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Covalently stabilized temperature and pH responsive four-layer nanoparticles fabricated from surface 'clickable' shell cross-linked micelles

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Soft Matter 2009年第7期5卷 1530-1538页

作者： Jiang, Xiaoze Zhang, Guoying Narain, Ravin Liu, Shiyong Department of Polymer Science and Engineering Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of China Hefei Anhui 230026 China Department of Chemistry and Biochemistry Biomolecular Sciences Program Laurentian University 935 Ramsey Lake Rd Sudbury ON P3E 2C6 Canada

Alkynyl-terminated double hydrophilic ABC triblock copolymer, poly(oligo(ethylene glycol) monomethyl ether methacrylate)-b-poly(2- (dimethylamino) ethyl methacrylate)-b-poly(2-(diethylamino) ethyl methacrylate) (alkynyl-POEGMA-b-PDMA-b-PDEA), was synthesized via atom transfer radical polymerization (ATRP) by sequential monomer addition using propargyl 2-bromoisobutyrate (PgBiB) as the initiator. The obtained triblock copolymer dissolves molecularly in acidic media and self-assembles into alkynyl surface-functionalized three-layer "onion-like" micelles consisting of a PDEA core, a PDMA inner shell, and a POEGMA corona at alkaline pH. Selective cross-linking of the PDMA inner shell with 2-bis(2-iodoethoxy)ethane (BIEE) results in structurally stable and surface 'clickable' shell cross-linked (SCL) micelles with pH-responsive PDEA cores. This new kind of SCL micelles could be further surface functionalized or conjugated with other azido- terminated polymer chains, functional groups, or biomolecules via Click chemistry. Four layer nanoparticles (SCL-PNIPAM) which have pH-responsive PDEA cores and temperature responsive PNIPAM outer coronas were fabricated from surface 'clickable' shell cross-linked (SCL) micelles and azide-terminated poly(N-isopropylacrylamide) (PNIPAM-N3) using Click chemistry. These novel four layer nanoparticles might act as suitable nano-sized drug delivery vehicles for the encapsulation and release of hydrophobic drugs as a function of either temperature or pH of the environment. © The Royal Society of Chemistry 2009.

关键词： Nanoparticles

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Solid state and solution self-assembly of helical polypeptides tethered to polyhedral oligomeric silsesquioxanes

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Macromolecules 2009年第5期42卷 1619-1626页

作者： Kuo, Shiao-Wei Lee, Hsin-Fang Huang, Wu-Jang Jeong, Kwang-Un Chang, Feng-Chih Department of Materials and Optoelectronic Science Center for Nanoscience and Nanotechnology National Sun Yat-Sen University Kaohsiung Taiwan Institute of Applied Chemistry National Chiao Tung University Hsin Chu Taiwan Department of Environmental Science and Engineering National Ping-Tun University of Science and Technology Ping-Tun Taiwan Department of Polymer-Nano Science and Technology Chonbuk National University Jeonju 561-756 Korea Republic of

New macromolecular self-assembling building blocks, polyhedral oligo- silsesquioxane (POSS)- helical polypeptide copolymers, have been synthesized through the ring-opening polymerization (ROP) of y-benzyl- L-glutamate N-carboxyanhydride (y-Bn-Glu NCA) using aminopropyl isobutyl-POSS as a macroinitiator. The incorporation of POSS units at the chain ends of PBLG moieties has two important effects: allowing intramolecular hydrogen bonding between the POSS and PBLG units to enhance the latter's α-helical conformations in the solid state and preventing the aggregation of nanoribbons through the POSS blocks' protrusion from the ribbons to allow the formation of clear gels in solution.© 2009 American Chemical Society.

关键词： Ring opening polymerization

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Effect of poly(γ-glutamic acid) on the gelation of Pluronic F127

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polymers for Advanced Technologies 2009年第8期20卷 703-705页

作者： Lee, Yen-Hsien Yang, Ming-Chien Program of Biomedical Engineering National Taiwan University of Science and Technology Taipei 106 Taiwan Department of Polymer Engineering National Taiwan University of Science and Technology Taipei 106 Taiwan

The gelation of Pluronic F127 aqueous solution was investigated in the presence of sodium poly(γ-glutamate) (PGA). The gelation temperature was determined based on the tube inversion technique. The gelation temperature increased greatly when the ratio of PGA to F127 was 0.2, and then decreased at higher ratios. The enthalpy of gelation (ΔHgel) was calculated based on the model of Eldridge and Ferry. A splitting in the model was observed when the PGA/F127 ratio was 0.2 which yielded both a maximum and a minimum of ΔHgel. These results indicate that PGA can significantly affect the gelation of F127. Copyright © 2008 John Wiley & Sons, Ltd.

