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Sample records for block copolymer pluronic

  1. Anomalous Micellization of Pluronic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Leonardi, Amanda; Ryu, Chang Y.

    2014-03-01

    Poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) (PEO-PPO-PEO) block copolymers, commercially known as Pluronics, are a unique family of amphiphilic triblock polymers, which self-assemble into micelles in aqueous solution. These copolymers have shown promise in therapeutic, biomedical, cosmetic, and nanotech applications. As-received samples of Pluronics contain low molecular weight impurities (introduced during the manufacturing and processing), that are ignored in most applications. It has been observed, however, that in semi-dilute aqueous solutions, at concentrations above 1 wt%, the temperature dependent micellization behavior of the Pluronics is altered. Anomalous behavior includes a shift of the critical micellization temperature and formation of large aggregates at intermediate temperatures before stable sized micelles form. We attribute this behavior to the low molecular weight impurities that are inherent to the Pluronics which interfere with the micellization process. Through the use of Dynamic Light Scattering and HPLC, we compared the anomalous behavior of different Pluronics of different impurity levels to their purified counterparts.

  2. Preclinical evaluation of radiosensitizing activity of Pluronic block copolymers

    PubMed Central

    Perera, Reshani H.; Patel, Ravi; Wu, Hanping; Gangolli, Mihika; Traughber, Bryan; Oleinick, Nancy; Exner, Agata A.

    2014-01-01

    Purpose Pluronic block copolymers are non-ionic surfactants with demonstrated sensitizing activity in chemotherapy and hyperthermia in various tumor cell lines. In the current study we investigated the potential activity of Pluronic as a radiosensitizing agent. Materials and methods As a possible mechanism, the effect of Pluronic on Hsp70 and Hsp90 was examined. Gli36 human glioma cells were treated with radiation alone as well as with a combination treatment of Pluronic and radiation. Results Clonogenic cell survival assays show that Pluronic has an elevated effect on radiosensitization (50% high, p < 0.01), even with radiation doses as low as 2 Gy. The Hsp90 level was reduced 24 h after the combined treatment in both in vitro and in vivo. Similarly, Hsp70 levels were also decreased 24 h post treatment. When Gli36 cells were exposed to Pluronic before and during irradiation, DNA DSB: double-strand breaks repair was reduced, and elevated apoptosis was also seen in tumor xenografts. Conclusion Data suggest the potential use of L10 as a radiosensitizer. While the mechanism of sensitization requires additional investigation, the presented results indicate that the effect may be due, in part, to a decrease in Hsp90 and 70 levels and increased DNA damage. PMID:23631609

  3. Micellar Packing in Aqueous Solutions of As-Received and Pure Pluronic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Ryu, Chang; Park, Han Jin

    2013-03-01

    Pluronic block copolymers (Pluronics) are produced on a commercial scale to enable wide range of novel applications from emulsification and colloidal stabilization as nonionic surfactants. While the Pluronic block copolymers offer the advantages of being readily available for such applications, it contains non-micellizable low molecular weight (MW) impurities that would interfere with the self-assembly and micellar packing of PEO-PPO-PEO triblock copolymers in aqueous solutions. The impacts of the low MW impurities will be discussed on the micellar packing of Pluronics F108 and F127 solutions, which form BCC and FCC. While as-received Pluronic samples typically contain about 20 wt.% low MW impurities, we were able to reduce the impurity level to less than 2 wt.% using our large scale purification technique. Comparative studies on small angle x-ray scattering (SAXS) experiments on as-received and purified Pluronics solutions revealed that the contents of triblock copolymers in solutions essentially governs the inter-micellar distance of Pluronic cubic structures. A universal relationship between triblock copolymer concentration and SAXS-based domain spacing has been finally discussed. Funding from Agency for Defense Development, Korea.

  4. Phase Behavior and Micellar Packing of Impurity-Free Pluronic Block Copolymers in Water

    NASA Astrophysics Data System (ADS)

    Ryu, Chang Yeol; Park, Hanjin

    We have investigated the impacts of the non-micellizable polymeric impurities on the micellar packing and solution phase behavior of Pluronic block copolymers in water. In particular, small angle x-ray scattering, rheology and dynamic light scattering techniques have been employed to elucidate how the low MW impurities affect the micellar packing and solution phase diagram in water, when ordered cubic structures of spherical micelles are formed. A silica slurry method has been developed using the competitive adsorption of the PEO-PPO-PEO triblock copolymers over the low MW polymeric impurities for a large scale purification of Pluronics and it purity of Pluronics has been assessed by interaction chromatography. Based on the comparative studies on micellar packing between As-Received (AR) and Purified (Pure) Pluronic F108 solutions, we found experimental evidence to support the hypothesis that the inter-micellar distance of Pluronic cubic structures in aqueous solution is governed by the effective polymer concentration in terms of PEO-PPO-PEO triblock copolymers. Removal of the impurities in AR F108 offers an important clue on window into the onset of BCC ordering via hydrodynamic contact between micelles in solution. NSF DMR Polymers.

  5. Mechanism of sensitization of MDR cancer cells by Pluronic block copolymers: Selective energy depletion

    PubMed Central

    Batrakova, E V; Li, S; Elmquist, W F; Miller, D W; Alakhov, V Y; Kabanov, A V

    2001-01-01

    This paper, for the first time, demonstrates that exposure of cells to the poly(ethylene oxide)-poly(propylene oxide) block copolymer, Pluronic P85, results in a substantial decrease in ATP levels selectively in MDR cells. Cells expressing high levels of functional P-glycoprotein (MCF-7/ADR, KBv; LLC-MDR1; Caco-2, bovine brain microvessel endothelial cells [BBMECs]) are highly responsive to Pluronic treatment, while cells with low levels of P-glycoprotein expression (MCF-7, KB, LLC-PK1, human umbilical vein endothelial cells [HUVECs] C2C12 myoblasts) are much less responsive to such treatment. Cytotoxicity studies suggest that Pluronic acts as a chemosensitizer and potentiates cytotoxic effects of doxorubicin in MDR cells. The ability of Pluronic to inhibit P-glycoprotein and sensitize MDR cells appears to be a result of ATP depletion. Because many mechanisms of drug resistance are energy dependent, a successful strategy for treating MDR cancer could be based on selective energy depletion in MDR cells. Therefore, the finding of the energy-depleting effects of Pluronic P85, in combination with its sensitization effects is of considerable theoretical and practical significance. © 2001 Cancer Research Campaign http://www.bjcancer.com PMID:11747344

  6. Interactions of Pluronic Block Copolymers on P-gp Efflux Activity: Experience With HIV-1 Protease Inhibitors

    PubMed Central

    SHAIK, NAVEED; PAN, GUOYU; ELMQUIST, WILLIAM F.

    2016-01-01

    The objective was to examine the influence of Pluronic block-copolymers on the interaction between the drug efflux transporter, P-glycoprotein and HIV-1 protease inhibitors (PIs). The ATPase assay determined the effect of various Pluronics on PI-stimulated P-gp ATPase activity. Cellular accumulation studies were conducted using MDCKII and LLC-PK1 cells transfected with human MDR1 to assess Pluronic modulation of PI efflux. Pluronic P85 inhibited both basal and nelfinavir-stimulated P-gp ATPase activity, while Pluronic F127 had no effect. In cell accumulation studies, Pluronic P85 restored the accumulation of nelfinavir in MDCKII-MDR1 cells while Pluronic F127 and F88 had no effect. Pluronic P85 increased saquinavir accumulation in wild-type and MDR1-transfected cells in both the MDCKII and LLC-PK1 cell models, suggesting inhibition of multiple transporters, including MRPs. In conclusion, this study provides evidence that a block-copolymer, Pluronic P85, effectively inhibits the interaction of P-gp with nelfinavir and saquinavir. These data indicate that effective inhibition of HIV-1 PI efflux by Pluronic P85 may influence the distribution of antiretroviral agents to sites protected by efflux mechanisms, such as the blood–brain barrier, and possibly increase the brain exposure of these drugs resulting in suppression of viral replication and reduction in the incidence of drug resistant mutants. PMID:18393290

  7. Microviscosity in Pluronic and Tetronic poly(ethylene oxide)-poly(propylene oxide) block copolymer micelles

    SciTech Connect

    Nivaggioli, T.; Tsao, B.; Alexandridis, P.; Hatton, T.A. )

    1995-01-01

    The micellar microviscosity afforded by Pluronic and Tetronic poly(ethylene oxide)-poly(propylene oxide) block copolymer aqueous solutions has been investigated by fluorescence and NMR spectroscopy. Comparison is made with bulk poly(propylene oxide) (PPO) samples of different molecular weights. The microviscosity in Pluronic PEO-PPO-PEO copolymer micelles is much larger than that observed in conventional surfactant micelles and depends strongly on the size of the hydrophobic PPO block: the larger this block, the higher the viscosity. Above the critical micellar temperature (CMT), as temperature increases, the microviscosity decreases. However, this decrease is not as important as that observed in bulk PPO. Hence, the relative microviscosity, defined as the ratio of the two observed phenomena, increases. This suggests structural transformation of the micelles resulting in a core becoming more and more compact as temperature increases. Such results have been confirmed by NMR studies that showed broadening of the PPO peak and relatively constant spin-lattice relaxation time, T[sub i], with increasing temperature while the PEO signal remained relatively sharp with an exponential increase in T[sub 1]. 30 refs., 9 figs., 1 tab.

  8. Horizontal Gene Transfer from Macrophages to Ischemic Muscles upon Delivery of Naked DNA with Pluronic Block Copolymers

    PubMed Central

    Mahajan, Vivek; Gaymalov, Zagit; Alakhova, Daria; Gupta, Richa; Zucker, Irving H.; Kabanov, Alexander V.

    2015-01-01

    Intramuscular administration of plasmid DNA (pDNA) with non-ionic Pluronic block copolymers increases gene expression in injected muscles and lymphoid organs. We studied the role of immune cells in muscle transfection upon inflammation. Local inflammation in murine hind limb ischemia model (MHLIM) drastically increased DNA, RNA and expressed protein levels in ischemic muscles injected with pDNA/Pluronic. The systemic inflammation (MHLIM or peritonitis) also increased expression of pDNA/Pluronic in the muscles. When pDNA/Pluronic was injected in ischemic muscles the reporter gene, Green Fluorescent Protein (GFP) co-localized with desmin+ muscle fibers and CD11b+ macrophages (MØs), suggesting transfection of MØs along with the muscle cells. P85 enhanced (~4 orders) transfection of MØs with pDNA in vitro. Moreover, adoptively transferred MØs were shown to pass the transgene to inflamed muscle cells in MHLIM. Using a co-culture of myotubes (MTs) and transfected MØs expressing a reporter gene under constitutive (cmv-luciferase) or muscle specific (desmin-luciferase) promoter we demonstrated that P85 enhances horizontal gene transfer from MØ to MTs. Therefore, MØs can play an important role in muscle transfection with pDNA/Pluronic during inflammation, with both inflammation and Pluronic contributing to the increased gene expression. pDNA/Pluronic has potential for therapeutic gene delivery in muscle pathologies that involve inflammation. PMID:26480472

  9. Horizontal gene transfer from macrophages to ischemic muscles upon delivery of naked DNA with Pluronic block copolymers.

    PubMed

    Mahajan, Vivek; Gaymalov, Zagit; Alakhova, Daria; Gupta, Richa; Zucker, Irving H; Kabanov, Alexander V

    2016-01-01

    Intramuscular administration of plasmid DNA (pDNA) with non-ionic Pluronic block copolymers increases gene expression in injected muscles and lymphoid organs. We studied the role of immune cells in muscle transfection upon inflammation. Local inflammation in murine hind limb ischemia model (MHLIM) drastically increased DNA, RNA and expressed protein levels in ischemic muscles injected with pDNA/Pluronic. The systemic inflammation (MHLIM or peritonitis) also increased expression of pDNA/Pluronic in the muscles. When pDNA/Pluronic was injected in ischemic muscles the reporter gene, Green Fluorescent Protein (GFP) co-localized with desmin(+) muscle fibers and CD11b(+) macrophages (MØs), suggesting transfection of MØs along with the muscle cells. P85 enhanced (∼ 4 orders) transfection of MØs with pDNA in vitro. Moreover, adoptively transferred MØs were shown to pass the transgene to inflamed muscle cells in MHLIM. Using a co-culture of myotubes (MTs) and transfected MØs expressing a reporter gene under constitutive (cmv-luciferase) or muscle specific (desmin-luciferase) promoter we demonstrated that P85 enhances horizontal gene transfer from MØ to MTs. Therefore, MØs can play an important role in muscle transfection with pDNA/Pluronic during inflammation, with both inflammation and Pluronic contributing to the increased gene expression. pDNA/Pluronic has potential for therapeutic gene delivery in muscle pathologies that involve inflammation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Pluronic-P105 PEO-PPO-PEO block copolymer in aqueous urea solutions. Micelle formation, structure, and microenvironment

    SciTech Connect

    Alexandridis, P.; Athanassiou, V.; Hatton, T.A.

    1995-07-01

    The effects of urea on the micellization properties of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) copolymer (commercially available as Pluronic P105) and on the structure and microenvironment of the micelles are reported. Urea increased the critical micelle concentration (cmc) and critical micelle temperature (cmt) of the PEO-PPO-PEO copolymer; the effect of urea on the cmt was more pronounced at low copolymer concentrations and diminished at concentrations of nearly 2.5%. The surface activity and the partial specific volume of the block copolymer decreased with an increase in the urea concentration, whereas the hydrodynamic radii of the copolymer micelles, determined using dynamic light scattering, remained unaffected by the presence of 4 M urea in the solution. The micropolarity in copolymer solutions in urea/water was probed as a function of temperature using the I{sub 1}/I{sub 3} intensity ratio of the pyrene vibrational fine structure recorded in fluorescence emission spectra; a small decrease in the micropolarity of the micelle core was observed in the presence of urea. The microviscosity in the micelle interior, estimated from the intramolecular excimer fluorescence of the hydrophobic probe bis(1-pyrenylmethyl) ether (dipyme), also exhibited a small decrease with an increase in the urea concentration. 80 refs., 8 figs.

  11. Physicochemical characterization, solubilization, and stabilization of 9-nitrocamptothecin using pluronic block copolymers.

    PubMed

    Saha, Sohodeb C; Patel, Deval; Rahman, Shahidur; Savva, Michalakis

    2013-10-01

    Solid-state properties and physicochemical characteristics of 9-nitrocamptothecin (9NC) were investigated with a view of molecular and bulk level understanding of its poor aqueous solubility and hydrolytic instability that prevent efficient drug delivery and pharmacological activity. 9NC bulk drug substance was found to be a nonhygroscopic, yellowish crystalline solid with long rectangular prism-shaped particle morphology and a sharp melting point at 264°C. Hydrolysis of 9NC-lactone occurs above pH 4, whereas complete conversion of lactone to carboxylate was recorded above pH 8. At saturated conditions, appreciable concentrations of 9NC-lactone were detected at pH as high as 11. 9NC undergoes oxidation in the presence of dimethyl sulfoxide with formation of 9NC-N-oxide. The total solubility of lactone and carboxylate forms of 9NC in deionized water was found to be less than 5 μg/mL, whereas the solubility of 9NC-lactone in aqueous acidic media was determined to be approximately 2.5 μg/mL. Incorporation of 10% pluronic copolymers P123, F127, and F68 in 10 mM HCl increased 9NC solubility by 13-fold, eightfold, and fivefold, respectively. The thermodynamic stability of drug-loaded pluronic micelles was evaluated under isothermal variable volume conditions and found F127, among all poloxamers, to offer the best hydrolytic protection efficacy for 9NC. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

  12. Micellar solubilization of tributylphosphate in aqueous solutions of Pluronic block copolymers. Part I. Effect of the copolymer structure and temperature on the phase behavior.

    PubMed

    Causse, J; Lagerge, S; de Menorval, L C; Faure, S

    2006-08-15

    Solubilization of tributylphosphate (TBP), a polar oil, in various micellar solutions of Pluronic has been investigated by turbidimetry emphasizing the effect of temperature and the role of the PPO and PEO blocks on the phase behavior of the three components systems (Pluronic-TBP-water). [Temperature-composition] diagrams allow monophasic and diphasic domains to be delimited. Two temperatures are shown to have a determining effect on the phase behavior (TBP solubilization); the well known cloud point temperature (CPT, here defined for the three components system) and the solubilization minimum temperature (SMT) which is defined as the lowest temperature allowing solubilization of TBP in the system. Both temperature depend on the copolymer structure and, interestingly, are directly related to the TBP concentration in the medium. Monophasic microemulsions are observed when the temperature ranges between the SMT and the CPT. When TCPT the system separates in two phase due to the co-precipitation of TBP and Pluronic. Moreover an unexpected evolution of the CPT with the TBP content clearly indicates the occurrence of a structural change of the microemulsions which allows higher quantities of TBP to be solubilized. But the structural change does not allow alone higher quantities of TBP to be solubilized. A well compromise between the SMT and the CPT must be also observed so as to obtain a large extent of monophasic domain after the restructuration. The best compromise is obtained with Pluronics with intermediate hydrophobic character. Reversely, hydrophobic and hydrophilic Pluronics exhibit a very small extent of monophasic domain after the restructuration which does not allow benefit by the structural change.

  13. Shape-controlled synthesis of gold icosahedra and nanoplates using Pluronic P123 block copolymer and sodium chloride

    SciTech Connect

    Lee, Won-Ki; Cha, Sang-Ho; Kim, Ki-Hyun; Kim, Byung-Woo; Lee, Jong-Chan

    2009-12-15

    Gold icosahedra with an average diameter of about 600 nm were easily prepared by heating an aqueous solution of the amphiphilic block copolymer, poly(ethylene oxide){sub 20}-poly(propylene oxide){sub 70}-poly(ethylene oxide){sub 20} (Pluronic P123), and hydrogen tetrachloroaurate(III) trihydrate (HAuCl{sub 4}.3H{sub 2}O) at 60 deg. C for 25 min. When sodium chloride (NaCl:HAuCl{sub 4} molar ratio=10:1) was added to this aqueous solution, gold nanoplates were produced. The chloride ion was found to be a key component in the formation of the gold nanoplates by facilitating the growth of {l_brace}111{r_brace} oriented hexagonal/triangular gold nanoplates, because similar gold nanoplates were produced when LiCl or KCl was added to the aqueous solution instead of NaCl, while gold nanocrystals having irregular shapes were produced when NaBr or NaI was added. - Graphical abstract: Gold icosahedra were prepared by heating an aqueous solution of Pluronic P123 and HAuCl{sub 4}. When NaCl was added to this solution, gold nanoplates were produced.

  14. Micellar solubilization of tributylphosphate in aqueous solutions of Pluronic block copolymers. Part II. Structural characterization inferred by 1H NMR.

    PubMed

    Causse, J; Lagerge, S; de Menorval, L C; Faure, S

    2006-08-15

    The solubilization of tributylphosphate (TBP), a polar oil, in various micellar solutions of Pluronic has been investigated by (1)H NMR spectroscopy. Partial phase diagrams of the three components systems (Pluronic-TBP-water) have shown two characteristic temperatures, called CPT and SMT, which control the phase behavior (see Part I); Both temperature depend on the copolymer structure and, interestingly, are directly related to the TBP concentration in the medium. Monophasic microemulsions are observed only when the temperature ranges between the SMT and the CPT. Moreover, the evolution of the CPT with the TBP content clearly indicated the occurrence of a structural change of the microemulsions which allows higher quantities of TBP to be solubilized. In this second part, (1)H NMR studies of TPB/micellar systems have essentially focused on elucidating the nature of the interactions between TBP and micelle, or on the location of the solubilized species, mainly from the dependence of chemical shifts or linewidths on TBP concentration. Especially, the NMR spectra of the microemulsions before and after the structural change have been compared with those obtained for pure solution of Pluronic in D(2)O at different temperatures and in CDCl(3). The analysis of the (1)H NMR chemical shifts suggests a structural transformation of the TBP-Pluronic micelles in the sense of an hydrophobic TBP-PPO core becoming more and more dense as the TBP concentration increases. Especially, (1)H NMR data evidence an evolution of the hydration state of the hydrophobic core following addition of TBP in the micellar solutions. During the addition of TBP, the microemulsion structure turns from spherical swelled micelles to nanodroplets of pure TBP stabilized by the Pluronic (pure nanophase of TBP stabilized by the copolymer). It is shown that the structural change strongly depends on the temperatures (CPT and SMT, see Part I) and on the copolymer structure.

  15. 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.

  16. Hydrogen-bonded polymer complexes and nanocages of weak polyacids templated by a Pluronic® block copolymer.

    PubMed

    Wang, Yuhao; Sukhishvili, Svetlana A

    2016-10-26

    We investigate the phase behavior, morphology, and temperature response of hydrogen-bonded assemblies formed by a triblock copolymer Pluronic® F127 (F127) and polycarboxylic acids of varied hydrophobicity and chain lengths. As confirmed by FTIR, the complexes of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) with F127 at acidic pH were stabilized by multiple hydrogen bonding between carboxylic acid groups of polyacids and ether groups of F127. The colloidal stability of the polyacid/F127 complexes (their occurrence as stable dispersions, slowly coagulating dispersions or precipitates) was dependent on the composition of complexes, polyacid molecular weight and hydrophobicity, as well as temperature. For both polyacids, complexes could not be solubilized in excess of polyacids, but excess of F127 resulted in the formation of colloidally stable nanostructured clusters whose size could be controlled from tens to hundreds of nanometers by the polyacid-to-F127 ratio, temperature, and the polyacid molecular weight. Hydrophobicity of polyacids had a dramatic effect on the temperature response of Pluronic®-enriched assemblies. While PMAA suppressed the LCST behavior of F127 due to binding within the temperature-responsive PPO core of F127, more hydrophilic PAA allowed F127 micellization and supported reversible, temperature-induced re-structuring of PAA-F127 clusters. At temperatures above the LCST of Pluronic®, low-molecular-weight PAA formed nanosized dispersed complexes, in which the polyacid chains were wrapped around individual F127 micelles. Chemical crosslinking of PAA in the shells of these complexes followed by removal of the templating F127 cores resulted in easy-to-prepare monodisperse pH-responsive polymer nanocages with controllable size and swelling amplitude.

  17. Temperature effects on structural properties of pluronic P104 and F108 PEO-PPO-PEO block copolymer solutions

    SciTech Connect

    Alexandridis, P.; Nivaggioli, T.; Hatton, T.A.

    1995-05-01

    The effects of temperature on the micellization properties and the structure of the micelles for two poly(ethylene-oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) copolymers, having similar size hydrophobic (PPO) blocks and different size hydrophilic (PEO) blocks, are reported. Critical micellization concentration (CMC) and temperature (CMT) values for aqueous copolymer solutions were obtained from a dye solubilization method and corroborated with differential scanning calorimetry, surface tension, density, light scattering intensity, and fluorescence spectroscopy experiments; very good agreement among the different techniques is observed. The extraction of CMC and CMT values from the characteristic features of the data obtained from the various techniques is discussed. The hydrodynamic radii of the copolymer micelles, determined using dynamic light scattering, remained constant over the temperature range investigated; the polydispersity of the micelle size decreased with temperature. The micropolarity in aqueous copolymer solutions was probed as a function of temperature using the I{sub 1}/I{sub 3} intensity ratio of the pyrene vibrational fine structure recorded in fluorescence emission spectra. The decreasing values for the intensity ratio, following the formation of micelles, were considered to be a linear combination of the temperature effects on polarity observed in bulk PEO and PPO homopolymers, and in water. 59 refs., 10 figs., 2 tabs.

  18. The Effect of the Nonionic Block Copolymer Pluronic P85 on Gene Expression in Mouse Muscle and Antigen Presenting Cells

    PubMed Central

    Gaymalov, Zagit Z.; Yang, Zhihui; Pisarev, Vladimir M.; Alakhov, Valery Yu.; Kabanov, Alexander V.

    2008-01-01

    DNA vaccines can be greatly improved by polymer agents that simultaneously increase transgene expression and activate immunity. We describe here Pluronic P85 (P85), a triblock copolymer of ethylene oxide (EO) and propylene oxide (PO) EO26-PO40-EO26,. Using a mouse model we demonstrate that co-administration of a bacterial plasmid DNA with P85 in a skeletal muscle greatly increases gene expression in the injection site and distant organs, especially the draining lymph nodes and spleen. The reporter expression colocalizes with the specific markers of myocytes and keratinocytes in the muscle, as well as dendritic cells (DC) and macrophages in the muscle, lymph nodes and spleen. Furthermore, DNA/P85 and P85 alone increase the systemic expansion of CD11c+ (DC), and local expansion of CD11c+, CD14+ (macrophages) and CD49b+ (natural killer) cell populations. DNA/P85 (but not P85) also increases maturation of local DC (CD11c+CD86+, CD11c+CD80+, and CD11c+CD40+). We suggest that DNA/P85 promotes the activation and recruitment of the antigen-presenting cells, which further incorporate, express and carry the transgene to the immune system organs. PMID:19064283

  19. Nimodipine-Loaded Pluronic® Block Copolymer Micelles: Preparation, Characterization, In-vitro and In-vivo Studies

    PubMed Central

    Sotoudegan, Farzaneh; Amini, Mohsen; Faizi, Mehrdad; Aboofazeli, Reza

    2016-01-01

    Nimodipine (NM), as a lipophilic calcium channel blocker indicated for the prevention and treatment of neurological disorders, suffers from an extensive first pass metabolism, resulting in low oral bioavailability. Polymeric micelles, self-assembled from amphiphilic polymers, have a core-shell structure which makes them unique nano-carriers with excellent performance as drug delivery. This investigation was aimed to develop NM-loaded polymeric micelles and evaluate their potential to cross the blood brain barrier (BBB). Micelles from Pluronics®P85, F127 and F68 were fabricated for the delivery of NM, using thin film hydration and direct dissolution techniques. Critical micelle concentration of the drug-free micelles was determined by pyrene fluorescence spectroscopy. Dynamic light scattering showed that in most cases, micelles less than 100 nm and low polydispersity indices were successfully developed. Transmission electron microscopy demonstrated spherical shape of micelles. The NM-loaded micelles were also characterized for particle size, morphology, entrapment efficiency, drug loading , in vitro drug release in phosphate buffer and artificial cerebrospinal fluid (CSF). Stability was assessed from size analysis, clarity of dispersion on standing and EE(%), following 3 months storage at room temperature. The in-vitro release of NM from polymeric micelles presented the sustained-release profile. Animal studies revealed the existence of fluorescein 5-isothiocyanate-labeled micelles in rat CSF following intraperitoneal administration, proving that the micelles crossed the BBB. Anticonvulsant effect of NM was shown to be significantly greater than that of NM solution. Our results confirmed that Pluronic micelles might serve as a potential nanocarrier to improve the activity of NM in brain. PMID:28243263

  20. The Membrane-Active Tri-Block Copolymer Pluronic F-68 Profoundly Rescues Rat Hippocampal Neurons from Oxygen–Glucose Deprivation-Induced Death through Early Inhibition of Apoptosis

    PubMed Central

    Shelat, Phullara B.; Plant, Leigh D.; Wang, Janice C.; Lee, Elizabeth

    2013-01-01

    Pluronic F-68, an 80% hydrophilic member of the Pluronic family of polyethylene-polypropylene-polyethylene tri-block copolymers, protects non-neuronal cells from traumatic injuries and rescues hippocampal neurons from excitotoxic and oxidative insults. F-68 interacts directly with lipid membranes and restores membrane function after direct membrane damage. Here, we demonstrate the efficacy of Pluronic F-68 in rescuing rat hippocampal neurons from apoptosis after oxygen–glucose deprivation (OGD). OGD progressively decreased neuronal survival over 48 h in a severity-dependent manner, the majority of cell death occurring after 12 h after OGD. Administration of F-68 for 48 h after OGD rescued neurons from death in a dose-dependent manner. At its optimal concentration (30 μm), F-68 rescued all neurons that would have died after the first hour after OGD. This level of rescue persisted when F-68 administration was delayed 12 h after OGD. F-68 did not alter electrophysiological parameters controlling excitability, NMDA receptor-activated currents, or NMDA-induced increases in cytosolic calcium concentrations. However, F-68 treatment prevented phosphatidylserine externalization, caspase activation, loss of mitochondrial membrane potential, and BAX translocation to mitochondria, indicating that F-68 alters apoptotic mechanisms early in the intrinsic pathway of apoptosis. The profound neuronal rescue provided by F-68 after OGD and the high level of efficacy with delayed administration indicate that Pluronic copolymers may provide a novel, membrane-targeted approach to rescuing neurons after brain ischemia. The ability of membrane-active agents to block apoptosis suggests that membranes or their lipid components play prominent roles in injury-induced apoptosis. PMID:23884935

  1. Study In Vivo Intraocular Biocompatibility of In Situ Gelation Hydrogels: Poly(2-Ethyl Oxazoline)-Block-Poly(ε-Caprolactone)-Block-Poly(2-Ethyl Oxazoline) Copolymer, Matrigel and Pluronic F127

    PubMed Central

    Hwang, Yih-Shiou; Chiang, Ping-Ray; Hong, Wei-Hsin; Chiao, Chuan-Chin; Chu, I-Ming; Hsiue, Ging-Ho; Shen, Chia-Rui

    2013-01-01

    The long term in vivo biocompatibility is an essential feature for the design and development of sustained drug release carriers. In the recent intraocular drug delivery studies, hydrogels were suggested as sustained release carriers. The biocompatibility test for these hydrogels, however, was commonly performed only through in vitro cell culture examination, which is insufficient before the clinical applications. We compared three thermosensitive hydrogels that have been suggested as the carriers for drugs by their gel-solution phase-change properties. A new block terpolymer (PEOz-PCL-PEOz, ECE) and two commercial products (Matrigel® and Pluronic F127) were studied. The results demonstrated that the ocular media remained translucent for ECE and Pluronic F127 in the first 2 weeks, but cataract formation for Matrigel occurred in 2 weeks and for Pluronic F127 in 1 month, while turbid media was observed for both Matrigel and Pluronic F127 in 2 months. The electrophysiology examinations showed significant neuroretinal toxicity of Matrigel and Pluronic F127 but good biocompatibility of ECE. The neuroretinal toxicity of Matrigel and Pluronic F127 and superior biocompatibility of ECE hydrogel suggests ECE as more appropriate biomaterial for use in research and potentially in intraocular application. PMID:23840873

  2. Study of Low Molecular Weight Impurities in Pluronic Triblock Copolymers using MALDI, Interaction Chromatography, and NMR

    NASA Astrophysics Data System (ADS)

    Helming, Z.; Zagorevski, D.; Ryu, C. Y.

    2014-03-01

    Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers are a group of commercial macromolecular amphiphilic surfactants that have been widely studied for their applications in polymer-based nanotechnology and drug-delivery. It has been well-established that the synthesis of commercial Pluronic triblocks results in low molecular weight ``impurities,'' which are generally disregarded in the applications and study of these polymers. These species have been shown to have significant effects on the rheological properties of the material, as well as altering the supramolecular ``micellar'' structures for which the polymers are most often used. We have isolated the impurities from the bulk Pluronic triblock using Interaction Chromatography (IC) techniques, and subjected them to analysis by H1 NMR and MALDI (Matrix-Assisted Laser Desorption Ionization) Mass Spectrometry to identify relative block composition and molecular weight information. We report significant evidence of at least two polymeric components: a low-molecular-weight homopolymer of poly(ethylene oxide) and a ``blocky'' copolymer of both poly(ethylene oxide) and poly(propylene oxide). This has significant implications, not only for the applied usage of Pluronic triblock copolymers, but for the general scientific acceptance of the impurities and their effects on Pluronic micelle and hydrogel formation.

  3. Protein based Block Copolymers

    PubMed Central

    Rabotyagova, Olena S.; Cebe, Peggy; Kaplan, David L.

    2011-01-01

    Advances in genetic engineering have led to the synthesis of protein-based block copolymers with control of chemistry and molecular weight, resulting in unique physical and biological properties. The benefits from incorporating peptide blocks into copolymer designs arise from the fundamental properties of proteins to adopt ordered conformations and to undergo self-assembly, providing control over structure formation at various length scales when compared to conventional block copolymers. This review covers the synthesis, structure, assembly, properties, and applications of protein-based block copolymers. PMID:21235251

  4. Block copolymer battery separator

    DOEpatents

    Wong, David; Balsara, Nitash Pervez

    2016-04-26

    The invention herein described is the use of a block copolymer/homopolymer blend for creating nanoporous materials for transport applications. Specifically, this is demonstrated by using the block copolymer poly(styrene-block-ethylene-block-styrene) (SES) and blending it with homopolymer polystyrene (PS). After blending the polymers, a film is cast, and the film is submerged in tetrahydrofuran, which removes the PS. This creates a nanoporous polymer film, whereby the holes are lined with PS. Control of morphology of the system is achieved by manipulating the amount of PS added and the relative size of the PS added. The porous nature of these films was demonstrated by measuring the ionic conductivity in a traditional battery electrolyte, 1M LiPF.sub.6 in EC/DEC (1:1 v/v) using AC impedance spectroscopy and comparing these results to commercially available battery separators.

  5. Tensile actuators of carbon nanotube coiled yarn based on polydiacetylene-pluronic copolymers as temperature indicators

    NASA Astrophysics Data System (ADS)

    Lee, Hee Uk; Kim, Hyunsoo; Chun, Kyoung-Yong; Kwon, Cheong Hoon; Lima, Márcio D.; Baughman, Ray H.; Kim, Seon Jeong

    2016-07-01

    Most polydiacetylenes (PDAs) have been studied as chromatic sensors or temperature indicators because of their phase transition that is accompanied by a color change from blue to red. Here, we focus on the structural change based on the polydiacetylene phase transition for a temperature-responsive tensile actuator at low temperature using a copolymer composed of PDA and pluronic in a multi-walled carbon nanotube (MWCNT) coiled yarn. In this paper, we do not focus on the general color change phenomenon of PDA. We demonstrate that the volume change of PDA in the MWCNT coiled yarn provides ˜180% tensile strain at low temperature (˜53 °C). Insertion of the pluronic copolymer into the coiled yarn composed of PDA and MWCNT caused the tensile actuation temperature to decrease by ˜6 °C (with tensile actuation of ˜230%) compared to an actuator without pluronic copolymer. Furthermore, we could verify that the large tensile actuation was also predominantly affected by the melting of the nonpolymerized diacetylene (DA) monomer and the pluronic copolymer. MWCNT coiled yarn actuators with PDA-pluronic copolymer can be easily prepared, have a large tensile actuation, and are actuated at low temperature. It could be used as temperature indicators in the food, drugs, and medical fields.

  6. Inhibition of Growth and Metastasis of Colon Cancer by Delivering 5-Fluorouracil-loaded Pluronic P85 Copolymer Micelles

    PubMed Central

    Zhu, Pengxi; Zhao, Naping; Sheng, Dandan; Hou, Jing; Hao, Chong; Yang, Xue; Zhu, Bing; Zhang, Shanshan; Han, Zhipeng; Wei, Lixin; Zhang, Li

    2016-01-01

    Hepatic metastasis is the leading cause of mortality of colon cancer, which is still lack of an effective therapy. A new delivery system, pluronic P85 block copolymers, conveying chemotherapeutic agent 5-fluorouracil (5-Fu) for inhibiting growth and metastasis of colon cancer was designed and developed. In this study, we demonstrated that 5-Fu produce strong pesticide effect at lower doses in the present of pluronic P85 compared with control groups. The migration and invasion of HCT116 cells and RKO cells were examined and the results showed that migration and invasion capacities of HCT116 cells and RKO cells were reduced by administering 5-Fu/P85 copolymer micelles in vitro and in vivo which indicating an effectively activity. Interestingly, the content of CD133 + CXCR4+ cells in HCT116 cancer cells and RKO cells treated by 5-Fu/P85 copolymer micelles was decreased. Importantly, the epithelial-mesenchymal transition (EMT) of CD133 + CXCR4+ cells, which was strongly associated with liver metastasis of colon cancer, was also suppressed by giving 5-Fu/P85 copolymer micelles. The results indicated that 5-Fu/P85 copolymer micelles could inhibit the growth and metastasis of colon cancer, which could be attributed to the decrease of the content of CD133 + CXCR4+ cells and suppression of EMT of CD133 + CXCR4+ cells. PMID:26864651

  7. Baroplastic Block copolymers

    NASA Astrophysics Data System (ADS)

    Hewlett, Sheldon A.

    2005-03-01

    Block copolymers with rubbery and glassy components have been observed to have pressure induced miscibility. These microphase-separated materials, termed baroplastics, were able to flow and be processed at temperatures below the Tg of the glassy component by simple compression molding and extrusion. Diblock and triblock copolymers of polystyrene and poly(butyl acrylate) or poly(2-ethyl hexyl acrylate) were synthesized by atom transfer radical polymerization (ATRP) and processed at room temperature into well defined transparent objects. SAXS and SANS measurements demonstrated partial mixing between components as a result of pressure during processing. DSC results also show the presence of distinct domains even after several processing cycles. Their mechanical properties after processing were tested and compared with commercial thermoplastic elastomers.

  8. Block copolymer investigations

    NASA Astrophysics Data System (ADS)

    Yufa, Nataliya A.

    The research presented in this thesis deals with various aspects of block copolymers on the nanoscale: their behavior at a range of temperatures, their use as scaffolds, or for creation of chemically striped surfaces, as well as the behavior of metals on block copolymers under the influence of UV light, and the healing behavior of copolymers. Invented around the time of World War II, copolymers have been used for decades due to their macroscopic properties, such as their ability to be molded without vulcanization, and the fact that, unlike rubber, they can be recycled. In recent years, block copolymers (BCPs) have been used for lithography, as scaffolds for nano-objects, to create a magnetic hard drive, as well as in photonic and other applications. In this work we used primarily atomic force microscopy (AFM) and transmission electron microscopy (TEM), described in Chapter II, to conduct our studies. In Chapter III we demonstrate a new and general method for positioning nanoparticles within nanoscale grooves. This technique is suitable for nanodots, nanocrystals, as well as DNA. We use AFM and TEM to demonstrate selective decoration. In Chapters IV and V we use AFM and TEM to study the structure of polymer surfaces coated with metals and self-assembled monolayers. We describe how the surfaces were created, exhibit their structure on the nanoscale, and prove that their macroscopic wetting properties have been altered compared to the original polymer structures. Finally, Chapters VI and VII report out in-situ AFM studies of BCP at high temperatures, made possible only recently with the invention of air-tight high-temperature AFM imaging cells. We locate the transition between disordered films and cylinders during initial ordering. Fluctuations of existing domains leading to domain coarsening are also described, and are shown to be consistent with reptation and curvature minimization. Chapter VII deals with the healing of PS-b-PMMA following AFM-tip lithography or

  9. Protein Conjugation with Amphiphilic Block Copolymers for Enhanced Cellular Delivery

    PubMed Central

    Yi, Xiang; Batrakova, Elena; Banks, William A.; Vinogradov, Serguei; Kabanov, Alexander V.

    2008-01-01

    Modification of a model protein, horseradish peroxidase (HRP), with amphiphilic block copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (Pluronic), was previously shown to enhance the transport of this protein across the blood—brain barrier in vivo and brain microvessel endothelial cells in vitro. This work develops procedures for synthesis and characterization of HRP with Pluronic copolymers, having different lengths of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) blocks. Four monoamine Pluronic derivatives (L81, P85, L121, P123) were synthesized and successfully conjugated to a model protein, HRP, via biodegradable or nondegradable linkers (dithiobis(succinimidyl propionate) (DSP), dimethyl 3,3′-dithiobispropionimidate (DTBP), and disuccinimidyl propionate (DSS)). The conjugation was confirmed by HRP amino group titration, matrix-assisted laser desorption/ionization-time of flight spectroscopy, and cation-exchange chromatography. HRP conjugates containing an average of one to two Pluronic moieties and retaining in most cases over 70% of the activity were synthesized. Increased cellular uptake of these conjugates was demonstrated using the Mardin-Derby canine kidney cell line and primary bovine brain microvessel endothelial cells. The optimal modifications included Pluronic L81 and P85. These copolymers have shorter PPO chains compared to Pluronic P123 and L121, which were less efficient. There was little if any dependence of the uptake on the length of the hydrophilic PEO block for the optimal modifications. The proposed modifications may be used to increase cellular uptake of other proteins. PMID:18447367

  10. Inhibition of Breast Cancer Metastasis by Pluronic Copolymers with Moderate Hydrophilic-Lipophilic Balance.

    PubMed

    Sun, Huiping; Meng, Qingshuo; Tang, Shan; Su, Jinghan; Yin, Qi; Chen, Lingli; Gu, Wangwen; Yu, Haijun; Zhang, Zhiwen; Wang, Siling; Li, Yaping

    2015-09-08

    Metastasis is the primary cause resulting in the high mortality of breast cancer. The inherent antimetastasis bioactivity of Pluronic copolymers with a wide range of hydrophilic-lipophilic balance (HLB) including Pluronic L61, P85, P123, F127, F68, and F108 was first explored on metastatic 4T1 breast cancer cells. The results indicated that P85 and P123 could strongly inhibit the migration and invasion of 4T1 cells. The effects of the polymers on cell healing, migration, and invasion exhibited bell-shaped dependencies on HLB of Pluronic copolymers, and the better antimetastasis effects of Pluronic copolymers could be achieved with the HLB between 8 and 16. P85 and P123 themselves could significantly inhibit pulmonary metastasis in 4T1 mammary tumor metastasis model in situ. In addition, a synergetic antimetastasis effect could be achieved during drug combination of doxorubicin hydrochloride (DOX) and P85 or P123 intravenously. The metastasis effects of P85 and P123 both in vitro and in vivo were partially attributed to the downregulation of matrix metalloproteinase-9 (MMP-9). Therefore, Pluronic copolymers with moderate HLB 8-16 such as P85 and P123 could be promising excipients with therapeutics in drug delivery systems to inhibit breast cancer metastasis.

  11. High-Concentration Aqueous Dispersions of Nanoscale 2D Materials Using Nonionic, Biocompatible Block Copolymers.

    PubMed

    Mansukhani, Nikhita D; Guiney, Linda M; Kim, Peter J; Zhao, Yichao; Alducin, Diego; Ponce, Arturo; Larios, Eduardo; Yacaman, Miguel Jose; Hersam, Mark C

    2016-01-20

    Conditions for the dispersion of molybdenum disulfide (MoS2) in aqueous solution at concentrations up to 0.12 mg mL(-1) using a range of nonionic, biocompatible block copolymers (i.e., Pluronics and Tetronics) are identified. Furthermore, the optimal Pluronic dispersant for MoS2 is found to be effective for a range of other 2D materials such as molybdenum diselenide, tungsten diselenide, tungsten disulfide, tin selenide, and boron nitride.

  12. Block coordination copolymers

    DOEpatents

    Koh, Kyoung Moo; Wong-Foy, Antek G.; Matzger, Adam J.; Benin, Annabelle I.; Willis, Richard R.

    2012-12-04

    The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

  13. Block coordination copolymers

    DOEpatents

    Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

    2012-11-13

    The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

  14. Block coordination copolymers

    DOEpatents

    Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

    2014-11-11

    The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

  15. Rolled knitted scaffolds based on PLA-pluronic copolymers for anterior cruciate ligament reinforcement: A step by step conception.

    PubMed

    Pinese, Coline; Leroy, Adrien; Nottelet, Benjamin; Gagnieu, Christian; Coudane, Jean; Garric, Xavier

    2016-01-05

    The aim of this study was to prepare a new knitted scaffold from PLA-Pluronic block copolymers for anterior cruciate ligament reconstruction. The impact of sterilization methods (beta-ray and gamma-ray sterilization) on copolymers was first evaluated in order to take into account the possible damages due to the sterilization process. Beta-ray radiation did not significantly change mechanical properties in contrast to gamma-ray sterilization. It was shown that ACL cells proliferate onto these copolymers, demonstrating their cytocompatibility. Thirdly, in order to study the influence of shaping on mechanical properties, several shapes were created with copolymers yarns: braids, ropes and linear or rolled knitted scaffolds. The rolled knitted scaffold presented interesting mechanical characteristics, similar to native anterior cruciate ligament (ACL) with a 67 MPa Young's Modulus and a stress at failure of 22.5 MPa. These findings suggest that this three dimensional rolled knitted scaffold meet the mechanical properties of ligament tissues and could be suitable as a scaffold for ligament reconstruction. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2016.

  16. Magnetic nanoparticles (MNPs) covalently coated by PEO-PPO-PEO block copolymer for drug delivery.

    PubMed

    Wang, Ning; Guan, Yueping; Yang, Liangrong; Jia, Lianwei; Wei, Xuetuan; Liu, Huizhou; Guo, Chen

    2013-04-01

    A stable drug carrier has been prepared by covalently coating magnetic nanoparticles (MNPs) with PEO-PPO-PEO block copolymer Pluronic P85. The particles were characterized by TEM, XRD, DLS, VSM, FTIR, and TGA. A typical product has a 15 nm magnetite core and a 100 nm hydrodynamic diameter with a narrow size distribution and is superparamagnetic with large saturation magnetization (57.102 emu/g) at room temperature. The covalently-coated Pluronic-MNPs (MagPluronics) were proven to be stable in different conditions, such as aqueous solution, 0.2 M PBS solution, and pH 13.5 solution, which would be significant for biological applications. Furthermore, MagPluronics also possess temperature-responsive property acquired from the Pluronic copolymer layer on their surface, which can cause conformational change of Pluronics and improve load and delivery efficiency of the particles. The temperature-controlled loading and releasing of hydrophobic model drug curcumin were tested with these particles. A loading efficiency of 81.3% and a sustained release of more than 4 days were achieved in simulated human body condition. It indicates that the covalently-coated MagPluronics are stable carriers with good drug-loading capacity and controlled-release property.

  17. Interaction of poloxamine block copolymers with lipid membranes: Role of copolymer structure and membrane cholesterol content.

    PubMed

    Sandez-Macho, Isabel; Casas, Matilde; Lage, Emilio V; Rial-Hermida, M Isabel; Concheiro, Angel; Alvarez-Lorenzo, Carmen

    2015-09-01

    Interactions of X-shaped poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block copolymers with cell membranes were investigated recording the π-A isotherms of monolayer systems of dipalmitoylphosphatidylcholine (DPPC):cholesterol 100:0; 80:20 and 60:40 mol ratio and evaluating the capability of the copolymers to trigger haemolysis or to protect from haemolytic agents. Four varieties of poloxamine (Tetronic 904, 908, 1107 and 1307) were chosen in order to cover a wide range of EO and PO units contents and molecular weights, and compared to a variety of poloxamer (Pluronic P85). The π-A isotherms revealed that the greater the content in cholesterol, the stronger the interaction of the block copolymers with the lipids monolayer. The interactions were particularly relevant at low pressures and low lipid proportions, mimicking the conditions of damaged membranes. Relatively hydrophobic copolymers bearing short PEO blocks (e.g., T904 and P85) intercalated among the lipids expanding the surface area (ΔGexc) but not effectively sealing the pores. These varieties showed haemolytic behavior. Oppositely, highly hydrophilic copolymers bearing long PEO blocks (e.g., T908, T1107 and T1307) caused membrane contraction and outer leaflet sealing due to strong interactions of PEO with cholesterol and diamine core with phospholipids. These later varieties were not haemolytic and exerted a certain protective effect against spontaneous haemolysis for both intact erythrocytes and cholesterol-depleted erythrocytes.

  18. Scanning probe block copolymer lithography

    PubMed Central

    Chai, Jinan; Huo, Fengwei; Zheng, Zijian; Giam, Louise R.; Shim, Wooyoung; Mirkin, Chad A.

    2010-01-01

    Integration of individual nanoparticles into desired spatial arrangements over large areas is a prerequisite for exploiting their unique electrical, optical, and chemical properties. However, positioning single sub-10-nm nanoparticles in a specific location individually on a substrate remains challenging. Herein we have developed a unique approach, termed scanning probe block copolymer lithography, which enables one to control the growth and position of individual nanoparticles in situ. This technique relies on either dip-pen nanolithography (DPN) or polymer pen lithography (PPL) to transfer phase-separating block copolymer inks in the form of 100 or more nanometer features on an underlying substrate. Reduction of the metal ions via plasma results in the high-yield formation of single crystal nanoparticles per block copolymer feature. Because the size of each feature controls the number of metal atoms within it, the DPN or PPL step can be used to control precisely the size of each nanocrystal down to 4.8 ± 0.2 nm. PMID:21059942

  19. Interfaces between Block Copolymer Domains

    NASA Astrophysics Data System (ADS)

    Kim, Jaeup; Jeong, Seong-Jun; Kim, Sang Ouk

    2011-03-01

    Block copolymers naturally form nanometer scale structures which repeat their geometry on a larger scale. Such a small scale periodic pattern can be used for various applications such as storage media, nano-circuits and optical filters. However, perfect alignment of block copolymer domains in the macroscopic scale is still a distant dream. The nanostructure formation usually occurs with spontaneously broken symmetry; hence it is easily infected by topological defects which sneak in due to entropic fluctuation and incomplete annealing. Careful annealing can gradually reduce the number of defects, but once kinetically trapped, it is extremely difficult to remove all the defects. One of the main reasons is that the defect finds a locally metastable morphology whose potential depth is large enough to prohibit further morphology evolution. In this work, the domain boundaries between differently oriented lamellar structures in thin film are studied. For the first time, it became possible to quantitatively study the block copolymer morphology in the transitional region, and it was shown that the twisted grain boundary is energetically favorable compared to the T-junction grain boundary. [Nano Letters, 9, 2300 (2010)]. This theoretical method successfully explained the experimental results.

  20. Imide/arylene ether block copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, B. J.; Hergenrother, P. M.; Bass, R. G.

    1991-01-01

    Two series of imide/arylene either block copolymers were prepared using an arylene ether block and either an amorphous or semi-crystalline imide block. The resulting copolymers were characterized and selected physical and mechanical properties were determined. These results, as well as comparisons to the homopolymer properties, are discussed.

  1. Development of stevioside Pluronic-F-68 copolymer based PLA-nanoparticles as an antidiabetic nanomedicine.

    PubMed

    Barwal, Indu; Sood, Anil; Sharma, Mohit; Singh, Bikram; Yadav, Subhash C

    2013-01-01

    Stevioside (FDA approved nontoxic natural non-caloric sweetener) has been reported to have very good antidiabetic potential but its use as therapeutic drug is restricted in human due to its deprived intestinal absorption and poor bioavailability. We have nano-bioconjugated this molecule on biodegradable Pluronic-F-68 copolymer based PLA nanoparticles by nanoprecipitation method (spherical, size range 110-130 nm) to overcome deprived intestinal absorption and to enhance the bioavailability. The drug loading calculated by the standard calibrated HPLC was 16.32±4% (w/w). The in vitro release study showed the initial burst followed by the sustained release. The half release and complete release were observed on 25±4 h and 200±10 h respectively. This newly formulated nanostevioside showed very high potential to be used as antidiabetic nanomedicine for safe and effective use in vivo. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Synthesis and Characterization of Block Copolymers.

    DTIC Science & Technology

    1987-07-01

    Polyether-Polyimide Block Copolymers; Three series of Polyether-Polyimide (PEPI) block copolymers were synthesized. Soft segments were poly( propylene ... glycol ) (PPO) Mn = 2,000 and 4,000. Hard segments were pyromellitic dianhydride (PMDA) and di-(2-hydroxyethyl)-dimethylhydantoin (H). The hard

  3. Synergism of Water Shock and a Biocompatible Block Copolymer Potentiates the Antibacterial Activity of Graphene Oxide.

    PubMed

    Karahan, H Enis; Wei, Li; Goh, Kunli; Wiraja, Christian; Liu, Zhe; Xu, Chenjie; Jiang, Rongrong; Wei, Jun; Chen, Yuan

    2016-02-17

    Graphene oxide (GO) is promising in the fight against pathogenic bacteria. However, the antibacterial activity of pristine GO is relatively low and concern over human cytotoxicity further limits its potential. This study demonstrates a general approach to address both issues. The developed approach synergistically combines the water shock treatment (i.e., a sudden decrease in environmental salinity) and the use of a biocompatible block copolymer (Pluronic F-127) as a synergist co-agent. Hypoosmotic stress induced by water shock makes gram-negative pathogens more susceptible to GO. Pluronic forms highly stable nanoassemblies with GO (Pluronic-GO) that can populate around bacterial envelopes favoring the interactions between GO and bacteria. The antibacterial activity of GO at a low concentration (50 μg mL(-1) ) increases from <30% to virtually complete killing (>99%) when complemented with water shock and Pluronic (5 mg mL(-1) ) at ≈2-2.5 h of exposure. Results suggest that the enhanced dispersion of GO and the osmotic pressure generated on bacterial envelopes by polymers together potentiate GO. Pluronic also significantly suppresses the toxicity of GO toward human fibroblast cells. Fundamentally, the results highlight the crucial role of physicochemical milieu in the antibacterial activity of GO. The demonstrated strategy has potentials for daily-life bacterial disinfection applications, as hypotonic Pluronic-GO mixture is both safe and effective.

  4. Amphiphilic Block Copolymers Enhance Cellular Uptake and Nuclear Entry of Polyplex-Delivered DNA

    PubMed Central

    Yang, Zhihui; Sahay, Gaurav; Sriadibhatla, Srikanth; Kabanov, Alexander V.

    2008-01-01

    This work for the first time demonstrates that synthetic polymers enhance uptake and nuclear import of plasmid DNA (pDNA) through the activation of cellular trafficking machinery. Nonionic block copolymers of poly(ethylene oxide) and poly(propylene oxide), Pluronics, are widely used as excipients in pharmaceutics. We previously demonstrated that Pluronics increase the phosphorylation of IκB and subsequent NFκB nuclear localization as well as upregulate numerous NFκB-related genes. In this study, we show that Pluronics enhance gene transfer by pDNA/polycation complexes (“polyplexes”) in a promoter-dependent fashion. Addition of Pluronic P123 or P85 to polyethyleneimine-based polyplexes had little effect on polyplex particle size but significantly enhanced pDNA cellular uptake, nuclear translocation and gene expression in several cell lines. When added to polyplex-transfected cells after transfection, Pluronics enhanced nuclear import of pDNA containing NFκB–binding sites, but have no effect on import of pDNA without these sites. All together, our studies suggest that Pluronics rapidly activate NFκB, which binds cytosolic pDNA that possesses promoters containing NFκB binding sites and consequently increases nuclear import of pDNA through NFκB nuclear translocation. PMID:18729495

  5. Method for making block siloxane copolymers

    DOEpatents

    Butler, N.L.; Jessop, E.S.; Kolb, J.R.

    1981-02-25

    A method for synthesizing block polysiloxane copolymers is disclosed. Diorganoscyclosiloxanes and an end-blocking compound are interacted in the presence of a ring opening polymerization catalyst, producing a blocked prepolymer. The prepolymer is then interacted with a silanediol, resulting in condensation polymerization of the prepolymers. A second end-blocking compound is subsequently introduced to end-cap the polymers and copolymers formed from the condensation polymerization.

  6. Method for making block siloxane copolymers

    DOEpatents

    Butler, Nora; Jessop, Edward S.; Kolb, John R.

    1982-01-01

    A method for synthesizing block polysiloxane copolymers. Diorganoscyclosiloxanes and an end-blocking compound are interacted in the presence of a ring opening polymerization catalyst, producing a blocked prepolymer. The prepolymer is then interacted with a silanediol, resulting in condensation polymerization of the prepolymers. A second end-blocking compound is subsequently introduced to end-cap the polymers and copolymers formed from the condensation polymerization.

  7. Block Copolymer Membranes for Biofuel Purification

    NASA Astrophysics Data System (ADS)

    Evren Ozcam, Ali; Balsara, Nitash

    2012-02-01

    Purification of biofuels such as ethanol is a matter of considerable concern as they are produced in complex multicomponent fermentation broths. Our objective is to design pervaporation membranes for concentrating ethanol from dilute aqueous mixtures. Polystyrene-b-polydimethylsiloxane-b-polystyrene block copolymers were synthesized by anionic polymerization. The polydimethylsiloxane domains provide ethanol-transporting pathways, while the polystyrene domains provide structural integrity for the membrane. The morphology of the membranes is governed by the composition of the block copolymer while the size of the domains is governed by the molecular weight of the block copolymer. Pervaporation data as a function of these two parameters will be presented.

  8. Block copolymer structures in nano-pores

    NASA Astrophysics Data System (ADS)

    Pinna, Marco; Guo, Xiaohu; Zvelindovsky, Andrei

    2010-03-01

    We present results of coarse-grained computer modelling of block copolymer systems in cylindrical and spherical nanopores on Cell Dynamics Simulation. We study both cylindrical and spherical pores and systematically investigate structures formed by lamellar, cylinders and spherical block copolymer systems for various pore radii and affinity of block copolymer blocks to the pore walls. The obtained structures include: standing lamellae and cylinders, ``onions,'' cylinder ``knitting balls,'' ``golf-ball,'' layered spherical, ``virus''-like and mixed morphologies with T-junctions and U-type defects [1]. Kinetics of the structure formation and the differences with planar films are discussed. Our simulations suggest that novel porous nano-containers can be formed by confining block copolymers in pores of different geometries [1,2]. [4pt] [1] M. Pinna, X. Guo, A.V. Zvelindovsky, Polymer 49, 2797 (2008).[0pt] [2] M. Pinna, X. Guo, A.V. Zvelindovsky, J. Chem. Phys. 131, 214902 (2009).

  9. Phase Behavior of Symmetric Sulfonated Block Copolymers

    SciTech Connect

    Park, Moon Jeong; Balsara, Nitash P.

    2008-08-21

    Phase behavior of poly(styrenesulfonate-methylbutylene) (PSS-PMB) block copolymers was studied by varying molecular weight, sulfonation level, and temperature. Molecular weights of the copolymers range from 2.9 to 117 kg/mol. Ordered lamellar, gyroid, hexagonally perforated lamellae, and hexagonally packed cylinder phases were observed in spite of the fact that the copolymers are nearly symmetric with PSS volume fractions between 0.45 and 0.50. The wide variety of morphologies seen in our copolymers is inconsistent with current theories on block copolymer phase behavior such as self-consistent field theory. Low molecular weight PSS-PMB copolymers (<6.2 kg/mol) show order-order and order-disorder phase transitions as a function of temperature. In contrast, the phase behavior of high molecular weight PSS-PMB copolymers (>7.7 kg/mol) is independent of temperature. Due to the large value of Flory-Huggins interaction parameter, x, between the sulfonated and non-sulfonated blocks, PSS-PMB copolymers with PSS and PMB molecular weights of 1.8 and 1.4 kg/mol, respectively, show the presence of an ordered gyroid phase with a 2.5 nm diameter PSS network. A variety of methods are used to estimate x between PSS and PMB chains as a function of sulfonation level. Some aspects of the observed phase behavior of PSS-PMB copolymers can be rationalized using x.

  10. Nanostructured high-performance dielectric block copolymers.

    PubMed

    Liu, Wenmei; Liao, Xiaojuan; Li, Yawei; Zhao, Qiuhua; Xie, Meiran; Sun, Ruyi

    2015-10-25

    A new type of insulating-conductive block copolymer was synthesized by metathesis polymerization. The copolymer can self-assemble into unique nanostructures of micelles or hollow spheres. It exhibits a high dielectric constant, low dielectric loss, and high stored/released energy density due to the strong dipolar and nano-interfacial polarization contributions.

  11. Electrostatic control of block copolymer morphology

    NASA Astrophysics Data System (ADS)

    Sing, Charles E.; Zwanikken, Jos W.; Olvera de La Cruz, Monica

    2014-07-01

    Energy storage is at present one of the foremost issues society faces. However, material challenges now serve as bottlenecks in technological progress. Lithium-ion batteries are the current gold standard to meet energy storage needs; however, they are limited owing to the inherent instability of liquid electrolytes. Block copolymers can self-assemble into nanostructures that simultaneously facilitate ion transport and provide mechanical stability. The ions themselves have a profound, yet previously unpredictable, effect on how these nanostructures assemble and thus the efficiency of ion transport. Here we demonstrate that varying the charge of a block copolymer is a powerful mechanism to predictably tune nanostructures. In particular, we demonstrate that highly asymmetric charge cohesion effects can induce the formation of nanostructures that are inaccessible to conventional uncharged block copolymers, including percolated phases desired for ion transport. This vastly expands the design space for block copolymer materials and is informative for the versatile design of battery electrolyte materials.

  12. Process-Accessible States of Block Copolymers

    NASA Astrophysics Data System (ADS)

    Sun, De-Wen; Müller, Marcus

    2017-02-01

    Process-directed self-assembly of block copolymers refers to thermodynamic processes that reproducibly direct the kinetics of structure formation from a starting, unstable state into a selected, metastable mesostructure. We investigate the kinetics of self-assembly of linear A C B triblock copolymers after a rapid transformation of the middle C block from B to A . This prototypical process (e.g., photochemical transformation) converts the initial, equilibrium mesophase of the A B B copolymer into a well-defined but unstable, starting state of the A A B copolymer. The spontaneous structure formation that ensues from this unstable state becomes trapped in a metastable mesostructure, and we systematically explore which metastable mesostructures can be fabricated by varying the block copolymer composition of the initial and final states. In addition to the equilibrium mesophases of linear A B diblock copolymers, this diagram of process-accessible states includes 7 metastable periodic mesostructures, inter alia, Schoen's F-RD periodic minimal surface. Generally, we observe that the final, metastable mesostructure of the A A B copolymer possesses the same symmetry as the initial, equilibrium mesophase of the A B B copolymer.

  13. Process-Accessible States of Block Copolymers.

    PubMed

    Sun, De-Wen; Müller, Marcus

    2017-02-10

    Process-directed self-assembly of block copolymers refers to thermodynamic processes that reproducibly direct the kinetics of structure formation from a starting, unstable state into a selected, metastable mesostructure. We investigate the kinetics of self-assembly of linear ACB triblock copolymers after a rapid transformation of the middle C block from B to A. This prototypical process (e.g., photochemical transformation) converts the initial, equilibrium mesophase of the ABB copolymer into a well-defined but unstable, starting state of the AAB copolymer. The spontaneous structure formation that ensues from this unstable state becomes trapped in a metastable mesostructure, and we systematically explore which metastable mesostructures can be fabricated by varying the block copolymer composition of the initial and final states. In addition to the equilibrium mesophases of linear AB diblock copolymers, this diagram of process-accessible states includes 7 metastable periodic mesostructures, inter alia, Schoen's F-RD periodic minimal surface. Generally, we observe that the final, metastable mesostructure of the AAB copolymer possesses the same symmetry as the initial, equilibrium mesophase of the ABB copolymer.

  14. Micellization of amphiphilic block copolymers in binary and ternary solvent mixtures.

    PubMed

    Sarkar, Biswajit; Ravi, Venkataramanan; Alexandridis, Paschalis

    2013-01-15

    Amphiphilic block copolymers of the poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) family (commercially available as Pluronics or Poloxamers) are well-known for self-assembling in water (selective solvent for PEO) into micelles with a PPO-rich core and a hydrated PEO corona. The micellization of two PEO-PPO-PEO block copolymers (Pluronic P105: EO(37)PO(56)EO(37) and Pluronic F127: EO(100)PO(65)EO(100)) has been studied in binary mixed solvents consisting of water and one of the following organic solvents: ethanol, glycerol, D(+)-glucose monohydrate, propylene carbonate, or triacetin, and also in ternary mixtures of water with 50/50 wt% ethanol+glycerol or 50/50 wt% ethanol+propylene carbonate. Glycerol, glucose, propylene carbonate and triacetin were found to promote micellization when added to water. Glycerol and glucose interact favorably with water, and reduce the block copolymer critical micelle concentration (cmc) by dehydrating the PEO-PPO interface as well as changing the bulk solvent properties. Propylene carbonate and triacetin act by locating at the PEO-PPO interface and increasing its hydrophobicity. The addition of ethanol to water provides better solvent conditions for the block copolymers compared to plain water, and disfavors the formation of micelles. In the case of ternary solvents consisting of water, ethanol (that prevents micelle formation), and glycerol or propylene carbonate (that favor micelle formation), the observed changes in the cmc are subtle. For Pluronic P105, the cmc increase is greater for ethanol+propylene carbonate (50/50 wt%) than for ethanol+glycerol (50/50 wt%). For Pluronic F127, the cmcs remain the same as in plain water, i.e., the effects of the two organic solvents compensate each other. The difference between the free energy of micellization in plain water and that in solvent mixtures varies linearly with the cosolvent concentration, and collapses into a single line for each solvent mixture type when normalized with

  15. 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.

