS core and a PS corona were formed upon oxidation of more than 50% of the ferrocenyl units by [N(C(6)H(4)Br-4)(3)][SbX(6)] (X = Cl, F). Analogous block copolymers containing a poly(ferrocenylethylmethylsilane) (PFEMS) metalloblock, which has a lower glass transition temperature, behaved similarly. However, in contrast, on replacement of the amorphous metallopolymer blocks by semicrystalline poly(ferrocenyldimethylsilane) (PFDMS) segments, a change in the observed morphology was detected with the formation of ribbon-like micelles upon oxidation of PS(535)-b-PFDMS(103) above the same threshold value. Again the coronas consisted of fully solvated PS and the core consisted of partially to fully oxidized PFS associated with the counteranions. When oxidation was performed with [N(C(6)H(4)Br-4)(3)][SbF(6)], reduction of the cores of the spherical or ribbon-like micelles with [Co(η-C(5)Me(5))(2)] enabled full recovery of the neutral chains and no significant chain scission was detected.

  16. Multiscale coarse graining of diblock copolymer self-assembly: from monomers to ordered micelles.

    PubMed

    Pierleoni, Carlo; Addison, Chris; Hansen, Jean-Pierre; Krakoviack, Vincent

    2006-03-31

    Starting from a microscopic lattice model, we investigate clustering, micellization, and micelle ordering in semidilute solutions of AB diblock copolymers in a selective solvent. To bridge the gap in length scales, from monomers to ordered micellar structures, we implement a two-step coarse-graining strategy, whereby the AB copolymers are mapped onto ultrasoft dumbells with monomer-averaged effective interactions between the centers of mass of the blocks. Monte Carlo simulations of this coarse-grained model yield clear-cut evidence for self-assembly into micelles with a mean aggregation number n approximately 100 beyond a critical concentration. At a slightly higher concentration the micelles spontaneously undergo a disorder-order transition to a cubic phase. We determine the effective potential between these micelles from first principles.

  17. Self-assembly of rod-shaped particles in diblock-copolymer templates.

    PubMed

    Tang, Qi-yun; Ma, Yu-qiang

    2009-07-30

    We investigate the self-assembly of hard rod-shaped particles with an affinity for A block in diblock AB copolymer templates. The results are consistent with a series of recent experimental findings. Furthermore, we construct the phase diagrams of the mixture with different aspect ratios of particles by changing the particle concentration phip and the volume fraction f of the A block. The variation of the aspect ratio in different particle concentrations will significantly influence the effective volume of the A component and consequent phase behavior of nanoparticle/copolymer hybrid systems, which may account for the emergence of some unexpected phenomena of morphological transitions. The present study provides insightful guidance to control the nanometer-length-scale structures of shaped particles for potential applications as functional devices.

  18. Defectivity study of directed self-assembly of cylindrical diblock copolymers in laterally confined thin channels

    NASA Astrophysics Data System (ADS)

    Kim, Bongkeun; Laachi, Nabil; Fredrickson, Glenn H.

    2013-03-01

    We use self-consistent field theory (SCFT) to study the directed self-assembly of cylinder-forming diblock copolymers laterally confined in narrow channels. The side walls and top/bottom surfaces of the channel are either all major block attractive, all minor block attractive, or a combination of major block attractive on the top surface and minor block attractive on the remaining film surfaces. We focus on systems in which the self-assembled cylinders form a monolayer oriented parallel to the sidewalls in a thin channel. Experimentally and theoretically, well-ordered perfect cylinders are observed in narrow channels, but undesirable defective structures are also found. We investigate the energetics of isolated, meta-stable defects and compare them with two types of defects (dislocations and disclinations) recently investigated in laterally confined lamellar block copolymer systems using SCFT. Our simulation results are also compared with defect energy estimates for lying down cylinder monolayers extracted from experimental work by Mishra and coworkers. Parametric studies include the effects of film thickness, domain spacing, χN, and composition on defect energies with various wall wetting conditions in narrow channels of varying widths. A major finding is that defects of cylindrical directed self-assembly in a confined channel have a smaller free energy cost (tens of kT) in comparison with defects in laterally confined, vertically oriented lamellae (many tens of kT). We also discovered a novel vertically branched cylinder defect in the case of neutral top and bottom surfaces with significantly lower defect energy than a corresponding dislocation defect. More broadly, this study reveals unexpected dependences of equilibrium defect densities on a wide range of parameters that must be carefully controlled in order to successfully implement a directed self-assembly process with block-copolymers.

  19. Self-assembled hydrophobic honokiol loaded MPEG-PCL diblock copolymer micelles.

    PubMed

    Gou, MaLing; Zheng, XiuLing; Men, Ke; Zhang, Juan; Wang, BiLan; Lv, Lei; Wang, XiuHong; Zhao, YinLan; Luo, Feng; Chen, LiJuan; Zhao, Xia; Wei, YuQuan; Qian, ZhiYong

    2009-09-01

    Honokiol showed potential application in cancer treatment, but its poor water solubility restricts its clinical application greatly. So, we designed a self-assembled monomethoxy poly(ethylene glycol)-poly(epsilon-caprolactone) (MPEG-PCL) micelle to load honokiol to overcome its poor water solubility. We synthesized MPEG-PCL diblock copolymer that could self-assemble into monodisperse micelles at the particle size of ca.18 nm in water. Honokiol was loaded into MPEG-PCL micelle by direct dissolution method assisted by ultrasound, without any surfactants, organic solvents, and vigorous stirring. The blank MPEG-PCL micelles (100 mg/mL) did not induce any hemolysis in vitro and showed very low toxicity ex vivo and in vivo. Honokiol could be molecularly incorporated into MPEG-PCL micelles at the drug loading of about 20% by direct dissolution method assisted by ultrasound. After loaded into MPEG-PCL micelles, honokiol maintained its molecular structure and anticancer activity in vitro. Honokiol could be sustained released from MPEG-PCL micelles in vitro. The honokiol loaded MPEG-PCL micelles could be lyophilized without any adjuvant. The prepared honokiol formulation based on self-assembled MPEG-PCL micelle was stable, safe, effective, easy to produce and scale up, and showed potential clinical application.

  20. Directed Self-Assembly of Diblock Copolymer Thin Films on Prepatterned Metal Nanoarrays.

    PubMed

    Chang, Tongxin; Huang, Haiying; He, Tianbai

    2016-01-01

    The sequential layer by layer self-assembly of block copolymer (BCP) nanopatterns is an effective approach to construct 3D nanostructures. Here large-scale highly ordered metal nano-arrays prepared from solvent annealed thin films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer are used to direct the assembly of the same BCP. The influence of initial loading concentration of metal precursor, the type of metal nanoparticle (gold, platinum, and silver), and the nanoparticle-substrate interaction on the directed assembly behavior of the upper BCP layer have been focused. It is found that the upper BCP film can be completely directed by the gold nanoarray with P2VP domain exclusively located between two adjacent gold nanowires or nanodots, which behaves the same way as on the platinum nanoarray. While the silver nanoarray can be destroyed during the upper BCP self-assembly with the silver nanoparticles assembled into the P2VP domain. Based on the discussions of the surface energy of nanoparticles and the interplay between nanoparticle-substrate interaction and nanoparticle-polymer interaction, it is concluded that the effect of immobilization of nanoparticles on the substrate, together with entropy effect to minimize the energetically unfavorable chain stretching contributes to the most effective alignment between each layer.

  1. Brownian molecular dynamics simulation on self-assembly behavior of diblock copolymers: influence of chain conformation.

    PubMed

    Lin, Shaoliang; He, Xiaohua; Li, Yongliang; Lin, Jiaping; Nose, Takuhei

    2009-10-22

    Brownian molecular dynamic simulations are applied on the self-assembly behavior of AB-type diblock copolymers. The influence of chain conformation of core-forming A-block changing from rigid to flexible on the aggregation structure formed by AB copolymers is investigated. It is found that at a high rigid fraction f(R) of A-block, a disk structure can be formed at a high aggregation interaction epsilon(AA) of A-bead pairs because of the tendency of orientational packing of rigid portion within the aggregate core. Transitions of aggregation structure from disk to string, further to small aggregates, and to unimers are observed with decreasing epsilon(AA). The packing of A-blocks becomes more random at relatively lower values of f(R), resulting in the formation of spherical structure. The region of string becomes narrower while the regions of the small aggregates and sphere become wider as decreasing f(R). Meanwhile, the onsets of string, disk, and sphere formation move to higher epsilon(AA). The phase diagrams for the influences of rigid potion location within the A-block and the chain rigidity of the A-block are mapped. The comparison of simulation results with existing experimental observations is also presented. Our simulation results tend to bridge a gap of different micellization behaviors between rod-coil block copolymers and coil-coil block copolymers and extend to investigate chain conformation influence on phase diagram.

  2. The impact of substrate interaction in directed self-assembly of symmetric diblock copolymer thin films

    NASA Astrophysics Data System (ADS)

    Seidel, Robert

    Block copolymers (BCP) are a class of materials that have attracted significant attention due to their ability to self-assemble into dense arrays of nanoscale features. These materials are being investigated for their use in applications such as nanolithography, but for commercial implementation require the ability to control or direct the self-assembly process. Chemoepitaxial directed self-assembly (DSA) is one avenue to achieving this control, where a BCP thin film self-assembles in the presence of precisely defined chemical boundary conditions. In such a process, the equilibrium structure of the BCP film and the kinetic pathways it evolves along to reach equilibrium are both a function of the thermodynamic landscape, which is in turn controlled by the chemical pattern. This thesis contributes to the significant body of work attempting to detail the relationship between chemical pattern parameters and the thermodynamics of assembly (both kinetic and equilibrium). We restrict our investigation to the assembly of lamellae-forming diblock copolymers on line/space chemical patterns that employ density multiplication, with a focus on developing technology for nanopatterning beyond the resolution limit of traditional lithography. In the first chapter we introduce the fundamental ideas of BCP DSA and develop the concepts of free energy balance that are crucial to framing the discussion in the following chapters. The second chapter explores using poly(methyl methacrylate) as a guide material and shows how the greater strength of guiding interaction for this system has the ability to guide complex, frustrated non-bulk morphologies. The third chapter develops a novel concept of using process conditions to generate so-called 'three-tone' chemical patterns with multiple guiding regions per patterned stripe. The fourth chapter looks at how guide stripe strength impacts and affects assembly kinetics, equilibrium structure, and process metrics such as line edge roughness (LER

  3. Synthesis of ATRP-induced dextran-b-polystyrene diblock copolymers and preliminary investigation of their self-assembly in water.

    PubMed

    Houga, Clément; Le Meins, Jean-François; Borsali, Redouane; Taton, Daniel; Gnanou, Yves

    2007-08-07

    Dextran-b-polystyrene diblock copolymers forming miscellaneous spherical self-assemblies in water were obtained by chemical modification of the anomeric extremity of a commercial dextran followed by atom transfer radical polymerisation of styrene.

  4. Microphase separation through competitive hydrogen bonding in self-assembled A-b-B/C diblock copolymer/homopolymer complexes

    NASA Astrophysics Data System (ADS)

    Hameed, Nishar; Salim, Nisa V.; Guo, Qipeng

    2009-12-01

    We present a study of microphase separation induced by competitive hydrogen bonding in A-b-B/C diblock copolymer/homopolymer complexes where the diblock copolymer A-b-B is immiscible and the homopolymer C can interact unequally with both A and B blocks through hydrogen bonding. A model system containing poly(2-vinyl pyridine)-block-poly(methyl methacrylate) (P2VP-b-PMMA) and poly(4-vinyl phenol) (PVPh) in tetrahydrofuran was investigated. In these self-assembled complexes, microphase separation takes place due to the disparity in intermolecular interactions. Specifically, PVPh and P2VP blocks interact strongly to form complex, whereas PVPh and PMMA blocks interact weakly. The hydrogen bonding interactions were revealed by infrared spectroscopy and analyzed in terms of the difference in interassociation constants (K), i.e., interaction parameters of each blocks of the block copolymer to the homopolymer and according to the random phase approximation. The phase behavior of the complexes was investigated with small-angle x-ray scattering and transmission electron microscopy. A series of morphologies including lamellae, hexagonal cylinders, wormlike microdomains, and hierarchical structures was documented as a function of the copolymer concentration. Moreover, we outlined how hydrogen bonding determines the self-assembly and causes morphological transitions in different A-b-B/C diblock copolymer/homopolymer systems with respect to the K values.

  5. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers.

    PubMed

    An, Hyosung; Mike, Jared; Smith, Kendall A; Swank, Lisa; Lin, Yen-Hao; L Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie L

    2015-09-22

    Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m(3)) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects.

  6. Self-assembly of diblock copolymer-maghemite nanoparticle hybrid thin films.

    PubMed

    Yao, Yuan; Metwalli, Ezzeldin; Moulin, Jean-François; Su, Bo; Opel, Matthias; Müller-Buschbaum, Peter

    2014-10-22

    The arrangement of maghemite (γ-Fe2O3) nanoparticles (NPs) in poly(styrene-d8-block-n-butyl methacrylate) P(Sd-b-BMA) diblock copolymer (DBC) films via a self-assembly process was investigated toward the fabrication of highly ordered maghemite-polymer hybrid thin films. The resulting thin films exhibited a perforated lamella with an enrichment layer containing NPs as investigated with X-ray reflectometry, scanning electron microscopy, atomic force microscopy, and time-of-flight grazing incidence small angle neutron scattering as a function of the NP concentrations. The NPs were selectively deposited in the PSd domains of the DBC during the microphase separation process. At low NP concentrations, the incorporation of the NPs within the DBC thin films resulted in an enhanced microphase separation process and formation of highly oriented and ordered nanostructured hybrid films. At higher NP concentrations, the aggregation of the NPs was dominating and large sized metal oxide clusters were observed. The superparamagnetic properties of the metal oxide-polymer hybrid films at various NP concentrations were probed by a superconducting quantum interference device magnetometer, which shows that the hybrid films are highly attractive for optical devices, magnetic sensors, and magnetic recording devices.

  7. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    An, Hyosung; Mike, Jared; Smith, Kendall A.; Swank, Lisa; Lin, Yen-Hao; L. Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie L.

    2015-09-01

    Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects.

  8. Solid-state nanostructured materials from self-assembly of a globular protein-polymer diblock copolymer.

    PubMed

    Thomas, Carla S; Glassman, Matthew J; Olsen, Bradley D

    2011-07-26

    Self-assembly of three-dimensional solid-state nanostructures containing approximately 33% by weight globular protein is demonstrated using a globular protein-polymer diblock copolymer, providing a route to direct nanopatterning of proteins for use in bioelectronic and biocatalytic materials. A mutant red fluorescent protein, mCherryS131C, was prepared by incorporation of a unique cysteine residue and site-specifically conjugated to end-functionalized poly(N-isopropylacrylamide) through thiol-maleimide coupling to form a well-defined model protein-polymer block copolymer. The block copolymer was self-assembled into bulk nanostructures by solvent evaporation from concentrated solutions. Small-angle X-ray scattering and transmission electron microscopy illustrated the formation of highly disordered lamellae or hexagonally perforated lamellae depending upon the selectivity of the solvent during evaporation. Solvent annealing of bulk samples resulted in a transition toward lamellar nanostructures with mCherry packed in a bilayer configuration and a large improvement in long-range ordering. Wide-angle X-ray scattering indicated that mCherry did not crystallize within the block copolymer nanodomains and that the β-sheet spacing was not affected by self-assembly. Circular dichroism showed no change in protein secondary structure after self-assembly, while UV-vis spectroscopy indicated approximately 35% of the chromophore remained optically active.

  9. Solid-State Nanostructured Materials from Self-Assembly of a Globular Protein-Polymer Diblock Copolymer

    PubMed Central

    Thomas, Carla S.; Glassman, Matthew J.; Olsen, Bradley D.

    2014-01-01

    Self-assembly of three-dimensional solid-state nanostructures containing approximately 33% by weight globular protein is demonstrated using a globular protein-polymer diblock copolymer, providing a route to direct nanopatterning of proteins for use in bioelectronic and biocatalytic materials. A mutant red fluorescent protein, mCherryS131C, was prepared by incorporation of a unique cysteine residue and site-specifically conjugated to end-functionalized poly(N-isopropylacrylamide) through thiol-maleimide coupling to form a well-defined model protein-polymer block copolymer. The block copolymer was self-assembled into bulk nanostructures by solvent evaporation from concentrated solutions. Small-angle X-ray scattering and transmission electron microscopy illustrated the formation of highly disordered lamellae or hexagonally perforated lamellae depending upon the selectivity of the solvent during evaporation. Solvent annealing of bulk samples resulted in a transition towards lamellar nanostructures with mCherry packed in a bilayer configuration and a large improvement in long range ordering. Wide-angle X-ray scattering indicated that mCherry did not crystallize within the block copolymer nanodomains and that the β-sheet spacing was not affected by self-assembly. Circular dichroism showed no change in protein secondary structure after self-assembly, while UV-vis spectroscopy indicated approximately 35% of the chromophore remained optically active. PMID:21696135

  10. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    DOE PAGES

    An, Hyosung; Mike, Jared; Smith, Kendall A.; ...

    2015-09-22

    Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued togethermore » with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects.« less

  11. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    PubMed Central

    An, Hyosung; Mike, Jared; Smith, Kendall A.; Swank, Lisa; Lin, Yen-Hao; L. Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie L.

    2015-01-01

    Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects. PMID:26391053

  12. Self-assembly of diblock copolymer confined in an array-structure space

    SciTech Connect

    He, Xuehao E-mail: hjliang@ustc.edu.cn; Zou, Zhixiang; Kan, Di; Liang, Haojun E-mail: hjliang@ustc.edu.cn

    2015-03-14

    The combination of top-down and bottom-up technologies is an effective method to create the novel nanostructures with long range order in the field of advanced materials manufacture. In this work, we employed a polymeric self-consistent field theory to investigate the pattern formation of diblock copolymer in a 2D confinement system designed by filling pillar arrays with various 2D shapes such as squares, rectangles, and triangles. Our simulation shows that in such confinement system, the microphase structure of diblock copolymer strongly depends on the pitch, shape, size, and rotation of the pillar as well as the surface field of confinement. The array structures can not only induce the formation of new phase patterns but also control the location and orientation of pattern structures. Finally, several methods to tune the commensuration and frustration of array-structure confinement are proposed and examined.

  13. Depletion Interactions: A New Control Parameter for the Self-Assembly of Diblock Copolymer Micelles

    SciTech Connect

    Abbas, Sayeed; Lodge, Timothy P.

    2007-09-28

    Small angle neutron scattering was performed on disordered mixtures of nonadsorbing homopolymer (A) chains and diblock (A-B) copolymer micelles in an A selective solvent. Increasing the molecular weight or concentration of A led to an increase in the aggregation number, and a decrease in the effective hard-sphere diameter of the micelles. Furthermore an intermicellar attractive force developed, which was successfully modeled by the Asakura-Oosawa depletion potential. Via an alternative model we also extracted information about mesoscopic clusters of micelles formed due to this attractive force.

  14. Mesosized Crystal-like Structure of Hexagonally Packed Hollow Hoops by Solution Self-Assembly of Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Zhang, Lifeng; Bartels, Carl; Yu, Yisong; Shen, Hongwei; Eisenberg, Adi

    1997-12-01

    Mesosize crystal-like aggregates with an internal structure of hexagonally packed hollow hoops (HHH) in a polystyrene matrix have been prepared in solution by self-assembly of asymmetric polystyrene-b-poly(acrylic acid) diblock copolymers. Most of the aggregates are cylindrical or in the shape of truncated cones. The external surface of the aggregates and the internal surface of the hollow hoops are lines with short poly(acrylic acid) chains. The hoop morphology is imposed because the end-capping energy of a rod on this size scale is more important than the curvature energy. A strong interdependence between the external shape and the internal structure in these mesosize particles is demonstrated.

  15. Impact of chain microstructure on solution and thin film self-assembly of PCHD-based semi-flexible/flexible diblock copolymers.

    PubMed

    Bornani, Kamlesh; Wang, Xu; Davis, Jesse L; Wang, Xiaojun; Wang, Weiyu; Hinestrosa, Juan Pablo; Mays, Jimmy W; Kilbey, S Michael

    2015-08-28

    Self-assembly of semi-flexible/flexible block copolymers in a selective solvent is examined using a set of diblock copolymers where the chain microstructure of the semi-flexible block is manipulated in order to tune chain stiffness. Conceptually, the reduced conformational space of the semi-flexible block is anticipated to alter the way the chains pack, potentially changing the structure of self-assembled aggregates in comparison to flexible diblock copolymer analogs. Semi-flexible/flexible diblock copolymers comprised of poly(styrene)-block-poly(1,3-cyclohexadiene) (PS-b-PCHD) having systematic changes in chain microstructure, as captured by the ratio of 1,4/1,2-linkages between cyclohexenyl repeat units, and molecular weight of the PCHD blocks were synthesized using anionic polymerization. These diblocks were dissolved in tetrahydrofuran (THF), which is a preferential solvent for PS, and the structures formed were examined using laser light scattering and complementary imaging techniques. Results show that PS-b-PCHD copolymers with a chain microstructure of 90% 1,4/10% 1,2 linkages between cyclohexenyl repeat units (referred to simply as 90/10) are able to micellize, forming spherical structures, while diblocks of 70/30 and 50/50 1,4-to-1,2 ratios remain as single chains and ill-defined aggregates, respectively, when dissolved in THF. With inferences drawn from simple structural models, we speculate that this self-assembly behavior arises due to the change in the chain configuration with increasing content of 1,2-links in the backbone. This renders the chain with higher 1,2 content incapable of swelling in response to solvent and unable to pack into well-defined self-assembled structures.

  16. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    An, Hyosung; Mike, Jared; Smith, Kendall; Swank, Lisa; Lin, Yen-Hao; Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie

    Structural energy storage materials combining load-bearing mechanical properties and high energy storage performance are desired for applications in wearable devices or flexible displays. Vanadium pentoxide (V2O5) is a promising cathode material for possible use in flexible battery electrodes, but it remains limited by low Li+ diffusion coefficient and electronic conductivity, severe volumetric changes upon cycling, and limited mechanical flexibility. Here, we demonstrate a route to address these challenges by blending a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT- b-PEO), with V2O5 to form a mechanically flexible, electro-mechanically stable hybrid electrode. V2O5 layers were arranged parallel in brick-and-mortar-like fashion held together by the P3HT- b-PEO binder. This unique structure significantly enhances mechanical flexibility, toughness and cyclability without sacrificing capacity. Electrodes comprised of 10 wt% polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes.

  17. Hydrogen bonding strength of diblock copolymers affects the self-assembled structures with octa-functionalized phenol POSS nanoparticles.

    PubMed

    Lu, Yi-Syuan; Yu, Chia-Yu; Lin, Yung-Chih; Kuo, Shiao-Wei

    2016-02-28

    In this study, the influence of the functional groups by the diblock copolymers of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP), poly(styrene-b-2-vinylpyridine) (PS-b-P2VP), and poly(styrene-b-methyl methacrylate) (PS-b-PMMA) on their blends with octa-functionalized phenol polyhedral oligomeric silsesquioxane (OP-POSS) nanoparticles (NPs) was investigated. The relative hydrogen bonding strengths in these blends follow the order PS-b-P4VP/OP-POSS > PS-b-P2VP/OP-POSS > PS-b-PMMA/OP-POSS based on the Kwei equation from differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopic analyses. Small-angle X-ray scattering and transmission electron microscopic analyses show that the morphologies of the self-assembly structures are strongly dependent on the hydrogen bonding strength at relatively higher OP-POSS content. The PS-b-P4VP/OP-POSS hybrid complex system with the strongest hydrogen bonds shows the order-order transition from lamellae to cylinders and finally to body-centered cubic spheres upon increasing OP-POSS content. However, PS-b-P2VP/OP-POSS and PS-b-PMMA/OP-POSS hybrid complex systems, having relatively weaker hydrogen bonds, transformed from lamellae to cylinder structures at lower OP-POSS content (<50 wt%), but formed disordered structures at relatively high OP-POSS contents (>50 wt%).

  18. Self-assembly of 21-arm star-like diblock copolymer in bulk and under cylindrical confinement.

    PubMed

    Xu, Yuci; Li, Weihua; Qiu, Feng; Lin, Zhiqun

    2014-06-21

    Phase behaviors of a 21-arm star-like diblock copolymer in bulk and under confinement were explored by using the pseudo-spectral method of a self-consistent mean field theory. An asymmetrical phase diagram in bulk was constructed by comparing the free energy of different structures. The gyroid phase was found to possess a large phase region when the inner block in the star-like diblock copolymer has a small volume fraction, suggesting the propensity to form the gyroid phase under this condition. Combined with the early experimental work, a scaling law correlating the period of lamellae D(multiarms) formed from multi-arm star-like block copolymers with the number of arms f was identified, that is, D(multiarms) = D/f(1/2), where D is the period of a linear diblock copolymer with the same degree of polymerization N as a star-like diblock copolymer. The scaling law was also substantiated by the scaling theory. The bridging fraction of the lamellae formed in a star-like diblock copolymer was nearly 100%, which is advantageous for improving its mechanical properties. Some interesting two-dimensional and three-dimensional morphologies were yielded under the cylindrical confinement, where a 3D double helix was found to be the most stable structure.

  19. Directed self-assembly of diblock copolymers in multi-VIA configurations: effect of chemopatterned substrates on defectivity

    NASA Astrophysics Data System (ADS)

    Carpenter, Corinne L.; Delaney, Kris T.; Fredrickson, Glenn H.

    2016-03-01

    Directed self-assembly (DSA) of block copolymers has gained much attention for its potential as a low-cost, high-throughput patterning tool to supplement existing lithographic techniques, and in particular for its ability to easily pattern vertical interconnect accesses (VIAs).1 Single-hole shrink has been extensively explored, but the continued push towards higher-resolution patterns requires more efficient, less space-consuming approaches. The lithographic resolution limits the minimum distance between two features, and the single-hole templates take up valuable real estate on the wafer.2 To accommodate denser features and relax the resolution requirements of the lithographic techniques, it is prudent to move to multi-VIA configurations in which two or more features are assembled in a single guiding template (such as a peanut,3 or a rounded rectangle4). This allows considerably denser feature patterning, but comes at the cost of more plentiful and complicated defect modes than those found in single-hole shrink features. Most systems contain persistent horizontal structures (eg. rings, U-defects, or bars as shown in Figure 1) that prove detrimental to the etch process and yield undesirable configurations. Largely unexplored is the tandem use of chemoepitaxy and graphoepitaxy to suppress defect modes in multi- VIA templates. Specifically, chemically selective patterning of the substrate beneath a template could act synergistically with the template's lateral guidance to lower defectivity. In this study, we use three-dimensional self-consistent field theory (SCFT) simulations to investigate the equilibrium and metastable defective configurations of di-block copolymer DSA systems in the presence of chemically selective or neutral template sidewalls and preferentially attractive striped substrates. We identify chemo-patterning schemes that maximize defect energies, including sidewall interaction strength and chemical preference. In addition, we discuss chemo

  20. Diblock-copolymer-mediated self-assembly of protein-stabilized iron oxide nanoparticle clusters for magnetic resonance imaging.

    PubMed

    Tähkä, Sari; Laiho, Ari; Kostiainen, Mauri A

    2014-03-03

    Superparamagnetic iron oxide nanoparticles (SPIONs) can be used as efficient transverse relaxivity (T2 ) contrast agents in magnetic resonance imaging (MRI). Organizing small (D<10 nm) SPIONs into large assemblies can considerably enhance their relaxivity. However, this assembly process is difficult to control and can easily result in unwanted aggregation and precipitation, which might further lead to lower contrast agent performance. Herein, we present highly stable protein-polymer double-stabilized SPIONs for improving contrast in MRI. We used a cationic-neutral double hydrophilic poly(N-methyl-2-vinyl pyridinium iodide-block-poly(ethylene oxide) diblock copolymer (P2QVP-b-PEO) to mediate the self-assembly of protein-cage-encapsulated iron oxide (γ-Fe2 O3 ) nanoparticles (magnetoferritin) into stable PEO-coated clusters. This approach relies on electrostatic interactions between the cationic N-methyl-2-vinylpyridinium iodide block and magnetoferritin protein cage surface (pI≈4.5) to form a dense core, whereas the neutral ethylene oxide block provides a stabilizing biocompatible shell. Formation of the complexes was studied in aqueous solvent medium with dynamic light scattering (DLS) and cryogenic transmission electron microcopy (cryo-TEM). DLS results indicated that the hydrodynamic diameter (Dh ) of the clusters is approximately 200 nm, and cryo-TEM showed that the clusters have an anisotropic stringlike morphology. MRI studies showed that in the clusters the longitudinal relaxivity (r1 ) is decreased and the transverse relaxivity (r2 ) is increased relative to free magnetoferritin (MF), thus indicating that clusters can provide considerable contrast enhancement.

  1. Fabrication of Nanohole Array via Nanodot Array Using Simple Self-Assembly Process of Diblock Copolymer

    NASA Astrophysics Data System (ADS)

    Matsuyama, Tsuyoshi; Kawata, Yoshimasa

    2007-06-01

    We present a simple self-assembly process for fabricating a nanohole array via a nanodot array on a glass substrate by dripping ethanol onto the nanodot array. It is found that well-aligned arrays of nanoholes as well as nanodots are formed on the whole surface of the glass. A dot is transformed into a hole, and the alignment of the nanodots strongly reflects that of the nanoholes. We find that the change in the depth of holes agrees well with the change in the surface energy with the ethanol concentration in the aqueous solution. We believe that the interfacial energy between the nanodots and the dripped ethanol causes the transformation from nanodots into nanoholes. The nanohole arrays are directly applicable to molds for nanopatterned media used in high-density near-field optical data storage. The bit data can be stored and read out using probes with small apertures.

  2. Self-Assembly of AB Diblock Copolymer Confined in a Soft Nano-Droplet: A Combination Study by Monte Carlo Simulation and Experiment.

    PubMed

    Yan, Nan; Zhu, Yutian; Jiang, Wei

    2016-11-23

    The self-assembly of AB-type diblock copolymers confined in a three-dimensional (3D) soft nanodroplet is investigated by the combination of Monte Carlo simulation and experiment. The influences of two critical factors, i.e., confinement degree of the imposed confinement space and the interfacial interaction between each individual block and boundary interface, on the 3D soft confined self-assembly are examined systematically. The simulation results reveal that block copolymer chains become more and more folded as the confinement degree (it can be monitored by the ratio of D/L, where L is the length of polymer chain and D is the reduced diameter of the final polymeric particle) is enhanced, causing a series of morphological transitions. Based on the simulation prediction, we perform the corresponding experiments by the 3D confined self-assembly of both symmetric and asymmetric block copolymers within the emulsion droplets. The experimental results well reproduce the confinement degree induced morphological transitions predicted by the simulations, such as the transition from segmented pupa-like particle to hamburger particle and the transition from raspberry-like particle to triangle-like particle, and then to hamburger particle. The current study implies that self-assembled nanostructures under 3D soft confinement can be simply controlled by tuning the confinement degree and interfacial property, i.e., the ratio of D/L and the interfacial interaction between each individual block and boundary interface.

  3. Vertical Conducting Nanodomains Self-Assembled from Poly(3-hexylthiophene)-Based Diblock Copolymer Thin Films

    SciTech Connect

    Y Lee; S Kim; H Yang; M Jang; S Hwang; H Lee; K Baek

    2011-12-31

    We have synthesized {pi}-conjugated poly(3-hexyl thiophene)-block-poly(methyl methacrylate) (P3HT-b-PMMA) with a P3HT molecular weight of 11 kDa and a PMMA volume fraction of 0.53, which potentially has several organic electronic applications. Its phase-separation behavior was investigated for various thicknesses cast from organic solvents. When cast onto 300 nm thick SiO{sub 2} dielectrics from toluene, in which the P3HT segments have limited solubility, the P3HT-b-PMMA films consist of nanofibrillar self-assemblies of laterally {pi}-stacked P3HT chains. In contrast, the P3HT segments were found to be highly mobile in chlorobenzene, generating a typical phase-separation morphology consisting of vertically conducting P3HT nanodomains on these dielectrics. As the thickness of the cast films increased, however, the topmost surface becomes covered with {pi}-conjugated nanofibrils that are laterally oriented with respect to the surface. Due to the anisotropic domain orientations of P3HT, top-gate organic field-effect transistors (OFETs) containing the P3HT-b-PMMA films exhibited enhanced electrical performance compared to bottom-gate OFETs.

  4. Selective area atomic layer deposited ZnO nanodot on self-assembled monolayer pattern using a diblock copolymer nano-template.

    PubMed

    Kim, Doyoung; Yoon, Jaehong; Kim, Hyungjun

    2012-02-01

    ZnO nanodots were prepared by selective area atomic layer deposition (SA-ALD) on an octadecyltrichlorosilane (ODTS) self-assembly monolayers (SAMs) patterns formed using a diblock co-polymer (DBC) nanotemplate. In order to transfer well-ordered nanaotemplate in SAMs, SiO2 sacrificial layer was inserted between DBC and SAMs. Cylindrical nanoholes under 16 nm diameters were well-formed on SiO2 layer. SA-ALD of ZnO was successfully performed on by ODTS SAMs.

  5. Effect of Small Molecule Osmolytes on the Self-Assembly and Functionality of Globular Protein-Polymer Diblock Copolymers

    SciTech Connect

    Thomas, Carla S.; Xu, Liza; Olsen, Bradley D.

    2013-12-05

    Blending the small molecule osmolytes glycerol and trehalose with the model globular protein–polymer block copolymer mCherry-b-poly(N-isopropyl acrylamide) (mCherry-b-PNIPAM) is demonstrated to improve protein functionality in self-assembled nanostructures. The incorporation of either additive into block copolymers results in functionality retention in the solid state of 80 and 100% for PNIPAM volume fractions of 40 and 55%, respectively. This represents a large improvement over the 50–60% functionality observed in the absence of any additive. Furthermore, glycerol decreases the thermal stability of block copolymer films by 15–20 °C, while trehalose results in an improvement in the thermal stability by 15–20 °C. These results suggest that hydrogen bond replacement is responsible for the retention of protein function but suppression or enhancement of thermal motion based on the glass transition of the osmolyte primarily determines thermal stability. While both osmolytes are observed to have a disordering effect on the nanostructure morphology with increasing concentration, this effect is less pronounced in materials with a larger polymer volume fraction. Glycerol preferentially localizes in the protein domains and swells the nanostructures, inducing disordering or a change in morphology depending on the PNIPAM coil fraction. In contrast, trehalose is observed to macrophase separate from the block copolymer, which results in nanodomains becoming more disordered without changing significantly in size.

  6. Synthesis and self-assembly of brush-type poly[poly(ethylene glycol)methyl ether methacrylate]-block-poly(pentafluorostyrene) amphiphilic diblock copolymers in aqueous solution.

    PubMed

    Tan, B H; Hussain, H; Liu, Y; He, C B; Davis, T P

    2010-02-16

    Well-defined fluorinated brush-like amphiphilic diblock copolymers of poly[poly(ethylene glycol)methyl ether methacrylate] (P(PEGMA)) and poly(pentafluorostyrene) (PPFS) have been successfully synthesized via atom transfer radical polymerization (ATRP). The self-assembly behavior of these polymers in aqueous solutions was studied using (1)H NMR, fluorescence spectrometry, static and dynamic light scattering and transmission electron microscopy techniques. The micellar structure comprised of PPFS as the core and brush-like (hydrophobic main chain and hydrophilic branches) polymers as the coronas. The hydrodynamic radius (R(h)) of the micelles in aqueous solution was in the nanometer range, independent of the polymer concentration, consistent with a closed association model. Diblock copolymers with a longer P(PEGMA) block formed micelles with smaller R(h) and lower aggregation numbers consistent with an improved solubilization of the core. The micelles possessed a thick hydration layer as verified by the ratio of the radius of gyration, R(g) to the hydrodynamic radius, R(h). The aggregation number and ratio of R(g) to R(h) were observed to increase with temperature (20-50 degrees C), while the R(h) of the micelle decreased slightly over the same temperature range. An increase in temperature induced the brush-like PEG segments in the corona to dehydrate and shrink while forming micelles with larger aggregation numbers.

  7. Aqueous self-assembly of poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) copolymers: disparate diblock copolymer compositions give rise to nano- and meso-scale bilayered vesicles.

    PubMed

    Qi, Wei; Ghoroghchian, P Peter; Li, Guizhi; Hammer, Daniel A; Therien, Michael J

    2013-11-21

    Nanoparticles formed from diblock copolymers of FDA approved PEO and PCL have generated considerable interest as in vivo drug delivery vehicles. Herein, we report the synthesis of the most extensive family PEO-b-PCL copolymers that vary over the largest range of number-average molecular weights (Mn: 3.6-57k), PEO weight fractions (fPEO: 0.08-0.33), and PEO chain lengths (0.75-5.8k) reported to date. These polymers were synthesized in order to establish the full range of aqueous phase behaviours of these diblock copolymers and to specifically identify formulations that were able to generate bilayered vesicles (polymersomes). Cryogenic transmission electron microscopy (cryo-TEM) was utilized in order to visualize the morphology of these structures upon aqueous self-assembly of dry polymer films. Nanoscale polymersomes were formed from PEO-b-PCL copolymers over a wide range of PEO weight fractions (fPEO: 0.14-0.27) and PEO molecular weights (0.75-3.8k) after extrusion of aqueous suspensions. Comparative morphology diagrams, which describe the nature of self-assembled structures as a function of diblock copolymer molecular weight and PEO weight fraction, show that in contrast to micron-scale polymersomes, which form only from a limited range of PEO-b-PCL diblock copolymer compositions, a multiplicity of PEO-b-PCL diblock copolymer compositions are able to give rise to nanoscale vesicles. These data underscore that PEO-b-PCL compositions that spontaneously form micron-sized polymersomes, as well as those that have previously been reported to form polymersomes via a cosolvent fabrication system, provide only limited insights into the distribution of PEO-b-PCL diblocks that give rise to nanoscale vesicles. The broad range of polymersome-forming PEO-b-PCL compositions described herein suggest the ability to construct extensive families of nanoscale vesicles of varied bilayer thickness, providing the ability to tune the timescales of vesicle degradation and encapsulant

  8. Arrangement of Maghemite Nanoparticles via Wet Chemical Self-Assembly in PS-b-PNIPAM Diblock Copolymer Films.

    PubMed

    Yao, Yuan; Metwalli, Ezzeldin; Su, Bo; Körstgens, Volker; Moseguí González, Daniel; Miasnikova, Anna; Laschewsky, Andre; Opel, Matthias; Santoro, Gonzalo; Roth, Stephan V; Müller-Buschbaum, Peter

    2015-06-17

    The structure and magnetic behavior of hybrid films composed of maghemite (γ-Fe2O3) nanoparticles (NPs) and an asymmetric diblock copolymer (DBC) polystyrene61-block-polyN-isopropylacrylamide115 are investigated. The NPs are coated with PS chains, which allow for a selective incorporation inside the PS domains at different NP concentrations. Upon incorporation of low amounts of NPs into the DBC thin films, the initial parallel (to film surface) cylinder morphology changes to a well ordered, perpendicularly oriented one. The characteristic domain distance of the DBC is increased due to the swelling of the PS domains with NPs. At higher NP concentrations, the excess NPs which can no longer be embedded in the PS domains, are accumulated at the film surface, and NP aggregates form. Irrespective of NP concentration, a superparamagnetic behavior of the metal oxide-DBC hybrid films is found. Such superparamagnetic properties make the established hybrid films interesting for high density magnetic storage media and thermoresponsive magnetic sensors.

  9. Preparation and Cross-Linking of All-Acrylamide Diblock Copolymer Nano-Objects via Polymerization-Induced Self-Assembly in Aqueous Solution

    PubMed Central

    2017-01-01

    Various carboxylic acid-functionalized poly(N,N-dimethylacrylamide) (PDMAC) macromolecular chain transfer agents (macro-CTAs) were chain-extended with diacetone acrylamide (DAAM) by reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization at 70 °C and 20% w/w solids to produce a series of PDMAC–PDAAM diblock copolymer nano-objects via polymerization-induced self-assembly (PISA). TEM studies indicate that a PDMAC macro-CTA with a mean degree of polymerization (DP) of 68 or higher results in the formation of well-defined spherical nanoparticles with mean diameters ranging from 40 to 150 nm. In contrast, either highly anisotropic worms or polydisperse vesicles are formed when relatively short macro-CTAs (DP = 40–58) are used. A phase diagram was constructed to enable accurate targeting of pure copolymer morphologies. Dynamic light scattering (DLS) and aqueous electrophoresis studies indicated that in most cases these PDMAC–PDAAM nano-objects are surprisingly resistant to changes in either solution pH or temperature. However, PDMAC40–PDAAM99 worms do undergo partial dissociation to form a mixture of relatively short worms and spheres on adjusting the solution pH from pH 2–3 to around pH 9 at 20 °C. Moreover, a change in copolymer morphology from worms to a mixture of short worms and vesicles was observed by DLS and TEM on heating this worm dispersion to 50 °C. Postpolymerization cross-linking of concentrated aqueous dispersions of PDMAC–PDAAM spheres, worms, or vesicles was performed at ambient temperature using adipic acid dihydrazide (ADH), which reacts with the hydrophobic ketone-functionalized PDAAM chains. The formation of hydrazone groups was monitored by FT-IR spectroscopy and afforded covalently stabilized nano-objects that remained intact on exposure to methanol, which is a good solvent for both blocks. Rheological studies indicated that the cross-linked worms formed a stronger gel compared to linear precursor

  10. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    SciTech Connect

    An, Hyosung; Mike, Jared; Smith, Kendall A.; Swank, Lisa; Lin, Yen-Hao; L. Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie L.

    2015-09-22

    Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects.

  11. Testing the Vesicular Morphology to Destruction: Birth and Death of Diblock Copolymer Vesicles Prepared via Polymerization-Induced Self-Assembly

    PubMed Central

    2014-01-01

    Small angle X-ray scattering (SAXS), electrospray ionization charge detection mass spectrometry (CD-MS), dynamic light scattering (DLS), and transmission electron microscopy (TEM) are used to characterize poly(glycerol monomethacrylate)55-poly(2-hydroxypropyl methacrylate)x (G55-Hx) vesicles prepared by polymerization-induced self-assembly (PISA) using a reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization formulation. A G55 chain transfer agent is utilized to prepare a series of G55-Hx diblock copolymers, where the mean degree of polymerization (DP) of the membrane-forming block (x) is varied from 200 to 2000. TEM confirms that vesicles with progressively thicker membranes are produced for x = 200–1000, while SAXS indicates a gradual reduction in mean aggregation number for higher x values, which is consistent with CD-MS studies. Both DLS and SAXS studies indicate minimal change in the overall vesicle diameter between x = 400 and 800. Fitting SAXS patterns to a vesicle model enables calculation of the membrane thickness, degree of hydration of the membrane, and the mean vesicle aggregation number. The membrane thickness increases at higher x values, hence the vesicle lumen must become smaller if the external vesicle dimensions remain constant. Geometric considerations indicate that this growth mechanism lowers the total vesicle interfacial area and hence reduces the free energy of the system. However, it also inevitably leads to gradual ingress of the encapsulated water molecules into the vesicle membrane, as confirmed by SAXS analysis. Ultimately, the highly plasticized membranes become insufficiently hydrophobic to stabilize the vesicle morphology when x exceeds 1000, thus this PISA growth mechanism ultimately leads to vesicle “death”. PMID:25526525

  12. Self-assembled architectures from biohybrid triblock copolymers.

    PubMed

    Reynhout, Irene C; Cornelissen, Jeroen J L M; Nolte, Roeland J M

    2007-02-28

    The synthesis and self-assembly behavior of biohybrid ABC triblock copolymers consisting of a synthetic diblock, polystyrene-b-polyethylene glycol (PSm-b-PEG113), where m is varied, and a hemeprotein, myoglobin (Mb) or horse radish peroxidase (HRP), is described. The synthetic diblock copolymer is first functionalized with the heme cofactor and subsequently reconstituted with the apoprotein or the apoenzyme to yield the protein-containing ABC triblock copolymer. The obtained amphiphilic block copolymers self-assemble in aqueous solution into a large variety of aggregate structures. Depending on the protein and the polystyrene block length, micellar rods, vesicles, toroids, figure eight structures, octopus structures, and spheres with a lamellar surface are formed.

  13. Self-assembly of diblock co-polymers at air-water interface: A microscopy and x-ray scattering study

    SciTech Connect

    Giri, R. P. Mukhopadhyay, M. K.

    2016-05-23

    The spontaneous surface aggregation of diblock copolymer, containing polystyrene-polydimethylsiloxane or PS-PDMS, have been studied at air-water interface using Brewster’s angle microscopy (BAM) and grazing incidence small angle x-ray scattering (GISAXS) technique. Pronounced differences in the molecular weight and solvent dependence of the size of aggregation on the water surface are observed. Structural characterization is done using atomic force microscopy (AFM) for a monolayer transferred to Si substrate. It shows that, individual polymer chains coalesce to form some disc like micelle aggregation on the Si surface which is also evident from the BAM image of the water floated monolayer. GISAXS study is also corroborating the same result.

  14. Chemical imaging of the surface of self-assembled polystyrene-b-poly(methyl methacrylate) diblock copolymer films using apertureless near-field IR microscopy.

    PubMed

    Mueller, Kerstin; Yang, Xiujuan; Paulite, Melissa; Fakhraai, Zahra; Gunari, Nikhil; Walker, Gilbert C

    2008-06-01

    The nanoscale chemical composition variations of the surfaces of thin films of polystyrene- b-poly(methyl methacrylate) (PS- b-PMMA) diblock copolymers are investigated using apertureless near-field IR microscopy. The scattering of the incident infrared beam from a modulated atomic force microscopy (AFM) tip is probed using homodyne detection and demodulation at the tip oscillation frequency. An increase in the IR attenuation is observed in the PMMA-rich domains with a wavenumber dependence that is consistent with the bulk absorption spectrum. The results indicate that even though a small topography-induced artifact can be observed in the near-field images, the chemical signature of the sample is detected clearly.

  15. Self-assembly of diblock co-polymers at air-water interface: A microscopy and x-ray scattering study

    NASA Astrophysics Data System (ADS)

    Giri, R. P.; Mukhopadhyay, M. K.

    2016-05-01

    The spontaneous surface aggregation of diblock copolymer, containing polystyrene-polydimethylsiloxane or PS-PDMS, have been studied at air-water interface using Brewster's angle microscopy (BAM) and grazing incidence small angle x-ray scattering (GISAXS) technique. Pronounced differences in the molecular weight and solvent dependence of the size of aggregation on the water surface are observed. Structural characterization is done using atomic force microscopy (AFM) for a monolayer transferred to Si substrate. It shows that, individual polymer chains coalesce to form some disc like micelle aggregation on the Si surface which is also evident from the BAM image of the water floated monolayer. GISAXS study is also corroborating the same result.

  16. Hyperviscous diblock copolymer vesicles

    NASA Astrophysics Data System (ADS)

    Dimova, R.; Seifert, U.; Pouligny, B.; Förster, S.; Döbereiner, H.-G.

    2002-03-01

    Giant vesicles prepared from the diblock copolymer polybutadien-b-polyethyleneoxide (PB-PEO) exhibit a shear surface viscosity, which is about 500 times higher than those found in common phospholipid bilayers. Our result constitutes the first direct measurement of the shear surface viscosity of such polymersomes. At the same time, we measure bending and stretching elastic constants, which fall in the range of values typical for lipid membranes. Pulling out a tether from an immobilized polymersome and following its relaxation back to the vesicle body provides an estimate of the viscous coupling between the two monolayers composing the polymer membrane. The detected intermonolayer friction is about an order of magnitude higher than the characteristic one for phospholipid membranes. Polymersomes are tough vesicles with a high lysis tension. This, together with their robust rheological properties, makes them interesting candidates for a number of technological applications.

  17. Synthesis, morphologies and applications of polyoxometalate-containing diblock copolymers

    NASA Astrophysics Data System (ADS)

    Chakraborty, Sanjiban

    Block copolymers by virtue of their ability to self assemble and microphase-separation due to the contrast in chemical and physical properties of the covalently linked blocks constitute the essential building blocks towards various nano or micro sized architectures. Polyoxometalates (POM), on the other hand, being an interesting class of metal-oxygen nanometer-sized anionic clusters, are regarded highly due to their excellent electron accepting capability. Combining POM clusters with diblock copolymers can lead to a fascinating class of hybrid materials where the POM cluster not only affect the self-assembly process of various diblock copolymers but also brings its unique electronic properties into the hybrid system. Herein we report the detailed synthesis and characterizations of two hybrid coil-coil diblock copolymers along with two hybrid rod-coil diblock copolymers through polymerization-hybridization approach. The coil-coil diblocks were synthesized via atom transfer radial polymerization (ATRP) of styryl-type monomers and 4-vinylpyridine in sequence. For rod-coil diblock copolymers, the coil block was synthesized through ATRP, followed by the conversion of the terminal bromide to an azide. Ethynyl terminated poly (p-phenylenevinylene) (PPV) and poly (3-hexylthiophene) (P3HT) were prepared separately as the rod blocks. The rod block and the coil block were connected through click chemistry to yield rod-coil diblock copolymers. After removing the phthalimide protecting groups to regenerate aryl amines, POM clusters were finally linked to the coil block of all diblock copolymers to yield the targeted hybrid diblock copolymers. The covalent cluster attachment was confirmed by UV-Vis spectroscopy, FTIR and cyclovoltammetry measurements. The structures, solution and film optical properties, self-assembled morphologies and solar cell performances of these hybrids have been studied. It has been found that solar cell devices based on hybrid P3HT exhibited rather poor

  18. Electrochemically controlled self-assembly of block copolymer nanostructures

    NASA Astrophysics Data System (ADS)

    Eitouni, Hany Basam

    Organometallic block copolymers, wherein one block is composed of alternating ferrocene and dialkylsilane units in the main chain, undergo self-assembly to form microphase-separated ordered structures similarly to typical organic block copolymers. The 1,1'-dimethylsilylferrocenophane monomer was synthesized and polymerized anionically with other monomers to make a variety of different organometallic block copolymers. The phase behavior and thermodynamic interactions of anionically synthesized poly(styrene-block-ferrocenyldimethylsilane) (SF) and poly(isoprene-block-ferrocenyldimethylsilane) (IF) copolymers were examined using depolarized light scattering, small angle x-ray and neutron scattering (SAXS and SANS), and transmission electron microscopy. The temperature-dependence of the Flory-Huggins parameter, chi, and the statistical segment lengths of SF and IF copolymers were determined by SAXS and SANS using the random phase approximation. The thermodynamic interactions in poly(ferrocenyldimethylsilane) diblock copolymers were systematically adjusted by oxidizing the ferrocene moieties with silver salts and examined using SAXS and depolarized light scattering. The polymers retained microphase separated ordered structures upon oxidation and showed systematic changes in the location of the order-disorder transition as a function of extent of oxidation. By controlling the redox properties of the ferrocene moiety in the backbone of the polymer, we present a method for controlling the self-assembled microstructure and hence bulk material properties. Using electrochemical techniques, a novel means of controlling the order-disorder transition of block copolymers was discovered. By applying very small electrical potentials to disordered solutions of organometallic block copolymers, oriented ordered grains were formed near one electrode, the result of electrochemical reactions. After reversing the electrical bias on the system, the ordered grains disappeared and new

  19. Crystallization in Ordered Polydisperse Polyolefin Diblock Copolymers

    SciTech Connect

    Li, Sheng; Register, Richard A.; Landes, Brian G.; Hustad, Phillip D.; Weinhold, Jeffrey D.

    2010-12-07

    The morphologies of polydisperse ethylene-octene diblock copolymers, synthesized via a novel coordinative chain transfer polymerization process, are examined using two-dimensional synchrotron small-angle and wide-angle X-ray scattering on flow-aligned specimens. The diblock copolymers comprise one amorphous block with high 1-octene content and one semicrystalline block with relatively low 1-octene content, and each block ideally exhibits the most-probable distribution. Near-symmetric diblocks with a sufficiently large octene differential between the amorphous and semicrystalline blocks show well-ordered lamellar domain structures with long periods exceeding 100 nm. Orientation of these domain structures persists through multiple melting/recrystallization cycles, reflecting a robust structure which self-assembles in the melt. The domain spacings are nearly 3-fold larger than those in near-monodisperse polyethylene block copolymers of similar molecular weights. Although the well-ordered lamellar domain structure established in the melt is preserved in the solid state, the crystallites are isotropic in orientation. These materials display crystallization kinetics consistent with a spreading growth habit, indicating that the lamellae do not confine or template the growing crystals. The exceptionally large domain spacings and isotropic crystal growth are attributed to interblock mixing resulting from the large polydispersity; short hard blocks dissolved in the soft-block-rich domains swell the domain spacing in the melt and allow hard block crystallization to proceed across the lamellar domain interfaces.

  20. Self-assembly of Random Copolymers

    PubMed Central

    Li, Longyu; Raghupathi, Kishore; Song, Cunfeng; Prasad, Priyaa; Thayumanavan, S.

    2014-01-01

    Self-assembly of random copolymers has attracted considerable attention recently. In this feature article, we highlight the use of random copolymers to prepare nanostructures with different morphologies and to prepare nanomaterials that are responsive to single or multiple stimuli. The synthesis of single-chain nanoparticles and their potential applications from random copolymers are also discussed in some detail. We aim to draw more attention to these easily accessible copolymers, which are likely to play an important role in translational polymer research. PMID:25036552

  1. Self-Assembly and Crystallization of Conjugated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Davidson, Emily Catherine

    This dissertation demonstrates the utility of molecular design in conjugated polymers to create diblock copolymers that robustly self-assemble in the melt and confine crystallization upon cooling. This work leverages the model conjugated polymer poly(3-(2'-ethyl)hexylthiophene) (P3EHT), which features a branched side chain, resulting in a dramatically reduced melting temperature (Tm 80°C) relative to the widely-studied poly(3-hexylthiophene) (P3HT) (Tm 200°C). This reduced melting temperature permits an accessible melt phase, without requiring that the segregation strength (chiN) be dramatically increased. Thus, diblock copolymers containing P3EHT demonstrate robust diblock copolymer self-assembly in the melt over a range of compositions and morphologies. Furthermore, confined crystallization in the case of both glassy (polystyrene (PS) matrix block) and soft (polymethylacrylate (PMA) matrix block) confinement is studied, with the finding that even in soft confinement, crystallization is constrained within the diblock microdomains. This success demonstrates the strategy of leveraging molecular design to decrease the driving force for crystallization as a means to achieving robust self-assembly and confined crystallization in conjugated block copolymers. Importantly, despite the relatively flexible nature of P3EHT in the melt, the diblock copolymer phase behavior appears to be significantly impacted by the stiffness (persistence length of 3 nm) of the P3EHT chain compared to the coupled amorphous blocks (persistence length 0.7 nm). In particular, it is shown that the synthesized morphologies are dominated by a very large composition window for lamellar geometries (favored at high P3EHT volume fractions); cylindrical geometries are favored when P3EHT is the minority fraction. This asymmetry of the composition window is attributed to impact of conformational asymmetry (the difference in chain stiffness, as opposed to shape) between conjugated and amorphous blocks

  2. Confined Crystallization in Poly(3-alkylthiophene)-containing Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Davidson, Emily; Ho, Victor; Beckingham, Bryan; Segalman, Rachel

    2014-03-01

    Confined crystallization within a diblock copolymer of a conjugated, semiconducting poly(3-alkylthiophene) (P3AT) block has been achieved by selecting an alkyl side chain that significantly depresses the crystalline driving force relative to the self-assembly driving force. Here, we demonstrate flow alignment of these P3AT-containing diblocks. In addition, we show that the chain axis of the semicrystalline P3AT orients preferentially relative to domain interfaces; the degree of crystalline orientation may be controlled as a function of domain width. Further work will examine the role of thermal treatments on crystallite orientation and morphology within confinement.

  3. Self-assembly of crystalline nanotubes from monodisperse amphiphilic diblock copolypeptoid tiles.

    PubMed

    Sun, Jing; Jiang, Xi; Lund, Reidar; Downing, Kenneth H; Balsara, Nitash P; Zuckermann, Ronald N

    2016-04-12

    The folding and assembly of sequence-defined polymers into precisely ordered nanostructures promises a class of well-defined biomimetic architectures with specific function. Amphiphilic diblock copolymers are known to self-assemble in water to form a variety of nanostructured morphologies including spheres, disks, cylinders, and vesicles. In all of these cases, the predominant driving force for assembly is the formation of a hydrophobic core that excludes water, whereas the hydrophilic blocks are solvated and extend into the aqueous phase. However, such polymer systems typically have broad molar mass distributions and lack the purity and sequence-defined structure often associated with biologically derived polymers. Here, we demonstrate that purified, monodisperse amphiphilic diblock copolypeptoids, with chemically distinct domains that are congruent in size and shape, can behave like molecular tile units that spontaneously assemble into hollow, crystalline nanotubes in water. The nanotubes consist of stacked, porous crystalline rings, and are held together primarily by side-chain van der Waals interactions. The peptoid nanotubes form without a central hydrophobic core, chirality, a hydrogen bond network, and electrostatic or π-π interactions. These results demonstrate the remarkable structure-directing influence of n-alkane and ethyleneoxy side chains in polymer self-assembly. More broadly, this work suggests that flexible, low-molecular-weight sequence-defined polymers can serve as molecular tile units that can assemble into precision supramolecular architectures.

  4. Self-assembly of crystalline nanotubes from monodisperse amphiphilic diblock copolypeptoid tiles

    DOE PAGES

    Sun, Jing; Jiang, Xi; Lund, Reidar; ...

    2016-03-28

    The folding and assembly of sequence-defined polymers into precisely ordered nanostructures promises a class of well-defined biomimetic architectures with specific function. Amphiphilic diblock copolymers are known to self-assemble in water to form a variety of nanostructured morphologies including spheres, disks, cylinders, and vesicles. In all of these cases, the predominant driving force for assembly is the formation of a hydrophobic core that excludes water, whereas the hydrophilic blocks are solvated and extend into the aqueous phase. However, such polymer systems typically have broad molar mass distributions and lack the purity and sequence-defined structure often associated with biologically derived polymers. Here,more » we demonstrate that purified, monodisperse amphiphilic diblock copolypeptoids, with chemically distinct domains that are congruent in size and shape, can behave like molecular tile units that spontaneously assemble into hollow, crystalline nanotubes in water. The nanotubes consist of stacked, porous crystalline rings, and are held together primarily by side-chain van der Waals interactions. The peptoid nanotubes form without a central hydrophobic core, chirality, a hydrogen bond network, and electrostatic or π-π interactions. These results demonstrate the remarkable structure-directing influence of n-alkane and ethyleneoxy side chains in polymer self-assembly. More broadly, this work suggests that flexible, low-molecular-weight sequence-defined polymers can serve as molecular tile units that can assemble into precision supramolecular architectures.« less

  5. Self-assembly of crystalline nanotubes from monodisperse amphiphilic diblock copolypeptoid tiles

    PubMed Central

    Sun, Jing; Jiang, Xi; Lund, Reidar; Downing, Kenneth H.; Balsara, Nitash P.; Zuckermann, Ronald N.

    2016-01-01

    The folding and assembly of sequence-defined polymers into precisely ordered nanostructures promises a class of well-defined biomimetic architectures with specific function. Amphiphilic diblock copolymers are known to self-assemble in water to form a variety of nanostructured morphologies including spheres, disks, cylinders, and vesicles. In all of these cases, the predominant driving force for assembly is the formation of a hydrophobic core that excludes water, whereas the hydrophilic blocks are solvated and extend into the aqueous phase. However, such polymer systems typically have broad molar mass distributions and lack the purity and sequence-defined structure often associated with biologically derived polymers. Here, we demonstrate that purified, monodisperse amphiphilic diblock copolypeptoids, with chemically distinct domains that are congruent in size and shape, can behave like molecular tile units that spontaneously assemble into hollow, crystalline nanotubes in water. The nanotubes consist of stacked, porous crystalline rings, and are held together primarily by side-chain van der Waals interactions. The peptoid nanotubes form without a central hydrophobic core, chirality, a hydrogen bond network, and electrostatic or π–π interactions. These results demonstrate the remarkable structure-directing influence of n-alkane and ethyleneoxy side chains in polymer self-assembly. More broadly, this work suggests that flexible, low–molecular-weight sequence-defined polymers can serve as molecular tile units that can assemble into precision supramolecular architectures. PMID:27035944

  6. Mesoscopic simulation of the self-assembly of the weak polyelectrolyte poly(ethylene oxide)-block-poly(methyl methacrylate) diblock copolymers.

    PubMed

    Mu, Dan; Li, Jian-Quan; Feng, Sheng-Yu

    2015-06-14

    We designed twelve types of weak polyelectrolytes (i.e., PEO-b-PMMA copolymers (BCP) in multi-arm structures, where six include EO blocks as joint points and the other six have MMA blocks as joint points). All of the BCPs with EO as the joint points form disordered phases with the exception of long-chained and four-armed BCP. The main mesophases of all of the BCPs with MMA as joint points are micelle-like and bicontinuous phases. In particular, the short-chained BCP with four-arms and EO segments outside form a new phase type (i.e., crossed lamellar phase). Using MesoDyn, we provide a comprehensive representation of the micelle and crossed lamellar phase formation mechanisms based on both thermodynamic and dynamic analyses. A shear force on a micelle-like phase could promote a hexagonal columnar phase, which is a good technique for generating an ordered arrangement of nanotube arrays. Blending homopolymers with the same constituents could promote uniformity of the micelle size and decrease the polydispersity, especially for blends with a high BCP concentration, which may provide a new approach for regulating the properties of materials.

  7. Ordered nanostructures self-assembled from block copolymer tethered nanoparticles.

    PubMed

    Zhu, Xiaomeng; Wang, Liquan; Lin, Jiaping; Zhang, Liangshun

    2010-09-28

    Combining the self-consistent field theory (SCFT) and the density functional theory (DFT), we investigated the self-assembly behavior of AB diblock copolymer tethered single spherical particle P (ABP molecules). Two cases were studied: one is where the particles are chemically neutral to both A and B blocks, and the other is where the particles are unfavorable to neither of the two blocks. For neutral particles, the ABP molecules self-assemble to typical equilibrium microstructures, such as lamellae and cylinders. The P particles are localized in B block domains, and the size of particles can influence the phase behavior. For unfavorable particles, the ABP molecules microphase separate to form distinct ordered structures. Hierarchical structures, such as cylinders with cylinders at the interfaces and lamellae with cylinders at the interfaces, were observed. These resulting hierarchical structures are mainly determined by two parameters: A block fraction f(A) and particle size R(P). On the basis of the calculation results, phase diagrams were constructed.

  8. Hierarchical Self-Assembly of Halogen-Bonded Block Copolymer Complexes into Upright Cylindrical Domains.

    PubMed

    Milani, Roberto; Houbenov, Nikolay; Fernandez-Palacio, Francisco; Cavallo, Gabriella; Luzio, Alessandro; Haataja, Johannes; Giancane, Gabriele; Saccone, Marco; Priimagi, Arri; Metrangolo, Pierangelo; Ikkala, Olli

    2017-03-09

    Self-assembly of block copolymers into well-defined, ordered arrangements of chemically distinct domains is a reliable strategy for preparing tailored nanostructures. Microphase separation results from the system, minimizing repulsive interactions between dissimilar blocks and maximizing attractive interactions between similar blocks. Supramolecular methods have also achieved this separation by introducing small-molecule additives binding specifically to one block by noncovalent interactions. Here, we use halogen bonding as a supramolecular tool that directs the hierarchical self-assembly of low-molecular-weight perfluorinated molecules and diblock copolymers. Microphase separation results in a lamellar-within-cylindrical arrangement and promotes upright cylindrical alignment in films upon rapid casting and without further annealing. Such cylindrical domains with internal lamellar self-assemblies can be cleaved by solvent treatment of bulk films, resulting in separated and segmented cylindrical micelles stabilized by halogen-bond-based supramolecular crosslinks. These features, alongside the reversible nature of halogen bonding, provide a robust modular approach for nanofabrication.

  9. Self-assembly of block copolymers grafted onto a flat substrate: Recent progress in theory and simulations

    NASA Astrophysics Data System (ADS)

    Zheng, Wang; Bao-Hui, Li

    2016-01-01

    Block copolymers are a class of soft matter that self-assemble to form ordered morphologies on the scale of nanometers, making them ideal materials for various applications. These applications directly depend on the shape and size of the self-assembled morphologies, and hence, a high degree of control over the self-assembly is desired. Grafting block copolymer chains onto a substrate to form copolymer brushes is a versatile method to fabricate functional surfaces. Such surfaces demonstrate a response to their environment, i.e., they change their surface topography in response to different external conditions. Furthermore, such surfaces may possess nanoscale patterns, which are important for some applications; however, such patterns may not form with spun-cast films under the same condition. In this review, we summarize the recent progress of the self-assembly of block copolymers grafted onto a flat substrate. We mainly concentrate on the self-assembled morphologies of end-grafted AB diblock copolymers, junction point-grafted AB diblock copolymers (i.e., Y-shaped brushes), and end-grafted ABA triblock copolymers. Special emphasis is placed on theoretical and simulation progress. Project supported by the National Natural Science Foundation of China (Grant Nos. 20990234, 20925414, and 91227121), the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT1257), the Programme of Introducing Talents of Discipline to Universities, China, and by the Tianhe No. 1, China.

  10. Unexpected Consequences of Block Polydispersity on the Self-Assembly of ABA Triblock Copolymers

    SciTech Connect

    Widin, Joan M.; Schmitt, Adam K.; Schmitt, Andrew L.; Im, Kyuhyun; Mahanthappa, Mahesh K.

    2012-05-09

    Controlled/'living' polymerizations and tandem polymerization methodologies offer enticing opportunities to enchain a wide variety of monomers into new, functional block copolymer materials with unusual physical properties. However, the use of these synthetic methods often introduces nontrivial molecular weight polydispersities, a type of chain length heterogeneity, into one or more of the copolymer blocks. While the self-assembly behavior of monodisperse AB diblock and ABA triblock copolymers is both experimentally and theoretically well understood, the effects of broadening the copolymer molecular weight distribution on block copolymer phase behavior are less well-explored. We report the melt-phase self-assembly behavior of SBS triblock copolymers (S = poly(styrene) and B = poly(1,4-butadiene)) comprised of a broad polydispersity B block (M{sub w}/M{sub n} = 1.73-2.00) flanked by relatively narrow dispersity S blocks (M{sub w}/M{sub n} = 1.09-1.36), in order to identify the effects of chain length heterogeneity on block copolymer self-assembly. Based on synchrotron small-angle X-ray scattering and transmission electron microscopy analyses of seventeen SBS triblock copolymers with poly(1,4-butadiene) volume fractions 0.27 {le} f{sub B} {le} 0.82, we demonstrate that polydisperse SBS triblock copolymers self-assemble into periodic structures with unexpectedly enhanced stabilities that greatly exceed those of equivalent monodisperse copolymers. The unprecedented stabilities of these polydisperse microphase separated melts are discussed in the context of a complete morphology diagram for this system, which demonstrates that narrow dispersity copolymers are not required for periodic nanoscale assembly.

  11. Rapid self-assembly of block copolymers to photonic crystals

    DOEpatents

    Xia, Yan; Sveinbjornsson, Benjamin R; Grubbs, Robert H; Weitekamp, Raymond; Miyake, Garret M; Atwater, Harry A; Piunova, Victoria; Daeffler, Christopher Scot; Hong, Sung Woo; Gu, Weiyin; Russell, Thomas P.

    2016-07-05

    The invention provides a class of copolymers having useful properties, including brush block copolymers, wedge-type block copolymers and hybrid wedge and polymer block copolymers. In an embodiment, for example, block copolymers of the invention incorporate chemically different blocks comprising polymer size chain groups and/or wedge groups that significantly inhibit chain entanglement, thereby enhancing molecular self-assembly processes for generating a range of supramolecular structures, such as periodic nanostructures and microstructures. The present invention also provides useful methods of making and using copolymers, including block copolymers.

  12. Programmable Crafting of Hierarchically Structured Block Copolymer/Nanoparticles (and Nanorods) via Flow Enabled Self-Assembly

    NASA Astrophysics Data System (ADS)

    Lin, Zhiqun; Li, Bo; Han, Wei

    2014-03-01

    Hierarchical assembly of diblock copolymer/nanocrystals (e.g., Au and CdSe nanoparticles and nanorods) was successfully crafted into parallel stripes by flow enabled self-assembly (FESA). They were precisely and programmably patterned at desired position on the substrate. Remarkably, a minimum spacing between two adjacent stripes was observed and a model was proposed to understand the relationship between the width of stripes and the minimum spacing. FESA of diblock copolymer/nanocrystals is a lithography-free method and facile to implement, offering opportunities for creating functional hierarchically structured materials and devices. We gratefully acknowledge support from NSF CBET 1159048 and 1332780.

  13. On the Use of Self-Assembling Block Copolymers to Toughen A Model Epoxy

    NASA Astrophysics Data System (ADS)

    Chen, Yilin

    Block copolymers have been receiving considerable attention in toughening epoxy due to their ability to form a wide variety of nanostructures. This study focuses on using both triblock and diblock copolymers to improve the fracture toughness of an aromatic-amine cured epoxy system. The curing system consisted of 1,3- phenylenediamine (mPDA) as curing agent and aniline as a chain extender. Three triblock copolymers and three diblock copolymers were incorporated in the same lightly crosslinked model epoxy system, which was chosen to mimic an underfill material in flip-chip packaging for the microelectronics industry. In this research, rubber particles were formed in situ using self-assembling block copolymers. Mechanical, thermal and microscopic studies were conducted with the main goal to study the relationship between the block parameters and the final morphologies and their effects on static and dynamic mechanical properties of the toughened resin, especially fracture toughness. In these block-copolymer-modified epoxies, spherical micelles and wormlike micelles were obtained by varying block lengths, molecular weight, polarities and compositions. It was found that miscibility of the epoxy-miscible block played a crucial role in the formation of different types of morphologies. At a low loading level, diblock copolymers were able to toughen the model epoxy as effectively as triblock copolymers. The fracture toughness was improved to almost three times with respect to that of the neat resin with addition of 10 phr AM*-27. At the same time, other mechanical properties, such as yield strength and modulus, were well retained. Incorporation of block copolymers did not have a significant effect on glass transition temperature but caused an increase in coefficient of thermal expansion (CTE) of the modified epoxy. Particle cavitation and matrix void growth were proved to be the toughening mechanisms for SBM-Modified epoxies. However, these typical toughening mechanisms for

  14. Self-organization of OPV-PEG diblock copolymers in THF/water.

    SciTech Connect

    Jurban, V.; Littrell, K. C.; Thiyagarajan, P.; Wang, H. B.; Wang, H. H.; Yu, L.

