Molar Composition (molar + composition)

Distribution by Scientific Domains


Selected Abstracts


Free-radical copolymerization of 2,2,2-trifluoroethyl methacrylate and 2,2,2-trichloroethyl ,-fluoroacrylate: Synthesis, kinetics of copolymerization, and characterization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2010
Jean-Marc Cracowski
Abstract Copolymers based on 2,2,2-trifluoroethyl methacrylate (MATRIFE) and 2,2,2-trichlororoethyl ,-fluoroacrylate (FATRICE) were synthesized in good yields by radical process initiated by tert -butyl 2,2-dimethylperoxypropanoate. Molar composition of the obtained poly(MATRIFE- co -FATRICE) copolymers were assessed by means of 1H and 19F nuclear magnetic resonance spectroscopy and by elemental analysis. The reactivity ratios, ri, of both comonomers were determined from the Kelen-Tüdos and Finneman-Ross methods (rMATRIFE = 1.52 ± 0.03 and rFATRICE = 0.61 ± 0.03 at 74 °C) showing unexpectedly that MATRIFE is the more reactive monomer in copolymerization. Molecular weights and polydispersity indexes of poly(MATRIFE- co -FATRICE) copolymers were ranging between 1.47 and 2.68 × 104 g·mol,1 and from 1.44 to 2.21, respectively. Thermal properties of the resulting polymers were examined and thermogravimetric analyses showed a satisfactory thermal stability, a thermal decomposition occurring from 220 to 295 °C as the molar ratio of FATRICE increased in the copolymer. Moreover, the glass transition temperatures of copolymers varied from 66 to 108 °C and also increased with FATRICE molar ratio in the copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2154,2161, 2010 [source]


Ethyl-paraben and nicotinamide mixtures: Apparent solubility, thermal behavior and X-ray structure of the 1:1 co-crystal,

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2008
S. Nicoli
Abstract This work aims at investigating the nicotinamide (NA),ethyl-paraben (EP) binary system both in solution and in the solid state. In particular, the apparent EP solubility in water was studied in the presence of different NA concentrations (between 0.28 and 1.64 M). It was found that the apparent EP solubility increase (nearly twofold) observed at the highest NA concentration tested can be ascribed to a change in the polarity of the solvent mixture, rather than to a direct effect of NA on EP. The effect of fusion and re-crystallization from water or ethanol solutions on EP and NA mixtures was investigated by means of differential scanning calorimetry, elemental analysis and X-ray diffraction both on powder and single crystal. It was discovered that EP and NA form a co-crystal having a 1:1 molar composition that can be easily crystallized from ethanol. Single crystal X-ray analysis of this species revealed that the NA and EP molecules form corrugated layers within which the two components are intimately associated by a dense network of hydrogen bonds. In the presence of an excess NA in solution, the EP-NA co-crystal has lower water solubility with respect to both the single co-crystal formers and precipitates in aqueous solutions at ambient temperature. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4830,4839, 2008 [source]


Synthesis and Photoresponsive Properties of Optically Active Methacrylic Polymers Bearing Side-Chain Azocarbazole Moieties

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2009
Luigi Angiolini
Abstract The synthesis of a novel optically active methacrylic monomer containing in the side chain the (S)-3-hydroxy- N -phenyl pyrrolidine ring linked to a 4-cyanophenylazocarbazole moiety [(S)- MCAPP - C] and of the analogous achiral monomer (MCAPE-C) is described. Both the monomers have been radically polymerized to produce the corresponding homopolymers as well as the copolymer at 50% molar composition. The photoinduction of birefringence has been assessed on thin films of the polymeric materials in order to evaluate their behavior as materials for optical data storage. Surface relief gratings (SRG) can also be inscribed over the material. The results are interpreted in terms of different cooperative performance and conformational stiffness of the chromophoric co-units in the polymeric derivatives. [source]


QSPR Analysis of Copolymers by Recursive Neural Networks: Prediction of the Glass Transition Temperature of (Meth)acrylic Random Copolymers

MOLECULAR INFORMATICS, Issue 8-9 2010
Carlo Giuseppe Bertinetto
Abstract The glass transition temperature (Tg) of acrylic and methacrylic random copolymers was investigated by means of Quantitative Structure-Property Relationship (QSPR) methodology based on Recursive Neural Networks (RNN). This method can directly take molecular structures as input, in the form of labelled trees, without needing predefined descriptors. It was applied to three data sets containing up to 615 polymers (340 homopolymers and 275,copolymers). The adopted representation was able to account for the structure of the repeating unit as well as average macromolecular characteristics, such as stereoregularity and molar composition. The best result, obtained on a data set focused on copolymers, showed a Mean Average Residual (MAR) of 4.9,K, a standard error of prediction (S) of 6.1,K and a squared correlation coefficient (R2) of 0.98 for the test set, with an optimal rate with respect to the training error. Through the treatment of homopolymers and copolymers both as separated and merged data sets, we also showed that the proposed approach is particularly suited for generalizing prediction of polymer properties to various types of chemical structures in a uniform setting. [source]


Characterization of a novel bioactive poly[(lactic acid)- co -(glycolic acid)] and collagen hybrid matrix for dermal regeneration

POLYMER INTERNATIONAL, Issue 10 2005
Kee Woei Ng
Abstract Different strategies have been explored for the purpose of autologous or allogeneic dermal regeneration. We have developed a hybrid matrix by lyophilizing collagen within a poly[(lactic acid) -co -(glycolic acid)] (10:90, molar composition) knitted mesh, in order to assimilate the advantages of natural and synthetic materials. The porosity of the mesh was found to be almost 95 %, using Micro-Computed Tomography Analysis, while the mechanical properties were comparable to native skin. In vitro biocompatibility was analyzed by culturing rat dermal fibroblasts in the matrices over 10 days. The cells were able to attach, proliferate and remain viable within the hybrid matrices. Subsequently, in vivo biocompatibility was analyzed by implanting the matrices subcutaneously in immunocompetent rats, for 2 weeks. Histological analysis showed that the poly[(lactic acid) -co -(glycolic acid)],collagen hybrid matrices evoked minimal host tissue response in vivo. This study forms the basis of using poly[(lactic acid) -co -(glycolic acid)],collagen hybrid matrices for our future work to develop a bioactive matrix for dermal regeneration. Copyright © 2005 Society of Chemical Industry [source]


Lower critical solution temperatures of thermo-responsive poly(N -isopropylacrylamide) copolymers with racemate or single enantiomer groups

POLYMER INTERNATIONAL, Issue 2 2009
Peng-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]