  16. Arbitrary lattice symmetries via block copolymer nanomeshes

    PubMed Central

    Majewski, Pawel W.; Rahman, Atikur; Black, Charles T.; Yager, Kevin G.

    2015-01-01

    Self-assembly of block copolymers is a powerful motif for spontaneously forming well-defined nanostructures over macroscopic areas. Yet, the inherent energy minimization criteria of self-assembly give rise to a limited library of structures; diblock copolymers naturally form spheres on a cubic lattice, hexagonally packed cylinders and alternating lamellae. Here, we demonstrate multicomponent nanomeshes with any desired lattice symmetry. We exploit photothermal annealing to rapidly order and align block copolymer phases over macroscopic areas, combined with conversion of the self-assembled organic phase into inorganic replicas. Repeated photothermal processing independently aligns successive layers, providing full control of the size, symmetry and composition of the nanoscale unit cell. We construct a variety of symmetries, most of which are not natively formed by block copolymers, including squares, rhombuses, rectangles and triangles. In fact, we demonstrate all possible two-dimensional Bravais lattices. Finally, we elucidate the influence of nanostructure on the electrical and optical properties of nanomeshes. PMID:26100566

  17. Enhanced efficacy of pluronic copolymer micelle encapsulated SCR7 against cancer cell proliferation.

    PubMed

    John, Franklin; George, Jinu; Vartak, Supriya V; Srivastava, Mrinal; Hassan, P A; Aswal, V K; Karki, Subhas S; Raghavan, Sathees C

    2015-04-01

    5,6-Bis(benzylideneamino)-2-mercaptopyrimidin-4-ol (SCR7) is a new anti cancer molecule having capability to selectively inhibit non-homologous end joining (NHEJ), one of the DNA double strand break (DSB) repair pathways inside the cells. In spite of the promising potential as an anticancer agent, hydrophobicity of SCR7 decreases its bioavailability. Herein the entrapment of SCR7 in Pluronic copolymer is reported. The size of the aggregates was determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) which yields an average diameter of 23 nm. SCR7 encapsulated micelles (ES) were also characterized by small-angle neutron scattering (SANS). Evaluation of its biological properties by using a variety of techniques, including Trypan blue, MTT and Live-dead cell assays, reveal that encapsulated SCR7 can induce cytotoxicity in cancer cell lines, being more effective in breast cancer cell line. Encapsulated SCR7 treatment resulted in accumulation of DNA breaks within the cells, resulting in cell cycle arrest at G1 phase and activation of apoptosis. More importantly, we found ≈ 5 fold increase in cell death, when encapsulated SCR7 was used in comparison with SCR7 alone. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. 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.

  19. RGD Peptides-Conjugated Pluronic Triblock Copolymers Encapsulated with AP-2α Expression Plasmid for Targeting Gastric Cancer Therapy in Vitro and in Vivo.

    PubMed

    Wang, Wei; Liu, Zhimin; Sun, Peng; Fang, Cheng; Fang, Hongwei; Wang, Yueming; Ji, Jiajia; Chen, Jun

    2015-07-17

    Gastric cancer, a high-risk malignancy, is a genetic disease developing from a cooperation of multiple gene mutations and a multistep process. Gene therapy is a novel treatment method for treating gastric cancer. Here, we developed a novel Arg-Gly-Asp (RGD) peptides conjugated copolymers nanoparticles-based gene delivery system in order to actively targeting inhibit the growth of gastric cancer cells. These transcription factor (AP-2α) expression plasmids were also encapsulated into pluronic triblock copolymers nanoparticles which was constituted of poly(ethylene glycol)-block-poly(propylene glycol)- block-poly(ethylene glycol) (PEO-block-PPO-block-PEO, P123). The size, morphology and composition of prepared nanocomposites were further characterized by nuclear magnetic resonance (NMR), transmission electron microscopy (TEM) and dynamic light scattering (DLS). In MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide) analysis, these nanocomposites have minor effects on the proliferation of GES-1 cells but significantly decreased the viability of MGC-803, suggesting they own low cytotoxicity but good antitumor activity. The following in vivo evaluation experiments confirmed that these nanocomposites could prevent the growth of gastric cancer cells in the tumor xenograft mice model. In conclusion, these unique RGD peptides conjugated P123 encapsulated AP-2α nanocomposites could selectively and continually kill gastric cancer cells by over-expression of AP-2α in vitro and in vivo; this exhibits huge promising applications in clinical gastric cancer therapy.

  20. Aqueous two-phase systems containing self-associating block copolymers. Partitioning of hydrophilic and hydrophobic biomolecules.

    PubMed

    Svensson, M; Berggren, K; Veide, A; Tjerneld, F

    1999-04-16

    A series of proteins and one membrane-bound peptide have been partitioned in aqueous two-phase systems consisting of micelle-forming block copolymers from the family of Pluronic block copolymers as one polymer component and dextran T500 as the other component. The Pluronic molecule is a triblock copolymer of the type PEO-PPO-PEO, where PEO and PPO are poly(ethylene oxide) and poly(propylene oxide), respectively. Two different Pluronic copolymers were used, P105 and F68, and the phase diagrams were determined at 30 degrees C for these polymer systems. Since the temperature is an important parameter in Pluronic systems (the block copolymers form micellar-like aggregates at higher temperatures) the partitioning experiments were performed at 5 and 30 degrees C, to explore the effect of temperature-triggered micellization on the partitioning behaviour. The temperatures correspond to the unimeric (single Pluronic chain) and the micellar states of the P105 polymer at the concentrations used. The degree of micellization in the F68 system was lower than that in the P105 system, as revealed by the phase behaviour. A membrane-bound peptide, gramicidin D, and five different proteins were partitioned in the above systems. The proteins were lysozyme, bovine serum albumin, cytochrome c, bacteriorhodopsin and the engineered B domain of staphylococcal protein A, named Z. The Z domain was modified with tryptophan-rich peptide chains in the C-terminal end. It was found that effects of salt dominated over the temperature effect for the water-soluble proteins lysozyme, bovine serum albumin and cytochrome c. A strong temperature effect was observed in the partitioning of the integral membrane protein bacteriorhodopsin, where partitioning towards the more hydrophobic Pluronic phase was higher at 30 degrees C than at 5 degrees C. The membrane-bound peptide gramicidin D partitioned exclusively to the Pluronic phase at both temperatures. The following trends were observed in the

  1. Salt Complexation in Block Copolymer Thin Films

    SciTech Connect

    Kim,S.; Misner, M.; Yang, L.; Gang, O.; Ocko, B.; Russell, T.

    2006-01-01

    Ion complexation within cylinder-forming block copolymer thin films was found to affect the ordering process of the copolymer films during solvent annealing, significantly enhancing the long-range positional order. Small amounts of alkali halide or metal salts were added to PS-b-PEO, on the order of a few ions per chain, where the salt complexed with the PEO block. The orientation of the cylindrical microdomains strongly depended on the salt concentration and the ability of the ions to complex with PEO. The process shows large flexibility in the choice of salt used, including gold or cobalt salts, whereby well-organized patterns of nanoparticles can be generated inside the copolymer microdomains. By further increasing the amount of added salts, the copolymer remained highly ordered at large degrees of swelling and demonstrated long-range positional correlations of the microdomains in the swollen state, which holds promise as a route to addressable media.

  2. Mixing thermodynamics of block-random copolymers

    NASA Astrophysics Data System (ADS)

    Beckingham, Bryan Scott

    Random copolymerization of A and B monomers represents a versatile method to tune interaction strengths between polymers, as ArB random copolymers will exhibit a smaller effective Flory interaction parameter chi; (or interaction energy density X) upon mixing with A or B homopolymers than upon mixing A and B homopolymers with each other, and the ArB composition can be tuned continuously. Thus, the incorporation of a random copolymer block into the classical block copolymer architecture to yield "block-random" copolymers introduces an additional tuning mechanism for the control of structure-property relationships, as the interblock interactions and physical properties can be tuned continuously through the random block's composition. However, typical living or controlled polymerizations produce compositional gradients along the "random" block, which can in turn influence the phase behavior. This dissertation demonstrates a method by which narrow-distribution copolymers of styrene and isoprene of any desired composition, with no measurable down-chain gradient, are synthesized. This synthetic method is then utilized to incorporate random copolymers of styrene and isoprene as blocks into block-random copolymers in order to examine the resulting interblock mixing thermodynamics. A series of well-defined near-symmetric block and block-random copolymers (S-I, Bd-S, I-SrI, S-SrI and Bd-S rI diblocks, where S is polystyrene, I is polyisoprene and Bd is polybutadiene), with varying molecular weight and random-block composition are synthesized and the mixing thermodynamics---via comparison of their interaction energy densities, X---of their hydrogenated derivatives is examined through measurement of the order-disorder transition (ODT) temperature. Hydrogenated derivatives of I-SrI and S-SrI block-random copolymers, both wherein the styrene aromaticity is retained and derivatives wherein the styrene units are saturated to vinylcyclohexane (VCH), are found to hew closely to the

  3. Interaction of Curcumin with PEO-PPO-PEO block copolymers: a molecular dynamics study.

    PubMed

    Samanta, Susruta; Roccatano, Danilo

    2013-03-21

    Curcumin, a naturally occurring drug molecule, has been extensively investigated for its various potential usages in medicine. Its water insolubility and high metabolism rate require the use of drug delivery systems to make it effective in the human body. Among various types of nanocarriers, block copolymer based ones are the most effective. These polymers are broadly used as drug-delivery systems, but the nature of this process is poorly understood. In this paper, we propose a molecular dynamics simulation study of the interaction of Curcumin with block copolymer based on polyethylene oxide (PEO) and polypropylene oxide (PPO). The study has been conducted considering the smallest PEO and PPO oligomers and multiple chains of the block copolymer Pluronic P85. Our study shows that the more hydrophobic 1,2-dimethoxypropane (DMP) molecules and PPO block preferentially coat the Curcumin molecule. In the case of the Pluronic P85, simulation shows formation of a drug-polymer aggregate within 50 ns. This process leaves exposed the PEO part of the polymers, resulting in better solvation and stability of the drug in water.

  4. 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

  5. Additive-driven assembly of block copolymers

    NASA Astrophysics Data System (ADS)

    Lin, Ying; Daga, Vikram; Anderson, Eric; Watkins, James

    2011-03-01

    One challenge to the formation of well ordered hybrid materials is the incorporation of nanoscale additives including metal, semiconductor and dielectric nanoparticles at high loadings while maintaining strong segregation. Here we describe the molecular and functional design of small molecule and nanoparticle additives that enhance phase segregation in their block copolymer host and enable high additive loadings. Our approach includes the use of hydrogen bond interactions between the functional groups on the additive or particle that serve as hydrogen bond donors and one segment of the block copolymer containing hydrogen bond acceptors. Further, the additives show strong selectively towards the targeted domains, leading to enhancements in contrast between properties of the phases. In addition to structural changes, we explore how large changes in the thermal and mechanical properties occur upon incorporation of the additives. Generalization of this additive-induced ordering strategy to various block copolymers will be discussed.

  6. Structure-property relationships in block copolymers

    NASA Technical Reports Server (NTRS)

    Mcgrath, J. E.

    1976-01-01

    Block copolymers are a class of relatively new materials which contain long sequences of two (or more) chemically different repeat units. Unlike random copolymers, each segment may retain some properties which are characteristic of its homopolymer. It is well known that most physical blends of two different homopolymers are incompatible on a macro-scale. By contrast most block copolymers display only a microphase (eg. 100-200 A domains) separation. Complete separation is restricted because of a loss in configurational entropy. The latter is due to presence of chemical bond(s) between the segments. Novel physical properties can be obtained because it is possible to prepare any desired combination of rubber-like, glassy, or crystalline blocks. The architecture and sequential arrangement of the segments can strongly influence mechanical behavior.

  7. Charge Transport in Conjugated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Smith, Brandon; Le, Thinh; Lee, Youngmin; Gomez, Enrique

    Interest in conjugated block copolymers for high performance organic photovoltaic applications has increased considerably in recent years. Polymer/fullerene mixtures for conventional bulk heterojunction devices, such as P3HT:PCBM, are severely limited in control over interfaces and domain length scales. In contrast, microphase separated block copolymers self-assemble to form lamellar morphologies with alternating electron donor and acceptor domains, thereby maximizing electronic coupling and local order at interfaces. Efficiencies as high as 3% have been reported in solar cells for one block copolymer, P3HT-PFTBT, but the details concerning charge transport within copolymers have not been explored. To fill this gap, we probed the transport characteristics with thin-film transistors. Excellent charge mobility values for electron transport have been observed on aluminum source and drain contacts in a bottom gate, bottom contact transistor configuration. Evidence of high mobility in ordered PFTBT phases has also been obtained following thermal annealing. The insights gleaned from our investigation serve as useful guideposts, revealing the significance of the interplay between charge mobility, interfacial order, and optimal domain size in organic block copolymer semiconductors.

  8. Fluorescence probe studies of pluronic copolymer solutions as a function of temperature

    SciTech Connect

    Nivaggioli, T.; Alexandridis, P.; Hatton, T.A.; Yekta, A.; Winnik, M.A.

    1995-03-01

    The temperature variation of the I{sub 1}/I{sub 3} ratio of pyrene vibrational fine structure has been studied in aqueous poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) copolymer solutions, in bulk PEO, PPO, and various organic solvents. Linear decreases were observed in organic solvents and in mixtures of bulk PEO and PPO. The data in aqueous PEO-PPO-PEO copolymer solutions reveal three distinct solution conditions: at low temperatures, the linear decrease with temperature parallels that for water; over a small intermediate temperature range there is a sharp decrease in the ratio, attributed to the formation of micelles; and at higher temperatures, a linear decrease is again observed. Values in this region are strongly dependent on the PPO block and are consistent with the representation of micelles with a core dominated by PPO. The composition of the micelle core was estimated using these data and indicated an increase of poly(ethylene oxide) as the polymer becomes more hydrophilic. In addition, the size of the micelles and their aggregation numbers were determined using light scattering and pyrene luminescence decay studies, respectively. These data showed an increase of the aggregation number with temperature while the hydrodynamic radius remained constant and were interpreted in terms of dehydration of the PEO block. 38 refs., 11 figs., 3 tabs.

  9. Lamellar structure of block copolymer poly(oxyethylene-oxypropylene-oxyethylene) in xylene/water mixtures

    SciTech Connect

    Wu, G; Ying, Q.; Chu, B. )

    1994-09-26

    Synchrotron small angle X-ray scattering (SAXS) was used to study the supramolecular structure formed by a block copolymer, Pluronic L64 (PEO[sub 13]PPO[sub 30]PEO[sub 13]), in xylene/water mixtures. Lamellar structure was observed at very high polymer concentrations (e.g., C[degree] > 0.53 g/ml). The lamellar spacing was determined by the amount of solubilized water and the copolymer concentration, with the amount of water playing a more important role on the lamellar spacing than the copolymer concentration. The lamellar spacing was almost independent of temperature. However the scattering peak became broader with increasing temperature, implying that the micellar size became smaller. Experimental data could be fitted by the Teubner-Strey model, and the resulting periodicity was in good agreement with the lamellar spacing derived by using the Bragg equation.

  10. Melt Rheology of Block Copolymers in Relation to Melt Structure.

    DTIC Science & Technology

    1980-06-23

    According to their theory, (A-B-A) type block copolymer melts are expected to exhibit a network response including a yield stress at very low shear rates ...observed the following very unusual flow behavior with SBS block copolymers . 1. The viscosities of SBS block copolymers at low shear rates go...unusual flow properties. One can expect from the probable two-phase structure in the melt that block copolymer melts would exhibit strong elastic

  11. Formation of Anisotropic Block Copolymer Gels

    NASA Astrophysics Data System (ADS)

    Liaw, Chya Yan; Shull, Kenneth; Henderson, Kevin; Joester, Derk

    2011-03-01

    Anisotropic, fibrillar gels are important in a variety of processes. Biomineralization is one example, where the mineralization process often occurs within a matrix of collagen or chitin fibers that trap the mineral precursors and direct the mineralization process. We wish to replicate this type of behavior within block copolymer gels. Particularly, we are interested in employing gels composed of cylindrical micelles, which are anisotropic and closely mimic biological fibers. Micelle geometry is controlled in our system by manipulating the ratio of molecular weights of the two blocks and by controlling the detailed thermal processing history of the copolymer solutions. Small-Angle X-ray Scattering and Dynamic Light Scattering are used to determine the temperature dependence of the gel formation process. Initial experiments are based on a thermally-reversible alcohol-soluble system, that can be subsequently converted to a water soluble system by hydrolysis of a poly(t-butyl methacrylate) block to a poly (methacrylic acid) block. MRSEC.

  12. Hybridization of Block Copolymer Micelles

    DTIC Science & Technology

    1993-01-01

    J. Macromol. Sci., Part A 1973, 7,601. (10) Tiara, M.; Ramireddy, C.; Webber, S. K; Munk,P. Collect. Czer" (14) 0snford, C. In The Hydrophobic Effect ...equilibrate In the first series of experiments we have studied the within 20 min, similarly as ASA-10 micelles do. However, effect of the copolymer...high. This may happen after a sudden The Johnston-Ogston effect 2’ 6- also may play a role in jump in temperature or in the composition of the mixed

  13. Chiral Block Copolymer Structures for Metamaterial Applications

    DTIC Science & Technology

    2015-01-27

    transformation. 15. SUBJECT TERMS Block Copolymers, Chiral Metamaterials, Gyroids, Nanotechnology, Nanoporous Materials , Networks...Chiral Metamaterials, Gyroids, Nanotechnology, Nanoporous Materials , Networks 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as... nanoporous materials for templating, in particular with network morphologies, as templates could be developed. BCPs comprising chiral entities were

  14. Block and graft copolymers and NanoGel copolymer networks for DNA delivery into cell.

    PubMed

    Lemieux, P; Vinogradov, S V; Gebhart, C L; Guérin, N; Paradis, G; Nguyen, H K; Ochietti, B; Suzdaltseva, Y G; Bartakova, E V; Bronich, T K; St-Pierre, Y; Alakhov, V Y; Kabanov, A V

    2000-01-01

    Self-assembling complexes from nucleic acids and synthetic polymers are evaluated for plasmid and oligonucleotide (oligo) delivery. Polycations having linear, branched, dendritic. block- or graft copolymer architectures are used in these studies. All these molecules bind to nucleic acids due to formation of cooperative systems of salt bonds between the cationic groups of the polycation and phosphate groups of the DNA. To improve solubility of the DNA/polycation complexes, cationic block and graft copolymers containing segments from polycations and non-ionic soluble polymers, for example, poly(ethylene oxide) (PEO) were developed. Binding of these copolymers with short DNA chains, such as oligos, results in formation of species containing hydrophobic sites from neutralized DNA polycation complex and hydrophilic sites from PEO. These species spontaneously associate into polyion complex micelles with a hydrophobic core from neutralized polyions and a hydrophilic shell from PEO. Such complexes are very small (10-40 nm) and stable in solution despite complete neutralization of charge. They reveal significant activity with oligos in vitro and in vivo. Binding of cationic copolymers to plasmid DNA forms larger (70-200 nm) complexes. which are practically inactive in cell transfection studies. It is likely that PEO prevents binding of these complexes with the cell membranes ("stealth effect"). However attaching specific ligands to the PEO-corona can produce complexes, which are both stable in solution and bind to target cells. The most efficient complexes were obtained when PEO in the cationic copolymer was replaced with membrane-active PEO-b-poly(propylene oxide)-b-PEO molecules (Pluronic 123). Such complexes exhibited elevated levels of transgene expression in liver following systemic administration in mice. To increase stability of the complexes, NanoGel carriers were developed that represent small hydrogel particles synthesized by cross-linking of PEI with double end

  15. Ionization of amphiphilic acidic block copolymers.

    PubMed

    Colombani, Olivier; Lejeune, Elise; Charbonneau, Céline; Chassenieux, Christophe; Nicolai, Taco

    2012-06-28

    The ionization behavior of an amphiphilic diblock copolymer poly(n-butyl acrylate(50%)-stat-acrylic acid(50%))(100)-block-poly(acrylic acid)(100) (P(nBA(50%)-stat-AA(50%))(100)-b-PAA(100), DH50) and of its equivalent triblock copolymer P(nBA(50%)-stat-AA(50%))(100)-b-PAA(200)-b-P(nBA(50%)-stat-AA(50%))(100) (TH50) were studied by potentiometric titration either in pure water or in 0.5 M NaCl. These polymers consist of a hydrophilic acidic block (PAA) connected to a hydrophobic block, P(nBA(50%)-stat-AA(50%))(100), whose hydrophobic character has been mitigated by copolymerization with hydrophilic units. We show that all AA units, even those in the hydrophobic block could be ionized. However, the AA units within the hydrophobic block were less acidic than those in the hydrophilic block, resulting in the preferential ionization of the latter block. The preferential ionization of PAA over that of P(nBA(50%)-stat-AA(50%))(100) was stronger at higher ionic strength. Remarkably, the covalent bonds between the PAA and P(nBA(50%)-stat-AA(50%))(100) blocks in the diblock or the triblock did not affect the ionization of each block, although the self-association of the block copolymers into spherical aggregates modified the environment of the PAA blocks compared to when PAA was molecularly dispersed.

  16. Morphologies of block copolymers composed of charged and neutral blocks

    SciTech Connect

    Kumar, Rajeev; Goswami, Monojoy; Mays, Jimmy; Sumpter, Bobby G; Wang, Xiaojun

    2012-01-01

    This article reviews current experimental observations and theoretical calculations devoted towards understanding micro-phase separation in charged block copolymer systems. We discuss bulk morphologies in melt and in solution, as well as some of the new emerging research directions. Overall, a comprehensive picture is beginning to emerge on the fundamental role of electrostatics in the microphase separation of charged block copolymers. This understanding provides exciting new insight that may be used to direct targeted structures that endow the materials with desired properties that can have tremendous potential in technological applications.

  17. Organosilane Polymers. III. Block Copolymers.

    DTIC Science & Technology

    1980-04-01

    5446 (1969) 9) R. West, J. Polym. Sci., C, 29, 65 (1970) 10) V.F. Traven and R. West, J. Am. Chem. Soc., 95, 6824 (1973) 11) W.G. Boberski and-A.L...COMPOSITION Alkyl H/Aryl H (2 ) Copolymer Method,1 , Calculated Found 111-3 A 0.72 0.73 B 0.72 0.73 111-5 A 0.80 0.85 B 0.80 0.80 111-8 A 1.0 1.4 B 1.0...1.1 (1) A: Chloro-oligomer added to lithio-oligomer. B : Lithio-oligomer added to chloro-oligomer. (2) By HI-NMR TABLE 2 INFRA-RED ABSORPTIONS

  18. Surface activity of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) copolymers

    SciTech Connect

    Alexandridis, P.; Athanassiou, V.; Fukuda, Shinya; Hatton, T.A. )

    1994-08-01

    The surface tension of aqueous solutions of seven poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) Pluronic copolymers, covering a wide range of molecular weights (3400-14600) and PPO/PEO ratios (0.19-1.79), was determined over the 10[sup [minus]5]-10% w/v concentration range, at two temperatures (25 and 35[degree]C). Two breaks (changes in slope) were observed in the surface tension vs log concentration curve for most of the copolymers. The low-concentration break, occurring at bulk copolymer concentrations of approximately 10[sup [minus]3]%, is believed to originate from rearrangement of the copolymer molecules on the surface at complete coverage of the air/water interface. The breaks at the high-concentration part of the surface tension curve occurred at concentrations that correspond to the critical micellization concentration values as determined by a dye solubilization technique. The surface area per copolymer molecule, A, increased as a function of the number of EO segments, N[sub EO], obeying a scaling law (A [approx] N[sub EO][sup 1/2]) similar to that of lower molecular weight C[sub i]E[sub j] nonionic surfactants. 56 refs., 6 figs., 2 tabs.

  19. Rapid ordering of block copolymer thin films

    DOE PAGES

    Majewski, Pawel W.; Yager, Kevin G.

    2016-08-18

    Block-copolymers self-assemble into diverse morphologies, where nanoscale order can be finely tuned via block architecture and processing conditions. However, the ultimate usage of these materials in real-world applications may be hampered by the extremely long thermal annealing times—hours or days—required to achieve good order. Here, we provide an overview of the fundamentals of block-copolymer self-assembly kinetics, and review the techniques that have been demonstrated to influence, and enhance, these ordering kinetics. We discuss the inherent tradeoffs between oven annealing, solvent annealing, microwave annealing, zone annealing, and other directed self-assembly methods; including an assessment of spatial and temporal characteristics. Here, wemore » also review both real-space and reciprocal-space analysis techniques for quantifying order in these systems.« less

  20. Rapid ordering of block copolymer thin films

    SciTech Connect

    Majewski, Pawel W.; Yager, Kevin G.

    2016-08-18

    Block-copolymers self-assemble into diverse morphologies, where nanoscale order can be finely tuned via block architecture and processing conditions. However, the ultimate usage of these materials in real-world applications may be hampered by the extremely long thermal annealing times—hours or days—required to achieve good order. Here, we provide an overview of the fundamentals of block-copolymer self-assembly kinetics, and review the techniques that have been demonstrated to influence, and enhance, these ordering kinetics. We discuss the inherent tradeoffs between oven annealing, solvent annealing, microwave annealing, zone annealing, and other directed self-assembly methods; including an assessment of spatial and temporal characteristics. Here, we also review both real-space and reciprocal-space analysis techniques for quantifying order in these systems.

  1. Rapid ordering of block copolymer thin films

    SciTech Connect

    Majewski, Pawel W.; Yager, Kevin G.

    2016-08-18

    Block-copolymers self-assemble into diverse morphologies, where nanoscale order can be finely tuned via block architecture and processing conditions. However, the ultimate usage of these materials in real-world applications may be hampered by the extremely long thermal annealing times—hours or days—required to achieve good order. Here, we provide an overview of the fundamentals of block-copolymer self-assembly kinetics, and review the techniques that have been demonstrated to influence, and enhance, these ordering kinetics. We discuss the inherent tradeoffs between oven annealing, solvent annealing, microwave annealing, zone annealing, and other directed self-assembly methods; including an assessment of spatial and temporal characteristics. Here, we also review both real-space and reciprocal-space analysis techniques for quantifying order in these systems.

  2. Rapid ordering of block copolymer thin films

    NASA Astrophysics Data System (ADS)

    Majewski, Pawel W.; Yager, Kevin G.

    2016-10-01

    Block-copolymers self-assemble into diverse morphologies, where nanoscale order can be finely tuned via block architecture and processing conditions. However, the ultimate usage of these materials in real-world applications may be hampered by the extremely long thermal annealing times—hours or days—required to achieve good order. Here, we provide an overview of the fundamentals of block-copolymer self-assembly kinetics, and review the techniques that have been demonstrated to influence, and enhance, these ordering kinetics. We discuss the inherent tradeoffs between oven annealing, solvent annealing, microwave annealing, zone annealing, and other directed self-assembly methods; including an assessment of spatial and temporal characteristics. We also review both real-space and reciprocal-space analysis techniques for quantifying order in these systems.

  3. Regulating block copolymer phases via selective homopolymers

    SciTech Connect

    Yang, Shuang E-mail: eqchen@pku.edu.cn; Lei, Zhen; Hu, Nan; Chen, Er-Qiang E-mail: eqchen@pku.edu.cn; Shi, An-Chang

    2015-03-28

    The phase behavior of strongly segregated AB diblock copolymer and selective C homopolymer blends is examined theoretically using a combination of strong stretching theory (SST) and self-consistent field theory (SCFT). The C-homopolymer is immiscible with the B-blocks but strongly attractive with the A-blocks. The effect of homopolymer content on the order-order phase transitions is analyzed. It is observed that, for AB diblock copolymers with majority A-blocks, the addition of the C-homopolymers results in lamellar to cylindrical to spherical phase transitions because of the A/C complexation. For diblock copolymers with minor A-blocks, adding C-homopolymers leads to transitions from spherical or cylindrical morphology with A-rich core to lamellae to inverted cylindrical and spherical morphologies with B-rich core. The results from analytical SST and numerical SCFT are in good agreement within most regions of the phase diagram. But the deviation becomes more obvious when the composition of A-blocks is too small and the content of added C-homopolymers is large enough, where the SCFT predicts a narrow co-existence region between different ordered phases. Furthermore, it is found that the phase behavior of the system is insensitive to the molecular weight of C-homopolymer.

  4. 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

  5. Rod-Coil Block Polyimide Copolymers

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Kinder, James D. (Inventor)

    2005-01-01

    This invention is a series of rod-coil block polyimide copolymers that are easy to fabricate into mechanically resilient films with acceptable ionic or protonic conductivity at a variety of temperatures. The copolymers consist of short-rigid polyimide rod segments alternating with polyether coil segments. The rods and coil segments can be linear, branched or mixtures of linear and branched segments. The highly incompatible rods and coil segments phase separate, providing nanoscale channels for ion conduction. The polyimide segments provide dimensional and mechanical stability and can be functionalized in a number of ways to provide specialized functions for a given application. These rod-coil black polyimide copolymers are particularly useful in the preparation of ion conductive membranes for use in the manufacture of fuel cells and lithium based polymer batteries.

  6. Rod-Coil Block Polyimide Copolymers

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Kinder, James D. (Inventor)

    2005-01-01

    This invention is a series of rod-coil block polyimide copolymers that are easy to fabricate into mechanically resilient films with acceptable ionic or protonic conductivity at a variety of temperatures. The copolymers consist of short-rigid polyimide rod segments alternating with polyether coil segments. The rods and coil segments can be linear, branched or mixtures of linear and branched segments. The highly incompatible rods and coil segments phase separate, providing nanoscale channels for ion conduction. The polyimide segments provide dimensional and mechanical stability and can be functionalized in a number of ways to provide specialized functions for a given application. These rod-coil black polyimide copolymers are particularly useful in the preparation of ion conductive membranes for use in the manufacture of fuel cells and lithium based polymer batteries.

  7. Solid-supported block copolymer membranes through interfacial adsorption of charged block copolymer vesicles.

    PubMed

    Rakhmatullina, Ekaterina; Meier, Wolfgang

    2008-06-17

    The properties of amphiphilic block copolymer membranes can be tailored within a wide range of physical parameters. This makes them promising candidates for the development of new (bio)sensors based on solid-supported biomimetic membranes. Here we investigated the interfacial adsorption of polyelectrolyte vesicles on three different model substrates to find the optimum conditions for formation of planar membranes. The polymer vesicles were made from amphiphilic ABA triblock copolymers with short, positively charged poly(2,2-dimethylaminoethyl methacrylate) (PDMAEMA) end blocks and a hydrophobic poly( n-butyl methacrylate) (PBMA) middle block. We observed reorganization of the amphiphilic copolymer chains from vesicular structures into a 1.5+/-0.04 nm thick layer on the hydrophobic HOPG surface. However, this film starts disrupting and dewetting upon drying. In contrast, adsorption of the vesicles on the negatively charged SiO2 and mica substrates induced vesicle fusion and formation of planar, supported block copolymer films. This process seems to be controlled by the surface charge density of the substrate and concentration of the block copolymers in solution. The thickness of the copolymer membrane on mica was comparable to the thickness of phospholipid bilayers.

  8. Block copolymer/ferroelectric nanoparticle nanocomposites

    NASA Astrophysics Data System (ADS)

    Pang, Xinchang; He, Yanjie; Jiang, Beibei; Iocozzia, James; Zhao, Lei; Guo, Hanzheng; Liu, Jin; Akinc, Mufit; Bowler, Nicola; Tan, Xiaoli; Lin, Zhiqun

    2013-08-01

    Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were first synthesized by exploiting amphiphilic unimolecular star-like poly(acrylic acid)-block-polystyrene (PAA-b-PS) diblock copolymers as nanoreactors. Subsequently, PS-functionalized BaTiO3 NPs were preferentially sequestered within PS nanocylinders in the linear cylinder-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer upon mixing the BaTiO3 NPs with PS-b-PMMA. The use of PS-b-PMMA diblock copolymers, rather than traditional homopolymers, offers the opportunity for controlling the spatial organization of PS-functionalized BaTiO3 NPs in the PS-b-PMMA/BaTiO3 NP nanocomposites. Selective solvent vapor annealing was utilized to control the nanodomain orientation in the nanocomposites. Vertically oriented PS nanocylinders containing PS-functionalized BaTiO3 NPs were yielded after exposing the PS-b-PMMA/BaTiO3 NP nanocomposite thin film to acetone vapor, which is a selective solvent for PMMA block. The dielectric properties of nanocomposites in the microwave frequency range were investigated. The molecular weight of PS-b-PMMA and the size of BaTiO3 NPs were found to exert an apparent influence on the dielectric properties of the resulting nanocomposites.Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were

  9. Sulfur-carbon nanocomposite cathodes improved by an amphiphilic block copolymer for high-rate lithium-sulfur batteries.

    PubMed

    Fu, Yongzhu; Su, Yu-Sheng; Manthiram, Arumugam

    2012-11-01

    A sulfur-carbon nanocomposite consisting of a commercial high-surface-area carbon (i.e., Black Pearls 2000, BET surface area >1000 m² g⁻¹) and sulfur has been synthesized by an in situ deposition method. The nanocomposite is in the form of agglomerated nanoparticles, with the micropores within the carbon filled with sulfur and the mesopores on the carbon surface almost completely covered by sulfur. The BET surface area of the nanocomposite containing a sulfur content of 63.5 wt % is significantly reduced to only 40 m² g⁻¹. Cathodes containing the nanocomposite and Pluronic F-127 block copolymer, which partially replaces the polyvinylidene fluoride binder, were prepared and evaluated in lithium cells by cyclic voltammetry and galvanostatic cycling. The nanocomposite cathodes with the copolymer show improved electrochemical stability and cyclability. The Pluronic copolymer helps retain a uniform nanocomposite structure within the electrodes, improving the electrochemical contact, which was manifested by scanning electron microscopy and electrochemical impedance spectroscopy. The sulfur-Black Pearls nanocomposite with the Pluronic copolymer as an additive in the electrodes is promising for high-rate rechargeable lithium-sulfur batteries.

  10. Block copolymer/ferroelectric nanoparticle nanocomposites.

    PubMed

    Pang, Xinchang; He, Yanjie; Jiang, Beibei; Iocozzia, James; Zhao, Lei; Guo, Hanzheng; Liu, Jin; Akinc, Mufit; Bowler, Nicola; Tan, Xiaoli; Lin, Zhiqun

    2013-09-21

    Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were first synthesized by exploiting amphiphilic unimolecular star-like poly(acrylic acid)-block-polystyrene (PAA-b-PS) diblock copolymers as nanoreactors. Subsequently, PS-functionalized BaTiO3 NPs were preferentially sequestered within PS nanocylinders in the linear cylinder-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer upon mixing the BaTiO3 NPs with PS-b-PMMA. The use of PS-b-PMMA diblock copolymers, rather than traditional homopolymers, offers the opportunity for controlling the spatial organization of PS-functionalized BaTiO3 NPs in the PS-b-PMMA/BaTiO3 NP nanocomposites. Selective solvent vapor annealing was utilized to control the nanodomain orientation in the nanocomposites. Vertically oriented PS nanocylinders containing PS-functionalized BaTiO3 NPs were yielded after exposing the PS-b-PMMA/BaTiO3 NP nanocomposite thin film to acetone vapor, which is a selective solvent for PMMA block. The dielectric properties of nanocomposites in the microwave frequency range were investigated. The molecular weight of PS-b-PMMA and the size of BaTiO3 NPs were found to exert an apparent influence on the dielectric properties of the resulting nanocomposites.

  11. Dynamics of Block Copolymer Nanocomposites

    SciTech Connect

    Mochrie, Simon G. J.

    2014-09-09

    A detailed study of the dynamics of cadmium sulfide nanoparticles suspended in polystyrene homopolymer matrices was carried out using X-ray photon correlation spectroscopy for temperatures between 120 and 180 °C. For low molecular weight polystyrene homopolymers, the observed dynamics show a crossover from diffusive to hyper-diffusive behavior with decreasing temperatures. For higher molecular weight polystyrene, the nanoparticle dynamics appear hyper-diffusive at all temperatures studied. The relaxation time and characteristic velocity determined from the measured hyper-diffusive dynamics reveal that the activation energy and underlying forces determined are on the order of 2.14 × 10-19 J and 87 pN, respectively. We also carried out a detailed X-ray scattering study of the static and dynamic behavior of a styrene– isoprene diblock copolymer melt with a styrene volume fraction of 0.3468. At 115 and 120 °C, we observe splitting of the principal Bragg peak, which we attribute to phase coexistence of hexagonal cylindrical and cubic double- gyroid structure. In the disordered phase, above 130 °C, we have characterized the dynamics of composition fluctuations via X-ray photon correlation spectroscopy. Near the peak of the static structure factor, these fluctuations show stretched-exponential relaxations, characterized by a stretching exponent of about 0.36 for a range of temperatures immediately above the MST. The corresponding characteristic relaxation times vary exponentially with temperature, changing by a factor of 2 for each 2 °C change in temperature. At low wavevectors, the measured relaxations are diffusive with relaxation times that change by a factor of 2 for each 8 °C change in temperature.

  12. "Clickable" PEG-dendritic block copolymers.

    PubMed

    Fernandez-Megia, Eduardo; Correa, Juan; Riguera, Ricardo

    2006-11-01

    Three generations of azido-terminated PEG-dendritic block copolymers have been synthesized and completely characterized by NMR and MALDI-TOF. A radial decrease of density, leading to more mobile protons at the outermost periphery, and an increasingly higher compactness of the core with generation have been determined by T(1) and T(2) relaxation time studies. The efficient surface decoration of these dendritic polymers by means of click chemistry has been demonstrated by the incorporation of unprotected carbohydrate units in very good to excellent yields. The reaction proceeds at room temperature, under aqueous conditions, and requires just catalytic amounts of Cu. The modified block copolymers are conveniently purified by ultrafiltration. The glycodendrimers functionalized with alpha-mannose form aggregates with concanavalin A as determined by absorbance experiments at 400 nm. This aggregation ability increases with generation.

  13. Hierarchical porous polymer scaffolds from block copolymers.

    PubMed

    Sai, Hiroaki; Tan, Kwan Wee; Hur, Kahyun; Asenath-Smith, Emily; Hovden, Robert; Jiang, Yi; Riccio, Mark; Muller, David A; Elser, Veit; Estroff, Lara A; Gruner, Sol M; Wiesner, Ulrich

    2013-08-02

    Hierarchical porous polymer materials are of increasing importance because of their potential application in catalysis, separation technology, or bioengineering. Examples for their synthesis exist, but there is a need for a facile yet versatile conceptual approach to such hierarchical scaffolds and quantitative characterization of their nonperiodic pore systems. Here, we introduce a synthesis method combining well-established concepts of macroscale spinodal decomposition and nanoscale block copolymer self-assembly with porosity formation on both length scales via rinsing with protic solvents. We used scanning electron microscopy, small-angle x-ray scattering, transmission electron tomography, and nanoscale x-ray computed tomography for quantitative pore-structure characterization. The method was demonstrated for AB- and ABC-type block copolymers, and resulting materials were used as scaffolds for calcite crystal growth.

  14. Oil-induced aggregation of block copolymer in aqueous solution.

    PubMed

    Ma, Jun-He; Wang, Yun; Guo, Chen; Liu, Hui-zhou; Tang, Ya-lin; Bahadur, Pratap

    2007-09-27

    The oil-induced aggregation behavior of PEO-PPO-PEO Pluronic P84 [(EO)19(PO)39(EO)19] in aqueous solutions has been systematically investigated by 1H NMR spectroscopy, freeze-fracture transmission electron microscopy (FF-TEM), and dynamic light scattering (DLS). The critical micellization temperature (CMT) for P84 in the presence of oils decreases with increasing oil concentration. The effectiveness of various oils in decreasing the CMT of block copolymer follows the order m-xylene (C(8)H(10)) > toluene (C(7)H(8)) > benzene (C(6)H(6)) > n-octane (C(8)H(18)) > n-hexane (C(6)H(14)) approximately cyclohexane (C(6)H(12)). It was found that the amount of anhydrous PO methyl groups increases whereas the amount of hydrated PO methyl groups decreases upon the addition of oils. At low oil concentration, the oil molecules are entrapped by the micellar core, but as the oil concentration increases above a certain value, the micellar core swells significantly as a result of the penetrated oil molecules, and much larger aggregates are formed. Intermolecular rotating-frame nuclear Overhauser effect (ROE) measurements between P84 and benzene were performed at 10 and 40 degrees C. The specific interaction between benzene and the methyl groups of PPO was determined, and it was observed that the interaction site remained unchanged as the temperature was increased.

  15. Cavitation in block copolymer modified epoxy

    NASA Astrophysics Data System (ADS)

    Declet-Perez, Carmelo; Francis, Lorraine; Bates, Frank

    2013-03-01

    Today, brittleness in epoxy networks limits most commercial applications. Significant toughness can be imparted by adding small amounts of micelle forming block copolymers (BCP) without compromising critical properties such as high use temperature and modulus. Curing the network locks in the self-assembled BCP micellar structures formed in the monomer resin providing control of the resulting morphology. Despite significant research over the last decade, a complete description of the parameters influencing toughness in block copolymer modified epoxies is still lacking. In this presentation we compare the ultimate mechanical behavior of epoxies modified with spherical micelle forming BCP's containing rubbery and glassy cores using real-time in-situ small-angle X-ray scattering (SAXS) performed during tensile deformation. Striking differences in the 2D SAXS patterns were documented for epoxies modified with rubbery (PEP) versus glassy (PS) micelle cores. Rubbery cores dilate by 100% in volume upon specimen yielding, while the glassy micelle cores deform at approximately constant volume. These results provide direct evidence of a cavitation mediated mechanism for toughness in block copolymer modified epoxies. We further interpret characteristic butterfly features in the 2D SAXS patterns in terms of epoxy network deformation. Support was provided by the NSF sponsored MRSEC at the University of Minnesota

  16. Block copolymer nanolithography for the fabrication of patterned media.

    SciTech Connect

    Warke, Vishal V; Bakker, Martin G; Hong, Kunlun; Mays, Jimmy; Britt, Phillip F; Li, Xuefa; Wang, Jin

    2008-01-01

    Abstract Bit patterned perpendicular media has the potential to increase the density of magnetic recording beyond what can be achieved by granular media. Self assembling diblock copolymers are of interest as templates for patterned media, as they potentially provide a low cost fabrication route. A method to fabricate the desired pattern using cylinder forming diblock copolymers of (PS-b-PMMA) as template is reported. Upon phase separation hexagonally packed cylinders of the minority phase (PMMA) surrounded by the continuous majority phase (PS) are obtained. The processing sequence began with spin coating the block copolymer on a suitable substrate, followed by annealing the block copolymer thin film in vacuum to orient it perpendicular to the substrate. Block copolymer templates were obtained by glacial acetic acid treatment which opened the pores in the block copolymer thin film. Ni was electrodeposited in the block copolymer templates and this pattern was then transferred onto the underlying substrate by ion milling

  17. Amphiphilic block copolymer membrane for vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Sylvia, James M.; Jacob, Monsy M.; Peramunage, Dharmasena

    2013-11-01

    An amphiphilic block copolymer comprised of hydrophobic polyaryletherketone (PAEK) and hydrophilic sulfonated polyaryletherketone (SPAEK) blocks has been synthesized and characterized. A membrane prepared from the block copolymer is used as the separator in a single cell vanadium redox flow battery (VRB). The proton conductivity, mechanical property, VO2+ permeability and single VRB cell performance of this block copolymer membrane are investigated and compared to Nafion™ 117. The block copolymer membrane showed significantly improved vanadium ion selectivity, higher mechanical strength and lower conductivity than Nafion™ 117. The VRB containing the block copolymer membrane exhibits higher coulombic efficiency and similar energy efficiency compared to a VRB using Nafion™ 117. The better vanadium ion selectivity of the block copolymer membrane has led to a much smaller capacity loss during 50 charge-discharge cycles for the VRB.

  18. Formulation of benzoporphyrin derivatives in Pluronics.

    PubMed

    Chowdhary, Rubinah K; Chansarkar, Namrata; Sharif, Isha; Hioka, Noboru; Dolphin, David

    2003-03-01

    This study investigates the potential of Pluronics for the formulation of tetrapyrrole-based photosensitizers, with a particular focus on B-ring benzoporphyrin derivatives. The B-ring derivatives have a high tendency to aggregate in aqueous solutions, and this poses a significant formulation problem. Pluronics are ABA-type triblock copolymers composed of a central hydrophobic polypropylene oxide section with two hydrophilic polyethylene oxide sections of equal length at either end. Out of a range of different commercially available block copolymers studied, it was found that the longer the hydrophobic block, the better the stabilization of tetrapyrrolic drugs in monomeric form in aqueous suspensions. Of these the best performance was observed in the micelle-forming Pluronic P123. Micelle size determination by laser light scattering confirmed that particle size in stable Pluronic formulations was around 20 nm. Pluronics such as L122 formed emulsions spontaneously without the need for emulsion stabilizers; emulsions were highly stable at ambient temperatures over several days and also highly effective as potential drug delivery agents.

  19. New functionalized block copolymers for bonding copper to epoxy

    SciTech Connect

    Kent, M.; Saunders, R.; Emerson, J.; Hurst, M.

    1995-11-01

    The authors are exploring the use of functionalized block copolymers for bonding copper to epoxy in printed wiring boards. The program involves four key elements: (i) synthesis of suitable functionalized block copolymers; (ii) characterization of the conformation of the copolymers at the relevant interfaces by neutron reflectivity; (iii) spectroscopic measurements of chemical bonding, and (iv) measurement of the mechanical properties of the interfaces. The copolymers are synthesized by living, ring-opening metathesis polymerization. This relatively new technique allows great flexibility for synthesis of functionalized block copolymers in that the initiators are relatively insensitive to a wide range of functional groups. Significant adhesion enhancement has been observed in lap shear tests.

  20. Polypeptide Point Modifications with Fatty Acid and Amphiphilic Block Copolymers for Enhanced Brain Delivery

    PubMed Central

    Batrakova, Elena V.; Vinogradov, Serguei V.; Robinson, Sandra M.; Niehoff, Michael L.; Banks, William A.; Kabanov, Alexander V.

    2009-01-01

    There is a tremendous need to enhance delivery of therapeutic polypeptides to the brain to treat disorders of the central nervous system (CNS). The brain delivery of many polypeptides is severely restricted by the blood—brain barrier (BBB). The present study demonstrates that point modifications of a BBB-impermeable polypeptide, horseradish peroxidase (HRP), with lipophilic (stearoyl) or amphiphilic (Pluronic block copolymer) moieties considerably enhance the transport of this polypeptide across the BBB and accumulation of the polypeptide in the brain in vitro and in vivo. The enzymatic activity of the HRP was preserved after the transport. The modifications of the HRP with amphiphilic block copolymer moieties through degradable disulfide links resulted in the most effective transport of the HRP across in vitro brain microvessel endothelial cell monolayers and efficient delivery of HRP to the brain. Stearoyl modification of HRP improved its penetration by about 60% but also increased the clearance from blood. Pluronic modification using increased penetration of the BBB and had no significant effect on clearance so that uptake by brain was almost doubled. These results show that point modification can improve delivery of even highly impermeable polypeptides to the brain. PMID:16029020

  1. Defect trapping in ABC block copolymers

    NASA Astrophysics Data System (ADS)

    Corte, Laurent; Yamauchi, Kazuhiro; Court, Francois; Cloitre, Michel; Hashimoto, Takeji; Leibler, Ludwik

    2004-03-01

    Equilibrium morphologies in molten ABC triblock terpolymers are much more difficult to attain than in AB diblocks. In practice, it is important to know whether and how synthesis conditions influence the morphology and properties of copolymer materials. It is also relevant to understand the mechanisms of defect formation and annihilation. Indeed, a potential use of copolymers in new applications such as lithography highly depends on the ability to produce regular structures with no or few defects. We show that even the simplest lamellar structures exhibit high sensitivity to preparation conditions and that strongly trapped structural defects inherent to ABC triblock architecture cannot be removed by long annealing. Annealing can induce a transition from a lamellar structure in which A and C blocks are mixed to a lamellar structure where A, B and C are segregated. We propose reorganization mechanisms that are at the origin of some characteristic defects.

  2. Comparing the morphology and phase diagram of H-shaped ABC block copolymers and linear ABC block copolymers.

    PubMed

    Ye, Xianggui; Yu, Xifei; Sun, Zhaoyan; An, Lijia

    2006-06-22

    By using a combinatorial screening method based on the self-consistent field theory (SCFT) for polymers, we have investigated the morphology of H-shaped ABC block copolymers (A2BC2) and compared them with those of the linear ABC block copolymers. By changing the ratios of the volume fractions of two A arms and two C arms, one can obtain block copolymers with different architectures ranging from linear block copolymer to H-shaped block copolymer. By systematically varying the volume fractions of block A, B, and C, the triangle phase diagrams of the H-shaped ABC block copolymer with equal interactions among the three species are constructed. In this study, we find four different morphologies (lamellar phase (LAM), hexagonal lattice phase (HEX), core-shell hexagonal lattice phase (CSH), and two interpenetrating tetragonal lattice (TET2)). Furthermore, the order-order transitions driven by architectural change are discussed.

  3. Responsive linear-dendritic block copolymers.

    PubMed

    Blasco, Eva; Piñol, Milagros; Oriol, Luis

    2014-06-01

    The combination of dendritic and linear polymeric structures in the same macromolecule opens up new possibilities for the design of block copolymers and for applications of functional polymers that have self-assembly properties. There are three main strategies for the synthesis of linear-dendritic block copolymers (LDBCs) and, in particular, the emergence of click chemistry has made the coupling of preformed blocks one of the most efficient ways of obtaining libraries of LDBCs. In these materials, the periphery of the dendron can be precisely functionalised to obtain functional LDBCs with self-assembly properties of interest in different technological areas. The incorporation of stimuli-responsive moieties gives rise to smart materials that are generally processed as self-assemblies of amphiphilic LDBCs with a morphology that can be controlled by an external stimulus. Particular emphasis is placed on light-responsive LDBCs. Furthermore, a brief review of the biomedical or materials science applications of LDBCs is presented. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Are block copolymer worms more effective Pickering emulsifiers than block copolymer spheres?

    PubMed

    Thompson, K L; Mable, C J; Cockram, A; Warren, N J; Cunningham, V J; Jones, E R; Verber, R; Armes, S P

    2014-11-21

    RAFT-mediated polymerisation-induced self-assembly (PISA) is used to prepare six types of amphiphilic block copolymer nanoparticles which were subsequently evaluated as putative Pickering emulsifiers for the stabilisation of n-dodecane-in-water emulsions. It was found that linear poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) diblock copolymer spheres and worms do not survive the high shear homogenisation conditions used for emulsification. Stable emulsions are obtained, but the copolymer acts as a polymeric surfactant; individual chains rather than particles are adsorbed at the oil-water interface. Particle dissociation during emulsification is attributed to the weakly hydrophobic character of the PHPMA block. Covalent stabilisation of these copolymer spheres or worms can be readily achieved by addition of ethylene glycol dimethacrylate (EGDMA) during the PISA synthesis. TEM studies confirm that the resulting cross-linked spherical or worm-like nanoparticles survive emulsification and produce genuine Pickering emulsions. Alternatively, stabilisation can be achieved by either replacing or supplementing the PHPMA block with the more hydrophobic poly(benzyl methacrylate) (PBzMA). The resulting linear spheres or worms also survive emulsification and produce stable n-dodecane-in-water Pickering emulsions. The intrinsic advantages of anisotropic worms over isotropic spheres for the preparation of Pickering emulsions are highlighted. The former particles are more strongly adsorbed at similar efficiencies compared to spheres and also enable smaller oil droplets to be produced for a given copolymer concentration. The scalable nature of PISA formulations augurs well for potential applications of anisotropic block copolymer nanoparticles as Pickering emulsifiers.

  5. Comparing Fluid and Elastic Block Copolymer Shells

    NASA Astrophysics Data System (ADS)

    Rozairo, Damith; Croll, Andrew B.

    2014-03-01

    Emulsions can be stabilized with the addition of an amphiphilic diblock copolymer, resulting in droplets surrounded and protected by a polymer monolayer. Such droplets show considerable promise as advanced cargo carriers in pharmaceuticals or cosmetics due to their strength and responsiveness. Diblock copolymer interfaces remain mostly fluid and may not be able to attain the mechanical performance desired by industry. To strengthen block copolymer emulsion droplets we have developed a novel method for creating thin elastic shells using polystyrene-b-poly(acrylic acid)-b-polystyrene (PS-PAA-PS). Characterization of the fluid filled elastic shells is difficult with traditional means which lead us to develop a new and general method of mechanical measurement. Specifically, we use laser scanning confocal microscopy to achieve a high resolution measure of the deformation of soft spheres under the influence of gravity. To prove the resilience of the technique we examine both a polystyrene-b-poly(ethylene oxide) (PS-PEO) stabilized emulsion and the PS-PAA-PS emulsion. The mechanical measurement allows the physics of the polymer at the interface to be examined, which will ultimately lead to the rational development of these technologies.

  6. Tunable Morphologies from Charged Block Copolymers

    SciTech Connect

    Goswami, Monojoy; Sumpter, Bobby G; Mays, Jimmy; Messman, Jamie M

    2010-01-01

    The bulk morphologies formed by a new class of charged block copolymers, 75 vol % fluorinated polyisoprene (FPI) 25 vol% sulfonated polystyrene (PSS) with 50% sulfonation, are characterized, and the fundamental underlying forces that promote the self-assembly processes are elucidated. The results show how the bulk morphologies are substantially different from their uncharged diblock counterparts (PS-PI) and also how morphology can be tuned with volume fraction of the charged block and the casting solvent. A physical understanding based on the underlying strong electrostatic interactions between the charged block and counterions is obtained using Monte Carlo (MC) and Molecular Dynamics (MD) simulations. The 75/25 FPI-PSS shows hexagonal morphologies with the minority blocks (PSS) forming the continuous phase due to charge percolation and the FPI blocks arranged in hexagonal cylinders. Some long-range order can be sustained even if lipophobicity is increased (addition of water), albeit with lower dimensional structures. However, thermal annealing provides sufficient energy to disrupt the percolated charges and promotes aggregation of ionic sites which leads to a disordered system. Diverse and atypical morphologies are readily accessible by simply changing the number distribution of the charges on PSS block.

  7. Well Ordered Melts from Low Molar Mass Pluronic Copolymers Blended with Poly (acrylic acid): Effect of Homopolymer Molar Mass

    NASA Astrophysics Data System (ADS)

    Daga, Vikram; Tirumala, Vijay; Romang, Alvin; Lin, Eric; Watkins, James

    2008-03-01

    The use of short chain block copolymer melts as nanostructured templates is often limited by their low segregation strength (χN). Since increasing molar mass to strengthen segregation also increases the interdomain spacing, it is more desirable to increase the segment-segment interaction parameter, χ to produce strong segregation. We have recently shown that block copolymer melts with a molar mass less than 15 kg/mol undergo disorder-to-order transition without a significant increase in interdomain spacing when blended with a selectively associating homopolymer, due to an apparent increase in effective χ. Here, we study the effect of homopolymer molar mass on the segregation of a disordered poly (oxyethylene-oxypropylene-oxyethylene) copolymer melt that forms lamellar microstructure in the ordered phase. Based on small-angle scattering measurements, we find that the melts remain ordered over a broad range of homopolymer chain lengths, ranging up to ten times that of the copolymer. This approach has many implications for the use of commodity block copolymer surfactants as inexpensive nanostructured templates for commercial applications.

  8. Development of chitosan graft pluronic®F127 copolymer nanoparticles containing DNA aptamer for paclitaxel delivery to treat breast cancer cells

    NASA Astrophysics Data System (ADS)

    Thach Nguyen, Kim; Le, Duc Vinh; Do, Dinh Ho; Huan Le, Quang

    2016-06-01

    HER-2/ErbB2/Neu(HER-2), a member of the epidermal growth factor receptor family, is specifically overexpressed on the surface of breast cancer cells and serves a therapeutic target for breast cancer. In this study, we aimed to isolate DNA aptamer (Ap) that specifically bind to a HER-2 overexpressing SK-BR-3 human breast cancer cell line, using SELEX strategy. We developed a novel multifunctional composite micelle with surface modification of Ap for targeted delivery of paclitaxel. This binary mixed system consisting of Ap modified pluronic®F127 and chitosan could enhance PTX loading capacity and increase micelle stability. Polymeric micelles had a spherical shape and were self-assemblies of block copolymers of approximately 86.22 ± 1.45 nm diameter. PTX could be loaded with high encapsulation efficiency (83.28 ± 0.13%) and loading capacity (9.12 ± 0.34%). The release profile were 29%-35% in the first 12 h and 85%-93% after 12 d at pH 7.5 of receiving media. The IC50 doses by MTT assay showed the greater activity of nanoparticles loaded paclitaxel over free paclitaxel and killed cells up to 95% after 6 h. These results demonstrated unique assembly with the capacity to function as an efficient detection and delivery vehicle in the biological living system.

  9. Interface-enforced complexation between copolymer blocks.

    PubMed

    Steinschulte, Alexander A; Xu, Weinan; Draber, Fabian; Hebbeker, Pascal; Jung, Andre; Bogdanovski, Dimitri; Schneider, Stefanie; Tsukruk, Vladimir V; Plamper, Felix A

    2015-05-14

    Binary diblock copolymers and corresponding ternary miktoarm stars are studied at oil-water interfaces. All polymers contain oil-soluble poly(propylene oxide) PPO, water-soluble poly(dimethylaminoethyl methacrylate) PDMAEMA and/or poly(ethylene oxide) PEO. The features of their Langmuir compression isotherms are well related to the ones of the corresponding homopolymers. Within the Langmuir-trough, PEO-b-PPO acts as the most effective amphiphile compared to the other PPO-containing copolymers. In contrast, the compression isotherms show a complexation of PPO and PDMAEMA for PPO-b-PDMAEMA and the star, reducing their overall amphiphilicity. Such complex formation between the blocks of PPO-b-PDMAEMA is prevented in bulk water but facilitated at the interface. The weakly-interacting blocks of PPO-b-PDMAEMA form a complex due to their enhanced proximity in such confined environments. Scanning force microscopy and Monte Carlo simulations with varying confinement support our results, which are regarded as compliant with the mathematical random walk theorem by Pólya. Finally, the results are expected to be of relevance for e.g. emulsion formulation and macromolecular engineering.

  10. Controlling Structure in Sulfonated Block Copolymer Membranes

    NASA Astrophysics Data System (ADS)

    Truong, Phuc; Stein, Gila; Strzalka, Joe

    2015-03-01

    In many ionic block copolymer systems, the strong incompatibility between ionic and non-ionic segments will trap non-equilibrium structures in the film, making it difficult to engineer the optimal domain sizes and transport pathways. The goal of this work is to establish a framework for controlling the solid-state structure of sulfonated pentablock copolymer membranes. They have ABCBA block sequence, where A is poly(t-butyl styrene), B is poly(hydrogenated isoprene), and C is poly(styrene sulfonate). To process into films, the polymer is dissolved in toluene/n-propanol solvent mixtures, where the solvent proportions and the polymer loading were both varied. Solution-state structure was measured with small angle X-ray scattering (SAXS). We detected micelles with radii that depend on the solvent composition and polymer loading. Film structure was measured with grazing-incidence SAXS, which shows (i) domain periodicity is constant throughout film thickness; (ii) domain periodicity depends on solvent composition and polymer loading, and approximately matches the micelle radii in solutions. The solid-state packing is consistent with a hard sphere structure factor. Results suggest that solid-state structure can be tuned by manipulating the solution-state self-assembly.

  11. Microphase Separated Block Copolymers in Pervaporation Membranes for Biofuels Processing

    NASA Astrophysics Data System (ADS)

    Greer, Douglas; Shin, Chae-Young; Ozcam, Evren; Skerker, Jeffrey; Basso, Thalita; Leon, Dacia; Bauer, Stefan; Balsara, Nitash; Energy Biosciences Institute Collaboration

    2014-03-01

    The production of transportation biofuels requires numerous continuous separation processes. We designed block copolymer membranes for pervaporation as a means to achieve these separations. These block copolymers contain a glassy structure block for support and a rubbery transport block for sorption and diffusion. We create membranes with nanoscale conducting channels using the unique trait of block copolymers to assemble into ordered morphologies. We have previously used nanostructured membranes to separate ethanol/water binary mixtures [J. Membr. Sci. 373, 112 (2011)], [J. Membr. Sci. 401, 125 (2012)]. We report this type of membranes is effective in other, more complex separations important to biofuel production. These separations increase yield and decrease process time.

  12. Piezoelectric Properties of Non-Polar Block Copolymers

    SciTech Connect

    Pester, Christian; Ruppel, Markus A; Schoberth, Heiko; Schmidt, K.; Liedel, Clemens; Van Rijn, Patrick; Littrell, Ken; Schindler, Kerstin; Hiltl, Stephanie; Czubak, Thomas; Mays, Jimmy; Urban, Volker S; Boker, Alexander

    2011-01-01

    Piezoelectric properties in non-polar block copolymers are a novelty in the field of electroactive polymers. The piezoelectric susceptibility of poly(styrene-b-isoprene) block copolymer lamellae is found to be up to an order of magnitude higher when compared to classic piezoelectric materials. The electroactive response increases with temperature and is found to be strongest in the disordered phase.

  13. Block Copolymer Directed Assembly for Nanomaterials and Nanodevices

    NASA Astrophysics Data System (ADS)

    Kim, Sang

    2013-03-01

    Block copolymer nanopatterning is a promising technology that can complement the inherent limitations of conventional photolithography. The spontaneous and parallel assembly of block copolymers may generate densely packed, periodic 10-nm-scale nanodomains in a scalable way. Furthermore, laterally ordered, device-oriented nanostructures are attainable by the directed self-assembly principles employing prepatterned substrates. In this presentation, the overview of my research achievements associated to block copolymer nanopatterning will be presented. My research group demonstrated the world-first successful integration of block copolymer nanopatterning with 193 nm ArF lithography. We also developed soft-graphoepitaxy, which generates highly aligned nanoscale metal and semiconductor nanostructures without any trace of structure-directing topographic pattern. Soft-graphoepitaxy could be further developed to ultralarge-area nanopatterning, where micrometer scale photoresist pattern can be completely transformed into large-area block copolymer nanopattern. My research group also developed various pattern transfer methods for block copolymer nanopatterning. Mussel-inspired block copolymer nanopatterning exploiting universal natural adhesive of mussel polydopamine enables the nanopatterning of low surface energy materials, such as gold, Teflon and graphene. Our recent transferrable and flexible nanopatterning employing chemically modified graphene films as pattern substrates makes it possible to apply block copolymer nanopatterning onto arbitrary nonplanar and flexible geometries and generates ideal three-dimensional assembly of carbon nanotubes and graphene.

  14. Block Copolymers for Alkaline Fuel Cell Membrane Materials

    DTIC Science & Technology

    2014-07-30

    113 CHAPTER 5 MONO METHOXY POLY( ETHYLENE GLYCOL) GRAFTED BLOCK COPOLYMERS FOR ALKALINE EXCHANGE MEMBRANE...polystyrene-poly( ethylene -co-butylene)-polystyrene (SEBS) copolymer.[37, 42] Chloromethylation of the polystyrene block and trimethylamine...temperature. The same graft and functionalization strategy was applied to poly( ethylene -co- tetrafluoroethylene) (ETFE) film leading to a promising

  15. Solvent enhanced block copolymer ordering in thin films

    NASA Astrophysics Data System (ADS)

    Misner, Matthew J.

