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Sample records for conjugated polymer films

  1. Semiconductor-nanocrystal/conjugated polymer thin films

    DOEpatents

    Alivisatos, A. Paul; Dittmer, Janke J.; Huynh, Wendy U.; Milliron, Delia

    2014-06-17

    The invention described herein provides for thin films and methods of making comprising inorganic semiconductor-nanocrystals dispersed in semiconducting-polymers in high loading amounts. The invention also describes photovoltaic devices incorporating the thin films.

  2. Semiconductor-nanocrystal/conjugated polymer thin films

    DOEpatents

    Alivisatos, A. Paul; Dittmer, Janke J.; Huynh, Wendy U.; Milliron, Delia

    2010-08-17

    The invention described herein provides for thin films and methods of making comprising inorganic semiconductor-nanocrystals dispersed in semiconducting-polymers in high loading amounts. The invention also describes photovoltaic devices incorporating the thin films.

  3. Thin Films Formed from Conjugated Polymers with Ionic, Water-Soluble Backbones.

    PubMed

    Voortman, Thomas P; Chiechi, Ryan C

    2015-12-30

    This paper compares the morphologies of films of conjugated polymers in which the backbone (main chain) and pendant groups are varied between ionic/hydrophilic and aliphatic/hydrophobic. We observe that conjugated polymers in which the pendant groups and backbone are matched, either ionic-ionic or hydrophobic-hydrophobic, form smooth, structured, homogeneous films from water (ionic) or tetrahydrofuran (hydrophobic). Mismatched conjugated polymers, by contrast, form inhomogeneous films with rough topologies. The polymers with ionic backbone chains are conjugated polyions (conjugated polymers with closed-shell charges in the backbone), which are semiconducting materials with tunable bad-gaps, not unlike uncharged conjugated polymers. PMID:25723354

  4. Microwave absorption of free carriers in doped conjugated polymer films

    NASA Astrophysics Data System (ADS)

    Rumbles, Garry

    Flash photolysis time-resolved microwave conductivity (fp-TRMC) is a powerful spectroscopic tool for the detection of mobile charges in organic systems, such as conjugated polymers. We will report on a study of charge carrier generation in a number of polymer systems where the solid-state microstructure (SSM) of the thin films can be controlled using both molecular structure and processing conditions. By incorporating a low concentration of molecular acceptors, such as metallo-phthalocyanines, as well as substituted fullerenes and perylenes, the driving force for photoinduced electron transfer can be controlled through the excited state energy and the reduction potential. Our results indicate the importance of the crystalline phase of the polymer to stabilise and reduce the rate of recombination of the holes with the electrons that remain trapped on the acceptor. In addition, the role that the SSM plays on the stabilization of bound electron-hole pairs, or charge-transfer (CT) states will be examined.

  5. Photoluminescence quenching in films of conjugated polymers by electrochemical doping

    NASA Astrophysics Data System (ADS)

    van Reenen, S.; Vitorino, M. V.; Meskers, S. C. J.; Janssen, R. A. J.; Kemerink, M.

    2014-05-01

    An important loss mechanism in organic electroluminescent devices is exciton quenching by polarons. Gradual electrochemical doping of various conjugated polymer films enabled the determination of the doping density dependence of photoluminescence quenching. Electrochemical doping was achieved by contacting the film with a solid electrochemical gate and an injecting contact. A sharp reduction in photoluminescence was observed for doping densities between 1018 and 1019 cm-3. The doping density dependence is quantitatively modeled by exciton diffusion in a homogeneous density of polarons followed by either Förster resonance energy transfer or charge transfer. Both mechanisms need to be considered to describe polaron-induced exciton quenching. Thus, to reduce exciton-polaron quenching in organic optoelectronic devices, both mechanisms must be prevented by reducing the exciton diffusion, the spectral overlap, the doping density, or a combination thereof.

  6. π-Conjugated Microporous Polymer Films: Designed Synthesis, Conducting Properties, and Photoenergy Conversions

    PubMed Central

    Gu, Cheng; Huang, Ning; Chen, Youchun; Qin, Leiqiang; Xu, Hong; Zhang, Shitong; Li, Fenghong; Ma, Yuguang; Jiang, Donglin

    2015-01-01

    Conjugated microporous polymers are a unique class of polymers that combine extended π-conjugation with inherent porosity. However, these polymers are synthesized through solution-phase reactions to yield insoluble and unprocessable solids, which preclude not only the evaluation of their conducting properties but also the fabrication of thin films for device implementation. Here, we report a strategy for the synthesis of thin films of π-conjugated microporous polymers by designing thiophene-based electropolymerization at the solution–electrode interface. High-quality films are prepared on a large area of various electrodes, the film thickness is controllable, and the films are used for device fabrication. These films are outstanding hole conductors and, upon incorporation of fullerenes into the pores, function as highly efficient photoactive layers for energy conversions. Our film strategy may boost the applications in photocatalysis, energy storage, and optoelectronics. PMID:26418672

  7. Measuring Exciton Diffusion in Conjugated Polymer Films with Super-resolution Microscopy

    NASA Astrophysics Data System (ADS)

    Penwell, Samuel; Ginsberg, Lucas; Noriega Manez, Rodrigo; Ginsberg, Naomi

    2015-03-01

    Conjugated polymers are highly tunable organic semiconductors, which can be solution processed to form thin films, making them prime candidates for organic photovoltaic devices. One of the most important parameters in a conjugated polymer solar cell is the exciton diffusion length, which depends on intermolecular couplings, and is typically on the order of 10 nm. This mean exciton migration can vary dramatically between films and within a single film due to heterogeneities in morphology on length scales of 10's to 100's nm. To study the variability of exciton diffusion and morphology within individual conjugated polymer films, we are adapting stimulated emission depletion microscopy. STED is typically used in biology with well-engineered fluorescent labels or on NV-centers in diamond. I will, however, describe how we have demonstrated STED in conjugated polymer films of MEH-PPV and CN-PPV by taking care to first understand the film's photophysical properties. This new approach provides a way to study exciton diffusion by utilizing subdiffraction optical excitation volumes. In this way, we will obtain a spatiotemporal map of exciton distributions that will help to correlate the energetic landscape to film morphology at the nanoscale. This research is supported in part by the Department of Energy Office of Science Graduate Fellowship Program (DOE SCGF), made possible in part by the American Recovery and Reinvestment Act of 2009, administered by ORISE-ORAU under Contract No. DE-AC05-06.

  8. Deviations of the glass transition temperature in amorphous conjugated polymer thin films

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Osuna Orozco, Rodrigo; Wang, Tao

    2013-08-01

    The deviations of the glass transition temperature (Tg) in thin films of an amorphous conjugated polymer poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) are reported. Monotonic and nonmonotonic Tg deviations are observed in TFB thin films supported on Si-SiOx and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), respectively. A three-layer model is developed to fit both monotonic and nonmonotonic Tg deviations in these films. A 5-nm PEDOT:PSS capping layer was not found to be effective to remove the free-surface effect in Si-SiOx supported TFB films.

  9. Measuring Exciton Migration in Conjugated Polymer Films with Ultrafast Time Resolved Stimulated Emission Depletion Microscopy

    NASA Astrophysics Data System (ADS)

    Penwell, Samuel

    Conjugated polymers are highly tunable organic semiconductors, which can be solution processed to form thin films, making them prime candidates for organic photovoltaic devices. One of the most important parameters in a conjugated polymer solar cell is the exciton diffusion length, which depends on intermolecular couplings, and is typically on the order of 10 nm. This mean exciton migration can vary dramatically between films and within a single film due to heterogeneities in morphology on length scales of 10's to 100's nm. To study the variability of exciton diffusion and morphology within individual conjugated polymer films, we are adapting stimulated emission depletion (STED) microscopy. STED is typically used in biology with sparse well-engineered fluorescent labels or on NV-centers in diamond. I will, however, describe how we have demonstrated the extension of STED to conjugated polymer films and nanoparticles of MEH-PPV and CN-PPV, despite the presence of two photon absorption, by taking care to first understand the material's photophysical properties. We then further adapt this approach, by introducing a second ultrafast STED pulse at a variable delay. Excitons that migrate away from the initial subdiffraction excitation volume during the ps-ns time delay, are preferentially quenched by the second STED pulse, while those that remain in the initial volume survive. The resulting effect of the second STED pulse is modulated by the degree of migration over the ultrafast time delay, thus providing a new method to study exciton migration. Since this technique utilizes subdiffraction optical excitation and detection volumes with ultrafast time resolution, it provides a means of spatially and temporally resolving measurements of exciton migration on the native length and time scales. In this way, we will obtain a spatiotemporal map of exciton distributions and migration that will help to correlate the energetic landscape to film morphology at the nanoscale.

  10. Deviations of the glass transition temperature in amorphous conjugated polymer thin films.

    PubMed

    Liu, Dan; Osuna Orozco, Rodrigo; Wang, Tao

    2013-08-01

    The deviations of the glass transition temperature (T(g)) in thin films of an amorphous conjugated polymer poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) are reported. Monotonic and nonmonotonic T(g) deviations are observed in TFB thin films supported on Si-SiOx and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), respectively. A three-layer model is developed to fit both monotonic and nonmonotonic T(g) deviations in these films. A 5-nm PEDOT:PSS capping layer was not found to be effective to remove the free-surface effect in Si-SiOx supported TFB films. PMID:24032856

  11. Effects of polymer side chains on the self-assembling of conjugated polymer in thin film

    NASA Astrophysics Data System (ADS)

    Jiang, Yunfei; Wang, Yiqing; Bunz, Uvw H. F.; Perahia, Dvora

    2006-03-01

    Conjugated polymers are inherently semi-conducting and optically active materials, with immense potential applications in organic electro-optical devices. The chemical structure of the polymer including the rigidity of the backbone and the nature of substituents affect their association as well as their electro-optical response. The following work reports the effects of different side chains on the structure and fluorescence of highly conjugated polymer, poly(para phenyleneethynylene) (PPE). When substituted by long polylactide side chains they self-assemble into wires with fingerprint-like arrangement, casting from chloroform solutions on oxidized silicon wafer. With increasing content of poor solvent, the dimension of the structures increased and then crystallized area appeared, as showed in AFM studies. The introducing of the long flexible polymer side chains has significantly reduced the stacking between rigid backbones. This in tern results in a frequency shift in their fluoresces response, indication changes in the electronic levels. Direct measurements of the electronic levels using ATM are currently in progress.

  12. Polarization anisotropy dynamics for thin films of a conjugated polymer aligned by nanoimprinting

    NASA Astrophysics Data System (ADS)

    Schmid, S. A.; Yim, K. H.; Chang, M. H.; Zheng, Z.; Huck, W. T. S.; Friend, R. H.; Kim, J. S.; Herz, L. M.

    2008-03-01

    Time-integrated and femtosecond time-resolved photoluminescence spectroscopy has been used to study the dynamic emission polarization anisotropy for thin films of a conjugated polymer whose chains had been aligned through a nanoimprinting technique. The results indicate a high degree of chain alignment, with the presence of a small fraction of unaligned chain domains in film regions far from the imprinted surface. The time-averaged emission from aligned domains is found to be slightly shifted to higher photon energies compared to that from more disordered film regions. This effect is attributed to a subtly different chain packing geometry in the more aligned regions of the film, which leads to a reduced exciton diffusivity and inhibits energetic relaxation of the exciton in the inhomogeneously broadened density of states. While for an unaligned reference film, exciton migration results in a nearly complete depolarization of the emission over the first 300 ps, for the aligned films, interchain exciton hopping from unaligned to aligned domains is found to increase the anisotropy over the same time scale. In addition, excitons generated in aligned film domains were found to be slightly more susceptible to nonradiative quenching effects than those in disordered regions deeper inside the film, suggesting a marginally higher defect density near the nanoimprinted surface of the aligned film.

  13. High efficiency THz-wave modulators based on conjugated polymer-based organic films

    NASA Astrophysics Data System (ADS)

    He, Ting; Zhang, Bo; Wang, Guo-cui; Zang, Meng-di; Hou, Yan-bing; Shen, Jing-ling

    2016-02-01

    A study of the modulation mechanisms of conjugated polymer-based organic films and high-efficiency, broadband and all-optically controlled terahertz modulators based on these films is presented in this paper. Under very low-level external laser excitation, modulation efficiency of more than 99% is achieved using MEH-PPV/Si, PFO/Si and F8BT/Si bilayers. By analyzing the changes in the photo-excited carrier density and photoconductivity with changes in the external laser intensity, we introduce a nonlinear photo-induced absorption process to explain the strong attenuation mechanism for the transmitted terahertz waves. Finally, a simple THz communication test is carried out to demonstrate the potential future applications of the high-efficiency all-optically controlled terahertz modulator.

  14. Langmuir-Blodgett films of conjugated polymers and their applications on optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Tseng, Chin-Jen

    1998-11-01

    Langmuir-Blodgett technique has been well known to produce ultra-thin films with controlled thickness and preferred orientation. In this research, this technique was used to produce conjugated polymer films and apply these films on optoelectronic devices such as the alignment layers for twisted nematic liquid crystal displays (TNLCDs) and the luminescent materials for light emitting diodes (LEDs). In the twisted nematic liquid crystal displays, oriented Langmuir-Blodgett films behave as alignment layers and provide required pretilt orientation. Poly(para- phenylene) (PPP) ultra thin films prepared by Langmuir- Blodgett technique were applied as homogeneous alignment layers. 10,12-nonacosadiynoic acid (16-8 DA) Langmuir- Blodgett films were applied as homeotropic alignment layers. In the light emitting diode, oriented PPP LB films perform as charge transfer complexes and emit polarized light without external polarizer. A precursor method was developed for the preparation of these PPP LB films. A salt (briefed as PDCP-NIII) formed with poly(2,5-dicarboxyl-1,4-phenelene) (PDCP) and o,o',o' - Trihexadecanoyltriethanolamine (NIII) was used as the precursor materials and transformed into PPP LB films via pyrolysis. Pretilt angle of 0.2o was measured via crystal rotation method on the antiparallel liquid crystal cells with PPP LB films as the homogeneous alignment layers. 10,12-nonacosadiynoic acid was synthesized via Cadiot- chodkiewicz reaction developed by Steven Walsh. Lithium salts of 16-8DA LB films were polymerized by UV lamp and used to behave as homeotropic alignment layers. Thermodynamic properties of these Langmuir films at the air-water interface such as isotherms and creep test were studied. Surface morphology was studied with Brewster Angle Microscopy (BAM) and surface rheology was studied with the Surface Light Scattering Spectroscopy (SLSS). These LB films were characterized by UV-Visible Spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR

  15. Controlled synthesis of conjugated microporous polymer films: versatile platforms for highly sensitive and label-free chemo- and biosensing.

    PubMed

    Gu, Cheng; Huang, Ning; Gao, Jia; Xu, Fei; Xu, Yanhong; Jiang, Donglin

    2014-05-01

    Conjugated microporous polymers (CMPs), in which rigid building blocks form robust networks, are usually synthesized as insoluble and unprocessable powders. We developed a methodology using electropolymerization for the synthesis of thin CMP films. The thickness of these films is synthetically controllable, ranging from nanometers to micrometers, and they are obtained on substrates or as freestanding films. The CMP films combine a number of striking physical properties, including high porosity, extended π conjugation, facilitated exciton delocalization, and high-rate electron transfer. We explored the CMP films as versatile platforms for highly sensitive and label-free chemo- and biosensing of electron-rich and electron-poor arenes, metal ions, dopamine, and hypochloroic acid, featuring rapid response, excellent selectivity, and robust reusability. PMID:24692401

  16. Polymer films

    DOEpatents

    Granick, Steve; Sukhishvili, Svetlana A.

    2004-05-25

    A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

  17. Polymer films

    DOEpatents

    Granick, Steve; Sukhishvili, Svetlana A.

    2008-12-30

    A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

  18. Langmuir-Schaefer films for aligned carbon nanotubes functionalized with a conjugate polymer and photoelectrochemical response enhancement.

    PubMed

    Sgobba, Vito; Giancane, Gabriele; Cannoletta, Donato; Operamolla, Alessandra; Omar, Omar Hassan; Farinola, Gianluca M; Guldi, Dirk M; Valli, Ludovico

    2014-01-01

    Single-walled carbon nanotubes (SWCNTs) were suspended in 1,2-dichloroethane by noncovalent functionalization with a low-band-gap conjugated polymer 1 alternating dialkoxyphenylene-bisthiophene units with benzo[c][2,1,3]thiadiazole monomeric units. The suspended 1/SWCNT blend was transferred onto different solid substrates by the Langmuir-Schaefer deposition method, resulting in films with a high percentage of aligned nanotubes. Photoelectrochemical characterization of 1/SWCNT thin films on indium-tin oxide showed the benefits of SWCNT alignment for photoconversion efficiency. PMID:24328296

  19. Multiplicative luminescence enhancement induced by chain relaxation in ultrathin films of a conjugated polymer (MEH-PPV)

    NASA Astrophysics Data System (ADS)

    Yang, Chih-Wei; Jou, Juo-Huei; Chang-Mou Yang, Arnold

    2006-03-01

    A surprising multiplication of light-emitting efficiency was observed in dewetting process of the conjugated luminescent polymer of poly (2-methoxy- 5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV). The luminescent efficiency increased with the dewetting process and became about six-fold when the polymer film ruptured into tiny droplets. This enhancement appeared to be related to the carrier transport mechanisms and the motions of polymer chains. The effects of inter-molecular energy transport and molecular deformation of polymer chains were studied by examining the emission behavior in liquid and solid solutions. It was found that the molecular movements during stretching in the glassy state were quite different from that in the dewetting process. The latter was dominated by disengagement of inter-molecular entanglements while the former was strongly influenced by trapping mechanisms of chain entanglements due to rapid local molecular strains. This work is supported by National Science Council of Taiwan.

  20. Synthesis of cyanopyridine based conjugated polymer.

    PubMed

    Hemavathi, B; Ahipa, T N; Pillai, Saju; Pai, Ranjith Krishna

    2016-06-01

    This data file contains the detailed synthetic procedure for the synthesis of two new cyanopyridine based conjugated polymer P1 and P2 along with the synthesis of its monomers. The synthesised polymers can be used for electroluminescence and photovoltaic (PV) application. The physical data of the polymers are provided in this data file along with the morphological data of the polymer thin films. The data provided here are in association with the research article entitled 'Cyanopyridine based conjugated polymer-synthesis and characterisation' (Hemavathi et al., 2015) [3]. PMID:27158642

  1. Synthesis of cyanopyridine based conjugated polymer

    PubMed Central

    Hemavathi, B.; Ahipa, T.N.; Pillai, Saju; Pai, Ranjith Krishna

    2016-01-01

    This data file contains the detailed synthetic procedure for the synthesis of two new cyanopyridine based conjugated polymer P1 and P2 along with the synthesis of its monomers. The synthesised polymers can be used for electroluminescence and photovoltaic (PV) application. The physical data of the polymers are provided in this data file along with the morphological data of the polymer thin films. The data provided here are in association with the research article entitled ‘Cyanopyridine based conjugated polymer-synthesis and characterisation’ (Hemavathi et al., 2015) [3]. PMID:27158642

  2. Processing Cyclic Peptide-polymer Conjugates in Block Copolymer Thin Films for Sub-nm Porous Membranes

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Xu, Ting

    2014-03-01

    Porous thin films containing subnanometer channels oriented normal to the surface exhibit unique transport and separation properties and can serve as selective membranes for separation. Inspired by natural protein channels, we have developed an approach using cyclic peptide nanotubes (CPNs) embedded in polymeric matrix to mimic the transport of natural channels. The co-assembly of polymer-covered CPNs in a block copolymer (BCP) thin film requires the synchronization of two self-assembly processes, namely the microphase separation of BCP and the nanotube growth of CP-polymer conjugates. We systematically investigated the co-assembly of isolated CP-poly(ethylene glycol) (CP-PEG) conjugates and polystyrene-b-poly (methyl methacrylate) (PS-b-PMMA) in thin films as a function of CP-PEG loading (fCP-PEG) and solvent-polymer interactions. We find that there is a strong dependence of the co-assembly process on fCP-PEG due to thermodynamic limit of incorporating one CPN in one PMMA microdomain, as well as the kinetic pathway in which favorable PEG-solvent interaction helps to disperse CPNs and thus lowers the activation energy barrier of the system. This study presents critical insights in guided assemblies of functional building blocks within nanoscopic frameworks. DOE-EFRC-Gas Separation, Army Research Office.

  3. Precisely Controlled Ultrathin Conjugated Polymer Films for Large Area Transparent Transistors and Highly Sensitive Chemical Sensors.

    PubMed

    Khim, Dongyoon; Ryu, Gi-Seong; Park, Won-Tae; Kim, Hyunchul; Lee, Myungwon; Noh, Yong-Young

    2016-04-01

    A uniform ultrathin polymer film is deposited over a large area with molecularlevel precision by the simple wire-wound bar-coating method. The bar-coated ultrathin films not only exhibit high transparency of up to 90% in the visible wavelength range but also high charge carrier mobility with a high degree of percolation through the uniformly covered polymer nanofibrils. They are capable of realizing highly sensitive multigas sensors and represent the first successful report of ethylene detection using a sensor based on organic field-effect transistors. PMID:26849096

  4. Influence of Morphological Disorder on In- and Out-of-Plane Charge Transport in Conjugated Polymer Films

    NASA Astrophysics Data System (ADS)

    Dong, Ban; Li, Anton; Green, Peter

    We report the unequal impacts of morphological disorder on in- and out-of-plane charge transport in thin films of poly(3-hexylthiophene) (P3HT) fabricated by both conventional spin-casting and the novel technique Matrix-Assisted Pulsed Laser Evaporation (MAPLE). MAPLE produces films with inhomogeneous globular subfeatures with dimensions on the order of 100 nm. Optical absorbance spectroscopy corroborates that MAPLE-deposited films are more energetically disordered, but possesses average conjugation lengths comparable to spin-cast P3HT. Both in- and out-of-plane carrier transport measurements of MAPLE-deposited films show characteristics that reflect a higher degree of energetic disorder and broadened density of states. Whereas in-plane carrier mobilities of MAPLE-deposited thin-film transistors are comparable to spin-cast analogues (8.3 x 10-3 cm2V-1s-1 versus 5.5 x 10-3 cm2V-1s-1) , the out-of-plane mobilities of MAPLE-deposited samples are nearly an order of magnitude lower (4.1 x 10-4 cm2V-1s-1 versus 2.7 x 10-3 cm2V-1s-1) . The unusual ensemble of properties and behaviors arising from the unique morphologies produced by MAPLE provide important perspectives on the extent to which disorder impacts different mechanisms of charge transport in conjugated polymers.

  5. Subgap Absorption in Conjugated Polymers

    DOE R&D Accomplishments Database

    Sinclair, M.; Seager, C. H.; McBranch, D.; Heeger, A. J; Baker, G. L.

    1991-01-01

    Along with X{sup (3)}, the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of < 10{sup {minus}5}, Photothermal Deflection Spectroscopy (PDS) is ideal for determining the absorption coefficients of thin films of transparent'' materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination.

  6. Distance and molecular weight dependence of surface enhanced fluorescence in conjugated polymer thin films

    NASA Astrophysics Data System (ADS)

    Griffo, Michael S.; Carter, Sue A.

    2008-08-01

    Photoluminescence (PL) of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) in the presence of Silver nanoparticles (NP) is studied. The purpose of this research is to understand the PL distance dependence of plasmon-polymer separation and a correlation between the surface enhanced fluorescence (SEF) and polymer molecular weight. Distinct peaks in PL are found for plasmon-polymer separations ranging from near the far field to the near field, under 100 nm. Extinction of the devices shows that changes in absorption cannot explain all enhancement in PL and suggests that a modification of the radiative lifetime is modified. The dependence of the photoluminescence of MEH-PPV on molecular weight shows variation but overall suggests chain length does not affect film quenching. This is largely attributed to the large polydispersity of the polymer materials used.

  7. Conjugated polymer network films of poly(p-phenylene vinylene) with hole-transporting carbazole pendants: dual photoluminescence and electrochromic behavior.

    PubMed

    Ponnapati, Ramakrishna; Felipe, Mary Jane; Muthalagu, Vetrichelvan; Puno, Katherine; Wolff, Birte; Advincula, Rigoberto

    2012-03-01

    A series of poly(p-phenylene vinylene) (PPV) copolymers functionalized with hole-transport and electrochemically active carbazole units as pendant moieties is reported. These polymers exhibit photoluminescence properties by virtue of the PPV analogous backbone. They were also designed as precursor polymer bearing the electroactive carbazole group to form conjugated polymer network (CPN) films by electrodeposition. The electrochemical polymerization of the pendant units eventually lead to a dual property electro-optically active thin film - photoluminescence (PL) behavior that can be attenuated with CPN formation, and a reversible doping and dedoping processes at controlled potentials that lead to an electrochromic behavior. This reveals the ability to incorporate complementary optical and electro-optical properties within the same film using the CPN approach. It should be possible to design and synthesize other PPV π-conjugated polymers with efficient pendant hole-transport groups exhibiting tunable PL and electrochromism with cross-linking. PMID:22329863

  8. Fabrication and mechanical characterization of semi-free-standing (conjugated) polymer thin films.

    PubMed

    Martín, Jaime; Muñoz, Miguel; Encinar, Mario; Calleja, Montserrat; Martín-González, Marisol

    2014-05-13

    Polymers undergo severe low-dimensionality effects when they are confined to ultrathin films since most of the structural and dynamical processes involving polymer molecules are correlated to length scales of the order of nanometers. However, the real influence of the size limitation over such processes is often hard to identify as it is masked by interfacial effects. We present the fabrication of a new type of nanostructure consisting of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) thin film that is held up exclusively over tips of poly(ether-ether-ketone) (PEEK) nanopillars. The fabrication method exploits the nonwetting behavior of PCDTBT onto an ordered PEEK nanopillar array when the mobility of the PCDTBT molecules is enhanced by a solvent annealing process. We use this new configuration to characterize the mechanical behavior of free-standing thin film regions, thus in the absence of underlaying substrate, by means of an atomic force microscope (AFM) setup. First, we study how the finite thickness and/or the presence of the underlying substrate influences the mechanical modulus of the material in the linear elastic regime. Moreover, we analyze deep indentations up to the rupture of the thin film, which allow for the measurement of important mechanical features of the nanoconfined polymer, such as its yield strain, the rupture strain, the bending rigidity, etc., which are impossible to investigate in thin films deposited on substrates. PMID:24111564

  9. Compositions for directed alignment of conjugated polymers

    DOEpatents

    Kim, Jinsang; Kim, Bong-Gi; Jeong, Eun Jeong

    2016-04-19

    Conjugated polymers (CPs) achieve directed alignment along an applied flow field and a dichroic ratio of as high as 16.67 in emission from well-aligned thin films and fully realized anisotropic optoelectronic properties of CPs in field-effect transistor (FET).

  10. Enhanced photophysics of conjugated polymers

    DOEpatents

    Chen, Liaohai; Xu, Su; McBranch, Duncan; Whitten, David

    2003-05-27

    The addition of oppositely charged surfactant to fluorescent ionic conjugated polymer forms a polymer-surfactant complex that exhibits at least one improved photophysical property. The conjugated polymer is a fluorescent ionic polymer that typically has at least one ionic side chain or moiety that interacts with the specific surfactant selected. The photophysical property improvements may include increased fluorescence quantum efficiency, wavelength-independent emission and absorption spectra, and more stable fluorescence decay kinetics. The complexation typically occurs in a solution of a polar solvent in which the polymer and surfactant are soluble, but it may also occur in a mixture of solvents. The solution is commonly prepared with a surfactant molecule:monomer repeat unit of polymer ratio ranging from about 1:100 to about 1:1. A polymer-surfactant complex precipitate is formed as the ratio approaches 1:1. This precipitate is recoverable and usable in many forms.

  11. Self-organizing conjugated polymers

    NASA Astrophysics Data System (ADS)

    Hong, Xiaoyong Michael

    2000-10-01

    A general and efficient synthetic route to semifluoroalkyl substituted thiophenes has been developed and a series of 3-semifluoroalkylthiophenes were synthesized. The lengths of the fluorocarbon chain and hydrocarbon spacer between thiophene and fluorocarbon were systematically altered to study their effect on the properties of the resulting polymers. Oxidative polymerization (FeCl3) and electrochemical polymerization of 3-semifluoroalkylthiophenes afforded regiorandom (head-to-tail coupling ˜70%) homopolymers. The solubility and thermal transition temperatures of the polymers are also dependent on the nature of side chains. The surface properties of the polymers are also a function of the length of fluoroalkyl side chains. From x-ray diffraction, the regiorandom polymers have low crystallinity. Two synthetic methods have been successfully utilized to prepare regioregular poly(3-semifluoroalkylthiophene)s (head-to-tail coupling >90%) and gave identical polymers. The regioregular polymers are highly conjugated and highly ordered. The long side chain substituted polythiophenes form a liquid crystal mesophase between the crystal solid and isotropic liquid phases. To prepare polymers bearing alternating 3-semifluoroalkylthiophene and alkylthiophene units, we developed synthetic methods to 3-semifluoroalkyl-4 '-alkyl-2,2'-bithiophenes. The 3-semifluoroalkyl-4 '-alkyl-2,2'-bithiophenes were polymerized to afford regiorandom and regioregular polymers. Regiorandom polymers have low crystallinity and conjugation. Regioregular, strictly alternating copolymer with 3-semifluoroalkylthiophene and alkylthiophene units are highly conjugated and ordered. The regioregular polymers self-assemble into bilayer structure in solid state due to phase separation between fluorocarbon and hydrocarbon. At high temperatures close to melting transition, the thiophene rings rotate and twist along the molecular axis to give a single layer structure. Methylene bridges were placed between the

  12. Conjugated Polymer Surfaces and Interfaces

    NASA Astrophysics Data System (ADS)

    Salaneck, W. R.; Stafstrom, S.; Brédas, J. L.

    2003-10-01

    The authors illustrate the basic physics and materials science of conjugated polymers and their interfaces, particularly, but not exclusively, as they are applied to polymer-based light emitting diodes. The approach is to describe the basic physical and associated chemical principles that apply to these materials, which in many instances are different from those that apply to their inorganic counterparts. The main aim of the authors is to highlight specific issues and properties of polymer surfaces and interfaces that are relevant in the context of the emerging field of polymer-based electronics in general, and polymer-based light emitting diodes in particular. Both theoretical and experimental methods used in the study of these systems are discussed. This book will be of interest to graduate students and research workers in departments of physics, chemistry, electrical engineering and materials sciences studying polymer surfaces and interfaces and their application in polymer-based electronics.

  13. Enhanced photophysics of conjugated polymers

    DOEpatents

    Chen, Liaohai

    2007-06-12

    A particulate fluorescent conjugated polymer surfactant complex and method of making and using same. The particles are between about 15 and about 50 nm and when formed from a lipsome surfactant have a charge density similar to DNA and are strongly absorbed by cancer cells.

  14. Single conjugated polymer nanoparticle capacitors

    NASA Astrophysics Data System (ADS)

    Palacios, Rodrigo E.; Lee, Kwang-Jik; Rival, Arnaud; Adachi, Takuji; Bolinger, Joshua C.; Fradkin, Leonid; Barbara, Paul F.

    2009-02-01

    The hole injection from a carbazole derivative hole transport layer into nanoparticles ( r = 25 ± 15 nm) of the conjugated polymer MEH-PPV was investigated by an indirect single-particle fluorescence-quenching technique. The results suggest that there is a kinetic barrier for hole injection that prevents polymer particles from being charged in the dark. This barrier can be overcome with the assistance of optical excitation of the MEH-PPV nanoparticles, achieving a thermodynamic population of injected holes at positive bias. The amount of injected holes at equilibrium is observed to depend upon the bias in a manner highly consistent with device simulations based on a continuum model. Overall, the results demonstrate that the hole injection into nano domains of conjugated polymers is a complex process depending upon molecular interfacial effects determined by device geometry and electrostatic interactions.

  15. Solution assembly of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Bokel, Felicia A.

    This dissertation focuses on the solution-state polymer assembly of conjugated polymers with specific attention to nano- and molecular-scale morphology. Understanding how to control these structures holds potential for applications in polymer-based electronics. Optimization of conjugated polymer morphology was performed with three objectives: 1) segregation of donor and acceptor materials on the nanometer length-scale, 2) achieving molecular-scale ordering in terms of crystallinity within distinct domains, and 3) maximizing the number and quality of well-defined donor/acceptor interfaces. Chapter 1 introduces the development of a mixed solvent method to create crystalline poly(3-hexyl thiophene) (P3HT) fibrils in solution. Chapter 2 describes fibril purification and approaches to robust and functional fibrils, while chapters 3 and 4 demonstrate the formation of hybrid nanocomposite wires of P3HT and cadmium selenide (CdSe) nanoparticles by two methods: 1) co-crystallization of free and P3HT-grafted CdSe for composite nanowires and 2) direct attachment of CdSe nanoparticles at fibril edges to give superhighway structures. These composite structures show great potential in the application of optoelectronic devices, such as the active layer of solar cells. Finally, ultrafast photophysical characterization of these polymers, using time-resolved photoluminescence and transient absorption, was performed to determine the aggregation types present in suspended fibrils and monitor the formation and decay of charged species in fibrils and donor-acceptor systems.

  16. Photoluminescence of Conjugated Star Polymers

    NASA Astrophysics Data System (ADS)

    Ferguson, J. B.; Prigodin, N. V.; Epstein, A. J.; Wang, F.

    2000-10-01

    Higher dimensionality "star" polymers provide new properties beyond those found in their linear analogs. They have been used to improving electronic properties for nonlinear optics through exciton transfer and molecular antenna structures for example (M. Kawa, J. M. J. Frechet, Chem. Mater. 10, 286 (1998).). We report on photoluminescence properties of star polymers with a hyperbranched core (both hyperbranched phenlyene and hyperbranched triphenylamine) and polyhexylthiophene arms. The arm is a conjugated oligomer of polythiophene that has been investigated extensively for metallic like conductivity when doped as well as utilized in field effect transistors in its undoped form (A. Tsumara, H. Koezuka, T. Ando, Appl. Phys. Lett. 49, 1210 (1986).). The cores are respectively, a nonconjugated polymer in the case of hyperbranched phenlyene and a conjugated polymer in the case of hyperbranched triphenylamine. The photoluminesce spectrum (λ_max at 575 nm) is identical for both star polymers with the two electronically different hyperbranched cores and for linear polythiophene alone. We conclude the wave functions of the core and arms do not strongly interact to form states different from their individual states and excitons formed on the hyperbranched cores migrate to the lower bandgap polythiophene before recombining.

  17. Molecular weight effects in the third-harmonic generation spectroscopy of thin films of the conjugated polymer MEH-PPV.

    PubMed

    Bahtiar, Ayi; Koynov, Kaloian; Ahn, Taek; Bubeck, Christoph

    2008-03-27

    Thin spin-cast films of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) were prepared from samples whose weight-average molecular weight (Mw) was varied in the range of 10-1600 kg/mol. We have characterized the films by means of transmission and reflection ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy to derive the linear optical constants, and third-harmonic generation spectroscopy with variable laser wavelengths to get the modulus and phase angles of the complex third-order nonlinear optical susceptibility chi(3). Increasing molecular weight yields films with significantly larger chi(3) values, absorption coefficients, and refractive indices. The chi(3) values of films from the largest and lowest Mw differ by a factor of 4, which is caused by chain orientation effects, local field effects, and changes of the effective conjugation length. PMID:18311961

  18. Semiconductor Conjugated Polymer-Quantum Dot Nanocomposites at the Air/Water Interface and Their Performance in Thin Film Solar Cells

    NASA Astrophysics Data System (ADS)

    Lin, Zhiqun; Goodman, Matthew; Xu, Jun; Wang, Jun

    2009-03-01

    Organic-inorganic nanocomposites consisting of electroactive conjugated polymer, poly(3-hexylthiophene) (P3HT) intimately tethered on the surface of semiconductor CdSe quantum dot (i.e., P3HT-CdSe nanocomposites) at the air/water interface formed via Langmuir isotherms were explored for the first time. The P3HT-CdSe nanocomposites displayed a high pressure plateau in the Langmuir isotherm, illustrating their complex packing at the air/water interface. Furthermore, photovoltaic devices fabricated from the LB depositions of the P3HT-CdSe nanocomposites exhibited a relatively high short circuit current, ISC, while maintaining a thin film profile. These studies provide insights into the fundamental behaviors of semiconductor organic-inorganic nanocomposites confined at the air/water interface as well as in the active layer of an organic-based photovoltaic device.

  19. Near-field scanning optical microscopy investigations of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Dearo, Jessie Ann

    The Near-Field Scanning Optical Microscopy (NSOM) studies of novel, optically active, conjugated polymers are presented. NSOM is a relatively new technique which produces super resolution (˜50--100 nm) optical images simultaneously with topography. The conjugated polymer poly(p-phenylene vinylene) (PPV) and derivatives of PPV are organic semiconductor-like materials with interesting and unique optical properties. Derivatives of PPV have been used in LEDs and have potential in other optoelectronic devices. NSOM provides a tool for investigation of the photoluminescence, absorption/reflection, photo-dynamics and photoconductivity of films of PPV and PPV derivatives on the length scale that these properties are fundamentally defined. The NSOM experiments have revealed mesoscale domains (˜100 nm) of varying photoluminescence emission and average molecular order in drop cast films of PPV. NSOM of stretch-oriented PPV have shown domains of perpendicular molecular orientation with low photoluminescence emission. Near-field photoconductivity experiments of stretch-oriented PPV have correlated the mesoscale topography with the photoconductivity properties of the polymer. NSOM experiments of films of poly(2-methoxy, 5-(2'-(ethyl(hexyloxy)-p-phenylene vinylene) (MEH-PPV) have shown that there is mesoscale spatial inhomogeneity in the photo-oxidation process which reduces photoluminescence emission. NSOM has also been used to create nanoscale photo-patterning in MEH-PPV films. The NSOM experiments of blended films of MEH-PPV in polystyrene have shown mesoscale phase separation directly correlated to variations in the optical properties of the film. Derivatives of PPV, stretch-oriented in polyethylene, show photoluminescence intensity variations perpendicular and parallel to the stretch-direction correlated to topography features. As a complement to the NSOM studies of conjugated polymers, single polymer molecule experiments of MEH-PPV are also presented. The

  20. Microfluidic Crystal Engineering of π-Conjugated Polymers.

    PubMed

    Wang, Gang; Persson, Nils; Chu, Ping-Hsun; Kleinhenz, Nabil; Fu, Boyi; Chang, Mincheol; Deb, Nabankur; Mao, Yimin; Wang, Hongzhi; Grover, Martha A; Reichmanis, Elsa

    2015-08-25

    Very few studies have reported oriented crystallization of conjugated polymers directly in solution. Here, solution crystallization of conjugated polymers in a microfluidic system is found to produce tightly π-stacked fibers with commensurate improved charge transport characteristics. For poly(3-hexylthiophene) (P3HT) films, processing under flow caused exciton bandwidth to decrease from 140 to 25 meV, π-π stacking distance to decrease from 3.93 to 3.72 Å and hole mobility to increase from an average of 0.013 to 0.16 cm(2) V(-1) s(-1), vs films spin-coated from pristine, untreated solutions. Variation of the flow rate affected thin-film structure and properties, with an intermediate flow rate of 0.25 m s(-1) yielding the optimal π-π stacking distance and mobility. The flow process included sequential cooling followed by low-dose ultraviolet irradiation that promoted growth of conjugated polymer fibers. Image analysis coupled with mechanistic interpretation supports the supposition that "tie chains" provide for charge transport pathways between nanoaggregated structures. The "microfluidic flow enhanced semiconducting polymer crystal engineering" was also successfully applied to a representative electron transport polymer and a nonhalogenated solvent. The process can be applied as a general strategy and is expected to facilitate the fabrication of high-performance electrically active polymer devices. PMID:26182171

  1. Mitochondria-specific Conjugated Polymer Nanoparticles

    PubMed Central

    Twomey, Megan; Mendez, Eladio; Manian, Rajesh Kumar

    2016-01-01

    Biodegradable conjugated polymer nanoparticles (CPNs) were prepared for high mitochondria targeting in live cancer cells. The degradable CPNs are nontoxic and specifically localized to mitochondria of live tumor cells through macropinocytosis followed by intracellular degradation and trafficking. PMID:26974193

  2. Compatibilization of All-Conjugated Polymer Blends for Organic Photovoltaics.

    PubMed

    Lombeck, Florian; Sepe, Alessandro; Thomann, Ralf; Friend, Richard H; Sommer, Michael

    2016-08-23

    Compatibilization of an immiscible binary blend comprising a conjugated electron donor and a conjugated electron acceptor polymer with suitable electronic properties upon addition of a block copolymer (BCP) composed of the same building blocks is demonstrated. Efficient compatibilization during melt-annealing is feasible when the two polymers are immiscible in the melt, i.e. above the melting point of ∼250 °C of the semicrystalline donor polymer P3HT. To generate immiscibility at these high temperatures, the acceptor polymer PCDTBT is equipped with fluorinated side chains leading to an increased Flory-Huggins interaction parameter. Compatibilization in bulk and thin films is demonstrated, showing that the photovoltaic performance of pristine microphase separated and nanostructured BCPs can also be obtained for compatibilized blend films containing low contents of 10-20 wt % BCP. Thermodynamically stable domain sizes range between several tens of microns for pure blends and ∼10 nm for pure block copolymers. In addition to controlling domain size, the amount of block copolymer added dictates the ratio of edge-on and face-on P3HT crystals, with compatibilized films showing an increasing amount of face-on P3HT crystals with increasing amount of compatibilizer. This study demonstrates the prerequisites and benefits of compatibilizing all-conjugated semicrystalline polymer blends for organic photovoltaics. PMID:27482842

  3. High-Performing Thin-Film Transistors in Large Spherulites of Conjugated Polymer Formed by Epitaxial Growth on Removable Organic Crystalline Templates.

    PubMed

    Kim, Jae Yoon; Yang, Da Seul; Shin, Jicheol; Bilby, David; Chung, Kyeongwoon; Um, Hyun Ah; Chun, Jaehee; Pyo, Seungmoon; Cho, Min Ju; Kim, Jinsang; Choi, Dong Hoon

    2015-06-24

    Diketopyrrolopyrrole (DPP)-based conjugated polymer PDTDPPQT was synthesized and was used to perform epitaxial polymer crystal growth on removable 1,3,5-trichlorobenzene crystallite templates. A thin-film transistor (TFT) was successfully fabricated in well-grown large spherulites of PDTDPPQT. The charge carrier mobility along the radial direction of the spherulites was measured to be 5.46-12.04 cm(2) V(-1) s(-1), which is significantly higher than that in the direction perpendicular to the radial direction. The dynamic response of charge transport was also investigated by applying a pulsed bias to TFTs loaded with a resistor (∼20 MΩ). The charge-transport behaviors along the radial direction and perpendicular to the radial direction were investigated by static and dynamic experiments through a resistor-loaded (RL) inverter. The RL inverter made of PDTDPPQT-based TFT operates well, maintaining a fairly high switching voltage ratio (Vout(ON)/Vout(OFF)) at a relatively high frequency when the source-drain electrodes are aligned parallel to the radial direction. PMID:26030474

  4. Electrochemical Sensors Based on Organic Conjugated Polymers

    PubMed Central

    Rahman, Md. Aminur; Kumar, Pankaj; Park, Deog-Su; Shim, Yoon-Bo

    2008-01-01

    Organic conjugated polymers (conducting polymers) have emerged as potential candidates for electrochemical sensors. Due to their straightforward preparation methods, unique properties, and stability in air, conducting polymers have been applied to energy storage, electrochemical devices, memory devices, chemical sensors, and electrocatalysts. Conducting polymers are also known to be compatible with biological molecules in a neutral aqueous solution. Thus, these are extensively used in the fabrication of accurate, fast, and inexpensive devices, such as biosensors and chemical sensors in the medical diagnostic laboratories. Conducting polymer-based electrochemical sensors and biosensors play an important role in the improvement of public health and environment because rapid detection, high sensitivity, small size, and specificity are achievable for environmental monitoring and clinical diagnostics. In this review, we summarized the recent advances in conducting polymer-based electrochemical sensors, which covers chemical sensors (potentiometric, voltammetric, amperometric) and biosensors (enzyme based biosensors, immunosensors, DNA sensors).

  5. Novel conjugates of peptides and conjugated polymers for optoelectronics and neural interfaces

    NASA Astrophysics Data System (ADS)

    Bhagwat, Nandita

    Peptide-polymer conjugates are a novel class of hybrid materials that take advantage of each individual component giving the opportunity to generate materials with unique physical, chemical, mechanical, optical, and electronic properties. In this dissertation peptide-polymer conjugates for two different applications are discussed. The first set of peptide-polymer conjugates were developed as templates to study the intermolecular interactions between electroactive molecules by manipulating the intermolecular distances at nano-scale level. A PEGylated, alpha-helical peptide template was employed to effectively display an array of organic chromophores (oxadiazole containing phenylenevinylene oligomers, Oxa-PPV). Three Oxa-PPV chromophores were strategically positioned on each template, at distances ranging from 6 to 17 A from each other, as dictated by the chemical and structural properties of the peptide. The Oxa-PPV modified PEGylated helical peptides (produced via Heck coupling strategies) were characterized by a variety of spectroscopic methods. Electronic contributions from multiple pairs of chromophores on a scaffold were detectable; the number and relative positioning of the chromophores dictated the absorbance and emission maxima, thus confirming the utility of these polymer--peptide templates for complex presentation of organic chromophores. The rest of the thesis is focused on using poly(3,4-alkylenedioxythiophene) based conjugated polymers as coatings for neural electrodes. This thiophene derivative is of considerable current interest for functionalizing the surfaces of a wide variety of devices including implantable biomedical electronics, specifically neural bio-electrodes. Toward these ends, copolymer films of 3,4-ethylenedioxythiophene (EDOT) with a carboxylic acid functional EDOT (EDOTacid) were electrochemically deposited and characterized as a systematic function of the EDOTacid content (0, 25, 50, 75, and 100%). The chemical surface characterization

  6. Conjugated Polymers Atypically Prepared in Water

    PubMed Central

    Invernale, Michael A.; Pendergraph, Samuel A.; Yavuz, Mustafa S.; Ombaba, Matthew; Sotzing, Gregory A.

    2010-01-01

    Processability remains a fundamental issue for the implementation of conducting polymer technology. A simple synthetic route towards processable precursors to conducting polymers (main chain and side chain) was developed using commercially available materials. These soluble precursor systems were converted to conjugated polymers electrochemically in aqueous media, offering a cheaper and greener method of processing. Oxidative conversion in aqueous and organic media each produced equivalent electrochromics. The precursor method enhances the yield of the electrochromic polymer obtained over that of electrodeposition, and it relies on a less corruptible electrolyte bath. However, electrochemical conversion of the precursor polymers often relies on organic salts and solvents. The ability to achieve oxidative conversion in brine offers a less costly and a more environmentally friendly processing step. It is also beneficial for biological applications. The electrochromics obtained herein were evaluated for electronic, spectral, and morphological properties. PMID:20959869

  7. Chemical Sensors: Precisely Controlled Ultrathin Conjugated Polymer Films for Large Area Transparent Transistors and Highly Sensitive Chemical Sensors (Adv. Mater. 14/2016).

    PubMed

    Khim, Dongyoon; Ryu, Gi-Seong; Park, Won-Tae; Kim, Hyunchul; Lee, Myungwon; Noh, Yong-Young

    2016-04-01

    A precise control over the film thickness is a vital requirement for achievement of high performance in thin-film electronic devices. On page 2752, Y.-Y. Noh and co-workers develop an effective way to deposit a large-area and uniform ultrathin polymer film with a molecular-level precision via a simple wire-wound bar-coating method for high-performance organic transistors and gas sensors. PMID:27062168

  8. Anisotropic field-effect hole mobility of liquid crystalline conjugated polymer layers formed on photoaligned polyimide films

    NASA Astrophysics Data System (ADS)

    Sakamoto, Kenji; Yasuda, Takeshi; Miki, Kazushi; Chikamatsu, Masayuki; Azumi, Reiko

    2011-01-01

    We have fabricated organic field-effect transistors (OFETs) with a highly oriented active layer of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-bithiophene] (F8T2), which was formed with the help of a photoaligned polyimide film. Photoalignment is an attractive technique for integrating OFETs with aligned active layers on the same substrate, because of its potential capability of two-dimensional alignment patterning. The F8T2 layer formed on the photoaligned polyimide film showed an absorption dichroic ratio greater than 15 after annealing at 285 °C. Top-gate/bottom-contact-type OFETs with a parylene gate insulating layer exhibited an enhanced hole mobility (0.016 cm2 V-1 s-1) along the alignment direction of the F8T2 backbone structure and a suppressed one (0.002 cm2 V-1 s-1) along the perpendicular direction. This result shows that the photoaligned polyimide film is an attractive alignment layer for fabricating and integrating OFETs with aligned active layers. Current-direction-dependent bias stress effect was observed for those OFETs; when the current flowed parallel to the alignment direction of the F8T2 backbone structures, a larger negative threshold voltage shift was observed. This anisotropic bias stress effect was discussed on the basis of a microstructure model of aligned F8T2 films.

  9. Metal-polymer and polymer-polymer interfaces: Application to conjugated polymer electronic devices

    NASA Astrophysics Data System (ADS)

    Smallfield, Julie Anne Osladil

    The study of metal-polymer and polymer-polymer interfaces is applied to conjugated polymer electronic devices. Conjugated polymers are a class of organic materials which have metallic or semiconducting properties which are being investigated as alternatives to traditional semiconducting materials. When conjugated polymers are used in devices, the interfaces are found to be critical to device performance. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS), which give information about the atomic and chemical composition, workfunction, and ionization potential of materials, are used to study these interfaces. In studying metal-polymer interfaces, it is shown that the interface between the conjugated polymer fully sulfonated polyaniline (NSPAN) and an aluminum alloy is an active interface, in which copper is extracted by the polymer from the aluminum alloy. This results in the aluminum alloy becoming more resistant to corrosion in a salty environment. The interface between aluminum and NSPAN, as it is found in some light emitting devices (LEDS), is also studied. It is concluded that negative charge is transferred from the aluminum to the polymer, resulting in a thin layer of oxidized aluminum and a more reduced form of the polymer at the interface. In studying polymer-polymer interfaces, it is proposed that NSPAN protonates a pyridine containing polymer at an interface which is also found in some LEDs. This is proposed to be responsible for color variation found in some LEDs. A model system was studied, and protonation at the polymer-polymer interface was directly observed, supporting the earlier proposals. Polymer-polymer interfaces found in SCALE devices, which are LEDs made with three polymer layers, are studied by UPS to determine the band structure of these devices. It is concluded that the EB layers decrease the hole barrier and increase the electron barrier, which leads to better charge balance and a better device. The EB

  10. Semiconducting conjugated polymer-inorganic tetrapod nanocomposites.

    PubMed

    Jung, Jaehan; Pang, Xinchang; Feng, Chaowei; Lin, Zhiqun

    2013-06-25

    Cadmium telluride (CdTe) tetrapods were synthesized via multiple injections of the Te precursor by utilizing bifunctional ligands. Subsequently, tetrapod-shaped semiconducting inorganic-organic nanocomposites (i.e., P3HT-CdTe tetrapod nanocomposites) were produced by directly grafting conjugated polymer ethynyl-terminated poly(3-hexylthiophene) (i.e., P3HT-≡) onto azide-functionalized CdTe tetrapods (i.e., CdTe-N3) via a catalyst-free click chemistry. The intimate contact between P3HT and CdTe tetrapod rendered the effective dispersion of CdTe tetrapods in nanocomposites and facilitated their efficient electronic interaction. The success of coupling reaction was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The grafting density of P3HT chains on the CdTe tetrapods was estimated by thermogravimetric analysis. The photophysical properties of P3HT-CdTe tetrapod nanocomposites were studied using UV-vis and photoluminescence spectroscopies. These intimate semiconducting conjugated polymer-tetrapod nanocomposites may offer a maximized interface between conjugated polymers and tetrapods for efficient charge separation and enhanced charge transport regardless of their orientation for potential application in hybrid solar cells with improved power conversion efficiency. PMID:23600796

  11. Solvent immersion nanoimprint lithography of fluorescent conjugated polymers

    SciTech Connect

    Whitworth, G. L.; Zhang, S.; Stevenson, J. R. Y.; Ebenhoch, B.; Samuel, I. D. W.; Turnbull, G. A.

    2015-10-19

    Solvent immersion imprint lithography (SIIL) was used to directly nanostructure conjugated polymer films. The technique was used to create light-emitting diffractive optical elements and organic semiconductor lasers. Gratings with lateral features as small as 70 nm and depths of ∼25 nm were achieved in poly(9,9-dioctylfluorenyl-2,7-diyl). The angular emission from the patterned films was studied, comparing measurement to theoretical predictions. Organic distributed feedback lasers fabricated with SIIL exhibited thresholds for lasing of ∼40 kW/cm{sup 2}, similar to those made with established nanoimprint processes. The results show that SIIL is a quick, convenient and practical technique for nanopatterning of polymer photonic devices.

  12. Conjugated polymer electrochromic and light-emitting devices

    NASA Astrophysics Data System (ADS)

    Dyer, Aubrey L.

    Conjugated conducting polymers are among some of the most versatile materials to emerge in the past 20 years. They have been researched for applications that range from photovoltaics, to light-emitting diodes, electrochromic windows, actuators, and field effect transistors. This work details the analytical characterization of pi-conjugated polymers to understand their redox and optical properties, along with the development of several new types of devices that employ these polymers as the active materials for both variable optical attenuators and as dual electrochromic/electroluminescent displays. Within this work, a phenomenon that we term unsymmetrical switching has been uncovered for the first time in reflective electrochromic cells. The unsymmetrical switching in these displays is explored and a model devised to illustrate that the presence of a conductive front propagating through the polymer film on electrochemical oxidation is the contributing cause for this observation. For these experiments, a variety of analytical techniques have been utilized to characterize the devices and materials contained therein and include electrochemistry, spectroelectrochemistry, and photometry. The first application utilizes the large near infrared electrochromic contrasts of some dioxythiophene-based polymers when incorporated in reflective electrochromic displays. For the first time, it is demonstrated that these devices can be utilized as electrochromic variable optical attenuators, important components for the optical telecommunications industry, exhibiting optical attenuation values of 12 decibels while maintaining optical loss values, in the off state, as low as 0.1 decibels. These devices offer the benefit of yielding mechanically flexible, miniaturized electrochromic variable optical attenuators that operate with a low drive voltage (+/-1.2 volts). A new concept is also introduced for conjugated conducting polymers as the active material in dual electrochromic

  13. Design, synthesis, characterization and study of novel conjugated polymers

    SciTech Connect

    Chen, W.

    1997-06-24

    After introducing the subject of conjugated polymers, the thesis has three sections each containing a literature survey, results and discussion, conclusions, and experimental methods on the following: synthesis, characterization of electroluminescent polymers containing conjugated aryl, olefinic, thiophene and acetylenic units and their studies for use in light-emitting diodes; synthesis, characterization and study of conjugated polymers containing silole unit in the main chain; and synthesis, characterization and study of silicon-bridged and butadiene-linked polythiophenes.

  14. Optical Control of Living Cells Electrical Activity by Conjugated Polymers.

    PubMed

    Martino, Nicola; Bossio, Caterina; Vaquero Morata, Susana; Lanzani, Guglielmo; Antognazza, Maria Rosa

    2016-01-01

    Hybrid interfaces between organic semiconductors and living tissues represent a new tool for in-vitro and in-vivo applications. In particular, conjugated polymers display several optimal properties as substrates for biological systems, such as good biocompatibility, excellent mechanical properties, cheap and easy processing technology, and possibility of deposition on light, thin and flexible substrates. These materials have been employed for cellular interfaces like neural probes, transistors for excitation and recording of neural activity, biosensors and actuators for drug release. Recent experiments have also demonstrated the possibility to use conjugated polymers for all-optical modulation of the electrical activity of cells. Several in-vitro study cases have been reported, including primary neuronal networks, astrocytes and secondary line cells. Moreover, signal photo-transduction mediated by organic polymers has been shown to restore light sensitivity in degenerated retinas, suggesting that these devices may be used for artificial retinal prosthesis in the future. All in all, light sensitive conjugated polymers represent a new approach for optical modulation of cellular activity. In this work, all the steps required to fabricate a bio-polymer interface for optical excitation of living cells are described. The function of the active interface is to transduce the light stimulus into a modulation of the cell membrane potential. As a study case, useful for in-vitro studies, a polythiophene thin film is used as the functional, light absorbing layer, and Human Embryonic Kidney (HEK-293) cells are employed as the biological component of the interface. Practical examples of successful control of the cell membrane potential upon stimulation with light pulses of different duration are provided. In particular, it is shown that both depolarizing and hyperpolarizing effects on the cell membrane can be achieved depending on the duration of the light stimulus. The reported

  15. Responsive Guest Encapsulation of Dynamic Conjugated Microporous Polymers

    NASA Astrophysics Data System (ADS)

    Xu, Lai; Li, Youyong

    2016-06-01

    The host-guest complexes of conjugated microporous polymers encapsulating C60 and dye molecules have been investigated systematically. The orientation of guest molecules inside the cavities, have different terms: inside the open cavities of the polymer, or inside the cavities formed by packing different polymers. The host backbone shows responsive dynamic behavior in order to accommodate the size and shape of incoming guest molecule or guest aggregates. Simulations show that the host-guest binding of conjugated polymers is stronger than that of non-conjugated polymers. This detailed study could provide a clear picture for the host-guest interaction for dynamic conjugated microporous polymers. The mechanism obtained could guide designing new conjugated microporous polymers.

  16. Responsive Guest Encapsulation of Dynamic Conjugated Microporous Polymers.

    PubMed

    Xu, Lai; Li, Youyong

    2016-01-01

    The host-guest complexes of conjugated microporous polymers encapsulating C60 and dye molecules have been investigated systematically. The orientation of guest molecules inside the cavities, have different terms: inside the open cavities of the polymer, or inside the cavities formed by packing different polymers. The host backbone shows responsive dynamic behavior in order to accommodate the size and shape of incoming guest molecule or guest aggregates. Simulations show that the host-guest binding of conjugated polymers is stronger than that of non-conjugated polymers. This detailed study could provide a clear picture for the host-guest interaction for dynamic conjugated microporous polymers. The mechanism obtained could guide designing new conjugated microporous polymers. PMID:27356483

  17. Responsive Guest Encapsulation of Dynamic Conjugated Microporous Polymers

    PubMed Central

    Xu, Lai; Li, Youyong

    2016-01-01

    The host-guest complexes of conjugated microporous polymers encapsulating C60 and dye molecules have been investigated systematically. The orientation of guest molecules inside the cavities, have different terms: inside the open cavities of the polymer, or inside the cavities formed by packing different polymers. The host backbone shows responsive dynamic behavior in order to accommodate the size and shape of incoming guest molecule or guest aggregates. Simulations show that the host-guest binding of conjugated polymers is stronger than that of non-conjugated polymers. This detailed study could provide a clear picture for the host-guest interaction for dynamic conjugated microporous polymers. The mechanism obtained could guide designing new conjugated microporous polymers. PMID:27356483

  18. Highly Sensitive Thin-Film Field-Effect Transistor Sensor for Ammonia with the DPP-Bithiophene Conjugated Polymer Entailing Thermally Cleavable tert-Butoxy Groups in the Side Chains.

    PubMed

    Yang, Yang; Zhang, Guanxin; Luo, Hewei; Yao, Jingjing; Liu, Zitong; Zhang, Deqing

    2016-02-17

    The sensing and detection of ammonia have received increasing attention in recent years because of the growing emphasis on environmental and health issues. In this paper, we report a thin-film field-effect transistor (FET)-based sensor for ammonia and other amines with remarkable high sensitivity and satisfactory selectivity by employing the DPP-bithiophene conjugated polymer pDPPBu-BT in which tert-butoxycarboxyl groups are incorporated in the side chains. This polymer thin film shows p-type semiconducting property. On the basis of TGA and FT-IR analysis, tert-butoxycarboxyl groups can be transformed into the -COOH ones by eliminating gaseous isobutylene after thermal annealing of pDPPBu-BT thin film at 240 °C. The FET with the thermally treated thin film of pDPPBu-BT displays remarkably sensitive and selective response toward ammonia and volatile amines. This can be attributed to the fact that the elimination of gaseous isobutylene accompanies the formation of nanopores with the thin film, which will facilitate the diffusion and interaction of ammonia and other amines with the semiconducting layer, leading to high sensitivity and fast response for this FET sensor. This FET sensor can detect ammonia down to 10 ppb and the interferences from other volatile analytes except amines can be negligible. PMID:26883723

  19. Conjugated polymer sensors for explosive vapor detection

    NASA Astrophysics Data System (ADS)

    Wang, Yue; Turnbull, Graham A.; Samuel, Ifor D. W.

    2011-10-01

    Explosive sensing is a promising, emerging application for conjugated polymers. One exciting potential area of application is to clear landmines left after military actions. In this work, we demonstrate three ways to detect 10 partsper- billion of the model explosive, 1,4-dinitrobenzene (DNB): by monitoring fluorescence intensity, by measuring fluorescence lifetime, and by distributed-feedback (DFB) laser emission. A quenching of the fluorescence is observed upon DNB exposure. The reversibility of the quenching process has been demonstrated by purging with nitrogen.

  20. Targeted polymer-drug conjugates: Current progress and future perspective.

    PubMed

    Xu, Hongyan; Ma, Haifeng; Yang, Peimin; Zhang, Xia; Wu, Xiangxia; Yin, Weidong; Wang, Hui; Xu, Dongmei

    2015-12-01

    The combination of polymer technology and targeted drug delivery may pave the way for more effective yet safer therapeutic options for cancer therapy. Polymer-drug conjugates belonging to polymer therapeutics represent an emerging approach for drug delivery. The development of smart targeted polymer-drug conjugates that can specifically deliver drugs at a sustained rate to tumor cells may substantially improve the therapeutic index of anticancer agents. In this update, we provide an overview of the most important targeting molecules, and systemically summarize the recent advances in the development of tumor-targeted polymer-drug conjugates. Additionally, several promising approaches for the future will also be presented. PMID:26513756

  1. Controlling Molecular Ordering in Solution-State Conjugated Polymers

    SciTech Connect

    Zhu, Jiahua; Han, Youngkyu; Kumar, Rajeev; Hong, Kunlun; Bonnesen, Peter V.; Sumpter, Bobby G.; Smith, Gregory Scott; Ivanov, Ilia N.; Do, Changwoo

    2015-07-17

    Rationally encoding molecular interactions that can control the assembly structure and functional expression in solution of conjugated polymers holds great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution, we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.

  2. Overcoming Film Quality Issues for Conjugated Polymers Doped with F4TCNQ by Solution Sequential Processing: Hall Effect, Structural, and Optical Measurements.

    PubMed

    Scholes, D Tyler; Hawks, Steven A; Yee, Patrick Y; Wu, Hao; Lindemuth, Jeffrey R; Tolbert, Sarah H; Schwartz, Benjamin J

    2015-12-01

    We demonstrate that solution-sequential processing (SqP) can yield heavily doped pristine-quality films when used to infiltrate the molecular dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) into pure poly(3-hexylthiophene) (P3HT) polymer layers. Profilometry measurements show that the SqP method produces doped films with essentially the same surface roughness as pristine films, and 2-D grazing-incidence wide-angle X-ray scattering (GIWAXS) confirms that SqP preserves both the size and orientation of the pristine polymer's crystallites. Unlike traditional blend-cast F4TCNQ/P3HT doped films, our sequentially processed layers have tunable and reproducible conductivities reaching as high as 5.5 S/cm even when measured over macroscopic (>1 cm) distances. The high conductivity and superb film quality allow for meaningful Hall effect measurements, which reveal p-type conduction and carrier concentrations tunable from 10(16) to 10(20) cm(-3) and hole mobilities ranging from ∼0.003 to 0.02 cm(2) V(-1) s(-1) at room temperature over the doping levels examined. PMID:26554820

  3. Spatial distribution of space charge in conjugated polymers

    SciTech Connect

    Feller, F.; Geschke, D.; Monkman, A. P.

    2001-08-06

    We demonstrate the pyroelectric effect in a conjugated polymer, poly(2,5-pyridinediyl) (PPY), and we use the laser intensity modulation method (LIMM) to resolve the spatial distribution of electric field and space charges inside a 5 {mu}m Au/PPY/Au sandwich device. The pyroelectric signal shows hysteresis behavior with respect to the applied bias indicating permanent storage of injected charges. From the analysis of the LIMM spectra we conclude that application of a bias leads to the accumulation of space charges near the electrodes, while a zone of opposite space charge may establish in a distance of about 1 {mu}m from it. The charged state retains after removing the bias and can lead to an internal electric field that is opposite to the external poling field in the bulk of the polymer film. {copyright} 2001 American Institute of Physics.

  4. Fluoro-Substituted n-Type Conjugated Polymers for Additive-Free All-Polymer Bulk Heterojunction Solar Cells with High Power Conversion Efficiency of 6.71.

    PubMed

    Jung, Jae Woong; Jo, Jea Woong; Chueh, Chu-Chen; Liu, Feng; Jo, Won Ho; Russell, Thomas P; Jen, Alex K-Y

    2015-06-01

    Fluorinated n-type conjugated polymers are used as efficient electron acceptor to demonstrate high-performance all-polymer solar cells. The exciton generation, dissociation, and charge-transporting properties of blend films are improved by using these fluorinated n-type polymers to result in enhanced photocurrent and suppressed charge recombination. PMID:25900070

  5. Ultrafast measurements of vibrational relaxation in the conjugated polymer poly(9,9-dioctylfluorene)

    NASA Astrophysics Data System (ADS)

    Wells, Jon-Paul R.; Lidzey, David G.; Phillips, P. Jonathan; Carder, Damian A.; Fox, A. Mark

    2004-10-01

    We report the resonant pump-probe measurements used to study the dynamics of molecular vibrations in the conjugated polymer poly(9,9-dioctlyfluorene) (PFO). Free-electron-laser excited, pump-probe measurements on a drop-cast polymer film yield the lifetime of a series of different infrared active, high frequency vibrational modes at 5K. A general trend of decreasing lifetime with increasing frequency of the vibrational mode seems consistent with an enhanced density of accepting states for high frequency modes. Our measurements provide an insight into the dissipation of energy in conjugated polymers, and have implications for exciton generation and dissociation mechanisms in organic optoelectronic devices.

  6. Enzyme linked immunoassay with stabilized polymer saccharide enzyme conjugates

    DOEpatents

    Callstrom, Matthew R.; Bednarski, Mark D.; Gruber, Patrick R.

    1997-01-01

    An improvement in enzyme linked immunoassays is disclosed wherein the enzyme is in the form of a water soluble polymer saccharide conjugate which is stable in hostile environments. The conjugate comprises the enzyme which is linked to the polymer at multiple points through saccharide linker groups.

  7. Method for synthesizing peptides with saccharide linked enzyme polymer conjugates

    DOEpatents

    Callstrom, Matthew R.; Bednarski, Mark D.; Gruber, Patrick R.

    1997-01-01

    A method is disclosed for synthesizing peptides using water soluble enzyme polymer conjugates. The method comprises catalyzing the peptide synthesis with enzyme which has been covalently bonded to a polymer through at least three linkers which linkers have three or more hydroxyl groups. The enzyme is conjugated at lysines or arginines.

  8. Method for synthesizing peptides with saccharide linked enzyme polymer conjugates

    DOEpatents

    Callstrom, M.R.; Bednarski, M.D.; Gruber, P.R.

    1997-06-17

    A method is disclosed for synthesizing peptides using water soluble enzyme polymer conjugates. The method comprises catalyzing the peptide synthesis with enzyme which has been covalently bonded to a polymer through at least three linkers which linkers have three or more hydroxyl groups. The enzyme is conjugated at lysines or arginines. 19 figs.

  9. Enzyme linked immunoassay with stabilized polymer saccharide enzyme conjugates

    DOEpatents

    Callstrom, M.R.; Bednarski, M.D.; Gruber, P.R.

    1997-11-25

    An improvement in enzyme linked immunoassays is disclosed wherein the enzyme is in the form of a water soluble polymer saccharide conjugate which is stable in hostile environments. The conjugate comprises the enzyme which is linked to the polymer at multiple points through saccharide linker groups. 19 figs.

  10. Emerging Synthetic Techniques for Protein-Polymer Conjugations

    PubMed Central

    Broyer, Rebecca M.; Grover, Gregory N.; Maynard, Heather D.

    2011-01-01

    Protein-polymer conjugates are important in diverse fields including drug delivery, biotechnology, and nanotechnology. This feature article highlights recent advances in the synthesis and application of protein-polymer conjugates by controlled radical polymerization techniques. Special emphasis on new applications of the materials, particularly in biomedicine, are highlighted. PMID:21229146

  11. Scattering from Colloid-Polymer Conjugates with Excluded Volume Effect

    SciTech Connect

    Li, Xin; Sanchez-Diaz, Luis E.; Smith, Gregory Scott; Chen, Wei-Ren

    2015-01-13

    This work presents scattering functions of conjugates consisting of a colloid particle and a self-avoiding polymer chain as a model for protein-polymer conjugates and nanoparticle-polymer conjugates in solution. The model is directly derived from the two-point correlation function with the inclusion of excluded volume effects. The dependence of the calculated scattering function on the geometric shape of the colloid and polymer stiffness is investigated. The model is able to describe the experimental scattering signature of the solutions of suspending hard particle-polymer conjugates and provide additional conformational information. This model explicitly elucidates the link between the global conformation of a conjugate and the microstructure of its constituent components.

  12. Singlet fission of hot excitons in π-conjugated polymers.

    PubMed

    Zhai, Yaxin; Sheng, Chuanxiang; Vardeny, Z Valy

    2015-06-28

    We used steady-state photoinduced absorption (PA), excitation dependence (EXPA(ω)) spectrum of the triplet exciton PA band, and its magneto-PA (MPA(B)) response to investigate singlet fission (SF) of hot excitons into two separated triplet excitons, in two luminescent and non-luminescent π-conjugated polymers. From the high energy step in the triplet EXPA(ω) spectrum of the luminescent polymer poly(dioctyloxy)phenylenevinylene (DOO-PPV) films, we identified a hot-exciton SF (HE-SF) process having threshold energy at E≈2E(T) (=2.8 eV, where ET is the energy of the lowest lying triplet exciton), which is about 0.8 eV above the lowest singlet exciton energy. The HE-SF process was confirmed by the triplet MPA(B) response for excitation at E>2E(T), which shows typical SF response. This process is missing in DOO-PPV solution, showing that it is predominantly interchain in nature. By contrast, the triplet EXPA(ω) spectrum in the non-luminescent polymer polydiacetylene (PDA) is flat with an onset at E=E(g) (≈2.25 eV). From this, we infer that intrachain SF that involves a triplet-triplet pair state, also known as the 'dark' 2A(g) exciton, dominates the triplet photogeneration in PDA polymer as E(g)>2E(T). The intrachain SF process was also identified from the MPA(B) response of the triplet PA band in PDA. Our work shows that the SF process in π-conjugated polymers is a much more general process than thought previously. PMID:25987576

  13. Singlet fission of hot excitons in π-conjugated polymers

    PubMed Central

    Zhai, Yaxin; Sheng, Chuanxiang; Vardeny, Z. Valy

    2015-01-01

    We used steady-state photoinduced absorption (PA), excitation dependence (EXPA(ω)) spectrum of the triplet exciton PA band, and its magneto-PA (MPA(B)) response to investigate singlet fission (SF) of hot excitons into two separated triplet excitons, in two luminescent and non-luminescent π-conjugated polymers. From the high energy step in the triplet EXPA(ω) spectrum of the luminescent polymer poly(dioctyloxy)phenylenevinylene (DOO-PPV) films, we identified a hot-exciton SF (HE-SF) process having threshold energy at E≈2ET (=2.8 eV, where ET is the energy of the lowest lying triplet exciton), which is about 0.8 eV above the lowest singlet exciton energy. The HE-SF process was confirmed by the triplet MPA(B) response for excitation at E>2ET, which shows typical SF response. This process is missing in DOO-PPV solution, showing that it is predominantly interchain in nature. By contrast, the triplet EXPA(ω) spectrum in the non-luminescent polymer polydiacetylene (PDA) is flat with an onset at E=Eg (≈2.25 eV). From this, we infer that intrachain SF that involves a triplet–triplet pair state, also known as the ‘dark’ 2Ag exciton, dominates the triplet photogeneration in PDA polymer as Eg>2ET. The intrachain SF process was also identified from the MPA(B) response of the triplet PA band in PDA. Our work shows that the SF process in π-conjugated polymers is a much more general process than thought previously. PMID:25987576

  14. Thin-film transistors based on organic conjugated semiconductors

    NASA Astrophysics Data System (ADS)

    Garnier, Francis

    1998-02-01

    The use of organic semiconductors as active layers in thin-film transistors has raised in the recent years a large interest, both for the fundamental understanding of the charge transport processes in organic materials, and also for the potential applications of these devices in the new field of flexible electronics. Short conjugated oligomers have been shown to possess much higher field-effect mobilities than their parent conjugated polymers. The origin of such increase in the efficiency of charge transport is mainly attributed to the close-packing and long-range structural organization displayed in thin films of conjugated oligomers. The various routes for controlling this organization are described, which allow to realize liquid crystal-like two-dimensional structures for these semiconductors, whose carrier mobility has now become equivalent to that of amorphous silicon. It is also shown that the effect of conjugation length on carrier mobility is not as critical as previously thought, but the associated increase of the band gap energy effects the efficiency of charge injection at the metal/semiconductor interface. This problem can be answered by realizing a local doping of the semiconductor, which allows the injection of charge to operate through an efficient tunneling mechanism. Organic-based thin-film transistors have now become viable devices.