关键词： Enthalpy

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Thermal stability study of Cu(MoN x ) seed layer on barrierless Si

Thermal stability study of Cu(MoN x ) seed layer on barrierl...

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作者： Chu, J.P. Lin, C.H. Leau, W.K. John, V.S. Department of Polymer Engineering National Taiwan University of Science and Technology Taipei 10607 Taiwan Department of Environmental Engineering Chin-Min Institute of Technology Tou-Fen 35153 Taiwan Institute of Materials Engineering National Taiwan Ocean University Keelung 20224 Taiwan Department of Physics T.D.M.N.S. College T. Kallikulam 627113 India

This study reports the good thermal stability of a sputtered Cu(MoN x ) seed layer on a barrierless Si substrate. A Cu film with a small amount of MoN x was deposited by reactive co-sputtering of Cu and Mo in an Ar/N2 gas mixture. After annealing at 560C for 1 h, no copper silicide formation was observed at the interface of Cu and Si. Leakage current and resistivity evaluations reveal the good thermal reliability of Cu with a dilute amount of MoN x at temperatures up to 560C, suggesting its potential application in advanced barrierless metallization. The thermal performance of Cu(MoN x ) as a seed layer was evaluated when pure Cu is deposited on top. X-ray diffraction, focused ion beam microscopy, and transmission electron microscopy results confirm the presence of an ∼10-nm-thick reaction layer formed at the seed layer/Si interface after annealing at 630C for 1 h. Although the exact composition and structure of this reaction layer could not be unambiguously identified due to trace amounts of Mo and N, this reaction layer protects Cu from a detrimental reaction with Si. The Cu(MoN x ) seed layer is thus considered to act as a diffusion buffer with stability up to 630C for the barrierless Si scheme. An electrical resistivity of 2.5 μΩ cm was obtained for the Cu/Cu(MoN x ) scheme after annealing at 630C. © 2008 TMS.

关键词： Metallizing

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Increases in the proton conductivity and selectivity of proton exchange membranes for direct methanol fuel cells by formation of nanocomposites having proton conducting channels

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Journal of Power Sources 2009年第1期194卷 206-213页

作者： Su, Yu-Huei Liu, Ying-Ling Wang, Da-Ming Lai, Juin-Yih Guiver, Michael D. Liu, Baijun Institute of Polymer Science and Engineering National Taiwan University Taipei 104 Taiwan R and D Center for Membrane Technology Department of Chemical Engineering Chung Yuan University Chungli Taoyuan 320 Taiwan Institute for Chemical Process and Environmental Technology National Research Council Ottawa Ont. K1A 0R6 Canada Alan G. MacDiarmid Institute Jilin University Changchun 130012 China

We explore an approach to effectively enhance the properties of cost-effective hydrocarbon proton-exchange membranes for application in the direct methanol fuel cell (DMFC). This approach utilizes sulfonated silica nanoparticles (SA-SNP) as additives to modify sulfonated poly(arylene ether ether ketone ketone) (SPAEEKK). The interaction between the sulfonic acid groups of SA-SNP and those of SPAEEKK combined with hydrophilic-hydrophobic phase separation induce the formation of proton conducting channels, as evidenced by TEM images, which contribute to increases in the proton conductivity of the SPAEEKK/SA-SNP nanocomposite membrane. The presence of SA-SNP nanoparticles also reduces methanol crossover in the membrane. Therefore, the SPAEEKK/SA-SNP nanocomposite membrane shows a high selectivity, which is 2.79-fold the selectivity of Nafion®117. The improved selectivity of the SPAEEKK/SNP nanocomposite membrane demonstrates potential of this approach in providing hydrocarbon-based PEMs as alternatives to Nafion in direct methanol fuel cells. © 2009 Elsevier B.V.