    Diblock copolymer self-assembly of materials is emerging as a key element in the fabrication of functional nanostructured materials. By solvent casting or solvent annealing block copolymer thin films, we have demonstrated methods to produce diblock copolymer films with highly oriented, close-packed arrays of nanoscopic cylindrical domains with a high degree of long-range lateral order with few defects. The solvent imparts a high degree of mobility in the microphase-separated copolymer that enables a rapid removal of defects and a high degree of lateral order. Though the use of a selective cosolvent during solvent casting, it was found that the microdomain size and spacing could be increased, leading to a size-tunable system. Additionally, the presence of water also led to the ability to control the microdomain orientation during solvent annealing. Ionic complexation within cylinder-forming PS- b-EO block copolymer thin films was also investigated, where added salts bind PEO block as the minor component. Small amounts of added salts, on the order a few ions per chain, show large effects on the ordering of the copolymer films during solvent annealing. By using gold or cobalt salts, well-organized patterns of nanoparticles can be generated in the copolymer microdomains. Topographically and chemically patterned surfaces were used as a route to sectorizing and controlling the lattice orientation of copolymer films. Topographically patterned surfaces allow well-defined boundaries to confine the copolymer microdomains on a surface and effectively direct the ordering and grain orientation of the copolymer microdomains. Chemically patterned surfaces provide a route to direct the block copolymer ordering on completely flat surface, which may have advantages in applications where adding additional topography may be undesirable. To generate nanoporous templates from PS-b-PEO bases materials several routs were followed. The first route was through the addition and selective

  16. Tough and Sustainable Graft Block Copolymer Thermoplastics

    SciTech Connect

    Zhang, Jiuyang; Li, Tuoqi; Mannion, Alexander M.; Schneiderman, Deborah K.; Hillmyer, Marc A.; Bates, Frank S.

    2016-03-15

    Fully sustainable poly[HPMC-g-(PMVL-b-PLLA)] graft block copolymer thermoplastics were prepared from hydroxypropyl methylcellulose (HPMC), β-methyl-δ-valerolactone (MVL), and l-lactide (LLA) using a facile two-step sequential addition approach. In these materials, rubbery PMVL functions as a bridge between the semirigid HPMC backbone and the hard PLLA end blocks. This specific arrangement facilitates PLLA crystallization, which induces microphase separation and physical cross-linking. By changing the backbone molar mass or side chain composition, these thermoplastic materials can be easily tailored to access either plastic or elastomeric behavior. Moreover, the graft block architecture can be utilized to overcome the processing limitations inherent to linear block polymers. Good control over molar mass and composition enables the deliberate design of HPMC-g-(PMVL-b-PLLA) samples that are incapable of microphase separation in the melt state. These materials are characterized by relatively low zero shear viscosities in the melt state, an indication of easy processability. The simple and scalable synthetic procedure, use of inexpensive and renewable precursors, and exceptional rheological and mechanical properties make HPMC-g-(PMVL-b-PLLA) polymers attractive for a broad range of applications.

  17. Light-emitting block copolymers composition, process and use

    DOEpatents

    Ferraris, John P.; Gutierrez, Jose J.

    2006-11-14

    Generally, and in one form, the present invention is a composition of light-emitting block copolymer. In another form, the present invention is a process producing a light-emitting block copolymers that intends polymerizing a first di(halo-methyl) aromatic monomer compound in the presence of an anionic initiator and a base to form a polymer and contacting a second di(halo-methyl) aromatic monomer compound with the polymer to form a homopolymer or block copolymer wherein the block copolymer is a diblock, triblock, or star polymer. In yet another form, the present invention is an electroluminescent device comprising a light-emitting block copolymer, wherein the electroluminescent device is to be used in the manufacturing of optical and electrical devices.

  18. Electric Field Induced Selective Disordering in Lamellar Block Copolymers

    SciTech Connect

    Ruppel, Markus A; Pester, Christian W; Langner, Karol M; Sevink, Geert; Schoberth, Heiko; Schmidt, Kristin; Urban, Volker S; Mays, Jimmy; Boker, Alexander

    2013-01-01

    External electric fields align nanostructured block copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the orderdisorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented parallel to the applied field prevail. The present study adds an additional mechanism to the experimentally corroborated suite of mechanistic pathways, by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the orderdisorder transition and well below it.

  19. Electric field induced selective disordering in lamellar block copolymers.

    PubMed

    Ruppel, Markus; Pester, Christian W; Langner, Karol M; Sevink, Geert J A; Schoberth, Heiko G; Schmidt, Kristin; Urban, Volker S; Mays, Jimmy W; Böker, Alexander

    2013-05-28

    External electric fields align nanostructured block copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the order-disorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented parallel to the applied field prevail. The present study adds an additional mechanism to the experimentally corroborated suite of mechanistic pathways, by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the order-disorder transition and well below it.

  20. Fabrication routes for one-dimensional nanostructures via block copolymers

    NASA Astrophysics Data System (ADS)

    Tharmavaram, Maithri; Rawtani, Deepak; Pandey, Gaurav

    2017-05-01

    Nanotechnology is the field which deals with fabrication of materials with dimensions in the nanometer range by manipulating atoms and molecules. Various synthesis routes exist for the one, two and three dimensional nanostructures. Recent advancements in nanotechnology have enabled the usage of block copolymers for the synthesis of such nanostructures. Block copolymers are versatile polymers with unique properties and come in many types and shapes. Their properties are highly dependent on the blocks of the copolymers, thus allowing easy tunability of its properties. This review briefly focusses on the use of block copolymers for synthesizing one-dimensional nanostructures especially nanowires, nanorods, nanoribbons and nanofibers. Template based, lithographic, and solution based approaches are common approaches in the synthesis of nanowires, nanorods, nanoribbons, and nanofibers. Synthesis of metal, metal oxides, metal oxalates, polymer, and graphene one dimensional nanostructures using block copolymers have been discussed as well.

  1. Nanoparticle-Loaded Multifunctional Block Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Bae, Jinhye; Lawrence, Jimmy; Miesch, Caroline; Ribbe, Alexander; Li, Weikun; Emrick, Todd; Zhu, Jintao; Hayward, Ryan

    2012-02-01

    We have studied the incorporation of pre-synthesized hydrophobic inorganic nanoparticles within the cores of amphiphilic polystyrene-block-poly(ethylene oxide) (PS-PEO) diblock copolymer micelles formed through solvent-evaporation-induced interfacial instabilities of emulsion droplets. Using iron oxide, gold, and cadmium selenide nanoparticles coated with native alkane ligands, highly uniform encapsulation is obtained for cylindrical micelles, while spherical micelles can be enriched to ˜ 90 % of loaded micelles through simple magnetic or centrifugal purification steps. Multiple different types of nanoparticles can easily be incorporated into each micelle, yielding multi-functional micelles. The ability to encapsulate both spherical and rod-like particles of different core chemistries and sizes ranging from ˜ 1 to 20 nm, without the necessity of coating particles with specially designed ligands, makes this a versatile route to prepare hybrid micelle structures.

  2. Ion transport through block copolymer electrolytes

    NASA Astrophysics Data System (ADS)

    Mullin, Scott; Panday, Ashoutosh; Balsara, Nitash

    2009-03-01

    Poly(styrene)-block-poly(ethylene oxide) (SEO) is a candidate material for electrolytes for rechargeable lithium metal batteries. The PS phase suppresses lithium dendrite growth on the anode during recharge, and the PEO phase solvates lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt to form conducting pathways. Complete electrochemical characterization of PEO/LiTFSI mixtures requires measurement of conductivity, salt diffusion coefficient, and lithium ion transference number. The present study covers SEO copolymers that exhibit lamellar and cylindrical morphologies in the absence of salt. The addition of salt affects morphology but the relationships between morphology and electrochemical characteristics have not yet been clarified. Some aspects of these relationships will be presented.

  3. Controlled release camptothecin tablets based on pluronic and poly(acrylic acid) copolymer. Effect of fabrication technique on drug stability, tablet structure, and release mode.

    PubMed

    Bromberg, Lev; Hatton, T Alan; Barreiro-Iglesias, Rafael; Alvarez-Lorenzo, Carmen; Concheiro, Angel

    2007-06-01

    Poly(ethylene oxide)-b-poly(propylene oxide)-b-(polyethylene oxide)-g-poly(acrylic acid), a graft-comb copolymer of Pluronic 127 and poly(acrylic acid) (Pluronic-PAA), was explored as an excipient for tablet dosage form of camptothecin (CPT). The tablets were prepared by either direct compression of the drug-polymer physical blend, suspension in ethanol followed by evaporation, or compression after kneading and characterized with respect to their physical structures, drug stability, and release behavior. Porosity and water uptake rate were strongly dependent on the fabrication procedure, ranking in the order: direct compression of physical blend > compression after suspension/evaporation in ethanol > compression after kneading. Tablets prepared by compression of physical blends swelled in water with a rapid surface gel layer formation that impeded swelling and disintegration of the tablets core. These tablets were able to sustain the CPT release for a period of time longer than those observed with the tablets made by either suspension/evaporation or kneading, which disintegrated within a few minutes. Despite the tablet disintegration, the CPT release was impeded for at least 6 hr, which was attributed to the ability of the Pluronic-PAA copolymers to form micellar aggregates at the hydrated surface of the particles. Physical mixing did not alter the fraction of CPT being in the pharmaceutically active lactone form, whilst the preparation of the tablets by the other two methods caused a significant reduction in the lactone form content. Tablets prepared from the physical blends demonstrated CPT release rates increasing with the pH due to the PAA ionization leading to the increase in the rate and extent of the tablet swelling. The results obtained demonstrate the potential of the Pluronic-PAA copolymers for the oral administration of chemotherapeutic agents.

  4. Block Copolymer Thin Films: Patterns and Patterning

    NASA Astrophysics Data System (ADS)

    Register, Richard A.

    2001-03-01

    The nanostructures ("microdomains") in thin block copolymer films make excellent contact masks for surface patterning on the nanoscale. Using these thin films as templates, we have developed techniques based on reactive ion etching to uniformly and completely pattern the underlying substrate with a dense periodic pattern of dots, holes, or lines, with widths of order 20 nm. In addition, we have fabricated arrays of metal dots by backfilling these holes, and GaAs quantum dots by regrowth onto patterned GaAs substrates. A key issue in this nanopatterning approach is controlling the pattern which forms within the mask. While the local structure of the pattern (e.g., spheres vs. cylinders) is easily controlled through block copolymer composition, the long-range order ("grain size") is more difficult to manipulate. For cylinder-forming diblocks, we find that the correlation length of the microdomains grows as a weak power of annealing time, approximately 1/4. The principal types of defects which destroy the long-range order of the microdomains are disclinations. Sequential AFM images taken on the same region of the film after varying annealing times can be strung together into "movies" (to be shown at the talk) which directly show that the principal mode of defect annihilation (and hence grain growth) is the annihilation of disclination quadrupoles (pairs of +1/2 and -1/2 disclinations). We propose a model for quadrupole annihilation which reproduces the 1/4 exponent. Preliminary results for sphere-forming systems suggest that the exponent there is even lower than 1/4, making it difficult to achieve a significant degree of coarsening by extending the annealing time. * in collaboration with D.H. Adamson, P.M. Chaikin, Z. Cheng, P.D. Dapkus (USC), C.K. Harrison, D.A. Huse, R.R. Li (USC), and M. Park.

  5. Block Copolymer Metastability: Scientific Nightmare or Engineering Dream?

    NASA Astrophysics Data System (ADS)

    Bates, Frank S.

    1997-03-01

    Most experimental studies and almost all theories that deal with block copolymers, or mixtures of block copolymers and homopolymers, have been designed from an equilibrium perspective. Yet a myriad of factors conspire to retard approach to equilibrium in these systems, including: subtle features in the free energy surface that are controlled by ordered state symmetry; a coupling between microphase separation and entanglement dynamics; complex molecular architectures such as multiblock, starblock, and miktoarm. Even unentangled low molecular weight diblock copolymers, the simplest and dynamically least encumbered materials, exhibit long-lived metastable states that confound attempts to validate equilibrium theories. However, this apparent dilemma can be exploited through clever processing strategies. This lecture will address two opposing consequences of block copolymer metastability. The first is a potential nightmare: Can we ever establish universal block copolymer phase diagrams? The second is the stuff of dreams: Self-assembled thermoset nanocomposites.

  6. Block copolymer adhesion promoters via ring-opening metathesis polymerization

    DOEpatents

    Kent, Michael S.; Saunders, Randall

    1997-01-01

    Coupling agents based on functionalized block copolymers for bonding thermoset polymers to solid materials. These are polymers which possess at least two types of functional groups, one which is able to attach to and react with solid surfaces, and another which can react with a thermoset resin, which are incorporated as pendant groups in monomers distributed in blocks (typically two) along the backbone of the chain. The block copolymers in this invention are synthesized by living ring-opening metathesis polymerization.

  7. Pentablock copolymers of pluronic F127 and modified poly(2-dimethyl amino)ethyl methacrylate for internalization mechanism and gene transfection studies

    PubMed Central

    Huang, Shih-Jer; Wang, Tzu-Pin; Lue, Sheng-I; Wang, Li-Fang

    2013-01-01

    Cationic polymers are one of the major nonviral gene delivery vectors investigated in the past decade. In this study, we synthesized several cationic copolymers using atom transfer radical polymerization (ATRP) for gene delivery vectors: pluronic F127-poly(dimethylaminoethyl methacrylate) (PF127-pDMAEMA), pluronic F127-poly (dimethylaminoethyl methacrylate-tert-butyl acrylate) (PF127-p(DMAEMA-tBA)), and pluronic F127-poly(dimethylaminoethyl methacrylate-acrylic acid) (PF127-p(DMAEMA-AA)). The copolymers showed high buffering capacity and efficiently complexed with plasmid deoxyribonucleic acid (pDNA) to form nanoparticles 80–180 nm in diameter and with positive zeta potentials. In the absence of 10% fetal bovine serum, PF127-p(DMAEMA-AA) showed the highest gene expression and the lowest cytotoxicity in 293T cells. After acrylic acid groups had been linked with a fluorescent dye, the confocal laser scanning microscopic image showed that PF127-p(DMAEMA-AA)/pDNA could efficiently enter the cells. Both clathrin-mediated and caveolae-mediated endocytosis mechanisms were involved. Our results showed that PF127-p(DMAEMA-AA) has great potential to be a gene delivery vector. PMID:23745045

  8. Morphological studies on block copolymer modified PA 6 blends

    NASA Astrophysics Data System (ADS)

    Poindl, M.; Bonten, C.

    2014-05-01

    Recent studies show that compounding polyamide 6 (PA 6) with a PA 6 polyether block copolymers made by reaction injection molding (RIM) or continuous anionic polymerization in a reactive extrusion process (REX) result in blends with high impact strength and high stiffness compared to conventional rubber blends. In this paper, different high impact PA 6 blends were prepared using a twin screw extruder. The different impact modifiers were an ethylene propylene copolymer, a PA PA 6 polyether block copolymer made by reaction injection molding and one made by reactive extrusion. To ensure good particle matrix bonding, the ethylene propylene copolymer was grafted with maleic anhydride (EPR-g-MA). Due to the molecular structure of the two block copolymers, a coupling agent was not necessary. The block copolymers are semi-crystalline and partially cross-linked in contrast to commonly used amorphous rubbers which are usually uncured. The combination of different analysis methods like atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) gave a detailed view in the structure of the blends. Due to the partial cross-linking, the particles of the block copolymers in the blends are not spherical like the ones of ethylene propylene copolymer. The differences in molecular structure, miscibility and grafting of the impact modifiers result in different mechanical properties and different blend morphologies.

  9. Morphological studies on block copolymer modified PA 6 blends

    SciTech Connect

    Poindl, M. E-mail: christian.bonten@ikt.uni-stuttgart.de; Bonten, C. E-mail: christian.bonten@ikt.uni-stuttgart.de

    2014-05-15

    Recent studies show that compounding polyamide 6 (PA 6) with a PA 6 polyether block copolymers made by reaction injection molding (RIM) or continuous anionic polymerization in a reactive extrusion process (REX) result in blends with high impact strength and high stiffness compared to conventional rubber blends. In this paper, different high impact PA 6 blends were prepared using a twin screw extruder. The different impact modifiers were an ethylene propylene copolymer, a PA PA 6 polyether block copolymer made by reaction injection molding and one made by reactive extrusion. To ensure good particle matrix bonding, the ethylene propylene copolymer was grafted with maleic anhydride (EPR-g-MA). Due to the molecular structure of the two block copolymers, a coupling agent was not necessary. The block copolymers are semi-crystalline and partially cross-linked in contrast to commonly used amorphous rubbers which are usually uncured. The combination of different analysis methods like atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) gave a detailed view in the structure of the blends. Due to the partial cross-linking, the particles of the block copolymers in the blends are not spherical like the ones of ethylene propylene copolymer. The differences in molecular structure, miscibility and grafting of the impact modifiers result in different mechanical properties and different blend morphologies.

  10. Cyclic block copolymers for controlling feature sizes in block copolymer lithography.

    PubMed

    Poelma, Justin E; Ono, Kosuke; Miyajima, Daigo; Aida, Takuzo; Satoh, Kotaro; Hawker, Craig J

    2012-12-21

    Block copolymer lithography holds promise as a next-generation technique to achieve the sub-20 nm feature sizes demanded by semiconductor roadmaps. While molecular weight and block immiscibility have traditionally been used to control feature size, this study demonstrates that macromolecular architecture is also a powerful tool for tuning domain spacing. To demonstrate this concept, a new synthetic strategy for cyclic block polymers based on highly efficient "click" coupling of difunctional linear chains is developed, and the thin film self-assembly of cyclic polystyrene-block-polyethylene oxide (cPS-b-PEO) is compared with the corresponding linear analogues. The reduced hydrodynamic radii of the cyclic systems result in ~30% decrease in domain spacing over the corresponding linear polymers.

  11. Molecular Transfer Printing Using Block Copolymers

    NASA Astrophysics Data System (ADS)

    Ji, Shengxiang; Liu, Chi-Chun; Liu, Guoliang; Nealey, Paul

    2009-03-01

    We report a new parallel patterning technique, molecular transfer printing (MTP), for replicating geometrically complex patterns over macroscopic areas with sub-15 nm feature dimensions, and the ability to replicate the same pattern multiple times. In MTP, inks are mixed with block copolymers (BCPs) and deposited as films on a substrate. The inks are compatible with only one block of the BCP, and sequestered into domains of nanometer scale dimensions after microphase separation. A second substrate is then placed in contact with the surface of the film. By designing the inks to react, adsorb, or otherwise interact with the second substrate, inks are transferred to the second substrate in the exact pattern of domains present at the surface of the ``master'' BCP film. Here we demonstrate high degrees of perfection on both line and dot patterns. We also show that 1) the master template can be regenerated, 2) the resultant replica can be used to direct the assembly of BCPs and as a daughter master for MTP, and 3) the master and daughter templates can be reused tens of times.

  12. Nanopatterning of recombinant proteins and viruses using block copolymer templates

    NASA Astrophysics Data System (ADS)

    Cresce, Arthur Von Wald

    The study of interfaces is important in understanding biological interactions, including cellular signaling and virus infection. This thesis is an original effort to examine the interaction between a block copolymer and both a protein and a virus. Block copolymers intrinsically form nanometer-scale structures over large areas without expensive processing, making them ideal for the synthesis of the nanopatterned surfaces used in this study. The geometry of these nanostructures can be easily tuned for different applications by altering the block ratio and composition of the block copolymer. Block copolymers can be used for controlled uptake of metal ions, where one block selectively binds metal ions while the other does not. 5-norbornene-2,3-dicarboxylic acid is synthesized through ring-opening metathesis polymerization. It formed spherical domains with spheres approximately 30 nm in diameter, and these spheres were then subsequently loaded with nickel ion. This norbornene block copolymer was tested for its ability to bind histidine-tagged green fluorescent protein (hisGFP), and it was found that the nickel-loaded copolymer was able to retain hisGFP through chelation between the histidine tag and the metal-containing portions of the copolymer surface. Poly(styrene-b-4-vinylpyridine) (PS/P4VP) was also loaded with nickel, forming a cylindrical microstructure. The binding of Tobacco mosaic virus and Tobacco necrosis virus was tested through Tween 20 detergent washes. Electron microscopy allowed for observation of both block copolymer nanostructures and virus particles. Results showed that Tween washes could not remove bound Tobacco mosaic virus from the surface of PS/P4VP. It was also seen that the size and tunability of block copolymers and the lack of processing needed to attain different structures makes them attractive for many applications, including microfluidic devices, surfaces to influence cellular signaling and growth, and as a nanopatterning surface for

  13. 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

  14. Fabrication of Ordered Mesoporous Silica with Encapsulated Iron Oxide Particles using Ferritin-Doped Block Copolymer Templates

    NASA Astrophysics Data System (ADS)

    Hess, D.; Watkins, J.; Naik, R.

    2006-03-01

    Recently, two-dimensional arrays of iron oxide clusters were fabricated by dip-coating a silica substrate into an aqueous solution. Here we report the encapsulation of ferritin in 3D mesoporous silica structures by the replication of block copolymer templates in supercritical CO2. In our approach, preparation of the highly ordered, doped template via spincasting and microphase separation and silica network formation occur in discreet steps. A solution of an amphiphilic PEO-PPO-PEO triblock copolymer (Pluronic) template, horse spleen ferritin and a low concentration of PTSA acid was prepared and spin-coated onto a Si wafer. Upon drying the block copolymer microphase separates resulting in partitioning of the acid catalyst and ferritin to the hydrophilic domain. The polymer template was then exposed to a solution of supercritical carbon dioxide and tetraethyl orthosilicate (TEOS) at 125 bar and 40^oC. Equilibrium limited CO2 sorption in the block copolymer template resulted in modest dialation of the microphase segregated structure. Under these conditions, the precursor was readily infused into the copolymer and reacted within the hydrophilic domain containing the acid catalyst. The resultant film was calcined in air at 400^oC for 6 hours producing a well-ordered iron oxide-doped mesoporous silica film. TEM and XRD revealed crystalline iron oxide structures within the mesoporous silica supports. Magnetic properties were analyzed using a superconducting quantum intereference device (SQUID).

  15. Nanostructured photovoltaic materials using conjugated block copolymer assemblies

    NASA Astrophysics Data System (ADS)

    Mastroianni, Sarah E.; Epps, Thomas H., III

    2011-03-01

    Block copolymers containing a conjugated block offer attractive possibilities for creating nanostructured organic photovoltaic (OPV) devices. Current OPV materials suffer from efficiency losses primarily due to a size-scale discrepancy between exciton diffusion length and domain sizes; excitons that do not reach the interface between electron and hole-conducting materials recombine, preventing charge carrier separation. The inherent nature of block-copolymers to self-assemble into well-defined nanoscale structures with domain spacings on the order of exciton diffusion length offers a potential solution for reducing exciton recombination. In this work, allyl-terminated poly(3-hexyl thiophene) or poly(3-decyl thiophene) acting as electron donors are incorporated into the block copolymer chain via a coupling reaction with poly(styrene) or poly(isoprene- b -styrene) derivatives synthesized by anionic polymerization. The resulting block copolymer morphologies are characterized by small angle X-ray scattering and transmission electron microscopy.

  16. 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

  17. Structure of micelles of a nonionic block copolymer determined by SANS and SAXS.

    PubMed

    Manet, Sabine; Lecchi, Amélie; Impéror-Clerc, Marianne; Zholobenko, Vladimir; Durand, Dominique; Oliveira, Cristiano L P; Pedersen, Jan Skov; Grillo, Isabelle; Meneau, Florian; Rochas, Cyrille

    2011-10-06

    The micellar state of Pluronic P123, which is a poly(ethylene oxide)-b-poly(propylene oxide)-b- poly(ethylene oxide) block polymer (EO(20)PO(70)EO(20)), has been investigated using SANS, SAXS, and differential scanning calorimetry under the conditions utilized in the synthesis of ordered mesoporous materials, such as SBA-15. The absolute intensity measurements, both with SANS and SAXS, have provided a detailed quantitative description of the P123 micelles in the framework of a simple core-shell spherical model. The model developed has been used to establish the structure of the copolymer micelles, including their size, shape, aggregation number and detailed composition, as well as the structural changes induced by varying reaction conditions. The effects of temperature, pH, acidic source and the addition of swelling agents (toluene and TMB) are reported and discussed. © 2011 American Chemical Society

  18. Asymmetric block copolymers for supramolecular templating of inorganic nanospace materials.

    PubMed

    Bastakoti, Bishnu Prasad; Li, Yunqi; Kimura, Tatsuo; Yamauchi, Yusuke

    2015-05-06

    This review focuses on polymeric micelles consisting of asymmetric block copolymers as designed templates for several inorganic nanospace materials with a wide variety of compositions. The presence of chemically distinct domains of asymmetric triblock and diblock copolymers provide self-assemblies with more diverse morphological and functional features than those constructed by EOn POm EOn type symmetric triblock copolymers, thereby affording well-designed nanospace materials. This strategy can produce unprecedented nanospace materials, which are very difficult to prepare through other conventional organic templating approaches. Here, the recent development on the synthesis of inorganic nanospace materials are mainly focused on, such as hollow spheres, tubes, and porous oxides, using asymmetric triblock copolymers.

  19. Manipulating Ordering Transitions in Interfacially Modified Block Copolymers

    SciTech Connect

    Singh, N.; Tureau, M; Epps, T

    2009-01-01

    We report a synthetic strategy that allows us to manipulate the interfacial region between blocks and control ordering transitions in poly(isoprene-b-styrene) [P(I-S)] block copolymers. This interfacial modification is accomplished by combining a semi-batch feed with anionic polymerization techniques. Using this approach, we are able to control the segmental composition and molecular interactions in our phase-separated block copolymers, independent of molecular weight and block constituents. A library of copolymers is prepared with various interfacial modifications to examine the effect of interfacial composition on copolymer self-assembly. The morphological characteristics of the self-assembled structures are investigated using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). Normal and inverse tapered block copolymers, containing approximately 15-35 vol% tapered material, show a measurable decrease in the order-disorder transition temperature (TODT) relative to the corresponding non-tapered diblock copolymers, with the inverse tapered materials showing the greatest deviation in TODT. Additionally, TODT was inversely related to the volume fraction of the tapered region in both normal and inverse tapered copolymer materials.

  20. Coarse-graining poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers using the MARTINI force field.

    PubMed

    Nawaz, Selina; Carbone, Paola

    2014-02-13

    The MARTINI coarse-grain (CG) force field is extended for a class of triblock block copolymers known as Pluronics. Existing MARTINI bead types are used to model the non-bonded part of the potential while single chain properties for both homopolymers, poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), are used to develop the bonded interactions. The new set of force field parameters reproduces structural and dynamical properties of high molecular weight homo- and copolymers. The CG model is moderately transferable in solvents of different polarity and concentration; however, the PEO homopolymer model presents a reduced thermodynamic transferability especially in water probably due to the lack of hydrogen bonds with the solvent. Our simulations of a monolayer of Pluronic L44 show polymer-brush-like characteristics for the PEO segments which protrude into the aqueous phase. Other membrane properties not easily accessible using experimental techniques such as its membrane thickness are also calculated.

  1. Ionic Block Copolymers for Anion Exchange Membranes

    NASA Astrophysics Data System (ADS)

    Tsai, Tsung-Han; Herbst, Dan; Giffin, Guinevere A.; di Noto, Vito; Witten, Tom; Coughlin, E. Bryan

    2013-03-01

    Anion exchange membrane (AEM) fuel cells have regained interest because it allows the use of non-noble metal catalysts. Until now, most of the studies on AEM were based on random polyelectrolytes. In this work, Poly(vinylbenzyltrimethylammonium bromide)-b- (methylbutylene) ([PVBTMA][Br]-b-PMB) was studied by SAXS, TEM and dielectric spectroscopy to understand the fundamental structure-conductivity relationship of ion transport mechanisms within well-ordered block copolymers. The ionic conductivity and the formation of order structure were dependent on the casting solvent. Higher ion exchange capacity (IEC) of the membranes showed higher conductivity at as IEC values below 1.8mmol/g, as above this, the ionic conductivity decreases due to more water uptake leading to dilution of charge density. The humidity dependence of morphology exhibited the shifting of d-spacing to higher value and the alteration in higher characteristic peak of SAXS plot as the humidity increase from the dry to wet state. This phenomenon can be further explained by a newly developed polymer brush theory. Three ionic conduction pathways with different conduction mechanism within the membranes can be confirmed by broadband electric spectroscopy. US Army MURI (W911NF1010520)

  2. Heat Capacity of Spider Silk-like Block Copolymers.

    PubMed

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

    2011-07-12

    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=1-3), comprising an alanine-rich hydrophobic block, A, a glycine-rich hydrophilic block, B, and a histidine tag, H. The reversing heat capacities, Cp(T), for temperatures below and above the glass transition, Tg, were measured by temperature modulated differential scanning calorimetry. For the solid state, we then calculated the heat capacities of our novel block copolymers based on the vibrational motions of the constituent poly(amino acid)s, whose heat capacities are known or can be estimated from the ATHAS Data Bank. For the liquid state, the heat capacity was estimated by using the rotational and translational motions in the polymer chain. Excellent agreement was found between the measured and calculated values of the heat capacity, showing that this method can serve as a standard by which to assess the Cp for other biologically inspired block copolymers. The fraction of beta sheet crystallinity of spider silk block copolymers was also determined by using the predicted Cp, and was verified by wide angle X-ray diffraction and Fourier transform infrared spectroscopy. The glass transition temperatures of spider silk block copolymer were fitted by Kwei's equation and the results indicate that attractive interaction exists between the A-block and B-block.

  3. Thin Film Assembly of Spider Silk-like Block Copolymers

    DTIC Science & Technology

    2011-01-01

    Film Assembly of Spider Silk -like Block Copolymers Sreevidhya T. Krishnaji,†,‡ Wenwen Huang,§ Olena Rabotyagova,†,‡ Eugenia Kharlampieva, ) Ikjun Choi...Received November 26, 2010 We report the self-assembly of monolayers of spider silk -like block copolymers. Langmuir isotherms were obtained for a series of...bioengineered variants of the spider silks , and stable monolayers were generated. Langmuir-Blodgett films were prepared by transferring the monolayers

  4. Thin Films of Bottlebrush Block Copolymers with Homopolymer

    NASA Astrophysics Data System (ADS)

    Jeong, Gajin; Sveinbjornsson, Benjamin R.; Grubbs, Robert Howard; Russell, Thomas P.; Polymer science; engineering department, University of Massachusetts Amherst Team; Chemistry department, California Institute of Technology Team

    2015-03-01

    We have investigated the self assembled structures of bottlebrush block copolymers (BrBCPs) in thin films by blending deuterated homopolymer. By use of neutron reflectivity (NR), the assemblies with microdomain oriented parallel to the substrate, the distribution of the homopolymer in the bottlebrush block copolymer was obtained. Polynorbornene-backbone-based bottlebrush BCPs with polylactide (PLA) and polystyrene (PS) side chains of different molecular weights were investigated. Small angle x-ray scattering was used to complement the NR studies.

  5. New adhesive systems based on functionalized block copolymers

    SciTech Connect

    Kent, M.; Saunders, R.; Hurst, M.; Small, J.; Emerson, J.; Zamora, D.

    1997-05-01

    The goal of this work was to evaluate chemically-functionalized block copolymers as adhesion promoters for metal/thermoset resin interfaces. Novel block copolymers were synthesized which contain pendant functional groups reactive toward copper and epoxy resins. In particular, imidazole and triazole functionalities that chelate with copper were incorporated onto one block, while secondary amines were incorporated onto the second block. These copolymers were found to self-assemble from solution onto copper surfaces to form monolayers. The structure of the adsorbed monolayers were studied in detail by neutron reflection and time-of-flight secondary ion mass spectrometry. The monolayer structure was found to vary markedly with the solution conditions and adsorption protocol. Appropriate conditions were found for which the two blocks form separate layers on the surface with the amine functionalized block exposed at the air surface. Adhesion testing of block copolymer-coated copper with epoxy resins was performed in both lap shear and peel modes. Modest enhancements in bond strengths were observed with the block copolymer applied to the native oxide. However, it was discovered that the native oxide is the weak link, and that by simply removing the native oxide, and then applying an epoxy resin before the native oxide can reform, excellent bond strength in the as-prepared state as well as excellent retention of bond strength after exposure to solder in ambient conditions are obtained. It is recommended that long term aging studies be performed with and without the block copolymer. In addition, the functionalized block copolymer method should be evaluated for another system that has inherently poor bonding, such as the nickel/silicone interface, and for systems involving metals and alloys which form oxides very rapidly, such as aluminum and stainless steel, where bonding strategies involve stabilizing the native oxide.

  6. Thermodynamics of block copolymers with and without salt.

    PubMed

    Teran, Alexander A; Balsara, Nitash P

    2014-01-09

    Ion-containing block copolymers are of interest for applications such as electrolytes in rechargeable lithium batteries. The addition of salt to these materials is necessary to make them conductive; however, even small amounts of salt can have significant effects on the phase behavior of these materials and consequently on their ion-transport and mechanical properties. As a result, the effect of salt addition on block copolymer thermodynamics has been the subject of significant interest over the past decade. This feature article describes a comprehensive study of the thermodynamics of block copolymer/salt mixtures over a wide range of molecular weights, compositions, salt concentrations, and temperatures. The Flory-Huggins interaction parameter was determined by fitting small-angle X-ray scattering data of disordered systems to predictions based on the random phase approximation. Experiments on neat block copolymers revealed that the Flory-Huggins parameter is a strong function of chain length. Experiments on block copolymer/salt mixtures revealed a highly nonlinear dependence of the Flory-Huggins parameter on salt concentration. These findings are a significant departure from previous results and indicate the need for improved theories for describing thermodynamic interactions in neat and salt-containing block copolymers.

  7. Electrically conductive doped block copolymer of polyacetylene and polyisoprene

    DOEpatents

    Aldissi, Mahmoud

    1985-01-01

    An electrically conductive block copolymer of polyisoprene and polyacetyl and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I.sub.2 to give it an electrical conductivity in the metallic regime.

  8. Self-doped microphase separated block copolymer electrolyte

    DOEpatents

    Mayes, Anne M.; Sadoway, Donald R.; Banerjee, Pallab; Soo, Philip; Huang, Biying

    2002-01-01

    A polymer electrolyte includes a self-doped microphase separated block copolymer including at least one ionically conductive block and at least one second block that is immiscible in the ionically conductive block, an anion immobilized on the polymer electrolyte and a cationic species. The ionically conductive block provides a continuous ionically conductive pathway through the electrolyte. The electrolyte may be used as an electrolyte in an electrochemical cell.

  9. Perpendicularly Aligned, Anion Conducting Nanochannels in Block Copolymer Electrolyte Films

    SciTech Connect

    Arges, Christopher G.; Kambe, Yu; Suh, Hyo Seon; Ocola, Leonidas E.; Nealey, Paul F.

    2016-03-08

    Connecting structure and morphology to bulk transport properties, such as ionic conductivity, in nanostructured polymer electrolyte materials is a difficult proposition because of the challenge to precisely and accurately control order and the orientation of the ionic domains in such polymeric films. In this work, poly(styrene-block-2-vinylpyridine) (PSbP2VP) block copolymers were assembled perpendicularly to a substrate surface over large areas through chemical surface modification at the substrate and utilizing a versatile solvent vapor annealing (SVA) technique. After block copolymer assembly, a novel chemical vapor infiltration reaction (CVIR) technique selectively converted the 2-vinylpyridine block to 2-vinyl n-methylpyridinium (NMP+ X-) groups, which are anion charge carriers. The prepared block copolymer electrolytes maintained their orientation and ordered nanostructure upon the selective introduction of ion moieties into the P2VP block and post ion-exchange to other counterion forms (X- = chloride, hydroxide, etc.). The prepared block copolymer electrolyte films demonstrated high chloride ion conductivities, 45 mS cm(-1) at 20 degrees C in deionized water, the highest chloride ion conductivity for anion conducting polymer electrolyte films. Additionally, straight-line lamellae of block copolymer electrolytes were realized using chemoepitaxy and density multiplication. The devised scheme allowed for precise and accurate control of orientation of ionic domains in nanostructured polymer electrolyte films and enables a platform for future studies that examines the relationship between polymer electrolyte structure and ion transport.

  10. Morphology and Proton Transport in Porous Block Copolymer Electrolyte Membranes

    NASA Astrophysics Data System (ADS)

    Chen, Chelsea; Kortright, Jeffrey; Wong, David; Balsara, Nitash

    2015-03-01

    Block copolymer electrolyte membranes consisting of a proton-conducting block and an uncharged structural block are attractive due to their potential in clean energy applications. Herein we demonstrate a novel approach of fabricating block copolymer electrolyte membranes, by inducing pores in the proton-conducting phase. We examine morphology of these membranes with contrast-matched resonant soft X-ray scattering (RSoXS) and electron tomography. Proton conductivity as a function of porosity and water activity is also investigated. By tuning the porosity of the membranes, we are able to adjust the water uptake of the membranes for improved proton conductivities, in both humid air and liquid water.

  11. Organically modified aluminosilicate mesostructures from block copolymer phases

    PubMed

    Templin; Franck; Du Chesne A; Leist; Zhang; Ulrich; Schadler; Wiesner

    1997-12-05

    Organically modified aluminosilicate mesostructures were synthesized from two metal alkoxides with the use of poly(isoprene-b-ethyleneoxide) block copolymers (PI-b-PEO) as the structure-directing molecules. By increasing the fraction of the inorganic precursors with respect to the polymer, morphologies expected from the phase diagrams of diblock copolymers were obtained. The length scale of the microstructures and the state of alignment were varied using concepts known from the study of block copolymers. These results suggest that the use of higher molecular weight block copolymer mesophases instead of conventional low-molecular weight surfactants may provide a simple, easily controlled pathway for the preparation of various silica-type mesostructures that extends the accessible length scale of these structures by about an order of magnitude.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Block-Copolymer Lithium Battery Electrolytes

    NASA Astrophysics Data System (ADS)

    Eitouni, Hany

    2011-03-01

    With high energy density at low cost, Li ion has become the most prevalent portable rechargeable battery chemistry in the world. As demand for smaller and lighter batteries grows, the energy density limitation of Li ion batteries presents a significant hurdle. Pushing the existing Li ion platform to higher energy densities compromises lifetime and safety, and these have emerged as the most pressing challenges in today's industry. The weakest link in terms of safety and stability of Li ion batteries is the organic liquid electrolyte that facilitates ionic transport between the electrodes. The continuous electrochemical degradation of the electrolyte at the electrodes causes poor cycle life of the batteries, and in some cases, runaway reactions that lead to explosions. Dry polymer electrolytes coupled to Li metal anodes had been considered a high energy alternative to liquid-based systems, as the solid-solid interface promised to alleviate the stability problems of the liquid electrolyte. However, repeated cycling of Li metal anodes leads to dendrite formation, reducing battery life and compromising safety. Recent theoretical work indicates that dendrite growth can be stopped if the shear modulus of current polymer electrolytes can be increased by three orders of magnitude without a significant decrease in ionic conductivity. Thus, the mechanical properties of polymer electrolytes are particularly important in rechargeable solid-state lithium batteries. Because ion transport in polymers is coupled to the motion of the molecules that are solvating the ions, the presence of mobile molecules is essential to allow for a conductive medium. However, the same mobility of molecules is detrimental to the polymer's structural integrity. There is, thus, a clear need to develop methodologies for decoupling the conductive and mechanical properties of polymer electrolytes. Electrolytes comprised of self-assembled block-copolymer nanostructures overcome this principal constraint.

  17. Patterned silica films using microphase separation of a block copolymer

    NASA Astrophysics Data System (ADS)

    Kataoka, Sho; Takeuchi, Yasutaka; Endo, Akira

    2014-11-01

    Block copolymers exhibit various nanoscale ordered morphologies induced by microphase separation. Here, we present a method for providing two types of patterned silica films on Si wafer substrates simply by shifting the phase equilibrium of a block copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-P4VP). In this method, siloxane is adsorbed onto poly(4-vinylpyridine) blocks of PS-P4VP whose structure varies with solvent polarity and is calcined to remove the block copolymer. Siloxane is in a dispersed phase with toluene as a solvent resulting in silica nanoparticle arrays, while siloxane is in a continuous phase with N, N-dimethylformamide (DMF) resulting in silica films with ordered mesopores. Since the pore size of silica films prepared in DMF is approximately 20 nm, the film has the ability to serve as a support for enzymes such as laccase.

  18. Combinatorial Block Copolymer Ordering on Tunable Rough

    SciTech Connect

    Kulkarni M. M.; Yager K.; Sharma, A.; Karim, A.

    2012-05-01

    Morphology control of block copolymer (BCP) thin films through substrate interaction via controlled roughness parameters is of significant interest for numerous high-tech applications ranging from solar cells to high-density storage media. While effects of substrate surface energy (SE) and roughness (R) on BCP morphology have been individually investigated, their synergistic effects have not been explored in any systematic manner. Interestingly, orientation response of BCP to changes in SE can be similar to what can be accomplished with variations in R. Here we present a novel approach for orienting lamellar BCP films of poly(styrene)-block-poly(methyl methacrylate) (PS-PMMA) on spin-coated xerogel (a dried gel of silica nanoparticle network) substrate with simultaneously tunable surface energy, {gamma}{sub s} {approx} 29-53 mJ/m{sup 2}, by UVO exposure and roughness, R{sub rms} {approx} 0.5-30 nm, by sol-gel processing steps of regulating the catalyst concentration and sol aging time. As in previous BCP orientation studies on 20 nm diameter monodisperse silica nanoparticle coated surface, we find a similar but broadened oscillatory BCP orientation behavior with film thickness due to the random rather than periodic rough surfaces. We also find that higher random roughness amplitude is not the necessary criteria for obtaining a vertical orientation of BCP lamellae. Rather, a high surface fractal dimension (D{sub f} > 2.4) of the rough substrate in conjunction with an optimal substrate surface energy {gamma}{sub s} 29 mJ/m{sup 2} results in 100% vertically oriented lamellar microdomains. The AFM measured film surface microstructure correlates well with the internal 3D BCP film structure probed by grazing incidence small-angle X-ray scattering (GISAXS) and rotational small-angle neutron scattering (SANS). In contrast to tunable self-assembled monolayer (SAM)-coated substrates, the xerogel films are very durable and retain their chemical properties over period of

  19. Gelation kinetics and viscoelastic properties of pluronic and α-cyclodextrin-based pseudopolyrotaxane hydrogels.

    PubMed

    Pradal, Clementine; Jack, Kevin S; Grøndahl, Lisbeth; Cooper-White, Justin J

    2013-10-14

    The results of a systematic investigation into the gelation behavior of α-cyclodextrin (α-CD) and Pluronic (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers) pseudopolyrotaxane (PPR) hydrogels are reported here in terms of the effects of temperature, α-CD concentration, and Pluronic type (Pluronic F68 and Pluronic F127). It was found that α-CD significantly modifies the gelation behavior of Pluronic solutions and that the PPR hydrogels are highly sensitive to changes in the α-CD concentration. In some cases, the addition of α-CD was found to be detrimental to the gelation process, leading to slower gelation kinetics and weaker gels than with Pluronic alone. However, in other cases, the hydrogels formed in the presence of the α-CDs reached higher moduli and showed faster gelation kinetics than with Pluronic alone and in some instances α-CD allowed the formation of hydrogels from Pluronic solutions that would normally not undergo gelation. Depending on composition and ratio of α-CD/Pluronic, these highly viscoelastic hydrogels displayed elastic shear modulus values ranging from 2 kPa to 7 MPa, gelation times ranging from a few seconds to a few hours and self-healing behaviors post failure. Using dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS), we probed the resident structure of these systems, and from these insights we have proposed a new molecular mechanism that accounts for the macroscopic properties observed.

  20. Ion Transport in Nanostructured Block Copolymer/Ionic Liquid Membranes

    NASA Astrophysics Data System (ADS)

    Hoarfrost, Megan Lane

    Incorporating an ionic liquid into one block copolymer microphase provides a platform for combining the outstanding electrochemical properties of ionic liquids with a number of favorable attributes provided by block copolymers. In particular, block copolymers thermodynamically self-assemble into well-ordered nanostructures, which can be engineered to provide a durable mechanical scaffold and template the ionic liquid into continuous ion-conducting nanochannels. Understanding how the addition of an ionic liquid affects the thermodynamic self-assembly of block copolymers, and how the confinement of ionic liquids to block copolymer nanodomains affects their ion-conducting properties is essential for predictable structure-property control. The lyotropic phase behavior of block copolymer/ionic liquid mixtures is shown to be reminiscent of mixtures of block copolymers with selective molecular solvents. A variety of ordered microstructures corresponding to lamellae, hexagonally close-packed cylinders, body-centered cubic, and face-centered cubic oriented micelles are observed in a model system composed of mixtures of imidazolium bis(trifluoromethylsulfonyl)imide ([Im][TFSI]) and poly(styrene- b-2-vinyl pyridine) (PS-b-P2VP). In contrast to block copolymer/molecular solvent mixtures, the interfacial area occupied by each PS-b-P2VP chain decreases upon the addition of [Im][TFSI], indicating a considerable increase in the effective segregation strength of the PS-b-P2VP copolymer with ionic liquid addition. The relationship between membrane structure and ionic conductivity is illuminated through the development of scaling relationships that describe the ionic conductivity of block copolymer/ionic liquid mixtures as a function of membrane composition and temperature. It is shown that the dominant variable influencing conductivity is the overall volume fraction of ionic liquid in the mixture, which means there

  1. Block copolymer adhesion promoters via ring-opening metathesis polymerization

    DOEpatents

    Kent, M.S.; Saunders, R.

    1997-02-18

    Coupling agents are disclosed based on functionalized block copolymers for bonding thermoset polymers to solid materials. These are polymers which possess at least two types of functional groups, one which is able to attach to and react with solid surfaces, and another which can react with a thermoset resin, which are incorporated as pendant groups in monomers distributed in blocks (typically two) along the backbone of the chain. The block copolymers in this invention are synthesized by living ring-opening metathesis polymerization. 18 figs.

  2. Catalytic production of olefin block copolymers via chain shuttling polymerization.

    PubMed

    Arriola, Daniel J; Carnahan, Edmund M; Hustad, Phillip D; Kuhlman, Roger L; Wenzel, Timothy T

    2006-05-05

    We report a catalytic system that produces olefin block copolymers with alternating semicrystalline and amorphous segments, achieved by varying the ratio of alpha-olefin to ethylene in the two types of blocks. The system uses a chain shuttling agent to transfer growing chains between two distinct catalysts with different monomer selectivities in a single polymerization reactor. The block copolymers simultaneously have high melting temperatures and low glass transition temperatures, and therefore they maintain excellent elastomeric properties at high temperatures. Furthermore, the materials are effectively produced in economically favorable, continuous polymerization processes.

  3. Catalytic Production of Olefin Block Copolymers via Chain Shuttling Polymerization

    NASA Astrophysics Data System (ADS)

    Arriola, Daniel J.; Carnahan, Edmund M.; Hustad, Phillip D.; Kuhlman, Roger L.; Wenzel, Timothy T.

    2006-05-01

    We report a catalytic system that produces olefin block copolymers with alternating semicrystalline and amorphous segments, achieved by varying the ratio of α-olefin to ethylene in the two types of blocks. The system uses a chain shuttling agent to transfer growing chains between two distinct catalysts with different monomer selectivities in a single polymerization reactor. The block copolymers simultaneously have high melting temperatures and low glass transition temperatures, and therefore they maintain excellent elastomeric properties at high temperatures. Furthermore, the materials are effectively produced in economically favorable, continuous polymerization processes.

  4. Block Copolymer Nanocomposites in Electric Fields: Kinetics of Alignment

    SciTech Connect

    Liedel, Clemens; Pester, Christian; Ruppel, Markus A; Lewin, Christian; Pavan, Mariela J.; Urban, Volker S; Shenhar, Roy; Bosecke, Peter; Boker, Alexander

    2013-01-01

    We investigate the kinetics of block copolymer/nanoparticle composite alignment in an electric field using in situ transmission small-angle X-ray scattering. As a model system, we employ a lamellae forming polystyrene-block-poly(2-vinyl pyridine) block copolymer with different contents of gold nanoparticles in thick films under solvent vapor annealing. While the alignment improves with increasing nanoparticle fraction, the kinetics slows down. This is explained by changes in the degree of phase separation and viscosity. Our findings provide extended insights into the basics of nanocomposite alignment.

  5. Reordering transitions during annealing of block copolymer cylinder phases

    SciTech Connect

    Majewski, Pawel W.; Yager, Kevin G.

    2015-10-06

    While equilibrium block-copolymer morphologies are dictated by energy-minimization effects, the semi-ordered states observed experimentally often depend on the details of ordering pathways and kinetics. In this study, we explore reordering transitions in thin films of block-copolymer cylinder-forming polystyrene-block-poly(methyl methacrylate). We observe several transient states as films order towards horizontally-aligned cylinders. In particular, there is an early-stage reorganization from randomly-packed cylinders into hexagonally-packed vertically-aligned cylinders; followed by a reorientation transition from vertical to horizontal cylinder states. These transitions are thermally activated. The growth of horizontal grains within an otherwise vertical morphology proceeds anisotropically, resulting in anisotropic grains in the final horizontal state. The size, shape, and anisotropy of grains are influenced by ordering history; for instance, faster heating rates reduce grain anisotropy. These results help elucidate aspects of pathway-dependent ordering in block-copolymer thin films.

  6. Morphology of Novel Semicrystalline Ethylene-α-Olefin Block Copolymers

    NASA Astrophysics Data System (ADS)

    Li, Sheng; Register, Richard; Landes, Brian

    2009-03-01

    In semicrystalline block copolymers, the solid-state structure can be set either by block incompatibility or by crystallization of one or more blocks. Depending on the block interaction strength, a wide array of solid-state morphologies may be observed, ranging from spherulitic to confined crystallization within preexisting microphase-separated domains. Dow Chemical has recently developed a novel chain shuttling polymerization process to produce olefin block copolymers with alternating amorphous and semicrystalline chain segments, where each block exhibits the most-probable distribution. We examined the melt and solid-state morphologies of these novel olefin block copolymers, having a high octene content in the amorphous block, using two- dimensional synchrotron small-angle and wide-angle x-ray scattering on specimens oriented by channel die compression. Multiblock and diblock copolymers with near-symmetric compositions showed well-ordered lamellar structures at room temperature with long periods exceeding 100 nm, with little dependence on thermal history, indicating the presence of a mesophase-separated melt which templates crystallization.

  7. 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.

  8. Morphology study in block copolymer electrolytes

    NASA Astrophysics Data System (ADS)

    Mullin, Scott; Wanakule, Nisita; Balsara, Nitash

    2008-03-01

    Poly(styrene-b-ethylene oxide)/lithium bis(trifluoromethane)sulfonimide (SEO/LiTFSI) is of interest in battery applications since the doped PEO phase can conduct ions and the glassy PS phase can prevent dendrite growth upon recharging. It is believed that the LiTFSI molecules are localized in the PEO microphases. Previous studies have shown that highly conducting electrolytes can be made from symmetric SEO copolymers. The purpose of this study is to explore the conductivity of asymmetric SEO copolymer systems doped with LiTFSI. Our studies encompass both neat asymmetric SEO copolymers and SEO copolymers blended with PS homopolymers to separate the effects of architecture of the copolymer molecules and morphology adopted by the system in the melt state. Conductivity is measured by AC impedance, morphology is determined by small angle X-ray scattering, and crystallinity of the PEO chains is determined by differential scanning calorimetry. All samples were prepared in hermetically sealed sample cells in an Argon glovebox.

  9. Thermoreversible, epitaxial fcc<-->bcc transitions in block copolymer solutions.

    PubMed

    Bang, Joona; Lodge, Timothy P; Wang, Xiaohui; Brinker, Kristin L; Burghardt, Wesley R

    2002-11-18

    Uncharged block copolymer micelles display thermoreversible transitions between close-packed and bcc lattices for a range of concentration, solvent selectivity, and copolymer composition. Using small-angle x-ray scattering on shear-oriented solutions, highly aligned fcc crystals are seen to transform epitaxially to bcc crystals, with fcc/bcc orientational relationships that are well established in martensitic transformations in metals. The transition is driven by decreasing solvent selectivity with increasing temperature, inducing solvent penetration of the micellar core.

  10. Method of forming oriented block copolymer line patterns, block copolymer line patterns formed thereby, and their use to form patterned articles

    DOEpatents

    Russell, Thomas P.; Hong, Sung Woo; Lee, Doug Hyun; Park, Soojin; Xu, Ting

    2015-10-13

    A block copolymer film having a line pattern with a high degree of long-range order is formed by a method that includes forming a block copolymer film on a substrate surface with parallel facets, and annealing the block copolymer film to form an annealed block copolymer film having linear microdomains parallel to the substrate surface and orthogonal to the parallel facets of the substrate. The line-patterned block copolymer films are useful for the fabrication of magnetic storage media, polarizing devices, and arrays of nanowires.

  11. Method of forming oriented block copolymer line patterns, block copolymer line patterns formed thereby, and their use to form patterned articles

    DOEpatents

    Russell, Thomas P.; Hong, Sung Woo; Lee, Dong Hyun; Park, Soojin; Xu, Ting

    2017-08-01

    A block copolymer film having a line pattern with a high degree of long-range order is formed by a method that includes forming a block copolymer film on a substrate surface with parallel facets, and annealing the block copolymer film to form an annealed block copolymer film having linear microdomains parallel to the substrate surface and orthogonal to the parallel facets of the substrate. The line-patterned block copolymer films are useful for the fabrication of magnetic storage media, polarizing devices, and arrays of nanowires.

  12. Nanopatterning of Viruses and Proteins Using Microphase Separated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Cresce, Arthur; Lewandowski, Angela; Bentley, William; Kofinas, Peter

    2006-03-01

    Diblock copolymers containing nickel ions have been prepared that are capable of selectively adsorbing histidine-tagged green fluorescent protein (hisGFP), and also binding tobacco mosaic virus (TMV). A block copolymer of norbornene and norbornene dicarboxylic acid was synthesized using ring-opening metathesis polymerization. A 400/50 block ratio achieved a spherical microphase-separated morphology with roughly 20 nm diameter dicarboxylic acid spheres. The spherical phase was exposed to nickel ions in solution, templating the formation of nickel nanoparticles. This process gave a nickel-loaded diblock copolymer film whose surface was used to chelate hisGFP. Fluorescence spectroscopy and TEM confirmed the presence of the protein on the polymer surface. A sulfonated triblock copolymer was loaded with nickel ions using a similar solution-doping procedure. The morphology of this copolymer was lamellar, and its sulfonated block was loaded with nickel ions. TEM studies revealed the presence of the virus on the surface of the copolymer and showed that the bond between the TMV and the polymer surface can withstand severe detergent washes.

  13. Radical-cured block copolymer-modified thermosets

    SciTech Connect

    Redline, Erica M.; Francis, Lorraine F.; Bates, Frank S.

    2013-01-10

    Poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) diblock copolymers were synthesized and added at 4 wt % to 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (BisGMA), a monomer that cures using free radical chemistry. In separate experiments, poly(ethylene glycol) dimethacrylate (PEGDMA) was combined as a secondary monomer with BisGMA and the monomers were loaded with 4 wt % PEP-PEO. The diblock copolymers self-assembled into well-dispersed spherical micelles with PEP cores and PEO coronas. No appreciable change in the final extent of cure of the thermosets was caused by the addition of diblock copolymer, except in the case of BisGMA, where the addition of the block copolymer increased extent of cure by 12%. Furthermore, the extent of cure was increased by 29% and 37% with the addition of 25 and 50 wt % PEGDMA, respectively. Elastic modulus and fracture resistance were also determined, and the values indicate that the addition of block copolymers does not significantly toughen the thermoset materials. This finding is surprising when compared with the large increase in fracture resistance seen in block copolymer-modified epoxies, and an explanation is proposed.

  14. Surface modification of nanoparticles by PEO/PPO block copolymers to minimize interactions with blood components and prolong blood circulation in rats.

    PubMed

    Tan, J S; Butterfield, D E; Voycheck, C L; Caldwell, K D; Li, J T

    1993-09-01

    The biological fate of injected foreign particles is believed to be closely related to their interactions with blood plasma proteins and cells. In order to verify this correlation, we have quantitatively measured protein adsorption and blood retention profiles in rats by using model polystyrene latex nanoparticles. The in vitro interactions of these non-biodegradable particles with plasma proteins and whole blood can be altered by modifying their surfaces with a family of amphiphilic polymeric surfactants, PEO/PPO Pluronic or Tetronic block copolymers. Protein adsorption was measured by several techniques, including photon correlation spectroscopy, centrifugation, high performance liquid chromatography and field-flow fractionation. Pluronic F108 and Tetronic 908 and 1508 copolymers (with PEO terminal block MWPEO > 5000, PPO middle block MWPPO > 3000, and HLB values > 24) were shown to be the most effective surface modifiers in reducing adsorption of plasma proteins on the particles. Minimum interaction of coated particles with whole blood was also observed by optical microscopy. The blood circulation half-life of the particles injected in rats was increased from 20 min to 13 h when the latex particles (75 nm) were precoated with these block copolymers. These results suggest that nanoparticles designed for use as injectable drugs or drug carriers should display similar surface characteristics provided by such amphiphilic surface modifiers.

  15. Thin Films of Polydimethylsiloxane-Containing Block Copolymers

    NASA Astrophysics Data System (ADS)

    Wadley, Maurice; Cavicchi, Kevin

    2009-03-01

    The self-assembly of block copolymers into ordered nanostructures such as spheres, cylinders, and lamellae in the range of 10-100 nm makes them interesting materials for patterning surfaces. Thin films of poly(dimethylsiloxane) (PDMS) containing block copolymers are attractive for patterning due to their high oxygen etch resistance compared to other polymers. The main disadvantage of these polymers for patterning is the low surface tension of PDMS. This causes the preferential migration of PDMS to the air/film interface driving the formation of domains parallel to the interface and surface wetting layers. In this work a series of AB block copolymers containing PDMS have been prepared via RAFT polymerization where the surface tension of the opposing block was varied. Using a macro chain transfer approach, it is possible to isolate the effect of changing the opposing block while keeping the PDMS the same in each different block copolymer. The effect of changing the surface tension mismatch between the blocks on the thin film morphology will be discussed.

  16. Preparation of Pluronic/Bile salt/Phospholipid Mixed Micelles as Drug Solubility Enhancer and Study the Effect of the PPO Block Size on the Solubility of Pyrene.

    PubMed

    Wang, Li; Peng, Min; Zhu, Yuan; Tong, Shan-Shan; Cao, Xia; Xu, Xi-Ming; Yu, Jiang-Nan

    2014-01-01

    Pluronic/bile salt/phospholipid mixed micelles (Pluronic/BS/PS-MM) drug carrier system for solubilization hydrophobic drugs was developed. A typical hydrophobic compound, pyrene, was selected as a representative hydrophobic compound to model the hydrophobic drugs. Five Pluronics, F68, F88, F98, F108, and F127 with different PPO chain length were studied. CMC data and solubilization capacities were obtained from a pyrene solubilization method. A closed association model was used to obtain the thermodynamic parameters: Gibbs free energy (ΔG°), enthalpy, (ΔH°) and entropy (ΔS°) of micellization. The results obtained from these experiments suggest that the mixed micelles was more stable and solubilize more pyrene than single one; and the solubilization of pyrene was strong effected by the PPO block size, thus accentuating synergistic interaction mechanism in Pluronic/BS/PS-MM. The study generated an important dataset so as to compare the effect of different Pluronics on solubility capacity of Pluronic/BS/PS-MM.

  17. Amphiphilic block copolymer nanocontainers as bioreactors

    NASA Astrophysics Data System (ADS)

    Nardin, C.; Widmer, J.; Winterhalter, M.; Meier, W.

    2001-04-01

    Self-assembly of an amphiphilic triblock copolymer carrying polymerizable end-groups is used to prepare nanometer-sized vesicular structures in aqueous solution. The triblock copolymer shells of the vesicles can be regarded as a mimetic of biological membranes although they are 2 to 3 times thicker than a conventional lipid bilayer. Nevertheless, they can serve as a matrix for membrane-spanning proteins. Surprisingly, the proteins remain functional despite the extreme thickness of the membranes and that even after polymerization of the reactive triblock copolymers. This opens a new field to create mechanically stable protein/polymer hybrid membranes. As a representative example we functionalize (polymerized) triblock copolymer vesicles by reconstituting a channel-forming protein from the outer cell wall of Gram-negative bacteria. The protein used (OmpF) acts as a size-selective filter, which allows only for passage of molecules with a molecular weight below 400 g mol^{-1}. Therefore substrates may still have access to enzymes encapsulated in such protein/polymer hybrid nanocontainers. We demonstrate this using the enzyme β -lactamase which is able to hydrolyze the antibiotic ampicillin. In addition, a transmembrane voltage above a given threshold causes a reversible gating transition of OmpF. This can be used to reversibly activate or deactivate the resulting nanoreactors.

  18. Non-native three-dimensional block copolymer morphologies

    SciTech Connect

    Rahman, Atikur; Majewski, Pawel W.; Doerk, Gregory; Black, Charles T.; Yager, Kevin G.

    2016-12-22

    Self-assembly is a powerful paradigm, wherein molecules spontaneously form ordered phases exhibiting well-defined nanoscale periodicity and shapes. However, the inherent energy-minimization aspect of self-assembly yields a very limited set of morphologies, such as lamellae or hexagonally packed cylinders. Here, we show how soft self-assembling materials—block copolymer thin films—can be manipulated to form a diverse library of previously unreported morphologies. In this iterative assembly process, each polymer layer acts as both a structural component of the final morphology and a template for directing the order of subsequent layers. Specifically, block copolymer films are immobilized on surfaces, and template successive layers through subtle surface topography. As a result, this strategy generates an enormous variety of three-dimensional morphologies that are absent in the native block copolymer phase diagram.

  19. Characterization of Lithium Polysulfide Salts in Homopolymers and Block Copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Dunyang; Wujcik, Kevin; Balsara, Nitash

    Ion-conducting polymers are important for solid-state batteries due to the promise of better safety and the potential to produce higher energy density batteries. Nanostructured block copolymer electrolytes can provide high ionic conductivity and mechanical strength through microphase separation. One of the potential use of block copolymer electrolytes is in lithium-sulfur batteries, a system that has high theoretical energy density wherein the reduction of sulfur leads to the formation of lithium polysulfide intermediates. In this study we investigate the effect of block copolymer morphology on the speciation and transport properties of the polysulfides. The morphology and conductivities of polystyrene-b-poly(ethylene oxide) (SEO) containing lithium polysulfides were studies using small-angle X-ray scattering and ac impedance spectroscopy. UV-vis spectroscopy is being used to determine nature of the polysulfide species in poly(ethylene oxide) and SEO. Department of Energy, Soft Matter Electron Microscopy Program and Battery Materials Research Program.

  20. Monte Carlo Simulations of Nano-Confined Block Copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Qiang

    Block copolymers consist of chemically distinct polymer chains (blocks) covalently bonded together. Unlike polymer blends exhibiting phase separation on a macroscopic scale, block copolymers spontaneously self-assemble into ordered microdomains on the length scale of tens of nanometers, a phenomenon known as microphase separation [1, 2]. Due to the uniformity and periodicity of these microdomains, block copolymers have great potential applications in nanotechnology (e.g., templates for nanolithography, nanowires, high-density storage devices, quantum dots, photonic crystals, nanostructured membranes, etc.) [3-5], where the size, shape and spatial arrangement of the microdomains (morphology) are utilized. Understanding, predicting and controlling the selfassembled morphology of block copolymers are therefore of paramount interest. For the simplest architecture of linear diblock copolymers AB, four morphologies have been determined to be thermodynamically stable in the bulk, depending on the temperature and the volume fractions of the two blocks: lamellae of alternating A-rich and B-rich layers, hexagonally packed cylinders of the minority component (A) in the matrix of the other component (B), A-spheres packed on a body-centered cubic lattice in the B-matrix, and bicontinuous gyroid phase [6,7]. For more complex molecular architectures such as linear triblock copolymers ABC, many other morphologies have been observed in experiments and their bulk phase behavior is not fully understood yet [2, 8]. In many applications, a solution of block copolymers is spin-coated on a supporting substrate (e.g., silicon wafer) to form a thin film of tens to hundreds of nanometers thick, and the copolymers microphase separate in the film upon solvent evaporation and/or annealing. Under such nano-confinement, the tendency to resemble the bulk morphology with its characteristic period L0, the surface-block interactions (surface preference) and the surface con- finement all have

  1. 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.