  15. Changes in the Solution Behavior of Conjugated Polymers with Light Absorption

    NASA Astrophysics Data System (ADS)

    Dadmun, Mark; Morgan, Brian

    2015-03-01

    Conjugated polymers are well established as functional materials in a broad range of applications including organic photovoltaics, chemical sensors, and organic light emitting diodes. This functionality is mainly derived from their ability to create electron-hole pair excitons through photoexcitation. The presence of these entities on the polymer chains may alter the chain conformation, solution behavior, and ultimately macroscopic morphology, of the conjugated polymer. Previous studies have shown significant changes in properties such as viscosity and photoluminescence upon exposure of select conjugated polymer films to white light. In order to expand upon these preliminary findings, we have performed small angle neutron scattering experiments on solutions of several semiconducting, conjugated polymers in both the presence and absence of incident light. Substantial differences are observed between the light vs dark samples, the magnitude of which are dependent on polymer dispersion, solvent choice, and solution concentration. Analysis of the neutron curves shows real difference in Kuhn lengths and radius of gyration of the polymer, suggesting possible rearrangement of polymer chain conformation or alteration of polymer chain-solvent interactions.

  16. Interfacial Widths of Conjugated Polymer Bilayers

    SciTech Connect

    NCSU; UC Berkeley; UCSB; Advanced Light Source; Garcia, Andres; Yan, Hongping; Sohn, Karen E.; Hexemer, Alexander; Nguyen, Thuc-Quyen; Bazan, Guillermo C.; Kramer, Edward J.; Ade, Harald

    2009-08-13

    The interfaces of conjugated polyelectrolyte (CPE)/poly[2-methoxy-5-(2{prime}-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) bilayers cast from differential solvents are shown by resonant soft X-ray reflectivity (RSoXR) to be very smooth and sharp. The chemical interdiffusion due to casting is limited to less than 0.6 nm, and the interface created is thus nearly 'molecularly' sharp. These results demonstrate for the first time and with high precision that the nonpolar MEH-PPV layer is not much disturbed by casting the CPE layer from a polar solvent. A baseline is established for understanding the role of interfacial structure in determining the performance of CPE-based polymer light-emitting diodes. More broadly, we anticipate further applications of RSoXR as an important tool in achieving a deeper understanding of other multilayer organic optoelectronic devices, including multilayer photovoltaic devices.

  17. Charge Injection and Transport in Conjugated Polymers.

    NASA Astrophysics Data System (ADS)

    Malliaras, George

    2007-03-01

    We will overview the state-of-the-art in our understanding of charge injection and transport in conjugated polymers. We start by discussing the identifying characteristics of this class of materials, especially in relation with their structure and morphology. We follow by reviewing the advantages and limitations of experimental techniques that are used to probe charge transport. We then embark on a discussion of the fundamentals of charge transport in organics. We follow a didactic approach, where we start from transport in crystalline semiconductors and gradually introduce corrections for space charge effects, for the influence of disorder on mobility, for high charge densities, and for electric field-dependent charge densities. We compare with experimental data from polyfluorenes. We then shift our attention to charge injection. We review some of the recent theories and compared their predictions to experimental data, again from polyfluorenes. We close by proposing directions for future work.

  18. In situ measurements of the optical absorption of dioxythiophene-based conjugated polymers

    NASA Astrophysics Data System (ADS)

    Hwang, J.; Schwendeman, I.; Ihas, B. C.; Clark, R. J.; Cornick, M.; Nikolou, M.; Argun, A.; Reynolds, J. R.; Tanner, D. B.

    2011-05-01

    Conjugated polymers can be reversibly doped by electrochemical means. This doping introduces new subband-gap optical absorption bands in the polymer while decreasing the band-gap absorption. To study this behavior, we have prepared an electrochemical cell allowing in situ measurements of the optical properties of the polymer. The cell consists of a thin polymer film deposited on gold-coated Mylar behind which is another polymer that serves as a counterelectrode. An infrared transparent window protects the upper polymer from ambient air. By adding a gel electrolyte and making electrical connections to the polymer-on-gold films, one may study electrochromism in a wide spectral range. As the cell voltage (the potential difference between the two electrodes) changes, the doping level of the conjugated polymer films is changed reversibly. Our experiments address electrochromism in poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-dimethylpropylenedioxythiophene) (PProDOT-Me2). This closed electrochemical cell allows the study of the doping induced subband-gap features (polaronic and bipolaronic modes) in these easily oxidized and highly redox switchable polymers. We also study the changes in cell spectra as a function of polymer thickness and investigate strategies to obtain cleaner spectra, minimizing the contributions of water and gel electrolyte features.

  19. Advances in Polymer and Polymeric Nanostructures for Protein Conjugation

    PubMed Central

    González-Toro, Daniella C.; Thayumanavan, S.

    2013-01-01

    Linear polymers have been considered the best molecular structures for the formation of efficient protein conjugates due to their biological advantages, synthetic convenience and ease of functionalization. In recent years, much attention has been dedicated to develop synthetic strategies that produce the most control over protein conjugation utilizing linear polymers as scaffolds. As a result, different conjugate models, such as semitelechelic, homotelechelic, heterotelechelic and branched or star polymer conjugates, have been obtained that take advantage of these well-controlled synthetic strategies. Development of protein conjugates using nanostructures and the formation of said nanostructures from protein-polymer bioconjugates are other areas in the protein bioconjugation field. Although several polymer-protein technologies have been developed from these discoveries, few review articles have focused on the design and function of these polymers and nanostructures. This review will highlight some recent advances in protein-linear polymer technologies that employ protein covalent conjugation and successful protein-nanostructure bioconjugates (covalent conjugation as well) that have shown great potential for biological applications. PMID:24058205

  20. Scattering from Colloid-Polymer Conjugates with Excluded Volume Effect

    DOE PAGESBeta

    Li, Xin; Sanchez-Diaz, Luis E.; Smith, Gregory Scott; Chen, Wei-Ren

    2015-01-13

    This work presents scattering functions of conjugates consisting of a colloid particle and a self-avoiding polymer chain as a model for protein-polymer conjugates and nanoparticle-polymer conjugates in solution. The model is directly derived from the two-point correlation function with the inclusion of excluded volume effects. The dependence of the calculated scattering function on the geometric shape of the colloid and polymer stiffness is investigated. The model is able to describe the experimental scattering signature of the solutions of suspending hard particle-polymer conjugates and provide additional conformational information. This model explicitly elucidates the link between the global conformation of a conjugatemore » and the microstructure of its constituent components.« less

  1. Thin film Z-scan measurements of the nonlinear response of novel conjugated silicon-ethynylene polymers and metal-containing complexes incorporated into polymeric matrices

    NASA Astrophysics Data System (ADS)

    Douglas, William E.; Klapshina, Larisa G.; Rubinov, Anatoly N.; Domrachev, George A.; Bushuk, Boris A.; Antipov, Oleg L.; Semenov, Vladimir V.; Kuzhelev, Alexander S.; Bushuk, Sergey B.; Kalvinkovskaya, Julia A.

    2000-11-01

    The third-order optical nonlinearities of new conjugated poly[(arylene)(ethynylene)silylene]s, and a variety of chromium, neodymium or cobalt complexes incorporated into polymeric matrices as thin sol-gel or polyacrylonitrile films have been determined by using a single beam Z-scan technique. The samples were pumped by a single ultrashort pulse of a mode-locked Nd-phosphate glass laser (wavelength 1054 nm) with a 5ps pulse duration (full width at half- maximum), the repetition rate of the Gaussian beam being low (0.3Hz) ro avoid thermal effects. The spot radius of the focused pulse was ca. 60micrometers , its beam waist being in the sample (intensity up to 4x1013 Wm-2). Calibration was done with chloroform and benzene, the value of N2 for the latter (2x10-12esu) being similar to that previously reported. A small-aperture Z-scan (S=0.03) was used to measure the magnitude and the sign of the nonlinear refractive index, n2. Very high nonlinear refractive indices were found for a film containing (a) a poly[(arylene)(ethynylene)silylene]s with pentacoordinated silicon (c 5 gl-1) in a sol-gel matrix (N2 = 6 x 10-13 cm2W-1), (b) a film containing a poly[(arylene)(ethynylene)silylene] with tetracoordinated silicon (c 0.5 gl-1) and a very small proportion of fullerene-C70 incorporated into an NH2-containing sol-gel matrix (n2 = 5x10-13 cm2W-1, and (c) a thin polyacrylonitrile film of polycyanoethylate bis-arenechromium(I) hydroxide (n2 = -5 x 10-12 cm(superscript 2W-1.

  2. Recent advances in conjugated polymers for light emitting devices.

    PubMed

    Alsalhi, Mohamad Saleh; Alam, Javed; Dass, Lawrence Arockiasamy; Raja, Mohan

    2011-01-01

    A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review. PMID:21673938

  3. Recent Advances in Conjugated Polymers for Light Emitting Devices

    PubMed Central

    AlSalhi, Mohamad Saleh; Alam, Javed; Dass, Lawrence Arockiasamy; Raja, Mohan

    2011-01-01

    A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review. PMID:21673938

  4. Nanostructured conjugated polymers in chemical sensors: synthesis, properties and applications.

    PubMed

    Correa, D S; Medeiros, E S; Oliveira, J E; Paterno, L G; Mattoso, Luiz C

    2014-09-01

    Conjugated polymers are organic materials endowed with a π-electron conjugation along the polymer backbone that present appealing electrical and optical properties for technological applications. By using conjugated polymeric materials in the nanoscale, such properties can be further enhanced. In addition, the use of nanostructured materials makes possible miniaturize devices at the micro/nano scale. The applications of conjugated nanostructured polymers include sensors, actuators, flexible displays, discrete electronic devices, and smart fabric, to name a few. In particular, the use of conjugated polymers in chemical and biological sensors is made feasible owning to their sensitivity to the physicochemical conditions of its surrounding environment, such as chemical composition, pH, dielectric constant, humidity or even temperature. Subtle changes in these conditions bring about variations on the electrical (resistivity and capacitance), optical (absorptivity, luminescence, etc.), and mechanical properties of the conjugated polymer, which can be precisely measured by different experimental methods and ultimately associated with a specific analyte and its concentration. The present review article highlights the main features of conjugated polymers that make them suitable for chemical sensors. An especial emphasis is given to nanostructured sensors systems, which present high sensitivity and selectivity, and find application in beverage and food quality control, pharmaceutical industries, medical diagnosis, environmental monitoring, and homeland security, and other applications as discussed throughout this review. PMID:25924296

  5. Intermolecular Interaction Effects on the Ultrafast Depolarization of the Optical Emission from Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Chang, M. H.; Frampton, M. J.; Anderson, H. L.; Herz, L. M.

    2007-01-01

    We have investigated the effect of interchain interactions on the ultrafast depolarization of the photoluminescence from solid films of a conjugated polymer. Accurate control was exercised over the interchain separation by threading of the conjugated chains with insulating macrocycles or complexation with an inert host polymer. Our measurements indicate that excitation into the higher electronic states of a chain aggregate is followed by a fast (<100fs) relaxation into lower excited states with an associated rotation of the transition dipole moment. These findings emphasize the need for consideration of initial excitonic delocalization across more than one polymeric chain.

  6. Highly emissive 'frozen-in' conjugated polymer nanofibers.

    PubMed

    Jin, Young-Jae; Lee, Wang-Eun; Lee, Chang-Lyoul; Kwak, Giseop

    2016-05-11

    Conjugated-polymer nanofibers with a thermodynamically stable, coarsened, disordered structure in an amorphous glassy state were fabricated via a freeze-drying method using a poly(diphenylacetylene) derivative. The nanofibers were extremely emissive, with a fluorescence (FL) quantum yield of approximately 0.34, which was much higher than that of both the cast film (0.02) and the solution (0.21). Similarly, the amplitude-weighted average FL lifetime of the nanofibers was 0.74 ns, which was much longer than that of the film (0.29 ns) and the solution (0.57 ns). This unusual and enhanced FL-emission behavior was attributed to the abruptly quenched chain structure that was created by the freeze-drying process. The polymer chains in the nanofibers remained frozen-in and the side phenyl rings were retained in a relaxed state. The metastable chains did not undergo vibrational relaxation and collisional quenching to generate the radiative emission decay effectively. PMID:27109600

  7. Controlling molecular ordering in solution-state conjugated polymers

    NASA Astrophysics Data System (ADS)

    Zhu, J.; Han, Y.; Kumar, R.; He, Y.; Hong, K.; Bonnesen, P. V.; Sumpter, B. G.; Smith, S. C.; Smith, G. S.; Ivanov, I. N.; Do, C.

    2015-09-01

    Rationally encoding molecular interactions that can control the assembly structure and functional expression in a solution of conjugated polymers hold great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with the desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution, we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.Rationally encoding molecular interactions that can control the assembly structure and functional expression in a solution of conjugated polymers hold great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with the desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution, we demonstrate that both chain conformation and degree of molecular ordering

  8. Peptide-Polymer Conjugates: From Fundamental Science to Application

    NASA Astrophysics Data System (ADS)

    Shu, Jessica Y.; Panganiban, Brian; Xu, Ting

    2013-04-01

    Peptide/protein-polymer conjugates make up a new class of soft matter comprising natural and synthetic building blocks. They have the potential to combine the advantages of proteins and synthetic polymers (i.e., the precise chemical structure and diverse functionalities of biomolecules and the stability and processability of synthetic polymers) to generate hybrid materials with properties yet to be realized with either component alone. Here we briefly discuss recent developments in the design, fundamental understanding, and self-assembly of various peptide-polymer conjugates, as well as emerging biological and nonbiological applications that range from nanomedicine, to separation, and beyond.

  9. Electronic structure of disordered conjugated polymers: Polythiophenes

    SciTech Connect

    Vukmirovic, Nenad; Wang, Lin-Wang

    2008-11-26

    Electronic structure of disordered semiconducting conjugated polymers was studied. Atomic structure was found from a classical molecular dynamics simulation and the charge patching method was used to calculate the electronic structure with the accuracy similar to the one of density functional theory in local density approximation. The total density of states, the local density of states at different points in the system and the wavefunctions of several states around the gap were calculated in the case of poly(3-hexylthiophene) (P3HT) and polythiophene (PT) systems to gain insight into the origin of disorder in the system, the degree of carrier localization and the role of chain interactions. The results indicated that disorder in the electronic structure of alkyl substituted polythiophenes comes from disorder in the conformation of individualchains, while in the case of polythiophene there is an additional contribution due to disorder in the electronic coupling between the chains. Each of the first several wavefunctions in the conduction and valence band of P3HT is localized over several rings of a single chain. It was shown that the localization can be caused in principle both by ring torsions and chain bending, however the effect of ring torsions is much stronger. PT wavefunctions are more complicated due to larger interchain electronic coupling and are not necessarily localized on a single chain.

  10. Photorefractive conjugated polymer-liquid crystal composites

    SciTech Connect

    Wasielewski, M. R.; Yoon, B. A.; Fuller, M.; Wiederrecht, G. P.; Niemczyk, M. P.; Svec, W. A.

    2000-05-15

    A new mechanism for space-charge field formation in photorefractive liquid crystal composites containing poly(2,5-bis(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene) (BEH-PPV) and the electron acceptor N,N{prime}-dioctyl-1,4:5,8-naphthalenediimide, NI, is observed. Using asymmetric energy transfer (beam coupling) measurements that are diagnostic for the photorefractive effect, the direction of beam coupling as a function of grating fringe spacing inverts at a spacing of 5.5 {micro}m. The authors show that the inversion is due to a change in the dominant mechanism for space-charge field formation. At small fringe spacings, the space-charge field is formed by ion diffusion in which the photogenerated anion is the more mobile species. At larger fringe spacings, the polarity of the space charge field inverts due to dominance of a charge transport mechanism in which photogenerated holes are the most mobile species due to hole migration along the BEH-PEV chains coupled with interchain hole hopping. Control experiments are presented, which use composites that can access only one of the two charge transport mechanisms. The results show that charge migration over long distances leading to enhanced photorefractive effects can be obtained using conjugated polymers dissolved in liquid crystals.

  11. Synthesis of capped TiO2 nanocrystals of controlled shape and their use with MEH-PPV conjugated polymer to develop nanocomposite films for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Mighri, F.; Duong, Vu Thi Thuy; On, Do Trong; Ajji, A.

    2014-05-01

    This study presents the synthesis details of titanium dioxide (TiO2) nanoparticles (NPs) of different shapes (nanospheres, nanorods and nanorhombics) using oleic acid (OA) and oleyl amine (OM) as capping agents. In order to develop nanocomposite thin films for photovoltaic cells, these TiO2 NPs were carefully dispersed in 2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene (MEH-PPV) matrix. The properties of synthesized TiO2 NPs and MEH-PPV/TiO2 nanocomposites were characterized using transmission electron microscopy (TEM), thermogravimetric analysis (TGA), UV-Visible spectroscopy, and Photoluminescence technique. It was found that the shape of NPs and the amount of OA and OM surfactants capped on their surface have an effect on their energy bandgap and also on the dispersion quality of MEH-PPV/TiO2 nanocomposites. Even though there was no evidence of chemical bonding between MEH-PPV matrix and TiO2 dispersed NPs, MEH-PPV/TiO2 nanocomposites showed very promising results for light absorption properties and charge transfer at the interface of the conjugated MEH-PPV matrix and TiO2 dispersed NPs, which are two main characteristics for photovoltaic materials.

  12. Synthesis of capped TiO{sub 2} nanocrystals of controlled shape and their use with MEH-PPV conjugated polymer to develop nanocomposite films for photovoltaic applications

    SciTech Connect

    Mighri, F. E-mail: Thi-Thuy-Duong.vu.1@ulaval.ca; Duong, Vu Thi Thuy E-mail: Thi-Thuy-Duong.vu.1@ulaval.ca; On, Do Trong; Ajji, A.

    2014-05-15

    This study presents the synthesis details of titanium dioxide (TiO{sub 2}) nanoparticles (NPs) of different shapes (nanospheres, nanorods and nanorhombics) using oleic acid (OA) and oleyl amine (OM) as capping agents. In order to develop nanocomposite thin films for photovoltaic cells, these TiO{sub 2} NPs were carefully dispersed in 2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene (MEH-PPV) matrix. The properties of synthesized TiO{sub 2} NPs and MEH-PPV/TiO{sub 2} nanocomposites were characterized using transmission electron microscopy (TEM), thermogravimetric analysis (TGA), UV-Visible spectroscopy, and Photoluminescence technique. It was found that the shape of NPs and the amount of OA and OM surfactants capped on their surface have an effect on their energy bandgap and also on the dispersion quality of MEH-PPV/TiO{sub 2} nanocomposites. Even though there was no evidence of chemical bonding between MEH-PPV matrix and TiO2 dispersed NPs, MEH-PPV/TiO{sub 2} nanocomposites showed very promising results for light absorption properties and charge transfer at the interface of the conjugated MEH-PPV matrix and TiO{sub 2} dispersed NPs, which are two main characteristics for photovoltaic materials.

  13. Lipid-peptide-polymer conjugates and nanoparticles thereof

    SciTech Connect

    Xu, Ting; Dong, He; Shu, Jessica

    2015-06-02

    The present invention provides a conjugate having a peptide with from about 10 to about 100 amino acids, wherein the peptide adopts a helical structure. The conjugate also includes a first polymer covalently linked to the peptide, and a hydrophobic moiety covalently linked to the N-terminus of the peptide, wherein the hydrophobic moiety comprises a second polymer or a lipid moiety. The present invention also provides helix bundles form by self-assembling the conjugates, and particles formed by self-assembling the helix bundles. Methods of preparing the helix bundles and particles are also provided.

  14. A supramolecular cross-linked conjugated polymer network for multiple fluorescent sensing.

    PubMed

    Ji, Xiaofan; Yao, Yong; Li, Jinying; Yan, Xuzhou; Huang, Feihe

    2013-01-01

    A supramolecular cross-linked network was fabricated and demonstrated to act as a multiple fluorescent sensor. It was constructed from a fluorescent conjugated polymer and a bisammonium salt cross-linker driven by dibenzo[24]crown-8/secondary ammonium salt host-guest interactions. Compared with the conjugated polymer, the network has weak fluorescence due to the aggregation of polymer chains. Thanks to the multiple stimuli-responsiveness of host-guest interactions, the fluorescence intensity of the system can be enhanced by four types of signals, including potassium cation, chloride anion, pH increase, and heating. Hence, the network can serve as a cation sensor, an anion sensor, a pH sensor, and a temperature sensor. It can be used in both solution and thin film. Interestingly, exposure of a film made from this supramolecular cross-linked network to ammonia leads to an increase of fluorescence, making it a good candidate for gas detection. PMID:23259828

  15. Electronic and Morphological Studies of Conjugated Polymers Incorporating a Disk-Shaped Polycyclic Aromatic Hydrocarbon Unit.

    PubMed

    He, Bo; Zhang, Benjamin A; Liu, Feng; Navarro, Amparo; Fernández-Liencres, M Paz; Lu, Ryan; Lo, Kelvin; Chen, Teresa L; Russell, Thomas P; Liu, Yi

    2015-09-16

    As more research findings have shown the correlation between ordering in organic semiconductor thin films and device performance, it is becoming more essential to exercise control of the ordering through structural tuning. Many recent studies have focused on the influence of side chain engineering on polymer packing orientation in thin films. However, the impact of the size and conformation of aromatic surfaces on thin film ordering has not been investigated in great detail. Here we introduce a disk-shaped polycyclic aromatic hydrocarbon building block with a large π surface, namely, thienoazacoronenes (TACs), as a donor monomer for conjugated polymers. A series of medium bandgap conjugated polymers have been synthesized by copolymerizing TAC with electron donating monomers of varying size. The incorporation of the TAC unit in such semiconducting polymers allows a systematic investigation, both experimentally and theoretically, of the relationships between polymer conformation, electronic structure, thin film morphology, and charge transport properties. Field effect transistors based on these polymers have shown good hole mobilities and photoresponses, proving that TAC is a promising building block for high performance optoelectronic materials. PMID:26302772

  16. Thin film-coated polymer webs

    DOEpatents

    Wenz, Robert P.; Weber, Michael F.; Arudi, Ravindra L.

    1992-02-04

    The present invention relates to thin film-coated polymer webs, and more particularly to thin film electronic devices supported upon a polymer web, wherein the polymer web is treated with a purifying amount of electron beam radiation.

  17. Controlling Molecular Ordering in Solution-State Conjugated Polymers

    DOE PAGESBeta

    Zhu, Jiahua; Han, Youngkyu; Kumar, Rajeev; Hong, Kunlun; Bonnesen, Peter V.; Sumpter, Bobby G.; Smith, Gregory Scott; Ivanov, Ilia N.; Do, Changwoo

    2015-07-17

    Rationally encoding molecular interactions that can control the assembly structure and functional expression in solution of conjugated polymers holds great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution,more » we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.« less

  18. Process for crosslinking and extending conjugated diene-containing polymers

    NASA Technical Reports Server (NTRS)

    Bell, Vernon L. (Inventor); Havens, Stephen J. (Inventor)

    1977-01-01

    A process using a Diels-Alder reaction which increases the molecular weight and/or crosslinks polymers by reacting the polymers with bisunsaturated dienophiles is developed. The polymer comprises at least 75% by weight based on the reaction product, has a molecular weight of at least 5000 and a plurality of conjugated 1,3-diene systems incorporated into the molecular structure. A dienophile reaction with the conjugated 1,3-diene of the polymer is at least 1% by weight based on the reaction product. Examples of the polymer include polyesters, polyamides, polyethers, polysulfones and copolymers. The bisunsaturated dienophiles may include bis-maleimides, bis maleic and bis tumaric esters and amides. This method for expanding the molecular weight chains of the polymers, preferable thermoplastics, is advantageous for processing or fabricating thermoplastics. A low molecular weight thermoplastic is converted to a high molecular weight plastic having improved strength and toughness for use in the completed end use article.

  19. Mesoscopic quantum emitters from deterministic aggregates of conjugated polymers

    PubMed Central

    Stangl, Thomas; Wilhelm, Philipp; Remmerssen, Klaas; Höger, Sigurd; Vogelsang, Jan; Lupton, John M.

    2015-01-01

    An appealing definition of the term “molecule” arises from consideration of the nature of fluorescence, with discrete molecular entities emitting a stream of single photons. We address the question of how large a molecular object may become by growing deterministic aggregates from single conjugated polymer chains. Even particles containing dozens of individual chains still behave as single quantum emitters due to efficient excitation energy transfer, whereas the brightness is raised due to the increased absorption cross-section of the suprastructure. Excitation energy can delocalize between individual polymer chromophores in these aggregates by both coherent and incoherent coupling, which are differentiated by their distinct spectroscopic fingerprints. Coherent coupling is identified by a 10-fold increase in excited-state lifetime and a corresponding spectral red shift. Exciton quenching due to incoherent FRET becomes more significant as aggregate size increases, resulting in single-aggregate emission characterized by strong blinking. This mesoscale approach allows us to identify intermolecular interactions which do not exist in isolated chains and are inaccessible in bulk films where they are present but masked by disorder. PMID:26417079

  20. Synthesis and study of conjugated polymers containing Di- or Triphenylamine

    SciTech Connect

    Sukwattanasinitt, M.

    1996-06-21

    This thesis consists of two separate parts. The first part addresses the synthesis and study of conjugated polymers containing di- or triphenylamine. Two types of polymers: linear polymers and dendrimers, were synthesized. The polymers were characterized by NMR, IR, UV, GPC, TGA and DSC. Electronic and optical properties of the polymers were studied through the conductivity measurements and excitation- emission spectra. the second part of this thesis deals with a reaction of electron-rich acetylenes with TCNE. The discovery of the reaction from charge transfer complex studies and the investigation of this reaction on various electron-rich acetylenes are presented.

  1. CONJUGATED POLYMERS AND POLYELECTROLYTES IN SOLAR PHOTOCONVERSION, Final Technical Report

    SciTech Connect

    Schanze, Kirk S

    2014-08-05

    This DOE-supported program investigated the fundamental properties of conjugated polyelectrolytes, with emphasis placed on studies of excited state energy transport, self-assembly into conjugated polyelectroyte (CPE) based films and colloids, and exciton transport and charge injection in CPE films constructed atop wide bandgap semiconductors. In the most recent grant period we have also extended efforts to examine the properties of low-bandgap donor-acceptor conjugated polyelectrolytes that feature strong visible light absorption and the ability to adsorb to metal-oxide interfaces.

  2. Conjugated polymer-assisted dispersion of single-wall carbon nanotubes: the power of polymer wrapping.

    PubMed

    Samanta, Suman Kalyan; Fritsch, Martin; Scherf, Ullrich; Gomulya, Widianta; Bisri, Satria Zulkarnaen; Loi, Maria Antonietta

    2014-08-19

    coordinates [(n,m) indices]. The polymer wrapping strategy enables the generation of SWNT dispersions containing exclusively semiconducting nanotubes. Toward the applications in electronic devices, until now most applied approach is a direct processing of such SWNT dispersions into the active layer of network-type thin film field effect transistors. However, to achieve promising transistor performance (high mobility and on-off ratio) careful removal of the wrapping polymer chains seems crucial, for example, by washing or ultracentrifugation. More defined positioning of the SWNTs can be accomplished in directed self-assembly procedures. One possible strategy uses diblock copolymers containing a conjugated polymer block as dispersing moiety and a second block for directed self-assembly, for example, a DNA block for specific interaction with complementary DNA strands. Another strategy utilizes reactive side chains for controlled anchoring onto patterned surfaces (e.g., by interaction of thiol-terminated alkyl side chains with gold surfaces). A further promising application of purified SWNT dispersions is the field of organic (all-carbon) or hybrid solar cell devices. PMID:25025887

  3. Digital memory versatility of fully π-conjugated donor-acceptor hybrid polymers.

    PubMed

    Ko, Yong-Gi; Kim, Dong Min; Kim, Kyungtae; Jung, Sungmin; Wi, Dongwoo; Michinobu, Tsuyoshi; Ree, Moonhor

    2014-06-11

    The fully π-conjugated donor-acceptor hybrid polymers Fl-TPA, Fl-TPA-TCNE, and Fl-TPA-TCNQ, which are composed of fluorene (Fl), triphenylamine (TPA), dimethylphenylamine, alkyne, alkyne-tetracyanoethylene (TCNE) adduct, and alkyne-7,7,8,8-tetracyanoquinodimethane (TCNQ) adduct, were synthesized. These polymers are completely amorphous in the solid film state and thermally stable up to 291-409 °C. Their molecular orbital levels and band gaps vary with their compositions. The TCNE and TCNQ units, despite their electron-acceptor characteristics, were found to enhance the π-conjugation lengths of Fl-TPA-TCNE and Fl-TPA-TCNQ (i.e., to produce red shifts in their absorption spectra and significant reductions in their band gaps). These changes are reflected in the electrical digital memory behavior of the polymers. Moreover, the TCNE and TCNQ units were found to diversify the digital memory modes and to widen the active polymer layer thickness window. In devices with aluminum top and bottom electrodes, the Fl-TPA polymer exhibits stable unipolar permanent memory behavior with high reliability. The Fl-TPA-TCNE and Fl-TPA-TCNQ devices exhibit stable unipolar permanent memory behavior as well as dynamic random access memory behavior with excellent reliability. These polymer devices were found to operate by either hole injection or hole injection along with electron injection, depending on the polymer composition. Overall, this study demonstrated that the incorporation of π-conjugated cyano moieties, which control both the π-conjugation length and electron-accepting power, is a sound approach for the design and synthesis of high-performance digital memory polymers. The TCNE and TCNQ polymers synthesized in this study are highly suitable active materials for the low-cost mass production of high-performance, polarity-free, programmable, volatile, and permanent memory devices that can be operated with very low power consumption, high ON/OFF current ratios, and high

  4. Fluorescent non-conjugated polymer dots for targeted cell imaging.

    PubMed

    Sun, Bin; Zhao, Bin; Wang, Dandan; Wang, Yibo; Tang, Qi; Zhu, Shoujun; Yang, Bai; Sun, Hongchen

    2016-05-14

    Through the chemical crosslinking of the sub-fluorophore, linear non-conjugated polymers can possess strong photoluminescence (PL), which is a very important fluorescence behavior and the non-conjugated polymer dots (PDs) are efficient bio-fluorophores for bio-based applications. Herein, the new type of non-conjugated polyethyleneimine (PEI) PDs was further modified by targeting molecules (folic acid) for a new generation of bio-fluorophores. The free folic acid can quench the PL of PDs by energy transfer, while the conjugated folic acid@PDs (FA@PDs) can still maintain their PL properties to a certain degree. The FA@PDs also possess lower toxicity compared with free PDs, which is possibly due to blocking of the amino groups. Moreover, we investigated the targeted bioimaging applications of the FA@PDs, which gave a very important direction for application of these types of materials. PMID:27120205

  5. Fluorescent non-conjugated polymer dots for targeted cell imaging

    NASA Astrophysics Data System (ADS)

    Sun, Bin; Zhao, Bin; Wang, Dandan; Wang, Yibo; Tang, Qi; Zhu, Shoujun; Yang, Bai; Sun, Hongchen

    2016-05-01

    Through the chemical crosslinking of the sub-fluorophore, linear non-conjugated polymers can possess strong photoluminescence (PL), which is a very important fluorescence behavior and the non-conjugated polymer dots (PDs) are efficient bio-fluorophores for bio-based applications. Herein, the new type of non-conjugated polyethyleneimine (PEI) PDs was further modified by targeting molecules (folic acid) for a new generation of bio-fluorophores. The free folic acid can quench the PL of PDs by energy transfer, while the conjugated folic acid@PDs (FA@PDs) can still maintain their PL properties to a certain degree. The FA@PDs also possess lower toxicity compared with free PDs, which is possibly due to blocking of the amino groups. Moreover, we investigated the targeted bioimaging applications of the FA@PDs, which gave a very important direction for application of these types of materials.Through the chemical crosslinking of the sub-fluorophore, linear non-conjugated polymers can possess strong photoluminescence (PL), which is a very important fluorescence behavior and the non-conjugated polymer dots (PDs) are efficient bio-fluorophores for bio-based applications. Herein, the new type of non-conjugated polyethyleneimine (PEI) PDs was further modified by targeting molecules (folic acid) for a new generation of bio-fluorophores. The free folic acid can quench the PL of PDs by energy transfer, while the conjugated folic acid@PDs (FA@PDs) can still maintain their PL properties to a certain degree. The FA@PDs also possess lower toxicity compared with free PDs, which is possibly due to blocking of the amino groups. Moreover, we investigated the targeted bioimaging applications of the FA@PDs, which gave a very important direction for application of these types of materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01909a

  6. Interference color modulation, tunable refractive index, and chiroptical electrochromism in a π-conjugated polymer with cholesteric liquid crystal order

    NASA Astrophysics Data System (ADS)

    Goto, Hiromasa

    2009-06-01

    A π-conjugated polymer film prepared by electrolytic polymerization using a cholesteric liquid crystal (CLC) is demonstrated to have a tunable interference function under electrochemical doping and dedoping. The polymer exhibits a CLC-like periodic structure with a potential-dependent refractive index and optical absorption properties. The interference color of the polymer film can thus be modulated dynamically by appropriate application of a voltage in the ±1 V range. This research involves structural chirality and tunable chiroptical properties, doping-dedoping driven tunable refractive index, electrochromism, and interference color modulation for the present polymer. The phenomena demonstrate the possibility of electrochemical photonics.

  7. Stability of Grafted Polymer Nanoscale Films toward Gamma Irradiation.

    PubMed

    Borodinov, Nikolay; Giammarco, James; Patel, Neil; Agarwal, Anuradha; O'Donnell, Katie R; Kucera, Courtney J; Jacobsohn, Luiz G; Luzinov, Igor

    2015-09-01

    The present article focuses on the influence of gamma irradiation on nanoscale polymer grafted films and explores avenues for improvements in their stability toward the ionizing radiation. In terms of applications, we concentrate on enrichment polymer layers (EPLs), which are polymer thin films employed in sensor devices for the detection of chemical and biological substances. Specifically, we have studied the influence of gamma irradiation on nanoscale poly(glycidyl methacrylate) (PGMA) grafted EPL films. First, it was determined that a significant level of cross-linking was caused by irradiation in pure PGMA films. The cross-linking is accompanied by the formation of conjugated ester, carbon double bonds, hydroxyl groups, ketone carbonyls, and the elimination of epoxy groups as determined by FTIR. Polystyrene, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, dimethylphenylsilanol, BaF2, and gold nanoparticles were incorporated into the films and were found to mitigate different aspects of the radiation damage. PMID:26259102

  8. Design, synthesis, and structure-property relationships of isoindigo-based conjugated polymers.

    PubMed

    Lei, Ting; Wang, Jie-Yu; Pei, Jian

    2014-04-15

    Conjugated polymers have developed rapidly due to their promising applications in low-cost, lightweight, and flexible electronics. The development of the third-generation donor-acceptor (D-A) polymers greatly improved the device performance in organic solar cells (OSCs) and field-effect transistors (FETs). However, for further improvement of device performance, scientists need to develop new building blocks, in particular electron-deficient aromatics, and gain an in-depth understanding of the structure-property relationships. Recently, isoindigo has been used as a new acceptor of D-A conjugated polymers. An isomer of indigo, isoindigo is a less well-known dye and can be isolated as a by-product from certain biological processes. It has two lactam rings and exhibits strong electron-withdrawing character. This electron deficiency gives isoindigo-based polymers intriguing properties, such as broad absorption and high open circuit voltage in OSCs, as well as high mobility and good ambient stability in FETs. In this Account, we review our recent progress on the design, synthesis, and structure-property relationship study of isoindigo-based polymers for FETs. Starting with some discussion on carrier transport in polymer films, we provide some basic strategies towards high-performance polymer FETs. We discuss the stability issue of devices, the impediment of the alkyl side chains, and the choice of the donor part of conjugated polymers. We demonstrate that introducing the isoindigo core effectively lowers the HOMO levels of polymers and provides FETs with long-time stability. In addition, we have found that when we use inappropriate alkyl side chains or non-centrosymmetric donors, the device performance of isoindigo polymers suffers. To further improve device performance and ambient stability, we propose several design strategies, such as using farther branched alkyl chains, modulating polymer energy levels, and extending π-conjugated backbones. We have found that using

  9. Approaching disorder-free transport in high-mobility conjugated polymers.

    PubMed

    Venkateshvaran, Deepak; Nikolka, Mark; Sadhanala, Aditya; Lemaur, Vincent; Zelazny, Mateusz; Kepa, Michal; Hurhangee, Michael; Kronemeijer, Auke Jisk; Pecunia, Vincenzo; Nasrallah, Iyad; Romanov, Igor; Broch, Katharina; McCulloch, Iain; Emin, David; Olivier, Yoann; Cornil, Jerome; Beljonne, David; Sirringhaus, Henning

    2014-11-20

    Conjugated polymers enable the production of flexible semiconductor devices that can be processed from solution at low temperatures. Over the past 25 years, device performance has improved greatly as a wide variety of molecular structures have been studied. However, one major limitation has not been overcome; transport properties in polymer films are still limited by pervasive conformational and energetic disorder. This not only limits the rational design of materials with higher performance, but also prevents the study of physical phenomena associated with an extended π-electron delocalization along the polymer backbone. Here we report a comparative transport study of several high-mobility conjugated polymers by field-effect-modulated Seebeck, transistor and sub-bandgap optical absorption measurements. We show that in several of these polymers, most notably in a recently reported, indacenodithiophene-based donor-acceptor copolymer with a near-amorphous microstructure, the charge transport properties approach intrinsic disorder-free limits at which all molecular sites are thermally accessible. Molecular dynamics simulations identify the origin of this long sought-after regime as a planar, torsion-free backbone conformation that is surprisingly resilient to side-chain disorder. Our results provide molecular-design guidelines for 'disorder-free' conjugated polymers. PMID:25383522

  10. Emerging Applications of Conjugated Polymers in Molecular Imaging

    PubMed Central

    Li, Junwei; Liu, Jie; Wei, Chen-Wei; Liu, Bin; O’Donnell, Matthew; Gao, Xiaohu

    2013-01-01

    In recent years, conjugated polymers have attracted considerable attention from the imaging community as a new class of contrast agent due to their intriguing structural, chemical, and optical properties. Their size and emission wavelength tunability, brightness, photostability, and low toxicity have been demonstrated in a wide range of in vitro sensing and cellular imaging applications, and have just begun to show impact in in vivo settings. In this Perspective, we summarize recent advances in engineering conjugated polymers as imaging contrast agents, their emerging applications in molecular imaging (referred to as in vivo uses in this paper), as well as our perspectives on future research. PMID:23860904

  11. Structure and Conformation of Ionic Conjugated Polymers: Polydots

    NASA Astrophysics Data System (ADS)

    Osti, Naresh; Etampawala, Thusitha; Wijesinghe, Sidath; Perahia, Dvora

    2014-03-01

    Conjugated polymers confining into nano dimension form long-lived highly luminescent tunable organic particles of having enormous potential for intracellular imaging and drug delivery. Even though the chains are not in their thermodynamically stable conformation, the poly-dots remain stable over long period of times. Incorporation of ionic groups into conjugated polymers introduces a configuration control factor that impacts their conformation and their applications as luminescent probes. The current work investigates the structure and stability of poly-dots of di-alkoxy para polyphenyleneethynylene (PPE) conjugated polymer substituted with carboxylate side chain. Our small angle neutron scattering (SANS) studies have shown that ionic PPE forms spherical poly-dots in water. Ionic Poly-dots remain stable up to a temperature of 800C compare to neutral conjugated polymer poly dots. These polymer dots were allowed to assemble at a solid surface and observed by AFM which showed the nano aggregates of different sizes that assembled in different ways depending on the concentration and molecular parameters of the ionic PPEs used.

  12. Synthesis of Maleimide-End Functionalized Star Polymers and Multimeric Protein-Polymer Conjugates

    PubMed Central

    Tao, Lei; Kaddis, Catherine S.; Loo, Rachel R. Ogorzalek; Grover, Gregory N.; Loo, Joseph A.; Maynard, Heather D.

    2011-01-01

    Protein-polymer conjugates exhibit superior properties to unmodified proteins, generating a high demand for these materials in the fields of medicine, biotechnology, and nanotechnology. Multimeric conjugates are predicted to surpass the activity of monomeric conjugates. Herein, we report a straightforward method to synthesize multimeric polymer-conjugates. Four armed poly(N-isopropylacrylamide) (pNIPAAm) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of a tetra-functionalized trithiocarbonate chain transfer agent (CTA). The polymer molecular weight, architecture and polydispersity index (PDI) were verified by gel permeation chromatography (GPC), dynamic light scattering gel permeation chromatography (DLS-GPC), and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. This approach afforded well-defined polymers (PDI's < 1.06) and the ability to target various molecular weights. Maleimide functional groups were introduced at the chain ends by heating the polymers in the presence of a furan-protected azo-initiator. This allowed for site-specific conjugation of V131C T4 lysozyme to the polymers to generate multimeric protein-polymer conjugates. MALDI-TOF mass spectrometry, electrospray ionization gas-phase electrophoretic-mobility macromolecule analysis (ESI-GEMMA), gel electrophoresis, and liquid chromatography tandem mass spectrometry (LC-MS/MS) of the trypsin digests demonstrated that multimeric protein-polymer conjugates had formed. This simple strategy provides ready access to star protein-polymer conjugates for application in the fields of drug discovery, drug delivery, and nanotechnology. PMID:21544227

  13. Exploring the origin of high optical absorption in conjugated polymers.

    PubMed

    Vezie, Michelle S; Few, Sheridan; Meager, Iain; Pieridou, Galatia; Dörling, Bernhard; Ashraf, Raja Shahid; Goñi, Alejandro R; Bronstein, Hugo; McCulloch, Iain; Hayes, Sophia C; Campoy-Quiles, Mariano; Nelson, Jenny

    2016-07-01

    The specific optical absorption of an organic semiconductor is critical to the performance of organic optoelectronic devices. For example, higher light-harvesting efficiency can lead to higher photocurrent in solar cells that are limited by sub-optimal electrical transport. Here, we compare over 40 conjugated polymers, and find that many different chemical structures share an apparent maximum in their extinction coefficients. However, a diketopyrrolopyrrole-thienothiophene copolymer shows remarkably high optical absorption at relatively low photon energies. By investigating its backbone structure and conformation with measurements and quantum chemical calculations, we find that the high optical absorption can be explained by the high persistence length of the polymer. Accordingly, we demonstrate high absorption in other polymers with high theoretical persistence length. Visible light harvesting may be enhanced in other conjugated polymers through judicious design of the structure. PMID:27183327

  14. Ultrafast photophysics of pi-conjugated polymers and polythiophene/fullerene blends for organic photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Singh, Sanjeev

    The present work reports studies of the ultrafast photoexcitations in various pristine n-conjugated polymers as well as compounds of polythiophene/fullerene blends, which act as the active layer of donor/acceptor in organic photovoltaic applications. The main technique used is the ultrafast (˜150 fs) transient photomodulation (PM) spectroscopy in the range of 0.25 to 2.5 eV using two different laser systems. In addition, two-photon-absorption and electroabsorption have also been complementary used. In organic photovoltaic studies, two different donor polymers namely, Regio-Regular-poly(3-hexylthiophene) (RR-P3HT) that forms lamellae, and Regio-Random-poly(3-hexylthiophene) (RRa-P3HT) that forms lamellae with lesser extent have been compared. The transient PM measurement of the most efficient RR-P3HT/fullerene blend shows that the decay of exciton does not result in the generation of polarons in the donor and acceptor materials, as assumed by the present model of charge dissociation in photovoltaic devices. On the contrary, the decay of exciton fits very well to the build-up of charge-transfer (CT) state in the fullerene phase, which indicates the migration of the photoexcited exciton in the polymer phase to the fullerene nano-domains. The transient PM measurement of RRa-P3HT/fullerene blend, which does not form phase-separated nano-domains, shows the formation of a CT state at the interface following by ultrafast geminate recombination. The transient PM measurement of poly(phenylene-vinylene) (PPV) derivatives show that in 2-methoxy-5-(2'-ethylhexyloxy) PPV (MEH-PPV) film there are two kinds of primary photoexcitations, namely, intrachain exciton and excimer, but only intra-chain exciton in other PPV derivative polymers. Furthermore the high-pressure study of MEHPPV film shows two kinds of polymer chain orders: isolated-chains and closely packed-chains. The high pressure mainly affects photoexcited excimers in the closely packed-chains. In contrast there is no

  15. Conjugated polymers/semiconductor nanocrystals hybrid materials--preparation, electrical transport properties and applications.

    PubMed

    Reiss, Peter; Couderc, Elsa; De Girolamo, Julia; Pron, Adam

    2011-02-01

    This critical review discusses specific preparation and characterization methods applied to hybrid materials consisting of π-conjugated polymers (or oligomers) and semiconductor nanocrystals. These materials are of great importance in the quickly growing field of hybrid organic/inorganic electronics since they can serve as active components of photovoltaic cells, light emitting diodes, photodetectors and other devices. The electronic energy levels of the organic and inorganic components of the hybrid can be tuned individually and thin hybrid films can be processed using low cost solution based techniques. However, the interface between the hybrid components and the morphology of the hybrid directly influences the generation, separation and transport of charge carriers and those parameters are not easy to control. Therefore a large variety of different approaches for assembling the building blocks--conjugated polymers and semiconductor nanocrystals--has been developed. They range from their simple blending through various grafting procedures to methods exploiting specific non-covalent interactions between both components, induced by their tailor-made functionalization. In the first part of this review, we discuss the preparation of the building blocks (nanocrystals and polymers) and the strategies for their assembly into hybrid materials' thin films. In the second part, we focus on the charge carriers' generation and their transport within the hybrids. Finally, we summarize the performances of solar cells using conjugated polymer/semiconductor nanocrystals hybrids and give perspectives for future developments. PMID:21152569

  16. Photoinduced electron transfer in binary blends of conjugated polymers

    SciTech Connect

    Jenekhe, A.A.; Paor, L.R. de; Chen, X.L.; Tarkka, R.M.

    1996-10-01

    The authors report observations concerning the intermolecular photoinduced electron transfer through blends of n-type/p-type {pi}-conjugated organic polymers. The results of transient absorption spectroscopy, fluorescence quenching analysis, and delocalized radical ion pair generation studies imply that these materials are supramolecular materials.

  17. Recent Advances in Conjugated Polymer Materials for Disease Diagnosis.

    PubMed

    Lv, Fengting; Qiu, Tian; Liu, Libing; Ying, Jianming; Wang, Shu

    2016-02-10

    The extraordinary optical amplification and light-harvesting properties of conjugated polymers impart sensing systems with higher sensitivity, which meets the primary demands of early cancer diagnosis. Recent advances in the detection of DNA methylation and mutation with polyfluorene derivatives based fluorescence resonance energy transfer (FRET) as a means to modulate fluorescent responses attest to the great promise of conjugated polymers as powerful tools for the clinical diagnosis of diseases. To facilitate the ever-changing needs of diagnosis, the development of detection approaches and FRET signal analysis are highlighted in this review. Due to their exceptional brightness, excellent photostability, and low or absent toxicity, conjugated polymers are verified as superior materials for in-vivo imaging, and provide feasibility for future clinical molecular-imaging applications. The integration of conjugated polymers with clinical research has shown profound effects on diagnosis for the early detection of disease-related biomarkers, as well as in-vivo imaging, which leads to a multidisciplinary scientific field with perspectives in both basic research and application issues. PMID:26679834

  18. Effects of thermal annealing on photoluminescence spectra in π-conjugated polymer film: evidence for dual emission by temperature dependent measurements

    NASA Astrophysics Data System (ADS)

    Wang, R. Z.; Yang, X.; Wang, Y. C.; Sheng, C.-X.; Chen, Q.

    2014-09-01

    Various spectroscopy techniques such as absorption, photoluminescence and photoinduced absorption (PIA) spectroscopy, were used to study the photophysics in poly [2-methoxy-5-(20-ethyl-hexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) films, which were dropped cast on glass substrates using its toluene solution and being annealed at various temperatures. With the analysis of temperature dependence PL intensities, we conclude that PL emission around 680 nm at low temperature is due to intertain excimers instead of intrachain excitons for 450 K annealed film. On the other hand, this relative intensity difference is much smaller in both unannealed and 500 K annealed films, in which the morphology is amorphous and microcrystalline, respectively. We conclude that the interchain photoexcitations play crucial roles in the photophysics of MEH-PPV films. The further measurements on PIA spectrum of MEH-PPV films suggest that the interchain photoexciation is also important for the generation of triplet excitons.

  19. Electroactive polymer-peptide conjugates for adhesive biointerfaces.

    PubMed

    Maione, Silvana; Gil, Ana M; Fabregat, Georgina; Del Valle, Luis J; Triguero, Jordi; Laurent, Adele; Jacquemin, Denis; Estrany, Francesc; Jiménez, Ana I; Zanuy, David; Cativiela, Carlos; Alemán, Carlos

    2015-10-15

    Electroactive polymer-peptide conjugates have been synthesized by combining poly(3,4-ethylenedioxythiophene), a polythiophene derivative with outstanding properties, and an Arg-Gly-Asp (RGD)-based peptide in which Gly has been replaced by an exotic amino acid bearing a 3,4-ethylenedioxythiophene ring in the side chain. The incorporation of the peptide at the ends of preformed PEDOT chains has been corroborated by both FTIR and X-ray photoelectron spectroscopy. Although the morphology and topology are not influenced by the incorporation of the peptide at the ends of PEDOT chains, this process largely affects other surface properties. Thus, the wettability of the conjugates is considerably higher than that of PEDOT, independently of the synthetic strategy, whereas the surface roughness only increases when the conjugate is obtained using a competing strategy (i.e. growth of the polymer chains against termination by end capping). The electrochemical activity of the conjugates has been found to be higher than that of PEDOT, evidencing the success of the polymer-peptide links designed by chemical similarity. Density functional theory calculations have been used not only to ascertain the conformational preferences of the peptide but also to interpret the electronic transitions detected by UV-vis spectroscopy. Electroactive surfaces prepared using the conjugates displayed the higher bioactivities in terms of cell adhesion, with the relative viabilities being dependent on the roughness, wettability and electrochemical activity of the conjugate. In addition to the influence of the peptide fragment in the initial cell attachment and subsequent cell spreading and survival, the results indicate that PEDOT promotes the exchange of ions at the conjugate-cell interface. PMID:26372182

  20. Carrier Transport Enhancement in Conjugated Polymers through Interfacial Self-Assembly of Solution-State Aggregates.

    PubMed

    Zhao, Kui; Khan, Hadayat Ullah; Li, Ruipeng; Hu, Hanlin; Amassian, Aram

    2016-08-01

    We demonstrate that local and long-range orders of poly(3-hexylthiophene) (P3HT) semicrystalline films can be synergistically improved by combining chemical functionalization of the substrate with solution-state disentanglement and preaggregation of P3HT in a θ solvent, leading to a very significant enhancement of the field effect carrier mobility. The preaggregation and surface functionalization effects combine to enhance the carrier mobility nearly 100-fold as compared with standard film preparation by spin-coating, and nearly 10-fold increase over the benefits of preaggregation alone. In situ quartz crystal microbalance with dissipation (QCM-D) experiments reveal enhanced deposition of preaggregates on surfaces modified with an alkyl-terminated self-assembled monolayer (SAM) in comparison to unaggregated polymer chains in the same conditions. Additional measurements reveal the combined preaggregation and surface functionalization significantly enhances local order of the conjugated polymer through planarization and extension of the conjugated backbone of the polymer which clearly translate to significant improvements of carrier transport at the semiconductor-dielectric interface in organic thin film transistors. This study points to opportunities in combining complementary routes, such as well-known preaggregation with substrate chemical functionalization, to enhance the polymer self-assembly and improve its interfacial order with benefits for transport properties. PMID:27410517

  1. Self-assembled breath figure arrays of conjugated conducting polymers for photovoltaic application

    NASA Astrophysics Data System (ADS)

    Routh, Prahlad Kumar; Venkatesh, T. A.; Cotlet, Mircea

    2014-03-01

    Ordered microporous polymer structures have potential application in catalysis, surface engineering and optoelectronics. The Breath Figure Technique (BFT) is a simple method of producing such ordered microporous structures. In this study BFT was applied to a series of commercial conjugated polymer polythiophene derivatives with varying side chain length (n =6,8,10,12). An in-depth study of processing parameters has been carried with the aim of controlling the morphology of the honeycomb film over large, PV relevant areas. Structural and spectroscopic characterization of honeycomb films were performed using Scanning Electron Microscopy (SEM), X-ray scattering, Fluorescence Lifetime Imaging (FLIM) and Spectroscopy. Blends of these polymers with a fullerene derivative, PCBM, were also subjected to BFT and characterized with similar methods to assess their potential use as active layers in PV solar cells. Center for Functional Nanomaterials, Brookhaven National Laboratory.

  2. Architectures for controlling solid state properties of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Nambiar, Rakesh R.

    Conjugated polymers and oligomers are great materials for use in the next generation devices namely organic field effect transistors, light emitting diodes and polymeric solar cells. Apart from having the potential for developing power-efficient, flexible, robust and inexpensive devices, conjugated polymers can also be tuned by molecular design to optimize device characteristics. One key problem for the full commercial exploitation of conjugated polymers is that the charge carrier mobility of the state-of-the-art polymer semiconductors is much lower than required for many applications. The performance of the devices is strongly dependent on the molecular structure and supermolecular assembly of the conjugated polymer chains. This thesis covers our attempts to design molecular structure to control and improve the solid state properties of conjugated polymers. The relative placement of side chains along the backbone has a great influence on the solid state ordering of conjugated polymers. Poly(2,5-disubstituted-1,4-phenylene ethynylene)s (PPE)s, an important class of conjugated polymers, are generally synthesized by Pd-catalyzed coupling polymerizations of appropriately substituted diiodo and diethynyl benzenes (i.e., A-A and B-B type monomers). In asymmetrically substituted PPEs, this results in an irregular substitution pattern of the side chains along the polymer backbone. We report a new synthetic approach to prepare regioregular unsymmetrically substituted PPEs by polymerization of 4-iodophenylacetylenes (i.e., A-B type monomer). We provide a detailed discussion of various approaches to the synthesis of PPEs with different regioregularities and provide a description of the differences between regioregular and regiorandom analogs. The effect of regioregularity becomes even more important when the two side chains are very dissimilar or amphiphilic. We explore the effect of relative placement hydrophobic (dodecyloxy)/hydrophilic (tri(ethylene glycol) and

  3. Dirac Cones in two-dimensional conjugated polymer networks

    NASA Astrophysics Data System (ADS)

    Adjizian, Jean-Joseph; Briddon, Patrick; Humbert, Bernard; Duvail, Jean-Luc; Wagner, Philipp; Adda, Coline; Ewels, Christopher

    2014-12-01

    Linear electronic band dispersion and the associated Dirac physics has to date been limited to special-case materials, notably graphene and the surfaces of three-dimensional (3D) topological insulators. Here we report that it is possible to create two-dimensional fully conjugated polymer networks with corresponding conical valence and conduction bands and linear energy dispersion at the Fermi level. This is possible for a wide range of polymer types and connectors, resulting in a versatile new family of experimentally realisable materials with unique tuneable electronic properties. We demonstrate their stability on substrates and possibilities for doping and Dirac cone distortion. Notably, the cones can be maintained in 3D-layered crystals. Resembling covalent organic frameworks, these materials represent a potentially exciting new field combining the unique Dirac physics of graphene with the structural flexibility and design opportunities of organic-conjugated polymer chemistry.

  4. Polymer film composite transducer

    DOEpatents

    Owen, Thomas E.

    2005-09-20

    A composite piezoelectric transducer, whose piezoeletric element is a "ribbon wound" film of piezolectric material. As the film is excited, it expands and contracts, which results in expansion and contraction of the diameter of the entire ribbon winding. This is accompanied by expansion and contraction of the thickness of the ribbon winding, such that the sound radiating plate may be placed on the side of the winding.

  5. Optical studies of Pt-rich π--conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Drori, Tomer; Tong, M.; Gambetti, A.; Singh, S.; Yang, C.; Vardeny, Z. V.; Tretiak, S.

    2008-03-01

    We have used a variety of steady state and ultrafast spectroscopies for studying the photophysics of platinum-containing conjugated polymers, which have potential applications as the active layer of light-emitting diodes. The heavy metal Pt atom that is incorporated in the polymer chain dramatically increases the spin-orbit coupling, and this influences both the intersystem crossing time, TISC, and the phosphorescence emission intensity. The Pt-polymers were newly synthesized, where the intrachain Pt atom was incorporated into the polymer either in each (Pt-1) or in every three (Pt-3) monomer units. We will discuss an interesting effect for the photoexcited triplets, which dramatically influence the phosphorescence spectral shape vs. temperature. We also observed the existence of circular polarization memory of the phosphorescence emission in Pt-1 polymers, in which the platinum atoms are separated by only one phenyl ring; but not in Pt-3.

  6. Light-evoked hyperpolarization and silencing of neurons by conjugated polymers.

    PubMed

    Feyen, Paul; Colombo, Elisabetta; Endeman, Duco; Nova, Mattia; Laudato, Lucia; Martino, Nicola; Antognazza, Maria Rosa; Lanzani, Guglielmo; Benfenati, Fabio; Ghezzi, Diego

    2016-01-01

    The ability to control and modulate the action potential firing in neurons represents a powerful tool for neuroscience research and clinical applications. While neuronal excitation has been achieved with many tools, including electrical and optical stimulation, hyperpolarization and neuronal inhibition are typically obtained through patch-clamp or optogenetic manipulations. Here we report the use of conjugated polymer films interfaced with neurons for inducing a light-mediated inhibition of their electrical activity. We show that prolonged illumination of the interface triggers a sustained hyperpolarization of the neuronal membrane that significantly reduces both spontaneous and evoked action potential firing. We demonstrate that the polymeric interface can be activated by either visible or infrared light and is capable of modulating neuronal activity in brain slices and explanted retinas. These findings prove the ability of conjugated polymers to tune neuronal firing and suggest their potential application for the in-vivo modulation of neuronal activity. PMID:26940513

  7. Light-evoked hyperpolarization and silencing of neurons by conjugated polymers

    NASA Astrophysics Data System (ADS)

    Feyen, Paul; Colombo, Elisabetta; Endeman, Duco; Nova, Mattia; Laudato, Lucia; Martino, Nicola; Antognazza, Maria Rosa; Lanzani, Guglielmo; Benfenati, Fabio; Ghezzi, Diego

    2016-03-01

    The ability to control and modulate the action potential firing in neurons represents a powerful tool for neuroscience research and clinical applications. While neuronal excitation has been achieved with many tools, including electrical and optical stimulation, hyperpolarization and neuronal inhibition are typically obtained through patch-clamp or optogenetic manipulations. Here we report the use of conjugated polymer films interfaced with neurons for inducing a light-mediated inhibition of their electrical activity. We show that prolonged illumination of the interface triggers a sustained hyperpolarization of the neuronal membrane that significantly reduces both spontaneous and evoked action potential firing. We demonstrate that the polymeric interface can be activated by either visible or infrared light and is capable of modulating neuronal activity in brain slices and explanted retinas. These findings prove the ability of conjugated polymers to tune neuronal firing and suggest their potential application for the in-vivo modulation of neuronal activity.

  8. Light-evoked hyperpolarization and silencing of neurons by conjugated polymers

    PubMed Central

    Feyen, Paul; Colombo, Elisabetta; Endeman, Duco; Nova, Mattia; Laudato, Lucia; Martino, Nicola; Antognazza, Maria Rosa; Lanzani, Guglielmo; Benfenati, Fabio; Ghezzi, Diego

    2016-01-01

    The ability to control and modulate the action potential firing in neurons represents a powerful tool for neuroscience research and clinical applications. While neuronal excitation has been achieved with many tools, including electrical and optical stimulation, hyperpolarization and neuronal inhibition are typically obtained through patch-clamp or optogenetic manipulations. Here we report the use of conjugated polymer films interfaced with neurons for inducing a light-mediated inhibition of their electrical activity. We show that prolonged illumination of the interface triggers a sustained hyperpolarization of the neuronal membrane that significantly reduces both spontaneous and evoked action potential firing. We demonstrate that the polymeric interface can be activated by either visible or infrared light and is capable of modulating neuronal activity in brain slices and explanted retinas. These findings prove the ability of conjugated polymers to tune neuronal firing and suggest their potential application for the in-vivo modulation of neuronal activity. PMID:26940513

  9. Highly emissive PEG-encapsulated conjugated polymer nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Yuqiong; Liu, Jie; Liu, Bin; Tomczak, Nikodem

    2012-08-01

    A novel bioimaging probe based on a conjugated polymer, poly(9,9-dihexylfluorene-alt-2,1,3-benzoxadiazole) (PFBD), is demonstrated. Transfer of the hydrophobic polymer into water using a short chain poly(ethylene glycol) (PEG) resulted in conjugated polymer nanoparticles (PEG-PFBD) with a fluorescence quantum yield of 46%. The PEG-PFBD nanoparticles possessed several desirable structural and photophysical properties, such as colloidal stability in a broad range of pH values, sub-20 nm particle size, the presence of surface chemical functionality, as well as desirable excitation and emission spectra, for bioimaging applications. PEG-PFBD nanoparticles were conjugated with cyclic RGDfK targeting peptide for labeling of membrane αVβ3 integrin receptors on live HT-29 adenocarcinoma cells. Single nanoparticle microscopy revealed that the PEG-capped PFBD nanoparticles exhibit at least ten times higher emitted photon counts than single quantum dots (QD655) of comparable size. In addition, Fluorescence Lifetime Imaging Microscopy (FLIM) of single PEG-PFBD nanoparticles revealed that the nanoparticles display a clearly resolvable single nanoparticle fluorescence lifetime.A novel bioimaging probe based on a conjugated polymer, poly(9,9-dihexylfluorene-alt-2,1,3-benzoxadiazole) (PFBD), is demonstrated. Transfer of the hydrophobic polymer into water using a short chain poly(ethylene glycol) (PEG) resulted in conjugated polymer nanoparticles (PEG-PFBD) with a fluorescence quantum yield of 46%. The PEG-PFBD nanoparticles possessed several desirable structural and photophysical properties, such as colloidal stability in a broad range of pH values, sub-20 nm particle size, the presence of surface chemical functionality, as well as desirable excitation and emission spectra, for bioimaging applications. PEG-PFBD nanoparticles were conjugated with cyclic RGDfK targeting peptide for labeling of membrane αVβ3 integrin receptors on live HT-29 adenocarcinoma cells. Single

  10. Acid diffusion through polymer films

    NASA Astrophysics Data System (ADS)

    Zhang, P. Linda; Eckert, Andrew R.; Willson, C. Grant; Webber, Stephen E.; Byers, Jeffrey D.

    1997-07-01

    In order to perform 0.2 micrometer processes, one needs to study the diffusion of photoacid generators within the photoresist system, since diffusion during post exposure bake time has an influence on the critical dimension (CD). We have developed a new method to study the diffusion of photoacid generators within a polymer film. This new method is based on monitoring the change of the fluorescence intensity of a pH- sensitive fluorescent dye caused by the reaction with photoacid. A simplified version of this experiment has been conducted by introducing acid vapor to quench the fluorescence intensity of this pH sensor. A thin polymer film is spin cast onto the sensor to create a barrier to the acid diffusion process. During the acid diffusion process, the fluorescence intensity of this pH sensor is measured in situ, using excitation and emission wavelengths at 466 nm and 516 nm, respectively. Fluoresceinamine, the pH sensitive fluorescent dye, is covalently bonded onto the treated quartz substrate to form a single dye layer. Poly(hydroxystyrene) (Mn equals 13k, Tg equals 180 degrees Celsius) in PGMEA (5% - 18% by weight) is spin cast onto this quartz substrate to form films with varying thickness. The soft bake time is 60 seconds at 90 degrees Celsius and a typical film has a thickness of 1.4 micrometers. Trifluoroacetic acid is introduced into a small chamber while the fluorescence from this quartz window is observed. Our study focuses on finding the diffusion constant of the vaporized acid (trifluoroacetic acid) in the poly(hydroxystyrene) polymer film. By applying the Fick's second law, (It - Io)/(I(infinity ) - Io) equals erfc [L/(Dt)1/2] is obtained. The change of fluorescence intensity with respect to the diffusion time is monitored. The above equation is used for the data analysis, where L represents the film thickness and t represents the average time for the acid to diffuse through the film. The diffusion constant is calculated to be at the order of 10

  11. Investigating the Impact of Polymer Functional Groups on the Stability and Activity of Lysozyme-Polymer Conjugates.

    PubMed

    Lucius, Melissa; Falatach, Rebecca; McGlone, Cameron; Makaroff, Katherine; Danielson, Alex; Williams, Cameron; Nix, Jay C; Konkolewicz, Dominik; Page, Richard C; Berberich, Jason A

    2016-03-14

    Polymers are often conjugated to proteins to improve stability; however, the impact of polymer chain length and functional groups on protein structure and function is not well understood. Here we use RAFT polymerization to grow polymers of different lengths and functionality from a short acrylamide oligomer with a RAFT end group conjugated to lysozyme. We show by X-ray crystallography that enzyme structure is minimally impacted by modification with the RAFT end group. Significant activity toward the negatively charged Micrococcus lysodeicticus cell wall was maintained when lysozyme was modified with cationic polymers. Thermal and chemical stability of the conjugates was characterized using differential scanning fluorimetry and tryptophan fluorescence. All conjugates had a lower melting temperature; however, conjugates containing ionic or substrate mimicking polymers were more resistant to denaturation by guanidine hydrochloride. Our results demonstrate that tailoring polymer functionality can improve conjugate activity and minimize enzymatic inactivation by denaturants. PMID:26866284

  12. Ultrafast polarisation spectroscopy of photoinduced charges in a conjugated polymer

    SciTech Connect

    Bakulin, A A; Loosdrecht, P van; Pshenichnikov, M S; Parashchuk, D Yu

    2009-07-31

    Tunable optical parametric generators and amplifiers (OPA), proposed and developed by Akhmanov and his colleagues, have become the working horses in exploration of dynamical processes in physics, chemistry, and biology. In this paper, we demonstrate the possibility of using ultrafast polarisation-sensitive two-colour spectroscopy, performed with a set of two OPAs, to study charge photogeneration and transport in conjugated polymers and their donor-acceptor blends. (special issue devoted to the 80th birthday of S.A. Akhmanov)

  13. Non-covalent interactions between carbon nanotubes and conjugated polymers

    NASA Astrophysics Data System (ADS)

    Tuncel, Dönüs

    2011-09-01

    Carbon nanotubes (CNTs) are interest to many different disciplines including chemistry, physics, biology, material science and engineering because of their unique properties and potential applications in various areas spanning from optoelectronics to biotechnology. However, one of the drawbacks associated with these materials is their insolubility which limits their wide accessibility for many applications. Various approaches have been adopted to circumvent this problem including modification of carbon nanotube surfaces by non-covalent and covalent attachments of solubilizing groups. Covalent approach modification may alter the intrinsic properties of carbon nanotubes and, in turn make them undesirable for many applications. On the other hand, a non-covalent approach helps to improve the solubility of CNTs while preserving their intrinsic properties. Among many non-covalent modifiers of CNTs, conjugated polymers are receiving increasing attention and highly appealing because of a number of reasons. To this end, the aim of this feature article is to review the recent results on the conjugated polymer-based non-covalent functionalization of CNTs with an emphasis on the effect of conjugated polymers in the dispersibility/solubility, optical, thermal and mechanical properties of carbon nanotubes as well as their usage in the purification and isolation of a specific single-walled nanotube from the mixture of the various tubes.

  14. Enhancing enzyme stability by construction of polymer-enzyme conjugate micelles for decontamination of organophosphate agents.

    PubMed

    Suthiwangcharoen, Nisaraporn; Nagarajan, Ramanathan

    2014-04-14

    Enhancing the stability of enzymes under different working environments is essential if the potential of enzyme-based applications is to be realized for nanomedicine, sensing and molecular diagnostics, and chemical and biological decontamination. In this study, we focus on the enzyme, organophosphorus hydrolase (OPH), which has shown great promise for the nontoxic and noncorrosive decontamination of organophosphate agents (OPs) as well as for therapeutics as a catalytic bioscavanger against nerve gas poisoning. We describe a facile approach to stabilize OPH using covalent conjugation with the amphiphilic block copolymer, Pluronic F127, leading to the formation of F127-OPH conjugate micelles, with the OPH on the micelle corona. SDS-PAGE and MALDI-TOF confirmed the successful conjugation, and transmission electron microscopy (TEM) and dynamic light scattering (DLS) revealed ∼100 nm size micelles. The conjugates showed significantly enhanced stability and higher activity compared to the unconjugated OPH when tested (i) in aqueous solutions at room temperature, (ii) in aqueous solutions at higher temperatures, (iii) after multiple freeze/thaw treatments, (iv) after lyophilization, and (v) in the presence of organic solvents. The F127-OPH conjugates also decontaminated paraoxon (introduced as a chemical agent simulant) on a polystyrene film surface and on a CARC (Chemical Agent Resistant Coating) test panel more rapidly and to a larger extent compared to free OPH. We speculate that, in the F127-OPH conjugates (both in the micellar form as well as in the unaggregated conjugate), the polypropylene oxide block of the copolymer interacts with the surface of the OPH and this confinement of the OPH reduces the potential for enzyme denaturation and provides robustness to OPH at different working environments. The use of such polymer-enzyme conjugate micelles with improved enzyme stability opens up new opportunities for numerous civilian and Warfighter applications. PMID

  15. Preparation of patterned ultrathin polymer films.

    PubMed

    Yang, Huige; Su, Meng; Li, Kaiyong; Jiang, Lei; Song, Yanlin; Doi, Masao; Wang, Jianjun

    2014-08-12

    Though patterned ultrathin polymer films (<100 nm) are of great importance in the fields of sensors and nanoelectronic devices, the fabrication of patterned ultrathin polymer films remains a great challenge. Herein, patterned ultrathin polymer films are fabricated facilely on hydrophobic substrates with different hydrophilic outline patterns by the pinning of three-phase contact lines of polymer solution on the hydrophilic outlines. This method is universal for most of the water-soluble polymers, and poly(vinyl alcohol) (PVA) has been selected as a model polymer due to its biocompatibility and good film-forming property. The results indicate that the morphologies of ultrathin polymer films can be precisely adjusted by the size of the hydrophilic outline pattern. Specifically, patterned hydrophilic outlines with sizes of 100, 60, and 40 μm lead to the formation of concave-shaped ultrathin PVA films, whereas uniform ultrathin PVA films are formed on 20 and 10 μm patterned substrates. The controllabilities of morphologies can be interpreted through the influences of the slip length and coffee ring effect. Theoretical analysis shows that when the size of the hydrophilic outline patterns is smaller than a critical value, the coffee ring effect disappears and uniform patterned ultrathin polymer films can be formed for all polymer concentrations. These results provide an effective methodology for the fabrication of patterned ultrathin polymer films and enhance the understanding of the coffee ring effect. PMID:25066958

  16. Molecules with enhanced electronic polarizabilities based on defect-like states in conjugated polymers

    NASA Technical Reports Server (NTRS)

    Beratan, David N. (Inventor)

    1991-01-01

    Highly conjugated organic polymers typically have large non-resonant electronic susceptibilities, which give the molecules unusual optical properties. To enhance these properties, defects are introduced into the polymer chain. Examples include light doping of the conjugated polymer and synthesis, conjugated polymers which incorporate either electron donating or accepting groups, and conjugated polymers which contain a photoexcitable species capable of reversibly transferring its electron to an acceptor. Such defects in the chain permit enhancement of the second hyperpolarizability by at least an order of magnitude.