    1999-07-02

    Oligo(phenylenevinylene)-poly(ethyleneglycol) (OPV-PEG) diblock copolymers in tetrahydrofuran (THF) solution at concentrations of 5 to 25 gl self-assemble into rod-like structures with a radius of about 80 {angstrom} for an OPV-PEG diblock copolymer comprising 13 PV and 45 EG monomers. These aggregates consist of a liquid crystalline OPV core and a PEG shell. Addition of about 10% water to the solution induces the formation of a phase of packed rods, as revealed by a sudden and dramatic transition of the scattering pattern. Further addition of water leads to swelling and at about 30% ultimately to disruption of the packed-rod phase.

  15. Polythiophene-block-polyfluorene and Polythiophene-blockpoly(fluorene-co-benzothiadiazole): Insights into the Self-Assembly of All-Conjugated Block Copolymers

    SciTech Connect

    Verduzco, R.; DiMasi, E.; Botiz, I.; Pickel, D.L.; Kilbey II, S.M.; Hong, K.; Darling, S.B.

    2010-12-07

    All-conjugated block copolymers have significant potential for solution-processed optoelectronic applications, in particular those relying on a p/n junction. Herein, we report the synthesis and structure of all-conjugated diblock copolymers poly(3-hexylthiophene)-block-poly(9,9-dioctylfluorene) and poly(3-hexylthiophene)-block-poly(9,9-dioctylfluorene-co-benzothiadiazole) in thin films and in the bulk. The diblock copolymers are prepared using a combination of Grignard metathesis polymerization and Suzuki polycondensation and characterized with NMR spectroscopy, size-exclusion chromatography, multiangle laser light scattering, and UV/vis spectroscopy. Structure in thin films and in the bulk is characterized using differential scanning calorimetry, X-ray diffraction, small-angle X-ray scattering, and atomic force microscopy. Diblock copolymer thin films self-assemble into a crystalline nanostructure with some long-range order after extended solvent annealing, and X-ray scattering measurements show that powder samples exhibit crystallinity throughout the bulk. By temperature dependent X-ray scattering measurements, we find that diblock copolymers self-assemble into crystalline nanowires with phase segregated block copolymer domains. These measurements show all-conjugated diblock copolymers may be useful for achieving solution-processed active layers in organic photovoltaics and light-emitting diodes with optimized structural and photophysical characteristics.

  16. Effects of shape anisotropy on microstructural evolution of diblock copolymers

    NASA Astrophysics Data System (ADS)

    Panday, Ashoutosh

    This dissertation discusses the effects of shape anisotropy on the evolved microstructure of diblock copolymers at various levels. Due to chain connectivity and microphase separation, the diblock copolymers self-assemble into ellipsoidal grains of lamellar and cylindrical morphologies. A grain-structure related phenomenon, Excluded Volume Epitaxy (E.V.E.) is explored in Chapter 2. E.V.E. is a local, inter-grain azimuthal orientational correlations effect, which results from a combination of sporadic nucleation and impingement of growing anisotropic shaped grains. Due to E.V.E., the ellipsoidal grains have a propensity for similar orientations in a local neighborhood, despite complete absence of global orientation in the sample. Simulations and experiments have verified this effect. The Avrami kinetics of anisotropic shaped grains is discussed in Chapter 3. Traditionally Avrami equation is used to model the growth kinetics of volume filling isotropic shaped grains. The probabilistic nature of Avrami kinetics produces a coupling between the grain shape and Poisson distribution. The Poisson-shape coupling remains latent for isotropic grains but becomes operative for anisotropic grains in random orientations scheme leading to inhibited growth kinetics. For unidirectional orientation of anisotropic grains, the growth kinetics remains uninhibited due to absence of Poisson-shape coupling. For two-dimensional case in simultaneous and continuous nucleation regimes, the inhibited kinetics scales as L1/2 where L is the shape anisotropy. The blends of highly shape anisotropic nanoclay, montmorillonite (MMT) and lamellar poly(styrene-b-isoprene), PS-PI are discussed in Appendix A. Annealing and cooling is sufficient to produce long-range lamellar order at 1 wt % clay loading. However at 5 wt % clay loading, shear force is additionally required. This system reveals the effect of shape anisotropy on evolution of long-range order in clay-block copolymer blends. The effect of shape

  17. Nanoporous Thin Films and Binary Nanoparticle Superlattices Created by Directed Self-Assembly of Block Copolymer Hybrid Materials.

    PubMed

    Pietsch, Torsten; Müller-Buschbaum, Peter; Mahltig, Boris; Fahmi, Amir

    2015-06-17

    The design and development of well-defined, functional nanostructures via self-assembly is one of the key objectives in current nanotechnology. Block copolymer-based hybrid materials are attractive candidates for the fabrication of multifunctional nanostructures, which provide the building blocks for more complex nanoarchitectures and nanodevices. However, one of the major challenges lies in controlling the structure formation in these hybrid materials by guiding the self-assembly of the block copolymer. Here, hierarchical nanoporous structures are fabricated via guided multistep self-assembly of diblock copolymer micellar solutions onto hydrophilic solid substrates. The core of polystyrene-block-poly[4-vinylpyridine] micelles serves as a nanoreactor for the preparation of size-controlled gold nanoparticles. Deposition of thin films of the micellar solution in combination with a nonselective cosolvent (THF), on hydrophilic surfaces leads to the formation of hierarchical nanoporous structures. The micellar films exhibit two different pore diameters and a total pore density of more than 10(10) holes per cm2. Control over the pore diameter is achieved by adapting the molecular weight of the polystyrene-block-poly[4-vinylpyridine] diblock copolymer. Moreover, the porous morphology is used as a template for the fabrication of bimetallic nanostructured thin films. The PS-b-P4VP template is subsequently removed by oxygen plasma etching, leaving behind binary nanoparticle structures that mimic the original thin film morphology.

  18. Thermal processing of diblock copolymer melts mimics metallurgy.

    PubMed

    Kim, Kyungtae; Schulze, Morgan W; Arora, Akash; Lewis, Ronald M; Hillmyer, Marc A; Dorfman, Kevin D; Bates, Frank S

    2017-05-05

    Small-angle x-ray scattering experiments conducted with compositionally asymmetric low molar mass poly(isoprene)-b-poly(lactide) diblock copolymers reveal an extraordinary thermal history dependence. The development of distinct periodic crystalline or aperiodic quasicrystalline states depends on how specimens are cooled from the disordered state to temperatures below the order-disorder transition temperature. Whereas direct cooling leads to the formation of documented morphologies, rapidly quenched samples that are then heated from low temperature form the hexagonal C14 and cubic C15 Laves phases commonly found in metal alloys. Self-consistent mean-field theory calculations show that these, and other associated Frank-Kasper phases, have nearly degenerate free energies, suggesting that processing history drives the material into long-lived metastable states defined by self-assembled particles with discrete populations of volumes and polyhedral shapes. Copyright © 2017, American Association for the Advancement of Science.

  19. Thermal processing of diblock copolymer melts mimics metallurgy

    NASA Astrophysics Data System (ADS)

    Kim, Kyungtae; Schulze, Morgan W.; Arora, Akash; Lewis, Ronald M.; Hillmyer, Marc A.; Dorfman, Kevin D.; Bates, Frank S.

    2017-05-01

    Small-angle x-ray scattering experiments conducted with compositionally asymmetric low molar mass poly(isoprene)-b-poly(lactide) diblock copolymers reveal an extraordinary thermal history dependence. The development of distinct periodic crystalline or aperiodic quasicrystalline states depends on how specimens are cooled from the disordered state to temperatures below the order-disorder transition temperature. Whereas direct cooling leads to the formation of documented morphologies, rapidly quenched samples that are then heated from low temperature form the hexagonal C14 and cubic C15 Laves phases commonly found in metal alloys. Self-consistent mean-field theory calculations show that these, and other associated Frank-Kasper phases, have nearly degenerate free energies, suggesting that processing history drives the material into long-lived metastable states defined by self-assembled particles with discrete populations of volumes and polyhedral shapes.

  20. Amine-reactive biodegradable diblock copolymers.

    PubMed

    Tessmar, Jörg K; Mikos, Antonios G; Göpferich, Achim

    2002-01-01

    A new class of diblock copolymers was synthesized from biodegradable poly(lactic acid) and poly(ethylene glycol)minus signmonoamine. These polymers were activated by covalently attaching linkers such as disuccinimidyl tartrate or disuccinimidyl succinate to the hydrophilic polymer chain. The polymers were characterized by (1)H NMR spectroscopy, (13)C NMR spectroscopy and gel permeation chromatography (GPC). These investigations indicated that the polymers were obtained with the correct composition, in high purities, and the expected molecular weight. By using dyes containing primary amine groups such as 5-aminoeosin as model substrates, it was possible to show that the polymers are able to bind such compounds covalently. The diblock copolymers were developed to suppress unspecific protein adsorption and allow the binding of bioactive molecules by instant surface modification. The polymers are intended to be used for tissue engineering applications where surface immobilized cell adhesion peptides or growth factors are needed to control cell behavior.

  1. Multicompartment nanoparticles from the self-assembly of mixtures of ABC and AC block copolymers in C-selective solvents

    NASA Astrophysics Data System (ADS)

    Sheng, Yuping; Yan, Nan; An, Jian; Zhu, Yutian

    2014-09-01

    The self-assembly of the mixtures of linear ABC triblock and AC diblock copolymers in C-selective solvents is studied by Monte Carlo simulation. The effects of various control parameters, including the block length, proportions of ABC and AC copolymers, solvent quality, and the incompatibility between different block components, on the micellar structures are examined. Some interesting multicompartment nanoparticles, such as the hamburger-like, ring-coiled-rod and reversed hamburger-like nanoparticles are predicted in our simulations. Moreover, the configurations of polymer chains in different multicompartment nanoparticles are revealed by the contact numbers between different components.

  2. Micellar cathodes from self-assembled nitroxide-containing block copolymers in battery electrolytes.

    PubMed

    Hauffman, Guillaume; Maguin, Quentin; Bourgeois, Jean-Pierre; Vlad, Alexandru; Gohy, Jean-François

    2014-01-01

    This contribution describes the synthesis of block copolymers containing electrochemically active blocks, their micellization, and finally their use as micellar cathodes in a lithium battery. The self-assembly of the synthesized poly(styrene)-block-poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PS-b-PTMA) diblock copolymers is realized in a typical battery electrolyte made of 1 m lithium trifluoromethanesulfonate dissolved in a mixture of ethylene carbonate/diethyl carbonate/dimethyl carbonate(1:1:1, in volume). Dynamic light scattering and atomic force micro-scopy indicate the formation of well-defined spherical micelles with a PS core and a PTMA corona. The electrochemical properties of those micelles are further investigated. Cyclic voltammograms show a reversible redox reaction at 3.6 V (vs Li(+) /Li). The charge/discharge profiles indicate a flat and reversible plateau around 3.6 V (vs Li(+) /Li). Finally, the cycling performances of the micellar cathodes are demonstrated. Such self-assembled block copolymers open new opportunities for nanostructured organic radical batteries. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Self-Assembly of Block Copolymers in an Ionic Liquid

    NASA Astrophysics Data System (ADS)

    He, Yiyong; Li, Zhibo; Lodge, Timothy P.

    2006-03-01

    Amphiphilic diblock copolymers poly((1,2-butadiene)-b-ethylene oxide) (PB-PEO) were shown to aggregate and form well-defined micelles in an ionic liquid, 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIM][PF6]). The universal sequence of micellar structures (spherical micelle, wormlike micelle, and bilayered vesicle) were all resolved by varying the block copolymer composition. For the first time, the nanostructures of PB-PEO micelles formed in an ionic liquid were directly visualized by cryogenic transmission electron microscopy (cryo-TEM). The detailed micelle structure information was extracted from cryo-TEM and dynamic light scattering (DLS) measurements, and compared to their aqueous counterparts. The work demonstrates the feasibility of controlling micellar nanostructures of amphiphilic block copolymers in ionic liquids, and also provides important knowledge for further applications of copolymers for forming microemulsions and ion gels.

  4. Nanoparticle-directed self-assembly of amphiphilic block copolymers.

    PubMed

    Kamps, Amanda C; Sanchez-Gaytan, Brenda L; Hickey, Robert J; Clarke, Nigel; Fryd, Michael; Park, So-Jung

    2010-09-07

    Nanoparticles can form unique cavity-like structures in core-shell type assemblies of block copolymers through the cooperative self-assembly of nanoparticles and block copolymers. We show that the self-assembly behavior is general for common as-synthesized alkyl-terminated nanoparticles for a range of nanoparticle sizes. We examined various self-assembly conditions such as solvent compositions, nanoparticle coordinating ligands, volume fraction of nanoparticles, and nanoparticle sizes in order to elucidate the mechanism of the radial assembly formation. These experiments along with strong segregation theory calculations indicated that both the enthalpic interaction and the polymer stretching energy are important factors in the coassembly formation. The slightly unfavorable interaction between the hydrophobic segment of polymers and alkyl-terminated nanoparticles causes the accumulation of nanoparticles at the interface between the polymer core and the shell, forming the unique cavity-like structure. The coassemblies were stabilized for a limited range of nanoparticle volume fractions within which the inclusion of nanoparticle layers reduces the polymer stretching. The volume fraction range yielding the well-defined radial coassembly structure was mapped out with varying nanoparticle sizes. The experimental and theoretical phase map provides the guideline for the coassembly formation of as-synthesized alkyl-terminated nanoparticles and amphiphilic block copolymers.

  5. Bicontinuous Polymeric Microemulsions from Polydisperse Diblock Copolymers

    SciTech Connect

    Ellison, Christopher J.; Meuler, Adam J.; Qin, Jian; Evans, Christopher M.; Wolf, Lynn M.; Bates, Frank S.

    2009-06-12

    Polymeric bicontinuous microemulsions are thermodynamically stable structures typically formed by ternary blends of immiscible A and B homopolymers and a macromolecular surfactant such as an AB diblock copolymer. Investigations of these bicontinuous morphologies have largely focused on model systems in which all components have narrow molecular weight distributions. Here we probe the effects of AB diblock polydispersity in ternary blends of polystyrene (PS), polyisoprene (PI), and poly(styrene-b-isoprene) (PS-PI). Three series of blends were prepared using the same PS and PI homopolymers; two of them contain nearly monodisperse components while the third includes a polydisperse PS-PI diblock. The PS and PI homopolymers and two of the PS-PI diblocks were prepared by anionic polymerization using sec-butyllithium and have narrow molecular weight distributions. The polydisperse PS-PI diblock was prepared by anionic polymerization using the functional organolithium 3-tert-butyldimethylsilyloxy-1-propyllithium; this diblock has a polydisperse PS block (M{sub w}/M{sub n} = 1.57) and a nearly monodisperse PI block (Mw/Mn < 1.1). The phase behavior of the three series of blends was probed using a combination of dynamic mechanical spectroscopy, small-angle X-ray scattering, and cloud point measurements, and a bicontinuous microemulsion channel was identified in each system. These results prove that monodisperse components are not required to form bicontinuous microemulsions and highlight the utility of polydispersity as a tool to tune polymer blend phase behavior. The random-phase approximation, originally advanced by de Gennes, and self-consistent field theory are used to provide a theoretical supplement to the experimental work. These theories are able to predict the directions of the polydispersity-driven shifts in domain spacing, order-disorder transition temperatures, and the location of the microemulsion channel. Self-consistent field theory is also used in conjunction

  6. Bicontinuous polymeric microemulsions from polydisperse diblock copolymers.

    PubMed

    Ellison, Christopher J; Meuler, Adam J; Qin, Jian; Evans, Christopher M; Wolf, Lynn M; Bates, Frank S

    2009-03-26

    Polymeric bicontinuous microemulsions are thermodynamically stable structures typically formed by ternary blends of immiscible A and B homopolymers and a macromolecular surfactant such as an AB diblock copolymer. Investigations of these bicontinuous morphologies have largely focused on model systems in which all components have narrow molecular weight distributions. Here we probe the effects of AB diblock polydispersity in ternary blends of polystyrene (PS), polyisoprene (PI), and poly(styrene-b-isoprene) (PS-PI). Three series of blends were prepared using the same PS and PI homopolymers; two of them contain nearly monodisperse components while the third includes a polydisperse PS-PI diblock. The PS and PI homopolymers and two of the PS-PI diblocks were prepared by anionic polymerization using sec-butyllithium and have narrow molecular weight distributions. The polydisperse PS-PI diblock was prepared by anionic polymerization using the functional organolithium 3-tert-butyldimethylsilyloxy-1-propyllithium; this diblock has a polydisperse PS block (Mw/Mn = 1.57) and a nearly monodisperse PI block (Mw/Mn < 1.1). The phase behavior of the three series of blends was probed using a combination of dynamic mechanical spectroscopy, small-angle X-ray scattering, and cloud point measurements, and a bicontinuous microemulsion channel was identified in each system. These results prove that monodisperse components are not required to form bicontinuous microemulsions and highlight the utility of polydispersity as a tool to tune polymer blend phase behavior. The random-phase approximation, originally advanced by de Gennes, and self-consistent field theory are used to provide a theoretical supplement to the experimental work. These theories are able to predict the directions of the polydispersity-driven shifts in domain spacing, order-disorder transition temperatures, and the location of the microemulsion channel. Self-consistent field theory is also used in conjunction with the

  7. Directed self-assembly of block copolymers for high breakdown strength polymer film capacitors

    SciTech Connect

    Samant, Saumil P.; Grabowski, Christopher A.; Kisslinger, Kim; Yager, Kevin G.; Yuan, Guangcui; Satija, Sushil K.; Durstock, Michael F.; Raghavan, Dharmaraj; Karim, Alamgir

    2016-03-04

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ~50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the “barrier effect”, where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. Lastly, this approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.

  8. Directed Self-Assembly of Block Copolymers for High Breakdown Strength Polymer Film Capacitors

    SciTech Connect

    Samant, Saumil P.; Grabowski, Christopher A.; Kisslinger, Kim; Yager, Kevin G.; Yuan, Guangcui; Satija, Sushil K.; Durstock, Michael F.; Raghavan, Dharmaraj; Karim, Alamgir

    2016-03-04

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ~50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the “barrier effect”, where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. This approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.

  9. Directed self-assembly of block copolymers for high breakdown strength polymer film capacitors

    DOE PAGES

    Samant, Saumil P.; Grabowski, Christopher A.; Kisslinger, Kim; ...

    2016-03-04

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayeredmore » films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ~50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the “barrier effect”, where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. Lastly, this approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.« less

  10. Directed Self-Assembly of Block Copolymers for High Breakdown Strength Polymer Film Capacitors.

    PubMed

    Samant, Saumil P; Grabowski, Christopher A; Kisslinger, Kim; Yager, Kevin G; Yuan, Guangcui; Satija, Sushil K; Durstock, Michael F; Raghavan, Dharmaraj; Karim, Alamgir

    2016-03-01

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ∼50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the "barrier effect", where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. This approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.

  11. Orthogonal self-assembly in folding block copolymers.

    PubMed

    Hosono, Nobuhiko; Gillissen, Martijn A J; Li, Yuanchao; Sheiko, Sergei S; Palmans, Anja R A; Meijer, E W

    2013-01-09

    We herein report the synthesis and characterization of ABA triblock copolymers that contain two complementary association motifs and fold into single-chain polymeric nanoparticles (SCPNs) via orthogonal self-assembly. The copolymers were prepared using atom-transfer radical polymerization (ATRP) and possess different pendant functional groups in the A and B blocks (alcohols in the A block and acetylenes in the B block). After postfunctionalization, the A block contains o-nitrobenzyl-protected 2-ureidopyrimidinone (UPy) moieties and the B block benzene-1,3,5-tricarboxamide (BTA) moieties. While the protected UPy groups dimerize after photoinduced deprotection of the o-nitrobenzyl group, the BTA moieties self-assemble into helical aggregates when temperature is reduced. In a two-step thermal/photoirradiation treatment under dilute conditions, the ABA block copolymer forms both BTA-based helical aggregates and UPy dimers intramolecularly. The sequential association of the two self-assembling motifs results in single-chain folding of the polymer, affording nanometer-sized particles with a compartmentalized interior. Variable-temperature NMR studies showed that the BTA and UPy self-assembly steps take place orthogonally (i.e., without mutual interference) in dilute solution. In addition, monitoring of the intramolecular self-assembly of BTA moieties into helical aggregates by circular dichroism spectroscopy showed that the stability of the aggregates is almost independent of UPy dimerization. Size-exclusion chromatography (SEC) and small-angle X-ray scattering analysis provided evidence of significant reductions in the hydrodynamic volume and radius of gyration, respectively, after photoinduced deprotection of the UPy groups; a 30-60% reduction in the size of the polymer chains was observed using SEC in CHCl(3). Molecular imaging by atomic force microscopy (AFM) corroborated significant contraction of individual polymer chains due to intramolecular association of the

  12. Mechanism for Rapid Self-Assembly of Block Copolymer Nanoparticles

    NASA Astrophysics Data System (ADS)

    Johnson, Brian K.; Prud'Homme, Robert K.

    2003-09-01

    Amphiphilic block copolymers in solution spontaneously self-assemble when the solvent quality for one block is selectively decreased. We demonstrate that, for supersaturation ratio changes [d(S)/dt] over 105 per second from equilibrium, nanoparticles are obtained with a formation mechanism and size dependent on the jumping rate and magnitude. The threshold rate for homogeneous precipitation is determined by the induction time of a particle, equivalent to the diffusion limited fusion of copolymer chains to form a corona of overlapping soluble brushes. Via determination of the induction time with a novel confined impinging jets mixer and use of a scaling relation, the interfacial free energy of a block copolymer nanoparticle was measured for the first time.

  13. Synthesis and Characterization of a Systematic Series of All-Conjugated Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Smith, Kendall; Verduzco, Rafael

    2012-02-01

    All-conjugated block copolymers can potentially self-assemble into nanoscale structures beneficial for charge separation and transport, but due to synthetic challenges a comprehensive investigation of all-conjugated block copolymers has not been carried out . Here we detail a novel synthetic approach to all-conjugated block copolymers and characterize the structure of a systematic series of materials. The materials are prepared via copper-catalyzed azide-alkyne click chemistry followed by selective solvent removal of homopolymer impurities. This allows us to readily vary the molecular weight and type of each block in order to systematically study the properties of a family of block copolymers. As a system relevant to organic photovoltatics, we investigate a series of diblock copolymers based on poly(9,9-dioctyl-fluorene) and poly(3-alkylthiophene). This series of block copolymers is characterized with respect to phase behavior, including micro-phase segregation and crystallinity, optical properties, and charge mobilities.

  14. Cubosomes from hierarchical self-assembly of poly(ionic liquid) block copolymers

    PubMed Central

    He, Hongkun; Rahimi, Khosrow; Zhong, Mingjiang; Mourran, Ahmed; Luebke, David R.; Nulwala, Hunaid B.; Möller, Martin; Matyjaszewski, Krzysztof

    2017-01-01

    Cubosomes are micro- and nanoparticles with a bicontinuous cubic two-phase structure, reported for the self-assembly of low molecular weight surfactants, for example, lipids, but rarely formed by polymers. These objects are characterized by a maximum continuous interface and high interface to volume ratio, which makes them promising candidates for efficient adsorbents and host-guest applications. Here we demonstrate self-assembly to nanoscale cuboidal particles with a bicontinuous cubic structure by amphiphilic poly(ionic liquid) diblock copolymers, poly(acrylic acid)-block-poly(4-vinylbenzyl)-3-butyl imidazolium bis(trifluoromethylsulfonyl)imide, in a mixture of tetrahydrofuran and water under optimized conditions. Structure determining parameters include polymer composition and concentration, temperature, and the variation of the solvent mixture. The formation of the cubosomes can be explained by the hierarchical interactions of the constituent components. The lattice structure of the block copolymers can be transferred to the shape of the particle as it is common for atomic and molecular faceted crystals. PMID:28091605

  15. Cubosomes from hierarchical self-assembly of poly(ionic liquid) block copolymers

    NASA Astrophysics Data System (ADS)

    He, Hongkun; Rahimi, Khosrow; Zhong, Mingjiang; Mourran, Ahmed; Luebke, David R.; Nulwala, Hunaid B.; Möller, Martin; Matyjaszewski, Krzysztof

    2017-01-01

    Cubosomes are micro- and nanoparticles with a bicontinuous cubic two-phase structure, reported for the self-assembly of low molecular weight surfactants, for example, lipids, but rarely formed by polymers. These objects are characterized by a maximum continuous interface and high interface to volume ratio, which makes them promising candidates for efficient adsorbents and host-guest applications. Here we demonstrate self-assembly to nanoscale cuboidal particles with a bicontinuous cubic structure by amphiphilic poly(ionic liquid) diblock copolymers, poly(acrylic acid)-block-poly(4-vinylbenzyl)-3-butyl imidazolium bis(trifluoromethylsulfonyl)imide, in a mixture of tetrahydrofuran and water under optimized conditions. Structure determining parameters include polymer composition and concentration, temperature, and the variation of the solvent mixture. The formation of the cubosomes can be explained by the hierarchical interactions of the constituent components. The lattice structure of the block copolymers can be transferred to the shape of the particle as it is common for atomic and molecular faceted crystals.

  16. Gyroid nickel nanostructures from diblock copolymer supramolecules.

    PubMed

    Vukovic, Ivana; Punzhin, Sergey; Voet, Vincent S D; Vukovic, Zorica; de Hosson, Jeff Th M; ten Brinke, Gerrit; Loos, Katja

    2014-04-28

    Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

  17. Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

    PubMed Central

    Vukovic, Ivana; Punzhin, Sergey; Voet, Vincent S. D.; Vukovic, Zorica; de Hosson, Jeff Th. M.; ten Brinke, Gerrit; Loos, Katja

    2014-01-01

    Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology. PMID:24797367

  18. pH-sensitive vesicles based on a biocompatible zwitterionic diblock copolymer.

    PubMed

    Du, Jianzhong; Tang, Yiqing; Lewis, Andrew L; Armes, Steven P

    2005-12-28

    Highly biocompatible pH-sensitive diblock copolymer vesicles were prepared from the self-assembly of a biocompatible zwitterionic copolymer, poly[2-(methacryloyloxy)ethyl phosphorylcholine-block-2-(diisopropylamino)ethyl methacrylate], PMPC-b-PDPA. Vesicle formation occurred spontaneously by adjusting the solution pH from pH 2 to above 6, with the hydrophobic PDPA chains forming the vesicle walls. Transmission electron microscopy (TEM), dynamic laser light scattering (DLS), and UV-visible absorption spectrophotometry were used to characterize these vesicles. Gold nanoparticle-decorated vesicles were also obtained by treating the vesicles with HAuCl4, followed by NaBH4.

  19. On the birefringence of multilayered symmetric diblock copolymer films

    SciTech Connect

    Kim, J.; Chin, I.; Smith, B.A.; Russell, T.P. ); Mays, J.W. . Dept. of Chemistry)

    1993-09-27

    The chain extension at lamellar interfaces was studied in thin films of symmetric diblock copolymers on gold substrates. The first copolymer consisted of blocks of polystyrene (PS) and poly(2-vinylpyridine) (P2VP), denoted P(S-b-2VP). The second was a diblock copolymer of PS and poly(methyl methacrylate) (PMMA), denoted P(S-b-MMA), on a gold substrate. Using attenuated total reflectance spectroscopy, the refractive indices parallel, n[sub [parallel

  20. Self-Assembly of a Selectively Modified Fluorinated Block Copolymer

    NASA Astrophysics Data System (ADS)

    Davidock, Drew; Hillmyer, Marc; Lodge, Timothy

    2002-03-01

    Selective modification can be used to systematically tune the strength of the thermodynamic interaction between the two segments of a block copolymer. It also offers an effective method for the preparation of model fluorinated block copolymers, which are difficult to synthesize directly. In this study, the effect of controlled difluorocarbene (CF_2) addition to the polyisoprene block on the self-assembly of a series of poly(ethylethylene)-b-polyisoprene (PEE-b-PI) copolymers was investigated. Equilibrium morphologies were determined by small-angle X-ray scattering (SAXS). An effective interaction parameter (\\chi_eff) between the PEE and FPI-s-PI was calculated from the domain spacing, and is found to increase by a factor of ~400 upon complete CF2 modification. The resulting materials also offer an opportunity to examine the phase behavior all the way from weak to strong segregation with one parent copolymer. Using a binary interaction model originally developed for homopolymer/copolymer blends, we were able to model the dependence of \\chi_eff on the extent of fluorination in a quantitative manner and obtain values for the three pairwise interaction parameters.

  1. Hollow flower micelles from a diblock copolymer

    NASA Astrophysics Data System (ADS)

    Changez, Mohammad; Kang, Nam-Goo; Kim, Dong Woo; Lee, Jae-Suk

    2013-11-01

    A poly(2-vinylpyridine)-block-poly(2-(4-vinylphenyl)pyridine) (P2VP106-b-PVPPy95) coil-coil diblock copolymer forms hollow flower micelles in a mixed solvent of methanol and water (95/5, v/v) in a one step process. The geometry and composition of the micelles allow formation of a Pt-Au bimetallic dendritic nanocatalyst with a Pt leaf at room temperature.A poly(2-vinylpyridine)-block-poly(2-(4-vinylphenyl)pyridine) (P2VP106-b-PVPPy95) coil-coil diblock copolymer forms hollow flower micelles in a mixed solvent of methanol and water (95/5, v/v) in a one step process. The geometry and composition of the micelles allow formation of a Pt-Au bimetallic dendritic nanocatalyst with a Pt leaf at room temperature. Electronic supplementary information (ESI) available: Experimental details. See DOI: 10.1039/c3nr03063f

  2. Multilayer block copolymer meshes by orthogonal self-assembly

    PubMed Central

    Tavakkoli K. G., Amir; Nicaise, Samuel M.; Gadelrab, Karim R.; Alexander-Katz, Alfredo; Ross, Caroline A.; Berggren, Karl K.

    2016-01-01

    Continued scaling-down of lithographic-pattern feature sizes has brought templated self-assembly of block copolymers (BCPs) into the forefront of nanofabrication research. Technologies now exist that facilitate significant control over otherwise unorganized assembly of BCP microdomains to form both long-range and locally complex monolayer patterns. In contrast, the extension of this control into multilayers or 3D structures of BCP microdomains remains limited, despite the possible technological applications in next-generation devices. Here, we develop and analyse an orthogonal self-assembly method in which multiple layers of distinct-molecular-weight BCPs naturally produce nanomesh structures of cylindrical microdomains without requiring layer-by-layer alignment or high-resolution lithographic templating. The mechanisms for orthogonal self-assembly are investigated with both experiment and simulation, and we determine that the control over height and chemical preference of templates are critical process parameters. The method is employed to produce nanomeshes with the shapes of circles and Y-intersections, and is extended to produce three layers of orthogonally oriented cylinders. PMID:26796218

  3. Self-assembled phases of block copolymer blend thin films.

    PubMed

    Yager, Kevin G; Lai, Erica; Black, Charles T

    2014-10-28

    The patterns formed by self-assembled thin films of blended cylindrical and lamellar polystyrene-b-poly(methyl methacrylate) block copolymers can be either a spatially uniform, single type of nanostructure or separate, coexisting regions of cylinders and lamellae, depending on fractional composition and molecular weight ratio of the blend constituents. In blends of block copolymers with different molecular weights, the morphology of the smaller molecular weight component more strongly dictates the resulting pattern. Although molecular scale chain mixing distorts microdomain characteristic length scales from those of the pure components, even coexisting morphologies exhibit the same domain spacing. We quantitatively account for the phase behavior of thin-film blends of cylinders and lamellae using a physical, thermodynamic model balancing the energy of chain distortions with the entropy of mixing.

  4. Nanoparticle string formation on self-assembled copolymer films

    NASA Astrophysics Data System (ADS)

    Jenczyk, J.; Woźniak-Budych, M.; Jarek, M.; Grzeszkowiak, M.; Nowaczyk, G.; Jurga, S.

    2017-06-01

    Nanoparticles (NP) string formations on self-assembled copolymeric substrates has been observed. These ;thread of beads; like structures develop via simple colloidal droplet evaporation during meniscus rim withdrawal on polystyrene-block-poly(ethylene oxide) (PS-PEO) copolymer surfaces. It is shown that the process is triggered by the presence of the substrate impurities, which lead to NP aggregate formations serving as string initiation sites. The growth mechanism of these linear structures seems to be capillarity-driven. Moreover, there is an exceptional alignment coupling between NP strips and the block copolymer (BC) domains observed. BC directed NP assembly stems from a gold nanocrystal surface functionalization, which introduces selective affinity for one particular type of BC domain. The presented results reveal a potential fabrication method of NP wires characterized by remarkably low width and thickness comparable with the size of the individual constituent NP.

  5. Rational synthesis of low-polydispersity block copolymer vesicles in concentrated solution via polymerization-induced self-assembly.

    PubMed

    Gonzato, Carlo; Semsarilar, Mona; Jones, Elizabeth R; Li, Feng; Krooshof, Gerard J P; Wyman, Paul; Mykhaylyk, Oleksandr O; Tuinier, Remco; Armes, Steven P

    2014-08-06

    Block copolymer self-assembly is normally conducted via post-polymerization processing at high dilution. In the case of block copolymer vesicles (or "polymersomes"), this approach normally leads to relatively broad size distributions, which is problematic for many potential applications. Herein we report the rational synthesis of low-polydispersity diblock copolymer vesicles in concentrated solution via polymerization-induced self-assembly using reversible addition-fragmentation chain transfer (RAFT) polymerization of benzyl methacrylate. Our strategy utilizes a binary mixture of a relatively long and a relatively short poly(methacrylic acid) stabilizer block, which become preferentially expressed at the outer and inner poly(benzyl methacrylate) membrane surface, respectively. Dynamic light scattering was utilized to construct phase diagrams to identify suitable conditions for the synthesis of relatively small, low-polydispersity vesicles. Small-angle X-ray scattering (SAXS) was used to verify that this binary mixture approach produced vesicles with significantly narrower size distributions compared to conventional vesicles prepared using a single (short) stabilizer block. Calculations performed using self-consistent mean field theory (SCMFT) account for the preferred self-assembled structures of the block copolymer binary mixtures and are in reasonable agreement with experiment. Finally, both SAXS and SCMFT indicate a significant degree of solvent plasticization for the membrane-forming poly(benzyl methacrylate) chains.

  6. Polymerization-Induced Self-Assembly of Block Copolymer Nano-objects via RAFT Aqueous Dispersion Polymerization

    PubMed Central

    2014-01-01

    In this Perspective, we discuss the recent development of polymerization-induced self-assembly mediated by reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization. This approach has quickly become a powerful and versatile technique for the synthesis of a wide range of bespoke organic diblock copolymer nano-objects of controllable size, morphology, and surface functionality. Given its potential scalability, such environmentally-friendly formulations are expected to offer many potential applications, such as novel Pickering emulsifiers, efficient microencapsulation vehicles, and sterilizable thermo-responsive hydrogels for the cost-effective long-term storage of mammalian cells. PMID:24968281

  7. Functionalized organic nanoparticles from core-crosslinked poly(4-vinylbenzocyclobutene-b-butadiene) diblock copolymer micelles

    SciTech Connect

    Sakellariou, Georgios; Avgeropoulos, Apostolos; Hadjichristidis, Nikos; Mays, Jimmy; Baskaran, Durairaj

    2009-01-01

    Sufface-functionalized polymeric nanoparticles were prepared by: a) self~assembly of poly(4-vinylbenzocyclobutene-b-butadiene) diblock copolymer (PVBCB-b-PB) to form spherical micelles (diameter:15-48 nm) in decane, a selective solvent for PB, b) crosslinking of the PVBCB core through thermal dimerization at 200-240 ~ C, and c) cleavage of the PB corona via ozonolysis and addition of dimethyl sulfide to afford aldehyde-functionalized nanoparticles (diameter: -16-20 nm), along with agglomerated nanoparticles ranging from - 30 to -100 nm in diameter. The characterization of the diblock copolymer precursors. the intermediate micelles and the final surface-functionalized crosslinked nanoparticles was carried alit by a combination of size exclusion chromatography, static and dynamic light scattering, viscometry, thermogravimetric analysis, 1 H NMR and FfIR spectroscopy and transmission electron microscopy.

  8. Self-oscillating AB diblock copolymer developed by post modification strategy

    SciTech Connect

    Ueki, Takeshi E-mail: ryo@cross.t.u-tokyo.ac.jp; Onoda, Michika; Tamate, Ryota; Yoshida, Ryo E-mail: ryo@cross.t.u-tokyo.ac.jp; Shibayama, Mitsuhiro

    2015-06-15

    We prepared AB diblock copolymer composed of hydrophilic poly(ethylene oxide) segment and self-oscillating polymer segment. In the latter segment, ruthenium tris(2,2′-bipyridine) (Ru(bpy){sub 3}), a catalyst of the Belousov-Zhabotinsky reaction, is introduced into the polymer architecture based on N-isopropylacrylamide (NIPAAm). The Ru(bpy){sub 3} was introduced into the polymer segment by two methods; (i) direct random copolymerization (DP) of NIPAAm and Ru(bpy){sub 3} vinyl monomer and (ii) post modification (PM) of Ru(bpy){sub 3} with random copolymer of NIPAAm and N-3-aminopropylmethacrylamide. For both the diblock copolymers, a bistable temperature region (the temperature range; ΔT{sub m}), where the block copolymer self-assembles into micelle at reduced Ru(bpy){sub 3}{sup 2+} state whereas it breaks-up into individual polymer chain at oxidized Ru(bpy){sub 3}{sup 3+} state, monotonically extends as the composition of the Ru(bpy){sub 3} increases. The ΔT{sub m} of the block copolymer prepared by PM is larger than that by DP. The difference in ΔT{sub m} is rationalized from the statistical analysis of the arrangement of the Ru(bpy){sub 3} moiety along the self-oscillating segments. By using the PM method, the well-defined AB diblock copolymer having ΔT{sub m} (ca. 25 °C) large enough to cause stable self-oscillation can be prepared. The periodic structural transition of the diblock copolymer in a dilute solution ([Polymer] = 0.1 wt. %) is closely investigated in terms of the time-resolved dynamic light scattering technique at constant temperature in the bistable region. A macroscopic viscosity oscillation of a concentrated polymer solution (15 wt. %) coupled with the periodic microphase separation is also demonstrated.

  9. Self-oscillating AB diblock copolymer developed by post modification strategy

    NASA Astrophysics Data System (ADS)

    Ueki, Takeshi; Onoda, Michika; Tamate, Ryota; Shibayama, Mitsuhiro; Yoshida, Ryo

    2015-06-01

    We prepared AB diblock copolymer composed of hydrophilic poly(ethylene oxide) segment and self-oscillating polymer segment. In the latter segment, ruthenium tris(2,2'-bipyridine) (Ru(bpy)3), a catalyst of the Belousov-Zhabotinsky reaction, is introduced into the polymer architecture based on N-isopropylacrylamide (NIPAAm). The Ru(bpy)3 was introduced into the polymer segment by two methods; (i) direct random copolymerization (DP) of NIPAAm and Ru(bpy)3 vinyl monomer and (ii) post modification (PM) of Ru(bpy)3 with random copolymer of NIPAAm and N-3-aminopropylmethacrylamide. For both the diblock copolymers, a bistable temperature region (the temperature range; ΔTm), where the block copolymer self-assembles into micelle at reduced Ru(bpy)32+ state whereas it breaks-up into individual polymer chain at oxidized Ru(bpy)33+ state, monotonically extends as the composition of the Ru(bpy)3 increases. The ΔTm of the block copolymer prepared by PM is larger than that by DP. The difference in ΔTm is rationalized from the statistical analysis of the arrangement of the Ru(bpy)3 moiety along the self-oscillating segments. By using the PM method, the well-defined AB diblock copolymer having ΔTm (ca. 25 °C) large enough to cause stable self-oscillation can be prepared. The periodic structural transition of the diblock copolymer in a dilute solution ([Polymer] = 0.1 wt. %) is closely investigated in terms of the time-resolved dynamic light scattering technique at constant temperature in the bistable region. A macroscopic viscosity oscillation of a concentrated polymer solution (15 wt. %) coupled with the periodic microphase separation is also demonstrated.

  10. Thermodynamics of the multi-stage self-assembly of pH-sensitive gradient copolymers in aqueous solutions.

    PubMed

    Černochová, Zulfiya; Bogomolova, Anna; Borisova, Olga V; Filippov, Sergey K; Černoch, Peter; Billon, Laurent; Borisov, Oleg V; Štěpánek, Petr

    2016-08-10

    The self-assembly thermodynamics of pH-sensitive di-block and tri-block gradient copolymers of acrylic acid and styrene was studied for the first time using isothermal titration calorimetry (ITC) and dynamic light scattering (DLS) performed at varying pH. We were able to monitor each step of micellization as a function of decreasing pH. The growth of micelles is a multi-stage process that is pH dependent with several exothermic and endothermic components. The first step of protonation of the acrylic acid monomer units was accompanied mainly by conformational changes and the beginning of self-assembly. In the second stage of self-assembly, the micelles become larger and the number of micelles becomes smaller. While solution acidity increases, the isothermal calorimetry data show a broad deep minimum corresponding to an exothermic process attributed to an increase in the size of hydrophobic domains and an increase in the structure's hydrophobicity. The minor change in heat capacity (ΔCp) confirms the structural changes during this exothermic process. The exothermic process terminates deionization of acrylic acid. The pH-dependence of the ζ-potential of the block gradient copolymer micelles exhibits a plateau in the regime corresponding to the pH-controlled variation of the micellar dimensions. The onset of micelle formation and the solubility of the gradient copolymers were found to be dependent on the length of the gradient block.

  11. Self-assembly behavior of ABA coil-rod-coil triblock copolymers: A Brownian dynamics simulation approach

    NASA Astrophysics Data System (ADS)

    Li, Yongliang; Lin, Shaoliang; He, Xiaohua; Lin, Jiaping; Jiang, Tao

    2011-07-01

    The self-assembly behavior of ABA coil-rod-coil triblock copolymers in a selective solvent was studied by a Brownian molecular dynamics simulation method. It was found that the rod midblock plays an important role in the self-assembly of the copolymers. With a decrease in the segregation strength, ɛRR, of rod pairs, the aggregate structure first varies from a smecticlike disk shape to a long twisted string micelle and then to small aggregates. The influence of the block length and the asymmetry of the triblock copolymer on the phase behavior were studied and the corresponding phase diagrams were mapped. It was revealed that the variation of these parameters has a profound effect on microstructure. The simulation results are consistent with experimental results. Compared to rod-coil diblock copolymers, the coil-rod-coil triblock copolymers has a larger entropy penalty associated with the interfacial grafting density of the aggregate, leading to a higher ɛRR value for structural transitions.

  12. Self-assembly behavior of ABA coil-rod-coil triblock copolymers: a Brownian dynamics simulation approach.

    PubMed

    Li, Yongliang; Lin, Shaoliang; He, Xiaohua; Lin, Jiaping; Jiang, Tao

    2011-07-07

    The self-assembly behavior of ABA coil-rod-coil triblock copolymers in a selective solvent was studied by a Brownian molecular dynamics simulation method. It was found that the rod midblock plays an important role in the self-assembly of the copolymers. With a decrease in the segregation strength, ɛ(RR), of rod pairs, the aggregate structure first varies from a smecticlike disk shape to a long twisted string micelle and then to small aggregates. The influence of the block length and the asymmetry of the triblock copolymer on the phase behavior were studied and the corresponding phase diagrams were mapped. It was revealed that the variation of these parameters has a profound effect on microstructure. The simulation results are consistent with experimental results. Compared to rod-coil diblock copolymers, the coil-rod-coil triblock copolymers has a larger entropy penalty associated with the interfacial grafting density of the aggregate, leading to a higher ɛ(RR) value for structural transitions.

  13. Interfacial properties of semifluorinated alkane diblock copolymers

    NASA Astrophysics Data System (ADS)

    Pierce, Flint; Tsige, Mesfin; Borodin, Oleg; Perahia, Dvora; Grest, Gary S.

    2008-06-01

    The liquid-vapor interfacial properties of semifluorinated linear alkane diblock copolymers of the form F3C(CF2)n-1(CH2)m-1CH3 are studied by fully atomistic molecular dynamics simulations. The chemical composition and the conformation of the molecules at the interface are identified and correlated with the interfacial energies. A modified form of the Optimized Parameter for Liquid Simulation All-Atom (OPLS-AA) force field of Jorgensen and co-workers [J. Am. Chem. Soc. 106, 6638 (1984); 118, 11225 (1996); J. Phys. Chem. A 105, 4118 (2001)], which includes specific dihedral terms for H-F blocks-and corrections to the H-F nonbonded interaction, is used together with a new version of the exp-6 force field developed in this work. Both force fields yield good agreement with the available experimental liquid density and surface tension data as well as each other over significant temperature ranges and for a variety of chain lengths and compositions. The interfacial regions of semifluorinated alkanes are found to be rich in fluorinated groups compared to hydrogenated groups, an effect that decreases with increasing temperature but is independent of the fractional length of the fluorinated segments. The proliferation of fluorine at the surface substantially lowers the surface tension of the diblock copolymers, yielding values near those of perfluorinated alkanes and distinct from those of protonated alkanes of the same chain length. With decreasing temperatures within the liquid state, chains are found to preferentially align perpendicular to the interface, as previously seen.

  14. A surface interaction model for self-assembly of block copolymers under soft confinement

    NASA Astrophysics Data System (ADS)

    Song, Jun-Qing; Liu, Yi-Xin; Zhang, Hong-Dong

    2016-12-01

    The surface interaction between substrates and block copolymers is one of the most important factors that control the alignment of self-assembled domains under thin film confinement. Most previous studies simply modeled substrates modified by grafting polymers as a hard wall with a specified surface energy, leading to an incomplete understanding of the role of grafted polymers. In this study, we propose a general model of surface interactions where the role of grafted polymers is decomposed into two independent contributions: the surface preference and the surface softness. Based on this model, we perform a numerical analysis of the stability competition between perpendicular and parallel lamellae of symmetric diblock copolymers on substrates modified by homopolymers using self-consistent field theory. The effects of the surface preference and the surface softness on the alignment of lamellar domains are carefully examined. A phase diagram of the alignment in the plane of the surface preference parameter and the surface softness parameter is constructed, which reveals a considerable parameter window for preparing stable perpendicular lamellae even on highly preferential substrates.

  15. Defects in the Self-Assembly of Block Copolymers and Their Relevance for Directed Self-Assembly.

    PubMed

    Li, Weihua; Müller, Marcus

    2015-01-01

    Block copolymer self-assembly provides a platform for fabricating dense, ordered nanostructures by encoding information in the chemical architecture of multicomponent macromolecules. Depending on the volume fraction of the components and chain topology, these macromolecules form a variety of spatially periodic microphases in thermodynamic equilibrium. The kinetics of self-assembly, however, often results in initial morphologies with defects, and the subsequent ordering is protracted. Different strategies have been devised to direct the self-assembly of copolymer materials by external fields to align and perfect the self-assembled nanostructures. Understanding and controlling the thermodynamics of defects, their response to external fields, and their dynamics is important because applications in microelectronics either require extremely low defect densities or aim at generating specific defects at predetermined locations to fabricate irregular device-oriented structures for integrated circuits. In this review, we discuss defect morphologies of block copolymers in the bulk and thin films, highlighting (a) analogies to and differences from defects in other crystalline materials, (b) the stability of defects and their dynamics, and (c) the influence of external fields.

  16. Complexation Between Cationic Diblock Copolymers and Plasmid DNA

    NASA Astrophysics Data System (ADS)

    Jung, Seyoung; Reineke, Theresa; Lodge, Timothy

    Deoxyribonucleic acids (DNA), as polyanions, can spontaneously bind with polycations to form polyelectrolyte complexes. When the polycation is a diblock copolymer with one cationic block and one uncharged hydrophilic block, the polyelectrolyte complexes formed with plasmid DNA (pDNA) are often colloidally stable, and show great promise in the field of polymeric gene therapy. While the resulting properties (size, stability, and toxicity to biological systems) of the complexes have been studied for numerous cationic diblocks, the fundamentals of the pDNA-diblock binding process have not been extensively investigated. Herein, we report how the cationic block content of a diblock influences the pDNA-diblock interactions. pDNA with 7164 base pairs and poly(2-deoxy-2-methacrylamido glucopyranose)-block-poly(N-(2-aminoethyl) methacrylamide) (PMAG-b-PAEMA) are used as the model pDNA and cationic diblock, respectively. To vary the cationic block content, two PMAG-b-PAEMA copolymers with similar PMAG block lengths but distinct PAEMA block lengths and a PAEMA homopolymer are utilized. We show that the enthalpy change from pDNA-diblock interactions is dependent on the cationic diblock composition, and is closely associated with both the binding strength and the pDNA tertiary structure.

  17. Disulfide-Functionalized Diblock Copolymer Worm Gels.

    PubMed

    Warren, Nicholas J; Rosselgong, Julien; Madsen, Jeppe; Armes, Steven P

    2015-08-10

    Two strategies for introducing disulfide groups at the outer surface of RAFT-synthesized poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA, or Gx-Hy for brevity) diblock copolymer worms are investigated. The first approach involved statistical copolymerization of GMA with a small amount of disulfide dimethacrylate (DSDMA, or D) comonomer to afford a G54-D0.50 macromolecular chain transfer agent (macro-CTA); this synthesis was conducted in relatively dilute solution in order to ensure mainly intramolecular cyclization and hence the formation of linear chains. Alternatively, a new disulfide-based bifunctional RAFT agent (DSDB) was used to prepare a G45-S-S-G45 (or (G45-S)2) macro-CTA. A binary mixture of a non-functionalized G55 macro-CTA was utilized with each of these two disulfide-based macro-CTAs in turn for the RAFT aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA). By targeting a PHPMA DP of 130 and systematically varying the molar ratio of the two macro-CTAs, a series of disulfide-functionalized diblock copolymer worm gels were obtained. For both formulations, oscillatory rheology studies confirmed that higher disulfide contents led to stronger gels, presumably as a result of inter-worm covalent bond formation via disulfide/thiol exchange. Using the DSDB-based macro-CTA led to the strongest worm gels, and this formulation also proved to be more effective in suppressing the thermosensitive behavior that is observed for the nondisulfide-functionalized control worm gel. However, macroscopic precipitation occurred when the proportion of DSDB-based macro-CTA was increased to 50 mol %, whereas the DSDMA-based macro-CTA could be utilized at up to 80 mol %. Finally, the worm gel modulus could be reduced to that of a nondisulfide-containing worm gel by reductive cleavage of the inter-worm disulfide bonds using excess tris(2-carboxyethyl)phosphine (TCEP) to yield thiol groups. These new biomimetic worm gels are

  18. Crystallization in sequence-defined peptoid diblock copolymers induced by microphase separation.

    PubMed

    Sun, Jing; Teran, Alexander A; Liao, Xunxun; Balsara, Nitash P; Zuckermann, Ronald N

    2014-02-05

    Atomic level synthetic control over a polymer's chemical structure can reveal new insights into the crystallization kinetics of block copolymers. Here, we explore the impact of side chain structure on crystallization behavior, by designing a series of sequence-defined, highly monodisperse peptoid diblock copolymers poly-N-decylglycine-block-poly-N-2-(2-(2-methoxyethoxy)ethoxy)ethylglycine (pNdc-b-pNte) with volume fraction of pNte (ϕNte) values ranging from 0.29 to 0.71 and polydispersity indices ≤1.00017. Both monomers have nearly identical molecular volumes, but the pNte block is amorphous while the pNdc block is crystalline. We demonstrate by X-ray scattering and calorimetry that all the block copolypeptoids self-assemble into lamellar microphases and that the self-assembly is driven by crystallization of the pNdc block. Interestingly, the microphase separated pNdc-b-pNte diblock copolymers form two distinct crystalline phases. Crystallization of the normally amorphous pNte chains is induced by the preorganization of the crystalline pNdc chains. We hypothesize that this is due to the similarity of chemical structure of the monomers (both monomers have linear side chains of similar lengths emanating from a polyglycine backbone). The pNte block remains amorphous when the pNdc block is replaced by another crystalline block, poly-N-isoamylglycine, suggesting that a close matching of the lattice spacings is required for induced crystallization. To our knowledge, there are no previous reports of crystallization of a polymer chain induced by microphase separation. These investigations show that polypeptoids provide a unique platform for examining the effect of intertwined roles of side chain organization on the thermodynamic properties of diblock copolymers.

  19. Diblock copolymer bilayers as model for polymersomes: A coarse grain approach.

    PubMed

    Grillo, Damián A; Albano, Juan M R; Mocskos, Esteban E; Facelli, Julio C; Pickholz, Mónica; Ferraro, Marta B

    2017-06-28

    This paper presents a new model for polymersomes developed using a poly(ethylene oxide)-poly(butadiene) diblock copolymer bilayer. The model is based on a coarse-grained approach using the MARTINI force field. Since no MARTINI parameters exist for poly(butadiene), we have refined these parameters using quantum mechanical calculations and molecular dynamics simulations. The model has been validated using extensive molecular dynamics simulations in systems with several hundred polymer units and reaching up to 6 μs. These simulations show that the copolymer coarse grain model self-assemble into bilayers and that NPT and NPNγT ensemble runs reproduce key structural and mechanical experimental properties for different copolymer length chains with a similar hydrophilic weight fraction.

  20. Diblock copolymer bilayers as model for polymersomes: A coarse grain approach

    NASA Astrophysics Data System (ADS)

    Grillo, Damián A.; Albano, Juan M. R.; Mocskos, Esteban E.; Facelli, Julio C.; Pickholz, Mónica; Ferraro, Marta B.

    2017-06-01

    This paper presents a new model for polymersomes developed using a poly(ethylene oxide)-poly(butadiene) diblock copolymer bilayer. The model is based on a coarse-grained approach using the MARTINI force field. Since no MARTINI parameters exist for poly(butadiene), we have refined these parameters using quantum mechanical calculations and molecular dynamics simulations. The model has been validated using extensive molecular dynamics simulations in systems with several hundred polymer units and reaching up to 6 μ s. These simulations show that the copolymer coarse grain model self-assemble into bilayers and that NPT and NPNγT ensemble runs reproduce key structural and mechanical experimental properties for different copolymer length chains with a similar hydrophilic weight fraction.

  1. Postmodification of PS-b-P4VP diblock copolymer membranes by ARGET ATRP.

    PubMed

    Keskin, Damla; Clodt, Juliana I; Hahn, Janina; Abetz, Volker; Filiz, Volkan

    2014-07-29

    The surfaces of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer membranes were modified in order to obtain polymer brushes by using surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Isoporous membranes were prepared by the combination of self-assembly of PS-b-P4VP diblock copolymers and the nonsolvent induced phase separation process, also known as "phase inversion". In order to allow further functionalization, the membranes were modified with an ATRP initiator, 2-bromoisobutyryl bromide (BIBB). Therefore, the mussel-inspired poly(dopamine) coating was used to attach BIBB on the membranes surface. In the next step the coated membranes were postmodified by using surface-initiated ARGET ATRP with the hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA). HEMA as a hydrophilic methacrylate was chosen for the modification in order to enhance the membrane characteristics and to obtain a surface with antifouling properties. The surface-initiated ARGET ATRP reaction was carried out using different reaction times and environments. PHEMA could successfully incorporate on the membrane surface as confirmed by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), (1)H nuclear magnetic resonance spectroscopy ((1)H NMR), scanning electron microscopy (SEM), and contact angle measurements. Furthermore, stability tests against heat and solvents were performed, and water flux was measured for the raw and modified membranes. Stability against heat and hydrophilicity could be increased with this type of modification for diblock copolymer membranes.

  2. Morphology, directed self-assembly and pattern transfer from a high molecular weight polystyrene-block-poly(dimethylsiloxane) block copolymer film

    NASA Astrophysics Data System (ADS)

    Cheng, Li-Chen; Bai, Wubin; Fernandez Martin, Eduardo; Tu, Kun-Hua; Ntetsikas, Konstantinos; Liontos, George; Avgeropoulos, Apostolos; Ross, C. A.

    2017-04-01

    The self-assembly of block copolymers with large feature sizes is inherently challenging as the large kinetic barrier arising from chain entanglement of high molecular weight (MW) polymers limits the extent over which long-range ordered microdomains can be achieved. Here, we illustrate the evolution of thin film morphology from a diblock copolymer of polystyrene-block-poly(dimethylsiloxane) exhibiting total number average MW of 123 kg mol‑1, and demonstrate the formation of layers of well-ordered cylindrical microdomains under appropriate conditions of binary solvent mix ratio, commensurate film thickness, and solvent vapor annealing time. Directed self-assembly of the block copolymer within lithographically patterned trenches occurs with alignment of cylinders parallel to the sidewalls. Fabrication of ordered cobalt nanowire arrays by pattern transfer was also implemented, and their magnetic properties and domain wall behavior were characterized.

  3. Morphology, directed self-assembly and pattern transfer from a high molecular weight polystyrene-block-poly(dimethylsiloxane) block copolymer film.

    PubMed

    Cheng, Li-Chen; Bai, Wubin; Fernandez Martin, Eduardo; Tu, Kun-Hua; Ntetsikas, Konstantinos; Liontos, George; Avgeropoulos, Apostolos; Ross, C A

    2017-04-07

    The self-assembly of block copolymers with large feature sizes is inherently challenging as the large kinetic barrier arising from chain entanglement of high molecular weight (MW) polymers limits the extent over which long-range ordered microdomains can be achieved. Here, we illustrate the evolution of thin film morphology from a diblock copolymer of polystyrene-block-poly(dimethylsiloxane) exhibiting total number average MW of 123 kg mol(-1), and demonstrate the formation of layers of well-ordered cylindrical microdomains under appropriate conditions of binary solvent mix ratio, commensurate film thickness, and solvent vapor annealing time. Directed self-assembly of the block copolymer within lithographically patterned trenches occurs with alignment of cylinders parallel to the sidewalls. Fabrication of ordered cobalt nanowire arrays by pattern transfer was also implemented, and their magnetic properties and domain wall behavior were characterized.

  4. Self-Assembling Diblock Polypeptide Hydrogels: Effects of Salt and Cell-Growth Media on the Self-assembly Process and Material Properties

    NASA Astrophysics Data System (ADS)

    Pakstis, Lisa; Ozbas, Bulent; Pochan, Darrin; Nowak, Andrew; Deming, Timothy

    2003-03-01

    Self-assembling peptide based hydrogels having a unique nano- and microscopic morphology are being studied for potential use as tissue engineering scaffolds. Low molecular weight ( 20 kg/mol), amphiphilic, diblock polypeptides of hydrophilic, polyelectrolyte cationic lysine (K) or anionic glutamic acid (E) and hydrophobic leucine (L) or valine (V) form hydrogels in aqueous solution at neutral pH and at very low volume fraction of polymer (vol. fraction polypeptide less than 0.5 wtbeen characterized using laser confocal microscopy (LCM), ultra-small angle neutron scattering (SANS), and cryogenic transmission electron microscopy (cryoTEM) imaging. Studies of the self-assembly process with and without significant ionic solution strength (i.e. in the presence of salt and cell growth medium) will be discussed. Interactions of the hydrogels with bacterial and mammalian cells reveal that these materials are non-cytotoxic and biocompatible. Hence, the chemistry of the assembled diblock polypeptides allows for cellular proliferation whereas the same chemistry in the homopolymeric form is cytotoxic. Proper molecular design for optimal cell viability and gel integrity in the presence of high ionic strength aqueous solution will be discussed.

  5. Real-Time observation of PS-PDMS block copolymer self-assembly under solvent vapor annealing

    NASA Astrophysics Data System (ADS)

    Bai, Wubin; Yager, Kevin; Ross, Caroline

    2015-03-01

    Solvent annealing provides a convenient way to produce microphase separation in films of block copolymers, but the morphology transition of the film during the solvent absorption, equilibrium solvent-BCP concentration and solvent desorption process are not well known. An in situ study of solvent annealing of polystyrene-block-polydimethylsiloxane (PS-PDMS, 16 kg/mol, fPDMS = 30%, period 17 nm) diblock copolymer was carried by synchrotron grazing-incidence small-angle X-ray scattering (GISAXS). The swollen film morphology was found to be strongly dependent on swelling ratio. A transition from the disordered state to a highly ordered state which contained multiple layers of in-plane cylinders was observed at a swelling ratio around 1.45 from samples with 100nm to 1000nm as-cast thickness. The rate of solvent absorption was found to be less important to the dried morphology, while the time of equilibrium solvent-BCP concentration stage was found to influence the orientation of self-assembled microdomains and the drying rate was found to affect the degree of structure deformation. The implications of the results to pattern generation for block copolymer directed self-assembly will be discussed. Semiconductor Research Corporation, National Science Foundation.

  6. Multiple patterns of diblock copolymer confined in irregular geometries with soft surface

    NASA Astrophysics Data System (ADS)

    Li, Ying; Sun, Min-Na; Zhang, Jin-Jun; Pan, Jun-Xing; Guo, Yu-Qi; Wang, Bao-Feng; Wu, Hai-Shun

    2015-12-01

    The different confinement shapes can induce the formation of various interesting and novel morphologies, which might inspire potential applications of materials. In this paper, we study the directed self-assembly of diblock copolymer confined in irregular geometries with a soft surface by using self-consistent field theory. Two types of confinement geometries are considered, namely, one is the concave pore with one groove and the other is the concave pore with two grooves. We obtain more novel and different structures which could not be produced in other two-dimensional (2D) confinements. Comparing these new structures with those obtained in regular square confinement, we find that the range of ordered lamellae is enlarged and the range of disordered structure is narrowed down under the concave pore confinement. We also compare the different structures obtained under the two types of confinement geometries, the results show that the effect of confinement would increase, which might induce the diblock copolymer to form novel structures. We construct the phase diagram as a function of the fraction of B block and the ratio of h/L of the groove. The simulation reveals that the wetting effect of brushes and the shape of confinement geometries play important roles in determining the morphologies of the system. Our results improve the applications in the directed self-assembly of diblock copolymer for fabricating the irregular structures. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20121404110004), the Research Foundation for Excellent Talents of Shanxi Provincial Department of Human Resources and Social Security, China, and the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province, China.

  7. Post-Self-Assembly Cross-Linking to Integrate Molecular Nanofibers with Copolymers in Oscillatory Hydrogels

    DTIC Science & Technology

    2013-05-09

    polymerizable sites for copolymerizing with N-isopropylacrylamide and for attaching a catalytic ruthenium bipyridine complex on the copolymer. The... ruthenium complex containing a vinyl group. This post- self-assembly cross-linking approach not only demonstrated the stability of the peptide bond under...attaching a catalytic ruthenium bipyridine complex on the copolymer. The combination of supramolecular self-assembly with copolymerization offers a

  8. Shear ordered diblock copolymers with tuneable optical properties.

    PubMed

    Parnell, Andrew J; Tzokova, Nadejda; Pryke, Andrew; Howse, Jonathan R; Mykhaylyk, Oleksandr O; Ryan, Anthony J; Panine, Pierre; Fairclough, J Patrick A

    2011-02-28

    A series of high molecular weight poly(styrene-b-isoprene) block copolymers with optical properties defined by composition in a non-selective solvent were studied using simultaneous ultra small angle X-ray scattering (USAXS) and optical spectrometry. A small magnitude shear produces ordered and oriented states in the copolymer solutions that persist for extended periods of time, and also have superior optical properties that are directly attributable to the mesoscopic block copolymer (BCP) morphology. We have demonstrated that the optical transmission of these materials can be tuned by the addition of low molecular weight poly(isoprene) and poly(styrene) to swell their respective domains within the diblock copolymer. The optical transmission peak for the diblocks could be tuned; from 380 nm-440 nm for the 670k diblock, 425 nm-540 nm for the 850k diblock and 541 nm-625 nm for the 1 million diblock by altering the solution concentration and composition. The full width at half maximum that can be achieved for the optical transmission peaks is as small as 15 nm at 473 nm with a Δλ/λ of 0.03, highlighting the high quality ordering in these systems. Also a small shift in the transmission peak wavelength was observed across a wide angle of view (15 nm at 30°) suggesting that these materials could be used for large area narrow band optical filters.

  9. Self-assembly of polypeptide-based copolymers into diverse aggregates.

    PubMed

    Cai, Chunhua; Wang, Liquan; Lin, Jiaping

    2011-10-28

    Recently, increasing attention has been given to the self-assembly behavior of polypeptide-based copolymers. Polypeptides can serve as either shell-forming or core-forming blocks in the formation of various aggregates. The solubility and rigidity of polypeptide blocks have been found to have a profound effect on the self-assembly behavior of polypeptide-based copolymers. Polypeptide graft copolymers combine the advantages of a grafting strategy and the characteristics of polypeptide chains and their self-assembly behavior can be easily adjusted by choosing different polymer chains and copolymer architectures. Fabricating hierarchical structures is one of the attractive topics of self-assembly research of polypeptide copolymers. These hierarchical structures are promising for use in preparing functional materials and, thus, attract increasing attention. Computer simulations have emerged as powerful tools to investigate the self-assembly behavior of polymers, such as polypeptides. These simulations not only support the experimental results, but also provide information that cannot be directly obtained from experiments. In this feature article, recent advances in both experimental and simulation studies for the self-assembly behavior of polypeptide-based copolymers are reviewed.

  10. Structure of Poly(styrene-b-ethylene-alt-propylene) Diblock Copolymer Micelles in Squalane

    SciTech Connect

    Choi, Soo-Hyung; Bates, Frank S.; Lodge, Timothy P.

    2009-11-04

    The temperature dependence of the micellar structures formed by poly(styrene-b-ethylene-alt-propylene) (SEP) diblock copolymers in squalane, a highly selective solvent for the PEP blocks, has been studied using dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). Four SEP diblock copolymers were prepared by sequential anionic polymerization of styrene and isoprene, followed by hydrogenation of the isoprene blocks, to yield SEP(17-73), SEP(26-66), SEP(36-69), and SEP(42-60), where the numbers indicate block molecular weights in kDa. All four polymers formed well-defined spherical micelles. In dilute solution, DLS provided the temperature-dependent mean hydrodynamic radius, R{sub h}, and its distribution, while detailed fitting of the SAXS profiles gave the core radius, R{sub c}, the equivalent hard sphere radius, R{sub hs}, and an estimate of the aggregation number, N{sub agg}. In general, the micelles became smaller as the critical micelle temperature (CMT) was approached, which was well above the glass transition of the core block. As concentration increased the micelles packed onto body centered cubic lattices for all four copolymers, which underwent order-disorder transitions upon heating near the dilute solution CMTs. The results are discussed in terms of current understanding of block copolymer solution self-assembly, and particular attention is paid to the issue of equilibration, given the high glass transition temperature of the core block.

  11. Relaxation processes in a lower disorder order transition diblock copolymer.

    PubMed

    Sanz, Alejandro; Ezquerra, Tiberio A; Hernández, Rebeca; Sprung, Michael; Nogales, Aurora

    2015-02-14

    The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition TODT, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.

  12. Relaxation processes in a lower disorder order transition diblock copolymer

    SciTech Connect

    Sanz, Alejandro; Ezquerra, Tiberio A.; Nogales, Aurora

    2015-02-14

    The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition T{sub ODT}, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.

  13. Surface self-assembled PEGylation of fluoro-based PVDF membranes via hydrophobic-driven copolymer anchoring for ultra-stable biofouling resistance.

    PubMed

    Lin, Nien-Jung; Yang, Hui-Shan; Chang, Yung; Tung, Kuo-Lun; Chen, Wei-Hao; Cheng, Hui-Wen; Hsiao, Sheng-Wen; Aimar, Pierre; Yamamoto, Kazuo; Lai, Juin-Yih

    2013-08-13

    Stable biofouling resistance is significant for general filtration requirements, especially for the improvement of membrane lifetime. A systematic group of hyper-brush PEGylated diblock copolymers containing poly(ethylene glycol) methacrylate (PEGMA) and polystyrene (PS) was synthesized using an atom transfer radical polymerization (ATRP) method and varying PEGMA lengths. This study demonstrates the antibiofouling membrane surfaces by self-assembled anchoring PEGylated diblock copolymers of PS-b-PEGMA on the microporous poly(vinylidene fluoride) (PVDF) membrane. Two types of copolymers are used to modify the PVDF surface, one with different PS/PEGMA molar ratios in a range from 0.3 to 2.7 but the same PS molecular weights (MWs, ∼5.7 kDa), the other with different copolymer MWs (∼11.4, 19.9, and 34.1 kDa) but the similar PS/PEGMA ratio (∼1.7 ± 0.2). It was found that the adsorption capacities of diblock copolymers on PVDF membranes decreased as molar mass ratios of PS/PEGMA ratio reduced or molecular weights of PS-b-PEGMA increased because of steric hindrance. The increase in styrene content in copolymer enhanced the stability of polymer anchoring on the membrane, and the increase in PEGMA content enhanced the protein resistance of membranes. The optimum PS/PEGMA ratio was found to be in the range between 1.5 and 2.0 with copolymer MWs above 20.0 kDa for the ultrastable resistance of protein adsorption on the PEGylated PVDF membranes. The PVDF membrane coated with such a diblock copolymer owned excellent biofouling resistance to proteins of BSA and lysozyme as well as bacterium of Escherichia coli and Staphylococcus epidermidis and high stable microfiltration operated with domestic wastewater solution in a membrane bioreactor.

  14. Performance Enhancement of Electronic and Energy Devices via Block Copolymer Self-Assembly.

    PubMed

    Yoo, Hyeon Gyun; Byun, Myunghwan; Jeong, Chang Kyu; Lee, Keon Jae

    2015-07-15

    The use of self-assembled block copolymers (BCPs) for the fabrication of electronic and energy devices has received a tremendous amount of attention as a non-traditional approach to patterning integrated circuit elements at nanometer dimensions and densities inaccessible to traditional lithography techniques. The exquisite control over the dimensional features of the self-assembled nanostructures (i.e., shape, size, and periodicity) is one of the most attractive properties of BCP self-assembly. Harmonic spatial arrangement of the self-assembled nanoelements at desired positions on the chip may offer a new strategy for the fabrication of electronic and energy devices. Several recent reports show the great promise in using BCP self-assembly for practical applications of electronic and energy devices, leading to substantial enhancements of the device performance. Recent progress is summarized here, with regard to the performance enhancements of non-volatile memory, electrical sensor, and energy devices enabled by directed BCP self-assembly.

  15. Filtration membranes from self-assembled block copolymers - a review on recent progress

    NASA Astrophysics Data System (ADS)

    Upadhyaya, L.; Semsarilar, M.; Nehache, S.; Deratani, A.; Quemener, D.

    2015-07-01

    The very recent developments in preparation of filtration membranes from self-assembled block copolymers (BCPs) are reviewed in this paper. We look into membranes with very sharp pore size distribution and the approaches for manufacture of nanoporous films, including etching and templating, the advantages of the new process based on micelle assembly and phase inversion. The paper is divided in two main sections. In the first part different strategies to prepare membranes from block copolymers are summarized. The second part looks into the different factors affecting the pore formation, morphology and the characteristics of the membranes made from self-assembly of block copolymers.