  2. Reactive block copolymer vesicles with an epoxy wall.

    PubMed

    Zhu, Hui; Liu, Qingchun; Chen, Yongming

    2007-01-16

    Recently, block copolymer vesicles have attracted considerable attention because of their properties in encapsulation and release. To explore their applications in biorelated fields, functionalization of the polymer vesicle is necessary. Herein, a reactive unilamellar vesicle is reported by self-assembly of poly(ethylene oxide)-block-poly(glycidyl methacrylate) copolymer (PEO-b-PGMA) in solution. When water was added into the PEO-b-PGMA solution in THF, unilamellar vesicles were produced. If hydrophobic primary amine additives, such as hexamethylenediamine (HDA) and dodecylamine (DA), were introduced during block copolymer assembling, the vesicular morphology remained unchanged; instead, the amines reacted with the epoxys and the vesicles were fixed by cross-linking. Furthermore, when 3-aminopropyl trimethoxysilane (APS) was applied, the organic/inorganic hybrid vesicles were obtained, which were stable against the solvent change. Therefore, this research not only supplies a new way to fix the vesicular morphology but also a reactive vesicle scaffold for introducing functional species.

  3. Non-native three-dimensional block copolymer morphologies

    PubMed Central

    Rahman, Atikur; Majewski, Pawel W.; Doerk, Gregory; Black, Charles T.; Yager, Kevin G.

    2016-01-01

    Self-assembly is a powerful paradigm, wherein molecules spontaneously form ordered phases exhibiting well-defined nanoscale periodicity and shapes. However, the inherent energy-minimization aspect of self-assembly yields a very limited set of morphologies, such as lamellae or hexagonally packed cylinders. Here, we show how soft self-assembling materials—block copolymer thin films—can be manipulated to form a diverse library of previously unreported morphologies. In this iterative assembly process, each polymer layer acts as both a structural component of the final morphology and a template for directing the order of subsequent layers. Specifically, block copolymer films are immobilized on surfaces, and template successive layers through subtle surface topography. This strategy generates an enormous variety of three-dimensional morphologies that are absent in the native block copolymer phase diagram. PMID:28004774

  4. Non-native three-dimensional block copolymer morphologies

    NASA Astrophysics Data System (ADS)

    Rahman, Atikur; Majewski, Pawel W.; Doerk, Gregory; Black, Charles T.; Yager, Kevin G.

    2016-12-01

    Self-assembly is a powerful paradigm, wherein molecules spontaneously form ordered phases exhibiting well-defined nanoscale periodicity and shapes. However, the inherent energy-minimization aspect of self-assembly yields a very limited set of morphologies, such as lamellae or hexagonally packed cylinders. Here, we show how soft self-assembling materials--block copolymer thin films--can be manipulated to form a diverse library of previously unreported morphologies. In this iterative assembly process, each polymer layer acts as both a structural component of the final morphology and a template for directing the order of subsequent layers. Specifically, block copolymer films are immobilized on surfaces, and template successive layers through subtle surface topography. This strategy generates an enormous variety of three-dimensional morphologies that are absent in the native block copolymer phase diagram.

  5. Non-native three-dimensional block copolymer morphologies

    DOE PAGES

    Rahman, Atikur; Majewski, Pawel W.; Doerk, Gregory; ...

    2016-12-22

    Self-assembly is a powerful paradigm, wherein molecules spontaneously form ordered phases exhibiting well-defined nanoscale periodicity and shapes. However, the inherent energy-minimization aspect of self-assembly yields a very limited set of morphologies, such as lamellae or hexagonally packed cylinders. Here, we show how soft self-assembling materials—block copolymer thin films—can be manipulated to form a diverse library of previously unreported morphologies. In this iterative assembly process, each polymer layer acts as both a structural component of the final morphology and a template for directing the order of subsequent layers. Specifically, block copolymer films are immobilized on surfaces, and template successive layers throughmore » subtle surface topography. As a result, this strategy generates an enormous variety of three-dimensional morphologies that are absent in the native block copolymer phase diagram.« less

  6. Controlling block copolymer phase behavior using ionic surfactant

    SciTech Connect

    Ray, D.; Aswal, V. K.

    2016-05-23

    The phase behavior of poly(ethylene oxide)-poly(propylene oxide-poly(ethylene oxide) PEO-PPO-PEO triblock copolymer [P85 (EO{sub 26}PO{sub 39}EO{sub 26})] in presence of anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution as a function of temperature has been studied using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations (1 wt%) of block copolymer and surfactants. Each of the individual components (block copolymer and surfactant) and the nanoparticle–surfactant mixed system have been examined at varying temperature. The block copolymer P85 forms spherical micelles at room temperature whereas shows sphere-to-rod like micelle transition at higher temperatures. On the other hand, SDS surfactant forms ellipsoidal micelles over a wide temperature range. Interestingly, it is found that phase behavior of mixed micellar system (P85 + SDS) as a function of temperature is drastically different from that of P85, giving the control over the temperature-dependent phase behavior of block copolymers.

  7. Controlling block copolymer phase behavior using ionic surfactant

    NASA Astrophysics Data System (ADS)

    Ray, D.; Aswal, V. K.

    2016-05-01

    The phase behavior of poly(ethylene oxide)-poly(propylene oxide-poly(ethylene oxide) PEO-PPO-PEO triblock copolymer [P85 (EO26PO39EO26)] in presence of anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution as a function of temperature has been studied using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations (1 wt%) of block copolymer and surfactants. Each of the individual components (block copolymer and surfactant) and the nanoparticle-surfactant mixed system have been examined at varying temperature. The block copolymer P85 forms spherical micelles at room temperature whereas shows sphere-to-rod like micelle transition at higher temperatures. On the other hand, SDS surfactant forms ellipsoidal micelles over a wide temperature range. Interestingly, it is found that phase behavior of mixed micellar system (P85 + SDS) as a function of temperature is drastically different from that of P85, giving the control over the temperature-dependent phase behavior of block copolymers.

  8. Synthesis and morphology characterization of polydimethylsiloxane-containing block copolymers

    NASA Astrophysics Data System (ADS)

    Wadley, Maurice

    The thin film morphology characteristics of polydimethylsiloxane-containing block copolymers have been investigated. For this investigation, a commercially available hydroxyl terminated PDMS was purchased from Gelest and attached to a carboxylic acid functional reversible addition-fragmentation chain transfer (RAFT) agent by Steglich esterification. This produced macro-RAFT agents to which styrene monomer was polymerized. By using this approach the generation of low polydispersity polystyrene-block-polydimethylsiloxane (PS-block-PDMS) copolymers of various molecular weights spanning a wide volume fraction range in which the PDMS block remained the same in each polymerization. Synthesized block copolymers were characterized by gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. Bulk and thin film characterization of PS-block-PDMS copolymers was done by small-angle x-ray scattering (SAXS), transmission electron microscopy (TEM), contact angle measurements, scanning force microscopy (SFM), and grazing incidence small-angle X-ray scattering (GISAXS). The following observations have been made. For PS-rich PS-block -PDMS copolymer thin films the low surface tension of PDMS caused it to migrate to the film surface regardless of solvent choice. The surface morphology was found to depend strongly on the solubility parameter of the solvent and exhibited SFM images consistent with parallel cylinder, perforated lamellar, and lamellar surface layers with increasing solvent solubility parameter. This behavior was due to the selective swelling of the individual blocks under slightly selective, good solvent conditions. A custom solvent annealing apparatus provided similar results in which order-order transitions in the thin films were observed with increasing solvent solubility parameter. Additionally improvements in the long-range order were observed after 1 h of solvent annealing. PS-rich PS-block-PDMS copolymer thin films also displayed PDMS

  9. Functional Microstructures from Iron-Containing Block Copolymers

    NASA Astrophysics Data System (ADS)

    Balsara, Nitash

    2005-03-01

    We have studied the properties of microstructures formed by diblock copolymers composed of an organic block such as polystyrene or polyisoprene, and an iron-containing block such as poly(vinyl ferrocene) or poly(ferrocenyldimethylsilane). We demonstrate that the thermodynamic state of these block copolymers can be controlled by altering the redox state of the ferrocene (Fc) moieties. Oxidizing only 8% of the Fc block results in a 40 K drop in the order-disorder transition temperature. Fc is catalytically active in the oxidized state. Thus one can obtain catalysts from iron-containing block copolymers wherein both the support and the active sites are formed by self-assembly. An interesting property of ferrocene is the fact that its oxidation state can be altered reversibly by the application of small electric fields (˜2V/cm). We are currently exploring the possibility of using electric fields to control the microstructure and function of our iron-containing block copolymers.

  10. Molecular origin of photovoltaic performance in donor-block-acceptor all-conjugated block copolymers

    DOE PAGES

    Smith, Kendall A.; Lin, Yen -Hao; Mok, Jorge W.; ...

    2015-11-03

    All-conjugated block copolymers may be an effective route to self-assembled photovoltaic devices, but we lack basic information on the relationship between molecular characteristics and photovoltaic performance. Here, we synthesize a library of poly(3-hexylthiophene) (P3HT) block poly((9,9-dialkylfluorene)-2,7-diyl-alt-[4,7-bis(alkylthiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (PFTBT) donor-block-acceptor all-conjugated block copolymers and carry out a comprehensive study of processing conditions, crystallinity, domain sizes, and side-chain structure on photovoltaic device performance. We find that all block copolymers studied exhibit an out-of-plane crystal orientation after deposition, and on thermal annealing at high temperatures the crystal orientation flips to an in-plane orientation. By varying processing conditions on polymer photovoltaic devices, we show thatmore » the crystal orientation has only a modest effect (15-20%) on photovoltaic performance. The addition of side-chains to the PFTBT block is found to decrease photovoltaic power conversion efficiencies by at least an order of magnitude. Through grazing-incidence X-ray measurements we find that the addition of side-chains to the PFTBT acceptor block results in weak segregation and small (< 10 nm) block copolymer self-assembled donor and acceptor domains. This work is the most comprehensive to date on all-conjugated block copolymer systems and suggests that photovoltaic performance of block copolymers depends strongly on the miscibility of donor and acceptor blocks, which impacts donor and acceptor domain sizes and purity. Lastly, strategies for improving the device performance of block copolymer photovoltaics should seek to increase segregation between donor and acceptor polymer domains.« less

  11. Novel RAFT amphiphilic brush copolymer steric stabilisers for cubosomes: poly(octadecyl acrylate)-block-poly(polyethylene glycol methyl ether acrylate).

    PubMed

    Chong, Josephine Y T; Mulet, Xavier; Postma, Almar; Keddie, Daniel J; Waddington, Lynne J; Boyd, Ben J; Drummond, Calum J

    2014-09-21

    Copolymers, particularly Pluronics®, are typically used to sterically stabilise colloidal nanostructured particles composed of a lyotropic liquid crystalline bicontinuous cubic phase (cubosomes). There is a need to design and assess new functionalisable stabilisers for these colloidal drug delivery systems. Six amphiphilic brush copolymers, poly(octadecyl acrylate)-block-poly(polyethylene glycol methyl ether acrylate) (P(ODA)-b-P(PEGA-OMe)), synthesised by reversible addition-fragmentation chain transfer (RAFT), were assessed as novel steric stabilisers for cubosomes. It was found that increasing the density of PEG on the nanostructured particle surface by incorporating a PEG brush design (i.e., brush copolymer), provided comparable and/or increased stabilisation effectiveness compared to a linear PEG structure, Pluronic® F127, which is extensively used for steric stabilisation of cubosomes. Assessment was conducted both prior to and following the removal of the dodecyl trithiocarbonate end-group, by free radical-induced reduction. The reduced (P(ODA)-b-P(PEGA-OMe) copolymers were more effective steric stabilisers for phytantriol and monoolein colloidal particle dispersions than their non-reduced analogues. High throughput characterisation methodologies, including an accelerated stability assay (ASA) and synchrotron small angle X-ray scattering (SAXS), were implemented in this study for the rapid assessment of steric stabiliser effectiveness and lyotropic liquid crystalline phase identification. Phytantriol cubosomes stabilised with P(ODA)-b-P(PEGA-OMe) copolymers exhibited a double diamond cubic phase (Q(2)(D)), whilst monoolein cubosomes exhibited a primitive cubic phase (Q(2)(P)), analogous to those formed using Pluronic® F127.

  12. Block and Graft Copolymers of Polyhydroxyalkanoates

    NASA Astrophysics Data System (ADS)

    Marchessault, Robert H.; Ravenelle, François; Kawada, Jumpei

    2004-03-01

    Polyhydroxyalkanoates (PHAs) were modified for diblock copolymer and graft polymer by catalyzed transesterification in the melt and by chemical synthesis to extend the side chains of the PHAs, and the polymers were studied by transmission electron microscopy (TEM) X-ray diffraction, thermal analysis and nuclear magnetic resonance (NMR). Catalyzed transesterification in the melt is used to produce diblock copolymers of poly[3-hydroxybutyrate] (PHB) and monomethoxy poly[ethylene glycol] (mPEG) in a one-step process. The resulting diblock copolymers are amphiphilic and self-assemble into sterically stabilized colloidal suspensions of PHB crystalline lamellae. Graft polymer was synthesized in a two-step chemical synthesis from biosynthesized poly[3-hydroxyoctanoate-co-3-hydroxyundecenoate] (PHOU) containing ca. 25 mol chains. 11-mercaptoundecanoic acid reacts with the side chain alkenes of PHOU by the radical addition creating thioether linkage with terminal carboxyl functionalities. The latter groups were subsequently transformed into the amide or ester linkage by tridecylamine or octadecanol, respectively, producing new graft polymers. The polymers have different physical properties than poly[3-hydroxyoctanoate] (PHO) which is the main component of the PHOU, such as non-stickiness and higher thermal stability. The combination of biosynthesis and chemical synthesis produces a hybrid thermoplastic elastomer with partial biodegradability.

  13. Ion Transport in Polymerized Ionic Liquid Block and Random Copolymers

    NASA Astrophysics Data System (ADS)

    Elabd, Yossef; Ye, Yuesheng; Choi, Jae-Hong; Winey, Karen

    2012-02-01

    Polymerized ionic liquid (PIL) block copolymers, a new type of solid-state polymer electrolyte, are of interest for energy conversion and storage devices, such as fuel cells, batteries, supercapacitors, and solar cells. In this study, a series of PIL diblock and random copolymers with various PIL compositions were synthesized. These consisted of an IL monomer and a non-ionic monomer, 1-[(2-methacryloyloxy)ethyl]-3-butylimidazolium bis(trifluoromethanesulfonyl)imide (MEBIm-TFSI) and methyl methacrylate (MMA), and 1-[(2-acryloyloxy)ethyl]-3-butylimidazolium bis(trifluoromethanesulfonyl)imide (AEBIm-TFSI) and styrene (S), respectively, were synthesized. The anion conductivity (ion transport) and morphology were measured in all of the polymers with EIS, SAXS/WAXS, and TEM. Ion transport in block copolymers are significantly higher than random copolymers at the same PIL composition and are highly dependent on the block copolymer nanostructure. The relationship between ion transport mechanisms and the phase behavior of these materials will be discussed.

  14. 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.

  15. BLOCK COPOLYMER THIN FILMS: Physics and Applications1

    NASA Astrophysics Data System (ADS)

    Fasolka, Michael J.; Mayes, Anne M.

    2001-08-01

    A two-part review of research concerning block copolymer thin films is presented. The first section summarizes experimental and theoretical studies of the fundamental physics of these systems, concentrating upon the forces that govern film morphology. The role of film thickness and surface energetics on the morphology of compositionally symmetric, amorphous diblock copolymer films is emphasized, including considerations of boundary condition symmetry, so-called hybrid structures, and surface chemical expression. Discussions of compositionally asymmetric systems and emerging research areas, e.g., liquid-crystalline and A-B-C triblock systems, are also included. In the second section, technological applications of block copolymer films, e.g., as lithographic masks and photonic materials, are considered. Particular attention is paid to means by which microphase domain order and orientation can be controlled, including exploitation of thickness and surface effects, the application of external fields, and the use of patterned substrates.

  16. Self-Assembly and Critical Aggregation Concentration Measurements of ABA Triblock Copolymers with Varying B Block Types: Model Development, Prediction, and Validation.

    PubMed

    Aydin, Fikret; Chu, Xiaolei; Uppaladadium, Geetartha; Devore, David; Goyal, Ritu; Murthy, N Sanjeeva; Zhang, Zheng; Kohn, Joachim; Dutt, Meenakshi

    2016-04-21

    The dissipative particle dynamics (DPD) simulation technique is a coarse-grained (CG) molecular dynamics-based approach that can effectively capture the hydrodynamics of complex systems while retaining essential information about the structural properties of the molecular species. An advantageous feature of DPD is that it utilizes soft repulsive interactions between the beads, which are CG representation of groups of atoms or molecules. In this study, we used the DPD simulation technique to study the aggregation characteristics of ABA triblock copolymers in aqueous medium. Pluronic polymers (PEG-PPO-PEG) were modeled as two segments of hydrophilic beads and one segment of hydrophobic beads. Tyrosine-derived PEG5K-b-oligo(desaminotyrosyl tyrosine octyl ester-suberate)-b-PEG5K (PEG5K-oligo(DTO-SA)-PEG5K) block copolymers possess alternate rigid and flexible components along the hydrophobic oligo(DTO-SA) chain, and were modeled as two segments of hydrophilic beads and one segment of hydrophobic, alternate soft and hard beads. The formation, structure, and morphology of the initial aggregation of the polymer molecules in aqueous medium were investigated by following the aggregation dynamics. The dimensions of the aggregates predicted by the computational approach were in good agreement with corresponding results from experiments, for the Pluronic and PEG5K-oligo(DTO-SA)-PEG5K block copolymers. In addition, DPD simulations were utilized to determine the critical aggregation concentration (CAC), which was compared with corresponding results from an experimental approach. For Pluronic polymers F68, F88, F108, and F127, the computational results agreed well with experimental measurements of the CAC measurements. For PEG5K-b-oligo(DTO-SA)-b-PEG5K block polymers, the complexity in polymer structure made it difficult to directly determine their CAC values via the CG scheme. Therefore, we determined CAC values of a series of triblock copolymers with 3-8 DTO-SA units using DPD

  17. Yield Stress Enhancement in Glassy-Polyethylene Block Copolymers

    NASA Astrophysics Data System (ADS)

    Mulhearn, William; Register, Richard

    Polyethylene (PE) has the highest annual production volume of all synthetic polymers worldwide, and is valuable across many applications due to its low cost, toughness, processability, and chemical resistance. However, PE is not well suited to certain applications due to its modest yield stress and Young's modulus (approximately 30 MPa and 1 GPa, respectively for linear, high-density PE). Irreversible deformation of PE results from dislocation of crystal stems and eventual crystal fragmentation under applied stress. The liquid-like amorphous fraction provides no useful mechanical support to the crystal fold surface in a PE homopolymer, so the only method to enhance the force required for crystal slip, and hence the yield stress, is crystal thickening via thermal treatment. An alternative route towards modifying the mechanical properties of PE involves copolymerization of a minority high-glass transition temperature block into a majority-PE block copolymer. In this work, we investigate a system of glassy/linear-PE block copolymers prepared via ring-opening metathesis polymerization of cyclopentene and substituted norbornene monomers followed by hydrogenation. We demonstrate that a large change in mechanical properties can be achieved with the addition of a short glassy block (e.g. a doubling of the yield stress and Young's modulus versus PE homopolymer with the addition of 25 percent glassy block). Furthermore, owing to the low interaction energy between PE and the substituted polynorbornene blocks employed, these high-yield PE block copolymers can exhibit single-phase melts for ease of processability.

  18. Block Copolymer Membranes for Efficient Capture of a Chemotherapy Drug

    DOE PAGES

    Chen, X. Chelsea; Oh, Hee Jeung; Yu, Jay F.; ...

    2016-07-23

    In this paper, we introduce the use of block copolymer membranes for an emerging application, “drug capture”. The polymer is incorporated in a new class of biomedical devices, referred to as ChemoFilter, which is an image-guided temporarily deployable endovascular device designed to increase the efficacy of chemotherapy-based cancer treatment. We show that block copolymer membranes consisting of functional sulfonated polystyrene end blocks and a structural polyethylene middle block (SSES) are capable of capturing doxorubicin, a chemotherapy drug. We focus on the relationship between morphology of the membrane in the ChemoFilter device and efficacy of doxorubicin capture measured in vitro. Usingmore » small-angle X-ray scattering and cryogenic scanning transmission electron microscopy, we discovered that rapid doxorubicin capture is associated with the presence of water-rich channels in the lamellar-forming S-SES membranes in aqueous environment.« less

  19. Block Copolymer Membranes for Efficient Capture of a Chemotherapy Drug

    PubMed Central

    2016-01-01

    We introduce the use of block copolymer membranes for an emerging application, “drug capture”. The polymer is incorporated in a new class of biomedical devices, referred to as ChemoFilter, which is an image-guided temporarily deployable endovascular device designed to increase the efficacy of chemotherapy-based cancer treatment. We show that block copolymer membranes consisting of functional sulfonated polystyrene end blocks and a structural polyethylene middle block (S-SES) are capable of capturing doxorubicin, a chemotherapy drug. We focus on the relationship between morphology of the membrane in the ChemoFilter device and efficacy of doxorubicin capture measured in vitro. Using small-angle X-ray scattering and cryogenic scanning transmission electron microscopy, we discovered that rapid doxorubicin capture is associated with the presence of water-rich channels in the lamellar-forming S-SES membranes in aqueous environment. PMID:27547493

  20. Nanostructured Block Copolymer Coatings for Biofouling Inhibition

    DTIC Science & Technology

    2015-06-30

    we hoped. Inhibition, but not highly tunable by change of MW ratio The inhibition of diatoms by the diblocks was not significant (See figure 13). M...OH O a. £ o EC o a. in £ 0 Cu Figure 13 - The initial attachment density of the diatom Navicula on PS-b-PMMA coatings after gentle...washing on glass-nylon supports. Diatom Settlement: no effect of diblock copolymer We did have some success with triblocks, and that work is on-going. We

  1. Reversible Tuning of a Block Copolymer Nanostructure via Electric Fields

    SciTech Connect

    Schmidt, K.; Schoberth, Heiko; Ruppel, Markus A.; Zettl, H; Weiss, Thomas; Urban, Volker S; Krausch, G; Boker, A.

    2007-01-01

    Block copolymers consisting of incompatible components self-assemble into microphase-separated domains yielding highly regular structures with characteristic length scales of the order of several tens of nanometres. Therefore, in the past decades, block copolymers have gained considerable potential for nanotechnological applications, such as in nanostructured networks and membranes, nanoparticle templates and high-density data storage media. However, the characteristic size of the resulting structures is usually determined by molecular parameters of the constituent polymer molecules and cannot easily be adjusted on demand. Here, we show that electric d.c. fields can be used to tune the characteristic spacing of a block-copolymer nanostructure with high accuracy by as much as 6% in a fully reversible way on a timescale in the range of several milliseconds. We discuss the influence of various physical parameters on the tuning process and study the time response of the nanostructure to the applied field. A tentative explanation of the observed effect is given on the basis of anisotropic polarizabilities and permanent dipole moments of the monomeric constituents. This electric-field-induced effect further enhances the high technological potential of block-copolymer-based soft-lithography applications.

  2. Order and Disorder in Polydisperse Block Copolymer Melts

    NASA Astrophysics Data System (ADS)

    Lynd, Nathaniel; Hillmyer, Marc

    2007-03-01

    Utilizing creative strategies for the synthesis of model controlled-polydispersity poly(ethylene-alt-propylene)-b-poly(d,l-lactide)(PEP-PLA) and polystyrene-b-polyisoprene(PS-PI) block copolymers, the effects of increased breadth in the molecular weight distribution on block copolymer self-assembly were investigated. Small-angle x-ray scattering and rheological measurements were carried out to characterize the morphological details of these self-assembled materials as a function of their polydispersity, interaction strengths, and compositions. A number of surprising consequences of increased breadth in the molecular weight distribution emerged; the domain spacing of the ordered structures increased, changes in morphology occurred, and the degree of segregation at the order-disorder transitions changed as well, particularly for asymmetric block copolymers. The change in the degree of segregation at the order-disorder transition as the polydispersity was increased was found to be dependent on the block copolymer composition, e.g., for PEP-PLA and PS-PI at asymmetric compositions, when the polydispersity was increased in the minority component, the degree of segregation at the order-disorder transition decreased, whereas when the polydispersity was increased in the majority component, the degree of segregation at the order-disorder transition increased.

  3. Fast assembly of ordered block copolymer nanostructures through microwave annealing.

    PubMed

    Zhang, Xiaojiang; Harris, Kenneth D; Wu, Nathanael L Y; Murphy, Jeffrey N; Buriak, Jillian M

    2010-11-23

    Block copolymer self-assembly is an innovative technology capable of patterning technologically relevant substrates with nanoscale precision for a range of applications from integrated circuit fabrication to tissue interfacing, for example. In this article, we demonstrate a microwave-based method of rapidly inducing order in block copolymer structures. The technique involves the usage of a commercial microwave reactor to anneal block copolymer films in the presence of appropriate solvents, and we explore the effect of various parameters over the polymer assembly speed and defect density. The approach is applied to the commonly used poly(styrene)-b-poly(methyl methacrylate) (PS-b-PMMA) and poly(styrene)-b-poly(2-vinylpyridine) (PS-b-P2VP) families of block copolymers, and it is found that the substrate resistivity, solvent environment, and anneal temperature all critically influence the self-assembly process. For selected systems, highly ordered patterns were achieved in less than 3 min. In addition, we establish the compatibility of the technique with directed assembly by graphoepitaxy.

  4. Block copolymer micelles: preparation, characterization and application in drug delivery.

    PubMed

    Gaucher, Geneviève; Dufresne, Marie-Hélène; Sant, Vinayak P; Kang, Ning; Maysinger, Dusica; Leroux, Jean-Christophe

    2005-12-05

    Block copolymer micelles are generally formed by the self-assembly of either amphiphilic or oppositely charged copolymers in aqueous medium. The hydrophilic and hydrophobic blocks form the corona and the core of the micelles, respectively. The presence of a nonionic water-soluble shell as well as the scale (10-100 nm) of polymeric micelles are expected to restrict their uptake by the mononuclear phagocyte system and allow for passive targeting of cancerous or inflamed tissues through the enhanced permeation and retention effect. Research in the field has been increasingly focused on achieving enhanced stability of the micellar assembly, prolonged circulation times and controlled release of the drug for optimal targeting. With that in mind, our group has developed a range of block copolymers for various applications, including amphiphilic micelles for passive targeting of chemotherapeutic agents and environment-sensitive micelles for the oral delivery of poorly bioavailable compounds. Here, we propose to review the innovations in block copolymer synthesis, polymeric micelle preparation and characterization, as well as the relevance of these developments to the field of biomedical research.

  5. Nanostructured Block Copolymer Solutions and Composites: Mechanical and Structural Properties

    NASA Astrophysics Data System (ADS)

    Walker, Lynn

    2015-03-01

    Self-assembled block copolymer templates are used to control the nanoscale structure of materials that would not otherwise order in solution. In this work, we have developed a technique to use close-packed cubic and cylindrical mesophases of a thermoreversible block copolymer (PEO-PPO-PEO) to impart spatial order on dispersed nanoparticles. The thermoreversible nature of the template allows for the dispersion of particles synthesized outside the template. This feature extends the applicability of this templating method to many particle-polymer systems, including proteins, and also permits a systematic evaluation of the impact of design parameters on the structure and mechanical properties of the nanocomposites. The criteria for forming co-crystals have been characterized using small-angle scatting and the mechanical properties of these soft crystals determined. Numerous crystal structures have been reported for the block copolymer system and we have taken advantage of several to generate soft co-crystals. The result of this templating is spatially ordered nanoparticle arrays embedded within the block copolymer nanostructure. These soft materials can be shear aligned into crystals with long range order and this shear alignment is discussed. Finally, the dynamics of nanoparticles within the nanostructured material are characterized with fluorescence recovery after photobleaching (FRAP). The applications and general behavior of these nanostructured hydrogels are outlined.

  6. Characterization of the paclitaxel loaded chitosan graft Pluronic F127 copolymer micelles conjugate with a DNA aptamer targeting HER-2 overexpressing breast cancer cells

    NASA Astrophysics Data System (ADS)

    Thach Nguyen, Kim; Nguyen, Thu Ha; Do, Dinh Ho; Huan Le, Quang

    2017-03-01

    In this work we report the isolation of DNA aptamer that is specifically bound to a HER-2 overexpressing SK-BR-3 human breast cancer cell line, using SELEX strategy. Paclitaxel (PTX) loaded chitosan graft Pluronic F127 copolymer micelles conjugate with a DNA aptamer was synthesized and its structure was confirmed by TEM image. This binary mixed system consisting of DNA aptamer modified Pluronic F127 and chitosan could enhance PTX loading capacity and increase micelle stability. Morphology images confirmed the existence of PTX micelles, with an average size of approximately 86.22 ± 1.45 nm diameters. Drug release profile showed that the PTX conjugate maintained a sustained PTX release. From in vitro cell experiment it was shown that 89%–93%, 50%–58%, 55%–62%, 24%–28% and 2%–7% of the SK-BR-3, NS-VN-67, LH-VN-48, HT-VN-26 and NV-VN-31, respectively, were dead after 6–48 h. These results demonstrated a novel DNA aptamer-micelle assembly for efficient detection and a system for the delivery of PTX targeting specific HER-2 overexpressing. We have also successfully cultivated cancer tissues of explants from Vietnamese patients on a type I collagen substrate. The NS-VN-67, LH-VN-48, HT-VN-26 and NV-VN-31cell lines were used as cellular model sources for the study of chemotherapy drug in cancer.

  7. Nanostructured Amphiphilic Star-Hyperbranched Block Copolymers for Drug Delivery.

    PubMed

    Seleci, Muharrem; Seleci, Didem Ag; Ciftci, Mustafa; Demirkol, Dilek Odaci; Stahl, Frank; Timur, Suna; Scheper, Thomas; Yagci, Yusuf

    2015-04-21

    A robust drug delivery system based on nanosized amphiphilic star-hyperbranched block copolymer, namely, poly(methyl methacrylate-block-poly(hydroxylethyl methacrylate) (PMMA-b-PHEMA) is described. PMMA-b-PHEMA was prepared by sequential visible light induced self-condensing vinyl polymerization (SCVP) and conventional vinyl polymerization. All of the synthesis and characterization details of the conjugates are reported. To accomplish tumor cell targeting property, initially cell-targeting (arginylglycylaspactic acid; RGD) and penetrating peptides (Cys-TAT) were binding to each other via the well-known EDC/NHS chemistry. Then, the resulting peptide was further incorporated to the surface of the amphiphilic hyperbranched copolymer via a coupling reaction between the thiol (-SH) group of the peptide and the hydroxyl group of copolymer by using N-(p-maleinimidophenyl) isocyanate as a heterolinker. The drug release property and targeting effect of the anticancer drug (doxorobucin; DOX) loaded nanostructures to two different cell lines were evaluated in vitro. U87 and MCF-7 were chosen as integrin αvβ3 receptor positive and negative cells for the comparison of the targeting efficiency, respectively. The data showed that drug-loaded copolymers exhibited enhanced cell inhibition toward U87 cells in compared to MCF-7 cells because targeting increased the cytotoxicity of drug-loaded copolymers against integrin αvβ3 receptor expressing tumor cells.

  8. Synthesis of mesoporous NiCo2S4 deposited on reduced graphite oxide assistant by co-polymer Pluronic F127 for high-performance supercapacitor

    NASA Astrophysics Data System (ADS)

    Qin, Huiya; Yang, Shuo; Zhao, Wenliang; Yang, Zhengchun; Li, Xuan; Li, Huijun; Yao, Pei

    2017-10-01

    Mesoporous NiCo2S4 particles deposited on reduced graphite oxide (RGO) sheets using the co-polymer Pluronic F127 as a structure-directing agent have been successfully prepared as a supercapacitor electrode. The formation of F127 micelles alleviated the aggregation of the RGO sheets and generated NiCo2S4 nanoparticles through hydrophilic affinity of ethylene oxide (EO) ends to produce porous channels during the hydrothermal process. This resulted in a large specific area of the prepared material, and superior electrochemical performance in terms of outstanding rate capability of 85.6% (from 1 A g-1 to 20 A g-1) and cycling stability (92.7% retention after 6500 cycles), features that are crucial for supercapacitors in practical application.

  9. Structure-Property Relationships in Polyolefin Block Copolymers

    NASA Astrophysics Data System (ADS)

    Mansour, Ameara Salah

    Poly(cyclohexylethylene) (PCHE for a homopolymer or C in a block copolymer) is created by hydrogenating polystyrene, and this polymer exhibits interesting properties, such as a high glass transition temperature (147 °C), high flexural modulus (2.8 GPa), low stress optical coefficient (-0.2 * 10-9 Pa-1), and low cost. However, the inherently brittle nature of PCHE prevents it from being used in applications that simultaneously require high modulus, ductility, thermal stability, and optical clarity. Previous research has shown that incorporating PCHE into a block copolymer with rubbery poly(ethylene-alt-propylene) (P) or poly(ethylethylene) (EE) or semicrystalline polyethylene (E) results in a tough material. In some cases, applications also require specific mechanical or optical properties. In order to tune these properties, this research examined tuning crystallinity using two methods: (1) by controlling the microstructure of the soft block by synthesizing a random copolymer of E and EE, and (2) by blending high C content pentablock copolymers with semicrystalline and rubbery minority components. In the first study, diblock copolymers of C(EcoEE) also were used to understand how the microstructure of the random copolymer affects the thermodynamics of the system. In the second study, CECEC and CPCPC, designed to form the same morphology (hexagonally packed cylinders with glassy C matrices), and have similar order-to-disorder transition temperatures and domain spacings, were blended together. Isothermal crystallization experiments were used to determine how the confining E and P in one domain affects the crystallization process. The effect of architecture, the state of the minority component, and the percent crystallinity on the mechanical properties of high glass content materials was also examined. These results were compared to the mechanical properties of homopolymer PCHE, polystyrene, and polycarbonate. The processing conditions needed to create smooth films of

  10. Dynamic photoinduced realignment processes in photoresponsive block copolymer films: effects of the chain length and block copolymer architecture.

    PubMed

    Sano, Masami; Shan, Feng; Hara, Mitsuo; Nagano, Shusaku; Shinohara, Yuya; Amemiya, Yoshiyuki; Seki, Takahiro

    2015-08-07

    A series of block copolymers composed of an amorphous poly(butyl methacrylate) (PBMA) block connected with an azobenzene (Az)-containing liquid crystalline (PAz) block were synthesized by changing the chain length and polymer architecture. With these block copolymer films, the dynamic realignment process of microphase separated (MPS) cylinder arrays of PBMA in the PAz matrix induced by irradiation with linearly polarized light was studied by UV-visible absorption spectroscopy, and time-resolved grazing incidence small angle X-ray scattering (GI-SAXS) measurements using a synchrotron beam. Unexpectedly, the change in the chain length hardly affected the realignment rate. In contrast, the architecture of the AB-type diblock or the ABA-type triblock essentially altered the realignment feature. The strongly cooperative motion with an induction period before realignment was characteristic only for the diblock copolymer series, and the LPL-induced alignment change immediately started for triblock copolymers and the PAz homopolymer. Additionally, a marked acceleration in the photoinduced dynamic motions was unveiled in comparison with a thermal randomization process.

  11. Block-copolymer-induced structure formation in microemulsions

    SciTech Connect

    Hilfiker, R.; Eicke, H.F.; Steeb, C.; Hofmeier, U. )

    1991-02-07

    Transient electric birefringence measurements were performed on water/AOT (sodium bis(2-ethylhexyl) sulfosuccinate)/isooctane microemulsions with various amounts of block-copoly(oxyethylene/isoprene/oxyethylene) added. The authors could show that addition of the copolymer leads to a formation of nanodroplet (ND)-copolymer-aggregates. The contributions of NDs and aggregates to the induced birefringence could easily be separated because the NDs exhibited a negative and the aggregates a positive induced birefringence and because the time scales corresponding to the two processes were different.

  12. Experimental diffusion measurements of entangled rod-coil block copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Muzhou; Timachova, Ksenia; Alexander-Katz, Alfredo; Olsen, Bradley

    2013-03-01

    A fundamental theory for the dynamics of rod-coil block copolymers is important for understanding diffusion, mechanics, and self-assembly kinetics in functional nanostructured materials for organic electronics and biomaterials. Recently our group has proposed a reptation theory for the diffusion of entangled rod-coil block copolymers, showing the slower dynamics of rod-coils is due to the mismatch between the curvature of the rod and coil blocks. Here we present experimental tracer diffusion measurements of model rod-coil diblock and coil-rod-coil triblock copolymers that support this theory. The model systems are composed of poly(ethylene oxide) coils and polyalanine α-helical rods synthesized by bacterial expression and bioconjugation, and tracer diffusion in entangled solutions is measured by forced Rayleigh scattering. The experiments support both the activated reptation and arm retraction mechanism for the small and large rod regimes that were previously presented in our theory. Comparison of both simulation and experiments between diblock and triblock copolymers suggests that the diffusion mechanisms are independent of the different symmetry and molecular architecture of the molecules.

  13. Pluronic-lysozyme conjugates as anti-adhesive and antibacterial bifunctional polymers for surface coating.

    PubMed

    Muszanska, Agnieszka K; Busscher, Henk J; Herrmann, Andreas; van der Mei, Henny C; Norde, Willem

    2011-09-01

    This paper describes the preparation and characterization of polymer-protein conjugates composed of a synthetic triblock copolymer with a central polypropylene oxide (PPO) block and two terminal polyethylene oxide (PEO) segments, Pluronic F-127, and the antibacterial enzyme lysozyme attached to the telechelic groups of the PEO chains. Covalent conjugation of lysozyme proceeded via reductive amination of aldehyde functionalized PEO blocks (CHO-Pluronic) and the amine groups of the lysine residues in the protein. SDS-PAGE gel electrophoresis together with MALDI-TOF mass spectrometry analysis revealed formation of conjugates of one or two lysozyme molecules per Pluronic polymer chain. The conjugated lysozyme showed antibacterial activity towards Bacillus subtilis. Analysis with a quartz crystal microbalance with dissipation revealed that Pluronic-lysozyme conjugates adsorb in a brush conformation on a hydrophobic gold-coated quartz surface. X-ray photoelectron spectroscopy indicated surface coverage of 32% by lysozyme when adsorbed from a mixture of unconjugated Pluronic and Pluronic-lysozyme conjugate (ratio 99:1) and of 47% after adsorption of 100% Pluronic-lysozyme conjugates. Thus, bifunctional brushes were created, possessing both anti-adhesive activity due to the polymer brush, combined with the antibacterial activity of lysozyme. The coating having a lower degree of lysozyme coverage proved to be more bactericidal.

  14. Gas Permeation through Polystyrene-Poly(ethylene oxide) Block Copolymers

    NASA Astrophysics Data System (ADS)

    Hallinan, Daniel, Jr.; Minelli, Matteo; Giacinti-Baschetti, Marco; Balsara, Nitash

    2013-03-01

    Lithium air batteries are a potential technology for affordable energy storage. They consist of a lithium metal anode and a porous air cathode separated by a solid polymer electrolyte membrane, such as PEO/LiTFSI (PEO = poly(ethylene oxide), LiTFSI = lithium bis-trifluoromethane sulfonimide). For extended operation of such a battery, the polymer electrolyte must conduct lithium ions while blocking electrons and gases present in air. In order to maintain a pressure difference the membrane must be mechanically robust, which can be achieved by incorporating the PEO into a block copolymer with a glassy block such as PS (PS = polystyrene). To protect the lithium electrode, the membrane must have low permeability to gases in air such as CO2, N2, and O2. We have therefore studied the permeation of pure gases through a PS-PEO block copolymer. A high molecular weight, symmetric block copolymer with a lamellar morphology was used to cast free-standing membranes. Gas permeability was measured through these membranes with a standard, pressure-based technique. A model was developed to account for transport through the polymer membrane consisting of semi-crystalline PEO lamellae and amorphous PS lamellae. PEO crystallinity was extracted from the permeation model and compares well with values from differential scanning calorimetry measurements.

  15. Ordered nanoscale domains by infiltration of block copolymers

    DOEpatents

    Darling, Seth B.; Elam, Jeffrey; Tseng, Yu-Chih; Peng, Qing

    2016-11-08

    A method of preparing tunable inorganic patterned nanofeatures by infiltration of a block copolymer scaffold having a plurality of self-assembled periodic polymer microdomains. The method may be used sequential infiltration synthesis (SIS), related to atomic layer deposition (ALD). The method includes selecting a metal precursor that is configured to selectively react with the copolymer unit defining the microdomain but is substantially non-reactive with another polymer unit of the copolymer. A tunable inorganic features is selectively formed on the microdomain to form a hybrid organic/inorganic composite material of the metal precursor and a co-reactant. The organic component may be optionally removed to obtain an inorganic features with patterned nanostructures defined by the configuration of the microdomain.

  16. Preparation and icephobic properties of polymethyltrifluoropropylsiloxane-polyacrylate block copolymers

    NASA Astrophysics Data System (ADS)

    Li, Xiaohui; Zhao, Yunhui; Li, Hui; Yuan, Xiaoyan

    2014-10-01

    Five polymethyltrifluoropropylsiloxane (PMTFPS)-polyacrylate block copolymers (PMTFPS-b-polyacrylate) were synthesized by free radical polymerization of methyl methacrylate, n-butyl acrylate and hydroxyethyl methacrylate using PMTFPS macroazoinitiator (PMTFPS-MAI) in range of 10-50 mass percentages. The morphology, surface chemical composition and wettability of the prepared copolymer films were investigated by transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle measurement. Delayed icing time and ice shear strength of the films were also detected for the icephobic purpose. The surface morphologies of the copolymers were different from those of the bulk because of the migration of the PMTFPS segments to the air interface during the film formation. Maximal delayed icing time (186 s at -15 °C) and reduction of the ice shear strength (301 ± 10 kPa) which was significantly lower than that of polyacrylates (804 ± 37 kPa) were achieved when the content of PMTFPS-MAI was 20 wt%. The icephobicity of the copolymers was attributed primarily to the enrichment of PMTFPS on the film surface and synergistic effect of both silicone and fluorine. Thus, the results show that the PMTFPS-b-polyacrylate copolymer can be used as icephobic coating materials potentially.

  17. Reordering transitions during annealing of block copolymer cylinder phases

    DOE PAGES

    Majewski, Pawel W.; Yager, Kevin G.

    2015-10-06

    While equilibrium block-copolymer morphologies are dictated by energy-minimization effects, the semi-ordered states observed experimentally often depend on the details of ordering pathways and kinetics. In this study, we explore reordering transitions in thin films of block-copolymer cylinder-forming polystyrene-block-poly(methyl methacrylate). We observe several transient states as films order towards horizontally-aligned cylinders. In particular, there is an early-stage reorganization from randomly-packed cylinders into hexagonally-packed vertically-aligned cylinders; followed by a reorientation transition from vertical to horizontal cylinder states. These transitions are thermally activated. The growth of horizontal grains within an otherwise vertical morphology proceeds anisotropically, resulting in anisotropic grains in the final horizontalmore » state. The size, shape, and anisotropy of grains are influenced by ordering history; for instance, faster heating rates reduce grain anisotropy. These results help elucidate aspects of pathway-dependent ordering in block-copolymer thin films.« less

  18. Design of block copolymer templated solid state batteries

    NASA Astrophysics Data System (ADS)

    Bullock, Steven Edward

    The advent of portable electronics has placed a great demand on the power requirements of battery systems. High power batteries for small devices, such as cell phones, laptop computers, and personal data assistants (PDA's) have focused primarily on lithium ion batteries. With the introduction of large flexible panel displays, the need for a flexible battery system is apparent. Ring Opening Metathesis Polymerization (ROMP) is a facile method for synthesizing block copolymers with polar functional groups. These functional groups allow the formation of metal oxide clusters via a template of the microphase separated block copolymer domains. In this thesis, the synthesis of a flexible polymer battery system is described. Diblock copolymers of an ionically conductive unsaturated polyethylene oxide block with a carboxylic acid functionalized block were synthesized and characterized with NMR, IR and Gel Permeation Chromatography (GPC). Characterization of polymer templated LiMn2O 4 clusters and nanocomposites synthesized for the study have a distributed cluster morphology within the polymer matrix. The nanocomposites were analyzed with transmission electron microscopy to determine the morphology of the nanocomposites. Battery performance was characterized with cyclic voltammetry and galvanostatic charge/discharge cycling for power capacity. The ionic conductivity was measured with impedance spectroscopy. The novel room temperature templating strategy used for the synthesis of these ionically conductive nanocomposites requires no thermal cycling steps. This makes it attractive for processing of sheet structures to power flexible displays.

  19. Simple, generalizable route to highly aligned block copolymer thin films

    NASA Astrophysics Data System (ADS)

    Qiang, Zhe; Cavicchi, Kevin; Vogt, Bryan; University of Akron Team

    Macroscopic alignment of block copolymer domains in thin films is desired for many applications, such as cell responsive surfaces or optical polarizers. Alignment generally requires specialized tools that apply external fields, shear force gradient, or produce topological patterned substrates. This requirement limits the broad academic application of aligned BCPs. Here, we describe a simple modification of commonly utilized solvent vapor annealing (SVA) process for macroscopic alignment of BCPs. Adhering a flat, crosslinked elastomer pad to the BCP film leads to differential swelling between the elastomer pad and BCP to produce a shear force that aligns the ordered BCP domains. The role of elastomer properties, solvent quality, drying rate and degree of segregation of the block copolymer will be discussed to provide generalized rules for alignment with this technique. Cylindrical nanostructures formed in polystyrene-block-polydimethylsiloxane can be transformed into arrays of silica lines and increasing the thickness from a monolayer to bilayer can effectively halve the spacing of the lines. These results illustrate a generalized method for BCP alignment and a potential route for the generation of complex hierarchical assembled structures. A generalized method for block copolymer thin film alignment: solvent vapor annealing with shear.

  20. Influence of Chirality in Ordered Block Copolymer Phases

    NASA Astrophysics Data System (ADS)

    Prasad, Ishan; Grason, Gregory

    2015-03-01

    Block copolymers are known to assemble into rich spectrum of ordered phases, with many complex phases driven by asymmetry in copolymer architecture. Despite decades of study, the influence of intrinsic chirality on equilibrium mesophase assembly of block copolymers is not well understood and largely unexplored. Self-consistent field theory has played a major role in prediction of physical properties of polymeric systems. Only recently, a polar orientational self-consistent field (oSCF) approach was adopted to model chiral BCP having a thermodynamic preference for cholesteric ordering in chiral segments. We implement oSCF theory for chiral nematic copolymers, where segment orientations are characterized by quadrupolar chiral interactions, and focus our study on the thermodynamic stability of bi-continuous network morphologies, and the transfer of molecular chirality to mesoscale chirality of networks. Unique photonic properties observed in butterfly wings have been attributed to presence of chiral single-gyroid networks, this has made it an attractive target for chiral metamaterial design.

  1. 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.

  2. DNA block copolymers: functional materials for nanoscience and biomedicine.

    PubMed

    Schnitzler, Tobias; Herrmann, Andreas

    2012-09-18

    We live in a world full of synthetic materials, and the development of new technologies builds on the design and synthesis of new chemical structures, such as polymers. Synthetic macromolecules have changed the world and currently play a major role in all aspects of daily life. Due to their tailorable properties, these materials have fueled the invention of new techniques and goods, from the yogurt cup to the car seat belts. To fulfill the requirements of modern life, polymers and their composites have become increasingly complex. One strategy for altering polymer properties is to combine different polymer segments within one polymer, known as block copolymers. The microphase separation of the individual polymer components and the resulting formation of well defined nanosized domains provide a broad range of new materials with various properties. Block copolymers facilitated the development of innovative concepts in the fields of drug delivery, nanomedicine, organic electronics, and nanoscience. Block copolymers consist exclusively of organic polymers, but researchers are increasingly interested in materials that combine synthetic materials and biomacromolecules. Although many researchers have explored the combination of proteins with organic polymers, far fewer investigations have explored nucleic acid/polymer hybrids, known as DNA block copolymers (DBCs). DNA as a polymer block provides several advantages over other biopolymers. The availability of automated synthesis offers DNA segments with nucleotide precision, which facilitates the fabrication of hybrid materials with monodisperse biopolymer blocks. The directed functionalization of modified single-stranded DNA by Watson-Crick base-pairing is another key feature of DNA block copolymers. Furthermore, the appropriate selection of DNA sequence and organic polymer gives control over the material properties and their self-assembly into supramolecular structures. The introduction of a hydrophobic polymer into DBCs

  3. Magnetic Alignment of Block Copolymer Microdomains by Intrinsic Chain Anisotropy

    NASA Astrophysics Data System (ADS)

    Rokhlenko, Yekaterina; Gopinadhan, Manesh; Osuji, Chinedum O.; Zhang, Kai; O'Hern, Corey S.; Larson, Steven R.; Gopalan, Padma; Majewski, Paweł W.; Yager, Kevin G.

    2015-12-01

    We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, Δ χ , that drives alignment and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding Δ χ ≈2 ×1 0-8. From field-dependent scattering data, we estimate that grains of ≈1.2 μ m are present during alignment. These results demonstrate that intrinsic anisotropy is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.

  4. 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.

  5. Thickness-dependence of block copolymer coarsening kinetics

    DOE PAGES

    Black, Charles T.; Forrey, Christopher; Yager, Kevin G.

    2017-03-31

    In spite of active research, many fundamental aspects of block copolymer ordering remain unresolved. We studied the thickness-dependence of block copolymer grain coarsening kinetics, and find that thinner films order more rapidly than thicker films. Bilayer films, or monolayers with partial layers of islands, order more slowly than monolayers because of the greater amount of material that must rearrange in a coordinated fashion. Sub-monolayer films order much more rapidly than monolayers, exhibiting considerably smaller activation energies, as well as larger exponents for the time-growth power-law. Furthermore, by using molecular dynamics simulations, we directly study the motion of defects in thesemore » film regimes. Here, we attribute the enhanced grain growth in sub-monolayers to the film boundaries, where defects can be spontaneously eliminated. The boundaries thus act as efficient sinks for morphological defects, pointing towards methods for engineering rapid ordering of self-assembling thin films.« less

  6. Recent advances in PEG-PLA block copolymer nanoparticles.

    PubMed

    Xiao, Ren Zhong; Zeng, Zhao Wu; Zhou, Guang Lin; Wang, Jun Jie; Li, Fan Zhu; Wang, An Ming

    2010-11-26

    Due to their small particle size and large and modifiable surface, nanoparticles have unique advantages compared with other drug carriers. As a research focus in recent years, polyethylene glycol-polylactic acid (PEG-PLA) block copolymer and its end-group derivative nanoparticles can enhance the drug loading of hydrophobic drugs, reduce the burst effect, avoid being engulfed by phagocytes, increase the circulation time of drugs in blood, and improve bioavailability. Additionally, due to their smaller particle size and modified surface, these nanoparticles can accumulate in inflammation or target locations to enhance drug efficacy and reduce toxicity. Recent advances in PEG-PLA block copolymer nanoparticles, including the synthesis of PEG-PLA and the preparation of PEG-PLA nanoparticles, were introduced in this study, in particular the drug release and modifiable characteristics of PEG-PLA nanoparticles and their application in pharmaceutical preparations.

  7. Magnetic alignment of block copolymer microdomains by intrinsic chain anisotropy

    SciTech Connect

    Rokhlenko, Yekaterina; Yager, Kevin G.; Gopinadhan, Manesh; Osuji, Chinedum O.; Zhang, Kai; O'Hern, Corey S.; Larson, Steven R.; Gopalan, Padma; Majewski, Pawel W.

    2015-12-18

    We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, Δχ, that drives alignment and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding Δχ ≈ 2×10–8. From field-dependent scattering data, we estimate that grains of ≈ 1.2 μm are present during alignment. Furthermore, these results demonstrate that intrinsic anisotropy is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.

  8. Magnetic alignment of block copolymer microdomains by intrinsic chain anisotropy

    DOE PAGES

    Rokhlenko, Yekaterina; Yager, Kevin G.; Gopinadhan, Manesh; ...

    2015-12-18

    We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, Δχ, that drives alignment and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding Δχ ≈ 2×10–8. From field-dependent scattering data, we estimate that grains of ≈ 1.2 μm are present during alignment. Furthermore, these results demonstrate that intrinsic anisotropymore » is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.« less

  9. Recent advances in PEG–PLA block copolymer nanoparticles

    PubMed Central

    Xiao, Ren Zhong; Zeng, Zhao Wu; Zhou, Guang Lin; Wang, Jun Jie; Li, Fan Zhu; Wang, An Ming

    2010-01-01

    Due to their small particle size and large and modifiable surface, nanoparticles have unique advantages compared with other drug carriers. As a research focus in recent years, polyethylene glycol–polylactic acid (PEG–PLA) block copolymer and its end-group derivative nanoparticles can enhance the drug loading of hydrophobic drugs, reduce the burst effect, avoid being engulfed by phagocytes, increase the circulation time of drugs in blood, and improve bioavailability. Additionally, due to their smaller particle size and modified surface, these nanoparticles can accumulate in inflammation or target locations to enhance drug efficacy and reduce toxicity. Recent advances in PEG–PLA block copolymer nanoparticles, including the synthesis of PEG–PLA and the preparation of PEG–PLA nanoparticles, were introduced in this study, in particular the drug release and modifiable characteristics of PEG–PLA nanoparticles and their application in pharmaceutical preparations. PMID:21170353

  10. Beyond Orientation: The Impact of Electric Fields on Block Copolymers

    SciTech Connect

    Liedel, Clemens; Boker, A.; Pester, Christian; Ruppel, Markus A; Urban, Volker S

    2012-01-01

    Since the first report on electric field-induced alignment of block copolymers (BCPs) in 1991, electric fields have been shown not only to direct the orientation of BCP nanostructures in bulk, solution, and thin films, but also to reversibly induce order-order transitions, affect the order-disorder transition temperature, and control morphologies' dimensions with nanometer precision. Theoretical and experimental results of the past years in this very interesting field of research are summarized and future perspectives are outlined.

  11. Hybrid, elastomeric hydrogels crosslinked by multifunctional block copolymer micelles

    PubMed Central

    Xiao, Longxi; Liu, Chao; Zhu, Jiahua; Pochan, Darrin J.; Jia, Xinqiao

    2010-01-01

    Amphiphlic block copolymers consisting of hydrophilic, poly(acrylic acid) randomly decorated with acrylate groups and hydrophobic, rubbery poly(n-butyl acrylate) self-assembled into well-defined micelles with an average diameter of ~21 nm. Radical polymerization of acrylamide in the presence of the crosslinkable micelles gave rise to hybrid, elastomeric hydrogels whose mechancial properties can be readily tuned by varying the BCM concentration. PMID:21278815

  12. Toward Strong Thermoplastic Elastomers with Asymmetric Miktoarm Block Copolymer Architectures

    DTIC Science & Technology

    2014-03-05

    plastic -to- rubber ” transition and can lead to higher recovery of the total strain (Figure S3 in Supporting Information).25 The miktoarm S(IS′)3...and elastic materials. A straightforward and very promising future direction consists in blending the miktoarm block copolymers with a second polymer...SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 See Attached

  13. Ionic Conductivity of Nanostructured Block Copolymer and Ionic Liquid Membranes

    NASA Astrophysics Data System (ADS)

    Hoarfrost, Megan L.; Virgili, Justin M.; Segalman, Rachel A.

    2010-03-01

    Block copolymer and ionic liquid mixtures are of interest for creating ionically conductive, thermally stable, and nanostructured membranes. For mixtures of poly(styrene-b-2-vinylpyridine) (S2VP) and the ionic liquid bis(trifluoromethanesulfonyl)imide ([Im][TFSI]), nanostructured ion-conducting domains are formed due to [Im][TFSI] selectively residing in the P2VP domains of the block copolymer. The dependence of ionic conductivity on temperature, ionic liquid loading, and volume fraction of PS in the neat block copolymer was investigated for membranes with the matrix phase being P2VP/[Im][TFSI]. It was determined that the temperature dependence of conductivity follows the Vogel-Tamman-Fulcher equation, with the activation energy determined by the ratio of [Im][TFSI] to 2VP monomers. The overall weight fraction of [Im][TFSI] in the mixtures, however, is the dominating factor determining conductivity, regardless of PS volume fraction. The insight gained from this work will be important for further investigation into the effect on the ion transport properties of ionic liquids when confined to minority nanostructured domains.

  14. 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.

  15. Electrically Tunable Soft-Solid Block Copolymer Structural Color.

    PubMed

    Park, Tae Joon; Hwang, Sun Kak; Park, Sungmin; Cho, Sung Hwan; Park, Tae Hyun; Jeong, Beomjin; Kang, Han Sol; Ryu, Du Yeol; Huh, June; Thomas, Edwin L; Park, Cheolmin

    2015-12-22

    One-dimensional photonic crystals based on the periodic stacking of two different dielectric layers have been widely studied, but the fabrication of mechanically flexible polymer structural color (SC) films, with electro-active color switching, remains challenging. Here, we demonstrate free-standing electric field tunable ionic liquid (IL) swollen block copolymer (BCP) films. Placement of a polymer/ionic liquid film-reservoir adjacent to a self-assembled poly(styrene-block-quaternized 2-vinylpyridine) (PS-b-QP2VP) copolymer SC film allowed the development of red (R), green (G), and blue (B) full-color SC block copolymer films by swelling of the QP2VP domains by the ionic liquid associated with water molecules. The IL-polymer/BCP SC film is mechanically flexible with excellent color stability over several days at ambient conditions. The selective swelling of the QP2VP domains could be controlled by both the ratio of the IL to a polymer in the gel-like IL reservoir layer and by an applied voltage in the range of -3 to +6 V using a metal/IL reservoir/SC film/IL reservoir/metal capacitor type device.

  16. Application of Bottlebrush Block Copolymers as Photonic Crystals.

    PubMed

    Liberman-Martin, Allegra L; Chu, Crystal K; Grubbs, Robert H

    2017-07-01

    Brush block copolymers are a class of comb polymers that feature polymeric side chains densely grafted to a linear backbone. These polymers display interesting properties due to their dense functionality, low entanglement, and ability to rapidly self-assemble to highly ordered nanostructures. The ability to prepare brush polymers with precise structures has been enabled by advancements in controlled polymerization techniques. This Feature Article highlights the development of brush block copolymers as photonic crystals that can reflect visible to near-infrared wavelengths of light. Fabrication of these materials relies on polymer self-assembly processes to achieve nanoscale ordering, which allows for the rapid preparation of photonic crystals from common organic chemical feedstocks. The characteristic physical properties of brush block copolymers are discussed, along with methods for their preparation. Strategies to induce self-assembly at ambient temperatures and the use of blending techniques to tune photonic properties are emphasized. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. 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.

  18. Influence of triblock copolymer (pluronic F127) on enhancing the physico-chemical properties and photocatalytic response of mesoporous TiO2

    NASA Astrophysics Data System (ADS)

    Samsudin, Emy Marlina; Hamid, Sharifah Bee Abd; Juan, Joon Ching; Basirun, Wan Jefrey

    2015-11-01

    The utilization of triblock copolymer, pluronic F127 as a structure directing agent for the preparation of TiO2 played an important role in enhancing the photocatalytic degradation rate of atrazine by a factor of 1.7. The mesoporous F127-TiO2 showed significant modification of morphology, particle and crystallite size, and presence of defect energy belt within the catalyst forbidden band as proven via photoluminescence spectra and x-ray photon spectroscopy. Hence the photogenerated carriers have longer lifespan to migrate to the catalyst surface for redox activities. Furtherance, surface reactive {0 0 1} facets proven by the formation of new geometrical single crystal of square and rhombus surfaces in F127-TiO2 facilitates atrazine degradation as well. The increased surface area of F127-TiO2 promotes greater atrazine absorption, thus governs improved interaction between absorbed atrazine molecules and surface generated active radicals as a pre-requisite for good photocatalytic activity. Interestingly, using the same synthesis procedure, it was observed that the addition of pluronic F127 significantly affects anatase crystal structure as opposed to the more thermodynamically stable rutile, generating 61% and 25% of total crystallite size modification for anatase and rutile, respectively. However, there were no changes on the final composition of anatase and rutile crystal structure. In overall, enhancement of the photocatalytic degradation of atrazine is ruled out to the following factors (1) modification of geometrical structures and size, (2) narrowing of band gap due to defect energy belt, (3) longer lifespan of photoexcited charges to the catalyst surface, (4) enhanced surface textural properties and (5) increased exposure of reactive {0 0 1} facets, which were all observed in F127-TiO2.

  19. Effect of water uptake on morphology of polymerized ionic liquid block copolymers and random copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Tsen-Shan; Ye, Yuesheng; Elabd, Yossef; Winey, Karen

    2012-02-01

    Dynamic studies of polymer morphology probe how the physical properties of polymerized ionic liquids are affected by the environment, such as temperature or moisture. For a series of poly(methyl methacrylate-b-1-[2-(methacryloyloxy)ethyl]-3-Butylimidazolium X^-) block and random copolymers with hydrophilic counterions (X^- = Br^-, HCO3^-, OH^-), the introduction of water vapor to the system can swell the ionic liquid block, causing enlarged hydrophilic domains and swollen channels for ion conduction. This expected expansion of ionic liquid domains in humid environments can be used to intelligently design these copolymers for use in technological applications. The effect of water vapor exposure in these imidazolium-based acrylate polymers is studied by small-angle X-ray scattering. These morphology results will be discussed alongside complementary studies of water uptake and ion conductivity.

  20. Comparative Fluorescence Resonance Energy-Transfer Study in Pluronic Triblock Copolymer Micelle and Niosome Composed of Biological Component Cholesterol: An Investigation of Effect of Cholesterol and Sucrose on the FRET Parameters.

    PubMed

    Roy, Arpita; Kundu, Niloy; Banik, Debasis; Sarkar, Nilmoni

    2016-01-14

    The formation of pluronic triblock copolymer (F127)-cholesterol-based niosome and its interaction with sugar (sucrose) molecules have been investigated. The morphology of F127-cholesterol -based niosome in the presence of sucrose has been successfully demonstrated using dynamic light scattering (DLS) and transmission electron microscopic (TEM) techniques. The DLS profiles and TEM images clearly suggest that the size of the niosome aggregates increases significantly in the presence of sucrose. In addition to structural characterization, a detailed comparative fluorescence resonance energy transfer (FRET) study has been carried out in these F127-containing aggregates, involving coumarin 153 (C153) as donor (D) and rhodamine 6G (R6G) as an acceptor (A) to monitor the dynamic heterogeneity of the systems. Besides, time-resolved anisotropy and fluorescence correlation spectroscopy measurements have been carried out to monitor the rotational and lateral diffusion motion in these F127-cholesterol-based aggregates using C153 and R6G, respectively. During the course of FRET study, we have observed multiple time constants of FRET inside the F127-cholesterol-based niosomes in contrast with the F127 micelle. This corresponds to the presence of more than one preferential donor-acceptor (D-A) distance in niosomes than in F127 micelle. FRET has also been successfully used to probe the effect of sucrose on the morphology of F127-cholesterol-based niosome. In the presence of sucrose, the time constant of FRET further increases as the D-A distances increase in sucrose-decorated niosome. Finally, the excitation-wavelength-dependent FRET studies have indicated that as the excitation of donor molecules varies from 408 to 440 nm the contribution of the faster rise component of the acceptor enhances considerably, which clearly establishes the dynamics heterogeneity of both systems. Our findings also indicate that FRET is completely intravesicular in nature in these block copolymer

  1. Hierarchical nanostructure control in rod-coil block copolymers with magnetic fields.

    PubMed

    Tao, Yuefei; Zohar, Hagar; Olsen, Bradley D; Segalman, Rachel A

    2007-09-01

    Magnetic field alignment of rod-coil block copolymers is shown to proceed through coupling to the diamagnetic moment of individual rod blocks. Block copolymer self-assembly then leads to alignment of the interfaces perpendicular to the field lines and long range order on a 10 nm lengthscale. This is in contrast to previously demonstrated alignment techniques, which couple to the block copolymer interfaces rather than individual molecules. Furthermore, alignment occurs without direct physical contact to samples millimeters in size.