  17. Conjugated Polymer Nanoparticle Hybrids: Structure, Dynamics and Forces

    NASA Astrophysics Data System (ADS)

    Perahia, Dvora

    2011-03-01

    While nanoparticles (NPs) have unique tunable elctro-optical properties and exceptional mechanical strength, it remains a challenge to integrate them into devices while retaining the advantages of the nanoscale. Tethering polymeric materials to the NPs surfaces has the potential to stabilize single NPs and direct their assembly. The polymers may serve in several capacities from a simple tether to a matrix to directed assembly tool taking advantage of the inherent structure of the polymers and as an active component in a complex material. However confining a large molecule to a highly curved surface affects the inherent configuration of the polymer. These effects are of particular interests in conjugated polymer-nanoparticle hybrids, where the conformation of the polymers affects not only the assembly of the nanoparticles but also the optical and electronic communication between the NPs. Using molecular dynamic simulations we have studied the structure of a single hybrid of para dialkyl phenylene ethynelyne (PPE) grafted nanoparticles. PPEs are polymers whose conformation determines their degree of conjugation and therefore their electro-optical response. Using simulations coupled with neutron scattering studies we have shown that PPE is a rigid polymer that is fully extended in dilute solutions in good and theta solvents but can be forced into a collapsed configuration in a poor a solvent. When confined to a nanoparticle surface, the PPE chains are fully extended but cluster as the solvent quality is reduced. Results for the conformation of grafted PPE molecules on a single nanoparticle and the forces between two nanoparticles as a function of chain length and solvent quality will be presented. These simulations provide insight to the interactions that result in formation of tunable hybrids. This work has been done in collaboration with Gary S. Grest.

  18. Synthesis of Heterotelechelic Polymers for Conjugation of Two Different Proteins

    PubMed Central

    Heredia, Karina L.; Grover, Gregory N.; Tao, Lei

    2011-01-01

    In this report we describe a straightforward approach to synthesize polymers with end-groups that bind site-specifically to two different proteins. Telechelic biotin, maleimide poly(N-isopropylacrylamide) (pNIPAAm) was synthesized for the formation of streptavidin (SAv)-bovine serum albumin (BSA) polymer conjugates. Reversible addition-fragmentation chain transfer (RAFT) polymerization of NIPAAm was conducted in the presence of biotinylated chain transfer agents (CTAs) with either ester or amide linkages, and the resultant α-biotinylated pNIPAAm were formed with low polydispersity indices (PDI ≤ 1.09). UV-Vis analysis of the trithiocarbonate chain-ends indicated 88% or greater retention of the group. A maleimide was introduced to the ω chain-end via a radical cross-coupling reaction with a functionalized azo-initiator. The polymer structures were characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). The resultant biotin-maleimide heterotelechelic polymer was used to form a SAv-BSA heterodimer conjugate. Bioconjugate formation was confirmed by gel electrophoresis. PMID:25378715

  19. Nanoparticles of Fluorescent Conjugated Polymers: Novel Ion-Selective Optodes.

    PubMed

    Kłucińska, Katarzyna; Stelmach, Emilia; Kisiel, Anna; Maksymiuk, Krzysztof; Michalska, Agata

    2016-06-01

    A novel type of ion-selective nano-optode is proposed, in which a conjugated polymer is used as optical transducer and nanoprobe material. Thus, contrary to most of the proposed optodes, the response does not require presence of pH-sensitive dye in the sensor. The conjugated polymer nanosensor material is in partially oxidized form-it is bearing positive charges and its emission is quenched. The receptor is an optically silent uncharged ionophore selective for the analyte cation. When a binding event occurs, positive charges are formed in the nanosphere, leading to a decrease in the oxidation state of the polymer, in the absence of redox potential change, resulting in increased emission. This general approach herein proposed results in a simple sensor, benefitting from a novel optical transduction mechanism and high lipophilicity of the polymer matrix that results in linear responses over a broad concentration range of analyte. For the model system studied, the linear dependence of emission intensity on the logarithm of analyte (K(+)) concentration was obtained for a broad range from 10(-5) M to 0.1 M. PMID:27136386

  20. Structure and Assembly of Polymeric Dots Formed by Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Osti, Naresh; Ratnaweera, Dilru; Etempawala, Thusitha; Shrestha, Umesh; Perahia, Dvora

    2012-02-01

    Rigid conjugated polymers assume extended conformation in dilute solution and often behave as colloidal suspensions. When forced into a collapsed configuration, they form highly fluorescing particles, or poly-dots, which have demonstrated potential as intracellular imaging markers, as well as building blocks for light harvesting devices. The current work investigates the structure and stability of poly-dots of di-alkyl para polyphenyleneethynylene (PPE) conjugated polymers in solution and follows their assembly at interfaces. Small angle neutron scattering measurements of the poly-dots in water have shown that at low concentrations, stable unimolecular spherical poly-dots are formed with a polydispersity that corresponds to that of the polymer itself. With increasing concentration, yet, below the critical micelle concentration of these rod-like polymers in good solvents, the size and density of the NPs increases, however the spherical symmetry is retained. The nature and length of the substituents affect the internal density and the degree of swelling of the poly dots. Atomic Force Microscopy results show that these PPE poly-dots assemble into arrays with different symmetries, depending on molecular parameters and assembly conditions.

  1. Glass transition dynamics and charge carrier mobility in conjugated polyfluorene thin films

    NASA Astrophysics Data System (ADS)

    Qin, Hui; Liu, Dan; Wang, Tao

    Conjugated polymers are commonly used in organic optoelectronic devices, e.g. organic photovoltaics (OPVs), light-emitting diodes (LEDs) and field effect transistors (FETs). In these devices, the conjugated polymers are prepared as thin films with thicknesses in the range of tens to hundreds of nanometers, and are interfaced with different function layers made from organic or inorganic materials. We have studied the glass transition temperature (Tg) of poly(9, 9-dioctylfluorene)-co-N-(1, 4-butylphenyl)diphenylamine) (TFB) thin films supported on different substrates, as well as their SCLC charge carrier mobility in photodiodes. Both Monotonic and non-monotonic Tg deviations are observed in TFB thin films supported on Si/SiOx and PEDOT:PSS, respectively. With low to moderate thermal crosslinking, the thickness dependent Tg deviation still exists, which diminishes in TFB films with a high crosslinking degree. The vertical charge carrier mobility of TFB thin films extracted from the SCLC measurements is found increase with film thickness, a value increases from 1 to 50 x 10-6 cm2 V-1 s-1 in the thickness range from 15 to 180 nm. Crosslinking was found to reduce the carrier mobility in TFB thin films. The Tg deviations are also discussed using the classic layered models in the literature. Our results provide a precise guide for the fabrication and design of high performance optoelectronic devices.

  2. Self-assembled multilayers of electroactive polymers: From highly conducting transparent thin films to light emitting diodes

    SciTech Connect

    Fou, A.; Onitsuka, O.; Ferreira, M.

    1995-12-01

    Layer-by-layer self-assembly has recently emerged as a most versatile means of processing conjugated polymers into ultrathin films with unprecedented control over thicknesses and molecular architectures. Multilayer heterostructures have been designed and fabricated from various combinations of conjugated polyions, p-type conducting polymers, sulfonated fullerenes, conjugated polymer precursors, molecular dyes, and a variety of nonconjugated polyions to study properties unique to the supramolecular organizations created. In this paper, we use layer-by-layer self-assembly to fabricate extremely thin, highly conductive films of p-doped conjugated polymers such as polypyrrole and polyaniline. Also complex multilayer heterostructures based on polyphenylene vinylene (PPV) are fabricated to study the intermolecular interactions between the PPV and other components of the film which give rise to {open_quotes}tunable{close_quotes} photoluminescence behavior. Finally, thin film light-emitting devices based on self-assembled PPV active layers are presented.

  3. Very Small Bandgap π-Conjugated Polymers with Extended Thienoquinoids.

    PubMed

    Kawabata, Kohsuke; Saito, Masahiko; Osaka, Itaru; Takimiya, Kazuo

    2016-06-22

    The introduction of quinoidal character to π-conjugated polymers is one of the effective approaches to reducing the bandgap. Here we synthesized new π-conjugated polymers (PBTD4T and PBDTD4T) incorporating thienoquinoids 2,2'-bithiophene-5,5'-dione (BTD) and benzo[1,2-b:4,5-b']dithiophene-2,6-dione (BDTD) as strong electron-deficient (acceptor) units. PBTD4T showed a deep LUMO energy level of -3.77 eV and a small bandgap of 1.28 eV, which are similar to those of the analog using thieno[3,2-b]thiophene-2,5-dione (TTD) (PTTD4T). PBDTD4T had a much deeper LUMO energy level of -4.04 eV and a significantly smaller bandgap of 0.88 eV compared to those of the other two polymers. Interestingly, PBDTD4T showed high transparency in the visible region. The very small bandgap of PBDTD4T can be rationalized by the enhanced contribution of the resonance backbone structure in which the p-benzoquinodimethane skeleton in the BDTD unit plays a crucial role. PBTD4T and PBDTD4T exhibited ambipolar charge transport with more balanced mobilities between the hole and the electron than PTTD4T. We believe that the very small bandgap, i.e., the high near-infrared activity, as well as the well-balanced ambipolar property of the π-conjugated polymers based on these units would be of particular interest in the fabrication of next-generation organic devices. PMID:27224874

  4. Drug Delivery Vehicles Based on Albumin-Polymer Conjugates.

    PubMed

    Jiang, Yanyan; Stenzel, Martina

    2016-06-01

    Albumin has been a popular building block to create nanoparticles for drug delivery purposes. The performance of albumin as a drug carrier can be enhanced by combining protein with polymers, which allows the design of carriers to encompass a broader spectrum of drugs while features unique to synthetic polymers such as stimuli-responsiveness are introduced. Nanoparticles based on polymer-albumin hybrids can be divided into two classes: one that carries album as a bioactive surface coating and the other that uses albumin as biocompatible, although nonbioactive, building block. Nanoparticles with bioactive albumin surface coating can either be prepared by self-assembly of albumin-polymer conjugates or by postcoating of existing nanoparticles with albumin. Albumin has also been used as building block, either in its native or denatured form. Existing albumin nanoparticles are coated with polymers, which can influence the degradation of albumin or impact on the drug release. Finally, an alternative way of using albumin by denaturing the protein to generate a highly functional chain, which can be modified with polymer, has been presented. These albumin nanoparticles are designed to be extremely versatile so that they can deliver a wide variety of drugs, including traditional hydrophobic drugs, metal-based drugs and even therapeutic proteins and siRNA. PMID:26947019

  5. Direct detection of RDX vapor using a conjugated polymer network.

    PubMed

    Gopalakrishnan, Deepti; Dichtel, William R

    2013-06-01

    1,3,5-Trinitroperhydro-1,3,5-triazine (RDX) is a principal component of plastic explosives used in acts of terrorism and within improvised explosive devices, among others. Approaches to detect RDX compatible with remote, "stand-off" sampling that do not require preconcentration strategies, such as the swabs commonly employed in airports, will benefit military and civilian security. Such detection remains a significant challenge because RDX is 10(3) less volatile than 1,3,5-trinitrotoluene (TNT), corresponding to a parts-per-trillion vapor pressure under ambient conditions. Therefore, while fluorescence quenching of conjugated polymers is sufficiently sensitive to detect TNT vapors, RDX vapor detection is undemonstrated. Here we report a cross-linked phenylene vinylene polymer network whose fluorescence is quenched by trace amounts of RDX introduced from solution or the vapor phase. Fluorescence quenching is reduced, but remains significant, when partially degraded RDX is employed, suggesting that the polymer responds to RDX itself. The polymer network also responds to TNT and PETN similarly introduced from solution or the vapor phase. Pure solvents, volatile amines, and the outgassed vapors from lipstick or sunscreen do not quench polymer fluorescence. The established success of TNT sensors based on fluorescence quenching makes this a material of interest for real-world explosive sensors and will motivate further interest in cross-linked polymers and framework materials for sensing applications. PMID:23641956

  6. RIR-MAPLE deposition of conjugated polymers and hybrid nanocomposites for application to optoelectronic devices

    SciTech Connect

    Stiff-Roberts, Adrienne D.; Pate, Ryan; McCormick, Ryan; Lantz, Kevin R.

    2012-07-30

    Resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) is a variation of pulsed laser deposition that is useful for organic-based thin films because it reduces material degradation by selective absorption of infrared radiation in the host matrix. A unique emulsion-based RIR-MAPLE approach has been developed that reduces substrate exposure to solvents and provides controlled and repeatable organic thin film deposition. In order to establish emulsion-based RIR-MAPLE as a preferred deposition technique for conjugated polymer or hybrid nanocomposite optoelectronic devices, studies have been conducted to demonstrate the value added by the approach in comparison to traditional solution-based deposition techniques, and this work will be reviewed. The control of hybrid nanocomposite thin film deposition, and the photoconductivity in such materials deposited using emulsion-based RIR-MAPLE, will also be reviewed. The overall result of these studies is the demonstration of emulsion-based RIR-MAPLE as a viable option for the fabrication of conjugated polymer and hybrid nanocomposite optoelectronic devices that could yield improved device performance.

  7. Combretastatin A-4 Conjugated Antiangiogenic Micellar Drug Delivery Systems Using Dendron-Polymer Conjugates.

    PubMed

    Sumer Bolu, Burcu; Manavoglu Gecici, Ece; Sanyal, Rana

    2016-05-01

    Employment of polymeric nanomaterials in cancer therapeutics is actively pursued since they often enable drug administration with increased efficacy along with reduced toxic side effects. In this study, drug conjugated micellar constructs are fabricated using triblock dendron-linear polymer conjugates where a hydrophilic linear polyethylene glycol (PEG) chain is flanked by well-defined hydrophobic biodegradable polyester dendrons bearing an antiangiogenic drug, combretastatin-A4 (CA4). Variation in dendron generation is utilized to obtain a library of micellar constructs with varying sizes and drug loadings. In particular, a family of drug appended dendron-polymer conjugates based on polyester dendrons of generations ranging from G1 to G3 and 10 kDa linear PEG were obtained using [3 + 2] Huisgen type "click" chemistry. The final constructs benefit from PEG's hydrophilicity and antibiofouling character, as well as biodegradable nature of the hydrophobic polyester dendrons. The hydrophobic-hydrophilic-hydrophobic character of these constructs leads to the formation of flower-like micelles in aqueous media. In addition to generation-dependent subnanomolar range critical micelle concentrations, the resulting micelles possess hydrodynamic diameters suitable for passive tumor targeting through enhanced permeability and retention (EPR) effect; thereby they are suitable candidates as controlled drug delivery agents. For all constructs, in vitro cytotoxicities were investigated and inhibitory effect of Comb-G3-PEG on tube formation was shown on human umbilical vein endothelial cells (HUVECs). PMID:27019335

  8. Liquid film/polymer interfaces

    SciTech Connect

    Allara, David L.

    2003-06-12

    The objectives were: (1) Through experimental studies, advance the fundamental understanding of the principles that govern adsorption and wetting phenomena at polymer and organic surfaces. (2) Establish a firm scientific basis for improving the design of coatings for metal fin cooling surfaces used to control the wetting of water condensate for optimum energy efficiency. Several important findings were: (1) water adsorbed at hydrophobic surfaces has a liquid-like structure, in contrast to the generally held view of an ordered structure; (2) Correlations of large amounts of contact angle wetting data of grafted alkyl chain compounds showed a distinct link between the contact angle and the conformational ordering of the chains; (3) water adsorption at long chain alkysiloxane films showed a strong pH dependence on the film stability, which can be attributed to interfacial chemical effects on the siloxane network.

  9. Blends of conjugated rigid-rod polymers: Novel supramolecular materials for electronics, optoelectronics and photonics

    SciTech Connect

    Jenekhe, S.A.

    1996-12-31

    Selected examples of binary blends of conjugated polymers will be presented to illustrate the vast scope of their supramolecular structures and electronic, optical, nonlinear optical, and optoelectronic properties.

  10. Shell thickness dependent photoinduced hole transfer in hybrid conjugated polymer/quantum dot nanocomposites: from ensemble to single hybrid level.

    PubMed

    Xu, Zhihua; Hine, Corey R; Maye, Mathew M; Meng, Qingping; Cotlet, Mircea

    2012-06-26

    Photoinduced hole transfer is investigated in inorganic/organic hybrid nanocomposites of colloidal CdSe/ZnS quantum dots and a cationic conjugated polymer, poly(9,9'-bis(6-N,N,N-trimethylammoniumhexyl)fluorene-alt-phenylene, in solution and in solid thin film, and down to the single hybrid level and is assessed to be a dynamic quenching process. We demonstrate control of hole transfer rate in these quantum dot/conjugated polymer hybrids by using a series of core/shell quantum dots with varying shell thickness, for which a clear exponential dependency of the hole transfer rate vs shell thickness is observed, for both solution and thin-film situations. Furthermore, we observe an increase of hole-transfer rate from solution to film and correlate this with changes in quantum dot/polymer interfacial morphology affecting the hole transfer rate, namely, the donor-acceptor distance. Single particle spectroscopy experiments reveal fluctuating dynamics of hole transfer at the single conjugated polymer/quantum dot interface and an increased heterogeneity in the hole-transfer rate with the increase of the quantum dot's shell thickness. Although hole transfer quenches the photoluminescence intensity of quantum dots, it causes little or no effect on their blinking behavior over the time scales probed here. PMID:22686521

  11. Role of redox centre in charge transport investigated by novel self-assembled conjugated polymer molecular junctions

    NASA Astrophysics Data System (ADS)

    Wang, Zongrui; Dong, Huanli; Li, Tao; Hviid, Rune; Zou, Ye; Wei, Zhongming; Fu, Xiaolong; Wang, Erjing; Zhen, Yonggang; Nørgaard, Kasper; Laursen, Bo W.; Hu, Wenping

    2015-06-01

    Molecular electronics describes a field that seeks to implement electronic components made of molecular building blocks. To date, few studies have used conjugated polymers in molecular junctions despite the fact that they potentially transport charge more efficiently than the extensively investigated small-molecular systems. Here we report a novel type of molecular tunnelling junction exploring the use of conjugated polymers, which are self-assembled into ultrathin films in a distinguishable `planar' manner from the traditional vertically oriented small-molecule monolayers. Electrical measurements on the junctions reveal molecular-specific characteristics of the polymeric molecules in comparison with less conjugated small molecules. More significantly, we decorate redox-active functionality into polymeric backbones, demonstrating a key role of redox centre in the modulation of charge transport behaviour via energy level engineering and external stimuli, and implying the potential of employing tailor-made polymeric components as alternatives to small molecules for future molecular-scale electronics.

  12. High temperature polymer dielectric film insulation

    NASA Technical Reports Server (NTRS)

    Jones, Robert J.

    1994-01-01

    PFPI polymers were invented in the late 1970's. Assessment of emerging requirements has dictated that 300 C performance is the goal for next generation wire insulation. TRW PFPI as superior 300 C polymer candidates is presented. Included is a comparison of promising PFPI film properties with Kapton. Also included are the promising bulk polymer or coating properties.

  13. Spray forming polymer membranes, coatings and films

    DOEpatents

    McHugh, K.M.; Watson, L.D.; McAtee, R.E.; Ploger, S.A.

    1993-10-12

    A method is described for forming a polymer film having controlled physical and chemical characteristics, wherein a plume of nebulized droplets of a polymer or polymer precursor is directed toward a substrate from a converging/diverging nozzle having a throat at which the polymer or a precursor thereof is introduced and an exit from which the nebulized droplets of the polymer or precursor thereof leave entrained in a carrier gas. Relative movement between the nozzle and the substrate is provided to form a polymer film. Physical and chemical characteristics can be controlled by varying the deposition parameters and the gas and liquid chemistries. Semipermeable membranes of polyphosphazene films are disclosed, as are a variety of other polymer systems, both porous and non-porous. 4 figures.

  14. Spray forming polymer membranes, coatings and films

    DOEpatents

    McHugh, Kevin M.; Watson, Lloyd D.; McAtee, Richard E.; Ploger, Scott A.

    1993-01-01

    A method of forming a polymer film having controlled physical and chemical characteristics, wherein a plume of nebulized droplets of a polymer or polymer precursor is directed toward a substrate from a converging/diverging nozzle having a throat at which the polymer or a precursor thereof is introduced and an exit from which the nebulized droplets of the polymer or precursor thereof leave entrained in a carrier gas. Relative movement between the nozzle and the substrate is provided to form a polymer film. Physical and chemical characteristics can be controlled by varying the deposition parameters and the gas and liquid chemistries. Semipermeable membranes of polyphosphazene films are disclosed, as are a variety of other polymer systems, both porous and non-porous.

  15. Alcohol vapor sensory properties of nanostructured conjugated polymers

    NASA Astrophysics Data System (ADS)

    Bearzotti, Andrea; Macagnano, Antonella; Pantalei, Simone; Zampetti, Emiliano; Venditti, Iole; Fratoddi, Ilaria; Vittoria Russo, Maria

    2008-11-01

    The response to relative humidity (RH) and alcohol vapors of resistive-type sensors based on nanobeads of conjugated polymers, namely polyphenylacetylene (PPA) and copolymer poly[phenylacetylene-(co-2-hydroxyethyl methacrylate)] (P(PA/HEMA)), were investigated. Sensors based on ordered arrays of these nanostructured polymeric materials showed stable and reproducible current intensity variations in the range 10-90% of relative humidity at room temperature. Both polymers also showed sensitivity to aliphatic chain primary alcohols, and a fine tuning of the sensor response was obtained by varying the chain length of the alcohol in relation to the polarity. The nanostructured feature of polymeric-based membranes seems to have an effect on the sensing response and an enhancement of the sensitivity was observed for the response to water and alcohol vapor variations with respect to previous studies based on amorphous polyphenylacetylene. High stability of the polymeric nanostructured membranes was detected with no aging after two weeks in continuum stressing measurement conditions.

  16. Hydrochromic conjugated polymers for human sweat pore mapping

    NASA Astrophysics Data System (ADS)

    Lee, Joosub; Pyo, Minkyeong; Lee, Sang-Hwa; Kim, Jaeyong; Ra, Moonsoo; Kim, Whoi-Yul; Park, Bum Jun; Lee, Chan Woo; Kim, Jong-Man

    2014-04-01

    Hydrochromic materials have been actively investigated in the context of humidity sensing and measuring water contents in organic solvents. Here we report a sensor system that undergoes a brilliant blue-to-red colour transition as well as ‘Turn-On’ fluorescence upon exposure to water. Introduction of a hygroscopic element into a supramolecularly assembled polydiacetylene results in a hydrochromic conjugated polymer that is rapidly responsive (<20 μs), spin-coatable and inkjet-compatible. Importantly, the hydrochromic sensor is found to be suitable for mapping human sweat pores. The exceedingly small quantities (sub-nanolitre) of water secreted from sweat pores are sufficient to promote an instantaneous colorimetric transition of the polymer. As a result, the sensor can be used to construct a precise map of active sweat pores on fingertips. The sensor technology, developed in this study, has the potential of serving as new method for fingerprint analysis and for the clinical diagnosis of malfunctioning sweat pores.

  17. Sustained gastrointestinal activity of dendronized polymer-enzyme conjugates

    NASA Astrophysics Data System (ADS)

    Fuhrmann, Gregor; Grotzky, Andrea; Lukić, Ružica; Matoori, Simon; Luciani, Paola; Yu, Hao; Zhang, Baozhong; Walde, Peter; Schlüter, A. Dieter; Gauthier, Marc A.; Leroux, Jean-Christophe

    2013-07-01

    Methods to stabilize and retain enzyme activity in the gastrointestinal tract are investigated rarely because of the difficulty of protecting proteins from an environment that has evolved to promote their digestion. Preventing the degradation of enzymes under these conditions, however, is critical for the development of new protein-based oral therapies. Here we show that covalent conjugation to polymers can stabilize orally administered therapeutic enzymes at different locations in the gastrointestinal tract. Architecturally and functionally diverse polymers are used to protect enzymes sterically from inactivation and to promote interactions with mucin on the stomach wall. Using this approach the in vivo activity of enzymes can be sustained for several hours in the stomach and/or in the small intestine. These findings provide new insight and a firm basis for the development of new therapeutic and imaging strategies based on orally administered proteins using a simple and accessible technology.

  18. Highly Ordered Single Conjugated Polymer Chain Rod Morphologies

    SciTech Connect

    Adachi, Takuji; Brazard, Johanna; Chokshi, Paresh; Ganesan, Venkat; Bolinger, Joshua; Barbara, Paul F.

    2010-10-15

    We have reexamined the fluorescence polarization anisotropy of single polymer chains of the prototypical conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) isolated in a poly(methyl methacrylate) (PMMA) matrix employing improved synthetic samples that contain a much smaller number of tetrahedral chemical defects per chain. The new measurements reveal a much larger fraction of highly anisotropic MEH-PPV chains, with >70% of the chains exhibiting polarization anisotropy values falling in the range of 0.6-0.9. High anisotropy is strong evidence for a rod-shaped conformation. A comparison of the experimental results with coarse grain, beads on a chain simulations reveals that simulations with the usual bead-bead pairwise additive potentials cannot reproduce the observed large fraction of high polarization values. Apparently, this type of potential lacks some yet to be identified molecular feature that is necessary to accurately simulate the experimental results.

  19. Conjugated polymer based active electric-controlled terahertz device

    NASA Astrophysics Data System (ADS)

    Zhong, Liang; Zhang, Bo; He, Ting; Lv, Longfeng; Hou, Yanbing; Shen, Jingling

    2016-03-01

    A modulation of terahertz response in a highly efficient, electric-controlled conjugated polymer-silicon hybrid device with low photo-excitation was investigated. The polymer-silicon forms a hybrid structure, where the active depletion region modifies the semiconductor conductivity in real time by applying an external bias voltage. The THz transmission was efficiently modulated by effective controlling. In a THz-TDS system, the modulation depth reached nearly 100% when the applied voltage was 3.8 V at an external laser intensity of 0.3 W/cm2. The saturation voltage decreased with increasing photo-excited intensity. In a THz-CW system, a significant decline in THz transmission was also observed with increasing applied bias voltage. This reduction in THz transmission is induced by the enhancement of carrier density.

  20. Diketopyrrolopyrrole-based Conjugated Polymers Bearing Branched Oligo(Ethylene Glycol) Side Chains for Photovoltaic Devices.

    PubMed

    Chen, Xingxing; Zhang, Zijian; Ding, Zicheng; Liu, Jun; Wang, Lixiang

    2016-08-22

    Conjugated polymers are essential for solution-processable organic opto-electronic devices. In contrast to the great efforts on developing new conjugated polymer backbones, research on developing side chains is rare. Herein, we report branched oligo(ethylene glycol) (OEG) as side chains of conjugated polymers. Compared with typical alkyl side chains, branched OEG side chains endowed the resulting conjugated polymers with a smaller π-π stacking distance, higher hole mobility, smaller optical band gap, higher dielectric constant, and larger surface energy. Moreover, the conjugated polymers with branched OEG side chains exhibited outstanding photovoltaic performance in polymer solar cells. A power conversion efficiency of 5.37 % with near-infrared photoresponse was demonstrated and the device performance could be insensitive to the active layer thickness. PMID:27258171

  1. Molding P3HT conjugated polymer in fibers by solvent-annealing-induced nanowetting in porous template

    NASA Astrophysics Data System (ADS)

    Cidade, Fernando N.; de Deus, Jeferson F.; Macedo, Andreia G.

    2015-07-01

    In this work, poly[3-hexyl-thiophene] (P3HT) polymer was assembled in fibers-like structures using a post-deposition treatment denoted as solvent-annealing-induced nanowetting in templates (SAINT). In this procedure, the as cast P3HT films deposited onto glass (or flexible) substrate are placed in contact with a porous template for instance, anodic alumina oxide (AAO), and then exposed to an atmosphere saturated with vapors of an organic solvent. This will induce a partial dissolution of the polymer and infiltration into the porous. After this, the template can be selectively removed and large areas containing tubular or fibers structures of polymer can be achieved. This is a simple procedure to produce fibers of conjugated polymer in films with enhanced optical and electrical properties that allows their application in optoelectronic devices.

  2. Polymer-assisted deposition of films

    DOEpatents

    McCleskey, Thomas M.; Burrell; Anthony K.; Jia; Quanxi; Lin; Yuan

    2009-10-20

    A polymer assisted deposition process for deposition of metal oxide films and the like is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures to yield metal oxide films and the like. Such films can be epitaxial in structure and can be of optical quality. The process can be organic solvent-free.

  3. Polymer-assisted deposition of films

    DOEpatents

    McCleskey, Thomas M.; Burrell, Anthony K.; Jia, Quanxi; Lin, Yuan

    2008-04-29

    A polymer assisted deposition process for deposition of metal oxide films is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures to yield metal oxide films. Such films can be epitaxial in structure and can be of optical quality. The process can be organic solvent-free.

  4. Carrier heating in disordered conjugated polymers in electric field

    SciTech Connect

    Vukmirovic, Nenad; Wang, Lin-Wang

    2010-01-26

    The electric field dependence of charge carrier transport and the effect of carrier heating in disordered conjugated polymers were investigated. A parameter-free multiscale methodology consisting of classical molecular dynamics simulation for the generation of the atomic structure, large system electronic structure and electron-phonon coupling constants calculations and the procedure for extracting the bulk polymer mobility, was used. The results suggested that the mobility of a fully disordered poly(3-hexylthiophene) (P3HT) polymer increases with electric field which is consistent with the experimental results on samples of regiorandom P3HT and different from the results on more ordered regioregular P3HT polymers, where the opposite trend is often observed at low electric fields. We calculated the electric field dependence of the effective carrier temperature and showed however that the effective temperature cannot be used to replace the joint effect of temperature and electric field, in contrast to previous theoretical results from phenomenological models. Such a difference was traced to originate from the use of simplified Miller-Abrahams hopping rates in phenomenological models in contrast to our considerations that explicitly take into account the electronic state wave functions and the interaction with all phonon modes.

  5. Photovoltaic and Spectral Properties of Conjugated Polymer Poly(3-octylthiophene) Doped with Various Acceptor Materials

    NASA Astrophysics Data System (ADS)

    Lee, Tsung-Hsien; Chen, Wei-Hsin; Su, Mu-Ting; Lai, Tzay-Shing; Lee, Wei

    2010-08-01

    We propose a novel approach for enhancement of efficiency of polymer-based photovoltaic devices by means of a low-molar-mass liquid crystal as a dopent. The active layers of the photovoltaic cells are primarily fabricated from the conjugated polymer poly(3-octylthiophene) as well as various acceptor substances including single-wall carbon nanotubes, buckminsterfullerene and the nematic liquid crystal E7 for comparison. The current-voltage characteristics are measured in dark and under green light illumination at wavelength of 514.5 nm. The power conversion efficiency for the active layer doped with E7 is the best among all cells in the simplest monolayer cell structure. Owing to the superior miscibility and orientational order of the nematic liquid crystal, E7 molecules may have promoted a composite film with fewer defects and locally helped the macromolecules align more orderly and consequently improved the charge-carrier transport, leading to the higher photocurrent and power conversion efficiency.

  6. Structure and segmental dynamics in amorphous conjugated polymers

    NASA Astrophysics Data System (ADS)

    Zhan, Pengfei; Maranas, Janna; Gomez, Enrique

    2015-03-01

    Although it is well established that the microstructure strongly affects charge transport in organic semiconductors, the role of fluctuations of the structure on charge mobilities is still not well understood. We have examined the dynamics and structure in amorphous conjugated polymers poly(3-alkylthiophene)s (P3ATs) with neutron and x-ray scattering. We measured the segmental dynamics in amorphous P3ATs with quasi-elastic neutron scattering (QENS). The structure of amorphous P3ATs is measured with small-angle neutron scattering (SANS) and grazing incidence X-ray diffraction (GIXRD). Using SANS, we observe phase separation between the backbone and side-chains in all polymer samples for regiorandom P3ATs. Additionally, the analysis of the QENS data shows that longer side-chains relax faster compared with shorter side-chains and our further analysis of the elastic incoherent structure factor (EISF) suggests that the amplitude of proton motion on the thiophene rings increases by a factor of 3 as the side-chain length increases from 6 to 12, demonstrating that longer side chains lead to enhanced motion of conjugated rings. This work is done under the support of Dow Chemical Company

  7. Polymer Conjugation as a Strategy for Long-Range Order in Supramolecular Polymers.

    PubMed

    Benjamin, Ari; Keten, Sinan

    2016-04-01

    Supramolecular polymers are polymers in which the individual subunits self-assemble via noncovalent and reversible bonds. An important axis of control for systems of mixed subunit composition is the order in which the subunit types assemble. Existing ordering techniques, which rely on pairwise interactions through the inclusion of highly specific chemistry, have the downside that patterns of length n require n specific chemistries, making long-range order complicated to attain. Here we present a simple alternative method: we attach varying numbers of polymers to self-assembling subunits, in our case ring shaped macrocycles, and the polymers' aversion to confinement imposes system order. We evaluate the feasibility of the strategy using coarse-grained molecular dynamics simulations of polymer-conjugated rings designed to model cyclic peptide nanotubes. We discuss the effects of polymer conjugation on the energetics of association and predict the equilibrium orderings for various ratios of ring types. The emergent patterns are associated with a certain stochastic disorder, which we quantify by deriving and employing a formula for the expected statistical weight of any pattern within the ensemble of all possible orderings. PMID:26938206

  8. Thiophene fused azacoronenes: regioselective synthesis, self organization, charge transport, and its incorporation in conjugated polymers

    DOEpatents

    Liu, Yi; He, Bo

    2015-09-15

    A regioselective synthesis of an azacoronene fused with two peripheral thiophene groups has been realized through a concise synthetic route. The resulting thienoazacoronene (TAC) derivatives show high degree of self-organization in solution, in single crystals, in the bulk, and in spuncast thin films. Spuncast thin film field-effect transistors of the TACs exhibited mobilities up to 0.028 cm.sup.2V.sup.-1 S.sup.-1, which is among the top field effect mobilities for solution processed discotic materials. Organic photovoltaic devices using TAC-containing conjugated polymers as the donor material exhibited a high open-circuit voltage of 0.89 V, which was ascribable to TAC's low-lying highest occupied molecular orbital energy level.

  9. Navigating conjugated polymer actuated neural probes in a brain phantom

    NASA Astrophysics Data System (ADS)

    Daneshvar, Eugene D.; Kipke, Daryl; Smela, Elisabeth

    2012-04-01

    Neural probe insertion methods have a direct impact on the longevity of the device in the brain. Initial tissue and vascular damage caused by the probe entering the brain triggers a chronic tissue response that is known to attenuate neural recordings and ultimately encapsulate the probes. Smaller devices have been found to evoke reduced inflammatory response. One way to record from undamaged neural networks may be to position the electrode sites away from the probe. To investigate this approach, we are developing probes with controllably movable electrode projections, which would move outside of the zone that is damaged by the insertion of the larger probe. The objective of this study was to test the capability of conjugated polymer bilayer actuators to actuate neural electrode projections from a probe shank into a transparent brain phantom. Parylene neural probe devices, having five electrode projections with actuating segments and with varying widths (50 - 250 μm) and lengths (200 - 1000 μm) were fabricated. The electroactive polymer polypyrrole (PPy) was used to bend or flatten the projections. The devices were inserted into the brain phantom using an electronic microdrive while simultaneously activating the actuators. Deflections were quantified based on video images. The electrode projections were successfully controlled to either remain flat or to actuate out-of-plane and into the brain phantom during insertion. The projection width had a significant effect on their ability to deflect within the phantom, with thinner probes deflecting but not the wider ones. Thus, small integrated conjugated polymer actuators may enable multiple neuro-experiments and applications not possible before.

  10. Macroscopic Alignment of One-Dimensional Conjugated Polymer Nanocrystallites for High-Mobility Organic Field-Effect Transistors.

    PubMed

    Chang, Mincheol; Choi, Dalsu; Egap, Eilaf

    2016-06-01

    Controlling the morphology of polymer semiconductors remains a fundamental challenge that hinders their widespread applications in electronic and optoelectronic devices and commercial feasibility. Although conjugated polymer nanowires (NWs) are envisioned to afford high charge-carrier mobility, the alignment of preformed conjugated polymer NWs has not been reported. Here, we demonstrate an extremely simple and effective strategy to generate well-aligned arrays of one-dimensional (1D) polymer semiconductors that exhibit remarkable enhancement in charge transport using a solution shear-coating technique. We show that solution shear coating of poly(alkylthiophene) NWs induces extension or coplanarization of the polymer backbone and highly aligned network films, which results in enhanced intra- and intermolecular ordering and reduced grain boundaries. Consequently, highly aligned poly(3-hexylthiophene) NWs exhibited over 33-fold enhancement in the average carrier mobility, with the highest mobility of 0.32 cm(2) V(-1) s(-1) compared to pristine films. The presented platform is a promising strategy and general approach for achieving well-aligned 1D nanostructures of polymer semiconductors and could enable the next generation of high-performance flexible electronic devices for a wide range of applications. PMID:27191819

  11. Infrared Studies of Optically Pumped Simple Conjugated Polymers.

    NASA Astrophysics Data System (ADS)

    Schaffer, Howard E.

    This dissertation presents the results of a series of infrared spectroscopic studies of optically pumped simple conjugated polymers. It had previously been shown that photoexcitation of the simplest of these polymers, trans -polyacetylene, produced infrared absorptions characteristic of solitons, which are self-localized defects that arise as solutions to the model Hamiltonian proposed by Su, Schrieffer and Heeger (SSH). Upon this foundation, four lines of research to study conjugated polymers were pursued. One, a highly sensitive repetition of the previous measurements for carefully isomerized samples of both (CH) _{x} and its deuterated analogue, (CD)_{x}, have allowed the observation of very weak absorptions, previously unobserved. The frequencies and intensities of these absorptions agree with those predicted by recent calculations, based on the SSH model, to be due to a third bound mode of the soliton defect. Two, comparison of the photoinduced absorption spectra of a series of samples of Shirakawa, Durham, and Naarman type polyacetylene samples has demonstrated the dependence of both frequencies and relative oscillator strengths of the infrared peaks upon sample preparation. The amplitude mode formalism, combined with the results of other experiments, allows these data to provide a connection between spectroscopy of excited states and sample morphology. Three, more complicated polymers have been studied. The four largest peaks characteristic of photogenerated bipolarons in polythiophene have similar interpretation to the stronger peaks in polyacetylene; smaller features have been interpreted similarly to the weak absorptions described in the previous paragraph. Absorptions at lower energy have been assigned as due to vibrations of the rings of polythiophene which are not related to the Peierls-type electron-phonon coupling described by SSH. Preliminary data on the newer polymer polyisothianaphthene is also presented. And, four, the inconclusive results of a

  12. Second-order dispersion interactions in π-conjugated polymers

    NASA Astrophysics Data System (ADS)

    Barford, William; Paiboonvorachat, Nattapong; Yaron, David

    2011-06-01

    We calculate the ground state and excited state second-order dispersion interactions between parallel π-conjugated polymers. The unperturbed eigenstates and energies are calculated from the Pariser-Parr-Pople model using CI-singles theory. Based on large-scale calculations using the molecular structure of trans-polyacetylene as a model system and by exploiting dimensional analysis, we find that: (1) For inter-chain separations, R, greater than a few lattice spacings, the ground-state dispersion interaction, Δ E_{GS}, satisfies, Δ E_{GS} ˜ L^2/R^6 for L ≪ R and Δ E_{GS} ˜ L/R^5 for R ≪ L, where L is the chain length. The former is the London fluctuating dipole-dipole interaction while the latter is a fluctuating line dipole-line dipole interaction. (2) The excited state screening interaction exhibits a crossover from fluctuating monopole-line dipole interactions to either fluctuating dipole-dipole or fluctuating line dipole-line dipole interactions when R exceeds a threshold Rc, where Rc is related to the root-mean-square separation of the electron-hole excitation. Specifically, the excited state screening interaction, ΔEn, satisfies, ΔEn ˜ L/R6 for Rc < L ≪ R and ΔEn ˜ L0/R5 for Rc < R ≪ L. For R < Rc < L, ΔEn ˜ R-ν, where ν ≃ 3. We also investigate the relative screening of the primary excited states in conjugated polymers, namely the n = 1, 2, and 3 excitons. We find that a larger value of n corresponds to a larger value of ΔEn. For example, for poly(para-phenylene), ΔEn = 1 ≃ 0.1 eV, ΔEn = 2 ≃ 0.6 eV, and ΔEn = 3 ≃ 1.2 eV (where n = 1 is the 11B1 state, n = 2 is the m1A state, and n = 3 is the n1B1 state). Finally, we find that the strong dependence of ΔEn on inter-chain separation implies a strong dependency of ΔEn on density fluctuations. In particular, a 10% density fluctuation implies a fluctuation of 13 meV, 66 meV, and 120 meV for the 11B1, m1A state, and n1B1 states of poly(para-phenylene), respectively. Our results

  13. Creating Ordered Antibody Arrays with Antibody-Polymer Conjugates

    NASA Astrophysics Data System (ADS)

    Dong, Xuehui; Obermeyer, Allie; Olsen, Bradley

    Antibodies are a category of functional proteins that play crucial roles in the immune system and have been widely applied in the area of cancer therapeutics, targeting delivery, signal detection, and sensors. Due to the extremely large size and lack of specific functional groups on the surface, it is challenging to functionalize antibodies and manipulate the ordered packing of antibodies in an array with high density and proper orientation, which is critical to achieve outstanding performance in materials. In this work, we demonstrate an efficient and facile approach for preparing antibody-polymer conjugates with two-step sequential ``click'' reaction to form antibody-polymer block copolymers. Highly ordered nanostructures are fabricated based on the principles of block copolymer self-assembly. The nanostructures are studied with both small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Lamellae with alternating antibody domain and polymer domain are observed with an overall domain size of ~50 nm. The nanostructure not only increases the packing density and promotes proper orientation of the antibody, but also provides possible channel to facilitate substrate transportation and improves the stability of the antibody.

  14. Conformation-Dependent Photostability among and within Single Conjugated Polymers.

    PubMed

    Park, Heungman; Hoang, Dat Tien; Paeng, Keewook; Yang, Jaesung; Kaufman, Laura J

    2015-11-11

    The relationship between photostability and conformation of 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene (MEH-PPV) conjugated polymers was studied via excitation polarization modulation depth (M) measurements. Upon partial photobleaching, M distributions of collapsed, highly ordered MEH-PPV molecules shifted toward lower values. Conversely, M distributions of MEH-PPV molecules with random coil conformations moved toward higher values after partial photobleaching. Monte Carlo simulations of randomly distributed dipole moments along polymer chains subjected to partial photobleaching revealed that a statistical effect leads to an increase in peak M value. Decreases in M values seen experimentally in the population of MEH-PPV molecules with high M values, however, are due to conformation-dependent photostability within single MEH-PPV polymers. We show that, while folded MEH-PPV molecules are relatively more photostable than extended MEH-PPV molecules in an ensemble, extended portions of particular molecules are more photostable than folded domains within single MEH-PPV molecules. PMID:26438977

  15. Making Glasses Conduct: Electrochemical Doping of Redox-Active Polymer Thin Films

    NASA Astrophysics Data System (ADS)

    Boudouris, Bryan

    Optoelectronically-active macromolecules have been established as promising materials in myriad organic electronic applications (e.g., organic field-effect transistors (OFETs) and organic photovoltaic (OPV) devices). To date, however, the majority of the work surrounding these materials has focused on materials with a great deal of conjugation along their macromolecular backbones and with varying degrees of crystalline structure. Here, we describe an emerging class of macromolecular charge conductors, radical polymers, that: (1) do not contain conjugation and (2) are completely amorphous glasses. Radical polymers contain non-conjugated macromolecular backbones and stable radical sites along the side chains of the electronically-active materials. In contrast to conjugated polymer systems, these materials conduct charge in the solid state through oxidation-reduction (redox) reactions along these pendant groups. Specifically, we demonstrate that controlling the chemical functionality of the pendant groups and the molecular mobility of the macromolecular backbones significantly impacts the charge transport ability of the pristine (i.e., not doped) radical polymers species. Through proper control of these crucial parameters, we show that radical polymers can have electrical conductivity and charge mobility values on par with commonly-used conjugated polymers. Importantly, we also highlight the ability to dope radical polymers with redox-active small molecule species. This doping, in turn, increases the electrical conductivity of the glassy radical polymer thin films in a manner akin to what is observed in traditional conjugated polymer systems. In this way, we establish a means by which to fabricate optically-transparent and colorless thin film glasses capable of conducting charge in a rather rapid manner. We anticipate that these fundamental insights will prove crucial in developing new transparent conducting layers for future electronic applications.

  16. Liver-Targeted SiRNA Delivery Using Biodegradable Poly(amide) Polymer Conjugates.

    PubMed

    Barrett, Stephanie E; Guidry, Erin N

    2016-01-01

    The realization of polymer conjugate-based RNA delivery as a clinical modality requires the development and optimization of novel formulations. Although many literature examples of polymer conjugate-based SiRNA delivery systems exist, the protocols described herein represent a robust and facile way of screening any poly(amine)-based polymer system for SiRNA delivery. In this chapter, we describe the synthetic methods used to prepare poly(amide) polymers using a controlled polymerization method, as well as the preparation of the resulting targeted SiRNA polymer conjugates. In addition, detailed methods are provided for the characterization of the biodegradable poly(peptides) as well as the polymer conjugate that ensues. PMID:26472438

  17. Polymer-assisted deposition of films

    DOEpatents

    McCleskey,Thomas M.; Burrell,Anthony K.; Jia,Quanxi; Lin,Yuan

    2012-02-28

    A polymer assisted deposition process for deposition of metal nitride films and the like is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures under a suitable atmosphere to yield metal nitride films and the like. Such films can be conformal on a variety of substrates including non-planar substrates. In some instances, the films can be epitaxial in structure and can be of optical quality. The process can be organic solvent-free.

  18. Electronic interaction in composites of a conjugated polymer and carbon nanotubes: first-principles calculation and photophysical approaches

    PubMed Central

    Wéry, Jany; Duvail, Jean-Luc; Lefrant, Serge; Yaya, Abu; Ewels, Chris

    2015-01-01

    Summary The mechanisms that control the photophysics of composite films made of a semiconducting conjugated polymer (poly(paraphenylene vinylene), PPV) mixed with single-walled carbon nanotubes (SWNT) up to a concentration of 64 wt % are determined by using photoexcitation techniques and density functional theory. Charge separation is confirmed experimentally by rapid quenching of PPV photoluminescence and changes in photocurrent starting at relatively low concentrations of SWNT. Calculations predict strong electronic interaction between the polymer and the SWNT network when nanotubes are semiconducting. PMID:26171290

  19. Parallel Synthesis of photoluminescent π-conjugated polymers by polymer reactions of an organotitanium polymer with a titanacyclopentadiene unit.

    PubMed

    Matsumura, Yoshimasa; Fukuda, Katsura; Inagi, Shinsuke; Tomita, Ikuyoshi

    2015-04-01

    A regioregular organometallic polymer with titanacyclopentadiene unit, obtained by the reaction of a 2,7-diethynylfluorene derivative and a low-valent titanium complex, is subjected to the reaction with three kinds of electrophiles (i.e., sulfur monochloride, hydrochloric acid, and dichlorophenylphosphine) to give π-conjugated polymers possessing both fluorene and building blocks originated from the transformation of the titanacycles in the main chain. For example, a phosphole-containing polymer whose number-average molecular weight is estimated as 5000 is obtained in 50% yield. The obtained thiophene, butadiene, and phosphole-containing polymers exhibit efficient photoluminescence (PL) with emission colors of blue, green, and yellow, respectively. For example, the phosphole-containing polymer exhibits yellow PL with an emission maximum (Emax ) of 533 nm and a quantum yield (Φ) of 0.37. PMID:25630490

  20. Supramolecular structure of electroactive polymer thin films

    NASA Astrophysics Data System (ADS)

    Kornilov, V. M.; Lachinov, A. N.; Karamov, D. D.; Nabiullin, I. R.; Kul'velis, Yu. V.

    2016-05-01

    This paper presents the results of an experimental investigation of the supramolecular structure of polydiphenylenephthalide thin films that exhibit effects of resistive switching. The supramolecular structure of the polymer has been investigated using small-angle neutron scattering in conjunction with atomic force microscopy. It has been found that the internal structure of polymer films consists of structural elements in the form of spheroids. The sizes of the structural elements, which were obtained from the neutron scattering data and analysis of the atomic force microscopy images, correlate well with each other. A model of the formation of polymer layers has been proposed. The observed structural elements in polymer films are formed due to the association of macromolecules in the initial polymer solution.

  1. Multicolor Conjugated Polymer Dots for Biological Fluorescence Imaging

    PubMed Central

    Wu, Changfeng; Bull, Barbara; Szymanski, Craig; Christensen, Kenneth; McNeill, Jason

    2009-01-01

    Highly fluorescent conjugated polymer dots were developed for demanding applications such as fluorescence imaging in live cells. These nanoparticles exhibit small particle diameters, extraordinary fluorescence brightness, and excellent photostability. Single particle fluorescence imaging and kinetic studies indicate much higher emission rates (∼108 s-1) and little or no blinking of the nanoparticles as compared to typical results for single dye molecules and quantum dots. Analysis of single particle photobleaching trajectories reveals excellent photostability — as many as 109 or more photons emitted per nanoparticle prior to irreversible photobleaching. The superior figures of merit of these new fluorescent probes, together with the demonstration of cellular imaging, indicate their enormous potential for demanding fluorescence-based imaging and sensing applications such as high speed super-resolution single molecule/particle tracking and highly sensitive assays. PMID:19206410

  2. Hydrophobic conjugated microporous polymers for sorption of human serum albumin

    NASA Astrophysics Data System (ADS)

    Zheng, Chunli; Du, Miaomiao; Feng, Shanshan; Sun, Hanxue; Li, An; He, Chi; Zhang, TianCheng; Wang, Qiaorui; Wei, Wei

    2016-02-01

    This paper investigated the sorption of human serum albumin (HSA) from water by three kinds of conjugated microporous polymers (CMPs) with surface hydrophobicity and intrinsic porosity. It was found that the three CMPs captured HSA with fast sorption kinetics and good working capacity. Equilibrium was obtained at 80 min for all the tests, and the maximum sorption quantity (qm) ranged from 0.07 to 0.14 mg/mg. With the increase in the particle external surface area of the CMPs, a greater extent of HSA sorption was achieved. Moreover, promoting the dispersion of CMPs in HSA aqueous solution was also beneficial to the extraction. Attenuated Total Reflection Fourier Transform Infrared spectroscopy verified the interactions between the CMPs and the Nsbnd H, Cdbnd O, and Csbnd N groups of HSA. This paper might provide fundamental guidance for the practical application of CMPs to proteins separation and recovery.

  3. Hopping approach towards exciton dissociation in conjugated polymers

    SciTech Connect

    Emelianova, E. V.; Auweraer, M. van der; Baessler, H.

    2008-06-14

    By employing random walk an analytic theory for the dissociation of singlet excitons in a random organic solid, for instance, a conjugated polymer, has been developed. At variance of conventional three-dimensional Onsager theory, it is assumed that an exciton with finite lifetime can first transfer endothermically an electron to an adjacent site, thereby generating a charge transfer state whose energy is above the energy of that of the initial exciton. In a second step the latter can fully dissociate in accordance with Onsager's concept Brownian motion. The results indicate that, depending of the energy required for the first jump, the first jump contributes significantly to the field dependence of the dissociation yield. Disorder weakens the temperature dependence of the yield dramatically and precludes extracting information on the exciton binding energy from it.

  4. Impurity effects on polaron-exciton formation in conjugated polymers

    SciTech Connect

    Ribeiro, Luiz Antonio Ferreira da Cunha, Wiliam; Neto de Oliveira, Pedro Henrique; Gargano, Ricardo; Magela e Silva, Geraldo

    2013-11-07

    Combining the one-dimensional tight-binding Su-Schrieffer-Heeger model and the extended Hubbard model, the collision of two oppositely charged polarons is investigated under the influence of impurity effects using a non-adiabatic evolution method. Results show that electron-electron interactions have direct influence on the charge distribution coupled to the polaron-exciton lattice defect. Additionally, the presence of an impurity in the collisional process reduces the critical electric field for the polaron-exciton formation. In the small electric field regime, the impurity effects open three channels and are of fundamental importance to favor the polaron-exciton creation. The results indicate that the scattering between polarons in the presence of impurities can throw a new light on the description of electroluminescence in conjugated polymer systems.

  5. Charging and discharging of single conjugated-polymer nanoparticles

    NASA Astrophysics Data System (ADS)

    Palacios, Rodrigo E.; Fan, Fu-Ren F.; Grey, John K.; Suk, Jungdon; Bard, Allen J.; Barbara, Paul F.

    2007-09-01

    Despite intense, long-term interest in organic semiconductors from both an applied and fundamental perspective, key aspects of the electronic properties of these materials remain poorly defined. A particularly challenging problem is the molecular nature of positive charge carriers, that is, holes or oxidized species in organics. Here, the unique ability of single-molecule spectroelectrochemistry (SMS-EC) to unravel complex electrochemical process in heterogeneous media is used to study the oxidation of nanoparticles of the conjugated polymer poly(9,9-dioctylfluorene-co-benzothiadiazole). A reversible hole-injection charging process has been observed that occurs primarily by initial injection of shallow (untrapped) holes, but soon after the injection, a small fraction of the holes becomes deeply trapped. Good agreement between experimental data and simulations strongly supports the presence of deep traps in the studied nanoparticles and highlights the ability of SMS-EC to study energetics and dynamics of deep traps in organic materials at the nanoscale.

  6. Theory of exciton transfer and diffusion in conjugated polymers

    SciTech Connect

    Barford, William; Tozer, Oliver Robert

    2014-10-28

    We describe a theory of Förster-type exciton transfer between conjugated polymers. The theory is built on three assumptions. First, we assume that the low-lying excited states of conjugated polymers are Frenkel excitons coupled to local normal modes, and described by the Frenkel-Holstein model. Second, we assume that the relevant parameter regime is ℏω < J, i.e., the adiabatic regime, and thus the Born-Oppenheimer factorization of the electronic and nuclear degrees of freedom is generally applicable. Finally, we assume that the Condon approximation is valid, i.e., the exciton-polaron wavefunction is essentially independent of the normal modes. The resulting expression for the exciton transfer rate has a familiar form, being a function of the exciton transfer integral and the effective Franck-Condon factors. The effective Franck-Condon factors are functions of the effective Huang-Rhys parameters, which are inversely proportional to the chromophore size. The Born-Oppenheimer expressions were checked against DMRG calculations, and are found to be within 10% of the exact value for a tiny fraction of the computational cost. This theory of exciton transfer is then applied to model exciton migration in conformationally disordered poly(p-phenylene vinylene). Key to this modeling is the assumption that the donor and acceptor chromophores are defined by local exciton ground states (LEGSs). Since LEGSs are readily determined by the exciton center-of-mass wavefunction, this theory provides a quantitative link between polymer conformation and exciton migration. Our Monte Carlo simulations indicate that the exciton diffusion length depends weakly on the conformation of the polymer, with the diffusion length increasing slightly as the chromophores became straighter and longer. This is largely a geometrical effect: longer and straighter chromophores extend over larger distances. The calculated diffusion lengths of ∼10 nm are in good agreement with experiment. The spectral

  7. Theory of optical transitions in conjugated polymers. I. Ideal systems

    NASA Astrophysics Data System (ADS)

    Barford, William; Marcus, Max

    2014-10-01

    We describe a theory of linear optical transitions in conjugated polymers. The theory is based on three assumptions. The first is that the low-lying excited states of conjugated polymers are Frenkel excitons coupled to local normal modes, described by the Frenkel-Holstein model. Second, we assume that the relevant parameter regime is ℏω ≪ J, i.e., the adiabatic regime, and thus the Born-Oppenheimer factorization of the electronic and nuclear degrees of freedom is generally applicable. Finally, we assume that the Condon approximation is valid, i.e., the exciton-polaron wavefunction is essentially independent of the normal modes. Using these assumptions we derive an expression for an effective Huang-Rhys parameter for a chain (or chromophore) of N monomers, given by S(N) = S(1)/IPR, where S(1) is the Huang-Rhys parameter for an isolated monomer. IPR is the inverse participation ratio, defined by IPR = (∑n|Ψn|4)-1, where Ψn is the exciton center-of-mass wavefunction. Since the IPR is proportional to the spread of the exciton center-of-mass wavefunction, this is a key result, as it shows that S(N) decreases with chain length. As in molecules, in a polymer S(N) has two interpretations. First, ℏωS(N) is the relaxation energy of an excited state caused by its coupling to the normal modes. Second, S(N) appears in the definition of an effective Franck-Condon factor, F0v(N) = S(N)vexp ( - S(N))/v! for the vth vibronic manifold. We show that the 0 - 0 and 0 - 1 optical intensities are proportional to F00(N) and F01(N), respectively, and thus the ratio of the 0 - 1 to 0 - 0 absorption and emission intensities are proportional to S(N). These analytical results are checked by extensive DMRG calculations and found to be generally valid, particularly for emission. However, for large chain lengths higher-lying quasimomentum exciton states become degenerate with the lowest vibrational excitation of the lowest exciton state. When this happens there is mixing of the

  8. Reversible Photoswitching of Spiropyran-Conjugated Semiconducting Polymer Dots

    PubMed Central

    Chan, Yang-Hsiang; Gallina, Maria Elena; Zhang, Xuanjun; Wu, I-Che; Jin, Yuhui; Sun, Wei; Chiu, Daniel T.

    2012-01-01

    Semiconducting polymer dots (Pdots) recently have emerged as a new class of ultrabright fluorescent probes with promising applications in biological detection and imaging. We developed photoswitchable Pdots by conjugating photochromic spiropyran molecules onto poly[9,9-dioctylfluorenyl-2,7-diyl)-co-1,4-benzo-{2,1′-3}-thiadiazole)] (PFBT). The modulation of fluorescence was achieved by ultraviolet irradiation, which converted spiropyran into its visible-absorbing merocyanine form. The merocyanine efficiently quenched the fluorescence of PFBT via Förster resonance energy transfer (FRET). We then reversed the quenching by subsequent irradiation with visible light to get back the fluorescence of PFBT. This FRET-based photomodulation of Pdot fluorescence could be repeated multiple times. We next conjugated biomolecules onto the surface of these photoswitchable Pdots and demonstrated their specific cellular and subcellular labeling to different types of cells without any noticeable nonspecific binding. We anticipate these photoswitchable and biocompatible Pdots will be useful in developing bio-imaging techniques in the future. PMID:23033991

  9. Design of hybrid conjugated polymer materials: 1) Novel inorganic/organic hybrid semiconductors and 2) Surface modification via grafting approaches

    NASA Astrophysics Data System (ADS)

    Peterson, Joseph J.

    synthesized and characterized, and the material is found to be a high MW, soluble blue emitter which shows a higher glass transition temperature and greater stability than a non-hybrid polymer. UV absorbance and fluorescence spectroscopy indicated some electronic interaction between the conjugated polymer and the cages, but they did not appear to be fully conjugated in the traditional sense. Chapter 4 describes the design, synthesis, and characterization of poly(fluorene) with o-carborane in the backbone. Profound changes in the behavior of the polymer, from its polymerization behavior to its emission characteristics, were observed and their origins are discussed. Experiments to explore the nature of the cage/polymer interactions were performed and possible applications which take advantage of the unique nature of the o-carborane hybrid polymer are explored and discussed. Hybrid conjugated polymer materials via grafting approaches to surfaces and surface modification are discussed starting in chapter 5. The synthesis of a dibromofluorene-based silane coupling agent for the surface functionalization of oxide surfaces is presented, and the surface directed Ni(0) dehalogenative polymerization of poly(dihexylfluorene) is explored. Chapter 6 focuses on the exploration of conjugated polymer/cellulose hybrid materials. Surface medication of cellulose materials with monomer-like anchor points is discussed. Grafting of the modified cellulose with conjugated polymers was explored and the grafting of three different repeat structures based on fluorene-, fluorenevinylene-, and fluoreneethynylene motifs were optimized to provide a general route to cellulose/conjugated polymer hybrid materials. Characterization and possible applications of such hybrid materials are discussed. Finally, chapter 7 is devoted to the simultaneous surface patterning and functionalization of poly(2-hydroxyethylmethacrylate) thin films using a silane infusion-based wrinkling technique. While not a conjugated

  10. Hydrochromic conjugated polymers for human sweat pore mapping

    PubMed Central

    Lee, Joosub; Pyo, Minkyeong; Lee, Sang-hwa; Kim, Jaeyong; Ra, Moonsoo; Kim, Whoi-Yul; Park, Bum Jun; Lee, Chan Woo; Kim, Jong-Man

    2014-01-01

    Hydrochromic materials have been actively investigated in the context of humidity sensing and measuring water contents in organic solvents. Here we report a sensor system that undergoes a brilliant blue-to-red colour transition as well as ‘Turn-On’ fluorescence upon exposure to water. Introduction of a hygroscopic element into a supramolecularly assembled polydiacetylene results in a hydrochromic conjugated polymer that is rapidly responsive (<20 μs), spin-coatable and inkjet-compatible. Importantly, the hydrochromic sensor is found to be suitable for mapping human sweat pores. The exceedingly small quantities (sub-nanolitre) of water secreted from sweat pores are sufficient to promote an instantaneous colorimetric transition of the polymer. As a result, the sensor can be used to construct a precise map of active sweat pores on fingertips. The sensor technology, developed in this study, has the potential of serving as new method for fingerprint analysis and for the clinical diagnosis of malfunctioning sweat pores. PMID:24781362

  11. Photorefractivity in liquid crystals doped with a soluble conjugated polymer.

    SciTech Connect

    Niemczyk, M. P.; Svec, W. A.; Wasielewski, M. R.; Wiederrecht, G. P.

    1999-07-07

    Photoconductive polymers are doped into liquid crystals to create a new mechanism for space-charge field formation in photorefractive liquid crystal composites. The composites contain poly(2,5-bis(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene) (BEH-PPV) and the electron acceptor N,N{prime}-dioctyl-1,4:5,8-naphthalenediimide, NI. Using asymmetric energy transfer (beam coupling) measurements that are diagnostic for the photorefractive effect, the direction of beam coupling as a function of grating fringe spacing inverts at a spacing of 5.5 {micro}m. We show that the inversion is due to a change in the dominant mechanism for space-charge field formation. At small fringe spacings, the space-charge field is formed by ion diffusion in which the photogenerated anion is the more mobile species. At larger fringe spacings, the polarity of the space charge field inverts due to dominance of a charge transport mechanism in which photogenerated holes are the most mobile species due to hole migration along the BEH-PPV chains coupled with interchain hole hopping. Control experiments are presented, which use composites that can access only one of the two charge transport mechanisms. The results show that charge migration over long distances leading to enhanced photorefractive effects can be obtained using conjugated polymers dissolved in liquid crystals.

  12. Functionalization of conjugated polymer nanoparticles for fluorescence photomodulation.

    PubMed

    Chamberlayne, Christian F; Lepekhina, Elena A; Saar, Brooklynd D; Peth, Kathryn A; Walk, Jordan T; Harbron, Elizabeth J

    2014-12-01

    The emission of conjugated polymer nanoparticles (CPNs or Pdots) is often tailored for specific uses by functionalizing CPNs with dyes that act as fluorescence resonance energy transfer (FRET) acceptors. A number of dye functionalization methods for CPNs have been developed, ranging from simple noncovalent doping to covalent attachment. We seek to develop guidelines for when noncovalent doping is acceptable and when covalent attachment is necessary to achieve the desired result. We present results of CPNs functionalized with photochromic spirooxazines by four different methods: simple doping, doping with an amphiphilic coating polymer, covalent functionalization prior to CPN formation, and covalent functionalization after CPN formation. The different CPNs are evaluated in terms of their fluorescence photomodulation properties to determine how the preparation method affects the CPN-dye photophysical interactions. Doping preparations yield the most efficient quenching of CPN emission due to shorter donor-acceptor distances in these CPNs compared to those with covalently tethered dyes. Aging studies reveal that the photochromic dyes in doped samples degrade over time to a far greater extent than those in covalently functionalized samples. These results suggest that dye-doped CPNs are appropriate for short-term experiments where highly efficient FRET is desired while covalent dye functionalization is a better choice for experiments executed over an extended time frame. PMID:25406070

  13. Photorefractivity in liquid crystals doped with a soluble conjugated polymer

    NASA Astrophysics Data System (ADS)

    Wiederrecht, Gary P.; Svec, Walter A.; Niemczyk, Mark P.; Wasielewski, Michael R.

    1999-10-01

    Photoconductive polymers are doped into liquid crystals to create a new mechanism for space-charge field formation in photorefractive liquid crystal composites. The composites contain poly(2,5-bis(2'-ethylhexyloxy)-1,4- phenylenevinylene) (BEH-PPV) and the electron acceptor N,N'- dioctyl-1,4:5,8-naphthalenediimide, NI. Using asymmetric energy transfer (beam coupling) measurements that are diagnostic for the photorefractive effect, the direction of beam coupling as a function of grating fringe spacing inverts at a spacing of 5.5 micrometers . We show that the inversion is due to a change in the dominant mechanism for space-charge field formation. At small fringe spacings, the space-charge field is formed by ion diffusion in which the photogenerated anion is the more mobile species. At larger fringe spacings, the polarity of the space charge field inverts due to dominance of a charge transport mechanism in which photogenerated holes are the most mobile spaces due to hole migration along the BEH-PPV chains coupled with interchain hole hopping. Control experiments are presented, which use composites that can access only one of the two charge transport mechanisms. The results show that charge migration over long distances leading to enhanced photorefractive effects can be obtained using conjugated polymers dissolved in liquid crystals.

  14. Morphology in electrochemically grown conducting polymer films

    DOEpatents

    Rubinstein, Israel; Gottesfeld, Shimshon; Sabatani, Eyal

    1992-01-01

    A conducting polymer film with an improved space filling is formed on a metal electrode surface. A self-assembling monolayer is formed directly on the metal surface where the monolayer has a first functional group that binds to the metal surface and a second chemical group that forms a chemical bonding site for molecules forming the conducting polymer. The conducting polymer is then conventioonally deposited by electrochemical deposition. In one example, a conducting film of polyaniline is formed on a gold electrode surface with an intermediate monolayer of p-aminothiophenol.

  15. Morphology in electrochemically grown conducting polymer films

    DOEpatents

    Rubinstein, I.; Gottesfeld, S.; Sabatani, E.

    1992-04-28

    A conducting polymer film with an improved space filling is formed on a metal electrode surface. A self-assembling monolayer is formed directly on the metal surface where the monolayer has a first functional group that binds to the metal surface and a second chemical group that forms a chemical bonding site for molecules forming the conducting polymer. The conducting polymer is then conventionally deposited by electrochemical deposition. In one example, a conducting film of polyaniline is formed on a gold electrode surface with an intermediate monolayer of p-aminothiophenol. 2 figs.

  16. Theory of optical transitions in conjugated polymers. II. Real systems

    NASA Astrophysics Data System (ADS)

    Marcus, Max; Tozer, Oliver Robert; Barford, William

    2014-10-01

    The theory of optical transitions developed in Barford and Marcus ["Theory of optical transitions in conjugated polymers. I. Ideal systems," J. Chem. Phys. 141, 164101 (2014)] for linear, ordered polymer chains is extended in this paper to model conformationally disordered systems. Our key result is that in the Born-Oppenheimer regime the emission intensities are proportional to S(1)/⟨IPR⟩, where S(1) is the Huang-Rhys parameter for a monomer. ⟨IPR⟩ is the average inverse participation ratio for the emitting species, i.e., local exciton ground states (LEGSs). Since the spatial coherence of LEGSs determines the spatial extent of chromophores, the significance of this result is that it directly relates experimental observables to chromophore sizes (where ⟨IPR⟩ is half the mean chromophore size in monomer units). This result is independent of the chromophore shape, because of the Born-Oppenheimer factorization of the many body wavefunction. We verify this prediction by density matrix renormalization group (DMRG) calculations of the Frenkel-Holstein model in the adiabatic limit for both linear, disordered chains and for coiled, ordered chains. We also model optical spectra for poly(p-phenylene) and poly(p-phenylene-vinylene) oligomers and polymers. For oligomers, we solve the fully quantized Frenkel-Holstein model via the DMRG method. For polymers, we use the much simpler method of solving the one-particle Frenkel model and employ the Born-Oppenheimer expressions relating the effective Franck-Condon factor of a chromophore to its inverse participation ratio. We show that increased disorder decreases chromophore sizes and increases the inhomogeneous broadening, but has a non-monotonic effect on transition energies. We also show that as planarizing the polymer chain increases the exciton band width, it causes the chromophore sizes to increase, the transition energies to decrease, and the broadening to decrease. Finally, we show that the absorption spectra are

  17. Contact cleaning of polymer film solar reflectors

    NASA Astrophysics Data System (ADS)

    Sansom, Christopher; Fernández-García, Aránzazu; Sutter, Florian; Almond, Heather; King, Peter

    2016-05-01

    This paper describes the accelerated ageing of polymer film reflecting surfaces under the conditions to be found during contact cleaning of Concentrating Solar Power (CSP) collectors in the presence of dust and sand particles. In these situations, contact cleaning using brushes and water is required to clean the reflecting surfaces. Whilst suitable for glass reflectors, this paper discusses the effects of existing cleaning processes on the optical and visual properties of polymer film surfaces, and then describes the development of a more benign but effective contact cleaning process for cleaning polymer reflectors. The effects of a range of cleaning brushes are discussed, with and without the presence of water, in the presence of sand and dust particles from selected representative locations. Reflectance measurements and visual inspection shows that a soft cleaning brush with a small amount of water can clean polymer film reflecting surfaces without inflicting surface damage or reducing specular reflectance.

  18. Fabrication and capacitive characteristics of conjugated polymer composite p-polyaniline/n-WO3 heterojunction

    NASA Astrophysics Data System (ADS)

    Amaechi, C. I.; Asogwa, P. U.; Ekwealor, A. B. C.; Osuji, R. U.; Maaza, M.; Ezema, F. I.

    2014-07-01

    A nanocrystalline and porous p-polyaniline/n-WO3 dissimilar heterojunction at ambient temperature is reported. The high-quality and well-reproducible conjugated polymer composite films have been fabricated by oxidative polymerization of anilinium ion on predeposited WO3 thin film by chemical bath deposition followed by thermal annealing at 573 K for 1 h. Atomic force microscopy (AFM) analyses reveal a homogenous but irregular cluster of faceted spherically shaped grains with pores. The scanning electron microscopy confirms the porous network of grains, which is in good agreement with the AFM result. The optical absorption analysis of polyaniline/WO3 hybrid films showed that direct optical transition exist in the photon energy range 3.50-4.00 eV with bandgap of 3.70 eV. The refractive index developed peak at 445 nm in the dispersion region while the high-frequency dielectric constant, ɛ ∞, and the carrier concentration to effective mass ratio, N/m*, was found to be 1.58 and 1.10 × 1039 cm-3, respectively. The temperature dependence of electrical resistivity of the deposited films follows the semiconductor behavior while the C-V characteristics (Mott-Schottky plots) show that the flat band potential was -791 and 830 meV/SCE for WO3 and polyaniline.

  19. Co-assembly of polymer covered cyclic peptide nanotubes and block copolymer in thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Lazzara, Thomas; Li, Changyi; Helmes, Brett; Xu, Ting

    2013-03-01

    Nanotubular structures have gained prevalent interest for their unique hollow structures and high aspect ratio and their potential applications ranging from molecular separation to nanocomposite membranes. We used nanotube forming cyclic peptide (CP) as the structural motif and studied the self-assembly of polymer conjugated CPs in block copolymer (BCP) matrix in thin films. The co-assembly process is mainly driven by thermodynamic quantities, namely Flory-Huggins polymer-polymer interactions that governs the interaction between CP and BCP, interfacial interactions that affects polymer chain orientation, and thin film commensurability. In addition, due to the dynamic nature of the nanotube formation, the co-assembly process is also pathway-dependent. Thus, processing conditions are critical in co-assembling CP nanotubes and BCP in thin films. Our result shows that the initial aggregation state of polymer covered CP nanotubes determines the pathway the system takes and hence the final morphology of the films. The co-assembly of polymer-conjugated CPs and BCPs demonstrates the feasibility of assembling 1D nanotubes in supramolecular thin films and opens up a new avenue for the generation of novel nanotubular structures.