  16. Rapidly recovering hydrogel scaffolds from self-assembling diblock copolypeptide amphiphiles

    NASA Astrophysics Data System (ADS)

    Nowak, Andrew P.; Breedveld, Victor; Pakstis, Lisa; Ozbas, Bulent; Pine, David J.; Pochan, Darrin; Deming, Timothy J.

    2002-05-01

    Protein-based hydrogels are used for many applications, ranging from food and cosmetic thickeners to support matrices for drug delivery and tissue replacement. These materials are usually prepared using proteins extracted from natural sources, which can give rise to inconsistent properties unsuitable for medical applications. Recent developments have utilized recombinant DNA methods to prepare artificial protein hydrogels with specific association mechanisms and responsiveness to various stimuli. Here we synthesize diblock copolypeptide amphiphiles containing charged and hydrophobic segments. Dilute solutions of these copolypeptides would be expected to form micelles; instead, they form hydrogels that retain their mechanical strength up to temperatures of about 90°C and recover rapidly after stress. The use of synthetic materials permits adjustment of copolymer chain length and composition, which we varied to study their effect on hydrogel formation and properties. We find that gelation depends not only on the amphiphilic nature of the polypeptides, but also on chain conformations-α-helix, β-strand or random coil. Indeed, shape-specific supramolecular assembly is integral to the gelation process, and provides a new class of peptide-based hydrogels with potential for applications in biotechnology.

  17. Bimetallic PdAg nanoparticle arrays from monolayer films of diblock copolymer micelles

    NASA Astrophysics Data System (ADS)

    Ehret, E.; Beyou, E.; Mamontov, G. V.; Bugrova, T. A.; Prakash, S.; Aouine, M.; Domenichini, B.; Cadete Santos Aires, F. J.

    2015-07-01

    The self-assembly technique provides a highly efficient route to generate well-ordered structures on a nanometer scale. In this paper, well-ordered arrays of PdAg alloy nanoparticles on flat substrates with narrow distributions of particle size (6-7 nm) and interparticle spacing (about 60 nm) were synthesized by the block copolymer micelle approach. A home-made PS-b-P4VP diblock copolymer was prepared to obtain a micellar structure in toluene. Pd and Ag salts were then successfully loaded in the micellar core of the PS-b-P4VP copolymer. A self-assembled monolayer of the loaded micelles was obtained by dipping the flat substrate in the solution. At this stage, the core of the micelles was still loaded with the metal precursor rather than with a metal. Physical and chemical reducing methods were used to reduce the metal salts embedded in the P4VP core into PdAg nanoparticles. HRTEM and EDX indicated that Pd-rich PdAg alloy nanoparticles were synthesized by chemical or physical reduction; UV-visible spectroscopy observations confirmed that metallic PdAg nanoparticles were quickly formed after chemical reduction; XPS measurements revealed that the PdAg alloy nanoparticles were in a metallic state after a short time of exposure to O2 plasma and after hydrazine reduction.

  18. Effect of ionic surfactant on the self-assembly of triblock copolymer

    NASA Astrophysics Data System (ADS)

    Ray, D.; Kohlbrecher, J.; Aswal, V. K.

    2017-05-01

    The effect of anionic surfactant sodium dodecyl sulfate (SDS) on the self-assembly of PEO-PPO-PEO triblock copolymer in aqueous solution has been studied using small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations (1 wt%) of block copolymer and surfactant, and at varying temperatures between 20 to 80°C. Micelles of pure ionic surfactants show little change in their sizes with increasing temperature, whereas structures of the non-ionic micelles increase significantly (sphere-to-rod transition for some block copolymers). Contrast variation SANS measurement suggests addition of SDS to aqueous copolymer solutions leads to the formation of mixed micelles. Interestingly, the self-assembly of block copolymer is found to get completely arrested by the ionic surfactant in the mixed micelles which gives a control over the block copolymer phase behavior.

  19. Visible light-responsive micelles formed from dialkoxyanthracene-containing block copolymers.

    PubMed

    Yan, Qiang; Hu, Jun; Zhou, Rong; Ju, Yong; Yin, Yingwu; Yuan, Jinying

    2012-02-11

    A class of dialkoxyanthracene-containing diblock copolymers is synthesized which possesses visible light-responsivity. These copolymers can self-assemble into a micellar structure in water. Green visible light (540 nm) is able to scissor these anthracene species and cleave the diblock copolymer into two fragments, inducing disassembly of the self-assembled micelles.

  20. Polypeptoids: A model system for exploring sequence and shape effects on block copolymer self-assembly

    NASA Astrophysics Data System (ADS)

    Segalman, Rachel

    2015-03-01

    While our ability to understand the detailed relationship between block copolymer chemistry and mesoscopic self-assembly has made remarkable progress over the last many years, yet we are still limited to a relatively small number of blocks in terms of structure-property understanding. Thus, there is a need to explore self-assembly phase space with sequence using a model system. Polypeptoids are non-natural, sequence specific polymers that offer the opportunity to probe the effect of sequence on self-assembly with much simpler molecular interactions and more scalable synthesis than traditional polypeptides. In this talk, I will discuss the use of this model system to understand the role of sequence on chain collapse and globule formation in solution, polymer crystallization, and block copolymer self-assembly. I will then discuss potential application as surface active agents for anti-fouling.

  1. Constructing a molecular theory of self-assembly: Interplay of ideas from surfactants and block copolymers.

    PubMed

    Nagarajan, Ramanathan

    2017-06-01

    Low molecular weight surfactants and high molecular weight block copolymers display analogous self-assembly behavior in solutions and at interfaces, generating nanoscale structures of different shapes. Understanding the link between the molecular structure of these amphiphiles and their self-assembly behavior has been the goal of theoretical studies. Despite the analogies between surfactants and block copolymers, models predicting their self-assembly behavior have evolved independent of one another, each overlooking the molecular feature considered critical to the other. In this review, we focus on the interplay of ideas pertaining to surfactants and block copolymers in three areas of self-assembly. First, we show how improved free energy models have evolved by applying ideas from surfactants to block copolymers and vice versa, giving rise to a unitary theoretical framework and better predictive capabilities for both classes of amphiphiles. Second we show that even though molecular packing arguments are often used to explain aggregate shape transitions resulting from self-assembly, the molecular packing considerations are more relevant in the case of surfactants whereas free energy criteria are relevant for block copolymers. Third, we show that even though the surfactant and block copolymer aggregates are small nanostructures, the size differences between them is significant enough to make the interfacial effects control the solubilization of molecules in surfactant micelles while the bulk interactions control the solubilization in block copolymer micelles. Finally, we conclude by identifying recent theoretical progress in adapting the micelle model to a wide variety of self-assembly phenomena and the challenges to modeling posed by emerging novel classes of amphiphiles with complex biological, inorganic or nanoparticle moieties. Published by Elsevier B.V.

  2. Topographically-designed triboelectric nanogenerator via block copolymer self-assembly.

    PubMed

    Jeong, Chang Kyu; Baek, Kwang Min; Niu, Simiao; Nam, Tae Won; Hur, Yoon Hyung; Park, Dae Yong; Hwang, Geon-Tae; Byun, Myunghwan; Wang, Zhong Lin; Jung, Yeon Sik; Lee, Keon Jae

    2014-12-10

    Herein, we report a facile and robust route to nanoscale tunable triboelectric energy harvesters realized by the formation of highly functional and controllable nanostructures via block copolymer (BCP) self-assembly. Our strategy is based on the incorporation of various silica nanostructures derived from the self-assembly of BCPs to enhance the characteristics of triboelectric nanogenerators (TENGs) by modulating the contact-surface area and the frictional force. Our simulation data also confirm that the nanoarchitectured morphologies are effective for triboelectric generation.

  3. Tuning metal surface diffusion on diblock copolymer films.

    SciTech Connect

    Darling, S.; Hoffmann, A.

    2007-07-01

    The authors have studied the effect of predeposition electron exposure on the diffusion behavior of silver evaporated on a diblock copolymer template. Unexposed regions display a highly selective adsorption of Ag clusters on the polystyrene domains. Exposure to the electron beam modifies the surface diffusion constants on each polymer block and produces a trend of smaller mean particle sizes with increased dose. While there is a loss of selectivity in this system upon exposure, alternative diblock chemistries or exposure procedures could enable one to engineer the selectivity of desired materials on polymer films.

  4. Dynamics of a diblock copolymer melt studied via XPCS

    NASA Astrophysics Data System (ADS)

    Mochrie, Simon; Falus, Peter

    2003-03-01

    Measurements will be presented of the equilibrium dynamics of an entangled, asymmetric, PS-PDMS diblock copolymer melt. Specifically, the emerging technique of x-ray photon correlation spectroscopy (XPCS), employing beamline 8-ID of the Advanced Photon Source and a new fast CCD-based x-ray detector, was used to characterize the sample relaxation times for wavevectors spanning the peak of the diblock static structure factor. The results will be compared to available theory. (This work was supported by the NSF via DMR 0071755.)

  5. Self-Assembled Asymmetric Block Copolymer Membranes: Bridging the Gap from Ultra- to Nanofiltration.

    PubMed

    Yu, Haizhou; Qiu, Xiaoyan; Moreno, Nicolas; Ma, Zengwei; Calo, Victor Manuel; Nunes, Suzana P; Peinemann, Klaus-Viktor

    2015-11-16

    The self-assembly of block copolymers is an emerging strategy to produce isoporous ultrafiltration membranes. However, thus far, it has not been possible to bridge the gap from ultra- to nanofiltration and decrease the pore size of self-assembled block copolymer membranes to below 5 nm without post-treatment. It is now reported that the self-assembly of blends of two chemically interacting copolymers can lead to highly porous membranes with pore diameters as small as 1.5 nm. The membrane containing an ultraporous, 60 nm thin separation layer can fully reject solutes with molecular weights of 600 g mol(-1) in aqueous solutions with a water flux that is more than one order of magnitude higher than the permeance of commercial nanofiltration membranes. Simulations of the membrane formation process by dissipative particle dynamics (DPD) were used to explain the dramatic observed pore size reduction combined with an increase in water flux.

  6. Simulated annealing study of gyroid formation in diblock copolymer solutions.

    PubMed

    Sun, Pingchuan; Yin, Yuhua; Li, Baohui; Chen, Tiehong; Jin, Qinghua; Ding, Datong; Shi, An-Chang

    2005-12-01

    Conditions for the formation of gyroid structures in diblock copolymer solutions are examined using a simulated annealing technique. The simulations were performed on diblock copolymer systems of A(NA)-b-B(NB) (with NAcopolymer concentrations between the hexagonally packed cylindrical and the lamellar phases and at an almost constant B-monomer concentration. It is also shown that the gyroid structure is especially sensitive to the B-solvent interaction (epsilonBS) and the length of the B block (NB). Phase diagrams for the diblock copolymer solutions are constructed. These predicted results are consistent with previous experimental observations. The three-dimensional isosurface contour plots of the simulated gyroid structure shows two interpenetrating strut networks. The projection along the [111] direction of the simulated gyroid structure and the spherically averaged structure factor are in good agreement with previous experimental results.

  7. Effect of Monomer Solubility on the Evolution of Copolymer Morphology during Polymerization-Induced Self-Assembly in Aqueous Solution

    PubMed Central

    2017-01-01

    Polymerization-induced self-assembly (PISA) has become a widely used technique for the rational design of diblock copolymer nano-objects in concentrated aqueous solution. Depending on the specific PISA formulation, reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization typically provides straightforward access to either spheres, worms, or vesicles. In contrast, RAFT aqueous emulsion polymerization formulations often lead to just kinetically-trapped spheres. This limitation is currently not understood, and only a few empirical exceptions have been reported in the literature. In the present work, the effect of monomer solubility on copolymer morphology is explored for an aqueous PISA formulation. Using 2-hydroxybutyl methacrylate (aqueous solubility = 20 g dm–3 at 70 °C) instead of benzyl methacrylate (0.40 g dm–3 at 70 °C) for the core-forming block allows access to an unusual “monkey nut” copolymer morphology over a relatively narrow range of target degrees of polymerization when using a poly(methacrylic acid) RAFT agent at pH 5. These new anisotropic nanoparticles have been characterized by transmission electron microscopy, dynamic light scattering, aqueous electrophoresis, shear-induced polarized light imaging (SIPLI), and small-angle X-ray scattering. PMID:28216792

  8. Nanopatterned Protein Films Directed by Ionic Complexation with Water-Soluble Diblock Copolymers

    PubMed Central

    Kim, Bokyung; Lam, Christopher N.; Olsen, Bradley D.

    2014-01-01

    The use of ionic interactions to direct both protein templating and block copolymer self-assembly into nanopatterned films with only aqueous processing conditions is demonstrated using block copolymers containing both thermally responsive and pH responsive blocks. Controlled reversible addition-fragmentation chain-transfer (RAFT) polymerization is employed to synthesize poly(N-isopropylacrylamide-b-2-(dimethylamino)ethyl acrylate) (PNIPAM-b-PDMAEA) diblock copolymers. The pH-dependent ionic complexation between the fluorescent protein, mCherry, and the ionic PDMAEA block is established using dynamic light scattering (DLS) and UV-Vis spectroscopy. DLS shows that the size of the resulting coacervate micelles depends strongly on pH, while UV-Vis spectroscopy shows a correlation between the protein’s absorption maximum and the ionic microenvironment. Zeta potential measurements clearly indicate the ionic nature of the complex-forming interactions. Spin casting was used to prepare nanostructured films from the protein-block copolymer coacervates. After film formation, the lower critical solution temperature (LCST) of the PNIPAM blocks allows the nanomaterial to be effectively immobilized in aqueous environments at physiological temperatures, enabling potential use as a controlled protein release material or polymer matrix for protein immobilization. At pH 9.2 and 7.8, the release rates are at least 10 times faster than that at pH 6.4 due to weaker interaction between protein and PNIPAM-b-PDMAEA (PND) diblock copolymer. Due to the ionic environment in which protein is confined, the majority of the protein (80%) remains active, independent of pH, even after having been dehydrated in vacuum and confined in the films. PMID:24904186

  9. Direct synthesis of inverse hexagonally ordered diblock copolymer/polyoxometalate nanocomposite films.

    PubMed

    Lunkenbein, Thomas; Kamperman, Marleen; Li, Zihui; Bojer, Carina; Drechsler, Markus; Förster, Stephan; Wiesner, Ulrich; Müller, Axel H E; Breu, Josef

    2012-08-01

    Nanostructured inverse hexagonal polyoxometalate composite films were cast directly from solution using poly(butadiene-block-2-(dimethylamino)ethyl methacrylate) (PB-b-PDMAEMA) diblock copolymers as structure directing agents for phosphomolybdic acid (H(3)[PMo(12)O(40)], H(3)PMo). H(3)PMo units are selectively incorporated into the PDMAEMA domains due to electrostatic interactions between protonated PDMAEMA and PMo(3-) anions. Long solvophilic PB chains stabilized the PDMAEMA/H(3)PMo aggregates in solution and reliably prevented macrophase separation. The choice of solvent is crucial. It appears that all three components, both blocks of the diblock copolymer as well as H(3)PMo, have to be soluble in the same solvent which turned out to be tetrahydrofuran, THF. Evaporation induced self-assembly resulted in highly ordered inverse hexagonal nanocomposite films as observed from transmission electron microscopy and small-angle X-ray scattering. This one-pot synthesis may represent a generally applicable strategy for integrating polyoxometalates into functional architectures and devices.

  10. Fluctuations/Correlations in Symmetric Diblock Copolymers: Simulations and Theories

    NASA Astrophysics Data System (ADS)

    Zong, Jing; Yang, Delian; Wang

    2012-02-01

    Modeling symmetric diblock copolymers as discrete Gaussian chains with soft, finite-range repulsions as commonly used in dissipative-particle dynamics simulations, we have performed fast off-lattice Monte Carlo (FOMC) simulations1 in a canonical ensemble with variable box lengths to study the thermodynamic and structural properties of both the disordered and lamellar phases. Our FOMC results for the disordered phase are further compared, without any parameter-fitting, to those from the reference interaction site model (RISM) and the polymer reference interaction site model (PRISM) theories, as well as the Gaussian fluctuation theory, based on the same model system. Such direct comparisons unambiguously and quantitatively reveal the consequences of various theoretical approximations and the validity of these theories in describing the fluctuations/correlations in disordered diblock copolymers. [4pt] [1] Q. Wang and Y. Yin, J. Chem. Phys., 130, 104903 (2009).

  11. High-Performance Field-Effect Transistors Based on Polystyrene-b-Poly(3-hexylthiophene) Diblock Copolymers

    SciTech Connect

    Geohegan, David B; Sumpter, Bobby G; Hong, Kunlun; Xiao, Kai; Lavrik, Nickolay V; Yu, Xiang; Chen, Jihua

    2011-01-01

    Polystyrene-b-poly(3-hexylthiophene) (PS-b-P3HT) block copolymers with fixed PS block length have been synthesized by combined atom transfer radical polymerization (ATRP) and Grignard metathesis (GRIM) polymerization. The self-assembled structures of these diblock copolymer thin films based on PS-b-P3HT have been studied by TEM, SAED, GIXD, AFM, and additionally by first principles modeling and simulation. These block copolymers undergo microphase separation and form nanostructured spheres, lamellae, nanofibers, or nanoribbons in the films dictated by the molecular weight of the P3HT block. Within the diblock copolymer thin film, PS blocks segregate to form amorphous domains, and the covalently bonded conjugated P3HT blocks exist as highly ordered crystalline domains through intermolecular packing with their alkyl side chains aligned normal to the substrate while the thiophene rings align parallel to the substrate through stacking. The conjugated PS-b-P3HT block copolymers exhibited significant improvements in organic field-effect transistor (OFET) performance and environmental stability as compared to P3HT homopolymers, with up to a factor of 2 increase in measured mobility (0.08 cm2/(V 3 s)) for the P4 (85 wt % P3HT). Overall, this work demonstrates that the high degree of molecular order induced by block copolymer phase separation can improve the transport properties and stability of conjugating polymers, which are critical for high-performance OFETs and other organic electronics.

  12. Degradation of PCL-MPEG diblock copolymer in rat plasma.

    PubMed

    Lin, Wen-Jen; Chang, Kai-Ling

    2008-06-01

    The poly(epsilon-caprolactone)-co-poly(ethylene glycol) (PCL-MPEG) amphiphilic diblock copolymer with molar ratio of epsilon-CL to MPEG 81:1 is synthesized via a ring-opening polymerization without a catalyst. The M(w) and M(n) molecular weights and the polydispersities are 18,000, 11,000 g/mole and 1.55, respectively. The pegylated amphiphilic copolymer forms micelles with a low critical micelle concentration 6.71 x 10(-8) mole/L, and the average particle size of copolymeric micelles is 62.3 +/- 12.9 nm. The degradation behavior of diblock copolymer was studied in rat plasma at 37 degrees C for 90 days. The changes of mass, composition, morphology, molecular weight, and thermal property of PCL-MPEG copolymer were investigated. The decrease of copolymer mass shows two phases with rate constants of 1.91 x 10(-1) day(-1) in the first-phase (1-24 h) and 1.77 x 10(-3) day(-1) in the second-phase (1-90 days). The degradation of labile ester linkage between PCL block and MPEG block accounts for continuous decrease of copolymer mass in plasma. The decrease of EG molar ratio from 1.30 to 0.67 and prominent reduction of enthalpy of fusion of remained copolymer from 116.5 to 85.2 J/g provide evidences of PCL-MPEG chain scission. On the other hand, the presence of partially degraded copolymers in the residuals results in its polydispersity increased from 1.55 to 2.24 at the end of 90 days. Nevertheless, the surface erosion of copolymer makes the molecular weight not quite different from its original value. Copyright 2007 Wiley Periodicals, Inc.

  13. Strategies for controlling intra- and intermicellar packing in block copolymer solutions: illustrating the flexibility of the self-assembly toolbox.

    PubMed

    Lodge, Timothy L; Bang, Joona; Li, Zhibo; Hillmyer, Marc A; Talmon, Yeshayhu

    2005-01-01

    Block copolymers constitute a class of self-assembling macromolecules that offer remarkable flexibility for controlling nanostructure, both in discrete objects and in bulk materials. Block copolymer micelles may be formed with multiple compartments by judicious choice of ingredients in an ABC triblock copolymer. For example, we have shown that a poly(ethylene oxide-b-styrene-b-fluorinated butadiene) triblock assembles in dilute aqueous solution into large, flat core/shell/corona disks, with the fluorine containing block forming the core. In contrast, the unfluorinated precursor generates large spherical micelles. A numerical analysis suggests that the disk-like motif is characteristic of the so-called superstrong segregation regime, whereby the interfacial tension becomes so large as to overwhelm the conformational entropy of the core blocks. For ABC miktoarm stars comprising polyethylene oxide, polyethylethylene, and polyhexafluoropropylene oxide arms, a much richer variety of micellar structures are observed. Prominent amongst these is a "segmented worm", in which alternating layers (5-7 nm thick) of hydrocarbon and fluorocarbon blocks form disks (6-10 nm in radius) that stack into cylindrical aggregates. The disk radii suggest almost fully stretched blocks, again consistent with the superstrong segregation regime. These structures are rationalized in terms of the constraints imposed by the star architecture, combined with the extremely strong interfacial tensions. In contrast, for lipids, surfactants, and aqueous diblock copolymers, increasing the interfacial tension can induce a transition from spheres to cylinders to flat bilayers; the disk-like motif is not usually seen. Interestingly, in aqueous diblocks both worm-like micelles and vesicles have been well-documented, whereas in "simple" organic systems they have not. We have shown that by suitable choice of block composition and solvent selectivity, the curvature sequence sphere/cylinder/vesicle can also be

  14. Block copolymer blend phase behavior: Binary diblock blends and amphiphilic block copolymer/epoxy mixtures

    NASA Astrophysics Data System (ADS)

    Lipic, Paul Martin

    The phase behavior of block copolymers and block copolymer blends has provided an extensive amount of exciting research and industrial applications for over thirty years. However, the unique nanoscale morphologies of microphase separated block copolymer systems is still not completely understood. This thesis examines the phase behavior of diblock copolymers and binary diblock copolymer blends in the strong segregation limit (SSL), and blends of an amphiphilic diblock copolymer with an epoxy resin. Studies of high molecular weight (˜84,000 g/mole) poly(ethylene)-poly(ethyl ethylene) (PE-PEE) diblock copolymers probed the ability of block copolymers to reach equilibrium in the SSL. Samples of pure diblocks or binary diblock blends prepared using different preparation techniques (solvent casting or precipitation) had different phase behaviors, as identified with transmission electron microscopy (TEM) and small-angle x-ray scattering (SAXS), confirming non-equilibrium phase behavior. This non-equilibrium behavior was metastable, and these results identify the caution that should be used when claiming equilibrium phase behavior in the SSL. Blends of an amphiphilic diblock copolymer, poly(ethylene oxide)-poly(ethylene-alt-propylene) (PEO-PEP) with a polymerizable epoxy resin selectively miscible with PEO, poly(Bisphenol-A-co-epichlorohydrin), supported theoretical calculations and increased the understanding of block copolymer/homopolymer blends. These blends formed different ordered structures (lamellae, bicontinuous cubic gyroid, hexagonally packed cylinders, cubic and hexagonally packed spheres) as well as a disordered spherical micellar structure, identified with SAXS and rheological measurements. Addition of hardener, methylene dianiline, to the system resulted in cross-linking of the epoxy resin and formation of a thermoset material. Macrophase separation between the epoxy and block copolymer did not occur, but local expulsion of the PEO from the epoxy was

  15. Kinetics of directed self-assembly of block copolymers on chemically patterned substrates

    NASA Astrophysics Data System (ADS)

    Müller, Marcus; Li, Weihua; Orozco Rey, Juan Carlos; Welling, Ulrich

    2015-09-01

    Chemically patterned surfaces have been successfully employed to direct the kinetics of self-assembly of block copolymers into dense, periodic morphologies (”chemoepitaxy”). Significant efforts have been directed towards understanding the kinetics of structure formation and, particularly, the formation and annihilation of defects. In the present manuscript we use computer simulations of a soft, coarse-grained polymer model to study the kinetics of structure formation of lamellar-forming block copolymer thin films on a chemical pattern of lines and spaces. The case where the copolymer material replicates the surface pattern and the more subtle scenario of sparse guiding patterns are considered. Our simulation results highlight (1) the importance of the early stages of pattern-directed self-assembly that template the subsequent morphology and (2) the dependence of the free-energy landscape on the incompatibility between the two blocks of the copolymer.

  16. The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes

    SciTech Connect

    Zhang, Bo; Edwards, Brian J.

    2015-06-07

    A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.

  17. The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes.

    PubMed

    Zhang, Bo; Edwards, Brian J

    2015-06-07

    A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.

  18. Large pore size nanoporous materials from the self-assembly of asymmetric bottlebrush block copolymers.

    PubMed

    Bolton, Justin; Bailey, Travis S; Rzayev, Javid

    2011-03-09

    Asymmetric polystyrene-polylactide (PS-PLA) bottlebrush block copolymers have been shown to self-assemble into a cylindrical morphology with large domain spacings. PLA cylinders can be selectively etched out of the shear-aligned polymer monoliths to generate nanoporous materials with an average cylindrical pore diameter of 55 nm. The remaining bottlebrush backbone provides a functional, hydrophilic coating inside the nanopores. This methodology significantly expands the range of pore sizes attainable in block copolymer based nanoporous materials.

  19. Controlling the Self-Assembly of Semiconducting Nanocrystals within Conjugated Rod-Coil Block Copolymers

    NASA Astrophysics Data System (ADS)

    McCulloch, Bryan L.; Urban, Jeff J.; Segalman, Rachel A.

    2010-03-01

    Blends of conjugated polymers and inorganic nanoparticles have been investigated for numerous optoelectronic applications however optimization relies on precise control over the nanoscale morphologies. Here, we show that conjugated rod-coil block copolymers can be designed to self assemble into controllable morphologies with the coil block templating nanocrystal location. We have constructed a model system where nanocrystals are blended with poly(alkoxy-phenylene vinylene-b-2-vinylpyridine) (PPV-b-P2VP), which self assembles into tunable morphologies. Semiconducting nanocrystals reside within the P2VP domain, due to the favorable interactions between P2VP and the nanoparticle surface as well as the exclusionary effects of the liquid crystalline PPV. The placement of the nanoparticles can be tuned by altering domain size, nanocrystal diameter and nanocrystal surface chemistry. These findings are used to develop a comprehensive understanding of the self assembly processes in conjugated rod-coil block copolymer nanocomposites.

  20. Poly(trimethylene carbonate)/Poly(malic acid) Amphiphilic Diblock Copolymers as Biocompatible Nanoparticles.

    PubMed

    Barouti, Ghislaine; Khalil, Ali; Orione, Clement; Jarnouen, Kathleen; Cammas-Marion, Sandrine; Loyer, Pascal; Guillaume, Sophie M

    2016-02-18

    Amphiphilic polycarbonate-poly(hydroxyalkanoate) diblock copolymers, namely, poly(trimethylene carbonate) (PTMC)-b-poly(β-malic acid) (PMLA), are reported for the first time. The synthetic strategy relies on commercially available catalysts and initiator. The controlled ring-opening polymerization (ROP) of trimethylene carbonate (TMC) catalyzed by the organic guanidine base 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), associated with iPrOH as an initiator, provided iPrO-PTMC-OH, which served as a macroinitiator in the controlled ROP of benzyl β-malolactonate (MLABe) catalyzed by the neodymium triflate salt (Nd(OTf)3). The resulting hydrophobic iPrO-PTMC-b-PMLABe-OH copolymers were then hydrogenolyzed into the parent iPrO-PTMC-b-PMLA-OH copolymers. A range of well-defined copolymers, featuring different sizes of segments (Mn,NMR up to 9300 g mol(-1) ; ÐM =1.28-1.40), were thus isolated in gram quantities, as evidenced by NMR spectroscopy, size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry, and contact angle analyses. Subsequently, PTMC-b-PMLA copolymers with different hydrophilic weight fractions (11-75 %) self-assembled in phosphate-buffered saline upon nanoprecipitation into well-defined nano-objects with Dh =61-176 nm, a polydispersity index <0.25, and a negative surface charge, as characterized by dynamic light scattering and zeta-potential analyses. In addition, these nanoparticles demonstrated no significant effect on cell viability at low concentrations, and a very low cytotoxicity at high concentrations only for PTMC-b-PMLA copolymers exhibiting hydrophilic fractions over 47 %, thus illustrating the potential of these copolymers as promising nanoparticles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Directed Self-Assembly of Triblock Copolymer on Chemical Patterns for Sub-10-nm Nanofabrication via Solvent Annealing.

    PubMed

    Xiong, Shisheng; Wan, Lei; Ishida, Yoshihito; Chapuis, Yves-Andre; Craig, Gordon S W; Ruiz, Ricardo; Nealey, Paul F

    2016-08-23

    Directed self-assembly (DSA) of block copolymers (BCPs) is a leading strategy to pattern at sublithographic resolution in the technology roadmap for semiconductors and is the only known solution to fabricate nanoimprint templates for the production of bit pattern media. While great progress has been made to implement block copolymer lithography with features in the range of 10-20 nm, patterning solutions below 10 nm are still not mature. Many BCP systems self-assemble at this length scale, but challenges remain in simultaneously tuning the interfacial energy atop the film to control the orientation of BCP domains, designing materials, templates, and processes for ultra-high-density DSA, and establishing a robust pattern transfer strategy. Among the various solutions to achieve domains that are perpendicular to the substrate, solvent annealing is advantageous because it is a versatile method that can be applied to a diversity of materials. Here we report a DSA process based on chemical contrast templates and solvent annealing to fabricate 8 nm features on a 16 nm pitch. To make this possible, a number of innovations were brought in concert with a common platform: (1) assembling the BCP in the phase-separated, solvated state, (2) identifying a larger process window for solvated triblock vs diblock BCPs as a function of solvent volume fraction, (3) employing templates for sub-10-nm BCP systems accessible by lithography, and (4) integrating a robust pattern transfer strategy by vapor infiltration of organometallic precursors for selective metal oxide synthesis to prepare an inorganic hard mask.

  2. Periodic nanostructures from self assembled wedge-type block-copolymers

    SciTech Connect

    Xia, Yan; Sveinbjornsson, Benjamin R.; Grubbs, Robert H.; Weitekamp, Raymond; Miyake, Garret M.; Piunova, Victoria; Daeffler, Christopher Scot

    2015-06-02

    The invention provides a class of wedge-type block copolymers having a plurality of chemically different blocks, at least a portion of which incorporates a wedge group-containing block providing useful properties. For example, use of one or more wedge group-containing blocks in some block copolymers of the invention significantly inhibits chain entanglement and, thus, the present block copolymers materials provide a class of polymer materials capable of efficient molecular self-assembly to generate a range of structures, such as periodic nanostructures and microstructures. Materials of the present invention include copolymers having one or more wedge group-containing blocks, and optionally for some applications copolymers also incorporating one or more polymer side group-containing blocks. The present invention also provides useful methods of making and using wedge-type block copolymers.

  3. Thermoreversible Morphology and Conductivity of a Conjugated Polymer Network Embedded in Block Copolymer Self-Assemblies

    DOE PAGES

    Han, Youngkyu; Carrillo, Jan-Michael Y.; Zhang, Zhe; ...

    2016-07-19

    Self-assembly of block copolymers provides numerous opportunities to create functional materials, utilizing self-assembled microdomains with a variety of morphology and periodic architectures as templates for functional nanofillers. Here new progress is reported toward the fabrication of thermally responsive and electrically conductive polymeric self-assemblies made from a water-soluble poly(thiophene) derivative with short poly(ethylene oxide) side chains and Pluronic L62 block copolymer solution in water. The structural and electrical properties of conjugated polymer-embedded self-assembled architectures are investigated by combining small-angle neutron and X-ray scattering, coarse-grained molecular dynamics simulations, and impedance spectroscopy. The L62 solution template organizes the conjugated polymers by stably incorporatingmore » them into the hydrophilic domains thus inhibiting aggregation. The changing morphology of L62 during the micellarto- lamellar phase transition defines the embedded conjugated polymer network. As a result, the conductivity is strongly coupled to the structural change of the templating L62 phase and exhibits thermally reversible behavior with no signs of quenching of the conductivity at high temperature. In conclusion, this study shows promise for enabling more flexibility in processing and utilizing water-soluble conjugated polymers in aqueous solutions for self-assembly based fabrication of stimuli-responsive nanostructures and sensory materials.« less

  4. Thermoreversible Morphology and Conductivity of a Conjugated Polymer Network Embedded in Block Copolymer Self-Assemblies

    SciTech Connect

    Han, Youngkyu; Carrillo, Jan-Michael Y.; Zhang, Zhe; Li, Yunchao; Hong, Kunlun; Sumpter, Bobby G.; Ohl, Michael; Paranthaman, Mariappan Parans; Smith, Gregory S.; Do, Changwoo

    2016-07-19

    Self-assembly of block copolymers provides numerous opportunities to create functional materials, utilizing self-assembled microdomains with a variety of morphology and periodic architectures as templates for functional nanofillers. Here new progress is reported toward the fabrication of thermally responsive and electrically conductive polymeric self-assemblies made from a water-soluble poly(thiophene) derivative with short poly(ethylene oxide) side chains and Pluronic L62 block copolymer solution in water. The structural and electrical properties of conjugated polymer-embedded self-assembled architectures are investigated by combining small-angle neutron and X-ray scattering, coarse-grained molecular dynamics simulations, and impedance spectroscopy. The L62 solution template organizes the conjugated polymers by stably incorporating them into the hydrophilic domains thus inhibiting aggregation. The changing morphology of L62 during the micellarto- lamellar phase transition defines the embedded conjugated polymer network. As a result, the conductivity is strongly coupled to the structural change of the templating L62 phase and exhibits thermally reversible behavior with no signs of quenching of the conductivity at high temperature. In conclusion, this study shows promise for enabling more flexibility in processing and utilizing water-soluble conjugated polymers in aqueous solutions for self-assembly based fabrication of stimuli-responsive nanostructures and sensory materials.

  5. Thermoreversible Morphology and Conductivity of a Conjugated Polymer Network Embedded in Block Copolymer Self-Assemblies.

    PubMed

    Han, Youngkyu; Carrillo, Jan-Michael Y; Zhang, Zhe; Li, Yunchao; Hong, Kunlun; Sumpter, Bobby G; Ohl, Michael; Paranthaman, Mariappan Parans; Smith, Gregory S; Do, Changwoo

    2016-09-01

    Self-assembly of block copolymers provides numerous opportunities to create functional materials, utilizing self-assembled microdomains with a variety of morphology and periodic architectures as templates for functional nanofillers. Here new progress is reported toward the fabrication of thermally responsive and electrically conductive polymeric self-assemblies made from a water-soluble poly(thiophene) derivative with short poly(ethylene oxide) side chains and Pluronic L62 block copolymer solution in water. The structural and electrical properties of conjugated polymer-embedded self-assembled architectures are investigated by combining small-angle neutron and X-ray scattering, coarse-grained molecular dynamics simulations, and impedance spectroscopy. The L62 solution template organizes the conjugated polymers by stably incorporating them into the hydrophilic domains thus inhibiting aggregation. The changing morphology of L62 during the micellar-to-lamellar phase transition defines the embedded conjugated polymer network. As a result, the conductivity is strongly coupled to the structural change of the templating L62 phase and exhibits thermally reversible behavior with no signs of quenching of the conductivity at high temperature. This study shows promise for enabling more flexibility in processing and utilizing water-soluble conjugated polymers in aqueous solutions for self-assembly based fabrication of stimuli-responsive nanostructures and sensory materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Thermoreversible Morphology and Conductivity of a Conjugated Polymer Network Embedded in Block Copolymer Self-Assemblies

    SciTech Connect

    Han, Youngkyu; Carrillo, Jan-Michael Y.; Zhang, Zhe; Li, Yunchao; Hong, Kunlun; Sumpter, Bobby G.; Ohl, Michael; Paranthaman, Mariappan Parans; Smith, Gregory S.; Do, Changwoo

    2016-07-19

    Self-assembly of block copolymers provides numerous opportunities to create functional materials, utilizing self-assembled microdomains with a variety of morphology and periodic architectures as templates for functional nanofillers. Here new progress is reported toward the fabrication of thermally responsive and electrically conductive polymeric self-assemblies made from a water-soluble poly(thiophene) derivative with short poly(ethylene oxide) side chains and Pluronic L62 block copolymer solution in water. The structural and electrical properties of conjugated polymer-embedded self-assembled architectures are investigated by combining small-angle neutron and X-ray scattering, coarse-grained molecular dynamics simulations, and impedance spectroscopy. The L62 solution template organizes the conjugated polymers by stably incorporating them into the hydrophilic domains thus inhibiting aggregation. The changing morphology of L62 during the micellarto- lamellar phase transition defines the embedded conjugated polymer network. As a result, the conductivity is strongly coupled to the structural change of the templating L62 phase and exhibits thermally reversible behavior with no signs of quenching of the conductivity at high temperature. In conclusion, this study shows promise for enabling more flexibility in processing and utilizing water-soluble conjugated polymers in aqueous solutions for self-assembly based fabrication of stimuli-responsive nanostructures and sensory materials.

  7. Nanoparticle-directed self-assembly of amphiphilic block-copolymers

    NASA Astrophysics Data System (ADS)

    Park, So-Jung

    2011-03-01

    The self-assembly of nanoparticles and amphiphilic polymers provides a powerful tool for the fabrication of functional composite materials for a range of applications spanning from nanofabrication to medicine. Here, we present how the incorporation of nanoparticles affects the self-assembly behavior of amphiphilic block-copolymers and how to control the morphology of nanoparticle-encapsulating polymer assemblies. Based on the approach, we have prepared various types of well-defined nanoparticle-encapsulating polymeric nanostructures, including polymersomes packed with magnetic nanoparticles and unique cavity-like quantum dot assembles. We found that the incorporation of nanoparticles drastically affects the self-assembly structure of block-copolymers by modifying the relative volume ratio between the hydrophobic block and the hydrophilic block. In addition, the nanoparticle-polymer and nanoparticle-solvent interactions impact the arrangement and the hybridization of nanoparticles in polymer matrix. These findings should form the basis for the design rules of the self-assembly of nanoparticles and polymer amphiphiles, which will allow one to create new hybrid structures with predesigned morphology and properties. Furthermore, we demonstrated that the morphology of nanoparticle-encapsulating polymer assemblies significantly affects their properties such as magnetic relaxation properties, underscoring the importance of the overall self-assembly structure and the nanoparticle arrangement in polymer matrixes. This work was supported by the NSF career award, the ARO young investigator award, and the MRSEC seed award (University of Pennsylvania).

  8. Selective directed self-assembly of coexisting morphologies using block copolymer blends

    SciTech Connect

    Stein, A.; Wright, G.; Yager, K. G.; Doerk, G. S.; Black, C. T.

    2016-08-02

    Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. We expand on traditional DSA chemical patterning. Moreover, a blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This contrasts with typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist.

  9. Selective directed self-assembly of coexisting morphologies using block copolymer blends

    NASA Astrophysics Data System (ADS)

    Stein, A.; Wright, G.; Yager, K. G.; Doerk, G. S.; Black, C. T.

    2016-08-01

    Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. Here we expand on traditional DSA chemical patterning. A blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This is in contrast to the typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist.

  10. Sequential Block Copolymer Self-Assemblies Controlled by Metal-Ligand Stoichiometry.

    PubMed

    Yin, Liyuan; Wu, Hongwei; Zhu, Mingjie; Zou, Qi; Yan, Qiang; Zhu, Liangliang

    2016-06-28

    While numerous efforts have been devoted to developing easy-to-use probes based on block copolymers for detecting analytes due to their advantages in the fields of self-assembly and sensing, a progressive response on block copolymers in response to a continuing chemical event is not readily achievable. Herein, we report the self-assembly of a 4-piperazinyl-1,8-naphthalimide based functional block copolymer (PS-b-PN), whose self-assembly and photophysics can be controlled by the stoichiometry-dependent metal-ligand interaction upon the side chain. The work takes advantages of (1) stoichiometry-controlled coordination-structural transformation of the piperazinyl moiety on PS-b-PN toward Fe(3+) ions, thereby resulting in a shrinkage-expansion conversion of the self-assembled nanostructures in solution as well as in thin film, and (2) stoichiometry-controlled competition between photoinduced electron transfer and spin-orbital coupling process upon naphthalimide fluorophore leading to a boost-decline emission change of the system. Except Fe(3+) ions, such a stoichiometry-dependent returnable property cannot be observed in the presence of other transition ions. The strategy for realizing the dual-channel sequential response on the basis of the progressively alterable nanomorphologies and emissions might provide deeper insights for the further development of advanced polymeric sensors.

  11. Aqueous Self-Assembly of Y-Shaped Amphiphilic Block Copolymers into Giant Vesicles.

    PubMed

    Li, Hanping; Jin, Yong; Fan, Baozhu; Lai, Shuangquan; Sun, Xiaopeng; Qi, Rui

    2017-02-06

    The preparation and aqueous self-assembly of newly Y-shaped amphiphilic block polyurethane (PUG) copolymers are reported here. These amphiphilic copolymers, designed to have two hydrophilic poly(ethylene oxide) (PEO) tails and one hydrophobic alkyl tail via a two-step coupling reaction, can self-assemble into giant unilamellar vesicles (GUVs) (diameter ≥ 1000 nm) with a direct dissolution method in aqueous solution, depending on their Y-shaped structures and initial concentrations. More interesting, the copolymers can self-assemble into various distinct nano-/microstructures, such as spherical micelles, small vesicles, and GUVs, with the increase of their concentrations. The traditional preparation methods of GUVs generally need conventional amphiphilic molecules and additional complicated conditions, such as alternating electrical field, buffer solution, or organic solvent. Therefore, the self-assembly of Y-shaped PUGs with a direct dissolution method in aqueous solution demonstrated in this study supplies a new clue to fabricate GUVs based on the geometric design of amphiphilic polymers.

  12. Self-assembly of ABC triblock copolymers under 3D soft confinement: a Monte Carlo study.

    PubMed

    Yan, Nan; Zhu, Yutian; Jiang, Wei

    2016-01-21

    Under three-dimensional (3D) soft confinement, block copolymers can self-assemble into unique nanostructures that cannot be fabricated in an un-confined space. Linear ABC triblock copolymers containing three chemically distinct polymer blocks possess relatively complex chain architecture, which can be a promising candidate for the 3D confined self-assembly. In the current study, the Monte Carlo technique was applied in a lattice model to study the self-assembly of ABC triblock copolymers under 3D soft confinement, which corresponds to the self-assembly of block copolymers confined in emulsion droplets. We demonstrated how to create various nanostructures by tuning the symmetry of ABC triblock copolymers, the incompatibilities between different block types, and solvent properties. Besides common pupa-like and bud-like nanostructures, our simulations predicted various unique self-assembled nanostructures, including a striped-pattern nanoparticle with intertwined A-cages and C-cages, a pyramid-like nanoparticle with four Janus B-C lamellae adhered onto its four surfaces, an ellipsoidal nanoparticle with a dumbbell-like A-core and two Janus B-C lamellae and a Janus B-C ring surrounding the A-core, a spherical nanoparticle with a A-core and a helical Janus B-C stripe around the A-core, a cubic nanoparticle with a cube-shape A-core and six Janus B-C lamellae adhered onto the surfaces of the A-cube, and a spherical nanoparticle with helical A, B and C structures, from the 3D confined self-assembly of ABC triblock copolymers. Moreover, the formation mechanisms of some typical nanostructures were also examined by the variations of the contact numbers with time and a series of snapshots at different Monte Carlo times. It is found that ABC triblock copolymers usually aggregate into a loose aggregate at first, and then the microphase separation between A, B and C blocks occurs, resulting in the formation of various nanostructures.

  13. Nanoscale arrangement of diblock copolymer micelles with Au nanorods

    NASA Astrophysics Data System (ADS)

    Kim, Hwan; Lim, Yirang; Kim, Sehee; Kim, Sung-Soo; Sohn, Byeong-Hyeok

    2014-11-01

    We fabricated a single-layered film consisting of spherical micelles of diblock copolymers and one-dimensional Au nanorods that were surface modified with the same polymer as the corona block of the copolymers. When the diameters of micelles were larger than the lengths of the nanorods, spherical micelles arranged in a hexagonal configuration surrounded by nanorods with their long axes perpendicular to the radial direction of the micelles. This arrangement provided selective organization of the Au nanorods and Ag nanoparticles which were selectively synthesized within the cores of the copolymer micelles. Thus, position-selective arrangement of Au nanorods and Ag nanoparticles was demonstrated at the nanometer scale such that a homogenous distribution of two different nanomaterials over a large area without aggregation was achieved.

  14. Universality between Experiment and Simulation of a Diblock Copolymer Melt

    NASA Astrophysics Data System (ADS)

    Beardsley, Thomas M.; Matsen, Mark W.

    2016-11-01

    The equivalent behavior among analogous block copolymer systems involving chemically distinct molecules or mathematically different models has long hinted at an underlying universality, but only recently has it been rigorously demonstrated by matching results from different simulations. The profound implication of universality is that simple coarse-grained models can be calibrated so as to provide quantitatively accurate predictions to experiment. Here, we provide the first compelling demonstration of this by simulating a polyisoprene-polylactide diblock copolymer melt using a previously calibrated lattice model. The simulation successfully predicts the peak in the disordered-state structure function, the position of the order-disorder transition, and the latent heat of the transition in excellent quantitative agreement with experiment. This could mark a new era of precision in the field of block copolymer research.

  15. Universality between Experiment and Simulation of a Diblock Copolymer Melt.

    PubMed

    Beardsley, Thomas M; Matsen, Mark W

    2016-11-18

    The equivalent behavior among analogous block copolymer systems involving chemically distinct molecules or mathematically different models has long hinted at an underlying universality, but only recently has it been rigorously demonstrated by matching results from different simulations. The profound implication of universality is that simple coarse-grained models can be calibrated so as to provide quantitatively accurate predictions to experiment. Here, we provide the first compelling demonstration of this by simulating a polyisoprene-polylactide diblock copolymer melt using a previously calibrated lattice model. The simulation successfully predicts the peak in the disordered-state structure function, the position of the order-disorder transition, and the latent heat of the transition in excellent quantitative agreement with experiment. This could mark a new era of precision in the field of block copolymer research.

  16. Sacrificial-post templating method for block copolymer self-assembly.

    PubMed

    Tavakkoli, Amir K G; Nicaise, Samuel M; Hannon, Adam F; Gotrik, Kevin W; Alexander-Katz, Alfredo; Ross, Caroline A; Berggren, Karl K

    2014-02-12

    A sacrificial-post templating method is presented for directing block copolymer self-assembly to form nanostructures consisting of monolayers and bilayers of microdomains. In this approach, the topographical post template is removed after self-assembly and therefore is not incorporated into the final microdomain pattern. Arrays of nanoscale holes of different shapes and symmetries, including mesh structures and perforated lamellae with a bimodal pore size distribution, are produced. The ratio of the pore sizes in the bimodal distributions can be varied via the template pitch, and agrees with predictions of self consistent field theory.

  17. Coil fraction-dependent phase behaviour of a model globular protein–polymer diblock copolymer

    SciTech Connect

    Thomas, Carla S.; Olsen, Bradley D.

    2014-01-01

    The self-assembly of the model globular protein–polymer block copolymer mCherry-b-poly(N-isopropyl acrylamide) is explored across a range of polymer coil fractions from 0.21 to 0.82 to produce a phase diagram for these materials as a function of molecular composition. Overall, four types of morphologies were observed: hexagonally packed cylinders, perforated lamellae, lamellae, and disordered nanostructures. Across all coil fractions and morphologies, a lyotropic re-entrant order–disorder transition in water was observed, with disordered structures below 30 wt% and above 70 wt% and well-ordered morphologies at intermediate concentrations. Solid state samples prepared by solvent evaporation show moderately ordered structures similar to those observed in 60 wt% solutions, suggesting that bulk structures result from kinetic trapping of morphologies which appear at lower concentrations. While highly ordered cylindrical nanostructures are observed around a bioconjugate polymer volume fraction of 0.3 and well-ordered lamellae are seen near a volume fraction of 0.6, materials at lower or higher coil fractions become increasingly disordered. Notable differences between the phase behaviour of globular protein–polymer block copolymers and coil–coil diblock copolymers include the lack of spherical nanostructures at either high or low polymer coil fractions as well as shifted phase boundaries between morphologies which result in an asymmetric phase diagram.

  18. Solution Self-Assembly of Globular Protein-Polymer Conjugate Block Copolymers

    NASA Astrophysics Data System (ADS)

    Olsen, Bradley

    2014-03-01

    Controlling the nanostructured self-assembly of globular proteins and enzymes can significantly advance the applications of soft materials as catalysts, sensors, and medical materials. However, the incorporation of globular proteins as one block in the block copolymer introduces changes in chain shape, chain entropy, and specific interactions that significantly impact the thermodynamics of self-assembly. Here, we explore the self-assembly of model globular protein-polymer block copolymers in concentrated solutions to form nanostructured materials. A phase diagram as a function of concentration and temperature for a model material mCherry-poly(N-isopropylacrylamide) (PNIPAM) is asymmetric, showing hexagonal cylinders for coil fractions less than 0.5 and a lamellar ordering for coil fractions greater than 0.5, divided by a narrow region of hexagonally perforated lamellae. Order-order transitions as a function of temperature are driven by the thermoresponsive desolvation of PNIPAM. Surprisingly, the materials exhibit reentrant order-disorder transition behavior, such that the conjugate block copolymers are disordered at both low and high concentrations but well-ordered at intermediate concentrations. Changing the polymer chemistry to monomers with different types of hydrogen bonding results in significant changes in the self-assembly, including the observation of a cubic phase that shows the same scattering pattern as the gyroid phase observed in traditional block copolymers. The choice of polymer also has a strong impact on the order-disorder transition concentration, demonstrating that the polymer-protein interaction plays a significant role in governing self-assembly in solution. Consistent with this effect, the order-disorder transition concentration is minimized in symmetric conjugates. Changing the protein from mCherry to myoglobin results in a reduction in ordering, suggesting that the regularity of the protein shape is important. This research was supported by

  19. Homochiral Evolution in Self-Assembled Chiral Polymers and Block Copolymers.

    PubMed

    Wen, Tao; Wang, Hsiao-Fang; Li, Ming-Chia; Ho, Rong-Ming

    2017-03-03

    The significance of chirality transfer is not only involved in biological systems, such as the origin of homochiral structures in life but also in man-made chemicals and materials. How the chiral bias transfers from molecular level (molecular chirality) to helical chain (conformational chirality) and then to helical superstructure or phase (hierarchical chirality) from self-assembly is vital for the chemical and biological processes in nature, such as communication, replication, and enzyme catalysis. In this Account, we summarize the methodologies for the examination of homochiral evolution at different length scales based on our recent studies with respect to the self-assembly of chiral polymers and chiral block copolymers (BCPs*). A helical (H*) phase to distinguish its P622 symmetry from that of normal hexagonally packed cylinder phase was discovered in the self-assembly of BCPs* due to the chirality effect on BCP self-assembly. Enantiomeric polylactide-containing BCPs*, polystyrene-b-poly(l-lactide) (PS-PLLA) and polystyrene-b-poly(d-lactide) (PS-PDLA), were synthesized for the examination of homochiral evolution. The optical activity (molecular chirality) of constituted chiral repeating unit in the chiral polylactide is detected by electronic circular dichroism (ECD) whereas the conformational chirality of helical polylactide chain can be explicitly determined by vibrational circular dichroism (VCD). The H* phases of the self-assembled polylactide-containing BCPs* can be directly visualized by 3D transmission electron microscopy (3D TEM) technique at which the handedness (hierarchical chirality) of the helical nanostructure is thus determined. The results from the ECD, VCD, and 3D TEM for the investigated chirality at different length scales suggest the homochiral evolution in the self-assembly of the BCPs*. For chiral polylactides, twisted lamellae in crystalline banded spherulite can be formed by dense packing scheme and effective interactions upon helical

  20. Polymerization of hydrogels inside self-assembled block copolymer vesicles.

    PubMed

    Gaspard, Jeffery; Hahn, Mariah S; Silas, James A

    2009-11-17

    Block copolymer vesicles are powerful tools for investigating cell adhesion since they display the fluid, deformable, semipermeable membrane properties of lipid vesicles while having greater chemical and mechanical stability. The aim of the present study was to fabricate block copolymer vesicles containing hydrogel interiors in order to extend achievable vesicle properties and, thereby, their range of cell-like behaviors. Block copolymer vesicles based on poly(butadiene-b-ethylene oxide) were demonstrated to compartmentalize and retain acrylamide solutions through particle dialysis and to allow for subsequent in situ hydrogel polymerization. Small molecule leakage studies of the resulting particles indicated that the cross-link density of the hydrogel interiors had minimal impact on vesicle permeability to small molecules (<430 Da) relative to vesicle membrane properties. In contrast, particle deformation analyses indicated that initial vesicle surface approach and adhesion was dominated by its membrane properties, whereas its ultimate deformation was primarily governed by the hydrogel interior. Thus, the hydrogel-containing vesicles allowed orthogonal control of particle surface and mechanical properties. Analysis of particle behavior in terms of Gibb's free energy minimization indicated that vesicle adhesion energy, membrane tension, and internal osmotic pressure dominated particle adhesion and deformation. Combined, the present work demonstrates the potential for designing compartmentalized, hierarchical polymer-based cell mimics with broadly tunable dynamic-mechanical properties and surface properties.

  1. Preparations, Properties, and Applications of Periodic Nano Arrays using Anodized Aluminum Oxide and Di-block Copolymer

    NASA Astrophysics Data System (ADS)

    Noh, Kunbae

    2011-12-01

    Self-ordered arrangements observed in various materials systems such as anodic aluminum oxide, polystyrene nanoparticles, and block copolymer are of great interest in terms of providing new opportunities in nanofabrication field where lithographic techniques are broadly used in general. Investigations on self-assembled nano arrays to understand how to obtain periodic nano arrays in an efficient yet inexpensive way, and how to realize advanced material and device systems thereof, can lead to significant impacts on science and technology for many forefront device applications. In this thesis, various aspects of periodic nano-arrays have been discussed including novel preparations, properties and applications of anodized aluminum oxide (AAO) and PS-b-P4VP (S4VP) di-block copolymer self-assembly. First, long-range ordered AAO arrays have been demonstrated. Nanoimprint lithography (NIL) process allowed a faithful pattern transfer of the imprint mold pattern onto Al thin film, and interesting self-healing and pattern tripling phenomena were observed, which could be applicable towards fabrication of the NIL master mold having highly dense pattern over large area, useful for fabrication of a large-area substrate for predictable positioning of arrayed devices. Second, S4VP diblock copolymer self-assembly and S4VP directed AAO self-assembly have been demonstrated in the Al thin film on Si substrate. Such a novel combination of two dissimilar self-assembly techniques demonstrated a potential as a versatile tool for nanopatterning formation on a Si substrate, capable of being integrated into Si process technology. As exemplary applications, vertically aligned Ni nanowires have been synthesized into an S4VP-guided AAO membrane on a Si substrate in addition to anti-dot structured [Co/Pd]n magnetic multilayer using S4VP self assembly. Third, a highly hexagonally ordered, vertically parallel aluminum oxide nanotube array was successfully fabricated via hard anodization technique

  2. Ion gels by self-assembly of a triblock copolymer in an ionic liquid.

    PubMed

    He, Yiyong; Boswell, Paul G; Bühlmann, Philippe; Lodge, Timothy P

    2007-05-10

    We report a new way of developing ion gels through the self-assembly of a triblock copolymer in a room-temperature ionic liquid. Transparent ion gels were achieved by gelation of a poly(styrene-block-ethylene oxide-block-styrene) (SOS) triblock copolymer in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) with as low as 5 wt % SOS triblock copolymer. The gelation behavior, ionic conductivity, rheological properties, and microstructure of the ion gels were investigated. The ionic conductivity of the ion gels is only modestly affected by the triblock copolymer network. Its temperature dependence nearly tracks that of the bulk ionic liquid viscosity. The ion gels are thermally stable up to at least 100 degrees C and possess significant mechanical strength. The results presented here suggest that triblock copolymer gelation is a promising way to develop highly conductive ion gels and provides many advantages in terms of variety and processing.

  3. Self-assembled morphologies of ABA triblock copolymer brushes in selective solvents.

    PubMed

    Xu, Jihua; Yin, Yuhua; Wang, Zheng; Jiang, Run; Li, Baohui; Shi, An-Chang

    2013-03-21

    A simulated annealing method is used to investigate the self-assembled morphologies of symmetric ABA triblock copolymer brushes, formed by one end of the A-blocks tethered onto a planar surface, immersed in a solvent selective for the middle B-blocks. The morphological dependences of the brushes on polymer grafting density and block lengths are investigated systematically. Phase diagrams for systems with different grafting densities are constructed. The simulation results show that the grafted amphiphilic triblock copolymers can self-assemble to form a variety of complicated morphologies which can be classified in terms of the number of A-rich layers in the morphology. In particular, the formation of the structures with one A-rich layer or called "folded" brush structures is consistent with the speculation from the experimental studies of ABA triblock copolymer brushes. More detailed structures depend on the grafting density and the lengths of the blocks. Furthermore, at a high grafting density, the effects of the lengths of blocks and the interaction energies between different species in the system on the conformation of chains are investigated to illustrate the formation mechanisms of self-assembled morphologies of the amphiphilic triblock copolymer brushes.

  4. Process-directed self-assembly of block copolymers: a computer simulation study.

    PubMed

    Müller, Marcus; Sun, De-Wen

    2015-05-20

    The free-energy landscape of self-assembling block copolymer systems is characterized by a multitude of metastable minima and concomitant protracted relaxation times of the morphology. Tailoring rapid changes (quench) of thermodynamic conditions, one can reproducibly trap the ensuing kinetics of self-assembly in a specific metastable state. To this end, it is necessary to (1) control the generation of well-defined, highly unstable states and (2) design the unstable state such that the ensuing spontaneous kinetics of structure formation reaches the desired metastable morphology. This process-directed self-assembly provides an alternative to fine-tuning molecular architecture by synthesis or blending, for instance, in order to fabricate complex network structures. Comparing our simulation results to recently developed free-energy techniques, we highlight the importance of non-equilibrium molecular conformations in the starting state and motivate the significance of the local conservation of density.

  5. Correlating self-assembly of block copolymers for their application in synthesis of gold nanoparticles.

    PubMed

    Ray, Debes; Aswall, Vinod Kumar; Srivastava, Dinesh

    2011-03-01

    We report the role of self-assembly of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) block copolymers for the synthesis of gold nanoparticles from hydrogen tetrachloroaureate (III) hydrate (HAuCl4 x 3H2O) in aqueous solution. The synthesis has been carried out using three different block copolymers P85 [EO26PO39EO26], F88 [EO103PO39EO103] and P105 [EO37PO56EO37], which not only have varying molecular weight but also differ in hydrophobicity to hydrophilicity ratio. The formation of gold nanoparticles is confirmed by the UV-Visible Spectroscopy. Transmission electron microscopy (TEM) provides the sizes of the nanoparticles formed in these systems. Small-Angle Neutron Scattering (SANS) and Dynamic Light Scattering (DLS) techniques are used to correlate the self-assembly of block copolymer to their propensity to form gold nanoparticles. The yield is found to be in the order P105 > P85 > F88 and is related to the higher tendency of block copolymer to self-assemble to give greater yield of gold nanoparticles. For all the block copolymers, SANS and DLS results suggests that the yield in the synthesis does not always increases with the salt concentration and is limited due to the fact that most of the block copolymers remain unassociated with the gold nanoparticles. By making use of these unassociated block copolymers, we propose two methods (i) step addition method and (ii) additional reductant method, where the synthesis yield of gold nanoparticles can be enhanced by manifold.

  6. Self-Assembled Morphologies of Linear and Miktoarm Star Triblock Copolymer Monolayers.

    PubMed

    Deng, Hanlin; Li, Weihua; Qiu, Feng; Shi, An-Chang

    2017-04-12

    Monolayers of linear and miktoarm star ABC triblock copolymers with equal A and C blocks are investigated using the self-consistent field theory. The monolayers of ABC triblock copolymers are formed between two parallel surfaces that are attractive to the A and C blocks. The repulsive interaction parameter $\\chi_{AC}N$ between the A and C blocks is chosen to be weaker than the A/B and B/C interactions, quantified by $\\chi_{AB}N$ and $\\chi_{BC}N$, such that the B blocks are confined at the A/C interface, resulting in various B-domains with different geometries and arrangements. It is observed that two variables, the strength of the surface fields and the film thickness, are dominant factors controlling the self-assembly of the B blocks into various morphologies. For the linear triblock copolymers, the morphologies of B domains include disks, stripes (parallel cylinders), and hexagonal network (inverse disks). For the miktoarm star triblock copolymers, the competition between the tendency to align the junction points along a straight line and the constraint on their arrangement from the surface interactions leads to richer ordered morphologies. As a result of packing the junction points of the ABC miktoarm star copolymers, a counterintuitive phase sequence from low curvature phases to high curvature phases with increasing the length of B block is predicted. The study indicates that the self-assembly of monolayers of ABC triblock copolymers provides an interesting platform to engineer novel morphologies.

  7. Controlled self-assembly of conjugated rod-coil block copolymers for applications in organic optoelectronics

    NASA Astrophysics Data System (ADS)

    Tao, Yuefei

    Organic electronics are of great interest in manufacturing light weight, mechanical flexible, and inexpensive large area devices. While significant improvements have been made over the last several years and it is now clear that morphology on the lengthscale of exciton diffusion (10nm) is of crucial importance, a clear relationship between structure and device properties has not emerged. This lack of understanding largely emerges from an inability to control morphology on this lengthscale. This thesis will center around an approach, based on block copolymer self-assembly, to generate equilibrium nanostructures on the 10 nm lengthscale of exciton diffusion and study their effects on device performance. Self-assembly of semiconducting block copolymers is complicated by the non-classical chain shape of conjugated polymers. Unlike classical polymers, the chains do not assume a Gaussian coil shape which is stretched near block copolymer interfaces, instead the chains are elongated and liquid crystalline. Previous work has demonstrated how these new molecular interactions and shapes control the phase diagram of so-called rod-coil block copolymers. Here, we will focus on controlling domain size, orientation, and chemical structure. While domain size can be controlled directly through molecular weight, this requires significant additional synthesis of domain size is to be varied. Here, the domain size is controlled by blending homopolymers into a self-assembling rod-coil block copolymer. When coil-like blocks are incorporated, the domains swell, as expected. When rod-like blocks are incorporated, they interdigitate with the rods of the block copolymers. This results in an increase in interfacial area which forces the coils to rearrange and an overall decrease in domain size with increasing rod content. Control over lamellar orientation is crucial in order to design and control charge transport pathways and exciton recombination or separation interfaces. While numerous

  8. Terminal groups control self-assembly of amphiphilic block copolymers in solution

    NASA Astrophysics Data System (ADS)

    Grzelakowski, M.; Kita-Tokarczyk, K.

    2016-03-01

    The terminal groups of amphiphilic block copolymers are shown to control macromolecular self-assembly in aqueous solutions, in the micellar/lamellar region of the phase diagram. At the same concentration and using the same self-assembly conditions, dramatic differences are observed in polymer hydration and the resulting nano-/microstructure for two series of polymers with identical block chemistry and hydrophilic-lipophilic balance (HLB). This suggests a strong contribution from end groups to the hydration as the initial step of the self-assembly process, and could be conveniently used to guide the particle morphology and size. Additionally, for polymers with those head groups which drive vesicular structures, differences in membrane organization affect their physical properties, such as permeability.The terminal groups of amphiphilic block copolymers are shown to control macromolecular self-assembly in aqueous solutions, in the micellar/lamellar region of the phase diagram. At the same concentration and using the same self-assembly conditions, dramatic differences are observed in polymer hydration and the resulting nano-/microstructure for two series of polymers with identical block chemistry and hydrophilic-lipophilic balance (HLB). This suggests a strong contribution from end groups to the hydration as the initial step of the self-assembly process, and could be conveniently used to guide the particle morphology and size. Additionally, for polymers with those head groups which drive vesicular structures, differences in membrane organization affect their physical properties, such as permeability. Electronic supplementary information (ESI) available: Fig. S1: Particle diameters for hydrated NH2-ABA-NH2 polymers with different degrees of functionalization; Fig. S2: TEM characterization of compound micelles from BA-OH polymer after extrusion; Fig. S3: Cryo-TEM and stopped flow characterization of lipid vesicles; Fig. S4 and S5: NMR spectra for ABA and BA polymers

  9. Conformational Asymmetry and Quasicrystal Approximants in Linear Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Schulze, Morgan W.; Lewis, Ronald M.; Lettow, James H.; Hickey, Robert J.; Gillard, Timothy M.; Hillmyer, Marc A.; Bates, Frank S.

    2017-05-01

    Small angle x-ray scattering experiments on three model low molar mass diblock copolymer systems containing minority polylactide and majority hydrocarbon blocks demonstrate that conformational asymmetry stabilizes the Frank-Kasper σ phase. Differences in block flexibility compete with space filling at constant density inducing the formation of polyhedral shaped particles that assemble into this low symmetry ordered state with local tetrahedral coordination. These results confirm predictions from self-consistent field theory that establish the origins of symmetry breaking in the ordering of block polymer melts subjected to compositional and conformational asymmetry.

  10. Synthesis and Self-Assembly of Rod2Coil Miktoarm Star Copolymers of Poly(3-dodecxylthiophene) and Poly(methyl methacrylate) with high rod fractions

    NASA Astrophysics Data System (ADS)

    Park, Jicheol; Moon, Hong Chul; Choi, Chung-Royng; Kim, Jin Kon

    2015-03-01

    Poly(3-dodecylthiophene)-b-poly(methyl methacrylate) diblock copolymer (P3DDT- b-PMMA) can self-assembled into various microdomains such as spheres, cylinders, and lamellae depending on weight fraction of P3DDT. However, only filbril morphology was formed when weight fraction of P3DDT (wP 3 DDT) was major (wP 3 DDT ~ 0.76). Here, we introduce a new approach to obtain microdomain structures even at high wP 3 DDT by using well-defined A2B miktoarm star copolymer composed of P3DDT and PMMA ((P3DDT)2PMMA. We found via small angle X-ray scattering and transmission electron microscopy that (P3DDT)2PMMA showed PMMA cylinder packed hexagonally in the matrix of P3DDT and body-centered-cubic spheres of PMMA for wP 3 DDT of 0.66 and 0.75, respectively. This because of much reduction of the rod-rod interaction in (P3DDT)2PMMA compared with P3DDT- b-PMMA diblock copolymers.

  11. Controlling the Self-Assembly of Inorganic Nanoparticles within Conjugated Rod-Coil Block Copolymers

    NASA Astrophysics Data System (ADS)

    McCulloch, Bryan; Segalman, Rachel

    2011-03-01

    Blends of conjugated polymers and inorganic nanoparticles have been investigated for numerous applications however optimization relies on precise control over the nanoscale morphology. We have designed a conjugated rod-coil block copolymer consisting of poly(3-(2'-ethyl)hexylthiophene)-b-poly(2-vinyl pyridine) (P3EHT-b-P2VP) which self assembles into controllable morphologies. Inorganic nanoparticles reside within the P2VP domain due to the favorable interactions between P2VP and the nanoparticle surface as well as the exclusionary effects of the liquid crystalline P3EHT. The nanoparticle location can be tuned by altering nanocrystal surface chemistry. These findings are used to develop a comprehensive understanding of the self assembly processes in conjugated rod-coil block copolymer nanocomposites.

  12. Self-assembly of miktoarm star-like ABn block copolymers: from wet to dry brushes.

    PubMed

    Xu, Yuci; Wang, Chao; Zhong, Shuo; Li, Weihua; Lin, Zhiqun

    2015-03-10

    Self-assembly of miktoarm star-like ABn block copolymer in both selective solvent (A- or B-selective) and miscible homopolymer matrix (A or B homopolymer), that is, formation of micelles, was for the first time investigated by theoretical calculations based on self-consistent mean field theory. Interestingly, the calculation revealed that the size of micelles in solvent was smaller than that in homopolymer under the same conditions. In B-selective solvent, with increasing number of B blocks n in miktoarm star-like ABn block copolymer at a fixed volume fraction of A block, the micellar size decreased gradually. In stark contrast, when miktoarm star-like ABn block copolymer dissolved in B homopolymer matrix at molecular weight ratio of B homopolymer to ABn block copolymer fH = 0.30, the overall micellar size decreased nonmonotonically as the number of B blocks n in ABn block copolymer increased. The largest micelle was formed in AB2 (i.e., n = 2). This intriguing finding can be attributed to a wet-to-dry brush transition that occurred from n = 1 to n = 2 in the micellization of miktoarm star-like ABn block copolymer. Moreover, the micellization behaviors of miktoarm star-like ABn block copolymer in A-selective solvent and A homopolymer matrix were also explored, where the overall micellar size in both scenarios was found to decrease monotonically as n in ABn block copolymer increased. These self-assembled nanostructures composed of miktoarm star-like ABn block copolymers may promise a wide range of applications in size-dependent drug delivery and bionanotechnology.

  13. Synthesis and Characterization of Stimuli Responsive Block Copolymers, Self-Assembly Behavior and Applications

    SciTech Connect

    Determan, Michael Duane

    2005-12-17

    The central theme of this thesis work is to develop new block copolymer materials for biomedical applications. While there are many reports of stimuli-responsive amphiphilic [19-21] and crosslinked hydrogel materials [22], the development of an in situ gel forming, pH responsive pentablock copolymer is a novel contribution to the field, Figure 1.1 is a sketch of an ABCBA pentablock copolymer. The A blocks are cationic tertiary amine methacrylates blocked to a central Pluronic F127 triblock copolymer. In addition to the prerequisite synthetic and macromolecular characterization of these new materials, the self-assembled supramolecular structures formed by the pentablock were experimentally evaluated. This synthesis and characterization process serves to elucidate the important structure property relationships of these novel materials, The pH and temperature responsive behavior of the pentablock copolymer were explored especially with consideration towards injectable drug delivery applications. Future synthesis work will focus on enhancing and tuning the cell specific targeting of DNA/pentablock copolymer polyplexes. The specific goals of this research are: (1) Develop a synthetic route for gel forming pentablock block copolymers with pH and temperature sensitive properties. Synthesis of these novel copolymers is accomplished with ATRP, yielding low polydispersity and control of the block copolymer architecture. Well defined macromolecular characteristics are required to tailor the phase behavior of these materials. (2) Characterize relationship between the size and shape of pentablock copolymer micelles and gel structure and the pH and temperature of the copolymer solutions with SAXS, SANS and CryoTEM. (3) Evaluate the temperature and pH induced phase separation and macroscopic self-assembly phenomenon of the pentablock copolymer. (4) Utilize the knowledge gained from first three goals to design and formulate drug delivery formulations based on the multi

  14. Stabilization of Bicontinuous Phases in Diblock Copolymer Systems

    NASA Astrophysics Data System (ADS)

    Escobedo, Fernando; Martinez-Veracoechea, Francisco

    2009-03-01

    We used a coarse-grained description of the copolymer chains (i.e., dissipative particle dynamics fluid), together with continuum-space Monte Carlo and Molecular Dynamics methods, to study systems of diblock copolymers melts that have been ``filled'' with selective additives (i.e., homopolymer, and nanoparticles). Approximate phase boundaries were found via free-energy calculations. We focus on the stabilization of bi-continuous phases and the strikingly different phase behavior observed when the nature of the selective filler is changed. Our results elucidate the origins of the packing frustration that limits the viability of the gyroid, double-diamond, and plumber's nightmare phases and provide insights for overcoming it. Attention is also focused on directly determining the areas of phase diagram where macro- phase separation occurs. We compare the particle-based simulation results with the results obtained by means of self- consistent filed theory calculations.