  2. Responsive block copolymer photonics triggered by protein-polyelectrolyte coacervation.

    PubMed

    Fan, Yin; Tang, Shengchang; Thomas, Edwin L; Olsen, Bradley D

    2014-11-25

    Ionic interactions between proteins and polyelectrolytes are demonstrated as a method to trigger responsive transitions in block copolymer (BCP) photonic gels containing one neutral hydrophobic block and one cationic hydrophilic block. Poly(2-vinylpyridine) (P2VP) blocks in lamellar poly(styrene-b-2-vinylpyridine) block copolymer thin films are quaternized with primary bromides to yield swollen gels that show strong reflectivity peaks in the visible range; exposure to aqueous solutions of various proteins alters the swelling ratios of the quaternized P2VP (QP2VP) gel layers in the PS-QP2VP materials due to the ionic interactions between proteins and the polyelectrolyte. Parameters such as charge density, hydrophobicity, and cross-link density of the QP2VP gel layers as well as the charge and size of the proteins play significant roles on the photonic responses of the BCP gels. Differences in the size and pH-dependent charge of proteins provide a basis for fingerprinting proteins based on their temporal and equilibrium photonic response. The results demonstrate that the BCP gels and their photonic effect provide a robust and visually interpretable method to differentiate different proteins.

  3. Block copolymers for alkaline fuel cell membrane materials

    NASA Astrophysics Data System (ADS)

    Li, Yifan

    Alkaline fuel cells (AFCs) using anion exchange membranes (AEMs) as electrolyte have recently received considerable attention. AFCs offer some advantages over proton exchange membrane fuel cells, including the potential of non-noble metal (e.g. nickel, silver) catalyst on the cathode, which can dramatically lower the fuel cell cost. The main drawback of traditional AFCs is the use of liquid electrolyte (e.g. aqueous potassium hydroxide), which can result in the formation of carbonate precipitates by reaction with carbon dioxide. AEMs with tethered cations can overcome the precipitates formed in traditional AFCs. Our current research focuses on developing different polymer systems (blend, block, grafted, and crosslinked polymers) in order to understand alkaline fuel cell membrane in many aspects and design optimized anion exchange membranes with better alkaline stability, mechanical integrity and ionic conductivity. A number of distinct materials have been produced and characterized. A polymer blend system comprised of poly(vinylbenzyl chloride)-b-polystyrene (PVBC-b-PS) diblock copolymer, prepared by nitroxide mediated polymerization (NMP), with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) or brominated PPO was studied for conversion into a blend membrane for AEM. The formation of a miscible blend matrix improved mechanical properties while maintaining high ionic conductivity through formation of phase separated ionic domains. Using anionic polymerization, a polyethylene based block copolymer was designed where the polyethylene-based block copolymer formed bicontinuous morphological structures to enhance the hydroxide conductivity (up to 94 mS/cm at 80 °C) while excellent mechanical properties (strain up to 205%) of the polyethylene block copolymer membrane was observed. A polymer system was designed and characterized with monomethoxy polyethylene glycol (mPEG) as a hydrophilic polymer grafted through substitution of pendent benzyl chloride groups of a PVBC

  4. Coarse-grained modeling of hybrid block copolymer system

    NASA Astrophysics Data System (ADS)

    Su, Yongrui

    This thesis is comprised of three major projects of my research. In the first project, I proposed a nanoparticle model and combined it with the Theoretically Informed Coarse Grained (TICG) model for pure polymer systems and the grand canonical slip springs model developed in our group to build a new model for entangled nanocomposites. With Molecule Dynamics(MD) simulation, I studied the mechanic properties of the nanocomposites, for example the influence of nanoparticles size and volume fraction on entanglements, the diffusion of polymers and nanoparticles, and the influence of nanoparticles size and volume fraction on viscosity et al.. We found that the addition of small-size nanoparticles reduces the viscosity of the nanocomposites, which is in contrary to what Einstein predicted a century ago. However, when particle increases its size to micrometers the Einstein predictions is recovered. From our simulation, we believe that small-size nanoparticles can more effectively decrease the entanglements of nanocomposites than larger particles. The free volume effect introduced by small-size nanoparticles also helps decrease the viscosity of the whole system. In the second project, I combined the Ohta-Kawasaki (OK) model [3] and the Covariance Matrix Adaptation Evolutionary Strategy(CMA-ES) to optimize the block copolymer blends self-assembly in the hole-shrink process. The aim is to predict the optimal composition and the optimal surface energy to direct the block copolymer blends self-assembly process in the confined hole. After optimization in the OK model, we calibrated the optimal results by the more reliable TICG model and got the same morphology. By comparing different optimization process, we found that the homopolymers which are comprised of the same monomers as either block of the block copolymer can form a perfect perforated hole and might have better performance than the pure block copolymer. While homopolymers which are comprised of a third-party monomers

  5. Morphology and phase diagram of complex block copolymers: ABC linear triblock copolymers.

    PubMed

    Tang, Ping; Qiu, Feng; Zhang, Hongdong; Yang, Yuliang

    2004-03-01

    Using a real space implementation of the self-consistent field theory for the polymeric system, we explore microphases of ABC linear triblock copolymers. For the sake of numerical tractability, the calculation is carried out in a two-dimensional (2D) space. Seven microphases are found to be stable for the ABC triblock copolymer in 2D, which include lamellae, hexagonal lattice, core-shell hexagonal lattice, tetragonal lattice, lamellae with beads inside, lamellae with beads at the interface, and hexagonal phase with beads at the interface. By systematically varying the composition, triangle phase diagrams are constructed for four classes of typical triblock polymers in terms of the relative strengths of the interaction energies between different species. In general, when both volume fractions and interaction energies of the three species are comparable, lamellar phases are found to be the most stable. While one of the volume fractions is large, core-shell hexagonal or tetragonal phases can be formed, depending on which of the blocks dominates. Furthermore, more complex morphologies, such as lamellae with beads inside, lamellae with beads at the interface, and hexagonal phases with beads at the interface compete for stability with lamellae structures, as the interaction energies between distinct blocks become asymmetric. Our study provides guidance for the design of microstructures in complex block copolymers.

  6. Morphology and Proton Transport in Humidified Phosphonated Peptoid Block Copolymers

    PubMed Central

    2016-01-01

    Polymers that conduct protons in the hydrated state are of crucial importance in a wide variety of clean energy applications such as hydrogen fuel cells and artificial photosynthesis. Phosphonated and sulfonated polymers are known to conduct protons at low water content. In this paper, we report on the synthesis phosphonated peptoid diblock copolymers, poly-N-(2-ethyl)hexylglycine-block-poly-N-phosphonomethylglycine (pNeh-b-pNpm), with volume fractions of pNpm (ϕNpm) values ranging from 0.13 to 0.44 and dispersity (Đ) ≤ 1.0003. The morphologies of the dry block copolypeptoids were determined by transmission electron microscopy and in both the dry and hydrated states by synchrotron small-angle X-ray scattering. Dry samples with ϕNpm > 0.13 exhibited a lamellar morphology. Upon hydration, the lowest molecular weight sample transitioned to a hexagonally packed cylinder morphology, while the others maintained their dry morphologies. Water uptake of all of the ordered samples was 8.1 ± 1.1 water molecules per phosphonate group. In spite of this, the proton conductivity of the ordered pNeh-b-pNpm copolymers ranged from 0.002 to 0.008 S/cm. We demonstrate that proton conductivity is maximized in high molecular weight, symmetric pNeh-b-pNpm copolymers. PMID:27134312

  7. Morphology and Proton Transport in Humidified Phosphonated Peptoid Block Copolymers.

    PubMed

    Sun, Jing; Jiang, Xi; Siegmund, Aaron; Connolly, Michael D; Downing, Kenneth H; Balsara, Nitash P; Zuckermann, Ronald N

    2016-04-26

    Polymers that conduct protons in the hydrated state are of crucial importance in a wide variety of clean energy applications such as hydrogen fuel cells and artificial photosynthesis. Phosphonated and sulfonated polymers are known to conduct protons at low water content. In this paper, we report on the synthesis phosphonated peptoid diblock copolymers, poly-N-(2-ethyl)hexylglycine-block-poly-N-phosphonomethylglycine (pNeh-b-pNpm), with volume fractions of pNpm (ϕNpm) values ranging from 0.13 to 0.44 and dispersity (Đ) ≤ 1.0003. The morphologies of the dry block copolypeptoids were determined by transmission electron microscopy and in both the dry and hydrated states by synchrotron small-angle X-ray scattering. Dry samples with ϕNpm > 0.13 exhibited a lamellar morphology. Upon hydration, the lowest molecular weight sample transitioned to a hexagonally packed cylinder morphology, while the others maintained their dry morphologies. Water uptake of all of the ordered samples was 8.1 ± 1.1 water molecules per phosphonate group. In spite of this, the proton conductivity of the ordered pNeh-b-pNpm copolymers ranged from 0.002 to 0.008 S/cm. We demonstrate that proton conductivity is maximized in high molecular weight, symmetric pNeh-b-pNpm copolymers.

  8. Metal Nanoparticle/Block Copolymer Composite Assembly and Disassembly

    PubMed Central

    Li, Zihui; Sai, Hiroaki; Warren, Scott C.; Kamperman, Marleen; Arora, Hitesh; Gruner, Sol M.; Wiesner, Ulrich

    2010-01-01

    Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-3-mercaptopropyl-N-3-methylammonium chloride as the ligand, which provided high solubility of NPs in various solvents as well as high affinity to PDMAEMA. From NP synthesis, existence of sub-1 nm Pt NPs was confirmed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. Estimations of the Pt NP ligand head group density based on HAADF-STEM images and thermogravimetric analysis (TGA) data yielded results comparable to what has been found for alkanethiol self-assembled monolayers (SAMs) on flat Pt {111} surfaces. Changing the volume fraction of Pt NPs in block copolymer-NP composites yielded hybrids with spherical micellar, wormlike micellar, lamellar and inverse hexagonal morphologies. Disassembly of hybrids with spherical, wormlike micellar, and lamellar morphologies generated isolated metal-NP based nano-spheres, cylinders and sheets, respectively. Results suggest the existence of powerful design criteria for the formation of metal-based nanostructures from designer blocked macromolecules. PMID:21103025

  9. Metal Nanoparticle/Block Copolymer Composite Assembly and Disassembly.

    PubMed

    Li, Zihui; Sai, Hiroaki; Warren, Scott C; Kamperman, Marleen; Arora, Hitesh; Gruner, Sol M; Wiesner, Ulrich

    2009-01-01

    Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-3-mercaptopropyl-N-3-methylammonium chloride as the ligand, which provided high solubility of NPs in various solvents as well as high affinity to PDMAEMA. From NP synthesis, existence of sub-1 nm Pt NPs was confirmed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. Estimations of the Pt NP ligand head group density based on HAADF-STEM images and thermogravimetric analysis (TGA) data yielded results comparable to what has been found for alkanethiol self-assembled monolayers (SAMs) on flat Pt {111} surfaces. Changing the volume fraction of Pt NPs in block copolymer-NP composites yielded hybrids with spherical micellar, wormlike micellar, lamellar and inverse hexagonal morphologies. Disassembly of hybrids with spherical, wormlike micellar, and lamellar morphologies generated isolated metal-NP based nano-spheres, cylinders and sheets, respectively. Results suggest the existence of powerful design criteria for the formation of metal-based nanostructures from designer blocked macromolecules.

  10. Hollow capsules prepared from all block copolymer micelle multilayers.

    PubMed

    Hong, Jinkee; Cho, Jinhan; Char, Kookheon

    2011-12-01

    We introduce a novel and versatile approach for preparing hollow multilayer capsules containing functional hydrophobic components. Protonated polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and anionic polystyrene-block-poly(acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films onto polystyrene (PS) colloids. After removing the PS colloids, the stabilities of the formed BCM hollow capsules were found to be strongly dependent on the charge density of the hydrophilic corona segments (i.e., P4VP and PAA block segments) as well as the relative molecular weight ratio of hydrophobic core (i.e., PS segments) blocks and hydrophilic corona shells. Furthermore, in the case of incorporating hydrophobic fluorescent dyes into the PS core blocks of micelles, the hairy/hairy BCM multilayers showed well-defined fluorescent images after colloidal template removal process. These phenomena are mainly caused by the relatively high degree of electrostatic interdigitation between the protonated and anionic corona block shells. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. Bicomponent Block Copolymers Derived from One or More Random Copolymers as an Alternative Route to Controllable Phase Behavior.

    PubMed

    Ashraf, Arman R; Ryan, Justin J; Satkowski, Michael M; Lee, Byeongdu; Smith, Steven D; Spontak, Richard J

    2017-09-01

    Block copolymers have been extensively studied due to their ability to spontaneously self-organize into a wide variety of morphologies that are valuable in energy-, medical-, and conservation-related (nano)technologies. While the phase behavior of bicomponent diblock and triblock copolymers is conventionally governed by temperature and individual block masses, it is demonstrated here that their phase behavior can alternatively be controlled through the use of blocks with random monomer sequencing. Block random copolymers (BRCs), i.e., diblock copolymers wherein one or both blocks are a random copolymer comprised of A and B repeat units, have been synthesized, and their phase behavior, expressed in terms of the order-disorder transition (ODT), has been investigated. The results establish that, depending on the block composition contrast and molecular weight, BRCs can microphase-separate. We also report that large variation in incompatibility can be generated at relatively constant molecular weight and temperature with these new soft materials. This sequence-controlled synthetic strategy is extended to thermoplastic elastomeric triblock copolymers differing in chemistry and possessing a random-copolymer midblock. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Studies on a novel multi-sensitive hydrogel: influence of the biomimetic phosphorylcholine end-groups on the PEO-PPO-PEO tri-block co-polymers.

    PubMed

    Meng, Sheng; Guo, Zhang; Wang, Qiong; Liu, ZongJun; Wang, QiHong; Zhong, Wei; Du, QiangGuo

    2011-01-01

    In the present study, a biomimetic phosphorylcholine group was employed in the end-capping modification of PEO-PPO-PEO tri-block co-polymers (Pluronic(®)). The structures of the resulting materials were characterized by (1)H-NMR and GPC. The effects of the additional phosphorylcholine end-groups to the thermo-sensitive sol-gel transition behaviors of the aqueous solutions of the resulting polymers were studied by rheology test in neutral (0.1 M NaCl) aqueous solutions and in acidic solutions (pH 3). It was found that the phosphorylcholine-end-capped Pluronic hydrogels still kept their thermo-sensitive mechanical properties with a slight change on the sol-gel transition behaviors. The phosphorylcholine-modified Pluronics exhibited a response to the change of the pH value, which made this kind of material a multi-sensitive hydrogel system. Also, the resulting polymers showed improved hemocompatibilities in the blood coagulation test using full human blood.

  13. Effect of sequence features on assembly of spider silk block copolymers.

    PubMed

    Tokareva, Olena S; Lin, Shangchao; Jacobsen, Matthew M; Huang, Wenwen; Rizzo, Daniel; Li, David; Simon, Marc; Staii, Cristian; Cebe, Peggy; Wong, Joyce Y; Buehler, Markus J; Kaplan, David L

    2014-06-01

    Bioengineered spider silk block copolymers were studied to understand the effect of protein chain length and sequence chemistry on the formation of secondary structure and materials assembly. Using a combination of in vitro protein design and assembly studies, we demonstrate that silk block copolymers possessing multiple repetitive units self-assemble into lamellar microstructures. Additionally, the study provides insights into the assembly behavior of spider silk block copolymers in concentrated salt solutions.

  14. Effect of Sequence Features on Assembly of Spider Silk Block Copolymers

    PubMed Central

    Tokareva, Olena S.; Lin, Shangchao; Jacobsen, Matthew M.; Huang, Wenwen; Rizzo, Daniel; Li, David; Simon, Marc; Staii, Cristian; Cebe, Peggy; Wong, Joyce Y.; Buehler, Markus J.; Kaplan, David L.

    2014-01-01

    Bioengineered spider silk block copolymers were studied to understand the effect of protein chain length and sequence chemistry on the formation of secondary structure and materials assembly. Using a combination of in vitro protein design and assembly studies, we demonstrate that silk block copolymers possessing multiple repetitive units self-assemble into lamellar microstructures. Additionally, the study provides insights into the assembly behavior of spider silk block copolymers in concentrated salt solutions. PMID:24613991

  15. Styrene-butadiene-styrene Tri-block Copolymers Modified wit Polyhedral Oligomeric Silsesquioxanes

    DTIC Science & Technology

    2006-05-31

    morphology.1-6 Polymer nano -composites are a new and active research area in the field of block copolymers. Block copolymers reinforced by various nano -sized...fillers have been prepared and studied; layered silicates-based nano -composites have drawn the most attention thus far. 7- 9 Although domain...morphology is not strongly influenced by the blending of layered- silicates, these nano -reinforced block copolymers have shown promising property enhancements

  16. Structure and Dynamics of Ionic Block Copolymer Melts: Computational Study

    DOE PAGES

    Aryal, Dipak; Agrawal, Anupriya; Perahia, Dvora; ...

    2017-09-06

    Structure and dynamics of melts of copolymers with an ABCBA topology, where C is an ionizable block, have been studied by fully atomistic molecular dynamics (MD) simulations. Introducing an ionizable block for functionality adds a significant element to the coupled set of interactions that determine the structure and dynamics of the macromolecule. The polymer consists of a randomly sulfonated polystyrene C block tethered to a flexible poly(ethylene-r-propylene) bridge B and end-capped with poly(tert-butylstyrene) A. The chemical structure and topology of these polymers constitute a model for incorporation of ionic blocks within a framework that provides tactility and mechanical stability. Heremore » in this paper we resolve the structure and dynamics of a structured polymer on the nanoscale constrained by ionic clusters. We find that the melts form intertwined networks of the A and C blocks independent of the degree of sulfonation of the C block with no long-range order. The cluster cohesiveness and morphology affect both macroscopic translational motion and segmental dynamics of all the blocks.« less

  17. Simple, generalizable route to highly aligned block copolymer thin films

    NASA Astrophysics Data System (ADS)

    Qiang, Zhe; Cavicchi, Kevin; Vogt, Bryan

    2015-03-01

    Macroscopic alignment of block copolymer domains in thin films is desired for many applications, such as cell responsive surfaces or optical polarizers. Alignment generally requires specialized tools that apply external fields, shear force gradient, or produce topological patterned substrates. This requirement limits the broad academic application of aligned BCPs. Here, we describe a simple modification of commonly utilized solvent vapor annealing (SVA) process for macroscopic alignment of BCPs. Adhering a flat, crosslinked elastomer pad to the BCP film leads to differential swelling between the elastomer pad and BCP to produce a shear force that aligns the ordered BCP domains. The role of elastomer properties, solvent quality, drying rate and degree of segregation of the block copolymer will be discussed to provide generalized rules for alignment with this technique. Cylindrical nanostructures formed in polystyrene-block-polydimethylsiloxane can be transformed into arrays of silica lines and increasing the thickness from a monolayer to bilayer can effectively halve the spacing of the lines. These results illustrate a generalized method for BCP alignment and a potential route for the generation of complex hierarchical assembled structures.

  18. Micellization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers in aqueous solutions: Thermodynamics of copolymer association

    SciTech Connect

    Alexandridis, P.; Hatton, T.A. . Dept. of Chemical Engineering); Holzwarth, J.F. )

    1994-04-25

    The critical micellization temperature (cmt) and critical micellization concentration (cmc) values of 12 Pluronic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers, covering a wide range of molecular weights (2,900--14,600) and PPO/PEO ratios (0.19--1.79), were determined employing a dye solubilization method. A closed association model was found to describe adequately the copolymer micellization process for the majority of the Pluronics and used to obtain the standard free energies ([Delta]G[degree]), enthalpies ([Delta]H[degree]), and entropies ([Delta]S[degree]) of micellization. It was determined that the micellization process is entropy-driven and has an endothermic micellization enthalpy. The hydrophobic part of the Pluronics, PPO, was responsible for the micellization, apparently due to diminishing hydrogen bonding between water and PPO with increasing temperature. The cmc dependence on temperature and size of headgroup (PEO) of Pluronics follows a similar trend with lower molecular weight C[sub i]E[sub j] nonionic surfactants, the effect of temperature being more pronounced with the Pluronics. The PEO-PPO-PEO block copolymers were compared to PPO-PEO-PPO block and PEO-PPO random copolymers, in an attempt to probe the effect of molecular architecture in the formation of micelles. No micelles were observed in aqueous PPO-PEO-PPO block copolymer solutions with increasing temperature, up to the cloud point.

  19. 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.

  20. In situ gelling stimuli-sensitive block copolymer hydrogels for drug delivery.

    PubMed

    He, Chaoliang; Kim, Sung Wan; Lee, Doo Sung

    2008-05-08

    Stimuli-sensitive block copolymer hydrogels, which are reversible polymer networks formed by physical interactions and exhibit a sol-gel phase-transition in response to external stimuli, have great potential in biomedical and pharmaceutical applications, especially in site-specific controlled drug-delivery systems. The drug may be mixed with a polymer solution in vitro and the drug-loaded hydrogel can form in situ after the in vivo administration, such as injection; therefore, stimuli-sensitive block copolymer hydrogels have many advantages, such as simple drug formulation and administration procedures, no organic solvent, site-specificity, a sustained drug release behavior, less systemic toxicity and ability to deliver both hydrophilic and hydrophobic drugs. Among the stimuli in the biomedical applications, temperature and pH are the most popular physical and chemical stimuli, respectively. The temperature- and/or pH-sensitive block copolymer hydrogels for biomedical applications have been extensively developed in the past decade. This review focuses on recent development of the preparation and application for drug delivery of the block copolymer hydrogels that respond to temperature, pH or both stimuli, including poly(N-substituted acrylamide)-based block copolymers, poloxamers and their derivatives, poly(ethylene glycol)-polyester block copolymers, polyelectrolyte-based block copolymers and the polyelectrolyte-modified thermo-sensitive block copolymers. In addition, the hydrogels based on other stimuli-sensitive block copolymers are discussed.

  1. Surfaces of Fluorinated Pyridinium Block Copolymers with Enhanced Antibacterial Activity

    SciTech Connect

    Krishnan,S.; Ward, R.; Hexemer, A.; Sohn, K.; Lee, K.; Angert, E.; Fischer, D.; Kramer, E.; Ober, C.

    2006-01-01

    Polystyrene-b-poly(4-vinylpyridine) copolymers were quaternized with 1-bromohexane and 6-perfluorooctyl-1-bromohexane. Surfaces prepared from these polymers were characterized by contact angle measurements, near-edge X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy. The fluorinated pyridinium surfaces showed enhanced antibacterial activity compared to their nonfluorinated counterparts. Even a polymer with a relatively low molecular weight pyridinium block showed high antimicrobial activity. The bactericidal effect was found to be related to the molecular composition and organization in the top 2-3 nm of the surface and increased with increasing hydrophilicity and pyridinium concentration of the surface.

  2. Gamma radiation induced degradation in PE-PP block copolymer

    SciTech Connect

    Ravi, H. R.; Sreepad, H. R.; Ahmed, Khaleel; Govindaiah, T. N.

    2012-06-05

    In the present investigation, effect of gamma irradiation on the PP-PE block copolymer has been studied. The polymer has been subjected to gamma irradiation from 100 to 500 Mrad dosages. Characterization of the polymer using XRD and FTIR was done both before irradiation and after irradiation in each step. Effect of irradiation on the electrical properties of the material has also been studied. FTIR study shows that the sample loses C - C stretching mode of vibration but gains C=C stretching mode of vibration after irradiation. Present investigation clearly indicates that though the electrical conductivity increases in the material, it undergoes degradation and shows brittleness due to irradiation.

  3. Biodegradable block copolymers as injectable drug-delivery systems

    NASA Astrophysics Data System (ADS)

    Jeong, Byeongmoon; Bae, You Han; Lee, Doo Sung; Kim, Sung Wan

    1997-08-01

    Polymers that display a physicochemical response to stimuli are widely explored as potential drug-delivery systems. Stimuli studied to date include chemical substances and changes in temperature, pH and electric field. Homopolymers or copolymers of N-isopropylacrylamide, and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (known as poloxamers) are typical examples of thermosensitive polymers, but their use in drug delivery is problematic because they are toxic and non-biodegradable. Biodegradable polymers used for drug delivery to date have mostly been in the form of injectable microspheres or implant systems, which require complicated fabrication processes using organic solvents. Such systems have the disadvantage that the use of organic solvents can cause denaturation when protein drugs are to be encapsulated. Furthermore, the solid form requires surgical insertion, which often results in tissue irritation and damage. Here we report the synthesis of a thermosensitive, biodegradable hydrogel consisting of blocks of poly(ethylene oxide) and poly(L-lactic acid). Aqueous solutions of these copolymers exhibit temperature-dependent reversible gel-sol transitions. The hydrogel can be loaded with bioactive molecules in an aqueous phase at an elevated temperature (around 45 °C), where they form a sol. In this form, the polymer is injectable. On subcutaneous injection and subsequent rapid cooling to body temperature, the loaded copolymer forms a gel that can act as a sustained-release matrix for drugs.

  4. (Electro)Mechanical Properties of Olefinic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Spontak, Richard

    2014-03-01

    Conventional styrenic triblock copolymers (SBCs) swollen with a midblock-selective oil have been previously shown to exhibit excellent electromechanical properties as dielectric elastomers. In this class of electroactive polymers, compliant electrodes applied as active areas to opposing surfaces of an elastomer attract each other, and thus compress the elastomer due to the onset of a Maxwell stress, upon application of an external electric field. This isochoric process is accompanied by an increase in lateral area, which yields the electroactuation strain (measuring beyond 300% in SBC systems). Performance parameters such as the Maxwell stress, transverse strain, dielectric breakdown, energy density and electromechanical efficiency are determined directly from the applied electric field and resulting electroactuation strain. In this study, the same principle used to evaluate SBC systems is extended to olefinic block copolymers (OBCs), which can be described as randomly-coupled multiblock copolymers that consist of crystallizable polyethylene hard segments and rubbery poly(ethylene-co-octene) soft segments. Considerations governing the development of a methodology to fabricate electroresponsive OBC systems are first discussed for several OBCs differing in composition and bulk properties. Evidence of electroactuation in selectively-solvated OBC systems is presented and performance metrics measured therefrom are quantitatively compared with dielectric elastomers derived from SBC and related materials.

  5. Generation of toxic degradation products by sonication of Pluronic® dispersants: implications for nanotoxicity testing.

    PubMed

    Wang, Ruhung; Hughes, Tyler; Beck, Simon; Vakil, Samee; Li, Synyoung; Pantano, Paul; Draper, Rockford K

    2013-11-01

    Poloxamers (known by the trade name Pluronic®) are triblock copolymer surfactants that contain two polyethylene glycol blocks and one polypropylene glycol block of various sizes. Poloxamers are widely used as nanoparticle dispersants for nanotoxicity studies wherein nanoparticles are sonicated with a dispersant to prepare suspensions. It is known that poloxamers can be degraded during sonication and that reactive oxygen species contribute to the degradation process. However, the possibility that poloxamer degradation products are toxic to mammalian cells has not been well studied. We report here that aqueous solutions of poloxamer 188 (Pluronic® F-68) and poloxamer 407 (Pluronic® F-127) sonicated in the presence or absence of multi-walled carbon nanotubes (MWNTs) can became highly toxic to cultured cells. Moreover, toxicity correlated with the sonolytic degradation of the polymers. These findings suggest that caution should be used in interpreting the results of nanotoxicity studies where the potential sonolytic degradation of dispersants was not controlled.

  6. Block copolymers for drug solubilisation: relative hydrophobicities of polyether and polyester micelle-core-forming blocks.

    PubMed

    Attwood, David; Booth, Colin; Yeates, Stephen G; Chaibundit, Chiraphon; Ricardo, Nágila M P S

    2007-12-10

    Published values of the critical micelle concentration are tabulated for diblock copolymers E(m)P(n), E(m)B(n), E(m)S(n), E(m)L(n), E(m)VL(n) and E(m)CL(n), where E denotes a chain unit derived from ethylene oxide, P from propylene oxide, B from 1,2-butylene oxide, S from styrene oxide, L from dl-lactide, VL from gamma-valerolactone and CL from epsilon-caprolactone, and the subscripts denote average chain lengths. Noting that log(cmc/moldm(-3) is proportional to the standard Gibbs energy of micellisation, the dependence of this quantity on hydrophobic block length (n) is explored for a given E-block length. Superposition of data allows ranking of the hydrophobicities of the chain units. The ratios relative to the least hydrophobic unit are: P : L : B : VL : S : CL = 1 : 4 : 6 : 10 : 12 : 12 Transitions in the slope of log(cmc) versus n are assigned to changes in the unimer-micelle equilibrium and related to the formation of unimolecular micelles and, at high values of n, to the completion of that process. The formation transition is seen in the plots for all the copolymers except the least hydrophobic, E(m)P(n). The completion transition is seen in the plots for E(m)CL(n) and E(m)L(n) copolymers, as these alone include results for copolymers with very lengthy hydrophobic blocks.

  7. 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

  8. Supramolecular hydrogels as a universal scaffold for stepwise delivering Dox and Dox/cisplatin loaded block copolymer micelles.

    PubMed

    Zhu, Wen; Li, Yanli; Liu, Lixin; Chen, Yongming; Xi, Fu

    2012-11-01

    A general and simple method was presented for preparing supramolecular hydrogels to deliver anticancer drugs. In this system, hydrophobic anticancer drug doxorubicin (Dox) was loaded into poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-b-PCL) amphiphilic block copolymer micelles by hydrophobic interaction. The drug loaded micelles were then mixed with α-cyclodextrin (α-CD) solution to generate the hydrogel. The α-CDs were threaded onto the PEG coronae of the micelles, and formed physical crosslinks of the molecular necklaces. Moreover, by mixing solutions of cisplatin complexed poly(ethylene glycol)-b-poly(acrylic acid) (PEG-b-PAA) micelles, Dox loaded PEG-b-PCL micelles and α-CDs together, a dual-drug loaded supramolecular hydrogel was generated. The gelation properties could be tuned by changing concentrations and polymerization degree of the polymers, and by adding PEG homopolymers or Pluronic copolymers as additives. Structures and properties of the drug loaded hydrogels were studied by wide-angle X-ray diffraction (XRD) and rheology measurement, respectively. In vitro drug release in PBS with different pH values was quantified. The erosion of hydrogels produced discrete micelles, from which the free drugs were released. In vitro cytotoxicity studies showed that the Dox loaded hydrogel inhibited the growth of human bladder carcinoma EJ cells, and the dual-drug loaded hydrogel showed even higher cytotoxicity. Copyright © 2012 Elsevier B.V. All rights reserved.

  9. Characterizing the interfaces of block copolymers with high χ

    NASA Astrophysics Data System (ADS)

    Sunday, Daniel; Maher, Michael; Blachut, Gregory; Asano, Yusuke; Tein, Summer; Willson, C. Grant; Ellison, Christopher; Kline, R. Joseph

    In order for block copolymer (BCP) directed self-assembly (DSA) to be able to pattern features below 10 nm there must be materials which can spontaneously assembly at the required length scales. For the smallest features this will require phase separation where the total chain lengths are under 50 monomer units, demanding very large interaction parameters (χ) to have an order-disorder transition. One of the key parameters for DSA will be the interfacial width between the blocks, which is expected to be correlated to the interaction parameter and will help determine the line edge roughness (LER). We have used resonant soft X-ray reflectivity to investigate a series of high χ BCPs with different compositions and molecular weights to determine the interfacial width and degree of phase separation. We use these results to estimate the value of χ and determine relationships between χ and the interfacial mixing.

  10. Hollow ZIF-8 Nanoworms from Block Copolymer Templates

    PubMed Central

    Yu, Haizhou; Qiu, Xiaoyan; Neelakanda, Pradeep; Deng, Lin; Khashab, Niveen M.; Nunes, Suzana P.; Peinemann, Klaus-Viktor

    2015-01-01

    Recently two quite different types of “nano-containers” have been recognized as attractive potential drug carriers; these are wormlike filamenteous micelles (“filomicelles”) on the one hand and metal organic frameworks on the other hand. In this work we combine these two concepts. We report for the first time the manufacturing of metal organic framework nanotubes with a hollow core. These worm-like tubes are about 200 nm thick and several μm long. The preparation is simple: we first produce long and flexible filament-shaped micelles by block copolymer self-assembly. These filomicelles serve as templates to grow a very thin layer of interconnected ZIF-8 crystals on their surface. Finally the block copolymer is removed by solvent extraction and the hollow ZIF-8 nanotubes remain. These ZIF-NTs are surprisingly stable and withstand purification by centrifugation. The synthesis method is straightforward and can easily be applied for other metal organic framework materials. The ZIF-8 NTs exhibit high loading capacity for the model anti cancer drug doxorubicin (DOX) with a pH-triggered release. Hence, a prolonged circulation in the blood stream and a targeted drug release behavior can be expected. PMID:26471862

  11. Making Carbon-Nanotube Arrays Using Block Copolymers: Part 2

    NASA Technical Reports Server (NTRS)

    Bronikowski, Michael

    2004-01-01

    Some changes have been incorporated into a proposed method of manufacturing regular arrays of precisely sized, shaped, positioned, and oriented carbon nanotubes. Such arrays could be useful as mechanical resonators for signal filters and oscillators, and as electrophoretic filters for use in biochemical assays. A prior version of the method was described in Block Copolymers as Templates for Arrays of Carbon Nanotubes, (NPO-30240), NASA Tech Briefs, Vol. 27, No. 4 (April 2003), page 56. To recapitulate from that article: As in other previously reported methods, carbon nanotubes would be formed by decomposition of carbon-containing gases over nanometer-sized catalytic metal particles that had been deposited on suitable substrates. Unlike in other previously reported methods, the catalytic metal particles would not be so randomly and densely distributed as to give rise to thick, irregular mats of nanotubes with a variety of lengths, diameters, and orientations. Instead, in order to obtain regular arrays of spaced-apart carbon nanotubes as nearly identical as possible, the catalytic metal particles would be formed in predetermined regular patterns with precise spacings. The regularity of the arrays would be ensured by the use of nanostructured templates made of block copolymers.

  12. Photosensitive cross-linked block copolymers with controllable release.

    PubMed

    Yu, Lili; Lv, Cong; Wu, LiZhu; Tung, ChenHo; Lv, WanLiang; Li, ZhongJin; Tang, XinJing

    2011-01-01

    We intend to form photosensitive block copolymer micelles for controllable release of encapsulated substances. Here, we designed and synthesized a new photocleavable cross-linker (2-nitrophenyl ethylene glycol dimethacrylate) for methyl methacrylate (MMA) atom transfer radical polymerization. Four different ratios (0:1, 1:26, 1:16, 1:8.8) of the photocleavable cross-linker to MMA monomer were used and four block copolymers (P0, P1, P2, P3) were synthesized with PEO-Br as the macroinitiator. Gel permeation chromatography and (1) H NMR studies showed that linear polymer molecules could be cross-linked by the photocleavable linker. The fluorescence studies of the encapsulated Nile Red (NR) showed that there were lower critical micelle concentrations for the polymer P1, P2 and P3 than polymer P0. And dynamic light scattering and SEM confirmed the formation of polymer micelles. Photolysis experiments demonstrated that NR encapsulated in the polymer micelles could be released upon UV irradiation (365 nm, 11 mW cm(-2)) due to the breakage of the photocleavable linker and the generation of more hydrophilic acid moieties, which destabilized polymer micelles. Our study shows a new strategy for the possibility of photocontrollable drug release for hydrophobic drugs.

  13. Hollow ZIF-8 Nanoworms from Block Copolymer Templates

    NASA Astrophysics Data System (ADS)

    Yu, Haizhou; Qiu, Xiaoyan; Neelakanda, Pradeep; Deng, Lin; Khashab, Niveen M.; Nunes, Suzana P.; Peinemann, Klaus-Viktor

    2015-10-01

    Recently two quite different types of “nano-containers” have been recognized as attractive potential drug carriers; these are wormlike filamenteous micelles (“filomicelles”) on the one hand and metal organic frameworks on the other hand. In this work we combine these two concepts. We report for the first time the manufacturing of metal organic framework nanotubes with a hollow core. These worm-like tubes are about 200 nm thick and several μm long. The preparation is simple: we first produce long and flexible filament-shaped micelles by block copolymer self-assembly. These filomicelles serve as templates to grow a very thin layer of interconnected ZIF-8 crystals on their surface. Finally the block copolymer is removed by solvent extraction and the hollow ZIF-8 nanotubes remain. These ZIF-NTs are surprisingly stable and withstand purification by centrifugation. The synthesis method is straightforward and can easily be applied for other metal organic framework materials. The ZIF-8 NTs exhibit high loading capacity for the model anti cancer drug doxorubicin (DOX) with a pH-triggered release. Hence, a prolonged circulation in the blood stream and a targeted drug release behavior can be expected.

  14. Transport of Water in Semicrystalline Block Copolymer Membranes

    NASA Astrophysics Data System (ADS)

    Hallinan, Daniel; Oparaji, Onyekachi

    Poly(styrene)-block-poly(ethylene oxide) (PS- b-PEO) is a semicrystalline block copolymer (BCP) with interesting properties. It is mechanically tough, amphiphilic, and has a polar phase. The mechanical toughness is due to the crystallinity of PEO and the high glass transition temperature of PS, as well as the morphological structure of the BCP. The polymer has high CO2, water, and salt solubility that derive from the polar PEO component. Potential applications include CO2 separation, water purification, and lithium air batteries. In all of the aforementioned applications, water transport is an important parameter. The presence of water can also affect thermal and mechanical properties. Water transport and thermal and mechanical properties of a lamellar PS- b-PEO copolymer have been measured as a function of water activity. Water transport can be affected by the heterogeneous nature of a semicrystalline BCP. Therefore, Fourier transform infrared - attenuated total reflectance (FTIR-ATR) spectroscopy has been employed, because water transport and polymer swelling can be measured simultaneously. The effect of BCP structure on transport has been investigated by comparing water transport in PS- b-PEO to a PEO homopolymer. The crystalline content of the PEO and the presence of glassy PS lamellae will be used to explain the transport results.

  15. Single Helix to Double Gyroid in Chiral Block Copolymers

    SciTech Connect

    C Chen; H Hsueh; Y Chiang; R Ho; S Akasaka; H Hasegawa

    2011-12-31

    An order-order phase transition of chiral block copolymers (BCPs*) from single helix to double gyroid (H* {yields} G) through a nucleation and growth process was demonstrated. The H* and G phases can be obtained by solution casting from fast and slow solvent evaporation, respectively, suggesting that the H* phase is a metastable phase. Consequently, the coexistence of H* and G phases can be found in the solution-cast samples from intermediate solvent evaporation. To truly examine the transition mechanism of the H* {yields} G, electron tomography was carried out to directly visualize the morphological evolution in real space, in particular, the transition zone at interface. Unlike the mechanisms for the transitions of block copolymers (BCPs) by considering the interdomain spacing matching, a significant mismatch in the lattices for the H* {yields} G was found. Consequently, the transition may require an adjustment on the geometric dimensions to justify corresponding lattice mismatch. As a result, the morphological observations from electron tomography offer new insights into BCP phase transitions.

  16. Injectible bodily prosthetics employing methacrylic copolymer gels

    DOEpatents

    Mallapragada, Surya K.; Anderson, Brian C.

    2007-02-27

    The present invention provides novel block copolymers as structural supplements for injectible bodily prosthetics employed in medical or cosmetic procedures. The invention also includes the use of such block copolymers as nucleus pulposus replacement materials for the treatment of degenerative disc disorders and spinal injuries. The copolymers are constructed by polymerization of a tertiary amine methacrylate with either a (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) polymer, such as the commercially available Pluronic.RTM. polymers, or a poly(ethylene glycol) methyl ether polymer.

  17. 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.

  18. Interactions between block copolymers and single-walled carbon nanotubes in aqueous solutions: a small-angle neutron scattering study.

    PubMed

    Granite, Meirav; Radulescu, Aurel; Pyckhout-Hintzen, Wim; Cohen, Yachin

    2011-01-18

    The amphiphilic copolymers of the Pluronic family are known to be excellent dispersants for single-walled carbon nanotubes (SWCNT) in water, especially F108 and F127, which have rather long end-blocks of poly(ethylene oxide) (PEO). In this study, the structure of the CNT/polymer hybrid formed in water is evaluated by measurements of small-angle neutron scattering (SANS) with contrast variation, as supported by cryo-transmission electron microscopy (cryo-TEM) imaging. The homogeneous, stable, inklike dispersions exhibited very small isolated bundles of carbon nanotubes in cryo-TEM images. SANS experiments were conducted at different D(2)O/H(2)O content of the dispersing solvent. The data for both systems showed surprisingly minimal intensity values at 70% D(2)O solvent composition, which is much higher than the expected value of 17% D(2)O that is based on the scattering length density (SLD) of PEO. At this near match point, the data exhibited a q(-1) power law relation of intensity to the scattering vector (q), indicating rodlike entities. Two models are evaluated, as extensions to Pederson's block copolymer micelles models. One is loosely adsorbed polymer chains on a rodlike CNT bundle. In the other, the hydrophobic block is considered to form a continuous hydrated shell on the CNT surface, whereas the hydrophilic blocks emanate into the solvent. Both models were found to fit the experimental data reasonably well. The model fit required special considerations of the tight association of water molecules around PEO chains and slight isotopic selectivity.

  19. 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

  20. Gold-Pluronic core-shell nanoparticles: synthesis, characterization and biological evaluation

    NASA Astrophysics Data System (ADS)

    Simon, Timea; Boca, Sanda; Biro, Dominic; Baldeck, Patrice; Astilean, Simion

    2013-04-01

    This study presents the synthesis of gold-Pluronic core-shell nanoparticles by a two-step method and investigates their biological impact on cancer cells, specifically nanoparticle internalization and cytotoxicity. Uniform, 9-10-nm-sized, hydrophobic gold nanoparticles were synthesized in organic phase by reducing gold salt with oleylamine, after which oleylamine-protected gold nanoparticles were phase-transferred into aqueous medium using Pluronic F127 block copolymer, resulting in gold-Pluronic core-shell nanoparticles with a mean hydrodynamic diameter of 35 nm. The formation and phase-transfer of gold nanoparticles were analyzed by UV-Vis absorption spectroscopy, transmission electron microscopy, and dynamic light scattering. The obtained gold-Pluronic core-shell nanoparticles proved to be highly stable in salted solution. Cytotoxicity tests showed no modification of cellular viability in the presence of properly purified particles. Furthermore, dark-field cellular imaging demonstrated that gold-Pluronic nanoparticles were able to be efficiently uptaken by cells, being internalized through nonspecific endocytosis. The high stability, proven biocompatibility, and imaging properties of gold-Pluronic core-shell nanoparticles hold promise for relevant intracellular applications, with such a design providing the feasibility to combine all multiple functionalities in one nanoparticle for simultaneous detection and imaging.

  1. Flocculation and stabilization of colloidal particles by adsorbed block copolymers: Role of polymer conformation

    SciTech Connect

    Walker, H.W.; Grant, S.B.

    1995-12-01

    The coagulation rate of colloidal particles in water is dramatically affected by the presence of adsorbing polymers, particularly amphipathic block copolymers. These molecules possess regions (or {open_quotes}blocks{close_quotes}) which are relatively adsorbing and blocks which are relatively nonadsorbing. In this study, a biochemical technique called hydroxyl radical footprinting (HRF) is used to probe the surface conformation of model block copolymers adsorbed to amidine- and sulfate-modified polystyrene latex microspheres. These results are used to explain the effect of block copolymers on observed coagulation rates.

  2. Impact of copolymer ratio on drug distribution in styrene-isobutylene-styrene block copolymers.

    PubMed

    McDermott, Martin K; Kim, Chang-Soo; Saylor, David M; Patwardhan, Dinesh V

    2013-10-01

    Drug-polymer composite coatings, composed of styrene-isobutylene-styrene (SIBS) tri-block copolymers, are frequently used in controlled drug release biomedical device applications. In this work, we used atomic force microscopy to characterize the effects of different drug loadings and polymer chemistries (i.e., block copolymer ratio) on the variation of surface structures and compositions of SIBS-tetracycline (SIBS-TC) cast composites including tetracycline (TC) drug amount, drug phase size distribution, and drug and polymer phase morphologies. We tested the structural variations by fabricating and characterizing two types of composite specimens, that is, SIBS15 and SIBS30, composed of 15 and 30 Wt % of polystyrene (PS), respectively. The differences in the distribution of TC drug, PS, and polyisobutylene (PIB) polymer phase structures observed in SIBS15 and SIBS30 resulted in more drug at the surface of SIBS30 compared to SIBS15. To support the experimental findings, we have determined the Hildebrand solubility parameter of TC using molecular dynamics (MD) computation and compared it to the polymer components, PS and PIB. The MD results show that the solubility parameter of TC is much closer to that of PS than PIB, which demonstrates a higher thermodynamic stability of TC-PS mixtures. Copyright © 2013 Wiley Periodicals, Inc., a Wiley Company.

  3. Effect of nanoscale morphology on selective ethanol transport through block copolymer membranes

    USDA-ARS?s Scientific Manuscript database

    We report on the effect of block copolymer domain size on transport of liquid mixtures through the membranes by presenting pervaporation data of an 8 wt% ethanol/water mixture through A-B-A and B-A-B triblock copolymer membranes. The A-block was chosen to facilitate ethanol transport while the B-blo...

  4. Master curve captures the effect of domain morphology on ethanol pervaporation through block copolymer membranes

    USDA-ARS?s Scientific Manuscript database

    We report on the effect of changing nanoscale morphology on pervaporation of ethanol/water mixtures through block copolymer membranes. Experiments were conducted using polystyrene-b-polybutadiene-b-polystyrene (SBS) copolymers with polybutadiene (PB) as the ethanol transporting block, using an 8 wt%...

  5. 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.

  6. Nanopatterned block copolymers for use as vascular biomaterials

    NASA Astrophysics Data System (ADS)

    Silverstein, Joshua S.

    Manipulation of surface topography or chemistry has been a growing trend in efforts to enhance the properties of medical devices. Understanding the interactions of biomolecules with nanoengineered surfaces is vital to assess the safety and efficacy of devices that incorporate these structures. In this dissertation, a model block copolymer (BCP) system based on poly(styrene)-block-poly(1,2-butadiene) was systematically modified using photochemical thiol-ene chemistry. Poly(1,2-butadiene) molecular weight and thiol-ene ratios were systematically varied based on a model monomer, boc-cysteamine, to determine the efficiency of the reaction. The results demonstrate the polydispersity index of modified BCPs significantly increased when low thiol-ene ratios were employed and sometimes induced gelation of the reacted polymers. Using a tenfold excess of thiol, functionalizations between 60-90% were obtained for an acid, amine, amide, and a pharmaceutical with a pendant thiol. Calorimetry showed a 30-60 °C increase in the glass transition temperature of the daughter polymers. Subsequently, films were cast from solvents found suitable to forming self-assembled BCP thin films. The synthetic and processing approach allows for the formation of nanopatterned block copolymer films with controlled chemistries from a single source material. The BCPs were further characterized using water contact angle measurements and atomic force microscopy in liquid. Significantly decreased contact angles were caused by selective swelling of charged BCP domains. Protein (fibrinogen, albumin, cytochrome C, immunoglobulin G) adsorption experiments were conducted under static and dynamic conditions with a quartz crystal microbalance with dissipation. The results indicate that nanopatterned chemistry and experimental conditions strongly impact adsorption dynamics. Adsorption behavior was dependent both on protein structure and the characteristics of the surface. Depending on the structural stability

  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. Hydrophilic block azidation of PCL-b-PEO block copolymers from epichlorohydrin.

    PubMed

    Liu, Junjie; Gan, Zhihua

    2014-05-01

    Amphiphilic diblock copolymers poly(ϵ-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) with well-controlled pendant azido groups along the hydrophilic PEO block, that is, poly(ϵ-caprolactone)-b-poly(ethylene oxide-co-glycidyl azide) (PCL-b-P(EO-co-GA)), are synthesized from poly(ϵ-caprolactone)-b-poly(ethylene oxide-co-epichlorohydrin) (PCL-b-P(EO-co-ECH)). The further conversion of those azido groups along the hydrophilic block of copolymers into amino or carboxyl groups via click chemistry is studied. The micelles self-assembled from PCL-b-P(EO-co-GA) with azido groups on the shell are crosslinked by the dialkynyl-PEO. The micelles with crosslinked shell show better stability, higher drug loading capacities, subsequent faster drug release rate, and higher cytotoxicity to cancer cells. The introduction of azido groups into PCL-b-PEO amphiphilic diblock copolymers from epichlorohydrin in PEO hydrophilic block in this work provides a new method for biofunctionalization of micelles via mild click chemistry.

  9. Ordering of lamellar block copolymers on oxidized silane coatings

    DOE PAGES

    Mahadevapuram, Nikhila; Mitra, Indranil; Sridhar, Shyam; ...

    2016-01-02

    Thin films of lamellar poly(styrene-b-methyl methacrylate) (PS-PMMA) block copolymers are widely investigated for surface patterning. These materials can generate dense arrays of nanoscale lines when the lamellar domains are oriented perpendicular to the substrate. To stabilize this preferred domain orientation, we tuned the substrate surface energy using oxidation of hydrophobic silane coatings. This simple approach is effective for a broad range of PS-PMMA film thicknesses when the oxidation time is optimized, which demonstrates that the substrate coating is energetically neutral with respect to PS and PMMA segments. The lamellar films are characterized by high densities of defects that exhibit amore » strong dependence on film thickness: in-plane topological defects disrupt the lateral order in ultrathin films, while lamellar domains in thick films can bend and tilt to large misorientation angles. As a result, the types and densities of these defects are similar to those observed with other classes of neutral substrate coatings, such as random copolymer brushes, which demonstrates that oxidized silanes can be used to control PS-PMMA self assembly in thin films.« less

  10. Continuous concentric lamellar block copolymer nanofibers with long range order.

    PubMed

    Ma, Minglin; Titievsky, Kirill; Thomas, Edwin L; Rutledge, Gregory C

    2009-04-01

    Fibers with long-range ordered internal structures have applications in various areas such as photonic band gap fibers, optical waveguides, wearable power, sensors, and sustained drug release. Up to now, such fibers have been formed by melt extrusion or drawing from a macroscopic preformed rod and were typically limited to diameters >10 microm with internal features >1 microm (Abouraddy, A. F.; et al. Nat. Mater. 2007, 6, 336). We describe a new class of continuous fibers and fibrous membranes with long-range ordered concentric lamellar structure that have fiber diameters and feature sizes 2-3 orders of magnitude smaller than those made by conventional methods. These fibers are created through confined self-assembly of block copolymers within core-shell electrospun filaments. In contrast to the copolymer in bulk or thin films, the domains of the concentric lamellar structure are shown here to vary quantitatively with (radial) position and to exhibit a novel dislocation that accommodates variations in fiber diameter robustly, permitting for the first time the realization of long-range order in technologically meaningful, continuous fibers with approximately 300 nm diameter and 50 nm radial period.

  11. Ordering of lamellar block copolymers on oxidized silane coatings

    SciTech Connect

    Mahadevapuram, Nikhila; Mitra, Indranil; Sridhar, Shyam; Strzalka, Joseph; Stein, Gila E.

    2016-01-02

    Thin films of lamellar poly(styrene-b-methyl methacrylate) (PS-PMMA) block copolymers are widely investigated for surface patterning. These materials can generate dense arrays of nanoscale lines when the lamellar domains are oriented perpendicular to the substrate. To stabilize this preferred domain orientation, we tuned the substrate surface energy using oxidation of hydrophobic silane coatings. This simple approach is effective for a broad range of PS-PMMA film thicknesses when the oxidation time is optimized, which demonstrates that the substrate coating is energetically neutral with respect to PS and PMMA segments. The lamellar films are characterized by high densities of defects that exhibit a strong dependence on film thickness: in-plane topological defects disrupt the lateral order in ultrathin films, while lamellar domains in thick films can bend and tilt to large misorientation angles. As a result, the types and densities of these defects are similar to those observed with other classes of neutral substrate coatings, such as random copolymer brushes, which demonstrates that oxidized silanes can be used to control PS-PMMA self assembly in thin films.

  12. Improved compositional analysis of block copolymers using diffusion ordered NMR spectroscopy.

    PubMed

    Viel, Stéphane; Mazarin, Michaël; Giordanengo, Rémi; Phan, Trang N T; Charles, Laurence; Caldarelli, Stefano; Bertin, Denis

    2009-11-03

    Block copolymers constitute a fascinating class of polymeric materials that are used in a broad range of applications. The performance of these materials is highly coupled to the physical and chemical properties of the constituting block copolymers. Traditionally, the composition of block copolymers is obtained by 1H NMR spectroscopy on purified copolymer fractions. Specifically, the integrals of a properly selected set of 1H resonances are compared and used to infer the number average molecular weight (M(n)) of one of the block from the (typically known) M(n) value of the other. As a corollary, compositional determinations achieved on imperfectly purified samples lead to serious errors, especially when isolation of the block copolymer from the initial macro initiator is tedious. This investigation shows that Diffusion Ordered NMR Spectroscopy (DOSY) can be used to provide a way to assess the advancement degree of the copolymerization purification/reaction, in order to optimize it and hence contribute to an improved compositional analysis of the resulting copolymer. To this purpose, a series of amphiphilic polystyrene-b-poly(ethylene oxide) block copolymers, obtained by controlled free-radical nitroxide mediated polymerization, were analyzed and it is shown that, under proper experimental conditions, DOSY allows for an improved compositional analysis of these block copolymers.

  13. Ionic conductivity of mesoporous block copolymer membranes in liquid electrolyte as a function of copolymer and homopolymer molecular weight

    NASA Astrophysics Data System (ADS)

    Wong, David; Mullin, Scott; Stone, Greg; Battaglia, Vincent; Balsara, Nitash

    2011-03-01

    Mesoporous block copolymer membranes have been synthesized using poly(styrene-block-ethylene-block-polystyrene) (SES). A series of symmetric SES copolymers and PS homopolymers have been studied at different blending fractions. Ionic conductivities of the porous films in a liquid electrolyte, 1.0 M Li PF6 in ethylene carbonate/diethyl carbonate, compare favorably to conventional battery separators and generally increase with internal surface area, as measured by nitrogen adsorption. Characterization of the effects of pore structure and SES morphology on conductivity will be presented. Support from the U.S. Department of Energy Office of Vehicles Technologies (FCVT) under the Batteries for Advanced Transportation Technologies (BATT) Program.

  14. 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.

  15. Conjugated block copolymers: A building block for high-performance organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Guo, Changhe

    State-of-the-art organic photovoltaics rely on kinetically trapped, partially phase-separated structures of donor/acceptor mixtures to create a high interfacial area for exciton dissociation and networks of bicontinuous phases for charge transport. Nevertheless, intrinsic structural disorder and weak intermolecular interactions in polymer blends limit the performance and stability of organic electronic devices. We demonstrate a potential strategy to control morphology and donor/acceptor heterojunctions through conjugated block copolymer poly(3-hexylthiophene)- block-poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(thiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (P3HT-b-PFTBT). Block copolymers can self-assemble into well-ordered nanostructures ideal for photovoltaic applications. When utilized as the photovoltaic active layer, P3HT-b-PFTBT block copolymer devices demonstrate thermal stability and photoconversion efficiency of 3% well beyond devices composed of the constituent polymer blends. Resonant soft X-ray scattering (RSOXS) is used to elucidate the structural origin for efficient block copolymer photovoltaics. Energy tuning in soft X-ray ranges gives RSOXS chemical sensitivity to characterize organic thin films with compositionally similar phases or complicated multiphase systems. RSOXS reveals that the remarkable performance of P3HT-b-PFTBT devices is due to self-assembly into nanoscale in-plane lamellar morphology, which not only establishes an equilibrium microstructure amenable for exciton dissociation but also provides pathways for efficient charge transport. Furthermore, we find evidence that covalent control of donor/acceptor interfaces in block copolymers has the potential to promote charge separation and optimize the photoconversion process by limiting charge recombination. To visualize the nanostructure in organic thin films, we introduce low energy-loss energy-filtered transmission electron microscopy (EFTEM) as an important alternative

  16. Nano-patterning on soluble block copolymer polyimide by nanoimprint

    NASA Astrophysics Data System (ADS)

    Suzuki, Kenta; Youn, Sung-Won; Hiroshima, Hiroshi; Takagi, Hideki

    2015-08-01

    It has been difficult to fabricate high-resolution patterns in polyimide film because a polyimide is difficult to dissolve out or to etch. In this paper, polyimide-based polymer patterning with several hundred nanometers took on the challenge of nanoimprinting on soluble block copolymer polyimide (SBC-PI) at a relatively low temperature of 130 °C. The high-resolution patterns with 118 nm in width and high-aspect-ratio patterns of 6.5 were successfully fabricated without any defects. After hard-baking at 200 °C to enhance the thermal stability, the pattern deformation ratios for height and width were less than approximately 10% for the patterns in a width of 100 nm.

  17. Microstructural organization of polydimethylsiloxane based polyurethane block copolymers

    NASA Astrophysics Data System (ADS)

    Hernandez, Rebeca; Weksler, Jadwiga; Padsalgikar, Ajay; Runt, James

    2007-03-01

    Microphase separation was investigated for polyurethane block copolymers synthesized from MDI and 1,4 butanediol as the hard segments, and poly(hexamethyleneoxide) (MW ˜ 700) and bis(6-hydroxyethoxypropyl) poly(dimethylsiloxane) as soft segments (MW ˜ 1000). The neat PDMS-based diol presents two segmental relaxations corresponding to the principle siloxane repeat unit and to the hydroxyethoxypropyl end group segments, respectively. When incorporated in the polyurethane, the siloxane units form a phase without intermixing with hard segments and the polyether end group segments are mixed with the second macrodiol and some short hard segment sequences. The microdomain morphology was characterized by atomic force microscopy and small-angle X-ray scattering, and the scattering data were analyzed using an approach based on a modified core-shell model. The model includes core hard segment particles (MDI-BDO), surrounded by a mixed polyether shell (PHMO and hydroxyethoxypropyl end group segments), and a matrix composed of the siloxane units.

  18. Block Copolymer Micellization as a Protection Strategy for DNA Origami.

    PubMed

    Agarwal, Nayan P; Matthies, Michael; Gür, Fatih N; Osada, Kensuke; Schmidt, Thorsten L

    2017-05-08

    DNA nanotechnology enables the synthesis of nanometer-sized objects that can be site-specifically functionalized with a large variety of materials. For these reasons, DNA-based devices such as DNA origami are being considered for applications in molecular biology and nanomedicine. However, many DNA structures need a higher ionic strength than that of common cell culture buffers or bodily fluids to maintain their integrity and can be degraded quickly by nucleases. To overcome these deficiencies, we coated several different DNA origami structures with a cationic poly(ethylene glycol)-polylysine block copolymer, which electrostatically covered the DNA nanostructures to form DNA origami polyplex micelles (DOPMs). This straightforward, cost-effective, and robust route to protect DNA-based structures could therefore enable applications in biology and nanomedicine where unprotected DNA origami would be degraded. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Correlative infrared nanospectroscopic and nanomechanical imaging of block copolymer microdomains

    PubMed Central

    Pollard, Benjamin

    2016-01-01

    Summary Intermolecular interactions and nanoscale phase separation govern the properties of many molecular soft-matter systems. Here, we combine infrared vibrational scattering scanning near-field optical microscopy (IR s-SNOM) with force–distance spectroscopy for simultaneous characterization of both nanoscale optical and nanomechanical molecular properties through hybrid imaging. The resulting multichannel images and correlative analysis of chemical composition, spectral IR line shape, modulus, adhesion, deformation, and dissipation acquired for a thin film of a nanophase separated block copolymer (PS-b-PMMA) reveal complex structural variations, in particular at domain interfaces, not resolved in any individual signal channel alone. These variations suggest that regions of multicomponent chemical composition, such as the interfacial mixing regions between microdomains, are correlated with high spatial heterogeneity in nanoscale material properties. PMID:27335750

  20. Intradomain Textures in Block Copolymers: Multizone Alignment and Biaxiality

    NASA Astrophysics Data System (ADS)

    Prasad, Ishan; Seo, Youngmi; Hall, Lisa M.; Grason, Gregory M.

    2017-06-01

    Block copolymer (BCP) melt assembly has been studied for decades, focusing largely on self-organized spatial patterns of periodically ordered segment density. Here, we demonstrate that underlying the well-known composition profiles (i.e., ordered lamella, cylinders, spheres, and networks) are generic and heterogeneous patterns of segment orientation that couple strongly to morphology, even in the absence of specific factors that promote intra or interchain segment alignment. We employ both self-consistent field theory and coarse-grained simulation methods to measure polar and nematic order parameters of segments in a freely jointed chain model of diblock melts. We show that BCP morphologies have a multizone texture, with segments predominantly aligned normal and parallel to interdomain interfaces in the respective brush and interfacial regions of the microdomain. Further, morphologies with anisotropically curved interfaces (i.e., cylinders and networks) exhibit biaxial order that is aligned to the principal curvature axes of the interface.

  1. Sprayable Elastic Conductors Based on Block Copolymer Silver Nanoparticle Composites

    PubMed Central

    2015-01-01

    Block copolymer silver nanoparticle composite elastic conductors were fabricated through solution blow spinning and subsequent nanoparticle nucleation. The reported technique allows for conformal deposition onto nonplanar substrates. We additionally demonstrated the ability to tune the strain dependence of the electrical properties by adjusting nanoparticle precursor concentration or localized nanoparticle nucleation. The stretchable fiber mats were able to display electrical conductivity values as high as 2000 ± 200 S/cm with only a 12% increase in resistance after 400 cycles of 150% strain. Stretchable elastic conductors with similar and higher bulk conductivity have not achieved comparable stability of electrical properties. These unique electromechanical characteristics are primarily the result of structural changes during mechanical deformation. The versatility of this approach was demonstrated by constructing a stretchable light emitting diode circuit and a strain sensor on planar and nonplanar substrates. PMID:25491507

  2. Extensible collagen in mussel byssus: a natural block copolymer.

    PubMed

    Coyne, K J; Qin, X X; Waite, J H

    1997-09-19

    To adhere to solid surfaces, marine mussels produce byssal threads, each of which is a stiff tether at one end and a shock absorber with 160 percent extensibility at the other end. The elastic extensibility of proximal byssus is extraordinary given its construction of collagen and the limited extension (less than 10 percent) of most collagenous materials. From the complementary DNA, we deduced that the primary structure of a collagenous protein (preCol-P) predominating in the extensible proximal portion of the threads encodes an unprecedented natural block copolymer with three major domain types: a central collagen domain, flanking elastic domains, and histidine-rich terminal domains. The elastic domains have sequence motifs that strongly resemble those of elastin and the amorphous glycine-rich regions of spider silk fibroins. Byssal thread extensibility may be imparted by the elastic domains of preCol-P.

  3. A new route for silicon containing block-copolymer synthesis

    SciTech Connect

    Madec, P.J.; Marechal, E.

    1993-12-31

    {alpha},{omega}-dibenzaldehyde oligosiloxanes have been synthesized by hydrosilylation of 4-allyloxy benzaldehyde by {alpha},{omega}-DiSiH oligosiloxanes. The hydrosilylating system has been studied to characterize the side-reactions and to determine the optimal conditions leading to well-defined telechelic oligosiloxanes. This new functionalization of oligosiloxanes turned attention towards its condensation with amine antagonist end-groups. Two examples are discussed: on one hand with diamino aromatic compounds to obtain new main-chain thermotropic polyazomethine-b-polysiloxane polymers, on the other with {alpha},{omega}-diamino aliphatic polyamides that led to polysiloxane-b-polyamide copolymers. In both cases the polyimination condensation was rapid and allowed the authors to obtain new block-polymers, whose average molar masses are in the 15,000-25,000 range.

  4. Nanopatterning of ultrananocrystalline diamond thin films via block copolymer lithography.

    SciTech Connect

    Ramanathan, M.; Darling, S. B.; Sumant, A. V.; Auciello, O.