  20. Tuning the entropic spring to dictate order and functionality in polymer conjugated peptide biomaterials

    NASA Astrophysics Data System (ADS)

    Keten, Sinan

    Hybrid peptide-polymer conjugates have the potential to combine the advantages of natural proteins and synthetic polymers, resulting in biomaterials with improved stability, controlled assembly, and tailored functionalities. However, the effect of polymer conjugation on peptide structural organization and functionality, along with the behavior of polymers at the interface with biomolecules remain to be fully understood. This talk will summarize our recent efforts towards establishing a modeling framework to design entropic forces in helix-polymer conjugates and polymer-conjugated peptide nanotubes to achieve hierarchical self-assembling systems with predictable order. The first part of the talk will discuss how self-assembly principles found in biology, combined with polymer physics concepts can be used to create artificial membranes that mimic certain features of ion channels. Thermodynamics and kinetics aspects of self-assembly and how it governs the growth and stacking sequences of peptide nanotubes will be discussed, along with its implications for nanoscale transport. The second part of the talk will review advances related to modeling polymer conjugated coiled coils at relevant length and time scales. Atomistic simulations combined with sampling techniques will be presented to discuss the energy landscapes governing coiled-coil stability, revealing cascades of events governing disassembly. This will be followed by a discussion of mechanisms through which polymers can stabilize small proteins, such as shielding of solvents, and how specific peptide sequences can reciprocate by altering polymer conformations. Correlations between mechanical and thermal stability of peptides will be discussed. Finally, coarse-grained simulations will provide insight into how the location of polymer attachment changes entropic forces and higher-level organization in helix bundle assemblies. Our findings set the stage for a materials-by-design capability towards dictating complex

  1. Emulsion-Based RIR-MAPLE Deposition of Conjugated Polymers: Primary Solvent Effect and Its Implications on Organic Solar Cell Performance.

    PubMed

    Ge, Wangyao; Li, Nan K; McCormick, Ryan D; Lichtenberg, Eli; Yingling, Yaroslava G; Stiff-Roberts, Adrienne D

    2016-08-01

    Emulsion-based, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) has been demonstrated as an alternative technique to deposit conjugated polymer films for photovoltaic applications; yet, a fundamental understanding of how the emulsion target characteristics translate into film properties and solar cell performance is unclear. Such understanding is crucial to enable the rational improvement of organic solar cell (OSC) efficiency and to realize the expected advantages of emulsion-based RIR-MAPLE for OSC fabrication. In this paper, the effect of the primary solvent used in the emulsion target is studied, both experimentally and theoretically, and it is found to determine the conjugated polymer cluster size in the emulsion as well as surface roughness and internal morphology of resulting polymer films. By using a primary solvent with low solubility-in-water and low vapor pressure, the surface roughness of deposited P3HT and PCPDTBT polymer films was reduced to 10 nm, and the efficiency of P3HT:PC61BM OSCs was increased to 3.2% (∼100 times higher compared to the first MAPLE OSC demonstration [ Caricato , A. P. ; Appl. Phys. Lett. 2012 , 100 , 073306 ]). This work unveils the mechanism of polymer film formation using emulsion-based RIR-MAPLE and provides insight and direction to determine the best ways to take advantage of the emulsion target approach to control film properties for different applications. PMID:27414167

  2. Theory of optical transitions in conjugated polymers. I. Ideal systems

    SciTech Connect

    Barford, William; Marcus, Max

    2014-10-28

    We describe a theory of linear optical transitions in conjugated polymers. The theory is based on three assumptions. The first is that the low-lying excited states of conjugated polymers are Frenkel excitons coupled to local normal modes, described by the Frenkel-Holstein model. Second, we assume that the relevant parameter regime is ℏω ≪ J, i.e., the adiabatic regime, and thus the Born-Oppenheimer factorization of the electronic and nuclear degrees of freedom is generally applicable. Finally, we assume that the Condon approximation is valid, i.e., the exciton-polaron wavefunction is essentially independent of the normal modes. Using these assumptions we derive an expression for an effective Huang-Rhys parameter for a chain (or chromophore) of N monomers, given by S(N) = S(1)/IPR, where S(1) is the Huang-Rhys parameter for an isolated monomer. IPR is the inverse participation ratio, defined by IPR = (∑{sub n}|Ψ{sub n}|{sup 4}){sup −1}, where Ψ{sub n} is the exciton center-of-mass wavefunction. Since the IPR is proportional to the spread of the exciton center-of-mass wavefunction, this is a key result, as it shows that S(N) decreases with chain length. As in molecules, in a polymer S(N) has two interpretations. First, ℏωS(N) is the relaxation energy of an excited state caused by its coupling to the normal modes. Second, S(N) appears in the definition of an effective Franck-Condon factor, F{sub 0v}(N) = S(N){sup v}exp ( − S(N))/v! for the vth vibronic manifold. We show that the 0 − 0 and 0 − 1 optical intensities are proportional to F{sub 00}(N) and F{sub 01}(N), respectively, and thus the ratio of the 0 − 1 to 0 − 0 absorption and emission intensities are proportional to S(N). These analytical results are checked by extensive DMRG calculations and found to be generally valid, particularly for emission. However, for large chain lengths higher-lying quasimomentum exciton states become degenerate with the lowest vibrational excitation of the

  3. Ultrafast photophysics of pi-conjugated polymers for organic light emitting diode applications

    NASA Astrophysics Data System (ADS)

    Olejnik, Ella

    In this work we used the pump-probe photomodulation (PM) spectroscopy technique to measure the transient PM spectrum and decay kinetics in various pi -- conjugated polymers (PCPs) films and blends. Using two ultrafast laser systems, we covered a broad spectral range from 0.25 -- 2.5 eV in the time domain from 200 fs to 1 ns with 150 fs time resolution. We also used continuous wave (CW) photomodulation spectroscopy, photoluminescence (PL), electro-absorption and doping-induced absorption to study the photoexcitations and other optical properties of PCPs and guest/ host blends. In particular we studied two different types of Poly(thienylenevinylene) polymer derivatives. One polymer type is the ordered regio-regular (RR) and regio-random (RRa) -- PTV in which the dark exciton, 2Ag is the lowest excited state. In these polymers the photoexcited exciton shows very fast decay kinetics due to the internal conversion to the dark exciton, which results in weak PL emission; thus these two polymers are non-luminescent. The other PTV derivative is the imide -- PTV which is more luminescent due to the proximity of 1Bu and 2Ag states, that results in longer decay kinetics and a difference between the calculated value of the QEPL (9%) and the measured one (1%). We also demonstrate transient strain spectroscopy in RR -- PTV thin films, where the ultrafast energy release associated with the exciton decay gives rise to substantial static and dynamic strains in the film that dramatically influences the film's transient PM response. We also study the photophysics of poly(dioctyloxy) phenylenevinylene polymer with different isotopes, where we substituted hydrogen (H-polymer) by deuterium (D-polymer), and 12C by 13C isotopes. From the transient decay kinetics measurements we found that the exciton recombination in DOO -- PPV consists of two processes. These are: intrinsic monomolecular, and exciton-exciton annihilation (bimolecular). In the D -- polymer, different probe frequencies of

  4. Characterization of Conjugated Polymer Actuation under Cerebral Physiological Conditions

    PubMed Central

    Daneshvar, Eugene Dariush; Smela, Elisabeth

    2014-01-01

    Conjugated polymer actuators have potential use in implantable neural interface devices for modulating the position of electrode sites within brain tissue or guiding insertion of neural probes along curved trajectories. The actuation of polypyrrole (PPy) doped with dodecylbenzenesulfonate (DBS) was characterized to ascertain whether it could be employed in the cerebral environment. Microfabricated bilayer beams were electrochemically cycled at either 22 or 37 °C in aqueous NaDBS or in artificial cerebrospinal fluid (aCSF). Nearly all the ions in aCSF were exchanged into the PPy – the cations Na+, K+, Mg2+, Ca2+, as well as the anion PO43−; Cl− was not present. Nevertheless, deflections in aCSF were comparable to those in NaDBS and they were monotonic with oxidation level: strain increased upon reduction, with no reversal of motion despite the mixture of ionic charges and valences being exchanged. Actuation depended on temperature. Upon warming, the cyclic voltammograms showed additional peaks and an increase of 70% in the consumed charge. Bending was, however, much less affected: strain increased somewhat (6-13%) but remained monotonic, and deflections shifted (up to 20%). These results show how the actuation environment must be taken into account, and demonstrate proof of concept for actuated implantable neural interfaces. PMID:24574101

  5. The Optical Signature of Charges in Conjugated Polymers

    PubMed Central

    2016-01-01

    Electrical charge flowing through organic semiconductors drives many of today’s mobile phone displays and television screens, suggesting an internally consistent model of charge-carrier properties in these materials to have manifested. In conjugated polymers, charges give rise to additional absorption of light at wavelengths longer than those absorbed by the electrically neutral species. These characteristic absorption bands are universally being related to the emergence of localized energy levels shifted into the forbidden gap of organic semiconductors due to local relaxation of the molecular geometry. However, the traditional view on these energy levels and their occupation is incompatible with expected changes in electron removal and addition energies upon charging molecules. Here, I demonstrate that local Coulomb repulsion, as captured by nonempirically optimized electronic-structure calculations, restores compatibility and suggests a different origin of the charge-induced optical transitions. These results challenge a widely accepted and long-established picture, but an improved understanding of charge carriers in molecular materials promises a more targeted development of organic and hybrid organic/inorganic (opto-)electronic devices. PMID:27280165

  6. The Optical Signature of Charges in Conjugated Polymers.

    PubMed

    Heimel, Georg

    2016-05-25

    Electrical charge flowing through organic semiconductors drives many of today's mobile phone displays and television screens, suggesting an internally consistent model of charge-carrier properties in these materials to have manifested. In conjugated polymers, charges give rise to additional absorption of light at wavelengths longer than those absorbed by the electrically neutral species. These characteristic absorption bands are universally being related to the emergence of localized energy levels shifted into the forbidden gap of organic semiconductors due to local relaxation of the molecular geometry. However, the traditional view on these energy levels and their occupation is incompatible with expected changes in electron removal and addition energies upon charging molecules. Here, I demonstrate that local Coulomb repulsion, as captured by nonempirically optimized electronic-structure calculations, restores compatibility and suggests a different origin of the charge-induced optical transitions. These results challenge a widely accepted and long-established picture, but an improved understanding of charge carriers in molecular materials promises a more targeted development of organic and hybrid organic/inorganic (opto-)electronic devices. PMID:27280165

  7. Mesoscale morphologies in polymer thin films.

    SciTech Connect

    Ramanathan, M.; Darling, S. B.

    2011-06-01

    In the midst of an exciting era of polymer nanoscience, where the development of materials and understanding of properties at the nanoscale remain a major R&D endeavor, there are several exciting phenomena that have been reported at the mesoscale (approximately an order of magnitude larger than the nanoscale). In this review article, we focus on mesoscale morphologies in polymer thin films from the viewpoint of origination of structure formation, structure development and the interaction forces that govern these morphologies. Mesoscale morphologies, including dendrites, holes, spherulites, fractals and honeycomb structures have been observed in thin films of homopolymer, copolymer, blends and composites. Following a largely phenomenological level of description, we review the kinetic and thermodynamic aspects of mesostructure formation outlining some of the key mechanisms at play. We also discuss various strategies to direct, limit, or inhibit the appearance of mesostructures in polymer thin films as well as an outlook toward potential areas of growth in this field of research.

  8. Conjugated polymers nanostructured as smart interfaces for controlling the catalytic properties of enzymes.

    PubMed

    Barbosa, Camila Gouveia; Caseli, Luciano; Péres, Laura Oliveira

    2016-08-15

    The search for new molecular architectures to improve the efficiency of enzymes entrapped in ultrathin films is useful to enhance the effectiveness of biosensors. In this present work, conjugated polymers, based on thiophene and fluorine, were investigated to verify their suitability as matrices for the immobilization of urease. The copolymer poly[(9,9-dioctylfluorene)-co-thiophene], PDOF-co-Th was spread on the air-water interface forming stable Langmuir monolayers as determined by surface pressure-area isotherms, polarization-modulation reflection-absorption infrared spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). Urease was incorporated in the floating monolayers being further transferred to solid supports as mixed Langmuir-Blodgett (LB) films. These films were then characterized with transfer ratio, fluorescence spectroscopy, PM-IRRAS and atomic force microscopy, confirming the co-transfer of the enzyme as well as its structuring in β-sheets. The catalytic activity was detected for urease, with a lower reaction rate than that encountered for the homogeneous environment. This was attributed to conformational constraints imposed to the biomacromolecule entrapped in the polymeric matrix. PMID:27232536

  9. High-Field-Effect Mobility of Low-Crystallinity Conjugated Polymers with Localized Aggregates.

    PubMed

    Son, Sung Y; Kim, Yebyeol; Lee, Junwoo; Lee, Gang-Young; Park, Won-Tae; Noh, Yong-Young; Park, Chan E; Park, Taiho

    2016-07-01

    Charge carriers typically move faster in crystalline regions than in amorphous regions in conjugated polymers because polymer chains adopt a regular arrangement resulting in a high degree of π-π stacking in crystalline regions. In contrast, the random polymer chain orientation in amorphous regions hinders connectivity between conjugated backbones; thus, it hinders charge carrier delocalization. Various studies have attempted to enhance charge carrier transport by increasing crystallinity. However, these approaches are inevitably limited by the semicrystalline nature of conjugated polymers. Moreover, high-crystallinity conjugated polymers have proven inadequate for soft electronics applications because of their poor mechanical resilience. Increasing the polymer chain connectivity by forming localized aggregates via π-orbital overlap among several conjugated backbones in amorphous regions provides a more effective approach to efficient charge carrier transport. A simple strategy relying on the density of random copolymer alkyl side chains was developed to generate these localized aggregates. In this strategy, steric hindrance caused by these side chains was modulated to change their density. Interestingly, a random polymer exhibiting low alkyl side chain density and crystallinity displayed greatly enhanced field-effect mobility (1.37 cm(2)/(V·s)) compared with highly crystalline poly(3-hexylthiophene). PMID:27149835

  10. Patterned cholesteric liquid crystal polymer film.

    PubMed

    Hsu, Wei-Liang; Ma, Ji; Myhre, Graham; Balakrishnan, Kaushik; Pau, Stanley

    2013-02-01

    Herein, the ability to create arbitrarily patterned circular polarized optical devices is demonstrated by using cholesteric liquid crystal polymer. Photoalignment with polarized ultraviolet light is utilized to create aligned cholesteric liquid crystal films. Two different methods, thermal annealing and solvent rinse, are utilized for patterning cholesteric liquid crystal films over large areas. The patterned cholesteric liquid crystal films are measured using a Mueller matrix imaging polarimeter, and the polarization properties, including depolarization index, circular diattenuation (CD), and circular retardance are derived. Patterned nonlinearly polarized optical devices can be fabricated with feature sizes as small as 20 μm with a CD of 0.812±0.015. Circular polarizing filters based on polymer cholesteric liquid crystal films have applications in three-dimensional displays, medical imaging, polarimetry, and interferometry. PMID:23456060

  11. Antimicrobial polymer films for food packaging

    NASA Astrophysics Data System (ADS)

    Concilio, S.; Piotto, S.; Sessa, L.; Iannelli, P.; Porta, A.; Calabrese, E. C.; Galdi, M. R.; Incarnato, L.

    2012-07-01

    New antimicrobial polymeric systems were realized introducing new antimicrobial azo compounds in PP and LDPE matrices. The polymeric materials containing different percentage of azo compounds were mold-casted and the obtained film were tested in vitro against Gram+ and Gram- bacteria and fungi. These results hold promise for the fabrication of bacteria-resistant polymer films by means of simple melt processing with antimicrobial azo-dyes.

  12. Molar mass profiling of synthetic polymers by free-solution capillary electrophoresis of DNA-polymer conjugates.

    PubMed

    Vreeland, W N; Desruisseaux, C; Karger, A E; Drouin, G; Slater, G W; Barron, A E

    2001-04-15

    The molar mass distribution of a polymer sample is a critical determinant of its material properties and is generally analyzed by gel permeation chromatography or more recently, by MALDI-TOF mass spectrometry. We describe here a novel method for the determination of the degree of polymerization of polydisperse, uncharged, water-soluble polymers (e.g., poly(ethylene glycol) (PEG)), based upon single-monomer resolution of DNA-polymer conjugates by free-solution capillary electrophoresis. This is accomplished by end-on covalent conjugation of a polydisperse, uncharged polymer sample (PEG) to a monodisperse, fluorescently labeled DNA oligomer, followed by electrophoretic analysis. The monodisperse, charged DNA "engine" confers to each conjugate an equal amount of electromotive force, while the varying contour lengths of the uncharged, polydisperse polymers engender different amounts of hydrodynamic drag. The balance of electromotive and hydrodynamic forces enables rapid, high-resolution separation of the DNA-polymer conjugates as a function of the size of the uncharged PEG tail. This provides a profile of the molar mass distribution of the original polymer sample that can be detected by laser-induced fluorescence through excitation of the dye-labeled DNA. We call this method free solution conjugate electrophoresis (FSCE). Theory-based analysis of the resulting electrophoresis data allows precise calculation of the degree of polymerization of the PEG portion of each conjugate molecule. Knowledge of the molecular mass of the uncharged polymer's repeat unit allows for direct calculation of the molar mass averages as well as sample polydispersity index. The results of these analyses are strikingly reminiscent of MALDI-TOF spectra taken of the same PEG samples. PEG samples of 3.4-, 5-, and 20-kDa nominal average molar mass were analyzed by FSCE and MALDI-TOF; the values of the molar mass averages, Mw and Mn, typically agree to within 5%. Measurements and molar mass

  13. Smart linkers in polymer-drug conjugates for tumor-targeted delivery.

    PubMed

    Chang, Minglu; Zhang, Fang; Wei, Ting; Zuo, Tiantian; Guan, Yuanyuan; Lin, Guimei; Shao, Wei

    2016-07-01

    To achieve effective chemotherapy, many types of drug delivery systems have been developed for the specific environments in tumor tissues. Polymer-drug conjugates are increasingly used in tumor therapy due to several significant advantages over traditional delivery systems. In the fabrication of polymer-drug conjugates, a smart linker is an important component that joins two fragments or molecules together and can be cleared by a specific stimulus, which results in targeted drug delivery and controlled release. By regulating the conjugation between the drug and the nanocarriers, stimulus-sensitive systems based on smart linkers can offer high payloads, certified stability, controlled release and targeted delivery. In this review, we summarize the current state of smart linkers (e.g. disulfide, hydrazone, peptide, azo) used recently in various polymer-drug conjugate-based delivery systems with a primary focus on their sophisticated design principles and drug delivery mechanisms as well as in vivo processes. PMID:26560242

  14. Photothermally responsive gold nanoparticle conjugated polymer-grafted porous hollow silica nanocapsules.

    PubMed

    Paramelle, David; Gorelik, Sergey; Liu, Ye; Kumar, Jatin

    2016-08-01

    Polymer-grafted porous hollow silica nanoparticles prepared by reversible addition-fragmentation chain transfer polymerisation have an upper critical solution temperature of 45 °C. Conjugation of 5 nm gold nanoparticles onto polymer-grafted porous hollow silica nanoparticles enables remarkable specific photothermally-induced controlled release of encapsulated Rhodamine B by laser-stimulation at physiological temperature. PMID:27427407

  15. Z-Group ketone chain transfer agents for RAFT polymer nanoparticle modification via hydrazone conjugation

    PubMed Central

    Bandyopadhyay, Saibal; Xia, Xin; Maiseiyeu, Andrei; Mihai, Georgeta; Rajagopalan, Sanjay

    2012-01-01

    A ketal-containing trithiocarbonyl compound has been synthesized and characterized as a chain transfer agent (CTA) in Reversible Addition Fragmentation Transfer (RAFT) polymerization. The ketal functionality does not interfere with RAFT polymerization of acrylate monomers, which proceeds as previously reported to yield macro-CTA polymers and block co-polymers. Post-polymerization ketal cleavage revealed ketone functionality at the polar terminus of an amphiphilic block co-polymer. Hydrazone-formation was facile in both organic solution as well as in aqueous buffer where polymer nanoparticle assemblies were formed, indicating a conjugation/end-functionalization yield of 40–50%. Conjugation was verified with fluorescein, biotin and Gd-DOTA derivatives, and though the trithiocarbonate linkage is hydrolytically labile, we observed stable conjugation for several days at pH 7.4. and 37°C. As expected, streptavidin binding to biotinylated polymer micelles was observed, and size-change based relaxivity increases were observed when Gd-DOTA hydrazide was conjugated to polymer micelles. Cell-uptake of fluorescently labeled polymer micelles was also readily tracked by FACS and fluorescence microscopy. These polymer derivatives demonstrate a range of potential theranostic/biotechnological applications for this conveniently accessible keto-CTA, which include ligand-based nanoparticle targeting and fluorescent/MR nanoparticle contrast agents. PMID:23148126

  16. Poly(N-isopropylacrylamide)-tethered silicate platelets for colloidal dispersion of conjugated polymers with thermoresponsive and photoluminescence properties.

    PubMed

    Lan, Yi-Fen; Hsieh, Bi-Zen; Lin, Hsiao-Chu; Su, Yu-An; Chan, Ying-Nan; Lin, Jiang-Jen

    2010-07-01

    Poly(N-isopropylacrylamide)-tethered nanosilicate platelets (NSP-PNiPAAm) have been synthesized by covalently bonding the polymer onto the surfaces of silicate platelets of nanometer dimension, and this class of nanohybrids has proved to be effective for dispersing water-insoluble conjugated polymers (CPs). Simple pulverization of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with NSP-PNiPAAm rendered the powder material dispersible in water, whereupon it displayed thermoresponsive properties at 37.5 degrees C and CP particle size variation between ca. 50 and 100 nm by SEM observation. The same dispersion had a maximum UV-vis absorption at 524 nm and PL emission at 605 nm. The PL emission was significantly higher at 4 degrees C than at 45 degrees C. Being coated as a film, it showed an orange emission under an ultraviolet lamp, consistent with the PL measurement. The water-borne process of dispersing the CP in aqueous media by the presence of NSP-PNiPAAm and followed by film formation to demonstrate a unique method of manipulating hydrophobic conjugated polymers in a facile manner. PMID:20302288

  17. Theoretical analysis of single molecule spectroscopy lineshapes of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Devi, Murali

    Conjugated Polymers(CPs) exhibit a wide range of highly tunable optical properties. Quantitative and detailed understanding of the nature of excitons responsible for such a rich optical behavior has significant implications for better utilization of CPs for more efficient plastic solar cells and other novel optoelectronic devices. In general, samples of CPs are plagued with substantial inhomogeneous broadening due to various sources of disorder. Single molecule emission spectroscopy (SMES) offers a unique opportunity to investigate the energetics and dynamics of excitons and their interactions with phonon modes. The major subject of the present thesis is to analyze and understand room temperature SMES lineshapes for a particular CP, called poly(2,5-di-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (DEH-PPV). A minimal quantum mechanical model of a two-level system coupled to a Brownian oscillator bath is utilized. The main objective is to identify the set of model parameters best fitting a SMES lineshape for each of about 200 samples of DEH-PPV, from which new insight into the nature of exciton-bath coupling can be gained. This project also entails developing a reliable computational methodology for quantum mechanical modeling of spectral lineshapes in general. Well-known optimization techniques such as gradient descent, genetic algorithms, and heuristic searches have been tested, employing an L2 measure between theoretical and experimental lineshapes for guiding the optimization. However, all of these tend to result in theoretical lineshapes qualitatively different from experimental ones. This is attributed to the ruggedness of the parameter space and inadequateness of the L2 measure. On the other hand, when the dynamic reduction of the original parameter space to a 2-parameter space through feature searching and visualization of the search space paths using directed acyclic graphs(DAGs), the qualitative nature of the fitting improved significantly. For a more

  18. Oriented thin films of perylenetetracarboxylic diimide on frictiontransferred polymer films

    NASA Astrophysics Data System (ADS)

    Tanigaki, Nobutaka; Heck, Claire; Mizokuro, Toshiko

    Perylenetetracarboxylic diimide (PTCDI) is a promising material for application in organic electronics. In this study we report on the preparation of oriented thin films of PTCDI on the surface of oriented polymer substrates, which were prepared by friction transfer method. Two polymers, poly(tetrafluoroethylene) (PTFE) and poly(p-phenylene) (PPP) were used as the orienting substrate for PTCDI for comparison studies. Characterization by polarized UV-vis absorption shows that the orienting ability of PPP is larger than that of PTFE substrate. Furthermore, polarization-sensitive photoelectric conversion devices were fabricated by using the oriented PTCDI thin film on the PPP substrate.

  19. Biocompatible conjugated polymer nanoparticles for efficient photothermal tumor therapy.

    PubMed

    Geng, Junlong; Sun, Chunyang; Liu, Jie; Liao, Lun-De; Yuan, Youyong; Thakor, Nitish; Wang, Jun; Liu, Bin

    2015-04-01

    Conjugated polymers (CPs) with strong near-infrared (NIR) absorption and high heat conversion efficiency have emerged as a new generation of photothermal therapy (PTT) agents for cancer therapy. An efficient strategy to design NIR absorbing CPs with good water dispersibility is essential to achieve excellent therapeutic effect. In this work, poly[9,9-bis(4-(2-ethylhexyl)phenyl)fluorene-alt-co-6,7-bis(4-(hexyloxy)phenyl)-4,9-di(thiophen-2-yl)-thiadiazoloquinoxaline] (PFTTQ) is synthesized through the combination of donor-acceptor moieties by Suzuki polymerization. PFTTQ nanoparticles (NPs) are fabricated through a precipitation approach using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG2000 ) as the encapsulation matrix. Due to the large NIR absorption coefficient (3.6 L g(-1) cm(-1) ), the temperature of PFTTQ NP suspension (0.5 mg/mL) could be rapidly increased to more than 50 °C upon continuous 808 nm laser irradiation (0.75 W/cm(2) ) for 5 min. The PFTTQ NPs show good biocompatibility to both MDA-MB-231 cells and Hela cells at 400 μg/mL of NPs, while upon laser irradiation, effective cancer cell killing is observed at a NP concentration of 50 μg/mL. Moreover, PFTTQ NPs could efficiently ablate tumor in in vivo study using a Hela tumor mouse model. Considering the large amount of NIR absorbing CPs available, the general encapsulation strategy will enable the development of more efficient PTT agents for cancer or tumor therapy. PMID:25367500

  20. Highly polarized emission of the liquid crystalline conjugated polymer by controlling the surface anchoring energy

    NASA Astrophysics Data System (ADS)

    In Jo, Soo; Kim, Youngsik; Baek, Ji-Ho; Yu, Chang-Jae; Kim, Jae-Hoon

    2014-01-01

    We demonstrated a highly polarized organic light-emitting diode (OLED) through the enhancement of the orientational ordering of the emitting polymer with a nematic liquid crystalline (LC) phase. The highly ordered state of the conjugate polymer was obtained by thermal annealing at the nematic temperature and strong azimuthal anchoring energy of the underlying polyimide. The order parameter of the conjugate polymer was analyzed using a second-harmonic generation model and the dichroic ratio was measured to be 22 : 1. Also, we applied our optimized OLED with high optical polarizability to an effective light source for a twisted nematic LC display.

  1. Unsubstituted Benzodithiophene-Based Conjugated Polymers for High-Performance Organic Field-Effect Transistors and Organic Solar Cells.

    PubMed

    Chen, Weichao; Xiao, Manjun; Han, Liangliang; Zhang, Jidong; Jiang, Huanxiang; Gu, Chuantao; Shen, Wenfei; Yang, Renqiang

    2016-08-01

    Unsubstituted benzo[1,2-b:4,5-b']dithiophene (BDT) was used to construct a high-performance conjugated polymer with 5,6-difluoro-4,7-bis[4-(2-octyldodecyl)thiophene-2-yl]benzo[c][1,2,5] thiadiazole (DTFFBT), named PBDT-DTFFBT. The polymer shows the low-lying highest occupied molecular orbital (HOMO) energy level (-5.40 eV) and a broad absorption spectra with strong vibronic absorption peak. Pure polymer films exhibit good crystallinity and edge-on orientation, partially attributed to the BDT units without any side chains, and as a result, the corresponding thin-film transistor showed excellent hole mobility over 1 cm(2) V(-1) s(-1). Interestingly, a well-distributed nanofibrillar polymer aggregation with face-on orientation was obviously formed when blending with PC71BM, which was in favor of the charge transportation. Consequently, the bulk heterojunction polymer solar cells based on the blends showed high power conversion efficiency of 9.29% with large short-current density (14.56 mA cm(-2)) and high fill factor (0.751) without any process additives or thermal annealing. PMID:27403850

  2. Directed Assembly of Nanofilled Polymer Thin Films

    NASA Astrophysics Data System (ADS)

    Karim, Alamgir

    Facile directed self-assembly (DSA) of multicomponent thin films is important for potential technological applications. This requires a fine control of a complex interplay of processing parameters that need to be properly optimized for different organized structures. This talk will discuss some of our recent success towards realizing tunable DSA of soft matter multicomponent systems involving a dispersion of polymer-grafted nanoparticles in block copolymer or homopolymer matrices. DSA methods for such multicomponent films will be discussed. These include the use of zone-annealing with soft-shear to create highly anisotropic nanoparticle arrays, while direct immersion annealing (DIA) has been used to order nanoparticle filled films by dipping the films into controlled solvent quality solvent mixtures. A recently observed phenomena of confinement driven entropic order and phase segregation of polymer grafted nanoparticles in similar and dissimilar polymer matrices in melt state will be discussed. A high density of nano particles of different types ranging from metallic to inorganic to organic were patterned almost exclusively into channels via topographical soft confinement using entropic forces. Enthalpic interactions between the nanoparticle grafted layer and the polymer matrix could be used as a further handle to tune the directed assembly of the nanoparticles. The phenomena will be discussed in terms of confinement parameters, partition coefficient, free energy gain and entropic versus enthalpic interactions.

  3. Methyllithium-Doped Naphthyl-Containing Conjugated Microporous Polymer with Enhanced Hydrogen Storage Performance.

    PubMed

    Xu, Dan; Sun, Lei; Li, Gang; Shang, Jin; Yang, Rui-Xia; Deng, Wei-Qiao

    2016-06-01

    Hydrogen storage is a primary challenge for using hydrogen as a fuel. With ideal hydrogen storage kinetics, the weak binding strength of hydrogen to sorbents is the key barrier to obtain decent hydrogen storage performance. Here, we reported the rational synthesis of a methyllithium-doped naphthyl-containing conjugated microporous polymer with exceptional binding strength of hydrogen to the polymer guided by theoretical simulations. Meanwhile, the experimental results showed that isosteric heat can reach up to 8.4 kJ mol(-1) and the methyllithium-doped naphthyl-containing conjugated microporous polymer exhibited an enhanced hydrogen storage performance with 150 % enhancement compared with its counterpart naphthyl-containing conjugated microporous polymer. These results indicate that this strategy provides a direction for design and synthesis of new materials that meet the US Department of Energy (DOE) hydrogen storage target. PMID:27106536

  4. Light Emitting Heterojunctions Based on Fully Conjugated Heterocyclic Aromatic Rigid-rod Polymer PBT

    NASA Astrophysics Data System (ADS)

    Bai, S. J.; Wu, C. C.; Cheng, H. Y.; Wang, W.

    2003-03-01

    Poly(p-phenylenebenzobisthiazole), PBT, is a heterocyclic aromatic rigid-rod polymer having a fully conjugated backbone, excellent stabilities and opto-electronic properties. We investigated multi-layer heterojunctions of PBT and low molar compounds of 3-(2-benzothiazoly)-7-(diethylamino), C6, and tris-(8-hydroxyquinoline) aluminum, Alq3, using PBT as a hole injecting and transporting material. A PBT polymer with an intrinsic viscosity of 18.0 dL/g was dissolved in Lewis acid and spin-coated onto an indium-tin-oxide (ITO) substrate. The acid was removed via coagulation. The low molar compounds were evaporated onto the ITO substrate or the thin PBT film on the ITO substrate. UV-Vis absorption spectra over 200 to 800 nm revealed different band gaps for PBT, C6 and Alq3. Scanning electron microscopy determined that the resultant PBT and low molar compound layer thicknesses were about 23 nm and 50 nm, respectively. Aluminum was evaporated onto the multilayer heterojunction as an electron injector for electroluminescence response leading to a lower I-V threshold voltage and a higher emission brightness. This was mainly because of significant balance in the numbers of the hole and the electron injected and transported in the heterojunctions.

  5. An investigation on focused electron/ion beam induced degradation mechanisms of conjugated polymers.

    PubMed

    Sezen, Meltem; Plank, Harald; Fisslthaler, Evelin; Chernev, Boril; Zankel, Armin; Tchernychova, Elena; Blümel, Alexander; List, Emil J W; Grogger, Werner; Pölt, Peter

    2011-12-01

    Irradiation damage, caused by the use of beams in the electron microscopes, leads to undesired physical/chemical material property changes or uncontrollable modification of structures that are being processed. Particularly, soft matter such as polymers or biological materials is highly susceptible and very much prone to react on irradiation by electron and ion beams. The effect is even higher when materials are subjected to energetic species such as ions that possess high momentum and relatively low mean path due to their mass. Especially when Ga(+) ions (used as the ion source in Focused Ion Beam (FIB) instruments) are considered, the end-effect might even be the total loss of the material's properties. This paper will discuss the possible types of degradation mechanisms and defect formations that can take place during ion and electron beam irradiation of the conjugated polymers: e.g. polyfluorene (PF) and poly-3-hexylthiophene (P3HT) thin films. For the investigation of the irradiation induced degradation mechanisms in this study, complementary analytical techniques such as Raman Spectroscopy (RS), Infrared Spectroscopy (IR), Electron Energy Loss Spectroscopy (EELS), Atomic Force Microscopy (AFM), and Fluorescence Microscopy including Photoluminescence (PL) and Electroluminescence (EL) Microscopy were applied. PMID:21993473

  6. Enhancing performing characteristics of organic semiconducting films by improved solution processing

    SciTech Connect

    Bazan, Guillermo C; Moses, Daniel; Peet, Jeffrey; Heeger, Alan J

    2014-05-13

    Improved processing methods for enhanced properties of conjugated polymer films are disclosed, as well as the enhanced conjugated polymer films produced thereby. Addition of low molecular weight alkyl-containing molecules to solutions used to form conjugated polymer films leads to improved photoconductivity and improvements in other electronic properties. The enhanced conjugated polymer films can be used in a variety of electronic devices, such as solar cells and photodiodes.

  7. Enhancing performance characteristics of organic semiconducting films by improved solution processing

    DOEpatents

    Bazan, Guillermo C.; Heeger, Alan J.; Moses, Daniel; Peet, Jeffrey

    2013-09-25

    Improved processing methods for enhanced properties of conjugated polymer films are disclosed, as well as the enhanced conjugated polymer films produced thereby. Addition of low molecular weight alkyl-containing molecules to solutions used to form conjugated polymer films leads to improved photoconductivity and improvements in other electronic properties. The enhanced conjugated polymer films can be used in a variety of electronic devices, such as solar cells and photodiodes.

  8. Enhancing performance characteristics of organic semiconducting films by improved solution processing

    DOEpatents

    Bazan, Guillermo C; Mikhailovsky, Alexander; Moses, Daniel; Nguyen, Thuc-Quyen; Peet, Jeffrey; Soci, Cesare

    2012-11-27

    Improved processing methods for enhanced properties of conjugated polymer films are disclosed, as well as the enhanced conjugated polymer films produced thereby. Addition of low molecular weight alkyl-containing molecules to solutions used to form conjugated polymer films leads to improved photoconductivity and improvements in other electronic properties. The enhanced conjugated polymer films can be used in a variety of electronic devices, such as solar cells and photodiodes.

  9. Deformation propagation in responsive polymer network films

    NASA Astrophysics Data System (ADS)

    Ghosh, Surya K.; Cherstvy, Andrey G.; Metzler, Ralf

    2014-08-01

    We study the elastic deformations in a cross-linked polymer network film triggered by the binding of submicron particles with a sticky surface, mimicking the interactions of viral pathogens with thin films of stimulus-responsive polymeric materials such as hydrogels. From extensive Langevin Dynamics simulations we quantify how far the network deformations propagate depending on the elasticity parameters of the network and the adhesion strength of the particles. We examine the dynamics of the collective area shrinkage of the network and obtain some simple relations for the associated characteristic decay lengths. A detailed analysis elucidates how the elastic energy of the network is distributed between stretching and compression modes in response to the particle binding. We also examine the force-distance curves of the repulsion or attraction interactions for a pair of sticky particles in the polymer network film as a function of the particle-particle separation. The results of this computational study provide new insight into collective phenomena in soft polymer network films and may, in particular, be applied to applications for visual detection of pathogens such as viruses via a macroscopic response of thin films of cross-linked hydrogels.

  10. Improving photo-stability of conjugated polymer MEH-PPV embedded in solid matrices by purification of the matrix polymer

    NASA Astrophysics Data System (ADS)

    Tian, Yuxi; Sheinin, Vladimir; Kulikova, Olga; Mamardashvili, Nugzar; Scheblykin, Ivan G.

    2014-04-01

    For single molecule spectroscopy (SMS), molecules under study are usually immobilized in a polymer matrix e.g. poly(methyl methacrylate). We show a very significant improvement of the conjugated polymer MEH-PPV photo-stability and decrease of the luminescence impurities concentration when the matrix is purified. We identify benzoyl peroxide (a common radical initiator) as a possible oxidizing agent which residuals in the polymer matrix destroy MEH-PPV. These results show that purification and selection of a matrix obtained by radical-free synthetic technique are of great importance for SMS as well as other technologies using polymer matrices as hosts for light-emitting materials.

  11. Direct Light-Driven Water Oxidation by a Ladder-Type Conjugated Polymer Photoanode

    PubMed Central

    2015-01-01

    A conjugated polymer known for high stability (poly[benzimidazobenzophenanthroline], coded as BBL) is examined as a photoanode for direct solar water oxidation. In aqueous electrolyte with a sacrificial hole acceptor (SO32–), photoelectrodes show a morphology-dependent performance. Films prepared by a dispersion-spray method with a nanostructured surface (feature size of ∼20 nm) gave photocurrents up to 0.23 ± 0.02 mA cm–2 at 1.23 VRHE under standard simulated solar illumination. Electrochemical impedance spectroscopy reveals a constant flat-band potential over a wide pH range at +0.31 VNHE. The solar water oxidation photocurrent with bare BBL electrodes is found to increase with increasing pH, and no evidence of semiconductor oxidation was observed over a 30 min testing time. Characterization of the photo-oxidation reaction suggests H2O2 or •OH production with the bare film, while functionalization of the interface with 1 nm of TiO2 followed by a nickel–cobalt catalyst gave solar photocurrents of 20–30 μA cm–2, corresponding with O2 evolution. Limitations to photocurrent production are discussed. PMID:26576469

  12. Functional Hybrid Biomaterials based on Peptide-Polymer Conjugates for Nanomedicine

    NASA Astrophysics Data System (ADS)

    Shu, Jessica Yo

    The focus of this dissertation is the design, synthesis and characterization of hybrid functional biomaterials based on peptide-polymer conjugates for nanomedicine. Generating synthetic materials with properties comparable to or superior than those found in nature has been a "holy grail" for the materials community. Man-made materials are still rather simplistic when compared to the chemical and structural complexity of a cell. Peptide-polymer conjugates have the potential to combine the advantages of the biological and synthetic worlds---that is they can combine the precise chemical structure and diverse functionality of biomolecules with the stability and processibility of synthetic polymers. As a new family of soft matter, they may lead to materials with novel properties that have yet to be realized with either of the components alone. In order for peptide-polymer conjugates to reach their full potential as useful materials, the structure and function of the peptide should be maintained upon polymer conjugation. The success in achieving desirable, functional assemblies relies on fundamentally understanding the interactions between each building block and delicately balancing and manipulating these interactions to achieve targeted assemblies without interfering with designed structures and functionalities. Such fundamental studies of peptide-polymer interactions were investigated as the nature of the polymer (hydrophilic vs. hydrophobic) and the site of its conjugation (end-conjugation vs. side-conjugation) were varied. The fundamental knowledge gained was then applied to the design of amphiphiles that self-assemble to form stable functional micelles. The micelles exhibited exceptional monodispersity and long-term stability, which is atypical of self-assembled systems. Thus such micelles based on amphiphilic peptide-polymer conjugates may meet many current demands in nanomedicine, in particular for drug delivery of hydrophobic anti-cancer therapeutics. Lastly

  13. Nanostructured Conjugated Polymers for Energy-Related Applications beyond Solar Cells.

    PubMed

    Xie, Jian; Zhao, Cui-E; Lin, Zong-Qiong; Gu, Pei-Yang; Zhang, Qichun

    2016-05-20

    To meet the ever-increasing requirements for the next generation of sustainable and versatile energy-related devices, conjugated polymers, which have potential advantages over small molecules and inorganic materials, are among the most promising types of green candidates. The properties of conjugated polymers can be tuned through modification of the structure and incorporation of different functional moieties. In addition, superior performances can be achieved as a result of the advantages of nanostructures, such as their large surface areas and the shortened pathways for charge transfer. Therefore, nanostructured conjugated polymers with different properties can be obtained to be applied in different energy-related organic devices. This review focuses on the application and performance of the recently reported nanostructured conjugated polymers for high-performance devices, including rechargeable lithium batteries, microbial fuel cells (MFCs), thermoelectric generators, and photocatalytic systems. The design strategies, reaction mechanisms, advantages, and limitations of nanostructured conjugated polymers are further discussed in each section. Finally, possible routes to improve the performances of the current systems are also included in the conclusion. PMID:26971875

  14. Synthesis of a Conjugated D-A Polymer with Bi(disilanobithiophene) as a New Donor Component.

    PubMed

    Nakashima, Makoto; Ooyama, Yousuke; Sugiyama, Takuya; Naito, Hiroyoshi; Ohshita, Joji

    2016-01-01

    A new conjugated donor-acceptor (D-A) polymer pDSBT2-BT containing bi(disilano-bisthiophene) and benzothiadiazole as donor and acceptor units, respectively, was prepared. The polymer showed a broad UV-vis absorption band at λmax = 599 nm in chlorobenzene. The absorption band was shifted to λmax = 629 nm when the polymer was measured as a film, indicating enhanced interchain interactions of the polymer. Bulk hetero-junction polymer solar cells (BHJ-PSCs) were fabricated using pDSBT2-BT and PC71BM as host and guest materials, respectively. Optimization of cell fabrication conditions provided a maximal power conversion efficiency of 3.3% and the following cell parameters: Voc = 0.86 V, Jsc = 7.56 mA/cm², and FF = 0.51. Although the efficiency still leaves much to be desired, these data underscore the potential of pDSBT2-BT as a high-voltage polymer solar cell material. PMID:27322229

  15. Porous Polyolefin Films via Polymer Blends

    NASA Astrophysics Data System (ADS)

    Macosko, Chris

    Porous polymer films have broad application including battery separators, membrane supports and filters. Polyolefins are attractive for these applications because of their solvent resistance, low electrical and thermal conductivity, easy fabrication and cost. We will describe fabrication of porous films using cocontinuous blends of a polyolefin with another polymer which can be readily removed with a solvent. Methods to image and control the cocontinuous morphology will be presented.Bell, J. R., K. Chang, C. R. Lopez-Barron, C. W. Macosko, and D. C. Morse, ''Annealing of cocontinuous polymer blends: effect of block copolymer molecular weight and architecture,'' Macromolecules 43, 5024-5032 (2010).Lopez-Barron, C. R., and C. W. Macosko, ''Direct measurement of interface anisotropy of bicontinuous structures via 3D image analysis,'' Langmuir 26, 14284-14293 (2010).Trifkovic, M., A. T. Hedegaard, K. Huston, M. Sheikhzadeh, and C. W. Macosko, ''Porous films via PE/PEO cocontinuous blends,'' Macromolecules 45, 6036-6044 (2012).Hedegaard, A.T., L.L. Gu and C. W. Macosko, ``Effect of Extensional Viscosity on Cocontinuity of Immiscible Polymer Blends'' J. Rheol. 59, 1397-1417 (2015).

  16. MISSE 6 Polymer Film Tensile Experiment

    NASA Technical Reports Server (NTRS)

    Miller, Sharon K. R.; Dever, Joyce A.; Banks, Bruce A.; Waters, Deborah L.; Sechkar, Edward; Kline, Sara

    2010-01-01

    The Polymer Film Tensile Experiment (PFTE) was flown as part of Materials International Space Station Experiment 6 (MISSE 6). The purpose of the experiment was to expose a variety of polymer films to the low Earth orbital environment under both relaxed and tension conditions. The polymers selected are those commonly used for spacecraft thermal control and those under consideration for use in spacecraft applications such as sunshields, solar sails, and inflatable and deployable structures. The dog-bone shaped samples of polymers that were flown were exposed on both the side of the MISSE 6 Passive Experiment Container (PEC) that was facing into the ram direction (receiving atomic oxygen, ultraviolet (UV) radiation, ionizing radiation, and thermal cycling) and the wake facing side (which was supposed to have experienced predominantly the same environmental effects except for atomic oxygen which was present due to reorientation of the International Space Station). A few of the tensile samples were coated with vapor deposited aluminum on the back and wired to determine the point in the flight when the tensile sample broke as recorded by a change in voltage that was stored on battery powered data loggers for post flight retrieval and analysis. The data returned on the data loggers was not usable. However, post retrieval observation and analysis of the samples was performed. This paper describes the preliminary analysis and observations of the polymers exposed on the MISSE 6 PFTE.

  17. Membranes and Films from Polymers.

    ERIC Educational Resources Information Center

    Blumberg, Avrom A.

    1986-01-01

    Provides background information on polymeric films and membranes including production methods, special industrial and medical applications, laboratory preparation, and an experimental investigation of a porous cellulose acetate membrane. Presents a demonstration to distinguish between high- and low-density polyethylene. (JM)

  18. Structure-property relationships of small bandgap conjugated polymers for solar cells.

    PubMed

    Hellström, Stefan; Zhang, Fengling; Inganäs, Olle; Andersson, Mats R

    2009-12-01

    Conjugated polymers as electron donors in solar cells based on donor/acceptor combinations are of great interest, partly due to the possibility of converting solar light with a low materials budget. Six small bandgap polymers with optical bandgap ranging from 1.0-1.9 eV are presented in this paper. All polymers utilize an electron donor-acceptor-donor (DAD) segment in the polymer backbone, creating a partial charge-transfer, to decrease the bandgap. The design, synthesis and the optical characteristics as well as the solar cell characteristics of the polymers are discussed. The positions of the energy levels of the conjugated polymer relative to the electron acceptor are of significant importance and determine not only the driving force for exciton dissociation but also the maximum open-circuit voltage. This work also focuses on investigating the redox behavior of the described conjugated polymers and electron acceptors using square wave voltammetry. Comparing the electrochemical data gives important information of the structure-property relationships of the polymers. PMID:19904430

  19. An in-depth analysis of polymer-analogous conjugation using DMTMM.

    PubMed

    Pelet, Jeisa M; Putnam, David

    2011-03-16

    Combinatorial libraries have become increasingly popular in the field of functional biomaterials. One approach for creating diverse polymer libraries is polymer-analogous conjugation of functional groups to polymer scaffolds. In this study, we show that a water-soluble condensing agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM), can be employed to conjugate two disparate model ligands, d-(+)-galactosamine (Gal) and agmatine (Agm), to the side chains of either poly(methacrylic acid) (pMAA) or poly(acrylic acid) (pAA) at various substitution ratios. The degree of substitution was found to be directly influenced by media pH, polymer concentration, structure of ligands, and polymer precursor. A nearly 2-fold increase in conjugation efficiencies for both ligands to pAA was achieved as compared to pMAA under identical conditions reaching up to 56% and 78% of Gal and Agm of total content, respectively. These two structurally similar polymers showed remarkably different performances, which reveals that the selection of a polymer precursor is crucial for the optimal design of polymeric libraries, particularly when complex structural ligands are involved. The approach employed provides a basis from which larger and more diverse combinatorial libraries of functionalized polymers with multiple moieties can be generated. PMID:21309584

  20. Dynamics of polymer thin films and surfaces

    NASA Astrophysics Data System (ADS)

    Fakhraai, Zahra

    2007-12-01

    The dynamics of thin polymer films display many differences from the bulk dynamics. Different modes of motions in polymers are affected by confinement in different ways. The enhancement in the dynamics of some modes of motion can cause anomalies in the glass transition temperature (Tg) of thin films, while other modes of motion such as diffusion can be substantially slowed down due to the confinement effects. In this thesis, different modes of dynamics are probed using different techniques. The interface healing of two identical polymer surfaces is used as a probe of segmental motion in the direction normal to the plane of the films and it is shown that this mode of motion is slowed down at temperatures above bulk glass transition, while the glass transition itself is decreased indicating that the type of motion responsible for the glass transition is enhanced. The glass transition measurements at different cooling rates indicate that this enhancement only happens at temperatures close to or below bulk glass transition temperature and it is not expected to be detected at higher temperatures where the system is in the melt state. It is shown that the sample preparation technique is not a factor in observing this enhanced dynamics, while the existence of the free surface can be important in observed reductions in the glass transition temperature. The dynamics near the free surface is further studied using a novel nano-deformation technique, and it is shown that the dynamics near the free surface is in fact enhanced compared to the bulk dynamics and this enhancement is increased as the temperature is decreased further below Tg. It is also shown that this mode of relaxation is much different from the bulk modes of relaxations, and a direct relationship between this enhanced motion and Tg reduction in thin films can be established. The results presented in this thesis can lead to a possible universal picture that can resolve the behavior of different modes of motions in

  1. Conjugated polymers containing diketopyrrolopyrrole units in the main chain

    PubMed Central

    Rabindranath, A Raman; Zhang, Kai; Zhu, Yu

    2010-01-01

    Summary Research activities in the field of diketopyrrolopyrrole (DPP)-based polymers are reviewed. Synthetic pathways to monomers and polymers, and the characteristic properties of the polymers are described. Potential applications in the field of organic electronic materials such as light emitting diodes, organic solar cells and organic field effect transistors are discussed. PMID:20978619

  2. Remarkable enhancement of charge carrier mobility of conjugated polymer field-effect transistors upon incorporating an ionic additive.

    PubMed

    Luo, Hewei; Yu, Chenmin; Liu, Zitong; Zhang, Guanxin; Geng, Hua; Yi, Yuanping; Broch, Katharina; Hu, Yuanyuan; Sadhanala, Aditya; Jiang, Lang; Qi, Penglin; Cai, Zhengxu; Sirringhaus, Henning; Zhang, Deqing

    2016-05-01

    Organic semiconductors with high charge carrier mobilities are crucial for flexible electronic applications. Apart from designing new conjugated frameworks, different strategies have been explored to increase charge carrier mobilities. We report a new and simple approach to enhancing the charge carrier mobility of DPP-thieno[3,2-b]thiophene-conjugated polymer by incorporating an ionic additive, tetramethylammonium iodide, without extra treatments into the polymer. The resulting thin films exhibit a very high hole mobility, which is higher by a factor of 24 than that of thin films without the ionic additive under the same conditions. On the basis of spectroscopic grazing incidence wide-angle x-ray scattering and atomic force microscopy studies as well as theoretical calculations, the remarkable enhancement of charge mobility upon addition of tetramethylammonium iodide is attributed primarily to an inhibition of the torsion of the alkyl side chains by the presence of the ionic species, facilitating a more ordered lamellar packing of the alkyl side chains and interchain π-π interactions. PMID:27386541

  3. Optical and magnetic probes of hot singlet exciton fission in π-conjugated polymers for organic photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Zhai, Yaxin; Olejnik, Ella; Vardeny, Z. Valy

    2015-09-01

    We used steady state and picosecond transient photoinduced absorption (PA), excitation dependence (EXPA(ω)) spectrum of the triplet exciton PA band, and its magneto-PA (MPA(B)) response to investigate singlet fission (SF) of hot-excitons into two separated triplet excitons in luminescent π-conjugated polymers. From the high energy step in the triplet EXPA(ω) spectrum of poly(dioctyloxy)-phenylenevinylene (DOO-PPV) films, we identified a hot-exciton SF (HE-SF) process having threshold energy at E≍2ET (=2.8 eV, where ET is the energy of the lowest lying triplet exciton), which is about 0.8 eV above the lowest singlet exciton energy. The picosecond transient PA with 3.1 eV pump excitation shows that in DOO-PPV film a triplet exciton is generated at time, t<500 ps. However the ultrafast triplet generation is missing in DOO-PPV solution, indicating that the HE-SF is predominantly interchain in nature. The HE-SF process was confirmed by the triplet MPA(B) response for excitation at E>2ET, which shows a typical SF response. Our work shows that the SF process in π-conjugated polymers is a much more general process than thought previously.

  4. Remarkable enhancement of charge carrier mobility of conjugated polymer field-effect transistors upon incorporating an ionic additive

    PubMed Central

    Luo, Hewei; Yu, Chenmin; Liu, Zitong; Zhang, Guanxin; Geng, Hua; Yi, Yuanping; Broch, Katharina; Hu, Yuanyuan; Sadhanala, Aditya; Jiang, Lang; Qi, Penglin; Cai, Zhengxu; Sirringhaus, Henning; Zhang, Deqing

    2016-01-01

    Organic semiconductors with high charge carrier mobilities are crucial for flexible electronic applications. Apart from designing new conjugated frameworks, different strategies have been explored to increase charge carrier mobilities. We report a new and simple approach to enhancing the charge carrier mobility of DPP-thieno[3,2-b]thiophene–conjugated polymer by incorporating an ionic additive, tetramethylammonium iodide, without extra treatments into the polymer. The resulting thin films exhibit a very high hole mobility, which is higher by a factor of 24 than that of thin films without the ionic additive under the same conditions. On the basis of spectroscopic grazing incidence wide-angle x-ray scattering and atomic force microscopy studies as well as theoretical calculations, the remarkable enhancement of charge mobility upon addition of tetramethylammonium iodide is attributed primarily to an inhibition of the torsion of the alkyl side chains by the presence of the ionic species, facilitating a more ordered lamellar packing of the alkyl side chains and interchain π-π interactions. PMID:27386541

  5. High-Temperature Capacitor Polymer Films

    NASA Astrophysics Data System (ADS)

    Tan, Daniel; Zhang, Lili; Chen, Qin; Irwin, Patricia

    2014-12-01

    Film capacitor technology has been under development for over half a century to meet various applications such as direct-current link capacitors for transportation, converters/inverters for power electronics, controls for deep well drilling of oil and gas, direct energy weapons for military use, and high-frequency coupling circuitry. The biaxially oriented polypropylene film capacitor remains the state-of-the-art technology; however, it is not able to meet increasing demand for high-temperature (>125°C) applications. A number of dielectric materials capable of operating at high temperatures (>140°C) have attracted investigation, and their modifications are being pursued to achieve higher volumetric efficiency as well. This paper highlights the status of polymer dielectric film development and its feasibility for capacitor applications. High-temperature polymers such as polyetherimide (PEI), polyimide, and polyetheretherketone were the focus of our studies. PEI film was found to be the preferred choice for high-temperature film capacitor development due to its thermal stability, dielectric properties, and scalability.

  6. Near-infrared (NIR) emitting conjugated polymers for biomedical applications (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Repenko, Tatjana; Kuehne, Alexander J. C.

    2015-10-01

    Fluorescent biomedical markers of today such as dye-infiltrated colloids, microgels and quantum dots suffer from fast bleaching, lack surface functionality (for targets or pharmaceutical agents) and potentially leach heavy metals in case of quantum dots (e.g. Cd). By contrast, conjugated polymer particles are non-cytotoxic, exhibit reduced bleaching, as the entire particle consists of fluorophore, they are hydrophobic and show high quantum yields. Consequently, conjugated polymer particles represent ideal materials for biological applications and imaging. However currently, conjugated polymer particles for biomedical imaging usually lack near-infrared (NIR) emission and are polydisperse. Fluorescent agents with emission in the NIR spectrum are interesting for biomedical applications due to their low photo-damage towards biological species and the ability of NIR radiation to penetrate deep into biological tissue.. I will present the development and synthesis of new conjugated polymers particles with fluorescence in the NIR spectral region for bio-imaging and clinical diagnosis. The particle synthesis proceeds in a one-step Pd or Ni-catalyzed dispersion polymerization of functional NIR emitters. The resulting monodisperse conjugated polymer particles are obtained as a dispersion in a non-hazardous solvent. Different sizes in the sub-micrometer range with a narrow size distribution can be produced. Furthermore biological recognition motifs can be easily attached to the conjugated polymers via thiol-yne click-chemistry providing specific tumor targeting without quenching of the fluorescence. References [1] Kuehne AJC, Gather MC, Sprakel J., Nature Commun. 2012, 3, 1088. [2] Repenko T, Fokong S, De Laporte L, Go D, Kiessling F, Lammers T, Kuehne AJC.,Chem Commun 2015, accepted.

  7. Nanoscale lubricating film formation by linear polymer in aqueous solution

    NASA Astrophysics Data System (ADS)

    Liu, Shuhai; Guo, Dan; Xie, Guoxin

    2012-11-01

    Film-forming properties of polymer in aqueous solution flowing through a nanogap have been investigated by using a thin film interferometry. The film properties of linear polymer in aqueous solution flowing through a confined nanogap depend on the ratio of water film thickness to averaged radius of polymer chains H0/RPolymer. It was found that the lubrication film thickness of linear polymer in aqueous solution decreases as the polymer molecular weight increasing when H0/RPolymer < 2 ˜ 3. A new lubrication map was proposed, which includes the lubrication regime of weak confinement influence, the lubrication regime of strong confinement influence (LRSCI), and the transition regime of confinement influence. It is very difficult to increase the lubrication film thickness using the higher molecule weight in the LRSCI regime. The lubrication mechanism inferred from our experimental results may help to better understand the dynamic film properties of linear polymer in aqueous solution flowing through a nanogap.

  8. Second and third order nonlinear optical properties of conjugated molecules and polymers

    NASA Technical Reports Server (NTRS)

    Perry, Joseph W.; Stiegman, Albert E.; Marder, Seth R.; Coulter, Daniel R.; Beratan, David N.; Brinza, David E.

    1988-01-01

    Second- and third-order nonlinear optical properties of some newly synthesized organic molecules and polymers are reported. Powder second-harmonic-generation efficiencies of up to 200 times urea have been realized for asymmetric donor-acceptor acetylenes. Third harmonic generation chi(3)s have been determined for a series of small conjugated molecules in solution. THG chi(3)s have also been determined for a series of soluble conjugated copolymers prepared using ring-opening metathesis polymerization. The results are discussed in terms of relevant molecular and/or macroscopic structural features of these conjugated organic materials.

  9. Effects of charge carrier concentration in hybrid conjugated polymer/oxide photovoltaic devices

    NASA Astrophysics Data System (ADS)

    White, Matthew Schuette

    2009-12-01

    of the polymer is a requisite for functional devices, but intentional doping of the oxide provides an additional degree of control over interfacial electric fields. By using planar hybrid heterojunctions, the utility of this effect is shown by increasing the driving force for charge separation. Interfacial barrier layers are required on highly doped ZnO to prevent recombination and preserve high fill factors. The measurable carrier concentration in the depletion region of polymer and polymer-fullerene blend films is shown to be significantly larger under illumination than in the dark. This effect is not related to breaking of the conjugated bonds in the polymer, as is the device aging phenomenon, but stems from low mobility of photo-generated electrons. The depletion width and maximum electric field in devices are influenced by the presence of an increased effective doping density under illumination.

  10. High-sensitivity DNA biosensor based on optical fiber taper interferometer coated with conjugated polymer tentacle.

    PubMed

    Huang, Yunyun; Tian, Zhuang; Sun, Li-Peng; Sun, Dandan; Li, Jie; Ran, Yang; Guan, Bai-Ou

    2015-10-19

    A sensitive bio-probe to in situ detect unlabeled single-stranded DNA targets based on optical microfiber taper interferometer coated by a high ordered pore arrays conjugated polymer has been presented. The polymer coating serves as tentacles to catch single-stranded DNA molecules by π-π conjugated interaction and varies the surface refractive index of the optical microfiber. The microfiber taper interferometer translates the refractive index information into wavelength shift of the interference fringe. The sensor exhibits DNA concentration sensitivity of 2.393 nm/log M and the lowest detection ability of 10(-10) M or even lower. PMID:26480357

  11. Germanium films by polymer-assisted deposition

    SciTech Connect

    Jia, Quanxi; Burrell, Anthony K.; Bauer, Eve; Ronning, Filip; McCleskey, Thomas Mark; Zou, Guifu

    2013-01-15

    Highly ordered Ge films are prepared directly on single crystal Si substrates by applying an aqueous coating solution having Ge-bound polymer onto the substrate and then heating in a hydrogen-containing atmosphere. A coating solution was prepared by mixing water, a germanium compound, ethylenediaminetetraacetic acid, and polyethyleneimine to form a first aqueous solution and then subjecting the first aqueous solution to ultrafiltration.

  12. Entropic (de)stabilization of surface-bound peptides conjugated with polymers

    NASA Astrophysics Data System (ADS)

    Carmichael, Scott P.; Shell, M. Scott

    2015-12-01

    In many emerging biotechnologies, functional proteins must maintain their native structures on or near interfaces (e.g., tethered peptide arrays, protein coated nanoparticles, and amphiphilic peptide micelles). Because the presence of a surface is known to dramatically alter the thermostability of tethered proteins, strategies to stabilize surface-bound proteins are highly sought. Here, we show that polymer conjugation allows for significant control over the secondary structure and thermostability of a model surface-tethered peptide. We use molecular dynamics simulations to examine the folding behavior of a coarse-grained helical peptide that is conjugated to polymers of various lengths and at various conjugation sites. These polymer variations reveal surprisingly diverse behavior, with some stabilizing and some destabilizing the native helical fold. We show that ideal-chain polymer entropies explain these varied effects and can quantitatively predict shifts in folding temperature. We then develop a generic theoretical model, based on ideal-chain entropies, that predicts critical lengths for conjugated polymers to effect changes in the folding of a surface-bound protein. These results may inform new design strategies for the stabilization of surface-associated proteins important for a range technological applications.

  13. Entropic (de)stabilization of surface-bound peptides conjugated with polymers.

    PubMed

    Carmichael, Scott P; Shell, M Scott

    2015-12-28

    In many emerging biotechnologies, functional proteins must maintain their native structures on or near interfaces (e.g., tethered peptide arrays, protein coated nanoparticles, and amphiphilic peptide micelles). Because the presence of a surface is known to dramatically alter the thermostability of tethered proteins, strategies to stabilize surface-bound proteins are highly sought. Here, we show that polymer conjugation allows for significant control over the secondary structure and thermostability of a model surface-tethered peptide. We use molecular dynamics simulations to examine the folding behavior of a coarse-grained helical peptide that is conjugated to polymers of various lengths and at various conjugation sites. These polymer variations reveal surprisingly diverse behavior, with some stabilizing and some destabilizing the native helical fold. We show that ideal-chain polymer entropies explain these varied effects and can quantitatively predict shifts in folding temperature. We then develop a generic theoretical model, based on ideal-chain entropies, that predicts critical lengths for conjugated polymers to effect changes in the folding of a surface-bound protein. These results may inform new design strategies for the stabilization of surface-associated proteins important for a range technological applications. PMID:26723588

  14. Role of Polymer Architecture on the Activity of Polymer-Protein Conjugates for the Treatment of Accelerated Bone Loss Disorders.

    PubMed

    Tucker, Bryan S; Stewart, Jon D; Aguirre, J Ignacio; Holliday, L Shannon; Figg, C Adrian; Messer, Jonathan G; Sumerlin, Brent S

    2015-08-10

    Polymers of similar molecular weights and chemical constitution but varying in their macromolecular architectures were conjugated to osteoprotegerin (OPG) to determine the effect of polymer topology on protein activity in vitro and in vivo. OPG is a protein that inhibits bone resorption by preventing the formation of mature osteoclasts from the osteoclast precursor cell. Accelerated bone loss disorders, such as osteoporosis, rheumatoid arthritis, and metastatic bone disease, occur as a result of increased osteoclastogenesis, leading to the severe weakening of the bone. OPG has shown promise as a treatment in bone disorders; however, it is rapidly cleared from circulation through rapid liver uptake, and frequent, high doses of the protein are necessary to achieve a therapeutic benefit. We aimed to improve the effectiveness of OPG by creating OPG-polymer bioconjugates, employing reversible addition-fragmentation chain transfer polymerization to create well-defined polymers with branching densities varying from linear, loosely branched to densely branched. Polymers with each of these architectures were conjugated to OPG using a "grafting-to" approach, and the bioconjugates were characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The OPG-polymer bioconjugates showed retention of activity in vitro against osteoclasts, and each bioconjugate was shown to be nontoxic. Preliminary in vivo studies further supported the nontoxic characteristics of the bioconjugates, and measurement of the bone mineral density in rats 7 days post-treatment via peripheral quantitative computed tomography suggested a slight increase in bone mineral density after administration of the loosely branched OPG-polymer bioconjugate. PMID:26151628

  15. Novel nature-inspired conjugated polymers for high performance transistors and solar cells (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Bronstein, Hugo A.; Falon, Kealan; Yaacobi-Gross, Nir; Ashraf, Raja Shahid; McCulloch, Iain; Anthopoulos, Thomas D.

    2015-10-01

    Novel, extremely narrow band-gap polymer with a structure based on natural indigo has been synthesised and exhibits high crystallinity, high ambipolar transport in OFET devices, and OPV device efficiencies up to 2.35% with light absorbance up to 950 nm, demonstrating potential in near-IR photovoltaics. We demonstrate that the use of a potentially bio-sustainable monomer unit in a conjugated polymer can give balanced ambipolar OFET mobilities in excess of 0.5 cm2/Vs. This novel monomer, and polymers are synthesized by rigidifying the structure of indigo by condensation with an aromatic acidic acid. The materials display high crystallinity which can be further enhanced by annealing and demonstrate that it can be used as a potentially biosustainable alternative to the commonly used DPP and iso-indigo monomers. We believe this is the first attempt to tackle the issue of sustainability in conjugated polymer synthesis.

  16. Ultralong-Range Polaron-Induced Quenching of Excitons in Isolated Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Bolinger, Joshua C.; Traub, Matthew C.; Adachi, Takuji; Barbara, Paul F.

    2011-02-01

    In conjugated polymers, radiative recombination of excitons (electron-hole pairs) competes with nonradiative thermal relaxation pathways. We visualized exciton quenching induced by hole polarons in single-polymer chains in a device geometry. The distance-scale for quenching was measured by means of a new subdiffraction, single-molecule technique—bias-modulated intensity centroid spectroscopy—which allowed the extraction of a mean centroid shift of 14 nanometers for highly ordered, single-polymer nanodomains. This shift requires energy transfer over distances an order of magnitude greater than previously reported for bulk conjugated polymers and far greater than predicted by the standard mechanism for exciton quenching, the unbiased diffusion of free excitons to quenching sites. Instead, multistep “energy funneling” to trapped, localized polarons is the probable mechanism for polaron-induced exciton quenching.

  17. METAL-CONTAINING CONJUGATED POLYMERS AS FLUORESCENT CHEMOSENSORS IN THE DETECTION OF TOXICANTS.

    PubMed

    Fegley, Megan E A; Pinnock, Sherryllene S; Malele, Catherine N; Jones, Wayne E

    2012-02-15

    Fluorescent conjugated polymers have received a great deal of recent interest due to their ability to act as chemosensors to detect various chemical species in both environmental and biological systems with sensitivity and selectivity. Examples from the literature include polymer chemosensors that operate on either fluorescence "turn-on" or "turn-off" as mechanisms of sensor response. These responses can be related to either photoinduced electron transfer or electronic energy transfer mechanisms. Recently, a series of metal-containing polymers or metallopolymers have been explored by various research groups for their use as chemosensors. In many cases, these metallopolymers have been shown to be more sensitive and selective for specific chemical species. This review focuses on fluorescent conjugated polymers as chemosensors, with a specific concentration on recent advances in metallopolymer chemosensors. PMID:22711916

  18. METAL-CONTAINING CONJUGATED POLYMERS AS FLUORESCENT CHEMOSENSORS IN THE DETECTION OF TOXICANTS

    PubMed Central

    Fegley, Megan E. A.; Pinnock, Sherryllene S.; Malele, Catherine N.; Jones, Wayne E.

    2012-01-01

    Fluorescent conjugated polymers have received a great deal of recent interest due to their ability to act as chemosensors to detect various chemical species in both environmental and biological systems with sensitivity and selectivity. Examples from the literature include polymer chemosensors that operate on either fluorescence “turn-on” or “turn-off” as mechanisms of sensor response. These responses can be related to either photoinduced electron transfer or electronic energy transfer mechanisms. Recently, a series of metal-containing polymers or metallopolymers have been explored by various research groups for their use as chemosensors. In many cases, these metallopolymers have been shown to be more sensitive and selective for specific chemical species. This review focuses on fluorescent conjugated polymers as chemosensors, with a specific concentration on recent advances in metallopolymer chemosensors. PMID:22711916

  19. Dendritic polymer imaging systems for the evaluation of conjugate uptake and cleavage

    NASA Astrophysics Data System (ADS)

    Krüger, Harald R.; Nagel, Gregor; Wedepohl, Stefanie; Calderón, Marcelo

    2015-02-01

    Fluorescent turn-on probes combined with polymers have a broad range of applications, e.g. for intracellular sensing of ions, small molecules, or DNA. In the field of polymer therapeutics, these probes can be applied to extend the in vitro characterization of novel conjugates beyond cytotoxicity and cellular uptake studies. This is particularly true in cases in which polymer conjugates contain drugs attached by cleavable linkers. Better information on the intracellular linker cleavage and drug release would allow a faster evaluation and optimization of novel polymer therapeutic concepts. We therefore developed a fluorescent turn-on probe that enables direct monitoring of pH-mediated cleavage processes over time. This is achieved by exploiting the fluorescence resonance energy transfer (FRET) between two dyes that have been coupled to a dendritic polymer. We demonstrate the use of this probe to evaluate polymer uptake and intracellular release of cargo in a cell based microplate assay that is suitable for high throughput screening.Fluorescent turn-on probes combined with polymers have a broad range of applications, e.g. for intracellular sensing of ions, small molecules, or DNA. In the field of polymer therapeutics, these probes can be applied to extend the in vitro characterization of novel conjugates beyond cytotoxicity and cellular uptake studies. This is particularly true in cases in which polymer conjugates contain drugs attached by cleavable linkers. Better information on the intracellular linker cleavage and drug release would allow a faster evaluation and optimization of novel polymer therapeutic concepts. We therefore developed a fluorescent turn-on probe that enables direct monitoring of pH-mediated cleavage processes over time. This is achieved by exploiting the fluorescence resonance energy transfer (FRET) between two dyes that have been coupled to a dendritic polymer. We demonstrate the use of this probe to evaluate polymer uptake and intracellular

  20. The Role of Morphology and Electronic Chain Aggregation on the Optical Gain Properties of Semiconducting Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Lampert, Zachary Evan

    Conjugated polymers (CPs) are a novel class of materials that exhibit the optical and electrical properties of semiconductors while still retaining the durability and processability of plastics. CPs are also intrinsically 4-level systems with high luminescence quantum efficiencies making them particularly attractive as organic gain media for solid-state laser applications. However, before CPs can emerge as a commercially available laser technology, a more comprehensive understanding of the morphological dependence of the photophysics is required. In this thesis, the morphology and chain conformation dependence of amplified spontaneous emission (ASE) and optical gain in thin films of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) was investigated. By changing the chemical nature of the solvent from which films were cast, as well as the temperature at which films were annealed, CP films with different morphologies, and hence different degrees of interchain interactions were achieved. Contrary to the common perception that polymer morphology plays a decisive role in determining the ASE behavior of thin CP films, we found that chromophore aggregation and degree of conformational order have minimal impact on optical gain. In fact, experimental results indicated that an extremely large fraction of interchain aggregate species and/or exciton dissociating defects are required to significantly alter the optical properties and suppress stimulated emission. These results are pertinent to the fabrication and optimization of an electrically pumped laser device, as improvements in charge carrier mobility through controlled increases in chain aggregation may provide a viable means of optimizing injection efficiency without significantly degrading optical gain. To offset charge-induced absorption losses under electrical pumping, and to enable the use of more compact and economical sources under optical pumping, conjugated polymers exhibiting low lasing

  1. Fluorescence Recovery after Photobleaching in Confined Polymer Thin Films

    NASA Astrophysics Data System (ADS)

    Gray, Laura A. G.; Brangwynne, Clifford P.; Priestley, Rodney D.