  15. Charged Diblock Copolymers at Interfaces: Micelle Dissociation Upon Compression

    SciTech Connect

    Theodoly, O.; Checco, A; Muller, P

    2010-01-01

    We use grazing incidence X-ray scattering to study the surface micellization of charged amphiphilic diblock copolymers poly(styrene-block-acrylic acid) at the air-water interface. Scattering interference peaks are consistent with the formation of hexagonally packed micelles. The remarkable increase of inter-micelle distance upon compression is explained by a dissociation of micelles into a brush. Hence, surface micelles reorganize, whereas micelles of the same copolymers in solutions are 'frozen'. We show indeed that the energetic cost of unimer extraction from micelles is much lower for surface than for solution. Finally, a model combining electrostatic interactions and micelle/brush equilibrium explains surface pressure vs. area without free parameters.

  16. Self-assembly scenarios of block copolymer stars

    NASA Astrophysics Data System (ADS)

    Koch, Christian; Likos, Christos N.; Panagiotopoulos, Athanassios Z.; Lo Verso, Federica

    2011-12-01

    We examine the self-organization scenarios of star-shaped AB-block copolymers, consisting of a solvophilic A-block and a solvophobic B-block, in which f such blocks are chemically anchored on a common centre on their A-parts, leaving the B-blocks exposed on their exterior. We employ a lattice model and we perform Grand Canonical Monte Carlo simulations for the case f = 6, varying thereby the percentage of attractive monomers as well as the concentration of stars. In agreement with previous studies on the low-functionality case f = 3 [F. Lo Verso, A.Z. Panagiotopoulos, and C.N. Likos, Phys. Rev. E 79, 010401(R) (2009)], we find that when the majority of monomers in the star are attractive, macrophase separation between two fluid phases at different concentrations of stars occurs below a system-dependent critical temperature. When the majority of monomers is repulsive, novel forms of self-organization arise, which include not only well-defined spherical micelles but also the coexistence of a multiply-connected percolating cluster with smaller micelles having a well-defined size. The morphological characteristics and the sizes of the ensuing aggregates are quantitatively analysed and a critical comparison with the case f = 3 and f = 10 is presented.

  17. Self-Assembly Properties of DNA Origami, Gold Nanostructures, and Diblock Compatibilizers

    NASA Astrophysics Data System (ADS)

    Estrich, Nicole Ashley

    The well-characterized structure and reliable formation of the DNA double-helix provides a method for biological self-assembly at the sub-10 nm length scale. The field of DNA origami was predicated on this simple and dependable methodology, using the selfassembling nature of DNA as a structural tool rather than a genetic encoding material, through which many structures have been demonstrated. Using attachment chemistry, nanoparticles and other nanometer-scaled components of a variety of materials can be site-specifically bound at docking positions on DNA origami, thus utilizing DNA origami as a templating method for simultaneously synthesizing a large number of copies (˜1012 ) of a pre-designed architecture. With this methodology in place, novel 3D wireframe DNA origami structures were designed and imaged using a positive-staining Transmission Electron Microscopy method never before used to image DNA origami. These architectures were designed such that specific incorporation of other nanocomponents can allow them to satisfy a number of intended uses, from applications ranging from optoelectronic sensing and detection to the fabrication of electronic device components and new types of computer architectures. However, obtaining high-yield products with high stability is a challenge. The goal of this dissertation is to explore the capabilities, limitations, and unique properties of DNA and gold nanoparticle self-assembly with block polypeptide protection as a fabrication tool for plasmonic, optical, and electronic nanostructures. (Abstract shortened by ProQuest.).

  18. Order-order transitions of diblock copolymer melts under cylindrical confinement

    NASA Astrophysics Data System (ADS)

    Liu, Meijiao; Li, Weihua; Wang, Xinping

    2017-09-01

    The self-assembly behavior of AB diblock copolymers under cylindrical confinement is investigated using the self-consistent field theory. We focus on the impact of the confinement on the order-order transitions of three-dimensional morphologies by constructing two types of phase diagrams with continuously varying block compositions. One type is with respect to the block composition and the immiscibility parameter for various pore sizes, in which the order-order transitions are shown to be strongly impacted by the pore curvature and thus largely different from the bulk ones. Note that the morphologies are categorized by the intrinsical geometry of their domains, i.e., that helical morphologies are regarded as one type of cylindrical phase. Another type of phase diagram is with respect to the block composition and the pore diameter, which exhibits a number of interesting order-order transitions, especially the transition sequence from a straight line of spheres, to one straight cylinder and stacked disks as the pore diameter increases. A critical point is observed at which the stability region of the straight cylinder vanishes and thereby the spheres transform into the stacked disks continuously. The mechanism of these phase transitions is rationalized in the context of the bulk factors as well as an additional factor, i.e., the competition between the spontaneous curvature of the copolymer and the imposed curvature by the nanopore.

  19. Order-order transitions of diblock copolymer melts under cylindrical confinement.

    PubMed

    Liu, Meijiao; Li, Weihua; Wang, Xinping

    2017-09-21

    The self-assembly behavior of AB diblock copolymers under cylindrical confinement is investigated using the self-consistent field theory. We focus on the impact of the confinement on the order-order transitions of three-dimensional morphologies by constructing two types of phase diagrams with continuously varying block compositions. One type is with respect to the block composition and the immiscibility parameter for various pore sizes, in which the order-order transitions are shown to be strongly impacted by the pore curvature and thus largely different from the bulk ones. Note that the morphologies are categorized by the intrinsical geometry of their domains, i.e., that helical morphologies are regarded as one type of cylindrical phase. Another type of phase diagram is with respect to the block composition and the pore diameter, which exhibits a number of interesting order-order transitions, especially the transition sequence from a straight line of spheres, to one straight cylinder and stacked disks as the pore diameter increases. A critical point is observed at which the stability region of the straight cylinder vanishes and thereby the spheres transform into the stacked disks continuously. The mechanism of these phase transitions is rationalized in the context of the bulk factors as well as an additional factor, i.e., the competition between the spontaneous curvature of the copolymer and the imposed curvature by the nanopore.

  20. Sulfate-based anionic diblock copolymer nanoparticles for efficient occlusion within zinc oxide

    NASA Astrophysics Data System (ADS)

    Ning, Y.; Fielding, L. A.; Andrews, T. S.; Growney, D. J.; Armes, S. P.

    2015-04-01

    Occlusion of copolymer particles within inorganic crystalline hosts not only provides a model for understanding the crystallisation process, but also may offer a direct route for the preparation of novel nanocomposite materials with emergent properties. In the present paper, a series of new well-defined anionic diblock copolymer nanoparticles are synthesised by polymerisation-induced self-assembly (PISA) via reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerisation and then evaluated as crystal habit modifiers for the in situ formation of ZnO in aqueous solution. Systematic studies indicate that both the chemical nature (i.e. whether sulfate-based or carboxylate-based) and the mean degree of polymerisation (DP) of the anionic stabiliser block play vital roles in determining the crystal morphology. In particular, sulfate-functionalised nanoparticles are efficiently incorporated within the ZnO crystals whereas carboxylate-functionalised nanoparticles are excluded, thus anionic character is a necessary but not sufficient condition for successful occlusion. Moreover, the extent of nanoparticle occlusion within the ZnO phase can be as high as 23% by mass depending on the sulfate-based nanoparticle concentration. The optical properties, chemical composition and crystal structure of the resulting nanocomposite crystals are evaluated and an occlusion mechanism is proposed based on the observed evolution of the ZnO morphology in the presence of sulfate-based anionic nanoparticles. Finally, controlled deposition of a 5 nm gold sol onto porous ZnO particles (produced after calcination of the organic nanoparticles) significantly enhances the rate of photocatalytic decomposition of a model rhodamine B dye on exposure to a relatively weak UV source.Occlusion of copolymer particles within inorganic crystalline hosts not only provides a model for understanding the crystallisation process, but also may offer a direct route for the preparation of novel

  1. Supramolecular block copolymers by kinetically controlled co-self-assembly of planar and core-twisted perylene bisimides

    PubMed Central

    Görl, Daniel; Zhang, Xin; Stepanenko, Vladimir; Würthner, Frank

    2015-01-01

    New synthetic methodologies for the formation of block copolymers have revolutionized polymer science within the last two decades. However, the formation of supramolecular block copolymers composed of alternating sequences of larger block segments has not been realized yet. Here we show by transmission electron microscopy (TEM), 2D NMR and optical spectroscopy that two different perylene bisimide dyes bearing either a flat (A) or a twisted (B) core self-assemble in water into supramolecular block copolymers with an alternating sequence of (AmBB)n. The highly defined ultralong nanowire structure of these supramolecular copolymers is entirely different from those formed upon self-assembly of the individual counterparts, that is, stiff nanorods (A) and irregular nanoworms (B), respectively. Our studies further reveal that the as-formed supramolecular block copolymer constitutes a kinetic self-assembly product that transforms into thermodynamically more stable self-sorted homopolymers upon heating. PMID:25959777

  2. The nature of protein interactions governing globular protein-polymer block copolymer self-assembly.

    PubMed

    Lam, Christopher N; Kim, Minkyu; Thomas, Carla S; Chang, Dongsook; Sanoja, Gabriel E; Okwara, Chimdimma U; Olsen, Bradley D

    2014-04-14

    The effects of protein surface potential on the self-assembly of protein-polymer block copolymers are investigated in globular proteins with controlled shape through two approaches: comparison of self-assembly of mCherry-poly(N-isopropylacrylamide) (PNIPAM) bioconjugates with structurally homologous enhanced green fluorescent protein (EGFP)-PNIPAM bioconjugates, and mutants of mCherry with altered electrostatic patchiness. Despite large changes in amino acid sequence, the temperature-concentration phase diagrams of EGFP-PNIPAM and mCherry-PNIPAM conjugates have similar phase transition concentrations. Both materials form identical phases at two different coil fractions below the PNIPAM thermal transition temperature and in the bulk. However, at temperatures above the thermoresponsive transition, mCherry conjugates form hexagonal phases at high concentrations while EGFP conjugates form a disordered micellar phase. At lower concentration, mCherry shows a two-phase region while EGFP forms homogeneous disordered micellar structures, reflecting the effect of changes in micellar stability. Conjugates of four mCherry variants with changes to their electrostatic surface patchiness also showed minimal change in phase behavior, suggesting that surface patchiness has only a small effect on the self-assembly process. Measurements of protein/polymer miscibility, second virial coefficients, and zeta potential show that these coarse-grained interactions are similar between mCherry and EGFP, indicating that coarse-grained interactions largely capture the relevant physics for soluble, monomeric globular protein-polymer conjugate self-assembly.

  3. Role of Solvent Water in the Temperature-Induced Self-Assembly of a Triblock Copolymer.

    PubMed

    Kundu, Achintya; Verma, Pramod Kumar; Cho, Minhaeng

    2017-07-06

    Water-soluble triblock copolymers have received much attention in industrial applications and scientific fields. We here show that femtosecond mid-IR pump-probe spectroscopy is useful to study the role of water in the temperature-induced self-assembly of triblock copolymers. Our experimental results suggest two distinct subpopulations of water molecules: those that interact with other water molecules and those involved in the hydration of a triblock copolymer surface. We find that the vibrational dynamics of bulk-like water is not affected by either micellation or gelation of triblock copolymers. The increased population of water interacting with ether oxygen atoms of the copolymer during the unimer to micelle phase transition is important evidence for the entropic role of water in temperature-induced micelle formation at a low copolymer concentration. In contrast, at the critical gelation temperature and beyond, the population of surface-associated water molecules interacting with ether oxygen atoms decreases, which indicates important enthalpic control by water. The present study on the roles of water in the two different phase transitions of triblock copolymers sheds new light on the underlying mechanisms of temperature-induced self-aggregation behaviors of amphiphiles that are ubiquitous in nature.

  4. Thermal analysis study of polysterene-poly(methyl methacrylate) (PS-PMMA) diblock copolymer thin films morphologies when annealed and sheared under vacuum in inert atmosphere

    NASA Astrophysics Data System (ADS)

    Pomales, Luis; Davila-Santana, Melissa; Rivera-Claudio, Mirna; Vedrine-Pauleus, Josee

    2011-03-01

    Diblock copolymers are made of two chemically bonded blocks, with incompatible monomers. This incompatibility gives the block the property to phase separate at temperatures above the glass transition (Tg). The ability to self-assemble into different mesophase structures is of great importance in nanolithography and nanofabrication. This research involves the morphological study of PS-PMMA thin films annealed under inert atmosphere. Our objective is to determine the microstructure properties of the PS-PMMA diblock copolymer as a function of film thickness, annealing temperature, and applied shear force. The PS-PMMA thin film is spin casted onto silicon substrates, and annealed under an inert atmosphere. Our initial results show that the samples have an incomplete formation of the microstructures. However, further film analysis is needed to study the morphological properties when annealed. Futures studies will focus on the effects of a shear force during annealing, to align the film microstructures.

  5. Rapid self-assembly of brush block copolymers to photonic crystals.

    PubMed

    Sveinbjörnsson, Benjamin R; Weitekamp, Raymond A; Miyake, Garret M; Xia, Yan; Atwater, Harry A; Grubbs, Robert H

    2012-09-04

    The reduced chain entanglement of brush polymers over their linear analogs drastically lowers the energetic barriers to reorganization. In this report, we demonstrate the rapid self-assembly of brush block copolymers to nanostructures with photonic bandgaps spanning the entire visible spectrum, from ultraviolet (UV) to near infrared (NIR). Linear relationships were observed between the peak wavelengths of reflection and polymer molecular weights. This work enables "bottom-up" fabrication of photonic crystals with application-tailored bandgaps, through synthetic control of the polymer molecular weight and the method of self-assembly. These polymers could be developed into NIR-reflective paints, to combat the "urban heat island effect" due to NIR photon thermalization.

  6. Tunable and rapid self-assembly of block copolymers using mixed solvent vapors

    SciTech Connect

    Park, Woon Ik; Tong, Sheng; Liu, Yuzi; Jung, Il Woong; Roelofs, Andreas; Hong, Seungbum

    2014-11-06

    Pattern generation of well-controlled block copolymers (BCPs) with a high Flory–Huggins interaction parameter (χ) is important for applications in sub-20 nm nanolithography. In this paper, we used mixed solvents of dimethylformamide (DMF) and toluene to control the morphology as well as the time to achieve the targeted morphology via self-assembly of BCPs. By precisely controlling the volume ratio of DMF and toluene, well-ordered line, honeycomb, circular hole, and lamellar nanostructures were obtained from a cylinder-forming poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) BCP with high χ. Furthermore, a well-aligned 12 nm line pattern was successfully achieved in the guiding template within one minute using the mixed solvents. Finally, this practical method may also be applicable to self-assembly of other BCPs, providing more opportunities for the next-generation sub-10 nm lithography applications.

  7. Tunable and rapid self-assembly of block copolymers using mixed solvent vapors

    DOE PAGES

    Park, Woon Ik; Tong, Sheng; Liu, Yuzi; ...

    2014-11-06

    Pattern generation of well-controlled block copolymers (BCPs) with a high Flory–Huggins interaction parameter (χ) is important for applications in sub-20 nm nanolithography. In this paper, we used mixed solvents of dimethylformamide (DMF) and toluene to control the morphology as well as the time to achieve the targeted morphology via self-assembly of BCPs. By precisely controlling the volume ratio of DMF and toluene, well-ordered line, honeycomb, circular hole, and lamellar nanostructures were obtained from a cylinder-forming poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) BCP with high χ. Furthermore, a well-aligned 12 nm line pattern was successfully achieved in the guiding template within one minute using themore » mixed solvents. Finally, this practical method may also be applicable to self-assembly of other BCPs, providing more opportunities for the next-generation sub-10 nm lithography applications.« less

  8. Block copolymer self-assembly-directed synthesis of mesoporous gyroidal superconductors.

    PubMed

    Robbins, Spencer W; Beaucage, Peter A; Sai, Hiroaki; Tan, Kwan Wee; Werner, Jörg G; Sethna, James P; DiSalvo, Francis J; Gruner, Sol M; Van Dover, Robert B; Wiesner, Ulrich

    2016-01-01

    Superconductors with periodically ordered mesoporous structures are expected to have properties very different from those of their bulk counterparts. Systematic studies of such phenomena to date are sparse, however, because of a lack of versatile synthetic approaches to such materials. We demonstrate the formation of three-dimensionally continuous gyroidal mesoporous niobium nitride (NbN) superconductors from chiral ABC triblock terpolymer self-assembly-directed sol-gel-derived niobium oxide with subsequent thermal processing in air and ammonia gas. Superconducting materials exhibit a critical temperature (T c) of about 7 to 8 K, a flux exclusion of about 5% compared to a dense NbN solid, and an estimated critical current density (J c) of 440 A cm(-2) at 100 Oe and 2.5 K. We expect block copolymer self-assembly-directed mesoporous superconductors to provide interesting subjects for mesostructure-superconductivity correlation studies.

  9. Self-assembly of block copolymers on lithographically patterned template with ordered posts.

    PubMed

    Xu, Dan; Liu, Hong; Xue, Yao-Hong; Sun, Yan-Bo

    2015-12-21

    Dissipative particle dynamics simulations are employed to study the self-assembly of block copolymers on a template modified with ordered posts. Templates with hexagonally arranged and rectangularly arranged posts are both studied. For the systems with hexagonally arranged posts, morphologies with bending alignments are seen most often. We find that the different kinds of patterns, which can be directly observed in experiments, are substantially induced by the pattern of the bottom layer. In the simulations with a template modified with rectangularly arranged posts, by finely adjusting the distances between neighboring posts in both x and y directions, mesh-shaped structures with different angles between the bottom and the sub-bottom layers can be obtained. These results shed light on the better design of lithographically patterned materials on the scale of 10 nm via the directed self-assembly of BCPs by templating.

  10. Developing directly photodefinable substrate guiding layers for block copolymer directed self-assembly (DSA) patterning

    NASA Astrophysics Data System (ADS)

    Cheng, Jing; Lawson, Richard A.; Yeh, Wei-Ming; Tolbert, Laren M.; Henderson, Clifford L.

    2011-04-01

    Directed self-assembly (DSA) of block copolymers has gained significant attention in recent years as a possible alternative for large area fabrication of future sub-30 nm lithographic patterns. To achieve this patterning, at least three critical pieces are needed: (1) a block copolymer with sufficient immiscibility of the two blocks to drive phase separation at the low molecular weights required to achieve such small phase domains, (2) a method for selectively removing one of the blocks after phase separation to achieve formation of a relief pattern, and (3) a method for producing the templated surfaces used to guide and register the phase separated patterns on the substrate of interest. Current methods for achieving the patterned substrate template, whether they are of chemoepitaxial or graphoepitaxial nature, are generally complex involving a large number of steps that are not easily applied to a variety of different substrate surfaces. For example, numerous substrates have been studied to provide neutral wettability to the styrene-methacrylate (PS-b- PMMA) block copolymers, such as random styrene-methacrylate copolymer films (PS-r-PMMA) or self-assembled monolayer (SAM) modified surfaces, which induce perpendicularly oriented morphologies for PS-b-PMMA self-assembly. In the case of chemical epitaxy processes, a layer of photoresist is generally then coated on such neutral substrate films and patterned to render commensurability to the periodicity of the PS-b-PMMA being used. The open (i.e. space) regions in the resist are then exposed to alter their chemistry, e.g. soft X-ray or oxygen plasma exposures have been used, to achieve hydrophilicity which should preferentially wet PMMA. Finally, the resist is stripped and the block copolymer is coated and assembled on the template surface. Obviously such multi-step processes would not be preferred if alternatives existed. As a step toward that goal of making DSA processes simpler, a photodefinable substrate film that

  11. Molecular Interaction Control in Diblock Copolymer Blends and Multiblock Copolymers with Opposite Phase Behaviors

    NASA Astrophysics Data System (ADS)

    Cho, Junhan

    2014-03-01

    Here we show how to control molecular interactions via mixing AB and AC diblock copolymers, where one copolymer exhibits upper order-disorder transition and the other does lower disorder-order transition. Linear ABC triblock copolymers possessing both barotropic and baroplastic pairs are also taken into account. A recently developed random-phase approximation (RPA) theory and the self-consistent field theory (SCFT) for general compressible mixtures are used to analyze stability criteria and morphologies for the given systems. It is demonstrated that the copolymer systems can yield a variety of phase behaviors in their temperature and pressure dependence upon proper mixing conditions and compositions, which is caused by the delicate force fields generated in the systems. We acknowledge the financial support from National Research Foundation of Korea and Center for Photofunctional Energy Materials.

  12. Effect of Chemical Oxidation on the Self-Assembly of Organometallic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Eitouni, Hany

    2005-03-01

    The thermodynamic interactions in ferrocenyldimethylsilane diblock copolymers were systematically adjusted by oxidation of the ferrocene moiety with silver nitrate and examined using small angle x-ray scattering and depolarized light scattering. The polymers retained microphase separated ordered structures upon oxidation and showed systematic changes in the location of the order-disorder transition as a function of ferrocenium nitrate content. The extent of oxidation can be controlled locally through electrochemical techniques and hence ordered and disordered regions can be maintained within a sample. By controlling the redox properties of the ferrocene moiety in the backbone of the polymer, we have provided a novel method of controlling microstructure and hence bulk properties.

  13. Selective directed self-assembly of coexisting morphologies using block copolymer blends

    PubMed Central

    Stein, A.; Wright, G.; Yager, K. G.; Doerk, G. S.; Black, C. T.

    2016-01-01

    Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. Here we expand on traditional DSA chemical patterning. A blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This is in contrast to the typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist. PMID:27480327

  14. Selective directed self-assembly of coexisting morphologies using block copolymer blends

    DOE PAGES

    Stein, A.; Wright, G.; Yager, K. G.; ...

    2016-08-02

    Directed self-assembly (DSA) of block copolymers is an emergent technique for nano-lithography, but is limited in the range of structures possible in a single fabrication step. We expand on traditional DSA chemical patterning. Moreover, a blend of lamellar- and cylinder-forming block copolymers assembles on specially designed surface chemical line gratings, leading to the simultaneous formation of coexisting ordered morphologies in separate areas of the substrate. The competing energetics of polymer chain distortions and chemical mismatch with the substrate grating bias the system towards either line/space or dot array patterns, depending on the pitch and linewidth of the prepattern. This contrastsmore » with typical DSA, wherein assembly of a single-component block copolymer on chemical templates generates patterns of either lines/spaces (lamellar) or hexagonal dot arrays (cylinders). In our approach, the chemical template encodes desired local spatial arrangements of coexisting design motifs, self-assembled from a single, sophisticated resist.« less

  15. The Influence of Charged Species on the Phase Behavior, Self-Assembly, and Electrochemical Performance of Block Copolymer Electrolytes

    NASA Astrophysics Data System (ADS)

    Thelen, Jacob Lloyd

    lithium metal anode. The increase in the specific energy of a battery upon replacing a graphite anode with lithium metal can offset the losses in performance due to the poor ion conduction of SPEs. However, BCEs that enable the use of a lithium anode and have improved performance would represent a major breakthrough for the development of high capacity batteries. The electrochemical performance of BCEs has a complex relationship with the nature of the microphase separated domains, which is not well-understood. The objective of this dissertation is to provide fundamental insight into the nature of microphase separation and self-assembly of block copolymer electrolytes. Specifically, I will focus on how the ion-polymer interactions within a diverse set of BCEs dictate nanostructure. Combining such insight with knowledge of how nanostructure influences ion motion will enable the rational design of new BCEs with enhanced performance and functionality. In order to facilitate the study of BCE nanostructure, synchrotron-based X-ray scattering techniques were used to study samples over a wide range of length-scales under conditions relevant to the battery environment. The development of the experimental aspects of the X-ray scattering techniques, as well as an improved treatment of scattering data, played a pivotal role in the success of this work. The dissemination of those developments will be the focus of the first section. The thermodynamic impact of adding salt to a neutral diblock copolymer was studied in a model BCE composed of a low molecular weight SEO diblock copolymer mixed with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), a common salt used in lithium batteries. In neutral block copolymers (BCPs), self-assembly is a thermodynamically driven process governed by a balance between unfavorable monomer contacts and the entropy of mixing. When the enthalpic and entropic contributions to free energy are similar in magnitude, a block copolymer can undergo a thermally

  16. The emulsion flocculation stability of protein-carbohydrate diblock copolymers.

    PubMed

    Wooster, Tim J; Augustin, Mary Ann

    2007-09-15

    The effect of the steric layer thickness on the flocculation stability of beta-lactoglobulin-carbohydrate diblock copolymers was assessed. The diblock copolymers were created by conjugating beta-lactoglobulin to maltose or a series of different M(n) maltodextrins using the Maillard reaction. The thickness and spatial arrangement of the interfacial layers were assessed via latex adsorption and selective enzymatic digestion studies. An increase in the molecular weight of the maltodextrin (900, 1900 and 3800 Da) increased the interfacial thickness (1.1, 2.5 and 7.3 nm, respectively). No detectable change to interfacial thickness was observed upon the attachment of maltose. The increase in the interfacial layer thickness scaled with the hydrodynamic size of the carbohydrate. The beta-lactoglobulin-maltodextrin conjugates were found to have a diblock architecture, with the protein anchored at the surface and the carbohydrate protruding into the aqueous continuous phase. The stability of oil-in-water emulsions formed using the conjugates was assessed by exposing them to salt (150 mM NaCl or 0-20 mM CaCl(2)), heat alone or heat in the presence of 150 mM NaCl. Conjugation of a 900 Da maltodextrin provided sufficient steric stabilization to prevent flocculation in high salt environments. The effect of the (number) density of the steric layer was also assessed by controlling the average number of maltodextrins attached per beta-lactoglobulin molecule. The steric layer density at which emulsions became unstable was a function of carbohydrate M(n). Emulsions made from the 900 Da maltodextrin conjugate became unstable below a steric layer density of one tail per 7.5 nm(2), whilst emulsions made from the 1900 Da maltodextrin were unstable below a steric layer density of one tail per 9.5 nm(2). This trend was expected and can be explained by the stronger van der Waals attraction that arises from the closer interdroplet separations that are permissible with the shorter

  17. Self-assembly of Si-containing block copolymers with high-segregation strength: toward sub-10nm features in directed self-assembly

    NASA Astrophysics Data System (ADS)

    Reboul, C.; Fleury, G.; Aissou, K.; Brochon, C.; Cloutet, E.; Nicolet, C.; Chevalier, X.; Navarro, C.; Tiron, R.; Cunge, G.; Hadziioannou, G.

    2014-03-01

    Ordered microstructures with nanometrically defined periodicity offer promising opportunities in microelectronic applications for the production of advanced CMOS digital logic circuits. To produce the features and arrays inherent to such technologies, the combination of the "bottom-up" block copolymer self-assembly with "top-down" guiding templates has been successfully introduced leading to new technological breakthroughs. Among the materials used in the direct self-assembly methodology, poly(styrene-b-methylmethacrylate) systems have reached an unprecedented level of maturity which will lead to their introduction into the next technological nodes. However, this system suffers from deficiencies such as a low Flory Huggins parameter (X = 0.04 at 25°C) and a low chemical contrast as regards to the etching processes which could be problematic for targeting sub-22 nm features. Consequently we have developed new systems based on Si-containing block copolymers which are characterized by high segregation strength as well as strong chemical etching contrast. In this contribution, we focus on a poly(lactic acid) / poly(dimethylsiloxane) system exhibiting a cylindrical mesostructure. By controlling the surface energy at the interface between the substrate and the block copolymer domains, we show the possibility to control the orientation of the mesostructure with a methodology comparable to the one used for poly(styrene) / poly(methyl methacrylate) system but with random copolymers having distinct monomers than the block copolymers.

  18. Device-oriented graphene nanopatterning by mussel-inspired directed block copolymer self-assembly.

    PubMed

    Park, Seokhan; Yun, Je Moon; Maiti, Uday Narayan; Moon, Hyoung-Seok; Jin, Hyeong Min; Kim, Sang Ouk

    2014-01-10

    Directed self-assembly of a block copolymer is successfully employed to fabricate device-oriented graphene nanostructures from CVD grown graphene. We implemented mussel-inspired polydopamine adhesive in conjunction with the graphoepitaxy principle to tailor graphene nanoribbon arrays and a graphene nanomesh located between metal electrodes. Polydopamine adhesive was utilized for facile and damage-free surface treatment to complement the low surface energy of pristine graphene. Our process minimizes the damage to the ideal graphitic structures and electrical properties of graphene during the nanopatterning process. Multi-channel graphene nanoribbon arrays and a graphene nanomesh were successfully fabricated between metal electrodes.

  19. Self-assembled ferromagnetic and superparamagnetic structures of hybrid Fe block copolymers

    NASA Astrophysics Data System (ADS)

    Sarantopoulou, E.; Kovač, J.; Pispas, S.; Kobe, S.; Kollia, Z.; Cefalas, A. C.

    2008-10-01

    Self-assembled 2D structures on thin films of block copolymers/Fe hybrid materials were fabricated on Si/Ta substrates, either by wet chemistry or laser irradiation at 157 nm. The polymer exhibits micelle-like structures with average dimensions of 5-10 nm and 30-50 nm for light and chemically reduced films respectively. For the laser processed films, SQUID measurements reveal a ferromagnetic response at 5 K, and 100 Oe coercivity was obtained for 2:1 iron concentration. For chemically reduced films, on the other hand, a superparamagnetic response with near zero coercivity at 5 K was obtained.

  20. Device-oriented graphene nanopatterning by mussel-inspired directed block copolymer self-assembly

    NASA Astrophysics Data System (ADS)

    Park, Seokhan; Yun, Je Moon; Narayan Maiti, Uday; Moon, Hyoung-Seok; Jin, Hyeong Min; Ouk Kim, Sang

    2014-01-01

    Directed self-assembly of a block copolymer is successfully employed to fabricate device-oriented graphene nanostructures from CVD grown graphene. We implemented mussel-inspired polydopamine adhesive in conjunction with the graphoepitaxy principle to tailor graphene nanoribbon arrays and a graphene nanomesh located between metal electrodes. Polydopamine adhesive was utilized for facile and damage-free surface treatment to complement the low surface energy of pristine graphene. Our process minimizes the damage to the ideal graphitic structures and electrical properties of graphene during the nanopatterning process. Multi-channel graphene nanoribbon arrays and a graphene nanomesh were successfully fabricated between metal electrodes.

  1. Porous Diblock Copolymer Thin Films in High-Performance Semiconductor Microelectronics

    SciTech Connect

    Black, C.T.

    2011-02-01

    The engine fueling more than 40 years of performance improvements in semiconductor integrated circuits (ICs) has been industry's ability to pattern circuit elements at ever-higher resolution and with ever-greater precision. Steady advances in photolithography - the process wherein ultraviolet light chemically changes a photosensitive polymer resist material in order to create a latent image - have resulted in scaling of minimum printed feature sizes from tens of microns during the 1980s to sub-50 nanometer transistor gate lengths in today's state-of-the-art ICs. The history of semiconductor technology scaling as well as future technology requirements is documented in the International Technology Roadmap for Semiconductors (ITRS). The progression of the semiconductor industry to the realm of nanometer-scale sizes has brought enormous challenges to device and circuit fabrication, rendering performance improvements by conventional scaling alone increasingly difficult. Most often this discussion is couched in terms of field effect transistor (FET) feature sizes such as the gate length or gate oxide thickness, however these challenges extend to many other aspects of the IC, including interconnect dimensions and pitch, device packing density, power consumption, and heat dissipation. The ITRS Technology Roadmap forecasts a difficult set of scientific and engineering challenges with no presently-known solutions. The primary focus of this chapter is the research performed at IBM on diblock copolymer films composed of polystyrene (PS) and poly(methyl-methacrylate) (PMMA) (PS-b-PMMA) with total molecular weights M{sub n} in the range of {approx}60K (g/mol) and polydispersities (PD) of {approx}1.1. These materials self assemble to form patterns having feature sizes in the range of 15-20nm. PS-b-PMMA was selected as a self-assembling patterning material due to its compatibility with the semiconductor microelectronics manufacturing infrastructure, as well as the significant body

  2. Architectural Effects on Solution Self-Assembly of Poly(3-hexylthiophene)-Based Graft Copolymers.

    PubMed

    Kim, Youngkwon; Kim, Hyeong Jun; Kim, Jin-Seong; Hayward, Ryan C; Kim, Bumjoon J

    2017-01-25

    While solution assembly of conjugated block copolymers has been widely used to produce long 1-D nanowires (NWs), it remains a great challenge to provide a higher level of control over structure and function of the NWs. Herein, for the first time, we report the solution assembly of graft copolymers containing a conjugated polymer backbone in a selective solvent and demonstrate that their self-assembly behaviors can be manipulated by the molecular structures of the graft copolymers. A series of poly(3-hexylthiophene)-graft-poly(2-vinylpyridine) (P3HT-g-P2VP) copolymers was designed with two different architectural parameters: grafting fraction (fg) and molecular weight of P2VP chains (Mn,P2VP) on the P3HT backbone. Interestingly, crystallization of the P3HT-g-P2VP copolymers was systematically modulated by changes in fg and Mn,P2VP, thus allowing for control of the growth kinetics and curvatures of solution-assembled NWs. When Mn,P2VP (4.4 to 15.1 kg/mol) or fg (2.8 to 9.2%) of the P3HT-g-P2VP polymers was increased, the crystallinity of the copolymers was reduced significantly. Steric hindrance from the grafted P2VP chains apparently modified the growth of NWs, leading to shorter NWs with a greater degree of curvature for graft copolymers with more hindrance. Therefore, we envision that such conjugated chain-based graft copolymers can be versatile building blocks for producing NWs with controlled length and shape, which can be important for tailoring the optical and electrical properties of NW-based devices.

  3. Self-assembly morphology effects on the crystallization of semicrystalline block copolymer thin film

    NASA Astrophysics Data System (ADS)

    Wei, Yuhan; Pan, Caiyuan; Li, Binyao; Han, Yanchun

    2007-03-01

    Self-assembly morphology effects on the crystalline behavior of asymmetric semicrystalline block copolymer polystyrene-block-poly(L-lactic acid) thin film were investigated. Firstly, a series of distinctive self-assembly aggregates, from spherical to ellipsoid and rhombic lamellar micelles (two different kinds of rhombic micelles, defined as rhomb 1 and rhomb 2) was prepared by means of promoting the solvent selectivity. Then, the effects of these self-assembly aggregates on crystallization at the early stage of film evolution were investigated by in situ hot stage atomic force microscopy. Heterogeneous nucleation initiated from the spherical micelles and dendrites with flat on crystals appeared with increasing temperature. At high temperature, protruding structures were observed due to the thickening of the flat-on crystals and finally more thermodynamically stable crystallization formed. Annealing the rhombic lamellar micelles resulted in different phenomena. Turtle-shell-like crystalline structure initiated from the periphery of the rhombic micelle 1 and spread over the whole film surface in the presence of mostly noncrystalline domain interior. Erosion and small hole appeared at the surface of the rhombic lamellar micelle 2; no crystallization like that in rhomb 1 occurred. It indicated that the chain-folding degree was different in these two micelles, which resulted in different annealing behaviors.

  4. Filtration on block copolymer solution used in directed self assembly lithography

    NASA Astrophysics Data System (ADS)

    Umeda, Toru; Takakura, Tomoyuki; Tsuzuki, Shuichi

    2016-03-01

    In this paper, we presented the filtration effects on block copolymers (BCP) that are commonly used in directed self-assembly lithographic (DSAL) imaging schemes. Specifically we focused on filtration effects on micro-contaminants such as metal ions and metal induced gels. Gel removal efficiency studies carried out with HDPE, Nylon and PTFE filters pointed out that Nylon 6,6 membrane is the most effective in removing gels in block copolymer (BCP) solutions. Metal removal efficiency studies were conducted using multistep filtrations such as repetitive filtration of single membrane material and combination of different type of membranes. Results showed that a combination of Nylon-6,6 and ion-exchange filters is highly effective in reducing metals such as Li, Mg and Al to > 99.99% efficiency. The mechanism of metal removal efficiency is discussed in detail.

  5. Sub-10 nm resistless nanolithography for directed self-assembly of block copolymers.

    PubMed

    Fernández-Regúlez, Marta; Evangelio, Laura; Lorenzoni, Matteo; Fraxedas, Jordi; Pérez-Murano, Francesc

    2014-12-10

    The creation of highly efficient guiding patterns for the directed self-assembly of block copolymers by resistless nanolithography using atomic force microscopy (AFM) is demonstrated. It is shown that chemical patterns consisting of arrays of lines defined on a brush layer by AFM allow the alignment of the blocks of lamella-forming polymers. The main advantage of this method relies on the capability to create high-resolution (sub-10 nm line-width) guiding patterns and the reduction of the number of process steps compared to the state-of-the-art methods for creating guiding patterns by chemical surface modification. It is found that the guiding patterns induce the block alignment very efficiently, allowing the achievement of a density multiplication factor of 7 for block copolymers of 14 nm half-pitch, which is attributed to the combined effect of topographical and chemical modification.

  6. Fluids Density Functional Theory of Diblock Copolymers for Electrolyte Applications

    NASA Astrophysics Data System (ADS)

    Brown, Jonathan R.; Hall, Lisa M.

    We use classical, fluids density functional theory (fDFT) to study microphase separation in block copolymer systems. We are motivated by systems used as battery electrolytes or in other transport applications, in which the two blocks of the system have different mechanical, dielectric, and transport properties that allow one phase to act as a charge/penetrant carrier and the other to make the film mechanically strong. We find density profiles of penetrants, showing to what degree they segregate into the A phase and their concentration near the interface, depending on the penetrant-A and penetrant-B interaction strengths as well as the A-B segregation strength. We also study the effect of tapering, or adding a gradient region (taper) between the pure A and B blocks of an AB diblock copolymer; the taper changes in composition along its length from pure A to pure B (or from B to A for an inverse taper). The effect of both penetrants and tapering on microphase domain spacing as a function of segregation strength will be discussed. Adjusting taper length allows one to tune the phase behavior of the system for easier processing or access to specific desired microphase structures. Based upon work supported by NSF Grant 1454343 and DOE Grant SC0014209.

  7. Clear antismudge unimolecular coatings of diblock copolymers on glass plates.

    PubMed

    Macoretta, Danielle; Rabnawaz, Muhammad; Grozea, Claudia M; Liu, Guojun; Wang, Yu; Crumblehulme, Alison; Wyer, Martin

    2014-12-10

    Two poly[3-(triisopropyloxysilyl)propyl methacrylate]-block-poly[2-(perfluorooctyl)ethyl methacrylate] (PIPSMA-b-PFOEMA) samples and one poly(perfluoropropylene oxide)-block-poly-[3-(triisopropyloxysilyl)propyl methacrylate] (PFPO-b-PIPSMA) sample were synthesized, characterized, and used to coat glass plates. These coatings were formed by evaporating a dilute polymer solution containing HCl, which catalyzed PIPSMA's sol-gel chemistry. Polymer usage was minimized by targeting at diblock copolymer unimolecular (brush) layers that consisted of a sol-gelled grafted PIPSMA layer and an oil- and water-repellant fluorinated surface layer. Investigated is the effect of varying the catalyst amount, polymer amount, as well as block copolymer type and composition on the structure, morphology, and oil- and water-repellency of the coatings. Under optimized conditions, the prepared coatings were optically clear and resistant to writing by a permanent marker. The marker's trace was the faintest on PFPO-b-PIPSMA coatings. In addition, the PFPO-b-PIPSMA coatings were far more wear-resistant than the PIPSMA-b-PFOEMA coatings.

  8. Modeling and self-assembly behavior of PEG-PLA-PEG triblock copolymers in aqueous solution

    NASA Astrophysics Data System (ADS)

    Wu, Xiaohan; Li, Suming; Coumes, Fanny; Darcos, Vincent; Lai Kee Him, Joséphine; Bron, Patrick

    2013-09-01

    A series of poly(ethylene glycol)-polylactide-poly(ethylene glycol) (PEG-PLA-PEG) triblock copolymers with symmetric or asymmetric chain structures were synthesized by combination of ring-opening polymerization and copper-catalyzed click chemistry. The resulting copolymers were used to prepare self-assembled aggregates by dialysis. Various architectures such as nanotubes, polymersomes and spherical micelles were observed from transmission electron microscopy (TEM), cryo-TEM and atomic force microscopy (AFM) measurements. The formation of diverse aggregates is explained by modeling from the angle of both geometry and thermodynamics. From the angle of geometry, a ``blob'' model based on the Daoud-Cotton model for star polymers is proposed to describe the aggregate structures and structural changes with copolymer composition and molar mass. In fact, the copolymer chains extend in aqueous medium to form single layer polymersomes to minimize the system's free energy if one of the two PEG blocks is short enough. The curvature of polymersomes is dependent on the chain structure of copolymers, especially on the length of PLA blocks. A constant branch number of aggregates (f) is thus required to preserve the morphology of polymersomes. Meanwhile, the aggregation number (Nagg) determined from the thermodynamics of self-assembly is roughly proportional to the total length of polymer chains. Comparing f to Nagg, the aggregates take the form of polymersomes if Nagg ~ f, and change to nanotubes if Nagg > f to conform to the limits from both curvature and aggregation number. The length of nanotubes is mainly determined by the difference between Nagg and f. However, the hollow structure becomes unstable when both PEG segments are too long, and the aggregates eventually collapse to yield spherical micelles. Therefore, this work gives new insights into the self-assembly behavior of PEG-PLA-PEG triblock copolymers in aqueous solution which present great interest for biomedical and

  9. Directed self-assembly of block copolymer films on atomically-thin graphene chemical patterns

    NASA Astrophysics Data System (ADS)

    Chang, Tzu-Hsuan; Xiong, Shisheng; Jacobberger, Robert M.; Mikael, Solomon; Suh, Hyo Seon; Liu, Chi-Chun; Geng, Dalong; Wang, Xudong; Arnold, Michael S.; Ma, Zhenqiang; Nealey, Paul F.

    2016-08-01

    Directed self-assembly of block copolymers is a scalable method to fabricate well-ordered patterns over the wafer scale with feature sizes below the resolution of conventional lithography. Typically, lithographically-defined prepatterns with varying chemical contrast are used to rationally guide the assembly of block copolymers. The directed self-assembly to obtain accurate registration and alignment is largely influenced by the assembly kinetics. Furthermore, a considerably broad processing window is favored for industrial manufacturing. Using an atomically-thin layer of graphene on germanium, after two simple processing steps, we create a novel chemical pattern to direct the assembly of polystyrene-block-poly(methyl methacrylate). Faster assembly kinetics are observed on graphene/germanium chemical patterns than on conventional chemical patterns based on polymer mats and brushes. This new chemical pattern allows for assembly on a wide range of guiding periods and along designed 90° bending structures. We also achieve density multiplication by a factor of 10, greatly enhancing the pattern resolution. The rapid assembly kinetics, minimal topography, and broad processing window demonstrate the advantages of inorganic chemical patterns composed of hard surfaces.

  10. All track directed self-assembly of block copolymers: process flow and origin of defects

    NASA Astrophysics Data System (ADS)

    Rincon Delgadillo, Paulina A.; Gronheid, Roel; Thode, Christopher J.; Wu, Hengpeng; Cao, Yi; Somervell, Mark; Nafus, Kathleen; Nealey, Paul F.

    2012-03-01

    Directed Self-Assembly (DSA) of block copolymers is considered to be a potential lithographic solution to achieve higher feature densities than can be obtained by current lithographic techniques. However, it is still not well-established how amenable DSA of block copolymers is to an industrial fabrication environment in terms of defectivity and processing conditions. Beyond production-related challenges, precise manipulation of the geometrical and chemical properties over the substrate is essential to achieve high pattern fidelity upon the self-assembly process. Using our chemo-epitaxy DSA approach offers control over the surface properties of the slightly preferential brush material as well as those of the guiding structures. This allows for a detailed assessment of the critical material parameters for defect reduction. The precise control of environment afforded by industrial equipment allows for the selective analysis of material and process related boundary conditions and assessment of their effect on defect generation. In this study, the previously reported implementation of our feature multiplication process was used to investigate the origin of defects in terms of the geometry of the initial pre-patterns. Additionally, programmed defects were used to investigate the ability of the BCP to heal defects in the resist patterns and will aid to assess the capture capability of the inspection tool. Finally, the set-up of the infrastructure that will allow the study the generation of defects due to the interaction of the BCP with the boundary conditions has been accomplished at imec.

  11. Redox-responsive micelles self-assembled from dynamic covalent block copolymers for intracellular drug delivery.

    PubMed

    Yang, Qinglai; Tan, Lianjiang; He, Changyu; Liu, Bingya; Xu, Yuhong; Zhu, Zhenggang; Shao, Zhifeng; Gong, Bing; Shen, Yu-Mei

    2015-04-01

    Redox-responsive micelles self-assembled from dynamic covalent block copolymers with double disulfide linkage in the backbone have been developed successfully. The amphiphilic block copolymers PEG-PLA associated with complementary H-bonding sequences can self-assemble into spherical micelles in aqueous media with sizes from 34 nm to 107 nm with different molar mass of PEG and PLA. Moreover, in vitro drug release analyses indicate that reductive environment can result in triggered drug release profiles. The glutathione (GSH) mediated intracellular drug delivery was investigated against HeLa human cervical carcinoma cell line. Flow cytometry and fluorescence microscopy measurements demonstrated that the micelles exhibited faster drug release in glutathione monoester (GSH-OEt) pretreated HeLa cells than that in the nonpretreated cells. Cytotoxicity assay of DOX-loaded micelles indicated the higher cellular proliferation inhibition against 10 mM of GSH-OEt pretreated HeLa cells than that of the nonpretreated ones. These reduction-responsive, biodegradable and biocompatibility micelles could provide a favorable platform to construct excellent drug delivery systems for cancer therapy.

  12. Directed self-assembly of block copolymer films on atomically-thin graphene chemical patterns

    PubMed Central

    Chang, Tzu-Hsuan; Xiong, Shisheng; Jacobberger, Robert M.; Mikael, Solomon; Suh, Hyo Seon; Liu, Chi-Chun; Geng, Dalong; Wang, Xudong; Arnold, Michael S.; Ma, Zhenqiang; Nealey, Paul F.

    2016-01-01

    Directed self-assembly of block copolymers is a scalable method to fabricate well-ordered patterns over the wafer scale with feature sizes below the resolution of conventional lithography. Typically, lithographically-defined prepatterns with varying chemical contrast are used to rationally guide the assembly of block copolymers. The directed self-assembly to obtain accurate registration and alignment is largely influenced by the assembly kinetics. Furthermore, a considerably broad processing window is favored for industrial manufacturing. Using an atomically-thin layer of graphene on germanium, after two simple processing steps, we create a novel chemical pattern to direct the assembly of polystyrene-block-poly(methyl methacrylate). Faster assembly kinetics are observed on graphene/germanium chemical patterns than on conventional chemical patterns based on polymer mats and brushes. This new chemical pattern allows for assembly on a wide range of guiding periods and along designed 90° bending structures. We also achieve density multiplication by a factor of 10, greatly enhancing the pattern resolution. The rapid assembly kinetics, minimal topography, and broad processing window demonstrate the advantages of inorganic chemical patterns composed of hard surfaces. PMID:27528258

  13. Directed Self-Assembly of Block Copolymers in Thin Films on Polymer Nano-Stripes

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Eun; Kang, Ho-Jong; Lee, Dong Hyun; Nano Functional Materials Lab. Team

    In this study, we report directed self-assembly (DSA) of block copolymers in thin films on nano-stripes of polymers. Unique nano-stripes of poly(tetrafluoro ethylene) (PTFE) having ~20 nm of amplitude and ~200 nm of pitch were simply generated by physically rubbing a PTFE bar on various substrates like Si wafers, glass, and polyimide due to its low friction coefficient and high wear rate. The resulting nano-stripes were extremely oriented along the rubbing direction. Then, various asymmetric polystyrene-block-poly(2-vinylpyridine) copolymers (PS- b-P2VP) were directly self-assembled on the nano-stripes of PTFE by solvent-annealing in vapor of tetrahydrofuran (THF). As a result, PS- b-P2VP exhibited extremely ordered P2VP cylinders oriented normal to the surface in large area on the underlying nano-stripes of PTFE. In addition, as utilizing the BCPs as templates, hexagonal arrays of metal nanoparticles were generated in large area for further application. BCP thin films and arrays of metal nanoparticles were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM).

  14. The potential of block copolymer's directed self-assembly for contact hole shrink and contact multiplication

    NASA Astrophysics Data System (ADS)

    Tiron, R.; Gharbi, A.; Argoud, M.; Chevalier, X.; Belledent, J.; Pimmenta Barros, P.; Servin, I.; Navarro, C.; Cunge, G.; Barnola, S.; Pain, L.; Asai, M.; Pieczulewski, C.

    2013-03-01

    The goal of this paper is to investigate the potential of Directed Self-Assembly (DSA) to address contact via level patterning, by either Critical Dimension (CD) shrink or contact multiplication. Using the 300mm pilot line available in LETI and Arkema materials, our approach is based on the graphoepitaxy of PS-b- PMMA block copolymers (BCP). The process consists in the following steps: a) the lithography of guiding patterns, b) the DSA of block copolymers and PMMA removal and finally c) the transfer of PS patterns into the under-layer by plasma etching. Several integration schemes using 193nm dry lithography are evaluated: negative tone development (NTD) resists, a tri-layer approach, frozen resists, etc. The advantages and limitations of each approach are reported. Furthermore, the impact of the BCP on the final patterns characteristics is investigated by tuning different parameters such as the molecular weight of the polymeric constituents and the interaction with the substrate. The optimization of the self-assembly process parameters in terms of film thickness or bake (temperature and time) is also reported. Finally, the transfer capabilities of the PS nanostructures in bulk silicon substrate by using plasma-etching are detailed. These results show that DSA has a high potential to be integrated directly into the conventional CMOS lithography process in order to achieve high-resolution contact holes. Furthermore, in order to prevent design restrictions, this approach may be extended to more complex structures with multiple contacts and nonhexagonal symmetries.

  15. Directing the self-assembly of semiconducting copolymers: the consequences of grafting linear or hyperbranched polyether side chains.

    PubMed

    zur Borg, Lisa; Schüll, Christoph; Frey, Holger; Zentel, Rudolf

    2013-08-01

    The synthesis and self-assembly of novel semiconducting rod-coil type graft block copolymers based on poly(para-phenylene vinylene) (PPV) copolymers is presented, focusing on the ordering effect of linear versus hyperbranched side chains. Using an additional reactive ester block, highly polar, linear poly(ethylene glycol), and hyperbranched polyglycerol side chains are attached in a grafting-to approach. Remarkably, the resulting novel semiconducting graft copolymers with polyether side chains show different solubility and side-chain directed self-assembly behavior in various solvents, e.g., cylindrical or spherical superstructures in the size range of 10 to 120 nm, as shown by TEM. By adjusting the molecular weight and the topology of the polyether segments, self-assembly into defined superstructures can be achieved, which is important for the efficient charge transport in potential electronic applications.

  16. Effect of angstrom-scale surface roughness on the self-assembly of polystyrene-polydimethylsiloxane block copolymer

    PubMed Central

    Kundu, Shreya; Ganesan, Ramakrishnan; Gaur, Nikita; Saifullah, Mohammad S. M.; Hussain, Hazrat; Yang, Hyunsoo; Bhatia, Charanjit S.

    2012-01-01

    Self-assembly of block copolymers has been identified as a potential candidate for high density fabrication of nanostructures. However, the factors affecting its reliability and reproducibility as a patterning technique on various kinds of surfaces are not well-established. Studies pertaining to block copolymer self-assembly have been confined to ultra-flat substrates without taking into consideration the effect of surface roughness. Here, we show that a slight change in the angstrom-scale roughness arising from the surface of a material creates a profound effect on the self-assembly of polystyrene-polydimethylsiloxane block copolymer. Its self-assembly was found to be dependent on both the root mean square roughness (Rrms) of the surface and the type of solvent annealing system used. It was observed that surface with Rrms< 5.0 Å showed self-assembly. Above this value, the kinetic hindrance posed by the surface roughness on the block copolymer leads to its conforming to the surface without observable phase separation. PMID:22943003

  17. Dissipative particle dynamics simulation study on self-assembly of amphiphilic hyperbranched multiarm copolymers with different degrees of branching.

    PubMed

    Tan, Haina; Wang, Wei; Yu, Chunyang; Zhou, Yongfeng; Lu, Zhongyuan; Yan, Deyue

    2015-11-21

    Hyperbranched multiarm copolymers (HMCs) have shown great potential to be excellent precursors in self-assembly to form various supramolecular structures in all scales and dimensions in solution. However, theoretical studies on the self-assembly of HMCs, especially the self-assembly dynamics and mechanisms, have been greatly lagging behind the experimental progress. Herein, we investigate the effect of degree of branching (DB) on the self-assembly structures of HMCs by dissipative particle dynamics (DPD) simulation. Our simulation results demonstrate that the self-assembly morphologies of HMCs can be changed from spherical micelles, wormlike micelles, to vesicles with the increase of DBs, which are qualitatively consistent with the experimental observations. In addition, both the self-assembly mechanisms and the dynamic processes for the formation of these three aggregates have been systematically disclosed through the simulations. These self-assembly details are difficult to be shown by experiments and are very useful to fully understand the self-assembly behaviors of HMCs.

  18. Development of block co-polymers as self-assembling templates for patterned media.

    SciTech Connect

    Warke, V.; Bakker, M. G.; Hong, K.; Mays, J.; Britt, P.; Li, X.; Wang, J.; X-Ray Science Division; Univ. of Alabama; ORNL

    2006-01-01

    Block copolymers that self-organize are of interest as templates for patterned media, as they potentially provide a low cost fabrication route. Poly(styrene)-Poly(methylmethacrylate) block co-polymers (PS-b-PMMA) of appropriate block length and PS to PMMA ratio self-assemble into a 2-D hexagonal phase in which the PS majority phase is continuous and surrounds cylinders of the minority, PMMA phase. For application of this phase to patterned media it is necessary that the cylinders of the minority phase be oriented perpendicular to the substrate surface. This can be achieved by a number of methods, including appropriate choice of substrate and use of a random co-polymer underlayer. Appropriate substrates include H-terminated silicon, some carbon coatings and some ITO glasses. Use of an acetic acid wash causes the minority PMMA component can be induced to be rearranged, giving rise to pores perpendicular to the substrate. Electrodeposition of a metal into the pores produces a hardmask which can be used with ion-milling to transfer the block co-polymer pattern onto a magnetic thin film.

  19. Three-Tone Chemical Patterns for Block Copolymer Directed Self-Assembly

    SciTech Connect

    Williamson, Lance D.; Seidel, Robert N.; Chen, Xuanxuan; Suh, Hyo Seon; Rincon Delgadillo, Paulina; Gronheid, Roel; Nealey, Paul F.

    2016-02-03

    Chemical patterns for directed self-assembly (DSA) of lamellaeforming block copolymers (BCP) with density multiplication can be fabricated by patterning resist on a cross-linked polystyrene layer, etching to create guide stripes, and depositing end-grafted brushes in between the stripes as background. To date, two-tone chemical patterns have been targeted with the guide stripes preferentially wet by one block of the copolymer and the background chemistry weakly preferentially wet by the other block. In the course of fabricating chemical patterns in an all-track process using 300 mm wafers, it was discovered that the etching process followed by brush grafting could produce a three-tone pattern. We characterized the three regions of the chemical patterns with a combination of SEM, grazing-incidence small-angle X-ray scattering (GISAXS), and assessment of BCP-wetting behavior, and evaluated the DSA behavior on patterns over a range of guide stripe widths. In its best form, the three-tone pattern consists of guide stripes preferentially wet by one block of the copolymer, each flanked by two additional stripes that wet the other block of the copolymer, with a third chemistry as the background. Three-tone patterns guide three times as many BCP domains as two-tone patterns and thus have the potential to provide a larger driving force for the system to assemble into the desired architecture with fewer defects in shorter time and over a larger process window.

  20. Loading of Silica Nanoparticles in Block Copolymer Vesicles during Polymerization-Induced Self-Assembly: Encapsulation Efficiency and Thermally Triggered Release

    PubMed Central

    2015-01-01

    Poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) diblock copolymer vesicles can be prepared in the form of concentrated aqueous dispersions via polymerization-induced self-assembly (PISA). In the present study, these syntheses are conducted in the presence of varying amounts of silica nanoparticles of approximately 18 nm diameter. This approach leads to encapsulation of up to hundreds of silica nanoparticles per vesicle. Silica has high electron contrast compared to the copolymer which facilitates TEM analysis, and its thermal stability enables quantification of the loading efficiency via thermogravimetric analysis. Encapsulation efficiencies can be calculated using disk centrifuge photosedimentometry, since the vesicle density increases at higher silica loadings while the mean vesicle diameter remains essentially unchanged. Small angle X-ray scattering (SAXS) is used to confirm silica encapsulation, since a structure factor is observed at q ≈ 0.25 nm–1. A new two-population model provides satisfactory data fits to the SAXS patterns and allows the mean silica volume fraction within the vesicles to be determined. Finally, the thermoresponsive nature of the diblock copolymer vesicles enables thermally triggered release of the encapsulated silica nanoparticles simply by cooling to 0–10 °C, which induces a morphological transition. These silica-loaded vesicles constitute a useful model system for understanding the encapsulation of globular proteins, enzymes, or antibodies for potential biomedical applications. They may also serve as an active payload for self-healing hydrogels or repair of biological tissue. Finally, we also encapsulate a model globular protein, bovine serum albumin, and calculate its loading efficiency using fluorescence spectroscopy. PMID:26600089

  1. Thermodynamics of Polymer Adsorption onto Nanoporous Silica and its Application in the Large Scale Purification of Poly(styrene)-block-Poly(alkyl methacrylate) Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Abdulahad, Asem Irfan

    As a result of unavoidable inconsistencies in their synthesis via controlled radical polymerization techniques, block copolymers inherently have distributions in chemical composition and molecular weight in each block that can have significant impact on their viscoelastic properties as well as their ability to self-assemble into ordered phases. High performance liquid chromatography is routinely utilized for determining the average molecular weight distribution that exist in synthetic polymers and is becoming increasingly popular for the fractionation and purification of chemically diverse complex polymer materials such as diblock copolymers. However, the inability of HPLC fractionation to provide meaningful quantities of purified complex polymers makes this method extremely inefficient and limits the ability to characterize purified fractions further. Overall, this dissertation work can be digested in two distinct parts. In the first part, high performance liquid chromatography was used as a tool for studying the influential parameters affecting the critical adsorption point of poly(styrene) and poly(alkyl methacrylate) homopolymers. The understanding gained in the first portion was depended on for the development of large scale fractionation procedures. In the second part, a chemically diverse variety of poly(alkyl methacrylate)-block-poly(styrene) diblock copolymers synthesized by atom transfer radical polymerization and anionic polymerization were purified by large scale adsorption-based fractionation procedures that included chromatographic filtration and the sequential adsorption/desorption of bulk diblock copolymer materials. The impact of diblock copolymer purification is addressed by comparing the molecular weight distribution, chemical composition distribution, viscoelastic properties, and small-angle X-ray scattering profiles.

  2. Coarse-grain molecular dynamics simulations of diblock copolymer surfactants interacting with a lipid bilayer

    NASA Astrophysics Data System (ADS)

    Srinivas, Goundla; Klein, Michael L.

    2004-01-01

    The interaction of surfactant diblock poly(ethylene oxide)-poly(ethylethylene) copolymers (PEO-PEE) with a lipid bilayer of dimyristoylphosphatidylcholine has been studied by means of coarse-grain molecular dynamics simulations. The effect of the surfactants on the lipid bilayer was studied over a wide range of diblock copolymer concentrations. The simulations show that the hydrophilic PEO chains adopt different structures at low and high concentrations. In particular, the computed density profiles reveal that the PEO chains extend over a longer range from the bilayer surface, with increasing copolymer concentration. The simulated density profiles are in agreement with the scaling law predictions.

  3. Propensity of Self-Assembled Leucine-Lysine Diblock Copolymeric α-Helical Peptides To Remain in Parallel and Antiparallel Alignments in Water.

    PubMed

    Sarkar, Sujit; Pandey, Prithvi Raj; Roy, Sudip

    2015-07-30

    Molecular dynamics simulation study of α-helical diblock copolypeptides preassembled in parallel and antiparallel alignments in water are presented. The assembled peptide lamellar structures were not disrupted even after performing three-step simulation protocols. Primarily hydrogen bonds between peptide are responsible for the stability. The analysis of the trajectory also suggests that water plays a significant role in favoring self-assembly. We have detected continuous hydrogen bonded network structure, which is further responsible for the stability of the lamellar structures. We have performed a detailed analysis of the hydrogen bonded network structure and its length. Further, free energy calculations revealed that the degree of stability for both lamellae are similar. The present study provides structural insight into the stability of self-assembled structures of block copolypeptides.

  4. Lamellae orientation in dynamically sheared diblock copolymer melts

    NASA Astrophysics Data System (ADS)

    Koppi, Kurt A.; Tirrell, Matthew; Bates, Frank S.; Almdal, Kristoffer; Colby, Ralph H.

    1992-11-01

    Two distinct lamellae orientaitons have been identified by small-angle neutron scattering (SANS) in dynamically sheared poly(ethylene-propylene)-poly(ethylethylene) (PEP-PEE) diblock copolymer melts. Near the order-disorder transition temperature, Tto T_ODT, and at low shear frequencies, the lamellae arrange with unit normal perpendicular to the flow direction and parallel to the velocity gradient direction (parallel orientation). Higher frequency processing leads to lamellae with unit normal permendicular to both the flow and velocity gradient directions (perpendicular orientation). The crossover from low to high frequency behavior occurs at ω≈tau^{-1} where tau is the relaxation time for local domain deformations. At temperatures further from the ODT, T<diblock copolymers. Nous avons identifié, par diffusion de neutrons aux petits angles, deux orientation différentes des lamelles dans des échantillons de copolymères séquencés poly(éthylène-propylène)- poly(éthylétylène) (PEP-PEE) qui ont été cisaillés dynamiquement. A des températures proches de la transition ordre-désordre et aux fréquences de cisaillement faibles, la normale aux couches est perpendiculaire à la direction d'écoulement et parallèle au gradient de vitesse (orientation parllèle). Aux fréquences plus élevées, la normale est perpendiculaire à la direction d'écoulement et au gradient de vitesse (orientation perpendiculaire). Le

  5. Crystalline free energies of micelles of diblock copolymer solutions.

    PubMed

    D'Adamo, Giuseppe; Pierleoni, Carlo

    2010-11-28

    We report a characterization of the relative stability and structural behavior of various micellar crystals of an athermal model of AB-diblock copolymers in solution. We adopt a previously developed coarse-graining representation of the chains which maps each copolymer on a soft dumbbell. Thanks to this strong reduction of degrees of freedom, we are able to investigate large aggregated systems and for a specific length ratio of the blocks f = M(A)∕(M(A) + M(B)) = 0.6, to locate the order-disorder transition of the system of micelles. Above the transition, mechanical and thermal properties are found to depend on the number of particles per lattice site in the simulation box, and the application of a recent methodology for multiple occupancy crystals [B. M. Mladek et al., Phys. Rev. Lett. 99, 235702 (2007)] is necessary to correctly define the equilibrium state. Within this scheme we have performed free energy calculations at two reduced density ρ∕ρ∗ = 4, 5 and for several cubic structures such as fcc, bcc, and A15. At both densities, the bcc symmetry is found to correspond to the minimum of the unconstrained free energy, that is to the stable symmetry among the few considered, while the A15 structure is almost degenerate, indicating that the present system prefers to crystallize in less packed structures. At ρ∕ρ∗ = 4 close to melting, the Lindemann ratio is fairly high (∼0.29) and the concentration of vacancies is roughly 6%. At ρ∕ρ∗ = 5 the mechanical stability of the stable bcc structure increases and the concentration of vacancies accordingly decreases. The ratio of the corona layer thickness to the core radius is found to be in good agreement with experimental data for poly(styrene-b-isoprene)(22-12) in isoprene selective solvent which is also reported to crystallize in the bcc structure.

  6. Sulfonated amphiphilic block copolymers : synthesis, self-assembly in water, and application as stabilizer in emulsion polymerization

    Treesearch

    Jiguang Zhang; Matthew R. Dubay; Carl J. Houtman; Steven J. Severtson

    2009-01-01

    Described is the synthesis of diblock copolymers generated via sequential atom transfer radical polymerization (ATRP) of poly(n-butyl acrylate) (PnBA) followed by chain augmentation with either sulfonated poly(2-hydroxyethyl methacrylate) (PHEMA) or poly(2-hydroxyethyl acrylate) (PHEA) blocks. ATRP of PHEMA or PHEA from PnBA macroinitiator was conducted in acetone/...

  7. Molecular Simulation of Bicontinuous Phases in Diblock Copolymer Melts

    NASA Astrophysics Data System (ADS)

    Martinez-Veracoechea, Francisco; Escobedo, Fernando

    2008-03-01

    Molecular simulations are used to study the stabilization of different bicontinuous phases in diblock copolymer (DBC) melts. The stabilization approach entails attempting to reduce the packing frustration inside the bicontinuous phases nodes by the addition of a ``filler'' with affinity for the A component. Two different strategies are considered: 1) addition of selective-solvent particles, and 2) addition of homopolymer. Approximate phase boundaries were found via free-energy calculations. A very dissimilar phase behavior is observed upon increasing the amount of the ``additive'' in the two different strategies. While with the first strategy (i.e., addition of selective solvent) we observed the progression Gyroid (G) -> Perforated Lamella -> Lamella -> Reversed-Gyroid. With the second strategy (i.e., addition of homopolymer) we observed the progression of morphologies G -> Cylinder -> Double Diamond (DD) -> Plumber's Nightmare (P). In both the DD and the P phases, the homopolymer concentrates preferentially in the nodes, suggesting the reduction of the nodes' packing frustration. In addition, a novel morphology was observed, wherein cylinders of two different diameters alternate in a tetragonal packing. The contrasting difference in the phase behavior observed for the two strategies is understood as a consequence of the difference in mixing entropy exhibited by the two additives.

  8. New self-assembling polyaspartylhydrazide copolymer micelles for anticancer drug delivery.

    PubMed

    Licciardi, Mariano; Cavallaro, Gennara; Di Stefano, Mauro; Pitarresi, Giovanna; Fiorica, Calogero; Giammona, Gaetano

    2010-08-30

    A new amphiphilic copolymer have been synthesized starting from the hydrosoluble polyaspartylhydrazide (PAHy) polymer, by grafting both hydrophilic PEG(2000) chains and hydrophobic palmitic acid (C(16)) moieties on polymer backbone, and the structure of obtained PAHy-PEG(2000)-C(16) copolymer have been characterized by 2D (1)H/(13)C NMR experiments. PAHy-PEG(2000)-C(16) copolymer showed the ability of self-assembling in aqueous media giving a core-shell structure and resulted potentially useful for encapsulating and dissolving hydrophobic drug. The formation of micellar core-shell structure has been investigated by 2D (1)H NMR NOESY experiments. The presence of cross-peaks for protons of C(16) and PAHy portions, indicated that the two domains are in close proximity forming micelle core. The critical aggregation concentration (CAC) values of PAHy-PEG(2000)-C(16) amphiphilic graft copolymer was determined in water by fluorescence technique, and it was demonstrated that PAHy-PEG(2000)-C(16) micelles are well suited to be micellar vehicle of highly hydrophobic molecules. Therefore, anticancer drug tamoxifen, used as a model hydrophobic molecule, was loaded into PAHy-PEG(2000)-C(16) micelles obtaining an increase of drug solubility of about 3000 times. Transmission electron microscopy (TEM) observations showed the spherical morphology of micelles formed by PAHy-PEG(2000)-C(16) copolymer with a mean diameter of about 30nm, as confirmed also by dynamic light scattering (DLS) studies. Finally, in vitro cell viability studies were carried out on human breast cancer cells (MCF-7) testing the pharmacological activity of tamoxifen-loaded PAHy-PEG(2000)-C(16) micelles, in comparison with free tamoxifen at different drug concentrations, demonstrating that tamoxifen-loaded PAHy-PEG(2000)-C(16) micelles exhibited a concentration-dependent cytotoxic activity. Copyright 2010 Elsevier B.V. All rights reserved.

  9. Hierarchical self-assembly of spider silk-like block copolymers

    NASA Astrophysics Data System (ADS)

    Krishnaji, Sreevidhya; Huang, Wenwen; Cebe, Peggy; Kaplan, David

    2011-03-01

    Block copolymers provide an attractive venue to study well-defined nano-structures that self-assemble to generate functionalized nano- and mesoporous materials. In the present study, a novel family of spider silk-like block copolymers was designed, bioengineered and characterized to study the impact of sequence chemistry, secondary structure and block length on assembled morphology. Genetic variants of native spider dragline silk (major ampullate spidroin I, Nephila clavipes) were used as polymer building blocks. Characterization by FTIR revealed increased ?-sheet content with increasing hydrophobic A blocks; SEM revealed spheres, rod-like structures, bowl-shaped and giant compound micelles. Langmuir Blodgett monolayers were prepared at the air-water interface at different surface pressures and monolayer films analyzed by AFM revealed oblate to prolate structures. Circular micelles, rod-like, densely packed circular structures were observed for HBA6 at increasing surface pressure. Exploiting hierarchical assembly provide a promising approach to rationale designs of protein block copolymer systems, allowing comparison to traditional synthetic systems.

  10. Self-Assembly of Rod-Coil Block Copolymers and Their Application in Electroluminescent Devices

    SciTech Connect

    Tao, Yuefei; Ma, Biwu; Segalman, Rachel A.