关键词： Ethers

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Enhanced glucose sensor linearity using poly(vinyl alcohol) hydrogels

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Journal of Diabetes science and Technology 2009年第4期3卷 863-874页

作者： Vaddiraju, SanthiSagar Singh, Hardeep Burgess, Diane J. Jain, Faquir C. Papadimitrakopoulos, Fotios Polymer Program Institute of Material Science University of Connecticut Storrs CT 06269 United States Department of Pharmaceutical Sciences University of Connecticut Storrs CT United States Nanomaterials Optoelectronics Laboratory Electrical and Computer Engineering University of Connecticut Storrs CT United States Department of Chemistry University of Connecticut Storrs CT United States

Background: High linearities, sensitivities, and low oxygen dependence constitute prime requisites for electrochemical glucose sensors. However, for implantable sensors the need to control tissue inflammation requires the use of outer membranes that permit inward analyte diffusion while continuously releasing anti-inflammatory drugs and other tissue response-modifying (TRM) agents. We have shown previously that while outer membranes based on layer-by-layer (LBL) assembly enhance linearity, poly(vinyl alcohol)(PVA) hydrogels loaded with TRM-containing microspheres enable a significant reduction in tissue inflammation. This article discusses the amperometric performance of glucose sensors coated with stacked LBL/PVA hydrogel outer membranes. Methods: Sensors were fabricated by immobilizing glucose oxidase enzyme on a 50-μm platinum wire followed by deposition of stacked LBL/PVA hydrogel outer membranes. The sensor response to various glucose concentrations was determined by applying 0.7 V vs an Ag/AgCl reference electrode in phosphate-buffered saline (37°C). Michaelis-Menten analysis was performed to quantify sensor performance in terms of linearity (Km,gluapp) and oxygen dependence (Km,O2app/[Glucose]). Results: When overlaid onto LBL-assembled outer membranes, PVA hydrogels improved sensor linearity by 60% from 10 to 16 m M of glucose and resulted in a twofold decrease in oxygen dependence. Conclusions: Enhancement in the performance of a PVA-coated sensor is attributed to the oxygen-storing capability of PVA hydrogel due to the formation of hydrophobic domains during its freezing and thawing employed to physical cross-link the PVA. Such membranes with the capability to release TRMs continuously while storing oxygen constitute a major improvement over current outer membrane technologies. © Diabetes Technology Society.

关键词： Apparent Michaelis-Menten constants Biosensor Freeze-thaw cycle Layer-by-layer assembly Linearity Outer membranes Oxygen content Oxygen dependence of biosensors PVA hydrogels

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environmental effect on the fluorescence lifetime and quantum yield of single extended luminescent conjugated polymers

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Journal of Physical Chemistry C 2009年第43期113卷 18681-18688页

作者： Rassamesard, Areefen Huang, Yi-Fang Lee, Hsu-Yang Lim, Tsong-Shin Li, Ming Chung White, Jonathon David Hodak, Jose Hector Osotchan, Tanakorn Peng, K.Y. Chen, S.A. Hsu, Jui-Hung Hayashi, Michitoshi Fann, Wunshain Institute of Atomic and Molecular Sciences Academia Sinica P.O. Box 23-166 Taipei 106 Taiwan Department of Physics Faculty of Science Mahidol University Rama 6 Rd. Bangkok 10400 Thailand Department of Physics Tunghai University Taichung 407 Taiwan Department of Chemistry National Tsing Hua University Hsinchu 30013 Taiwan Molecular Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei 115 Taiwan Center for Condensed Matter Sciences National Taiwan University Taipei 106 Taiwan Department of Photonics Engineering Yuan Ze University Taoyuan Taiwan ThEP Center Commission of Higher Education 328 Si Ayuthaya Rd Bangkok 10400 Thailand Department of Chemical Engineering National Tsing Hua University Hsinchu 300 Taiwan Department of Materials and Optoelectronic Science National Sun Yat-sen University Kaohsiung Taiwan Institute of Polymer Science and Engineering National Taiwan University Taipei 106 Taiwan Department of Physics National Taiwan University Taipei 106 Taiwan

To investigate the local environment's effect on the lifetime and quantum yield of extended polymer chains in the absence of intra-and interchain aggregation, short, rodlike polymers of poly(2,5-di-n-octyloxy-1,4- phenylenevinylene) (DO-PPV) were dissolved in chloroform and then embedded in a polystyrene matrix. The fluorescence lifetime was found to increase by 45% in moving from the solution to the matrix form. By using the absorption and emission spectra of the chloroform solution to estimate the radiative and nonradiative rate constants for the polymer in solution, along with calculations based on an exciton model, the corresponding decay rate constants for the polymer embedded in the matrix were obtained. The close agreement between the calculated and experimental values of fluorescent lifetime in the matrix proved the applicability of the exciton model used. On the basis of the model, the average quantum yield of isolated polymers in the matrix was calculated to be a factor of 2 higher than in solutionsan effect arising from a 59% decrease in the nonradiative rate constant and, to a smaller extent, from a 20% increase in the radiative decay rate due to the different dielectric constants of the environments. These results suggest that by extending and isolating single luminescent polymers, high quantum yield devices are possible. © 2009 American Chemical Society.