    Over the past twenty years many studies have shown a reduction in the glass transition temperature (Tg) of thin polymer films confined on the nanoscale when supported on non-attractive substrates or free-standing. The depth dependence of Tg has been measured using thin layers of fluorescently tagged polymer to localize the dye within a larger polymer film stack, revealing a decrease in local Tg tens of nanometers into the film. These results have been explained by the propagation of enhanced mobility from the free-surface into the polymer film. Fewer direct measurements of molecular mobility have been made in confined polymer systems. Here, we present the results of fluorescence recovery after photobleaching (FRAP) experiments investigating the mobility of fluorescently doped and labeled methacrylate-based polymers confined in thin film geometries. Bleaching and recovery was monitored using a laser-scanning confocal microscope that enabled us to bleach arbitrary micron-sized shapes to monitor diffusion in polymer melts.

  2. An insight into non-emissive excited states in conjugated polymers.

    PubMed

    Hu, Zhongjian; Willard, Adam P; Ono, Robert J; Bielawski, Christopher W; Rossky, Peter J; Vanden Bout, David A

    2015-01-01

    Conjugated polymers in the solid state usually exhibit low fluorescence quantum yields, which limit their applications in many areas such as light-emitting diodes. Despite considerable research efforts, the underlying mechanism still remains controversial and elusive. Here, the nature and properties of excited states in the archetypal polythiophene are investigated via aggregates suspended in solvents with different dielectric constants (ɛ). In relatively polar solvents (ɛ>∼ 3), the aggregates exhibit a low fluorescence quantum yield (QY) of 2-5%, similar to bulk films, however, in relatively nonpolar solvents (ɛ<∼ 3) they demonstrate much higher fluorescence QY up to 20-30%. A series of mixed quantum-classical atomistic simulations illustrate that dielectric induced stabilization of nonradiative charge-transfer (CT) type states can lead to similar drastic reduction in fluorescence QY as seen experimentally. Fluorescence lifetime measurement reveals that the CT-type states exist as a competitive channel of the formation of emissive exciton-type states. PMID:26391514

  3. An insight into non-emissive excited states in conjugated polymers

    PubMed Central

    Hu, Zhongjian; Willard, Adam P.; Ono, Robert J.; Bielawski, Christopher W.; Rossky, Peter J.; Vanden Bout, David A.

    2015-01-01

    Conjugated polymers in the solid state usually exhibit low fluorescence quantum yields, which limit their applications in many areas such as light-emitting diodes. Despite considerable research efforts, the underlying mechanism still remains controversial and elusive. Here, the nature and properties of excited states in the archetypal polythiophene are investigated via aggregates suspended in solvents with different dielectric constants (ɛ). In relatively polar solvents (ɛ>∼ 3), the aggregates exhibit a low fluorescence quantum yield (QY) of 2–5%, similar to bulk films, however, in relatively nonpolar solvents (ɛ<∼ 3) they demonstrate much higher fluorescence QY up to 20–30%. A series of mixed quantum-classical atomistic simulations illustrate that dielectric induced stabilization of nonradiative charge-transfer (CT) type states can lead to similar drastic reduction in fluorescence QY as seen experimentally. Fluorescence lifetime measurement reveals that the CT-type states exist as a competitive channel of the formation of emissive exciton-type states. PMID:26391514

  4. Altering the Conjugation Pathway for Improved Performance of Benzobisoxazole-Based Polymer Guest Emitters in Polymer Light-Emitting Diodes

    SciTech Connect

    Intemann, Jeremy J.; Hellerich, Emily S.; Tlach, Brian C.; Ewan, Monique D.; Barnes, Charles A.; Bhuwalka, Achala; Cai, Min; Shinar, Joseph; Shinar, Ruth; Jeffries-EL, Malika

    2012-08-27

    Benzobisoxazoles (BBOs) are known to increase the electron affinities and improve the electron transporting properties of materials containing them. However, BBO copolymers generally do not perform well as emissive guests in guest–host PLEDs due to inefficient Förster resonance energy transfer (FRET) between host and guest. The incomplete FRET results in a large amount of host emission and limits the potential efficiencies of the devices. In all previously reported BBO copolymers, the conjugation pathway was through the oxazole rings. Herein we report six new BBO copolymers with backbone connectivity directly on the central benzene ring, resulting in a conjugation pathway for the polymers that is perpendicular to the previously reported pathway. Guest–host PLEDs made using these polymers show that the new conjugation pathway improves FRET between the poly(N-vinylcarbazole) host and the BBO-containing polymer guest. Because of highly efficient FRET, no host emission is observed even at lower guest concentrations. The improved energy transfer results in devices with luminous efficiencies up to 3.1 Cd/A, a 3-fold improvement over previously reported BBO-based PLEDs. These results indicate that the conjugation pathway plays a critical role in designing emissive materials for guest–host PLEDs.

  5. DNA-Polymer Conjugates for Immune Stimulation through Toll-like Receptor 9 Mediated Pathways

    PubMed Central

    Levenson, Eric A.; Kiick, Kristi L.

    2014-01-01

    Oligodeoxynucleotides (ODN) containing unmethylated CpG dinucleotide motifs are agonists of Toll-like receptor 9 and are currently being investigated for use as vaccine adjuvants through promotion of type I immunity. Several classes of ODN have been developed which differ in their propensity to aggregate, which in turn, alter cytokine profiles and cellular subsets activated. Although aggregation state is correlated with the change in cytokine response, it is unknown if this results from a change in the number of ODN available for binding and/or the possible engagement of multiple TLR9 molecules. Here, we examined the role of ligand valency on the activation of TLR9 through the synthesis of ODN-poly(acrylic acid) (PAA) conjugates. The compositions and size of the conjugates were characterized by UV-Vis spectroscopy, 1H NMR, gel permeation chromatography, and dynamic light scattering. ELISA-based assays of cytokine secretion by murine-like macrophages indicate that these ODN-PAA polymer conjugates show enhanced immunostimulation at 100-fold lower concentrations than those required for ODN alone, for both TNF-α and IL-6 release, and are more potent than any other previously reported multivalent ODN constructs. Increasing valency was shown to significantly enhance cytokine expression, particularly for IL-6. Knockdown by siRNA demonstrates that these polymer conjugates are specific to TLR9. Our results define valency as a critical design parameter and polymer conjugation as an advantageous strategy for producing ODN immunomodulatory agents. PMID:24316364

  6. DNA-polymer conjugates for immune stimulation through Toll-like receptor 9 mediated pathways.

    PubMed

    Levenson, Eric A; Kiick, Kristi L

    2014-03-01

    Oligodeoxynucleotides (ODNs) containing unmethylated CpG dinucleotide motifs are agonists of Toll-like receptor 9 and are currently being investigated for use as vaccine adjuvants through the promotion of type I immunity. Several classes of ODN have been developed which differ in their propensity to aggregate, which in turn alters cytokine profiles and cellular subsets activated. Although aggregation state is correlated with the change in cytokine response, it is unknown if this results from a change in the number of ODNs available for binding and/or the possible engagement of multiple TLR9 molecules. Here, we examined the role of ligand valency on the activation of TLR9 through the synthesis of ODN-poly(acrylic acid) (PAA) conjugates. The compositions and size of the conjugates were characterized by UV-vis spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography and dynamic light scattering. Enzyme-linked immunosorbent assays of cytokine secretion by murine-like macrophages indicate that these ODN-PAA polymer conjugates show enhanced immunostimulation at 100-fold lower concentrations than those required for ODN alone, for both TNF-α and IL-6 release, and are more potent than any other previously reported multivalent ODN constructs. Increasing valency was shown to significantly enhance cytokine expression, particularly for IL-6. Knockdown by siRNA demonstrates that these polymer conjugates are specific to TLR9. Our results define valency as a critical design parameter and polymer conjugation as an advantageous strategy for producing ODN immunomodulatory agents. PMID:24316364

  7. Polymer-conjugated inhibitors of tumor necrosis factor-α for local control of inflammation.

    PubMed

    Washburn, Newell R; Prata, Joseph E; Friedrich, Emily E; Ramadan, Mohamed H; Elder, Allison N; Sun, Liang Tso

    2013-01-01

    Burns, chronic wounds, osteoarthritis, and uveitis are examples of conditions characterized by local, intense inflammatory responses that can impede healing or even further tissue degradation. The most powerful anti-inflammatory drugs available are often administered systemically, but these carry significant side effects and are not compatible for patients that have underlying complications associated with their condition. Conjugation of monoclonal antibodies that neutralize pro-inflammatory cytokines to high molecular weight hydrophilic polymers has been shown to be an effective strategy for local control of inflammation. Lead formulations are based on antibody inhibitors of tumor necrosis factor-α conjugated to hyaluronic acid having molecular weight greater than 1 MDa. This review will discuss fundamental aspects of medical conditions that could be treated with these conjugates and design principles for preparing these cytokine-neutralizing polymer conjugates. Results demonstrating that infliximab, an approved inhibitor of tumor necrosis factor-α, can be incorporated into the conjugates using a broad range of water-soluble polymers are also presented, along with a prospectus for clinical translation. PMID:23903893

  8. Dual-Color Fluorescence Imaging of Magnetic Nanoparticles in Live Cancer Cells Using Conjugated Polymer Probes

    PubMed Central

    Sun, Minjie; Sun, Bin; Liu, Yun; Shen, Qun-Dong; Jiang, Shaojun

    2016-01-01

    Rapid growth in biological applications of nanomaterials brings about pressing needs for exploring nanomaterial-cell interactions. Cationic blue-emissive and anionic green-emissive conjugated polymers are applied as dual-color fluorescence probes to the surface of negatively charged magnetic nanoparticles through sequentially electrostatic adsorption. These conjugated polymers have large extinction coefficients and high fluorescence quantum yield (82% for PFN and 62% for ThPFS). Thereby, one can visualize trace amount (2.7 μg/mL) of fluorescence-labeled nanoparticles within cancer cells by confocal laser scanning microscopy. Fluorescence labeling by the conjugated polymers is also validated for quantitative determination of the internalized nanoparticles in each individual cell by flow cytometry analysis. Extensive overlap of blue and green fluorescence signals in the cytoplasm indicates that both conjugated polymer probes tightly bind to the surface of the nanoparticles during cellular internalization. The highly charged and fluorescence-labeled nanoparticles non-specifically bind to the cell membranes, followed by cellular uptake through endocytosis. The nanoparticles form aggregates inside endosomes, which yields a punctuated staining pattern. Cellular internalization of the nanoparticles is dependent on the dosage and time. Uptake efficiency can be enhanced three-fold by application of an external magnetic field. The nanoparticles are low cytotoxicity and suitable for simultaneously noninvasive fluorescence and magnetic resonance imaging application. PMID:26931282

  9. Photophysics of poly(p-pyridine): Blue electroluminescent devices from a soluble conjugated polymer

    SciTech Connect

    Jessen, S.W.; Gebler, D.D.; Wang, Y.Z.

    1995-12-01

    Poly({rho}-pyridine) (PPy) is a conjugated polymer which luminesces strongly in the blue wavelength region. PPy is soluble in hydrochloric or formic acid and is stable in air. We report the fluorescence and transient absorption spectrum of PPy in the visible region.

  10. A novel cationic conjugated polymer for homogeneous fluorescence-based DNA detection.

    PubMed

    Peng, Hui; Soeller, Christian; Travas-Sejdic, Jadranka

    2006-09-21

    A novel water-soluble cationic conjugated polymer, poly({2,5-bis[3-(N,N-diethylamino)-1-oxapropyl]-para-phenylenevinylene}-alt-para-phenylenevinylene) dibromide, was synthesized and used to develop a simple label-free DNA detection essay. PMID:17047828

  11. Dual-Color Fluorescence Imaging of Magnetic Nanoparticles in Live Cancer Cells Using Conjugated Polymer Probes.

    PubMed

    Sun, Minjie; Sun, Bin; Liu, Yun; Shen, Qun-Dong; Jiang, Shaojun

    2016-01-01

    Rapid growth in biological applications of nanomaterials brings about pressing needs for exploring nanomaterial-cell interactions. Cationic blue-emissive and anionic green-emissive conjugated polymers are applied as dual-color fluorescence probes to the surface of negatively charged magnetic nanoparticles through sequentially electrostatic adsorption. These conjugated polymers have large extinction coefficients and high fluorescence quantum yield (82% for PFN and 62% for ThPFS). Thereby, one can visualize trace amount (2.7 μg/mL) of fluorescence-labeled nanoparticles within cancer cells by confocal laser scanning microscopy. Fluorescence labeling by the conjugated polymers is also validated for quantitative determination of the internalized nanoparticles in each individual cell by flow cytometry analysis. Extensive overlap of blue and green fluorescence signals in the cytoplasm indicates that both conjugated polymer probes tightly bind to the surface of the nanoparticles during cellular internalization. The highly charged and fluorescence-labeled nanoparticles non-specifically bind to the cell membranes, followed by cellular uptake through endocytosis. The nanoparticles form aggregates inside endosomes, which yields a punctuated staining pattern. Cellular internalization of the nanoparticles is dependent on the dosage and time. Uptake efficiency can be enhanced three-fold by application of an external magnetic field. The nanoparticles are low cytotoxicity and suitable for simultaneously noninvasive fluorescence and magnetic resonance imaging application. PMID:26931282

  12. Energy transfer from conjugated polymer to bacterial light-harvesting complex

    NASA Astrophysics Data System (ADS)

    Buczynska, D.; Bujak, Ł.; Loi, M. A.; Brotosudarmo, T. H. P.; Cogdell, R.; Mackowski, S.

    2012-10-01

    Energy transfer from a conjugated polymer blend (poly(9,9-dioctylfluorenyl-2,7-diyl):poly (2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene) to a light-harvesting complex 2 from purple bacteria has been demonstrated using time-resolved fluorescence spectroscopy. For our hybrid nanostructure, we observe a 30% reduction of the fluorescence lifetime of the polymer emission as compared to the pure polymer layer. This result is an important step towards integrating naturally evolved biomolecules with synthetic materials into biohybrid organic electronic systems.

  13. Nanoscale structural and mechanical characterization of bamboo-like polymer/silicon nanocomposite films

    NASA Astrophysics Data System (ADS)

    Ni, Hai; Li, Xiaodong; Gao, Hongsheng; Nguyen, Thien-Phap

    2005-09-01

    In an attempt to mimic the bamboo's architecture, bamboo-like polymer/silicon nanocomposites were synthesized by filling silicon nanopores with two conjugated polymers, namely poly(p-phenylene vinylene) (PPV) and its derivative poly(2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene) (MEHPPV). The microstructure, elastic modulus, hardness, nanoscratch resistance, and fracture toughness of the bamboo-like polymer/nanoporous silicon (PS) films were investigated using different functions of an atomic force microscope and nanoindentation techniques. The fracture toughness of MEHPPV- and PPV-filled PS films is 2 and 1.6 times higher than that of PS, respectively, although their elastic modulus and hardness decrease compared to PS. Strengthening and deformation mechanisms are discussed in conjunction with nanocomposite structure, hardness, elastic modulus and nanoscratch resistance.

  14. π-Conjugated Organometallic Isoindigo Oligomer and Polymer Chromophores: Singlet and Triplet Excited State Dynamics and Application in Polymer Solar Cells.

    PubMed

    Goswami, Subhadip; Gish, Melissa K; Wang, Jiliang; Winkel, Russell W; Papanikolas, John M; Schanze, Kirk S

    2015-12-01

    An isoindigo based π-conjugated oligomer and polymer that contain cyclometalated platinum(II) "auxochrome" units were subjected to photophysical characterization, and application of the polymer in bulk heterojunction polymer solar cells with PCBM acceptor was examined. The objective of the study was to explore the effect of the heavy metal centers on the excited state properties, in particular, intersystem crossing to a triplet (exciton) state, and further how this would influence the performance of the organometallic polymer in solar cells. The materials were characterized by electrochemistry, ground state absorption, emission, and picosecond-nanosecond transient absorption spectroscopy. Electrochemical measurements indicate that the cyclometalated units have a significant impact on the HOMO energy level of the chromophores, but little effect on the LUMO, which is consistent with localization of the LUMO on the isoindigo acceptor unit. Picosecond-nanosecond transient absorption spectroscopy reveals a transient with ∼100 ns lifetime that is assigned to a triplet excited state that is produced by intersystem crossing from a singlet state on a time scale of ∼130 ps. This is the first time that a triplet state has been observed for isoindigo π-conjugated chromophores. The performance of the polymer in bulk heterojunction solar cells was explored with PC61BM as an acceptor. The performance of the cells was optimum at a relatively high PCBM loading (1:6, polymer:PCBM), but the overall efficiency was relatively low with power conversion efficiency (PCE) of 0.22%. Atomic force microscopy of blend films reveals that the length scale of the phase separation decreases with increasing PCBM content, suggesting a reason for the increase in PCE with acceptor loading. Energetic considerations show that the triplet state in the polymer is too low in energy to undergo charge separation with PCBM. Further, due to the relatively low LUMO energy of the polymer, charge transfer

  15. Scanning Tunneling Microscopy analysis of space-exposed polymer films

    NASA Technical Reports Server (NTRS)

    Kalil, Carol R.; Young, Philip R.

    1993-01-01

    The characterization of the surface of selected space-exposed polymer films by Scanning Tunneling Microscopy (STM) is reported. Principles of STM, an emerging new technique for materials analysis, are reviewed. The analysis of several films which received up to 5.8 years of low Earth orbital (LEO) exposure onboard the NASA Long Duration Exposure Facility (LDEF) is discussed. Specimens included FEP Teflon thermal blanket material, Kapton film, and several experimental polymer films. Ultraviolet and atomic oxygen-induced crazing and erosion are described. The intent of this paper is to demonstrate how STM is enhancing the understanding of LEO space environmental effects on polymer films.

  16. Enhancing charge storage of conjugated polymer electrodes with phenolic acids

    NASA Astrophysics Data System (ADS)

    Wagner, Michal; Rębiś, Tomasz; Inganäs, Olle

    2016-01-01

    We here present studies of electrochemical doping of poly(1-aminoanthraquinone) (PAAQ) films with three structurally different phenolic acids. The examined phenolic acids (sinapic, ferulic and syringic acid) were selected due to their resemblance to redox active groups, which can be found in lignin. The outstanding electrochemical stability of PAAQ films synthesized for this work enabled extensive cycling of phenolic acid-doped PAAQ films. Potentiodynamic and charge-discharge studies revealed that phenolic acid-doped PAAQ films exhibited enhanced capacitance in comparison to undoped PAAQ films, together with appearance of redox activity characteristics specific for each dopant. Electrochemical kinetic studies performed on microelectrodes affirmed the fast electron transfer for hydroquinone-to-quinone reactions with these phenolic compounds. These results imply the potential application of phenolic acids in cheap and degradable energy storage devices.

  17. Nanoscale imaging of nonequilibrium polymer films

    NASA Astrophysics Data System (ADS)

    King, John; Granick, Steve

    2015-03-01

    In recent years there have been exciting advances in sub-diffraction limited imaging based on fluorescence microscopy. While most applications of super-resolution microscopy focus on static biological imaging, we are interested in extending these techniques to the study of polymer dynamics. To this end, we couple stimulated emission depletion (STED) with spectroscopic detection, relying on spectral features of fluorescence emission to serve as the imaging contrast agent. We aim to adapt fluorescent dyes responsive to environmental properties (polarity, mobility, current, temperature, ect.) to STED imaging. Using the fluorescent spectral response as a contrast agent allows for nanoscopic environments to be directly imaged without the need for specific labeling. Rapid acquisition of images allows for slow dynamic processes in nonequilibrium polymer films to be imaged in real time. We demonstrate the power of super-resolution spectroscopic imaging by directly imaging several topical problems in materials science.

  18. Fundamental Studies on Donor-acceptor Conjugated Polymers Containing 'Heavy' Group 14 and Group 16 Elements

    NASA Astrophysics Data System (ADS)

    Gibson, Gregory Laird

    One advantage of conjugated polymers as organic materials is that their properties may be readily tuned through covalent modifications. This thesis presents studies on the structure-property relationships resulting from single- and double-atom substitutions on an alternating donor-acceptor conjugated polymer. Specifically, single selenium and tellurium atoms have been incorporated into the acceptor monomer in place of sulfur; silicon and germanium atoms have been substituted in place of carbon at the donor monomer bridge position. The carbon-donor/ tellurium-acceptor polymer was synthesized by a post-polymerization reaction sequence and demonstrated the utility of heavy group 16 atoms to red shift a polymer absorption spectrum. Density functional theory calculations point to a new explanation for this result invoking the lower heavy atom ionization energy and reduced aromaticity of acceptor monomers containing selenium and tellurium compared to sulfur. Absorption and emission experiments demonstrate that both silicon and germanium substitutions in the donor slightly blue shift the polymer absorption spectrum. Polymers containing sulfur in the acceptor are the strongest light absorbers of all polymers studied here. Molecular weight and phenyl end capping studies show that molecular weight appears to affect polymer absorption to the greatest degree in a medium molecular weight regime and that these effects have a significant aggregation component. Solar cell devices containing either the silicon- or germanium-donor/selenium-acceptor polymer display improved red light harvesting or hole mobility relative to their structural analogues. Overall, these results clarify the effects of single atom substitution on donor-acceptor polymers and aid in the future design of polymers containing heavy atoms.

  19. Polymer-drug conjugates for intracellar molecule-targeted photoinduced inactivation of protein and growth inhibition of cancer cells

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Yuan, Huanxiang; Zhu, Chunlei; Yang, Qiong; Lv, Fengting; Liu, Libing; Wang, Shu

    2012-10-01

    For most molecule-targeted anticancer systems, intracellular protein targets are very difficult to be accessed by antibodies, and also most efforts are made to inhibit protein activity temporarily rather than inactivate them permanently. In this work we firstly designed and synthesized multifunctional polymer-drug conjugates (polythiophene-tamoxifen) for intracellular molecule-targeted binding and inactivation of protein (estrogen receptor α, ERα) for growth inhibition of MCF-7 cancer cells. Small molecule drug was conjugated to polymer side chain for intracellular signal protein targeting, and simultaneously the fluorescent characteristic of polymer for tracing the cellular uptake and localization of polythiophene-drug conjugates by cell imaging. Under light irradiation, the conjugated polymer can sensitize oxygen to produce reactive oxygen species (ROS) that specifically inactivate the targeted protein, and thus inhibit the growth of tumor cells. The conjugates showed selective growth inhibition of ERα positive cancer cells, which exhibits low side effect for our intracellular molecule-targeted therapy system.

  20. Synthesis, characterization, and relaxivity of two linear Gd(DTPA)-polymer conjugates.

    PubMed

    Duarte, M G; Gil, M H; Peters, J A; Colet, J M; Elst, L V; Muller, R N; Geraldes, C F

    2001-01-01

    Two linear polyamide conjugates of Gd(DTPA)2- were synthesized and characterized by high-resolution nuclear magnetic resonance (NMR) spectroscopy and size exclusion chromatography (SEC). DTPA was copolymerized with two different diamines, 1,6-hexanediamine and trans-1,4-cyclohexanediamine, yielding the polymers DTPA-HMD and DTPA-CHD, with low polydispersity. Their molecular flexibility in solution was studied using 13C spin-lattice relaxation time measurements, indicating that the cyclohexanediamine linking moiety of the DTPA-HMD polymer is more rigid than that of DTPA-CHD. The influence of the flexibility of the linking functionalities on the relaxivity of the Gd3+-DTPA-polymer conjugates was studied by water nuclear magnetic relaxation dispersion (NMRD). The relaxivity of the Gd(DTPA-CHD) polymer was only slightly higher than that of the Gd(DTPA-HMD) polymer, and only two times higher than the usual values for small Gd-DTPA-like chelates. The low relaxivities obtained for both polymers, much lower than expected from the polymer apparent molecular weights, result from their substantial residual flexibility, and also from a too long, nonoptimal, value of the inner-sphere water exchange rate. These polymeric compounds are also cleared very quickly from the blood of rats, indicating that they are of limited value as blood pool contrast agents for MRA. PMID:11312677

  1. Temporal switching of homo-FRET pathways in single-chromophore dimer models of π-conjugated polymers.

    PubMed

    Stangl, Thomas; Bange, Sebastian; Schmitz, Daniela; Würsch, Dominik; Höger, Sigurd; Vogelsang, Jan; Lupton, John M

    2013-01-01

    A set of π-conjugated oligomer dimers templated in molecular scaffolds is presented as a model system for studying the interactions between chromophores in conjugated polymers (CPs). Single-molecule spectroscopy was used to reveal energy transfer dynamics between two oligomers in either a parallel or oblique-angle geometry. In particular, the conformation of single molecules embedded in a host matrix was investigated via polarized excitation and emission fluorescence microscopy in combination with fluorescence correlation spectroscopy. While the intramolecular interchromophore conformation was found to have no impact on the fluorescence quantum yield, lifetime, or photon statistics (antibunching), the long-term nonequilibrium dynamics of energy transfer within these bichromophoric systems was accessible by studying the linear dichroism in emission at the single-molecule level, which revealed reversible switching of the emission between the two oligomers. In bulk polymer films, interchromophore coupling promotes the migration of excitation energy to quenching sites. Realizing the presence and dynamics of such interactions is crucial for understanding limitations on the quantum efficiency of larger CP materials. PMID:23268555

  2. Solution-phase laser processing of π-conjugated polymers: Switching between different molecular states

    NASA Astrophysics Data System (ADS)

    Takada, K.; Tomioka, A.

    2012-04-01

    Liquid-phase laser processing, where the laser-irradiated target material is immersed in water for cooling, has been reported as a promising processing technique for thermally fragile organic materials. Although nanometer-sized particles have been reported to be obtained with the liquid-phase laser processing, the physical property did not change because quantum-mechanical size effect does not exhibit itself in the zero-radius Frenkel excitons. In the present study, we step further to use solution droplets as a target material, where organic molecules are molecularly dispersed in organic solvent and, therefore, expected to easily alter the conformation and the energy state upon laser irradiation. Small volume organic solvent is quickly evaporated upon laser irradiation, letting the bare organic molecule placed in water and rapidly cooled. To prevent the chemical decomposition of the target π-conjugated molecule, the specimen was resonantly irradiated by a ns-pulse green laser, not by a conventional UV laser. When the solid state spin-coat film made from MEH-PPV chloroform solution was used as a irradiation target immersed in water, resulting MEH-PPV particles showed similar photoluminescence (PL) like the PL of the spin-coat film and PL of the chloroform solution, including the 0→1, 0→2 vibrational transitions: this indicates that the energy levels were not modified from the spin-coat film. In comparison, when tiny droplets of MEH-PPV chloroform solution (orange color) were suspended in water, laser irradiation gave rise to yellow MEH-PPV particles which showed 550 nm and 530 nm PL (type B), blue-shifted from the spin-coat film PL 580 nm (type A), suggesting a successful phase transition of MEH-PPV polymer to type B. Further solution-phase laser processing left the type B state unchanged. The irreversible phase transition from type A to type B suggests that the type B ground state has lower energy than type A, which is consistent with the blue-shifted PL of

  3. Polymer compositions, polymer films and methods and precursors for forming same

    DOEpatents

    Klaehn, John R; Peterson, Eric S; Orme, Christopher J

    2013-09-24

    Stable, high performance polymer compositions including polybenzimidazole (PBI) and a melamine-formaldehyde polymer, such as methylated, poly(melamine-co-formaldehyde), for forming structures such as films, fibers and bulky structures. The polymer compositions may be formed by combining polybenzimidazole with the melamine-formaldehyde polymer to form a precursor. The polybenzimidazole may be reacted and/or intertwined with the melamine-formaldehyde polymer to form the polymer composition. For example, a stable, free-standing film having a thickness of, for example, between about 5 .mu.m and about 30 .mu.m may be formed from the polymer composition. Such films may be used as gas separation membranes and may be submerged into water for extended periods without crazing and cracking. The polymer composition may also be used as a coating on substrates, such as metal and ceramics, or may be used for spinning fibers. Precursors for forming such polymer compositions are also disclosed.

  4. Design principle for increasing charge mobility of π-conjugated polymers using regularly localized molecular orbitals

    PubMed Central

    Terao, Jun; Wadahama, Akihisa; Matono, Akitoshi; Tada, Tomofumi; Watanabe, Satoshi; Seki, Shu; Fujihara, Tetsuaki; Tsuji, Yasushi

    2013-01-01

    The feasibility of using π-conjugated polymers as next-generation electronic materials is extensively studied; however, their charge mobilities are lower than those of inorganic materials. Here we demonstrate a new design principle for increasing the intramolecular charge mobility of π-conjugated polymers by covering the π-conjugated chain with macrocycles and regularly localizing π-molecular orbitals to realize an ideal orbital alignment for charge hopping. Based on theoretical predictions, insulated wires containing meta-junctioned poly(phenylene–ethynylene) as the backbone units were designed and synthesized. The zigzag wires exhibited higher intramolecular charge mobility than the corresponding linear wires. When the length of the linear region of the zigzag wires was increased to 10 phenylene–ethynylene units, the intramolecular charge mobility increased to 8.5 cm2 V−1 s−1. Theoretical analysis confirmed that this design principle is suitable for obtaining ideal charge mobilities in π-conjugated polymer chains and that it provides the most effective pathways for inter-site hopping processes. PMID:23575695

  5. A heparin-mimicking polymer conjugate stabilizes basic fibroblast growth factor

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi H.; Kim, Sung-Hye; Decker, Caitlin G.; Wong, Darice Y.; Loo, Joseph A.; Maynard, Heather D.

    2013-03-01

    Basic fibroblast growth factor (bFGF) is a protein that plays a crucial role in diverse cellular functions, from wound healing to bone regeneration. However, a major obstacle to the widespread application of bFGF is its inherent instability during storage and delivery. Here, we describe the stabilization of bFGF by covalent conjugation with a heparin-mimicking polymer, a copolymer consisting of styrene sulfonate units and methyl methacrylate units bearing poly(ethylene glycol) side chains. The bFGF conjugate of this polymer retained bioactivity after synthesis and was stable to a variety of environmentally and therapeutically relevant stressors—such as heat, mild and harsh acidic conditions, storage and proteolytic degradation—unlike native bFGF. Following the application of stress, the conjugate was also significantly more active than the control conjugate system in which the styrene sulfonate units were omitted from the polymer structure. This research has important implications for the clinical use of bFGF and for the stabilization of heparin-binding growth factors in general.

  6. Slow-Positron Generator For Studying Polymer Films

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; St. Clair, Terry L.; Eftekhari, Abe

    1992-01-01

    Aspects of molecular structures probed by positron-annihilation spectroscopy (PAS). Slow-positron-beam generator suitable for PAS measurements in thin polymer films. Includes Na22 source of positrons and two moderators made of well-annealed tungsten foil. With proper choice of voltage, positrons emitted by inward-facing surfaces of moderators made to stop in polymer films tested.

  7. Amplified spontaneous emission from the exciplex state of a conjugated polymer "PFO" in oleic acid

    NASA Astrophysics Data System (ADS)

    Idriss, Hajo; Taha, Kamal K.; Aldaghri, O.; Alhathlool, R.; AlSalhi, M. S.; Ibnaouf, K. H.

    2016-09-01

    The amplified spontaneous emission (ASE) characteristics of a conjugated polymer poly (9, 9-dioctylfluorenyl-2, 7-diyl) (PFO) in oleic acid have been studied under different concentrations and temperatures. Here, the ASE spectra of PFO in oleic acid have been obtained using a transverse cavity configuration where the conjugated PFO was pumped by laser pulses from the third harmonic of Nd: YAG laser (355 nm). The PFO in oleic acid produces ASE from an exciplex state - a new molecular species. The obtained results were compared with the PFO in benzene. Such ASE spectra from the exciplex state have not been observed for the PFO in benzene.

  8. Brownian dynamics simulations of charge mobility on conjugated polymers in solution

    NASA Astrophysics Data System (ADS)

    Albu, Nicolae M.; Yaron, David J.

    2013-06-01

    A model is developed for the mobility of a charge carrier along a conjugated polymer dissolved in solution, as measured by time-resolved microwave conductivity. Each unit cell of the polymer is assigned a torsional degree of freedom, with Brownian dynamics used to include the effects of solvent on the torsions. The barrier to torsional motion is substantially enhanced in the vicinity of the charge, leading to self-trapping of the charge onto a planarized region of the polymer chain. Within the adiabatic approximation used here, motion arises when regions of the polymer on either side of the charge fluctuate into planarity and the wavefunction spreads in the corresponding direction. Well-converged estimates for the mobility are obtained for model parameters where the adiabatic approximation holds. For the parameters expected for conjugated polymers, where crossing between electronic surfaces may lead to breakdown in the adiabatic approximation, estimates for the mobility are obtained via extrapolation. Nonadiabatic contributions from hopping between electronic surfaces are therefore ignored. The resulting mobility is inversely proportional to the rotational diffusion time, trot, of a single unit cell about the polymer axis in the absence of intramolecular forces. For trot of 75 ps, the long-chain mobility of poly(para-phenylene vinylene) is estimated to be between 0.09 and 0.4 cm2/Vs. This is in reasonable agreement with experimental values for the polymer, however, the nonadiabatic contribution to the mobility is not considered, nor are effects arising from stretching degrees of freedom or breaks in conjugation.

  9. Hot pen and laser writable photonic polymer films

    NASA Astrophysics Data System (ADS)

    Moirangthem, Monali; Stumpel, Jelle E.; Alp, Baran; Teunissen, Pit; Bastiaansen, Cees W. M.; Schenning, Albertus P. H. J.

    2016-03-01

    An orange-reflecting photonic polymer film has been fabricated based on a hydrogen-bonded cholesteric liquid crystalline (CLC) polymer consisting of non-reactive (R)-(+)-3-methyladipic acid as the chiral dopant. This polymer film can be patterned easily by evaporating the chiral dopant at specific locations with a hot pen or a laser beam. Removal of chiral dopant leads to a decrease in the helical pitch at the heat treated areas leading to a change in color from orange to green revealing a high contrast pattern. The photonic patterns are irreversible and stable at ambient conditions. This makes such a CLC polymer film interesting as writable photonic paper.

  10. Multivalent Polymers for Drug Delivery and Imaging: The Challenges of Conjugation

    PubMed Central

    2015-01-01

    Multivalent polymers offer a powerful opportunity to develop theranostic materials on the size scale of proteins that can provide targeting, imaging, and therapeutic functionality. Achieving this goal requires the presence of multiple targeting molecules, dyes, and/or drugs on the polymer scaffold. This critical review examines the synthetic, analytical, and functional challenges associated with the heterogeneity introduced by conjugation reactions as well as polymer scaffold design. First, approaches to making multivalent polymer conjugations are discussed followed by an analysis of materials that have shown particular promise biologically. Challenges in characterizing the mixed ligand distributions and the impact of these distributions on biological applications are then discussed. Where possible, molecular-level interpretations are provided for the structures that give rise to the functional ligand and molecular weight distributions present in the polymer scaffolds. Lastly, recent strategies employed for overcoming or minimizing the presence of ligand distributions are discussed. This review focuses on multivalent polymer scaffolds where average stoichiometry and/or the distribution of products have been characterized by at least one experimental technique. Key illustrative examples are provided for scaffolds that have been carried forward to in vitro and in vivo testing with significant biological results. PMID:25120091

  11. Photovoltaic properties of conjugated polymer/methanofullerene composites embedded in a polystyrene matrix

    NASA Astrophysics Data System (ADS)

    Brabec, C. J.; Padinger, F.; Sariciftci, N. S.; Hummelen, J. C.

    1999-05-01

    Bulk donor-acceptor heterojunctions between conjugated polymers and fullerene derivatives have been utilized successfully for photovoltaic devices showing monochromatic energy conversion efficiencies above 1%. The photovoltaic response of these devices is based on the ultrafast, photoinduced electron transfer from the conjugated polymer to the fullerene [N. S. Sariciftci and A. J. Heeger, Handbook of Organic Conductive Molecules and Polymers, (Wiley, New York, 1997), pp. 413-455]. In this work we present efficiency data of solar cells based on a soluble derivative of p-phenylene vinylene (PPV), poly [2-methoxy, 5-(3',7'-dimethyl-octyloxy)]-p-phenylene vinylene (MDMO-PPV), and a highly soluble methanofullerene, [6,6]-phenyl C61-butyric acid methyl ester (PCBM), embedded into a conventional polymer, polystyrene (PS). By the blending of the optimized donor-acceptor components into the conventional polymer matrix, the percolation threshold for photovoltaic response of the three component systems is found to be determined by percolation of the methanofullerene in the polymer matrix. We present current/voltage data of PS-MDMO-PPV-PCBM devices with various PS concentrations as well as photoinduced absorption studies in the infrared [(PIA) Fourier transform infrared] and light induced electron spin resonance studies on the electron transfer in these composites. At low light intensities, the monochromatic power conversion efficiency ηe and the photon carrier collection efficiency ηc of the PS free device are calculated with 1.5% and 18%, respectively.

  12. Random Conjugated Copolymers with Panchromatic Absorption for High-Efficiency Polymer Solar Cells

    NASA Astrophysics Data System (ADS)

    Jung, Jae Woong; Jo, Won Ho

    2013-03-01

    One of the most important issues for polymer solar cells (PSCs) is to develop conjugated polymers with broad light absorption, high mobility and appropriate orientation to provide effective pathways to electrode. Particularly, the broad light absorption of the polymer is important to enhance the power conversion efficiency because the limited absorption leads to low current in comparison with other inorganic-based solar cells. A fascinating approach to extend light absorption is the synthesis of copolymers composed of several chromophores. Among various building blocks, diketopyrrolo[3,4-c]pyrrole (DPP) and 6,6'-[3,3']biindolylidene-2,2'-dione (isoindigo) have attracted much interest since they are easily accessible and exhibit promising optoelectronic properties. Here, we report random conjugated copolymers consisting of DPP and isoindigo as co-electron acceptor of donor-acceptor conjugated polymer. The random copolymers exhibited not only broad light absorption but also low-lying HOMO levels. Also, the predominant face-on orientation of the copolymers is beneficial for vertical charge transport in PSCs. The combination of excellent optoelectrical properties and favorable molecular conformation makes copolymers promising candidate for active material in high performance PSCs.

  13. The electronic and transport properties of two-dimensional conjugated polymer networks including disorder

    NASA Astrophysics Data System (ADS)

    Adjizian, Jean-Joseph; Lherbier, Aurélien; M.-M. Dubois, Simon; Botello-Méndez, Andrés Rafael; Charlier, Jean-Christophe

    2016-01-01

    Two-dimensional (2D) conjugated polymers exhibit electronic structures analogous to that of graphene with the peculiarity of π-π* bands which are fully symmetric and isolated. In the present letter, the suitability of these materials for electronic applications is analyzed and discussed. In particular, realistic 2D conjugated polymer networks with a structural disorder such as monomer vacancies are investigated. Indeed, during bottom-up synthesis, these irregularities are unavoidable and their impact on the electronic properties is investigated using both ab initio and tight-binding techniques. The tight-binding model is combined with a real space Kubo-Greenwood approach for the prediction of transport characteristics for monomer vacancy concentrations ranging from 0.5% to 2%. As expected, long mean free paths and high mobilities are predicted for low defect densities. At low temperatures and for high defect densities, strong localization phenomena originating from quantum interferences of multiple scattering paths are observed in the close vicinity of the Dirac energy region while the absence of localization effects is predicted away from this region suggesting a sharp mobility transition. These predictions show that 2D conjugated polymer networks are good candidates to pave the way for the ultimate scaling and performances of future molecular nanoelectronic devices.Two-dimensional (2D) conjugated polymers exhibit electronic structures analogous to that of graphene with the peculiarity of π-π* bands which are fully symmetric and isolated. In the present letter, the suitability of these materials for electronic applications is analyzed and discussed. In particular, realistic 2D conjugated polymer networks with a structural disorder such as monomer vacancies are investigated. Indeed, during bottom-up synthesis, these irregularities are unavoidable and their impact on the electronic properties is investigated using both ab initio and tight-binding techniques. The

  14. Novel enzyme-polymer conjugates for biotechnological applications

    PubMed Central

    Romero, Oscar; Rivero, Cintia W.; Guisan, Jose M.

    2013-01-01

    In the present research, a rapid, simple and efficient chemoselective method for the site-directed incorporation of tailor-made polymers into protein to create biocatalysts with excellent properties for pharmaceutical industrial purpose has been performed. First we focused on the protein engineering of the Geobacillus thermocatenulatus lipase 2 (BTL2) to replace the two cysteines (Cys65, Cys296) in the wild type enzyme (BTL-WT) by two serines. Then, by similar mode, a unique cysteine was introduced in the lid area of the protein. For the site-directed polymer incorporation, a set of different tailor-made thiol-ionic-polymers were synthesized and the protein cysteine was previously activated with 2,2-dithiodipyridine (2-PDS) to allow the disulfide exchange. The protected BTL variants were specifically modified with the different polymers in excellent yields, creating a small library of new biocatalysts. Different and important changes in the catalytic properties, possible caused by structural changes in the lid region, were observed. The different modified biocatalysts were tested in the synthesis of intermediates of antiviral and antitumor drugs, like nucleoside analogues and derivatives of phenylglutaric acid. In the hydrolysis of per-acetylated thymidine, the best biocatalyst was the BTL*-193-DextCOOH , where the activity was increased in 3-fold and the regioselectivity was improved, reaching a yield of 92% of 3’-O-acetyl-thymidine. In the case of the asymmetric hydrolysis of dimethyl phenylglutarate, the best result was found with BTL*-193-DextNH2-6000, where the enzyme activity was increased more than 5-fold and the enantiomeric excess was >99%. PMID:23638362

  15. Measurements of Photo-induced Changes in Conjugated Polymers

    DOE R&D Accomplishments Database

    Seager, C. H.; Sinclair, M. B.; Mc Branch, D.; Heeger, A. J.; Baker, G. L.

    1991-01-01

    We have used the highly sensitive technique of Photothermal Deflection Spectroscopy (PDS) to measure changes in the infrared absorption spectra of MEHPPV, P3HT and Polydiacetylene-4BCMU induced by pumping these polymers with light above the {pi} - {pi}* transition energy. In contrast to previous chopped light transmission measurements of these effects, the PDS technique can directly measure the buildup or decay of the absorption coefficient, {alpha}, on the time scale of second to days. In the case of MEHPPV we observe that the time scale of seconds to days. In the case of MEHPPV we observe that above-gap light causes the appearance of a broad infrared peak in {alpha}, which continues to grow-in hours after the pump light is first applied. For this polymer the general shape of the absorption spectra in the unpumped state mimics the photo-induced changes, suggesting that remnant photo-induced states determine the maximum transparency observed under normal experimental conditions. For P3HT and to a lesser extent, MEHPPV, we also observe irreversible photo-induced absorption components which we tentatively identify with photo-induced oxidation of the polymer matrix.

  16. Selective Template Wetting Routes to Hierarchical Polymer Films: Polymer Nanotubes from Phase-Separated Films via Solvent Annealing.

    PubMed

    Ko, Hao-Wen; Cheng, Ming-Hsiang; Chi, Mu-Huan; Chang, Chun-Wei; Chen, Jiun-Tai

    2016-03-01

    We demonstrate a novel wetting method to prepare hierarchical polymer films with polymer nanotubes on selective regions. This strategy is based on the selective wetting abilities of polymer chains, annealed in different solvent vapors, into the nanopores of porous templates. Phase-separated films of polystyrene (PS) and poly(methyl methacrylate) (PMMA), two commonly used polymers, are prepared as a model system. After anodic aluminum oxide (AAO) templates are placed on the films, the samples are annealed in vapors of acetic acid, in which the PMMA chains are swollen and wet the nanopores of the AAO templates selectively. As a result, hierarchical polymer films containing PMMA nanotubes can be obtained after the AAO templates are removed. The distribution of the PMMA nanotubes of the hierarchical polymer films can also be controlled by changing the compositions of the polymer blends. This work not only presents a novel method to fabricate hierarchical polymer films with polymer nanotubes on selective regions, but also gives a deeper understanding in the selective wetting ability of polymer chains in solvent vapors. PMID:26831764

  17. Precursors for the polymer-assisted deposition of films

    DOEpatents

    McCleskey, Thomas M.; Burrell, Anthony K.; Jia, Quanxi; Lin, Yuan

    2013-09-10

    A polymer assisted deposition process for deposition of metal oxide films is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures to yield metal oxide films. Such films can be epitaxial in structure and can be of optical quality. The process can be organic solvent-free.

  18. Time-dependent energy transfer rates in a conjugated polymer guest-host system

    NASA Astrophysics Data System (ADS)

    Herz, L. M.; Silva, C.; Grimsdale, A. C.; Müllen, K.; Phillips, R. T.

    2004-10-01

    We have investigated the energy transfer dynamics in films of a conjugated polyindenofluorene host doped with covalently attached perylene guests. By performing time-resolved measurements of the host luminescence decay under site-selective excitation conditions, we have examined the influence of exciton migration within the host on the temporal evolution of the host-guest energy transfer. We find that highly mobile excitons created at the peak of the host’s inhomogeneous density of states transfer to guests considerably faster than more localized excitons created in the low-energy tail, indicating a strong contribution of exciton migration to the overall energy transfer. These effects are significantly more pronounced at low temperature (7K) than at ambient temperature, suggesting that for the latter, up-hill migration of excitons in the host and a broadening of their homogeneous linewidth may prevent truly site-selective excitation of localized excitons. In the asymptotic long-time limit, the observed dynamics are compatible with long-range single-step Förster energy transfer. However, at early times (≲10ps) after excitation, the behavior notably deviates from this description, suggesting that diffusion-assisted energy transfer is more important in this regime. The measured changes in excitation transfer rates with temperature and excitation energy correlate well with those observed for the dynamic energy shifts of the vibronic emission peaks from the undoped polymer. Our results therefore indicate that energy-transfer rates in polymeric guest-host systems are strongly time-dependent, owing to a contribution both from exciton relaxation through incoherent hopping within the host’s density of states and direct Förster energy transfer.

  19. Self-Assembly of Differently Shaped Protein-Polymer Conjugates through Modification of the Bioconjugation Site.

    PubMed

    Huang, Aaron; Olsen, Bradley D

    2016-08-01

    Self-assembly of protein-polymer block copolymers is an attractive route for preparing biocatalytic materials. To clarify the effect of bioconjugate shape on self-assembly without changing the chemical details of either block, four different conjugation sites are selected on the surface of the model globular protein mCherry at residues 3, 108, 131, and 222 to alter the colloidal shape of the bioconjugate. All four mCherry-b-poly(N-isopropylacrylamide) bioconjugates show qualitatively similar phase diagrams, indicating that self-assembly is robust with respect to changes in conjugation site. However, protein orientation has an effect on the location of the order-disorder transition concentration, and the stability of the disordered micellar phase is shown to be different for each conjugate. Differences in domain spacing also suggest changes in protein orientation within the lamellae. PMID:27322114

  20. Renewable Cathode Materials from Biopolymer/Conjugated Polymer Interpenetrating Networks

    NASA Astrophysics Data System (ADS)

    Milczarek, Grzegorz; Inganäs, Olle

    2012-03-01

    Renewable and cheap materials in electrodes could meet the need for low-cost, intermittent electrical energy storage in a renewable energy system if sufficient charge density is obtained. Brown liquor, the waste product from paper processing, contains lignin derivatives. Polymer cathodes can be prepared by electrochemical oxidation of pyrrole to polypyrrole in solutions of lignin derivatives. The quinone group in lignin is used for electron and proton storage and exchange during redox cycling, thus combining charge storage in lignin and polypyrrole in an interpenetrating polypyrrole/lignin composite.

  1. Delocalization in weakly coupled disordered wires: application to conjugated polymers.

    PubMed

    Martens, H C F

    2006-02-24

    It is well known that even for minimal disorder one-dimensional wires are insulators: all 1D electron states are localized. Here, the influence of interwire coupling on delocalization of 1D states is examined. Based on perturbation theoretic arguments for the formation of 3D states in coupled wires and subsequent scaling analysis, practical expressions for the microscopic conditions of electronic delocalization and coherent conductivity of coupled 1D wires are obtained. The model quantitatively explains the temperature dependent dc conductivity in conducting polymers at both sides of the metal-insulator transition and links the experimental data to microscopic material parameters. PMID:16606118

  2. Stimulation of immune systems by conjugated polymers and their potential as an alternative vaccine adjuvant

    NASA Astrophysics Data System (ADS)

    Gong, Hua; Xiang, Jian; Xu, Ligeng; Song, Xuejiao; Dong, Ziliang; Peng, Rui; Liu, Zhuang

    2015-11-01

    Recently, conjugated polymers have been widely explored in the field of nanomedicine. Careful evaluations of their biological effects are thus urgently needed. Hereby, we systematically evaluated the biological effects of different types of conjugated polymers on macrophages and dendritic cells (DCs), which play critical roles in the innate and adaptive immune systems, respectively. While naked poly-(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) exhibits a high level of cytotoxicity, polyethylene glycol (PEG) modified PEDOT:PSS (PEDOT:PSS-PEG) shows greatly reduced toxicity to various types of cells. To our surprise, PEGylation of PEDOT:PSS could obviously enhance the cellular uptake of these nanoparticles, leading to subsequent immune stimulations of both macrophages and DCs. In contrast, another type of conjugated polymer, polypyrrole (PPy), is found to be an inert material with neither significant cytotoxicity nor noticeable immune-stimulation activity. Interestingly, utilizing ovalbumin (OVA) as a model antigen, it is further uncovered in our ex vivo experiment that PEDOT:PSS-PEG may serve as an adjuvant to greatly enhance the immunogenicity of OVA upon simple mixing. Our study on the one hand suggests the promise of developing novel nano-adjuvants based on conjugated polymers, and on the other hand highlights the importance of careful evaluations of the impacts of any new nanomaterials developed for nanomedicine on the immune systems.Recently, conjugated polymers have been widely explored in the field of nanomedicine. Careful evaluations of their biological effects are thus urgently needed. Hereby, we systematically evaluated the biological effects of different types of conjugated polymers on macrophages and dendritic cells (DCs), which play critical roles in the innate and adaptive immune systems, respectively. While naked poly-(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) exhibits a high level of cytotoxicity

  3. Reversible Supramolecular Surface Attachment of Enzyme-Polymer Conjugates for the Design of Biocatalytic Filtration Membranes.

    PubMed

    Moridi, Negar; Corvini, Philippe F-X; Shahgaldian, Patrick

    2015-12-01

    To be used successfully in continuous reactor systems, enzymes must either be retained using filtration membranes or immobilized on a solid component of the reactor. Whereas the first approach requires large amounts of energy, the second approach is limited by the low temporal stability of enzymes under operational conditions. To circumvent these major stumbling blocks, we have developed a strategy that enables the reversible supramolecular immobilization of bioactive enzyme-polymer conjugates at the surface of filtration membranes. The polymer is produced through a reversible addition-fragmentation transfer method; it contains multiple adamantyl moieties that are used to bind the resulting conjugate at the surface of the membrane which has surface-immobilized cyclodextrin macrocycles. This supramolecular modification is stable under operational conditions and allows for efficient biocatalysis, and can be reversed by competitive host-guest interactions. PMID:26461451

  4. Research on the electronic and optical properties of polymer and other organic molecular thin films

    SciTech Connect

    1997-02-01

    The main goal of the work is to find materials and methods of optimization of organic layered electroluminescent cells and to study such properties of polymers and other organic materials that can be used in various opto-electronic devices. The summary of results obtained during the first year of work is presented. They are: (1) the possibility to produce electroluminescent cells using a vacuum deposition photoresist technology for commercial photoresists has been demonstrated; (2) the idea to replace the polyaryl polymers by other polymers with weaker hole conductivity for optimization of electroluminescent cells with ITO-Al electrodes has been suggested. The goal is to obtain amorphous processable thin films of radiative recombination layers in electroluminescent devices; (3) procedures of preparation of high-quality vacuum-deposited poly (p-phenylene) (PPP) films on various substrates have been developed; (4) it was found for the first time that the fluorescence intensity of PPP films depends on the degree of polymerization; (5) the role of interfaces between organic compounds, on one side, and metals or semiconductors, on the other side, has been studied and quenching of the fluorescence caused by semiconductor layer in thin sandwiches has been observed; (6) studies of the dynamics of photoexcitations revealed the exciton self-trapping in quasi-one-dimensional aggregates; and (7) conditions for preparation of highly crystalline fullerene C{sub 60} films by vacuum deposition have been found. Composites of C{sub 60} with conjugated polymers have been prepared.

  5. Preparation of redox polymer cathodes for thin film rechargeable batteries

    DOEpatents

    Skotheim, Terje A.; Lee, Hung S.; Okamoto, Yoshiyuki

    1994-11-08

    The present invention relates to the manufacture of thin film solid state electrochemical devices using composite cathodes comprising a redox polymer capable of undergoing oxidation and reduction, a polymer solid electrolyte and conducting carbon. The polymeric cathode material is formed as a composite of radiation crosslinked polymer electrolytes and radiation crosslinked redox polymers based on polysiloxane backbones with attached organosulfur side groups capable of forming sulfur-sulfur bonds during electrochemical oxidation.

  6. Electroluminescence from multilayer conjugated polymer devices: Spatial control of exciton formation and emission

    NASA Astrophysics Data System (ADS)

    Brown, A. R.; Greenham, N. C.; Burroughes, J. H.; Bradley, D. D. C.; Friend, R. H.; Burn, P. L.; Kraft, A.; Holmes, A. B.

    1992-11-01

    We have constructed electroluminescent diodes using several layers of conjugated polymers with differing band gaps; these provide a range of different colour light-emitting layers and can be used to control charge injection and transport. Poly(1,4-phenylenevinylene, PPV, and derivatives have been used, with indium/tin oxide as hole-injecting layer and calcium as electron-injecting contact layer. For this selection of materials, we show that the ordering of the polymer layers allows control of the colour of device emission. Emission can be produced in more than one layer.

  7. Charge carrier motion in disordered conjugated polymers: a multiscale ab-initio study

    SciTech Connect

    Vukmirovic, Nenad; Wang, Lin-Wang

    2009-11-10

    We developed an ab-initio multiscale method for simulation of carrier transport in large disordered systems, based on direct calculation of electronic states and electron-phonon coupling constants. It enabled us to obtain the never seen before rich microscopic details of carrier motion in conjugated polymers, which led us to question several assumptions of phenomenological models, widely used in such systems. The macroscopic mobility of disordered poly(3- hexylthiophene) (P3HT) polymer, extracted from our simulation, is in agreement with experimental results from the literature.

  8. Targeted conjugation of breast anticancer drug tamoxifen and its metabolites with synthetic polymers.

    PubMed

    Sanyakamdhorn, S; Agudelo, D; Bekale, L; Tajmir-Riahi, H A

    2016-09-01

    Conjugation of antitumor drug tamoxifen and its metabolites, 4-hydroxytamxifen and ednoxifen with synthetic polymers poly(ethylene glycol) (PEG), methoxypoly (ethylene glycol) polyamidoamine (mPEG-PAMAM-G3) and polyamidoamine (PAMAM-G4) dendrimers was studied in aqueous solution at pH 7.4. Multiple spectroscopic methods, transmission electron microscopy (TEM) and molecular modeling were used to characterize the drug binding process to synthetic polymers. Structural analysis showed that drug-polymer binding occurs via both H-bonding and hydrophobic contacts. The order of binding is PAMAM-G4>mPEG-PAMAM-G3>PEG-6000 with 4-hydroxttamoxifen forming more stable conjugate than tamoxifen and endoxifen. Transmission electron microscopy showed significant changes in carrier morphology with major changes in the shape of the polymer aggregate as drug encapsulation occurred. Modeling also showed that drug is located in the surface and in the internal cavities of PAMAM with the free binding energy of -3.79 for tamoxifen, -3.70 for 4-hydroxytamoxifen and -3.69kcal/mol for endoxifen, indicating of spontaneous drug-polymer interaction at room temperature. PMID:27137803

  9. Optically detected magnetic resonance studies on {pi}-conjugate polymers and novel carbon allotropes

    SciTech Connect

    Partee, J.

    1999-02-12

    This report describes the following: introduction to photoluminescence detected magnetic resonance (PLDMR); introduction to {pi}-conjugated systems; PLDMR measurements on poly(p-phenylene)-type ladder polymers; PLMDR measurements on poly(p-phenylene ethylene); and PLDMR measurements on C{sub 70}, polythiophene, poly(p-phenylene vinylene) and Dan-40. Appendices to this report describe: Operation of ODMR (optically detected magnetic resonance) spectrometer; ODMR system parameters; and Special purpose circuitry.

  10. Broadband optical limiting and nonlinear optical absorption properties of a novel hyperbranched conjugated polymer

    NASA Astrophysics Data System (ADS)

    Li, Chao; Liu, Chunling; Li, Quanshui; Gong, Qihuang

    2004-12-01

    The nonlinear transmittance of a novel hyperbranched conjugated polymer named DMA-HPV has been measured in CHCl 3 solution using a nanosecond optical parametric oscillator. DMA-HPV shows excellent optical limiting performance in the visible region from 490 to 610 nm. An explanation based on the combination of two-photon absorption and reverse saturable absorption was proposed for its huge and broadband nonlinear optical absorption.

  11. Ionic two photon states and optical nonlinearity in. pi. -conjugated polymers

    SciTech Connect

    Dixit, S.N. ); Guo, D.; Mazumdar, S. . Dept. of Physics)

    1990-11-06

    A microscopic mechanism of optical nonlinearity in {pi}-conjugated polymers is presented. It is shown that the bulk of the nonlinearity is determined by only two well defined channels, even though an infinite number of channels are possible in principle. The above conclusion is true for both short and long range Coulomb interactions. The complete frequency dependence of the third harmonic generation in both trans-polyacetylene and polydiacetylene are explained within the same theoretical picture. 19 refs., 4 figs.

  12. Graphene oxide-cationic polymer conjugates: Synthesis and application as gene delivery vectors.

    PubMed

    Teimouri, Mohsen; Nia, Azadeh Hashem; Abnous, Khalil; Eshghi, Hossein; Ramezani, Mohammad

    2016-01-01

    Nanomedicine as the interface between nanotechnology and medical sciences is a new area that has attracted the attention of vast groups of researchers. Carbon nanomaterials are common platform for synthesis of nanoparticles for biomedical applications due to their low cytotoxicity and feasible internalization into mammalian cell lines (Yang et al., 2007; Arora et al., 2014; Oh and Park, 2014). Synthesis of vectors based on various cationic polymers polyethylenimine (PEI), polypropylenimine (PPI) and polyamidoamine (PAMAM) and their derivatives were considered as a strategy for transferring plasmid DNA and treatment of genetic diseases. Considering the low cytotoxicity of graphene, chemical modification of its surface has led to fabrication of novel gene delivery systems based on graphene and graphene oxide. Herein we report the synthesis of three groups of vectors based on conjugation of graphene oxide (GO) with alkylated derivatives of three different cationic polymers (polyethylenimine (PEI), polypropylenimine (PPI) and polyamidoamine (PAMAM)) through different linkers including surface carboxyl group, glycine and spermidine. Two main challenges in design of gene delivery vectors is decreasing cytotoxicity while improving the transfection efficiency. All synthesized vectors showed significantly lower cellular toxicity compared to bare polymer. A plasmid encoding green fluorescent protein (GFP) was used to evaluate the transfection efficiency of nanoparticles both qualitatively using live cell fluorescent imaging and quantitatively using flow cytometry and each vector was compared to its polymer base. Most successful conjugation strategy was observed in the case of PEI conjugates among which most efficient vector was PEI-GO conjugate bearing glycine linker. This vector was 9 fold more effective in terms of the percent of EGFP transfected cells. PMID:27072918

  13. Spectral engineering in π-conjugated polymers with intramolecular donor-acceptor interactions.

    PubMed

    Beaujuge, Pierre M; Amb, Chad M; Reynolds, John R

    2010-11-16

    With the development of light-harvesting organic materials for solar cell applications and molecular systems with fine-tuned colors for nonemissive electrochromic devices (e.g., smart windows, e-papers), a number of technical challenges remain to be overcome. Over the years, the concept of "spectral engineering" (tailoring the complex interplay between molecular physics and the various optical phenomena occurring across the electromagnetic spectrum) has become increasingly relevant in the field of π-conjugated organic polymers. Within the spectral engineering toolbox, the "donor-acceptor" approach uses alternating electron-rich and electron-deficient moieties along a π-conjugated backbone. This approach has proved especially valuable in the synthesis of dual-band and broadly absorbing chromophores with useful photovoltaic and electrochromic properties. In this Account, we highlight and provide insight into a present controversy surrounding the origin of the dual band of absorption sometimes encountered in semiconducting polymers structured using the "donor-acceptor" approach. Based on empirical evidence, we provide some schematic representations to describe the possible mechanisms governing the evolution of the two-band spectral absorption observed on varying the relative composition of electron-rich and electron-deficient substituents along the π-conjugated backbone. In parallel, we draw attention to the choice of the method employed to estimate and compare the absorption coefficients of polymer chromophores exhibiting distinct repeat unit lengths, and containing various extents of solubilizing side-chains along their backbone. Finally, we discuss the common assumption that "donor-acceptor" systems should have systematically lower absorption coefficients than their "all-donor" counterparts. The proposed models point toward important theoretical parameters which could be further explored at the macromolecular level to help researchers take full advantage of the

  14. Nanocomposites obtained by embedding of conjugated polymers in porous silicon and silica

    NASA Astrophysics Data System (ADS)

    Errien, N.; Vellutini, L.; Froyer, G.; Louarn, G.; Simos, C.; Skarka, V.; Haesaert, S.; Joubert, P.

    2005-06-01

    Porous silicon and porous silica matrices are filled up by conjugated polymers in order to obtain nanocomposite with enhanced third order optical nonlinearity. The active component is either PDA-TS thermally polymerized in situ or PT12 electropolymerized in porous silicon. The first measurements of the nonlinear properties of these nanocomposites give evidence of a significant increase of the nonlinear refractive index with respect to the standard optical materials.

  15. Synthesis and evaluation of optical and electrochemical properties of a new conjugated polymer containing substituted thiophene and non-conjugation linkers

    NASA Astrophysics Data System (ADS)

    R, Prashanth Kumar K.; D, Udayakumar; K, Siji Narendran N.; K, Chandrasekharan

    2014-10-01

    Conjugated polymers have been developed in a variety of applied fields owing to their promising optoelectronic properties. These are pursuing considerable interest as opto-electrical material because of their chemical stability and processability. This paper describes the synthesis and study of electro-optical properties of a new donoracceptor polymer composed of substituted thiophene and 4,4'-propane-2,2-diyldiphenol units as electron rich moieties and 1,3,4-oxadiazole unit as electron deficient moiety. The optical properties of the polymer are studied using UV-visible absorption spectroscopy and fluorescent emission spectroscopy. From the electrochemical data, HOMO and LUMO energy levels of the polymer are calculated.

  16. Self-assembly of Open-Shell-containing Block Polymer Thin Films

    NASA Astrophysics Data System (ADS)

    Boudouris, Bryan; Rostro, Lizbeth; Baradwaj, Aditya; Laster, Jennifer

    Radical polymers, where a stable open-shell group is present on each repeat unit of a non-conjugated macromolecular backbone, are emerging as promising materials in organic electronic and magnetic applications. As such, designing molecular motifs that allow for the self-assemble of these open-shell species into nanostructured domains could be beneficial in a host of next-generation flexible electronic applications. In addition, the relatively flexible nature of their macromolecular backbone and ability to conduct charge in the amorphous state offer distinct advantages regarding their self-assembly relative to block polymers based on conjugated semiconducting polymers. Here, we demonstrate the controlled synthesis and self-assembly of diblock copolymers containing radical polymer moieties. In fact, we show that A-B diblock copolymers, where the A moiety contains nitroxide radical functionalities and the B moiety is a closed-shell, low glass transition temperature polymer, self-assemble into ordered structures with domain spacing values that are consistent with common coil-coil diblock copolymers (d = 30 nm). In this way, we present a means by which to readily generate electronically-active macromolecules that self-assemble into nanostructured thin films with controlled morphologies over long ranges.

  17. Energetics of conjugated polymer and electrode interfaces in light emitting diode

    NASA Astrophysics Data System (ADS)

    Hwang, Jaehyung

    Recently, polymers have emerged as strong candidates for various semiconductor device applications. The physical and electrical properties of these polymer semiconductors are drastically different from those of inorganic semiconductors, and a solid understanding of these properties is necessary in order to further develop polymer electronics. This work concentrates on polymers for light emitting diode (LED) devices, which is the most promising application in polymer electronics. Understanding and control of charge injection from anode/cathode to active (light emitting) layer are crucial for high efficiency LED. To understand the charge injection efficiency, the energy band alignment and their impact on charge injection at polymer-electrode interfaces are investigated with a range of electron spectroscopies and electrical measurements. First, electronic structure of the best known hole injecting polymer (i.e., anode), poly(3,4-ethylene-dioxythiophene) -- poly(styrene-sulfonate) (PEDOT-PSS) is studied. We investigate the unique shell -- like structure of the PEDOT-PSS and its impact on the electrical properties. The role of PSS surface layer in enhancing the hole injection efficiency into the active layer is discussed. The electronic structures of two light emitting conjugated polymers, poly(9,9'-dioctylfluorene) (F8, also known as PFO) and poly(9,9'-dioctylfluorene- co-bis-N,N'-(4-butylphenyl) diphenylamine) (TFB), are also studied by various methods. The alignment of the energy levels at the anode and the cathode interfaces is investigated in detail. Different mechanisms seem to apply for the energy level alignment at the anode and the cathode. We discuss the difference in the light of different degrees of contamination at the interface which results from different processing conditions. Finally, a modification of energetics of polymer-anode interface by doping is discussed. We propose a co-solution doping method suitable for solution processed polymer material

  18. The electronic and transport properties of two-dimensional conjugated polymer networks including disorder.

    PubMed

    Adjizian, Jean-Joseph; Lherbier, Aurélien; M-M Dubois, Simon; Botello-Méndez, Andrés Rafael; Charlier, Jean-Christophe

    2016-01-21

    Two-dimensional (2D) conjugated polymers exhibit electronic structures analogous to that of graphene with the peculiarity of π-π* bands which are fully symmetric and isolated. In the present letter, the suitability of these materials for electronic applications is analyzed and discussed. In particular, realistic 2D conjugated polymer networks with a structural disorder such as monomer vacancies are investigated. Indeed, during bottom-up synthesis, these irregularities are unavoidable and their impact on the electronic properties is investigated using both ab initio and tight-binding techniques. The tight-binding model is combined with a real space Kubo-Greenwood approach for the prediction of transport characteristics for monomer vacancy concentrations ranging from 0.5% to 2%. As expected, long mean free paths and high mobilities are predicted for low defect densities. At low temperatures and for high defect densities, strong localization phenomena originating from quantum interferences of multiple scattering paths are observed in the close vicinity of the Dirac energy region while the absence of localization effects is predicted away from this region suggesting a sharp mobility transition. These predictions show that 2D conjugated polymer networks are good candidates to pave the way for the ultimate scaling and performances of future molecular nanoelectronic devices. PMID:26692370

  19. Rational Design of Porous Conjugated Polymers and Roles of Residual Palladium for Photocatalytic Hydrogen Production.

    PubMed

    Li, Lianwei; Cai, Zhengxu; Wu, Qinghe; Lo, Wai-Yip; Zhang, Na; Chen, Lin X; Yu, Luping

    2016-06-22

    Developing highly efficient photocatalyts for water splitting is one of the grand challenges in solar energy conversion. Here, we report the rational design and synthesis of porous conjugated polymer (PCP) that photocatalytically generates hydrogen from water splitting. The design mimics natural photosynthetics systems with conjugated polymer component to harvest photons and the transition metal part to facilitate catalytic activities. A series of PCPs have been synthesized with different light harvesting chromophores and transition metal binding bipyridyl (bpy) sites. The photocatalytic activity of these bpy-containing PCPs can be greatly enhanced due to the improved light absorption, better wettability, local ordering structure, and the improved charge separation process. The PCP made of strong and fully conjugated donor chromophore DBD (M4) shows the highest hydrogen production rate at ∼33 μmol/h. The results indicate that copolymerization between a strong electron donor and weak electron acceptor into the same polymer chain is a useful strategy for developing efficient photocatalysts. This study also reveals that the residual palladium in the PCP networks plays a key role for the catalytic performance. The hydrogen generation activity of PCP photocatalyst can be further enhanced to 164 μmol/h with an apparent quantum yield of 1.8% at 350 nm by loading 2 wt % of extra platinum cocatalyst. PMID:27254306

  20. Metalizable Polymer Thin Films in Supercritical Carbon Dioxide

    SciTech Connect

    Koga,T.; Jerome, J.; Rafailovich, M.; Sokolov, J.; Gordon, C.

    2005-01-01

    We report an environmentally 'green' method to improve adhesion at a polymer/metal interface by using supercritical carbon dioxide (scCO 2 ). Spun-cast polystyrene (PS) and poly(methyl methacrylate) (PMMA) thin films on cleaned Si wafers were used for this study. Film thicknesses of both polymer films were prepared in the range of 100 Angstroms to 1600 Angstroms. We exposed the films to scCO 2 in the pressure-temperature (P-T) range corresponding to the density-fluctuation ridge, where the excess swelling of both polymer films occurred, and then froze the swollen structures by quick evaporation of CO2. A chromium (Cr) layer with film thickness of 300-400 Angstroms was deposited onto the exposed film by using an E-beam evaporator. X-ray reflectivity (XR) measurements showed that the interfacial width between the Cr and exposed polymer layers increased by a factor of about two compared with that without exposure to scCO 2. In addition, the large interfacial broadening was found to occur irrespective of the thickness of both polymer films. After the XR measurements, the dewetting structures of the PS/Cr films induced by additional annealing were characterized by using atomic force microscopy, showing improved surface morphology in the exposed films. Contact angle measurements showed that a decrease in interfacial tension with exposure to scCO 2 accompanied the increase in interfacial width.

  1. Slip effects in polymer thin films.

    PubMed

    Bäumchen, O; Jacobs, K

    2010-01-27

    Probing the fluid dynamics of thin films is an excellent tool for studying the solid/liquid boundary condition. There is no need for external stimulation or pumping of the liquid, due to the fact that the dewetting process, an internal mechanism, acts as a driving force for liquid flow. Viscous dissipation, within the liquid, and slippage balance interfacial forces. Thus, friction at the solid/liquid interface plays a key role towards the flow dynamics of the liquid. Probing the temporal and spatial evolution of growing holes or retracting straight fronts gives, in combination with theoretical models, information on the liquid flow field and, especially, the boundary condition at the interface. We review the basic models and experimental results obtained during the last several years with exclusive regard to polymers as ideal model liquids for fluid flow. Moreover, concepts that aim to explain slippage on the molecular scale are summarized and discussed. PMID:21386275

  2. Use of side-chain for rational design of n-type diketopyrrolopyrrole-based conjugated polymers: what did we find out?

    PubMed

    Kanimozhi, Catherine; Yaacobi-Gross, Nir; Burnett, Edmund K; Briseno, Alejandro L; Anthopoulos, Thomas D; Salzner, Ulrike; Patil, Satish

    2014-08-28

    The primary role of substituted side chains in organic semiconductors is to increase their solubility in common organic solvents. In the recent past, many literature reports have suggested that the side chains play a critical role in molecular packing and strongly impact the charge transport properties of conjugated polymers. In this work, we have investigated the influence of side-chains on the charge transport behavior of a novel class of diketopyrrolopyrrole (DPP) based alternating copolymers. To investigate the role of side-chains, we prepared four diketopyrrolopyrrole-diketopyrrolopyrrole (DPP-DPP) conjugated polymers with varied side-chains and carried out a systematic study of thin film microstructure and charge transport properties in polymer thin-film transistors (PTFTs). Combining results obtained from grazing incidence X-ray diffraction (GIXD) and charge transport properties in PTFTs, we conclude side-chains have a strong influence on molecular packing, thin film microstructure, and the charge carrier mobility of DPP-DPP copolymers. However, the influence of side-chains on optical properties was moderate. The preferential "edge-on" packing and dominant n-channel behavior with exceptionally high field-effect electron mobility values of >1 cm(2) V(-1) s(-1) were observed by incorporating hydrophilic (triethylene glycol) and hydrophobic side-chains of alternate DPP units. In contrast, moderate electron and hole mobilities were observed by incorporation of branched hydrophobic side-chains. This work clearly demonstrates that the subtle balance between hydrophobicity and hydrophilicity induced by side-chains is a powerful strategy to alter the molecular packing and improve the ambipolar charge transport properties in DPP-DPP based conjugated polymers. Theoretical analysis supports the conclusion that the side-chains influence polymer properties through morphology changes, as there is no effect on the electronic properties in the gas phase. The exceptional

  3. Pressure Modulation of Backbone Conformation and Intermolecular Distance of Conjugated Polymers Toward Understanding the Dynamism of π-Figuration of their Conjugated System.