    2008-11-18

    The formation of alternating electron transporting and hole transporting 15 nm lamellae within the active layer of an organic light-emitting diode (OLED) is demonstrated to improve device performance. A new multifunctional bipolar rod-coil block copolymer containing a poly(alkoxy phenylenevinylene) (PPV) rod-shaped block as the hole transporting and emitting material and a poly(vinyloxadiazole) coil-shaped electron transporting block is synthesized. This new block copolymer is the active material of a self-assembling multicomponent electroluminescent device that can be deposited in a single step. In the thin film, grazing incidence X-ray scattering and transmission electron microscopy demonstrate that the layers form grains which are oriented bimodally: parallel and perpendicular from the anode. In this mixed orientation, the device demonstrates better performance than those with either pure PPV or a blend of the two analogous homopolymers as the active materials, i.e., higher external quantum efficiency (EQE) and brightness. This improved device performance is mainly attributed to the bipolar functionality and microphase separation of the block copolymer, which provide highly efficient hole and electron recombination at the nanodomain interfaces.

  11. Self-Assembly of Rod-Coil Block Copolymers And Their Application in Electroluminescent Devices

    SciTech Connect

    Tao, Y.; Ma, B.; Segalman, R.A.

    2009-05-26

    The formation of alternating electron transporting and hole transporting 15 nm lamellae within the active layer of an organic light-emitting diode (OLED) is demonstrated to improve device performance. A new multifunctional bipolar rod-coil block copolymer containing a poly(alkoxy phenylenevinylene) (PPV) rod-shaped block as the hole transporting and emitting material and a poly(vinyloxadiazole) coil-shaped electron transporting block is synthesized. This new block copolymer is the active material of a self-assembling multicomponent electroluminescent device that can be deposited in a single step. In the thin film, grazing incidence X-ray scattering and transmission electron microscopy demonstrate that the layers form grains which are oriented bimodally: parallel and perpendicular from the anode. In this mixed orientation, the device demonstrates better performance than those with either pure PPV or a blend of the two analogous homopolymers as the active materials, i.e., higher external quantum efficiency (EQE) and brightness. This improved device performance is mainly attributed to the bipolar functionality and microphase separation of the block copolymer, which provide highly efficient hole and electron recombination at the nanodomain interfaces.

  12. Patchy nanoparticles self-assembled from linear triblock copolymers under spherical confinement: a simulated annealing study.

    PubMed

    Yu, Bin; Deng, Jianhua; Li, Baohui; Shi, An-Chang

    2014-09-21

    The self-assembly of linear ABC triblock copolymers confined in spherical nanopores is studied using a simulated annealing technique. Morphological phase diagrams as a function of the pore diameter, the selectivity of the pore-wall to the terminal blocks, and the copolymer composition are constructed. A variety of patchy nanoparticles and multiple morphological transitions are identified. Janus nanoparticles, which can be regarded as particles with one patch, are observed inside small nanopores. With increasing the pore diameter, the number of patches on a nanoparticle surface increases from one to two, four, five, six, and seven. The size of each patch increases periodically. The number of patches also increases with increasing the wall selectivity. The distribution of the patches on the surface of a given particle is highly symmetric. The interior structures of the patchy nanoparticles and the morphological transition are investigated by calculating the bridging fraction, the mean square end-to-end distance and the average contact number between different components. A series of entropy-driven morphological transitions is predicted. Furthermore, it is found that the overall patchy morphology is largely controlled by the volume fraction of the middle B-block, while the internal structure is largely controlled by the volume fraction ratio of the two terminal blocks. Our study demonstrates that the size of nanopores, the pore-wall selectivity, and the copolymer composition could be utilized as effective means to tune the structure and properties of the anisotropic nanoparticles.

  13. Effect of chain shape on the self-assembly of bioinspired block copolymers

    NASA Astrophysics Data System (ADS)

    Rosales, Adrianne M.; Murnen, Hannah K.; Zuckermann, Ronald N.; Segalman, Rachel A.

    2012-02-01

    Polymer chain shape has been shown to affect both polymer properties and block copolymer self-assembly. Polypeptoids, a class of sequence-specific bioinspired polymer, have a chain shape that can be tuned by the introduction of monomers with bulky, chiral side chains, allowing one to change the polymer conformation while preserving the chemical nature of the side chains. Here, it is shown that introducing chiral, aromatic monomers into the polypeptoid chain increases the glass transition by 20 C for a chiral, helical polypeptoid compared to its achiral, non-structured analog. Incorporation of these polypeptoids into block copolymers with poly(methyl acrylate) enables a systematic study of the effect of chain shape while maintaining similar enthalpic interactions. For two otherwise analogous block copolymers, conformational asymmetry is shown to affect both the morphological domain spacing and the order-disorder transition temperature. Future work will focus on interfacial segregation experiments to determine the effect of conformational asymmetry on the Flory-Huggins parameter.

  14. Tuning the Chirality of Block Copolymers: From Twisted Morphologies to Nanospheres by Self-Assembly.

    PubMed

    Suárez-Suárez, Silvia; Carriedo, Gabino A; Presa Soto, Alejandro

    2015-09-28

    New advances into the chirality effect in the self-assembly of block copolymers (BCPs) have been achieved by tuning the helicity of the chiral-core-forming blocks. The chiral BCPs {[N=P(R)-O2C20H12](200-x)[N=P(OC5H4N)2](x)}-b-[N=PMePh]50 ((R)-O2C20H12 = (R)-1,1'-binaphthyl-2,2'-dioxy, OC5H4N = 4-pyridinoxy (OPy); x = 10, 30, 60, 100 for 3 a-d, respectively), in which the [N=P(OPy)2] units are randomly distributed within the chiral block, have been synthesised. The chiroptical properties of the BCPs ([α]D vs. T and CD) demonstrated that the helicity of the BCP chains may be simply controlled by the relative proportion of the chiral and achiral (i.e., [N=P(R)-O2C20H12] and [N=P(OPy)2], respectively) units. Thus, although 3 a only contained only 5% [N=P(OPy)2] units and exhibited a preferential helical sense, 3 d with 50% of this unit adopted non-preferred helical conformations. This gradual variation of the helicity allowed us to examine the chirality effect on the self-assembly of chiral and helical BCPs (i.e., 3 a-c) and chiral but non-helical BCPs (i.e., 3 d). The very significant influence of the helicity on the self-assembly of these materials resulted in a variety of morphologies that extend from helical nanostructures to pearl-necklace aggregates and nanospheres (i.e., 3 b and 3 d, respectively). We also demonstrate that the presence of pyridine moieties in BCPs 3 a-d allows specific decoration with gold nanoparticles.

  15. How Do Spherical Diblock Copolymer Nanoparticles Grow during RAFT Alcoholic Dispersion Polymerization?

    PubMed Central

    2015-01-01

    A poly(2-(dimethylamino)ethyl methacrylate) (PDMA) chain transfer agent (CTA) is used for the reversible addition–fragmentation chain transfer (RAFT) alcoholic dispersion polymerization of benzyl methacrylate (BzMA) in ethanol at 70 °C. THF GPC analysis indicated a well-controlled polymerization with molecular weight increasing linearly with conversion. GPC traces also showed high blocking efficiency with no homopolymer contamination apparent and Mw/Mn values below 1.35 in all cases. 1H NMR studies confirmed greater than 98% BzMA conversion for a target PBzMA degree of polymerization (DP) of up to 600. The PBzMA block becomes insoluble as it grows, leading to the in situ formation of sterically stabilized diblock copolymer nanoparticles via polymerization-induced self-assembly (PISA). Fixing the mean DP of the PDMA stabilizer block at 94 units and systematically varying the DP of the PBzMA block enabled a series of spherical nanoparticles of tunable diameter to be obtained. These nanoparticles were characterized by TEM, DLS, MALLS, and SAXS, with mean diameters ranging from 35 to 100 nm. The latter technique was particularly informative: data fits to a spherical micelle model enabled calculation of the core diameter, surface area occupied per copolymer chain, and the mean aggregation number (Nagg). The scaling exponent derived from a double-logarithmic plot of core diameter vs PBzMA DP suggests that the conformation of the PBzMA chains is intermediate between the collapsed and fully extended state. This is in good agreement with 1H NMR studies, which suggest that only 5−13% of the BzMA residues of the core-forming chains are solvated. The Nagg values calculated from SAXS and MALLS are in good agreement and scale approximately linearly with PBzMA DP. This suggests that spherical micelles grow in size not only as a result of the increase in copolymer molecular weight during the PISA synthesis but also by exchange of individual copolymer chains between micelles

  16. Building non-tortuous ion-conduction pathways using self-assembled block copolymers

    NASA Astrophysics Data System (ADS)

    Kim, Onnuri; Park, Moon Jeong

    Ion-containing polymers with self-assembled morphologies are becoming important ingredients of a wide range of electrochemical devices such as lithium-ion batteries, fuel cells and electroactive actuators. Although several studies have reported the relationship between morphologies and ion transport properties of such polymers, the most of quantitative analysis have been limited to two-dimensional morphologies as they occupy a large window of the phase diagrams. In present study, we investigated the effects of morphology on the ion transport efficiency with a focus on three-dimensional symmetry. A range of three-dimensional self-assembled morphologies, i.e., ill-defined cubic, orthorhombic network (O70) , and face-centered cubic phases (fcc) were achieved for a single sulfonated block copolymer upon the addition of non-stoichiometric ionic liquids. The type of three-dimensional lattice was found out to play a crucial role in determining the ion transport properties of composite membranes, where the most efficient ion-conduction was demonstrated for fcc phases with lowest tortuosity of 1 over orthorhombic networks phases (tortuosity:1.5). This intriguing result suggests a new avenue to designing polymer electrolytes with improved transport properties.

  17. Amphiphilic Graft Copolymer Nanospheres: From Colloidal Self-Assembly to CO2 Capture Membranes.

    PubMed

    Jeon, Harim; Kim, Dong Jun; Park, Min Su; Ryu, Du Yeol; Kim, Jong Hak

    2016-04-13

    Colloidal nanosphere self-assembly effectively generates ordered nanostructures, prompting tremendous interest in many applications such as photonic crystals and templates for inverse opal fabrication. Here we report the self-assembly of low-cost, graft copolymer nanospheres for CO2 capture membranes. Specifically, poly(dimethylsiloxane)-graft-poly(4-vinylpyridine) (PDMS-g-P4VP) is synthesized via one-pot, free radical dispersion polymerization to give discrete monodisperse nanospheres. These nanospheres comprise a surface-anchored highly permeable PDMS layer and internal CO2-philic P4VP spherical core. Their diameter is controllable below the submicrometer range by varying grafting ratios. The colloidal dispersion forms a long-range, close-packed hexagonal array on a substrate by inclined deposition and convective assembly. The array shows dispersion medium-dependent packing characteristics. A thermodynamic correlation is determined using different solvents to obtain stable PDMS-g-P4VP dispersions and interpreted in terms of Flory-Huggins interaction parameter. As a proof-of-concept, the implementation of these nanospheres into membranes simultaneously enhances the CO2 permeability and CO2/N2 selectivity of PDMS-based transport matrixes. Upon physical aging of the solution, the CO2/N2 selectivity is improved up to 26, one of the highest values for highly permeable PDMS-based polymeric membranes.

  18. Directed block copolymer self-assembly implemented via surface-embedded electrets

    PubMed Central

    Wu, Mei-Ling; Wang, Dong; Wan, Li-Jun

    2016-01-01

    Block copolymer (BCP) nanolithography is widely recognized as a promising complementary approach to circumvent the feature size limits of conventional photolithography. The directed self-assembly of BCP thin film to form ordered nanostructures with controlled orientation and localized pattern has been the key challenge for practical nanolithography applications. Here we show that BCP nanopatterns can be directed on localized surface electrets defined by electron-beam irradiation to realize diverse features in a simple, effective and non-destructive manner. Charged electrets can generate a built-in electric field in BCP thin film and induce the formation of perpendicularly oriented microdomain of BCP film. The electret-directed orientation control of BCP film can be either integrated with mask-based patterning technique or realized by electron-beam direct-writing method to fabricate microscale arbitrary lateral patterns down to single BCP cylinder nanopattern. The electret-directed BCP self-assembly could provide an alternative means for BCP-based nanolithography, with high resolution. PMID:26876792

  19. [INVITED] Hyperbolic-by-design self-assembled metamaterial based on block copolymers lamellar phases

    NASA Astrophysics Data System (ADS)

    Wang, Xuan; Ehrhardt, Kevin; Tallet, Clémence; Warenghem, Marc; Baron, Alexandre; Aradian, Ashod; Kildemo, Morten; Ponsinet, Virginie

    2017-02-01

    Hyperbolic metamaterials use the concept of controlling the propagative modes through the engineering of the dispersion relation, and are considered highly promising to reach different meta-properties. Here we propose a novel bottom-up fabrication technique for uniaxial anisotropic metamaterials presenting a strongly anisotropic dispersion relation in the visible wavelength range, using self-assembled nanostructured block copolymers hybridized with gold nanoparticles. The materials consist in periodic lamellar stacks of period 28 nm, of alternating layers of pure polymer (dielectric) and layers of composite of polymer loaded with a high density of 7 nm gold nanoparticles. The spectral variation of their anisotropic effective dielectric permittivity is determined by variable-angle spectroscopic ellipsometry using appropriate effective medium models, as a function of the density of plasmonic nanoparticles. For large gold loading and close to the plasmon resonance of the nanoparticles, the lamellar stack presents ordinary and extraordinary components of the dielectric function of opposite signs. We therefore demonstrate for the first time the possibility of using a self-assembly methodology for the fabrication of bulk hyperbolic metamaterial.

  20. Thermoresponsive Nanoparticles of Self-Assembled Block Copolymers as Potential Carriers for Drug Delivery and Diagnostics.

    PubMed

    Rahikkala, Antti; Aseyev, Vladimir; Tenhu, Heikki; Kauppinen, Esko I; Raula, Janne

    2015-09-14

    Thermally responsive hydrogel nanoparticles composed of self-assembled polystyrene-b-poly(N-isopropylacrylamide)-b-polystyrene block copolymers and fluorescent probe 1-anilinonaphthalene-8-sulfonic acid have been prepared by aerosol flow reactor method. We aimed exploring the relationship of intraparticle morphologies, that were, PS spheres and gyroids embedded in PNIPAm matrix, as well PS-PNIPAm lamellar structure, to probe release in aqueous solution below and above the cloud point temperature (CPT) of PNIPAm. The release was detected by fluorescence emission given by the probe binding to bovine serum albumin. Also, the colloidal behavior of hydrogel nanoparticles at varying temperatures were examined by scattering method. The probe release was faster below than above the CPT from all the morphologies of which gyroidal morphology showed the highest release. Colloidal behavior varied from single to moderately aggregated particles in order spheres-gyroids-lamellar. Hydrogel nanoparticles with tunable intra particle self-assembled morphologies can be utilized designing carrier systems for drug delivery and diagnostics.

  1. Directed block copolymer self-assembly implemented via surface-embedded electrets

    NASA Astrophysics Data System (ADS)

    Wu, Mei-Ling; Wang, Dong; Wan, Li-Jun

    2016-02-01

    Block copolymer (BCP) nanolithography is widely recognized as a promising complementary approach to circumvent the feature size limits of conventional photolithography. The directed self-assembly of BCP thin film to form ordered nanostructures with controlled orientation and localized pattern has been the key challenge for practical nanolithography applications. Here we show that BCP nanopatterns can be directed on localized surface electrets defined by electron-beam irradiation to realize diverse features in a simple, effective and non-destructive manner. Charged electrets can generate a built-in electric field in BCP thin film and induce the formation of perpendicularly oriented microdomain of BCP film. The electret-directed orientation control of BCP film can be either integrated with mask-based patterning technique or realized by electron-beam direct-writing method to fabricate microscale arbitrary lateral patterns down to single BCP cylinder nanopattern. The electret-directed BCP self-assembly could provide an alternative means for BCP-based nanolithography, with high resolution.

  2. Block copolymer templated self-assembly of disk-shaped molecules

    NASA Astrophysics Data System (ADS)

    Aragones, J. L.; Alexander-Katz, A.

    2017-08-01

    Stacking of disk-shaped organic molecules is a promising strategy to develop electronic and photovoltaic devices. Here, we investigate the capability of a soft block copolymer matrix that microphase separates into a cylindrical phase to direct the self-assembly of disk-shaped molecules by means of molecular simulations. We show that two disk molecules confined in the cylinder domain experience a depletion force, induced by the polymer chains, which results in the formation of stacks of disks. This entropic interaction and the soft confinement provided by the matrix are both responsible for the structures that can be self-assembled, which include slanted or columnar stacks. In addition, we evidence the transmission of stresses between the different minority domains of the microphase, which results in the establishment of a long-ranged interaction between disk molecules embedded in different domains; this interaction is of the order of the microphase periodicity and may be exploited to direct assembly of disks at larger scales.

  3. Molecular transport through nanoporous silicon nitride membranes produced from self-assembling block copolymers.

    PubMed

    Montagne, Franck; Blondiaux, Nicolas; Bojko, Alexandre; Pugin, Raphaël

    2012-09-28

    To achieve fast and selective molecular filtration, membrane materials must ideally exhibit a thin porous skin and a high density of pores with a narrow size distribution. Here, we report the fabrication of nanoporous silicon nitride membranes (NSiMs) at the full wafer scale using a versatile process combining block copolymer (BCP) self-assembly and conventional photolithography/etching techniques. In our method, self-assembled BCP micelles are used as templates for creating sub-100 nm nanopores in a thin low-stress silicon nitride layer, which is then released from the underlying silicon wafer by etching. The process yields 100 nm thick free-standing NSiMs of various lateral dimensions (up to a few mm(2)). We show that the membranes exhibit a high pore density, while still retaining excellent mechanical strength. Permeation experiments reveal that the molecular transport rate across NSiMs is up to 16-fold faster than that of commercial polymeric membranes. Moreover, using dextran molecules of various molecular weights, we also demonstrate that size-based separation can be achieved with a very good selectivity. These new silicon nanosieves offer a relevant technological alternative to commercially available ultra- and microfiltration membranes for conducting high resolution biomolecular separations at small scales.

  4. Self-Assembly and Relaxation Behavior of Graphene Containing Acrylic Triblock Copolymer Gels

    NASA Astrophysics Data System (ADS)

    Zabet, Mahla; Hashemnejad, Seyedmeysam; Kundu, Santanu

    2015-03-01

    Investigation of gel mechanical properties as a function of their structure is a significant research interest. This study presents the effect of graphene (or few-layer graphene) on the self-assembly and the relaxation behavior of a thermoreversible gel consists of a physically cross-linked poly (methyl methacrylate)-poly (n-butyl acrylate)-poly (methyl methacrylate) [PMMA-PnBA-PMMA] triblock copolymer in 2-ethyl-1-hexanol, a midblock selective solvent. Graphene was obtained by sonicating exfoliated graphite in 2-ethyl-1-hexanol at various concentrations. Filtration technique and spectrophotometry were utilized to measure the graphene concentration in the dispersions. The dispersed graphene was then incorporated in a series of gels and the effect of graphene on mechanical properties, including the relaxation behavior were studied. Small angle X-ray scattering (SAXS) was used to investigate the microstructure of these gels at room temperature. SAXS data were analyzed to estimate the number of end blocks per junction zone, the average spacing between the junctions, and the change of these properties as a function of graphene concentration. The results indicate that the presence of graphene affects the self-assembly process.

  5. Frequency multiplication of lamellar phase block copolymers with grapho-epitaxy directed self-assembly sensitivity to prepattern

    NASA Astrophysics Data System (ADS)

    Gronheid, Roel; Rincon Delgadillo, Paulina A.; Younkin, Todd R.; Pollentier, Ivan; Somervell, Mark; Hooge, Joshua S.; Nafus, Kathleen; Nealey, Paul F.

    2012-07-01

    The optimization of a grapho-epitaxy process flow for lamellar phase block copolymer frequency multiplication on full 300 mm wafers is discussed. The process uses a dedicated photoresist that, after hardening, allows direct coating and annealing of the block copolymer over it. Some of the critical parameters for optimization of this process were found to be the selection of the neutral layer material and reduction of the prepattern resist height. Process window analysis was done by determining the best dose and focus settings for generating high quality directed self-assembly structures with the prepattern process. A very small process window for good self-assembly and an offset in the optimum dose and focus settings for these two stages of the process were found. Finally, the sensitivity of the process to programmed prepattern imperfections was studied. Programmed protrusions in the prepattern as small as 6 nm were found to cause self-assembly defects.

  6. Self-assembly of amphiphilic and nanoparticle containing block copolymer films

    NASA Astrophysics Data System (ADS)

    Xu, Chen

    The self-assembly of amphiphilic and nanoparticle containing block copolymer films is explored in this thesis. We first present the stimuli-responsive nanostructures assembled from amphiphilic block copolymers. Amphiphilic block copolymer poly(styrene-b-acrylic acid) (PS-b-PAA) or poly(styrene-b-acrylic anhydride) (PS-b-PAAn) are derived via thermochemical evolution of the tert-butyl groups in poly(styrene-b-tert-butyl acrylate) (PS- b-PtBA). This novel approach leads to the formation of nanostructures containing perpendicular hydrophilic cylinders or ordered spherical domains on silicon substrates. The surface morphology and properties of the nanostructured PS-b-PAA films depend on external stimuli, i.e., selective solvents (water and toluene) and pH. Upon exposure to water, the hydrophilic PAA cylinders swell above the surface and transform to PAA mushrooms that render the entire surface hydrophilic. Upon exposure to toluene, the hydrophobic PS matrix swells above the surface and results in a hydrophobic surface. Because PAA is a weak polyelectrolyte, the films exhibit three unique nanostructured morphologies across three pH regimes. Film wettability can be tuned by directing the arrangement of PAA chains via external stimulation, demonstrating that the nanostructured PS-b-PAA films can display self-adaptive surface properties. This dissertation also explores the dispersion of poly(methyl methacrylate) (PMMA)-grafted magnetic magnetite (Fe3O4) NPs in PMMA and poly(styrene-b-methyl methacrylate) (PS-b-PMMA) films, as well as the self-assembly of PS-b-PMMA/Fe 3O4 NP nanocomposite films. The Fe3O4 NPs are grafted with PMMA brushes of three different molecular weights, i.e., 2700, 13300 and 35700 g/mol (i.e., Fe3O4-2.7K, Fe 3O4-13.3K and Fe3O4-35.7K). The Fe 3O4-35.7K NPs are uniformly dispersed in PMMA films, whereas the Fe3O4 NPs with short brushes form aggregates. This behavior is consistent with the wet and dry brush theory. However, for NPs in PS-b-PMMA films an

  7. ELEMENTARY APPROACH TO SELF-ASSEMBLY AND ELASTIC PROPERTIES OF RANDOM COPOLYMERS

    SciTech Connect

    S. M. CHITANVIS

    2000-10-01

    The authors have mapped the physics of a system of random copolymers onto a time-dependent density functional-type field theory using techniques of functional integration. Time in the theory is merely a label for the location of a given monomer along the extent of a flexible chain. We derive heuristically within this approach a non-local constraint which prevents segments on chains in the system from straying too far from each other, and leads to self-assembly. The structure factor is then computed in a straightforward fashion. The long wave-length limit of the structure factor is used to obtain the elastic modulus of the network. It is shown that there is a surprising competition between the degree of micro-phase separation and the elastic moduli of the system.

  8. Highly tunable refractive index visible-light metasurface from block copolymer self-assembly

    NASA Astrophysics Data System (ADS)

    Kim, Ju Young; Kim, Hyowook; Kim, Bong Hoon; Chang, Taeyong; Lim, Joonwon; Jin, Hyeong Min; Mun, Jeong Ho; Choi, Young Joo; Chung, Kyungjae; Shin, Jonghwa; Fan, Shanhui; Kim, Sang Ouk

    2016-09-01

    The refractive index of natural transparent materials is limited to 2-3 throughout the visible wavelength range. Wider controllability of the refractive index is desired for novel optical applications such as nanoimaging and integrated photonics. We report that metamaterials consisting of period and symmetry-tunable self-assembled nanopatterns can provide a controllable refractive index medium for a broad wavelength range, including the visible region. Our approach exploits the independent control of permeability and permittivity with nanoscale objects smaller than the skin depth. The precise manipulation of the interobject distance in block copolymer nanopatterns via pattern shrinkage increased the effective refractive index up to 5.10. The effective refractive index remains above 3.0 over more than 1,000 nm wavelength bandwidth. Spatially graded and anisotropic refractive indices are also obtained with the design of transitional and rotational symmetry modification.

  9. Highly tunable refractive index visible-light metasurface from block copolymer self-assembly.

    PubMed

    Kim, Ju Young; Kim, Hyowook; Kim, Bong Hoon; Chang, Taeyong; Lim, Joonwon; Jin, Hyeong Min; Mun, Jeong Ho; Choi, Young Joo; Chung, Kyungjae; Shin, Jonghwa; Fan, Shanhui; Kim, Sang Ouk

    2016-09-29

    The refractive index of natural transparent materials is limited to 2-3 throughout the visible wavelength range. Wider controllability of the refractive index is desired for novel optical applications such as nanoimaging and integrated photonics. We report that metamaterials consisting of period and symmetry-tunable self-assembled nanopatterns can provide a controllable refractive index medium for a broad wavelength range, including the visible region. Our approach exploits the independent control of permeability and permittivity with nanoscale objects smaller than the skin depth. The precise manipulation of the interobject distance in block copolymer nanopatterns via pattern shrinkage increased the effective refractive index up to 5.10. The effective refractive index remains above 3.0 over more than 1,000 nm wavelength bandwidth. Spatially graded and anisotropic refractive indices are also obtained with the design of transitional and rotational symmetry modification.

  10. Creating periodic local strain in monolayer graphene with nanopillars patterned by self-assembled block copolymer

    SciTech Connect

    Mi, Hongyi; Mikael, Solomon; Seo, Jung-Hun; Gui, Gui; Ma, Alice L.; Ma, Zhenqiang E-mail: mazq@engr.wisc.edu; Liu, Chi-Chun; Nealey, Paul F. E-mail: mazq@engr.wisc.edu

    2015-10-05

    A simple and viable method was developed to produce biaxial strain in monolayer graphene on an array of SiO{sub 2} nanopillars. The array of SiO{sub 2} nanopillars (1 cm{sup 2} in area, 80 nm in height, and 40 nm in pitch) was fabricated by employing self-assembled block copolymer through simple dry etching and deposition processes. According to high resolution micro-Raman spectroscopy and atomic force microscopy analyses, 0.9% of maximum biaxial tensile strain and 0.17% of averaged biaxial tensile strain in graphene were created. This technique provides a simple and viable method to form biaxial tensile strain in graphene and offers a practical platform for future studies in graphene strain engineering.

  11. Highly tunable refractive index visible-light metasurface from block copolymer self-assembly

    PubMed Central

    Kim, Ju Young; Kim, Hyowook; Kim, Bong Hoon; Chang, Taeyong; Lim, Joonwon; Jin, Hyeong Min; Mun, Jeong Ho; Choi, Young Joo; Chung, Kyungjae; Shin, Jonghwa; Fan, Shanhui; Kim, Sang Ouk

    2016-01-01

    The refractive index of natural transparent materials is limited to 2–3 throughout the visible wavelength range. Wider controllability of the refractive index is desired for novel optical applications such as nanoimaging and integrated photonics. We report that metamaterials consisting of period and symmetry-tunable self-assembled nanopatterns can provide a controllable refractive index medium for a broad wavelength range, including the visible region. Our approach exploits the independent control of permeability and permittivity with nanoscale objects smaller than the skin depth. The precise manipulation of the interobject distance in block copolymer nanopatterns via pattern shrinkage increased the effective refractive index up to 5.10. The effective refractive index remains above 3.0 over more than 1,000 nm wavelength bandwidth. Spatially graded and anisotropic refractive indices are also obtained with the design of transitional and rotational symmetry modification. PMID:27683077

  12. Nanostructured Colloidal Particles by Confined Self-Assembly of Block Copolymers in Evaporative Droplets

    NASA Astrophysics Data System (ADS)

    Kim, Minsoo; Yi, Gi-Ra

    2015-06-01

    Block copolymers (BCPs) can create various morphology by self-assembly in bulk or film. Recently, using BCPs in confined geometries such as thin film (one-dimension), cylindrical template (two-dimension), or emulsion droplet (three-dimension), nanostructured BCP particles have been prepared, in which unique nanostructures of the BCP are formed via solvent annealing process and can be controlled depending on molecular weight ratio and interaction parameter of the BCPs, and droplet size. Moreover, by tuning interfacial property of the BCP particles, anisotropic particles with unique nanostructures have been prepared. Furthermore, for practical application such as drug delivery system, sensor, self-healing, metamaterial, and optoelectronic device, functional nanoparticles can be incorporated inside BCP particles. In this article, we summarize recent progress on the production of structured BCP particles and composite particles with metallic nanoparticles.

  13. Placement error in directed self-assembly of block copolymers for contact hole application

    NASA Astrophysics Data System (ADS)

    Bouanani, Shayma; Tiron, Raluca; Bos, Sandra; Gharbi, Ahmed; Barros, Patricia Pimenta; Hazart, Jérôme; Robert, Frédéric; Lapeyre, Céline; Ostrovsky, Alain; Monget, Cédric

    2016-04-01

    Directed self-assembly (DSA) of block copolymers has shown interesting results for contact hole application, as a vertical interconnection access for CMOS sub-10 nm technology. The control of critical dimension uniformity (CDU), defectivity, and placement error (PE) is challenging and depends on multiple processes and material parameters. This paper reports the work done using the 300-mm pilot line available in materials to integrate the DSA process on contact and via level patterning. In the first part, a reliable methodology for PE measurement is defined. By tuning intrinsic edge detection parameters on standard reference images, the working window is determined. The methodology is then implemented to analyze the experimental data. The impact of the planarization process on PE and the importance of PE as a complement of CDU and hole open yield for process window determination are discussed.

  14. Hierarchical volume gratings by combining holographic-patterning and block copolymer self-assembly

    NASA Astrophysics Data System (ADS)

    Birnkrant, Michael; Marron, Russell; Li, Christopher; Natarajan, Lalgudi; Tondiglia, Vincent; Bunning, Timothy

    2009-03-01

    A novel hierarchical photonic crystal (HPC) was fabricated by combining top-down and bottom-up nanomanufacturing techniques. The hierarchical structure was fabricated from a volume of material by combining holographic patterning (HP) and block copolymer (BCP) self assembly. The structure of the HPC was investigated as a function of the BCP architecture, BCP concentration and crystallization temperature. Upon heating the photonic crystal a red shift in the reflected wavelength occurs; but, an initial decrease in diffraction efficiency (DE) followed by an increase in DE indicates a non-monotonic change in the structure of the HPC. Upon cooling the reverse occurs reflecting the dynamic change in the hierarchical structure. Transmission electron microscopy, in-situ FTIR and optical spectroscopy were used to correlate the optical property change with BCP/HPC morphology. This approach could open a gateway to fabricating multifunctional hierarchical nanostructures.

  15. Self-assembled block copolymer photonic crystal for selective fructose detection.

    PubMed

    Ayyub, Omar B; Ibrahim, Michael B; Briber, Robert M; Kofinas, Peter

    2013-08-15

    The use of one-dimensional photonic crystals fabricated from a self-assembled lamellar block copolymer as a sensitive and selective fructose sensor is investigated. The polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) films are functionalized with 2-(bromomethyl)phenylboronic acid. The boronic acid moiety confined within the lamellar morphology can reversibly bind to sugars such as fructose, imparting the photonic properties of the PS-b-P2VP film. The films exhibit a detection limit of 500 μM in water and 1mM in phosphate buffered saline. Exposure to a 50 mM solution of fructose invokes a highly visible color change from blue to orange. The films are also able to selectively recognize and respond to fructose in competitive studies in the presence of glucose, mannose and sucrose.

  16. Phase Behavior and Ionic Conductivity of Concentrated Solutions of Polystyrene-Poly(ethylene oxide) Diblock Copolymers in an Ionic Liquid

    SciTech Connect

    Simone, Peter M.; Lodge, Timothy P.

    2010-03-16

    Concentrated solutions of poly(styrene-b-ethylene oxide) (PS-PEO) diblock copolymers were prepared using the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMI][TFSI] as the solvent. The self-assembled microstructures adopted by the copolymer solutions have been characterized using small-angle X-ray scattering. Lyotropic mesophase transitions were observed, with a progression from hexagonally packed cylinders of PEO, to lamellae, to hexagonally packed cylinders of PS upon increasing [EMI][TFSI] content. The change in lamellar domain spacing with ionic liquid concentration was found to be comparable to that reported for other block copolymers in strongly selective solvents. The ionic conductivity of the concentrated PS-PEO/[EMI][TFSI] solutions was measured via impedance spectroscopy, and ranged from 1 x 10{sup -7} to 1 x 10{sup -3} S/cm at temperatures from 25-100 C. Additionally, the ionic conductivity of the solutions was found to increase with both ionic liquid concentration and molecular weight of the PEO blocks. The ionic conductivity of PEO homopolymer/[EMI][TFSI] solutions was also measured in order to compare the conductivity of the PS-PEO solutions to the expected limit for a lamellar sample with randomly oriented microstructure grains.

  17. A new strategy to fabricate composite thin films with tunable micro- and nanostructures via self-assembly of block copolymers.

    PubMed

    Zhao, Xingjuan; Wang, Qian; Lee, Yong-Ill; Hao, Jingcheng; Liu, Hong-Guo

    2015-12-04

    A new and facile strategy to fabricate composite thin films with tunable morphologies via self-assembly of block copolymer molecules at the air/liquid interface is first reported. The morphologies (parallel nanowires and foams) of these freestanding thin films can be tuned by varying the molecular structure or other experimental conditions.

  18. Self-assembly of well-defined ferrocene triblock copolymers and their template synthesis of ordered iron oxide nanoparticles.

    PubMed

    Hardy, Christopher G; Ren, Lixia; Ma, Shuguo; Tang, Chuanbing

    2013-05-14

    Well-defined ferrocene-containing triblock copolymers were synthesized by atom transfer radical polymerization and self-assembled into highly ordered hexagonal arrays of cylinders via solvent annealing. The thin films were further used as a template and converted into highly ordered iron oxide nanoparticles (α-Fe2O3) by UV/ozonolysis and thermal pyrolysis.

  19. Synthesis of amphiphilic tadpole-shaped linear-cyclic diblock copolymers via ring-opening polymerization directly initiating from cyclic precursors and their application as drug nanocarriers.

    PubMed

    Wan, Xuejuan; Liu, Tao; Liu, Shiyong

    2011-04-11

    We report on the facile synthesis of well-defined amphiphilic and thermoresponsive tadpole-shaped linear-cyclic diblock copolymers via ring-opening polymerization (ROP) directly initiating from cyclic precursors, their self-assembling behavior in aqueous solution, and the application of micellar assemblies as controlled release drug nanocarriers. Starting from a trifunctional core molecule containing alkynyl, hydroxyl, and bromine moieties, alkynyl-(OH)-Br, macrocyclic poly(N-isopropylacrylamide) (c-PNIPAM) bearing a single hydroxyl functionality was prepared by atom transfer radical polymerization (ATRP), the subsequent end group transformation into azide functionality, and finally the intramacromolecular ring closure reaction via click chemistry. The target amphiphilic tadpole-shaped linear-cyclic diblock copolymer, (c-PNIPAM)-b-PCL, was then synthesized via the ROP of ε-caprolactone (CL) by directly initiating from the cyclic precursor. In aqueous solution at 20 °C, (c-PNIPAM)-b-PCL self-assembles into spherical micelles consisting of hydrophobic PCL cores and well-solvated coronas of cyclic PNIPAM segments. For comparison, linear diblock copolymer with comparable molecular weight and composition, (l-PNIPAM)-b-PCL, was also synthesized. It was found that the thermoresponsive coronas of micelles self-assembled from (c-PNIPAM)-b-PCL exhibit thermoinduced collapse and aggregation at a lower critical thermal phase transition temperature (T(c)) compared with those of (l-PNIPAM)-b-PCL. Temperature-dependent drug release profiles from the two types of micelles of (c-PNIPAM)-b-PCL and (l-PNIPAM)-b-PCL loaded with doxorubicin (Dox) were measured, and the underlying mechanism for the observed difference in releasing properties was proposed. Moreover, MTT assays revealed that micelles of (c-PNIPAM)-b-PCL are almost noncytotoxic up to a concentration of 1.0 g/L, whereas at the same polymer concentration, micelles loaded with Dox lead to ∼60% cell death. Overall, chain

  20. Kinetics of pH-Induced formation and dissociation of polymeric vesicles assembled from a water-soluble zwitterionic diblock copolymer.

    PubMed

    Shen, Lei; Du, Jianzhong; Armes, Steven P; Liu, Shiyong

    2008-09-16

    The kinetics of pH-induced formation and dissociation of vesicles self-assembled from a biocompatible zwitterionic diblock copolymer, poly(2-(methacryloyloxy)ethyl phosphorylcholine)-b-poly(2-(diisopropylamino)ethyl methacrylate) (PMPC- b-PDPA), was investigated in detail via a combination of stopped-flow light scattering and laser light scattering (LLS). Upon jumping from pH 2 to 10, stopped-flow light scattering reveals three distinct relaxation processes for the early stages of vesicle self-assembly (0-40 s). Kinetic sequences associated with the obtained three characteristic relaxation times have been tentatively proposed. Moreover, the kinetics of vesicle formation in the later stage (from 3 min onward) was investigated by dynamic LLS. It was found that both the intensity-averaged hydrodynamic radius, R h, and the polydispersity, mu2/Gamma (2), decrease exponentially, yielding a characteristic relaxation time of approximately 350 s. To our knowledge, this is the first report on the kinetics of the unimer-to-vesicle transition of a stimulus-responsive diblock copolymer. The kinetics of vesicle dissociation for a pH jump from 12 to 2 was also investigated. The breakdown of polymeric vesicles is extremely fast and is independent of polymer concentration; it is complete within approximately 5 ms and is in marked contrast to the much slower rate of vesicle formation.

  1. Selectivity and temperature dependence of phase and phase transition in diblock copolymer solution.

    PubMed

    Zhang, Lingyun; Wang, Peng-Ye

    2011-04-01

    In order to study the effects of solvent selectivity and temperature on phase behavior and transition of diblock copolymer solution, self-consistent field theory is modified to incorporate the short-range interaction and non-local effects. Inhomogeneous free-energy density is shown to be dependent on solvent selectivity, temperature and copolymer concentration. Enthalpic quantity and entropic contributions are crucial to phase diagrams of diblock copolymer solution. Three selective strengths of solvent --weak, moderate and strong-- are chosen for comparison. For a weakly selective solvent, theoretical and experimental results illustrate the same variation tendency in the phase boundary of the order-disorder transition for a symmetric diblock of polystyrene and polyisoprene. Self-consistent field equations can be used to calculate the exact FCC-BCC structural phase transition temperatures in moderately and strongly selective solvents. Detailed comparison with the experimental phase diagrams including lamellar, cylindrical and spherical structures is presented.

  2. Microphase separation in thin films of lamellar forming polydisperse di-block copolymers

    DOE PAGES

    Kumar, Rajeev; Lokitz, Bradley S.; Sides, Scott W.; ...

    2015-02-03

    Despite the ubiquity of polydispersity in chain lengths of di-block copolymers, its effects on microphase separation in thin films have eluded a clear understanding. In this paper, we have studied effects of polydispersity on the microphase separation in thin films of lamellar forming di-block copolymers using self-consistent field theory (SCFT) and neutron reflectivity experiments. Di-block copolymers containing a polydisperse block of poly(glycidylmethacrylate) (PGMA) connected to a near-monodisperse block poly(2-vinyl-4,4-dimethyl-d6 azlactone) (PVDMA-d6) are considered in this work. Effects of chain length polydispersity, film thickness, substrate–monomer and monomer–monomer interactions on the microphase segregation are studied using SCFT. The theoretical study reveals thatmore » in comparison to a film created with monodisperse di-block copolymers, an increase in polydispersity tends to decrease the number of lamellar strata that can be packed in a film of given thickness. This is a direct consequence of an increase in lamellar domain spacing with an increase in polydispersity index. Furthermore, it is shown that polydispersity induces conformational asymmetry and an increase in the polydispersity index leads to an increase in the effective Kuhn segment length of the polydisperse blocks. It is shown that the conformational asymmetry effects, which are entropic in origin and of increasing importance as film thickness decreases, drive the polydisperse blocks to the middle of the films despite favorable substrate interactions. These predictions are verified by results from neutron reflectivity experiments on thin films made from moderately polydisperse PGMA-PVDMA-d6 di-block copolymer deposited on silicon substrates. In conclusion, results from SCFT are used to predict neutron reflectivity profiles, providing a facile and robust route to obtain useful physical insights into the structure of polydisperse diblock copolymers at interfaces.« less

  3. Microphase separation in thin films of lamellar forming polydisperse di-block copolymers

    SciTech Connect

    Kumar, Rajeev; Lokitz, Bradley S.; Sides, Scott W.; Chen, Jihua; Heller, William T.; Ankner, John F.; Browning, James F.; Kilbey, II, S. Michael; Sumpter, Bobby G.

    2015-02-03

    Despite the ubiquity of polydispersity in chain lengths of di-block copolymers, its effects on microphase separation in thin films have eluded a clear understanding. In this paper, we have studied effects of polydispersity on the microphase separation in thin films of lamellar forming di-block copolymers using self-consistent field theory (SCFT) and neutron reflectivity experiments. Di-block copolymers containing a polydisperse block of poly(glycidylmethacrylate) (PGMA) connected to a near-monodisperse block poly(2-vinyl-4,4-dimethyl-d6 azlactone) (PVDMA-d6) are considered in this work. Effects of chain length polydispersity, film thickness, substrate–monomer and monomer–monomer interactions on the microphase segregation are studied using SCFT. The theoretical study reveals that in comparison to a film created with monodisperse di-block copolymers, an increase in polydispersity tends to decrease the number of lamellar strata that can be packed in a film of given thickness. This is a direct consequence of an increase in lamellar domain spacing with an increase in polydispersity index. Furthermore, it is shown that polydispersity induces conformational asymmetry and an increase in the polydispersity index leads to an increase in the effective Kuhn segment length of the polydisperse blocks. It is shown that the conformational asymmetry effects, which are entropic in origin and of increasing importance as film thickness decreases, drive the polydisperse blocks to the middle of the films despite favorable substrate interactions. These predictions are verified by results from neutron reflectivity experiments on thin films made from moderately polydisperse PGMA-PVDMA-d6 di-block copolymer deposited on silicon substrates. In conclusion, results from SCFT are used to predict neutron reflectivity profiles, providing a facile and robust route to obtain useful physical insights into the structure of polydisperse diblock copolymers at

  4. Microphase separation in thin films of lamellar forming polydisperse di-block copolymers

    SciTech Connect

    Kumar, Rajeev; Lokitz, Bradley S.; Sides, Scott W.; Chen, Jihua; Heller, William T.; Ankner, John F.; Browning, James F.; Kilbey II, S. Michael; Sumpter, Bobby G.

    2015-01-01

    Despite the ubiquity of polydispersity in chain lengths of di-block copolymers, its effects on microphase separation in thin films have eluded a clear understanding. In this work, we have studied effects of polydispersity on the microphase separation in thin films of lamellar forming di-block copolymers using self-consistent field theory (SCFT) and neutron reflectivity experiments. Di-block copolymers containing a polydisperse block of poly(glycidylmethacrylate) (PGMA) connected to a near-monodisperse block poly(2-vinyl-4,4-dimethyl-d6 azlactone) (PVDMA-d6) are considered in this work. Effects of chain length polydispersity, film thickness, substrate-monomer and monomer-monomer interactions on the microphase segregation are studied using SCFT. The theoretical study reveals that in comparison to a film created with monodisperse di-block copolymers, an increase in polydispersity tends to decrease the number of lamellar strata that can be packed in a film of given thickness. This is a direct consequence of an increase in lamellar domain spacing with an increase in polydispersity index. Furthermore, it is shown that polydispersity induces conformational asymmetry and an increase in the polydispersity index leads to an increase in the effective Kuhn segment length of the polydisperse blocks. It is shown that the conformational asymmetry effects, which are entropic in origin and of increasing importance as film thickness decreases, drive the polydisperse blocks to the middle of the films despite favorable substrate interactions. These predictions are verified by results from neutron reflectivity experiments on thin films made from moderately polydisperse PGMA-PVDMA-d6 di-block copolymer deposited on silicon substrates. Finally, results from SCFT are used to predict neutron reflectivity profiles, providing a facile and robust route to obtain useful physical insights into the structure of polydisperse diblock copolymers at interfaces.

  5. Simulation study of the effect of molar mass dispersity on domain interfacial roughness in lamellae forming block copolymers for directed self-assembly

    NASA Astrophysics Data System (ADS)

    Peters, Andrew J.; Lawson, Richard A.; Nation, Benjamin D.; Ludovice, Peter J.; Henderson, Clifford L.

    2015-09-01

    A coarse-grained molecular dynamics model was used to study the thin film self-assembly and resulting pattern properties of block copolymer (BCP) systems with various molar mass dispersities. Diblock copolymers (i.e. A-b-B type) were simulated in an aligned lamellar state, which is one of the most common patterns of potential use for integrated circuit fabrication via directed self-assembly of BCPs. Effects of the molar mass dispersity (Ð) on feature pitch and interfacial roughness, which are critical lithographic parameters that have a direct impact on integrated circuit performance, were simulated. It was found that for a realistic distribution of polymer molecular weights, modeled by a Wesslau distribution, both line edge roughness (LER) and line width roughness (LWR) increase approximately linearly with increasing Ð, up to ˜45% of the monodisperse value at Ð = 1.5. Mechanisms of compensation for increased A-A and B-B roughness were considered. It was found that long and short chain positions were not correlated, and that long chains were significantly deformed in shape. The increase in LWR was due to the increase in LER and a constant correlation between the line edges. Unaligned systems show a correlation between domain width and local molecular weight, while systems aligned on an alternating pattern of A and B lines did not show any correlation. When the volume fraction of individual chains was allowed to vary, similar results were found when considering the Ð of the block as opposed to the Ð of the entire system.

  6. Block copolymer self-assembly fundamentals and applications in formulation of nano-structured fluids

    NASA Astrophysics Data System (ADS)

    Sarkar, Biswajit

    Dispersions of nanoparticles in polymer matrices form hybrid materials that can exhibit superior structural and functional properties and find applications in e.g. thermo-plastics, electronics, polymer electrolytes, catalysis, paint formulations, and drug delivery. Control over the particle location and orientation in the polymeric matrices are essential in order to realize the enhanced mechanical, electrical, and optical properties of the nanohybrids. Block copolymers, composed of two or more different monomers, are promising for controlling particle location and orientation because of their ability to organize into ordered nanostructures. Fundamental questions pertaining to nanoparticle-polymer interfacial interactions remain open and formulate the objectives of our investigation. Particle-polymer enthalpic and entropic interactions control the nanoparticle dispersion in polymer matrices. Synthetic chemical methods for modifying the particle surface in order to control polymer-particle interactions are involved and large scale production is not possible. In the current approach, a physical method is employed to control polymer-particle interactions. The use of commercially available solvents is found to be effective in modifying particle-polymer interfacial interactions. The approach is applicable to a wide range of particle-polymer systems and can thereby enable large scale processing of polymer nanohybrids. The systems of silica nanoparticles dispersed in long-range or short-range self-assembled structures of aqueous poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers (Pluronics) is considered here. The effect of various parameters such as the presence of organic solvents, pH, and particle size on the block copolymer organization and the ensuing particle-polymer interactions are investigated. Favorable surface interactions between the deprotonated silica nanoparticle and PEO-rich domain facilitate particle

  7. Shear Alignment of Diblock Copolymers for Patterning Nanowire Meshes

    SciTech Connect

    Gustafson, Kyle T.

    2016-09-08

    Metallic nanowire meshes are useful as cheap, flexible alternatives to indium tin oxide – an expensive, brittle material used in transparent conductive electrodes. We have fabricated nanowire meshes over areas up to 2.5 cm2 by: 1) mechanically aligning parallel rows of diblock copolymer (diBCP) microdomains; 2) selectively infiltrating those domains with metallic ions; 3) etching away the diBCP template; 4) sintering to reduce ions to metal nanowires; and, 5) repeating steps 1 – 4 on the same sample at a 90° offset. We aligned parallel rows of polystyrene-b-poly(2-vinylpyridine) [PS(48.5 kDa)-b-P2VP(14.5 kDa)] microdomains by heating above its glass transition temperature (Tg ≈ 100°C), applying mechanical shear pressure (33 kPa) and normal force (13.7 N), and cooling below Tg. DiBCP samples were submerged in aqueous solutions of metallic ions (15 – 40 mM ions; 0.1 – 0.5 M HCl) for 30 – 90 minutes, which coordinate to nitrogen in P2VP. Subsequent ozone-etching and sintering steps yielded parallel nanowires. We aimed to optimize alignment parameters (e.g. shear and normal pressures, alignment duration, and PDMS thickness) to improve the quality, reproducibility, and scalability of meshes. We also investigated metals other than Pt and Au that may be patterned using this technique (Cu, Ag).

  8. Dodecagonal quasicrystalline order in a diblock copolymer melt

    PubMed Central

    Gillard, Timothy M.; Lee, Sangwoo; Bates, Frank S.

    2016-01-01

    We report the discovery of a dodecagonal quasicrystalline state (DDQC) in a sphere (micelle) forming poly(isoprene-b-lactide) (IL) diblock copolymer melt, investigated as a function of time following rapid cooling from above the order–disorder transition temperature (TODT = 66 °C) using small-angle X-ray scattering (SAXS) measurements. Between TODT and the order–order transition temperature TOOT = 42 °C, an equilibrium body-centered cubic (BCC) structure forms, whereas below TOOT the Frank–Kasper σ phase is the stable morphology. At T < 40 °C the supercooled disordered state evolves into a metastable DDQC that transforms with time to the σ phase. The times required to form the DDQC and σ phases are strongly temperature dependent, requiring several hours and about 2 d at 35 °C and more than 10 and 200 d at 25 °C, respectively. Remarkably, the DDQC forms only from the supercooled disordered state, whereas the σ phase grows directly when the BCC phase is cooled below TOOT and vice versa upon heating. A transition in the rapidly supercooled disordered material, from an ergodic liquid-like arrangement of particles to a nonergodic soft glassy-like solid, occurs below ∼40 °C, coincident with the temperature associated with the formation of the DDQC. We speculate that this stiffening reflects the development of particle clusters with local tetrahedral or icosahedral symmetry that seed growth of the temporally transient DDQC state. This work highlights extraordinary opportunities to uncover the origins and stability of aperiodic order in condensed matter using model block polymers. PMID:27118844

  9. Chiral imprinting of diblock copolymer single-chain particles.

    PubMed

    Njikang, Gabriel; Liu, Guojun; Hong, Liangzhi

    2011-06-07

    This Article reports the molecular imprinting of polymer single-chain particles that have a radius ∼3.7 nm. For this, the template L-phenylalanine anilide or L-ΦAA and a diblock copolymer PtBA-b-P(CEMA-r-CA) were used. Here, PtBA denotes poly(tert-butyl acrylate), and P(CEMA-r-CA) denotes a random block consisting of cinnamoyloxyethyl methacrylate (CEMA) and carboxyl-bearing (CA) units. In CHCl(3)/cyclohexane (CHX) with 64 vol % of CHX or at f(CHX) = 64%, a block-selective solvent for PtBA, PtBA-b-P(CEMA-r-CA) formed spherical micelles. The core consisted of the insoluble P(CEMA-r-CA) block and L-ΦAA, which complexed with the CA groups. Pumping slowly this micellar solution into stirred CHCl(3)/(CHX) at f(CHX) = 64% triggered micelle dissociation into single-chain micelles, which comprised presumably a solubilized PtBA tail and a collapsed P(CEMA-r-CA)/L-ΦAA head. Because the solvent reservoir was under constant UV irradiation, the photo-cross-linkable units in the P(CEMA-r-CA) head cross-linked, and the single-chain micelles were converted into cross-linked single-chain micelles or tadpoles. Synchronizing the micelle addition and photoreaction rates allowed the preparation, from this protocol, of essentially pure tadpoles at high final polymer concentrations. Imprinted tadpoles were procured after L-ΦAA was extracted from the tadpole heads. Under optimized conditions, the produced imprinted tadpoles had exceptionally high binding capacity and high selectivity for L-ΦAA. In addition, the rates of L-ΦAA release from and rebinding by the particles were high.

  10. The self-assembly mechanism of fibril-forming silk-based block copolymers.

    PubMed

    Schor, Marieke; Bolhuis, Peter G

    2011-06-14

    Triblock copolymers consisting of a silk-based ((Gly-Ala)(3)Gly-Glu) repeat flanked by hydrophilic outer blocks self-assemble into micrometer long fibrils in response to a trigger. Since the exact mechanism of the fibril formation remains unclear, we employ a multiscale modelling approach in combination with rare event simulations to elucidate key processes. Atomistic scale simulations on the silk-based block suggest a mechanism in which a polypeptide prefolded into a β-roll structure docks to the growing end of a fibril through the formation of Glu-Glu sidechain contacts. Subsequently it can slide to the optimal position before water is expelled to form a dry interface between the fibril end and the attaching block copolymer. In addition, we find that the folded state of the silk-based block is further stabilised through interactions with its neighboring block. Templated folding may also play a role in case a partially folded polypeptide attaches. The coarse-grained simulations indicate that the attachment and subsequent sliding is mediated by the hydrophilic flanks in a size dependent manner. The hydrophilic blocks prevent random aggregation and allow growth only at the end of the fibril. Our multiscale approach may be used for other fibril-forming peptides. This journal is © the Owner Societies 2011

  11. Novel self-assembly graft copolymers as carriers for anti-inflammatory drug delivery.

    PubMed

    Bury, Katarzyna; Neugebauer, Dorota

    2014-01-02

    Indomethacin (IMC) and quercetin (QUE) as typical models of anti-inflammatory drugs were loaded into the micelles of new amphiphilic graft copolymers, comprising caprolactone 2-(methacryloyloxy)ethyl ester (CLMA) units in the main chain and poly(meth)acrylic acid side chains (PAA/PMAA), which were studied as the carriers of drugs. The macromolecules were self-assembled by solvent evaporation or dialysis. The critical micelle concentration (CMC) ranged from 0.015 to 0.199 mg/ml. The copolymer composition, grafting degree and length of side chains, nature and content of hydrophobic/hydrophilic part, were investigated as the main parameters responsible for the properties of nanoparticles including their stability, core-drug interactions, improved drug solubility, and in consequence the efficiency of drug-loading and drug release profiles. The hydrodynamic diameters of particles measured by dynamic light scattering (DLS) ranged from 50 to 275 nm, and increased after loading with drug. In vitro release experiments performed at various pH (5.0 and 7.4) indicated faster release behavior from nanoparticles in acidic conditions (55-95% vs. 25-45% within 75 h).

  12. Polydispersity-Driven Block Copolymer Amphiphile Self-Assembly into Prolate-Spheroid Micelles

    SciTech Connect

    Schmitt, Andrew L.; Repollet-Pedrosa, Milton H.; Mahanthappa, Mahesh K.

    2013-09-26

    The aqueous self-assembly behavior of polydisperse poly(ethylene oxide-b-1,4-butadiene-b-ethylene oxide) (OBO) macromolecular triblock amphiphiles is examined to discern the implications of continuous polydispersity in the hydrophobic block on the resulting aqueous micellar morphologies of otherwise monodisperse polymer surfactants. The chain length polydispersity and implicit composition polydispersity of these samples furnishes a distribution of preferred interfacial curvatures, resulting in dilute aqueous block copolymer dispersions exhibiting coexisting spherical and rod-like micelles with vesicles in a single sample with a O weight fraction, w{sub O}, of 0.18. At higher w{sub O} = 0.51-0.68, the peak in the interfacial curvature distribution shifts and we observe the formation of only American football-shaped micelles. We rationalize the formation of these anisotropically shaped aggregates based on the intrinsic distribution of preferred curvatures adopted by the polydisperse copolymer amphiphiles and on the relief of core block chain stretching by chain-length-dependent intramicellar segregation.

  13. Photoresponsive Polymeric Reversible Nanoparticles via Self-Assembly of Reactive ABA Triblock Copolymers and Their Transformation to Permanent Nanostructures

    PubMed Central

    Ding, Liang; Li, Juan; Jiang, Ruiyu; Song, Wei

    2016-01-01

    Azobenzene-functionalized ABA triblock copolymers with controlled molecular weights are prepared first via a sequential ring-opening metathesis polymerization and acyclic diene metathesis polymerization in one-pot, which are readily converted, by a facile esterification, to the modified ABA triblock copolymers. Then, these reactive triblock copolymers can spontaneously self-assemble in a selective solvent to form reproducible and reversible polymeric core-shell nanoparticles. Finally, the stable and permanent shell-crosslinked nanoparticles are obtained by an intramolecular crosslinking reaction in dilute solution under UV light irradiation. These as-prepared polymeric nanoparticles and their precursor incorporating azobenzene chromophores exhibit distinct photoresponsive performance and morphological variation. PMID:28774100

  14. Controlled synthesis of amino acid-based pH-responsive chiral polymers and self-assembly of their block copolymers.

    PubMed

    Bauri, Kamal; Roy, Saswati Ghosh; Pant, Shashank; De, Priyadarsi

    2013-02-26

    Leucine/isoleucine side chain polymers are of interest due to their hydrophobicity and reported role in the formation of α-helical structures. The synthesis and reversible addition-fragmentation chain transfer (RAFT) polymerization of amino acid-based chiral monomers, namely Boc-L-leucine methacryloyloxyethyl ester (Boc-L-Leu-HEMA, 1a), Boc-L-leucine acryloyloxyethyl ester (Boc-L-Leu-HEA, 1b), Boc-L-isoleucine methacryloyloxyethyl ester (Boc-L-Ile-HEMA, 1c), and Boc-L-isoleucine acryloyloxyethyl ester (Boc-L-Ile-HEA, 1d), are reported. The controlled nature of the polymerization of the said chiral monomers in N, N-dimethylformamide (DMF) at 70 °C is evident from the formation of narrow polydisperse polymers, the molecular weight controlled by the monomer/chain transfer agent (CTA) molar ratio and the linear relationship between molecular weight and monomer conversion. The resulting well-defined polymers were used as macro-CTAs to prepare corresponding diblock copolymers by RAFT polymerization of methyl (meth)acrylate monomers. Deprotection of Boc groups in the homopolymers and block copolymers under acidic conditions produced cationic, pH-responsive polymers with primary amine moieties at the side chains. The optical activity of the homopolymers and block copolymers were studied using circular dichroism (CD) spectroscopy and specific rotation measurements. The self-assembling nature of the block copolymers to produce highly ordered structures was illustrated through dynamic light scattering (DLS) and atomic force microscopy (AFM) studies. The side chain amine functionality instills pH-responsive behavior, which makes these cationic polymers attractive candidates for drug delivery applications, as well as for conjugation of biomolecules.

  15. Synthesis and characterization of a novel polydepsipeptide contained tri-block copolymer (mPEG-PLLA-PMMD) as self-assembly micelle delivery system for paclitaxel.

    PubMed

    Zhao, Yanlei; Li, Juan; Yu, Hua; Wang, Guangji; Liu, Wen

    2012-07-01

    A series of biodegradable polydepsipeptides based new triblock copolymers, poly (ethylene glycol)-poly(L-lactide)-poly(3(S)-methyl-morpholine-2,5-dione) (mPEG-PLLA-PMMD) have been synthesized and characterized as self-assembly micelle delivery system for paclitaxel (PTX). Compared to the mPEG(2000)-PLLA(2000) diblock copolymers, the triblock copolymers present more benefits such as lower CMC value, positive-shifted zeta potential, better drug loading efficiency and stability. Among the triblock polymers, mPEG(2000)-PLLA(2000)-PMMD(1400) micelles present low cytotoxicity and promote the anti-cancer activity of PTX on A-549 and HCT-116cells. In addition, mPEG(2000)-PLLA(2000)-PMMD(1400) micelles prolongs the circulation time of PTX in rat after i.v. injection (5 mg/kg) than that of mPEG(2000)-PLLA(2000) micelles and Taxol. The half life (t(1/2β)), mean residence time (MRT), AUC(0-∞) and clearance (CL) for PTX-loaded mPEG(2000)-PLLA(2000)-PMMD(1400) micelles are determined to be 1.941 h, 2.683 h, 5.220 μg/m Lh (1.8-fold to mPEG(2000)-PLLA(2000) group), 0.967 L/h kg(-1), respectively. In conclusion, mPEG(2000)-PLLA(2000)-PMMD(1400) copolymer could be developed as one of the promising vectors to anti-cancer agents for chemotherapeutics. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. The self-organization of diblock copolymers at polymer blend interafaces

    NASA Astrophysics Data System (ADS)

    Schnell, R.; Stamm, M.

    1997-02-01

    Diblock copolymers can be used as emulsifiers to optimize the mechanical properties of polymer blends. We investigate the interface in thin polyparamethylstyrene(PMS)/polystyrene(PS) bilayer films with and without the presence of diblock copolymer P(S-b-PMS). Components are incompatible, but close to miscibility. Neutron reflectivity (NR) measurements were first carried out with PMS/PS bilayers at varying molecular weights and temperatures. The fits of the data reveal interface widths in the range between 9.4 and 19.6 nm. This corresponds in the framework of mean field theory to segment interaction parameters (χ) between 0.0033 and 0.0058 and a mean segment length ( b) of 0.8 nm and is in good agreement to SANS investigations. For higher molecular weights the presence of diblock copolymer in homopolymer blends results in the segregation of the diblock copolymers to the interfaces and to an increase of the interface width between the two layers, which is in good agreement to other polymer systems. In nearly compatible systems, on the other hand, no significant segregation of the copolymer to the interface was observed.

  17. Phase-field modeling of the formation of lamellar nanostructures in diblock copolymer thin films under inplanar electric fields.

    PubMed

    Wu, Xiang-Fa; Dzenis, Yuris A

    2008-03-01

    Recent experiments show that external inplanar electric field can be employed to guide the molecular self-assembly in diblock copolymer (BCP) thin films to form lamellar nanostructures with potential applications in nanotechnology. We study this self-assembly process through a detailed coarse-grained phase-separation modeling. During the process, the free energy of the BCP films is modeled as the Ginzburg-Landau free energy with nonlocal interaction and electrostatic coupling. The resulting Cahn-Hilliard (CH) equation is solved using an efficient semi-implicit Fourier-spectral algorithm. Numerical results show that the morphology of order parameter formed in either symmetric or asymmetric BCP thin films is strongly influenced by the electric field. For symmetrical BCPs, highly ordered lamellar nanostructures evolved along the direction of the electric field. Phase nucleation and dislocation climbing in the BCP films predicted by the numerical simulation are in a good agreement with those observed in recent BCP electronanolithography. For asymmetrical BCPs, numerical simulation shows that nanodots are guided to align to the electric field. Furthermore, in the case of high electric field, nanodots formed in asymmetrical BCPs may further convert into highly ordered lamellar nanostructures (sphere-to-cylinder transition) parallel to the electric field. Effects of the magnitude of electric field, BCP asymmetry, and molecular interaction of BCPs on the self-assembly process are examined in detail using the numerical scheme developed in this study. The present study can be used for the prediction of the formation of nanostructures in BCP thin films and the quality control of BCP-based nanomanufacturing through optimizing the external electric fields.

  18. Nanoscale spirals by directed self-assembly

    NASA Astrophysics Data System (ADS)

    Choi, Hong Kyoon; Chang, Jae-Byum; Hannon, Adam F.; Yang, Joel K. W.; Berggren, Karl K.; Alexander-Katz, Alfredo; Ross, Caroline A.

    2017-06-01

    Archimedean spiral patterns are formed by the directed self-assembly of diblock copolymer thin films within a circular template. The presence of a notch in the template promotes the formation of a spiral compared to concentric rings, and the notch shape determines the chirality of the spiral. Double spirals occur when the notch width is increased or when there are two notches. The spiral followed an Archimedean form with exponent ≈0.9. Self-consistent field theory reproduces the experimentally observed morphologies and demonstrates the templating of spirals in cylindrical-morphology block copolymer films.

  19. Controlling Directed Self-Assembly and Sintering of Gold Nanorods in Patterned Block Copolymer Thin Films

    NASA Astrophysics Data System (ADS)

    Lai, Fengyuan

    As the miniaturization of electronic devices continues, proper thermal management is crucial to ensure the optimum performance and reliability of such devices within their specification. Of primary interest are the so-called thermal interface materials to minimize the thermal resistance between the heat source and the heat sink. To this end, polymer nanocomposites composed of a polymer matrix and nanoscale fillers with high thermal conductivity have attracted tremendous attention. It has been demonstrated that the formation of a nanoparticle assembly inside the polymer matrix provides a continuous pathway for efficient heat transfer, and thus it is essential for achieving high thermal conductivity. In this work, we explored the ability to direct the self-assembly of gold nanorods (AuNRs) via patterned block copolymer (BCP) thin films. Selective sequestration of AuNRs with various aspect ratios in one block domain was achieved, with over 30% of the surface covered by an ordered AuNR assembly orienting parallel to the geometric confinement. The final nanostructure resulting from the directed self-assembly process is determined by the competition between thermodynamic consideration and kinetic factors. The coalescence and sintering of the AuNR assembly was accomplished by both furnace thermal annealing and rapid thermal annealing at low temperatures. The mechanism through which efficient sintering occurred is investigated with scanning electron microscopy. It is found that the sintering process initially takes place locally, resulting in small AuNR aggregates. Eventually the aggregates grow into a globally continuous, percolating network structure. In addition, the overall heat transfer coefficient was measured in an environmental scanning electron microscope by following droplet growth over time. The present study opens up new opportunities to accomplish controlled assembly of nanoparticles with high concentration for different nanorod-based applications as well as

  20. Reinforcement of Shear Thinning Protein Hydrogels by Responsive Block Copolymer Self-Assembly

    PubMed Central

    Glassman, Matthew J.; Chan, Jacqueline

    2014-01-01

    Shear thinning hydrogels are promising materials that exhibit rapid self-healing following the cessation of shear, making them attractive for a variety of applications including injectable biomaterials. In this work, self-assembly is demonstrated as a strategy to introduce a reinforcing network within shear thinning artificially engineered protein gels, enabling a responsive transition from an injectable state at low temperatures with a low yield stress to a stiffened state at physiological temperatures with resistance to shear thinning, higher toughness, and reduced erosion rates and creep compliance. Protein-polymer triblock copolymers capable of the responsive self-assembly of two orthogonal networks have been synthesized by conjugating poly(N-isopropylacrylamide) to the N- and C- termini of a protein midblock decorated with coiled-coil self-associating domains. Midblock association forms a shear-thinning network, while endblock aggregation at elevated temperatures introduces a second, independent physical network into the protein hydrogel. These new, reversible crosslinks introduce extremely long relaxation times and lead to a five-fold increase in the elastic modulus, significantly larger than is expected from transient network theory. Thermoresponsive reinforcement reduces the high temperature creep compliance by over four orders of magnitude, decreases the erosion rate by at least a factor of five, and increases the yield stress by up to a factor of seven. The reinforced hydrogels also exhibit enhanced resistance to plastic deformation and failure in uniaxial compression. Combined with the demonstrated potential of shear thinning artificial protein hydrogels for various uses, including the minimally-invasive implantation of bioactive scaffolds, this reinforcement mechanism broadens the range of applications that can be addressed with shear-thinning physical gels. PMID:25568642

  1. Morphologies of strongly-segregated polystyrene - polydimethylsiloxane diblock copolymers

    SciTech Connect

    Rangarajan, P.; Adams, J.L., Register, R.A.

    1995-12-31

    Five polystyrene-polydimethylsiloxane (PS/PDMS) diblocks were synthesized by sequential anionic polymerization, and their morphologies characterized by small-angle x-ray scattering (SAXS) and transmission electron microscopy (TEM). All materials are microphase-separated in toluene-cast films, and estimates of the interaction parameter {chi} indicate that these materials are all strongly segregated. The strength of segregation is confirmed by differential scanning calorimetry, which indicates that the glass transition temperature of the PDMS phase is independent of molecular weight and composition, and essentially identical to that of PDMS homopolymer. The experimentally-determined phase diagram is strongly skewed towards low styrene volume fractions, even more than the styrene-isoprene (SI) diblock phase diagram, even though little conformational asymmetry should exist in the PS/PDMS system. The PS/PDMS diblocks form substantially larger microdomain structures than analogous SI diblocks reflecting the stronger segregation strength.

  2. Synthesis and characterization of PHV-block-mPEG diblock copolymer and its formation of amphiphilic nanoparticles for drug delivery.

    PubMed

    Shah, Mohsin; Choi, Mun Hwan; Ullah, Najeeb; Kim, Myeong Ok; Yoon, Sung Chul

    2011-07-01

    Despite the recent research interest in the field of nanoparticles delivery system, their structure modification and transport behavior of various hydrophobic drugs is poorly developed. In this article the synthesis of novel amphiphilic diblock copolymer poly([R]-3-hydroxyvalerate)-block-monomethoxy poly(ethylene glycol) (PHV-block-mPEG) was undertaken by modifying the structure of biodegradable and hydrophobic poly([R]-3-hydroxyvalerate) (PHV) with hydrophilic monomethoxy poly(ethylene glycol) (mPEG). The chemical combination of the two blocks was carried out in the melt using bis(2-ethylhexanoate) tin as transesterification catalyst. The synthesized product was characterized by gel permeation chromatography (GPC), 1H nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) analysis. The block copolymer self-assembled into amphiphilic nanoparticles with a core of hydrophobic PHV and a shell of hydrophilic mPEG in aqueous solution. Characterization of the nanoparticles showed the formation of discrete, spherically shaped nanoparticles with mean particle size of 200 +/- 1 nm and zeta potential of -14 +/- 1 mV. A hydrophobic drug thymoquinone was efficiently incorporated into the core hydrophobic domain of the nanoparticles and its release kinetics was studied in vitro. The amphiphilic PEGylated nanoparticles showed biocompatibility when checked in neuronal hippocampal cells of prenatal rat. Our results suggest that the amphiphilic nanoparticles with core-shell structures are potentially useful to develop novel drug carriers.

  3. Tuning thermoresponsive behavior of diblock copolymers and their gold core hybrids: part 1. Importance of placement of amphiphilic end groups on the diblock copolymers.

    PubMed

    Chen, Ning; Xiang, Xu; Tiwari, Ashutosh; Heiden, Patricia A

    2013-02-01

    We report the effects of use and placement of amphiphilic end groups as a valuable tool to achieve significant changes in the thermoresponsive properties of diblock copolymers without the need to resort to compositional changes. We prepared diblock copolymers of di(ethylene glycol) methyl ether methacrylate and oligo(ethylene glycol) methyl ether acrylate with phenyl dithioester and carboxylic acid chain ends and compared the effects of placement of these amphiphilic chain ends on the cloud points of the copolymers. All the copolymers were high molecular weight (greater than 20 kDa) with a polydispersity between 1.1 and 1.2, and the cloud points were measured by UV-vis spectrophotometry and reported as the temperature at 50% normalized transmission. The thermoresponse showed a significant dependency on end group placement, reaching as much as a 28°C difference in measured cloud point simply by exchanging end group placement rather than compositional changes. The effect is attributed to changes in the solvation and mobility from chain end placement affecting the degree of association of the chains. The underlying effect is due to the hydrophilic/hydrophobic balance in combination with the use of amphiphilic chain end placement that can be applied to copolymers with different blocks at the chain ends. This work shows that substantial changes in thermo-response properties can be achieved by re-arranging monomer components rather than changing monomer composition. This may have value in biomedical materials where the range of acceptable monomers is limited.

