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Spectroscopy Results (spectroscopy + result)
Selected AbstractsLateral Inhomogeneity in the Electronic Structure of a Conjugated Poly(3-hexylthiophene) Thin FilmADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Kaname Kanai Abstract How annealing influences the morphology of a highly regioregular poly(3-hexylthiophene) (RR-P3HT) film at the substrate interface as well as the lateral inhomogeneity in the electronic structure of the film are elucidated. Whereas previous studies have reported that high-molecular-weight (MW) RR-P3HT films tend to show low crystallinity even after annealing, it is found that high-MW RR-P3HT does show high crystallinity after annealing at high temperature for a long time. Photoemission electron microscopy (PEEM), X-ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy results clearly resolve a considerable lateral inhomogeneity in the morphology of RR-P3HT film, which results in a variation of the electronic structure depending on the local crystallinity. The PEEM results show how annealing facilitates crystal growth in a high-MW RR-P3HT film. [source] Functional finishing by using atmospheric pressure plasma: Grafting of PET nonwoven fabricJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Younsook Shin Abstract Poly (ethylene terephtalate) (PET) nonwoven fabric was treated with He/O2 plasma to produce peroxides and grafted with acrylic acid (AA) for introducing carboxyl groups onto PET surface. The graft yield increased with AA concentration from 1.5M to 2.5M, and then decreased with further increase in AA concentration. Graft yield increased with sodium pyrosulfite (SPS) concentration from 0.005M to 0.02M, and then decreased with further increase of SPS concentration. X-ray photoelectron spectroscopy results indicated that both of plasma treatment and AA grafting increased oxygen content and decreased carbon content on the PET nonwoven fabric surface. The grafted PET nonwoven fabric showed increase in moisture regain and dye uptake. And drastic increase in wettability was observed after grafting. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3655,3659, 2007 [source] Integrated surface modification of fully polymeric microfluidic devices using living radical photopolymerization chemistryJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2006Robert P. Sebra Abstract Surface modification using living radical polymerization (LRP) chemistry is a powerful technique for surface modification of polymeric substrates. This research demonstrates the ability to use LRP as a polymer substrate surface-modification platform for covalently grafting polymer chains in a spatially and temporally controlled fashion. Specifically, dithiocarbamate functionalities are introduced onto polymer surfaces using tetraethylthiuram disulfide. This technique enables integration of LRP-based grafting for the development of an integrated, covalent surface-modification method for microfluidic device construction. The unique photolithographic method enables construction of devices that are not substrate-limited. To demonstrate the utility of this approach, both controlled fluid flow and cell patterning applications were demonstrated upon modification with various chemical functionalities. Specifically, poly(ethylene glycol) (375) monoacrylate and trifluoroethyl acrylate were grafted to control fluidic flow on a microfluidic device. Before patterning, surface-functionalized samples were characterized with both goniometric and infrared spectroscopy to ensure that photografting was occurring through pendant dithiocarbamate functionalities. Near-infrared results demonstrated conversion of grafted monomers when dithiocarbamate-functionalized surfaces were used, as compared to dormant control surfaces. Furthermore, attenuated total reflectance/infrared spectroscopy results verified the presence of dithiocarbamate functionalities on the substrate surfaces, which were useful in grafting chains of various functionalities whose contact angles ranged from 7 to 86°. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1404,1413, 2006 [source] Toughening effects of poly(butylene terephthalate) with blocked isocyanate-functionalized poly(ethylene octene)POLYMER INTERNATIONAL, Issue 8 2009Ligang Yin Abstract BACKGROUND: Blocked isocyanate-functionalized polyolefins have great potential for use in semicrystalline polymer blends to obtain toughened polymers. In this study, poly(butylene terephthalate) (PBT) was blended with allyl N -[2-methyl-4-(2-oxohexahydroazepine-1-carboxamido)phenyl] carbamate-functionalized poly(ethylene octene) (POE- g -AMPC). RESULTS: New peaks at 2272 and 1720 cm,1, corresponding to the stretching vibrations of NCO and the carbonyl of NHCON, respectively, in AMPC, appeared in the infrared spectrum of POE- g -AMPC. Both rheological and X-ray photoelectron spectroscopy results indicated a new copolymer was formed in the reactive blends. Compared to uncompatibilized PBT/POE blends, smaller dispersed particle sizes with narrower distribution were found in the compatibilized PBT/POE- g -AMPC blends. There was a marked increase in impact strength by about 10-fold over that of PBT/POE blends with the same rubber content and almost 30-fold higher than that of pure PBT when the POE- g -AMPC content was 25 wt%. CONCLUSION: The blocked isocyanate-functionalized POE is an effective toughener for semicrystalline polymers. Super-toughened PBT blends can be obtained when the POE- g -AMPC content is equal to or more than 15 wt%. Copyright © 2009 Society of Chemical Industry [source] The effect of temperature and lipid on the conformational transition of gramicidin A in lipid vesicles,BIOPOLYMERS, Issue 4 2005Ta-Hsien Lin Abstract The present study investigated the effect of temperature and lipid/peptide molar ratio on the conformational changes of the membrane peptide gramicidin A from a double-stranded helix to a single-stranded helical dimmer in 1,2-dimyristoyl-glycerol-3-phosphochloine (DMPC) vesicles. Tryptophan fluorescence spectroscopy results suggested that the conformational transition fitted a three-state (two-step) "folding" model. Rate constants, k1 and k2, were determined for each of the two steps. Since k1 and k2 increased with an increase in temperature, we hypothesized that the process corresponded to the breakage and formation of the backbone hydrogen bonds. The k1 was from 10 to 45 folds faster than k2, except for lipid/peptide molar ratios above 89.21, where k2 increased rapidly. At molar ratios below 89.21, k2 was insensitive to changes in lipid concentration. To account for this phenomenon, we proposed that while the driving interaction at high molar ratios is between the indole rings of the tryptophan residues and the lipid head groups, at low molar ratios there may be an intermolecular interaction between the tryptophan residues that causes gramicidin A to form an organized aggregated network. This aggregated network, caused by the tryptophan,tryptophan interaction, may be the main effect responsible for the slow down of the conformation change. © 2005 Wiley Periodicals, Inc. Biopolymers 78: 179,186, 2005 [source] | ||||||||||