The Experts below are selected from a list of 29580 Experts worldwide ranked by ideXlab platform

Timothy M Swager - One of the best experts on this subject based on the ideXlab platform.

  • synthesis and application of poly phenylene ethynylene s for bioconjugation a conjugated Polymer based fluorogenic probe for proteases
    Journal of the American Chemical Society, 2005
    Co-Authors: Jordan H Wosnick, Charlene M Mello, Timothy M Swager
    Abstract:

    A set of carboxylate-functionalized poly(phenylene ethynylene)s (PPEs) has been synthesized in which the carboxylic acid groups are separated from the Polymer Backbone by oligo(ethylene glycol) spacer units. These Polymers are soluble in water and organic solvents and have photophysical properties that are sensitive to solvent conditions, with high salt content and the absence of surfactant promoting the formation of aggregates of relatively low quantum yield and long fluorescence lifetime. Quenching of these materials by the dinitrophenyl (DNP) chromophore (K(SV) approximately 10(4)) is also highly solvent-dependent. The presence of carboxylate groups far from the Polymer Backbone appended to each repeating unit allows for the postPolymerization modification of these PPEs with peptides by methods analogous to those described for carboxylate-functionalized small-molecule dyes. Covalent attachment of the fluorescence-quenching 14-mer Lys(DNP)-GPLGMRGLGGGGK to the PPE results in a nonemissive substrate whose fluorescence is restored upon treatment with trypsin. The rate of fluorescence turn-on in this case is increased 3-fold by the presence of surfactant, though the actual rate of peptide hydrolysis remains the same. A small-molecule mimic of the Polymer-peptide system shows a smaller fluorescence enhancement upon treatment with trypsin, illustrating the value of Polymer-based amplification in this sensory scheme.

  • synthesis and application of poly phenylene ethynylene s for bioconjugation a conjugated Polymer based fluorogenic probe for proteases
    Journal of the American Chemical Society, 2005
    Co-Authors: Jordan H Wosnick, Charlene M Mello, Timothy M Swager
    Abstract:

    A set of carboxylate-functionalized poly(phenylene ethynylene)s (PPEs) has been synthesized in which the carboxylic acid groups are separated from the Polymer Backbone by oligo(ethylene glycol) spacer units. These Polymers are soluble in water and organic solvents and have photophysical properties that are sensitive to solvent conditions, with high salt content and the absence of surfactant promoting the formation of aggregates of relatively low quantum yield and long fluorescence lifetime. Quenching of these materials by the dinitrophenyl (DNP) chromophore (KSV ∼ 104) is also highly solvent-dependent. The presence of carboxylate groups far from the Polymer Backbone appended to each repeating unit allows for the postPolymerization modification of these PPEs with peptides by methods analogous to those described for carboxylate-functionalized small-molecule dyes. Covalent attachment of the fluorescence-quenching 14-mer Lys(DNP)-GPLGMRGLGGGGK to the PPE results in a nonemissive substrate whose fluorescence i...

  • molecular design of free volume as a route to low κ dielectric materials
    Journal of the American Chemical Society, 2003
    Co-Authors: Timothy M Long, Timothy M Swager
    Abstract:

    Polymers incorporating the triptycene subunit were prepared for the molecular-level design of low dielectric constant (low-κ) materials that can be used to manufacture faster integrated circuits. Triptycenes having restricted rotation by multiple point attachment to the Polymer Backbone are shown to introduce free volume into the films, thereby lowering their dielectric constants. The triptycene containing Polymers exhibit a number of desirable properties including low-water absorption and high thermal stability. Systematic studies wherein comparisons are made between two separate classes of triptycene Polymers and their non-triptycene containing analogues demonstrate that proper insertion of triptycenes into a Polymer Backbone can give rise to a reduction in the material's dielectric constant while also improving its mechanical properties. These characteristics are desired by the semiconductor industry for the next generation of microprocessors and memory to provide insulation of the increasingly shrinki...

Si Kim - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis and characterization of new polyimides containing calix[4]arenes in the Polymer Backbone
    'Indiana University Press (Project Muse)', 2019
    Co-Authors: Si Kim, Tj Shin, Ree M, Gt Hwang, Bh Kim, Hs Han, Seo J
    Abstract:

    Two diaminocalix[4]arene monomers were synthesized from p-tert-butylcalix[4]arene through a 4-step reaction sequence. New copoly(amic acid)s containing calix[4]arene moieties on the Polymer Backbone were successfully synthesized in N-methyl-2-pyrrolidone by polycondensations of 4,4'-oxydiphthalic anhydride (ODPA) with the diaminocalix[4]arene monomers using 4,4'-oxydiphenylene diamine (ODA) as a comonomer. These copoly(amic acid)s were soluble in aprotic polar solvents, so that they can be processed in various ways. The copoly(amic acid) precursors were thermally converted to the corresponding copolyimides in films. The copolyimide films are amorphous, but insoluble in common solvents. They are thermally stable up to 366 degrees C. The copolyimides exhibit relatively high TEC's, low T-g's, low refractive index, low dielectric constant, low optical anisotropy, low dielectric anisotropy, and low water uptake, compared to those of conventional ODPA-ODA polyimide. These property characteristics were interpreted in regard to bulky, cone-like calix[4]arene moieties and their effects on the chain conformation and morphological structure. The processability and property characteristics support that both of the copolyimides containing calix[4]arene moieties are potential candidate materials suitable for membranes, antioxidant additives, chemical sensor devices, and microelectronic devices. (C) 1999 John Wiley & Sons, Inc.X14

  • Synthesis and characterization of new polyimides containing calix[4]arenes in the Polymer Backbone
    'Wiley', 2019
    Co-Authors: Si Kim, Tj Shin, Ree M, Gt Hwang, Bh Kim, Hs Han, Seo J
    Abstract:

    Two diaminocalix[4]arene monomers were synthesized from p-tert-butylcalix[4]arene through a 4-step reaction sequence. New copoly(amic acid)s containing calix[4]arene moieties on the Polymer Backbone were successfully synthesized in N-methyl-2-pyrrolidone by polycondensations of 4,4'-oxydiphthalic anhydride (ODPA) with the diaminocalix[4]arene monomers using 4,4'-oxydiphenylene diamine (ODA) as a comonomer. These copoly(amic acid)s were soluble in aprotic polar solvents, so that they can be processed in various ways. The copoly(amic acid) precursors were thermally converted to the corresponding copolyimides in films. The copolyimide films are amorphous, but insoluble in common solvents. They are thermally stable up to 366 degrees C. The copolyimides exhibit relatively high TEC's, low T-g's, low refractive index, low dielectric constant, low optical anisotropy, low dielectric anisotropy, and low water uptake, compared to those of conventional ODPA-ODA polyimide. These property characteristics were interpreted in regard to bulky, cone-like calix[4]arene moieties and their effects on the chain conformation and morphological structure. The processability and property characteristics support that both of the copolyimides containing calix[4]arene moieties are potential candidate materials suitable for membranes, antioxidant additives, chemical sensor devices, and microelectronic devices. (C) 1999 John Wiley & Sons, Inc.X1148sciescopu

  • Structure and properties of various poly(amic diisopropyl ester-alt-imide)s and their alternating copolyimides
    'Society for Leukocyte Biology', 2019
    Co-Authors: Si Kim, Tj Shin, Ree M, Lee H, Chang T, Lee C, Th Woo, Sb Rhee
    Abstract:

    Several poly(amic diisopropyl ester-alt-imide)s have been synthesized, which are a new type of polyimide precursors. The precursors consist of amic ester and imide units alternatively on the Backbone, so that they are hydrolytically stable as well as low shrinkable through thermal imidization. These precursors have an easy processability because of their good solubility in common solvents that are widely used as good solvents for most polyimide precursors. The precursors and their alternating copolyimides in films have exhibited structural orders that are estimated to have a dimension of 15-42 Angstrom (along the chain axis) and 8-16 Angstrom (along the lateral direction), depending upon the Polymer Backbone chemistry. However, all the precursors and resultant copolyimides were laterally packed in an irregular way. Their crystallinities were apparently low. These results might be attributed mainly to the bend or kinked units on the Polymer Backbone. In addition, properties of the precursors and their polyimides in films: optical and dielectric properties, glass transition, thermal imidization characteristics, thermal stability, thermal expansion and residual stress, were investigated in detail. Overall, the precursor Polymers, as well as the resultant alternating copolyimides were characterized to have relatively good properties suitable for applications in the fabrication of microelectronic devices. (C) 2000 Elsevier Science Ltd. All rights reserved.X11

  • Structure and properties of various poly(amic diisopropyl ester-alt-imide)s and their alternating copolyimides
    'Elsevier BV', 2019
    Co-Authors: Si Kim, Tj Shin, Ree M, Lee H, Chang T, Lee C, Th Woo, Sb Rhee
    Abstract:

    Several poly(amic diisopropyl ester-alt-imide)s have been synthesized, which are a new type of polyimide precursors. The precursors consist of amic ester and imide units alternatively on the Backbone, so that they are hydrolytically stable as well as low shrinkable through thermal imidization. These precursors have an easy processability because of their good solubility in common solvents that are widely used as good solvents for most polyimide precursors. The precursors and their alternating copolyimides in films have exhibited structural orders that are estimated to have a dimension of 15-42 Angstrom (along the chain axis) and 8-16 Angstrom (along the lateral direction), depending upon the Polymer Backbone chemistry. However, all the precursors and resultant copolyimides were laterally packed in an irregular way. Their crystallinities were apparently low. These results might be attributed mainly to the bend or kinked units on the Polymer Backbone. In addition, properties of the precursors and their polyimides in films: optical and dielectric properties, glass transition, thermal imidization characteristics, thermal stability, thermal expansion and residual stress, were investigated in detail. Overall, the precursor Polymers, as well as the resultant alternating copolyimides were characterized to have relatively good properties suitable for applications in the fabrication of microelectronic devices. (C) 2000 Elsevier Science Ltd. All rights reserved.X1118sciescopu

  • surface morphology molecular reorientation and liquid crystal alignment properties of rubbed nanofilms of a well defined brush polyimide with a fully rodlike Backbone
    Macromolecules, 2002
    Co-Authors: Boknam Chae, Byeongdu Lee, Si Kim, Seung Bin Kim, Seungwoo Lee, Wooyoung Choi, Moonhor Ree, Kyung Hoon Lee, Jin Chul Jung
    Abstract:

    Nanoscaled films of poly{p-phenylene 3,6-bis[4-(n-butoxy)phenyloxy]pyromellitimide} (C4-PMDA-PDA PI), a well-defined brush polyimide (PI) composed of aromatic−aliphatic bristles set into a fully rodlike Polymer Backbone (two bristles per chemical repeat unit of the Polymer Backbone), were studied by atomic force microscopy, optical retardation, prism coupling, and linearly polarized IR spectroscopy before and after mechanical rubbing with velvet fabric, and their liquid crystal (LC) aligning abilities were investigated. Uniform, homogeneous LC alignment was achieved at the rubbed film surfaces of PIs with positively birefringent characteristics. Surprisingly, however, the LC alignment director for this PI is perpendicular to the rubbing direction as well as to the reorientation direction of the Polymer main chains. This is the first time that LCs on a PI surface have been induced to align in the direction perpendicular to the rubbing direction, a significant departure from the LC alignment observed for al...

Jordan H Wosnick - One of the best experts on this subject based on the ideXlab platform.

  • synthesis and application of poly phenylene ethynylene s for bioconjugation a conjugated Polymer based fluorogenic probe for proteases
    Journal of the American Chemical Society, 2005
    Co-Authors: Jordan H Wosnick, Charlene M Mello, Timothy M Swager
    Abstract:

    A set of carboxylate-functionalized poly(phenylene ethynylene)s (PPEs) has been synthesized in which the carboxylic acid groups are separated from the Polymer Backbone by oligo(ethylene glycol) spacer units. These Polymers are soluble in water and organic solvents and have photophysical properties that are sensitive to solvent conditions, with high salt content and the absence of surfactant promoting the formation of aggregates of relatively low quantum yield and long fluorescence lifetime. Quenching of these materials by the dinitrophenyl (DNP) chromophore (KSV ∼ 104) is also highly solvent-dependent. The presence of carboxylate groups far from the Polymer Backbone appended to each repeating unit allows for the postPolymerization modification of these PPEs with peptides by methods analogous to those described for carboxylate-functionalized small-molecule dyes. Covalent attachment of the fluorescence-quenching 14-mer Lys(DNP)-GPLGMRGLGGGGK to the PPE results in a nonemissive substrate whose fluorescence i...

  • synthesis and application of poly phenylene ethynylene s for bioconjugation a conjugated Polymer based fluorogenic probe for proteases
    Journal of the American Chemical Society, 2005
    Co-Authors: Jordan H Wosnick, Charlene M Mello, Timothy M Swager
    Abstract:

    A set of carboxylate-functionalized poly(phenylene ethynylene)s (PPEs) has been synthesized in which the carboxylic acid groups are separated from the Polymer Backbone by oligo(ethylene glycol) spacer units. These Polymers are soluble in water and organic solvents and have photophysical properties that are sensitive to solvent conditions, with high salt content and the absence of surfactant promoting the formation of aggregates of relatively low quantum yield and long fluorescence lifetime. Quenching of these materials by the dinitrophenyl (DNP) chromophore (K(SV) approximately 10(4)) is also highly solvent-dependent. The presence of carboxylate groups far from the Polymer Backbone appended to each repeating unit allows for the postPolymerization modification of these PPEs with peptides by methods analogous to those described for carboxylate-functionalized small-molecule dyes. Covalent attachment of the fluorescence-quenching 14-mer Lys(DNP)-GPLGMRGLGGGGK to the PPE results in a nonemissive substrate whose fluorescence is restored upon treatment with trypsin. The rate of fluorescence turn-on in this case is increased 3-fold by the presence of surfactant, though the actual rate of peptide hydrolysis remains the same. A small-molecule mimic of the Polymer-peptide system shows a smaller fluorescence enhancement upon treatment with trypsin, illustrating the value of Polymer-based amplification in this sensory scheme.