  4. Morphology of Highly Textured Polyethylene/Polyethylene-Propylene Semicrystalline Diblock Copolymers

    DTIC Science & Technology

    1993-12-03

    Polyethylene / Polyethylene -propylene Semicrystalline Diblock Copolymer . Reproduction in whole or in part is permitted for any purpose of the U.S...lamellar microdomains present in the het- erogeneous melt phase of the block copolymers . Bates and co-workers [4] [5] [6] have studied the lamellar...hydrogenation procedure is described in detail elsewhere 1111 [12]. Hydrogenated PB thus resembles low- density polyethylene (E) and hydrogenated PI is

  5. Prediction of Electric Field Effects on Defect-Free Self-Assembled Nano-Patterning of Block Copolymer.

    PubMed

    Kim, Sang-Kon

    2016-03-01

    For future semiconductor device scaling, self-assembly, directed self-assembly (DSA) of block copolymers (BCPs), is a promising method with simplified processing conditions; however, critical challenge is defect control for fine pattern. Electric field is a method for the defect control. In this paper, for electric field effects to jog defects, the electric field induced self-assembled patterns is modeled and simulated by using the Monte Carlo method of dielectric polymers, the self-consistent-field theory (SCFT), and the Navier-Stokes equation. Electric field effects are quantified by using defect degree. Defective patterns are forced to undergo a phase transition to lamellar phase under electric field. For the high electric field, the excess free energy for the defect-free state becomes small. Simulation results can help to optimize electric field and process time in terms of defect area.

  6. In Situ Visualization of Block Copolymer Self-Assembly in Organic Media by Super-Resolution Fluorescence Microscopy.

    PubMed

    Boott, Charlotte E; Laine, Romain F; Mahou, Pierre; Finnegan, John R; Leitao, Erin M; Webb, Stephen E D; Kaminski, Clemens F; Manners, Ian

    2015-12-14

    Analytical methods that enable visualization of nanomaterials derived from solution self-assembly processes in organic solvents are highly desirable. Herein, we demonstrate the use of stimulated emission depletion microscopy (STED) and single molecule localization microscopy (SMLM) to map living crystallization-driven block copolymer (BCP) self-assembly in organic media at the sub-diffraction scale. Four different dyes were successfully used for single-colour super-resolution imaging of the BCP nanostructures allowing micelle length distributions to be determined in situ. Dual-colour SMLM imaging was used to measure and compare the rate of addition of red fluorescent BCP to the termini of green fluorescent seed micelles to generate block comicelles. Although well-established for aqueous systems, the results highlight the potential of super-resolution microscopy techniques for the interrogation of self-assembly processes in organic media.

  7. Directing the self-assembly of block copolymers into a metastable complex network phase via a deep and rapid quench.

    PubMed

    Müller, Marcus; Sun, De-Wen

    2013-12-27

    The free-energy landscape of self-assembling block copolymer systems is characterized by a multitude of metastable minima. Using particle-based simulations of a soft, coarse-grained model, we explore opportunities to reproducibly direct the spontaneous ordering of these self-assembling systems into a metastable complex network morphology--specifically, Schoen's I-WP periodic minimal surface--starting from a highly unstable state that is generated by a rapid expansion. This process-directed self-assembly provides an alternative to fine-tuning molecular architecture or blending for fabricating complex network structures. Comparing our particle-based simulation results to recently developed free-energy techniques, we critically assess their ability to predict spontaneous formation and highlight the importance of nonequilibrium molecular conformations in the starting state and the local conservation of density.

  8. Template-Free Bottom-Up Method for Fabricating Diblock Copolymer Patchy Particles.

    PubMed

    Ye, Xianggui; Li, Zhan-Wei; Sun, Zhao-Yan; Khomami, Bamin

    2016-05-24

    Patchy particles are one of most important building blocks for hierarchical structures because of the discrete patches on their surface. We have demonstrated a convenient, simple, and scalable bottom-up method for fabricating diblock copolymer patchy particles through both experiments and dissipative particle dynamics (DPD) simulations. The experimental method simply involves reducing the solvent quality of the diblock copolymer solution by the slow addition of a nonsolvent. Specifically, the fabrication of diblock copolymer patchy particles begins with a crew-cut soft-core micelle, where the micelle core is significantly swelled by the solvent. With water addition at an extremely slow rate, the crew-cut soft-core micelles first form a larger crew-cut micelle. With further water addition, the corona-forming blocks of the crew-cut micelles begin to aggregate and eventually form well-defined patches. Both experiments and DPD simulations indicate that the number of patches has a very strong dependence on the diblock copolymer composition-the particle has more patches on the surface with a lower volume fraction of patch-forming blocks. Furthermore, particles with more patches have a greater ability to assemble, and particles with fewer patches have a greater ability to merge once assembled.

  9. Formation of Frank-Kasper σ-phase from polydisperse diblock copolymers

    NASA Astrophysics Data System (ADS)

    Liu, Meijiao; Li, Weihua; Shi, An-Chang

    Recent experimental and theoretical studies have revealed a number of complex spherical phases including the complex Frank-Kasper σ-phase, which consists of 30 spheres in a unit cell. It is desirable to understand the mechanisms for the formation of the complex spherical phases such as the A15-phase and the Frank-Kasper σ-phase in block copolymers. Based on the observation that the A15-phase and the Frank-Kasper σ-phase are composed of spherical domains with different sizes, we hypothesize that polydispersity of the block copolymers could be used to obtain these complex phases. We tested this hypothesis by carrying out self-consistent field theory for polydisperse AB diblock copolymers. Specially we studied the relative stability of various spherical phases, including the fcc, bcc, A15 and Frank_Kasper σ-phase, in binary blends composed of AB block copolymers different lengths of the A-blocks. Our results revealed that the Frank-Kasper σ-phase could be stabilized by tailoring the length ratio as well as the compositions of the two diblock copolymers. The distribution of the diblocks in the system indicates that copolymer segregation is the origin of the formation of spherical domains with different sizes.

  10. Cross-linked cationic diblock copolymer worms are superflocculants for micrometer-sized silica particles.

    PubMed

    Penfold, Nicholas J W; Ning, Yin; Verstraete, Pierre; Smets, Johan; Armes, Steven P

    2016-12-01

    A series of linear cationic diblock copolymer nanoparticles are prepared by polymerization-induced self-assembly (PISA) via reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA) using a binary mixture of non-ionic and cationic macromolecular RAFT agents, namely poly(ethylene oxide) (PEO113, Mn = 4400 g mol(-1); Mw/Mn = 1.08) and poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride) (PQDMA125, Mn = 31 800 g mol(-1), Mw/Mn = 1.19). A detailed phase diagram was constructed to determine the maximum amount of PQDMA125 stabilizer block that could be incorporated while still allowing access to a pure worm copolymer morphology. Aqueous electrophoresis studies indicated that zeta potentials of +35 mV could be achieved for such cationic worms over a wide pH range. Core cross-linked worms were prepared via statistical copolymerization of glycidyl methacrylate (GlyMA) with HPMA using a slightly modified PISA formulation, followed by reacting the epoxy groups of the GlyMA residues located within the worm cores with 3-aminopropyl triethoxysilane (APTES), and concomitant hydrolysis/condensation of the pendent silanol groups with the secondary alcohol on the HPMA residues. TEM and DLS studies confirmed that such core cross-linked cationic worms remained colloidally stable when challenged with either excess methanol or a cationic surfactant. These cross-linked cationic worms are shown to be much more effective bridging flocculants for 1.0 μm silica particles at pH 9 than the corresponding linear cationic worms (and also various commercial high molecular weight water-soluble polymers.). Laser diffraction studies indicated silica aggregates of around 25-28 μm diameter when using the former worms but only 3-5 μm diameter when employing the latter worms. Moreover, SEM studies confirmed that the cross-linked worms remained intact after their adsorption onto the silica particles, whereas the much more

  11. Thermo-responsive Diblock Copolymer Worm Gels in Non-polar Solvents

    PubMed Central

    2014-01-01

    Benzyl methacrylate (BzMA) is polymerized using a poly(lauryl methacrylate) macromolecular chain transfer agent (PLMA macro-CTA) using reversible addition–fragmentation chain transfer (RAFT) polymerization at 70 °C in n-dodecane. This choice of solvent leads to an efficient dispersion polymerization, with polymerization-induced self-assembly (PISA) occurring via the growing PBzMA block to produce a range of PLMA–PBzMA diblock copolymer nano-objects, including spheres, worms, and vesicles. In the present study, particular attention is paid to the worm phase, which forms soft free-standing gels at 20 °C due to multiple inter-worm contacts. Such worm gels exhibit thermo-responsive behavior: heating above 50 °C causes degelation due to the onset of a worm-to-sphere transition. Degelation occurs because isotropic spheres interact with each other much less efficiently than the highly anisotropic worms. This worm-to-sphere thermal transition is essentially irreversible on heating a dilute solution (0.10% w/w) but is more or less reversible on heating a more concentrated dispersion (20% w/w). The relatively low volatility of n-dodecane facilitates variable-temperature rheological studies, which are consistent with eventual reconstitution of the worm phase on cooling to 20 °C. Variable-temperature 1H NMR studies conducted in d26-dodecane confirm partial solvation of the PBzMA block at elevated temperature: surface plasticization of the worm cores is invoked to account for the observed change in morphology, because this is sufficient to increase the copolymer curvature and hence induce a worm-to-sphere transition. Small-angle X-ray scattering and TEM are used to investigate the structural changes that occur during the worm-to-sphere-to-worm thermal cycle; experiments conducted at 1.0 and 5.0% w/w demonstrate the concentration-dependent (ir)reversibility of these morphological transitions. PMID:24678949

  12. Simulation of free energies of bicontinuous morphologies formed through block copolymer/homopolymer self-assembly

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Poornima; Martinez-Veracoechea, Francisco; Escobedo, Fernando

    Different types of bicontinuous phases can be formed from A-B diblock copolymers by the addition of A-type homopolymers over a range of compositions and relative chain lengths. Particle-based molecular simulations were used to study three bicontinuous phases - double gyroid (G), double diamond (D) and plumber's nightmare (P) - near their triple point of coexistence. For 3-D ordered phases, the stability of the morphology formed in simulation is highly sensitive to box size whose exact size is unknown a-priori. Accurate free energy estimates are required to ascertain the stable phase, particularly when multiple competing phases spontaneously form at the conditions of interest. A variant of thermodynamic integration was implemented to obtain free energies and hence identify the stable phases and their optimal box sizes by tracing a reversible path that connects the ordered and disordered phases. Clear evidence was found of D-G and D-P phase coexistence, consistent with previous predictions for the same blend using Self-consistent field theory. Our simulations also allowed us to examine the microscopic details of these coexisting bicontinuous phases and detect key differences between the microstructure of their nodes and struts.

  13. The effect of hydrophilic and hydrophobic block length on the rheology of amphiphilic diblock Polystyrene-b-Poly(sodium methacrylate) copolymers prepared by ATRP.

    PubMed

    Raffa, Patrizio; Stuart, Marc C A; Broekhuis, Antonius A; Picchioni, Francesco

    2014-08-15

    Following our previous investigation on the effect of molecular architecture on the rheology of Polystyrene-b-Poly(sodium methacrylate) copolymers (PS-b-PMAA), we consider here diblock PS-b-PMAA copolymers characterized by a different length of either the hydrophilic or the hydrophobic block. Various copolymers characterized by different PS or PMAA block length have been prepared by ATRP (kinetics is also discussed) and studied from the point of view of their rheological behaviour in water. To the best of our knowledge, this is the first systematic investigation concerning the effect of block length on the rheology of diblock polyelectrolytes. We found that the hydrophobic block length has small influence on the rheology. Surprisingly, the polymers with shortest PMAA blocks yield the strongest gels at high concentration. A simple model based on the classical theories of self-assembly and percolation of amphiphilic polymers has been here developed in order to explain the observed data. Copyright © 2014 Elsevier Inc. All rights reserved.

  14. Post-directed-self-assembly membrane fabrication for in situ analysis of block copolymer structures

    NASA Astrophysics Data System (ADS)

    Ren, J.; Ocola, L. E.; Divan, R.; Czaplewski, D. A.; Segal-Peretz, T.; Xiong, S.; Kline, R. J.; Arges, C. G.; Nealey, P. F.

    2016-10-01

    Full characterization of the three-dimensional structures resulting from the directed self-assembly (DSA) of block copolymers (BCP) remains a difficult challenge. Transmission electron microscope (TEM) tomography and resonant soft x-ray scattering have emerged as powerful and complementary methods for through-film characterization; both techniques require samples to be prepared on specialized membrane substrates. Here we report a generalizable process to implement BCP DSA with density multiplication on silicon nitride membranes. A key feature of the process developed here is that it does not introduce any artefacts or damage to the polymer assemblies as DSA is performed prior to back-etched membrane formation. Because most research and applications of BCP lithography are based on silicon substrates, process variations introduced by implementing DSA on a silicon nitride/silicon stack versus silicon were identified and mitigated. Using full-wafers, membranes were fabricated with different sizes and layouts to enable both TEM and x-ray characterization. Finally, both techniques were used to characterize structures resulting from the DSA of lamella-forming BCP with density multiplication.

  15. Post-directed-self-assembly membrane fabrication for in situ analysis of block copolymer structures.

    PubMed

    Ren, J; Ocola, L E; Divan, R; Czaplewski, D A; Segal-Peretz, T; Xiong, S; Kline, R J; Arges, C G; Nealey, P F

    2016-09-23

    Full characterization of the three-dimensional structures resulting from the directed self-assembly (DSA) of block copolymers (BCP) remains a difficult challenge. Transmission electron microscope (TEM) tomography and resonant soft x-ray scattering have emerged as powerful and complementary methods for through-film characterization; both techniques require samples to be prepared on specialized membrane substrates. Here we report a generalizable process to implement BCP DSA with density multiplication on silicon nitride membranes. A key feature of the process developed here is that it does not introduce any artefacts or damage to the polymer assemblies as DSA is performed prior to back-etched membrane formation. Because most research and applications of BCP lithography are based on silicon substrates, process variations introduced by implementing DSA on a silicon nitride/silicon stack versus silicon were identified and mitigated. Using full-wafers, membranes were fabricated with different sizes and layouts to enable both TEM and x-ray characterization. Finally, both techniques were used to characterize structures resulting from the DSA of lamella-forming BCP with density multiplication.

  16. Biomimetic Nanocomposites of Calcium Phosphate and Self-Assembling Triblock and Pentablock Copolymers

    SciTech Connect

    Enlow, Drew Lenzen

    2006-01-01

    In an effort to mimic the growth of natural bone, self-assembling, micelle and gel-forming copolymers were used as a template for calcium phosphate precipitation. Because of the cationic characteristics imparted by PDEAEM end group additions to commercially available Pluronic{reg_sign} Fl27, a direct ionic attraction mechanism was utilized and a polymer-brushite nanocomposite spheres were produced. Brushite coated spherical micelles with diameters of ~40 nm, and agglomerates of these particles (on the order of 0.5 μm) were obtained. Thickness and durability of the calcium phosphate coating, and the extent of agglomeration were studied. The coating has been shown to be robust enough to retain its integrity even below polymer critical micelle concentration and/or temperature. Calcium phosphate-polymer gel nanocomposites were also prepared. Gel samples appeared as a single phase network of agglomerated spherical micelles, and had a final calcium phosphate concentration of up to 15 wt%. Analysis with x-ray diffraction and NMR indicated a disordered brushite phase with the phosphate groups linking inorganic phase to the polymer.

  17. Directed Self-Assembly of Block Copolymers in 3D Templates Fabricated by Multiphoton Lithography

    NASA Astrophysics Data System (ADS)

    Singer, Jonathan; Thomas, Edwin

    2012-02-01

    Confinement of block-copolymers (BCP) within physical templates has been used as a method to both enhance the microdomain order and manipulate the morphology. Previous investigations have focused on 1D or quasi-2D templates (e.g. trenches, cylindrical pores) patterned at a variety of length scales. We have sought to employ the nearly-arbitrary structural fabrication afforded by multiphoton direct write lithography (MPL) to extend these stereolithographic control techniques to 3D directed assembly. Complex architectures, for example those formed by large scale lithographic techniques such as interference lithography or self-assembly, can be broken down into simplifier component structures: e.g. multibranch junctions, bends, and symmetric or asymmetric connecting pores. By utilizing MPL, we can fabricate model geometries possessing these features written in photoresist at various scales. We then infiltrate these structures with PS-PDMS BCP and observe the resulting morphology by SEM from focused ion beam cross-sections, allowing development of design rules that may be applied towards progressively more complex templates and the fabrication of 3D hierarchical structures with highly ordered and novel domain features spanning from the micron to the 10 nm scale.

  18. Templated fabrication of fiber-basket polymersomes via crystallization-driven block copolymer self-assembly.

    PubMed

    Jia, Lin; Tong, Lemuel; Liang, Yi; Petretic, Amy; Guerin, Gerald; Manners, Ian; Winnik, Mitchell A

    2014-11-26

    Immobilizing uniform nanostructures on a mesoscale substrate is a promising approach to prepare nanometer to micrometer sized materials with new functionalities. The hierarchical structures formed depend on both the nature of the substrate and the components deposited. In this paper, we describe the use of colloidal polystyrene microbeads as a sacrificial template to create a nanofibrous network coating consisting of elongated block copolymer micelles. This network has a secondary structure very different from that of conformal coatings obtained by other methods. In addition, the fibers of the network could be elongated by crystallization-driven self-assembly. The network was locked in place by cross-linking the micelles through in situ generation of small Pt nanoparticles. Subsequent removal of the sacrificial template gave an open vesicular structure. To demonstrate further transformation of the membrane, we showed that the cross-linked micelles could also be used to embed silver nanoparticles. The sacrificial template contained known amounts of Tb and Tm ions, allowing us to estimate via atomic mass spectrometry that 85% of the template surface was covered with micelle seeds. This approach to fabricating hierarchical coating structures expands the generality and scope of template-assisted synthesis to build advanced hierarchical materials with precise morphological control.

  19. Thermal scanning probe lithography for the directed self-assembly of block copolymers.

    PubMed

    Gottlieb, S; Lorenzoni, M; Evangelio, L; Fernández-Regúlez, M; Ryu, Y K; Rawlings, C; Spieser, M; Knoll, A W; Perez-Murano, F

    2017-04-28

    Thermal scanning probe lithography (t-SPL) is applied to the fabrication of chemical guiding patterns for directed self-assembly (DSA) of block copolymers (BCP). The two key steps of the overall process are the accurate patterning of a poly(phthalaldehyde) resist layer of only 3.5 nm thickness, and the subsequent oxygen-plasma functionalization of an underlying neutral poly(styrene-random-methyl methacrylate) brush layer. We demonstrate that this method allows one to obtain aligned line/space patterns of poly(styrene-block-methyl methacrylate) BCP of 18.5 and 11.7 nm half-pitch. Defect-free alignment has been demonstrated over areas of tens of square micrometres. The main advantages of t-SPL are the absence of proximity effects, which enables the realization of patterns with 10 nm resolution, and its compatibility with standard DSA methods. In the brush activation step by oxygen-plasma exposure, we observe swelling of the brush. This effect is discussed in terms of the chemical reactions occurring in the exposed areas. Our results show that t-SPL can be a suitable method for research activities in the field of DSA, in particular for low-pitch, high-χ BCP to achieve sub-10 nm line/space patterns.

  20. Solvent-induced size reduction of self-assembled siRNA/copolymer nanoparticles

    NASA Astrophysics Data System (ADS)

    Qu, Wei; Wu, Juan; Mao, Hai-Quan; Luijten, Erik

    2013-03-01

    Small interfering RNA (siRNA) therapeutics has a demonstrated potential for treating numerous liver diseases. However, traditional polycation vectors used for siRNA delivery typically produce siRNA-containing particles of large size (> 100 nm), along with high cytotoxicity and low colloidal stability. Inspired by earlier work on nanoparticles for plasmid DNA delivery, we graft hydrophilic and biocompatible polyethylene glycol (PEG) blocks to the polycation vector to overcome these limitations. We find that the PEG-grafted polycations result in slightly larger particle size, even though the hydrophilic PEG blocks are expected to hinder the formation of larger aggregates. To explain this observation, we investigate siRNA/copolymer self-assembly via computer simulations of coarse-grained polymer and siRNA models. Our calculations suggest that hydrogen bonding between PEG and the polycation leads to the increased particle size, and that smaller particles can be obtained by inhibiting hydrogen bonding in such system. Subsequent experiments employing solvents of lower polarity indeed lead to particles with smaller size.

  1. Tuning the strength of chemical patterns for directed self-assembly of block copolymers

    NASA Astrophysics Data System (ADS)

    Williamson, Lance; Lin, Guanyang; Cao, Yi; Gronheid, Roel; Nealey, Paul

    2014-03-01

    Directed self-assembly (DSA) of block copolymers (BCP) via chemo-epitaxy is a potential lithographic solution to patterns of dense features. The LiNe (Liu-Nealey) flow was used to fabricate the chemical pattern, which guides the BCP due to the different wetting behavior of the materials. Fine control of both the chemical pattern chemistry and geometry are important for DSA of BCP. Furthermore, wetting behavior considerations for DSA extend beyond pattern design and include the surrounding region. BCP DSA would be easier to integrate into device design if the patterned region were isolated with a featureless region (horizontal lamellar BCP assembly) rather than undirected BCP fingerprint structures. This paper addresses two processing steps found to be modifying the guide material. For one, the backfill brush grafts to the cross-linked polystyrene (XPS), albeit at a lower rate than the brush grafts to the exposed substrate. Undersaturating the backfill brush only moderately improves the XPS wetting behavior, but also negatively impacts the background region of the chemical pattern. Replacing the brush grafting functionality so that the brush grafts at lower annealing conditions also did not avoid the side reaction between the brush and the XPS. The other step modifying the XPS is the trim etch. Replacing the trim etch process was effective at generating a chemical pattern that can orient the BCP horizontally on a stripe 11 L0 wide passing through a field of chemical pattern.

  2. Peptide-directed self-assembly of functionalized polymeric nanoparticles part I: design and self-assembly of peptide-copolymer conjugates into nanoparticle fibers and 3D scaffolds.

    PubMed

    Ding, Xiaochu; Janjanam, Jagadeesh; Tiwari, Ashutosh; Thompson, Martin; Heiden, Patricia A

    2014-06-01

    A robust self-assembly of nanoparticles into fibers and 3D scaffolds is designed and fabricated by functionalizing a RAFT-polymerized amphiphilic triblock copolymer with designer ionic complementary peptides so that the assembled core-shell polymeric nanoparticles are directed by peptide assembly into continuous "nanoparticle fibers," ultimately leading to 3D fiber scaffolds. The assembled nanostructure is confirmed by FESEM and optical microscopy. The assembly is not hindered when a protein (insulin) is incorporated within the nanoparticles as an active ingredient. MTS cytotoxicity tests on SW-620 cell lines show that the peptides, copolymers, and peptide-copolymer conjugates are biocompatible. The methodology of self-assembled nanoparticle fibers and 3D scaffolds is intended to combine the advantages of a flexible hydrogel scaffold with the versatility of controlled release nanoparticles to offer unprecedented ability to incorporate desired drug(s) within a self-assembled scaffold system with individual control over the release of each drug.

  3. Self-assembled, thermoresponsive micelles based on triblock PMMA-b-PNIPAAm-b-PMMA copolymer for drug delivery

    NASA Astrophysics Data System (ADS)

    Li, Y. Y.; Zhang, X. Z.; Zhu, J. L.; Cheng, H.; Cheng, S. X.; Zhuo, R. X.

    2007-05-01

    A novel thermosensitive amphiphilic ABA triblock poly(methyl methacrylate)-b-poly(N-isopropylacrylamide)-b-poly(methyl methacrylate) copolymer (PMMA-b-PNIPAAm-b-PMMA) comprised of two hydrophobic PMMA segments and one hydrophilic PNIPAAm segment was designed and synthesized. The structure of the copolymer was characterized by FT-IR, 1HNMR, and GPC analysis. The cytotoxicity study showed that the PMMA-b-PNIPAAm-b-PMMA copolymer exhibited low cytotoxicity. The copolymer was capable of self-assembling into micelles in water and demonstrated temperature sensitivity at around 34.5 °C. Transmission electron microscopy (TEM) showed that the micelles exhibit nanosized spherical morphology within a size range of 60 nm with a critical micellar concentration (CMC) at 10 mg l-1. The drug-loading PMMA-b-PNIPAAm-b-PMMA micelles showed thermosensitive-controlled release which indicates the potential of PMMA-b-PNIPAAm-b-PMMA micelles as drug carriers.

  4. Mechanically Tunable, Readily Processable Ion Gels by Self-Assembly of Block Copolymers in Ionic Liquids.

    PubMed

    Lodge, Timothy P; Ueki, Takeshi

    2016-10-05

    Room temperature ionic liquids are of great interest for many advanced applications, due to the combination of attractive physical properties with essentially unlimited tunability of chemical structure. High chemical and thermal stability, favorable ionic conductivity, and complete nonvolatility are just some of the most important physical characteristics that make ionic liquids promising candidates for emerging technologies. Examples include separation membranes, actuators, polymer gel electrolytes, supercapacitors, ion batteries, fuel cell membranes, sensors, printable plastic electronics, and flexible displays. However, in these and other applications, it is essential to solidify the ionic liquid, while retaining the liquid state properties of interest. A broadly applicable solidification strategy relies on gelation by addition of suitable triblock copolymers with the ABA architecture, producing ion gels or ionogels. In this paradigm, the A end blocks are immiscible with the ionic liquid, and consequently self-assemble into micellar cores, while some fraction of the well-solvated B midblocks bridge between micelles, forming a percolating network. The chemical structures of the A and B repeat units, the molar mass of the blocks, and the concentration of the copolymer in the ionic liquid are all independently tunable to attain desired property combinations. In particular, the modulus of the resulting ion gel can be readily varied between 100 Pa and 1 MPa, with little sacrifice of the transport properties of the ionic liquid, such as ionic conductivity or gas diffusivity. Suitable A blocks can impart thermoreversible gelation (with solidification either on heating or cooling) or even photoreversible gelation. By virtue of the nonvolatility of ionic liquids, a wide range of processing strategies can be employed directly to prepare ion gels in thin or thick film forms, including solvent casting, spin coating, aerosol jet printing, photopatterning, and transfer

  5. Nano-defect management in directed self-assembly of block copolymers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Azuma, Tsukasa; Seino, Yuriko; Sato, Hironobu; Kasahara, Yusuke; Kodera, Katsuyoshi; Jiravanichsakul, Phubes; Hayakawa, Teruaki; Yoshimoto, Kenji; Takenaka, Mikihito

    2017-03-01

    Directed self-assembly (DSA) of block copolymers (BCPs) has been expected to become one of the most promising next generation lithography candidates for sub-15 nm line patterning and sub-20 nm contact hole patterning. In order to provide the DSA lithography to practical use in advanced semiconductor device manufacturing, defect mitigation in the DSA materials and processes is the primary challenge. We need to clarify the defect generation mechanism using in-situ measurement of self-assembling processes of BCPs in cooperation with modeling approaches to attain the DSA defect mitigation. In this work, we thus employed in-situ atomic force microscope (AFM) and grazing-incidence small angle X-ray scattering (GI-SAXS) and investigated development of surface morphology as well as internal structure during annealing processes. Figure 1 shows series of the AFM images of PMAPOSS-b-PTFEMA films during annealing processes. The images clearly show that vitrified sponge-like structure without long-range order in as-spun film transforms into lamellar structure and that the long range order of the lamellar structure increases with annealing temperature. It is well-known that ordering processes of BCPs from disordered state in bulk progress via nucleation and growth. In contrary to the case of bulk, the observed processes seem to be spinodal decomposition. This is because the structure in as-spun film is not the concentration fluctuation of disordered state but the vitrified sponge-like structure. The annealing processes induce order-order transition from non-equilibrium ordered-state to the lamellar structure. The surface tension assists the transition and directs the orientation. Figure 2 shows scattering patterns of (a) vicinity of film top and (b) whole sample of the GI-SAXS. We can find vertically oriented lamellar structure in the vicinity of film top while horizontally oriented lamellar structures in the vicinity of film bottom, indicating that the GI-SAXS measurement can

  6. Molecular Dynamics Simulations of Penetrants in Microphase Separated Tapered Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Seo, Youngmi; Brown, Jonathan R.; Hall, Lisa M.

    Tapered AB diblock copolymers contain pure A and B monomer blocks on the ends with a tapered midblock of intermediate composition, providing taper length as an additional tuning parameter to control microphase separation and interfacial behavior. We model the midblock as a statistical linear gradient from pure A to pure B. Recent experiments with salt dissolved in one of microphases show that a certain length of taper increases ion conductivity while the same length of inverse taper lowers conductivity. We perform coarse-grained molecular dynamics simulations of tapered copolymers with monomer sized penetrants, which have preferential interactions with one microphase, to better understand this observation and the general effects of tapering on dynamics. We calculate penetrant diffusion, polymer relaxation times, and other quantities over the range from 0% (diblock) to 100% (full gradient) taper length, with the taper direction either normal or inverse (with the A side of the taper connected to the pure B block). Normal taper results typically lie between those of diblocks and full gradients, while inverse tapers show strong nonmonotonic behavior as a function of taper length. For intermediate length inverse tapers, penetrant and monomer dynamics are significantly slower than those of diblocks or normal tapers, and this relates to the folding of the inverse chains back and forth across the interface. To provide further insight, we also compare to the dynamics of random copolymers of various compositions. Based upon work supported by NSF Grant 1454343.

  7. Agarose hydrogels embedded with pH-responsive diblock copolymer micelles for triggered release of substances.

    PubMed

    Jin, Naixiong; Morin, Emily A; Henn, Daniel M; Cao, Yu; Woodcock, Jeremiah W; Tang, Shuangcheng; He, Wei; Zhao, Bin

    2013-08-12

    Hybrid agarose hydrogels embedded with pH-responsive diblock copolymers micelles were developed to achieve functional hydrogels capable of stimulus-triggered drug release. Specifically, a well-defined poly(ethylene oxide) (PEO)-based diblock copolymer, PEO-b-poly(2-(N,N-diisopropylamino)ethyl methacrylate) (PEO(113)-b-PDPAEMA(31), where the subscripts represent the degrees of polymerization of two blocks), was synthesized by atom transfer radical polymerization. PDPAEMA is a pH-responsive polymer with a pKa value of 6.3. The PEO(113)-b-PDPAEMA(31) micelles were formed by a solvent-switching method, and their pH-dependent dissociation behavior was investigated by dynamic light scattering and fluorescence spectroscopy. Both studies indicated that the micelles were completely disassembled at pH = 6.40. The biocompatibility of PEO(113)-b-PDPAEMA(31) micelles was demonstrated by in vitro primary cortical neural culture. Hybrid agarose hydrogels were made by cooling 1.0 wt % agarose solutions that contained various amounts of PEO(113)-b-PDPAEMA(31) micelles at either 2 or 4 °C. Rheological measurements showed that the mechanical properties of gels were not significantly adversely affected by the incorporation of diblock copolymer micelles with a concentration as high as 5.0 mg/g. Using Nile Red as a model hydrophobic drug, its incorporation into the core of diblock copolymer micelles was demonstrated. Characterized by fluorescent spectroscopy, the release of Nile Red from the hybrid hydrogel was shown to be controllable by pH due to the responsiveness of the block copolymer micelles. Based on the prominent use of agarose gels as scaffolds for cell transplantation for neural repair, the hybrid hydrogels embedded with stimuli-responsive block copolymer micelles could allow the controlled delivery of hydrophobic neuroprotective agents to improve survival of transplanted cells in tune with signals from the surrounding pathological environment.

  8. Complex macrophase-separated nanostructure induced by microphase separation in binary blends of lamellar diblock copolymer thin films.

    PubMed

    Zhang, Jianqi; Posselt, Dorthe; Smilgies, Detlef-M; Perlich, Jan; Kyriakos, Konstantinos; Jaksch, Sebastian; Papadakis, Christine M

    2014-09-01

    The nanostructures of thin films spin-coated from binary blends of compositionally symmetric polystyrene-b-polybutadiene (PS-b-PB) diblock copolymer having different molar masses are investigated by means of atomic force microscopy (AFM) and grazing-incidence small-angle X-ray scattering (GISAXS) after spin-coating and after subsequent solvent vapor annealing (SVA). In thin films of the pure diblock copolymers having high or low molar mass, the lamellae are perpendicular or parallel to the substrate, respectively. The as-prepared binary blend thin films feature mainly perpendicular lamellae in a one-phase state, indicating that the higher molar mass diblock copolymer dominates the lamellar orientation. The lamellar thickness decreases linearly with increasing volume fraction of the low molar mass diblock copolymer. After SVA, well-defined macrophase-separated nanostructures appear, which feature parallel lamellae near the film surface and perpendicular ones in the bulk.

  9. Self-assembled Oniontype Multiferroic Nanostructures

    NASA Astrophysics Data System (ADS)

    Ren, Shenqiang; Briber, Robert M.; Wuttig, Manfred

    2009-03-01

    Spontaneously self-assembled oniontype multiferroic nanostructures based on block copolymers as templating materials are reported. Diblock copolymer containing two different magnetoelectric precursors separately segregated to the two microdomains have been shown to form well-ordered templated lamellar structures. Onion-type multilamellar ordered multiferroic (PZT/CoFe2O4) nanostructures have been induced by room temperature solvent annealing in a magnetic field oriented perpendicular to the plane of the film. The evolution of the onion-like microstructure has been characterized by AFM, MFM, and TEM. The structure retains lamellar periodicity observed at zero field. The onion structure is superparamagnetic above and antiferromagnetic below the blocking temperature. This templating process opens a route for nanometer-scale patterning of magnetic toroids by means of self-assembly on length scales that are difficult to obtain by standard lithography techniques.

  10. Controlling the self-assembly structure of magnetic nanoparticles and amphiphilic block-copolymers: from micelles to vesicles.

    PubMed

    Hickey, Robert J; Haynes, Alyssa S; Kikkawa, James M; Park, So-Jung

    2011-02-09

    We report how to control the self-assembly of magnetic nanoparticles and a prototypical amphiphilic block-copolymer composed of poly(acrylic acid) and polystyrene (PAA-b-PS). Three distinct structures were obtained by controlling the solvent-nanoparticle and polymer-nanoparticle interactions: (1) polymersomes densely packed with nanoparticles (magneto-polymersomes), (2) core-shell type polymer assemblies where nanoparticles are radially arranged at the interface between the polymer core and the shell (magneto-core shell), and (3) polymer micelles where nanoparticles are homogeneously incorporated (magneto-micelles). Importantly, we show that the incorporation of nanoparticles drastically affects the self-assembly structure of block-copolymers by modifying the relative volume ratio between the hydrophobic block and the hydrophilic block. As a consequence, the self-assembly of micelle-forming block-copolymers typically produces magneto-polymersomes instead of magneto-micelles. On the other hand, vesicle-forming polymers tend to form magneto-micelles due to the solubilization of nanoparticles in polymer assemblies. The nanoparticle-polymer interaction also controls the nanoparticle arrangement in the polymer matrix. In N,N-dimethylformamide (DMF) where PS is not well-solvated, nanoparticles segregate from PS and form unique radial assemblies. In tetrahydrofuran (THF), which is a good solvent for both nanoparticles and PS, nanoparticles are homogeneously distributed in the polymer matrix. Furthermore, we demonstrated that the morphology of nanoparticle-encapsulating polymer assemblies significantly affects their magnetic relaxation properties, emphasizing the importance of the self-assembly structure and nanoparticle arrangement as well as the size of the assemblies.

  11. Dissipative particle dynamics simulations on self-assembly of rod-coil-rod triblock copolymers in a rod-selective solvent

    NASA Astrophysics Data System (ADS)

    Huang, Jian-Hua; Fan, Zhong-Xiang; Ma, Ze-Xin

    2013-08-01

    Self-assembly of rod-coil-rod ABA triblock copolymers in a rod-selective solvent is investigated by using dissipative particle dynamics simulations. The morphologies of the self-assembled aggregates are dependent on the number of copolymers in the aggregate and the rod length of the copolymer. We observe vesicles at short rod block and bowl-like aggregates at slightly longer rod block. In the vesicle region near the phase boundary, metastable bowl-like aggregates can be observed and be transformed into vesicles by annealing process. A transition from the bowl-like structure to the vesicle is observed by increasing the solvophobicity of the mid-coil block. In this study, the difference between the self-assembly of fully flexible ABA triblock copolymer and that of rod-coil-rod triblock copolymer is also discussed.

  12. Synthesis of Polystyrene-Polylactide Bottlebrush Block Copolymers and Their Melt Self-Assembly into Large Domain Nanostructures

    SciTech Connect

    Rzayev, J.

    2009-04-07

    High molecular weight polystyrene-polylactide (PS-PLA) bottlebrush block copolymers have been shown to self-assemble into highly ordered lamellae structures with domain spacings as large as 163 nm, as identified by ultrasmall-angle X-ray scattering. Bottlebrush block copolymers were synthesized by a combination of living radical and ring-opening polymerizations. The backbone was prepared by RAFT block copolymerization of solketal methacrylate (SM) and 2-(bromoisobutyryl)ethyl methacrylate (BIEM). Polystyrene branches were grafted by ATRP from poly(BIEM) block, and PLA branches were grafted from the poly(SM) block after the removal of ketal groups. The investigation into the self-assembly of PS-PLA bottlebrush block copolymers with varying lengths of branches and backbones revealed a number of unusual trends, which were attributed to their dynamic, three-dimensional structure. The results suggest that in phase-separated melts the bottlebrush block copolymer backbone, while extended, still possesses a certain degree of flexibility to accommodate for different interfacial areas necessary to pack into lamellae microstructures.

  13. Aqueous Self-Assembly of Non-Ionic Bottlebrush Block Copolymer Surfactants with Tunable Molecular Shapes

    NASA Astrophysics Data System (ADS)

    Rzayev, Javid

    2015-03-01

    Polymer amphiphiles provide a robust and versatile platform for the fabrication of nanostructured soft matter. In this research, we explore a new class of polymer surfactants based on comb-like bottlebrush architecture as highly tunable molecular building blocks for aqueous self-assembly. Excluded volume interactions between densely grafted polymer side chains in the bottlebrush architecture are alleviated by backbone stretching, which leads to the formation of shape-persistent cylindrical macromolecules whose molecular dimensions can be precisely tailored during chemical synthesis. Amphiphilic bottlebrush block copolymers containing hydrophobic polylactide (PLA) and hydrophilic poly(oligoethylene oxide methacrylate) (PEO) side chains of various lengths were synthesized by a combination of controlled radical and ring-opening polymerizations. In dilute aqueous solutions, bottlebrush surfactants rapidly assembled into spherical, cylindrical and bilayer aggregates, as visualized by cryogenic transmission electron microscopy (cryo-TEM). Depending on the compositional side chain asymmetry, the formation of spherical micelles with different sizes and dispersities was observed. The molecular shape-dependent assembly was analyzed with help of a packing parameter (p) computed from the molecular composition data akin to small molecule surfactants, with most uniform spherical aggregates observed for bottlebrush amphiphiles with p close to 0.3. The formation of highly uniform micelles and the presence of a rich morphological diagram with relatively narrow compositional windows were attributed to the lack of conformational freedom in bottlebrush surfactants. Similarly, the unusual formation of cylindrical micelles with long aspect ratios for such high molecular weight amphiphiles was attributed to their inability to stabilize morphological defects, such as Y-junctions, with large deviations from mean curvature. Financial support for this work was provided by the National

  14. Toughening of epoxies based on self-assembly of nano-sized amphiphilic block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Liu, Jia

    As a part of a larger effort towards the fundamental understanding of mechanical behaviors of polymers toughened by nanoparticles, this dissertation focuses on the structure-property relationship of epoxies modified with nano-sized poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) block copolymer (BCP) micelle particles. The amphiphilic BCP toughener was incorporated into a liquid epoxy resin and self-assembled into well-dispersed 15 nm spherical micelle particles. The nano-sized BCP, at 5 wt% loading, can significantly improve the fracture toughness of epoxy (ca. 180% improvement) without reducing modulus at room temperature and exhibits only a slight drop (ca. 5°C) in glass transition temperature (Tg). The toughening mechanisms were found to be BCP micelle nanoparticle cavitation, followed by matrix shear banding, which mainly accounted for the observed remarkable toughening effect. The unexpected "nano-cavitation" phenomenon cannot be predicted by existing physical models. The plausible causes for the observed nano-scale cavitation and other mechanical behaviors may include the unique structural characteristics of BCP micelles and the influence from the surrounding epoxy network, which is significantly modified by the epoxy-miscible PEO block. Other mechanisms, such as crack tip blunting, may also play a role in the toughening. Structure-property relationships of this nano-domain modified polymer are discussed. In addition, other important factors, such as strain rate dependence and matrix crosslink density effect on toughening, have been investigated. This BCP toughening approach and conventional rubber toughening techniques are compared. Insights on the decoupling of modulus, toughness, and Tg for designing high performance thermosetting materials with desirable physical and mechanical properties are discussed.

  15. Streamlined etch integration with a unique neutral layer for self-assembled block copolymers (BCPs)

    NASA Astrophysics Data System (ADS)

    Hockey, Mary Ann; Xu, Kui; Wang, Yubao; Guerrero, Douglas J.; Calderas, Eric

    2014-03-01

    A multifunctional hardmask neutral layer (HM NL) was developed to improve etch resistance capabilities, enhance reflectance control, and match the surface energy properties required for polystyrene block copolymers (PS-b-PMMA). This HM NL minimizes the number of substrate deposition steps required in graphoepitaxy directed self-assembly (DSA) process flows. A separate brush layer is replaced by incorporating neutral layer properties into the hardmask to achieve microphase separation of BCP during thermal annealing. The reflection control and etch resistance capabilities are inherent in the chemical composition, thus eliminating the need for separate thin film layers to address absorbance and etch criteria. We initially demonstrated successful implementation of the HM NL using conventional PS-b-PMMA. A series of BCP formulations were synthesized with L0 values ranging from 28 nm to 17 nm to test the versatility of the HM NL. Quality "fingerprint" patterns or microphase separation using 230°-250°C annealing for 3-5 minutes was achieved for an array of modified BCP materials. The HM NL had water contact angles at 78°-80° and polarities in the 5-6 dyne/cm range. The scope of BCP platform compositions evaluated consists of a 20° water contact angle variance and a 10-dyne/cm range in polarities. All BCP derivatives were coated directly onto the HM NL followed by thermal annealing followed by SEM analysis for effective "fingerprint" patterns. We offer a simplified alternative path for high etch resistance in a graphoepitaxy DSA flow employing a single-layer hardmask for etch resistance demonstrated to be compatible with diverse BCP-modified chemical formulations.

  16. Effect of sequence dispersity on morphology of tapered diblock copolymers from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Levine, William G.; Seo, Youngmi; Brown, Jonathan R.; Hall, Lisa M.

    2016-12-01

    Tapered diblock copolymers are similar to typical AB diblock copolymers but have an added transition region between the two blocks which changes gradually in composition from pure A to pure B. This tapered region can be varied from 0% (true diblock) to 100% (gradient copolymer) of the polymer length, and this allows some control over the microphase separated domain spacing and other material properties. We perform molecular dynamics simulations of linearly tapered block copolymers with tapers of various lengths, initialized from fluids density functional theory predictions. To investigate the effect of sequence dispersity, we compare systems composed of identical polymers, whose taper has a fixed sequence that most closely approximates a linear gradient, with sequentially disperse polymers, whose sequences are created statistically to yield the appropriate ensemble average linear gradient. Especially at high segregation strength, we find clear differences in polymer conformations and microstructures between these systems. Importantly, the statistical polymers are able to find more favorable conformations given their sequence, for instance, a statistical polymer with a larger fraction of A than the median will tend towards the A lamellae. The conformations of the statistically different polymers can thus be less stretched, and these systems have higher overall density. Consequently, the lamellae formed by statistical polymers have smaller domain spacing with sharper interfaces.

  17. Diblock copolymer adsorption onto a solid surface as revealed by evanescent wave ellipsometry

    SciTech Connect

    Kim, M.W. ); Russell, T.P. . Almaden Research Center); Moses, T.; Chen, W.; Shen, Y.R. . Center for Advanced Materials Univ. of California, Berkeley, CA . Dept. of Physics)

    1994-12-05

    The interfacial behavior of diblock copolymers play an important role in many practical applications, for example, polymer compatibilization, adhesion, and colloid stabilization. There has been considerable theoretical and experimental effort to understand the adsorption behavior of diblock copolymers from a solution onto a solid surface. Recent neutron reflectivity measurements on solutions of symmetric diblock copolymers of polystyrene and poly(methyl methacrylate), denoted P(S-b-MMA), near a quartz wall have shown that the PMMA segments adsorb preferentially onto the quartz forming a dense layer. However, the segmental concentration of polystyrene (PS) was too low to be observable. Evanescent wave ellipsometry, EWE, on the other hand, allows one to determine the density of molecules adsorbed onto a surface without labeling the segments with deuterium. Here, EWE results on P(S-b-MMA) adsorbed onto a solid substrate are presented as a function of molecular weight. It is shown that the adsorbed amount of copolymer is maximized for a particular molecular weight. This result contradicts theoretical predictions, and a possible origin of this discrepancy is provided.

  18. Amphiphilic graft copolymers with ethyl cellulose backbone: Synthesis, self-assembly and tunable temperature-CO2 response.

    PubMed

    Yuan, Weizhong; Zou, Hui; Shen, Jin

    2016-01-20

    Amphiphilic ethyl cellulose-graft-poly(N,N-dimethylaminoethyl methacrylate) (EC-g-PDMAEMA) and ethyl cellulose-graft-poly(2-(2-methoxyethoxy)ethyl methacrylate-co-N,N-dimethylaminoethyl methacrylate) (EC-g-P(MEO2MA-co-DMAEMA)) graft copolymers were easily synthesized by atom transfer radical polymerization (ATRP). The micelles self-assembled from the copolymer presented switchable temperature-CO2 dually responsive properties. The value of lower critical solution temperature (LCST) for the copolymer micelle solutions could be adjusted by CO2/Ar. Moreover, due to the alteration of the ratio of DMAEMA to MEO2MA, the LCST values of the micelle solutions decreased with the increase of MEO2MA in copolymer. The temperature-CO2 dually responsive properties of the copolymer were reversible and could be accomplished through altering the temperature and bubbling CO2/Ar. The hydrodynamic radius (Rh) of the copolymer micelles was also influenced by the ratio of DMAEMA to MEO2MA and the stimuli of temperature and CO2/Ar. As a drug release system, the copolymer micelles could achieve the control release of doxorubicin (DOX) by changing the temperature and alternatively bubbling CO2/Ar.

  19. Investigation of Universal Behavior in Symmetric Diblock Copolymer Melts

    NASA Astrophysics Data System (ADS)

    Medapuram, Pavani

    Coarse-grained theories of dense polymer liquids such as block copolymer melts predict a universal dependence of equilibrium properties on a few dimensionless parameters. For symmetric diblock copolymer melts, such theories predict a universal dependence on only chieN and N¯, where chie is an effective interaction parameter, N is the degree of polymerization, and N¯ is a measure of overlap. This thesis focuses on testing the universal behavior hypothesis by comparing results for various properties obtained from different coarse-grained simulation models to each other. Specifically, results from pairs of simulations of different models that have been designed to have matched values of N¯ are compared over a range of values of chiN. The use of vastly different simulation models allows us to cover a vast range of chi eN ≃ 200 - 8000 that includes most of the experimentally relevant range. Properties studied here include collective and single-chain correlations in the disordered phase, block and chain radii of gyration in the disordered phase, the value of chieN at the order-disorder transition (ODT), the free energy per chain, the latent heat of transition, the layer spacing, the composition profile, and compression modulus in the ordered phase. All results strongly support the universal scaling hypothesis, even for rather short chains, confirming that it is indeed possible to give an accurate universal description of simulation models that differ in many details. The underlying universality becomes apparent, however, only if data are analyzed using an adequate estimate of chie, which we obtained by fitting the structure factor S( q) in the disordered state to predictions of the recently developed renormalized one-loop (ROL) theory. The ROL theory is shown to provide an excellent description of the dependence of S(q on chain length and thermodynamic conditions for all models, even for very short chains, if we allow for the existence of a nonlinear dependence of

  20. Diblock copolymers with tunable pH transitions for gene delivery

    PubMed Central

    Manganiello, M.J.; Cheng, C.; Convertine, A.J.; Bryers, J.D.; Stayton, P.S.

    2012-01-01

    A series of diblock copolymers containing an endosomal-releasing segment composed of diethylaminoethyl methacrylate (DEAEMA) and butyl methacrylate (BMA) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The materials were designed to condense plasmid DNA (pDNA) through electrostatic interactions with a cationic poly(N,N-dimethylaminoethyl methacrylate) (DMAEMA) first block. The pDMAEMA was employed as a macro chain transfer agent (macroCTA) for the synthesis of a series in which the relative feed ratios of DEAEMA and BMA were systematically varied from 20% to 70% BMA. The resultant diblock copolymers exhibited low polydispersity (PDI ≤ 1.06) with similar molecular weights (Mn = 19.3 – 23.1 kDa). Dynamic light scattering (DLS) measurements in combination with 1H-NMR D2O studies demonstrated that the free copolymers assemble into core-shell micelles at physiological pH. Reduction of the solution pH to values representative of endosomal/lysosomal compartments induced an increase in the net cationic charge of the core through protonation of the DEAEMA residues. This protonation promotes micelle destabilization and exposure of the hydrophobic BMA residues that destabilize biological membranes. The pH value at which this micelle-to-unimer transition occurred was dependent on the hydrophobic content of the copolymer, with higher BMA-containing copolymer compositions exhibiting pH-induced transitions to the membrane-destabilizing state at successively lower pH values. The ability of the diblock copolymers to deliver pDNA was subsequently investigated using a GFP expression vector in two monocyte cell lines. High levels of DNA transfection were observed for the copolymer compositions exhibiting the sharpest pH transitions and membrane destabilizing activities, demonstrating the importance of tuning the endosomal-releasing segment composition. PMID:22169826

  1. Polyelectrolyte multilayers of diblock copolymer micelles with temperature-responsive cores.

    PubMed

    Xu, Li; Zhu, Zhichen; Sukhishvili, Svetlana A

    2011-01-04

    We report on assembly and stimuli-response behavior of layer-by-layer (LbL) films of pH- and temperature-responsive cationic diblock copolymer micelles (BCMs) of poly(2-(dimethylamino)ethyl methacrylate)-block-poly(N-isopropylacrylamide) (PDMA-b-PNIPAM) and a linear polyanion polystyrene sulfonate (PSS). As a function of solution pH at temperatures above lower critical solution temperature (LCST) of PNIPAM, PDMA-b-PNIPAM micelles have been demonstrated earlier to exhibit an abrupt change in micellar aggregation number and hydrodynamic size between larger and smaller BCMs (LBCMs and SBCMs, respectively). Here, LBCMs or SBCMs were included within LbL films through self-assembly with a polyanion, and film pH and temperature responses were studied using ellipsometry and atomic force microscopy (AFM). Both types of micelle preserved their micellar morphology when adsorbed at the surface of oxidized silicon wafers coated with PSS-terminated precursor layer at a constant pH. Response of adsorbed BCMs to temperature and pH variations was strongly dependent on whether or not BCMs were coated with the PSS layer. While monolayers of LBCMs lost their original dry morphology in response to pH or temperature variations, depositing a PSS layer atop LBCMs inhibited such irreversible restructuring. As a result of wrapping around and strong binding of PSS chains with LBCM micelles, BCM/PSS assemblies preserved their original dry state morphology despite the application of pH and temperature triggers. However, the wet-state film response to pH and temperature stimuli was drastically different. Swelling of BCM/PSS multilayers was strongly affected by temperature but was almost independent of pH due to neutralization of BCM PDMA's coronal charge with PSS. Cycling the temperature below and above PNIPAM's LCST caused PNIPAM chains within BCM cores to swell or collapse, resulting in reversible swelling transitions in the entire BCM/PSS assemblies. Temperature-controlled switching between

  2. Combination chemotherapy using core-shell nanoparticles through the self-assembly of HPMA-based copolymers and degradable polyester.

    PubMed

    Jäger, Eliézer; Jäger, Alessandro; Chytil, Petr; Etrych, Tomáš; Ríhová, Blanka; Giacomelli, Fernando Carlos; Stěpánek, Petr; Ulbrich, Karel

    2013-01-28

    The preparation of core-shell polymeric nanoparticles simultaneously loaded with docetaxel (DTXL) and doxorubicin (DOX) is reported herein. The self-assembly of the aliphatic biodegradable copolyester PBS/PBDL (poly(butylene succinate-co-butylene dilinoleate)) and HPMA-based copolymers (N-(2-hydroxypropyl)methacrylamide-based copolymers) hydrophobically modified by the incorporation of cholesterol led to the formation of narrow-size-distributed (PDI<0.10) sub-200-nm polymeric nanoparticles suitable for passive tumor-targeting drug delivery based on the size-dependent EPR (enhanced permeability and retention) effect. The PHPMA provided to the self-assembled nanoparticle stability against aggregation as evaluated in vitro. The highly hydrophobic drug docetaxel (DTXL) was physically entrapped within the PBS/PBDL copolyester core and the hydrophilic drug doxorubicin hydrochloride (DOX·HCl) was chemically conjugated to the reactive PHPMA copolymer shell via hydrazone bonding that allowed its pH-sensitive release. This strategy enabled the combination chemotherapy by the simultaneous DOX and DTXL drug delivery. The structure of the nanoparticles was characterized in detail using static (SLS), dynamic (DLS) and electrophoretic (ELS) light scattering besides transmission electron microscopy (TEM). The use of nanoparticles simultaneously loaded with DTXL and DOX provided a more efficient suppression of tumor-cell growth in mice bearing EL-4 T cell lymphoma when compared to the effect of nanoparticles loaded with either DTXL or DOX separately. Additionally, the obtained self-assembled nanoparticles enable further development of targeting strategies based on the use of multiple ligands attached to an HPMA copolymer on the particle surface for simultaneous passive and active targeting and different combination therapies.

  3. Occlusion of Sulfate-Based Diblock Copolymer Nanoparticles within Calcite: Effect of Varying the Surface Density of Anionic Stabilizer Chains

    PubMed Central

    2016-01-01

    Polymerization-induced self-assembly (PISA) offers a highly versatile and efficient route to a wide range of organic nanoparticles. In this article, we demonstrate for the first time that poly(ammonium 2-sulfatoethyl methacrylate)-poly(benzyl methacrylate) [PSEM–PBzMA] diblock copolymer nanoparticles can be prepared with either a high or low PSEM stabilizer surface density using either RAFT dispersion polymerization in a 2:1 v/v ethanol/water mixture or RAFT aqueous emulsion polymerization, respectively. We then use these model nanoparticles to gain new insight into a key topic in materials chemistry: the occlusion of organic additives into inorganic crystals. Substantial differences are observed for the extent of occlusion of these two types of anionic nanoparticles into calcite (CaCO3), which serves as a suitable model host crystal. A low PSEM stabilizer surface density leads to uniform nanoparticle occlusion within calcite at up to 7.5% w/w (16% v/v), while minimal occlusion occurs when using nanoparticles with a high PSEM stabilizer surface density. This counter-intuitive observation suggests that an optimum anionic surface density is required for efficient occlusion, which provides a hitherto unexpected design rule for the incorporation of nanoparticles within crystals. PMID:27509298

  4. Selective area epitaxy of ultra-high density InGaN quantum dots by diblock copolymer lithography

    PubMed Central

    2011-01-01

    Highly uniform InGaN-based quantum dots (QDs) grown on a nanopatterned dielectric layer defined by self-assembled diblock copolymer were performed by metal-organic chemical vapor deposition. The cylindrical-shaped nanopatterns were created on SiNx layers deposited on a GaN template, which provided the nanopatterning for the epitaxy of ultra-high density QD with uniform size and distribution. Scanning electron microscopy and atomic force microscopy measurements were conducted to investigate the QDs morphology. The InGaN/GaN QDs with density up to 8 × 1010 cm-2 are realized, which represents ultra-high dot density for highly uniform and well-controlled, nitride-based QDs, with QD diameter of approximately 22-25 nm. The photoluminescence (PL) studies indicated the importance of NH3 annealing and GaN spacer layer growth for improving the PL intensity of the SiNx-treated GaN surface, to achieve high optical-quality QDs applicable for photonics devices. PMID:21711862

  5. Inducing an Order–Order Morphological Transition via Chemical Degradation of Amphiphilic Diblock Copolymer Nano-Objects

    PubMed Central

    2016-01-01

    The disulfide-based cyclic monomer, 3-methylidene-1,9-dioxa-5,12,13-trithiacyclopentadecane-2,8-dione (MTC), is statistically copolymerized with 2-hydroxypropyl methacrylate to form a range of diblock copolymer nano-objects via reversible addition–fragmentation chain transfer (RAFT) polymerization. Poly(glycerol monomethacrylate) (PGMA) is employed as the hydrophilic stabilizer block in this aqueous polymerization-induced self-assembly (PISA) formulation, which affords pure spheres, worms or vesicles depending on the target degree of polymerization for the core-forming block. When relatively low levels (<1 mol %) of MTC are incorporated, high monomer conversions (>99%) are achieved and high blocking efficiencies are observed, as judged by 1H NMR spectroscopy and gel permeation chromatography (GPC), respectively. However, the side reactions that are known to occur when cyclic allylic sulfides such as MTC are statistically copolymerized with methacrylic comonomers lead to relatively broad molecular weight distributions. Nevertheless, the worm-like nanoparticles obtained via PISA can be successfully transformed into spherical nanoparticles by addition of excess tris(2-carboxyethyl)phosphine (TCEP) at pH 8–9. Surprisingly, DLS and TEM studies indicate that the time scale needed for this order–order transition is significantly longer than that required for cleavage of the disulfide bonds located in the worm cores indicated by GPC analysis. This reductive degradation pathway may enable the use of these chemically degradable nanoparticles in biomedical applications, such as drug delivery systems and responsive biomaterials. PMID:27228898

  6. Poly(ethylene oxide)-b-poly(L-lactide) diblock copolymer/carbon nanotube-based nanocomposites: LiCl as supramolecular structure-directing agent.

    PubMed

    Meyer, Franck; Raquez, Jean-Marie; Verge, Pierre; Martínez de Arenaza, Inger; Coto, Borja; Van Der Voort, Pascal; Meaurio, Emilio; Dervaux, Bart; Sarasua, Jose-Ramon; Du Prez, Filip; Dubois, Philippe

    2011-11-14

    This work relies on the CNT dispersion in either solution or a polymer matrix through the formation of a three-component supramolecular system composed of PEO-b-PLLA diblock copolymer, carbon nanotubes (CNTs), and lithium chloride. According to a one-pot procedure in solution, the "self-assembly" concept has demonstrated its efficiency using suspension tests of CNTs. Characterizations of the supramolecular system by photon correlation spectroscopy, Raman spectroscopy, and molecular dynamics simulations highlight the charge transfer interaction from the CNTs toward the PEO-b-PLLA/LiCl complex. Finally, this concept was successfully extended in bulk (absence of solvent) via melt-processing techniques by dispersing these complexes in a commercial polylactide (PLA) matrix. Electrical conductivity measurements and transmission electron microscopy attested for the remarkable dispersion of CNTs, confirming the design of high-performance PLA-based materials.

  7. Diblock copolymers of polyethylene glycol and a polymethacrylamide with side-chains containing twin ortho ester rings: synthesis, characterization, and evaluation as potential pH-responsive micelles.

    PubMed

    Zhou, Xiaojing; Luo, Shi; Tang, Rupei; Wang, Rui; Wang, Jun

    2015-03-01

    The diblock copolymer, PEG-b-PMEA, was synthesized by reversible-addition fragmentation chain transfer polymerization (RAFT). The PMEA block contained a polymethacrylamide backbone and twin ortho ester rings in the side-chains. At neutral pH, PEG-b-PMEA self-assembled to form stable micelles. At pH 5, the twin ortho ester rings were quickly hydrolyzed to completion in 12 h, and releasing nearly 70% of the encapsulated Nile Red dye. The PEG-b-PMEA micelles were completely nontoxic to cultured cells as determined by the MTT assay. Paclitaxel (PTX)-loaded micelles showed toxicity toward lung cancer cells comparable to that of the free PTX at equivalent doses. These results suggest that the PEG-b-PMEA micelles could be useful nano-carriers for pH-responsive delivery of poorly soluble anticancer drugs.

  8. Dual-responsive polypseudorotaxanes based on block-selected inclusion between polyethylene-block-poly(ethylene glycol) diblock copolymers and 1,4-diethoxypillar[5]arene.

    PubMed

    Chen, Jianzhuang; Li, Nan; Gao, Yongping; Sun, Fugen; He, Jianping; Li, Yongsheng

    2015-10-21

    Based on the selective recognition of the polyethylene (PE) block of polyethylene-block-poly(ethylene glycol) (PE-b-PEG) by 1,4-diethoxypillar[5]arene (DEP5A), two novel thermo and competitive guest (1,4-dibromobutane or hexanedinitrile) responsive polypseudorotaxanes (PPRs) have been successfully constructed. The formation of PPRs both in solution and in the solid state was demonstrated by (1)H NMR, 2D NOESY, and WAXD analyses. TGA data illustrate that PPRs exhibit higher thermal stability than their precursor diblock copolymers. Moreover, intriguing porous disk-like aggregates are produced by electrospraying of PPRs in CHCl3 and the self-assembled structures of PPRs are totally changed by the addition of 1,4-dibromobutane or hexanedinitrile, demonstrating their competitive guest stimuli-responsiveness.

  9. Kinetic pathways of sphere-to-cylinder transition in diblock copolymer melt under electric field.

    PubMed

    Ly, D Q; Pinna, M; Honda, T; Kawakatsu, T; Zvelindovsky, A V M

    2013-02-21

    Phase transition from body-centered-cubic spheres to cylinders in a diblock copolymer melt under an external electric field is investigated by means of real-space dynamical self-consistent field theory. Different phase transition kinetic pathways and different cylindrical domains arrangements of the final phase are observed depending on the strength and direction of the applied electric field. Various transient states have been identified depending on the electric field being applied along [111], [100], and [110] directions. The electric field should be above a certain threshold value in order the transition to occur. A "dynamic critical exponent" of the transition is found to be about 3/2, consistent with other order-order transitions in diblock copolymers under electric field.

  10. Furan-functionalized co-polymers for targeted drug delivery: characterization, self-assembly and drug encapsulation.

    PubMed

    Shi, Meng; Shoichet, Molly S

    2008-01-01

    We have previously reported furan-maleimide Diels-Alder chemistry as a new methodology to couple maleimide-modified antibodies on furan-functionalized polymeric carriers in the preparation of immuno-nanoparticles for targeted drug delivery. In this report, we focus on the characterization, self-assembly behavior and drug encapsulation of two types of furan-functionalized co-polymers: poly(2-methyl, 2-carboxytrimethylene carbonate-co-D,L-lactide)-furan (poly(TMCC-co-LA)-furan) and poly(2-methyl, 2-carboxytrimethylene carbonate-co-D,L-lactide)-graft-poly(ethylene glycol)-furan (poly(TMCC-co-LA)-g-PEG-furan). The co-polymers were synthesized by modifying the carboxylic acid groups on the poly(TMCC-co-LA) backbone by either furfurylamine or PEG-furan to generate either linear co-polymers of poly(TMCC-co-LA)-furan with furan pendant groups or graft co-polymers of poly(TMCC-co-LA)-g-PEG-furan with furan-terminated PEG grafts, respectively. Using a membrane dialysis method, both of the co-polymers were self-assembled into nanoparticles in aqueous environments driven by the hydrophobic association among polymer chains. The hydrophobic domains in the nanoparticles were confirmed by the incorporation of pyrene molecules and the critical aggregation concentrations were determined to be approximately 5 x 10(-5) mM for poly(TMCC-co-LA)-furan and 2 x 10(-4) mM for poly(TMCC-co-LA)-g-PEG-furan. By the addition of borate buffer in the organic solvent used to dissolve the co-polymers in the dialysis procedure, we were able to control the size of the nanoparticles: 54-169 nm for poly(TMCC-co-LA)-furan and 28-283 nm for poly(TMCC-co-LA)-g-PEG-furan. This unique feature can be explained by the ionization of carboxylic acid groups along the co-polymer backbone. A hydrophobic anticancer drug, doxorubicin (DOX), was encapsulated within the nanoparticles, with the larger size nanoparticles incorporating greater amounts of DOX. Combining the strategy of antibody-mediated targeting, these

  11. Self-Organization of FePt Nanoparticles on Photochemically Modified Diblock Copolymer Templates

    DTIC Science & Technology

    2005-01-01

    30, 6507. Self-Organization of FePt Nanoparticles on Photochemically Modified Diblock Copolymer Templates** By Seth B. Darling, Nataliya A. Yufa...60637 (USA) [**] The authors thank Ward Lopes for useful discussions and A. C. Sa- mia, J. Schleuter, and X. M. Lin for providing the FePt nanoparticles...REPORT DATE 2005 2. REPORT TYPE 3. DATES COVERED 00-00-2005 to 00-00-2005 4. TITLE AND SUBTITLE Self-Organization of FePt Nanoparticles on

  12. Fabrication of a Cu nanodot array based on electroless plating employing a diblock copolymer nanotemplate

    NASA Astrophysics Data System (ADS)

    Asakura, Shuichi; Hozumi, Atsushi; Fuwa, Akio

    2005-07-01

    An array of copper (Cu) nanodots was fabricated onto a Si substrate covered with native oxide (SiO2/Si) using a diblock copolymer as a resist film. First, polystyrene/polymethylmethacrylate (PS/PMMA) diblock copolymer was spin-coated on a SiO2/Si substrate and then annealed for 24 h in a vacuum oven maintained at 170 °C to achieve good phase separation. To prepare a nanotemplate, this phase-separated diblock copolymer film was photodecomposed selectively using 172 nm vacuum ultraviolet (VUV) light. Due to the difference in photoetching rate between PS and PMMA domains, the latter regions were preferentially decomposed. By controlling the VUV irradiation conditions, that is, exposure time and atmospheric pressure, we were able to prepare a diblock copolymer template comprised of a nanoporous PS matrix on the SiO2/Si surface. Next, the nanopore regions were site-selectively modified through a vapor phase chemisorption of an amino-terminated organosilane. Palladium (Pd[II]) particles were then immobilized onto the amino-terminated nanopore regions through donor and accepter reactions and, subsequently, Cu was selectively electroless-plated onto these Pd-activated regions. As evidenced by atomic force microscopy, due to the elimination of the residual PS nanotemplate by VUV irradiation, we fabricated an array of Cu nanodots 3.0 to ~4.3 nm in height and 10 to ~25 nm in diameter on the entire 10×10 mm2 area of the SiO2/Si substrate.

  13. Considerations in binding diblock copolymers on hydrophilic alginate beads for providing an immunoprotective membrane

    PubMed Central

    Spasojevic, Milica; Bhujbal, Swapnil; Paredes, Genaro; de Haan, Bart J; Schouten, Arend J; de Vos, Paul

    2014-01-01

    Alginate-based microcapsules are being proposed for treatment of many types of diseases. A major obstacle however in the successes is that these capsules are having large lab-to-lab variations. To make the process more reproducible, we propose to cover the surface of alginate capsules with diblock polymers that can form polymer brushes. In the present study, we describe the stepwise considerations for successful application of diblock copolymer of polyethylene glycol (PEG) and poly-l-lysine (PLL) on the surface of alginate beads. Special procedures had to be designed as alginate beads are hydrophilic and most protocols are designed for hydrophobic biomaterials. The successful attachment of diblock copolymer and the presence of PEG blocks on the surface of the capsules were studied by fluorescence microscopy. Longer time periods, that is, 30–60 min, are required to achieve saturation of the surface. The block lengths influenced the strength of the capsules. Shorter PLL blocks resulted in less stable capsules. Adequate permeability of the capsules was achieved with poly(ethylene glycol)-block-poly(l-lysine hydrochloride) (PEG454-b-PLL100) diblock copolymers. The capsules were a barrier for immunoglobulin G. The PEG454-b-PLL100 capsules have similar mechanical properties as PLL capsules. Minor immune activation of nuclear factor κB in THP-1 monocytes was observed with both PLL and PEG454-b-PLL100 capsules prepared from purified alginate. Our results show that we can successfully apply block copolymers on the surface of hydrophilic alginate beads without interfering with the physicochemical properties. PMID:23853069

  14. Block copolymer strands with internal microphase separation structure via self-assembly at the air-water interface.

    PubMed

    Price, Eric W; Guo, Yunyong; Wang, C-W; Moffitt, Matthew G

    2009-06-02

    Block copolymer microphase separation in the bulk is coupled to amphiphilic block copolymer self-assembly at the air-water interface to yield hierarchical Langmuir-Blodgett (LB) structures combining organization at the meso- and nanoscales. A blend of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) (Mn=141K, 11.4 wt % PEO) and polystyrene-b-poly(butadiene) (PS-b-PB) (Mn=31.9K, 28.5 wt % PB) containing a PS-b-PB weight fraction of f=0.75 was deposited at the air-water interface, resulting in the spontaneous generation of aggregates with multiscale organization, including nanoscale cylinders in mesoscale strands, via evaporation of the spreading solvent. The resulting features were characterized in LB films via AFM and TEM and at the air-water interface via Langmuir compression isotherms. Blends containing lower PS-b-PB contents formed mesoscale aggregate morphologies of continents and strands (f=0.50) or mesoscale continents with holes (f=0.25), but without the internal nanoscale organization found in the f=0.75 blend. The interfacial self-assembly of pure PS-b-PB at the air-water interface (f=1) yielded taller and more irregularly shaped aggregates than blends containing PS-b-PEO, indicating the integral role of the amphiphilic copolymer in regulating the mesoscale organization of the hierarchically structured features.

  15. Lamellar orientation of block copolymer using polarity switch of nitrophenyl self-assembled monolayer induced by electron beam

    NASA Astrophysics Data System (ADS)

    Yamamoto, Hiroki; Dawson, Guy; Kozawa, Takahiro; Robinson, Alex P. G.