    PubMed

    Noguchi, Yuki; Saeki, Akinori; Fujiwara, Takenori; Yamanaka, Sho; Kumano, Masataka; Sakurai, Tsuneaki; Matsuyama, Naoto; Nakano, Motohiro; Hirao, Naohisa; Ohishi, Yasuo; Seki, Shu

    2015-06-18

    Continuous tuning of the backbone conformation and interchain distance of a π-conjugated polymer is an essential prerequisite to unveil the inherent electrical and optical features of organic electronics. To this end, applying pressure in a hydrostatic medium or diamond anvil cell is a facile approach without the need for side-chain synthetic engineering. We report the development of high-pressure, time-resolved microwave conductivity (HP-TRMC) and evaluation of transient photoconductivity in the regioregular poly(3-hexylthiophene) (P3HT) film and its bulk heterojunction blend with methanofullerene (PCBM). X-ray diffraction experiments under high pressure were performed to detail the pressure dependence of π-stacking and interlamellar distances in P3HT crystallites and PCBM aggregates. The HP-TRMC results were further correlated with high-pressure Raman spectroscopy and density functional theory calculation. The increased HP-TRMC conductivity of P3HT under pressure was found to be relevant to the planarity of the backbone conformation and intramolecular hole mobility. The effects of pressure on the backbone planarity are estimated to be ∼0.3 kJ mol(-1) based on the compressibility derived from the X-ray diffraction under high pressure, suggesting the high enough energy to cause modulation of the planarity in terms of the Landau-de Gennes free energy of isolated P3HT chains as 0.23 kJ mol(-1). In contrast, the P3HT:PCBM blend showed a simple decrease in photoconductivity irrespective of the identical compressive behavior of P3HT. A mechanistic insight into the interplay of intra- and intermolecular mobilities is a key to tailoring the dynamic π-figuration associated with electrical properties, which may lead to the use of HP-TRMC for exploring divergent π-conjugated materials at the desired molecular arrangement and conformation. PMID:25563063

  4. RESEARCH ON THE ELECTRONIC AND OPTICAL PROPERTIES OF POLYMER AND OTHER ORGANIC MOLECULAR THIN FILMS

    SciTech Connect

    ALEXEI G. VITUKHNOVSKY; IGOR I. SOBELMAN - RUSSIAN ACADEMY OF SCIENCES

    1995-09-06

    Optical properties of highly ordered films of poly(p-phenylene) (PPP) on different substrates, thin films of mixtures of conjugated polymers, of fullerene and its composition with polymers, molecular J-aggregates of cyanine dyes in frozen matrices have been studied within the framework of the Agreement. Procedures of preparation of high-quality vacuum deposited PPP films on different substrates (ITO, Si, GaAs and etc.) were developed. Using time-correlated single photon counting technique and fluorescence spectroscopy the high quality of PPP films has been confirmed. Dependence of structure and optical properties on the conditions of preparation were investigated. The fluorescence lifetime and spectra of highly oriented vacuum deposited PPP films were studied as a function of the degree of polymerization. It was shown for the first time that the maximum fluorescence quantum yield is achieved for the chain length approximately equal to 35 monomer units. The selective excitation of luminescence of thin films of PPP was performed in the temperature range from 5 to 300 K. The total intensity of luminescence monotonically decreases with decreasing temperature. Conditions of preparation of highly cristallyne fullerene C{sub 60} films by the method of vacuum deposition were found. Composites of C{sub 60} with conjugated polymers PPV and polyacetylene (PA) were prepared. The results on fluorescence quenching, IR and resonant Raman spectroscopy are consistent with earlier reported ultrafast photoinduced electron transfer from PPV to C{sub 60} and show that the electron transfer is absent in the case of the PA-C{sub 60} composition. Strong quenching of PPV fluorescence was observed in the PPV-PA blends. The electron transfer from PPV to PA can be considered as one of the possible mechanisms of this quenching. The dynamics of photoexcitations in different types of J-aggregates of the carbocyanine dye was studied at different temperatures in frozen matrices. The optical

  5. Charge carrier mobility in conjugated organic polymers: simulation of an electron mobility in a carbazole-benzothiadiazole-based polymer

    NASA Astrophysics Data System (ADS)

    Li, Yaping; Lagowski, Jolanta B.

    2011-08-01

    Inorganic (mostly silicon based) solar cells are important devices that are used to solve the world energy and environmental needs. Now days, organic solar cells are attracting considerable attention in the field of photovoltaic cells because of their low cost and processing flexibility. Often conjugated polymers are used in the construction of the organic solar cells. We study the conjugated polymers' charge transport using computational approach that involves the use of the density functional theory (DFT), semiempirical (ZINDO), and Monte Carlo (MC) theoretical methods in order to determine their transfer integrals, reorganization energies, transfer rates (with the use of Marcus-Hush equation) and mobilities. We employ the experimentally determined three dimensional (3D) structure of poly(9,9'-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) to estimate the electron mobility in a similar co-alternating polymer consisting of carbazole and benzothiadiazole units (C8BT). In agreement with our previous work, we found that including an orientational disorder in the crystal reduces the electron mobility in C8BT. We hope that the proposed computational approach can be used to predict charge mobility in organic materials that are used in solar cells.

  6. Interfacial exciplex formation in bilayers of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Nobuyasu, R. S.; Araujo, K. A. S.; Cury, L. A.; Jarrosson, T.; Serein-Spirau, F.; Lère-Porte, J.-P.; Dias, F. B.; Monkman, A. P.

    2013-10-01

    The donor-acceptor interactions in sequential bilayer and blend films are investigated. Steady-state and time-resolved photoluminescence (PL) were measured to characterize the samples at different geometries of photoluminescence collection. At standard excitation, with the laser incidence at 45° of the normal direction of the sample surface, a band related to the aggregate states of donor molecules appears for both blend and bilayer at around 540 nm. For the PL spectra acquired from the edge of the bilayer, with the laser incidence made at normal direction of the sample surface (90° geometry), a new featureless band emission, red-shifted from donor and acceptor emission regions was observed and assigned as the emission from interfacial exciplex states. The conformational complexity coming from donor/acceptor interactions at the heterojunction interface of the bilayer is at the origin of this interfacial exciplex emission.

  7. New paradigm for stabilization of liquid polymer films on solids

    NASA Astrophysics Data System (ADS)

    Koga, Tad; Jiang, Naisheng; Wang, Jiaxun; di, Xiaoyu; Cheung, Justin; Endoh, Maya

    2015-03-01

    We report that wetting/dewetting behavior of liquid polymer films on solids can be controlled by nanoscale architectures of polymer chains irreversibly adsorbed on the impenetrable surfaces. Monodisperse polystyrene (PS) ultrathin films (20 nm in thickness) with different molecular weights on silicon (Si) substrates with a natural amorphous Si dioxide layer were used as models. The PS thin films were annealed at high temperatures at T>Tg (Tg is the bulk glass transition temperature) for several days, and the surface structures were studied by using optical and atomic force microscopes. At the same time, the annealed PS films were further leached with a good solvent and the residue films (i.e., irreversibly adsorbed layers) were characterized by x-ray reflectivity. The experimental data reveals a strong correlation between the conformations of the adsorbed polymer chains and the stability of the liquid films on top. T. K. acknowledges the partial financial support from NSF Grant No. CMMI-1332499.

  8. Uniform polymer-protein conjugate by aqueous AGET ATRP using protein as a macroinitiator.

    PubMed

    Zhu, Binbin; Lu, Diannan; Ge, Jun; Liu, Zheng

    2011-05-01

    In situ aqueous activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) in air, using an enzyme as a macroinitiator, has been proposed to prepare uniform polymer-protein conjugates with improved stability under adverse conditions. In the first step, an initiator, 2-bromoisobutyryl bromide (BIB), was grafted onto the protein surface by reaction with the amino groups. The second step was in situ AGET ATRP polymerization in air using CuBr(2)/1,1,4,7,7-pentamethyldiethylenetriamine as a catalyst and ascorbic acid as a reducing agent. The effectiveness of this method has been demonstrated using horseradish peroxidase (HRP) as a model protein and acrylamide as the monomer, which yielded HRP-polyacrylamide conjugate with a mean particle size of about 20-30 nm. The grafting of BIB onto HRP and the subsequent polymerization yielding a polyacrylamide chain were confirmed by nuclear magnetic resonance and matrix-assisted laser desorption ionization time-of-flight spectrometry analysis. The size of the conjugate was shown to be a function of monomer loading and reaction time. The HRP conjugates yielded essentially retained the catalytic behavior of HRP in free form, as shown by K(m) and V(max) values, but exhibited significantly enhanced thermal stability against high temperature and trypsin digestion. The use of protein as the macroinitiator prevented the formation of copolymer and thus facilitated purification of the protein conjugate. The uniform size indicates a well-defined composition of protein and polymer, which is essential for applications that request a precise control of the dosage of enzyme activity. PMID:21277397

  9. Stability Enhancing N-Terminal PEGylation of Oxytocin Exploiting Different Polymer Architectures and Conjugation Approaches.

    PubMed

    Collins, Jennifer; Kempe, Kristian; Wilson, Paul; Blindauer, Claudia A; McIntosh, Michelle P; Davis, Thomas P; Whittaker, Michael R; Haddleton, David M

    2016-08-01

    Oxytocin, a cyclic nine amino acid neurohypophyseal hormone therapeutic, is effectively used in the control of postpartum hemorrhaging (PPH) and is on the WHO List of Essential Medicines. However, oxytocin has limited shelf life stability in aqueous solutions, particularly at temperatures in excess of 25 °C and injectable aqueous oxytocin formulations require refrigeration (<8 °C). This is particularly problematic in the hot climates often found in many developing countries where daytime temperatures can exceed 40 °C and where reliable cold-chain storage is not always achievable. The purpose of this study was to develop N-terminal amine targeted PEGylation strategies utilizing both linear PEG and polyPEG "comb" polymers as an effective method for stabilizing solution formulations of this peptide for prolonged storage in the absence of efficient cold-chain storage. The conjugation chemistries investigated herein include irreversible amine targeted conjugation methods utilizing NHS ester and aldehyde reductive amination chemistry. Additionally, one reversible conjugation method using a Schiff base approach was explored to allow for the release of the native peptide, thus, ensuring that biological activity remains unaffected. The reversibility of this approach was investigated for the different polymer architectures, alongside a nonpolymer oxytocin analogue to monitor how pH can tune native peptide release. Elevated temperature degradation studies of the polymer conjugates were evaluated to assess the stability of the PEGylated analogues in comparison to the native peptide in aqueous formulations to mimic storage conditions in developing nations and regions where storage under appropriate conditions is challenging. PMID:27419537

  10. Self-lubricating polymer composites and polymer transfer film lubrication for space applications

    NASA Technical Reports Server (NTRS)

    Fusaro, Robert L.

    1990-01-01

    The use of self-lubricating polymers and polymer composites in space is somewhat limited today. In general, they are only used when other methods are inadequate. There is potential, however, for these materials to make a significant impact on future space missions if properly utilized. Some of the different polymers and fillers used to make self-lubricating composites are surveyed. The mechanisms of composite lubrication and wear, the theory behind transfer film lubricating mechanisms, and some factors which affect polymer composite wear and transfer are examined. In addition, some of the current space tribology application areas for self-lubricating polymer composites and polymer transfer are mentioned.

  11. Fabrication of a Conjugated Polymer on Surfaces Studied by Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Jinnai, Hiroshi; Higuchi, Takeshi; Murakami, Daiki; Suga, Mitsuo; Takahara, Atsushi

    2014-03-01

    A controlled ``in-situ'' nano-patterning is highly demanded in various fields of nano-technology. A nano-rod array oriented perpendicular to the substrate is one of the typical nano-structures useful in energy, biomimetic and memory applications. We here proposed a novel nano-patterning method to synthesize polymers by irradiation of electron beam into monomer liquid under atmospheric pressure and concurrently to pattern nano-rod array by scanning the beam. A polymer that can be synthesized by this method includes the poly(3-hexylthiophene), one of the most frequently used conjugated polymers in an organic photovoltaic device. The ``Atmospheric Scanning Electron Microscope (ASEM),'' which enables us to observe morphologies and dynamic phenomena in liquid under atmospheric pressure, was used for fabricating nano-rod structures in this study.

  12. Efficient inverted polymer solar cells based on conjugated polyelectrolyte and zinc oxide modified ITO electrode

    SciTech Connect

    Yuan, Tao; Zhu, Xiaoguang; Tu, Guoli; Zhou, Lingyu; Zhang, Jian

    2015-02-23

    Efficient inverted polymer solar cells (PSCs) were constructed by utilizing a conjugated polyelectrolyte PF{sub EO}SO{sub 3}Na and zinc oxide to modify the indium tin oxide (ITO) electrode. The ITO electrode modified by PF{sub EO}SO{sub 3}Na and zinc oxide possesses high transparency, increased electron mobility, smoothened surface, and lower work function. PTB7:PC{sub 71}BM inverted PSCs containing the modified ITO electrode achieved a high power conversion efficiency (PCE) of 8.49%, exceeding that of the control device containing a ZnO modified ITO electrode (7.48%). Especially, PCE-10:PC{sub 71}BM inverted polymer solar cells achieved a high PCE up to 9.4%. These results demonstrate a useful approach to improve the performance of inverted polymer solar cells.

  13. UV-Induced Tetrazole-Thiol Reaction for Polymer Conjugation and Surface Functionalization.

    PubMed

    Feng, Wenqian; Li, Linxian; Yang, Chengwu; Welle, Alexander; Trapp, Oliver; Levkin, Pavel A

    2015-07-20

    A UV-induced 1,3-dipolar nucleophilic addition of tetrazoles to thiols is described. Under UV irradiation the reaction proceeds rapidly at room temperature, with high yields, without a catalyst, and in both polar protic and aprotic solvents, including water. This UV-induced tetrazole-thiol reaction was successfully applied for the synthesis of small molecules, protein modification, and rapid and facile polymer-polymer conjugation. The reaction has also been demonstrated for the formation of micropatterns by site-selective surface functionalization. Superhydrophobic-hydrophilic micropatterns were successfully created by sequential modifications of a tetrazole-modified porous polymer surface with hydrophobic and hydrophilic thiols. A biotin-functionalized surface could be fabricated in aqueous solutions under long-wavelength UV irradiation. PMID:26059870

  14. Fluorescent-conjugated polymer superquenching facilitates highly sensitive detection of proteases

    NASA Astrophysics Data System (ADS)

    Kumaraswamy, Sriram; Bergstedt, Troy; Shi, Xiaobo; Rininsland, Frauke; Kushon, Stuart; Xia, Wensheng; Ley, Kevin; Achyuthan, Komandoor; McBranch, Duncan; Whitten, David

    2004-05-01

    Sensor formats have been developed for detecting the activity of proteolytic enzymes based on fluorescent conjugated polymer superquenching. These sensors employ a reactive peptide sequence within a tether linking a quencher to a biotin. The peptide binds to sensors containing colocated biotin-binding protein and fluorescent polymer by means of biotin-biotin binding protein interactions, resulting in a strong quenching of polymer fluorescence. Enzyme-mediated cleavage of the peptide results in a reversal of the fluorescence quenching. These assays for protease activity are simple, sensitive, fast, and have the specificity required for screening chemical libraries for novel protease inhibitors in a high-throughput screening assay environment. These assays have been demonstrated for enterokinase, caspase-3/7, and -secretase.

  15. Carbon Nanotube Effects on Electroluminescence and Photovoltaic Response in Conjugated Polymers

    SciTech Connect

    Xu, Zhihua; Wu, Yue; Hu, Bin; Ivanov, Ilia N; Geohegan, David B

    2005-01-01

    This letter reports the experimental results of enhanced electroluminescence (EL) and photovoltaic (PV) response upon doping single-wall carbon nanotubes (SWNTs) into conjugated polymer poly[2-methoxy-5-(2{prime}-ethylhexyloxy)-1, 4-phenylenevinylene] (MEHPPV) based on single-layer light-emitting diodes. We found that the dispersed SWNTs result in two processes: charge transport and exciton dissociation at the tube-chain interface in the SWNT/polymer composites. The detailed EL and PV studies indicate that low SWNT doping concentrations mainly improve the bipolar charge injection, leading to enhanced both reverse and forward EL with reduced threshold voltage. As the SWNT doping concentration continues to increase, the interfacial exciton dissociation becomes dominated, giving rise to an increased PV response. This SWNT concentration-dependent charge transport and exciton dissociation present a pathway to individually address the dual EL and PV functionalities of SWNT-doped polymer composites by controlling the doping level of the SWNTs.

  16. Amphiphilic Polymerizable Porphyrins Conjugated to a Polyglycerol Dendron Moiety as Functional Surfactants for Multifunctional Polymer Particles.

    PubMed

    Moriishi, Masako; Kitayama, Yukiya; Ooya, Tooru; Takeuchi, Toshifumi

    2015-12-01

    An amphiphilic polyglycerol dendron (PGD) conjugated porphyrin (PGP) bearing a polymerizable group was successfully synthesized. The PGP was used as an effective surfactant in emulsion and microsuspension polymerization systems to prepare styrene and methacrylate polymer particles, and the use of PGP provided the simple polymer particles with fluorescence derived from the metalloporphyrin and high colloidal stability due to the PGD. Furthermore, based on confocal laser scanning microscopy, we observed that the particles spontaneously formed a core-shell morphology with the PGP localized in the shell region during the polymerization and demonstrated drug loading in the shell region using rhodamine B as a model drug. The results indicate that the use of the functional surfactant PGP led to the preparation of multifunctional polymer particles from simple monomer species, and the resulting particles possessed high colloidal stability, fluorescence, and drug loading capability. PMID:26569154

  17. Adaptive sliding mode control of tri-layer conjugated polymer actuators

    NASA Astrophysics Data System (ADS)

    Wang, Xiangjiang; Alici, Gursel; Nguyen, Chuc Huu

    2013-02-01

    This paper proposes an adaptive sliding mode control methodology to enhance the positioning ability of conducting polymer actuators typified by tri-layer conjugated polymer actuators. This is motivated by the search for an effective control strategy to command such actuators to a desired configuration in the presence of parametric uncertainties and unmodeled disturbances. After analyzing the stability of the adaptive sliding mode control system, experiments were conducted to demonstrate its satisfactory tracking ability, based on a series of experimental results. Implementation of the control law requires a valid model of the conducting polymer actuator and boundaries of the uncertainties and disturbances. Based on the theoretical and experimental results presented, the adaptive sliding mode control methodology is very attractive in the field of smart actuators which contain significant uncertainties and disturbances.

  18. Fluorescent-conjugated polymer superquenching facilitates highly sensitive detection of proteases.

    PubMed

    Kumaraswamy, Sriram; Bergstedt, Troy; Shi, Xiaobo; Rininsland, Frauke; Kushon, Stuart; Xia, Wensheng; Ley, Kevin; Achyuthan, Komandoor; McBranch, Duncan; Whitten, David

    2004-05-18

    Sensor formats have been developed for detecting the activity of proteolytic enzymes based on fluorescent conjugated polymer superquenching. These sensors employ a reactive peptide sequence within a tether linking a quencher to a biotin. The peptide binds to sensors containing colocated biotin-binding protein and fluorescent polymer by means of biotin-biotin binding protein interactions, resulting in a strong quenching of polymer fluorescence. Enzyme-mediated cleavage of the peptide results in a reversal of the fluorescence quenching. These assays for protease activity are simple, sensitive, fast, and have the specificity required for screening chemical libraries for novel protease inhibitors in a high-throughput screening assay environment. These assays have been demonstrated for enterokinase, caspase-3/7, and beta-secretase. PMID:15136731

  19. Efficient polymer solar cells employing a non-conjugated small-molecule electrolyte

    NASA Astrophysics Data System (ADS)

    Ouyang, Xinhua; Peng, Ruixiang; Ai, Ling; Zhang, Xingye; Ge, Ziyi

    2015-08-01

    Polymer solar cells have drawn a great deal of attention due to the attractiveness of their use in renewable energy sources that are potentially lightweight and low in cost. Recently, numerous significant research efforts have resulted in polymer solar cells with power conversion efficiencies in excess of 9% (ref. 1). Nevertheless, further improvements in performance are sought for commercial applications. Here, we report polymer solar cells with a power conversion efficiency of 10.02% that employ a non-conjugated small-molecule electrolyte as an interlayer. The material offers good contact for photogenerated charge carrier collection and allows optimum photon harvesting in the device. Furthermore, the enhanced performance is attributed to improved electron mobility, enhanced active-layer absorption and properly active-layer microstructures with optimal horizontal phase separation and vertical phase gradation. Our discovery opens a new avenue for single-junction devices by fully exploiting the potential of various material systems with efficiency over 10%.

  20. Multicolor Luminescence from Conjugates of Genetically Encoded Elastin-like Polymers and Terpyridine-Lanthanides

    DOE PAGESBeta

    Ghosh, Koushik; Balog, Eva Rose M.; Kahn, Jennifer L.; Shepherd, Douglas P.; Martinez, Jennifer S.; Rocha, Reginaldo C.

    2015-08-20

    Functional hybrid materials with optically active metal-ligand moieties embedded within a polymer matrix have a great potential in (bio)materials science, including applications in light-emitting diode devices. Here, we report a simple strategy to incorporate terpyridine derivatives into the side chains of elastin-like polymers (ELPs). The further binding of trivalent lanthanide ions with the terpyridine ligands generated an array of photoluminescence ranging from the visible to the near-infrared regions. Lastly, as thin films, these ELP-based optical materials also exhibited distinct morphologies that depend upon the temperature of the aqueous solutions from which the hybrid polymers were spin coated or drop cast.

  1. Site-selective in situ growth of fluorescent polymer-antibody conjugates with enhanced antigen detection by signal amplification.

    PubMed

    Zhang, Libin; Zhao, Wenguo; Liu, Xinyu; Wang, Guilin; Wang, Yang; Li, Dong; Xie, Liangzhi; Gao, Yan; Deng, Haiteng; Gao, Weiping

    2015-09-01

    This paper reports a new and general in situ methodology to grow fluorescent polymer conjugates from the interchain disulfide bridging sites of a monoclonal antibody. Atom transfer radical polymerization (ATRP) initiators were attached to a monoclonal antibody at its interchain disulfide bridging sites by disulfide re-bridging to yield a macroinitiator. Subsequent in situ ATRP of PEG-like monomers with dye-functionalized monomers from the macroinitiator formed antibody-polymer-dye conjugates with site-selectivity and tunable dye-to-antibody ratios. Notably, these conjugates can amplify antigen detection signal by reducing label-density dependent fluorescence quenching and by increasing dye-to-antibody ratios. The method developed may be applicable to a variety of antibodies, dyes and drugs to create a number of antibody-polymer-dye/drug conjugates for advanced diagnosis and therapy of diseases. PMID:26102329

  2. A soluble and fluorescent new type thienylpyrrole based conjugated polymer: optical, electrical and electrochemical properties.

    PubMed

    Soganci, Tugba; Soyleyici, Hakan Can; Ak, Metin

    2016-06-01

    Recently, increased attention has been focused on the synthesis of soluble and processable conducting polymers due to interest in their potential application. For this purpose a new type electroactive 2,5-di(2-thienyl)pyrrole derivative was synthesized and its novel solution-processable and fluorescent polymer, namely poly(N-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)-3,4,5-tris(dodecyloxy)benzamide) (P(TPDOB)), was electrochemically synthesized. Characterization of the monomer and the polymer was performed by (1)H-NMR, (13)C-NMR, cyclic voltammetry, and UV-vis and fluorescence spectroscopy. This soluble polymer has very well-defined and reversible redox processes in the acetonitrile-lithium perchlorate (ACN/LiClO4) couple. Moreover, P(TPDOB) shows multielectrochromic behavior: blue in the oxidized state, caesious in the intermediate state and greenish in the neutral state. Also the copolymer consists of EDOT and TPDOB was synthesized by cyclic voltammetry. A copolymer film has superior electrochromic and electrical properties when compared with a homopolymer. Furthermore, the fluorescence features of the monomer and the polymer were investigated. Although the monomer is a violet light emitter, its polymer is a yellow light emitter. Synthesis of this new type solution-processable and fluorescent conducting polymer is an alternative to the conventional synthesis of soluble conducting polymers which allows the direct application of the conductive polymer to any desired surface for potential technological applications. PMID:27171850

  3. Dispersing nanoparticles in a polymer film via solvent evaporation

    DOE PAGESBeta

    Cheng, Shengfeng; Grest, Gary S.

    2016-05-19

    Large-scale molecular dynamics simulations are used to study the dispersion of nanoparticles (NPs) in a polymer film during solvent evaporation. As the solvent evaporates, a dense polymer-rich skin layer forms at the liquid/vapor interface, which is either NP rich or poor depending on the strength of the NP/polymer interaction. When the NPs are strongly wet by the polymer, the NPs accumulate at the interface and form layers. However, when the NPs are only partially wet by the polymer, most NPs are uniformly distributed in the bulk of the polymer film, with the dense skin layer serving as a barrier tomore » prevent the NPs from moving to the interface. Furthermore, our results point to a possible route to employ less favorable NP/polymer interactions and fast solvent evaporation to uniformly disperse NPs in a polymer film, contrary to the common belief that strong NP/polymer attractions are needed to make NPs well dispersed in polymer nanocomposites.« less

  4. Extraordinary Capability for Water Treatment Achieved by a Perfluorous Conjugated Microporous Polymer

    PubMed Central

    Yang, Rui-Xia; Wang, Ting-Ting; Deng, Wei-Qiao

    2015-01-01

    Oils, organic solvents, dyes, and heavy metal ions are primary pollutants in water resources. Currently, no sorbent material can effectively remove these types of pollutants simultaneously. Here we report a perfluorous conjugated microporous polymer with superhydrophobicity and a large surface area, which exhibits outstanding adsorption capacities, kinetics, and recyclability for a wide range of organic solvents, oils, dyes, and heavy metal ions. The adsorption capacities of this polymer, 1376.7 mg g−1 for Congo red, 808.2 mg g−1 for Pb(II) and 303.2 mg g−1 for As(V), are higher than the adsorption capacities of any previously described porous materials. Our theoretical calculation reveals that the superior properties of this polymer are due to fluorination and triple bonds within the polymer. A benchmark experiment indicates that this polymer can efficiently remove these pollutants simultaneously. Application of this polymer may lead to the development of next-generation reusable and portable water purification appliances. PMID:25974738

  5. Extraordinary Capability for Water Treatment Achieved by a Perfluorous Conjugated Microporous Polymer

    NASA Astrophysics Data System (ADS)

    Yang, Rui-Xia; Wang, Ting-Ting; Deng, Wei-Qiao

    2015-05-01

    Oils, organic solvents, dyes, and heavy metal ions are primary pollutants in water resources. Currently, no sorbent material can effectively remove these types of pollutants simultaneously. Here we report a perfluorous conjugated microporous polymer with superhydrophobicity and a large surface area, which exhibits outstanding adsorption capacities, kinetics, and recyclability for a wide range of organic solvents, oils, dyes, and heavy metal ions. The adsorption capacities of this polymer, 1376.7 mg g-1 for Congo red, 808.2 mg g-1 for Pb(II) and 303.2 mg g-1 for As(V), are higher than the adsorption capacities of any previously described porous materials. Our theoretical calculation reveals that the superior properties of this polymer are due to fluorination and triple bonds within the polymer. A benchmark experiment indicates that this polymer can efficiently remove these pollutants simultaneously. Application of this polymer may lead to the development of next-generation reusable and portable water purification appliances.

  6. Development of polymer film solar collectors: A status report

    NASA Astrophysics Data System (ADS)

    Wilhelm, W. G.; Andrews, J. W.

    1982-08-01

    Solar energy collector panels using polymer film and laminate technology were developed which demonstrate low cost and high thermal performance for residential and commercial applications. This device uses common water in the absorber/heat exchanger which is constructed with polymer film adhesively laminated to aluminum foil as the outer surfaces. Stressed polymer films are also used for the outer window and back surface of the panel forming a high strength structural composite. Rigid polymer foam complements the design by contributing insulation and structural definition. This design resulted in very low weight (3.5 kg/m(2)), potentially very low manufacturing cost (aprox. $11/m(2)), and high thermal performance. The development of polymer materials for this technology will be a key to early commercial success.

  7. Conjugated Polymer Actuators for Articulating Neural Probes and Electrode Interfaces

    NASA Astrophysics Data System (ADS)

    Daneshvar, Eugene Dariush

    This thesis investigated the potential use of polypyrrole (PPy) doped with dodecylbenzenesulfonate (DBS) to controllably articulate (bend or guide) flexible neural probes and electrodes. PPy(DBS) actuation performance was characterized in the ionic mixture and temperature found in the brain. Nearly all the ions in aCSF were exchanged into the PPy---the cations Na +, K+, Mg2+, Ca2+, as well as the anion PO43-; Cl- was not present. Nevertheless, deflections in aCSF were comparable to those in NaDBS and they were monotonic with oxidation level: strain increased upon reduction, with no reversal of motion despite the mixture of ionic charges and valences being exchanged. Actuation depended on temperature. Upon warming, the cyclic voltammograms showed additional peaks and an increase of 70% in the consumed charge. Actuation strain was monotonic under these conditions, demonstrating that conducting polymer actuators can indeed be used for neural interface and neural probe applications. In addition, a novel microelectro-mechanical system (MEMS) was developed to measure previously disregarded residual stress in a bilayer actuator. Residual stresses are a major concern for MEMS devices as that they can dramatically influence their yield and functionality. This device introduced a new technique to measure micro-scaled actuation forces that may be useful for characterization of other MEMS actuators. Finally, a functional movable parylene-based neural electrode prototype was developed. Employing PPy(DBS) actuators, electrode projections were successfully controlled to either remain flat or actuate out-of-plane and into a brain phantom during insertion. An electrode projection 800 microm long and 50 microm wide was able to deflect almost 800 microm away from the probe substrate. Applications that do not require insertion into tissue may also benefit from the electrode projections described here. Implantable neural interface devices are a critical component to a broad class of

  8. Morphology of conjugated polymer/insulating polymer blends from inkjet printing and its correlation to the function of field-effect transistors

    NASA Astrophysics Data System (ADS)

    Chen, Huipeng; Zheng, Guochen; Hu, Liqin; Yang, Huihuang; Guo, Tailiang

    Printed electronics is a rapidly developing field of research which covers any electronic devices or circuits that can be processed using direct printing techniques. Among those printing techniques, inkjet printing is a technique of increasing interest for organic field-effect transistors (FETs) due to its fully data driven and direct patterning. In this work, the morphology of conjugated polymer/insulating polymer blends from inkjet printing and their FET properties has been investigated. The crystallinity and packing of conjugated polymer has been examined by synchrotron x-ray diffraction. The detailed information about the interface and domains of polymer blends were investigated by small angle neutron scattering. It is found that the domains and polymer interface were crucial to the FET properties. Finally, the relationship between morphology and function has been established for polymer blends FET from inkjet printing.

  9. Structures and Elastic Moduli of Polymer Nanocomposite Thin Films

    NASA Astrophysics Data System (ADS)

    Yuan, Hongyi; Karim, Alamgir; University of Akron Team

    2014-03-01

    Polymeric thin films generally possess unique mechanical and thermal properties due to confinement. In this study we investigated structures and elastic moduli of polymer nanocomposite thin films, which can potentially find wide applications in diverse areas such as in coating, permeation and separation. Conventional thermoplastics (PS, PMMA) and biopolymers (PLA, PCL) were chosen as polymer matrices. Various types of nanoparticles were used including nanoclay, fullerene and functionalized inorganic particles. Samples were prepared by solvent-mixing followed by spin-coating or flow-coating. Film structures were characterized using X-ray scattering and transmission electron microscopy. Elastic moduli were measured by strain-induced elastic buckling instability for mechanical measurements (SIEBIMM), and a strengthening effect was found in certain systems due to strong interaction between polymers and nanoparticles. The effects of polymer structure, nanoparticle addition and film thickness on elastic modulus will be discussed and compared with bulk materials.

  10. Elements of adaptive optics based on metallized polymer films

    NASA Astrophysics Data System (ADS)

    Voliak, T. B.; Krasiuk, I. K.; Pashinin, P. P.

    Results of an experimental study of the stability of metallized polymer films exposed to laser radiation at wavelengths of 1.06 and 10.6 microns are reported, and methods for fabricating variable-curvature mirrors from these films are discussed. Formulas are presented for calculating the shape of film mirrors as a function of the pressure acting on the film, mounting contour, and film properties. The performance of film mirrors is investigated experimentally in a pulsed CO2 laser with stable and unstable resonators.

  11. A Polymer-Based Antibody-Vinca Drug Conjugate Platform: Characterization and Preclinical Efficacy.

    PubMed

    Yurkovetskiy, Alexander V; Yin, Mao; Bodyak, Natalya; Stevenson, Cheri A; Thomas, Joshua D; Hammond, Charles E; Qin, LiuLiang; Zhu, Bangmin; Gumerov, Dmitry R; Ter-Ovanesyan, Elena; Uttard, Alex; Lowinger, Timothy B

    2015-08-15

    Antibody-drug conjugates (ADC) are an emerging drug class that uses antibodies to improve cytotoxic drug targeting for cancer treatment. ADCs in current clinical trials achieve a compromise between potency and physicochemical/pharmacokinetic properties by conjugating potent cytotoxins directly to an antibody at a 4:1 or less stoichiometric ratio. Herein, we report a novel, polyacetal polymer-based platform for creating ADC that use poly-1-hydroxymethylethylene hydroxymethyl-formal (PHF), also known as Fleximer. The high hydrophilicity and polyvalency properties of the Fleximer polymer can be used to produce ADC with high drug loading without compromising physicochemical and pharmacokinetic properties. Using trastuzumab and a vinca drug derivative to demonstrate the utility of this platform, a novel Fleximer-based ADC was prepared and characterized in vivo. The ADC prepared had a vinca-antibody ratio of 20:1. It exhibited a high antigen-binding affinity, an excellent pharmacokinetic profile and antigen-dependent efficacy, and tumor accumulation in multiple tumor xenograft models. Our findings illustrate the robust utility of the Fleximer platform as a highly differentiated alternative to the conjugation platforms used to create ADC currently in clinical development. PMID:26113086

  12. Capture and Reversible Storage of Volatile Iodine by Novel Conjugated Microporous Polymers Containing Thiophene Units.

    PubMed

    Qian, Xin; Zhu, Zhao-Qi; Sun, Han-Xue; Ren, Feng; Mu, Peng; Liang, Weidong; Chen, Lihua; Li, An

    2016-08-17

    Conjugated microporous polymers having thiophene building blocks (SCMPs), which originated from ethynylbenzene monomers with 2,3,5-tribromothiophene, were designedly synthesized through Pd(0)/CuI catalyzed Sonogashira-Hagihara cross-coupling polymerization. The morphologies, structure and physicochemical properties of the as-synthesized products were characterized through scanning electron microscope (SEM), thermogravimeter analysis (TGA), (13)C CP/MAS solid state NMR and Fourier transform infrared spectroscope (FTIR) spectra. Nitrogen sorption-desorption analysis shows that the as-synthesized SCMPs possesses a high specific surface area of 855 m(2) g(-1). Because of their abundant porosity, π-conjugated network structure, as well as electron-rich thiophene building units, the SCMPs show better adsorption ability for iodine and a high uptake value of 222 wt % was obtained, which can compete with those nanoporous materials such as silver-containing zeolite, metal-organic frameworks (MOFs) and conjugated microporous polymers (CMPs), etc. Our study might provide a new possibility for the design and synthesis of functional CMPs containing electron-rich building units for effective capture and reversible storage of volatile iodine to address environmental issues. PMID:27458782

  13. Contribution of Increased Extraction Efficiency to Increased Photo-Luminescence in Strained Polymer Films

    NASA Astrophysics Data System (ADS)

    Chen, Po-Jui; Yang, Arnold Chang-Mou; Hsu, Jui-Hung; White, Jonathon D.

    2011-03-01

    Potential applications of Luminescent Conjugated Polymers in thin film diodes, solar cells and flat panel displays have been limited by low efficiency. Craze formation in MEH-PPV/polystyrene thin films leads to a factor of 2 or 3 increase in collected photo-luminescence (PL) due to a combination of factors such as MEH-PPV chain conformation and increased extraction efficiency of PL. In order to determine the contribution of the latter effect, we used Monte Carlo based Ray Tracing to analyze the trajectory of photons generated in the thin film under different strain conditions. Our results indicate that increased PL extraction due to the existence of crazes contributes ~ 50 % of the observed increase in PL, the majority of this being due to light emitted near the craze edges.

  14. Contribution of Increased Extraction Efficiency to Increased Photo-Luminescence in Strained Polymer Films

    NASA Astrophysics Data System (ADS)

    Chen, Po-Jui; Chang-Mou Yang, Arnold; Hsu, Jui-Hung; White, Jonathon D.

    2012-02-01

    Potential applications of Luminescent Conjugated Polymers in thin film diodes, solar cells and flat panel displays have been limited by low efficiency. Craze formation in MEH-PPV/polystyrene thin film leads to a factor of 2 or 3 increase in collected photo-luminescence (PL) due to a combination of factors such as MEH-PPV chain conformation and increased extraction efficiency of PL. In order to determine the contribution of the latter effect, we used Monte Carlo based Ray Tracing to analyze the trajectory of photons generated in the thin film under different strain conditions. Our results indicate that increased PL extraction due to the existence of crazes contributes ˜15% of the observed increase in PL, the majority of this being due to light emitted near the craze edges.

  15. Triphenylmethane dye-doped gelatin films for low-power optical phase-conjugation

    NASA Astrophysics Data System (ADS)

    Geethakrishnan, T.; Sakthivel, P.; Palanisamy, P. K.

    2015-01-01

    We have studied degenerate four-wave mixing (DFWM) based optical phase-conjugation (OPC) in few triphenylmethane (Acid blue 7, Acid blue 9, Acid blue 1 and Methyl green) dye-doped gelatin films using a 633 nm He-Ne laser radiation of total power 35 mW. Phase-conjugate (PC) reflectivity from the dye films was measured by varying the experimental parameters such as incident angle between the pump-probe beams in the DFWM geometry, dopant concentrations of the gelatin film, probe beam intensity and read-out beam intensity. The maximum PC reflectivity was observed in the Acid blue 7, Acid blue 9, Acid blue 1 and Methyl green sensitized gelatin films were 0.22%, 0.24%, 0.07% and 0.13%, respectively. The origin of the mechanism of the PC wave generation from these dye films is also reported.

  16. Atomic-force microscopy of submicron films of electroactive polymer

    NASA Astrophysics Data System (ADS)

    Karamov, D. D.; Kornilov, V. M.; Lachinov, A. N.; Kraikin, V. A.; Ionova, I. A.

    2016-07-01

    Atomic-force microscopy is used to study the supramolecular structure of submicron films of electroactive thermally stable polymer (polydiphenylenephthalide (PDP)). It has been demonstrated that PDP films produced using centrifuging are solid homogeneous films with thicknesses down to several nanometers, which correspond to two or three monomolecular layers. The film volume is structurized at thicknesses greater than 100 nm. The study of the rheological properties of solutions used for film production yields a crossover point that separates the domains of strongly diluted and semidiluted solutions. A transition from the globular structure to the associate structure is observed in films that are produced using solutions with a boundary concentration. A model of the formation of polymer film that involves the presence of associates in the original solution is discussed.

  17. Multiplexed detection of protein cancer markers on Au/Ag-barcoded nanorods using fluorescent-conjugated polymers.

    PubMed

    Zheng, Weiming; He, Lin

    2010-07-01

    Integration of fluorescent-conjugated polymers as detection moiety with metallic striped nanorods for multiplexed detection of clinically important cancer marker proteins in an immunoassay format was demonstrated in this report. Specifically, cationic conjugated polymers were introduced to protein complexes through electrostatic binding to negatively charged double-stranded DNA, which was tagged on detection antibodies prior to antigen recognition. The intense fluorescence emission of conjugated polymers resulted in highly sensitive detection of cancer marker proteins wherein an undiluted bovine serum sample as low as approximately 25 target molecules captured on each particle was detectable. Meanwhile, the use of polymer molecules as the detection probe did not obscure the optical pattern of underlying nanorods, i.e., the encoding capability of barcoded nanorods was preserved, which allowed simultaneous detection of three cancer marker proteins with good specificity. PMID:20496173

  18. In situ polarization of polymer films in microsensors

    NASA Astrophysics Data System (ADS)

    Kranz, M.; Allen, M. G.; Hudson, T.

    2012-04-01

    Electret and polymer piezoelectric films have been previously integrated into Micro Electro Mechanical System (MEMS) acoustic sensors and energy harvesters. Common techniques employed in MEMS polymer integration include corona discharge [1] and backlighted thyratron [2], followed by macro-scale assembly of the polymer into the micro device. In contrast, this paper reports a method for post-fabrication in-situ polarization of polymer films embedded within the MEMS device itself. The method utilizes microplasma discharges with self-aligned charging grids integrated within the device to charge fluoropolymer films in a fashion similar to the common corona discharge technique. This in-situ approach enables the integration of uncharged polymer films into MEMS and subsequent post-fabrication and post-packaging polarization, simultaneously enabling the formation of buried or encapsulated electrets as well as eliminating the need to restrict fabrication and packaging processes that might otherwise discharge pre-charged materials. Using the in situ approach, a microscale charging grid structure is fabricated and suspended a short distance above the polymer film. After fabrication of the charging grid, standard microfabrication steps are performed to build MEMS sensors. After completing the entire fabrication and packaging flow, the polarization process is performed. When energized by a high voltage, the sharp metal edges of the charging grid lead to high dielectric fields that ionize the air in the gap and force electric charge onto the polymer surface. This paper presents modeling and results for this in situ polarization process.

  19. Rapid synthesis of flexible conductive polymer nanocomposite films

    NASA Astrophysics Data System (ADS)

    Blattmann, C. O.; Sotiriou, G. A.; Pratsinis, S. E.

    2015-03-01

    Polymer nanocomposite films with nanoparticle-specific properties are sought out in novel functional materials and miniaturized devices for electronic and biomedical applications. Sensors, capacitors, actuators, displays, circuit boards, solar cells, electromagnetic shields and medical electrodes rely on flexible, electrically conductive layers or films. Scalable synthesis of such nanocomposite films, however, remains a challenge. Here, flame aerosol deposition of metallic nanosliver onto bare or polymer-coated glass substrates followed by polymer spin-coating on them leads to rapid synthesis of flexible, free-standing, electrically conductive nanocomposite films. Their electrical conductivity is determined during their preparation and depends on substrate composition and nanosilver deposition duration. Accordingly, thin (<500 nm) and flexible nanocomposite films are made having conductivity equivalent to metals (e.g. 5 × 104 S cm-1), even during repetitive bending.

  20. Rapid synthesis of flexible conductive polymer nanocomposite films.

    PubMed

    Blattmann, C O; Sotiriou, G A; Pratsinis, S E

    2015-03-27

    Polymer nanocomposite films with nanoparticle-specific properties are sought out in novel functional materials and miniaturized devices for electronic and biomedical applications. Sensors, capacitors, actuators, displays, circuit boards, solar cells, electromagnetic shields and medical electrodes rely on flexible, electrically conductive layers or films. Scalable synthesis of such nanocomposite films, however, remains a challenge. Here, flame aerosol deposition of metallic nanosliver onto bare or polymer-coated glass substrates followed by polymer spin-coating on them leads to rapid synthesis of flexible, free-standing, electrically conductive nanocomposite films. Their electrical conductivity is determined during their preparation and depends on substrate composition and nanosilver deposition duration. Accordingly, thin (<500 nm) and flexible nanocomposite films are made having conductivity equivalent to metals (e.g. 5  × 10(4) S cm(-1)), even during repetitive bending. PMID:25736387

  1. The total chemical synthesis of polymer/graphene nanocomposite films.

    PubMed

    Salvatierra, Rodrigo V; Cava, Carlos E; Roman, Lucimara S; Oliveira, Marcela M; Zarbin, Aldo J G

    2016-01-28

    A versatile and room temperature synthesis of thin films of polymer/graphene is reported. Drastically differing from other methods, not only the polymer but also the graphene are completely built from their simplest monomers (thiophene and benzene) in a one-pot polymerization reaction at a liquid-liquid interface. The materials were characterized and electronic properties are presented. PMID:26658554

  2. Surfactant-free, low band gap conjugated polymer nanoparticles and polymer:fullerene nanohybrids with potential for organic photovoltaics.

    PubMed

    Wang, Suxiao; Singh, Amita; Walsh, Nichola; Redmond, Gareth

    2016-06-17

    Stable, aqueous dispersions of nanoparticles based on the low band gap polymers poly [2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (APFO-3) and poly [N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) were prepared, using a flexible, surfactant-free reprecipitation method, and characterized by a variety of optical techniques. Light scattering measurements indicated average nanoparticle hydrodynamic diameters of approximately 40 nm. The particles presented wide-bandwidth absorption and photoluminescence excitation spectra with high absorption cross-sections on the order of 10(-12) cm(2). Nanoparticle emission spectra were significantly red-shifted, with decreased emission quantum yields and lifetimes, consistent with increased inter-polymer chain interactions in the condensed phase. Single particle photoluminescence studies highlighted the multi-chromophoric nature of the polymer nanoparticles and confirmed their favorable photostabilities. When the nanoparticles were doped with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), the correspondence of photoluminescence emission quenching, quantum yield decreases, emission lifetime shortening, and increased non-radiative rates with increasing PCBM concentration suggested efficient photo-induced donor-to-acceptor charge transfer between the conjugated polymers and the fullerene dopants co-localized in the nanoparticle cores. Taken together, the data suggest that these surfactant-free hybrid nanomaterials may be useful for integration with future nanostructured organic photovoltaics technologies. PMID:27159927

  3. Tuning the photophysical properties of an ionic conjugated polymer through interaction with conventional polyelectrolytes.

    SciTech Connect

    Abe, S.; Chen, L.; Biosciences Division

    2003-07-15

    Ionic conjugated polymers (ICPs), polyions with electronically conjugated backbones, have been the subject of intensive studies recently. As newly emerging polymer materials, ICPs exhibit great potential for a variety of applications ranging from separations to biosensors. One of the most fascinating properties of ICPs is that their intrinsic optical properties can be tuned by a molecular assemblage process rather than by cumbersome synthetic changes to the chemical structures of the repeat unit. For example, in previous studies, we have found that the fluorescence quantum efficiency (FQE) of an ICP can be enhanced through its interactions with small amounts of certain detergents. Using a combination of steady-state and ultrafast spectroscopy we have established that the fluorescence enhancement results from the formation of a complex [polymer{sup (-)}/detergent{sup (+)}], which induces ordered conformation and, therefore, changes the optical properties of an ICP. Because many desirable properties of ICPs rely on their intense fluorescence and highly delocalized electronic properties, we report here another avenue for tuning the properties of ICPs through the interactions of ICPs with conventional polyelectrolytes.

  4. Directed alignment of conjugated polymers for enhanced long-range photocurrent collection

    NASA Astrophysics Data System (ADS)

    Li, Anton; Bilby, David; Dong, Ban; Kim, Jinsang; Green, Peter

    2015-03-01

    To realize the full potential of conjugated polymers, possessing anisotropic structure and properties, it is often desirable to extend their organization to larger length scales. An epitaxy-directing solvent additive 1,3,5-trichlorobenzene was combined with an off-center spin-casting technique to produce poly(3-hexylthiophene) (P3HT) fibers with uniaxial in-plane alignment on the centimeter scale, which were incorporated into planar heterojunction solar cells with PCBM acceptor. Topography and photocurrent were mapped by photoconductive AFM; in devices with aligned P3HT, local photocurrent measured on fibers was over 4 times higher than in control devices with unaligned polymer. Even at large distances (>200 μm) between laser spot (carrier excitation) and conductive probe (charge extraction), significant long-range photocurrent was measured in the aligned devices, especially when the separation was oriented parallel to the fiber alignment. Complementary TFT measurements of neat P3HT fibers revealed that the anisotropy of in-plane carrier mobilities was greater than a factor of 3. Together, these findings highlight the importance of conjugated polymer alignment for improving carrier transport and ultimately the performance of solar cells and other devices.

  5. Multiantigenic peptide-polymer conjugates as therapeutic vaccines against cervical cancer.

    PubMed

    Hussein, Waleed M; Liu, Tzu-Yu; Jia, Zhongfan; McMillan, Nigel A J; Monteiro, Michael J; Toth, Istvan; Skwarczynski, Mariusz

    2016-09-15

    Immunotherapy is one of the most promising strategies for the treatment of cancer. Human papillomavirus (HPV) is responsible for virtually all cases of cervical cancer. The main purpose of a therapeutic HPV vaccine is to stimulate CD8(+) cytotoxic T lymphocytes (CTLs) that can eradicate HPV infected cells. HPV oncoproteins E6 and E7 are continuously expressed and are essential for maintaining the growth of HPV-associated tumor cells. We designed polymer-based multi-antigenic formulations/constructs that were comprised of the E6 and E7 peptide epitopes. We developed an N-terminus-based epitope conjugation to conjugate two unprotected peptides to poly tert-butyl acrylate. This method allowed for the incorporation of the two antigens into a polymeric dendrimer in a strictly equimolar ratio. The most effective formulations eliminated tumors in up to 50% of treated mice. Tumor recurrence was not observed up to 3months post initial challenge. PMID:27475535

  6. Polymer-Chlorambucil Drug Conjugates: A Dynamic Platform of Anticancer Drug Delivery.

    PubMed

    Saha, Biswajit; Haldar, Ujjal; De, Priyadarsi

    2016-07-01

    Recently, polymer drug conjugates (PDCs) have attracted considerable attention in the treatment of cancer. In this work, a simple strategy has been developed to make PDCs of an antitumor alkylating agent, chlorambucil, using a biocompatible disulphide linker. Chlorambucil-based chain transfer agent was used to prepare various homopolymers and block copolymers in a controlled fashion via reversible addition-fragmentation chain transfer polymerization. Chlorambucil conjugated block copolymer, poly(polyethylene glycol monomethyl ether methacrylate)-b-poly(methyl methacrylate), formed nanoaggregates in aqueous solutions, which are characterized by dynamic light scattering and field emission-scanning electron microscopy. Finally, the simplicity of the design is exemplified by performing a release study of chlorambucil under reducing condition by using D,L-dithiothreitol. PMID:27159378

  7. Novel thiophene-bearing conjugated microporous polymer honeycomb-like porous spheres with ultrahigh iodine uptake.

    PubMed

    Ren, Feng; Zhu, Zhaoqi; Qian, Xin; Liang, Weidong; Mu, Peng; Sun, Hanxue; Liu, Jiehua; Li, An

    2016-07-28

    Two conjugated microporous polymers containing thiophene-moieties (SCMPs) were obtained by the polymerization of 3,3',5,5'-tetrabromo-2,2'-bithiophene and ethynylbenzene monomers through the palladium-catalyzed Sonogashira-Hagihara crosscoupling reaction. The resulting SCMPs show high thermal stability with a decomposition temperature above 300 °C. Scanning electron microscopy images show that the resulting SCMPs formed as an aggregation composed of micrometer-sized SCMP spheres, in which honeycomb-like porous spheres with penetrated pores on the surface were observed. Taking advantage of such a unique honeycomb-like porous morphology as well as π-conjugated structures, the SCMPs show ultrahigh absorption performance for iodine vapour with an uptake of up to 345 wt% obtained, which is the highest value reported to date for CMPs, thus making the resulting SCMPs ideal absorbent materials for reversible iodine capture to address environmental issues. PMID:27417941

  8. Fracture and fatigue of ultrathin nanoporous polymer films

    NASA Astrophysics Data System (ADS)

    Kearney, Andrew V.

    Nanoporous polymer layers are being considered for a range of emerging nanoscale applications, from low permittivity materials for interlayer dielectrics in microelectronics and anti-reflective coatings in optical technologies, to biosensors and size-selective membranes for biological applications. Polymer thin films have inherently low elastic modulus, strength and hardness, but exhibit fracture properties that are higher than those reported for glass, ceramic, and even some metal layers. However, constraint of a ductile polymer between two elastic layers is expected to affect the local plasticity ahead of a crack tip and its contribution to the film adhesion with films below a micron in thickness. Additionally, nanoporosity would be expected to have a deleterious effect on mechanical properties, producing materials and layers that are structurally weaker than fully dense versions they replace. Therefore, the integration of these nanoporous polymer layer at nanometer thicknesses would present significantly processing and mechanical reliability challenges. In this dissertation, surprising evidence is presented that nanoporous polymer films exhibit increasing fracture energy with increasing porosity. Such behavior is in stark contrast to a wide range of reported behavior for porous solids. A ductile nano-void growth and coalescence fracture mechanics-based model is presented to rationalize the increase in fracture toughness of the voided polymer film. The model is shown to explain the behavior in terms of a specific scaling of the size of the pores with pore volume fraction. It is demonstrated that the pore size must increase with close to a linear dependence on the volume fraction in order to increase rather than decrease the fracture energy. Independent characterization of the pore size as a function of volume fraction is shown to confirm predictions made by the model. The fracture behavior of these constrained polymer films are also examined with film thickness

  9. Donor-acceptor conjugated polymers based on multifused ladder-type arenes for organic solar cells.

    PubMed

    Wu, Jhong-Sian; Cheng, Sheng-Wen; Cheng, Yen-Ju; Hsu, Chain-Shu

    2015-03-01

    Harvesting solar energy from sunlight to generate electricity is considered as one of the most important technologies to address the future sustainability of humans. Polymer solar cells (PSCs) have attracted tremendous interest and attention over the past two decades due to their potential advantage to be fabricated onto large area and light-weight flexible substrates by solution processing at a lower cost. PSCs based on the concept of bulk heterojunction (BHJ) configuration where an active layer comprises a composite of a p-type (donor) and an n-type (acceptor) material represents the most useful strategy to maximize the internal donor-acceptor interfacial area allowing for efficient charge separation. Fullerene derivatives such as [6,6]-phenyl-C61 or 71-butyric acid methyl ester (PCBM) are the ideal n-type materials ubiquitously used for BHJ solar cells. The major effort to develop photoactive materials is numerously focused on the p-type conjugated polymers which are generally synthesized by polymerization of electron-rich donor and electron-deficient acceptor monomers. Compared to the development of electron-deficient comonomers (acceptor segments), the development of electron-rich donor materials is considerably flourishing. Forced planarization by covalently fastening adjacent aromatic and heteroaromatic subunits leads to the formation of ladder-type conjugated structures which are capable of elongating effective conjugation, reducing the optical bandgap, promoting intermolecular π-π interactions and enhancing intrinsic charge mobility. In this review, we will summarize the recent progress on the development of various well-defined new ladder-type conjugated materials. These materials serve as the superb donor monomers to prepare a range of donor-acceptor semi-ladder copolymers with sufficient solution-processability for solar cell applications. PMID:25322211

  10. Special Polymer/Carbon Composite Films for Detecting SO2

    NASA Technical Reports Server (NTRS)

    Homer, Margie; Ryan, Margaret; Yen, Shiao-Pin; Kisor, Adam; Jewell, April; Shevade, Abhijit; Manatt, Kenneth; Taylor, Charles; Blanco, Mario; Goddard, William

    2008-01-01

    A family of polymer/carbon films has been developed for use as sensory films in electronic noses for detecting SO2 gas at concentrations as low as 1 part per million (ppm). Most previously reported SO2 sensors cannot detect SO2 at concentrations below tens of ppm; only a few can detect SO2 at 1 ppm. Most of the sensory materials used in those sensors (especially inorganic ones that include solid oxide electrolytes, metal oxides, and cadmium sulfide) must be used under relatively harsh conditions that include operation and regeneration at temperatures greater than 100 C. In contrast, the present films can be used to detect 1 ppm of SO2 at typical opening temperatures between 28 and 32 C and can be regenerated at temperatures between 36 and 40 C. The basic concept of making sensing films from polymer/carbon composites is not new. The novelty of the present family of polymer/carbon composites lies in formulating the polymer components of these composites specifically to optimize their properties for detecting SO2. First-principles quantum-mechanical calculations of the energies of binding of SO2 molecules to various polymer functionalities are used as a guide for selecting polymers and understanding the role of polymer functionalities in sensing. The polymer used in the polymer-carbon composite is a copolymer of styrene derivative units with vinyl pyridine or substituted vinyl pyridine derivative units. To make a substituted vinyl pyridine for use in synthesizing such a polymer, poly(2-vinyl pyridine) that has been dissolved in methanol is reacted with 3-chloropropylamine that has been dissolved in a solution of methanol. The methanol is then removed to obtain the copolymer. Later, the copolymer can be dissolved in an appropriate solvent with a suspension of carbon black to obtain a mixture that can be cast and then dried to obtain a sensory film.

  11. Effect of introduction of chondroitin sulfate into polymer-peptide conjugate responding to intracellular signals

    NASA Astrophysics Data System (ADS)

    Tomiyama, Tetsuro; Toita, Riki; Kang, Jeong-Hun; Koga, Haruka; Shiosaki, Shujiro; Mori, Takeshi; Niidome, Takuro; Katayama, Yoshiki

    2011-09-01

    We recently developed a novel tumor-targeted gene delivery system responding to hyperactivated intracellular signals. Polymeric carrier for gene delivery consists of hydrophilic neutral polymer as main chains and cationic peptide substrate for target enzyme as side chains, and was named polymer-peptide conjugate (PPC). Introduction of chondroitin sulfate (CS), which induces receptor-medicated endocytosis, into polymers mainly with a high cationic charge density such as polyethylenimine can increase tumor-targeted gene delivery. In the present study, we examined whether introduction of CS into PPC containing five cationic amino acids can increase gene expression in tumor cells. Size and zeta potential of plasmid DNA (pDNA)/PPC/CS complex were <200 nm and between -10 and -15 mV, respectively. In tumor cell experiments, pDNA/PPC/CS complex showed lower stability and gene regulation, compared with that of pDNA/PPC. Moreover, no difference in gene expression was identified between positive and negative polymer. These results were caused by fast disintegration of pDNA/PPC/CS complexes in the presence of serum. Thus, we suggest that introduction of negatively charged CS into polymers with a low charge density may lead to low stability and gene regulation of complexes.

  12. Improved morphology in electrochemically grown conducting polymer films

    SciTech Connect

    Rubinstein, I.; Gottesfeld, S.; Sabatani, E.

    1990-12-31

    A conducting polymer film with an improved space filling is formed on a metal electrode surface. A self-assembling monolayer is formed directly on the metal surface where the monolayer has a first functional group that binds to the metal surface and a second chemical group that forms a chemical bonding site for molecules forming the conducting polymer. The conducting polymer is then conventionally deposited by electrochemical deposition. In one example, a conducting film of polyaniline is formed on a gold electrode surface with an intermediate monolayer of p-aminothiophenol.

  13. Oriented Liquid Crystalline Polymer Semiconductor Films with Large Ordered Domains.

    PubMed

    Xue, Xiao; Chandler, George; Zhang, Xinran; Kline, R Joseph; Fei, Zhuping; Heeney, Martin; Diemer, Peter J; Jurchescu, Oana D; O'Connor, Brendan T

    2015-12-01

    Large strains are applied to liquid crystalline poly(2,5-bis(3-tetradecylthiophen-2yl)thieno(3,2-b)thiophene) (pBTTT) films when held at elevated temperatures resulting in in-plane polymer alignment. We find that the polymer backbone aligns significantly in the direction of strain, and that the films maintain large quasi-domains similar to that found in spun-cast films on hydrophobic surfaces, highlighted by dark-field transmission electron microscopy imaging. The highly strained films also have nanoscale holes consistent with dewetting. Charge transport in the films is then characterized in a transistor configuration, where the field effect mobility is shown to increase in the direction of polymer backbone alignment, and decrease in the transverse direction. The highest saturated field-effect mobility was found to be 1.67 cm(2) V(-1) s(-1), representing one of the highest reported mobilities for this material system. The morphology of the oriented films demonstrated here contrast significantly with previous demonstrations of oriented pBTTT films that form a ribbon-like morphology, opening up opportunities to explore how differences in molecular packing features of oriented films impact charge transport. Results highlight the role of grain boundaries, differences in charge transport along the polymer backbone and π-stacking direction, and structural features that impact the field dependence of charge transport. PMID:26552721

  14. Polymer-assisted aqueous deposition of metal oxide films

    DOEpatents

    Li, DeQuan; Jia, Quanxi

    2003-07-08

    An organic solvent-free process for deposition of metal oxide thin films is presented. The process includes aqueous solutions of necessary metal precursors and an aqueous solution of a water-soluble polymer. After a coating operation, the resultant coating is fired at high temperatures to yield optical quality metal oxide thin films.

  15. Explosives sensing based on suspended core fiber coated with conjugated polymer

    NASA Astrophysics Data System (ADS)

    Chu, Fenghong; Tsiminis, Georgios; Spooner, Nigel A.; Monro, Tanya M.

    2014-05-01

    Suspended core fibers with voids surrounding the core coated with conjugate polymer were used to detect nitroaromatic explosives based on the fluorescence quenching technique. The background Raman signal from a suspended core fiber was used as reference to optimize coupled into the core of the fiber. The fluorescence spectra were integrated across all wavelengths to extract the integrated fluorescence intensity at regular time intervals. Fluorescence decay lifetimes were obtained by fitting a single exponential decay and were used to detect 1,4-dinitrobenzene (DNB), a member of the nitroaromatics family of explosives, in acetone solutions at concentrations as low as 6.3 ppm.

  16. Fluorescence quenching of water-soluble conjugated polymer by metal cations and its application in sensor

    NASA Astrophysics Data System (ADS)

    Chen, Yan-Guo; Zhao, Dan; He, Zhi-Ke; Ai, Xin-Ping

    2007-02-01

    The effects of different metal cations on the fluorescence of water-soluble conjugated polymer (CP) and their quenching mechanism have been explored. Most transition metal cations, especially noble metal cations, such as Pd 2+, Ru 3+, and Pt 2+ possessed higher quenching efficiency to CP fluorescence than that of the main group metal cations and other transition metal cations, which have filled or half-full outmost electron layer configurations. Base on this, rapid, sensitive detection of noble metal cations can be realized and a novel quencher-tether-ligand (QTL) probe was developed to detect avidin and streptavidin.

  17. ICP-MS-Based Multiplex Profiling of Glycoproteins Using Lectins Conjugated to Lanthanide-Chelating Polymers

    PubMed Central

    Leipold, Michael D.; Herrera, Isaac; Ornatsky, Olga; Baranov, Vladimir; Nitz, Mark

    2009-01-01

    Lectins have been increasingly important in the study of glycoproteins. Here we report a glycoprofiling method based on the covalent attachment of metal-chelating polymers to lectins for use in an ICP-MS-based assays. The labeled lectins are able to distinguish between glycoproteins covalently attached to a microtiter plate and their binding can be directly quantified by ICP-MS. Since each conjugate contains a different lanthanide, the assays can be conducted in a single or multiplex fashion, and may be readily elaborated to many different assay formats. PMID:19072657

  18. One-step nanopatterning of conjugated polymers by electron-beam-assisted electropolymerization

    PubMed Central

    Higuchi, Takeshi; Nishiyama, Hidetoshi; Suga, Mitsuo; Watanabe, Hirohmi; Takahara, Atsushi; Jinnai, Hiroshi

    2015-01-01

    We propose a one-step nanopatterning method where liquid monomers are polymerized directly with an electron beam under an atmospheric pressure. The method allows precise positional control of an electron beam that induces electropolymerization based on an anodic oxidation only in the irradiated areas. Various versatile conjugated polymers, including polypyrrole, polyaniline and poly(3-hexylthiophene), have been directly polymerized from monomers without solvents and patterned by our one-step nanopatterning method. Vertically oriented arrays of nanorods several hundred nanometers in diameter with an aspect ratio (height to diameter) of around two were fabricated. PMID:25825510

  19. Microporous polymer films and methods of their production

    DOEpatents

    Aubert, J.H.

    1995-06-06

    A process is described for producing thin microporous polymeric films for a variety of uses. The process utilizes a dense gas (liquefied gas or supercritical fluid) selected to combine with a solvent-containing polymeric film so that the solvent is dissolved in the dense gas, the polymer is substantially insoluble in the dense gas, and two phases are formed. A microporous film is obtained by removal of a dense gas-solvent phase. 9 figs.

  20. Electroluminescence from multilayer conjugated polymer devices--spatial control of exciton formation and emission

    NASA Astrophysics Data System (ADS)

    Greenham, Neil C.; Brown, Adam R.; Burroughes, Jeremy H.; Bradley, Donal D. C.; Friend, Richard H.; Burn, Paul L.; Kraft, Arno; Holmes, Andrew B.

    1993-08-01

    We have constructed electroluminescent diodes using several layers of conjugated polymers with differing energy gaps; these provide a range of different color light-emitting layers and can be used to control charge injection and transport. Poly(1,4-phenylenevinylene), PPV, and derivatives have been used, with indium tin oxide as hole-injecting electrode and calcium as electron-injecting electrode. For this selection of materials, we show that the sequence of the polymer layers allows control of the color of device emission. Emission from more than one layer can be produced simultaneously. The position and breadth of the light-emitting region of the device provides information about the mechanisms of charge transport and of exciton motion. Various models for multilayer emission are discussed in the paper.

  1. Gd-containing conjugated polymer nanoparticles: bimodal nanoparticles for fluorescence and MRI imaging

    NASA Astrophysics Data System (ADS)

    Hashim, Zeina; Green, Mark; Chung, Pei Hua; Suhling, Klaus; Protti, Andrea; Phinikaridou, Alkystis; Botnar, Rene; Khanbeigi, Raha Ahmad; Thanou, Maya; Dailey, Lea Ann; Nicola J., Commander; Rowland, Caroline; Scott, Jo; Jenner, Dominic

    2014-06-01

    Aqueous bifunctional semiconductor polymer nanoparticles (SPNs), approximately 30 nm in diameter (as measured from electron microscopy), were synthesised using hydrophobic conjugated polymers, amphiphilic phospholipids and a gadolinium-containing lipid. Their fluorescence quantum yields and extinction coefficients were determined, and their MRI T1-weighted relaxation times in water were measured. The bimodal nanoparticles were readily taken up by HeLa and murine macrophage-like J774 cells as demonstrated by confocal laser scanning microscopy, and were found to be MRI-active, generating a linear relationship between T1-weighted relaxation rates and gadolinium concentrations The synthesis is relatively simple, and can easily result in milligrams of materials, although we fully expect scale-up to the gram level to be easily realised.

  2. Gd-containing conjugated polymer nanoparticles: bimodal nanoparticles for fluorescence and MRI imaging.

    PubMed

    Hashim, Zeina; Green, Mark; Chung, Pei Hua; Suhling, Klaus; Protti, Andrea; Phinikaridou, Alkystis; Botnar, Rene; Khanbeigi, Raha Ahmad; Thanou, Maya; Dailey, Lea Ann; Commander, Nicola J; Rowland, Caroline; Scott, Jo; Jenner, Dominic

    2014-07-21

    Aqueous bifunctional semiconductor polymer nanoparticles (SPNs), approximately 30 nm in diameter (as measured from electron microscopy), were synthesised using hydrophobic conjugated polymers, amphiphilic phospholipids and a gadolinium-containing lipid. Their fluorescence quantum yields and extinction coefficients were determined, and their MRI T₁-weighted relaxation times in water were measured. The bimodal nanoparticles were readily taken up by HeLa and murine macrophage-like J774 cells as demonstrated by confocal laser scanning microscopy, and were found to be MRI-active, generating a linear relationship between T₁-weighted relaxation rates and gadolinium concentrations The synthesis is relatively simple, and can easily result in milligrams of materials, although we fully expect scale-up to the gram level to be easily realised. PMID:24941427

  3. Solvent-modified ultrafast decay dynamics in conjugated polymer/dye labeled single stranded DNA

    NASA Astrophysics Data System (ADS)

    Kim, Inhong; Kang, Mijeong; Woo, Han Young; Oh, Jin-Woo; Kyhm, Kwangseuk

    2015-07-01

    We have investigated that organic solvent (DMSO, dimethyl sulfoxide) modifies energy transfer efficiency between conjugated polymers (donors) and fluorescein-labeled single stranded DNAs (acceptors). In a mixture of buffer and organic solvent, fluorescence of the acceptors is significantly enhanced compared to that of pure water solution. This result can be attributed to change of the donor-acceptor environment such as decreased hydrophobicity of polymers, screening effect of organic solvent molecules, resulting in an enhanced energy transfer efficiency. Time-resolved fluorescence decay of the donors and the acceptors was modelled by considering the competition between the energy harvesting Foerster resonance energy transfer and the energy-wasting quenching. This enables to quantity that the Foerster distance (R0 = 43.3 Å) and resonance energy transfer efficiency (EFRET = 58.7 %) of pure buffer solution become R0 = 38.6 Å and EFRET = 48.0 % when 80% DMSO/buffer mixture is added.

  4. pH-responsive fluorescence chemical sensor constituted by conjugated polymers containing pyridine rings.

    PubMed

    Adachi, Naoya; Kaneko, Yuki; Sekiguchi, Kazuki; Sugiyama, Hiroki; Sugeno, Masafumi

    2015-12-01

    Poly(p-pyridinium phenylene ethynylene)s (PPyPE) functionalized with alternating donor-acceptor repeat units were synthesized by a Pd-catalyzed Sonogashira coupling reaction between diethynyl monomer and di-iodopyridine for use as a pH-responsive fluorescence chemical sensor. The synthesized PPyPE, containing pyridine units, was characterized by FT-IR, (1)H and (13)C NMR, UV-visible and fluorescence spectroscopies. We investigated the relationship between changes of optical properties and protonation/deprotonation of PPyPE containing pyridine units in solution. Addition of HCl decreased and red-shifted the fluorescence intensity of the conjugated polymers that contained pyridine rings; fluorescence intensity of the polymers increased upon addition of NaOH solution. The synthesized PPyPE was found to be an effective and reusable chemical sensor for pH sensing. PMID:25828634

  5. Optically induced mode splitting in self-assembled, high quality-factor conjugated polymer microcavities

    PubMed Central

    Braam, Daniel; Kushida, Soh; Niemöller, Robert; Prinz, Günther M.; Saito, Hitoshi; Kanbara, Takaki; Kuwabara, Junpei; Yamamoto, Yohei; Lorke, Axel

    2016-01-01

    We investigate the whispering gallery modes (WGMs) of self-assembled single microspheres. They consist of a recently developed highly fluorescent π-conjugated copolymer and exhibit excellent optical properties with Q-factors up to 104. Under continuous laser irradiation, we observe a splitting of the highly degenerate spherical WGMs into a multiplet of lines. Comparison with the calculated spectral response of a weakly distorted sphere shows that the optical excitation induces a change of the optical path length in the microcavity so that it resembles a prolate spheroid. The separation of the lines is given by the ellipticity and the azimuthal mode number. Measurements in various gaseous environments suggest that the distortion is caused by light induced oxidation of the polymer. Our findings show that photooxidation can be a beneficial mechanism for in-situ tuning of optically active polymer structures. PMID:26781838

  6. Deviations from Liquidlike Behavior in Molten Polymer Films at Interfaces

    NASA Astrophysics Data System (ADS)

    Seo, Young-Soo; Koga, T.; Sokolov, J.; Rafailovich, M. H.; Tolan, M.; Sinha, S.

    2005-04-01

    We have performed x-ray specular and diffuse scattering on liquid polymer films and analyzed the spectra as a function of film thickness and molecular weight. The results show that films whose molecular weight is close to the entanglement length behave as simple liquids except that the shortest wavelength is determined by the radius of gyration (Rg) rather than the monomer-monomer distance. When the molecular weight is higher than the entanglement length, the strong deviations from liquidlike behavior are observed. We find that the long wavelength cutoff vector, ql,c, scales with film thickness, d as d-1.1±0.1 rather than the usual d-2 expected for simple liquids. If we assume that these deviations are due to surface pinning of the polymer chains, then our results are consistent with the formalism developed by Fredrickson et al. to explain the capillary wave spectrum that can propagate in a polymer brush.

  7. Composite membranes from photochemical synthesis of ultrathin polymer films

    NASA Astrophysics Data System (ADS)

    Liu, Chao; Martin, Charles R.

    1991-07-01

    THERE has recently been a resurgence of interest in synthetic membranes and membrane-based processes1-12. This is motivated by a wide variety of technological applications, such as chemical separations1-7, bioreactors and sensors8,9, energy conversion10,11 and drug-delivery systems12. Many of these technologies require the ability to prepare extremely thin, defect-free synthetic (generally polymeric) films, which are supported on microporous supports to form composite membranes. Here we describe a method for producing composite membranes of this sort that incorporate high-quality polymer films less than 50-nm thick. The method involves interfacial photopolymerization of a thin polymer film on the surface of the microporous substrate. We have been able to use this technique to synthesize a variety of functionalized ultrathin films based on electroactive, photoactive and ion-exchange polymers. We demonstrate the method here with composite membranes that show exceptional gas-transport properties.