    2010-07-01

    Nanopatterning of diamond surfaces is critical for the development of diamond-based microelectromechanical system/nanoelectromechanical system (MEMS/NEMS), such as resonators or switches. Micro-/nanopatterning of diamond materials is typically done using photolithography or electron beam lithography combined with reactive ion etching (RIE). In this work, we demonstrate a simple process, block copolymer (BCP) lithography, for nanopatterning of ultrananocrystalline diamond (UNCD) films to produce nanostructures suitable for the fabrication of NEMS based on UNCD. In BCP lithography, nanoscale self-assembled polymeric domains serve as an etch mask for pattern transfer. The authors used thin films of a cylinder-forming organic-inorganic BCP, poly(styrene-block-ferrocenyldimethylsilane), PS-b-PFS, as an etch mask on the surface of UNCD films. Orientational control of the etch masking cylindrical PFS blocks is achieved by manipulating the polymer film thickness in concert with the annealing treatment. We have observed that the surface roughness of UNCD layers plays an important role in transferring the pattern. Oxygen RIE was used to etch the exposed areas of the UNCD film underneath the BCP. Arrays of both UNCD posts and wirelike structures have been created using the same starting polymeric materials as the etch mask.

  5. Fluorinated polyphenylenevinylene (PPV) block co-polymers for nanophotonics

    NASA Astrophysics Data System (ADS)

    Sun, Sam-Shajing; Nguyen, Thuong; Brooks, Jaleesa

    2013-09-01

    Polymer based optoelectronic materials and thin film devices exhibit great potential in future space applications due to their flexibility, light weight, large light absorption coefficient, and promising radiation tolerance in space environment as compared to their inorganic semiconductor counterparts. Since carbon-fluorine (C-F) chemical bonds are much stronger than the carbon-hydrogen (C-H) bonds, fluorinated polymer films offer great potential for space applications due their expected resistance to oxidation, thermal stability, excellent wear properties, and low coefficients of friction. Their use in a space environment is extremely attractive since they are expected to retain their lubricating characteristics in vacuum, unlike many solid lubricants. Current existing polymer photovoltaic materials and devices suffer low photoelectric power conversion efficiencies due to a number factors including poor morphologies at nano scale that hinder the charge separation and transport. This paper reports our recent work on a fluorinated DBfA type block copolymer system where the donor (D) block contains a donor substituted and hydrocarbon based polyphenylenevinylene (PPV), acceptor (fA) block contains a fluorinated and a sulfone acceptor substituted polyphenylenevinylene (f-PPV), and B is a non-conjugated and flexible bridge unit. Preliminary studies reveal DBfA exhibits better nano phase morphologies and over 100 times more efficient optoelectronic conversion efficiencies as compared to D/fA blend.

  6. Dynamics of Chain Exchange in Block Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Lodge, Timothy

    Block copolymer micelles are rarely at equilibrium. The primary reason is the large number of repeat units in the insoluble block, Ncore, which makes the thermodynamic penalty for extracting a single chain (``unimer exchange'') substantial. As a consequence, the critical micelle concentration (CMC) is rarely accessed experimentally; however, in the proximity of a critical micelle temperature (CMT), equilibration is possible. We have been using time-resolved small angle neutron scattering (TR-SANS) to obtain a detailed picture of the mechanisms and time scales for chain exchange, at or near equilibrium. Our model system is poly(styrene)-block-poly(ethylene-alt-propylene)) (PS-PEP), in the PEP-selective solvent squalane (C30H62) . Equivalent micelles with either normal (hPS) or perdeuterated (dPS) cores are initially mixed in a blend of isotopically substituted squalane, designed to contrast-match a 50:50 hPS:dPS core. Samples are then annealed at a target temperature, and chain exchange is revealed quantitatively by the temporal decay in scattered intensity. The rate of exchange as function of concentration, temperature, Ncore, Ncorona, and chain architecture (diblock versus triblock) will be discussed.

  7. Superlattice Formation in Binary Mixtures of Block Copolymer Micelles

    SciTech Connect

    Abbas, Sayeed; Lodge, Timothy P.

    2008-08-26

    Two distinct diblock copolymers, poly(styrene-b-isoprene) (SI) and poly(styrene-b-dimethylsiloxane) (SD), were codissolved at various concentrations in the polystyrene selective solvent diethyl phthalate. Two SI diblocks, with block molar masses of 12000-33000 and 30000-33000, and two SD diblocks, with block molar masses of 19000-6000 and 16000-9000, were employed. The size ratio of the smaller SD micelles (S) to the larger SI micelles (L) varied from approximately 0.5 to 0.6, based on hydrodynamic radii determined by dynamic light scattering on dilute solutions containing only one polymer component. Due to incompatibility between the polyisoprene and polydimethylsiloxane blocks, a binary mixture of distinct SI and SD micelles was formed in each mixed solution, as confirmed by cryogenic transmission electron microscopy. When the total concentration of polymer was increased to 20--30%, the micelles adopted a superlattice structure. Small angle X-ray scattering revealed the lattice to be the full LS{sub 13} superlattice (space group Fm{sub 3}c) in all cases, with unit cell dimensions in excess of 145 nm. A coexistent face-centered cubic phase composed of SD micelles was also observed when the number ratio of S to L micelles was large.

  8. Deep in vivo two-photon imaging of blood vessels with a new dye encapsulated in pluronic nanomicelles

    NASA Astrophysics Data System (ADS)

    Maurin, Mathieu; Stéphan, Olivier; Vial, Jean-Claude; Marder, Seth R.; van der Sanden, Boudewijn

    2011-03-01

    Our purpose is to test if Pluronic® fluorescent nanomicelles can be used for in vivo two-photon imaging of both the normal and the tumor vasculature. The nanomicelles were obtained after encapsulating a hydrophobic two-photon dye: di-stryl benzene derivative, in Pluronic block copolymers. Their performance with respect to imaging depth, blood plasma staining, and diffusion across the tumor vascular endothelium is compared to a classic blood pool dye Rhodamin B dextran (70 kDa) using two-photon microscopy. Pluronic nanomicelles show, like Rhodamin B dextran, a homogeneous blood plasma staining for at least 1 h after intravenous injection. Their two-photon imaging depth is similar in normal mouse brain, using 10 times less injected mass. In contrast with Rhodamin B dextran, no extravasation is observed in leaky tumor vessels due to their large size: 20-100 nm. In conclusion, Pluronic nanomicelles can be used as a blood pool dye, even in leaky tumor vessels. The use of Pluronic block copolymers is a valuable approach for encapsulating two-photon fluorescent dyes that are hydrophobic and not suitable for intravenous injection.

  9. Characterization of two new stable block copolymer mesophases by synchrotron small-angle scattering

    NASA Astrophysics Data System (ADS)

    Burger, C.; Micha, M. A.; Oestreich, S.; Förster, S.; Antonietti, M.

    1998-05-01

    Block copolymers made of polystyrene and fluorinated blocks represent a new class of polymers with a very strong incompatibility between the two blocks. They exhibit new stable block copolymer mesophases which are not considered in the phase diagrams of diblock copolymers in the strong and super-strong segregation regime. The solid-state structures of two polymers with different compositions are characterized by synchrotron small-angle X-ray scattering and transmission electron microscopy, thus proving the existence of a quadratically perforated layer phase and a 2D phase of sanidically degenerated cylinders.

  10. Molecular origin of photovoltaic performance in donor-block-acceptor all-conjugated block copolymers

    SciTech Connect

    Smith, Kendall A.; Lin, Yen -Hao; Mok, Jorge W.; Yager, Kevin G.; Strzalka, Joseph; Nie, Wanyi; Mohite, Aditya D.; Verduzco, Rafael

    2015-11-03

    All-conjugated block copolymers may be an effective route to self-assembled photovoltaic devices, but we lack basic information on the relationship between molecular characteristics and photovoltaic performance. Here, we synthesize a library of poly(3-hexylthiophene) (P3HT) block poly((9,9-dialkylfluorene)-2,7-diyl-alt-[4,7-bis(alkylthiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (PFTBT) donor-block-acceptor all-conjugated block copolymers and carry out a comprehensive study of processing conditions, crystallinity, domain sizes, and side-chain structure on photovoltaic device performance. We find that all block copolymers studied exhibit an out-of-plane crystal orientation after deposition, and on thermal annealing at high temperatures the crystal orientation flips to an in-plane orientation. By varying processing conditions on polymer photovoltaic devices, we show that the crystal orientation has only a modest effect (15-20%) on photovoltaic performance. The addition of side-chains to the PFTBT block is found to decrease photovoltaic power conversion efficiencies by at least an order of magnitude. Through grazing-incidence X-ray measurements we find that the addition of side-chains to the PFTBT acceptor block results in weak segregation and small (< 10 nm) block copolymer self-assembled donor and acceptor domains. This work is the most comprehensive to date on all-conjugated block copolymer systems and suggests that photovoltaic performance of block copolymers depends strongly on the miscibility of donor and acceptor blocks, which impacts donor and acceptor domain sizes and purity. Lastly, strategies for improving the device performance of block copolymer photovoltaics should seek to increase segregation between donor and acceptor polymer domains.

  11. Thermodynamics of Surfactants, Block Copolymers and Their Mixtures in Water: The Role of the Isothermal Calorimetry

    PubMed Central

    De Lisi, Rosario; Milioto, Stefania; Muratore, Nicola

    2009-01-01

    The thermodynamics of conventional surfactants, block copolymers and their mixtures in water was described to the light of the enthalpy function. The two methodologies, i.e. the van’t Hoff approach and the isothermal calorimetry, used to determine the enthalpy of micellization of pure surfactants and block copolymers were described. The van’t Hoff method was critically discussed. The aqueous copolymer+surfactant mixtures were analyzed by means of the isothermal titration calorimetry and the enthalpy of transfer of the copolymer from the water to the aqueous surfactant solutions. Thermodynamic models were presented to show the procedure to extract straightforward molecular insights from the bulk properties. PMID:19742173

  12. DNA electrophoresis in tri-block copolymer gels--experiments and Brownian dynamics simulation

    NASA Astrophysics Data System (ADS)

    Wei, Ling; van Winkle, David H.

    2015-03-01

    The mobility of double-stranded DNA ladders in Pluronics®P105, P123 and F127, was measured by two-dimensional gel electrophoresis. Pluronics®are triblock copolymers which form gel-like phases of micelles arranged with cubic order at room temperature. A 10 base pair and a 25 base pair DNA ladder were used as samples in gel electrophoresis. The monotonically decreasing mobility with increasing length observed in the agarose separations is not observed in separations in Pluronics®. Rather, a complicated dependence of mobility on DNA length is observed, where mobility vs. length increases for short DNA molecules then decreases for longer molecules. There is also a variation of mobility with length correlated to the micelle diameter. Brownian dynamics simulations of a discrete wormlike chain model were performed to simulate short DNA molecules migrating in free solution and in a face-centered cubic matrix. By incorporating hydrodynamic interactions, the trend of simulated length-dependent mobility qualitatively agrees with experimental measurements.

  13. Poly(lactide)-block-poly([epsilon]-caprolactone-co-[epsilon]-decalactone)-block-poly(lactide) copolymer elastomers

    SciTech Connect

    Schneiderman, Deborah K.; Hill, Erin M.; Martello, Mark T.; Hillmyer, Marc A.

    2015-08-28

    Batch ring opening transesterification copolymerization of ε-caprolactone and ε-decalactone was used to generate statistical copolymers over a wide range of compositions and molar masses. Reactivity ratios determined for this monomer pair, rCL = 5.9 and rDL = 0.03, reveal ε-caprolactone is added preferentially regardless of the propagating chain end. Relative to poly(ε-caprolactone) the crystallinity and melting point of these statistical copolymers were depressed by the addition of ε-decalactone; copolymers containing greater than 31 mol% (46 wt%) ε-decalactone were amorphous. Poly(lactide)-block-poly(ε-caprolactone-co-ε-decalactone)-block-poly(lactide) triblock polymers were also prepared and used to explore the influence of midblock composition on the temperature dependent Flory-Huggins interaction parameter (χ). In addition, uniaxial extension tests were used to determine the effects of midblock composition, poly(lactide) content, and molar mass on the mechanical properties of these new elastomeric triblocks.

  14. Anionic synthesis of block copolymers for photonics applications

    NASA Astrophysics Data System (ADS)

    Garces Cortes, Camila

    Anionic synthesis of well-defined polystyrene-block-polyvinylpyridine copolymers required the use of special conditions including lithium chloride and 1,1-diphenylethylene as additives, low temperature of reaction (-78°C), highly diluted monomer at -78°C and efficient stirring (Morton-type, creased reactor). Low molecular weight polystyrene-block-poly(2-vinylpyridine) copolymers (Mn = 6000 g/mol) were synthesized with average-molecular weights in agreement with the theoretically calculated Mns and narrow Mw/Mns (≤1.1). Polystyrene-block-polyvinylpyridine copolymers were selected for the fabrication of uniformly dispersed metal oxide nanoparticles (cobalt and iron oxides) due to the coordinating ligand character of the vinylpyridine units. The incorporation of the inorganic salts (1 mol-eq of inorg. salt per mol of vinylpyridine units) was 57 wt% when polystyrene- block-poly(2-vinylpyridine-co-4-vinylpyridine) (M n = 59,000 g/mol, Mw/Mn = 1.09, fv PVP = 0.19) was used and 18 wt% when polystyrene-block-poly(2-vinylpyridine) (Mn = 39,000 g/mol, Mw/Mn = 1.07, f v PVP = 0.14) was used. The end-capping reaction of polymeric chain-ends with 1,1-diphenylethylene (DPE) was studied using 2D NMR spectroscopic and MALDI-TOF mass spectrometric analyses. Oligomerization of DPE was observed using a 15-fold excess of DPE in the end-capping of poly(butadienyl)lithium (Mn = 2,200 g/mol, Mw/Mn = 1.06) but not in the case of poly(styryl)lithium (Mn = 2,000 g/mol, Mw/Mn = 1.02). Although oligomerization of DPE has been previously reported in the synthesis of 1,1-diphenylhexyllithium (6-11% oligomer with 5.4-fold excess of DPE), there are no studies showing the presence of DPE oligomer in the end-capping reaction of polymeric living carbanions. Additionally, the synthesis of poly(para-phenylene) has been studied using different precursor polymers [poly(1,3-cyclohexadienes) (Mn = 1,600 and 3,100 g/mol, Mw/Mn = 1.1 and 1.03) and poly(2-phenyl-1,3-cyclohexadiene) (Mn = 10,000 g/mol, Mw

  15. Pluronic-poly (acrylic acid)-cysteine/Pluronic L121 mixed micelles improve the oral bioavailability of paclitaxel.

    PubMed

    Zhao, Yanli; Li, Yanli; Ge, Jianjun; Li, Na; Li, Ling-Bing

    2014-11-01

    The aim of the study is to synthesize a thiolated Pluronic copolymer, Pluronic-poly (acrylic acid)-cysteine copolymer, to construct a mixed micelle system with the Pluronic-poly (acrylic acid)-cysteine copolymer and Pluronic L121 (PL121) and to evaluate the potential of these mixed micelles as an oral drug delivery system for paclitaxel. Compared with Pluronic-poly (acrylic acid)-cysteine micelles, drug-loading capacity of Pluronic-poly (acrylic acid)-cysteine/PL121 mixed micelles was increased from 0.4 to 2.87%. In vitro release test indicated that Pluronic-poly (acrylic acid)-cysteine/PL121 mixed micelles exhibited a pH sensitivity. The permeability of drug-loaded micelles in the intestinal tract was studied with an in situ perfusion method in rats. The presence of verapamil and Pluronic both improved the intestinal permeability of paclitaxel, which further certified the inhibition effect of thiolated Pluronic on P-gp. In pharmacokinetic study, the area under the plasma concentration-time curve (AUC0→∞) of paclitaxel-loaded mixed micelles was four times greater than that of the paclitaxel solution (p < 0.05). In general, Pluronic-poly (acrylic acid)-cysteine/PL121 micelles were proven to be a potential oral drug delivery system for paclitaxel.

  16. 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.

  17. How to Place Block Copolymer Molecules at the Interface of a Binary Blend

    NASA Astrophysics Data System (ADS)

    Chen, Zhong-Ren; Xu, Yuci; Zhong, Shuo

    2015-03-01

    Block copolymers have been used to reduce the domain size of immiscible polymer blends and thus improve the mechanical and other properties. The effectiveness of this method, however, depends on the percentage of these polymeric surfactants residing at the interface of the blend. In fact, theoretical as well as experimental work indicate that a large percentage of block copolymers form micelles in the bulk of one or both of the component polymers. These micelles may serve as weak spots initiating crack propagation. Previous work have been focused on the design of molecular architecture and synthesis of new block copolymers to address this problem. In this presentation, a simple mixing strategy is applied to make each block copolymer molecule stay at the interface. As one example, when this strategy is used to mix natural rubber (NR) with butadiene rubber (BR), a small amount of low molecular weight block copolymer (LIR) improves both processing characteristics such as melt viscosity and mechanical properties of cured samples, such as crack resistance. AFM micrographs show the much smaller domain size; and an original real-time monitoring system reveals the lowest crack growth rate. Using a model A/B/A-B binary blend, we have witnessed by microscopy that all block copolymer molecules form micelles at the first mixing step, and all of these micelles are disappeared and all block copolymer molecules stay at the interface after the second mixing step.

  18. Controlling sub-microdomain structure in microphase-ordered block copolymers and their nanocomposites

    NASA Astrophysics Data System (ADS)

    Bowman, Michelle Kathleen

    Block copolymers exhibit a wealth of morphologies that continue to find ubiquitous use in a diverse variety of mature and emergent (nano)technologies, such as photonic crystals, integrated circuits, pharmaceutical encapsulents, fuel cells and separation membranes. While numerous studies have explored the effects of molecular confinement on such copolymers, relatively few have examined the sub-microdomain structure that develops upon modification of copolymer molecular architecture or physical incorporation of nanoscale objects. This work will address two relevant topics in this vein: (i) bidisperse brushes formed by single block copolymer molecules and (ii) copolymer nanocomposites formed by addition of molecular or nanoscale additives. In the first case, an isomorphic series of asymmetric poly(styrene-b -isoprene-b-styrene) (S1IS2) triblock copolymers of systematically varied chain length has been synthesized from a parent SI diblock copolymer. Small-angle x-ray scattering, coupled with dynamic rheology and self-consistent field theory (SCFT), reveals that the progressively grown S2 block initially resides in the I-rich matrix and effectively reduces the copolymer incompatibility until a critical length is reached. At this length, the S2 block co-locates with the S1 block so that the two blocks generate a bidisperse brush (insofar as the S1 and S2 lengths differ). This single-molecule analog to binary block copolymer blends affords unique opportunities for materials design at sub-microdomain length scales and provides insight into the transition from diblock to triblock copolymer (and thermoplastic elastomeric nature). In the second case, I explore the distribution of molecular and nanoscale additives in microphase-ordered block copolymers and demonstrate via SCFT that an interfacial excess, which depends strongly on additive concentration, selectivity and relative size, develops. These predictions are in agreement with experimental findings. Moreover, using a

  19. Flexible Battery Cathodes Enabled by Conductive Block Copolymers

    NASA Astrophysics Data System (ADS)

    Lutkenhaus, Jodie; Verduzco, Rafael; An, Hyosung; Lin, Yen-Hao; Lutkenhaus Laboratory Collaboration; Verduzco Laboratory Collaboration

    2015-03-01

    Alone, or as part of hybrid electrodes, conductive polymers are poised to play an integral role in the new and growing field of flexible or ``plastic'' power. Here we demonstrate that even small amounts of a poly(3-hexylthiophene)-block-poly(ethylene oxide) (P3HT-b-PEO) block copolymer, acting as an ion and electron conductor, can bring about significant improvements in energy storage and mechanical flexibility for V2O5 hybrid cathodes for Li-ion batteries. By following this approach, traditional inert polymer binders and carbon black additives are not needed. V2O5 alone has a high theoretical capacity that is limited in practical application by low conductivity. Further, V2O5 alone is brittle and breaks upon repeated flexure. P3HT-b-PEO serves to address both these issues. This presentation will cover how these hybrid electrodes are formed and the resulting physicochemical properties that lead to its enhanced flexibility and energy storage.

  20. Bicontinuous ceramics with high surface area from block copolymer templates.

    PubMed

    Hsueh, Han-Yu; Ho, Rong-Ming

    2012-06-05

    Mesoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-b-poly(L-lactide) (PS-PLLA), followed by hydrolysis of PLLA block. Well-defined polymer/ceramic nanohybrid materials with inorganic gyroid nanostructures in a PS matrix can be obtained by using the mesoporous PS as a template for sol-gel reaction. Titanium tetraisopropoxide (TTIP) is used as a precursor to give a model system for the fabrication of metal oxide nanostructures from reactive transition metal alkoxides. By controlling the rates of capillary-driven pore filling and sol-gel reaction, the templated synthesis can be well-developed. Also, by taking advantage of calcination, bicontinuous TiO(2) with controlled crystalline phase (i.e., anatase phase) can be fabricated after removal of the PS template and crystallization of TiO(2) by calcination leading to high photocatalytic efficiency. This new approach provides an easy way to fabricate high-surface-area and high-porosity ceramics with self-supporting structure and controlled crystalline phase for practical applications. As a result, a platform technology to fabricate precisely controlled polymer/ceramic nanohybrids and mesoporous ceramic materials can be established.

  1. Surface Modification of Block Copolymer Through Sulfur Containing Plasma Treatment.

    PubMed

    Choi, Sang Wook; Shin, Jae Hee; Jeon, Min Hwan; Mun, Jeong Ho; Kim, Sang Ouk; Yeom, Geun Young; Kim, Kyong Nam

    2015-10-01

    Some of the important issues of block copolymer (BCP) as an application to the potential low cost next generation lithography are thermal stability and deformation during pattern transfer process in addition to defect density, line edge/width roughness, etc. In this study, sulfur containing plasma treatment was used to modify the BCP and the effects of the plasma on the properties of plasma treated BCP were investigated. The polystyrene hole pattern obtained from polystyrene polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) was initially degraded when the polystyrene hole was annealed at 190 °C for 15 min. However, when the hole pattern was treated using sulfur containing plasmas using H2S or SF6 up to 2 min, possibly due to the sulfurization of the polystyrene hole surface, no change in the hole pattern was observed after the annealing even though there is a slight change in hole shapes during the plasma treatment. The optimized plasma treated polystyrene pattern showed the superior characteristics as the mask layer by showing better thermal stability, higher chemical inertness, and higher etch selectivity during plasma etching.

  2. Functional Thin Films from Aligned Block Copolymers and Blends

    NASA Astrophysics Data System (ADS)

    Vogt, Bryan; Qiang, Zhe; Cavicchi, Kevin

    Block copolymer (BCP) self-assembly provides a simple, cost effective route to fabricating nanoscale patterns. Here we describe how we can modulate the alignment/orientation of BCP films using a modified solvent vapor anealing (SVA) method where the BCP is covered with an elastomer during SVA and controlled deswelling of the elastomer macroscopically produces a shear force that aligns the BCP domains. By proper selection of the BCP or BCP + functional precursors, functional nanopatterns can be obtained. Thin films of cylindrical forming polystyrene-block-polydimethylsiloxane (PS-b-PDMS) are shear aligned. High temperature calcination converts the PDMS to silica and removes the PS to yield the silica nanolines. The spacing of these features is effectively halved by the use of bilayer films. Sequential shear-alignment of two distinct layers can generate arbitrary line based nanostructured features such as a rhombic array, but the size of the features is defined by the BCP. Oligomeric phenolic resin can effectively modulate the size and morphology of amphiphilic BCPs even at high loadings (>70 wt

  3. [Antitumor drug delivery system: the progress of researches on block copolymer micelle and its compositive materials].

    PubMed

    Yan, Ke; Wang, Chi

    2009-08-01

    In antitumor drug delivery system, the block copolymer micelle is a sort of new colloidal state drug carrier in recent years, and it has lots of remarkable properties such as high stability in vitro and in vivo, favourable biocompatibility, controlling of drug release, and targeting to tumor tissue. At present, a great deal of researches have been madeon its compositive materials. Except commonly used micelle materials, the new developmental intelligent micelle materials have been becoming the hotspots of researches on block copolymer micelle. This review is presented with emphasis on the block copolymer micelle and its compositive materials.

  4. 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.

  5. Electric-Field-Induced Alignment of Block Copolymer/Nanoparticle Blends

    SciTech Connect

    Liedel, Clemens; Schindler, Kerstin; Pavan, Mariela J.; Lewin, Christian; Pester, Christian W; Ruppel, Markus A; Urban, Volker S; Shenhar, Roy; Boker, Alexander

    2013-01-01

    External electric fi elds readily align birefringent block-copolymer mesophases. In this study the effect of gold nanoparticles on the electric-fi eld-induced alignment of a lamellae-forming polystyrene- block -poly(2-vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric-fi eldassisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such fi lms under benign experimental conditions.

  6. Non-immunogenic, hydrophilic/cationic block copolymers and uses thereof

    DOEpatents

    Scales, Charles W.; Huang, Faqing; McCormick, Charles L.

    2010-05-18

    The present invention provides novel non-immunogenic, hydrophilic/cationic block copolymers comprising a neutral-hydrophilic polymer and a cationic polymer, wherein both polymers have well-defined chain-end functionality. A representative example of such a block copolymer comprises poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) and poly(N-[3-(dimethylamino)propyl]methacrylamide) (PDMAPMA). Also provided is a synthesis method thereof in aqueous media via reversible addition fragmentation chain transfer (RAFT) polymerization. Further provided are uses of these block copolymers as drug delivery vehicles and protection agents.

  7. Nanostructure in block copolymer solutions: Rheology and small-angle neutron scattering

    SciTech Connect

    Habas, Jean-Pierre; Pavie, Emmanuel; Perreur, Christelle; Lapp, Alain; Peyrelasse, Jean

    2004-12-01

    Triblock copolymers composed of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) present an amphiphilic character in aqueous solutions. Since PPO is less hydrophilic than PEO and since their solubilities decrease when the temperature increases, the copolymers self-assemble spontaneously, forming micelles at moderate temperatures. For higher temperatures or concentrations, the copolymers or the micelles are ordered because of repulsive interactions and form lyotropic liquid crystalline phases. These are phases of very great viscosity with the aspect of gels, and transitions between different crystalline phases can occur at fixed concentration during an increase of temperature. We studied solutions of three different copolymers. The first two have a star structure. They are both composed of four branches (EO){sub x}(PO){sub y} fixed on an ethylene diamine, but differ by the values of x and y. Their commercial name is Tetronic 908 (x=114, y=21) and Tetronic 704 (x=16, y=18). The third copolymer (EO){sub 37}(PO){sub 56}(EO){sub 37} is linear and is known under the name of Pluronic P105. The measurements of the shear complex elastic modulus according to the temperature is used to determine the temperatures of the different transitions. Then, small-angle neutron scattering on samples under flow and true crystallographic arguments make it possible to identify the nature of the crystalline phases. For the systems studied, we show that the branched copolymers form only one type of liquid crystalline phase, which is bcc for the T908 and lamellar for the T704. For the linear copolymer, it is possible to identify three transitions: micellar solution to hexagonal phase, hexagonal phase to body-centered cubic phase, and finally body-centered cubic phase to lamellar phase.

  8. Efficacy of Different Block Copolymers in Facilitating Microemulsion Phases in Polymer Blend Systems

    NASA Astrophysics Data System (ADS)

    Pandav, Gunja; Ganesan, Venkat

    2014-03-01

    Polymeric microemulsions are formed in a narrow range of phase diagram when a blend of immiscible homopolymers is compatibilized by copolymers. In this study, we consider the ternary blend system of A and B homopolymers mixed with block copolymers containing A and B segments, and probe the efficacy of different copolymer configurations in promoting the formation of microemulsion phases. Specifically, we consider: (a) Monodisperse diblock copolymers; (b) Diblock copolymers with bidisperse molecular weights (MW); (c) Block copolymers having MW polydispersity in one of the blocks; (d) Diblock copolymers having monodisperse MW but bidispersity in average composition; and (e) Gradient copolymers exhibiting a linear variation in the average composition. Using single chain in mean field simulations effected in two dimensions, we probe the onset of formation and the width of the bicontinuous microemulsion channel in the ternary phase diagram of homopolymer blended with compatibilizer. We rationalize our results by explicitly quantifying the interfacial activity and the influence of fluctuation effects in the respective copolymer systems.

  9. A strategy to explore stable and metastable ordered phases of block copolymers.

    PubMed

    Xu, Weiquan; Jiang, Kai; Zhang, Pingwen; Shi, An-Chang

    2013-05-02

    Block copolymers with their rich phase behavior and ordering transitions have become a paradigm for the study of structured soft materials. A major challenge in the study of the phase behavior of block copolymers is to obtain different stable and metastable phases of the system. A strategy to discover complex ordered phases of block copolymers within the self-consistent field theory framework is developed by a combination of fast algorithms and novel initialization procedures. This strategy allows the generation of a large number of candidate structures, which can then be used to construct phase diagrams. Application of the strategy is illustrated using ABC star triblock copolymers as an example. A large number of candidate structures, including many three-dimensionally ordered phases, of the system are obtained and categorized. A phase diagram is constructed for symmetrically interacting ABC star triblock copolymers.

  10. Controlled release of volatile fragrance molecules from PEO-b-PPO-b-PEO block copolymer micelles in ethanol-water mixtures.

    PubMed

    Berthier, Damien L; Schmidt, Isabelle; Fieber, Wolfgang; Schatz, Christophe; Furrer, Anton; Wong, Kenneth; Lecommandoux, Sébastien

    2010-06-01

    Active materials that can solubilize in different compartments of a sample show release properties which might be of interest in some applications where a delayed release of solutes for instance is required. We studied perfume solutes in compartments of Pluronic block copolymers of different compositions and molecular weights over a range of ethanol-water mixtures. Phase diagrams were constructed to identify and map micellar phases, then dynamic light scattering was used to characterize the solute-swollen micelles; NMR provided with the partition of solutes between solvent and micelles, and equilibrium constants K(c) were estimated using headspace analysis. Finally solute-evaporation rates were measured by thermogravimetry. We focused on two typical behaviors: when solubilization in a micellar compartment occurs, delayed release increased with K(c). When solubilization was limited or absent, either because no micelles form or, in the presence of micelles, because solubilization was minor or absent, delayed release was correspondingly absent.

  11. Microfluidic Fabrication of Pluronic Vesicles with Controlled Permeability.

    PubMed

    do Nascimento, Débora F; Arriaga, Laura R; Eggersdorfer, Max; Ziblat, Roy; Marques, Maria de Fátima V; Reynaud, Franceline; Koehler, Stephan A; Weitz, David A

    2016-05-31

    Block copolymers with a low hydrophilic-to-lipophilic balance form membranes that are highly permeable to hydrophilic molecules. Polymersomes with this type of membrane enable the controllable release of molecules without membrane rupture. However, these polymersomes are difficult to assemble because of their low hydrophobicity. Here, we report a microfluidic approach to the production of these polymersomes using double-emulsion drops with ultrathin shells as templates. The small thickness of the middle oil phase enables the attraction of the hydrophobic blocks of the polymers adsorbed at each of the oil/water interfaces of the double emulsions; this results in the dewetting of the oil from the surface of the innermost water drops of the double emulsions and the ultimate formation of the polymersome. This approach to polymersome fabrication enables control of the vesicle size and results in the efficient encapsulation of hydrophilic ingredients that can be released through the polymer membrane without membrane rupture. We apply our approach to the fabrication of Pluronic L121 vesicles and characterize the permeability of their membranes. Furthermore, we show that membrane permeability can be tuned by blending different Pluronic polymers. Our work thus describes a route to producing Pluronic vesicles that are useful for the controlled release of hydrophilic ingredients.

  12. Effect of chain length on binding of fatty acids to Pluronics in microemulsions.

    PubMed

    James-Smith, Monica A; Shekhawat, Dushyant; Cheung, Sally; Moudgil, Brij M; Shah, Dinesh O

    2008-03-15

    We investigated the effect of fatty acid chain length on the binding capacity of drug and fatty acid to Pluronic F127-based microemulsions. This was accomplished by using turbidity experiments. Pluronic-based oil-in-water microemulsions of various compositions were synthesized and titrated to turbidity with concentrated Amitriptyline, an antidepressant drug. Sodium salts of C(8), C(10), or C(12) fatty acid were used in preparation of the microemulsion and the corresponding binding capacities were observed. It has been previously determined that, for microemulsions prepared with sodium caprylate (C(8) fatty acid soap), a maximum of 11 fatty acid molecules bind to the microemulsion per 1 molecule of Pluronic F127 and a maximum of 12 molecules of Amitriptyline bind per molecule of F127. We have found that with increasing the chain length of the fatty acid salt component of the microemulsion, the binding capacity of both the fatty acid and the Amitriptyline to the microemulsion decreases. For sodium salts of C(8), C(10) and C(12) fatty acids, respectively, a maximum of approximately 11, 8.4 and 8.3 molecules of fatty acid molecules bind to 1 Pluronic F127 molecule. We propose that this is due to the decreasing number of free monomers with increasing chain length. As chain length increases, the critical micelle concentration (cmc) decreases, thus leading to fewer monomers. Pluronics are symmetric tri-block copolymers consisting of propylene oxide (PO) and ethylene oxide (EO). The polypropylene oxide block, PPO is sandwiched between two polyethylene oxide (PEO) blocks. The PEO blocks are hydrophilic while PPO is hydrophobic portion in the Pluronic molecule. Due to this structure, we propose that the fatty acid molecules that are in monomeric form most effectively diffuse between the PEO "tails" and bind to the hydrophobic PPO groups.

  13. Thin Film Morphology of Block Copolymers Containing Polydimethylsiloxane as a Function of the Surface Tension of the Opposing Block

    NASA Astrophysics Data System (ADS)

    Wadley, Maurice; Cavicchi, Kevin

    2008-03-01

    The self-assembly of block copolymers into ordered nanostructures such as spheres, cylinders, and lamellae in the range of 10-100 nm makes them interesting materials for patterning surfaces. Thin films of block copolymers containing poly(dimethylsiloxane) (PDMS) are attractive for patterning due to their high oxygen etch resistance compared to other polymers. The main disadvantage of these polymers for patterning is the low surface tension of PDMS. This causes the preferential migration of PDMS to the air/film interface driving the formation of domains parallel to the interface and surface wetting layers. In this work a series of AB block copolymers containing PDMS have been prepared where the surface tension of the opposing block was varied. The effect of changing the surface tension mismatch between the blocks on the thin film morphology will be discussed.

  14. Immunization of Mice by BCG Formulated HCV Core Protein Elicited Higher Th1-Oriented Responses Compared to Pluronic-F127 Copolymer

    PubMed Central

    Yazdanian, Maryam; Memarnejadian, Arash; Mahdavi, Mehdi; Sadat, Seyed Mehdi; Motevali, Fatemeh; Vahabpour, Rouhollah; Khanahmad, Hossein; Siadat, Seyed Davar; Aghasadeghi, Mohammad Reza; Roohvand, Farzin

    2013-01-01

    Background A supreme vaccine for Hepatitis C virus (HCV) infection should elicit strong Th1-oriented cellular responses. In the absence of a Th1-specific adjuvant, immunizations by protein antigens generally induce Th2-type and weak cellular responses. Objectives To evaluate the adjuvant effect of BCG in comparison with nonionic copolymer-Pluronic F127 (F127) as a classic adjuvant in the formulation of HCV core protein (HCVcp) as a candidate vaccine for induction of Th1 immune responses. Materials and Methods Expression of N-terminally His-Tagged HCVcp (1-122) by pIVEX2.4a-core vector harboring the corresponding gene under the control of arabinose-inducible (araBAD) promoter was achieved in BL21-AI strain of E.coli and purified through application of nitrilotriacetic acid (Ni-NTA) chromatography. Mice were immunized subcutaneously (s.c.) in base of the tail with 100 μl of immunogen (F127+HCVcp or BCG+HCVcp; 5 μgHCVcp/mouse/dose) or control formulations (PBS, BCG, F127) at weeks 0, 3, 6. Total and subtypes of IgG, as well as cellular immune responses (Proliferation, In vivo CTL and IFN-γ/IL-4 ELISpot assays against a strong and dominant H2-d restricted, CD8+-epitopic peptide, core 39-48; RRGPRLGVRA of HCVcp) were compared in each group of immunized animals. Results Expression and purification of core protein around the expected size (21 kDa) was confirmed by Western blotting. The HCVcp + BCG vaccinated mice showed significantly higher lymphocyte proliferation and IFN-γ production but lower levels of cell lysis (45% versus 62% in CTL assay) than the HCVcp+F127 immunized animals. “Besides, total anti-core IgG and IgG1 levels were significantly higher in HCVcp + F127 immunized mice as compared to HCVcp + BCG vaccinated animals, indicating relatively higher efficacy of F127 for the stimulation of humoral and Th2-oriented immune responses”. Conclusions Results showed that HCVcp + BCG induced a moderate CTL and mixed Th1/Th2 immune responses with higher levels of

  15. 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

  16. Formation of nanophases in epoxy thermosets containing amphiphilic block copolymers with linear and star-like topologies.

    PubMed

    Wang, Lei; Zhang, Chongyin; Cong, Houluo; Li, Lei; Zheng, Sixun; Li, Xiuhong; Wang, Jie

    2013-07-11

    In this work, we investigated the effect of topological structures of block copolymers on the formation of the nanophase in epoxy thermosets containing amphiphilic block copolymers. Two block copolymers composed of poly(ε-caprolactone) (PCL) and poly(2,2,2-trifluoroethyl acrylate) (PTFEA) blocks were synthesized to possess linear and star-shaped topologies. The star-shaped block copolymer composed a polyhedral oligomeric silsesquioxane (POSS) core and eight poly(ε-caprolactone)-block-poly(2,2,2-trifluoroethyl acrylate) (PCL-b-PTFEA) diblock copolymer arms. Both block copolymers were synthesized via the combination of ring-opening polymerization and reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process; they were controlled to have identical compositions of copolymerization and lengths of blocks. Upon incorporating both block copolymers into epoxy thermosets, the spherical PTFEA nanophases were formed in all the cases. However, the sizes of PTFEA nanophases from the star-like block copolymer were significantly lower than those from the linear diblock copolymer. The difference in the nanostructures gave rise to the different glass transition behavior of the nanostructured thermosets. The dependence of PTFEA nanophases on the topologies of block copolymers is interpreted in terms of the conformation of the miscible subchain (viz. PCL) at the surface of PTFEA microdomains and the restriction of POSS cages on the demixing of the thermoset-philic block (viz. PCL).

  17. Method of producing nanopatterned articles using surface-reconstructed block copolymer films

    DOEpatents

    Russell, Thomas P; Park, Soojin; Wang, Jia-Yu; Kim, Bokyung

    2013-08-27

    Nanopatterned surfaces are prepared by a method that includes forming a block copolymer film on a substrate, annealing and surface reconstructing the block copolymer film to create an array of cylindrical voids, depositing a metal on the surface-reconstructed block copolymer film, and heating the metal-coated block copolymer film to redistribute at least some of the metal into the cylindrical voids. When very thin metal layers and low heating temperatures are used, metal nanodots can be formed. When thicker metal layers and higher heating temperatures are used, the resulting metal structure includes nanoring-shaped voids. The nanopatterned surfaces can be transferred to the underlying substrates via etching, or used to prepare nanodot- or nanoring-decorated substrate surfaces.

  18. Synthesis of PHBV block copolymers driven by an oscillatory genetic network.

    PubMed

    Iadevaia, Sergio; Mantzaris, Nikos V

    2007-02-20

    Artificial genetic networks constitute a powerful tool to achieve various biotechnological objectives. In this work, we propose the modification of an oscillatory genetic network, known as the repressilator, to drive synthesis of poly(3hydroxybutyrate-co-3hydroxyvalerate) (PHBV) block copolymer chains in recombinant Escherichia coli cells. To study the feasibility of this idea, we developed a detailed mathematical model describing the dynamics of the genetic network, which drive the formation of monomer units that are subsequently incorporated into actively growing block copolymer chains. Extensive simulation studies have shown that appropriate choice of the molecular characteristics of the network and manipulation of extracelllular conditions lead to tight control of both the micro- and macro-structures of the resulting block copolymer chains. Thus, the model can guide network design aiming at producing block copolymer structures with desirable characteristics.

  19. Mussel-inspired block copolymer lithography for low surface energy materials of teflon, graphene, and gold.

    PubMed

    Kim, Bong Hoon; Lee, Duck Hyun; Kim, Ju Young; Shin, Dong Ok; Jeong, Hu Young; Hong, Seonki; Yun, Je Moon; Koo, Chong Min; Lee, Haeshin; Kim, Sang Ouk

    2011-12-15

    Mussel-inspired interfacial engineering is synergistically integrated with block copolymer (BCP) lithography for the surface nanopatterning of low surface energy substrate materials, including, Teflon, graphene, and gold. The image shows the Teflon nanowires and their excellent superhydrophobicity.

  20. Block Copolymer Ordering on Soft, Patternable and Flexible Substrates

    NASA Astrophysics Data System (ADS)

    Hayirlioglu, Arzu; Singh, Gurpreet; Karim, Alamgir

    2012-02-01

    Directed assembly of cylinder and lamellae forming block copolymer films via flexible PDMS substrate is examined to investigate the ordering properties of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) films. We study the cases where the PS-b-PMMA films are either directly coated on patterned PDMS flexible substrates, or coated on a flat PDMS substrate with a top patterned and flexible PDMS confinement. The surface energy of the PDMS substrates was modified to vary from 20 to 68 mJ/m^2 by exposing them to UV-ozone (UVO) for controlled wettability and orientation control. We replicated different patterned media and observed perpendicular lamellar orientation and parallel cylindrical orientation on patterned flexible substrate at higher surface energies in preliminary measurements. Characterization of orientation was investigated with Grazing-Incidence Small Angle X-ray Scattering (GISAXS) measurement as well as with Atomic Force Microscope (AFM) results. Optical Microscope (OM) was also used to study of the surface morphology of the BCP films.

  1. Binder-block copolymer micelle interactions in bactericidal filter paper.

    PubMed

    Mansur-Azzam, Nura; Woo, Su Gyeong; Eisenberg, Adi; van de Ven, Theo G M

    2013-08-06

    We previously produced a bactericidal filter paper loaded with PAA47-b-PS214 block copolymer micelles containing the biocide triclosan (TCN), using cationic polyacryamide (cPAM) as a binder. However, we encountered a very slow filtration, resulting in long bacteria deactivation times. Slow drainage occurred only when the filter paper was left to dry. It appears that the filter paper with cPAM and micelles develops hydrophobic properties responsible for this very slow filtration. Three approaches were taken to accelerate the very slow drainage all based on modification of binder-micelle interactions: (i) keeping the micelles wet, (ii) modification of the corona, and (iii) replacing cPAM with smaller and more highly charged cationic poly(isopropanol dimethylammonium) chloride (PIDMAC). In all cases, the drainage time of bactericidal filter paper became close to that of untreated filter paper, without decreasing its efficiency. Moreover, replacing cPAM with PIDMAC led to a much more efficient bactericidal filter paper that reduced bacteria viability by more than 6 orders of magnitude. In addition to resolving the hydrophobic drainage hurdle, the three solutions also offer a better understanding of the interaction between cPAM and micelles in the filter paper.

  2. Direct Immersion Annealing (DIA) of Block Copolymer Thin Film

    NASA Astrophysics Data System (ADS)

    Modi, Arvind; Karim, Alamgir

    2014-03-01

    Solvent Vapor Annealing (SVA) methodologies of block copolymer (BCP) films have demonstrated excellent potential for control of nanostructures and morphologies. However, SVA designs require sophisticated instrumentation, and fine control of system parameters in batch processing mode which is relatively complex and limits its feasibility. We developed a faster and robust solvent immersion strategy for microphase separation and nanostructure control of as-cast BCP thin films with minimal sophistication. Our Direct Immersion Annealing (DIA) method requires immersion in a mixture of non-solvent and good solvent (for BCP) for annealing. A non-solvent component prevents dissolution of the film resting on substrate while a good solvent percolates through the film, plasticizes it, and shifts glass-transition below room temperature leading to microphase separation and ordering. Our study of PS-PMMA system demonstrates that a robust control over thin film ordering and transient swelling could be achieved through a fine control of solubility parameter of solvent mixture and temperature with no dead-time. Further, we exhibit the utility of DIA for alignment of BCP domains on topographically patterned substrates. University of Akron Research Foundation (UARF).

  3. Direct Immersion Annealing of Block Copolymer Thin Films

    NASA Astrophysics Data System (ADS)

    Karim, Alamgir

    We demonstrate ordering of thin block copolymer (BCP) films via direct immersion annealing (DIA) at enhanced rate leading to stable morphologies. The BCP films are immersed in carefully selected mixtures of good and marginal solvents that can impart enhanced polymer mobility, while inhibiting film dissolution. DIA is compatible with roll-to-roll assembly manufacturing and has distinct advantages over conventional thermal annealing and batch processing solvent-vapor annealing methods. We identify three solvent composition-dependent BCP film ordering regimes in DIA for the weakly interacting polystyrene -poly(methyl methacrylate) (PS -PMMA) system: rapid short range order, optimal long-range order, and a film instability regime. Kinetic studies in the ``optimal long-range order'' processing regime as a function of temperature indicate a significant reduction of activation energy for BCP grain growth compared to oven annealing at conventional temperatures. An attractive feature of DIA is its robustness to ordering other BCP (e.g. PS-P2VP) and PS-PMMA systems exhibiting spherical, lamellar and cylindrical ordering. Inclusion of nanoparticles in these films at high concentrations and fast ordering kinetics study with neutron reflectivity and SANS will be discussed. This is (late) Contributed Talk Abstract for Dillon Medal Symposium at DPOLY - discussed with DPOLY Chair Dvora Perahia.

  4. 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

  5. Dynamics of entangled rod-coil block copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Muzhou; Timachova, Ksenia; Alexander-Katz, Alfredo; Likhtman, Alexei E.; Olsen, Bradley D.

    2014-03-01

    Polymer science is exploring advanced materials which combine functional domains such as proteins and semiconducting polymers with traditional flexible polymers onto the same molecule. While many studies have focused on equilibrium structure-property relationships, little is known about how the conformational restrictions of rigid domains affect dynamical phenomena such as mechanical properties, processing pathways, and self-assembly kinetics. We have recently introduced a reptation theory for entangled rod-coil block copolymers as a model for this wider class of functional polymeric materials. The theory hypothesizes that the motion of rod-coils is slowed relative to rod and coil homopolymers because of a mismatch between the curvature of the rod and coil entanglement tubes. This effect leads to activated reptation and arm retraction as two relaxation mechanisms that govern the short and long rod regimes, respectively. These results were verified by tracer diffusion measurements using molecular dynamics simulation and forced Rayleigh scattering in both the rod-coil diblock and coil-rod-coil triblock configurations. The tracer diffusion results were then compared to experimental self-diffusion measurements which require a consideration of the motion of the surrounding chains.

  6. Complexation-tailored morphology of asymmetric block copolymer membranes.

    PubMed

    Madhavan, Poornima; Peinemann, Klaus-Viktor; Nunes, Suzana P

    2013-08-14

    Hydrogen-bond formation between polystyrene-b-poly (4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) and -OH/-COOH functionalized organic molecules was used to tune morphology of asymmetric nanoporous membranes prepared by simultaneous self-assembly and nonsolvent induced phase separation. The morphologies were characterized by field emmision scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Hydrogen bonds were confirmed by infrared (IR), and the results were correlated to rheology characterization. The OH-functionalized organic molecules direct the morphology into hexagonal order. COOH-functionalized molecules led to both lamellar and hexagonal structures. Micelle formation in solutions and their sizes were determined using dynamic light scattering (DLS) measurements and water fluxes of 600-3200 L/m(2)·h·bar were obtained. The pore size of the plain BCP membrane was smaller than with additives. The following series of additives led to pores with hexagonal order with increasing pore size: terephthalic acid (COOH-bifunctionalized) < rutin (OH-multifunctionalized) < 9-anthracenemethanol (OH-monofunctionalized) < 3,5-dihydroxybenzyl alcohol (OH-trifunctionalized).

  7. Electrical biomolecule detection using nanopatterned silicon via block copolymer lithography.

    PubMed

    Jeong, Chang Kyu; Jin, Hyeong Min; Ahn, Jae-Hyuk; Park, Tae Jung; Yoo, Hyeon Gyun; Koo, Min; Choi, Yang-Kyu; Kim, Sang Ouk; Lee, Keon Jae

    2014-01-29

    An electrical biosensor exploiting a nanostructured semiconductor is a promising technology for the highly sensitive, label-free detection of biomolecules via a straightforward electronic signal. The facile and scalable production of a nanopatterned electrical silicon biosensor by block copolymer (BCP) nano-lithography is reported. A cost-effective and large-area nanofabrication, based on BCP self-assembly and single-step dry etching, is developed for the hexagonal nanohole patterning of thin silicon films. The resultant nanopatterned electrical channel modified with biotin molecules successfully detects the two proteins, streptavidin and avidin, down to nanoscale molarities (≈1 nm). The nanoscale pattern comparable to the Debye screening length and the large surface area of the three-dimensional silicon nanochannel enable excellent sensitivity and stability. A device simulation confirms that the nanopatterned structure used in this work is effective for biomolecule detection. This approach relying on the scalable self-assembly principle offers a high-throughput manufacturing process for clinical lab-on-a-chip diagnoses and relevant biomolecular studies.

  8. Square Grains in Asymmetric Rod-Coil Block Copolymers

    SciTech Connect

    Olsen, B.D.; Toney, M.F.; Segalman, R.A.; /UC, Berkeley /LBL, Berkeley /SLAC, SSRL

    2009-04-30

    Unlike the rounded grains that are well known to form in most soft materials, square grains of microphase-separated lamellae are observed in thin films of a rod-coil block copolymer because of hierarchical structuring originating from the molecular packing of the rods. The square grains are oriented with lamellar layers parallel to the film interface and result from growth along orthogonal low-surface-energy directions as a result of the effects of the tetragonal crystalline lattice that forms within the rod-rich lamellar nanodomains of poly(2,5-di(2{prime}-ethylhexyloxy)-1,4-phenylene vinylene)-b-polyisoprene (PPV-b-PI). These grain shapes form only for a narrow range of coil volume fractions around 72% as a result of kinetic barriers at lower coil fractions and disordering of the lattice at higher coil fractions, and the polydisperse grain size suggests that growth is nucleation-limited. The grains form in both weakly and moderately segregated polymers at all annealing temperatures below the order-disorder transition, and they are observed for all thicknesses at which parallel-oriented grains are grown.

  9. Non-crosslinked, amorphous, block copolymer electrolyte for batteries

    DOEpatents

    Mayes, Anne M.; Ceder, Gerbrand; Chiang, Yet-Ming; Sadoway, Donald R.; Aydinol, Mehmet K.; Soo, Philip P.; Jang, Young-Il; Huang, Biying

    2006-04-11

    Solid battery components are provided. A block copolymeric electrolyte is non-crosslinked and non-glassy through the entire range of typical battery service temperatures, that is, through the entire range of at least from about 0.degree. C. to about 70.degree. C. The chains of which the copolymer is made each include at least one ionically-conductive block and at least one second block immiscible with the ionically-conductive block. The chains form an amorphous association and are arranged in an ordered nanostructure including a continuous matrix of amorphous ionically-conductive domains and amorphous second domains that are immiscible with the ionically-conductive domains. A compound is provided that has a formula of Li.sub.xM.sub.yN.sub.zO.sub.2. M and N are each metal atoms or a main group elements, and x, y and z are each numbers from about 0 to about 1. y and z are chosen such that a formal charge on the M.sub.yN.sub.z portion of the compound is (4-x). In certain embodiments, these compounds are used in the cathodes of rechargeable batteries. The present invention also includes methods of predicting the potential utility of metal dichalgogenide compounds for use in lithium intercalation compounds. It also provides methods for processing lithium intercalation oxides with the structure and compositional homogeneity necessary to realize the increased formation energies of said compounds. An article is made of a dimensionally-stable, interpenetrating microstructure of a first phase including a first component and a second phase, immiscible with the first phase, including a second component. The first and second phases define interphase boundaries between them, and at least one particle is positioned between a first phase and a second phase at an interphase boundary. When the first and second phases are electronically-conductive and ionically-conductive polymers, respectively, and the particles are ion host particles, the arrangement is an electrode of a battery.

  10. 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.

  11. Supramolecular hydrogels from cisplatin-loaded block copolymer nanoparticles and α-cyclodextrins with a stepwise delivery property.

    PubMed

    Zhu, Wen; Li, Yanli; Liu, Lixin; Chen, Yongming; Wang, Chun; Xi, Fu

    2010-11-08

    A stepwise anticancer drug delivery system based on an injectable supramolecular hydrogel was presented. In this system, poly(ethylene glycol)-b-poly(acrylic acid) (PEG-b-PAA) block copolymer nanoparticles containing cisplatin were released by erosion of the hydrogels and then the cisplatin was released from the nanoparticles by exchanging with chloride ions. By mixing α-cyclodextrins (α-CDs) and the PEG-b-PAA micelles with their PAA cores loaded with the cisplatin in water, the novel supramolecular hydrogels were generated by threading α-CDs onto the PEG segments and forming physical cross-links of molecular necklaces. The gelation properties could be tuned by changing concentrations of the polymers and cisplatin, their feeds, and by adding PEG homopolymers or Pluronic copolymers as additives. Structures and properties of the supramolecular hydrogels containing cisplatin were studied by wide-angle X-ray diffraction (XRD) and rheology measurements, respectively. The thixotropic effect of the hydrogels and their reversible sol-gel transition were confirmed. In vitro hydrogel erosion experiments were conducted and cisplatin release in saline and pure water was quantified. Hydrogel erosion produced discrete nanoparticles from which cisplatin was released completely in saline. In contrast, the hydrogels were eroded into nanoparticles in pure water, but no cisplatin could be released. In vitro cytotoxicity studies showed that the cisplatin-loaded hydrogels inhibited the growth of human bladder carcinoma EJ cells with a similar potency as that of the free cisplatin, whereas the hydrogels without cisplatin showed no cytotoxicity. These results suggested that the cisplatin-coordinated PEG-b-PAA/α-CD supramolecular hydrogels hold great potential as an injectable system for sustained delivery of cisplatin in cancer therapy.

  12. NEXAFS Depth Profiling of Surface Segregation in Block Copolymer Thin Films

    SciTech Connect

    Krishnan, S.; Paik, M; Ober, C; Martinelli, E; Galli, G; Sohn, K; Kramer, E; Fischer, D

    2010-01-01

    NEXAFS spectroscopy was used to probe the surface composition and under-water surface reconstruction of thin films of comb-like diblock copolymers with cylindrical and spherical microphases. The polymers consisted of a polystyrene block, and a second block prepared from a styrenic monomer grafted with fluoroalkyl-tagged poly(ethylene glycol) side chains. Compositional depth profiling of the microphase separated block copolymer films, in the top 1-3 nm of the film, was performed to understand the role of block copolymer microstructure and self-assembly on surface composition. Using experimentally determined concentration profiles, the surface concentration of phenyl ring carbon atoms was quantified and compared with those of homopolymer and random copolymer controls. The carbon atoms from the relatively high surface energy phenyl groups were depleted or excluded from the surface, in favor of the low surface-energy fluoroalkyl groups. While it is expected that block copolymer surfaces will be completely covered by a wetting lamellar layer of the lower surface energy block, a significant amount of the higher surface energy polystyrene block was found to be present in the surface region of the cylinder-forming block copolymer. Evidently, the spontaneous formation of the cylindrical polystyrene microdomains in the near-surface region compensated for the lowering of the free energy that could have been achieved by completely covering the surfaces with a lamellar layer of the lower surface energy fluorinated block. All surfaces underwent molecular reconstruction after immersion in water. The experimental concentration depth profiles indicated an increased surface depletion of phenyl ring carbon atoms in the water-immersed thin films, due to the tendency of hydrophilic PEG side groups to be present at the polymer-water interface. Such a detailed characterization of the outermost layers of the block copolymer surfaces was possible because of the exceptional depth resolution

  13. Morphology and phase diagram of comb block copolymer Am+1(BC)m.

    PubMed

    Jiang, Zhibin; Wang, Rong; Xue, Gi

    2009-05-28

    The morphologies and the phase diagram of comb copolymer Am+1(BC)m are investigated by the self-consistent field theory. By changing the volume fractions of the blocks, the interaction parameters between the different blocks, and the side chain number, nine phases are found, including the two-colored lamellar phase, three-colored lamellar phase, hexagonal lattice phase, core shell hexagonal lattice phase, two interpenetrating tetragonal lattice, core shell tetragonal lattice, lamellar phase with beads inside, lamellar phase with alternating beads, and disordered phase. The phase diagrams are constructed for Am+1(BC)m with different side chain numbers of m=1, 2, 3, and 5. Due to the asymmetric topology of comb copolymer Am+1(BC)m, the phases and the diagrams are very different from linear ABC triblock copolymer or star ABC triblock copolymer. When the volume fraction of one of the blocks is the domination, the (core shell) hexagonal phase or two interpenetrating tetragonal lattice can form, depending on which block dominates and the interaction between the blocks. The (core shell) hexagonal phase easily forms at the corner of the block A (fA>or=0.5). The side chain number m affects the phase diagram largely due to the fact that the architecture of a comb copolymer is not invariant under the interchange between the three different monomers. Due to the connectivity of the blocks B and the inner blocks A, Am+1(BC)m comb copolymers with the longer main chain A or longer side chain with short block C, i.e., longer block B, are difficult to phase separate. The results are helpful to design nano- or biomaterials with complex architecture or tailor the phase behavior of comb copolymers.

  14. Mechano-responsive hydrogels crosslinked by reactive block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Xiao, Longxi

    Hydrogels are crosslinked polymeric networks that can swell in water without dissolution. Owing to their structural similarity to the native extracelluar matrices, hydrogels have been widely used in biomedical applications. Synthetic hydrogels have been designed to respond to various stimuli, but mechanical signals have not incorporated into hydrogel matrices. Because most tissues in the body are subjected to various types of mechanical forces, and cells within these tissues have sophisticated mechano-transduction machinery, this thesis is focused on developing hydrogel materials with built-in mechano-sensing mechanisms for use as tissue engineering scaffolds or drug release devices. Self-assembled block copolymer micelles (BCMs) with reactive handles were employed as the nanoscopic crosslinkers for the construction of covalently crosslinked networks. BCMs were assembled from amphiphilic diblock copolymers of poly(n-butyl acrylate) and poly(acrylic acid) partially modified with acrylate. Radical polymerization of acrylamide in the presence of micellar crosslinkers gave rise to elastomeric hydrogels whose mechanical properties can be tuned by varying the BCM composition and concentration. TEM imaging revealed that the covalently integrated BCMs underwent strain-dependent reversible deformation. A model hydrophobic drug, pyrene, loaded into the core of BCMs prior to the hydrogel formation, was dynamically released in response to externally applied mechanical forces, through force-induced reversible micelle deformation and the penetration of water molecules into the micelle core. The mechano-responsive hydrogel has been studied for tissue repair and regeneration purposes. Glycidyl methacrylate (GMA)-modified hyaluronic acid (HA) was photochemically crosslinked in the presence of dexamethasone (DEX)-loaded crosslinkable BCMs. The resultant HA gels (HAxBCM) contain covalently integrated micellar compartments with DEX being sequestered in the hydrophobic core. Compared

  15. Field-theoretic simulations of block copolymer nanocomposites in a constant interfacial tension ensemble

    NASA Astrophysics Data System (ADS)

    Koski, Jason P.; Riggleman, Robert A.

    2017-04-01

    Block copolymers, due to their ability to self-assemble into periodic structures with long range order, are appealing candidates to control the ordering of functionalized nanoparticles where it is well-accepted that the spatial distribution of nanoparticles in a polymer matrix dictates the resulting material properties. The large parameter space associated with block copolymer nanocomposites makes theory and simulation tools appealing to guide experiments and effectively isolate parameters of interest. We demonstrate a method for performing field-theoretic simulations in a constant volume-constant interfacial tension ensemble (n V γ T ) that enables the determination of the equilibrium properties of block copolymer nanocomposites, including when the composites are placed under tensile or compressive loads. Our approach is compatible with the complex Langevin simulation framework, which allows us to go beyond the mean-field approximation. We validate our approach by comparing our n V γ T approach with free energy calculations to determine the ideal domain spacing and modulus of a symmetric block copolymer melt. We analyze the effect of numerical and thermodynamic parameters on the efficiency of the n V γ T ensemble and subsequently use our method to investigate the ideal domain spacing, modulus, and nanoparticle distribution of a lamellar forming block copolymer nanocomposite. We find that the nanoparticle distribution is directly linked to the resultant domain spacing and is dependent on polymer chain density, nanoparticle size, and nanoparticle chemistry. Furthermore, placing the system under tension or compression can qualitatively alter the nanoparticle distribution within the block copolymer.

  16. Effect of Morphology on Ion Transport in Polymerized Ionic Liquid Block Copolymers

    NASA Astrophysics Data System (ADS)

    Choi, Jae-Hong; Ye, Yuesheng; Elabd, Yossef; Winey, Karen

    2013-03-01

    We investigate the impact of morphology on ion transport in single-ion conductor polymerized ionic liquid (PIL) diblock copolymers. The morphology for two types of PIL block copolymers with different degrees of miscibility between blocks was studied using small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). For poly(methyl methacrylate-b-1-[(2-methacryloyloxy)ethyl]-3-butylimidazolium-bis(trifluoromethylsulfonyl)imide) (MMA-b-MEBIm-TFSI) PIL diblock copolymers, the partial miscibility between the MEBIm-TFSI and MMA blocks resulted in a weakly microphase-separated morphology without long-range order. In poly(styrene-b-1-[(2-acryloyloxy)ethyl]-3-butylimidazolium-TFSI) (S-b-AEBIm-TFSI) PIL block copolymers, a variety of self-assembled nanostructures including hexagonally packed cylinders, lamellae, and coexisting lamellae and network morphologies were observed by varying PIL composition. A comparison of ionic conductivity between PMMA- and PS-based PIL block copolymers suggests that strong microphase separation with well-defined structures can improve ionic conductivity. The local ion concentration and connectivity of the conducting microdomains also play an important role in ion conduction in these PIL block copolymers.

  17. Non-random crosslinking of polysulphone-polysiloxane alternating block copolymers under irradiation

    NASA Astrophysics Data System (ADS)

    Xinfang, Chen; Chunshan, Zhang

    In this paper the effects of radiation on polysulphone-polysiloxane segmented copolymers have been investigated. The experimental observations indicate that the crosslinking reaction occurs primarily between siloxane segments and the intermolecular crosslinking of isopropylidene groups of adjacent polysulphone segments also takes place after the irradiation of higher doses. From the non-randon radiation crosslinking model which the block copolymer follows, the relationship between sol fraction and crosslink density is derived by a statistical method. The radiation crosslinking structure of block copolymers prepared by polycondensation of prepolymers, polysulphone and polysiloxane, can be controled by changing the average molecular weights of two prepolymers and the ratio of one component to the other.

  18. Nonlinear optical properties of gold nanoparticles selectively introduced into the periodic microdomains of block copolymers.

    PubMed

    Tsuchiya, Kosuke; Nagayasu, Satoshi; Okamoto, Shigeru; Hayakawa, Tomokatsu; Hihara, Takehiko; Yamamoto, Katsuhiro; Takumi, Ichi; Hara, Shigeo; Hasegawa, Hirokazu; Akasaka, Satoshi; Kosikawa, Naokiyo

    2008-04-14

    Nonlinear-optical nanocomposite materials with a photonic crystal structure were fabricated using block copolymers and gold nanoparticles. By dispersing the gold nanoparticles into the selective microdomains of the block copolymers, we could achieve the enhancement of nonlinear optical properties as revealed by the Z-scan technique. The optical nonlinearities were enhanced by the local field effect and the effect of the periodic distribution of the microdomains filled with gold nanoparticles. Furthermore, the highest optical nonlinearity was achieved by matching the domain spacing of the copolymers with the frequency of the surface plasmon resonance peak of the gold.

  19. Electrically conductive doped block copolymer of polyacetylene and polyisoprene. [Soluble in organic solvents

    DOEpatents

    Aldissi, M.

    1984-06-27

    An electrically conductive block copolymer of polyisoprene and polyacetylene and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I/sub 2/ to give it an electrical conductivity in the metallic regime.

