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Molar Content (molar + content)
Selected AbstractsPreparation and characterization of soluble terpolymers from m -phenylenediamine, o -anisidine, and 2,3-xylidineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2001Xin-Gui Li Abstract A series of terpolymers were synthesized by the chemical oxidative polymerization of m -phenylenediamine (MPD), o -anisidine (AS), and 2,3-xylidine (XY) in hydrochloride aqueous medium. The yield, intrinsic viscosity, and solubility of the terpolymers were studied by changing the MPD/AS/XY molar ratio from 100/0/0 to 53/39/8 to 0/100/0. It was discovered that the MPD/AS/XY terpolymers exhibit a higher polymerization yield and better solubility than MPD/AS and MPD/XY bipolymers having the same MPD molar content. The as-prepared MPD/AS/XY terpolymer bases were characterized by Fourier transform infrared, ultraviolet,visible, 1H NMR, and high-resolution solid-state 13C NMR spectroscopies; wide-angle X-ray diffraction; and thermogravimetry. The results suggested that the oxidative polymerization from MPD, AS, and XY is exothermic, and the resulting terpolymers are more easily soluble in some organic solvents than MPD homopolymer. The copolymer obtained was a real terpolymer containing MPD, AS, and XY units, and the actual MPD/AS/XY molar ratio calculated by solid-state 13C NMR spectra of the polymers is very close to the feed ratio, although the AS content calculated on the basis of the 1H NMR spectrum of the soluble part of the polymer is higher than the feed AS content. The terpolymers and MPD homopolymer exhibit a higher polymerization yield and much higher intrinsic viscosity and are more amorphous than the AS homopolymer. At a fixed MPD content of 70 mol %, the terpolymers exhibit an increased thermostability and activation energy of the major degradation in nitrogen and air with an increasing AS content. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3989,4000, 2001 [source] Liquid crystal alignment property of n -alkylthiomethyl- or n -alkylsulfonylmethyl-substituted polystyrenesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2009Hyo Kang Abstract We synthesized a series of n -alkylthiomethyl-substituted polystyrenes (#T-PS, #,=,4, 8, 12, and 16) and n -alkylsulfonylmethyl-substituted polystyrenes (#S-PS, #,=,4, 8, 12, and 16), where # is the number of carbon atoms in the n -alkyl side group of the polymers, using polymer analogous reactions to investigate their liquid crystal (LC) alignment properties. In general, the LC cell fabricated using the polymer film having a longer n -alkyl side group, a thioether linkage group, and a higher molar content of n -alkyl side group showed homeotropic LC alignment behavior with a pretilt angle of about 90°. The homeotropic alignment behavior was well correlated with the surface energy of the polymer films; when the positive dielectric anisotropic LC (ZLI-5900-000 from Merck) and negative dielectric anisotropic LC (MLC-7026-000 from Merck) were used to fabricate the LC cells, homeotropic alignment was observed when the surface energy values of the polymer were smaller than about 25 and 32,mJ/m2, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] Bioencapsulation of apomyoglobin in nanoporous organosilica sol,gel glasses: Influence of the siloxane network on the conformation and stability of a model proteinBIOPOLYMERS, Issue 11 2009Bouzid Menaa Abstract Nanoporous sol,gel glasses were used as host materials for the encapsulation of apomyoglobin, a model protein employed to probe in a rational manner the important factors that influence the protein conformation and stability in silica-based materials. The transparent glasses were prepared from tetramethoxysilane (TMOS) and modified with a series of mono-, di- and tri-substituted alkoxysilanes, RnSi(OCH3)4,n (R = methyl-, n = 1; 2; 3) of different molar content (5, 10, 15%) to obtain the decrease of the siloxane linkage (SiOSi). The conformation and thermal stability of apomyoglobin characterized by circular dichroism spectroscopy (CD) was related to the structure of the silica host matrix characterized by 29Si MAS NMR and N2 adsorption. We observed that the protein transits from an unfolded state in unmodified glass (TMOS) to a native-like helical state in the organically modified glasses, but also that the secondary structure of the protein was enhanced by the decrease of the siloxane network with the methyl modification (n = 0 < n = 1 < n = 2 < n = 3; 0 < 5 < 10 < 15 mol %). In 15% trimethyl-modified glass, the protein even reached a maximum molar helicity (,24,000 deg. cm2 mol,1) comparable to the stable folded heme-bound holoprotein in solution. The protein conformation and stability induced by the change of its microlocal environment (surface hydration, crowding effects, microstructure of the host matrix) were discussed owing to this trend dependency. These results can have an important impact for the design of new efficient biomaterials (sensors or implanted devices) in which properly folded protein is necessary. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 895,906, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Synthesis and nonlinear optical properties of methacrylate polymers based on 2-[4-(N -methyl,N -hydroxyethylamino)phenylazo]-phenyl-6-nitrobenzoxazole chromophoreJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2003Paola Persico Abstract Methacrylate polymers containing different molar contents of nonlinear optical (NLO) active molecular segments based on 2-[4-(N -methyl,N -hydroxyethylamino)phenylazo]-phenyl-6-nitrobenzoxazole chromophores were synthesized, and their phase behavior and second-order NLO properties were investigated. Polymers containing 6,17 mol % chromophore segments allowed the preparation of amorphous and optically clear thin films. Some mesomorphic structuration was exhibited by a polymer with 33 mol % chromophoric units. However, this feature did not prevent the possibility of investigating the NLO properties. Nonlinear resonance-enhanced d33 coefficients were determined by second harmonic generation experiments on spin-coated, corona-poled thin films at , = 1064 nm. Values ranging from 40 to 60 pm/V were measured with increasing chromophore molar contents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1841,1847, 2003 [source] Lower critical solution temperatures of thermo-responsive poly(N -isopropylacrylamide) copolymers with racemate or single enantiomer groupsPOLYMER INTERNATIONAL, Issue 2 2009Peng-Fei Li Abstract BACKGROUND: Thermo-responsive copolymers with racemate or single enantiomer groups are attracting increasing attention due to their fascinating functional properties and potential applications. However, there is a lack of systematic information about the lower critical solution temperature (LCST) of poly(N -isopropylacrylamide)-based thermo-responsive chiral recognition systems. In this study, a series of thermo-responsive chiral recognition copolymers, poly[(N -isopropylacrylamide)- co -(N -(S)- sec -butylacrylamide)] (PN- S -B) and poly[(N -isopropylacrylamide)- co -(N -(R,S)- sec -butylacrylamide)] (PN- R,S -B), with different molar compositions, were prepared. The effects of heating and cooling processes, optical activity and amount of chiral recognition groups in the copolymers on the LCSTs of the prepared copolymers were systematically studied. RESULTS: LCST hysteresis phenomena are found in the phase transition processes of PN- S -B and PN- R,S -B copolymers in a heating and cooling cycle. The LCSTs of PN- S -B and PN- R,S -B during the heating process are higher than those during the cooling process. With similar molar ratios of N -isopropylacrylamide groups in the copolymers, the LCST of the copolymer containing a single enantiomer (PN- S -B) is lower than that of the copolymer containing racemate (PN- R,S -B) due to the steric structural difference. The LCSTs of PN- R,S -B copolymers are in inverse proportion to the molar contents of the hydrophobic R,S -B moieties in these copolymers. CONCLUSION: The results provide valuable guidance for designing and fabricating thermo-responsive chiral recognition systems with desired LCSTs. Copyright © 2008 Society of Chemical Industry [source] | ||||||||||