  8. Ion-Conducting Polymer Films as Chemical Sensors

    SciTech Connect

    Hughes, R.C.; Patel, S.V.; Pfeifer, K.B.; Yelton, W.G.

    1999-05-03

    Solid Polymer Electrolytes (SPE) are widely used in batteries and fuel cells because of the high ionic conductivity that can be achieved at room temperature. The ions are usually Li or protons, although other ions can be shown to conduct in these polymer films. There has been very little work on using these films as chemical sensors. We have found that thin films of polymers like polyethyleneoxide (PEO) are very sensitive to low concentrations of volatile organic compounds (VOCS) like common solvents. We will present impedance spectroscopy of PEO films in the frequency range 0.01 Hz to 1 MHz for different concentrations of VOCS. We find that the measurement frequency is important for distinguishing ionic conductivity from the double layer capacitance and parasitic capacitances.

  9. Electrochemically Directed Self-Assembly and Conjugated Polymer Semiconductors for Organic Electronic Applications

    NASA Astrophysics Data System (ADS)

    Pillai, Rajesh Gopalakrishna

    2011-07-01

    The research work presented in this thesis investigates the mechanistic details of conventional as well as electrochemically directed self-assembly of alkylthiosulfates and explores the use of conjugated semiconducting polymers for organic electronic applications. Here, the significance of the use of conjugated polymers is twofold; first, to explore their applications in nanoelectronics and second, the possibility of using them as a top contact on the self-assembled monolayers (SAMs) for molecular electronic applications. Throughout this work, deposition of the organic materials was performed on prefabricated device structures that required no further lithographic or metal deposition steps after modification of the electrodes with the organic molecules. Self-assembly of alkylthiosulfates on gold are reported to form monolayers identical to those formed from the corresponding alkanethiols. However, these self-assembly processes follow more complex mechanisms of monolayer formation than originally recognized. Studies on the mechanism of alkylthiosulfate chemisorption on gold shows that the self-assembly process is influenced by electrolyte and solvent. Plausible mechanisms have been proposed for the role of trace water in the solvent on conventional as well as electrochemically assisted self-assembly of alkylthiosulfates on gold. Electroanalytical and spectroscopic techniques have been used to explore the mechanistic details of electrochemically directed self-assembly of alkylthiosulfates on gold. It has been found that the self-assembly process is dynamic under electrochemical conditions and the heterogeneous electron transfer process between the organosulfur compound and gold is mediated through gold surface oxide and accompanied by corrosion. Conducting polymers are serious candidates for organic electronic applications since their properties can be controlled by the manipulation of molecular architecture. Unique electronic properties of conjugated polypyrrole

  10. Controlled release of tocopherols from polymer blend films

    NASA Astrophysics Data System (ADS)

    Obinata, Noe

    Controlled release packaging has great potential to increase storage stability of foods by releasing active compounds into foods continuously over time. However, a major limitation in development of this technology is the inability to control the release and provide rates useful for long term storage of foods. Better understanding of the factors affecting active compound release is needed to overcome this limitation. The objective of this research was to investigate the relationship between polymer composition, polymer processing method, polymer morphology, and release properties of active compounds, and to provide proof of principle that compound release is controlled by film morphology. A natural antioxidant, tocopherol was used as a model active compound because it is natural, effective, heat stable, and soluble in most packaging polymers. Polymer blend films were produced from combination of linear low density polyethylene (LLDPE) and high density polyethylene (HDPE), polypropylene (PP), or polystyrene (PS) with 3000 ppm mixed tocopherols using conventional blending method and innovative blending method, smart blending with a novel mixer using chaotic advection. Film morphologies were visualized with scanning electron microscopy (SEM). Release of tocopherols into 95% ethanol as a food simulant was measured by UV/Visible spectrophotometry or HPLC, and diffusivity of tocopherols in the polymers was estimated from this data. Polymer composition (blend proportions) and processing methods have major effects on film morphology. Four different types of morphologies, dispersed, co-continuous, fiber, and multilayer structures were developed by either conventional extrusion or smart blending. With smart blending of fixed polymer compositions, different morphologies were progressively developed with fixed polymer composition as the number of rod rotations increased, providing a way to separate effects of polymer composition and morphology. The different morphologies

  11. Metal-Organic-Framework-Templated Polyelectrolyte Nanocapsules for the Encapsulation and Delivery of Small-Molecule-Polymer Conjugates.

    PubMed

    Liu, Shuo; Chen, Jianbin; Bao, Xiaojia; Li, Tao; Ling, Yunyang; Li, Chunxiang; Wu, Chuanliu; Zhao, Yibing

    2016-06-21

    Herein, we report a strategy for exploiting nanoscale metal-organic frameworks (nano-MOFs) as templates for the layer-by-layer (LbL) assembly of polyelectrolytes. Because small-molecule drugs or imaging agents cannot be efficiently encapsulated by polyelectrolyte nanocapsules, we investigated two promising and biocompatible polymers (comb-shaped polyethylene glycol (PEG) and hyperbranched polyglycerol-based PEG) for the conjugation of model drugs and imaging agents, which were then encapsulated inside the nano-MOF-templated nanocapsules. Furthermore, we also systemically explored the release kinetics of the encapsulated conjugates, and examined how the encapsulation and/or release processes could be controlled by varying the composition and architecture of the polymers. We envision that our nano-MOFs-templated nanocapsules, through combining with small-molecule-polymer conjugates, will represent a new type of delivery system that could open up new opportunities for biomedical applications. PMID:27123998

  12. Vacuum deposited polymer/metal films for optical applications

    SciTech Connect

    Affinito, J.D.; Martin, P.M.; Gross, M.E.; Coronado, C.; Greenwell, E.

    1995-04-01

    Vacuum deposited Polymer/Silver/Polymer reflectors and Tantalum/Polymer/Aluminum Fabry-Perot interference filters were fabricated in a vacuun web coating operation on polyester substrates with a new, high speed deposition process. Reflectivities were measured in the wavelength range from 0.3 to 0.8{mu}m. This new vacuum processing technique has been shown to be capable of deposition line speeds in excess of 500 linear meters/minute. Central to this technique is a new position process for the high rate deposition of polymer films. This polymer process involves the flash evaporation of an acrylic monomer onto a moving substrate. The monomer is subsequently cured by an electron beam or ultraviolet light. This high speed polymer film deposition process has been named the PML process -- for Polymer Multi-Layer. Also, vacuum deposited, index matched, polymer/CaF{sub 2} composites were fabricated from monomer slurries that were subsequently cured with LTV light. This second technique is called the Liquid Multi-Layer (or LML) process. Each of these polymer processes is compatible with each other and with conventional vacuum deposition processes such as sputtering or evaporation.

  13. Electrodeposition and Screening of Photoelectrochemical Activity in Conjugated Polymers Using Scanning Electrochemical Cell Microscopy.

    PubMed

    Aaronson, Barak D B; Garoz-Ruiz, Jesus; Byers, Joshua C; Colina, Alvaro; Unwin, Patrick R

    2015-11-24

    A number of renewable energy systems require an understanding and correlation of material properties and photoelectrochemical activity on the micro to nanoscale. Among these, conducting polymer electrodes continue to be important materials. In this contribution, an ultrasensitive scanning electrochemical cell microscopy (SECCM) platform is used to electrodeposit microscale thin films of poly(3-hexylthiophene) (P3HT) on an optically transparent gold electrode and to correlate the morphology (film thickness and structural order) with photoactivity. The electrochemical growth of P3HT begins with a thin ordered film up to 10 nm thick, after which a second more disordered film is deposited, as revealed by micro-Raman spectroscopy. A decrease in photoactivity for the thicker films, measured in situ immediately following film deposition, is attributed to an increase in bulk film disorder that limits charge transport. Higher resolution ex situ SECCM phototransient measurements, using a smaller diameter probe, show local variations in photoactivity within a given deposit. Even after aging, thinner, more ordered regions within a deposit exhibit sustained enhanced photocurrent densities compared to areas where the film is thicker and more disordered. The platform opens up new possibilities for high-throughput combinatorial correlation studies, by allowing materials fabrication and high spatial resolution probing of processes in photoelectrochemical materials. PMID:26502089

  14. Origin of Near-Infrared Absorption for Azulene-Containing Conjugated Polymers upon Protonation or Oxidation.

    PubMed

    Tang, Tao; Lin, Tingting; Wang, FuKe; He, Chaobin

    2015-06-25

    A series of azulene-containing conjugated polymers were studied to elucidate their tunable absorption properties in near-infrared (NIR) regions (i.e., 1.2-2.5 μm) upon protonation/oxidation. Density function theory (DFT) revealed that protonation-induced intramolecular charge transfer (ICT) in the polymer backbone lead to strong NIR absorption. Distinct spectral change was observed when tiny amount of peroxide was added to the protonated polymer in trifluoroacetic acid/chloroform solution. Electron paramagnetic resonance (EPR) study confirmed the presence of radical cation, which results in the occurrence of newly formed absorption band after the addition of peroxide. The spectro-electrochemical results and DFT study indicate that polarons and polaron pairs were formed during p-doping process, and both the chemical oxidation and electrochemical oxidation could be facilitated by TFA protonation. This represents the first reported mechanisms of NIR absorption under various protonation/oxidation conditions in a single polymer system. PMID:25993246

  15. Excitation Dependence of Photoinduced Absorption (PA) in Π-Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Zhai, Yaxin; Basel, Tek; Vardeny, Z. Valy

    2014-03-01

    In order to study the process of singlet fission (SF), where a singlet exciton decomposes into a pair of triplets S0 +S1 -->T1 +T1 , we have investigated the excitation dependence of the photoinduced absorption band of triplet exciton (EXPA) and photoluminescence (EXPL) in various luminescent and non-luminescent π-conjugated polymers. We found that the EXPA spectrum of luminescent polymers is composed of two steps, showing that two different channels are operative for triplet photogeneration. One process starts at the optical gap and has flat response similar to that of the EXPL spectrum. We therefore identify this process as due to intersystem crossing from the lowest lying singlet exciton. Whereas the second process with an onset at E ~ 2ET , where ET is the triplet energy is due to singlet fission of hot excitons. We also found that the EXPA spectrum of some non luminescent polymers is different from that of the luminescent polymers. Supported in part by the NSF-MRSEC program at the University of Utah.

  16. Long Circulating Micelles based on Helix Bundle-Forming Peptide-Polymer Conjugates

    NASA Astrophysics Data System (ADS)

    Shu, Jessica; Dong, He; Dube, Nikhil; Seo, Jai Woong; Ma, Yu Fei; Ferrara, Katherine; Xu, Ting

    2012-02-01

    Stable, multi-functional organic nanoparticles that combine long in vivo circulation, the ability to cross vessel walls to reach tumor tissues and controlled disassembly for eventual clearance will have a significant impact in nanomedicine. Although current self-assemblies of amphiphiles provide a versatile platform to generate modular organic nanoparticles, it remains a significant challenge to simultaneously control nanoparticle size in the range of 10-30 nm, enhance particle stability and tailor disassembly within suitable timescales. We have advanced this goal by designing a new family of amphiphiles based on coiled-coil 3-helix bundle forming peptide-polymer conjugates. By attaching a polymer chain to the middle of a helical peptide, the protein tertiary structures are used to position entropic forces of compressed polymer chains comprising the headgroups so as to effectively slow down the subunit desorption rate and enhance the in vivo stability. The resultant monodispersed nanoparticles are composed of subunits, < 4 nm in size, that form highly stable 15-17 nm diameter particles and demonstrate an in vivo circulation half life-time of 28 hrs, minimal accumulation in the liver and spleen and effective urinary clearance. By uniquely combining the configurational entropy of a polymer chain with a common protein structure, i.e. coiled-coil helix bundle, and a lipid core, self-assembled nanoparticles have been engineered with tunable stability and disassembly.

  17. Conjugated Polymer Blend Microspheres for Efficient, Long-Range Light Energy Transfer.

    PubMed

    Kushida, Soh; Braam, Daniel; Dao, Thang Duy; Saito, Hitoshi; Shibasaki, Kosuke; Ishii, Satoshi; Nagao, Tadaaki; Saeki, Akinori; Kuwabara, Junpei; Kanbara, Takaki; Kijima, Masashi; Lorke, Axel; Yamamoto, Yohei

    2016-05-24

    Highly luminescent π-conjugated polymeric microspheres were fabricated through self-assembly of energy-donating and energy-accepting polymers and their blends. To avoid macroscopic phase separation, the nucleation time and growth rate of each polymer in the solution were properly adjusted. Photoluminescence (PL) studies showed that efficient donor-to-acceptor energy transfer takes place inside the microspheres, revealing that two polymers are well-blended in the microspheres. Focused laser irradiation of a single microsphere excites whispering gallery modes (WGMs), where PL generated inside the sphere is confined and resonates. The wavelengths of the PL lines are finely tuned by changing the blending ratio, accompanying the systematic yellow-to-red color change. Furthermore, when several microspheres are coupled linearly, the confined PL propagates the microspheres through the contact point, and a cascade-like process converts the PL color while maintaining the WGM characteristics. The self-assembly strategy for the formation of polymeric nano- to microstructures with highly miscible polymer blends will be advantageous for optoelectronic and photonic device applications. PMID:27135760

  18. Single molecule spectroscopy of conjugated polymer chains in an electric field-aligned liquid crystal.

    PubMed

    Chang, Wei-Shun; Link, Stephan; Yethiraj, Arun; Barbara, Paul F

    2008-01-17

    Using single molecule polarization spectroscopy, we investigated the alignment of a polymer solute with respect to the liquid crystal (LC) director in an LC device while applying an external electric field. The polymer solute is poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (or MEH-PPV), and the LC solvent is 5CB. The electric field induces a change in the LC director orientation from a planar alignment (no electric field) to a perpendicular (homeotropic) alignment with an applied field of 5.5 x 103 V/cm. We find that the polymer chains align with the LC director in both planar and homeotropic alignment when measured in the bulk of the LC solution away from the device interface. Single molecule polarization distributions measured as a function of distance from the LC device interface reveal a continuous change of the MEH-PPV alignment from planar to homeotropic. The observed polarization distributions are modeled using a conventional elastic model that predicts the depth profile of the LC director orientation for the applied electric field. The excellent agreement between experiment and simulations shows that the alignment of MEH-PPV follows the LC director throughout the LC sample. Furthermore, our results suggest that conjugated polymers such as MEH-PPV can be used as sensitive local probes to explore complex (and unknown) structures in anisotropic media. PMID:17975912

  19. Biological Functionalization of Conjugated Polymer Nanoparticles for Targeted Imaging and Photodynamic Killing of Tumor Cells.

    PubMed

    Feng, Liheng; Zhu, Jiarong; Wang, Zhijun

    2016-08-01

    Conjugated polymer nanoparticles composed of PFT/PS as a core and PEG-COOH on the surface were prepared by a reprecipitating method. The CPNs diaplay excellet properties such as good photostability, low cytotoxicity, and strong brightness, etc. The average diamater of CPNs is 30 nm with a spherical morphology. To realize specific imaging in different parts of tumor cells, the bare CPNs with the carboxyls on the surface were conjugated with antibody or peptide by a covalent mode. Studies display that CPNs modified with anti-EpCAM can recognize MCF-7 tumor cells and locate on the membrane, while CPNs conjugated with transcriptional activator protein (Tat) specifically locate in the cytoplasm of MCF-7 cells. On the basis of the ability of CPNs for producing reactive oxygen species (ROS) under light irradiation, photodynamic therapy for tumor cells was investigated. Due to the long distance and wide diffusion range, MCF-7 tumor cells with CPNs/anti-EpCAM have no obvious change with or without white light irradiation. However, CPNs/Tat exhibits higher killing ability for MCF-7 cells. Noticeably, multifunctional CPNs linked with anti-EpCAM and Tat simultaneously not only can specifically target MCF-7 tumor cells, but also may inhibit and kill these cells. This work develops a potential application platform for multifunctional CPNs in locating imaging, photodynamic therapy, and other aspects. PMID:27406913

  20. Protonation process of conjugated polyelectrolytes on enhanced power conversion efficiency in the inverted polymer solar cells

    NASA Astrophysics Data System (ADS)

    Yi, Chao; Hu, Rong; Ren, He; Hu, Xiaowen; Wang, Shu; Gong, Xiong; Cao, Yong

    2014-01-01

    In this study, two conjugated polyelectrolytes, polythiophene derivative (PTP) and poly[(9,9-bis [6‧-N, N, N-trimethylammonium] hexyl)-fluorenylene-phenylene] dibromide (PFP), are utilized to modify the surface properties of ZnO electron extraction layer (EEL) in the inverted polymer solar cells (PSCs). Both higher short-circuit current densities and larger open-circuit voltages were observed from the inverted PSCs with ZnO/PFP or ZnO/PTP as compared with those only with ZnO EEL. The protonation process for PTP and PFP in solution is distinguished. Overall, more than 40% enhanced power conversion efficiency (PCE) from the inverted PSCs with ZnO/PFP, in which the PFP could be fully ionized in deionized water, and more than 30% enhanced PCE from the inverted PSCs with ZnO/PTP, as the case that the PTP could not be fully ionized in deionized water, as compared with the inverted PSCs with ZnO EEL were observed, respectively. These results demonstrate that the conjugated polyelectrolytes play an important role in enhancement of device performance of inverted PSCs and that the protonation process of the conjugated polyelectrolytes is critical to the modification for EEL in PSCs.

  1. Photoluminescence and solid state properties of rigid pi- conjugated polymers with applications to LED: Alkyl- substituted p-phenyleneethynylene polymers and triblock copolymers

    NASA Astrophysics Data System (ADS)

    Huang, Wen-Yao

    A series of substituted poly(p-phenyleneethynylene)s, PPE, were synthesized by alkyne metathesis. The substituents dibutyl (a), dioctyl (b), ditetradecyl (c), di-2-ethylhexyl (d) and di-2-cyclohexylethyl; (e)were placed on the 2,5 positions of the phenyl rings. X-ray diffraction studies indicated that the main chains of each polymer were arranged in regular, layered arrays. Liquid crystalline structures were observed by polarized optical microscopy in PPE 4b, 4c and 4d. The temperatures of isotropization of the liquid crystalline structures coincided with the disordering temperatures determined by differential scanning calorimetry. The UV absorption spectra showed a gradual blue shift of the λmax for all these polymers, suggesting a decrease in the electronic delocalization along the chain as the size and geometry of the side group changed. The photoluminescence spectra in dilute toluene solutions are consistent with vibronic coupling and emission from localized excited states. The emission spectra of thin films show characteristics typical of excimer or aggregate formation in the solid state. Lastly, an improved method of molecular weight determination by end group analysis was devised. Molecular organization and orientation in thin films (~100 nm) of a triblock copolymer, PPEPEG, was studied. The morphology of the thin film can be visualized as consisting of PMMA as the major phase in which domains of vertically oriented triblock copolymers are dispersed with PEG groups facing the air-film interface. The molecular and supramolecular structure of a series of well-defined fully conjugated poly(2,5- diakyl-p-phenyleneethynylene)s, PPE, in toluene has been studied in the sol state and in the gel state by surface tension and photoluminescence measurements. Poly (2,6[4- phenyl quinoline]), I, and poly (2,6[p-phenylene] 4- phenyl quinoline), II, were synthesized by the self- condensation of 5-acetyl-2-aminobezophenone and 4-amino- 4 '-acetyl-3-benzoyl biphenyl

  2. Creating Patterned Conjugated Polymer Images Using Water-Compatible Reactive Inkjet Printing.

    PubMed

    Jeon, Seongho; Park, Sumin; Nam, Jihye; Kang, Youngjong; Kim, Jong-Man

    2016-01-27

    The fabrication of patterned conjugated polymer images on solid substrates has gained significant attention recently. Office inkjet printers can be used to generate flexible designs of functional materials on substrates on a large scale and in an inexpensive manner. Although creating patterns of conjugated polymers on paper using common office inkjet printers has been reported, only a few examples exist, such as polyaniline (PANI) and poly(3,4-ethylenedioxythiophene) (PEDOT), because only water-compatible inks can be utilized. Herein, we describe the production of poly(phenylenevinylene) (PPV) patterns on paper by employing a reactive inkjet printing (RIJ) method. In this process, printing of a hydrophilic terephthaldehyde, bis(triphenylphosphonium salt) and potassium t-butoxide using a common office inkjet printer leads to formation PPV patterns as a consequence of an in situ Wittig reaction. In addition, microarrayed PPV patterns are also readily generated on solid substrates, such as glass and PDMS, when a piezoelectric dispenser system is employed. The in situ prepared PPV was found to be insoluble in water and chloroform. As a result, unreacted excess reagents and byproducts can be efficiently removed by washing with these solvents. PMID:26731170

  3. Selective crystallization of conjugated polymers into nanowires from graphene coated surfaces

    NASA Astrophysics Data System (ADS)

    Acevedo-Cartagena, Daniel; Zhu, Jiaxin; Trabanino, Elvira; Pentzer, Emily; Emrick, Todd; Briseño, Alejandro; Nonnenmann, Stephen; Hayward, Ryan

    Solution-based crystallization of conjugated polymers offers a scalable and attractive route to develop hierarchical structures for organic electronic devices, especially solar cells. The introduction of well-defined nucleation sites into metastable supersaturated solutions provides a way to regulate the crystallization behavior, and therefore the morphology of the material. We focus on metastable solutions of poly(3-hexylthiophene) (P3HT) dissolved in mixtures of m-xylene, a marginal solvent, and chlorobenzene, a good solvent. Appropriate levels of supersaturation are identified to suppress homogenous nucleation of crystals at room temperature, while allowing for crystallization on heterogeneous nucleation sites. We show that in these metastable solutions, P3HT selectively crystallizes on graphene-coated surfaces. Through in situ atomic force microscopy, we confirm that nanowires grow vertically in a face-on orientation from highly oriented pyrolytic graphite and graphene. Moreover, this method can be successfully extended to other conjugated polymers with superior electronic properties, such as poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b] thiophene]. Therefore, this method is a promising route to improve the performance of organic electronics.

  4. Effect of the Pauli exclusion principle on the singlet exciton yield in conjugated polymers

    NASA Astrophysics Data System (ADS)

    Thilagam, A.

    2016-03-01

    Optical devices fabricated using conjugated polymer systems give rise to singlet exciton yields which are high compared to the statistically predicted estimate of 25 % obtained using simple recombination schemes. In this study, we evaluate the singlet exciton yield in conjugated polymers systems by fitting to a model that incorporates the Pauli exclusion principle. The rate equations which describe the exciton dynamics include quantum dynamical components (both density and spin-dependent) which arise during the spin-allowed conversion of composite intra-molecular excitons into loosely bound charge-transfer (CT) electron-hole pairs. Accordingly, a crucial mechanism by which singlet excitons are increased at the expense of triplet excitons is incorporated in this work. Non-ideal triplet excitons which form at high densities, are rerouted via the Pauli exclusion mechanism to form loosely bound CT states which subsequently convert to singlet excitons. Our derived expression for the yield in singlet exciton incorporates the purity measure and provides a realistic description of the carrier dynamics at high exciton densities.

  5. Formation and characterization of stable fluorescent complexes between neutral conjugated polymers and cyclodextrins.

    PubMed

    Martínez-Tomé, Maria José; Esquembre, Rocío; Mallavia, Ricardo; Mateo, C Reyes

    2013-01-01

    Solubilisation and stabilization of conjugated polymers, CPs, in aqueous media remains a challenge for many researches trying to extend the biological and environmental applications of this kind of polymers. A number of different alternatives have been considered to address this problem, which are mostly based on the enhancement of the macromolecule polarity, by appending hydrophilic side chains on the polymer backbone. In this work we have investigated a new strategy in which water solubilization is reached by external addition of classical cyclodextrins (α-, β- and γ-CDs) to a solution of non-polar CPs. This strategy allows working with such polymers eliminating the need to synthesize new water-soluble species. The polymer selected for the study was poly-[9,9-bis(6'-bromohexyl-2,7-fluoren-dyil)-co-alt-(benzene-1,4-diy)], PFPBr(2), a polyfluorene previously synthesized in our laboratory. Results show that PFPBr(2) forms fluorescent complexes in aqueous media with β-CD and γ-CD, and much less efficiently with α-CD, probably due to the small size of its cavity. The new PFPBr(2)/CD complexes are stable in time and in a large range of pH, however, at high concentration and temperature, they tend to aggregate and precipitate. In order to increase stabilization and minimize polymer aggregation, complexes were encapsulated inside the pores of silica glasses fabricated using the sol-gel process, obtaining transparent and fluorescent hybrid matrices which were stable in time and temperature. In addition, immobilization of the complexes allows an easy manipulation of the material, thus offering promising applications in the development of biological and chemical sensors. PMID:22993121

  6. Dielectric breakdown in silica-amorphous polymer nanocomposite films: the role of the polymer matrix.

    PubMed

    Grabowski, Christopher A; Fillery, Scott P; Westing, Nicholas M; Chi, Changzai; Meth, Jeffrey S; Durstock, Michael F; Vaia, Richard A

    2013-06-26

    The ultimate energy storage performance of an electrostatic capacitor is determined by the dielectric characteristics of the material separating its conductive electrodes. Polymers are commonly employed due to their processability and high breakdown strength; however, demands for higher energy storage have encouraged investigations of ceramic-polymer composites. Maintaining dielectric strength, and thus minimizing flaw size and heterogeneities, has focused development toward nanocomposite (NC) films; but results lack consistency, potentially due to variations in polymer purity, nanoparticle surface treatments, nanoparticle size, and film morphology. To experimentally establish the dominant factors in broad structure-performance relationships, we compare the dielectric properties for four high-purity amorphous polymer films (polymethyl methacrylate, polystyrene, polyimide, and poly-4-vinylpyridine) incorporating uniformly dispersed silica colloids (up to 45% v/v). Factors known to contribute to premature breakdown-field exclusion and agglomeration-have been mitigated in this experiment to focus on what impact the polymer and polymer-nanoparticle interactions have on breakdown. Our findings indicate that adding colloidal silica to higher breakdown strength amorphous polymers (polymethyl methacrylate and polyimide) causes a reduction in dielectric strength as compared to the neat polymer. Alternatively, low breakdown strength amorphous polymers (poly-4-vinylpyridine and especially polystyrene) with comparable silica dispersion show similar or even improved breakdown strength for 7.5-15% v/v silica. At ∼15% v/v or greater silica content, all the polymer NC films exhibit breakdown at similar electric fields, implying that at these loadings failure becomes independent of polymer matrix and is dominated by silica. PMID:23639183

  7. Simulated Space Vacuum Ultraviolet (VUV) Exposure Testing for Polymer Films

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; Pietromica, Anthony J.; Stueber, Thomas J.; Sechkar, Edward A.; Messer, Russell K.

    2002-01-01

    Vacuum ultraviolet (VUV) radiation of wavelengths between 115 and 200 nm produced by the sun in the space environment can cause degradation to polymer films producing changes in optical, mechanical, and chemical properties. These effects are particularly important for thin polymer films being considered for ultra-lightweight space structures, because, for most polymers, VUV radiation is absorbed in a thin surface layer. NASA Glenn Research Center has developed facilities and methods for long-term ground testing of polymer films to evaluate space environmental VUV radiation effects. VUV exposure can also be used as part of sequential simulated space environmental exposures to determine combined damaging effects. This paper will describe the effects of VUV on polymer films and the necessity for ground testing. Testing practices used at Glenn Research Center for VUV exposure testing will be described including characterization of the VUV radiation source used, calibration procedures traceable to the National Institute of Standards and Technology (NIST), and testing techniques for VUV exposure of polymer surfaces.

  8. Patterning Thin Polymer Films by Photodirecting the Marangoni Effect

    NASA Astrophysics Data System (ADS)

    Ellison, Christopher; Kim, Chae Bin; Janes, Dustin; Katzenstein, Joshua

    2014-03-01

    New methodologies for patterning micro- and nano- scale features in polymer thin films are desired because of their high technological relevance to a range of applications, including microelectronics fabrication. A new non-contact strategy for high-speed patterning of arbitrary shapes in polymer films that involves photochemically directing the Marangoni effect will be described. The Marangoni effect drives the formation of thin film topography by causing liquid flow in response to surface energy gradients. In this approach, a topographical pattern can be preprogrammed and stored in a smooth glassy film using light activated chemistry to pattern surface energy gradients. The topography can be later revealed by heating the film to the liquid state without use of a wet or dry etch step, unlike traditional photoresist methods. The use of grafting reactions from small molecule photosensitizers to change the surface energy locally in polymers that do not intrinsically undergo photochemical reactions will also be discussed. Judicious selection of the photosensitizing compound in an otherwise transparent polymer expands the use of this method to more readily available light sources. We believe this methodology will be potentially useful as a facile and ubiquitous patterning technique for many polymers.

  9. Lattice cluster theory for dense, thin polymer films

    NASA Astrophysics Data System (ADS)

    Freed, Karl F.

    2015-04-01

    While the application of the lattice cluster theory (LCT) to study the miscibility of polymer blends has greatly expanded our understanding of the monomer scale molecular details influencing miscibility, the corresponding theory for inhomogeneous systems has not yet emerged because of considerable technical difficulties and much greater complexity. Here, we present a general formulation enabling the extension of the LCT to describe the thermodynamic properties of dense, thin polymer films using a high dimension, high temperature expansion. Whereas the leading order of the LCT for bulk polymer systems is essentially simple Flory-Huggins theory, the highly non-trivial leading order inhomogeneous LCT (ILCT) for a film with L layers already involves the numerical solution of 3(L - 1) coupled, highly nonlinear equations for the various density profiles in the film. The new theory incorporates the essential "transport" constraints of Helfand and focuses on the strict imposition of excluded volume constraints, appropriate to dense polymer systems, rather than the maintenance of chain connectivity as appropriate for lower densities and as implemented in self-consistent theories of polymer adsorption at interfaces. The ILCT is illustrated by presenting examples of the computed profiles of the density, the parallel and perpendicular bonds, and the chain ends for free standing and supported films as a function of average film density, chain length, temperature, interaction with support, and chain stiffness. The results generally agree with expected general trends.

  10. Lattice cluster theory for dense, thin polymer films

    SciTech Connect

    Freed, Karl F.

    2015-04-07

    While the application of the lattice cluster theory (LCT) to study the miscibility of polymer blends has greatly expanded our understanding of the monomer scale molecular details influencing miscibility, the corresponding theory for inhomogeneous systems has not yet emerged because of considerable technical difficulties and much greater complexity. Here, we present a general formulation enabling the extension of the LCT to describe the thermodynamic properties of dense, thin polymer films using a high dimension, high temperature expansion. Whereas the leading order of the LCT for bulk polymer systems is essentially simple Flory-Huggins theory, the highly non-trivial leading order inhomogeneous LCT (ILCT) for a film with L layers already involves the numerical solution of 3(L − 1) coupled, highly nonlinear equations for the various density profiles in the film. The new theory incorporates the essential “transport” constraints of Helfand and focuses on the strict imposition of excluded volume constraints, appropriate to dense polymer systems, rather than the maintenance of chain connectivity as appropriate for lower densities and as implemented in self-consistent theories of polymer adsorption at interfaces. The ILCT is illustrated by presenting examples of the computed profiles of the density, the parallel and perpendicular bonds, and the chain ends for free standing and supported films as a function of average film density, chain length, temperature, interaction with support, and chain stiffness. The results generally agree with expected general trends.

  11. First-principles calculation of optical absorption spectra in conjugated polymers: Role of electron-hole interaction

    SciTech Connect

    Rohlfing, Michael; Tiago, M.L.; Louie, Steven G.

    2000-03-20

    Experimental and theoretical studies have shown that excitonic effects play an important role in the optical properties of conjugated polymers. The optical absorption spectrum of trans-polyacetylene, for example, can be understood as completely dominated by the formation of exciton bound states. We review a recently developed first-principles method for computing the excitonic effects and optical spectrum, with no adjustable parameters. This theory is used to study the absorption spectrum of two conjugated polymers: trans-polyacetylene and poly-phenylene-vinylene(PPV).

  12. Effect of crystalline microstructure on the photophysical performance of polymer/perylene composite films

    NASA Astrophysics Data System (ADS)

    Feng, Wei; Xu, You-Long; Yi, Wen-Hui; Zhou, Feng; Wang, Xiao-Gong; Katsumi, Yoshino

    2003-04-01

    To obtain high carrier mobility, better charge injection capability and high photovoltaic device conversion efficiency, a powerful strategy is to improve the morphology of the polymer/dye composite films. Conjugated conducting polymer (CP) thin films doped with perylene derivative (PV) of various concentrations were prepared by spin-casting method and their morphology and photovoltaic characteristics were examined. The change in morphology and molecular reorientation occurring in CP-PV composite films upon annealing at different temperatures was investigated using scanning electron microscopy, x-ray diffraction, Fourier transform infrared and UV-vis absorption. By changing the annealing temperature, PV microcrystallines of 8-10µm in size lying parallel to the substrate surface can be obtained. Annealing effect improved the photovoltaic performance of ITO/CP-PV/Al Schottky-type solar cells, which can be attributed to the formation of an electron conducting PV crystal network. Preliminary studies indicate that the morphological structure in CP-PV composite films has an important influence to their photovoltaic properties.

  13. Thieno[3,4-c]Pyrrole-4,6-Dione and Dithiophene-Based Conjugated Polymer for Organic Field Effect Transistors: High Mobility Induced by Synergic Effect of H-Bond and Vinyl Linkage.

    PubMed

    Qing, Wanmei; Gong, Xiaodi; Liang, Xianfeng; Wang, Yuancheng; Yang, Sifen; Tan, Luxi; Ma, Yanping; Liu, Zitong; Li, Jing

    2016-08-01

    Here, a conjugated polymer VTTPD based on thieno[3,4-c]pyrrole-4,6-dione (TPD) and dithiophene with vinyl as linker is synthesized and characterized. Electrochemical and optical studies indicate the LUMO and HOMO energies of the polymer are -3.70 and -5.39 eV. Theoretical calculation with density functional theory suggests that H-bonds are formed between the TPD carbonyl (O) and its neighboring vinyl (H) which benefit the planarity and π-conjugation of the polymer backbone. Bottom contact bottom gate organic field effect transistor devices based on VTTPD are fabricated and examined in air. After annealing at 160 °C, the devices exhibit excellent performance of μh = 0.4 cm(2) V(-1) s(-1) , Ion/off = 10(6) , Vth within -10 V to -5 V. Thin film morphologies before and after the annealing process are also investigated with XRD and AFM. PMID:27304842

  14. Surfactant-free, low band gap conjugated polymer nanoparticles and polymer:fullerene nanohybrids with potential for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Wang, Suxiao; Singh, Amita; Walsh, Nichola; Redmond, Gareth

    2016-06-01

    Stable, aqueous dispersions of nanoparticles based on the low band gap polymers poly [2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4‧,7‧-di-2-thienyl-2‧,1‧,3‧-benzothiadiazole)] (APFO-3) and poly [N-9‧-heptadecanyl-2,7-carbazole-alt-5,5-(4‧,7‧-di-2-thienyl-2‧,1‧,3‧-benzothiadiazole)] (PCDTBT) were prepared, using a flexible, surfactant-free reprecipitation method, and characterized by a variety of optical techniques. Light scattering measurements indicated average nanoparticle hydrodynamic diameters of approximately 40 nm. The particles presented wide-bandwidth absorption and photoluminescence excitation spectra with high absorption cross-sections on the order of 10‑12 cm2. Nanoparticle emission spectra were significantly red-shifted, with decreased emission quantum yields and lifetimes, consistent with increased inter-polymer chain interactions in the condensed phase. Single particle photoluminescence studies highlighted the multi-chromophoric nature of the polymer nanoparticles and confirmed their favorable photostabilities. When the nanoparticles were doped with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), the correspondence of photoluminescence emission quenching, quantum yield decreases, emission lifetime shortening, and increased non-radiative rates with increasing PCBM concentration suggested efficient photo-induced donor-to-acceptor charge transfer between the conjugated polymers and the fullerene dopants co-localized in the nanoparticle cores. Taken together, the data suggest that these surfactant-free hybrid nanomaterials may be useful for integration with future nanostructured organic photovoltaics technologies.

  15. Stabilization of resveratrol in blood circulation by conjugation to mPEG and mPEG-PLA polymers: investigation of conjugate linker and polymer composition on stability, metabolism, antioxidant activity and pharmacokinetic profile.

    PubMed

    Siddalingappa, Basavaraj; Benson, Heather A E; Brown, David H; Batty, Kevin T; Chen, Yan

    2015-01-01

    Resveratrol is naturally occurring phytochemical with diverse biological activities such as chemoprevention, anti-inflammatory, anti-cancer, anti-oxidant. But undergoes rapid metabolism in the body (half life 0.13h). Hence Polymer conjugation utilizing different chemical linkers and polymer compositions was investigated for enhanced pharmacokinetic profile of resveratrol. Ester conjugates such as α-methoxy-ω-carboxylic acid poly(ethylene glycol) succinylamide resveratrol (MeO-PEGN-Succ-RSV) (2 and 20 kDa); MeO-PEG succinyl ester resveratrol (MeO-PEGO-Succ-RSV) (2 kDa); α-methoxy poly(ethylene glycol)-co-polylactide succinyl ester resveratrol (MeO-PEG-PLAO-Succ-RSV) (2 and 6.6kDa) were prepared by carbodiimide coupling reactions. Resveratrol-PEG ethers (2 and 5 kDa) were synthesized by alkali-mediated etherification. All polymer conjugates were fully characterized in vitro and the pharmacokinetic profile of selected conjugates was characterized in rats. Buffer and plasma stability of conjugates was dependent on polymer hydrophobicity, aggregation behavior and PEG corona, with MeO-PEG-PLAO-Succ-RSV (2 kDa) showing a 3h half-life in rat plasma in vitro. Polymer conjugates irrespective of linker chemistry protected resveratrol against metabolism in vitro. MeO-PEG-PLAO-Succ-RSV (2 kDa), Resveratrol-PEG ether (2 and 5 kDa) displayed improved pharmacokinetic profiles with significantly higher plasma area under curve (AUC), slower clearance and smaller volume of distribution, compared to resveratrol. PMID:25799413

  16. Stabilization of Resveratrol in Blood Circulation by Conjugation to mPEG and mPEG-PLA Polymers: Investigation of Conjugate Linker and Polymer Composition on Stability, Metabolism, Antioxidant Activity and Pharmacokinetic Profile

    PubMed Central

    Siddalingappa, Basavaraj; Benson, Heather A. E.; Brown, David H.; Batty, Kevin T.; Chen, Yan

    2015-01-01

    Resveratrol is naturally occurring phytochemical with diverse biological activities such as chemoprevention, anti-inflammatory, anti-cancer, anti-oxidant. But undergoes rapid metabolism in the body (half life 0.13h). Hence Polymer conjugation utilizing different chemical linkers and polymer compositions was investigated for enhanced pharmacokinetic profile of resveratrol. Ester conjugates such as α-methoxy-ω-carboxylic acid poly(ethylene glycol) succinylamide resveratrol (MeO-PEGN-Succ-RSV) (2 and 20 kDa); MeO-PEG succinyl ester resveratrol (MeO-PEGO-Succ-RSV) (2 kDa); α-methoxy poly(ethylene glycol)-co-polylactide succinyl ester resveratrol (MeO-PEG-PLAO-Succ-RSV) (2 and 6.6kDa) were prepared by carbodiimide coupling reactions. Resveratrol-PEG ethers (2 and 5 kDa) were synthesized by alkali-mediated etherification. All polymer conjugates were fully characterized in vitro and the pharmacokinetic profile of selected conjugates was characterized in rats. Buffer and plasma stability of conjugates was dependent on polymer hydrophobicity, aggregation behavior and PEG corona, with MeO-PEG-PLAO-Succ-RSV (2 kDa) showing a 3h half-life in rat plasma in vitro. Polymer conjugates irrespective of linker chemistry protected resveratrol against metabolism in vitro. MeO-PEG-PLAO-Succ-RSV (2 kDa), Resveratrol-PEG ether (2 and 5 kDa) displayed improved pharmacokinetic profiles with significantly higher plasma area under curve (AUC), slower clearance and smaller volume of distribution, compared to resveratrol. PMID:25799413

  17. Synthesis and evaluation of optical and electrochemical properties of a new conjugated polymer containing substituted thiophene and non-conjugation linkers

    SciTech Connect

    R, Prashanth Kumar K D, Udayakumar; K, Siji Narendran N; K, Chandrasekharan

    2014-10-15

    Conjugated polymers have been developed in a variety of applied fields owing to their promising optoelectronic properties. These are pursuing considerable interest as opto-electrical material because of their chemical stability and processability. This paper describes the synthesis and study of electro-optical properties of a new donoracceptor polymer composed of substituted thiophene and 4,4′-propane-2,2-diyldiphenol units as electron rich moieties and 1,3,4-oxadiazole unit as electron deficient moiety. The optical properties of the polymer are studied using UV-visible absorption spectroscopy and fluorescent emission spectroscopy. From the electrochemical data, HOMO and LUMO energy levels of the polymer are calculated.

  18. Thin polymer films of block copolymers and blend/nanoparticle composites

    NASA Astrophysics Data System (ADS)

    Kalloudis, Michail

    In this thesis, atomic force microscopy (AFM), transmission electron microscopy (TEM) and optical microscopy techniques were used to investigate systematically the self-assembled nanostructure behaviour of two different types of spin-cast polymer thin films: poly(isoprene-b-ethylene oxide), PI-b-PEO diblock copolymers and [poly(9,9-dioctylfluorene-co-benzothiadiazole)]:poly[9,9- dioctyfluorene-co-N-(4-butylphenyl)-diphenylamine], F8BT:TFB conjugated polymer blends. In the particular case of the polymer blend thin films, the morphology of their composites with cadmium selenide (CdSe) quantum dot (QD) nanoparticles was also investigated. For the diblock copolymer thin films, the behaviour of the nanostructures formed and the wetting behaviour on mica, varying the volume fraction of the PEO block (fPEO) and the average film thickness was explored. For the polymer blend films, the effect of the F8BT/TFB blend ratio (per weight), spin-coating parameters and solution concentration on the phase-separated nanodomains was investigated. The influence of the quantum dots on the phase separation when these were embedded in the F8BT:TFB thin films was also examined. It was found that in the case of PI-b-PEO copolymer thin films, robust nanostructures, which remained unchanged after heating/annealing and/or ageing, were obtained immediately after spin coating on hydrophilic mica substrates from aqueous solutions. The competition and coupling of the PEO crystallisation and the phase separation between the PEO and PI blocks determined the ultimate morphology of the thin films. Due to the great biocompatible properties of the PEO block (protein resistance), robust PEO-based nanostructures find important applications in the development of micro/nano patterns for biological and biomedical applications. It was also found that sub-micrometre length-scale phase-separated domains were formed in F8BT:TFB spin cast thin films. The nanophase-separated domains of F8BT-rich and TFB-rich areas

  19. Electrochemical formation of a composite polymer-aluminum oxide film

    NASA Astrophysics Data System (ADS)

    Runge-Marchese, Jude Mary

    1997-10-01

    The formation of polymer films through electrochemical techniques utilizing electrolytes which include conductive polymer is of great interest to the coatings and electronics industries as a means for creating electrically conductive and corrosion resistant finishes. One of these polymers, polyamino-benzene (polyaniline), has been studied for this purpose for over ten years. This material undergoes an insulator-to-metal transition upon doping with protonic acids in an acid/base type reaction. Review of prior studies dealing with polyaniline and working knowledge of aluminum anodization has led to the development of a unique process whereby composite polymer-aluminum oxide films are formed. The basis for the process is a modification of the anodizing electrolyte which results in the codeposition of polyaniline during aluminum anodization. A second process, which incorporates electrochemical sealing of the anodic layer with polyaniline was also developed. The formation of these composite films is documented through experimental processing, and characterized by way of scientific analysis and engineering tests. Analysis results revealed the formation of unique dual phase anodic films with fine microstructures which exhibited full intrusion of the columnar aluminum oxide structure with polyaniline, indicating the polymer was deposited as the metal oxidation proceeded. An aromatic amine derivative of polyaniline with aluminum sulfate was determined to be the reaction product within the aluminum oxide phase of the codeposited films. Scientific characterization determined the codeposition process yields completely chemically and metallurgically bound composite films. Engineering studies determined the films, obtained through a single step, exhibited superior wear and corrosion resistance to conventionally anodized and sealed films processed through two steps, demonstrating the increased manufacturing process efficiency that can be realized with the modification of the

  20. Detecting Airborne Mercury by Use of Polymer/Carbon Films

    NASA Technical Reports Server (NTRS)

    Shevade, Abhijit; Ryan, Margaret; Homer, Margie; Kisor, Adam; Jewell, April; Yen, Shiao-Pin; Manatt, Kenneth; Blanco, Mario; Goddard, William

    2009-01-01

    Films made of certain polymer/carbon composites have been found to be potentially useful as sensing films for detecting airborne elemental mercury at concentrations on the order of tens of parts per billion or more. That is to say, when the polymer/carbon composite films are exposed to air containing mercury vapor, their electrical resistances decrease by measurable amounts. Because airborne mercury is a health hazard, it is desirable to detect it with great sensitivity, especially in enclosed environments in which there is a risk of a mercury leak from lamps or other equipment. The present effort to develop polymerbased mercury-vapor sensors complements the work reported in NASA Tech Briefs Detecting Airborne Mercury by Use of Palladium Chloride (NPO- 44955), Vol. 33, No. 7 (July 2009), page 48 and De tecting Airborne Mer cury by Use of Gold Nanowires (NPO-44787), Vol. 33, No. 7 (July 2009), page 49. Like those previously reported efforts, the present effort is motivated partly by a need to enable operation and/or regeneration of sensors under relatively mild conditions more specifically, at temperatures closer to room temperature than to the elevated temperatures (greater than 100 C ) needed for regeneration of sensors based on noble-metal films. The present polymer/carbon films are made from two polymers, denoted EYN1 and EYN2 (see Figure 1), both of which are derivatives of poly-4-vinyl pyridine with amine functional groups. Composites of these polymers with 10 to 15 weight percent of carbon were prepared and solution-deposited onto the JPL ElectronicNose sensor substrates for testing. Preliminary test results showed that the resulting sensor films gave measurable indications of airborne mercury at concentrations on the order of tens of parts per billion (ppb) or more. The operating temperature range for the sensing films was 28 to 40 C and that the sensor films regenerated spontaneously, without heating above operating temperature (see Figure 2).

  1. Ferritin-Polymer Conjugates: Grafting Chemistry and Integration into Nanoscale Assemblies

    SciTech Connect

    Y Hu; D Samanta; S Parelkar; S Hong; Q Wang; T Russell; T Emrick

    2011-12-31

    Controlled free radical polymerization chemistry is used to graft polymer chains to the corona of horse spleen ferritin (HSF) nanocages. Specifically, poly(methacryloyloxyethyl phosphorylcholine) (polyMPC) and poly(PEG methacrylate) (polyPEGMA) chains are grafted onto the nanocages by atom transfer radical polymerization (ATRP), in which the molecular weight of the polymer grafts is controlled by the monomer-to-initiator feed ratio. PolyMPC and polyPEGMA-grafted ferritin show a generally suppressed inclusion into diblock copolymer films relative to native ferritin, and the polymer coating is seen to mask the ferritin nanocages from antibody recognition. The solubility of polyPEGMA-coated ferritin in organic solvents enables its processing with polystyrene-block-poly(ethylene oxide) copolymers, and selective integration into the PEO domains of microphase-separated copolymer structures.

  2. Triarylboron-Linked Conjugated Microporous Polymers: Sensing and Removal of Fluoride Ions.

    PubMed

    Li, Zhongping; Li, He; Xia, Hong; Ding, Xuesong; Luo, Xiaolong; Liu, Xiaoming; Mu, Ying

    2015-11-23

    A luminescent conjugated microporous polymer (BCMP-3) has been synthesized in high yield by a carbon-carbon coupling reaction using triarylboron as a building unit. BCMP-3 was fully characterized by using powder X-ray diffraction analysis, Fourier transform infrared spectroscopy, (13) C solid-state NMR spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, and nitrogen and carbon dioxide adsorption. The new three-dimensional conjugated framework possess a high Brunauer-Emmett-Teller (BET) specific surface area up to 950 m(2)  g(-1) with a pore volume of 0.768 cm(3)  g(-1) , good stability, and abundant boron sites in the skeleton. Under excited-light irradiation, BCMP-3 exhibits strong fluorescent emission at 488 nm with a high absolute quantum yield of 18 % in the solid state. Polymer BCMP-3 acts as a colorimetric and fluorescent chemosensor with high sensitivity and selectivity for F(-) over other common anions. In addition, the polymer also works as an adsorbent for F(-) removal and shows good adsorption capacities of up to 24 mg g(-1) at equilibrium F(-) concentrations of 16 mg L(-1) and a temperature of 298 K. The adsorption kinetics and isotherm were analyzed by fitting experimental data with pseudo-second-order kinetics and Langmuir equations. Furthermore, we highlight that BCMP-3 is an adsorbent for fluoride removal that can be efficiently reused many times without loss of adsorption efficiency. PMID:26463890

  3. Light-induced electron paramagnetic resonance evidence of charge transfer in electrospun fibers containing conjugated polymer/fullerene and conjugated polymer/fullerene/carbon nanotube blends

    NASA Astrophysics Data System (ADS)

    Shames, Alexander I.; Bounioux, Céline; Katz, Eugene A.; Yerushalmi-Rozen, Rachel; Zussman, Eyal

    2012-03-01

    Electrospun sub-micron fibers containing conjugated polymer (poly(3-hexylthiophene), P3HT) with a fullerene derivative, phenyl-C61-butyric acid methylester (PCBM) or a mixture of PCBM and single-walled carbon nanotubes (SWCNTs) were studied by light-induced electron paramagnetic resonance spectroscopy. The results provide experimental evidence of electron transfer between PCBM and P3HT components in both fiber systems and suggest that the presence of a dispersing block-copolymer, which acts via physical adsorption onto the PCBM and SWCNT moieties, does not prevent electron transfer at the P3HT-PCBM interface. These findings suggest a research perspective towards utilization of fibers of functional nanocomposites in fiber-based organic optoelectronic and photovoltaic devices. The latter can be developed in the textile-type large area photovoltaics or individual fiber-based solar cells that will broaden energy applications from macro-power tools to micro-nanoscale power conversion devices and smart textiles.

  4. Light-induced electron paramagnetic resonance evidence of charge transfer in electrospun fibers containing conjugated polymer/fullerene and conjugated polymer/fullerene/carbon nanotube blends

    SciTech Connect

    Shames, Alexander I.; Bounioux, Celine; Katz, Eugene A.; Yerushalmi-Rozen, Rachel; Zussman, Eyal

    2012-03-12

    Electrospun sub-micron fibers containing conjugated polymer (poly(3-hexylthiophene), P3HT) with a fullerene derivative, phenyl-C61-butyric acid methylester (PCBM) or a mixture of PCBM and single-walled carbon nanotubes (SWCNTs) were studied by light-induced electron paramagnetic resonance spectroscopy. The results provide experimental evidence of electron transfer between PCBM and P3HT components in both fiber systems and suggest that the presence of a dispersing block-copolymer, which acts via physical adsorption onto the PCBM and SWCNT moieties, does not prevent electron transfer at the P3HT-PCBM interface. These findings suggest a research perspective towards utilization of fibers of functional nanocomposites in fiber-based organic optoelectronic and photovoltaic devices. The latter can be developed in the textile-type large area photovoltaics or individual fiber-based solar cells that will broaden energy applications from macro-power tools to micro-nanoscale power conversion devices and smart textiles.

  5. Metal-Free, Multicomponent Synthesis of Pyrrole-Based π-Conjugated Polymers from Imines, Acid Chlorides, and Alkynes.

    PubMed

    Kayser, Laure V; Vollmer, Moritz; Welnhofer, Merve; Krikcziokat, Hanna; Meerholz, Klaus; Arndtsen, Bruce A

    2016-08-24

    Multicomponent coupling reactions (MCRs) are becoming increasingly used in the synthesis of macromolecules, as they can allow the rapid generation of libraries of materials as a method to tune properties. MCRs could prove particularly useful in the synthesis of π-conjugated polymers in which structural changes are necessary for fine-tuning of electronic properties. We describe here the first metal-free multicomponent approach to conjugated polymers. This reaction exploits the coupling of imines, acid chlorides, and (catechyl)PPh to generate phospha-münchnone-containing polymers, which can be converted to poly(pyrroles) via cycloaddition. The platform allows for the efficient synthesis of families of high molecular weight polymers in one step from readily available monomers. PMID:27471822

  6. Polymer crystallization in thin films: morphology and physical properties

    NASA Astrophysics Data System (ADS)

    Kelly, Giovanni; Albert, Julie

    Polymer crystallization has been studied both computationally and experimentally for decades, elucidating many of the mysteries surrounding crystallization kinetics and thermodynamics. However, many unanswered questions remain pertaining to the relationships between crystallization phenomena and material properties needed for specific applications that range from drug delivery and tissue engineering to optical devices and mechanically robust membranes. One of the especially interesting facets of polymer crystallization is the behavior observed when these long chain molecules are spatially confined in thin and ultrathin films. Confined geometry leads to chain configurations, and therefore thermal, mechanical, and optical properties, sometimes far removed from reported bulk values. This project aims to study the phenomena exhibited by linear semi-crystalline polymers in thin films as well as the way in which blending with homopolymers, block copolymers, and novel polymer chain architectures affect morphology, biodegradation, optical, thermal, and mechanical properties.

  7. Transiently responsive protein-polymer conjugates via a 'grafting-from' RAFT approach for intracellular co-delivery of proteins and immune-modulators.

    PubMed

    Vanparijs, N; De Coen, R; Laplace, D; Louage, B; Maji, S; Lybaert, L; Hoogenboom, R; De Geest, B G

    2015-09-21

    We report on transiently responsive protein-polymer conjugates that temporarily change their protein conformation from the soluble to the particle-like state. 'Grafting-from' RAFT polymerization of a dioxolane-containing acrylamide with a protein macroCTA is used to design polymer-protein conjugates that self-assemble into nanoparticles at physiological temperature and pH. Acid triggered hydrolysis of the dioxolane units into diol moeities rendered the conjugates fully water soluble irrespective of temperature. PMID:26242974

  8. Sensors employing Functionalized Conducting Polymer Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Tanese, M. C.; Torsi, L.; Cioffi, N.; Sabbatini, L.; Zambonin, P. G.

    2003-12-01

    Functionalized conducting polymers are employed as active layers in sensors with a thin film transistor (TFT) device structure. Such devices can work as multi-parameter sensors with responses that are fast, repeatable and reversible at room temperature. In this work, a strategy is proposed to enhance the chemical selectivity of organic TFT sensors, by selecting active layers that are made of conducting polymers bearing chemically different substituents. A modulation of the devices sensitivity towards analytes such as alcohols and ketones is demonstrated.

  9. Spatial confinement effects on ultrathin semiconducting polymer heterojunction thin films

    SciTech Connect

    Xuejun Zhang; Jenekhe, S.A.

    1996-12-31

    Thin and ultrathin films of electroactive and photoactive polymers are of growing interest for applications in electronic and optoelectronic devices such as thin film transistors, light emitting diodes, solar cells, and xerographic photoreceptors. Although spatial confinement effects on the electronic, optical, optoelectronic, magnetic, and mechanical properties of inorganic semiconductors, metals, oxides, and ceramics are well known and understood, very little is currently known about nanoscale size effects in electroactive and photoactive polymers. Therefore, we recently initiated studies aimed at the understanding of spatial confinement effects on electroactive and photoactive nanostructured polymers and related thin film devices. We have extensively investigated layered nanoscale semiconducting polymer heterojunctions by applying several experimental techniques including photoluminescence, optical absorption, transient absorption, electroluminescence, cyclic voltammetry, and current-voltage measurements. Our findings reveal clear evidence of spatial confinement effects, including: dramatic enhancement of photoconductivity in ultrathin films; enhancement of electroluminescence efficiency and performance characteristics in nanoscale heterojunction devices; observation of novel phenomena in nanoscale devices. These spatial confinement effects in nanostructured semiconducting polymers can be understood in terms of classical charge transport and interfacial processes without invoking quantum size effects.

  10. Air shear driven flow of thin perfluoropolyether polymer films

    NASA Astrophysics Data System (ADS)

    Scarpulla, Michael A.; Mate, C. Mathew; Carter, Malika D.

    2003-02-01

    We have studied the wind driven movement of thin perfluoropolyether (PFPE) polymer films on silicon wafers and CNx overcoats using the blow-off technique. The ease with which a liquid polymer film moves across a surface when sheared is described by a shear mobility χS, which can be interpreted both in terms of continuum flow and in terms of wind driven diffusion. Generally, we find that the movement of PFPE films can be described as a flow process with an effective viscosity, even when the film thickness is smaller than the polymer's diameter of gyration. Only in the special case of sparse coverage of a polymer with neutral end groups is the motion better described by a wind driven diffusion process. The addition of alcohol end groups to the PFPE polymer chain results in strong interactions with the substrate, creating a restricted layer having an effective viscosity an order of magnitude larger than the mobile layer that sits on top of the restricted layer.

  11. Simulation of conductivity of polymer films on metal surface

    NASA Astrophysics Data System (ADS)

    Maksimova, O. G.; Maksimov, A. V.; Baidganov, A. R.

    2015-09-01

    In this paper, protective properties of polymer films are analyzed. The simulation is performed by means of the Monte-Carlo method on the basis of three-dimensional lattice model of polymer system with orientational interactions [1]. Initially, configuration of polymer system is calculated by the Metropolis algorithm taking into account the characteristics of the internal structure (constants of intermolecular interactions etc.), temperature regime and metal quality. Further, for the study of conductivity, the motion of charged particles within the proposed lattice model is investigated on the basis of the calculated configuration. The interaction energy of the oxygen atom with eight neighboring links of polymer chains and electric double layer on the metallic surface is accounted. The direction of movement of charged particles is calculated by the Monte-Carlo method according to the energy advantage of its position. This method allows to calculate the number of charged particles passing through the polymer film and reaching the metal sheet surface. The dependences of conductivity on temperature, film thickness, and distance between molecular layers are obtained. It is shown that there is an optimum density for the given film thickness at which it possesses protective properties. The adequacy of the developed mathematical models and calculated dependences are verified by comparison with laboratory data and production testing.

  12. Tumor tropic delivery of doxorubicin-polymer conjugates using mesenchymal stem cells for glioma therapy.

    PubMed

    Zhang, Xiaofeng; Yao, Sen; Liu, Chang; Jiang, Yanyan

    2015-01-01

    Mesenchymal stem cells (MSCs) possess inherent tropism to malignant cells and home to disseminated tumor foci, making MSCs an ideal candidate as targeting vehicle for drug delivery. Our previously synthesized doxorubicin (DOX)-polymer conjugates (PPCD) modified by RGD (RGD-PPCD) harness tremendous potential with active targeting and sustained release. To further enhance the conjugates penetrability and tumor tracking capability, MSCs-mediated RGD-/PPCD delivery system was created and constructed by spontaneous incorporation. The present study investigated the anti-tumor activities of MSCs loaded with RGD-/PPCD (MSCsRGD-/PPCD), compared to their corresponding RGD-/PPCD and MSCs loaded with DOX (MSCsDOX), especially. MTT assay demonstrated that although RGD-/PPCD could inhibit MSCs proliferation, there was no direct cytotoxicity to MSCs. After optimization, maximum drug loading amount was obtained by incubating MSCs for 12 h at the drug concentration of 50 μg/mL (DOX-equiv.). Further drug release and intracellular retention proved that, compared to MSCsDOX, MSCsRGD-/PPCD delayed the release peak to 12-48 h with continuous drug liberation more than 5 days, declaring the time dependent release behavior and lasting stability of conjugates in MSCs for cell-directed tumoritropic delivery. For MSCsRGD-/PPCD, intrinsic cell functions without compromise were verified by cell cycle analysis, transmigration assay and tumor penetration, while MSCsDOX showed observable but not significant suppression. As for in vivo studies, among all groups, mice intracranially administrated with MSCsPPCD and MSCsRGD-PPCD acquired the longest survival time with median being 41 and 45 days, and increased life span with 34% and 46.8% versus RGD-PPCD treatment group, respectively. Additionally, MSCsRGD-/PPCD exhibited more extensive penetration and enhanced tumor cell apoptosis than MSCsDOX. As proof of the concept, without any genetic manipulation and chemical modification, a novel modality

  13. Swelling Behavior of Ultrathin Polymer Films in Supercritical Ethane

    NASA Astrophysics Data System (ADS)

    Ji, Yuan; Koga, Tadanori; Seo, Young-Soo; Rafailovich, Miriam; Sokolov, Jonathan; Satija, Sushil

    2003-03-01

    Swelling behavior of ultrathin polymer films in supercritical ethane (T_c=32^oC, P_c=4.86MPa) was investigated by using in situ neutron reflectivity (NR). The polymers used in this study were deuterated polystyrene(dPS), deuterated styrene-butadiene copolymer(dSBR), deuterated polymethylmethacrylate(dPMMA), deuterated polybutadiene(dPB) and the films were spun cast on the HF etched cleaned silicon wafers. NR experiments were conducted with the pressure range of 0.1-15 MPa at T=37^oC by using NG7 reflectometer at NIST. As a result, we found that all the polymers used showed anomalous peak in the linear dilation (S_f) curve at P=5.5MPa, i.e., the density fluctuation ridge of ethane while the Sf values for the rubbery polymers were significantly larger (0.8) than those of glassy polymers (0.3). In this presentation, we will also discuss about the universality in the swelling behavior of the polymer thin films in the presence of the supercritical fluids.

  14. New Molecular Theory for Dense, Thin Polymer Films

    NASA Astrophysics Data System (ADS)

    Freed, Karl

    2015-03-01

    The development of a molecular theory for dense polymer systems ranks among the most challenging problems in the statistical mechanics of complex matter. These difficulties become compounded when considering the influence of molecular details on thermodynamic properties of thin polymer films, properties deviating from those of the bulk phases. A new theory of dense polymer films is developed as a significant generalization of methods used to devise the lattice cluster theory, an extension of Flory-Huggins theory that include details of monomer structure and short range correlations (neglected in FH theory) and that has successfully been applied to a wide range of polymer systems. The new theory incorporates the essential ``transport'' constraints of Helfand and focuses on the strict imposition of excluded volume constraints, appropriate to dense polymer systems, rather than the maintenance of chain connectivity as appropriate for lower densities and implemented in self-consistent theories of polymer adsorption at interfaces. The theory is illustrated by presenting examples of the computed density and chain end profiles for free standing films as a function of bulk density, chain length, temperature, and chain semi-flexibility.

  15. Reversible thermochromic polymer film embedded with fluorescent organogel nanofibers.

    PubMed

    Kim, Hyungwoo; Chang, Ji Young

    2014-11-18

    We report a reversible thermochromic nanocomposite polymer film composed of fluorescent organogel fibers and a highly cross-linked polymer matrix. A series of cyano-substituted oligo(p-phenylenevinylene) (CN-OPV) derivatives were synthesized by the reaction of dialdehydes with phenyl or naphthyl acetonitrile under basic conditions. Among the CN-OPV derivatives, NA-DBA having naphtyl moieties and dodecyloxy chains formed a stable organogel in a cross-linkable monomeric solvent (ethylene glycol dimethacrylate). The organogel showed a thermoreversible sol-gel transition, accompanying the emission color change. A nanocomposite polymer film obtained by photopolymerization of the organogel between two quartz plates also exhibited reversible thermochromism. Under 365 nm irradiation, the orange color of the film at 25 °C became yellowish green at 120 °C. The fluorescence spectroscopy, DSC, and microscopy results determined that the thermally reversible self-assembly of NA-DBA occurred in the polymer matrix, resulting in reversible thermochromism. The melted gelator molecules at 120 °C did not diffuse into the polymer matrix probably because of poor interactions of the gelator molecules with the polymer matrix. The NA-DBA molecules dispersed in poly(methyl methacrylate), without forming a supramolecular structure, did not show thermochromism. PMID:25340308

  16. Polymer thin film instability from a patterned edge

    NASA Astrophysics Data System (ADS)

    Guo, Yunlong; Zhang, Chuan; Priestley, Rodney D.

    2014-07-01

    Patterning of polymer thin films with nanoscale features is a critical step in nanoscale technologies. Here, we investigate the dewetting process from both a mechanically patterned edge (ME) and a hole edge of a thin polymer film, as a means to assess the influence of residual stresses induced during patterning on stability. At low temperature in which hole nucleation is not observed dewetting can still proceed from the ME. Under conditions in which dewetting proceeded from both edges that from the ME exhibited a crossover to a dramatically reduced dewetting velocity. These results suggest mechanical stress concentrated along the ME remarkably depresses the dewetting process by decreasing the rim growth rate.

  17. Electrical conductivity studies on individual conjugated polymer nanowires: two-probe and four-probe results.

    PubMed

    Long, Yunze; Duvail, Jeanluc; Li, Mengmeng; Gu, Changzhi; Liu, Zongwen; Ringer, Simon P

    2009-01-01

    Two- and four-probe electrical measurements on individual conjugated polymer nanowires with different diameters ranging from 20 to 190 nm have been performed to study their conductivity and nanocontact resistance. The two-probe results reveal that all the measured polymer nanowires with different diameters are semiconducting. However, the four-probe results show that the measured polymer nanowires with diameters of 190, 95-100, 35-40 and 20-25 nm are lying in the insulating, critical, metallic and insulting regimes of metal-insulator transition, respectively. The 35-40 nm nanowire displays a metal-insulator transition at around 35 K. In addition, it was found that the nanocontact resistance is in the magnitude of 104Ω at room temperature, which is comparable to the intrinsic resistance of the nanowires. These results demonstrate that four-probe electrical measurement is necessary to explore the intrinsic electronic transport properties of isolated nanowires, especially in the case of metallic nanowires, because the metallic nature of the measured nanowires may be coved by the nanocontact resistance that cannot be excluded by a two-probe technique. PMID:20652139

  18. Functionalization of emissive conjugated polymer nanoparticles by coprecipitation: consequences for particle photophysics and colloidal properties.

    PubMed

    Singh, Amita; Bezuidenhout, Michael; Walsh, Nichola; Beirne, Jason; Felletti, Riccardo; Wang, Suxiao; Fitzgerald, Kathleen T; Gallagher, William M; Kiely, Patrick; Redmond, Gareth

    2016-07-29

    The functionalization of polyfluorene (PFO) nanoparticles by coprecipitation of the conjugated polymer with an amphiphilic comb polymer, consisting of a hydrophobic polystyrene backbone with hydrophilic, carboxylic acid-terminated polyethylene oxide side-chains (PS-PEG-COOH), is investigated. The comb polymer affects the properties of the formed hybrid nanoparticles. Non-functionalized particles are typically larger (28 nm) than functionalized ones (20 nm); peak molar extinction coefficients are found to differ in a similar trend. Zeta potentials are negative, consistent with negative surface charge on PFO particles due to chemical defect formation, with additional charge on functionalized particles due to the pendant carboxylic acid groups. Emission quantum yields of functionalized particles are typically larger, consistent with lower efficiency of energy transfer to quenchers in smaller particles and weaker PFO interchain interactions due to chain dilution. The trend in per-particle fluorescence brightness values, as confirmed by single particle fluorescence imaging, reflects the nanoparticle extinction coefficients. Photostability studies on aqueous dispersions of hybrid particles indicate mild photobrightening under continuous illumination while PFO particles exhibit slow exponential emission decay. Functionalized particles are also resistant to aggregation during exposure to adenocarcinoma cells. Generally, the hybrid particles exhibit more favorable time-, pH- and medium-dependent stabilities, likely due to steric and electrostatic stabilization by PEG-carboxylic acid functionalities. Overall, the functionalized particles exhibit attractive properties: Reasonably small size, tight size distribution, high absorption cross section, radiative rate and emission quantum yield, excellent brightness and photostability, and good colloidal stability. PMID:27306338

  19. Initiator Control of Conjugated Polymer Topology in Ring-Opening Alkyne Metathesis Polymerization.

    PubMed

    von Kugelgen, Stephen; Bellone, Donatela E; Cloke, Ryan R; Perkins, Wade S; Fischer, Felix R

    2016-05-18

    Molybdenum carbyne complexes [RC≡Mo(OC(CH3)(CF3)2)3] featuring a mesityl (R = Mes) or an ethyl (R = Et) substituent initiate the living ring-opening alkyne metathesis polymerization of the strained cyclic alkyne, 5,6,11,12-tetradehydrobenzo[a,e][8]annulene, to yield fully conjugated poly(o-phenylene ethynylene). The difference in the steric demand of the polymer end-group (Mes vs Et) transferred during the initiation step determines the topology of the resulting polymer chain. While [MesC≡Mo(OC(CH3)(CF3)2)3] exclusively yields linear poly(o-phenylene ethynylene), polymerization initiated by [EtC≡Mo(OC(CH3)(CF3)2)3] results in cyclic polymers ranging in size from n = 5 to 20 monomer units. Kinetic studies reveal that the propagating species emerging from [EtC≡Mo(OC(CH3)(CF3)2)3] undergoes a highly selective intramolecular backbiting into the butynyl end-group. PMID:27120088

  20. Effects of polarons on static polarizabilities and second order hyperpolarizabilities of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Wang, Ya-Dong; Meng, Yan; Di, Bing; Wang, Shu-Ling; An, Zhong

    2010-12-01

    According to the one-dimensional tight-binding Su—Schrieffer—Heeger model, we have investigated the effects of charged polarons on the static polarizability, αxx, and the second order hyperpolarizabilities, γxxxx, of conjugated polymers. Our results are consistent qualitatively with previous ab initio and semi-empirical calculations. The origin of the universal growth is discussed using a local-view formalism that is based on the local atomic charge derivatives. Furthermore, combining the Su-Schrieffer-Heeger model and the extended Hubbard model, we have investigated systematically the effects of electron-electron interactions on αxx and γxxxx of charged polymer chains. For a fixed value of the nearest-neighbour interaction V, the values of αxx and γxxxx increase as the on-site Coulomb interaction U increases for U < Uc and decrease with U for U > Uc, where Uc is a critical value of U at which the static polarizability or the second order hyperpolarizability reaches a maximal value of αmax or γmax. It is found that the effect of the e-e interaction on the value of αxx is dependent on the ratio between U and V for either a short or a long charged polymer. Whereas, that effect on the value of γxxxx is sensitive both to the ratio of U to V and to the size of the molecule.

  1. Conjugated polymer dots-on-electrospun fibers as a fluorescent nanofibrous sensor for nerve gas stimulant.

    PubMed

    Jo, Seonyoung; Kim, Jongho; Noh, Jaeguk; Kim, Daigeun; Jang, Geunseok; Lee, Naeun; Lee, Eunji; Lee, Taek Seung

    2014-12-24

    A novel chemical warfare agent sensor based on conjugated polymer dots (CPdots) immobilized on the surface of poly(vinyl alcohol) (PVA)-silica nanofibers was prepared with a dots-on-fibers (DoF) hybrid nanostructure via simple electrospinning and subsequent immobilization processes. We synthesized a polyquinoxaline (PQ)-based CP as a highly emissive sensing probe and employed PVA-silica as a host polymer for the elctrospun fibers. It was demonstrated that the CPdots and amine-functionalized electrospun PVA-silica nanofibers interacted via an electrostatic interaction, which was stable under prolonged mechanical force. Because the CPdots were located on the surface of the nanofibers, the highly emissive properties of the CPdots could be maintained and even enhanced, leading to a sensitive turn-off detection protocol for chemical warfare agents. The prepared fluorescent DoF hybrid was quenched in the presence of a chemical warfare agent simulant, due to the electron transfer between the quinoxaline group in the polymer and the organophosphorous simulant. The detection time was almost instantaneous, and a very low limit of detection was observed (∼1.25 × 10(-6) M) with selectivity over other organophosphorous compounds. The DoF hybrid nanomaterial can be developed as a rapid, practical, portable, and stable chemical warfare agent-detecting system and, moreover, can find further applications in other sensing systems simply by changing the probe dots immobilized on the surface of nanofibers. PMID:25431844

  2. Functionalization of emissive conjugated polymer nanoparticles by coprecipitation: consequences for particle photophysics and colloidal properties

    NASA Astrophysics Data System (ADS)

    Singh, Amita; Bezuidenhout, Michael; Walsh, Nichola; Beirne, Jason; Felletti, Riccardo; Wang, Suxiao; Fitzgerald, Kathleen T.; Gallagher, William M.; Kiely, Patrick; Redmond, Gareth

    2016-07-01

    The functionalization of polyfluorene (PFO) nanoparticles by coprecipitation of the conjugated polymer with an amphiphilic comb polymer, consisting of a hydrophobic polystyrene backbone with hydrophilic, carboxylic acid-terminated polyethylene oxide side-chains (PS-PEG-COOH), is investigated. The comb polymer affects the properties of the formed hybrid nanoparticles. Non-functionalized particles are typically larger (28 nm) than functionalized ones (20 nm); peak molar extinction coefficients are found to differ in a similar trend. Zeta potentials are negative, consistent with negative surface charge on PFO particles due to chemical defect formation, with additional charge on functionalized particles due to the pendant carboxylic acid groups. Emission quantum yields of functionalized particles are typically larger, consistent with lower efficiency of energy transfer to quenchers in smaller particles and weaker PFO interchain interactions due to chain dilution. The trend in per-particle fluorescence brightness values, as confirmed by single particle fluorescence imaging, reflects the nanoparticle extinction coefficients. Photostability studies on aqueous dispersions of hybrid particles indicate mild photobrightening under continuous illumination while PFO particles exhibit slow exponential emission decay. Functionalized particles are also resistant to aggregation during exposure to adenocarcinoma cells. Generally, the hybrid particles exhibit more favorable time-, pH- and medium-dependent stabilities, likely due to steric and electrostatic stabilization by PEG-carboxylic acid functionalities. Overall, the functionalized particles exhibit attractive properties: Reasonably small size, tight size distribution, high absorption cross section, radiative rate and emission quantum yield, excellent brightness and photostability, and good colloidal stability.