    2017-03-01

    Directed self-assembly (DSA) was investigated on self-assembled monolayers (SAMs) of 6-(4-nitrophenoxy) hexane-1-thiol (NPHT), which were chemically modified by electron beam (EB) irradiation. By irradiating a responsive interfacial surface, the orientation and selective patterning of block copolymer domains could be achieved. We demonstrated that spatially-selective lamellar orientation of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) could be induced via modification of an underlying SAM; for instance the conversion of an NO2 group to an NH2 group, induced by EB. The lamellar orientation of PS-b-PMMA was controlled by the change in the polarity of different regions of the SAM using EB lithography. The reductive treatment of SAM substrates plays a crucial role in the orientation of block copolymer. This method might greatly simplify block copolymer DSA processes as compared to the conventional multi-step chemo-epitaxy DSA process. By examining the lamellae orientation by EB, we found that the vertical orientation persists only for appropriate an irradiation dose and annealing temperature.

  16. Molecular dynamics study on microstructures of diblock copolymer melts with soft potential and potential recovery

    NASA Astrophysics Data System (ADS)

    Ryu, Ji Ho; Wee, Han Sol; Lee, Won Bo

    2016-09-01

    Various microstructures are obtained through the self-assembly of block copolymers on the basis of the compositional fractions and repulsive interactions among different types of beads. The inhomogeneity of block copolymers can be studied by molecular dynamics. However, preparing initial configurations of various self-assembled structures directly by molecular dynamics requires extensive computational time because of topological constraints. Furthermore, manual preparation often becomes a complicated and time-consuming procedure even for the simplest structures, such as a lamellar phase, not to mention three-dimensional bicontinuous cubic phases such as a gyroid phase. In this paper, this difficulty is overcome by using a soft potential, which allows the system to reach a self-assembled state quickly (within 3 τd ). Once a self-assembled microstructure is obtained, the normal potential is restored and equilibration steps are performed to enable the calculation of various properties of the microstructures. Various equilibrated phase structures—including S (spherical), H (hexagonal), G (gyroid), and L (lamellar) phases—are obtained by this approach. To verify our method, static and dynamic properties of the lamellar phase are examined and compared with previous results.

  17. Superhydrophobic hierarchically assembled films of diblock copolymer hollow nanospheres and nanotubes.

    PubMed

    He, Guping; Hu, Jiwen; Liu, Guojun; Li, Yinhui; Zhang, Ganwei; Liu, Feng; Sun, Jianpin; Zou, Hailiang; Tu, Yuanyuan; Xiao, Dingshu

    2013-04-10

    Reported are the formation of rough particulate films from cross-linked diblock copolymer vesicles and nanotubes and the wetting properties of the resultant films. The diblock copolymers used were F66M200 and F95A135, where the subscripts denote the repeat unit numbers, whereas M, A, and F denote poly(2-cinnamoyloxyethyl methacrylate), poly(2-cinnamoyloxyethyl acrylate), and poly(2,2,2-trifluoroethyl methacrylate), respectively. The precursory polymers to F66M200 and F95A135 were prepared by atom transfer radical polymerization. In 2,2,2-trifluoroethyl methacrylate (FEMA), a selective solvent for F, vesicles and tubular micelles were prepared from F66M200 and F95A135, respectively. Photo-cross-linking the M and A blocks of these aggregates yielded hollow nanospheres and nanotubes bearing F coronal chains. These particles were dispersed into CH2Cl2/methanol, where CH2Cl2 was a good solvent for both blocks and methanol was a poor solvent for F. Casting CH2Cl2/methanol dispersions of these particles yielded films consisting of hierarchically assembled diblock copolymer nanoparticles. For example, the hollow nanospheres fused into microspheres bearing nanobumps after being cast from CH2Cl2/methanol at methanol volume fractions of 30 and 50%. The roughness of these films increased as the methanol volume fraction increased. The films that were cast at high methanol contents were superhydrophobic, possessing water contact angles of ∼160° and water sliding angles of ∼3°.

  18. Dynamics and order-disorder transitions in bidisperse diblock copolymer blends

    NASA Astrophysics Data System (ADS)

    Wang, Yueqiang; Li, Xuan; Tang, Ping; Yang, Yuliang

    2011-03-01

    We employ the dynamic extension of self-consistent field theory (DSCFT) to study dynamics and order-disorder transitions (ODT) in AB diblock copolymer binary mixtures of two different monodisperse chain lengths by imitating the dynamic storage modulus G‧ corresponding to any given morphology in the oscillatory shear measurements. The different polydispersity index (PDI) is introduced by binary blending AB diblock copolymers with variations in chain lengths and chain number fractions. The simulation results show that the increase of polydispersity in the minority or symmetric block introduces a decrease in the segregation strength at the ODT, ( χN) ODT, whereas the increase of polydispersity in the majority block results in a decrease, then increase and final decrease again in ( χN) ODT. To the best of our knowledge, our DSCFT simulations, for the first time, predict an increase in ( χN) ODT with the PDI in the majority block, which produces the experimental results. The simulations by previous SCFT, which generally speaking, is capable of describing equilibrium morphologies, however, contradict the experimental data. The polydispersity acquired by properly tuning the chain lengths and number fractions of binary diblock copolymer blends should be a convenient and efficient way to control the microphase separation strength at the ODT.

  19. Morphological Control of Anisotropic Self-Assemblies from Alternating Poly(p-dioxanone)-poly(ethylene glycol) Multiblock Copolymer Depending on the Combination Effect of Crystallization and Micellization.

    PubMed

    Wang, Mei-Jia; Wang, Hao; Chen, Si-Chong; Chen, Cheng; Liu, Ya

    2015-06-30

    A novel and facile method was developed for morphological controlling of self-assemblies prepared by crystallization induced self-assembly of crystalline-coil copolymer depending on the combination effect of crystallization and micellization. The morphological evolution of the self-assemblies of alternating poly(p-dioxanone)-block-poly(ethylene glycol) (PPDO-PEG) multiblock copolymer prepared by different solvent mixing methods in aqueous solution were investigated. "Chrysanthemum"-like and "star anise"-like self-assemblies were obtained at different rates of solvent mixing. The results suggested gradually change in solvent quality (slowly dropping water into DMF solution) leaded to a hierarchical micellization-crystallization process of core-forming PPDO blocks, and flake-like particles were formed at the initial stage of crystallization. Meanwhile, crystallization induced micellization process occurred when solvent quality changed drastically. Shuttle-like particles, which have much smaller size than those of flake-like particles, were formed at the initial stage of crystallization when quickly injecting water into DMF solution of the copolymer. Therefore, owing to the different changing rate of solvent quality, which may result in different combination effect of crystallization and micellization during self-assembly of the copolymer, PPDO-PEG self-assemblies with different hierarchical morphology in nano scale could be obtained.

  20. Assembly of diblock copolymer grafted nanoparticles in a homopolymer blend matrix

    NASA Astrophysics Data System (ADS)

    Estridge, Cara; Jayaraman, Arthi

    2014-03-01

    Hybrid materials comprised of nanoscale fillers embedded in a polymer matrix, also terms polymer nanocomposites, are used in many applications, such as photovoltaics, photonics, automobile parts, where their macroscopic properties are governed by the nanocomposite morphology. The structure and composite morphology is controlled by the interactions of the nanoscale fillers and the polymer matrix. In this talk we show using molecular simulations that functionalization of the nanoparticle surface with AB diblock copolymer grafts is a way to tune the interactions between the grafted particle and the A and B homopolymer blend matrix. Specifically, our work demonstrates that by tailoring the copolymer composition and the copolymer grafting density one can tune the location of the copolymer grafted particles in the matrix, (e.g. within a domain versus interface of two domains). Additionally, in the case where the grafted particles locate themselves at the interface between the two domains, the interfacial tension is reduced below that possible with bare ungrafted particles at the interface.

  1. Synthesis and self-assembly behavior of a biodegradable and sustainable soybean oil-based copolymer nanomicelle

    NASA Astrophysics Data System (ADS)

    Bao, Lixia; Bian, Longchun; Zhao, Mimi; Lei, Jingxin; Wang, Jiliang

    2014-08-01

    Herein, we report a novel amphiphilic biodegradable and sustainable soybean oil-based copolymer (SBC) prepared by grafting hydrophilic and biocompatible hydroxyethyl acrylate (HEA) polymeric segments onto the natural hydrophobic soybean oil chains. FTIR, H1-NMR, and GPC measurements have been used to investigate the molecular structure of the obtained SBC macromolecules. Self-assembly behaviors of the prepared SBC in aqueous solution have also been extensively evaluated by fluorescence spectroscopy and transmission electron microscopy. The prepared SBC nanocarrier with the size range of 40 to 80 nm has a potential application in the biomedical field.

  2. Self-assembling gradient copolymers of vinylimidazol and (acrylic)ibuprofen with anti-inflammatory and zinc chelating properties.

    PubMed

    Suárez, Patricia; Rojo, Luis; González-Gómez, Álvaro; Román, Julio San

    2013-09-01

    Novel gradient copolymers of hydrophilic 1-vinylimidazol and hydrophobic methacrylic derivative of ibuprofen prepared by free radical polymerization are described. The heterogeneous distribution of monomeric units along the polymeric chains leads to a gradient distribution of the hydrophobic and hydrophilic sequences responsible of nanoparticles formation through a self-assembling mechanism, capable of tune the water permeation due to the ionizable imidazole moieties and their gradient profile along the macromolecules, exhibiting pH and composition dependent effect in terms of diameter, zeta potential, acid-base buffering, ibuprofen release and chelating capacities, responsible of matrix metalloproteinase dysfunction showing anti-inflammatory activity in a nitric oxide inhibition assay.

  3. A biodegradable, injectable, gel system based on MPEG-b-(PCL-ran-PLLA) diblock copolymers with an adjustable therapeutic window.

    PubMed

    Kang, Yun Mi; Lee, Sang Hyo; Lee, Ju Young; Son, Jin Soo; Kim, Byung Soo; Lee, Bong; Chun, Heung Jae; Min, Byoung Hyun; Kim, Jae Ho; Kim, Moon Suk

    2010-03-01

    In situ-forming gel systems have drawn increasing attention for their potential use in a variety of biomedical applications. Here, we examined an in situ-forming gel system comprised of MPEG-b-PCL and MPEG-b-(PCL-ran-PLLA) diblock copolymers with different PLLA contents (0-10 mol%) in the PCL segment. The crystalline region of the PCL-ran-PLLA segment decreased with increasing PLLA content. The MPEG-b-(PCL-ran-PLLA) diblock copolymer solutions were liquid at room temperature and only MPEG-b-(PCL-ran-PLLA) diblock copolymer solutions with a PLLA content < or = 5 mol% in the PCL segment showed a sol-to-gel transition as the temperature was increased. The viscosity change associated with sol-to-gel phase transition depended on the PLLA content in the PCL segment. A MPEG-b-PCL diblock copolymer solution incubated in vitro showed increasing viscosity without degradation, whereas the viscosity of MPEG-b-(PCL-ran-PLLA) diblock copolymer solutions continuously and sharply decreased with increasing PLLA content in the PCL segment. As the amount of PLLA increased, the size of in vivo-formed MPEG-b-(PCL-ran-PLLA) gels after initial injection tended to gradually decrease because of hydrolytic degradation of the PLLA in the PCL-ran-PLLA segment. An immunohistochemical examination showed that in vivo MPEG-b-(PCL-ran-PLLA) diblock copolymer gels provoked only a modest inflammatory response. Collectively, our results show that the MPEG-b-(PCL-ran-PLLA) diblock copolymer gel described here could serve as a minimally invasive, therapeutic, in situ-forming gel system that offers an experimental window adjustable from a few weeks to a few months. Copyright 2009 Elsevier Ltd. All rights reserved.

  4. Self-assembly in block polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Yang, Shuang; Vishnyakov, Aleksey; Neimark, Alexander V.

    2011-02-01

    The self-consistent field theory (SCFT) complemented with the Poisson-Boltzmann equation is employed to explore self-assembly of polyelectrolyte copolymers composed of charged blocks A and neutral blocks B. We have extended SCFT to dissociating triblock copolymers and demonstrated our approach on three characteristic examples: (1) diblock copolymer (AB) melt, (2) symmetric triblock copolymer (ABA) melt, (3) triblock copolymer (ABA) solution with added electrolyte. For copolymer melts, we varied the composition (that is, the total fraction of A-segments in the system) and the charge density on A blocks and calculated the phase diagram that contains ordered mesophases of lamellar, gyroid, hexagonal, and bcc symmetries, as well as the uniform disordered phase. The phase diagram of charged block copolymer melts in the charge density - system composition coordinates is similar to the classical phase diagram of neutral block copolymer melts, where the composition and the Flory mismatch interaction parameter χ _{AB} are used as variables. We found that the transitions between the polyelectrolyte mesophases with the increase of charge density occur in the same sequence, from lamellar to gyroid to hexagonal to bcc to disordered morphologies, as the mesophase transitions for neutral diblocks with the decrease of χ _{AB}. In a certain range of compositions, the phase diagram for charged triblock copolymers exhibits unexpected features, allowing for transitions from hexagonal to gyroid to lamellar mesophases as the charge density increases. Triblock polyelectrolyte solutions were studied by varying the charge density and solvent concentration at a fixed copolymer composition. Transitions from lamellar to gyroid and gyroid to hexagonal morphologies were observed at lower polymer concentrations than the respective transitions in the similar neutral copolymer, indicating a substantial influence of the charge density on phase behavior.

  5. Hierarchical patterns of three-dimensional block-copolymer films formed by electrohydrodynamic jet printing and self-assembly

    NASA Astrophysics Data System (ADS)

    Onses, M. Serdar; Song, Chiho; Williamson, Lance; Sutanto, Erick; Ferreira, Placid M.; Alleyne, Andrew G.; Nealey, Paul F.; Ahn, Heejoon; Rogers, John A.

    2013-09-01

    Self-assembly of block-copolymers provides a route to the fabrication of small (size, <50 nm) and dense (pitch, <100 nm) features with an accuracy that approaches even the demanding specifications for nanomanufacturing set by the semiconductor industry. A key requirement for practical applications, however, is a rapid, high-resolution method for patterning block-copolymers with different molecular weights and compositions across a wafer surface, with complex geometries and diverse feature sizes. Here we demonstrate that an ultrahigh-resolution jet printing technique that exploits electrohydrodynamic effects can pattern large areas with block-copolymers based on poly(styrene-block-methyl methacrylate) with various molecular weights and compositions. The printed geometries have diameters and linewidths in the sub-500 nm range, line edge roughness as small as ~45 nm, and thickness uniformity and repeatability that can approach molecular length scales (~2 nm). Upon thermal annealing on bare, or chemically or topographically structured substrates, such printed patterns yield nanodomains of block-copolymers with well-defined sizes, periodicities and morphologies, in overall layouts that span dimensions from the scale of nanometres (with sizes continuously tunable between 13 nm and 20 nm) to centimetres. As well as its engineering relevance, this methodology enables systematic studies of unusual behaviours of block-copolymers in geometrically confined films.

  6. Hierarchical patterns of three-dimensional block-copolymer films formed by electrohydrodynamic jet printing and self-assembly.

    PubMed

    Onses, M Serdar; Song, Chiho; Williamson, Lance; Sutanto, Erick; Ferreira, Placid M; Alleyne, Andrew G; Nealey, Paul F; Ahn, Heejoon; Rogers, John A

    2013-09-01

    Self-assembly of block-copolymers provides a route to the fabrication of small (size, <50 nm) and dense (pitch, <100 nm) features with an accuracy that approaches even the demanding specifications for nanomanufacturing set by the semiconductor industry. A key requirement for practical applications, however, is a rapid, high-resolution method for patterning block-copolymers with different molecular weights and compositions across a wafer surface, with complex geometries and diverse feature sizes. Here we demonstrate that an ultrahigh-resolution jet printing technique that exploits electrohydrodynamic effects can pattern large areas with block-copolymers based on poly(styrene-block-methyl methacrylate) with various molecular weights and compositions. The printed geometries have diameters and linewidths in the sub-500 nm range, line edge roughness as small as ∼45 nm, and thickness uniformity and repeatability that can approach molecular length scales (∼2 nm). Upon thermal annealing on bare, or chemically or topographically structured substrates, such printed patterns yield nanodomains of block-copolymers with well-defined sizes, periodicities and morphologies, in overall layouts that span dimensions from the scale of nanometres (with sizes continuously tunable between 13 nm and 20 nm) to centimetres. As well as its engineering relevance, this methodology enables systematic studies of unusual behaviours of block-copolymers in geometrically confined films.

  7. Development of a novel endosomolytic diblock copolymer for siRNA delivery

    PubMed Central

    Convertine, Anthony J.; Benoit, Danielle S.W.; Duvall, Craig L.; Hoffman, Allan S.; Stayton, Patrick S.

    2011-01-01

    The gene knockdown activity of small interfering RNA (siRNA) has led to their use as target validation tools and as potential therapeutics for a variety of diseases. The delivery of these double-stranded RNA macromolecules has proven to be challenging, however, and in many cases, is a barrier to their deployment. Here we report the development of a new diblock copolymer family that was designed to enhance the systemic and intracellular delivery of siRNA. These diblock copolymers were synthesized using the controlled reversible addition fragmentation chain transfer polymerization (RAFT) method and are composed of a positively-charged block of dimethylaminoethyl methacrylate (DMAEMA) to mediate siRNA condensation, and a second endosomal-releasing block composed of DMAEMA and propylacrylic acid (PAA) in roughly equimolar ratios, together with butyl methacylate (BMA). A related series of diblock compositions were characterized, with the cationic block kept constant, and with the ratio of DMAEMA and PAA to BMA varied. These carriers became sharply hemolytic at endosomal pH regimes, with increasing hemolytic activity seen as the percentage of BMA in the second block was systematically increased. The diblock copolymers condensed siRNA into 80–250 nm particles with slightly positive Zeta potentials. SiRNA-mediated knockdown of a model protein, namely glyceraldehyde 3-phosphate dehydrogenase (GAPDH), in HeLa cells generally followed the hemolytic activity trends, with the most hydrophobic second block (highest BMA content) exhibiting the best knockdown. This pH-responsive carrier designed to mediate endosomal release shows significant promise for the intracellular delivery of siRNA. PMID:18973780

  8. Understanding self-assembly of charged-neutral block copolymer (BCP) and surfactant complexes using molecular dynamics (MD) simulation

    NASA Astrophysics Data System (ADS)

    Goswami, Monojoy; Sumpter, Bobby; Kilbey, Michael

    Here we report the formation of phase separated BCP-surfactant complexes resulting from the electrostatic self-assembly of charge-neutral block copolymers with oppositely charged surfactants. Complexation behaviors of oppositely charged polyelectrolytes has gained considerable attention in the field of soft condensed matter physics due to their potential application as functional nanomaterials for batteries, wastewater treatment and drug delivery systems. Numerous experiments have examined the self-assembled structures resulting from complexation of charge-neutral BCP and surfactants, however, there is a lack of comprehensive understanding at the fundamental level. To help bridge this gap, we use, MD simulations to study self-assembly and dynamics of the BCP-surfactant complex at the molecular level. Our results show an overcharging effect in BCPs with hydrophobic neutral blocks and a formation of core-shell colloidal structure. Hydrophilic neutral blocks, on the other hand, show stable, hairy colloidal structures with neutral blocks forming a loosely-bound, fuzzy outer layer. Our results qualitatively agree with previous SANS and SAXS experiments. This work was supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Materials Science and Engineering Division.

  9. John H. Dillon Medal: Tapered Block Copolymers: Tuning Self-Assembly and Properties by Manipulating Monomer Segment Distributions

    NASA Astrophysics Data System (ADS)

    Epps, Thomas

    The self-assembly of block copolymers (BCPs) presents unique opportunities to design materials with attractive chemical and mechanical properties based on the ability of BCPs to form periodic structures with nanoscale domain spacings. One area of recent progress in our group focuses on the behavior of tapered BCPs in which the segment distribution at the interface between blocks is synthetically varied to tune morphology, domain density profiles, thermal transitions as well as mechanical and transport properties. Two application targets for these materials are lithium-ion conducting membranes for batteries and nanostructured thin films for nanotemplates and barrier membranes. In the first target area, we found that the taper volume fraction and composition allow us to manipulate the self-assembly of salt-doped BCPs in a well-defined manner that permits optimization of morphology and ion-content. Additionally, we found that the tapered interfaces influence the glass-transition behavior of the ion-conducting block leading to significant changes in lithium-ion transport (ion conductivity). In the second target area, we found the taper content alters the rate of self-assembly as well as the rate of island/hole formation (and ultimate island/hole size) upon thermal annealing. Additionally, using reflectivity techniques, we probed the domain density profiles as a function of taper composition and linked these profiles to changes in domain spacing and glass transition temperature. Overall, these studies show the versatility of tapering to provide a unique handle for simultaneously optimizing multiple materials properties.

  10. Self-assembly of amphiphilic block copolymer-tethered nanoparticles: a new approach to nanoscale design of functional materials.

    PubMed

    Liu, Yi; Liu, Yijing; Yin, Jun-Jie; Nie, Zhihong

    2015-04-01

    Colloidal molecules constructed from polymers and nanoparticles (NPs) have recently emerged as a novel class of building blocks for assembling functional hybrid materials. Particularly, self-assembly of amphiphilic block copolymer (BCP)-tethered NPs (BNPs) has shown great promise in the nanoscale design of functional hybrid materials. On the one hand, structurally the BNPs can be considered as molecular equivalents that are capable of self-assembly at multiple hierarchical levels. On the other hand, the assembly of BNPs shows significant differences from molecular assembly due to their large dimension, complex geometry, and multi-scale interactions involved in the assembly process. The manipulation of BCPs localized near the surface of the NPs offers an effective tool for engineering the interactions between NPs and hence the complexity of NP assembly. In this Feature Article, recent progresses on the self-assembly of BNPs into functional materials are summarized. First, major strategies for assembling amphiphilic BNPs are highlighted. Secondly, the application of hybrid nanostructures (e.g., vesicles) assembled from BNPs in the field of biomedical imaging and delivery is discussed. Finally, current challenges and perspectives at this frontier are outlined.

  11. Enzymatic polymerization of high molecular weight DNA amphiphiles that self-assemble into star-like micelles.

    PubMed

    Tang, Lei; Tjong, Vinalia; Li, Nan; Yingling, Yaroslava G; Chilkoti, Ashutosh; Zauscher, Stefan

    2014-05-21

    High molecular weight ssDNA amphiphiles are synthesized by enzymatic polymerization. These highly asymmetric diblock DNA copolymers self-assemble into "hairy", star-like micelles, shown in the AFM image and the DPD snapshot. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Molecular modeling of directed self-assembly of block copolymers: Fundamental studies of processing conditions and evolutionary pattern design

    NASA Astrophysics Data System (ADS)

    Khaira, Gurdaman Singh

    Rapid progress in the semi-conductor industry has pushed for smaller feature sizes on integrated electronic circuits. Current photo-lithographic techniques for nanofabrication have reached their technical limit and are problematic when printing features small enough to meet future industrial requirements. "Bottom-up'' techniques, such as the directed self-assembly (DSA) of block copolymers (BCP), are the primary contenders to compliment current "top-down'' photo-lithography ones. For industrial requirements, the defect density from DSA needs to be less than 1 defect per 10 cm by 10 cm. Knowledge of both material synthesis and the thermodynamics of the self-assembly process are required before optimal operating conditions can be found to produce results adequate for industry. The work present in this thesis is divided into three chapters, each discussing various aspects of DSA as studied via a molecular model that contains the essential physics of BCP self-assembly. Though there are various types of guiding fields that can be used to direct BCPs over large wafer areas with minimum defects, this study focuses only on chemically patterned substrates. The first chapter addresses optimal pattern design by describing a framework where molecular simulations of various complexities are coupled with an advanced optimization technique to find a pattern that directs a target morphology. It demonstrates the first ever study where BCP self-assembly on a patterned substrate is optimized using a three-dimensional description of the block-copolymers. For problems pertaining to DSA, the methodology is shown to converge much faster than the traditional random search approach. The second chapter discusses the metrology of BCP thin films using TEM tomography and X-ray scattering techniques, such as CDSAXS and GISAXS. X-ray scattering has the advantage of being able to quickly probe the average structure of BCP morphologies over large wafer areas; however, deducing the BCP morphology

  13. Directed self-assembly of poly(styrene)-block-poly(acrylic acid) copolymers for sub-20nm pitch patterning

    NASA Astrophysics Data System (ADS)

    Cheng, Jing; Lawson, Richard A.; Yeh, Wei-Ming; Jarnagin, Nathan D.; Peters, Andrew; Tolbert, Laren M.; Henderson, Clifford L.

    2012-03-01

    Directed self-assembly (DSA) of block copolymers is a promising technology for extending the patterning capability of current lithographic exposure tools. For example, production of sub-40 nm pitch features using 193nm exposure technologies is conceivably possible using DSA methods without relying on time consuming, challenging, and expensive multiple patterning schemes. Significant recent work has focused on demonstration of the ability to produce large areas of regular grating structures with low numbers of defects using self-assembly of poly(styrene)-b-poly(methyl methacrylate) copolymers (PS-b-PMMA). While these recent results are promising and have shown the ability to print pitches approaching 20 nm using DSA, the ability to advance to even smaller pitches will be dependent upon the ability to develop new block copolymers with higher χ values and the associated alignment and block removal processes required to achieve successful DSA with these new materials. This paper reports on work focused on identifying higher χ block copolymers and their associated DSA processes for sub-20 nm pitch patterning. In this work, DSA using polystyrene-b-polyacid materials has been explored. Specifically, it is shown that poly(styrene)-b-poly(acrylic acid) copolymers (PS-b-PAA) is one promising material for achieving substantially smaller pitch patterns than those possible with PS-b-PMMA while still utilizing simple hydrocarbon polymers. In fact, it is anticipated that much of the learning that has been done with the PS-b-PMMA system, such as development of highly selective plasma etch block removal procedures, can be directly leveraged or transferred to the PS-b-PAA system. Acetone vapor annealing of PS-b-PAA (Mw=16,000 g/mol with 50:50 mole ratio of PS:PAA) and its self-assembly into a lamellar morphology is demonstrated to generate a pattern pitch size (L0) of 21 nm. The χ value for PS-b-PAA was estimated from fingerprint pattern pitch data to be approximately 0.18 which

  14. Study of polystyrene-poly(ethylene oxide) diblock copolymer monolayers as barriers to protein adsorption

    NASA Astrophysics Data System (ADS)

    Jogikalmath, Gangadhar

    Protein adsorption resistant surfaces find use in many biomedical applications, such as catheters, dialysis devices and biosensors that involve blood contacting surfaces. To ensure long-term functioning of a device in an environment containing protein, there is a need to produce homogeneous surfaces that are resistant to protein adsorption. A polymer brush covered surface, produced by either physical adsorption or chemical grafting of hydrophilic polymers to surfaces, is one of the approaches used in creating such surfaces. High grafting densities needed to make an effective barrier are usually not realized in chemical grafting/adsorption from solution, due to self-exclusion of surface grafted molecules. In this dissertation polymer brush surfaces formed by chemically grafted PEO molecules and transferred monolayers of PS-b-PEO diblock copolymers are investigated using atomic force microscopy (AFM), surface plasmon resonance (SPR) and surface pressure measurement techniques. An AFM adhesion mapping technique was used to evaluate the surface heterogeneity of chemically modified PEO and transferred diblock copolymer monolayer surfaces. The behavior of PS-b-PEO molecules at the air-water interface was studied using Langmuir trough. The stability of transferred diblock copolymer monolayers was investigated using AFM. Using SPR, protein adsorption to the diblock copolymer layers was investigated as a function of protein size (using HSA and ferritin) as a function of grafting density of PEO in the monolayer. It was seen that a lower density of the PS-b-PEO monolayer was sufficient to prevent ferritin adsorption (larger protein) while a higher density brush layer was required to achieve complete prevention of HSA adsorption to the surface. The effect of mobility of the polymer brush layer on protein adsorption prevention was analyzed using SPR and surface pressure measurements. It was seen that the copolymer monolayer (at the air-buffer interface) rearranged itself to

  15. Mechanical characterization of diblock copolymer ``armored'' emulsion droplets

    NASA Astrophysics Data System (ADS)

    Rozairo, Damith; Croll, Andrew

    2013-03-01

    There has been an increased interest in block copolymer vesicles due to a plethora of possible application ranging from targeted drug delivery to cosmetically active agents. In this regard, understanding the physics of the block copolymer vesicle and its morphology is critical to the rational development of these technologies. As a step towards more complex vesicle structures, we describe experiments in which we carefully examine the interface and morphology of polystyrene-b-polyethyleneoxide (PS-PEO) emulsion drops. In our study, PS-PEO acts as a surfactant and at the toluene-water interface creates a monolayer, inhibiting drop recombination and minimizing interfacial energies. Our experiments are conducted in a water cell where the buoyant force is exploited to push drops against a thin sheet of mica. The shape of the drops is measured using an upright confocal microscope and compared with a Bashforth-Adams model in order to examine the mechanical response to the buoyant force. We observe unique dynamics as the drops buckle at short timescales trapping a small pocket of fluid which slowly drains away. Furthermore, the influence of polymer concentration, changes in pH and block copolymer architecture on the morphology and dynamics of the droplets is examined.

  16. Ordering transition in salt-doped diblock copolymers

    DOE PAGES

    Qin, Jian; de Pablo, Juan J.

    2016-04-26

    Lithium salt-doped block copolymers offer promise for applications as solid electrolytes in lithium ion batteries. Control of the conductivity and mechanical properties of these materials, for membrane applications relies critically on the ability to predict and manipulate their microphase separation temperature. Past attempts to predict the so-called "order-disorder transition temperature" of copolymer electrolytes have relied on approximate treatments of electrostatic interactions. In this work, we introduce a coarse-grained simulation model that treats Coulomb interactions explicitly, and we use it to investigate the ordering transition of charged block copolymers. The order-disorder transition temperature is determined from the ordering free energy, whichmore » we calculate with a high level of precision using a density-of-states approach. Our calculations allow us to discern a delicate competition between two physical effects: ion association, which raises the transition temperature, and solvent dilution, which lowers the transition temperature. Lastly, in the intermediate salt concentration regime, our results predict that the order-disorder transition temperature increases with salt content, in agreement with available experimental data.« less

  17. Self-assembly of block copolymers on topographically patterned polymeric substrates

    SciTech Connect

    Russell, Thomas P.; Park, Soojin; Lee, Dong Hyun; Xu, Ting

    2016-05-10

    Highly-ordered block copolymer films are prepared by a method that includes forming a polymeric replica of a topographically patterned crystalline surface, forming a block copolymer film on the topographically patterned surface of the polymeric replica, and annealing the block copolymer film. The resulting structures can be used in a variety of different applications, including the fabrication of high density data storage media. The ability to use flexible polymers to form the polymeric replica facilitates industrial-scale processes utilizing the highly-ordered block copolymer films.

  18. Shielding of quantum dots using diblock copolymers: implementing copper catalyzed click chemistry to fluorescent quantum dots

    NASA Astrophysics Data System (ADS)

    Merkl, Jan-Philip; Ostermann, Johannes; Schmidtke, Christian; Kloust, Hauke; Eggers, Robin; Feld, Artur; Wolter, Christopher; Kreuziger, Anna-Marlena; Flessau, Sandra; Mattoussi, Hedi; Weller, Horst

    2014-03-01

    We describe the design and optimization of an amphiphilic diblock copolymer and its use to provide surface functionalization of colloidal semiconductor nanoparticles (quantum dots, QDs). This polymer coating promotes hydrophilicity of the nanocrystals while providing numerous functional groups ideally suited for biofunctionalization of the QDs using copper-catalyzed azide alkyne Husigen 1,3-cyloaddition (i.e., cupper catalyzed "click" reaction). Copper ions are known to quench the fluorescence of QDs in solution. Thus effective shielding of the nanocrystal surface is essential to apply copper-catalyzed reactions to luminescent QDs without drastically quenching their emission. We have applied a strategy based on micellar encapsulation within poly(isoprene-block- ethylene oxide) diblock-copolymers (PI-b-PEO), where three critical factors promote and control the effectiveness of the shielding of copper ion penetration: 1) The excess of PI-b-PEO, 2) the size of PI-b-PEO and 3) insertion of an additional PS-shell grown via seeded emulsion polymerization (EP) reaction. Due to the amphiphilic character of the block-copolymer, this approach provides a shielding layer surrounding the particles, preventing metal ions from reaching the QD surfaces and maintaining high photoluminescence. The effective shielding allowed the use of copper-catalyzed azide-alkyne 1,3-cycloaddition (CuAAC) to hydrophilic and highly fluorescent QDs, opening up great possibilities for the bio functionalization of QDs.

  19. Directed Self-Assembly of Hierarchical Supramolecular Block Copolymer Thin Films on Chemical Patterns

    SciTech Connect

    Wu, Guang-Peng; Liu, Xiaoying; Chen, Xuanxuan; Suh, Hyo Seon; Li, Xiao; Ren, Jiaxing; Arges, Christopher G.; Li, Faxue; Jiang, Zhang; Nealey, Paul F.

    2016-03-18

    A long-range ordered lamellae-within-lamellae hierarchical structure is reported for the first time through the directed self-assembly of supramolecular polymer-surfactant thin films on chemical patterns with density multiplication. The coassembly of supramolecular system with gold nanoparticles is further achieved to create a hybrid material with well-organized nanoparticle arrays, expanding the palette of morphologies and structures available for nanoscale fabrication.

  20. Three Dimensional Assembly in Directed Self-assembly of Block Copolymers

    SciTech Connect

    Segal-Peretz, Tamar; Zhou, Chun; Ren, Jiaxing; Dazai, Takahiro; Ocola, Leonidas E.; Divan, Ralu N. S.; Nealey, Paul F.

    2016-09-02

    The three-dimensional assembly of poly (styrene-b-methyl methacrylate) (PS-b-PMMA) in chemoepitaxy and graphoepitaxy directed self-assembly (DSA) was investigated using scanning transmission electron microscopy (STEM) tomography. The tomographic characterization revealed hidden morphologies and defects at the BCP- chemical pattern interface in lamellar DSA, and probed the formation of cylinders at the bottom of cylindrical DSA for contact hole shrink. Lastly, future work will include control over 3D assembly in sub-10 nm processes.

  1. Effect of chemical oxidation on the self-assembly of organometallic block copolymers.

    PubMed

    Eitouni, Hany B; Balsara, Nitash P

    2004-06-23

    The thermodynamic interactions in poly(styrene-block-ferrocenyldimethylsilane) and poly(isoprene-block-ferrocenyldimethylsilane) copolymers were systematically tuned by oxidation of the ferrocene moieties with silver nitrate. Small-angle X-ray scattering experiments show that oxidizing 8% of the ferrocene moieties lowers the order-disorder transition temperature of the copolymers by as much as 40 degrees C.

  2. Frank-Kasper σ phase in polybutadiene-poly(ɛ-caprolactone) diblock copolymer/polybutadiene blends

    NASA Astrophysics Data System (ADS)

    Takagi, Hideaki; Hashimoto, Ryo; Igarashi, Noriyuki; Kishimoto, Shunji; Yamamoto, Katsuhiro

    2017-05-01

    Microphase-separated structures in a polybutadiene-poly(ɛ-caprolactone) diblock copolymer (PB-PCL)/polybutadiene homopolymer (PB) blend were investigated by small-angle x-ray scattering (SAXS). Non-equilibrium spherical micelles were observed at temperatures ranging between 60 and 100 °C. An SAXS profile with  >60 scattering peaks was recorded at 140 °C. All the peak positions were in good agreement with theoretical Frank-Kasper σ phase peak positions. Thus, these results indicate the formation of a Frank-Kasper σ phase in the PB-PCL/PB blend at 140 °C.

  3. Cobaltocenium-containing block copolymers: ring-opening metathesis polymerization, self-assembly and precursors for template synthesis of inorganic nanoparticles.

    PubMed

    Ren, Lixia; Zhang, Jiuyang; Hardy, Christopher G; Ma, Shuguo; Tang, Chuanbing

    2012-04-13

    Side-chain cobaltocenium-containing block copolymers are prepared by ring-opening metathesis polymerization (ROMP). These block copolymers include one cobaltocenium-containing block, with the second block being either a nonmetal-containing segment or a cobaltocenium-containing segment with different counterions. These block copolymers are self-assembled into spherical core/shell micelles in solutions. A template strategy is used to prepare cobalt (II or III)-containing nanoparticles by treating the self-assembled micelles via UV/ozonolysis and pyrolysis. Characterization by X-ray photon spectroscopy and X-ray diffraction indicates that these nanoparticles consist of different oxidants of cobalt, depending on the chemical compositions of block copolymers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Synthesis and self-assembly of temperature-responsive copolymers based on N-vinylpyrrolidone and triethylene glycol methacrylate

    PubMed Central

    Jumeaux, Coline; Chapman, Robert; Chandrawati, Rona; Stevens, Molly M.

    2017-01-01

    Polyvinylpyrrolidone (PVP) is a biocompatible, water-soluble polymer with unique physicochemical properties and attractive biological features that has found widespread use in several industries. Owing to advances in controlled polymerisation techniques, PVP can be easily synthesised with robust control over its architecture. However, the synthesis of PVP copolymers, which can allow tailoring of its properties and expand the scope of this polymeric material, is challenging and rarely reported. Here, we demonstrate the synthesis of well-defined, temperature-responsive polyvinylpyrrolidone-co-poly(triethylene glycol methacrylate) (PVP-co-pTEGMA) block copolymers via successive Reversible Addition-Fragmentation chain Transfer (RAFT) and Activators ReGenerated by Electron Transfer Atom Transfer Radical Polymerisation (ARGET-ATRP) techniques. We show that PVP-co-pTEGMA block copolymers display temperature-responsive behaviour and self-assemble above their cloud point temperature (Tcp) to form spherical nanostructures of 100-200 nm in diameter. Finally, we demonstrate stabilisation of these assemblies below their Tcp by cross-linking through the PVP block. PMID:28458725

  5. Directed self-assembly of high-chi block copolymer for nano fabrication of bit patterned media via solvent annealing

    NASA Astrophysics Data System (ADS)

    Xiong, Shisheng; Chapuis, Yves-Andre; Wan, Lei; Gao, He; Li, Xiao; Ruiz, Ricardo; Nealey, Paul F.

    2016-10-01

    We report the formation of nanoimprint master templates that can be used for the fabrication of bit patterned media (BPM). The template was formed by directed self-assembly, with solvent annealing, of a symmetric ABA triblock copolymer to form perpendicularly oriented lamellae on chemical patterns. We used a high-χ block copolymer, poly(2-vinyl pyridine)-block-polystyrene-block-poly(2-vinyl pyridine) to achieve smaller feature sizes than are possible with polystyrene-block-poly(methyl methacrylate). The work shows that triblock copolymers can provide a large processing window in terms of pitch commensurability. Using block-selective infiltration (atomic layer deposition with sequential long soaking/purge cycles), an alumina composite with high etch resistance was specifically incorporated into the polar and hydrophilic P2VP domains. Subsequently, the surface pattern was successfully transferred into underlying Si substrates by etching with a fluorine-containing plasma to create a nanoimprint master. The line/space pattern of the nanoimprint master met the BPM fabrication requirement of defectivity <10-3. For demonstration purposes, the nanoimprint master was used to imprint a replica pattern of photoresist on a quartz wafer.

  6. Effects of block copolymer self-assembly on optical anisotropy in azobenzene-containing PS-b-PMMA films.

    PubMed

    Orofino, A B; Camezzana, M F; Galante, M J; Oyanguren, P A; Zucchi, I A

    2012-03-23

    Polystyrene-b-polymethylmethacrylate (PS-b-PMMA) was selected as the host for 4-(4-nitrophenylazo)aniline (Disperse Orange 3, DO3) based on a previous study of DO3/PMMA and DO3/PS binary blends. Selective location of DO3 into the PMMA block of the copolymer was expected during self-assembly of the block copolymer since a preferential interaction of DO3 with PMMA has been demonstrated. However, surface segregation of DO3 was found during the thermal annealing used to nanostructure the copolymer. To avoid this, a thermoplastic polymer (Azo-TP) was synthesized from the bulk reaction of DO3 and diglycidyl ether of bisphenol A (DGEBA). The choice of DGEBA as a co-reactant was an attempt to encourage the selective location of azo groups in the PMMA phase of PS-b-PMMA. An inspection of solutions of Azo-TP in PS and PMMA, corroborates the preferential affinity of Azo-TP for PMMA. The Azo-TP could be satisfactorily dissolved in PS-b-PMMA. We have investigated the growth and decay processes of the optically induced birefringence in films of PS-b-PMMA containing 12 wt% Azo-TP. The resulting materials showed a good photoinduced time response, high maximum birefringence and an elevated fraction of remnant anisotropy.

  7. Pulsed transfer etching of PS-PDMS block copolymers self-assembled in 193 nm lithography stacks.

    PubMed

    Girardot, Cécile; Böhme, Sophie; Archambault, Sophie; Salaün, Mathieu; Latu-Romain, Eddy; Cunge, Gilles; Joubert, Olivier; Zelsmann, Marc

    2014-09-24

    This work presents the graphoepitaxy of high-χ block copolymers (BCP) in standard industry-like lithography stacks and their transfer into the silicon substrate The process includes conventional 193 nm photolithography, directed self-assembly of polystyrene-block-polydimethylsiloxane (PS-b-PDMS) and pulsed plasma etching to transfer the obtained features into the substrate. PS-b-PDMS has a high Flory-Huggins interaction parameter (high-χ) and is capable of achieving sub-10 nm feature sizes. The photolithography stack is fabricated on 300 mm diameter silicon wafers and is composed of three layers: spin-on-carbon (SoC), silicon-containing anti-reflective coating (SiARC) and 193 nm photolithography resist. Sixty-nanometer-deep trenches are first patterned by plasma etching in the SiARC/SoC stack using the resist mask. The PS-b-PDMS is then spread on the substrate surface. Directed self-assembly (DSA) of the BCP is induced by a solvent vapor annealing process and PDMS cylinders parallel to the substrate surface are obtained. The surface chemistry based on SoC permits an efficient etching process into the underlying silicon substrate. The etching process is performed under dedicated pulsed plasma etching conditions. Fifteen nanometer half-pitch dense line/space features are obtained with a height up to 90 nm.

  8. Iterative Exponential Growth Synthesis and Assembly of Uniform Diblock Copolymers.

    PubMed

    Jiang, Yivan; Golder, Matthew R; Nguyen, Hung V-T; Wang, Yufeng; Zhong, Mingjiang; Barnes, Jonathan C; Ehrlich, Deborah J C; Johnson, Jeremiah A

    2016-08-03

    Studies on the phase segregation of unimolecular block copolymers (BCPs) are limited by a lack of reliable, versatile methods for the synthesis of such polymers on the preparative scale. Herein, we describe an advancement of Iterative Exponential Growth (IEG) wherein chiral allyl-based IEG oligomers are subjected to thiol-ene reactions and converted into unimolecular BCPs. With this strategy we have synthesized uniform BCPs with molar masses up to 12.1 kDa on ∼1 g scale. BCPs composed of decane-based side chains and either triethyleneglycol- or thioglycerol-based side chains phase-segregate into hexagonal cylinder morphologies. The assembly is not driven by side-chain crystallization, but is instead the result of amorphous BCP assembly.

  9. Ordered phases of diblock copolymers in selective solvent.

    PubMed

    Grason, Gregory M

    2007-03-21

    The authors propose a mean-field model to explore the equilibrium coupling between micelle aggregation and lattice choice in neutral copolymer and selective solvent mixtures. They find both thermotropic and lyotropic transitions from face-centered cubic to body-centered cubic ordered phases of spherical micelles, in agreement with experimental observations of these systems over a broad range of conditions. The stability of the nonclosed packed phase can be attributed to two physical mechanisms: the large entropy of lattice phonons near crystal melting and the preference of the intermicelle repulsions for the body-centered cubic structure when the lattice becomes sufficiently dense at higher solution concentrations. Both mechanisms are controlled by the decrease of micelle aggregation and subsequent increase of lattice density as solvent selectivity is reduced. These results shed new light on the relationship between micelle structure--"crewcut" or "hairy"--and long-range order in micelle solutions.

  10. Liquid-liquid interfaces of semifluorinated alkane diblock copolymers with water, alkanes, and perfluorinated alkanes.

    PubMed

    Pierce, Flint; Tsige, Mesfin; Perahia, Dvora; Grest, Gary S

    2008-12-18

    The liquid-liquid interface between semifluorinated alkane diblock copolymers of the form F3C(CF2)n-1-(CH2)m-1CH3 and water, protonated alkanes, and perfluorinated alkanes are studied by fully atomistic molecular dynamics simulations. A modified version of the OPLS-AA (Optimized Parameter for Liquid Simulation All-Atom) force field of Jorgensen et al. has been used to study the interfacial behavior of semifluorinated diblocks. Aqueous interfaces are found to be sharp, with correspondingly large values of the interfacial tension. Due to the reduced hydrophobicity of the protonated block compared to the fluorinated block, hydrogen enhancement is observed at the interface. Water dipoles in the interfacial region are found to be oriented nearly parallel to the liquid-liquid interface. A number of protonated alkanes and perfluorinated alkanes are found to be mutually miscible with the semifluorinated diblocks. For these liquids, interdiffusion follows the expected Fickian behavior, and concentration-dependent diffusivities are determined.

  11. Liquid-liquid interfaces of semifluorinated alkane diblock copolymers with water, alkanes, and perfluorinated alkanes.

    SciTech Connect

    Perahia, Dvora, Dr.; Pierce, Flint; Tsige, Mesfin; Grest, Gary Stephen, Dr.

    2008-08-01

    The liquid-liquid interface between semifluorinated alkane diblock copolymers of the form F3C(CF2)n-1-(CH2)m-1CH3 and water, protonated alkanes, and perfluorinated alkanes are studied by fully atomistic molecular dynamics simulations. A modified version of the OPLS-AA (Optimized Parameter for Liquid Simulation All-Atom) force field of Jorgensen et al. has been used to study the interfacial behavior of semifluorinated diblocks. Aqueous interfaces are found to be sharp, with correspondingly large values of the interfacial tension. Due to the reduced hydrophobicity of the protonated block compared to the fluorinated block, hydrogen enhancement is observed at the interface. Water dipoles in the interfacial region are found to be oriented nearly parallel to the liquid-liquid interface. A number of protonated alkanes and perfluorinated alkanes are found to be mutually miscible with the semifluorinated diblocks. For these liquids, interdiffusion follows the expected Fickian behavior, and concentration-dependent diffusivities are determined.

  12. Directed self-assembly of solvent-vapor-induced non-bulk block copolymer morphologies on nanopatterned substrates.

    PubMed

    Wan, Lei; Ji, Shengxiang; Liu, Chi-Chun; Craig, Gordon S W; Nealey, Paul F

    2016-03-21

    We report a study on directed self-assembly (DSA) with solvent annealing to induce the formation of non-bulk block copolymer microdomains on chemical patterns. Ultrathin films of symmetric polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) display morphologies of PMMA dots, stripes, and PS hexagons with increasing exposure time to acetone vapor, a PMMA-selective solvent. All three nanostructures form long-range-ordered and registered arrays on striped chemical patterns with periods (LS) commensurate to the solvated PS-b-PMMA microdomain period (L0,s). Solvent annealing is shown to facilitate DSA on non-regular chemical patterns, on which the local periods are incommensurate to L0,s. DSA with feature density multiplication, via solvent annealing, is also demonstrated.

  13. Assessing the Local Nanomechanical Properties of Self-Assembled Block Copolymer Thin Films by Peak Force Tapping.

    PubMed

    Lorenzoni, Matteo; Evangelio, Laura; Verhaeghe, Sophie; Nicolet, Célia; Navarro, Christophe; Pérez-Murano, Francesc

    2015-10-27

    The mechanical properties of several types of block copolymer (BCP) thin films have been investigated using PeakForce quantitative nanomechanical mapping. The samples consisted of polystyrene/poly(methylmethacrylate) (PS/PMMA)-based BCP thin films with different pitches both randomly oriented and self-assembled. The measured films have a critical thickness below 50 nm and present features to be resolved of less than 22 nm. Beyond measuring and discriminate surface elastic modulus and adhesion forces of the different phases, we tuned the peak force parameters in order to reliably image those samples, avoiding plastic deformation. The method is able to detect the changes in mechanical response associated with the orientation of the PMMA cylinders with respect to the substrate (parallel versus vertical). The nanomechanical investigation is also capable of recognizing local stiffening due to the preferential growth of alumina deposited by atomic layer deposition on BCP samples, opening up new possibilities in the field of hard mask materials characterization.

  14. Supramolecular Organometallic Polymer Chemistry: Self-Assembly of a Novel Poly(ferrocene)-b-polysiloxane-b-poly(ferrocene) Triblock Copolymer in Solution.

    PubMed

    Resendes; Massey; Dorn; Power; Winnik; Manners

    1999-09-01

    Micelles with unprecedented flowerlike arrangements of the poly(ferrocene) cores (shown in the TEM image) are among the supramolecular architectures generated in the self-assembly of a novel organometallic triblock copolymer from silicon-bridged [1]ferrocenophane monomers and [Me(2)SiO](3) in hexane, a solvent selective for the central polysiloxane block.

  15. Polymerization Induced Self-Assembly of Alginate Based Amphiphilic Graft Copolymers Synthesized by Single Electron Transfer Living Radical Polymerization.

    PubMed

    Kapishon, Vitaliy; Whitney, Ralph A; Champagne, Pascale; Cunningham, Michael F; Neufeld, Ronald J

    2015-07-13

    Alginate-based amphiphilic graft copolymers were synthesized by single electron transfer living radical polymerization (SET-LRP), forming stable micelles during polymerization induced self-assembly (PISA). First, alginate macroinitiator was prepared by partial depolymerization of native alginate, solubility modification and attachment of initiator. Depolymerized low molecular weight alginate (∼12 000 g/mol) was modified with tetrabutylammonium, enabling miscibility in anhydrous organic solvents, followed by initiator attachment via esterification yielding a macroinitiator with a degree of substitution of 0.02, or 1-2 initiator groups per alginate chain. Then, methyl methacrylate was polymerized from the alginate macroinitiator in mixtures of water and methanol, forming poly(methyl methacrylate) grafts, prior to self-assembly, of ∼75 000 g/mol and polydispersity of 1.2. PISA of the amphiphilic graft-copolymer resulted in the formation of micelles with diameters of 50-300 nm characterized by light scattering and electron microscopy. As the first reported case of LRP from alginate, this work introduces a synthetic route to a preparation of alginate-based hybrid polymers with a precise macromolecular architecture and desired functionalities. The intended application is the preparation of micelles for drug delivery; however, LRP from alginate can also be applied in the field of biomaterials to the improvement of alginate-based hydrogel systems such as nano- and microhydrogel particles, islet encapsulation materials, hydrogel implants, and topical applications. Such modified alginates can also improve the function and application of native alginates in food and agricultural applications.

  16. Amphiphilic copolymers based on polyoxazoline and grape seed vegetable oil derivatives: self-assemblies and dynamic light scattering

    NASA Astrophysics Data System (ADS)

    Travelet, Christophe; Stemmelen, Mylène; Lapinte, Vincent; Dubreuil, Frédéric; Robin, Jean-Jacques; Borsali, Redouane

    2013-06-01

    The self-assembly in solution of original structures of amphiphilic partially natural copolymers based on polyoxazoline [more precisely poly(2-methyl-2-oxazoline) (POx)] and grape seed vegetable oil derivatives (linear, T-, and trident-structure) is investigated. The results show that such systems are found, using dynamic light scattering (DLS), to spontaneously self-organize into monomodal, narrow-size, and stable nanoparticles in aqueous medium. The obtained hydrodynamic diameters ( D h) range from 8.6 to 32.5 nm. Specifically, such size increases strongly with increasing natural block (i.e., lipophilic species) length due to higher hydrophobic interactions (from 10.1 nm for C19 to 19.2 nm for C57). Furthermore, increasing the polyoxazoline (i.e., hydrophilic block) length leads to a moderate linear increase of the D h-values. Therefore, the first-order size effect comes from the natural lipophilic block, whereas the characteristic size can be tuned more finely (i.e., in a second-order) by choosing appropriately the polyoxazoline length. The DLS results in terms of characteristic size are corroborated using nanoparticle tracking analysis (NTA), and also by atomic force microscopy (AFM) and transmission electron microscopy (TEM) imaging where well-defined spherical and individual nanoparticles exhibit a very good mechanical resistance upon drying. Moreover, changing the lipophilic block architecture from linear to T-shape, while keeping the same molar mass, generates a branching and thus a shrinking by a factor of 2 of the nanoparticle volume, as observed by DLS. In this paper, it is clearly shown that the self-assemblies of amphiphilic block copolymer obtained from grape seed vegetable oil derivatives (sustainable renewable resources) as well as their tunability are of great interest for biomass valorization at the nanoscale level [continuation of the article by Stemmelen et al. (Polym Chem 4:1445-1458, 2013)].

  17. Highly stable chiral (A)6-B supramolecular copolymers: a multivalency-based self-assembly process.

    PubMed

    Chen, Shi-Gui; Yu, Yue; Zhao, Xin; Ma, Yuguo; Jiang, Xi-Kui; Li, Zhan-Ting

    2011-07-27

    A novel type of chiral layered supramolecular copolymer with high molecular weight has been assembled from a hydrogen bonded C(6)-symmetric zinc porphyrin hexamer and chiral C(3)-symmetric pyridine hexadentate linkers driven by multivalent zinc porphyrin-pyridine coordination. UV-vis, circular dichroism, and static light scattering experiments revealed that the formation of the layered supramolecular copolymers is at first dynamically controlled and then becomes thermodynamically controlled.

  18. A self-consistent field study of diblock copolymer/charged particle system morphologies for nanofiltration membranes

    SciTech Connect

    Zhang, Bo; Ye, Xianggui; Edwards, Brian J.

    2013-12-28

    A combination of self-consistent field theory and density functional theory was used to examine the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Both neutral and interacting particles were examined, with and without favorable/unfavorable energetic potentials between the particles and the block segments. The phase diagrams of the various systems were constructed, allowing the identification of three types of ordered mesophases composed of lamellae, hexagonally packed cylinders, and spheroids. In particular, we examined the conditions under which the mesophases could be generated wherein the tethered particles were primarily located within the interface between the two blocks of the copolymer. Key factors influencing these properties were determined to be the particle position along the diblock chain, the interaction potentials of the blocks and particles, the block copolymer composition, and molecular weight of the copolymer.

  19. A self-consistent field study of diblock copolymer/charged particle system morphologies for nanofiltration membranes

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Ye, Xianggui; Edwards, Brian J.

    2013-12-01

    A combination of self-consistent field theory and density functional theory was used to examine the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Both neutral and interacting particles were examined, with and without favorable/unfavorable energetic potentials between the particles and the block segments. The phase diagrams of the various systems were constructed, allowing the identification of three types of ordered mesophases composed of lamellae, hexagonally packed cylinders, and spheroids. In particular, we examined the conditions under which the mesophases could be generated wherein the tethered particles were primarily located within the interface between the two blocks of the copolymer. Key factors influencing these properties were determined to be the particle position along the diblock chain, the interaction potentials of the blocks and particles, the block copolymer composition, and molecular weight of the copolymer.

  20. A self-consistent field study of diblock copolymer/charged particle system morphologies for nanofiltration membranes.

    PubMed

    Zhang, Bo; Ye, Xianggui; Edwards, Brian J

    2013-12-28

    A combination of self-consistent field theory and density functional theory was used to examine the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Both neutral and interacting particles were examined, with and without favorable/unfavorable energetic potentials between the particles and the block segments. The phase diagrams of the various systems were constructed, allowing the identification of three types of ordered mesophases composed of lamellae, hexagonally packed cylinders, and spheroids. In particular, we examined the conditions under which the mesophases could be generated wherein the tethered particles were primarily located within the interface between the two blocks of the copolymer. Key factors influencing these properties were determined to be the particle position along the diblock chain, the interaction potentials of the blocks and particles, the block copolymer composition, and molecular weight of the copolymer.

  1. Self-assembled pH-responsive MPEG-b-(PLA-co-PAE) block copolymer micelles for anticancer drug delivery.

    PubMed

    Zhang, Can Yang; Yang, You Qiang; Huang, Tu Xiong; Zhao, Bin; Guo, Xin Dong; Wang, Ju Fang; Zhang, Li Juan

    2012-09-01

    A series of amphiphilic pH-responsive poly (ethylene glycol) methyl ether-b-(poly lactic acid-co-poly (β-amino esters)) (MPEG-b-(PLA-co-PAE)) block copolymers with different PLA/PAE ratios were designed and synthesized via a Michael-type step polymerization. The molecular structures of the copolymers were confirmed with (1)H NMR and gel permeation chromatography (GPC). These amphiphilic copolymers were shown to self-assemble into core/shell micelles in aqueous solution at low concentrations, and their critical micelle concentrations (CMC) in water were 1.2-9.5 mg/L. The pH-responsive PAE segment was insoluble at pH 7.4, but it became positively charged and soluble via protonation of amino groups at pH lower than 6.5. The average particle size and zeta potential of micelles increased from 180 nm and 15 mV to 220 nm and 40 mV, respectively, when the pH decreased from 7.4 to 5.0. Doxorubicin (DOX) was loaded into the core of these micelles with a high drug loading of 18%. The in vitro DOX release from the micelles was significantly accelerated when solution pH decreased from 7.4 to 5.0. DOX release in the first 10 h appeared to follow Fickian diffusion mechanism. Toxicity test showed that the copolymers had low toxicity whereas the DOX-loaded micelles remained high cytotoxicity for HepG2 cells. The results indicate the pH-sensitive MPEG-b-(PLA-co-PAE) micelle may be a potential hydrophobic drug delivery carrier for cancer targeting therapy with sustained release. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  2. Microphase separation patterns in diblock copolymers on curved surfaces using a nonlocal Cahn-Hilliard equation.

    PubMed

    Jeong, Darae; Kim, Junseok

    2015-11-01

    We investigate microphase separation patterns on curved surfaces in three-dimensional space by numerically solving a nonlocal Cahn-Hilliard equation for diblock copolymers. In our model, a curved surface is implicitly represented as the zero level set of a signed distance function. We employ a discrete narrow band grid that neighbors the curved surface. Using the closest point method, we apply a pseudo-Neumann boundary at the boundary of the computational domain. The boundary treatment allows us to replace the Laplace-Beltrami operator by the standard Laplacian operator. In particular, we can apply standard finite difference schemes in order to approximate the nonlocal Cahn-Hilliard equation in the discrete narrow band domain. We employ a type of unconditionally stable scheme, which was introduced by Eyre, and use the Jacobi iterative to solve the resulting implicit discrete system of equations. In addition, we use the minimum number of grid points for the discrete narrow band domain. Therefore, the algorithm is simple and fast. Numerous computational experiments are provided to study microphase separation patterns for diblock copolymers on curved surfaces in three-dimensional space.

  3. Effect of diblock copolymer properties on the photophysical properties of dendrimer silicon phthalocyanine nanoconjugates

    NASA Astrophysics Data System (ADS)

    Chen, Kuizhi; Pan, Sujuan; Zhuang, Xuemei; Lv, Hafei; Que, Shoulin; Xie, Shusen; Yang, Hongqin; Peng, Yiru

    2016-07-01

    1-2 generation poly(benzyl aryl ether) dendrimer silicon phthalocyanines with axially disubstituted cyano terminal functionalities (G n -DSiPc(CN)4 n , (G n = n-generation dendrimer, n = 1-2)) were synthesized. Their structures were characterized by elemental analysis, IR, 1H NMR, and ESI-MS. Polymeric nanoparticles (G n -DSiPc(CN)4 n /m) were formed through encapsulating G n -DSiPc(CN)4 n into three monomethoxyl poly(ethylene glycol)-poly(ɛ-caprolactone) diblock copolymers (MPEG-PCL) with different hydrophilic/hydrophobic proportion, respectively. The effect of dendritic generation and the hydrophilic/hydrophobic proportion of diblock copolymers on the UV/Vis and fluorescence spectra of G n -DSiPc(CN)4 n and G n -DSiPc(CN)4 n /m were studied. The photophysical properties of polymeric nanoparticles exhibited dendritic generation and hydrophilic/hydrophobic proportion dependence. The fluorescence intensities and lifetimes of G n -DSiPc(CN)4 n /m were lower than the corresponding free dendrimer phthalocyanines. G n -DSiPc(CN)4 n encapsulated into MPEG-PCL with hydrophilic/hydrophobic molecular weight ratio 2000:4000 exhibited excellent photophysical property. The mean diameter of MPEG2000-PCL2000 micelles was about 70 nm, which decreased when loaded with G n -DSiPc(CN)4 n .

  4. Quantifying Fluctuation Effects on the Order-Disorder Transition of Symmetric Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Zong, Jing; Wang

    2012-02-01

    How fluctuations change the order-disorder transition (ODT) of symmetric diblock copolymers is a classic yet unsolved problem in polymer physics.ootnotetextL. Leibler, Macromolecules, 13, 1602 (1980); G. H. Fredrickson and E. Helfand, J. Chem. Phys., 87, 697 (1987). Here we unambiguously quantify the fluctuation effects by direct comparisons between fast off-lattice Monte Carlo (FOMC) simulationsootnotetextQ. Wang and Y. Yin, J. Chem. Phys., 130, 104903 (2009). and mean-field theory using exactly the same model system (Hamiltonian), thus without any parameter-fitting. The symmetric diblock copolymers are modeled as discrete Gaussian chains with soft, finite-range repulsions as commonly used in dissipative-particle dynamics simulations. The effects of chain discretization and finite-range interactions on ODT are properly accounted for in our mean-field theory.ootnotetextQ. Wang, J. Chem. Phys., 129, 054904 (2008); 131, 234903 (2009). Our FOMC simulations are performed in a canonical ensemble with variable box lengths to eliminate the adverse effects of fixed box sizes on ODT.ootnotetextQ. Wang et al., J. Chem. Phys., 112, 450 (2000). Furthermore, with a new order parameter for the lamellar phase, we use replica exchange and multiple histogram reweighting to accurately locate ODT in our simulations.

  5. Real-space evidence of the equilibrium ordered bicontinuous double diamond structure of a diblock copolymer.

    PubMed

    Chu, C Y; Jiang, X; Jinnai, H; Pei, R Y; Lin, W F; Tsai, J C; Chen, H L

    2015-03-14

    The ordered bicontinuous double diamond (OBDD) structure has long been believed to be an unstable ordered network nanostructure, which is relative to the ordered bicontinuous double gyroid (OBDG) structure for diblock copolymers. Using electron tomography, we present the first real-space observation of the thermodynamically stable OBDD structure in a diblock copolymer composed of a stereoregular block, syndiotactic polypropylene-block-polystyrene (sPP-b-PS), in which the sPP tetrapods are interconnected via a bicontinuous network with Pn3̄m symmetry. The OBDD structure underwent a thermally reversible order-order transition (OOT) to OBDG upon heating, and the transition was accompanied with a slight reduction of domain spacing, as demonstrated both experimentally and theoretically. The thermodynamic stability of the OBDD structure was attributed to the ability of the configurationally regular sPP block to form helical segments, even above its melting point, as the reduction of internal energy associated with the helix formation may effectively compensate the greater packing frustration in OBDD relative to that in the tripods of OBDG.

  6. Controlled Solution Self-Assembly of a Midblock-Sulfonated Pentablock Copolymer

    NASA Astrophysics Data System (ADS)

    Mineart, Kenneth; Gradzielski, Michael; Spontak, Richard

    The solution self-assembly of midblock-sulfonated block ionomers (SBIs) has been shown to translate to their bulk, solution-cast morphology, which can further impact their function in applications such as desalination, fuel cell, and photovoltaic membranes. Previous studies have identified that increasing the degree of sulfonation (DOS) in SBIs dispersed in a nonpolar solvent results in the growth of micellar aggregates due to increased interfacial energy. However, these works have not attempted to control the assembly at a given DOS by tuning the solvent environment. The current study probes the tunability of SBI aggregation behavior using a nonpolar/polar solvent mixture varying in composition. A combination of light scattering (SLS and DLS) and small angle X-ray scattering (SAXS) independently confirm that SBI micelles grow larger, both in core and corona, as the solvent environment becomes more nonpolar. The increases in both core and corona size will be explained using polymer thermodynamics and further supported through presentation of small angle neutron scattering (SANS) data. In addition, these results will be compared with SBI self-assembly in a single solvent, which is expected to distribute between the micelle cores and bulk solvent environment. We would like to acknowledge funding from NSF IRES (App #1065466) and MANN+HUMMEL GmbH.

  7. Structural, Viscoelastic, and Electrochemical Characteristics of Self-Assembled Amphiphilic Comblike Copolymers in Aqueous Solutions.

    PubMed

    Talantikite, Malika; Aoudia, Kahina; Benyahia, Lazhar; Chaal, Lila; Chassenieux, Christophe; Deslouis, Claude; Gaillard, Cédric; Saidani, Boualem

    2017-02-02

    Self-assembly in aqueous solutions of an amphiphilic comblike polyelectrolyte (80C12) that consists of a polystyrene (PS) backbone onto which quaternary ammonium pendant moieties have been grafted has been investigated by light scattering and cryo-transmission electron microscopy measurements in the presence of KCl and methylviologen dication (MV(2+)) under conditions mimicking those for electrochemical measurements. Polymer chains self-assemble within branched cylindrical micelles that display viscoelastic properties, characterized by a relaxation time of 4 s. To tune this time, 80C12 was mixed with a polyoxyethylene nonionic surfactant (Brij C12E10). Relatively increasing the amount of the latter leads to a decrease in the relaxation time of the 80C12 solution. Correlatively, electrochemical experiments with a rotating disk electrode show a transition of the mass transport rate, which deviates from the classical Newtonian behavior in the same velocity domain. This result generalizes what has been already observed with solutions of linear polymers of high molecular weight and wormlike micelles based on surfactants subjected to elongational deformations. Moreover, the critical times derived from rheological and electrochemical experiments display the same trend.

  8. Tissue anti-adhesion potential of ibuprofen-loaded PLLA-PEG diblock copolymer films.

    PubMed

    Lee, Jin Ho; Go, Ae Kyung; Oh, Se Heang; Lee, Ka Eul; Yuk, Soon Hong

    2005-02-01

    This study was designed to evaluate the effect of polyethylene glycol (PEG) and nonsteroidal anti-inflammatory drug (ibuprofen) on the prevention of postsurgical tissue adhesion. For this, poly(L-lactic acid) (PLLA)-PEG diblock copolymers were synthesized by ring opening polymerization of L-lactide and methoxy polyethylene glycol (Mw 5000) of different compositions. The synthesized copolymers were characterized by gel permeation chromatography and 1H-nuclear magnetic resonance spectroscopy. PLLA-PEG copolymer films were prepared by solvent casting. The prepared copolymer films were more flexible and hydrophilic than the control PLLA film, as investigated by the measurements of glass transition temperature, water absorption content, and water contact angle. The drug release behavior from the ibuprofen (10 wt%)-loaded copolymer films was examined by high performance liquid chromatography. It was observed that the drug was released gradually up to about 40% of total loading amount after 20 days, depending on PEG composition; more drug release from the films with higher PEG compositions. In vitro cell adhesions on the copolymer films with/without drug were compared by the culture of NIH/3T3 mouse embryo fibroblasts on the surfaces. For in vivo evaluation of tissue anti-adhesion potential, the copolymer films with/without drug were implanted between the cecum and peritoneal wall defects of rats and their tissue adhesion extents were compared. It was observed that the ibuprofen-containing PLLA-PEG films with high PEG composition (particularly PLLA113-PEG113 film with PEG composition, 50 mol%) were very effective in preventing cell or tissue adhesion on the film surfaces, probably owing to the synergistic effects of highly mobile, hydrophilic PEG and anti-inflammatory drug, ibuprofen.

  9. Compatibilizing Effect of a Diblock Copolymer of Isotactic Polystyrene and Isotactic Polypropylene in Blends of the Corresponding Homopolymers.

    DTIC Science & Technology

    1984-08-10

    Ital.y 1I. KEY WORDS (Continue on revere a .it nece.say and Identitp by block na b") semicrystalline diblock copolymer dynamic mechanical properties...differences in dynamic mechanical behavior are also seen when the copolymer and the homopolymer blend are compared. Figure 7 shows the results of free...in modulus shown by this sample in Figure 7. -7- Taken all together, the comparative information obtained fron the various microscopy and dynamic

  10. Preparation and characterization of self-assembled nanoparticles formed by poly(ethylene oxide)-block-poly(epsilon-caprolactone) copolymers with long poly(epsilon-caprolactone) blocks in aqueous solutions.

    PubMed

    Sachl, Radek; Uchman, Mariusz; Matĕjícek, Pavel; Procházka, Karel; Stĕpánek, Miroslav; Spírková, Milena

    2007-03-13

    Aqueous solutions of self-assembled nanoparticles formed by biocompatible diblock copolymers of poly(epsilon-caprolactone)-block-poly(ethylene oxide) (PCL-PEO) with the same molar mass of the PEO block (5000 g mol-1) and three different molar masses of the PCL block (5000, 13 000, and 32 000 g mol-1) have been prepared by a fast mixing the copolymer solution in a mild selective solvent, tetrahydrofuran (THF)/water, with an excess of water, that is, by quenching the reversible micellization equilibrium, and a subsequent removal of THF by dialysis of the water-rich solution against water. The prepared nanoparticles have been characterized by static and dynamic light scattering and atomic force microscopy imaging. It was found that stable monodisperse nanoparticles are formed only if the initial mixed solvent contained 90 vol % THF. The results show that the prepared nanoparticles are spherical vesicles with relatively thick hydrophobic walls, that is, spherical core/shell nanoparticles with the hollow core filled with the solvent.

  11. Challenges with soft stamps for guiding of diblock copolymers

    NASA Astrophysics Data System (ADS)

    Steinberg, Christian; Gubert, Malte; Papenheim, Marc; Wang, Si; Scheer, Hella-Christin; Zajadacz, Joachim; Zimmer, Klaus

    2015-11-01

    The preparation of nanostructures by guiding the phase separation of a block copolymer (BCP) is an attractive technique to overcome the limitations of conventional lithography. Well-established methods for guiding are to provide a topographical pattern (grapho-epitaxy) or a chemical pattern (chemo-epitaxy) on the substrate before BCP application. This paper reports on an alternative technique, the guiding of the BCP without pre-patterning the substrate, by providing the guiding pattern from the top, by nanoimprint. This approach offers the benefit of a multiple use of the same stamp. In the work reported here, we use an elastomeric stamp and examine capillary force lithography (CFL) with respect to guiding. The processing temperature is chosen high in order to provide fast phase separation. For the control of the surface energy of the substrate, a silane deposition from the gas phase is utilized. The ordering behavior of a lamellar polystyrene-polymethylmethacrylate BCP with CFL is studied. In particular, the issues specific with phase separation in an imprint situation are addressed, the locally differing layer thickness and the fact that two surface energies contribute to the ordering process, the one of the substrate and the one of the stamp. Though further optimization is required to make use of CFL for efficient guiding, the first results reported here indicate the potential of this technique for stamp-induced guiding of BCPs. As it allows a multiple use of the stamp, such guiding is interesting and may replace the time- and cost-consuming pre-patterning of each substrate.