  20. Surface functionalization of carbon nanotubes by direct encapsulation with varying dosages of amphiphilic block copolymers

    NASA Astrophysics Data System (ADS)

    Yao, Xueping; Li, Jie; Kong, Liang; Wang, Yong

    2015-08-01

    Encapsulation of carbon nanotubes (CNTs) by amphiphilic block copolymers is an efficient way to stabilize CNTs in solvents. However, the appropriate dosages of copolymers and the assembled structures are difficult to predict and control because of the insufficient understanding on the encapsulation process. We encapsulate multiwalled CNTs with polystyrene-block-poly (4-vinyl pyridine) (PS-b-P4VP) by directly mixing them in acetic acid under sonication. The copolymer forms a lamellar structure along the surface of CNTs with the PS blocks anchoring on the tube wall and the P4VP blocks exposed to the outside. The encapsulated CNTs achieve good dispersibility in polar solvents over long periods. To increase our understanding of the encapsulation process we investigate the assembled structures and stability of copolymer/CNTs mixtures with changing mass ratios. Stable dispersions are obtained at high mass ratios between the copolymer and CNTs, i.e. 2 or 3, with the presence of free spherical micelles. Transmission electron microscopy and thermal gravimetric analysis determine that the threshold for the complete coverage of CNTs by the copolymer occurs at the mass ratio of 1.5. The coated copolymer layer activates the surface of CNTs, enabling further functionalization of CNTs. For instance, atomic layer deposition of TiO2 produces conformal thin layers on the encapsulated CNTs while isolated TiO2 bumps are produced on the pristine, inert CNTs.

  1. Transmission electron microscopy of polymer blends and block copolymers

    NASA Astrophysics Data System (ADS)

    Gomez, Enrique Daniel

    -consistent field theory (SCFT). The liquid-like nature of this system at room temperature makes traditional staining methods for the enhancement of contrast ineffective. As an alternative, we take advantage of the large inelastic scattering cross-section of soft materials to generate contrast in zero-loss TEM images. Independent spatially resolved thickness measurements enable quantification of electron scattering. This enabled a comparison between the TEM data and predictions based on SCFT without any adjustable parameters. The second example involves the utilization of energy-filtered transmission electron microscopy (EFTEM) to compute elemental maps by taking advantage of ionization events. Elemental mapping of lithium is used to determine the distribution of salt in nanostructured poly(styrene-block-ethylene oxide) (SEO) copolymer/lithium salt electrolytes. Surprisingly, the concentration of lithium within a poly(ethylene oxide) (PEO) domain is found to be inhomogeneous; the salt is localized to the middle of the channels. Self-consistent field theory simulations suggest that localization of lithium is due to chain stretching at the interface, which increases with molecular weight. EFTEM and SCFT results show that the segregation of lithium salt to the middle of the PEO lamellae is greater for higher molecular weight polymers. This is correlated with the ionic conductivity of the copolymer electrolyte, which is found to show a higher conductivity for thinner lithium lamellae.

  2. Tunable Encapsulation Structure of Block Copolymer Coated Single-Walled Carbon Nanotubes in Aqueous Solution

    SciTech Connect

    Han, Youngkyu; Ahn, Suk-Kyun; Zhang, Zhe; Smith, Gregory Scott; Do, Changwoo

    2015-05-15

    The nano-sized and shape-tunable molecular building blocks can provide great opportunities for the fabrication of precisely controlled nanostructures. In this work, we have fabricated a molecular building block of single-walled carbon nanotubes (SWNTs) coated by PPO-PEO-PPO block copolymers whose encapsulation structure can be controlled via temperature or addition of small molecules. The structure and optical properties of SWNT-block copolymers have been investigated by small angle neutron scattering (SANS), ultraviolet-visible (UV-vis) spectroscopy, atomic force microscopy (AFM), and molecular dynamics (MD) simulation. The structure of the hydrated block copolymer layer surrounding SWNT can be controlled reversibly by varying temperature as well as by irreversibly adding 5-methylsalicylic acid (5MS). Increasing hydrophobicity of the polymers with temperature and strong tendency of 5MS to interact with both block copolymers and orbitals of the SWNTs are likely to be responsible for the significant structural change of the block copolymer encapsulation layer, from loose corona shell to tightly encapsulating compact shell. These result shows an efficient and simple way to fabricate and manipulate carbon-based nano building blocks in aqueous systems with tunable structure.

  3. Tunable Encapsulation Structure of Block Copolymer Coated Single-Walled Carbon Nanotubes in Aqueous Solution

    DOE PAGES

    Han, Youngkyu; Ahn, Suk-Kyun; Zhang, Zhe; ...

    2015-05-15

    The nano-sized and shape-tunable molecular building blocks can provide great opportunities for the fabrication of precisely controlled nanostructures. In this work, we have fabricated a molecular building block of single-walled carbon nanotubes (SWNTs) coated by PPO-PEO-PPO block copolymers whose encapsulation structure can be controlled via temperature or addition of small molecules. The structure and optical properties of SWNT-block copolymers have been investigated by small angle neutron scattering (SANS), ultraviolet-visible (UV-vis) spectroscopy, atomic force microscopy (AFM), and molecular dynamics (MD) simulation. The structure of the hydrated block copolymer layer surrounding SWNT can be controlled reversibly by varying temperature as well asmore » by irreversibly adding 5-methylsalicylic acid (5MS). Increasing hydrophobicity of the polymers with temperature and strong tendency of 5MS to interact with both block copolymers and orbitals of the SWNTs are likely to be responsible for the significant structural change of the block copolymer encapsulation layer, from loose corona shell to tightly encapsulating compact shell. These result shows an efficient and simple way to fabricate and manipulate carbon-based nano building blocks in aqueous systems with tunable structure.« less

  4. Ionic Interactions for Aqueous Templating of Biofunctional Molecules in Block Copolymer Nanostructures

    NASA Astrophysics Data System (ADS)

    Olsen, Bradley; Kim, Bokyung; Lam, Christopher; Stewart-Sloan, Charlotte; Gkikas, Emmanouil

    2013-03-01

    The use of ionic interactions to direct both biomolecular 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. Reversible addition-fragmentation chain transfer (RAFT) polymerization is employed to synthesize diblock copolymers with one neutral thermoresponsive and one polycationic block and the pH-dependnent complexation between model proteins or biomimetic J-aggregating chromophores and the polycationic block is demonstrated. Spin casting is used to prepare nanostructured films from the protein-block copolymer and chromophore-block copolymer coacervates. After film formation, the lower critical solution temperature (LCST) of the thermoresponsive block allows the nanomaterial to be effectively immobilized in aqueous environments at physiological temperatures, enabling use of the materials for biomolecule immobilization and controlled release. In the case of protein nanotemplating, the ionic environment in which the protein is confined enables the majority of the protein (80%) to retain its activity, even after having been dehydrated in vacuum and confined in the thin film.

  5. Synthesis of Carboxylic Block Copolymers via Reversible Addition Fragmentation Transfer Polymerization for Tooth Erosion Prevention

    PubMed Central

    Lei, Y.; Wang, T.; Mitchell, J.W.; Qiu, J.; Kilpatrick-Liverman, L.

    2014-01-01

    Dental professionals are seeing a growing population of patients with visible signs of dental erosion. The approach currently being used to address the problem typically leverages the enamel protection benefits of fluoride. In this report, an alternative new block copolymer with a hydrophilic polyacrylic acid (PAA) block and a hydrophobic poly(methyl methacrylate) (PMMA) block was developed to similarly reduce the mineral loss from enamel under acidic conditions. This series of PMMA-b-PAA block copolymers was synthesized by reversible addition fragmentation transfer (RAFT) polymerization. Their structures were characterized by gel permeation chromatography (GPC) and 1H nuclear magnetic resonance (NMR) spectra. The molar fractions of acrylic acid (AA) in the final block copolymer were finely controlled from 0.25 to 0.94, and the molecular weight (Mn) of PMMA-b-PAA was controlled from 10 kDa to 90 kDa. The binding capability of the block copolymer with hydroxyapatite (HAP) was investigated by ultraviolet–visible spectroscopy (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy. FTIR spectra confirmed that the PMMA-b-PAA block copolymer could bind to HAP via bridging bidentate bonds. Both UV-Vis and FTIR spectra additionally indicated that a high polymer concentration and low solution pH favored the polymer binding to HAP. The erosion-preventing efficacy of the PMMA-b-PAA block copolymer in inhibiting HAP mineral loss was quantitatively evaluated by atomic absorption spectroscopy (AAS). Based on the results, polymer treatment reduced the amount of calcium released by 27% to 30% in comparison with the unprotected samples. Scanning electron microscope (SEM) observations indicated that PMMA-b-PAA polymer treatment protected enamel from acid erosion. This new amphiphilic block copolymer has significant potential to be integrated into dentifrices or mouthrinses as an alternative non-fluoride ingredient to reduce tooth erosion. PMID:25248611

  6. Synthesis of carboxylic block copolymers via reversible addition fragmentation transfer polymerization for tooth erosion prevention.

    PubMed

    Lei, Y; Wang, T; Mitchell, J W; Qiu, J; Kilpatrick-Liverman, L

    2014-12-01

    Dental professionals are seeing a growing population of patients with visible signs of dental erosion. The approach currently being used to address the problem typically leverages the enamel protection benefits of fluoride. In this report, an alternative new block copolymer with a hydrophilic polyacrylic acid (PAA) block and a hydrophobic poly(methyl methacrylate) (PMMA) block was developed to similarly reduce the mineral loss from enamel under acidic conditions. This series of PMMA-b-PAA block copolymers was synthesized by reversible addition fragmentation transfer (RAFT) polymerization. Their structures were characterized by gel permeation chromatography (GPC) and (1)H nuclear magnetic resonance (NMR) spectra. The molar fractions of acrylic acid (AA) in the final block copolymer were finely controlled from 0.25 to 0.94, and the molecular weight (Mn) of PMMA-b-PAA was controlled from 10 kDa to 90 kDa. The binding capability of the block copolymer with hydroxyapatite (HAP) was investigated by ultraviolet-visible spectroscopy (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy. FTIR spectra confirmed that the PMMA-b-PAA block copolymer could bind to HAP via bridging bidentate bonds. Both UV-Vis and FTIR spectra additionally indicated that a high polymer concentration and low solution pH favored the polymer binding to HAP. The erosion-preventing efficacy of the PMMA-b-PAA block copolymer in inhibiting HAP mineral loss was quantitatively evaluated by atomic absorption spectroscopy (AAS). Based on the results, polymer treatment reduced the amount of calcium released by 27% to 30% in comparison with the unprotected samples. Scanning electron microscope (SEM) observations indicated that PMMA-b-PAA polymer treatment protected enamel from acid erosion. This new amphiphilic block copolymer has significant potential to be integrated into dentifrices or mouthrinses as an alternative non-fluoride ingredient to reduce tooth erosion. © International & American

  7. 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.

  8. High-Tg Polynorbornene-Based Block and Random Copolymers for Butanol Pervaporation Membranes

    NASA Astrophysics Data System (ADS)

    Register, Richard A.; Kim, Dong-Gyun; Takigawa, Tamami; Kashino, Tomomasa; Burtovyy, Oleksandr; Bell, Andrew

    Vinyl addition polymers of substituted norbornene (NB) monomers possess desirably high glass transition temperatures (Tg); however, until very recently, the lack of an applicable living polymerization chemistry has precluded the synthesis of such polymers with controlled architecture, or copolymers with controlled sequence distribution. We have recently synthesized block and random copolymers of NB monomers bearing hydroxyhexafluoroisopropyl and n-butyl substituents (HFANB and BuNB) via living vinyl addition polymerization with Pd-based catalysts. Both series of polymers were cast into the selective skin layers of thin film composite (TFC) membranes, and these organophilic membranes investigated for the isolation of n-butanol from dilute aqueous solution (model fermentation broth) via pervaporation. The block copolymers show well-defined microphase-separated morphologies, both in bulk and as the selective skin layers on TFC membranes, while the random copolymers are homogeneous. Both block and random vinyl addition copolymers are effective as n-butanol pervaporation membranes, with the block copolymers showing a better flux-selectivity balance. While polyHFANB has much higher permeability and n-butanol selectivity than polyBuNB, incorporating BuNB units into the polymer (in either a block or random sequence) limits the swelling of the polyHFANB and thereby improves the n-butanol pervaporation selectivity.

  9. Surface affinity role in graphoepitaxy of lamellar block copolymers

    NASA Astrophysics Data System (ADS)

    Claveau, Guillaume; Quemere, Patrick; Argoud, Maxime; Hazart, Jerome; Barros, Patricia Pimenta; Sarrazin, Aurelien; Posseme, Nicolas; Tiron, Raluca; Chevalier, Xavier; Nicolet, Celia; Navarro, Christophe

    2016-07-01

    Overcoming the optical limitations of 193-nm immersion lithography can be achieved using directed self-assembly (DSA) of block-copolymers (BCPs) as a low-cost and versatile complementary technique. The goal of this paper is to investigate the potential of DSA to address line and space (L/S) high-resolution patterning by performing the density multiplication of lines with the graphoepitaxy approach. As surface affinity is a key parameter in self-assembly, three variations, or "flavors," of DSA template affinity are investigated regarding several success criteria such as morphology control or defectivity. More precisely, both the methodology to register DSA defects and the impact of process parameters on defectivity are detailed. Using the 300-mm pilot line available in LETI and Arkema's advanced materials, we investigate process optimization of DSA line/space patterning of a 38-nm period lamellar PS-b-PMMA BCP (L38). Our integration scheme is based on BCP self-assembly inside organic hard mask guiding patterns obtained using 193i-nm lithography. Defect analysis coupled with the fine tuning of process parameters (annealing, brush material) provided the optimum conditions for the L38 self-assembly. Using such conditions, DSA using the three affinity flavors is investigated by means of SEM top-view and cross-section review. Lithographic performances of one selected flavor are then evaluated with the comparison of process windows function of either commensurability, morphology, or roughness. This work is meant as a guideline for the graphoepitaxy optimization of materials and process parameters on a 300-mm platform.

  10. Preparation of Pickering Double Emulsions Using Block Copolymer Worms

    PubMed Central

    2015-01-01

    The rational formulation of Pickering double emulsions is described using a judicious combination of hydrophilic and hydrophobic block copolymer worms as highly anisotropic emulsifiers. More specifically, RAFT dispersion polymerization was utilized to prepare poly(lauryl methacrylate)–poly(benzyl methacrylate) worms at 20% w/w solids in n-dodecane and poly(glycerol monomethacrylate)–poly(2-hydroxypropyl methacrylate)–poly(benzyl methacrylate) worms at 13% w/w solids in water by polymerization-induced self-assembly (PISA). Water-in-oil-in-water (w/o/w) double emulsions can be readily prepared with mean droplet diameters ranging from 30 to 80 μm using a two-stage approach. First, a w/o precursor emulsion comprising 25 μm aqueous droplets is prepared using the hydrophobic worms, followed by encapsulation within oil droplets stabilized by the hydrophilic worms. The double emulsion droplet diameter and number of encapsulated water droplets can be readily varied by adjusting the stirring rate employed during the second stage. For each stage, the droplet volume fraction is relatively high at 0.50. The double emulsion nature of the final formulation was confirmed by optical and fluorescence microscopy studies. Such double emulsions are highly stable to coalescence, with little or no change in droplet diameter being detected over storage at 20 °C for 10 weeks as judged by laser diffraction. Preliminary experiments indicate that the complementary o/w/o emulsions can also be prepared using the same pair of worms by changing the order of homogenization, although somewhat lower droplet volume fractions were required in this case. Finally, we demonstrate that triple and even quadruple emulsions can be formulated using these new highly anisotropic Pickering emulsifiers. PMID:25834923

  11. Surface affinity role in graphoepitaxy of lamellar block copolymers

    NASA Astrophysics Data System (ADS)

    Claveau, G.; Quemere, P.; Argoud, M.; Hazart, J.; Pimenta Barros, P.; Sarrazin, A.; Posseme, N.; Tiron, R.; Chevalier, X.; Nicolet, C.; Navarro, C.

    2016-03-01

    Overcoming the optical limitations of 193nm immersion lithography can be achieved using Directed Self Assembly (DSA) of block-copolymers (BCPs) as a low-cost and versatile complementary technique. The goal of this paper is to investigate the potential of DSA to address line and space (L/S) high resolution patterning by performing the density multiplication of lines with the graphoepitaxy approach. As surface affinity is a key parameter in self-assembly, three variations, or "flavors", of DSA template affinity are investigated regarding several success criteria such as morphology control or defectivity. More precisely, both the methodology to register DSA defects and the impact of process parameters on defectivity are detailed. Using the 300mm pilot line available in LETI and Arkema's advanced materials, we investigate process optimization of DSA line/space patterning of a 38nm period lamellar PS-b-PMMA BCP (L38). For this study, our integration scheme, depicted in figure 2-1, is based on BCP self-assembly inside organic hard mask guiding patterns obtained using 193i nm lithography. Defect analysis coupled with the fine tuning of process parameters (annealing, brush material) provided the optimum conditions for the L38 self-assembly. Using such conditions, DSA using the three affinity flavors is investigated by means of SEM top-view and cross-section review. Lithographic performances of one selected flavor are then evaluated with the comparison of Process Windows (PWs) function of either commensurability, morphology or LWR. This work is a first step in finding the best process for an industrial graphoepitaxy approach.

  12. Control of Crystallization to Promote Microphase Separation in Fully Conjugated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Lee, Youngmin; Le, Thinh P.; Seibers, Zach; Kilbey, S. Michael, II; Wang, Qing; Gomez, Enrique D.

    Donor -acceptor fully conjugated block copolymers, where donor and acceptor conjugated polymers are covalently bonded together, are interesting as single-component active-layer materials for photovoltaics because it can adopt mesoscale microphase separated structures with length scales comparable to the exciton diffusion length. Nevertheless, due to the strong crystallization of poly(3-hexylthiophene-2,5-diyl) (P3HT), morphologies of fully conjugated block copolymers containing P3HT are predominantly driven by crystallization as opposed to microphase separation. We control the crystallization in block copolymers to promote microphase separation in fully conjugated block copolymers through the addition of small amounts of 3-octylthiophene to the polymerization of P3HT. Poly(3-hexylthiophene-2,5-diyl- r-3-octylthiophene-2,5-diyl)-block-poly((9,9-dioctylfluorene-2,7-diyl)-alt-(4,7-di(thiophene-2-yl)-2,1,3-benzothiadiazole)-5',5''-diyl) (P3HT- b-PFTBT) copolymers were prepared by Grignard metathesis for the alkylthiophene block followed by chain extension through a Suzuki-Miyaura polycondensation. We compare the crystallization, self-assembly and performance in devices of P3HT-b-PFTBT with a few mole percent of 3-octylthiophene in the P3HT block. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831.

  13. Poly(vinylidene fluoride)/nickel nanocomposites from semicrystalline block copolymer precursors.

    PubMed

    Voet, Vincent S D; Tichelaar, Martijn; Tanase, Stefania; Mittelmeijer-Hazeleger, Marjo C; ten Brinke, Gerrit; Loos, Katja

    2013-01-07

    The fabrication of nanoporous poly(vinylidene fluoride) (PVDF) and PVDF/nickel nanocomposites from semicrystalline block copolymer precursors is reported. Polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PS-b-PVDF-b-PS) is prepared through functional benzoyl peroxide initiated polymerization of VDF, followed by atom transfer radical polymerization (ATRP) of styrene. The crystallization of PVDF plays a dominant role in the formation of the block copolymer structure, resulting in a spherulitic superstructure with an internal crystalline-amorphous lamellar nanostructure. The block copolymer promotes the formation of the ferroelectric β-polymorph of PVDF. Selective etching of the amorphous regions with nitric acid leads to nanoporous PVDF, which functions as a template for the generation of PVDF/Ni nanocomposites. The lamellar nanostructure and the β-crystalline phase are conserved during the etching procedure and electroless nickel deposition.

  14. Low-Temperature Processable Block Copolymers That Preserve the Function of Blended Proteins.

    PubMed

    Iwasaki, Yasuhiko; Takemoto, Kyohei; Tanaka, Shinya; Taniguchi, Ikuo

    2016-07-11

    Low-temperature processable polymers have attracted increasing interest as ecological materials because of their reduced energy consumption during processing and suitability for making composites with heat-sensitive biomolecules at ambient temperature. In the current study, low-temperature processable biodegradable block copolymers were synthesized by ring-opening polymerization of l-lactide (LLA) using polyphosphoester as a macroinitiator. The polymer films could be processed under a hydraulic pressure of 35 MPa. The block copolymer films swelled in water because the polyphosphoester block was partially hydrated. Interestingly, the swelling ratio of the films changed with temperature. The pressure-induced order-to-disorder transition of the block copolymers was characterized by small-angle X-ray scattering; a crystallinity reduction in the block copolymers was observed after application of pressure. The crystallinity of the block copolymers was recovered after removing the applied pressure. The Young's modulus of the block copolymer films increased as the LLA unit content increased. Moreover, the modulus did not change after multiple processing cycles and the recyclability of the block copolymers was also confirmed. Finally, polymer films with embedded proteinase K as a model protein were prepared. The activity of catalase loaded into the polymer films was evaluated after processing at different temperatures. The activity of catalase was preserved when the polymer films were processed at room temperature but was significantly reduced after high-temperature processing. The suitability of low-temperature processable biodegradable polymers for making biofunctional composites without reducing protein activity was clarified. These materials will be useful for biomedical and therapeutic applications.

  15. Aggregation behavior of poly(ethylene glycol-bl-propylene sulfide) di- and triblock copolymers in aqueous solution.

    PubMed

    Cerritelli, Simona; O'Neil, Conlin P; Velluto, Diana; Fontana, Antonella; Adrian, Marc; Dubochet, Jacques; Hubbell, Jeffrey A

    2009-10-06

    Block copolymers of poly(ethylene glycol)-bl-poly(propylene sulfide) (PEG-PPS) have recently emerged as a new macromolecular amphiphile capable of forming a wide range of morphologies when dispersed in water. To understand better the relationship between stability and morphology in terms of the relative and absolute block compositions, we have synthesized a collection of PEG-PPS block copolymers and quantified their critical aggregation concentration and observed their morphology using cryogenic transmission electron microscopy after thin film hydration with extrusion and after solvent dispersion from tetrahydrofuran, a solvent for both blocks. By understanding the relationship between aggregate character and block copolymer architecture, we have observed that whereas the relative block lengths control morphology, the stability of the aggregates upon dilution is determined by the absolute block length of the hydrophobic PPS block. We have compared results obtained with PEG-PPS to those obtained with poly(ethylene glycol)-bl-poly(propylene oxide)-bl-poly(ethylene glycol) block copolymers (Pluronics). The results reveal that the PEG-PPS aggregates are substantially more stable than Pluronic aggregates, by more than an order of magnitude. PEG-PPS can form a wide variety of stable or metastable morphologies in dilute solution within normal time and temperature ranges, whereas Pluronics can generally form only spherical micelles under the same conditions. On the basis of these results, block copolymers of PEG with poly(propylene sulfide) may present distinct advantages over those with poly(propylene glycol) for a number of applications.

  16. 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

  17. Effect of Pluronic P85 on ATPase Activity of Drug Efflux Transporters

    PubMed Central

    Batrakova, Elena V.; Li, Shu; Li, Yili; Alakhov, Valery Yu.; Kabanov, Alexander V.

    2009-01-01

    Purpose Pluronic block copolymers are potent sensitizers of multi-drug resistant (MDR) cancer cells. The sensitization effect by Pluronics is a result of two processes acting in concert: i) intracellular ATP depletion, and ii) inhibition of ATPase activity of drug efflux proteins. This work characterizes effects of Pluronic P85 on ATPase activities of Pgp, MRP1, and MRP2 drug efflux transport proteins and interaction of these proteins with their substrates, vinblastine, and leucotriene C4. Methods Using membranes overexpressing Pgp, MRP1, and MRP2, the current study evaluates effects of Pluronic P85 (P85) on the kinetic parameters (Vmax, Km, Vmax/Km) of ATP hydrolysis by these ATPases. Results The decreases in the maximal reaction rates (Vmax) and increases in apparent Michaelis constants (Km) for these transporters in the presence of various concentrations of P85 were observed. The mechanism of these effects may involve i) conformational changes of the transporter due to membrane fluidization and/or ii) nonspecific steric hindrance of the drug-binding sites by P85 chains embedded into cellular membranes. The extent of these alterations was increased in the row MRP1 < MRP2 << Pgp. Conclusions These data suggest that there are unifying pathways for the inhibition of Pgp and MRPs by the block copolymer. However, the effect of P85 on Pgp ATPase activity is considerably greater compared with the effects on MRP1 and MRP2 ATPases. This may be a reason for greater inhibitory effects of Pluronic in Pgp- compared with MRP-overexpressing cells. PMID:15648254

  18. Poly(vinylidene fluoride)/nickel nanocomposites from semicrystalline block copolymer precursors

    NASA Astrophysics Data System (ADS)

    Voet, Vincent S. D.; Tichelaar, Martijn; Tanase, Stefania; Mittelmeijer-Hazeleger, Marjo C.; ten Brinke, Gerrit; Loos, Katja

    2012-12-01

    The fabrication of nanoporous poly(vinylidene fluoride) (PVDF) and PVDF/nickel nanocomposites from semicrystalline block copolymer precursors is reported. Polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PS-b-PVDF-b-PS) is prepared through functional benzoyl peroxide initiated polymerization of VDF, followed by atom transfer radical polymerization (ATRP) of styrene. The crystallization of PVDF plays a dominant role in the formation of the block copolymer structure, resulting in a spherulitic superstructure with an internal crystalline-amorphous lamellar nanostructure. The block copolymer promotes the formation of the ferroelectric β-polymorph of PVDF. Selective etching of the amorphous regions with nitric acid leads to nanoporous PVDF, which functions as a template for the generation of PVDF/Ni nanocomposites. The lamellar nanostructure and the β-crystalline phase are conserved during the etching procedure and electroless nickel deposition.The fabrication of nanoporous poly(vinylidene fluoride) (PVDF) and PVDF/nickel nanocomposites from semicrystalline block copolymer precursors is reported. Polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PS-b-PVDF-b-PS) is prepared through functional benzoyl peroxide initiated polymerization of VDF, followed by atom transfer radical polymerization (ATRP) of styrene. The crystallization of PVDF plays a dominant role in the formation of the block copolymer structure, resulting in a spherulitic superstructure with an internal crystalline-amorphous lamellar nanostructure. The block copolymer promotes the formation of the ferroelectric β-polymorph of PVDF. Selective etching of the amorphous regions with nitric acid leads to nanoporous PVDF, which functions as a template for the generation of PVDF/Ni nanocomposites. The lamellar nanostructure and the β-crystalline phase are conserved during the etching procedure and electroless nickel deposition. Electronic supplementary information (ESI) available

  19. Combinatorial Block Copolymer Ordering on Tunable Rough Substrates

    SciTech Connect

    Kulkarni, Manish M.; Yager, Kevin G.; Sharma, Ashutosh; Karim, Alamgir

    2012-10-25

    Morphology control of block copolymer (BCP) thin films through substrate interaction via controlled roughness parameters is of significant interest for numerous high-tech applications ranging from solar cells to high-density storage media. While effects of substrate surface energy (SE) and roughness (R) on BCP morphology have been individually investigated, their synergistic effects have not been explored in any systematic manner. Interestingly, orientation response of BCP to changes in SE can be similar to what can be accomplished with variations in R. Here we present a novel approach for orienting lamellar BCP films of poly(styrene)-block-poly(methyl methacrylate) (PS-PMMA) on spin-coated xerogel (a dried gel of silica nanoparticle network) substrate with simultaneously tunable surface energy, {gamma}{sub s} {approx} 29-53 mJ/m{sup 2}, by UVO exposure and roughness, R{sub rms} {approx} 0.5-30 nm, by sol-gel processing steps of regulating the catalyst concentration and sol aging time. As in previous BCP orientation studies on 20 nm diameter monodisperse silica nanoparticle coated surface, we find a similar but broadened oscillatory BCP orientation behavior with film thickness due to the random rather than periodic rough surfaces. We also find that higher random roughness amplitude is not the necessary criteria for obtaining a vertical orientation of BCP lamellae. Rather, a high surface fractal dimension (D{sub f} > 2.4) of the rough substrate in conjunction with an optimal substrate surface energy {gamma}{sub s} {approx} 29 mJ/m{sup 2} results in 100% vertically oriented lamellar microdomains. The AFM measured film surface microstructure correlates well with the internal 3D BCP film structure probed by grazing incidence small-angle X-ray scattering (GISAXS) and rotational small-angle neutron scattering (SANS). In contrast to tunable self-assembled monolayer (SAM)-coated substrates, the xerogel films are very durable and retain their chemical properties over period

  20. Design and Synthesis of Novel Block Copolymers for Efficient Opto-Electronic Applications

    NASA Technical Reports Server (NTRS)

    Sun, Sam-Shajing; Fan, Zhen; Wang, Yiqing; Taft, Charles; Haliburton, James; Maaref, Shahin

    2002-01-01

    It has been predicted that nano-phase separated block copolymer systems containing electron rich donor blocks and electron deficient acceptor blocks may facilitate the charge carrier separation and migration in organic photovoltaic devices due to improved morphology in comparison to polymer blend system. This paper presents preliminary data describing the design and synthesis of a novel Donor-Bridge-Acceptor (D-B-A) block copolymer system for potential high efficient organic optoelectronic applications. Specifically, the donor block contains an electron donating alkyloxy derivatized polyphenylenevinylene (PPV), the acceptor block contains an electron withdrawing alkyl-sulfone derivatized polyphenylenevinylene (PPV), and the bridge block contains an electronically neutral non-conjugated aliphatic hydrocarbon chain. The key synthetic strategy includes the synthesis of each individual block first, then couple the blocks together. While the donor block stabilizes and facilitates the transport of the holes, the acceptor block stabilizes and facilitates the transport of the electrons, the bridge block is designed to hinder the probability of electron-hole recombination. Thus, improved charge separation and stability are expected with this system. In addition, charge migration toward electrodes may also be facilitated due to the potential nano-phase separated and highly ordered block copolymer ultra-structure.

  1. Antimicrobial activity of poly(acrylic acid) block copolymers.

    PubMed

    Gratzl, Günther; Paulik, Christian; Hild, Sabine; Guggenbichler, Josef P; Lackner, Maximilian

    2014-05-01

    The increasing number of antibiotic-resistant bacterial strains has developed into a major health problem. In particular, biofilms are the main reason for hospital-acquired infections and diseases. Once formed, biofilms are difficult to remove as they have specific defense mechanisms against antimicrobial agents. Antimicrobial surfaces must therefore kill or repel bacteria before they can settle to form a biofilm. In this study, we describe that poly(acrylic acid) (PAA) containing diblock copolymers can kill bacteria and prevent from biofilm formation. The PAA diblock copolymers with poly(styrene) and poly(methyl methacrylate) were synthesized via anionic polymerization of tert-butyl acrylate with styrene or methyl methacrylate and subsequent acid-catalyzed hydrolysis of the tert-butyl ester. The copolymers were characterized via nuclear magnetic resonance spectroscopy (NMR), size-exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), elemental analysis, and acid-base titrations. Copolymer films with a variety of acrylic acid contents were produced by solvent casting, characterized by atomic force microscopy (AFM) and tested for their antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The antimicrobial activity of the acidic diblock copolymers increased with increasing acrylic acid content, independent of the copolymer-partner, the chain length and the nanostructure. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Hybrid titanium dioxide/PS-b-PEO block copolymer nanocomposites based on sol-gel synthesis

    NASA Astrophysics Data System (ADS)

    Gutierrez, J.; Tercjak, A.; Garcia, I.; Peponi, L.; Mondragon, I.

    2008-04-01

    The poly(styrene)-b-poly(ethylene oxide) (SEO) amphiphilic block copolymer, with two different molecular weights, has been used as a structure directing agent for generating nanocomposites of TiO2/SEO via the sol-gel process. SEO amphiphilic block copolymers are designed with a hydrophilic PEO-block which can interact with inorganic molecules, as well as a hydrophobic PS-block which builds the matrix. The addition of different amounts of sol-gel provokes strong variations in the self-assembled morphology of TiO2/SEO nanocomposites with respect to the neat block copolymer. As confirmed by atomic force microscopy (AFM), TiO2/PEO-block micelles get closer, forming well-ordered spherical domains, in which TiO2 nanoparticles constitute the core surrounded by a corona of PEO-blocks. Moreover, for 20 vol% sol-gel the generated morphology changes to a hexagonally ordered structure for both block copolymers. The cylindrical structure of these nanocomposites has been confirmed by the two-dimensional Fourier transform power spectrum of the corresponding AFM height images. Affinity between titanium dioxide precursor and PEO-block of SEO allows us to generate hybrid inorganic/organic nanocomposites, which retain the optical properties of TiO2, as evaluated by UV-vis spectroscopy.

  3. 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.

  4. 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.

  5. Frank-Kasper sigma phase stabilized by tailored architectures of block copolymers

    NASA Astrophysics Data System (ADS)

    Li, Weihua; Liu, Meijiao; Xie, Nan; Qiu, Feng; Shi, An-Chang

    Block copolymer self-assembly forms diverse interesting ordered morphologies, of which the spherical phase is of particular interest because it resembles the similar space symmetry as atomic crystals and has a tunable period on nanoscale. Moreover, the packing lattice of spherical domains dictated by the adjustable competition between the entropic and interfacial energies is programmable. For AB diblock copolymers, it has been known that the stable spherical phase is mainly bcc except for a very narrow region of fcc at the vicinity of the order-disorder transition. When introducing variable number of blocks and architectures to form complex AB-type block copolymers, the A15 phase was predicted as stable. However, a striking experiment observed a new spherical phase, the complex Frank-Kasper sigma phase that consists of 30 spheres in a unit cell, in the PI-b-PLA diblock copolymer as well as a SISO tetrablock terpolymer. Inspired by this experiment, we studied the stability of all known spherical phases of fcc, bcc, A15 and sigma in various block copolymers including conformationally asymmetric AB diblock, ABm miktoarm, and BABC tetrablock copolymers. We have revealed the formation mechanism of the nonclassical A15 and sigma phases due to the tailored architectures.

  6. Chirality plays critical roles in enhancing the aqueous solubility of nocathiacin I by block copolymer micelles.

    PubMed

    Feng, Kun; Wang, Shuzhen; Ma, Hairong; Chen, Yijun

    2013-01-01

    Although drug solubilization by block copolymer micelles has been extensively studied, the rationale behind the choice of appropriate block copolymer micelles for various poorly water-soluble drugs has been of relatively less concern. The objective of this study was to use methoxy-poly(ethylene glycol)-polylactate micelles (MPEG-PLA) to solubilize glycosylated antibiotic nocathiacin I and to compare the effects of chirality on the enhancement of aqueous solubility. Nocathiacin I-loaded MPEG-PLA micelles with opposite optical property in PLA were synthesized and characterized. The drug release profile, micelle stability and preliminary safety properties of MPEG-PLA micelles were evaluated. Meanwhile, three other poorly water-soluble chiral compound-loaded micelles were also prepared and compared.  The aqueous solubility of nocathiacin I was greatly enhanced by both L- and D-copolymers, with the degree of enhancement appearing to depend on the chirality of the copolymers. Comparison of different chiral compounds confirmed the trend that aqueous solubility of chiral compounds can be more effectively enhanced by block copolymer micelles with specific stereochemical configuration. The present study introduced chiral concept on the selection and preparation of block copolymer micelles for the enhancement of aqueous solubility of poorly water-soluble drugs. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

  7. Novel multi-responsive P2VP-block-PNIPAAm block copolymers via nitroxide-mediated radical polymerization

    PubMed Central

    Corten, Cathrin; Kretschmer, Katja

    2010-01-01

    Summary Linear soluble multi-responsive block copolymers are able to form so called schizophrenic micelles in aqueous solution. Here, such polymers are prepared via nitroxide-mediated radical polymerization (NMRP). In a first step nitroxide-terminated poly(2-vinylpyridine) (P2VP) was prepared with different molecular weights and narrow molecular weight distributions. The best reaction conditions, optimized by kinetic studies, were bulk polymerization at 110 °C. Using P2VP as a macroinitiator, the synthesis of new soluble linear block copolymers of P2VP and poly(N-isopropylacrylamide) (PNIPAAm) (P2VP-block-PNIPAAm) was possible. The nitroxide terminated polymers were characterized by nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Thermal properties were investigated by the differential scanning calorimetry (DSC). Block copolymers showed pH- and temperature-responsive solubility in aqueous media. By increasing the P2VP content, the phase transition temperature shifted to lower temperatures (e.g. 26 °C for P2VP114-block-PNIPAAm180). Depending on the resulting block length, temperature and pH value of aqueous solution, the block copolymers form so called schizophrenic micelles. The hydrodynamic radius R h of these micelles associated with pH values and temperature was analyzed by dynamic light scattering (DLS). Such kind of block copolymers has potential for many applications, such as controlled drug delivery systems. PMID:20978627

  8. 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

  9. 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

  10. 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.

  11. Lithium-Salt-Containing High-Molecular-Weight Polystyrene-block-Polyethylene Oxide Block Copolymer Films.

    PubMed

    Metwalli, Ezzeldin; Rasool, Majid; Brunner, Simon; Müller-Buschbaum, Peter

    2015-08-10

    Ionic conductivity in relation to the morphology of lithium-doped high-molecular-weight polystyrene-block-polyethylene oxide (PS-b-PEO) diblock copolymer films was investigated as solid-state membranes for lithium-ion batteries. The tendency of the polyethylene (PEO) block to crystallize was highly suppressed by increasing both the salt-doping level and the temperature. The PEO crystallites completely vanished at a salt-doping ratio of Li/EO>0.08, at which the PEO segments were hindered from entering the crystalline unit of the PEO chain. A kinetically trapped lamella morphology of PS-b-PEO was observed, due to PEO crystallization. The increase in the lamella spacing with increasing salt concentration was attributed to the conformation of the PEO chain rather than the volume contribution of the salt or the previously reported increase in the effective interaction parameter. Upon loading the salt, the PEO chains changed from a compact/highly folded conformation to an amorphous/expanded-like conformation. The ionic conductivity was enhanced by amorphization of PEO and thereby the mobility of the PEO blocks increased upon increasing the salt-doping level.

  12. Hemocompatibility of styrenic block copolymers for use in prosthetic heart valves.

    PubMed

    Brubert, Jacob; Krajewski, Stefanie; Wendel, Hans Peter; Nair, Sukumaran; Stasiak, Joanna; Moggridge, Geoff D

    2016-02-01

    Certain styrenic thermoplastic block copolymer elastomers can be processed to exhibit anisotropic mechanical properties which may be desirable for imitating biological tissues. The ex-vivo hemocompatibility of four triblock (hard-soft-hard) copolymers with polystyrene hard blocks and polyethylene, polypropylene, polyisoprene, polybutadiene or polyisobutylene soft blocks are tested using the modified Chandler loop method using fresh human blood and direct contact cell proliferation of fibroblasts upon the materials. The hemocompatibility and durability performance of a heparin coating is also evaluated. Measures of platelet and coagulation cascade activation indicate that the test materials are superior to polyester but inferior to expanded polytetrafluoroethylene and bovine pericardium reference materials. Against inflammatory measures the test materials are superior to polyester and bovine pericardium. The addition of a heparin coating results in reduced protein adsorption and ex-vivo hemocompatibility performance superior to all reference materials, in all measures. The tested styrenic thermoplastic block copolymers demonstrate adequate performance for blood contacting applications.

  13. Block copolymers exhibiting simultaneous electronic and ionic conduction for use in lithium battery electrodes

    NASA Astrophysics Data System (ADS)

    Javier, Anna; Patel, Shrayesh; Hallinan, Daniel; Balsara, Nitash

    2011-03-01

    A block copolymer system that can demonstrate both electronic and ionic conductivity is analyzed for its performance in rechargeable lithium batteries. Here, the electrically active polymer is poly(3-hexylthiophene), while poly(ethylene oxide) is used as the lithium ion conductor. This block copolymer is then mixed with LiFe PO4 and used as the cathode material. Other components in the battery include a lithium metal anode and poly(styrene)-block-poly(ethylene oxide) (SEO) as the solid electrolyte. Lithium bis(trifluoromethane)sulfonimide (LiTFSI) is utilized to facilitate ionic conductivity in both the electrolyte and the cathode. The synthesis of the block copolymer and its device performance in rechargeable lithium metal batteries will be presented.

  14. Shear-Assisted Fabrication of Block Copolymer Agglomerates with Various Morphologies in Viscous Medium.

    PubMed

    Yang, Zongpeng; Chen, Xiaoli; Xu, Zhou; Xiao, Meina; Hong, Liangzhi; Ngai, To

    2017-03-21

    In this work, we have investigated the effect of laminar flow shearing on the formation of block copolymer agglomerates in viscous medium. Under a laminar flow shearing, the block copolymer solution droplets were spontaneously emulsified and were then elongated into protofibers, which in turn transformed into particles with various morphologies. Besides micro-/nanorods, which were previously reported for homopolymers, sphere and sheetlike structures were unexpectedly fabricated from block copolymers depending on the solvent quality, solvent exchange rates, and the entanglement of the polymer chains. In particular, the sheet structure, fabricated from poly(ethylene glycol)-b-polystyrene (PEG-b-PS), can be fixed by UV irradiation when photo-crosslinkable azide groups were introduced onto the polystyrene block. Surprisingly, we found that the fixed sheetlike structures show demulsification capability in tens of seconds, which may have great potential application in the separation of oil from emulsions.

  15. Effect of matrix crystallinity on the ionic conductivity in microstructured block copolymer solid electrolytes

    NASA Astrophysics Data System (ADS)

    Young, Nicholas; Balsara, Nitash

    2012-02-01

    Polyethylene oxide (PEO)-based block copolymers have been studied extensively for use as solid electrolytes for rechargeable lithium metal batteries. Previous work has concentrated on block copolymers containing an amorphous second block, such as polystyrene, for which the modulus is sufficiently high to resist growth of dendrites that would lead to short circuiting. In this work, we instead focus on using semicrystalline polyethylene as the mechanically robust component. Polyethylene-polyethylene oxide (EEO) block copolymers doped with lithium bis(trifluoromethanesulfone) imide (LiTFSI) were characterized using AC impedance spectroscopy over a range of temperature, molecular weight, and composition values in order to determine the effect of crystallinity in the structural microphase on the conductivity of this material.

  16. Multi-block sulfonated poly(phenylene) copolymer proton exchange membranes

    DOEpatents

    Fujimoto, Cy H [Albuquerque, NM; Hibbs, Michael [Albuquerque, NM; Ambrosini, Andrea [Albuquerque, NM

    2012-02-07

    Improved multi-block sulfonated poly(phenylene) copolymer compositions, methods of making the same, and their use as proton exchange membranes (PEM) in hydrogen fuel cells, direct methanol fuel cells, in electrode casting solutions and electrodes. The multi-block architecture has defined, controllable hydrophobic and hydrophilic segments. These improved membranes have better ion transport (proton conductivity) and water swelling properties.

  17. Processing-structure-mechanical Property Relationships of Semicrystalline Polyolefin-based Block Copolymers

    SciTech Connect

    Deplace, F.; Wang, Z; Lynd, N; Hotta, A; Rose, J; Hustad, P; Tian, J; Ohtaki, H; Coates, J; et. al.

    2010-01-01

    The incremental plastic deformation of the crystals of block copolymers made of semicrystalline polypropylene endblocks and amorphous ethylene-r-propylene midblocks occurring during step cycle tensile tests has dramatic effects on the stress-strain curves. This can be understood from the evolution of the morphology and of the microstructure of the crystalline blocks revealed by X-ray scattering experiments.

  18. Interfacial Segregation in Disordered Block Copolymers: Effect of Tunable Surface Potentials

    SciTech Connect

    Mansky, P.; Russell, T.P.; Hawker, C.J.; Mays, J.; Cook, D.C.; Satija, S.K.

    1997-07-01

    The response of disordered P({ital d}-S-{ital b}-MMA) diblock copolymers to variable strength surface fields has been studied by neutron reflectivity. Surface interactions were controlled by end grafting P(S-{ital r}-MMA) random copolymers with various styrene contents onto Si substrates. The degree interfacial segregation of the block copolymer was proportional to the surface potential. A first-order transition in the degree of segregation was observed as the brush composition was varied. Conditions were found which yielded neutral boundary conditions {ital simultaneously} at the vacuum and substrate interfaces. {copyright} {ital 1997} {ital The American Physical Society}

  19. Toward a Block-Copolymer-Emulsified, Tough Blend of Isotactic Polystyrene and Polybutadiene: HIiPS.

    DTIC Science & Technology

    1991-02-14

    OFFICE OF NAVAL RESEARCH Contract N00014-91-J-1045 R&T Code 4132047 --- 02-1 TECNICA RPORT NO. 2 Toward a Block-Copolymer-Emulsified, Tough Blend of... molecular weight polydispersities in the final materials (>6) due to the continuous restructuring of the catalytic sites; some chains break off and die...presented an opportunity to mix and match different molecular weight polystyrenes and polybutadienes so as to tailor-make diblock copolymers of varying

  20. Melt and Solid-State Structures of Polydisperse Polyolefin Block Copolymers

    NASA Astrophysics Data System (ADS)

    Register, Richard; Li, Sheng

    2013-03-01

    Recent developments in coordinative chain transfer polymerization have enabled the synthesis of ethylene-co-octene block copolymers, where the blocks are either crystallizable (an ethylene-co-octene random copolymer block with low octene content) or amorphous (analogous block with high octene content). With a suitable choice of catalyst type(s) and reactor train configuration, accessible chain architectures include diblock, where each block ideally has the most-probable distribution of chain lengths, and multiblock, where both the individual blocks and the number of blocks per chain follow the most-probable distribution. With a sufficiently large interblock octene differential, block copolymers of both architectures, containing roughly equal masses of the two types of block, self-assemble in the melt into well-ordered lamellar structures, despite the large polydispersity. Interblock mixing, induced by the modest Flory interaction parameter and the broad distribution of block lengths, yields an enormous domain spacing (> 100 nm) despite the relatively low average block molecular weights (< 50 kg/mol). Extensive interblock mixing also allows the polyethylene crystals to grow freely and nearly isotropically across the domain interfaces, while preserving the domain structure present in the melt; in the solid state, the optical and x-ray contrasts between dissimilar domains are greatly enhanced due to their different levels of crystallinity. (Work conducted in collaboration with Jeffrey Weinhold, Philip Hustad, and Brian Landes of Dow Chemical Core R&D.) Support from the NSF Polymers Program (DMR-1003942).

  1. Synthesis of manganese oxide supported on mesoporous titanium oxide: Influence of the block copolymer

    SciTech Connect

    Schmit, F.; Bois, L.; Chiriac, R.; Toche, F.; Chassagneux, F.; Besson, M.; Descorme, C.; Khrouz, L.

    2015-01-15

    Manganese oxides supported on mesoporous titanium oxides were synthesized via a sol–gel route using block copolymer self-assembly. The oxides were characterized by X-ray diffraction, infrared spectroscopy, thermal analyses, nitrogen adsorption/desorption, electron microscopy and electronic paramagnetic resonance. A mesoporous anatase containing amorphous manganese oxide particles could be obtained with a 0.2 Mn:Ti molar ratio. At higher manganese loading (0.5 Mn:Ti molar ratio), segregation of crystalline manganese oxide occurred. The influence of block copolymer and manganese salt on the oxide structure was discussed. The evolution of the textural and structural characteristics of the materials upon hydrothermal treatment was also investigated. - Graphical abstract: One-pot amorphous MnO{sub 2} supported on mesoporous anataseTiO{sub 2}. - Highlights: • Mesoporous manganese titanium oxides were synthesized using block copolymer. • Block copolymers form complexes with Mn{sup 2+} from MnCl{sub 2}. • With block copolymer, manganese oxide can be dispersed around the titania crystallites. • With Mn(acac){sub 2}, manganese is dispersed inside titania. • MnOOH crystallizes outside mesoporous titania during hydrothermal treatment.

  2. Brownian dynamics simulation of amphiphilic block copolymers with different tail lengths, comparison with theory and comicelles.

    PubMed

    Hafezi, Mohammad-Javad; Sharif, Farhad

    2015-11-01

    Study on the effect of amphiphilic copolymers structure on their self assembly is an interesting subject, with important applications in the area of drug delivery and biological system treatments. Brownian dynamics simulations were performed to study self-assembly of the linear amphiphilic block copolymers with the same hydrophilic head, but hydrophobic tails of different lengths. Critical micelle concentration (CMC), gyration radius distribution, micelle size distribution, density profiles of micelles, shape anisotropy, and dynamics of micellization were investigated as a function of tail length. Simulation results were compared with predictions from theory and simulation for mixed systems of block copolymers with long and short hydrophobic tail, reported in our previous work. Interestingly, the equilibrium structural and dynamic parameters of pure and mixed block copolymers were similarly dependant on the intrinsic/apparent hydrophobic block length. Log (CMC) was, however; proportional to the tail length and had a different behavior compared to the mixed system. The power law scaling relation of equilibrium structural parameters for amphiphilic block copolymers predicts the same dependence for similar hydrophobic tail lengths, but the power law prediction of CMC is different, which is due to its simplifying assumptions as discussed here.

  3. Conjugated block copolymer photovoltaics with near 3% efficiency through microphase separation.

    PubMed

    Guo, Changhe; Lin, Yen-Hao; Witman, Matthew D; Smith, Kendall A; Wang, Cheng; Hexemer, Alexander; Strzalka, Joseph; Gomez, Enrique D; Verduzco, Rafael

    2013-06-12

    Organic electronic materials have the potential to impact almost every aspect of modern life including how we access information, light our homes, and power personal electronics. Nevertheless, weak intermolecular interactions and disorder at junctions of different organic materials limit the performance and stability of organic interfaces and hence the applicability of organic semiconductors to electronic devices. Here, we demonstrate control of donor-acceptor heterojunctions through microphase-separated conjugated block copolymers. When utilized as the active layer of photovoltaic cells, block copolymer-based devices demonstrate efficient photoconversion well beyond devices composed of homopolymer blends. The 3% block copolymer device efficiencies are achieved without the use of a fullerene acceptor. X-ray scattering results reveal that the remarkable performance of block copolymer solar cells is due to self-assembly into mesoscale lamellar morphologies with primarily face-on crystallite orientations. Conjugated block copolymers thus provide a pathway to enhance performance in excitonic solar cells through control of donor-acceptor interfaces.

  4. Thermodynamics and phase behavior of acid-tethered block copolymers with ionic liquids.

    PubMed

    Jung, Ha Young; Park, Moon Jeong

    2016-12-21

    We investigate the phase behavior of acid-tethered block copolymers with and without ionic liquids. Two phosphonated block copolymers and their sulfonated analogs were synthesized by fine-tuning the degree of polymerization and the acid content. The block copolymers carrying acid groups with ionic liquids exhibited rich phase sequences, i.e., disorder-lamellae (LAM), gyroid-LAM, gyroid-hexagonal cylinder (HEX), and gyroid-A15 lattice, and the cation/anion ratio in the ionic liquid exerted profound effects on the segregation strength and topology of the self-assembled structures. Additionally, using ionic liquids with excessive cation content was found to enhance the effective Flory-Huggins interaction parameter, χeff, of the samples. However, as the anion content of the ionic liquids increased the segregation strength decreased. This is attributed to the packing frustration accompanied by the prevailing repulsive electrostatic interactions of the anions in the ionic liquid and the polymer matrix. As the hydrophobicity of the ionic liquids increased, well-defined ordered phases emerged in the phosphonated block copolymers with increased anion content, contrary to the disordered phases of the sulfonated samples. Thus, the balance between solvation energy of the anions and the electrostatic interactions is a key determinant of the thermodynamics of acid-tethered block copolymers containing ionic liquids.

  5. The effect of RAFT-derived cationic block copolymer structure on gene silencing efficiency.

    PubMed

    Hinton, Tracey M; Guerrero-Sanchez, Carlos; Graham, Janease E; Le, Tam; Muir, Benjamin W; Shi, Shuning; Tizard, Mark L V; Gunatillake, Pathiraja A; McLean, Keith M; Thang, San H

    2012-10-01

    In this work a series of ABA tri-block copolymers was prepared from oligo(ethylene glycol) methyl ether methacrylate (OEGMA(475)) and N,N-dimethylaminoethyl methacrylate (DMAEMA) to investigate the effect of polymer composition on cell viability, siRNA uptake, serum stability and gene silencing. Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization was used as the method of polymer synthesis as this technique allows the preparation of well-defined block copolymers with low polydispersity. Eight block copolymers were prepared by systematically varying the central cationic block (DMAEMA) length from 38 to 192 monomer units and the outer hydrophilic block (OEGMA(475)) from 7 to 69 units. The polymers were characterized using size exclusion chromatography and (1)H NMR. Chinese Hamster Ovary-GFP and Human Embryonic Kidney 293 cells were used to assay cell viability while the efficiency of block copolymers to complex with siRNA was evaluated by agarose gel electrophoresis. The ability of the polymer-siRNA complexes to enter into cells and to silence the targeted reporter gene enhanced green fluorescent protein (EGFP) was measured by using a CHO-GFP silencing assay. The length of the central cationic block appears to be the key structural parameter that has a significant effect on cell viability and gene silencing efficiency with block lengths of 110-120 monomer units being the optimum. The ABA block copolymer architecture is also critical with the outer hydrophilic blocks contributing to serum stability and overall efficiency of the polymer as a delivery system.

  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. Structure and ionic conductivity of block copolymer electrolytes over a wide salt concentration range

    NASA Astrophysics Data System (ADS)

    Chintapalli, Mahati; Le, Thao; Venkatesan, Naveen; Thelen, Jacob; Rojas, Adriana; Balsara, Nitash

    Block copolymer electrolytes are promising materials for safe, long-lasting lithium batteries because of their favorable mechanical and ion transport properties. The morphology, phase behavior, and ionic conductivity of a block copolymer electrolyte, SEO mixed with LiTFSI was studied over a wide, previously unexplored salt concentration range using small angle X-ray scattering, differential scanning calorimetry and ac impedance spectroscopy, respectively. SEO exhibits a maximum in ionic conductivity at twice the salt concentration that PEO, the homopolymer analog of the ion-containing block, does. This finding is contrary to prior studies that examined a more limited range of salt concentrations. In SEO, the phase behavior of the PEO block and LiTFSI closely resembles the phase behavior of homopolymer PEO and LiTFSI. The grain size of the block copolymer morphology was found to decrease with increasing salt concentration, and the ionic conductivity of SEO correlates with decreasing grain size. Structural effects impact the ionic conductivity-salt concentration relationship in block copolymer electrolytes. SEO: polystyrene-block-poly(ethylene oxide); also PS-PEO LiTFSI: lithium bis(trifluoromethanesulfonyl imide

  8. Instantaneous Directional Growth of Block Copolymer Nanowires During Heterogeneous Radical Polymerization (HRP).

    PubMed

    Lu, Chunliang; Urban, Marek W

    2016-04-13

    Polymeric nanowires that consist of ultrahigh molecular weight block copolymers were instantaneously prepared via one-step surfactant-free heterogeneous radical polymerization (HRP). Under heterogeneous reaction and initiator-starvation conditions, the sequential copolymerization of hydrophilic and hydrophobic monomers facilitates the formation of amphiphilic ultrahigh molecular weight block copolymers, which instantaneously assemble to polymeric nanowires. As polymerization progresses, initially formed nanoparticles exhibit the directional growth due to localized repulsive forces of hydrophilic blocks and confinement of the hydrophobic blocks that adopt favorable high aspect ratio nanowire morphologies. Using one-step synthetic approach that requires only four ingredients (water as a solvent, two polymerizable monomers (one hydrophilic and one hydrophobic), and water-soluble initiator), block copolymer nanowires ∼70 nm in diameter and hundreds of microns in length are instantaneously grown. For example, when 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) and styrene (St) were copolymerized, high aspect ratio nanowires consist of ultrahigh (>10(6) g/mol) molecular weight pDMAEMA-b-St block copolymers and the presence of temperature responsive pDMAEMA blocks facilitates nanowire diameter changes as a function of temperature. These morphologies may serve as structural components of the higher order biological constructs at micro and larger length scales, ranging from single strand nanowires to engineered biomolecular networks capable of responding to diverse and transient environmental signals, and capable of dimensional changes triggered by external stimuli.

  9. Mass-action model analysis of the apparent molar volume and heat capacity of pluronics in water and liposome suspensions at 25 °C.

    PubMed

    Quirion, François; Meilleur, Luc; Lévesque, Isabelle

    2013-07-09

    Pluronics are block copolymers composed of a central block of polypropylene oxide and two side chains of polyethylene oxide. They are used in water to generate aggregates and gels or added to phospholipid suspensions to prepare microparticles for drug delivery applications. The structure of these systems has been widely investigated. However, little is known about the mechanisms leading to these structures. This investigation compares the apparent molar volumes and heat capacities of Pluronics F38, F108, F127, P85, P104, and P103 at 25 °C in water and in the presence of lecithin liposomes. The changes in molar volumes, heat capacities, and enthalpies generated by a mass-action model are in good agreement with the loss of hydrophobic hydration of the polypropylene oxide central block of the Pluronics. However, the molecularity of the endothermic transitions is much smaller than the aggregation numbers reported in the literature for the same systems. It is suggested that Pluronics go through dehydration of their central block to form unimolecular or small entities having a hydrophobic polypropylene oxide core. In water, these entities would assemble athermally to form larger aggregates. In the presence of liposomes, they would be transferred into the hydrophobic lecithin bilayers of the liposomes. Light transmission experiments suggest that the liposome suspensions are significantly altered only when the added Pluronics are in the dehydrated state.

  10. Order-Disorder Transitions in Cross-Linked Block Copolymer Solids

    SciTech Connect

    Das, J.

    2005-01-12

    With a view toward creating solid block copolymers wherein the order-disorder transition can be accessed many times they investigated the nature of order-disorder transitions in cross-linked diblock copolymer melts using synergistic theory and experiment. A mean-field theory based on a coarse grained free-energy and the Random Phase Approximation (RPA) is developed for the system of interest. The quenched distribution of cross-links is averaged using the replica method. The phase behavior of a particular A-B block copolymer melt with a randomly cross-linked B-Block is determined as a function of the Florry-Huggins interaction parameter ({chi}) and the average number of cross-links per chain N{sub c}. They find for a cross-link density greater than N*{sub c} the B monomers are localized within a region of size {zeta} {approx} (N{sub c} - N*{sub c}){sup -1/2}. The cross-links strongly oppose ordering in the system as {zeta} becomes comparable to the radius of gyration of the block copolymer chain. As such the order-disorder transition temperature T{sub ODT} decreases precipitously when N{sub c} > N*{sub c}. When N{sub c} < N*{sub c}, T{sub ODT} increases weakly with N{sub c}. Experiments were conducted on cross-linked polystyrene-block-polyisoprene copolymer samples wherein the polyisoprene block was selectively cross-linked at a temperature well above the order-disorder transition temperature of the pure block copolymer. Small angle X-ray scattering (SAXS) and birefringence measurements on the cross-linked samples are consistent with the theoretical prediction. T{sub ODT} decreases rapidly when the cross-linking density exceeds the critical cross-linking density.

  11. Modification of the adhesive properties of silicone-based coatings by block copolymers.

    PubMed

    Ngo, T Chinh; Kalinova, Radostina; Cossement, Damien; Hennebert, Elise; Mincheva, Rosica; Snyders, Rony; Flammang, Patrick; Dubois, Philippe; Lazzaroni, Roberto; Leclère, Philippe

    2014-01-14

    The improvement of the (bio)adhesive properties of elastomeric polydimethylsiloxane (PDMS) coatings is reported. This is achieved by a surface modification consisting of the incorporation of block copolymers containing a PDMS block and a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) block in a PDMS matrix, followed by matrix cross-linking and immersion of the obtained materials in water. Contact angle measurements (CA), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) showed the presence of the PDMAEMA block at the surface, drastic morphology changes, and improved adhesion properties after immersion in water. Finally, underwater bioadhesion tests show that mussels adhere only to block copolymer-filled coatings and after immersion in water, i.e., when the PDMAEMA blocks have been brought to the coating surface. These observations highlight the significant role of hydrophilic groups in the surface modification of silicone coatings.

  12. Manipulating Interfaces through Surface Confinement of Poly(glycidyl methacrylate)-block-poly(vinyldimethylazlactone), a Dually Reactive Block Copolymer

    SciTech Connect

    Lokitz, Bradley S; Wei, Jifeng; Hinestrosa Salazar, Juan P; Ivanov, Ilia N; Browning, James B; Ankner, John Francis; Kilbey, II, S Michael; Messman, Jamie M

    2012-01-01

    The assembly of dually reactive, well-defined diblock copolymers incorporating the chemoselective/functional monomer, 4,4-dimethyl-2-vinylazlactone (VDMA) and the surface-reactive monomer glycidyl methacrylate (GMA) is examined to understand how competition between surface attachment and microphase segregation influences interfacial structure. Reaction of the PGMA block with surface hydroxyl groups not only anchors the copolymer to the surface, but limits chain mobility, creating brush-like structures comprising PVDMA blocks, which contain reactive azlactone groups. The block copolymers are spin coated at various solution concentrations and annealed at elevated temperature to optimize film deposition to achieve a molecularly uniform layer. The thickness and structure of the polymer thin films are investigated by ellipsometry, infrared spectroscopy, and neutron reflectometry. The results show that deposition of PGMA-b-PVDMA provides a useful route to control film thickness while preserving azlactone groups that can be further modified with biotin-poly(ethylene glycol)amine to generate designer surfaces. The method described herein offers guidance for creating highly functional surfaces, films, or coatings through the use of dually reactive block copolymers and postpolymerization modification.

  13. Polybenzimidazole block copolymers for fuel cell: synthesis and studies of block length effects on nanophase separation, mechanical properties, and proton conductivity of PEM.

    PubMed

    Maity, Sudhangshu; Jana, Tushar

    2014-05-14

    A series of meta-polybenzimidazole-block-para-polybenzimidazole (m-PBI-b-p-PBI), segmented block copolymers of PBI, were synthesized with various structural motifs and block lengths by condensing the diamine terminated meta-PBI (m-PBI-Am) and acid terminated para-PBI (p-PBI-Ac) oligomers. NMR studies and existence of two distinct glass transition temperatures (Tg), obtained from dynamical mechanical analysis (DMA) results, unequivocally confirmed the formation of block copolymer structure through the current polymerization methodology. Appropriate and careful selection of oligomers chain length enabled us to tailor the block length of block copolymers and also to make varieties of structural motifs. Increasingly distinct Tg peaks with higher block length of segmented block structure attributed the decrease in phase mixing between the meta-PBI and para-PBI blocks, which in turn resulted into nanophase segregated domains. The proton conductivities of proton exchange membrane (PEM) developed from phosphoric acid (PA) doped block copolymer membranes were found to be increasing substantially with increasing block length of copolymers even though PA loading of these membranes did not alter appreciably with varying block length. For example when molecular weight (Mn) of blocks were increased from 1000 to 5500 then the proton conductivities at 160 °C of resulting copolymers increased from 0.05 to 0.11 S/cm. Higher block length induced nanophase separation between the blocks by creating less morphological barrier within the block which facilitated the movement of the proton in the block and hence resulting higher proton conductivity of the PEM. The structural varieties also influenced the phase separation and proton conductivity. In comparison to meta-para random copolymers reported earlier, the current meta-para segmented block copolymers were found to be more suitable for PBI-based PEM.