  3. Thin film instabilities on heated substrates: conjugate heat transfer

    NASA Astrophysics Data System (ADS)

    Dallaston, Michael; Tseluiko, Dmitri; Kalliadasis, Serafim

    2015-11-01

    Heat transported from a surface by a thin coating film of liquid is greatly affected by instabilities on the free surface of the film. If the solid substrate is heated above the ambient temperature, the hydrodynamic instability of the flow at sufficiently large Reynolds number is exacerbated by Marangoni stresses that result due to the temperature gradient in the fluid. Most studies of this phenomenon assume constant temperature or heat flux at the wall. Here we discuss the less-studied but more realistic situation in which the heat flow within the liquid film is coupled to conduction within the solid substrate, which has a complicated effect on the stability of the free surface. Analytical progress is made possible by linear stability analysis and low-dimensional nonlinear evolution equations derived using a weighted residual method.

  4. Probing nano-rheology in thin polymer films

    NASA Astrophysics Data System (ADS)

    Dalnoki-Veress, Kari

    2013-03-01

    In this talk I will summarize our recent work on using stepped films to uncover some of the physics relevant to polymer rheology on length scales comparable to the size of polymer molecules. The work presented will focus on the efforts of a larger collaboration (Elie Raphael's theory group in Paris and James Forrest's group in Waterloo). The simple geometry of a polymer film on a substrate with a step at the free surface is unfavourable due to the excess interface induced by the step. Laplace pressure will drive flow within the film which can be studied with optical and atomic force microscopies. Because of the excellent agreement between theory and experiment when we probe ``bulk-like'' properties, these studies provide an opportunity to study how such systems transition from the bulk to confined. Starting with some of the results of levelling experiments on simple stepped films as well as the levelling of polymer droplets on thin films, I will finish with a discussion on our more recent efforts to elucidate confinement effects.

  5. Patterning dewetting in thin polymer films by spatially directed photocrosslinking.

    PubMed

    Carroll, Gregory T; Turro, Nicholas J; Koberstein, Jeffrey T

    2010-11-15

    In this report we examine the dewetting of spin-cast poly (styrene) films in a confined geometry. We designed a platform for laterally confining PS by photo-patterning crosslinks in spin-coated thin films. Heating the patterned film above the glass transition temperature of PS results in localized dewetting patterns in regions that were not crosslinked, while the crosslinked pattern serves as a rigid barrier that confines the retraction of the uncrosslinked polymer in micron-sized domains. The barriers also provide a favorable surface that the liquid PS wets onto, forming a rim at the boundary of crosslinked and uncrosslinked polymer. The resulting patterns are shown to be dependent on the irradiation and annealing time, the dimensions of the uncrosslinked region and the thickness of the film. PMID:20728089

  6. Using Molecular Simulations to Link Chemical and Physical Features of Conjugated Polymers and Fullerene Derivatives to Bulk Heterojunction Morphology for Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Marsh, Hilary; Jankowski, Eric; Jayaraman, Arthi

    2014-03-01

    The morphology of blends of conjugated polymers (electron donors) and fullerene derivatives (electron acceptors) strongly affects the charge transport, charge separation and the overall efficiency of organic photovoltaic devices. In this talk we will present coarse-grained molecular simulation studies to understand how molecular-level features such as alkyl side chain length, alkyl side chain spacing along thiophene polymer backbone and fullerene functionalization (and in turn miscibility with the conjugated polymer) affect the blend morphology. Our coarse-grained models are validated by reproducing neat polymer (without acceptors) morphologies observed in experiments, such as lamellae and hexagonally packed cylinders. Furthermore, for blends of conjugated polymers and fullerene derivatives, this work shows how conjugated polymer architecture and acceptor miscibility can be tuned to obtain new blend morphologies with features that are known to enhance efficiency of organic solar cells.

  7. Synthesis and structure of high-quality films of copper polyphthalocyanine – 2D conductive polymer

    SciTech Connect

    Sedlovets, Darya M.; Shuvalov, Maksim V.; Vishnevskiy, Yury V.; Volkov, Vladimir T.; Khodos, Igor I.; Trofimov, Oleg V.; Korepanov, Vitaly I.

    2013-10-15

    Graphical abstract: - Highlights: • 2D polymers show a big promise for science and technology. • We develop a new procedure for the direct synthesis of copper polyphthalocyanine. • We obtain reliable experimental data on the CuPPC structure. • With the support of quantum chemical calculations we describe electronic structure of CuPPC. - Abstract: Copper polyphthalocyanine (CuPPC), a 2D conjugated polymer, is a promising material for electronics and photovoltaics, but its applications were hindered by a poor processability. We propose an experimental approach, by which thin films of CuPPC, can be directly synthesized in a chemical vapor deposition (CVD) set-up at mild temperature (420 °C). High polymerization degree and high crystallinity of the films were confirmed by TEM, FTIR and UV–vis studies. From XRD and TEM electron diffraction, we conclude that the polymer has AA layer stacking with the inter-layer distance of 0.32 nm. The assignment of X-ray and TEM diffraction patterns was based on quantum-chemical calculations. Based on the latter, we also discuss electronic structure and conclude that CuPPC is rather a semi-metal than semi-conductor.

  8. Vacuum deposited polymer films: Past, present, and future applications

    SciTech Connect

    Affinito, J.; Martin, P.; Gross, M.; Bennett, W.

    1994-11-01

    Two extremely high rate processes have been developed for the vacuum deposition of polymer thin films. Dubbed the PML (for Polymer Multi-Layer) and LML (for Liquid Multi-Layer) processes, the PML technique was originally developed for the manufacture of polymer/aluminum surface mount capacitors while the LML method arose from a need to fabricate lithium polymer batteries. These processes have since been found to be compatible with most other vacuum deposition techniques in, integrated, in-line coating processes. Battelle has developed an extensive program, and a great deal of hardware, to pursue a wide variety of PML and LML applications which integrate these two process technologies with other, conventional, vacuum deposition methods. The historical development of the technologies is reviewed and the Battelle PML/LML facilities are described. Current Battelle work involving solar thermal control films, PML QWOTs, and polymer/metal high reflectors are also discussed. Battelle PML work that is just starting, involving non-linear optical materials/devices, lithium polymer battery fabrication, electrochromic devices, and polymer/oxide multilayers, is discussed as well.

  9. Nanowear on polymer films of different architecture.

    PubMed

    Berger, R; Cheng, Y; Förch, R; Gotsmann, B; Gutmann, J S; Pakula, T; Rietzler, U; Schärtl, W; Schmidt, M; Strack, A; Windeln, J; Butt, H-J

    2007-03-13

    In this paper, we describe atomic force microscope (AFM) friction experiments on different polymers. The aim was to analyze the influence of the physical architecture of the polymer on the degree and mode of wear and on the wear mode. Experiments were carried out with (1) linear polystyrene (PS) and cycloolefinic copolymers of ethylene and norbornene, which are stabilized by entanglements, (2) mechanically stretched PS, (3) polyisoprene-b-polystyrene diblock copolymers, with varying composition, (4) brush polymers consisting of a poly(methyl methacrylate) (PMMA) backbone and PS side chains, (5) PMMA and PS brushes grafted from a silicon wafer, (6) plasma-polymerized PS, and (7) chemically cross-linked polycarbonate. For linear polymers, wear depends critically on the orientation of the chains with respect to the scan direction. With increasing cross-link density, wear was reduced and ripple formation was suppressed. The cross-linking density was the dominating material parameter characterizing wear. PMID:17279781

  10. Consequences of Residual Stresses in Thin Polymer Films

    NASA Astrophysics Data System (ADS)

    Reiter, Guenter

    2010-03-01

    In our quest for making functional devices smaller, the thickness of polymer films has reached values even smaller than the diameter of the unperturbed molecule. However, despite enormous efforts over the last decade, our understanding of the origin of some puzzling properties of such thin films is still not satisfactory and several peculiar observations remain rather mysterious. In this context, we explore the consequences of the transition from a dilute polymer solution to the glassy state with respect to the properties of polymers in thin films. This transition is likely to result in residual stresses, arising from out-of-equilibrium chain conformations due to rapid solvent loss. Consequently, depending on thermal history and ageing time, such films exhibit significant changes even in the glassy state ^ which we quantify by performing detailed studies of viscoelastic dewetting of thin polystyrene films on solid substrates. We explored relaxation times, residual stresses, and temporal changes of the stability of non-equilibrated thin films as they progress toward stable equilibrium behaviors. To do so, we have focused primarily on times shorter than the reptation time of the polymer. The number of spontaneously nucleated holes per unit area is seen to decrease as the films were aged below the glass transition, showing the meta-stability of the system. The ratio of stress over elastic modulus was found to increase strongly with decreasing film thickness and increasing chain length. Full equilibration of chain conformations required long times comparable to bulk reptation times. However, for chains longer than about 3000 monomers, the residual stress relaxed faster, at a rate independent of chain length. We present some tentative ideas on the relation between these observed atypical mechanical and relaxational behaviors and meta-stable states introduced by sample preparation.

  11. Acoustic resonant spectroscopy for characterization of thin polymer films

    NASA Astrophysics Data System (ADS)

    Tohmyoh, Hironori; Imaizumi, Takuya; Saka, Masumi

    2006-10-01

    An acoustic resonant spectroscopy technique for measuring the acoustic impedance, ultrasonic velocity, and density of micron-scale polymer films is developed. The method, which is based on spectral analysis, observes the acoustic resonance between water, the film, and a tungsten plate with high acoustic impedance in the frequency range of 20-70MHz. The interface between the film being examined and the plate is vacuum sealed, enabling us to characterize the low-density polyethylene film with acoustic impedances as low as about 1.9MNm-3s and the poly(vinyl chloride) film as thin as about 8μm. The error in the film density measurements is found to be less than 1%, and the validity of the technique is verified.

  12. Simple push coating of polymer thin-film transistors.

    PubMed

    Ikawa, Mitsuhiro; Yamada, Toshikazu; Matsui, Hiroyuki; Minemawari, Hiromi; Tsutsumi, Jun'ya; Horii, Yoshinori; Chikamatsu, Masayuki; Azumi, Reiko; Kumai, Reiji; Hasegawa, Tatsuo

    2012-01-01

    Solution processibility is a unique advantage of organic semiconductors, permitting the low-cost production of flexible electronics under ambient conditions. However, the solution affinity to substrate surfaces remains a serious dilemma; liquid manipulation is more difficult on highly hydrophobic surfaces, but the use of such surfaces is indispensable for improving device characteristics. Here we demonstrate a simple technique, which we call 'push coating', to produce uniform large-area semiconducting polymer films over a hydrophobic surface with eliminating material loss. We utilize a poly(dimethylsiloxane)-based trilayer stamp whose conformal contact with the substrate enables capillarity-induced wetting of the surface. Films are formed through solvent sorption and retention in the stamp, allowing the stamp to be peeled perfectly from the film. The planar film formation on hydrophobic surfaces also enables subsequent fine film patterning. The technique improves the crystallinity and field-effect mobility of stamped semiconductor films, constituting a major step towards flexible electronics production. PMID:23132026

  13. Electronic structures of new π-conjugated cyclic polymers with quinoid structures

    NASA Astrophysics Data System (ADS)

    Hong, Sung Y.; Kwon, Si J.; Kim, Shi C.

    1995-08-01

    Geometrical and electronic structures of new π-conjugated five-membered ring polymers were theoretically investigated. These polymers are analogous to heterocyclic polymers, but adopt as bridging groups ≳CH2, ≳CF2, ≳SiH2, ≳SiF2, ≳C=CH2, ≳C=O and ≳C=S moieties instead of heteroatoms. The ground-state geometries of the polymers were predicted to be quinoid from semiempirical band calculations with AM1 Hamiltonian. The electronic properties of these systems were obtained using the modified extended Hückel method. The calculated band gaps (Eg) were analyzed in terms of geometrical relaxations and electronic effect of the bridging groups using the equation of Eg=ΔEδr+ΔE1-4+ΔEel. The effect of bond-length alternation (ΔEδr) amounts to 1.1-1.4 eV for the aromatic forms and 1.8-1.9 eV for the quinoid forms of the polymers. The interactions (ΔE1-4) between C1 and C4 atoms of the cis-PA type backbone tend to decrease the band gaps of the aromatic forms and to increase the gaps of the quinoid forms as much as 0.2-0.5 eV, depending on the size of a bridging atom. It is found that the electronic effect (ΔEel) of these bridging groups is quite small compared to that found in heterocyclic polymers such as polythiophene, polypyrrole, and polyfuran. ΔEel of ≳CF2, ≳SiH2, and ≳SiF2 bridging groups are negligible and that of the other groups amounts to 0.3-1.0 eV. Therefore, the band gaps of these systems almost correspond to the ΔEδr values which arise from the bond-length alternations, except the case of the polymers with ≳C=O and ≳C=S bridging groups whose π* orbitals strongly interact with the π system of the polymeric backbone.

  14. Measuring the Thickness and Elastic Properties of Electroactive Thin-Film Polymers Using Platewave Dispersion Data

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Lih, Shyh-Shiuh; El-Azab, A.; Mal, Ajit K.

    1996-01-01

    Electroactive thin-film polymers are candidate sensors and actuators materials. They are also finding significant potential in muscle mechanisms and microelectromechanical systems (MEMS). In these applications, polymer thin films of thickness varying between 20 and 300 micrometers are utilized. The authors are currently studying the potential use of platewave dispersion curve measurements as an effective gauging tool for electroactive thin-film polymers.

  15. Process optimization of ultrasonic spray coating of polymer films.

    PubMed

    Bose, Sanjukta; Keller, Stephan S; Alstrøm, Tommy S; Boisen, Anja; Almdal, Kristoffer

    2013-06-11

    In this work we have performed a detailed study of the influence of various parameters on spray coating of polymer films. Our aim is to produce polymer films of uniform thickness (500 nm to 1 μm) and low roughness compared to the film thickness. The coatings are characterized with respect to thickness, roughness (profilometer), and morphology (optical microscopy). Polyvinylpyrrolidone (PVP) is used to do a full factorial design of experiments with selected process parameters such as temperature, distance between spray nozzle and substrate, and speed of the spray nozzle. A mathematical model is developed for statistical analysis which identifies the distance between nozzle and substrate as the most significant parameter. Depending on the drying of the sprayed droplets on the substrate, we define two broad regimes, "dry" and "wet". The optimum condition of spraying lies in a narrow window between these two regimes, where we obtain a film of desired quality. Both with increasing nozzle-substrate distance and temperature, the deposition moves from a wet state to a dry regime. Similar results are also achieved for solvents with low boiling points. Finally, we study film formation during spray coating with poly (D,L-lactide) (PDLLA). The results confirm the processing knowledge obtained with PVP and indicate that the observed trends are identical for spraying of other polymer films. PMID:23631433

  16. Electrically conducting novel polymer films containing pi-stacks

    NASA Astrophysics Data System (ADS)

    Duan, Robert Gang

    1997-12-01

    The primary focus of this thesis is to expand our knowledge of ion radicals of π-dimers and π- stacks in solutions and apply these insights in the development and understanding of new electrically conducting polymers. Two types of the conducting polymers were investigated. The first is the conducting polymer composites embedded with π-stacks of ion radicals. Flexible and air stable n-typed conducting thin films were prepared from imide/poly(vinyl alcohol) aqueous solutions. Conducting thin films of terthiophene/poly(methyl methacrylate) were cast from hexafluoro-2-propanol. Effects of casting conditions on the morphology and conductivity of the films were investigated. These films were fully characterized by UV- vis, NIR, IR, XRD, SEM and ESR. In the second type of conducting polymer system, PAMAM dendrimers generation 1 through 5 were peripherally modified with cationically substituted naphthalene diimide anion radicals. NMR, UV, IR, CV and Elemental Analysis were used to characterize modified dendrimers. Reduction with sodium dithionite in solution showed anion radicals were aggregated into π-dimers and π- stacks. Formamide was used to cast conducting dendrimer films. ESCA, SEM and optical microscope were used to study the composition and the morphology of the films. XRD showed complete amorphous nature of these films. NIR revealed that the π-stack aggregation depend strongly on the casting temperature and the degree of reduction. Four- probe co-liner conductivity of the films is on the order of 10-2 to 10-1/ S/ cm-1. ESR and conductivity measurements also revealed the isotropic nature of the conductivity. Conductivity/humidity relationship was discovered by accidental breathing over the films. Using a home-made controlled humidity device and PACERTM hygrometer, the conductivity of the films can be varied quickly and reversibly within two orders of a magnitude. This phenomenon was probed with NIR, XRD and quartz crystal microbalance techniques. These

  17. Smart conjugated polymer nanocarrier for healthy weight loss by negative feedback regulation of lipase activity.

    PubMed

    Chen, Yu-Lei; Zhu, Sha; Zhang, Lei; Feng, Pei-Jian; Yao, Xi-Kuang; Qian, Cheng-Gen; Zhang, Can; Jiang, Xi-Qun; Shen, Qun-Dong

    2016-02-14

    Healthy weight loss represents a real challenge when obesity is increasing in prevalence. Herein, we report a conjugated polymer nanocarrier for smart deactivation of lipase and thus balancing calorie intake. After oral administration, the nanocarrier is sensitive to lipase in the digestive tract and releases orlistat, which deactivates the enzyme and inhibits fat digestion. It also creates negative feedback to control the release of itself. The nanocarrier smartly regulates activity of the lipase cyclically varied between high and low levels. In spite of high fat diet intervention, obese mice receiving a single dose of the nanocarrier lose weight over eight days, whereas a control group continues the tendency to gain weight. Daily intragastric administration of the nanocarrier leads to lower weight of livers or fat pads, smaller adipocyte size, and lower total cholesterol level than that of the control group. Near-infrared fluorescence of the nanocarrier reveals its biodistribution. PMID:26790821

  18. Controlling self-assembly of DNA-polymer conjugates for applications in imaging and drug delivery.

    PubMed

    Peterson, Amberlyn M; Heemstra, Jennifer M

    2015-01-01

    Amphiphilic supramolecular structures such as micelles and vesicles can be formed through phase-driven self-assembly of monomer units having discrete hydrophilic and hydrophobic blocks. These structures show great promise for use in medical and biological applications, and incorporating DNA as the hydrophilic block of the amphiphilic monomers enables the creation of assemblies that also take advantage of the unique information storage and molecular recognition capabilities of DNA. Recently, significant advances have been made in the synthesis of DNA-polymer conjugates (DPCs), controlling the morphology of DPC assemblies by altering monomer structure, and probing the effect of assembly on DNA stability and hybridization. Together, these investigations have laid the framework for using DPCs in drug delivery, cellular imaging, and other applications in materials science and chemistry. PMID:25327363

  19. Synthesis of a new conjugated polymer for DNA alkylation and gene regulation.

    PubMed

    Nie, Chenyao; Zhu, Chunlei; Feng, Liheng; Lv, Fengting; Liu, Libing; Wang, Shu

    2013-06-12

    A new polyfluorene derivative containing pendent alkylating chlorambucil (PFP-Cbl) was synthesized and characterized. Under direct incubation with DNA in vitro, PFP-Cbl could undergo an efficient DNA alkylating reaction and induce DNA cross-linking. In vitro transcription and translation experiment exhibited that the PFP-Cbl significantly down-regulated the gene expression of luciferase reporter plasmid. The down-regulation of gene expression was also verified through the transfection experiment of p-EGFP plasmid, which showed decreased green fluorescent protein (GFP) in cells. Meanwhile, the self-luminous property of PFP-Cbl could make it able to trace the internalized PFP-Cbl and plasmid complexes resulted from cross-linking in cells by fluorescent microscopy. Combining the features of alkylating function, multivalent binding sites, and fluorescent characteristics, PFP-Cbl provides a new insight in the area of gene regulation and extends the new applications of conjugated polymers (CPs). PMID:23548104

  20. Supramolecular Ensembles Formed between Charged Conjugated Polymers and Glycoprobes for the Fluorogenic Recognition of Receptor Proteins.

    PubMed

    Dou, Wei-Tao; Zeng, Ya-Li; Lv, Ying; Wu, Jiatao; He, Xiao-Peng; Chen, Guo-Rong; Tan, Chunyan

    2016-06-01

    This paper describes the simple construction of a unique class of supramolecular ensembles formed by electrostatic self-assembly between charged conjugated polymers and fluorophore-coupled glycoligands (glycoprobes) for the selective fluorogenic detection of receptor proteins at both the molecular and cellular levels. We show that positively and negatively charged diazobenzene-containing poly(p-phenylethynylenes) (PPEs) can be used to form stable fluorogenic probes with fluorescein-based (negatively charged) and rhodamine B based (positively charged) glycoprobes by electrostatic interaction. The structures of the ensembles have been characterized by spectroscopic and microscopic techniques. The supramolecular probes formed show quenched fluorescence in an aqueous buffer solution, which can be specifically recovered, in a concentration-dependent manner, through competitive complexation with a selective protein receptor, over a range of other unselective proteins. The ensembles also show selective fluorescence enhancement with a live cell that expresses the glycoligand receptor but not a control cell without receptor expression. PMID:27159586

  1. Conjugation polymer nanobelts: a novel fluorescent sensing platform for nucleic acid detection.

    PubMed

    Wang, Lei; Zhang, Yingwei; Tian, Jingqi; Li, Hailong; Sun, Xuping

    2011-03-01

    In this article, we report on the facile and rapid synthesis of conjugation polymer poly(p-phenylenediamine) nanobelts (PNs) via room temperature chemical oxidation polymerization of p-phenylenediamine monomers by ammonium persulfate in aqueous medium. We further demonstrate the proof-of-concept that PNs can be used as an effective fluorescent sensing platform for nucleic acid detection for the first time. The general concept used in this approach lies in the facts that the adsorption of the fluorescently labeled single-stranded DNA probe by PN leads to substantial fluorescence quenching, followed by specific hybridization with the complementary region of the target DNA sequence. This results in desorption of the hybridized complex from PN surface and subsequent recovery of fluorescence. We also show that the sensing platform described herein can be used for multiplexing detection of nucleic acid sequences. PMID:21183465

  2. Anodic, cathodic, and annihilation electrochemiluminescence emissions from hydrophilic conjugated polymer dots in aqueous medium.

    PubMed

    Dai, Ruiping; Wu, Fanmin; Xu, Huifeng; Chi, Yuwu

    2015-07-22

    Hydrophilic poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) conjugated polymer dots (CP-dots) capped by Triton X-100 were synthesized. For the first time, the electrochemiluminescence (ECL) emission of CP-dots was investigated in aqueous solution. At the glassy carbon/water interface, the CP-dots have excellent and multichannel ECL properties, such as having annihilation ECL activity in the absence of coreactants, and give bright anodic and cathodic ECL emission (590 nm) in the presence of tri-n-propylamine (TPrA) and peroxydisulfate (S2O8(2-)), respectively. The versatile ECL properties of the hydrophilic CP-dots combined with their low cytotoxicity, good biocompatibility, and easy bioconjugation may suggest promising applications of this new type of ECL nanomaterial in novel biosensing and bioimaging, and new types of light-emitting devices. PMID:26115552

  3. Conjugated Polymers with Repeated Sequences of Group 16 Heterocycles Synthesized through Catalyst-Transfer Polycondensation.

    PubMed

    Tsai, Chia-Hua; Fortney, Andria; Qiu, Yunyan; Gil, Roberto R; Yaron, David; Kowalewski, Tomasz; Noonan, Kevin J T

    2016-06-01

    Periodic π-conjugated polymers of the group 16 heterocycles (furan, thiophene, and selenophene) were synthesized with controlled chain lengths and relatively low dispersities using catalyst-transfer polycondensation. The optical gap and redox potentials of these copolymers were fine-tuned by altering the heterocycle sequence, and atomic force microscopy revealed nanofibrillar morphologies for all the materials. Grazing incidence wide-angle X-ray scattering of the thiophene-selenophene copolymers indicated that the π-stacking distance increased with incorporation of the larger heteroatom (from ∼3.7-4.0 Å), while the lamellar spacing decreased (from ∼15.8-15.2 Å). The study also revealed that periodic sequences allow electronic properties to be tuned while retaining nanofibrillar morphologies similar to those observed for poly(3-hexylthiophene). PMID:27104362

  4. Theory of non-Condon emission from the interchain exciton in conjugated polymer aggregates

    NASA Astrophysics Data System (ADS)

    Bittner, Eric R.; Karabunarliev, Stoyan; Herz, Laura M.

    2007-05-01

    The authors present here a simple analysis that explains the apparent strengthening of electron phonon interaction upon aggregation in conjugated polymer materials. The overall scheme is that of an intermolecular Herzberg-Teller effect whereby sidebands of a forbidden transition are activated by oppositely phased vibrations. The authors show that upon aggregation, the 0-0 emission becomes symmetry forbidden and the apparent redshift and remaining vibronic structure are due to sideband (0-1,0-2, etc.) emission. At higher temperatures, the 0-0 peak is due to thermal population in a higher lying even-parity vibronic state rather than direct emission from the odd-paritied lowest intermolecular vibronic state.

  5. Ratiometric Array of Conjugated Polymers-Fluorescent Protein Provides a Robust Mammalian Cell Sensor.

    PubMed

    Rana, Subinoy; Elci, S Gokhan; Mout, Rubul; Singla, Arvind K; Yazdani, Mahdieh; Bender, Markus; Bajaj, Avinash; Saha, Krishnendu; Bunz, Uwe H F; Jirik, Frank R; Rotello, Vincent M

    2016-04-01

    Supramolecular complexes of a family of positively charged conjugated polymers (CPs) and green fluorescent protein (GFP) create a fluorescence resonance energy transfer (FRET)-based ratiometric biosensor array. Selective multivalent interactions of the CPs with mammalian cell surfaces caused differential change in FRET signals, providing a fingerprint signature for each cell type. The resulting fluorescence signatures allowed the identification of 16 different cell types and discrimination between healthy, cancerous, and metastatic cells, with the same genetic background. While the CP-GFP sensor array completely differentiated between the cell types, only partial classification was achieved for the CPs alone, validating the effectiveness of the ratiometric sensor. The utility of the biosensor was further demonstrated in the detection of blinded unknown samples, where 121 of 128 samples were correctly identified. Notably, this selectivity-based sensor stratified diverse cell types in minutes, using only 2000 cells, without requiring specific biomarkers or cell labeling. PMID:26967961

  6. Metal/conjugated polymer interfaces: A local density functional study of aluminum/polyene interactions

    NASA Astrophysics Data System (ADS)

    Fredriksson, C.; Lazzaroni, R.; Brédas, J. L.; Ouhlal, A.; Selmani, A.

    1994-06-01

    The interactions between aluminum atoms and model molecules representing trans-polyacetylene are studied quantum chemically by a local density functional method. We focus on the chemical and electronic structure of the organoaluminum complexes. Special emphasis is put on a comparison between results at the local spin density approximation and ab initio Hartree-Fock levels. In unmetallized polyenes, the density functional method provides a very good description of the carbon-carbon bond lengths of conjugated systems; in the case of hexatriene, it reproduces the bond dimerization in very good agreement with experimental measurements. Upon metallization, a strong covalent interaction between aluminum and carbon is found. The Al-C bond formation induces an interruption of the bond alternation pattern and reduces the π-conjugation in the oligomer, in qualitative agreement with photoelectron spectroscopy data and previous theoretical results at the Hartree-Fock level. Notably, the π-electron levels in the organoaluminum complexes maintain delocalization. In contrast to Hartree-Fock results where an aluminum atom binds to a single carbon, the interactions calculated with the local spin density approximation lead to (i) formation of multicenter aluminum-carbon bonding; (ii) near planarity of the polyene molecule; and (iii) a lower degree of charge transfer from the metal atom to the polymer.

  7. Nanostructures of an amphiphilic zinc phthalocyanine polymer conjugate for photodynamic therapy of psoriasis.

    PubMed

    Jin, Yiguang; Zhang, Xiaohan; Zhang, Baolei; Kang, Hongxiang; Du, Lina; Li, Miao

    2015-04-01

    Psoriasis is a chronic inflammatory skin disease affecting 2-5% of the population worldwide and it severely affects patient quality of life. In this study, an amphiphilic zinc phthalocyanine polymer conjugate (ZPB) was synthesized, in which zinc phthalocyanine (ZnPc) was conjugated with the poly(ethylene glycol) (PEG) chain of Brij 58. ZPB showed two maximum UV-vis absorption wavelengths, 348 nm and 678 nm. A monomolecular micelle of ZPB formed in water with a mean size of 25 nm and zeta potential of -15 mV. The nanostructures aggregated into cloudy precipitates, which were easily dispersed. The nanostructure showed the shell-core structure with the ZnPc segments as the core and the PEG chains as the shell. The anti-psoriasis effect of the ZPB nanostructure was explored using a guinea pig psoriasis model. After comparing the anti-psoriasis effects of saline, light alone, ZPB alone, and the combination of light and ZPB, the combination of light and ZPB showed the best photodynamic therapy of psoriasis based on the light excitation of the photosensitizer ZPB and the psoriasis was nearly cured according to the histopathological investigation. The ZPB nanostructure is a promising anti-psoriasis nanomedicine based on photodynamic therapy. PMID:25766924

  8. Near-infrared light-triggered thermochemotherapy of cancer using a polymer-gold nanorod conjugate.

    PubMed

    Ko, Hyewon; Son, Soyoung; Bae, Seonghwan; Kim, Joo-Hyung; Yi, Gi-Ra; Park, Jae Hyung

    2016-04-29

    A biocompatible polymer-gold nanorod (P-AuNR) conjugate was developed as a thermo-chemotherapeutic nano-sized drug carrier for cancer therapy using near-infrared (NIR) light as an external trigger. The amphiphilic polymer, poly(ethylene glycol)-block-poly(caprolactone) (PEG-b-PCL) bearing a disulfide bond, was prepared using a facile synthetic route via copper(I)-free click chemistry and covalently linked to AuNR. The chemical structures and successful conjugation of PEG-b-PCL were analyzed using (1)H NMR and FT-IR. Doxorubicin (DOX), a hydrophobic anticancer drug, was effectively loaded into the hydrophobic PCL domain of P-AuNR through a simple dialysis method. P-AuNR showed longitudinal plasmon resonance absorption at the NIR region, thus generating heat under irradiation at 808 nm. Interestingly, exposure of P-AuNRs to NIR induced a structural change in the PCL block from a crystalline to an amorphous state, leading to the temporally controlled release of DOX. No significant release of DOX was observed from P-AuNRs under physiological conditions (pH 7.4), whereas the release rate of DOX was remarkably enhanced in response to NIR irradiation. In vitro cellular experiments to assess cytotoxicity and intracellular drug release behavior of DOX-P-AuNRs demonstrated that the release of DOX could be selectively regulated by NIR irradiation. Overall, DOX-P-AuNRs might have the potential to overcome the indiscriminate toxicity of free DOX. PMID:26987360

  9. Smart conjugated polymer nanocarrier for healthy weight loss by negative feedback regulation of lipase activity

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Lei; Zhu, Sha; Zhang, Lei; Feng, Pei-Jian; Yao, Xi-Kuang; Qian, Cheng-Gen; Zhang, Can; Jiang, Xi-Qun; Shen, Qun-Dong

    2016-02-01

    Healthy weight loss represents a real challenge when obesity is increasing in prevalence. Herein, we report a conjugated polymer nanocarrier for smart deactivation of lipase and thus balancing calorie intake. After oral administration, the nanocarrier is sensitive to lipase in the digestive tract and releases orlistat, which deactivates the enzyme and inhibits fat digestion. It also creates negative feedback to control the release of itself. The nanocarrier smartly regulates activity of the lipase cyclically varied between high and low levels. In spite of high fat diet intervention, obese mice receiving a single dose of the nanocarrier lose weight over eight days, whereas a control group continues the tendency to gain weight. Daily intragastric administration of the nanocarrier leads to lower weight of livers or fat pads, smaller adipocyte size, and lower total cholesterol level than that of the control group. Near-infrared fluorescence of the nanocarrier reveals its biodistribution.Healthy weight loss represents a real challenge when obesity is increasing in prevalence. Herein, we report a conjugated polymer nanocarrier for smart deactivation of lipase and thus balancing calorie intake. After oral administration, the nanocarrier is sensitive to lipase in the digestive tract and releases orlistat, which deactivates the enzyme and inhibits fat digestion. It also creates negative feedback to control the release of itself. The nanocarrier smartly regulates activity of the lipase cyclically varied between high and low levels. In spite of high fat diet intervention, obese mice receiving a single dose of the nanocarrier lose weight over eight days, whereas a control group continues the tendency to gain weight. Daily intragastric administration of the nanocarrier leads to lower weight of livers or fat pads, smaller adipocyte size, and lower total cholesterol level than that of the control group. Near-infrared fluorescence of the nanocarrier reveals its biodistribution

  10. Near-infrared light-triggered thermochemotherapy of cancer using a polymer-gold nanorod conjugate

    NASA Astrophysics Data System (ADS)

    Ko, Hyewon; Son, Soyoung; Bae, Seonghwan; Kim, Joo-Hyung; Yi, Gi-Ra; Park, Jae Hyung

    2016-04-01

    A biocompatible polymer-gold nanorod (P-AuNR) conjugate was developed as a thermo-chemotherapeutic nano-sized drug carrier for cancer therapy using near-infrared (NIR) light as an external trigger. The amphiphilic polymer, poly(ethylene glycol)-block-poly(caprolactone) (PEG-b-PCL) bearing a disulfide bond, was prepared using a facile synthetic route via copper(I)-free click chemistry and covalently linked to AuNR. The chemical structures and successful conjugation of PEG-b-PCL were analyzed using 1H NMR and FT-IR. Doxorubicin (DOX), a hydrophobic anticancer drug, was effectively loaded into the hydrophobic PCL domain of P-AuNR through a simple dialysis method. P-AuNR showed longitudinal plasmon resonance absorption at the NIR region, thus generating heat under irradiation at 808 nm. Interestingly, exposure of P-AuNRs to NIR induced a structural change in the PCL block from a crystalline to an amorphous state, leading to the temporally controlled release of DOX. No significant release of DOX was observed from P-AuNRs under physiological conditions (pH 7.4), whereas the release rate of DOX was remarkably enhanced in response to NIR irradiation. In vitro cellular experiments to assess cytotoxicity and intracellular drug release behavior of DOX-P-AuNRs demonstrated that the release of DOX could be selectively regulated by NIR irradiation. Overall, DOX-P-AuNRs might have the potential to overcome the indiscriminate toxicity of free DOX.

  11. Development and validation of an in vitro pharmacokinetic/pharmacodynamic model to test the antibacterial efficacy of antibiotic polymer conjugates.

    PubMed

    Azzopardi, Ernest A; Ferguson, Elaine L; Thomas, David W

    2015-04-01

    This study describes the use of a novel, two-compartment, static dialysis bag model to study the release, diffusion, and antibacterial activity of a novel, bioresponsive dextrin-colistin polymer conjugate against multidrug resistant (MDR) wild-type Acinetobacter baumannii. In this model, colistin sulfate, at its MIC, produced a rapid and extensive drop in viable bacterial counts (<2 log10 CFU/ml at 4 h); however, a marked recovery was observed thereafter, with regrowth equivalent to that of control by 48 h. In contrast, dextrin-colistin conjugate, at its MIC, suppressed bacterial growth for up to 48 h, with 3 log10 CFU/ml lower bacterial counts after 48 h than those of controls. Doubling the concentration of dextrin-colistin conjugate (to 2× MIC) led to an initial bacterial killing of 3 log10 CFU/ml at 8 h, with a similar regrowth profile to 1× MIC treatment thereafter. The addition of colistin sulfate (1× MIC) to dextrin-colistin conjugate (1× MIC) resulted in undetectable bacterial counts after 4 h, followed by suppressed bacterial growth (3.5 log10 CFU/ml lower than that of control at 48 h). Incubation of dextrin-colistin conjugates with infected wound exudate from a series of burn patients (n = 6) revealed an increasing concentration of unmasked colistin in the outer compartment (OC) over time (up to 86.3% of the initial dose at 48 h), confirming that colistin would be liberated from the conjugate by endogenous α-amylase within the wound environment. These studies confirm the utility of this model system to simulate the pharmacokinetics of colistin formation in humans administered dextrin-colistin conjugates and further supports the development of antibiotic polymer conjugates in the treatment of MDR infections. PMID:25512401

  12. Static properties of equilibrium polymers confined in ultrathin films

    NASA Astrophysics Data System (ADS)

    Cavallo, Anna; Wittmer, Joachim P.; Johner, Albert; Baschnagel, Joerg

    2008-03-01

    The static properties of equilibrium polymer melts confined in ultrathin films are studied by means of Monte Carlo simulations of a lattice model: the bond fluctuation model. In this work we focus on the effects of ultrathin film confinement between two parallel and neutral walls on chain size and molecular weight distribution. We compare our numerical results to analytical calculations by Semenov and Johner [Eur. Phy. J. E, 12, 469 (2003)] who predicted for ultrathin films, logarithmic corrections to the leading mean-field behavior. Our simulation data are compatible with the theoretical results.

  13. Non-Fullerene Polymer Solar Cells Based on Alkylthio and Fluorine Substituted 2D-Conjugated Polymers Reach 9.5% Efficiency.

    PubMed

    Bin, Haijun; Zhang, Zhi-Guo; Gao, Liang; Chen, Shanshan; Zhong, Lian; Xue, Lingwei; Yang, Changduk; Li, Yongfang

    2016-04-01

    Non-fullerene polymer solar cells (PSCs) with solution-processable n-type organic semiconductor (n-OS) as acceptor have seen rapid progress recently owing to the synthesis of new low bandgap n-OS, such as ITIC. To further increase power conversion efficiency (PCE) of the devices, it is of a great challenge to develop suitable polymer donor material that matches well with the low bandgap n-OS acceptors thus providing complementary absorption and nanoscaled blend morphology, as well as suppressed recombination and minimized energy loss. To address this challenge, we synthesized three medium bandgap 2D-conjugated bithienyl-benzodithiophene-alt-fluorobenzotriazole copolymers J52, J60, and J61 for the application as donor in the PSCs with low bandgap n-OS ITIC as acceptor. The three polymers were designed with branched alkyl (J52), branched alkylthio (J60), and linear alkylthio (J61) substituent on the thiophene conjugated side chain of the benzodithiophene (BDT) units for studying effect of the substituents on the photovoltaic performance of the polymers. The alkylthio side chain, red-shifted absorption down-shifted the highest occupied molecular orbital (HOMO) level and improved crystallinity of the 2D conjugated polymers. With linear alkylthio side chain, the tailored polymer J61 exhibits an enhanced JSC of 17.43 mA/cm(2), a high VOC of 0.89 V, and a PCE of 9.53% in the best non-fullerene PSCs with the polymer as donor and ITIC as acceptor. To the best of our knowledge, the PCE of 9.53% is one of the highest values reported in literature to date for the non-fullerene PSCs. The results indicate that J61 is a promising medium bandgap polymer donor in non-fullerene PSCs. PMID:26997357

  14. Threshold-like complexation of conjugated polymers with small molecule acceptors in solution within the neighbor-effect model.

    PubMed

    Sosorev, Andrey Yu; Parashchuk, Olga D; Zapunidi, Sergey A; Kashtanov, Grigoriy S; Golovnin, Ilya V; Kommanaboyina, Srikanth; Perepichka, Igor F; Paraschuk, Dmitry Yu

    2016-02-14

    In some donor-acceptor blends based on conjugated polymers, a pronounced charge-transfer complex (CTC) forms in the electronic ground state. In contrast to small-molecule donor-acceptor blends, the CTC concentration in polymer:acceptor solution can increase with the acceptor content in a threshold-like way. This threshold-like behavior was earlier attributed to the neighbor effect (NE) in the polymer complexation, i.e., next CTCs are preferentially formed near the existing ones; however, the NE origin is unknown. To address the factors affecting the NE, we record the optical absorption data for blends of the most studied conjugated polymers, poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and poly(3-hexylthiophene) (P3HT), with electron acceptors of fluorene series, 1,8-dinitro-9,10-antraquinone (), and 7,7,8,8-tetracyanoquinodimethane () in different solvents, and then analyze the data within the NE model. We have found that the NE depends on the polymer and acceptor molecular skeletons and solvent, while it does not depend on the acceptor electron affinity and polymer concentration. We conclude that the NE operates within a single macromolecule and stems from planarization of the polymer chain involved in the CTC with an acceptor molecule; as a result, the probability of further complexation with the next acceptor molecules at the adjacent repeat units increases. The steric and electronic microscopic mechanisms of NE are discussed. PMID:26799407

  15. Well-Defined Protein/Peptide-Polymer Conjugates by Aqueous Cu-LRP: Synthesis and Controlled Self-Assembly.

    PubMed

    Zhang, Qiang; Li, Muxiu; Zhu, Chongyu; Nurumbetov, Gabit; Li, Zaidong; Wilson, Paul; Kempe, Kristian; Haddleton, David M

    2015-07-29

    The synthesis of well-defined protein/peptide-polymer conjugates with interesting self-assembly behavior via single electron transfer living radical polymerization in water is described. A range of protein/peptides with different physical and chemical properties have been modified to macroinitiators and optimized polymerization conditions ensure successful polymerization from soluble, insoluble, and dispersed protein/peptide molecules or protein aggregates. This powerful strategy tolerates a range of functional monomers and mediates efficient homo or block copolymerization to generate hydrophilic polymers with controlled molecular weight (MW) and narrow MW distribution. The polymerizations from bovine insulin macroinitiators follow surface-initiated "grafting from" polymerization mechanism and may involve a series of self-assembly and disassembly processes. Synthesized insulin-polymer conjugates form spheres in water, and the self-assembly behavior could be controlled via thermal control, carbohydrate-protein interaction, and protein denaturation. PMID:26149497

  16. Co-polymer Films for Sensors

    NASA Technical Reports Server (NTRS)

    Ryan, Margaret A. (Inventor); Homer, Margie L. (Inventor); Yen, Shiao-Pin S. (Inventor); Kisor, Adam (Inventor); Jewell, April D. (Inventor); Shevade, Abhijit V. (Inventor); Manatt, Kenneth S. (Inventor); Taylor, Charles (Inventor); Blanco, Mario (Inventor); Goddard, William A. (Inventor)

    2012-01-01

    Embodiments include a sensor comprising a co-polymer, the co-polymer comprising a first monomer and a second monomer. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is polystyrene and the second monomer is poly-2-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium benzylamine chloride. Other embodiments are described and claimed.

  17. Co-polymer films for sensors

    NASA Technical Reports Server (NTRS)

    Ryan, Margaret A. (Inventor); Homer, Margie L. (Inventor); Yen, Shiao-Pin S. (Inventor); Kisor, Adam (Inventor); Jewell, April D. (Inventor); Shevade, Abhijit V. (Inventor); Manatt, Kenneth S. (Inventor); Taylor, Charles (Inventor); Blanco, Mario (Inventor); Goddard, William A. (Inventor)

    2010-01-01

    Embodiments include a sensor comprising a co-polymer, the co-polymer comprising a first monomer and a second monomer. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is polystyrene and the second monomer is poly-2-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium benzylamine chloride. Other embodiments are described and claimed.

  18. Simultaneous Vapor Deposition and Phase Separation of Polymer Films

    NASA Astrophysics Data System (ADS)

    Tao, Ran; Anthamatten, Mitchell

    2012-02-01

    Initiated chemical vapor deposition (iCVD) is a solventless, free radical technique used predominately to deposit homogeneous films of linear and crosslinked polymers directly from gas phase feeds. The major goal of this research is to force and arrest phase separation of deposited species by co-depositing non-reactive molecules (porogens) with reactive monomers and crosslinkers. We introduce these species during iCVD to force and quench polymer induced phase separation (PIPS) during film growth as a step toward tunable pore-size, density, and morphology. Polymerization, crosslinking and PIPS are intended to occur simultaneously on the substrate, resulting in a vitrified microstructure. Cahn-Hilliard theory predicts that the length scale of phase separation depends on the polymer-porogen interaction energy, the polymerization rate and the species' mobility. A series of films were grown by varying deposition rate, porogen type, and reagent flowrates. Crosslinkers were introduced to limit the growth of phase separated domains and to provide mechanical support during porogen removal. To elucidate how phase separation competes with polymerization and film growth, deposited films were studied using a combination of electron microscopy, profilometry and spectroscopic techniques.

  19. Transparent lithiated polymer films for thermal neutron detection

    NASA Astrophysics Data System (ADS)

    Mabe, Andrew N.; Auxier, John D.; Urffer, Matthew J.; Penumadu, Dayakar; Schweitzer, George K.; Miller, Laurence F.

    2013-09-01

    Novel water-soluble 6Li loaded copolymer scintillation films have been designed and fabricated to detect thermal neutrons. Styrene and maleic anhydride were copolymerized to form an alternating copolymer, then the anhydride functionality was hydrolyzed using 6Li hydroxide. The resulting poly(styrene-co-lithium maleate) was mixed with salicylic acid as a fluor and cast as a thin film from water. The maximum 6Li loading obtained that resulted in a transparent film was 4.36% by mass (6Li to polymer). The optimum fluorescence output was obtained for 11.7% salicylic acid by mass, presumably in the form of lithium salicylate, resulting in an optimum film containing 3.85% by mass of 6Li. A facile and robust synthesis method, film fabrication protocol, photoluminescence results, and scintillation responses are reported herein.

  20. Synthesis and Characterization of a New Conjugated Polymer Bearing Pyrazole and Thiophene Moieties as Potent NLO Material

    NASA Astrophysics Data System (ADS)

    Vishnumurthy, K. A.; Adhikari, A. Vasudeva; Sunitha, M. S.; Philip, Reji

    2011-10-01

    In this communication we describe the design and synthesis of a new conjugated polymer (P) carrying 3,4-dialkoxythiophene, 1,3,4 oxadiazole and pyrazole units, from its monomers through condensation polymerization method. The structure of newly synthesized polymer was established by FT-IR, 1H NMR, elemental analysis and gel permeation chromatographic techniques. Further, its electrochemical, linear and nonlinear optical properties of the polymer have been investigated. The optical and electrochemical band gap was found to be 2.39 eV. Z-scan results reveal that the polymer exhibits strong optical limiting behavior due to effective three-photon absorption (3PA). The value of 3PA coefficient was found to be 1.1×10-20 m3/W2, which is comparable to that of good optical limiting materials. The fluorescence quantum yield of the polymer in solution was determined using quinine sulfate as standard and it was found to be 42%.

  1. Nanomolding the Surface of Polymer Films.

    PubMed

    Foschini, Mauricio; Da Silva, Silésia Fátima Curcino; Tozoni, José Roberto; Zadra-Armond, Raigna Augusta Da Silva; Oliveira, Osvaldo N; Marletta, Alexandre

    2015-08-01

    Slight changes in the experimental procedures of the micro contact printing (ACP) technique are introduced here, which allow for using polymers soluble in distinct solvents to fabricate submicrometric 2D periodic structures. Highly reproducible secondary and tertiary poly(dimethylsiloxane) (PDMS) molds could be produced, as demonstrated in atomic force microscopy images and light diffraction experiments. The replication of tertiary molds with no residues of PDMS demonstrates the feasibility of large-scale production with distinct polymers. The plane wave propagation along the tertiary poly(3,4-ethylenedioxythiophene) with poly(hydrogen 4-styrene sulfonate) molds was simulated with a finite-difference time-domain algorithm. A strong wave propagation was observed in the region containing the structures acting as a wave guide, in agreement with the results from the experimental absorption measurements. Furthermore, we show that the optical properties of the molds and their roughness can be tuned by choosing the polymers (including biopolymers) for printing pillars and tracks, thus bringing new possibilities for nanomolding of polymer surfaces for photonics, organic electronics and bioelectronics. PMID:26369185

  2. Photorefractivity in nematic liquid crystals doped with a conjugated polymer: Mechanisms for enhanced charge transport

    SciTech Connect

    Wiederrecht, G.P.; Niemczyk, M.P.; Svec, W.A.; Wasielewski, M.R. |

    1999-06-01

    New organic materials that exhibit photorefractive effects are of wide interest for potential optical signal processing applications. The authors report on a photorefractive nematic liquid crystal composite containing the conjugated polymer poly(2,5-bis(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene), BEH-PPV that exhibits a novel fringe spacing dependent inversion of the polarity of the space-charge field due to competition between the ionic diffusion and charge drift transport mechanisms. A eutectic mixture of 35% (wt %) 4{prime}-(n-octyloxy)-4-cyanobiphenyl, 8OCB, and 65% 4{prime}(n-pentyl)-4-cyanobiphenyl, 5CB, was doped with 10{sup {minus}5} M BEH-PPV (200 kD by GPC), as the electron donor. The molecular weight of the BEH-PPV polymer implies that 500 repeat units of the monomer are present with an extended chain length of 0.35 {micro}m. N,N{prime}-Dioctyl-1,4:5,8-naphthalenediimide, NI, 8 {times} 10{sup {minus}3} M, was added as the electron acceptor. The free energy change for the photoinduced electron-transfer reaction, (BEH-PPV) + NI {yields} (BEH-PPV){sup +} + NI{sup {minus}}, is {minus}1.0 eV. Two other liquid-crystal composites were also studied as controls.

  3. Exciton and polaron interactions in self-assembled conjugated polymer aggregates

    NASA Astrophysics Data System (ADS)

    Grey, John K.; Thomas, Alan K.; Gao, Jian

    2015-08-01

    We study exciton coupling and interconversion between neutral and charged states of different spin in pi-stacked conjugated polymer aggregates. Rigorous self-assembly approaches are used to prepare aggregate nanofibers that permit reliable control of polymer chain conformational and packing (intra- and interchain) order within these structures. Exciton coupling can be tuned between the H- and J-aggregate limits, which has important implications for determining the fates of excitons and polarons. Single molecule intensity modulation spectroscopy was performed on individual nanofibers and large quenching depths of emissive singlet excitons by triplets are found in J-aggregate type structures. We propose that high intrachain order leads to exciton delocalization that effectively lowers singlet-triplet energy splittings thus increasing triplet yields. Exciton-polaron and polaron-polaron interactions are next investigated in both H- and J-type nanofibers where polarons are injected by charge transfer doping. We find that the enhanced intrachain order of J-aggregates enables efficient intrachain polaron transport and leads to significantly larger doping efficiencies than less ordered H-aggregates. As polaron densities increase, signatures of spin-spin interactions between polarons on adjacent chains become appreciable leading to the formation of a spinless bipolaron. Overall, these studies demonstrate the potential for controlling and directing exciton and polaron interactions via tuning of subtle intra- and interchain ordering characteristics of aggregates, which could benefit various polymeric optoelectronic applications.

  4. White light generation tuned by dual hybridization of nanocrystals and conjugated polymers

    NASA Astrophysics Data System (ADS)

    Demir, Hilmi Volkan; Nizamoglu, Sedat; Ozel, Tuncay; Mutlugun, Evren; Ozge Huyal, Ilkem; Sari, Emre; Holder, Elisabeth; Tian, Nan

    2007-10-01

    Dual hybridization of highly fluorescent conjugated polymers and highly luminescent nanocrystals (NCs) is developed and demonstrated in multiple combinations for controlled white light generation with high color rendering index (CRI) (> 80) for the first time. The generated white light is tuned using layer-by-layer assembly of CdSe/ZnS core-shell NCs closely packed on polyfluorene, hybridized on near-UV emitting nitride-based light emitting diodes (LEDs). The design, synthesis, growth, fabrication and characterization of these hybrid inorganic organic white LEDs are presented. The following experimental realizations are reported: (i) layer-by-layer hybridization of yellow NCs (λPL=580 nm) and blue polyfluorene (λPL=439 nm) with tristimulus coordinates of (x, y)=(0.31, 0.27), correlated color temperature of Tc=6962 K and CRI of Ra=53.4; (ii) layer-by-layer assembly of yellow and green NCs (λPL=580 and 540 nm) and blue polyfluorene (λPL=439 nm) with (x, y)=(0.23, 0.30), Tc=14395 K and Ra=65.7; and (iii) layer-by-layer deposition of yellow, green and red NCs (λPL=580, 540 and 620 nm) and blue polyfluorene (λPL=439 nm) with (x, y)=(0.38, 0.39), Tc=4052 K and Ra= 83.0. The CRI is demonstrated to be well controlled and significantly improved by increasing multi-chromaticity of the NC and polymer emitters.

  5. Investigation of intermolecular interactions between fluorene-based conjugated polymers using the dispersion-corrected DFT

    NASA Astrophysics Data System (ADS)

    Ayoub, Sarah; Lagowski, Jolanta B.

    2015-03-01

    Alternating triphenylamine-fluorene, TPAFn (n=1-3), and fluorene-oxadiazole OxFn (n=1-3) conjugated copolymers are important components of novel high-efficiency multi-layer organic light-emitting diodes (OLEDs). In this work, we investigate the intermolecular interactions between the various combinations of monomers of OxFn-TPAFn (n=1-3) copolymers using the dispersion-corrected density functional theory (B97D) method. The monomer combinations are taken with and without the presence of long alkyl chains in order to study the effect of side-chains on the polymer backbone intermolecular interactions. The dispersion effect is studied by comparing the structures of the interacting monomers with those in vacuum. In addition, we calculate intermolecular distances, energy gaps and binding energies of monomer dimers corresponding to different pairings of OxFn-TPAFn (n=1-3) monomers. Our results show that the combination of OxF3-TPAF2 monomers exhibites the highest binding energy, closest intermolecular distance, and the best matching of chain lengths amongst all of the combinations of OxFn-TPAFn (n=1-3) monomers. Experiments have shown that OxF3-TPAF2 combination gives the best performance for OLEDS made of OxF-TPAF polymer layers.

  6. Charge mobility induced by Brownian fluctuations in π-conjugated polymers in solution.

    PubMed

    Poole, Jessica Ellen; Damry, Djamshid Ahmud; Tozer, Oliver Robert; Barford, William

    2016-01-28

    We study the motion of a doped charge in a π-conjugated polymer chain in solution subject to Brownian fluctuations. Specifically, we take poly(para-phenylene) to be our model system where the Brownian fluctuations cause rotational motion of the phenylene rings. The instantaneous torsional fluctuations cause Anderson localization of the charge wavefunction, with the lower-energy spectrum being composed of local ground states and the higher-energy spectrum being composed of quasi-extended states. At low temperatures, additional charge localization occurs via torsional relaxation. The dynamical torsional fluctuations lead to two distinct modes of motion of the charge: adiabatic and non-adiabatic. Adiabatic motion is a 'crawling' motion of the charge along the polymer chain while the charge remains in its local ground state. Non-adiabatic motion is a rapid 'hopping' motion as the charge is excited into higher energy quasi-extended states and travels ballistically along the chain before relaxing into a local ground state. The adiabatic motion dominates at low temperatures, and exhibits a linear temperature dependence and thus a constant zero-field charge mobility. Non-adiabatic motion begins to dominate as the temperature is increased, as the charge is thermally excited into higher energy states. At high temperatures the diffusion constant becomes almost temperature independent, indicating a decrease in the charge mobility with increasing temperature, which we attribute to the charge localization length being a decreasing function of temperature at high temperatures. PMID:26699806

  7. Thin film conductive polymer for microactuator and micromuscle applications

    SciTech Connect

    Lee, A.P.; Hong, K.; Trevino, J.; Northrup, M.A.

    1994-04-14

    Conductive polymer/polyimide bimorphic microcantilevers have been actuated vertically (out-of-plane) upon the volumetric changes induced by electrochemical doping of the polymer. The microcantilevers that are 200-500 {mu}m in length and 50-100 {mu}m in width can be fully extended from a circularly-curled geometry, and thus generate more than 100 {mu}m displacement. Dynamically the microcantilevers have been driven as fast as 1.2 Hz and the polymer was stable for over a week stored in air and light. Residual stresses in the polymer film is estimated to be as high as 254 MPa, and actuation stresses are as high as 50 MPa.

  8. Extension of in vivo half-life of biologically active peptides via chemical conjugation to XTEN protein polymer.

    PubMed

    Podust, Vladimir N; Sim, Bee-Cheng; Kothari, Dharti; Henthorn, Lana; Gu, Chen; Wang, Chia-wei; McLaughlin, Bryant; Schellenberger, Volker

    2013-11-01

    XTEN, unstructured biodegradable proteins, have been used to extend the in vivo half-life of genetically fused therapeutic proteins and peptides. To expand the applications of XTEN technology to half-life extension of other classes of molecules, XTEN protein polymers and methods for chemical XTENylation were developed. Two XTEN precursors were engineered to contain enzymatically removable purification tags. The proteins were readily expressed in bacteria and purified to homogeneity by chromatography techniques. As proof-of-principle, GLP2-2G peptide was chemically conjugated to each of the two XTEN protein polymers using maleimide-thiol chemistry. The monodisperse nature of XTEN protein polymer enabled reaction monitoring as well as the detection of peptide modifications in the conjugated state using reverse phase-high performance liquid chromatography (RP-HPLC) and electrospray ionization mass spectrometry. The resulting GLP2-2G-XTEN conjugates were purified by preparative RP-HPLC to homogeneity. In comparison with recombinantly fused GLP2-2G-XTEN, chemically conjugated GLP2-2G-XTEN molecules exhibited comparable in vitro activity, in vitro plasma stability and pharmacokinetics in rats. These data suggest that chemical XTENylation could effectively extend the half-life of a wide spectrum of biologically active molecules, therefore broadening its applicability. PMID:24133142

  9. Drying of polymer films: study of demixing phenomena

    NASA Astrophysics Data System (ADS)

    Fichot, Julie; Heyd, Rodolphe; Saboungi, Marie-Louise; Josserend, Christophe; Combard, Emilie; Tranchant, Jean Francois

    2011-03-01

    Understanding the mechanisms that control the stability of polymeric films is important in beauty care. We have prepared films starting from a water-soluble organic polymer, a preservative and water. We study the drying of these films as a function of several physicochemical parameters that control their interfaces such as temperature, humidity and the nature of the support. The viscoelastic properties of the solutions before spreading out are analyzed with a rheometer in order to adjust the temperature. The topography of the films is observed by optical microscopy and the evolution of the drying is determined with a precision gravimetric balance. The behavior of the films on a nanometric scale is followed by AFM. During the drying process, droplets appear on the surface of the film, made up of water surrounded by a shell of preservative. As the films dries, the water evaporates from the droplets and the preservative spreads on the surface of the film, leading to the formation of craters on the surface of the dried film. The dimensions and numbers of the craters depend strongly on the type and concentration of the preservative employed.

  10. Updated evaluation of polymer films for electrical insulation

    SciTech Connect

    McCoy, H.E. Jr.

    1990-08-01

    Several types of tests have been run on polymer film materials that could be useful for electrical insulation. The polymers studied were polyethylene terephtalate, polycarbonate, polysulfone, polyetherimide, ultrahigh-molecular-weight polyethylene, polyimide, polybutylene terephthalate, and a laminate of Kraft paper and polypropylene. Thermal aging tests were run to 60,000 h on several of the polymers, and the samples were evaluated by tensile tests, electrical breakdown tests, and immersion density measurements. Because of the wide range of potential service conditions, tensile tests were run on as-received materials over the temperature range of {minus}196 to 200{degree}C. Polyimide is probably the only material suitable for the extremes of this temperature range, but many of the other polymers would be suitable for intermediate temperatures. Creep tests were run in nitrogen and transformer oil at 90{degree}C. It was found that some polymers are weaker and less ductile in oil than in nitrogen and that other polymers have equivalent properties in the two environments. A means of applying mechanical, thermal, and electrical stresses simultaneously to polymer samples was developed. Tests were run at 90{degree}C in transformer oil on polyethylene terephthalate, polyimide, and polyethersulfone. Tests thus far do not indicate that the creep rate is affected by the application of a 5 kV dc potential. 7 refs., 30 figs., 16 tabs.

  11. Parallel, open-channel lateral flow (immuno) assay substrate based on capillary-channeled polymer films.

    PubMed

    Zhang, Lynn X; Jiang, Liuwei; Willett, Daniel R; Marcus, R Kenneth

    2016-02-01

    Presented here is a novel implementation of polypropylene capillary-channeled polymer (C-CP) films, functionalized for bioaffinity separations and implemented as a platform for lateral flow (immuno) assays. The parallel ∼80 μm × 80 μm channels pass test solutions down the 30 mm film length via spontaneous wicking action, setting up the possibility for immobilizing different capture agents in the respective channels. The base-film modification process is divided into two steps: ultraviolet light treatment to improve hydrophillicity of the polypropylene substrate and the physical adsorption of a functionalized lipid tethered ligand (LTL) as a selective capture agent. The entire modification procedure is performed under ambient conditions in an aqueous solution without extreme pH conditions. In this demonstration, physical adsorption of a biotinylated-LTL onto the UV-treated PP surface selectively captures Texas Red-labeled streptavidin (SAv-TR) in the presence of enhanced green fluorescence protein (EGFP), which passes without retention in less than 5 s. In addition to the fluorescence imaging of the protein solutes, matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS) was used to confirm the formation of the LTL-SAv conjugates on the channel surface as well as to demonstrate an alternative means of probing the capture step. The present effort sets the groundwork for further development of C-CP films as a parallel, multi-analyte LFA platform; a format that to-date has not been described. PMID:26646022

  12. A Conducting Polymer Film Stronger Than Aluminum

    NASA Astrophysics Data System (ADS)

    Shi, Gaoquan; Jin, Shi; Xue, Gi; Li, Cun

    1995-02-01

    Polythiophene (Pth) was electrochemically deposited onto stainless steel substrate from freshly distilled boron fluoride-ethyl ether containing 10 millimoles of thiophene per liter. The free-standing Pth film obtained at an applied potential of 1.3 volts (versus Ag/AgCl) had a conductivity of 48.7 siemens per centimeter. Its tensile strength (1200 to 1300 kilograms per square centimeter) was greater than that of aluminium (1000 to 1100 kilograms per square centimeter). This Pth film behaves like a metal sheet and can be easily cut into various structures with a knife or a pair of scissors.

  13. Deformation Hysteresis of Electrohydrodynamic Patterning on a Thin Polymer Film.

    PubMed

    Yang, Qingzhen; Li, Ben Q; Tian, Hongmiao; Li, Xiangming; Shao, Jinyou; Chen, Xiaoliang; Xu, Feng

    2016-07-13

    Electrohydrodynamic patterning is a technique that enables micro/nanostructures via imposing an external voltage on thin polymer films. In this investigation, we studied the electrohydrodynamic patterning theoretically and experimentally, with special interest focused on the equilibrium state. It is found that the equilibrium structure height increases with the voltage. In addition, we have observed, and believe it to be the first time, a hysteresis phenomenon exists in the relationship between the voltage and structure height. With an increase in the voltage, a critical value (the first critical voltage) is noticed, above which the polymer film would increase dramatically until it comes into contact with the template. However, with a decrease in the voltage, a smaller voltage (the second critical voltage) is needed to detach the polymer from the template. The mismatch of the first and second critical voltages distorts the voltage-structure height curve into an "S" shape. Such a phenomenon is verified for three representative templates and also by experiments. Furthermore, the effects of some parameters (e.g., polymer film thickness and dielectric constant) on this hysteresis phenomenon are also discussed. PMID:27326791

  14. Surface analysis of the selective excimer laser patterning of a thin PEDOT:PSS film on flexible polymer films

    NASA Astrophysics Data System (ADS)

    Schaubroeck, David; De Smet, Jelle; Willems, Wouter; Cools, Pieter; De Geyter, Nathalie; Morent, Rino; De Smet, Herbert; Van Steenbeerge, Geert

    2016-07-01

    Fast patterning of highly conductive polymers like PEDOT:PSS (poly (3,4-ethylene dioxythiophene): polystyrene sulfonate) with lasers can contribute to the development of industrial production of liquid crystal displays on polymer foils. In this article, the selective UV laser patterning of a PEDOT:PSS film on flexible polymer films is investigated. Based on their optical properties, three polymer films are investigated: polyethylene terephthalate (PET), polymethyl methacrylate (PMMA) and cellulose triacetate (TAC). Ablation parameters for a 110 nm PEDOT:PSS film on these polymer films are optimized. A detailed study of the crater depth, topography and surface composition are provided using optical profilometry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The electrical insulation of the lines is measured and correlated to the crater analyses for different laser settings. Finally, potential ablation parameters for each of the polymer films are derived.

  15. The optical and electrical properties of graphene oxide with water-soluble conjugated polymer composites by radiation.

    PubMed

    Jungo, Seung Tae; Oh, Seung-Hwan; Kim, Hyun Bin; Jeun, Joon-Pyo; Lee, Bum-Jae; Kang, Phil-Hyun

    2013-11-01

    In order to overcome the difficulty of dispersion and low conductivity in composite containing graphene, graphene oxide (GO) has been used instead of neat graphene. And the GO treated by radiation, could give improved conductivity of the GO-containing polymer composite. In this study, fluorene based water-soluble conjugated polymer (WPF-6-oxy-F) was introduced in GO solution to investigate the change of optical and electrical properties through radiation process. UV-Vis absorption of irradiated WPF-6-oxy-F-GO composite was red shifted and I(D)/I(G) ratio of Raman spectra decreased. XPS analysis showed that C-N bonds was formed after the irradiation and confirmed the increased bonds between the GO and the water-soluble conjugated polymer matrix. From the AFM and XPS analysis, it was found that the water-soluble conjugated polymer matrix was stacked between the modified GO in the morphology of irradiated WPF-6-oxy-F-GO composite was increased after gamma ray irradiation up to 10(-2) S/cm. PMID:24245255

  16. Thermo-reversible morphology and conductivity of a conjugated polymer network embedded in polymeric self-assembly

    NASA Astrophysics Data System (ADS)

    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

    Self-assembly of block copolymers provides opportunities to create nano hybrid materials, utilizing self-assembled micro-domains with a variety of morphology and periodic architectures as templates for functional nano-fillers. Here we report new progress towards the fabrication of a thermally responsive conducting polymer self-assembly made from a water-soluble poly(thiophene) derivative with short PEO side chains and Pluronic L62 solution in water. The structural and electrical properties of conjugated polymer-embedded nanostructures were investigated by combining SANS, SAXS, CGMD 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. 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. The research was sponsored by the Scientific User Facilities Division, Office of BES, U.S. DOE and Laboratory Directed Research and Development Program of ORNL, managed by UT-Battelle, LLC.

  17. Influence of the backbone structure on the release of bioactive volatiles from maleic acid-based polymer conjugates.

    PubMed

    Berthier, Damien L; Paret, Nicolas; Trachsel, Alain; Herrmann, Andreas

    2010-11-17

    Poly(maleic acid monoester)-based β-mercapto ketones were synthesized and investigated as potential delivery systems for the controlled release of bioactive, volatile, α,β-unsaturated enones (such as damascones and damascenones) by retro 1,4-addition. The bioconjugates were prepared in a one-pot synthesis using 2-mercaptoethanol as a linker. The thiol group of 2-mercaptoethanol adds to the double bond of the enone to form a β-mercapto ketone, which was then grafted via nucleophilic ring-opening of the remaining alcohol function onto a series of alternating copolymers of maleic anhydride and 1-octadecene, ethylene, isobutylene, and methyl vinyl ether. The influence of copolymer backbones on the release of δ-damascone was investigated in buffered aqueous solution as a function of pH and time. In the presence of a cationic surfactant, the polymer conjugates were transferred from an aqueous medium to a cotton surface. The deposition and the release of δ-damascone from the cotton surface as a function of the polymer backbone structure were measured by fluorescence spectroscopy and dynamic headspace analysis, respectively. All polymer conjugates were found to deliver higher amounts of the volatile into the headspace than the reference consisting of unmodified δ-damascone. Polymers with a hydrophobic backbone were generally efficiently deposited on the cotton surface, but released δ-damascone only moderately in solution. Conjugates with a more hydrophilic backbone release the active compound more efficiently in water, but are deposited to a lower extent onto the target surface. A good balance of the hydrophobicity and hydrophilicity of the polymer backbone is the key factor to maximize the deposition of the conjugates on the target surface and to optimize the release of the bioactive volatiles. PMID:20936844

  18. Inorganic-polymer-derived dielectric films

    DOEpatents

    Brinker, C.J.; Keefer, K.D.; Lenahan, P.M.

    1985-02-25

    A method is disclosed for coating a substrate with a thin film of a predetermined porosity. The method comprises: depositing the thin film on the substrate from a non-gelled solution comprising at least one metal alkoxide of a polymeric network forming cation, water, an alcohol compatible with the hydrolysis and the polymerization of the metal alkoxide, and an acid or a base; prior to said depositing step, controlling the porosity and structure of said coating for a given composition of said solution exclusive of the acid or base component and the water component, by adjusting each of the water content, the pH, the temperature and the time of standing of said solution, increasing/descreasing the water content or the pH to increase/decrease the pore size of said coating, and increasing/decreasing the temperature or time of standing of said solution to increase/decrease the pore size of said coating; and curing said deposited film at a temperature effective for curing whereby there is obtained a thin film coating of a predetermined porosity on the substrate.

  19. Site-specific in situ growth of an interferon-polymer conjugate that outperforms PEGASYS in cancer therapy.

    PubMed

    Hu, Jin; Wang, Guilin; Zhao, Wenguo; Liu, Xinyu; Zhang, Libin; Gao, Weiping

    2016-07-01

    Conjugating poly(ethylene glycol) (PEG), PEGylation, to therapeutic proteins is widely used as a means to improve their pharmacokinetics and therapeutic potential. One prime example is PEGylated interferon-alpha (PEGASYS). However, PEGylation usually leads to a heterogeneous mixture of positional isomers with reduced bioactivity and low yield. Herein, we report site-specific in situ growth (SIG) of a PEG-like polymer, poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), from the C-terminus of interferon-alpha to form a site-specific (C-terminal) and stoichiometric (1:1) POEGMA conjugate of interferon-alpha in high yield. The POEGMA conjugate showed significantly improved pharmacokinetics, tumor accumulation and anticancer efficacy as compared to interferon-alpha. Notably, the POEGMA conjugate possessed a 7.2-fold higher in vitro antiproliferative bioactivity than PEGASYS. More importantly, in a murine cancer model, the POEGMA conjugate completely inhibited tumor growth and eradicated tumors of 75% mice without appreciable systemic toxicity, whereas at the same dose, no mice treated with PEGASYS survived for over 58 days. The outperformance of a site-specific POEGMA conjugate prepared by SIG over PEGASYS that is the current gold standard for interferon-alpha delivery suggests that SIG is of interest for the development of next-generation protein therapeutics. PMID:27152679

  20. Interactions H.I.F.U. / polymer films

    NASA Astrophysics Data System (ADS)

    Hallez, L.; Touyeras, F.; Hihn, J.-Y.; Bailly, Y.

    2010-01-01

    In order to obtain the modification of a defined volume of a polymer layer, preliminary tests of sonication (HIFU 0.75 and 3 MHz) were carried out to obtain an accurate characterization of the acoustic fields as well as convective flow velocities measured close to the surface by Particle Image Velocimetry and luminol mapping. Then, sonication of a delimited zone of an acrylic resin deposited upon a stainless steel thin substrate highlighted a strong dependence of the polymerization or reticulation degree, with different exposure times and different power thresholds for the same final modification. The point was to examine the ability of the thin polymer film to absorb ultrasonic energy or to act as a perfect reflector which induces asymmetric cavitation and therefore violent collapses to take place close to the surface. In the first case, the wave absorption by the film is converted into heat and then acts for the polymer alteration under the high convective flow velocities. For the highest acoustic intensities and for the hardest films, cavitation occurs and the produced microbubbles oscillated and grow close to the surface. Then, the shocks resulting of the bubble collapse eroded mechanically the film.