  12. Synthesis and Melt Self-Assembly of PS-PMMA-PLA Triblock Bottlebrush Copolymers

    SciTech Connect

    Bolton, Justin; Rzayev, Javid

    2014-07-03

    Polystyrene–poly(methyl methacrylate)–polylactide (PS–PMMA–PLA) triblock bottlebrush copolymer with nearly symmetric volume fractions was synthesized by grafting from a symmetrical triblock backbone and the resulting melt was characterized by scanning electron microscopy and small-angle X-ray scattering. The copolymer backbone was prepared by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization of solketal methacrylate (SM), 2-(bromoisobutyryl)ethyl methacrylate (BIEM), and 5-(trimethylsilyl)-4-pentyn-1-ol methacrylate (TPYM). PMMA branches were grafted by atom transfer radical polymerization from the poly(BIEM) segment, PS branches were grafted by RAFT polymerization from the poly(TPYM) block after installment of the RAFT agents, while PLA side chains were grafted from the deprotected poly(SM) block. The resulting copolymer was found to exhibit a lamellae morphology with a domain spacing of 79 nm. Differential scanning calorimetry analysis indicated that PMMA was preferentially mixing with PS while phase separating from PLA domains.

  13. Ordered porous mesostructured materials from nanoparticle-block copolymer self-assembly

    SciTech Connect

    Warren, Scott; Wiesner, Ulrich; DiSalvo, Jr., Francis J

    2013-10-29

    The invention provides mesostructured materials and methods of preparing mesostructured materials including metal-rich mesostructured nanoparticle-block copolymer hybrids, porous metal-nonmetal nanocomposite mesostructures, and ordered metal mesostructures with uniform pores. The nanoparticles can be metal, metal alloy, metal mixture, intermetallic, metal-carbon, metal-ceramic, semiconductor-carbon, semiconductor-ceramic, insulator-carbon or insulator-ceramic nanoparticles, or combinations thereof. A block copolymer/ligand-stabilized nanoparticle solution is cast, resulting in the formation of a metal-rich (or semiconductor-rich or insulator-rich) mesostructured nanoparticle-block copolymer hybrid. The hybrid is heated to an elevated temperature, resulting in the formation of an ordered porous nanocomposite mesostructure. A nonmetal component (e.g., carbon or ceramic) is then removed to produce an ordered mesostructure with ordered and large uniform pores.

  14. Prediction of solvent-induced morphological changes of polyelectrolyte diblock copolymer micelles.

    PubMed

    Li, Nan K; Fuss, William H; Tang, Lei; Gu, Renpeng; Chilkoti, Ashutosh; Zauscher, Stefan; Yingling, Yaroslava G

    2015-11-14

    Self-assembly processes of polyelectrolyte block copolymers are ubiquitous in industrial and biological processes; understanding their physical properties can also provide insights into the design of polyelectrolyte materials with novel and tailored properties. Here, we report systematic analysis on how the ionic strength of the solvent and the length of the polyelectrolyte block affect the self-assembly and morphology of the polyelectrolyte block copolymer materials by constructing a salt-dependent morphological phase diagram using an implicit solvent ionic strength (ISIS) method for dissipative particle dynamics (DPD) simulations. This diagram permits the determination of the conditions for the morphological transition into a specific shape, namely vesicles or lamellar aggregates, wormlike/cylindrical micelles, and spherical micelles. The scaling behavior for the size of spherical micelles is predicted, in terms of radius of gyration (R(g,m)) and thickness of corona (Hcorona), as a function of solvent ionic strength (c(s)) and polyelectrolyte length (NA), which are R(g,m) ∼ c(s)(-0.06)N(A)(0.54) and Hcorona ∼ c(s)(-0.11)N(A)(0.75). The simulation results were corroborated through AFM and static light scattering measurements on the example of the self-assembly of monodisperse, single-stranded DNA block-copolynucleotides (polyT50-b-F-dUTP). Overall, we were able to predict the salt-responsive morphology of polyelectrolyte materials in aqueous solution and show that a spherical-cylindrical-lamellar change in morphology can be obtained through an increase in solvent ionic strength or a decrease of polyelectrolyte length.

  15. Modeling the Heat Capacity of Spider Silk Inspired Di-block Copolymers

    NASA Astrophysics Data System (ADS)

    Huang, W.; Krishnaji, S.; Kaplan, D.; Cebe, P.

    2011-03-01

    We synthesized and characterized a new family of di-block copolymers based on the amino acid sequences of Nephila clavipes major ampulate dragline spider silk, having the form HABn and HBAn (n=1-6), comprising an alanine-rich hydrophobic block, A, a glycine-rich hydrophilic block, B, and a histidine tag, H. Using temperature modulated differential scanning calorimetry (TMDSC), we captured the effect of bound water acting as a plasticizer for copolymer films which had been cast from water solution and dried. We determined the water content by thermogravimetry and used the weight loss vs. temperature to correct the mass in TMDSC experiments. Our result shows that non-freezing bound water has a strong plasticization effect which lowers the onset of the glass transition by about 10circ; C. The reversing heat capacities, Cp(T), for temperatures below and above the glass transition were also characterized by TMDSC. We then calculated the solid state heat capacities of our novel block copolymers below the glass transition (Tg) based on the vibrational motions of the constituent poly(amino acid)s, whose heat capacities are known from the ATHAS Data Bank. Excellent agreement was found between the measured and calculated values of the heat capacity, showing that this model can serve as a standard method to predict the solid state Cp for other biologically inspired block copolymers. Support was provided from the NSF CBET-0828028 and the MRI Program under DMR-0520655 for thermal analysis instrumentation.

  16. Sub-10-nm patterning via directed self-assembly of block copolymer films with a vapour-phase deposited topcoat

    NASA Astrophysics Data System (ADS)

    Suh, Hyo Seon; Kim, Do Han; Moni, Priya; Xiong, Shisheng; Ocola, Leonidas E.; Zaluzec, Nestor J.; Gleason, Karen K.; Nealey, Paul F.

    2017-07-01

    Directed self-assembly (DSA) of the domain structure in block copolymer (BCP) thin films is a promising approach for sub-10-nm surface patterning. DSA requires the control of interfacial properties on both interfaces of a BCP film to induce the formation of domains that traverse the entire film with a perpendicular orientation. Here we show a methodology to control the interfacial properties of BCP films that uses a polymer topcoat deposited by initiated chemical vapour deposition (iCVD). The iCVD topcoat forms a crosslinked network that grafts to and immobilizes BCP chains to create an interface that is equally attractive to both blocks of the underlying copolymer. The topcoat, in conjunction with a chemically patterned substrate, directs the assembly of the grating structures in BCP films with a half-pitch dimension of 9.3 nm. As the iCVD topcoat can be as thin as 7 nm, it is amenable to pattern transfer without removal. The ease of vapour-phase deposition, applicability to high-resolution BCP systems and integration with pattern-transfer schemes are attractive properties of iCVD topcoats for industrial applications.

  17. Sub-10-nm patterning via directed self-assembly of block copolymer films with a vapour-phase deposited topcoat

    DOE PAGES

    Suh, Hyo Seon; Kim, Do Han; Moni, Priya; ...

    2017-03-27

    Directed self-assembly (DSA) of the domain structure in block copolymer (BCP) thin films is a promising approach for sub-10-nm surface patterning. DSA requires the control of interfacial properties on both interfaces of a BCP film to induce the formation of domains that traverse the entire film with a perpendicular orientation. Here we show a methodology to control the interfacial properties of BCP films that uses a polymer topcoat deposited by initiated chemical vapour deposition (iCVD). The iCVD topcoat forms a crosslinked network that grafts to and immobilizes BCP chains to create an interface that is equally attractive to both blocksmore » of the underlying copolymer. The topcoat, in conjunction with a chemically patterned substrate, directs the assembly of the grating structures in BCP films with a half-pitch dimension of 9.3 nm. As the iCVD topcoat can be as thin as 7 nm, it is amenable to pattern transfer without removal. As a result, the ease of vapour-phase deposition, applicability to high-resolution BCP systems and integration with pattern-transfer schemes are attractive properties of iCVD topcoats for industrial applications.« less

  18. Microfluidic Fabrication of Bio-compatible Vesicles by Self-assembly in Double Emulsions

    NASA Astrophysics Data System (ADS)

    Cheung Shum, Ho; Kim, Jinwoong; Lee, Daeyeon; Weitz, David

    2008-03-01

    Vesicles are compartments surrounded by bilayered membranes of amphiphilic molecules such as diblock copolymers and phospholipids. To minimize the exposure of their hydrophobic part to water, amphiphilic molecules self-assemble into aggregates of different structures. When the hydrophobic to hydrophilic ratio is close to unity, amphiphiles self assemble into bilayers, which tend to fold themselves into vesicles. These vesicles are useful for encapsulating and transporting actives such as drugs, flavor, and fragrance. To solve the problems of low encapsulation efficiency and large vesicle size distributions afforded by traditional techniques to create vesicles, we engineer a novel route to generate vesicles using monodisperse double emulsions prepared in microfluidics as templates. The double emulsion-to-vesicle transition exhibits different behaviors depending on the properties of the amphiphilic molecules such as the hydrophobic-to-hydrophilic ratio. Using this technique, we have fabricated both bio-compatible diblock copolymer vesicles, also known as polymersomes, and also lipid vesicles with high encapsulation efficiency.

  19. Self-assembly in poly(dimethylsiloxane)-poly(ethylene oxide) block copolymer template directed synthesis of Linde type A zeolite.

    PubMed

    Bonaccorsi, Lucio; Calandra, Pietro; Kiselev, Mikhail A; Amenitsch, Heinz; Proverbio, Edoardo; Lombardo, Domenico

    2013-06-11

    We describe the hydrothermal synthesis of zeolite Linde type A (LTA) submicrometer particles using a water-soluble amphiphilic block copolymer of poly(dimethylsiloxane)-b-poly(ethylene oxide) as a template. The formation and growth of the intermediate aggregates in the presence of the diblock copolymer have been monitored by small-angle X-ray scattering (SAXS) above the critical micellar concentration at a constant temperature of 45 °C. The early stage of the growth process was characterized by the incorporation of the zeolite LTA components into the surface of the block copolymer micellar aggregates with the formation of primary units of 4.8 nm with a core-shell morphology. During this period, restricted to an initial time of 1-3 h, the core-shell structure of the particles does not show significant changes, while a subsequent aggregation process among these primary units takes place. A shape transition of the SAXS profile at the late stage of the synthesis has been connected with an aggregation process among primary units that leads to the formation of large clusters with fractal characteristics. The formation of large supramolecular assemblies was finally verified by scanning electron microscopy, which evidenced the presence of submicrometer aggregates with size ranging between 100 and 300 nm, while X-ray diffraction confirmed the presence of crystalline zeolite LTA. The main finding of our results gives novel insight into the mechanism of formation of organic-inorganic mesoporous materials based on the use of a soft interacting nanotemplate as well as stimulates the investigation of alternative protocols for the synthesis of novel hybrid materials with new characteristics and properties.

  20. New glycosylated conjugate copolymer N-acetyl-β-D-glucosaminyl-pluronic: Synthesis, self-assembly and biological assays.

    PubMed

    Frizon, Tiago Elias Allievi; Micheletto, Yasmine Miguel Serafini; Westrup, José Luiz; Wakabayashi, Priscila Sayoko Silva; Serafim, Francieli Rocha; Damiani, Adriani Paganini; Longaretti, Luiza Martins; de Andrade, Vanessa Moraes; Giacomelli, Fernando Carlos; Fort, Sébastien; Dal Bó, Alexandre Gonçalves

    2015-09-01

    This work describes the synthesis of a new glycosylated conjugate copolymer, GlcNAc-PEO75-PPO30-PEO75-GlcNAc (GlcNAc-PluronicF68-GlcNAc), using click chemistry from Pluronic(®) F68 and propargyl-2-N-acetamido-2-deoxy-β-D-glucopyranoside. Micelles were prepared by the self-assembly of GlcNAc-PluronicF68-GlcNAc in phosphate-buffered solution. The critical micelle concentration was determined by fluorescence spectroscopy, and the value was found to be equal to 5.8mgmL(-1). The Gibbs free energy (ΔG) of micellization is negative, indicating that the organization of amphiphiles is governed by the hydrophobic effects in an entropy-driven process. The scattering characterization of GlcNAc-PluronicF68-GlcNAc micelles showed a hydrodynamic radius of 8.7nm and negative zeta potential (-21.0±0.9mV). The TEM image evidences the spherical shape of the objects self-assemble into highly regular micelles having a mean diameter of 10nm. The SAXS profile confirmed the spherical shape of the assemblies comprising a swollen PPO core (Rcore=2.25nm) stabilized by PEO chains following Gaussian statistics. The results of the comet assay showed that the GlcNAc-PluronicF68-GlcNAc micelles were not genotoxic, and the cell viability test was higher than 97% for all concentrations, demonstrating that GlcNAc-PluronicF68-GlcNAc is not toxic.

  1. Synthesis of Coordination Polymer Nanoparticles using self-assembled Block Copolymers as Template.

    PubMed

    Weber, Birgit

    2017-09-12

    Nowadays there is a high demand in specialized functional materials e.g. for applications as sensors in biomedicine. For the realization of such applications, nano-structures and the integration in a composite matrix are indispensable. Coordination polymers and networks, for example with spin crossover properties, are a highly promising family of switchable materials where the switching process can be triggered by various external stimuli. An overview over different strategies for the synthesis of nanoparticles of such systems is given. A special focus is set on the use of block copolymer micelles as template for the synthesis of nano-composites. The block copolymer defines the final size and shape of the nanoparticle core. Additionally it allows a further functionalization of the obtained nanoparticles by variation of the polymer blocks and an easy deposition of the composite material on surfaces. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Selective deposition and self-assembly of triblock copolymers into matrix arrays for membrane protein production.

    PubMed

    Andreasson-Ochsner, Mirjam; Fu, Zhikang; May, Sylvia; Xiu, Low Ying; Nallani, Madhavan; Sinner, Eva-Kathrin

    2012-01-31

    To improve the stability of cell membrane mimics, there has been growing interest in the use of block copolymers. Here, we present an easy approach to create an array of planar polymeric matrices capable of hosting membrane proteins. The array of polymeric matrices was formed by the selective deposition of triblock copolymers onto an array of hydrophilic islands situated within a hydrophobic background. The thickness of these matrices corresponds to the length of a single polymer chain. These polymeric matrices were used to host cell-free expressed membrane proteins, and offers a prototype from which a membrane protein array can be created for diagnostics or drug discovery purposes. © 2011 American Chemical Society

  3. Novel stereocomplexed sol-gel transition hydrogels prepared from physical packing of self-assembled PEO-PPO-PEO and PPO-PEO-PPO copolymer nanoscale micelles.

    PubMed

    Lee, Yuhan; Park, Sung Young; Park, Tae Gwan

    2008-10-01

    A new class of stereocomplex-induced hydrogels was synthesized based on self-assembled PEO-PPO-PEO and PPO-PEO-PPO copolymers having multiple hydroxyl groups in the PPO segment. The copolymers were grafted with enantiomeric oligo(L-lactic acid) or oligo(D-lactic acid) chains using ring opening polymerization onto the PPO segment. WAXS and DSC analysis were used to investigate the stereocomplex formation of the equimolar mixture of the copolymers. The copolymer hydrogels having stereocomplexed crystalline domains as crosslinking loci exhibited significantly altered temperature-sensitive sol-gel transition behaviors, and showed more delayed erosion and sustained protein release behaviors, compared to Pluronic F127 copolymer hydrogels. The current hydrogels are expected to be used as useful injectable hydrogel materials for macromolecular drug delivery.

  4. Hydrodynamic-flow-driven phase evolution in a polymer blend film modified by diblock copolymers

    NASA Astrophysics Data System (ADS)

    Rysz, J.; Ermer, H.; Budkowski, A.; Bernasik, A.; Lekki, J.; Juengst, G.; Brenn, R.; Kowalski, K.; Camra, J.; Lekka, M.; Jedliński, J.

    We have studied surface-directed phase separation in thin films of deuterated polystyrene and poly(bromostyrene) (with 22.7% of monomers brominated) using ^{{3}}He nuclear reaction analysis, dynamic secondary ion mass spectroscopy and atomic force microscopy combined with preferential dissolution. The crossover from competing to neutral surfaces of the critical blend film (cast onto Au) was commenced: polyisoprene-polystyrene diblock copolymers were added and segregated to both surfaces reducing in a tuneable manner the effective interactions. Two main stages of phase evolution are characterised by i) the growth of two surface layers and by ii) the transition from the four-layer to the final bilayer morphology. For increasing copolymer content the kinetics of the first stage is hardly affected but the amplitude of composition oscillations is reduced indicating more fragmented inner layers. As a result, a faster mass flow to the surfaces and an earlier completion of the second stage were observed. The hydrodynamic flow mechanism, driving both stages, is evidenced by nearly linear growth of the surface layer and by mass flow channels extending from the surface layer into the bulk. The final bilayer structure, formed even for the surfaces covered by strongly overlapped copolymers, is indicative of long-range (antisymmetric) surface forces.

  5. Self-diffusion of Asymmetric Diblock Copolymers with a Spherical Domain Structure

    NASA Astrophysics Data System (ADS)

    Yokoyama, H.; Kramer, E. J.

    1997-03-01

    The molecular weight and temperature dependence of the self-diffusion coefficient D of spherically ordered asymmetric diblock copolymers of deuterated polystyrene-b-2vinylpyridine (dPS-PVP) in protonated hPS-PVP has been investigated using forward recoil spectrometry (FRES). In cases where the product of the number of segments of the PVP core block, N_PVP, and the interaction parameter, \\chi, exceeds roughly 10, D is much smaller than that of a homopolystyrene with the same molecular weight and D decreases exponentially with N_PVP. The temperature dependence of D is different from WLF, reflecting instead the temperature dependence of \\chi(T) in D = Aexp(-α\\chiN_PVP) where A and α are constants. On the other hand, when \\chiN_PVP is about 5, we did not observe a significant difference between D of the block copolymer and that of homopolystyrene. At this \\chiN_PVP, as well as at all larger values, an ordered spherical morphology is observed by TEM. The diffusion process at high \\chiN_PVP is thought to involve an thermally activated "hopping" mechanism in which single block copolymer chains diffuse by hopping from one spherical domain to another.

  6. Tailoring Membrane Surface Properties and Ultrafiltration Performances via the Self-Assembly of Polyethylene Glycol-block-Polysulfone-block-Polyethylene Glycol Block Copolymer upon Thermal and Solvent Annealing.

    PubMed

    Wang, Ning; Wang, Tao; Hu, Yunxia

    2017-09-13

    Recently, ultrafiltration (UF) membranes have faced great challenges including the fine control of membrane surfaces for high filtration performances and antifouling properties in treating complex solution systems. Here, a particular type of amphiphilic block copolymer polyethylene glycol-block-polysulfone-block-polyethylene glycol (PEG-b-PSf-b-PEG) was synthesized through one-pot step-growth polymerization with mPEG [monomethylpoly(ethylene glycol)] as two ends to achieve the mobility of hydrophilic polymer chains. Without any other polymers or additives involved, the PEG-b-PSf-b-PEG triblock copolymer UF membrane was fabricated through the non-solvent-induced phase separation (NIPS) method. The surface properties and filtration performances of UF membranes were tailored through the self-assembly of PEG-b-PSf-b-PEG triblock copolymers combining the thermal and solvent annealing treatments in water at 90 °C for 16 h. The annealed PEG-b-PSf-b-PEG triblock copolymer membrane significantly enhanced its water flux resulting from the increased mean pore size with the improved porosity, as well as the decreased skin layer thickness, upon annealing. More importantly, the PEG-b-PSf-b-PEG triblock copolymer membrane surface turned from hydrophobic to hydrophilic upon annealing with the PEG enrichment on the surface, and exhibited improved protein antifouling performances. Our research opens a new avenue to tailor the membrane structure and surface properties by self-assembly of amphiphilic block copolymers upon thermal and solvent annealing treatments.

  7. Crystallization in diblock copolymer thin films at different degrees of supercooling.

    PubMed

    Darko, C; Botiz, I; Reiter, G; Breiby, D W; Andreasen, J W; Roth, S V; Smilgies, D-M; Metwalli, E; Papadakis, C M

    2009-04-01

    The crystalline structures in thin films of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblock copolymers were studied in dependence on the degree of supercooling. Atomic force microscopy showed that the crystalline domains (lamellae) consist of grains, which are macroscopic at low and intermediate degrees of supercooling, but of submicrometer size for strong supercooling. Using grazing-incidence wide-angle x-ray scattering, we could determine the grain orientation distribution function which shows that the chain stems are perpendicular to the lamellae at low supercooling, but tilted at intermediate and strong supercooling. These results suggest that, at intermediate and strong supercooling, the crystalline PEO lamellae do not grow homogeneously, but by the formation of small crystallites at the growth front.

  8. Amphiphilic, cross-linkable diblock copolymers for multifunctionalized nanoparticles as biological probes

    NASA Astrophysics Data System (ADS)

    Schmidtke, Christian; Pöselt, Elmar; Ostermann, Johannes; Pietsch, Andrea; Kloust, Hauke; Tran, Huong; Schotten, Theo; Bastús, Neus G.; Eggers, Robin; Weller, Horst

    2013-07-01

    Nanoparticles (NPs) play an increasingly important role in biological labeling and imaging applications. However, preserving their useful properties in an aqueous biological environment remains challenging, even more as NPs therein have to be long-time stable, biocompatible and nontoxic. For in vivo applications, size control is crucial in order to route excretion pathways, e.g. renal clearance vs. hepato-biliary accumulation. Equally necessary, cellular and tissue specific targeting demands suitable linker chemistry for surface functionalization with affinity molecules, like peptides, proteins, carbohydrates and nucleotides. Herein, we report a three stage encapsulation process for NPs comprised of (1) a partial ligand exchange by a multidentate polyolefinic amine ligand, PI-N3, (2) micellar encapsulation with a precisely tuned amphiphilic diblock PI-b-PEG copolymer, in which the PI chains intercalate to the PI-N3 prepolymer and (3) radical cross-linking of the adjacent alkenyl bonds. As a result, water-soluble NPs were obtained, which virtually maintained their primal physical properties and were exceptionally stable in biological media. PEG-terminal functionalization of the diblock PI-b-PEG copolymer with numerous functional groups was mostly straightforward by chain termination of the living anionic polymerization (LAP) with the respective reagents. More complex affinity ligands, e.g. carbohydrates or biotin, were introduced in a two-step process, prior to micellar encapsulation. Advantageously, this pre-assembly approach opens up rapid access to precisely tuned multifunctional NPs, just by using mixtures of diverse functional PI-b-PEG polymers in a combinatorial manner. All constructs showed no toxicity from 0.001 to 1 μM (particle concentration) in standard WST and LDH assays on A549 cells, as well as only marginal unspecific cellular uptake, even in serum-free medium.Nanoparticles (NPs) play an increasingly important role in biological labeling and imaging

  9. Phase transition of a symmetric diblock copolymer induced by nanorods with different surface chemistry

    NASA Astrophysics Data System (ADS)

    Guo, Yu-qi; Pan, Jun-xing; Sun, Min-na; Zhang, Jin-jun

    2017-01-01

    We investigate the phase transition of a symmetric diblock copolymer induced by nanorods with different surface chemistry. The results demonstrate that the system occurs the phase transition from a disordered structure to ordered parallel lamellae and then to the tilted layered structure as the number of rods increases. The dynamic evolution of the domain size and the order parameter of the microstructure are also examined. Furthermore, the influence of rod property, rod-phase interaction, rod-rod interaction, rod length, and polymerization degree on the behavior of the polymer system is also investigated systematically. Moreover, longer amphiphilic nanorods tend to make the polymer system form the hexagonal structure. It transforms into a perpendicular lamellar structure as the polymerization degree increases. Our simulations provide an efficient method for determining how to obtain the ordered structure on the nanometer scales and design the functional materials with optical, electronic, and magnetic properties.

  10. Efficient and accurate numerical schemes for a hydro-dynamically coupled phase field diblock copolymer model

    NASA Astrophysics Data System (ADS)

    Cheng, Qing; Yang, Xiaofeng; Shen, Jie

    2017-07-01

    In this paper, we consider numerical approximations of a hydro-dynamically coupled phase field diblock copolymer model, in which the free energy contains a kinetic potential, a gradient entropy, a Ginzburg-Landau double well potential, and a long range nonlocal type potential. We develop a set of second order time marching schemes for this system using the ;Invariant Energy Quadratization; approach for the double well potential, the projection method for the Navier-Stokes equation, and a subtle implicit-explicit treatment for the stress and convective term. The resulting schemes are linear and lead to symmetric positive definite systems at each time step, thus they can be efficiently solved. We further prove that these schemes are unconditionally energy stable. Various numerical experiments are performed to validate the accuracy and energy stability of the proposed schemes.

  11. Surface Engineering of Cellulose Nanofiber by Adsorption of Diblock Copolymer Dispersant for Green Nanocomposite Materials.

    PubMed

    Sakakibara, Keita; Yano, Hiroyuki; Tsujii, Yoshinobu

    2016-09-21

    An effective approach for the dispersion of hydrophilic cellulose nanofiber (CNF) in hydrophobic high-density polyethylene (HDPE) is presented using adsorption of a diblock copolymer dispersant. The dispersant consists of both resin compatible poly(lauryl methacrylate) (PLMA) and cellulose interactive poly(2-hydroxyethyl methacrylate) blocks. The PLMA-adsorbed CNFs are characterized by FT-IR and contact angle measurement, revealing successful hydrophobization. X-ray CT imaging shows there are apparently less CNF aggregates in the nanocomposites if adding amount of the dispersant was enough. The good dispersion results in a high mechanical reinforcement, corresponding to 140% higher Young's modulus and 84% higher tensile strength than the neat HDPE. This approach is broadly applicable and allows for easy manufacturing process for strong and lightweight CNF-reinforced nanocomposite materials.

  12. Structural rearrangements in a lamellar diblock copolymer thin film during treatment with saturated solvent vapor

    PubMed Central

    Di, Zhenyu; Posselt, Dorthe; Smilgies, Detlef-M.; Papadakis, Christine M.

    2010-01-01

    We have investigated the structural changes in thin films of lamellar poly(styrene-b-butadiene) diblock copolymers during treatment with saturated cyclohexane vapor, a solvent slightly selective for polybutadiene. Using real-time, in-situ grazing-incidence small-angle X-ray scattering (GISAXS), the swelling and the rearrangement of the lamellae were investigated with a time resolution of a few seconds, and the underlying processes on the molecular level were identified. After a few minutes in vapor, a transient state with a more well-defined and more long-range ordered lamellar orientation was encountered. Additional parallel lamellae formed which we attribute to the increased degree of coiling of the polymers in the swollen state. Eventually, the film became disordered. These changes are attributed to the increased mobility of the swollen polymers and the gradually decreasing segment-segment interaction parameter in the film as solvent is absorbed. PMID:20305742

  13. Phase diagram of rod-coil diblock copolymer melts by self-consistent field theory

    NASA Astrophysics Data System (ADS)

    Yan, Dadong; Tang, Jiuzhou; Jiang, Ying; Zhang, Xinghua; Chen, Jeff

    A unified phase diagram is presented for rod-coil diblock copolymer melts in the isotropic phase regime as a function of the asymmetric parameter. The study is based on free-energy calculation, which incorporates three-dimensional spatial variations of the volume fraction with angular dependence. The wormlike-chain model is used in a self-consistent field treatment. Body-centered cubic, A15, hexagonal, gyroid, and lamellar structures where the rod segments are packed inside the convex rod-coil interface are found stable. As the conformational asymmetric parameter increases, the A15 phase region expands and the gyroid phase region reduces. The stability of the structures is analyzed by concepts such as packing frustration, spinodal limit, and interfacial curvature.

  14. A comparison of implicit- and explicit-solvent simulations of self-assembly in block copolymer and solute systems

    NASA Astrophysics Data System (ADS)

    Spaeth, Justin R.; Kevrekidis, Ioannis G.; Panagiotopoulos, Athanassios Z.

    2011-04-01

    We have developed explicit- and implicit-solvent models for the flash nanoprecipitation process, which involves rapid coprecipitation of block copolymers and solutes by changing solvent quality. The explicit-solvent model uses the dissipative particle dynamics (DPD) method and the implicit-solvent model uses the Brownian dynamics (BD) method. Each of the two models was parameterized to match key properties of the diblock copolymer (specifically, critical micelle concentration, diffusion coefficient, polystyrene melt density, and polyethylene glycol radius of gyration) and the hydrophobic solute (aqueous solubility, diffusion coefficient, and solid density). The models were simulated in the limit of instantaneous mixing of solvent with antisolvent. Despite the significant differences in the potentials employed in the implicit- and explicit-solvent models, the polymer-stabilized nanoparticles formed in both sets of simulations are similar in size and structure; however, the dynamic evolution of the two simulations is quite different. Nanoparticles in the BD simulations have diffusion coefficients that follow Rouse behavior (D ∝ M-1), whereas those in the DPD simulations have diffusion coefficients that are close to the values predicted by the Stokes-Einstein relation (D ∝ R-1). As the nanoparticles become larger, the discrepancy between diffusion coefficients grows. As a consequence, BD simulations produce increasingly slower aggregation dynamics with respect to real time and result in an unphysical evolution of the nanoparticle size distribution. Surface area per polymer of the stable explicit-solvent nanoparticles agrees well with experimental values, whereas the implicit-solvent nanoparticles are stable when the surface area per particle is roughly two to four times larger. We conclude that implicit-solvent models may produce questionable results when simulating nonequilibrium processes in which hydrodynamics play a critical role.

  15. A comparison of implicit- and explicit-solvent simulations of self-assembly in block copolymer and solute systems.

    PubMed

    Spaeth, Justin R; Kevrekidis, Ioannis G; Panagiotopoulos, Athanassios Z

    2011-04-28

    We have developed explicit- and implicit-solvent models for the flash nanoprecipitation process, which involves rapid coprecipitation of block copolymers and solutes by changing solvent quality. The explicit-solvent model uses the dissipative particle dynamics (DPD) method and the implicit-solvent model uses the Brownian dynamics (BD) method. Each of the two models was parameterized to match key properties of the diblock copolymer (specifically, critical micelle concentration, diffusion coefficient, polystyrene melt density, and polyethylene glycol radius of gyration) and the hydrophobic solute (aqueous solubility, diffusion coefficient, and solid density). The models were simulated in the limit of instantaneous mixing of solvent with antisolvent. Despite the significant differences in the potentials employed in the implicit- and explicit-solvent models, the polymer-stabilized nanoparticles formed in both sets of simulations are similar in size and structure; however, the dynamic evolution of the two simulations is quite different. Nanoparticles in the BD simulations have diffusion coefficients that follow Rouse behavior (D ∝ M(-1)), whereas those in the DPD simulations have diffusion coefficients that are close to the values predicted by the Stokes-Einstein relation (D ∝ R(-1)). As the nanoparticles become larger, the discrepancy between diffusion coefficients grows. As a consequence, BD simulations produce increasingly slower aggregation dynamics with respect to real time and result in an unphysical evolution of the nanoparticle size distribution. Surface area per polymer of the stable explicit-solvent nanoparticles agrees well with experimental values, whereas the implicit-solvent nanoparticles are stable when the surface area per particle is roughly two to four times larger. We conclude that implicit-solvent models may produce questionable results when simulating nonequilibrium processes in which hydrodynamics play a critical role.

  16. Role of solution structure in self-assembly of conjugated block copolymer thin films

    DOE PAGES

    Brady, Michael A.; Ku, Sung -Yu; Perez, Louis A.; ...

    2016-10-24

    Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)-block-poly(diketopyrrolopyrrole–terthiophene) (P3HT-b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT-b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering. In contrast tomore » the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. Finally, these results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block copolymers.« less

  17. Synergistic templated self-assembly of cellulose nanocrystals in thin block copolymer films

    NASA Astrophysics Data System (ADS)

    Grolman, Danielle; Gilman, Jeffrey; Davis, Chelsea; Karim, Alamgir

    2015-03-01

    Nanofillers in thin polymer films offer unique advantage to potentially modify the film's thermal, optical, electrical and mechanical properties due to the high surface area to volume ratio and intrinsic property change at the nanoscale. Nanofilled polymer films have been shown to exhibit unusual film stability to dewetting with a nonmonotonic behavior with nanofiller loading, potentially arising from factors such as competitive phase behavior and filler aggregation, particularly in the high nanofiller concentration limit. In this regard, block copolymer films can act as ideal nanoscale structured templates to selectively sequester and organize nanofillers. In conjunction with incorporated cellulose nanocrystals (CNCs), we seek to understand how individual anisotropic nanofillers can provide synergistic reinforcement to inherently anisotropic nanostructured block copolymer films. A clear enhancement in the Young's Modulus was observed with increased CNC loading using strain-induced elastic buckling instability for mechanical measurements (SIEBIMM) for thin films. To this end, we examine the nanoscale to microscale morphology of the blend film through AFM, TEM and grazing incidence small-angle x-ray scattering (GISAXS), and CNC dispersion and percolation through high-intensity grazing incidence wide-angle x-ray scattering (GIWAXS) analysis.

  18. Process-directed self-assembly of multiblock copolymers: Solvent casting vs spray coating

    NASA Astrophysics Data System (ADS)

    Tang, Q.; Tang, J.; Müller, M.

    2016-10-01

    Using computer simulation of a soft, coarse-grained model and self-consistent field theory we investigate how collapsed, globular chain conformations in the initial stages of structure formation, which are produced by spray-coating, affect the single-chain structure and morphology of microphase-separated multiblock copolymers. Comparing spray-coated films with films that start from a disordered state of Gaussian chains, we observe that the collapsed molecular conformations in the initial stage give rise to (1) a smaller fraction of blocks that straddle domains (bridges), (2) a significant reduction of the molecular extension normal to the internal interfaces, and (3) a slightly larger lamellar domain spacing in the final morphology. The relaxation of molecular conformations towards equilibrium is very protracted for both processes - solvent casting and spray coating. These findings illustrate that the process conditions of the copolymer materials may significantly affect materials properties (such as mechanical properties) because the system does not reach thermal equilibrium on the relevant time scales.

  19. Role of solution structure in self-assembly of conjugated block copolymer thin films

    SciTech Connect

    Brady, Michael A.; Ku, Sung -Yu; Perez, Louis A.; Cochran, Justin E.; Schmidt, Kristin; Weiss, Thomas M.; Toney, Michael F.; Ade, Harald; Hexemer, Alexander; Wang, Cheng; Hawker, Craig J.; Kramer, Edward J.; Chabinyc, Michael L.

    2016-10-24

    Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)-block-poly(diketopyrrolopyrrole–terthiophene) (P3HT-b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT-b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering. In contrast to the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. Finally, these results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block copolymers.

  20. Role of solution structure in self-assembly of conjugated block copolymer thin films

    DOE PAGES

    Brady, Michael A.; Ku, Sung -Yu; Perez, Louis A.; ...

    2016-10-24

    Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)-block-poly(diketopyrrolopyrrole–terthiophene) (P3HT-b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT-b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering. In contrast tomore » the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. Finally, these results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block copolymers.« less

  1. Tartaric Acid-Assisted Self-Assembly of Hybrid Block Copolymer Composites

    NASA Astrophysics Data System (ADS)

    Yao, Li; Lin, Ying; Watkins, James

    2014-03-01

    Enantiopure tartaric acid was used as an additive to increase the segregation strength of poly(ethylene oxide-block-tert-butyl acrylate) (PEO-b-PtBA) copolymers through strong, selective interactions with one of the polymer chain segments. Addition of tartaric acid to PEO-b-PtBA exhibiting cylindrical morphologies resulted in the formation of helical superstructures as observed by transmission electron microscopy. It was also found that this small acid additive can also enable phase-selective ultra-high loading of nanoparticles (NPs) into target domains of the block copolymer composites. The loading of tartaric acid can increase enthalpically favorable interactions between the nanoparticle ligands and the host domain and mitigate entropic penalties associated with NP incorporation into the target domain. A metal content of over 40 weight percent by mass of the resulting well ordered composites was achieved as measured by thermal gravimetric analysis in PEO-b-PtBA/tartaric acid/4-hydroxythiophenol functionalized Au NP hybrid system. Funding from Center for Hierarchical Manufacturing (CHM); Facility support from Materials Research Science and Engineering Center at UMass Amherst.

  2. Role of solution structure in self-assembly of conjugated block copolymer thin films

    SciTech Connect

    Brady, Michael A.; Ku, Sung -Yu; Perez, Louis A.; Cochran, Justin E.; Schmidt, Kristin; Weiss, Thomas M.; Toney, Michael F.; Ade, Harald; Hexemer, Alexander; Wang, Cheng; Hawker, Craig J.; Kramer, Edward J.; Chabinyc, Michael L.

    2016-10-24

    Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)-block-poly(diketopyrrolopyrrole–terthiophene) (P3HT-b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT-b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering. In contrast to the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. Finally, these results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block copolymers.

  3. Intermolecular interactions and solvent diffusion in ordered nanostructures formed by self-assembly of block copolymers

    NASA Astrophysics Data System (ADS)

    Gu, Zhiyong

    Hydrogels formed by Poloxamer poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block copolymers find various pharmaceutical and biomedical applications. A variety of ordered structures can be exhibited by Poloxamer block copolymers in selective solvents such as water, for example, micellar cubic phase, hexagonal phase, lamellar phase, etc. We are interested in the thermodynamic and transport properties of water in such hydrogels that have an ordered (lyotropic liquid crystalline) structure. We have investigated the time evolution of water loss from Poloxamer gel films under a driving force of known water vapor pressure in the air in contact with the film. The experimental data on the drying process have been fitted to the diffusion equation for water in the film, under a boundary condition that includes the water concentration in the gel at infinite time; the water diffusion coefficient and other parameters have thus been obtained. The water chemical potential and osmotic pressure in the gel have been obtained from osmotic stress measurements. The osmotic pressure (force), together with data on the corresponding lyotropic liquid crystal spacing (distance) that we obtained from Small Angle X-Ray Scattering (SAXS) measurements, have been analyzed to provide information on the prevailing intermolecular (inter-assembly) forces in the gel. The forces in the gel reveal interactions that occur at two levels, that of the PEO coil and that of the PEO segment.

  4. Controllable Heparin-Based Comb Copolymers and Their Self-assembled Nanoparticles for Gene Delivery.

    PubMed

    Nie, Jing-Jun; Zhao, Weiyi; Hu, Hao; Yu, Bingran; Xu, Fu-Jian

    2016-04-06

    Polysaccharide-based copolymers have attracted much attention due to their effective performances. Heparin, as a kind of polysaccharide with high negative charge densities, has attracted much attention in biomedical fields. In this work, we report a flexible way to adjust the solubility of heparin from water to oil via the introduction of tetrabutylammonium groups for further functionalization. A range of heparin-based comb copolymers with poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMEMA), poly(dimethylaminoethyl methacrylate) (PDMAEMA), or PPEGMEMA-b-PDMAEMA side chains were readily synthesized in a MeOH/dimethylsulfoxide mixture via atom-transfer radical polymerization. The heparin-based polymer nanoparticles involving cationic PDMAEMA were produced due to the electrostatic interaction between the negatively charged heparin backbone and PDMAEMA grafts. Then the pDNA condensation ability, cytotoxicity, and gene transfection efficiency of the nanoparticles were characterized in comparison with the reported gene vectors. The nanoparticles were proved to be effective gene vectors with low cytotoxicity and high transfection efficiency. This study demonstrates that by adjusting the solubility of heparin, polymer graft functionalization of heparin can be readily realized for wider applications.

  5. A Quantitative Study of Tethered Chains in Various Solution Conditions Using Langmuir Diblock Copolymer Monolayers

    SciTech Connect

    Kent, Michael S.

    1999-08-13

    This article summarizes our investigations of tethered chain systems using Langmuir monolayer of polydimethysiloxane-poly styrene (PDMS-PS) diblock copolymers on organic liquids. In this system, the PDMS block adsorbs to the air surface while the PS block dangles into the subphase liquid. The air surface can be made either repulsive or attractive for the tethered PS chain segments by choosing a subphase liquid which has a surface tension lower or greater than that of PS, respectively. The segment profile of the PS block is determined by neutron reflection as a function of the surface density, the molecular weights of the PS and PDMS blocks, and the solution conditions. We cover the range of reduced surface density (SIGMA) characteristic of the large body of data in the literature for systems of chains tethered onto solid surfaces from dilute solution in good or theta solvent conditions (SIGMA < 12). We emphasize quantitative comparisons with analytical profile forms and scaling predictions. We find that the strong-stretching limit invoked in analytical SCF and scaling theories is not valid over this Z range. On the other hand, over a large portion of this range (SIGMA < 5) tethered layers are well described by a renormalization group theory addressing weakly interacting or noninteracting chains. Simultaneous with the study of the profile form, the free energy of the chains is examined through the surface tension. A strong increase in the surface pressure is observed with increasing surface density which determines the maximum surface density which can be achieved. This apparently nonequilibrium effect is attributed to steric interactions and limited lateral interpenetration. This effect may explain several outstanding discrepancies regarding the adsorption of end-functionalized chains and diblock copolymers onto solid surfaces.

  6. Self-assembly of high-resolutions PS-b-PMMA block-copolymers: processes capabilities and integration on 300mm track

    NASA Astrophysics Data System (ADS)

    Chevalier, X.; Nicolet, C.; Tiron, R.; Gharbi, A.; Chamiot-Maitral, G.; Jullian, K.; Pimenta-Barros, P.; Argoud, M.; Peyre, J.-L.; Van Spaandonk, R.; Fleury, G.; Hadziioannou, G.; Navarro, C.

    2014-03-01

    Careful control and reproducibility of BCP's synthesis are mandatory parameters to push-down PS-b-PMMA block-copolymer systems toward its lowest dimensions for microelectronic applications. The self-assembly process optimization of different high-resolution cylindrical PS-b-PMMA block-copolymers (i.e. L0 period below 25 nm) is studied to highlight processes-variations as regard to more classical PS-b-PMMA systems while the characterizations of bulk materials provide deeper insights on the parameters addressing the self-assembly of such materials. The integration of a high-resolution BCP on 300 mm track is then studied to check the capabilities of such materials in terms of lithographic applications. CD uniformity measurements in contact hole shrink approach, as well as the transfer of the BCP mask into typical industrial under-layer stacks leading to aggressive features, show that these materials exhibit promising potentials for advanced lithographic nodes.

  7. Nanostructured Silicon Photocathodes for Solar Water Splitting Patterned by the Self-Assembly of Lamellar Block Copolymers.

    PubMed

    Shen, Lang; He, Chunlin; Qiu, Jing; Lee, Sung-Min; Kalita, Abinasha; Cronin, Stephen B; Stoykovich, Mark P; Yoon, Jongseung

    2015-12-02

    We studied a type of nanostructured silicon photocathode for solar water splitting, where one-dimensionally periodic lamellar nanopatterns derived from the self-assembly of symmetric poly(styrene-block-methyl methacrylate) block copolymers were incorporated on the surface of single-crystalline silicon in configurations with and without a buried metallurgical junction. The resulting nanostructured silicon photocathodes with the characteristic lamellar morphology provided suppressed front-surface reflection and increased surface area, which collectively contributed to the enhanced photocatalytic performance in the hydrogen evolution reaction. The augmented light absorption in the nanostructured silicon directly translated to the increase of the saturation current density, while the onset potential decreased with the etching depth because of the increased levels of surface recombination. The pp(+)-silicon photocathodes, compared to the n(+)pp(+)-silicon with a buried solid-state junction, exhibited a more pronounced shift of the current density-potential curves upon the introduction of the nanostructured surface owing to the corresponding increase in the liquid/silicon junction area. Systematic studies on the morphology, optical properties, and photoelectrochemical characteristics of nanostructured silicon photocathodes, in conjunction with optical modeling based on the finite-difference time-domain method, provide quantitative description and optimal design rules of lamellar-patterned silicon photocathodes for solar water splitting.

  8. Hierarchically Self-Assembled Block Copolymer Blends for Templating Hollow Phase-Change Nanostructures with an Extremely Low Switching Current

    DOE PAGES

    Park, Woon Ik; Kim, Jong Min; Jeong, Jae Won; ...

    2015-03-17

    Phase change memory (PCM) is one of the most promising candidates for next-generation nonvolatile memory devices because of its high speed, excellent reliability, and outstanding scalability. But, the high switching current of PCM devices has been a critical hurdle to realize low-power operation. Although one solution is to reduce the switching volume of the memory, the resolution limit of photolithography hinders further miniaturization of device dimensions. Here, we employed unconventional self-assembly geometries obtained from blends of block copolymers (BCPs) to form ring-shaped hollow PCM nanostructures with an ultrasmall contact area between a phase-change material (Ge2Sb2Te5) and a heater (TiN) electrode.more » The high-density (approximately 0.1 terabits per square inch) PCM nanoring arrays showed extremely small switching current of 2-3 mu A. Furthermore, the relatively small reset current of the ring-shaped PCM compared to the pillar-shaped devices is attributed to smaller switching volume, which is well supported by electro-thermal simulation results. Our approach may also be extended to other nonvolatile memory device applications such as resistive switching memory and magnetic storage devices, where the control of nanoscale geometry can significantly affect device performances.« less

  9. Hierarchically Self-Assembled Block Copolymer Blends for Templating Hollow Phase-Change Nanostructures with an Extremely Low Switching Current

    SciTech Connect

    Park, Woon Ik; Kim, Jong Min; Jeong, Jae Won; Hur, Yoon Hyoung; Choi, Young Joong; Kwon, Se-Hun; Hong, Seungbum; Yin, You; Jung, Yeon Sik; Kim, Kwang Ho

    2015-03-17

    Phase change memory (PCM) is one of the most promising candidates for next-generation nonvolatile memory devices because of its high speed, excellent reliability, and outstanding scalability. But, the high switching current of PCM devices has been a critical hurdle to realize low-power operation. Although one solution is to reduce the switching volume of the memory, the resolution limit of photolithography hinders further miniaturization of device dimensions. Here, we employed unconventional self-assembly geometries obtained from blends of block copolymers (BCPs) to form ring-shaped hollow PCM nanostructures with an ultrasmall contact area between a phase-change material (Ge2Sb2Te5) and a heater (TiN) electrode. The high-density (approximately 0.1 terabits per square inch) PCM nanoring arrays showed extremely small switching current of 2-3 mu A. Furthermore, the relatively small reset current of the ring-shaped PCM compared to the pillar-shaped devices is attributed to smaller switching volume, which is well supported by electro-thermal simulation results. Our approach may also be extended to other nonvolatile memory device applications such as resistive switching memory and magnetic storage devices, where the control of nanoscale geometry can significantly affect device performances.

  10. Model photo-responsive elastomers based on the self-assembly of side group liquid crystal triblock copolymers (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Kurji, Zuleikha; Kornfield, Julia A.; Kuzyk, Mark G.

    2015-10-01

    We report the synthesis of azobenzene-containing coil-liquid crystal-coil triblock copolymers that form uniform and highly reproducible elastomers by self-assembly. To serve as actuators to (non-invasively) steer a fiber optic, for example in deep brain stimulation, the polymers are designed to become monodomain "single liquid crystal" elastomers during the fiber-draw process and to have a large stress/strain response to stimulation with either light or heat. A fundamental scientific question that we seek to answer is how the interplay between the concentration of photoresponsive mesogens and the proximity to the nematic-isotropic transition governs the sensitivity of the material to stimuli. Specifically, a matched pair of polymers, one with ~5% azobenzene-containing side groups (~95% cyanobiphenyl side groups) and the other with 100% cyanobiphenyl side groups were synthesized from identical triblock pre-polymers (with polystyerene end blocks and 1,2-polybutadiene midblocks). These can be blended in various ratios to prepare a series of elastomers that are precisely matched in terms of the backbone length between physical crosslinks (because each polymer is derived from the same pre-polymer), while differing in % azobenzene side groups, allowing the effect of concentration of photoresponsive groups to be unambiguously determined.

  11. Investigation of cross-linking poly(methyl methacrylate) as a guiding material in block copolymer directed self-assembly

    NASA Astrophysics Data System (ADS)

    Seidel, Robert; Rincon Delgadillo, Paulina; Ramirez-Hernandez, Abelardo; Wu, Hengpeng; Her, Youngjun; Yin, Jian; Nealey, Paul; de Pablo, Juan; Gronheid, Roel

    2014-03-01

    Directed self-assembly (DDSA) of block copolymers ((BCP) is attracting a growing amount of interest as a techhnique to expand traditional lithography beyond its current limits. It has reecently been demonstrated that chemoepitaxy can be used to successfully ddirect BCP assembly to form large arrays off high-density features. The imec DSA LiNe flow uses lithography and trim-etch to produce a "prepattern" of cross-linked polystyrene (PS) stripes, which in turn guide the formation of assembled BCPP structures. Thhe entire process is predicated on the preferential interaction of the respective BCP domains with particular regionss of the underlying prepattern. The use of polystyrene as the guiding material is not uniquely required, however, and in fact may not even be preferable. This study investigates an alternate chemistry -- crosslinked poly(methyl methacrylate), X-PMMA, -- as the underlying polymer mat, providing a route to higher auto-affinity and therefore a stronger guiding ability. In addition to tthe advantages of the chemistry under investigation, this study explores the broader theme of extending BCP DSA to other materials.

  12. Co-delivery of drugs and DNA from cationic core-shell nanoparticles self-assembled from a biodegradable copolymer

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Gao, Shujun; Ye, Wen-Hui; Yoon, Ho Sup; Yang, Yi-Yan

    2006-10-01

    Non-viral gene-delivery systems are safer to use and easier to produce than viral vectors, but their comparatively low transfection efficiency has limited their applications. Co-delivery of drugs and DNA has been proposed to enhance gene expression or to achieve the synergistic/combined effect of drug and gene therapies. Attempts have been made to deliver drugs and DNA simultaneously using liposomes. Here we report cationic core-shell nanoparticles that were self-assembled from a biodegradable amphiphilic copolymer. These nanoparticles offer advantages over liposomes, as they are easier to fabricate, and are more readily subject to modulation of their size and degree of positive charge. More importantly, they achieve high gene-transfection efficiency and the possibility of co-delivering drugs and genes to the same cells. Enhanced gene transfection with the co-delivery of paclitaxel has been demonstrated by in vitro and in vivo studies. In particular, the co-delivery of paclitaxel with an interleukin-12-encoded plasmid using these nanoparticles suppressed cancer growth more efficiently than the delivery of either paclitaxel or the plasmid in a 4T1 mouse breast cancer model. Moreover, the co-delivery of paclitaxel with Bcl-2-targeted small interfering RNA (siRNA) increased cytotoxicity in MDA-MB-231 human breast cancer cells.

  13. Flexible one diode-one phase change memory array enabled by block copolymer self-assembly.

    PubMed

    Mun, Beom Ho; You, Byoung Kuk; Yang, Se Ryeun; Yoo, Hyeon Gyun; Kim, Jong Min; Park, Woon Ik; Yin, You; Byun, Myunghwan; Jung, Yeon Sik; Lee, Keon Jae

    2015-04-28

    Flexible memory is the fundamental component for data processing, storage, and radio frequency communication in flexible electronic systems. Among several emerging memory technologies, phase-change random-access memory (PRAM) is one of the strongest candidate for next-generation nonvolatile memories due to its remarkable merits of large cycling endurance, high speed, and excellent scalability. Although there are a few approaches for flexible phase-change memory (PCM), high reset current is the biggest obstacle for the practical operation of flexible PCM devices. In this paper, we report a flexible PCM realized by incorporating nanoinsulators derived from a Si-containing block copolymer (BCP) to significantly lower the operating current of the flexible memory formed on plastic substrate. The reduction of thermal stress by BCP nanostructures enables the reliable operation of flexible PCM devices integrated with ultrathin flexible diodes during more than 100 switching cycles and 1000 bending cycles.

  14. Self-assembling of hydrophobic-hydrophilic copolymers in hydrophobic nanocylindrical tubes: formation of channels.

    PubMed

    Feng, Jie; Ruckenstein, Eli

    2008-02-21

    By employing Monte Carlo simulations, the phase behavior of hydrophobic-hydrophilic copolymers confined in hydrophobic nanocylindrical tubes has been investigated by changing the hydrophobic-hydrophilic distribution, the ratio of the hydrophobic to hydrophilic segments, the hydrophobicity of the tube surface, and the tube diameter. The ratio of hydrophobic to hydrophilic segments, the number of blocks in a chain, and the number of segments in a block affected the generation of channels in the central region. Such channels were formed when the hydrophobicity of the tube surface was sufficiently strong for its attraction for the hydrophobic segments to overcome the attraction between the hydrophobic segments. When the numbers of hydrophobic and hydrophilic beads in a chain are constant, the number of blocks has opposite effects in small and large tubes. In the former, the formation of channels is stimulated by a larger number of blocks, while in the latter, it is stimulated by a smaller number of blocks.

  15. Hierarchical Self-Assembled Structures from POSS-Containing Block Copolymers Synthesized by Living Anionic Polymerization

    SciTech Connect

    Hirai, Tomoyasu; Leolukman, Melvina; Jin, Sangwoo; Goseki, Raita; Ishida, Yoshihito; Kakimoto, Masa-aki; Hayakawa, Teruaki; Ree, Moonhor; Gopalan, Padma

    2010-03-16

    Two kinds of polyhedral oligomeric silsesquioxane (POSS)-containing block copolymers (BCPs), namely PS-b-PMAPOSS and PMMA-b-PMAPOSS, were synthesized by living anionic polymerization. A wide range of molecular weights were obtained with a very narrow polydispersity index of less than 1.09. The bulk samples prepared by slow evaporation from a polymer solution in chloroform exhibit well-defined microphase-separated structures with long-range order. Thermal annealing induced hierarchical structures consisting of a smaller length scale ordered crystalline POSS domains within the larger microphase-separated structures. We report detailed structural characterization of these hierarchical structures in bulk and thin films by transmission electron microscopy and grazing incidence wide-angle X-ray scattering (GIWAXS). On the basis of this structural analysis, we propose a model for the formation of an orthorhombic lattice structure through the aggregation of POSS segments which formed a helix-like structure.

  16. Self-Assembly of Pluronic Block Copolymers in Solutions: Simulation and Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Zhang, Zhe; Hong, Kunlun; Do, Changwoo; Biology and Soft-Matter Division, Oak Ridge National Laboratory Team; Chemical Science Division, Oak Ridge National Laboratory Team

    2014-03-01

    Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers in water solution display various phase behaviors such as micellar, lamellar, and hexagonal phases and have been of great interest to researchers for their wide range of applications including templates of various nanostructures in solar cell and transportation of nanoparticles in drug delivery. In this study, we combined density functional theory-based mesoscale simulation and small-angle neutron scattering (SANS) experiments to investigate equilibrium structures of L62/water systems at different concentrations. Various simulation parameters found in the literature have been revisited with the experimental findings. Scattering experiments were found to be an excellent. This research is supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Energy Division.

  17. Structure-Property Relationships in CO2-philic (Co)polymers: Phase Behavior, Self-Assembly, and Stabilization of Water/CO2 Emulsions.

    PubMed

    Girard, Etienne; Tassaing, Thierry; Marty, Jean-Daniel; Destarac, Mathias

    2016-04-13

    This Review provides comprehensive guidelines for the design of CO2-philic copolymers through an exhaustive and precise coverage of factors governing the solubility of different classes of polymers. Starting from computational calculations describing the interactions of CO2 with various functionalities, we describe the phase behavior in sc-CO2 of the main families of polymers reported in literature. The self-assembly of amphiphilic copolymers of controlled architecture in supercritical carbon dioxide and their use as stabilizers for water/carbon dioxide emulsions then are covered. The relationships between the structure of such materials and their behavior in solutions and at interfaces are systematically underlined throughout these sections.

  18. Giant Gyroid and Templates from High-Molecular-Weight Block Copolymer Self-assembly

    NASA Astrophysics Data System (ADS)

    Park, Sungmin; Kim, Yeongsik; Ahn, Hyungju; Kim, Jong Hak; Yoo, Pil J.; Ryu, Du Yeol

    2016-11-01

    We present a feasible approach to the direct development of three-dimensionally (3D) bicontinuous gyroid (GYR) nanostructure in high-molecular-weight, composition-controlled polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) films. The use of a neutral solvent vapor to elaborately control the swelling of block copolymer (BCP) films is essential to generate a direct pathway to GYR (or giant GYR) structure through a hexagonal (HEX) cylindrical morphology in the same material, because the thermal ordering of highly entangled BCP imposes the limit on the chain mobility. Along with the improved mechanical strength arising from the high molecular weight property of the polymers, the structural integrity and overall excellence of a large-scale GYR morphology were confirmed by the results of membrane performance, which showed greater permeability through the nanoporous GYR structure up to by a factor of three than that through the HEX structure. Moreover, a 3D nanoporous GYR template was applied to an affordable material to reproduce an inverse skeletal replica of the GYR structure with its structure being uniformly interconnected. This simple approach to the GYR template, owing to its structural tunability in a controlled composition of BCP, is anticipated to be applicable to a wide range of materialization for practical systems.

  19. Self-assembled pentablock copolymers for selective and sustained gene delivery

    SciTech Connect

    Zhang, Bingqi

    2011-05-15

    The poly(diethylaminoethyl methacrylate) (PDEAEM) - Pluronic F127 - PDEAEM pentablock copolymer (PB) gene delivery vector system has been found to possess an inherent selectivity in transfecting cancer cells over non-cancer cells in vitro, without attaching any targeting ligands. In order to understand the mechanism of this selective transfection, three possible intracellular barriers to transfection were investigated in both cancer and non-cancer cells. We concluded that escape from the endocytic pathway served as the primary intracellular barrier for PB-mediated transfection. Most likely, PB vectors were entrapped and rendered non-functional in acidic lysosomes of non-cancer cells, but survived in less acidic lysosomes of cancer cells. The work highlights the importance of identifying intracellular barriers for different gene delivery systems and provides a new paradigm for designing targeting vectors based on intracellular differences between cell types, rather than through the use of targeting ligands. The PB vector was further developed to simultaneously deliver anticancer drugs and genes, which showed a synergistic effect demonstrated by significantly enhanced gene expression in vitro. Due to the thermosensitive gelation behavior, the PB vector packaging both drug and gene was also investigated for its in vitro sustained release properties by using polyethylene glycol diacrylate as a barrier gel to mimic the tumor matrix in vivo. Overall, this work resulted in the development of a gene delivery vector for sustained and selective gene delivery to tumor cells for cancer therapy.

  20. Giant Gyroid and Templates from High-Molecular-Weight Block Copolymer Self-assembly

    PubMed Central

    Park, Sungmin; Kim, Yeongsik; Ahn, Hyungju; Kim, Jong Hak; Yoo, Pil J.; Ryu, Du Yeol

    2016-01-01

    We present a feasible approach to the direct development of three-dimensionally (3D) bicontinuous gyroid (GYR) nanostructure in high-molecular-weight, composition-controlled polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) films. The use of a neutral solvent vapor to elaborately control the swelling of block copolymer (BCP) films is essential to generate a direct pathway to GYR (or giant GYR) structure through a hexagonal (HEX) cylindrical morphology in the same material, because the thermal ordering of highly entangled BCP imposes the limit on the chain mobility. Along with the improved mechanical strength arising from the high molecular weight property of the polymers, the structural integrity and overall excellence of a large-scale GYR morphology were confirmed by the results of membrane performance, which showed greater permeability through the nanoporous GYR structure up to by a factor of three than that through the HEX structure. Moreover, a 3D nanoporous GYR template was applied to an affordable material to reproduce an inverse skeletal replica of the GYR structure with its structure being uniformly interconnected. This simple approach to the GYR template, owing to its structural tunability in a controlled composition of BCP, is anticipated to be applicable to a wide range of materialization for practical systems. PMID:27808242

  1. Self-Assembly of Asymmetrically Interacting ABC Star Triblock Copolymer Melts.

    PubMed

    Jiang, Kai; Zhang, Juan; Liang, Qin

    2015-11-12

    The phase behavior of asymmetrically interacting ABC star triblock copolymer melts is investigated by the self-consistent field theory (SCFT). Motivated by the experimental systems, in this study, we focus on the systems in which the Flory-Huggins interaction parameters satisfy χAC > χ BC ≈ χAB. Using various initialization strategies, a large number of periodic structures have been obtained in our calculations. A fourth-order pseudospectral algorithm combined with Anderson mixing method is used to compute the free energy of candidate structures carefully. The stability has been analyzed in detail by splitting the free energy into internal and entropic parts. A complete and complex triangular phase diagram is presented for a model with χAC > χBC = χAB in which 15 ordered phases, including two- and three-dimensional structures, have been predicted to be stable from the SCFT calculations. Generally speaking, with the asymmetrical interactions, the hierarchical structures tend to be formed near the B-rich corner of the triangular phase diagram. This work broadens the previous theoretical results from equal interaction systems to unequal interaction systems. The predicted phase behavior is in good agreement with experimental observations and previous theoretical results.

  2. Morphology and Dynamics of Tapered Diblock Copolymers from fDFT-initialized MD Simulations

    NASA Astrophysics Data System (ADS)

    Hall, Lisa M.; Seo, Youngmi; Brown, Jonathan R.

    2015-03-01

    Tapered block copolymers are similar to AB diblock copolymers, but with a statistical A-to-B (normal) or B-to-A (inverse) gradient ``taper'' between the A and B blocks. Depending on the sequence of monomers along the chain and the segregation strength, the A and B monomers are known to microphase separate into various ordered morphologies. Tapering introduces an additional parameter, independent of molecular weight or polymer choice, to tune morphology, and has been shown previously to widen the gyroid region of the phase diagram.In this study, we use classical, fluids density functional theory (fDFT) and molecular dynamics (MD) simulations to study the morphology and dynamics of tapered systems. Using fDFT allows us to accurately compare free energies between different potential microphases as a function of interaction parameter and fraction of A. Because of the similarity of the fDFT and MD models, the fDFT results map very closely with the corresponding MD model. We use the fDFT density profiles to generate the initial state of the chains for the simulations. Lamellae, cylinders, and other phases can be generated in this way with approximately correct spacing and density. We apply the streamlined simulation setup to analyze the effect of tapering on conformations and dynamics.

  3. Correlation in SANS χ upon heating and pressurization for a diblock copolymer

    NASA Astrophysics Data System (ADS)

    Cho, Junhan; Lee, Jumi; Ryu, Du Yeol

    2011-03-01

    The response of phase behavior to pressure for an A- b -B diblock copolymer in the disordered state has been studied by small-angle neutron scattering (SANS). Deuterated polystyrene- b -poly(n-propyl methacrylate) (dPS- b -PPrMA) copolymer, which possesses ordering transition upon heating and baroplasticity (suppressed demixing by pressurization), was taken as our model system. It was shown that effective Flory-Huggins parameter χF from scattering intensity profiles upon heating and pressurization forms a characteristic curve that is a function of pressure increment ΔP (≡ P -P0) divided by temperature dependent bulk modulus B0 at a reference pressure P0 . Each isotherm of χF is superposed into the curve by a scale factor τ determined by B0 . The scattering intensity maxima Imax , which is governed by χF , were also shown to reveal a similar superposition. The authors acknowledge support from NRF of Korea through Regional Scientist program and Nuclear R&D program.

  4. Dynamic Monte Carlo simulations of double crystallization accelerated in microdomains of diblock copolymers

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Ma, Yu; Li, Juan; Jiang, Xiaoming; Hu, Wenbing

    2012-03-01

    We report dynamic Monte Carlo simulations of microphase separated diblock copolymers, to investigate how crystallization of one species could accelerate the subsequent crystallization of another species. Although the lattice copolymer model brings a boundary constraint to the long periods of microdomains, the single-molecular-level force balance between two blocks and its change can be revealed in this simple approach. We found two contrastable acceleration mechanisms: (1) the metastable lamellar crystals of one species become thicker at higher crystallization temperatures, sacrificing its microphase interfacial area to make a larger coil-stretching of another amorphous species and hence to accelerate subsequent crystallization of the latter with a more favorable conformation. (2) While in the case allowing chain-sliding in the crystal, the equilibrated lamellar crystals of one species become thinner at higher temperatures, sacrificing its thermal stability to gain a higher conformational entropy of another amorphous species and hence to accelerate subsequent crystallization of the latter with a stronger tension at the block junction. Parallel situations of experiments have been discussed.

  5. Phase behavior of diblock copolymer/star-shaped polymer thin film mixtures.

    PubMed

    Zhao, Junnan; Sakellariou, Georgios; Green, Peter F

    2016-05-07

    We investigated the phase behavior of thin film, thickness h≈ 100 nm, mixtures of a polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer with star-shaped polystyrene (SPS) molecules of varying functionalities f, where 4 ≤f≤ 64, and molecular weights per arm Marm. The miscibility of the system and the surface composition varied appreciably with Marm and f. For large values of Marm, regardless of f, the miscibility of the system was qualitatively similar to that of linear chain PS/PS-b-P2VP mixtures - the copolymer chains aggregate to form micelles, each composed of an inner P2VP core and PS corona, which preferentially segregate to the free surface. On the other hand, for large f and small Marm, SPS molecules preferentially resided at the free surface. Moreover, blends containing SPS molecules with the highest values of f and lowest values of Marm were phase separated. These observations are rationalized in terms of competing entropic interactions and the dependence of the surface tension of the star-shaped molecules on Marm and f.

  6. Structural Evolution of Low-Molecular-Weight Poly(ethylene oxide)-block-polystyrene Diblock Copolymer Thin Film

    PubMed Central

    Huang, Xiaohua

    2013-01-01

    The structural evolution of low-molecular-weight poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer thin film with various initial film thicknesses on silicon substrate under thermal annealing was investigated by atomic force microscopy, optical microscopy, and contact angle measurement. At film thickness below half of the interlamellar spacing of the diblock copolymer (6.2 nm), the entire silicon is covered by a polymer brush with PEO blocks anchored on the Si substrate due to the substrate-induced effect. When the film is thicker than 6.2 nm, a dense polymer brush which is equal to half of an interlamellar layer was formed on the silicon, while the excess material dewet this layer to form droplets. The droplet surface was rich with PS block and the PEO block crystallized inside the bigger droplet to form spherulite. PMID:24302862

  7. Structural evolution of low-molecular-weight poly(ethylene oxide)-block-polystyrene diblock copolymer thin film.

    PubMed

    Wu, Hui; Huang, Xiaohua

    2013-01-01

    The structural evolution of low-molecular-weight poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer thin film with various initial film thicknesses on silicon substrate under thermal annealing was investigated by atomic force microscopy, optical microscopy, and contact angle measurement. At film thickness below half of the interlamellar spacing of the diblock copolymer (6.2 nm), the entire silicon is covered by a polymer brush with PEO blocks anchored on the Si substrate due to the substrate-induced effect. When the film is thicker than 6.2 nm, a dense polymer brush which is equal to half of an interlamellar layer was formed on the silicon, while the excess material dewet this layer to form droplets. The droplet surface was rich with PS block and the PEO block crystallized inside the bigger droplet to form spherulite.

  8. Effects of interaction range and compressibility on the microphase separation of diblock copolymers: Mean-field analysis.

    PubMed

    Wang, Qiang

    2008-08-07

    Using the random-phase approximation and self-consistent field calculations, we have investigated the effects of finite interaction range and compressibility on the order-disorder transition (ODT) and the lamellar structure of symmetric diblock copolymers. While the compressibility does not affect the ODT, both the values of chiN and bulk lamellar period at the ODT increase with increasing interaction range. On the other hand, both the free-energy density and bulk period of the lamellae increase with either increasing interaction range or decreasing compressibility. Even with a finite compressibility, the mean-field ODT is still a second-order phase transition. The scaling exponent of bulk lamellar period with chiN, however, decreases with increasing compressibility. Our mean-field analysis provides a well understood reference for the study of fluctuation effects in diblock copolymers with finite interaction range and compressibility.

  9. Hemicellulose block copolymers made from woods for wide-range directed self-assembly lithography enabling wider range of applicable patterning size

    NASA Astrophysics Data System (ADS)

    Morita, Kazuyo; Yamamoto, Kimiko

    2017-03-01

    Xylan, one of hemicellulose family, block copolymer was newly developed for wide-range directed self-assembly lithography (DSA). Xylan is higher hydrophilic material because of having many hydroxy groups in one molecule. It means that xylan block copolymer has a possibility of high-chi block copolymer. Generally, DSA is focused on microphase separation for smaller size with high-chi block copolymer and not well known for larger size. In this study, xylan block copolymer was confirmed enabling wider range of patterning size, from smaller size to larger size. The key of xylan block copolymer is a new molecular structure of block copolymer and sugar chain control technology. Sugar content is the important parameter for not only micro-phase separation property but also line edge roughness (LER) and defects. Based on the sugar control technology, wide-range (hp 8.3nm to 26nm L/S and CD 10nm to 51nm hole) DSA patterning was demonstrated. Additionally it was confirmed that xylan block copolymer is suitable for sequential infiltration synthesis (SIS) process.

  10. Diblock copolymers of polystyrene-b-poly(1,3-cyclohexadiene) exhibiting unique three-phase microdomain morphologies

    DOE PAGES

    Misichronis, Konstantinos; Chen, Jihua; Kahk, Jong K.; ...

    2016-03-29

    Here, the synthesis and molecular characterization of a series of conformationally asymmetric polystyrene-block-poly(1,3-cyclohexadiene) (PS-b-PCHD) diblock copolymers (PCHD: ~90% 1,4 and ~10% 1,2), by sequential anionic copolymerization high vacuum techniques, is reported. A wide range of volume fractions (0.27 ≤ ΦPS ≤ 0.91) was studied by transmission electron microscopy and small-angle X-ray scattering in order to explore in detail the microphase separation behavior of these flexible/semiflexible diblock copolymers. Unusual morphologies, consisting of PCHD core(PCHD-1,4)–shell(PCHD-1,2) cylinders in PS matrix and three-phase (PS, PCHD-1,4, PCHD-1,2) four-layer lamellae, were observed suggesting that the chain stiffness of the PCHD block and the strong dependence ofmore » the interaction parameter χ on the PCHD microstructures are important factors for the formation of this unusual microphase separation behavior in PS-b-PCHD diblock copolymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1564–1572« less

  11. Diblock copolymers of polystyrene-b-poly(1,3-cyclohexadiene) exhibiting unique three-phase microdomain morphologies

    SciTech Connect

    Misichronis, Konstantinos; Chen, Jihua; Kahk, Jong K.; Imel, Adam; Dadmun, Mark; Hong, Kunlun; Hadjichristidis, Nikos; Mays, Jimmy W.; Avgeropoulos, Apostolos

    2016-03-29

    Here, the synthesis and molecular characterization of a series of conformationally asymmetric polystyrene-block-poly(1,3-cyclohexadiene) (PS-b-PCHD) diblock copolymers (PCHD: ~90% 1,4 and ~10% 1,2), by sequential anionic copolymerization high vacuum techniques, is reported. A wide range of volume fractions (0.27 ≤ ΦPS ≤ 0.91) was studied by transmission electron microscopy and s