  14. Morphological and physical characterization of poly(styrene-isobutylene-styrene) block copolymers and ionomers thereof

    NASA Astrophysics Data System (ADS)

    Baugh, Daniel Webster, III

    Poly(styrene-isobutylene-styrene) block copolymers made by living cationic polymerization using a difunctional initiator and the sequential monomer addition technique were analyzed using curve-resolution software in conjunction with high-resolution GPC. Fractional precipitation and selective solvent extraction were applied to a representative sample in order to confirm the identity of contaminating species. The latter were found to be low molecular weight polystyrene homopolymer, diblock copolymer, and higher molecular weight segmented block copolymers formed by intermolecular electrophilic aromatic substitution linking reactions occurring late in the polymerization of the styrene outer blocks. Solvent-cast films of poly(styrene-isobutylene-styrene) (PS-PIB-PS) block copolymers and block ionomers were analyzed using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Four block copolymer samples with center block molecular weights of 52,000 g/mol and PS volume fractions (o sbPS) ranging from 0.17 to 0.31 were studied. All samples exhibited hexagonally packed cylinders of PS within the PIB matrix. Cylinder spacing was in the range 32 to 36 nm for most samples, while cylinder diameters varied from 14 to 21 nm. Porod analysis of the scattering data indicated the presence of isolated phase mixing and sharp phase boundaries. PS-PIB-PS block copolymers and ionomers therefrom were analyzed using dynamic mechanical analysis (DMA) and tensile testing. The study encompassed five block copolymer samples with similar PIB center blocks with molecular weights of approx52,000 g/mol and PS weight fractions ranging from 0.127 to 0.337. Ionomers were prepared from two of these materials by lightly sulfonating the PS outer blocks. Sulfonation levels varied from 1.7 to 4.7 mol % and the sodium and potassium neutralized forms were compared to the parent block copolymers. Dynamic mechanical analysis (DMA) of the block copolymer films indicated the existence

  15. 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.

  16. Millisecond ordering of block-copolymer films via photo-thermal gradients

    SciTech Connect

    Majewski, Pawel W.; Yager, Kevin G.

    2015-03-12

    For the promise of self-assembly to be realized, processing techniques must be developed that simultaneously enable control of the nanoscale morphology, rapid assembly, and, ideally, the ability to pattern the nanostructure. Here, we demonstrate how photo-thermal gradients can be used to control the ordering of block-copolymer thin films. Highly localized laser heating leads to intense thermal gradients, which induce a thermophoretic force on morphological defects. This increases the ordering kinetics by at least 3 orders-of-magnitude, compared to conventional oven annealing. By simultaneously exploiting the thermal gradients to induce shear fields, we demonstrate uniaxial alignment of a block-copolymer film in less than a second. Finally, we provide examples of how control of the incident light-field can be used to generate prescribed configurations of block-copolymer nanoscale patterns.

  17. Controlling size and patchiness of soft nanoparticles via kinetically arrested co-assembly of block copolymers

    NASA Astrophysics Data System (ADS)

    Santos, Jose; Herrera-Alonso, Margarita

    2013-03-01

    Engineering patchy particles from block copolymers provides an effective route for the preparation of nanoparticles with surface heterogeneity and unique properties. In the current work, co-assembly of block copolymers amphiphiles with distinct macromolecular architectures under kinetically arrested conditions was used to control the size and patchiness of polymeric nanoparticles. The block copolymer mixture is composed of linear and linear-dendritic polymeric amphiphiles, the later of which provides pre-assembled ``patches'' with well-controlled dimensions and chemical functionality. Parameters including but not limited to the molecular diffusity of the amphiphiles and the kinetics of self-assembly were found to play an important role on the control of the particle size and formation of the patches. The patchy particles are stable for several months and its stability against protein/blood plasma solutions can be tuned. We will also discuss the use of these constructs to probe nanoparticle-cell interactions.

  18. Millisecond ordering of block-copolymer films via photo-thermal gradients

    DOE PAGES

    Majewski, Pawel W.; Yager, Kevin G.

    2015-03-12

    For the promise of self-assembly to be realized, processing techniques must be developed that simultaneously enable control of the nanoscale morphology, rapid assembly, and, ideally, the ability to pattern the nanostructure. Here, we demonstrate how photo-thermal gradients can be used to control the ordering of block-copolymer thin films. Highly localized laser heating leads to intense thermal gradients, which induce a thermophoretic force on morphological defects. This increases the ordering kinetics by at least 3 orders-of-magnitude, compared to conventional oven annealing. By simultaneously exploiting the thermal gradients to induce shear fields, we demonstrate uniaxial alignment of a block-copolymer film in lessmore » than a second. Finally, we provide examples of how control of the incident light-field can be used to generate prescribed configurations of block-copolymer nanoscale patterns.« less

  19. Structural Color for Additive Manufacturing: 3D-Printed Photonic Crystals from Block Copolymers.

    PubMed

    Boyle, Bret M; French, Tracy A; Pearson, Ryan M; McCarthy, Blaine G; Miyake, Garret M

    2017-03-28

    The incorporation of structural color into 3D printed parts is reported, presenting an alternative to the need for pigments or dyes for colored parts produced through additive manufacturing. Thermoplastic build materials composed of dendritic block copolymers were designed, synthesized, and used to additively manufacture plastic parts exhibiting structural color. The reflection properties of the photonic crystals arise from the periodic nanostructure formed through block copolymer self-assembly during polymer processing. The wavelength of reflected light could be tuned across the visible spectrum by synthetically controlling the block copolymer molecular weight and manufacture parts that reflected violet, green, or orange light with the capacity to serve as selective optical filters and light guides.

  20. 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.

  1. 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.

  2. Individually addressable thermo- and redox-responsive block copolymers by combining anionic polymerization and RAFT protocols.

    PubMed

    Schmidt, Bernhard V K J; Elbert, Johannes; Barner-Kowollik, Christopher; Gallei, Markus

    2014-04-01

    A novel diblock copolymer consisting of poly(vinylferrocene) (PVFc) and poly(N,N-diethylacrylamide) (PDEA) is synthesized via a combination of anionic and RAFT polymerization. The use of a novel route to hydroxyl-end-functionalized metallopolymers in anionic polymerization and subsequent esterification with a RAFT agent leads to a PVFc macro-CTA (M¯n = 3800 g mol(-1) ; Đ = 1.17). RAFT polymerization with DEA affords block copolymers as evidenced by (1) H NMR spectroscopy as well as size exclusion chromatography (6400 ≤ M¯n≤ 33700 g mol(-1) ; 1.31 ≤ Đ 1.28). Self-assembly of the amphiphilic block copolymers in aqueous solution leads to micelles as shown via TEM. Importantly, the distinct thermo-responsive and redox-responsive character of the blocks is probed via dynamic light scattering and found to be individually and repeatedly addressable.

  3. The versatility in morphology and physical properties offered by chain shuttled olefin block copolymers

    NASA Astrophysics Data System (ADS)

    Weinhold, Jeffrey

    2014-03-01

    Chain shuttling catalysis enables the production of olefin block copolymers (OBCs) with a wide range of block compositions. Unique morphology and property combinations can be achieved with highly crystalline hard blocks and low crystallinity or fully amorphous soft blocks. The effect of the amount of comonomer in the soft blocks on phase behavior, morphology and properties will be the focus of this presentation. In one class of materials, the soft blocks contain just enough octene comonomer to give elastic behavior but, unlike a random copolymer-based olefin elastomer, the soft segments are held together by thick crystals formed by the hard blocks. In addition to strengthening the network, these crystals provide temperature resistance and, by solidifying at higher temperature, they allow faster product fabrication. Increasing the soft block's octene content yields the next class of materials which have improved compatibility with polypropylene. This property allows the formation of fine, uniformly-dispersed OBC elastomer particles in PP. Since the impact strength of toughened PP increases as the particle size is reduced, a lower amount of elastomer is required to achieve an application's target for toughness. The direct benefit of lower elastomer loading is an increase in modulus, which enables lightweighting in applications. With further increases in the soft block's octene content, the incompatibility between the hard and soft blocks becomes large enough to cause the OBCs to form ordered melt morphologies. In the solid state, the alternating crystalline and amorphous regions have surprisingly large domain spacings and, due to the difference in refractive index between the domains, the periodicity results in a partial photonic band gap for frequencies in the visible spectrum. Comparisons to the morphology of monodisperse block copolymers and the predictions of theories will be presented. Also, the results of an extension to strong segregation theory will be shown

  4. A comparative kinetics study of thermal degradation of some novel ABA block copolymers

    NASA Astrophysics Data System (ADS)

    Blanco, Ignazio; Cicala, Gianluca; Mamo, Antonino; Latteri, Alberta; Recca, Antonino

    2012-07-01

    Some novel ABA block copolymers, synthesized with three different molecular weights, where the block A is a PPO while the block B is a random copoly(aryl ether sulfone), were studied by TGA and DTA techniques, in both flowing nitrogen and static air atmosphere, in order to draw useful information about their resistance to thermal degradation. The results obtained for the various compounds investigated were discussed and compared with each other and a thermal stability classifications in the studied environments were made.

  5. Slip-spring model of entangled rod-coil block copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Muzhou; Likhtman, Alexei E.; Olsen, Bradley D.

    2015-03-01

    Understanding the dynamics of rod-coil block copolymers is important for optimal design of functional nanostructured materials for organic electronics and biomaterials. Recently, we proposed a reptation theory of entangled rod-coil block copolymers, predicting the relaxation mechanisms of activated reptation and arm retraction that slow rod-coil dynamics relative to coil and rod homopolymers, respectively. In this work, we introduce a coarse-grained slip-spring model of rod-coil block copolymers to further explore these mechanisms. First, parameters of the coarse-grained model are tuned to match previous molecular dynamics simulation results for coils, rods, and block copolymers. For activated reptation, rod-coil copolymers are shown to disfavor configurations where the rod occupies curved portions of the entanglement tube of randomly varying curvature created by the coil ends. The effect of these barriers on diffusion is quantitatively captured by considering one-dimensional motion along an entanglement tube with a rough free energy potential. Finally, we analyze the crossover between the two mechanisms. The resulting dynamics from both mechanisms acting in combination is faster than from each one individually.

  6. Phase Behavior of Block Copolymer directed Nanostructured Organic/Inorganic Hybrids

    NASA Astrophysics Data System (ADS)

    Wiesner, Ulrich

    2002-03-01

    The study of amphiphilic polymer based polymer-ceramic hybrid materials is an exciting emerging research area offering enormous scientific and technological promise. By choice of the appropriate block copolymer system (PI-b-PEO) as well as ceramic precursors (organically modified ceramic precursors, ormocers) unprecedented morphology control on the nanoscale is obtained. It is based on a unique polymer-ceramic interface that can be characterized in detail by solid-state NMR measurements. The hydrophilic parts of the block copolymers are completely integrated into the ceramic phase, analogous to what is often found in biological hybrid materials. The resulting composites can be described as a 'quasi two-phase system' allowing for a more rational hybrid morphology design based on the current understanding of the phase behavior of block copolymers and copolymer-homopolymer mixtures. The structures generated on the nanoscale are a result of a fine balance of competing interactions, another feature of complex biological systems. In the present contribution the synthesis and characterization of nanostructured hybrids based on aluminosilicates will be described. Besides morphologies known from other polymer studies the existence of a 'Plumber's Nightmare' phase is suggested. This indicates subtle, not yet understood differences of the ternary 'pseudo' phase diagram (morphology diagram) of these systems to behavior of conventional block copolymers. Implications of these findings for further explorations of the complex phase space of the present novel nanostructured organic-inorganic hybrid systems will be discussed.

  7. PEG–Polypeptide Block Copolymers as pH-Responsive Endosome-Solubilizing Drug Nanocarriers

    PubMed Central

    2015-01-01

    Herein we report the potential of click chemistry-modified polypeptide-based block copolymers for the facile fabrication of pH-sensitive nanoscale drug delivery systems. PEG–polypeptide copolymers with pendant amine chains were synthesized by combining N-carboxyanhydride-based ring-opening polymerization with post-functionalization using azide–alkyne cycloaddition. The synthesized block copolymers contain a polypeptide block with amine-functional side groups and were found to self-assemble into stable polymersomes and disassemble in a pH-responsive manner under a range of biologically relevant conditions. The self-assembly of these block copolymers yields nanometer-scale vesicular structures that are able to encapsulate hydrophilic cytotoxic agents like doxorubicin at physiological pH but that fall apart spontaneously at endosomal pH levels after cellular uptake. When drug-encapsulated copolymer assemblies were delivered systemically, significant levels of tumor accumulation were achieved, with efficacy against the triple-negative breast cancer cell line, MDA-MB-468, and suppression of tumor growth in an in vivo mouse model. PMID:24813025

  8. Mixing a sol and a precipitate of block copolymers with different block ratios leads to an injectable hydrogel.

    PubMed

    Yu, Lin; Zhang, Zheng; Zhang, Huan; Ding, Jiandong

    2009-06-08

    A facile method to obtain a thermoreversible physical hydrogel was found by simply mixing an aqueous sol of a block copolymer with a precipitate of a similar copolymer but with a different block ratio. Two ABA-type triblock copolymers poly(D,L-lactic acid-co-glycolic acid)-B-poly(ethylene glycol)-B-poly(D,L-lactic acid-co-glycolic acid) (PLGA-PEG-PLGA) were synthesized. One sample in water was a sol in a broad temperature region, while the other in water was just a precipitate. The mixture of these two samples with a certain mix ratio underwent, however, a sol-to-gel-to-precipitate transition upon an increase of temperature. A dramatic tuning of the sol-gel transition temperature was conveniently achieved by merely varying mix ratio, even in the case of a similar molecular weight. Our study indicates that the balance of hydrophobicity and hydrophilicity within this sort of amphiphilic copolymers is critical to the inverse thermal gelation in water resulting from aggregation of micelles. The availability of encapsulation and sustained release of lysozyme, a model protein by the thermogelling systems was confirmed. This "mix" method provides a very convenient approach to design injectable thermogelling biomaterials with a broad adjustable window, and the novel copolymer mixture platform is potentially used in drug delivery and other biomedical applications.

  9. Structural characterization and adsorption properties of pluronic F127 onto iron oxides magnetic nanoparticles.

    PubMed

    Dehvari, Khalilalrahman; Lin, Kuen-Song; Wang, Steven S S

    2014-03-01

    Superparamagnetic iron oxide nanoparticles coated with polymers have shown low toxicity and chemical stability in physiological condition, thereby can be used to deliver encapsulated drugs throughout the body by external magnetic fields. In this study, magnetic nanoparticles were synthesized thorough co-precipitation method and their interaction with Pluronic F127 block copolymer as well as adsorption properties of polymer onto nanoparticles were investigated. Adsorption measurement revealed different adsorption behaviors below and above the polymer's critical micelle concentration. The Freundlich isotherm was found to better describe the adsorption behavior of Pluronic F127 onto SIONPs particles below the block copolymer critical micelle concentration. At higher concentration, the adsorbed amount is likely to diminish due to interpenetration of the adsorbed macromolecular micelles and volume-excluded effects for block copolymers. Furthermore, magnetic nanocomposites with different concentration of polymers were prepared through hydrothermal method. The crystalline structure, morphology, pore structure, and magnetic properties of magnetic nanoparticles/nanocomposites products at different pH and polymer concentration were studied. Results showed that due to the hematite impurities, magnetic nanocomposites synthesized at higher pH have lower magnetization.

  10. The structure of pH dependent block copolymer micelles: charge and ionic strength dependence

    SciTech Connect

    Pople, John A

    2002-08-06

    We characterize the structures of various polyelectrolyte block copolymer micelles in dilute aqueous solution as a function of pH and ionic strength. The block copolymers carry a common core block 2-(diethylamino) ethyl methacrylate (DEAEMA) and one of three coronal blocks: 2-(dimethylamino) ethyl methacrylate (DMAEMA), polyethylene oxide (PEO), and DMAEMA whose side-chain amine groups are selectively quaternized with benzyl chloride (Q-DMAEMA). The PEO-DEAEMA, DMAEMA-DEAEMA, and Q-DMAEMA-DEAEMA copolymers form micelles with electrostatically neutral, weakly charged, and highly charged coronae, respectively. We adjust the fractional charge a on the DEAEMA and DMAEMA blocks by adjusting the solution pH. For DMAEMA-DEAEMA micelles increasing the fractional charge a swells the micelle corona while decreasing the aggregation number due to electrostatic repulsions. The decrease in aggregation number is also observed with increasing a for the PEO-DEAEMA and Q-DMAEMA-DEAEMA micelles, due to electrostatic repulsions between the hydrophobic DEAEMA blocks. Increasing the ionic strength causes the DMAEMA-DEAEMA micelle corona to shrink as the salt screens electrostatic repulsions within the corona. In all three copolymers increases in the ionic strength causes the micelle aggregation number to increase by screening the electrostatic repulsions between chains. Trends in the corona thickness with varying fractional charge and ionic strength are compared with a number of theoretical models providing additional insight into the micelle structure.

  11. Collapse transitions in thermosensitive multi-block copolymers: A Monte Carlo study

    SciTech Connect

    Rissanou, Anastassia N.; Tzeli, Despoina S.; Anastasiadis, Spiros H.; Bitsanis, Ioannis A.

    2014-05-28

    Monte Carlo simulations are performed on a simple cubic lattice to investigate the behavior of a single linear multiblock copolymer chain of various lengths N. The chain of type (A{sub n}B{sub n}){sub m} consists of alternating A and B blocks, where A are solvophilic and B are solvophobic and N = 2nm. The conformations are classified in five cases of globule formation by the solvophobic blocks of the chain. The dependence of globule characteristics on the molecular weight and on the number of blocks, which participate in their formation, is examined. The focus is on relative high molecular weight blocks (i.e., N in the range of 500–5000 units) and very differing energetic conditions for the two blocks (very good—almost athermal solvent for A and bad solvent for B). A rich phase behavior is observed as a result of the alternating architecture of the multiblock copolymer chain. We trust that thermodynamic equilibrium has been reached for chains of N up to 2000 units; however, for longer chains kinetic entrapments are observed. The comparison among equivalent globules consisting of different number of B-blocks shows that the more the solvophobic blocks constituting the globule the bigger its radius of gyration and the looser its structure. Comparisons between globules formed by the solvophobic blocks of the multiblock copolymer chain and their homopolymer analogs highlight the important role of the solvophilic A-blocks.

  12. Polarized photoluminescence from poly(p-phenylene-ethynylene) via a block copolymer nanotemplate.

    PubMed

    Breen, Craig A; Deng, Tao; Breiner, Thomas; Thomas, Edwin L; Swager, Timothy M

    2003-08-20

    A new approach based on a conjugated polymer/block copolymer guest/host system for the generation of polarized photoluminescence is reported. Synthetic modification of a poly(p-phenylene-ethynylene) (PPE) conjugated polymer is used for domain-specific incorporation into a cylindrical morphology block copolymer host matrix. Subsequent ordering of the host nanostructure via roll cast processing templates uniaxial alignment of the guest PPE. The ordered films are optically anisotropic displaying both polarized absorption with a dichroic ratio of 3.0 at 440 nm and polarized emission with a polarization ratio of 7.3 at 472 nm.

  13. Ocular permeability of pirenzepine hydrochloride enhanced by methoxy poly(ethylene glycol)-poly(D, L-lactide) block copolymer.

    PubMed

    Tu, Jiasheng; Pang, Hui; Yan, Zhen; Li, Pengmei

    2007-10-01

    Methoxy poly(ethylene glycol)-poly(D, L-lactide) block copolymer was tested as an ocular permeation enhancer for pirenzepine hydrochloride. The block copolymers with the methoxy poly(ethylene glycol) to poly(D, L-lactide) weight ratio of 80/20, 50/50, 40/60 were synthesized by a ring-opening polymerization procedure. In vitro transcorneal experiments demonstrated that the block copolymer 80/20 significantly enhanced the transcorneal permeation of pirenzepine at the mass ratio of 1/1.4 (pirenzepine hydrochloride/copolymer). Interaction between pirenzepine and copolymer was identified by infrared spectroscopy analysis and dialysis experiments. Ocular pharmacokinetics of pirenzepine/copolymer preparation by in vivo instillation experiments confirmed that block copolymer could enhance the ocular penetration of pirenzepine. Ocular chronic toxicity experiments of block copolymer and pirenzepine/copolymer preparation were studied on rabbits, and no significant toxicity in both groups was observed within 9 months. It could conclude that pirenzepine/copolymer preparation is effective and safe in ocular delivery of pirenzepine.

  14. Block copolymer morphologies confined by square-shaped particle: Hard and soft confinement

    NASA Astrophysics Data System (ADS)

    Zhang, Qiyi; Yang, Wenyan; Hu, Kaiyan

    2016-11-01

    The self-assembly of diblock copolymers confined around one square-shaped particle is studied systematically within two-dimensional self-consistent field theory (SCFT). In this model, we assume that the thin block copolymer film is confined in the vicinity of a square-shaped particle by a homopolymer melt, which is equivalent to the poor solvents. Multiple sequences of square-shaped particle-induced copolymer aggregates with different shapes and self-assembled internal morphologies are predicted as functions of the particle size, the structural portion of the copolymer, and the volume fraction of the copolymer. A rich variety of aggregates are found with complex internal self-assembled morphologies including complex structures of the vesicle, with one or several inverted micelle surrounded by the outer monolayer with the particle confined in the core. These results demonstrate that the assemblies of diblock copolymers formed around the square-shaped particle in poor solvents are of immediate interest to the assembly of copolymer and the morphology of biomembrane in the confined environment, as well as to the transitions of vesicles to micelles. Project supported by the National Natural Science Foundation of China (Grant No. 20804060) and the Research Foundation of Chongqing University of Science and Technology, China (Grant No. CK2013B16).

  15. Simultaneous conduction of electronic charge and lithium ions in block copolymers.

    PubMed

    Patel, Shrayesh N; Javier, Anna E; Stone, Greg M; Mullin, Scott A; Balsara, Nitash P

    2012-02-28

    The main objective of this work is to study charge transport in mixtures of poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-PEO) block copolymers and lithium bis(trifluoromethanesulfonyl) imide salt (LiTFSI). The P3HT-rich microphase conducts electronic charge, while the PEO-rich microphase conducts ionic charge. The nearly symmetric P3HT-PEO copolymer used in this study self-assembles into a lamellar phase. In contrast, the morphologies of asymmetric copolymers with P3HT as the major component are dominated by nanofibrils. A combination of ac and dc impedance measurements was used to determine the electronic and ionic conductivities of our samples. The ionic conductivities of P3HT-PEO/LiTFSI mixtures are lower than those of mixtures of PEO homopolymer and LiTFSI, in agreement with published data obtained from other block copolymer/salt mixtures. In contrast, the electronic conductivities of the asymmetric P3HT-PEO copolymers are significantly higher than those of the P3HT homopolymer. This is unexpected because of the presence of the nonelectronically conducting PEO microphase. This implies that the intrinsic electronic conductivity of the P3HT microphase in P3HT-PEO copolymers is significantly higher than that of P3HT homopolymers.

  16. A Failure and Structural Analysis of Block Copolymer Electrolytes for Rechargeable Lithium Metal Batteries

    NASA Astrophysics Data System (ADS)

    Stone, Gregory Michael

    The dissertation reports on the use of block copolymer electrolytes in rechargeable lithium metal batteries. The block copolymer studied is a polystyrene- block-poly(ethylene oxide) (SEO) block copolymer with roughly equal volume fractions of each block. A variety of molecular weights these symmetric SEO copolymers are reported on. A series of poly(ethylene oxide) (PEO) homopolymer electrolytes are also studied to serve as controls. The focus of this dissertation is on the failure of batteries with these block copolymer electrolytes and the structure of the block copolymer electrolytes during operation. The failure mechanism of interest is dendrite formation on the lithium metal electrode during recharge. These dendrites grow through the electrolyte, reach the other electrode, and short-circuit the battery. A comparative study was performed with both the SEO and PEO electrolytes. The study focuses on the total operation time of these electrolytes before the short-circuit occurs. The SEO electrolytes microphase separated into a lamellar microstructure. The microstructure of the SEO electrolytes increase that amount of charge that can be passed before short-circuit by a factor of 11-48 over PEO electrolytes indicating an enhanced resistance to dendrite formation. A disordered SEO electrolyte (no microstructure) showed no improvement over PEO electrolytes. The applied current density and charging time were also varied to determine the effect these experimental conditions have on short-circuit due to dendrite formation in SEO electrolytes. To further understand this failure mechanism, the coverage and size of nonuniform, dendritic structures is studied using scanning electron microscopy (SEM). For the homopolymer electrolyte after short-circuit, the fractional surface coverage of these nonuniform structures on the lithium metal electrode is low (0.11 ± 0.04). For the microstructured block copolymer electrolyte, the fractional surface coverage of

  17. Differential Metabolic Responses to Pluronic in MDR and non-MDR Cells: A Novel Pathway for Chemosensitization of Drug Resistant Cancers

    PubMed Central

    Alakhova, Daria Yu.; Rapoport, Nataliya Y.; Batrakova, Elena V.; Timoshin, Alexander A.; Li, Shu; Nicholls, David; Alakhov, Valery Yu.; Kabanov, Alexander V.

    2011-01-01

    A synthetic amphiphilic block copolymer, Pluronic, is a potent chemosensitizer of multidrug resistant (MDR) cancers that has shown promise in clinical trials. It has unique activities in MDR cells, which include a decrease in ATP pools and inhibition of P-glycoprotein (Pgp) resulting in increased drug accumulation in cells. This work demonstrates that Pluronic rapidly (15 min) translocates into MDR cells and co-localizes with the mitochondria. It inhibits complex I and complex IV of the mitochondria respiratory chain, decreases oxygen consumption and causes ATP depletion in MDR cells. These effects are selective and pronounced for MDR cells compared to non-MDR counterparts and demonstrated for both drug-selected and Pgp-transfected cell models. Furthermore, inhibition of Pgp functional activity also abolishes effects of Pluronic on intracellular ATP levels in MDR cells suggesting that Pgp contributes to increased responsiveness of molecular “targets” of Pluronic in the mitochondria of MDR cells. The Pluronic-caused impairment of respiration in mitochondria of MDR cells is accompanied with a decrease in mitochondria membrane potential, production of ROS, and release of cytochrome c. Altogether these effects eventually enhance drug-induced apoptosis and contribute to potent chemosensitization of MDR tumors by Pluronic. PMID:19815037

  18. Synthesis and micellar characterization of short block length methoxy poly(ethylene glycol)-block-poly(caprolactone) diblock copolymers.

    PubMed

    Letchford, Kevin; Zastre, Jason; Liggins, Richard; Burt, Helen

    2004-05-15

    A series of short block length methoxy poly(ethylene glycol)-block-poly(caprolactone) diblock copolymers was synthesized and characterized in order to assess the potential of these copolymers as a micellar drug-delivery system. Varying the caprolactone:MePEG weight ratio in the reaction mixture allowed the synthesis of diblock copolymers with a MePEG molecular weight of 750 g/mol and PCL block lengths of 2, 5 or 10 repeat units. Phase diagrams of aqueous solutions of the copolymers were constructed which displayed characteristic cloud points and Krafft points. As the degree of polymerization of PCL increased, critical micelle concentration (CMC) values decreased from 6.97 x 10(-1) to 3.38 x 10(-3) g/l, partition equilibrium coefficients (Kv) increased from 1.09 x 10(4) to 22.2 x 10(4),and hydrodynamic diameters increased from 12.2 to 19.5 nm. The micelle morphology was determined to be spherical by transmission electron microscopy.

  19. Characterization of high performance randomly segmented poly(urethane siloxane) and poly(imide siloxane) block copolymers

    NASA Astrophysics Data System (ADS)

    Doǧan, Türkan; Baydoǧan, Nilgün; Köken, Nesrin

    2016-03-01

    Poly(imide siloxane) block copolymers with the same polydimethlysiloxane(APPS) were prepared by using 4,4'-oxydianiline (ODA) and Benzofenon-3,3,4,4-tetrakarboksilik dianhydride(BTDA) to compose the polyimide hard block. APPS and BTDA composed the polysiloxane soft block. The length of polysiloxane soft blocks increased with increasing the length of polyimide hard block. Copolymerization of soft and hard segments were determined by using this method. Copolymer structures could be obtained by holding constant hard block segments and by adjusting and increasing soft block segments. Thus, more flexible randomly segmented poly(imide siloxane) block copolymers can be obtained. These composed structure as flexible and high performance copolymers were characterized by FT-IR and evaluated. The structures were tested mechanically to detect their elastic recovery property as flexible material. The characterization of the samples enabled to examine flexible substrates in order to use in solar cell, aerospace applications and microelectronic devices.

  20. Enantiomeric PLA-PEG block copolymers and their stereocomplex micelles used as rifampin delivery

    NASA Astrophysics Data System (ADS)

    Chen, Li; Xie, Zhigang; Hu, Junli; Chen, Xuesi; Jing, Xiabin

    2007-10-01

    A novelty approach to self-assembling stereocomplex micelles by enantiomeric PLA-PEG block copolymers as a drug delivery carrier was described. The particles were encapsulated by enantiomeric PLA-PEG stereocomplex to form nanoscale micelles different from the microspheres or the single micelles by PLLA or PDLA in the reported literatures. First, the block copolymers of enantiomeric poly( l-lactide)-poly(ethylene-glycol) (PLLA-PEG) and poly( D-lactide)-poly(ethylene-glycol) (PDLA-PEG) were synthesized by the ring-opening polymerization of l-lactide and d-lactide in the presence of monomethoxy PEG, respectively. Second, the stereocomplex block copolymer micelles were obtained by the self-assembly of the equimolar mixtures of enantiomeric PLA-PEG copolymers in water. These micelles possessed partially the crystallized hydrophobic cores with the critical micelle concentrations (cmc) in the range of 0.8-4.8 mg/l and the mean hydrodynamic diameters ranging from 40 to 120 nm. The micelle sizes and cmc values obviously depended on the hydrophobic block PLA content in the copolymer. Compared with the single PLLA-PEG or PDLA-PEG micelles, the cmc values of the stereocomplex micelles became lower and the sizes of the stereocomplex micelles formed smaller. And lastly, the stereocomplex micelles encapsulated with rifampin were tested for the controlled release application. The rifampin loading capacity and encapsulation efficiency by the stereocomplex micelles were higher than those by the single polymer micelles, respectively. The drug release time in vitro was depending on the composites of the block copolymers and also could be controlled by the polymer molecular weight and the morphology of the polymer micelles.

  1. Topcoat approaches for directed-assembly of copolymer films with blocks exhibiting differences in surface energy

    NASA Astrophysics Data System (ADS)

    Suh, Hyo Seon; in Lee, Jeong; Ramirez-Hernandez, Abelardo; Tada, Yasuhiko; Yoshida, Hiroshi; Wan, Lei; Ruiz, Ricardo; de Pablo, Juan; Nealey, Paul

    2013-03-01

    Fabricating patterns with feature dimensions smaller than 10 nm scale using block copolymer lithography requires the use of materials with large Flory-Huggins interaction parameters. Because such block copolymers (BCPs) typically show the large differences in surface energy between the blocks, one block (with lower surface energy) tends to segregate to the free surface of films and precludes the assembly of the desired through-film perpendicularly oriented structures. Here we describe a generalizable strategy to overcome this limitation. By coating the BCP film with an additional layer, a topcoat, thermodynamically favorable boundary conditions at the top surface of the film can be engineered for directed self-assembly. The allowable properties of the topcoats depend on the interfacial energies of the layer with the blocks of the copolymer, and the block-block interfacial energy. The strategy is demonstrated experimentally by directing the assembly of polystyrene-block-poly-2-vinylpyridine (PS- b-P2VP) films on chemically nanopatterned substrates with different topcoat materials.

  2. Polystyrene/wood composites and hydrophobic wood coatings from water-based hydrophilic-hydrophobic block copolymers

    Treesearch

    Marja-Leena Kosonen; Bo Wang; Gerard T. Caneba; Douglas J. Gardner; Tim G. Rials

    2000-01-01

    The combination of synthetic thermoplastic polymers and wood is normally problematic because wood surfaces are hydrophilic while typical thermoplastic polymers are hydrophobic. A possible solution is to use block copolymer coupling agents. In this work we show the use of a potentially useful synthetic method of producing hydrophilic-hydrophobic block copolymers as...

  3. Effects of block copolymer properties on nanocarrier protection from in vivo clearance

    PubMed Central

    D’Addio, Suzanne M.; Saad, Walid; Ansell, Steven M.; Squiers, John J.; Adamson, Douglas; Herrera-Alonso, Margarita; Wohl, Adam R.; Hoye, Thomas R.; Macosko, Christopher W.; Mayer, Lawrence D.; Vauthier, Christine; Prud’homme, Robert K.

    2012-01-01

    Drug nanocarrier clearance by the immune system must be minimized to achieve targeted delivery to pathological tissues. There is considerable interest in finding in vitro tests that can predict in vivo clearance outcomes. In this work, we produce nanocarriers with dense PEG layers resulting from block copolymer-directed assembly during rapid precipitation. Nanocarriers are formed using block copolymers with hydrophobic blocks of polystyrene (PS), poly-ε-caprolactone (PCL), poly-D,L-lactide (PLA), or poly-lactide-co-glycolide (PLGA), and hydrophilic blocks of polyethylene glycol (PEG) with molecular weights from 1.5 kg/mol to 9 kg/mol. Nanocarriers with paclitaxel prodrugs are evaluated in vivo in Foxn1nu mice to determine relative rates of clearance. The amount of nanocarrier in circulation after 4 h varies from 10% to 85% of initial dose, depending on the block copolymer. In vitro complement activation assays are conducted in an effort to correlate the protection of the nanocarrier surface from complement binding and activation and in vivo circulation. Guidelines for optimizing block copolymer structure to maximize circulation of nanocarriers formed by rapid precipitation and directed assembly are proposed, relating to the relative size of the hydrophilic and hydrophobic block, the hydrophobicity of the anchoring block, the absolute size of the PEG block, and polymer crystallinity. The in vitro results distinguish between the poorly circulating PEG5k-PCL9k and the better circulating nanocarriers, but could not rank the better circulating nanocarriers in order of circulation time. Analysis of PEG surface packing on monodisperse 200 nm latex spheres indicates that the sizes of the hydrophobic PCL, PS, and PLA blocks are correlated with the PEG blob size, and possibly the clearance from circulation. Suggestions for next step in vitro measurements are made. PMID:22732478

  4. Continuous equilibrated growth of ordered block copolymer thin films by electrospray deposition.

    PubMed

    Hu, Hanqiong; Rangou, Sofia; Kim, Myungwoong; Gopalan, Padma; Filiz, Volkan; Avgeropoulos, Apostolos; Osuji, Chinedum O

    2013-04-23

    Deposition of block copolymer thin films is most often accomplished in a serial process where material is spin coated onto a substrate and subsequently annealed, either thermally or by solvent vapor, to produce a well-ordered morphology. Here we show that under appropriate conditions, well-ordered block copolymer films may be continuously grown under substrate equilibrated conditions by slow deposition of discrete subattoliter quantities of material using electrospray. We conduct time-resolved observations and investigate the effects of process parameters that underpin film morphology including solvent selectivity, substrate temperature, block-substrate selectivity, and flow rate of the feed solution. For a PEO cylinder-forming poly(styrene-b-ethylene oxide) block copolymer, we uncover a wide temperature window from 90 to 150 °C and an ideal flow rate of 2 μL/min for ordered film deposition from dilute acetone solutions. PEO cylinders aligned with their long axes perpendicular to the film-air interface at optimal spray conditions. Using poly(styrene-b-methyl methacrylate) deposited onto neutrally selective surfaces, we show that the substrate-equilibrated process results in vertically oriented microdomains throughout the film, indicating a preservation of the initial substrate-dictated morphology during the film deposition. Electrospray offers a new and potentially exciting route for controlled, continuous growth of block copolymer thin films and manipulation of their microstructure.

  5. Phase Behavior of poly(2-vinyl pyridine)-block-poly(4-vinyl pridine) Copolymers

    NASA Astrophysics Data System (ADS)

    Han, Sung Hyun; Lee, Dong Hyun; Kim, Jin Kon

    2007-03-01

    Phase behavior of a block copolymer depends on the volume fraction (f) of one block, total degree of polymerization (N), and the segmental interaction parameter (χ). Recently, we found that the order-to-disorder transition temperature (TODT) of polystyrene-block-poly(2-vinylpridine) copolymer (PS-P2VP) was much lower than that of PS-block-poly(4-vinylpridine) copolymer (PS-P4VP) at similar values of f and N. The only difference between PS-P2VP and PS-P4VP is the different location of the nitrogen group in phenyl ring (2 versus 4-position). In this study, we studied, via small angle X-ray scattering (SAXS), rheometry, and birefringence, the phase behavior P2VP-block-P4VP copolymers (P2VP-P4VP) with various f and N. We determined the temperature dependence of χ between P2VP and P4VP from SAXS profiles in the disordered states with the aid of the random phase approximation. We found that the value of χ between P2VP and P4VP was relatively large. For instance, it is larger than χ between PS and P2VP. Thus, even when the molecular weight of symmetric P2VP-P4VP is ca. 12000, the TODT is larger than 280 ^oC. This work was supported by Creative Research Initiative Program supported by KOSEF

  6. 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.

  7. Microvesicles Produced by Poly(dimethylsiloxane-b-ferrocenylsilane) Block Copolymers in Selective Solvents

    NASA Astrophysics Data System (ADS)

    Frankowski, David; Power-Billard, Nicole; Raez, Jose; Khan, Saad; Manners, Ian; Spontak, Richard

    2004-03-01

    The formation of nanoscopic aggregates via the self-assembly of block copolymers in a selective solvent for one of the blocks is currently a flourishing area of polymer and materials science, and shows tremendous potential for encapsulation applications. In this work, we use transmission electron microscopy (TEM) to investigate the self-organized morphologies of poly(dimethylsiloxaneb-ferrocenylsilane) (PDMS-b-PFS) diblock copolymers in the presence of a selective solvent. In aqueous medium, one copolymer containing a hydrophilic cationic polyferrocene block organizes into microvesicles with a diameter of ˜85 nm in which the organometallic block is located on both the outside and the inside of the aggregates. Cyclic voltammetry confirms that the ferrocene units are subject to sequential oxidation and reduction, in which case these nanoscopic aggregates are considered redox-active. Exposure of a highly asymmetric PDMS-b-PFS copolymer capable of forming nanotubes to high-pressure CO2, a selective solvent for the PDMS block, results in the gradual breakup of the nanotubes and the concurrent formation of micelles. The size of these micelles is sensitive to CO2 pressure and saturation time. At elevated temperatures, microvesicles measuring ˜63 nm in diameter develop.

  8. 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.

  9. Effect of Macromolecular Architecture on the Morphology of Polystyrene Polyisoprene Block Copolymers

    SciTech Connect

    Kumar, Rajeev; Goswami, Monojoy; Mays, Jimmy; Sides, Scott; Sumpter, Bobby G; Dadmun, Mark D; Dyer, Caleb W; Driva, Paraskevi; Chen, Jihua

    2013-01-01

    The impact of block connectivity on the morphologies of four block copolymers of varying architecture containing polystyrene (PS) and polyisoprene (PI) has been studied. The volume fraction of PS and molecular weight are held constant while varying the architecture from a linear PS-PI diblock copolymer to three different miktoarm star architectures: PS2PI, PSPI2, and PS2PI2. Morphologies of the PS2PI and PSPI2 miktoarm stars are different from those observed for the linear copolymer and dependent on the connectivity of the copolymer blocks. The change in morphology with connectivity indicates that combining two chains at a junction point leads to chain crowding, where subsequent excluded volume effects drive the change in morphology for each sample. The PS2PI2 miktoarm star exhibits the same morphology as the linear diblock but with a reduction in the size of the domains. The extent of the decrease in domain size indicates that chain stretching impacts the formation of this morphology. Experimentally observed morphologies for different chain architectures are generally consistent with three-dimensional self-consistent field theory simulations, taking into account conformational asymmetry and experimental uncertainty in the copolymer composition. Furthermore, these results generally agree with analytical theory predictions that account for architectural and conformational asymmetry.

  10. Effect of cosolvents on the self-assembly of a non-ionic polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer in the protic ionic liquid ethylammonium nitrate.

    PubMed

    Chen, Zhengfei; Greaves, Tamar L; Caruso, Rachel A; Drummond, Calum J

    2015-03-01

    The effect of water and methanol on the self-assembled structures formed by the polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer Pluronic P123 in ethylammonium nitrate was investigated by small angle X-ray scattering (SAXS). Two ternary phase diagrams were established. The addition of water had only a minor effect on the liquid crystal structures, however methanol had a significant effect, which was attributed to methanol being a good solvent for both the PEO and PPO blocks of the polymer. No lyotropic liquid crystal phases were retained when methanol reached 25 wt%. The phase behaviour did not change significantly over the temperature range from 25 to 45°C. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. RAFT polymerization of temperature- and salt-responsive block copolymers as reversible hydrogels

    PubMed Central

    Hemp, Sean T.; Smith, Adam E.; Bunyard, W. Clayton; Rubinstein, Michael H.; Long, Timothy E.

    2016-01-01

    Reversible-addition fragmentation chain transfer (RAFT) polymerization enabled the synthesis of novel, stimuli-responsive, AB and ABA block copolymers. The B block contained oligo(ethylene glycol) methyl ether methacrylate (OEG) and was permanently hydrophilic in the conditions examined. The A block consisted of diethylene glycol methyl ether methacrylate (DEG) and [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TMA). The A block displayed both salt- and temperature-response with lower critical solution temperatures (LCSTs) dependent on the molar content of TMA and the presence of salt. Higher TMA content in the AB diblock copolymers increased the critical micelle temperatures (CMT) in HPLC-grade water due to an increased hydrophilicity of the A block. Upon addition of 0.9 wt% NaCl, the CMTs of poly(OEG-b-DEG95TMA5) decreased from 50 °C to 36 °C due to screening of electrostatic repulsion between the TMA units. ABA triblock copolymers displayed excellent hydrogel properties with salt- and temperature-dependent gel points. TMA incorporation in the A block increased the gel points for all triblock copolymers, and salt-response increased with higher TMA composition in the A block. For example, poly(DEG98TMA2-b-OEG-b-DEG98TMA2) formed a hydrogel at 40 °C in HPLC-grade water and 26 °C in 0.9 wt% NaCl aqueous solution. These salt- and temperature-responsive AB diblock and ABA triblock copolymers find applications as drug delivery vehicles, adhesives, and hydrogels. PMID:27041771

  12. Photochemical modification and patterning of polymer surfaces by surface adsorption of photoactive block copolymers.

    PubMed

    Pan, F; Wang, P; Lee, K; Wu, A; Turro, N J; Koberstein, J T

    2005-04-12

    We report a simple photolithographic approach for the creation and micropatterning of chemical functionality on polymer surfaces by use of surface-active block copolymers that contain protected photoactive functional groups. The block copolymers self-assemble at the substrate-air interface to generate a surface that is initially hydrophobic with low surface tension but that can be rendered hydrophilic and functional by photodeprotection with UV radiation. The block copolymer employed, poly(styrene-b-tert butyl acrylate), segregates preferentially to the surface of a polystyrene substrate because of the low surface tension of the polyacrylate blocks. The strong adsorption of block copolymers causes a bilayer structure to form presenting a photoactive polyacrylate layer at the surface. In the example described, the tert-butyl ester groups on the polyacrylate blocks are deprotected by exposure to UV radiation in the presence of added photoacid generators to form surface carboxylic acid groups. Surface micropatterns of carboxylic acid groups are generated by UV exposure through a contact mask. The success of surface chemical modification and pattern formation is demonstrated by X-ray photoelectron spectroscopy and contact angle measurements along with imaging by optical and fluorescence microscopy methods. The resultant chemically patterned surfaces are then used to template patterns of various biomolecules by means of selective adsorption, covalent bonding and molecular recognition mechanisms. The surface modification/patterning concept can be applied to virtually any polymeric substrate because protected functional groups have intrinsically low surface tensions, rendering properly designed block copolymers surface active in almost all polymeric substrates.

  13. Phase inversion in polylactide/soybean oil blends compatibilized by poly(isoprene-b-lactide) block copolymers.

    PubMed

    Chang, Kwanho; Robertson, Megan L; Hillmyer, Marc A

    2009-10-01

    Renewable composites were prepared by melt blending of polylactide and soybean oil. The blend morphology was tuned by the addition of poly(isoprene-b-lactide) block copolymers. Due to the extreme difference in the viscosities of soybean oil and polylactide, a critical block copolymer composition was found to induce a phase inversion point at which the minor soybean oil phase became the matrix surrounding polylactide particles. This transition was due to the thermodynamic interactions between the block copolymer and the two phases and shear forces acting on the mixture during blending. The size of the soybean oil droplets in the polylactide matrix was also highly dependent on the block copolymer composition. In binary polylactide/soybean oil blends, there was a limiting concentration of soybean oil that could be incorporated into the polylactide matrix (6% of the total blend weight), which could be increased up to 20% by the addition of block copolymers.

  14. 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

  15. Achieving Continuous Anion Transport Domains Using Block Copolymers Containing Phosphonium Cations

    SciTech Connect

    Zhang, Wenxu; Liu, Ye; Jackson, Aaron C.; Savage, Alice M.; Ertem, S. Piril; Tsai, Tsung-Han; Seifert, Soenke; Beyer, Frederick L.; Liberatore, Matthew W.; Herring, Andrew M.; Coughlin, E. Bryan

    2016-06-22

    Triblock and diblock copolymers based on isoprene (Ip) and chloromethylstyrene (CMS) were synthesized in this paper by sequential polymerization using reversible addition–fragmentation chain transfer radical polymerization (RAFT). The block copolymers were quaternized with tris(2,4,6-trimethoxyphenyl)phosphine (Ar3P) to prepare soluble ionomers. The ionomers were cast from chloroform to form anion exchange membranes (AEMs) with highly ordered morphologies. At low volume fractions of ionic blocks, the ionomers formed lamellar morphologies, while at moderate volume fractions (≥30% for triblock and ≥22% for diblock copolymers) hexagonal phases with an ionic matrix were observed. Ion conductivities were higher through the hexagonal phase matrix than in the lamellar phases. Finally, promising chloride conductivities (20 mS/cm) were achieved at elevated temperatures and humidified conditions.

  16. Achieving Continuous Anion Transport Domains Using Block Copolymers Containing Phosphonium Cations

    DOE PAGES

    Zhang, Wenxu; Liu, Ye; Jackson, Aaron C.; ...

    2016-06-22

    Triblock and diblock copolymers based on isoprene (Ip) and chloromethylstyrene (CMS) were synthesized in this paper by sequential polymerization using reversible addition–fragmentation chain transfer radical polymerization (RAFT). The block copolymers were quaternized with tris(2,4,6-trimethoxyphenyl)phosphine (Ar3P) to prepare soluble ionomers. The ionomers were cast from chloroform to form anion exchange membranes (AEMs) with highly ordered morphologies. At low volume fractions of ionic blocks, the ionomers formed lamellar morphologies, while at moderate volume fractions (≥30% for triblock and ≥22% for diblock copolymers) hexagonal phases with an ionic matrix were observed. Ion conductivities were higher through the hexagonal phase matrix than in themore » lamellar phases. Finally, promising chloride conductivities (20 mS/cm) were achieved at elevated temperatures and humidified conditions.« less

  17. Quantitative study of temperature-dependent order in thin films of cylindrical morphology block copolymer

    NASA Astrophysics Data System (ADS)

    Mishra, Vindhya; Kramer, Edward

    2010-03-01

    Disordering and defect generation in block copolymer systems at high temperatures is of significance to get a better understanding of the physics governing these systems, which can also direct efforts to minimize them. We have studied the smectic-nematic-isotropic transition in confined monolayers and bilayers of cylindrical morphology poly (styrene-b-2vinyl pyridine) diblock copolymer. Previous studies of melting phenomena in block copolymer thin films have relied on quantitative AFM studies alone. We have supplemented AFM studies with grazing incidence small angle X-ray diffraction lineshape analysis to quantify the decay of translational and orientational order with increasing temperature. The results have been interpreted in the context of the Toner-Nelson theory of melting for layered systems.

  18. Humidity-Induced Phase Transitions in Ion-Containing Block Copolymer Membranes

    SciTech Connect

    Park, Moon Jeong; Nedoma, Alisyn J.; Geissler, Phillip L.; Balsara, Nitash P.; Jackson, Andrew; Cookson, David

    2008-08-21

    The phase behavior of ion-containing block copolymer membranes in equilibrium with humidified air is studied as a function of the relative humidity (RH) of the surrounding air, ion content of the copolymer, and temperature. Increasing RH at constant temperature results in both disorder-to-order and order-to-order transitions. In-situ small-angle neutron scattering experiments on the open block copolymer system, when combined with water uptake measurement, indicate that the disorder-to-order transition is driven by an increase in the partial molar entropy of the water molecules in the ordered phase relative to that in the disordered phase. This is in contrast to most systems wherein increasing entropy results in stabilization of the disordered phase.

  19. 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.

  20. Discovery of a Frank-Kasper sigma phase in sphere-forming block copolymer melts.

    PubMed

    Lee, Sangwoo; Bluemle, Michael J; Bates, Frank S

    2010-10-15

    Sphere-forming block copolymers are known to self-assemble into body-centered cubic crystals near the order-disorder transition temperature. Small-angle x-ray scattering and transmission electron microscopy experiments on diblock and tetrablock copolymer melts have revealed an equilibrium phase characterized by a large tetragonal unit cell containing 30 microphase-separated spheres. This structure, referred to as the sigma (σ) phase by Frank and Kasper more than 50 years ago, nucleates and grows from the body-centered cubic phase similar to its occurrence in metal alloys and is a crystal approximant to dodecagonal quasicrystals. Formation of the σ phase in undiluted linear block copolymers (and certain branched dendrimers) appears to be mediated by macromolecular packing frustration, an entropic contribution to the interparticle interactions that control the sphere-packing geometry.

  1. Effects of copolymer composition, film thickness, and solvent vapor annealing time on dewetting of ultrathin block copolymer films.

    PubMed

    Huang, Changchun; Wen, Gangyao; Li, Jingdan; Wu, Tao; Wang, Lina; Xue, Feifei; Li, Hongfei; Shi, Tongfei

    2016-09-15

    Effects of copolymer composition, film thickness, and solvent vapor annealing time on dewetting of spin-coated polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) films (<20nm thick) were mainly investigated by atomic force microscopy. Surface chemical analysis of the ultrathin films annealed for different times were performed using X-ray photoelectron spectroscopy and contact angle measurement. With the annealing of acetone vapor, dewetting of the films with different thicknesses occur via the spinodal dewetting and the nucleation and growth mechanisms, respectively. The PS-b-PMMA films rupture into droplets which first coalesce into large ones to reduce the surface free energy. Then the large droplets rupture into small ones to increase the contact area between PMMA blocks and acetone molecules resulting from ultimate migration of PMMA blocks to droplet surface, which is a novel dewetting process observed in spin-coated films for the first time.

  2. Calorimetric Study of Gradient Block-copolymers of Poly(butylacrylate) and Poly(methylmethacrylate)

    NASA Astrophysics Data System (ADS)

    Buzin, A. I.; Pyda, M.; Matyjaszewski, K.; Wunderlich, B.

    2002-03-01

    The miscibility and phase separation in the diblock (AB) and triblock (ABA) copolymers consisting of poly(butyl acrylate) (block B) and gradient copolymers of butyl acrylate and methyl methacrylate (block A) were investigated by means of conventional DSC as a function of the composition of the blocks A. In all copolymers studied, both blocks are presented by two separate glass transition temperatures. The low-temperature transition corresponds to devitrification of block B and is independent of composition and temperature is close to that of pure poly(butyl acrylate), while the higher transition corresponds to glass transition of the copolymeric block A, which decreases and broadens with increasing methylmethacrylate content in block A. The immiscible polymers are connected by chemical bonds, so that the mobilities of the phases influence each other. Shifts in the glass transition temperature and the broadening of the transitions as well as their asymmetry are discussed. --- Supported by NSF, Polymers Program, DMR-9703692, and the Div. of Mat. Sci., BES, DOE at ORNL, managed by UT-Batelle, LLC, for the U.S. Department of Energy, under contract number DOE-AC05-00OR22725.

  3. High-concentration graphene dispersion stabilized by block copolymers in ethanol.

    PubMed

    Perumal, Suguna; Lee, Hyang Moo; Cheong, In Woo

    2017-07-01

    This article describes a comprehensive study for the preparation of graphene dispersions by liquid-phase exfoliation using amphiphilic diblock copolymers; poly(ethylene oxide)-block-poly(styrene) (PEO-b-PS), poly(ethylene oxide)-block-poly(4-vinylpyridine) (PEO-b-PVP), and poly(ethylene oxide)-block-poly(pyrenemethyl methacrylate) (PEO-b-PPy) with similar block lengths. Block copolymers were prepared from PEO using the Steglich coupling reaction followed by reversible addition-fragmentation chain transfer (RAFT) polymerization. Graphite platelets (G) and reduced graphene oxide (rGO) were used as graphene sources. The dispersion stability of graphene in ethanol was comparatively investigated by on-line turbidity, and the graphene concentration in the dispersions was determined gravimetrically. Our results revealed that the graphene dispersions with PEO-b-PVP were much more stable and included graphene with fewer defects than that with PEO-b-PS or PEO-b-PPy, as confirmed by turbidity and Raman analyses. Gravimetry confirmed that graphene concentrations up to 1.7 and 1.8mg/mL could be obtained from G and rGO dispersions, respectively, using PEO-b-PVP after one week. Distinctions in adhesion forces of PS, VP, PPy block units with graphene surface and the variation in solubility of the block copolymers in ethanol medium significantly affected the stability of the graphene dispersion.

  4. Block Copolymer Electrolytes: Thermodynamics, Ion Transport, and Use in Solid- State Lithium/Sulfur Cells

    NASA Astrophysics Data System (ADS)

    Teran, Alexander Andrew

    Nanostructured block copolymer electrolytes containing an ion-conducting block and a modulus-strengthening block are of interest for applications in solid-state lithium metal batteries. These materials can self-assemble into well-defined microstructures, creating conducting channels that facilitate ion transport. The overall objective of this dissertation is to gain a better understanding of the behavior of salt-containing block copolymers, and evaluate their potential for use in solid-state lithium/sulfur batteries. Anionically synthesized polystyrene-b-poly(ethylene oxide) (SEO) copolymers doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt were used as a model system. This thesis investigates the model system on several levels: from fundamental thermodynamic studies to bulk characterization and finally device assembly and testing. First, the thermodynamics of neat and salt-containing block copolymers was studied. The addition of salt to these materials is necessary to make them conductive, however even small amounts of salt can have significant effects on their phase behavior, and consequently their iontransport and mechanical properties. As a result, the effect of salt addition on block copolymer thermodynamics has been the subject of significant interest over the last decade. A comprehensive study of the thermodynamics of block copolymer/salt mixtures over a wide range of molecular weights, compositions, salt concentrations and temperatures was conducted. Next, the effect of molecular weight on ion transport in both homopolymer and copolymer electrolytes were studied over a wide range of chain lengths. Homopolymer electrolytes show an inverse relationship between conductivity and chain length, with a plateau in the infinite molecular weight limit. This is due to the presence of two mechanisms of ion conduction in homopolymers; the first mechanism is a result of the segmental motion of the chains surrounding the salt ions, 2 creating a liquid

  5. 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.

  6. Amphiphilic block copolymer-based photonic platform towards efficient protein detection

    NASA Astrophysics Data System (ADS)

    Petropoulou, Afroditi; Gibson, Thomas J.; Themistou, Efrosyni; Pispas, Stergios; Riziotis, Christos

    2016-11-01

    The development of a low complexity fiber optic based protein sensor by functionalizing the surface of silica optical fibers using block copolymers having both hydrophobic poly(methyl methacrylate) (PMMA) and hydrophilic poly[2- (dimethylamino)ethyl methacrylate] (PDMAEMA) blocks is presented here. The amphiphilic thiol-functionalized PMMA117-b-P(DMAEMA17-st-TEMA2) and vinyl-sulfone PMMA117-b-P(DMAEMA17-st-VSTEMA2) block copolymers designed and synthesized in this work contain a cationic hydrophilic PDMAEMA block that can electrostatically bind selected oppositely charged proteins and also appropriate functional groups for reversible or non-reversible protein binding, respectively, leading to a refractive index change of the overlayer and hence, enabling the sensing. The developed PMMA117-b-PDMAEMA16-based platform has been evaluated for bovine serum albumin (BSA) sensing, exhibiting linear response to detected BSA concentrations.

  7. 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.

  8. Stability of the fcc structure in block copolymer systems.

    PubMed

    Nonomura, Makiko

    2008-11-19

    The stability of the face-centered cubic (fcc) structure in microphase separated copolymers is investigated by a coarse-grained approach. Direct simulations of the equation for the microphase separation in three dimensions indicate that there is a narrow area above a certain degree of segregation in the phase diagram, where the fcc structure is the most stable structure. By employing the mode expansion, we have confirmed that the fcc structure can form as a metastable structure even in the weak segregation regime.

  9. 2-D Hierarchical Structure of a Block Copolymer and Bio-nanoparticle Composites

    NASA Astrophysics Data System (ADS)

    Shin, Dongseok; Lin, Yao; Wang, Qian; Russell, Thomas

    2007-03-01

    2-dimensional hierarchical structures were generated by combining two different self assembling systems; block copolymer and bio-nanoparticle. For this study, a block copolymer having a positively charged component, i.e. poly (styrene-b-N-methyl-4-vinylpyridinium iodide), was used. Thin film composites of this block copolymer and bio-nanoparticles were fabricated by adsorbing bio-particles on the polymer film and subsequently annealing the sample under the presence of solvent vapor. 2-dimensional hierarchical structures, where block copolymer chains microphase separated inside of discrete grains surrounded by bio-nanoparticles, were obtained with rod- like bio-particles (tobacco mosaic virus and M13 phage) as well as with spherical one (ferritin). The pH effect on the assembly of rod-like bio-particles and the morphology of composites was investigated. When the pH of the solution used for the adsorption of bio-particles was low, the bio-molecules aggregated and formed large bundles, while they were dispersed well at high pH. This difference was reflected in the morphology of the resultant complexes.

  10. NEXAFS Depth Profiling of Surface Segregation in Block Copolymer Thin Films

    DTIC Science & Technology

    2010-01-01

    by 1H NMR spectroscopy. The block copolymers were synthesized by atom transfer radical polymerization ( ATRP ). Homopolymer H and random copoly- mer R...average and number-averagemolecular weights were 1.77 for S and 1.51 for C. The ATRP controlled radical polymeriza- tion resulted in polymers with

  11. Design of surface properties of PET films: effect of fluorinated block copolymers.

    PubMed

    Pilati, F; Montecchi, M; Fabbri, P; Synytska, A; Messori, M; Toselli, M; Grundke, K; Pospiech, D

    2007-11-01

    This paper demonstrates that the addition of fluorinated block copolymers to PET solutions can be used to prepare PET films with controlled surface morphology, porosity and chemical composition, by exploiting the phenomenon known as breath figures (BF) formation during a spin-coating procedure. Surface features, such as number, depth and diameter of pores and chemical composition, can be tuned by varying the experimental conditions: relative humidity, solution composition and amount of the fluorinated block copolymer added to the PET solutions (in the range of 0.5-10 wt% with respect to PET). BF patterns are more evident at relatively high concentrations of PET (3 wt%) and content of fluorinated block copolymer (10 wt% with respect to PET) in the solution. According to the obtained results, the fluorinated block copolymer seems to play a role in different steps of the mechanism of BF formation. XPS measurements showed a surface composition much richer in fluorinated segments than expected from bulk composition. The combined surface roughness and surface segregation of fluorinated segments have only a limited effect on the macroscopic wettability of the surfaces.

  12. 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.

  13. Asymmetric block copolymer membranes with ultrahigh porosity and hierarchical pore structure by plain solvent evaporation.

    PubMed

    Yu, H; Qiu, X; Behzad, A R; Musteata, V; Smilgies, D-M; Nunes, S P; Peinemann, K-V

    2016-10-04

    Membranes with a hierarchical porous structure could be manufactured from a block copolymer blend by pure solvent evaporation. Uniform pores in a 30 nm thin skin layer supported by a macroporous structure were formed. This new process is attractive for membrane production because of its simplicity and the lack of liquid waste.

  14. Antimicrobial films obtained from latex particles functionalized with quaternized block copolymers.

    PubMed

    Alvarez-Paino, Marta; Juan-Rodríguez, Rafael; Cuervo-Rodríguez, Rocío; Tejero, Rubén; López, Daniel; López-Fabal, Fátima; Gómez-Garcés, José L; Muñoz-Bonilla, Alexandra; Fernández-García, Marta

    2016-04-01

    New amphiphilic block copolymers with antimicrobial properties were obtained by atom transfer radical polymerization (ATRP) and copper catalyzed cycloaddition following two approaches, a simultaneous strategy or a two-step synthesis, which were proven to be very effective methods. These copolymers were subsequently quaternized using two alkyl chains, methyl and butyl, to amplify their antimicrobial properties and to investigate the effect of alkyl length. Antimicrobial experiments in solution were performed with three types of bacteria, two gram-positive and one gram-negative, and a fungus. Those copolymers quaternized with methyl iodide showed better selectivities on gram-positive bacteria, Staphylococcus aureus and Staphylococcus epidermidis, against red blood cells, demonstrating the importance of the quaternizing agent chosen. Once the solution studies were performed, we prepared poly(butyl methacrylate) latex particles functionalized with the antimicrobial copolymers by emulsion polymerization of butyl methacrylate using such copolymers as surfactants. The characterization by various techniques served to test their effectiveness as surfactants. Finally, films were prepared from these emulsions, and their antimicrobial activity was studied against the gram-positive bacteria. The results indicate that the antimicrobial efficiency of the films depends not only on the copolymer activity but also on other factors such as the surface segregation of the antimicrobial agent to the interface. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Phase behavior of ABC-type triple-hydrophilic block copolymers in aqueous solutions.

    PubMed

    Zheng, Lingfei; Wu, Jianqi; Wang, Zheng; Yin, Yuhua; Jiang, Run; Li, Baohui

    2016-07-01

    The phase behavior of symmetric ABC triple-hydrophilic triblock copolymers in concentrated aqueous solutions is investigated using a simulated annealing technique. Two typical cases, in which the hydrophilicity of the middle B-block is either stronger or weaker than that of the end A- and C-blocks, are studied. In these two cases, a variety of phase diagrams are constructed as a function of the volume fraction of the B-block and the copolymer concentration ([Formula: see text] for both non-frustrated and frustrated copolymers. Structures, such as two-color alternatingly packed cylinders or gyroid, and lamellae-in-lamellae etc. that do not occur in the melt system, are obtained in solutions. Rich phase transition sequences, especially re-entrant phase transitions involving complex continuous networks of alternating gyroid and alternating diamond are observed for a given copolymer with decreasing [Formula: see text] . The difference in hydrophilicity among different blocks can result in inhomogeneous distribution of solvent molecules in the morphology, and with the decrease of [Formula: see text] , the distribution of solvent molecules presents a non-monotonic variation. This results in a non-monotonic variation of the effective volume fraction of each domain with the decrease of [Formula: see text] , which induces the re-entrant phase transitions. The presence of a good solvent for all the blocks can cause changes in the effective segregation strengths between different blocks and also in chain conformations, hence can alter the bulk phases and results in the occurrence of new structures and phase transitions. Especially, structures having A-C interfaces or A-C mixed domains can be obtained even in the non-frustrated copolymer systems, and structures obtained in the frustrated systems may be similar to those obtained in the non-frustrated systems. The window of the alternating gyroid structures may occupy a large part of the phase diagram for non

  16. NMR spectra and electrochemical behavior of catechol-bearing block copolymer micelles

    PubMed Central

    Hasegawa, Urara; Moriyama, Masaki; Uyama, Hiroshi; van der Vlies, André J.

    2015-01-01

    Here, we provide the NMR spectra and AFM data for antioxidant micelles prepared from amphiphilic PAM-PDA block copolymers composed of a poly(N-acryloyl morpholine) and a redox-active catechol-bearing block with different catechol content. We also provide details of the electrochemical analysis that showed micelles higher catechol content had a similar redox potential with the small catechol compound dopamine, but slowed down the redox reaction (Hasegawa et al., Polymer (in press)). PMID:26217751

  17. Pluronic-PEI copolymers enhance exon-skipping of 2'-O-methyl phosphorothioate oligonucleotide in cell culture and dystrophic mdx mice.

    PubMed

    Wang, M; Wu, B; Lu, P; Tucker, J D; Milazi, S; Shah, S N; Lu, Q L

    2014-01-01

    A series of small-size polyethylenimine (PEI)-conjugated pluronic polycarbamates (PCMs) have been investigated for the ability to modulate the delivery of 2'-O-methyl phosphorothioate RNA (2'-OMePS) in vitro and in dystrophic mdx mice. The PCMs retain strong binding capacity to negatively charged oligomer as demonstrated by agarose gel retardation assay, with the formation of condensed polymer/oligomer complexes at a wide-range weight ratio from 1:1 to 20:1. T