关键词： Rate constants

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Study on the crystallization, miscibility, morphology, properties of poly(lactic acid)/poly(Ε-caprolactone) blends

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polymer - Plastics Technology and engineering 2009年第6期48卷 571-578页

作者： Yeh, Jen-Taut Wu, Ching-Ju Tsou, Chi-Hui Chai, Wan-Lan Chow, Jing-Dong Huang, Chi-Yuan Chen, Kan-Nan Wu, Chin-San Department and Graduate School of Polymer Engineering National Taiwan University of Science and Technology Taipei Taiwan Faculty of Chemistry and Material Science HuBei University Wuhan China Institute of Textile and Materials Wuhan University of Science and Engineering Wuhan China Department of Environmental Engineering Vanung University Tao-Yuan Taiwan Department of Materials Engineering Tatung University Taipei Taiwan Department of Chemistry Tamkang University Tamsui Taiwan Department of Chemical and Biochemical Engineering Kao Yuan University Kaohsiung County Taiwan

A series of blends of poly(lactic acid) (PLA) and poly(Ε-caprolactone) (PCL) with different mass ratio were prepared by means of the melt blending method to study their crystallization, miscibility, morphology, and thermal and mechanical properties. The result of DSC tests showed that the melting temperatures of PLA and PCL shifted toward each other, and that the largest shift appeared at the PLA70PCL30 blend. This result reveals that the PLA70PCL30 blend gives the strongest interaction intensity among the blends. Combined the result of dynamic mechanical analysis and SEM morphologies, it was found that PLA and PCL form a partial miscible blend, in which an amount of amorphous PCL (amorphous PLA) is dissolved in the PLA-rich phase (PCL-rich phase), leading to a depression of the Tg. value. The polarized optical micrographs showed that PCL can serve as a nucleating agent to promote PLA crystallization in the PLA/PCL blend. Moreover, the PLA70PCL30 blend gave the largest growth rate of PLA spherulite. Finally, the mechanical property of PLA/PCL blends indicated that PLA can easily be tuned from rigid to ductile by the addition of PCL. © Taylor & Francis Group, LLC.

关键词： Solubility

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Properties of PET Composites Containing Amine-Polyhedral Oligomeric Silsesquioxane

Properties of PET Composites Containing Amine-Polyhedral Oli...

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IUPAC 5th International Symposium on Novel Materials and their Synthesis,19th International Symposium on Fine Chemistry and Functional polymers(IUPAC 第五届国际新型材料及其制备学术研讨会暨第19届国际精细化学和功能高分子学术讨论会)

作者： Hyeon Ju Ryu Sang Ha Hwang Kwan Han Yoon Jae-Cheol Park Deparment of Polymer Science and Engineering Kumon National Institute of Technology1 Yangho-dongGumiGyeongbuk730-701Korea Department of Environmental EngineeringKumon National Institute of Technology1 Yangho-dongGumiGyeongbuk730-701Korea

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Site-specific forest-assembly of single-wall carbon nanotubes on electron-beam patterned SiOx/Si substrates

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Materials science and engineering C 2008年第8期28卷 1366-1371页

作者： Wei, Haoyan Kim, Sang Nyon Kim, Sejong Huey, Bryan D. Papadimitrakopoulos, Fotios Marcus, Harris L. Materials Science and Engineering Program Department of Chemical Materials and Biomolecular Engineering Institute of Materials Science Storrs CT 06269 United States Nanomaterials Optoelectronics Laboratory Polymer Program Institute of Materials Science Storrs CT 06269 United States

Based on electron-beam direct writing on the SiOx/Si substrates, favorable absorption sites for ferric cations (Fe3+ ions) were created on the surface oxide layer. This allowed Fe3+-assisted self-assembled arrays of single-wall carbon nanotube (SWNT) probes to be produced. Auger investigation indicated that the incident energetic electrons depleted oxygen, creating more dangling bonds around Si atoms at the surface of the SiOx layer. This resulted in a distinct difference in the friction forces from unexposed regions as measured by lateral force microscopy (LFM). Atomic force microscopy (AFM) affirmed that the irradiated domains absorbed considerably more Fe3+ ions upon immersion into pH 2.2 aqueous FeCl3 solution. This rendered a greater yield of FeO(OH)/FeOCl precipitates, primarily FeO(OH), upon subsequent washing with lightly basic dimethylformamide (DMF) solution. Such selective metal-functionalization established the basis for the subsequent patterned forest-assembly of SWNTs as demonstrated by resonance Raman spectroscopy. © 2008 Elsevier B.V. All rights reserved.

关键词： Chlorine compounds

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