Changduk Yang - One of the best experts on this subject based on the ideXlab platform.

  • synthesis of pcdtbt based fluorinated Polymers for high open circuit voltage in organic photovoltaics towards an understanding of relationships between Polymer energy levels engineering and ideal morphology control
    ACS Applied Materials & Interfaces, 2014
    Co-Authors: Seojin Ko, Gitish K Dutta, Mijin Moon, Song Yi Park, Changduk Yang
    Abstract:

    The introduction of fluorine (F) atoms onto conjugated Polymer Backbone has verified to be an effective way to enhance the overall performance of Polymer-based bulk-heterojunction (BHJ) solar cells, but the underlying working principles are not yet fully uncovered. As our attempt to further understand the impact of F, herein we have reported two novel fluorinated analogues of PCDTBT, namely, PCDTFBT (1F) and PCDT2FBT (2F), through inclusion of either one or two F atoms into the benzothiadiazole (BT) unit of the Polymer Backbone and the characterization of their physical properties, especially their performance in solar cells. Together with a profound effect of fluorination on the optical property, nature of charge transport, and molecular organization, F atoms are effective in lowering both the HOMO and LUMO levels of the Polymers without a large change in the energy bandgaps. PCDTFBT-based BHJ solar cell shows a power conversion efficiency (PCE) of 3.96 % with high open-circuit voltage (VOC) of 0.95 V, m...

  • synthesis of fluorinated analogues of a practical Polymer tq for improved open circuit voltages in Polymer solar cells
    Polymer Chemistry, 2014
    Co-Authors: Gitish K Dutta, Dong Suk Kim, Taehyo Kim, Hyosung Choi, Junghoon Lee, Jin Young Kim, Changduk Yang
    Abstract:

    In an attempt to further lower the HOMO of a cost-effective Polymer poly(2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-dyl-alt-thiophene-2,5-diyl) (TQ) by adding F atoms onto the existing quinoxaline acceptor within the Polymer Backbone, we have synthesized two structurally identical fluorinated analogues of TQ (TQ-F (single F) and TQ-FF (double F)), except for the number of F atoms. The effects of inclusion of F atoms on the optical properties, nature of charge transport, and molecular organization are thoroughly investigated. The resulting two fluorinated Polymers show a decrease in both the HOMO and the LUMO energy levels relative to non-fluorinated TQ. Moreover, the fluorination of the Polymer Backbone has lowered the HOMOs more than the LUMOs, slightly widening the energy bandgaps as the number of F atoms increases. Thus, use of these Polymers in bulk-heterojunction (BHJ) solar cells, in all cases, leads to large VOC values. The power conversion efficiency (PCE) of the optimized PSCs based on TQ-F reaches 4.41%. In addition, it is interesting to note that, despite TQ-FF having the PCE that is lower than that of TQ-F, an unprecedentedly high VOC of 1.00 V is achieved, which is nearly equal to the highest VOC values ever reported for Polymers.

Thomas P Russell - One of the best experts on this subject based on the ideXlab platform.

  • highly crystalline low band gap Polymer based on thieno 3 4 c pyrrole 4 6 dione for high performance Polymer solar cells with a 400 nm thick active layer
    ACS Applied Materials & Interfaces, 2015
    Co-Authors: Jae Woong Jung, Thomas P Russell
    Abstract:

    Two thieno[3,4-c]pyrrole-4,6-dione (TPD)-based coPolymers combined with 2,2′-bithiophene (BT) or (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TV) have been designed and synthesized to investigate the effect of the introduction of a vinylene group in the Polymer Backbone on the optical, electrochemical, and photovoltaic properties of the Polymers. Although both Polymers have shown similar optical band gaps and frontier energy levels, regardless of the introduction of vinylene bridge, the introduction of a π-extended vinylene group in the Polymer Backbone substantially enhances the charge transport characteristics of the resulting Polymer due to its strong tendency to self-assemble and thus to enhance the crystallinity. An analysis on charge recombination in the active layer of a solar cell device indicates that the outstanding charge transport (μ = 1.90 cm2·V–1·s–1) of PTVTPD with a vinylene group effectively suppresses the bimolecular recombination, leading to a high power conversion efficiency (PCE) up to 7....