Arslan, Hülya | Hazer, Baki | Kowalczuk, Marek

Article | 2002 | JOURNAL OF APPLIED POLYMER SCIENCE85 ( 5 ) , pp.965 - 973

Poly [(R, S)-3-hydroxybutyratel oligomers containing dihyroxyl (PHB-diol), dicarboxylic acid (PHB-diacid) and hydroxyl-carboxylic acid (a-PHB) end functionalities were obtained by the anionic polymerization of beta-butyrolacton (beta-BL). Ring opening anionic polymerization of beta-BL was initiated by a complex of 18-Crown-6 with gamma-bydroxybutyric acid sodium salts (for PHB-diol and a-PHB) or succinic acid disodium salt (for PHB-diacid). Dihydroxyl functionalization was formed by the termination of polymerization with bromo-ethanol or bromo-decanol while the others were done by protonation. Hydroxyl and/or carboxylic acid functio . . .nalized PHB oligomers with eerie salts were used to initiate the polymerization of methylmethacrylate (MXIA). PHB-b-PMMA block copolymers obtained by this way were purified by fractional precipitation and characterized using H-1-NMR and C-13-NMR, gel permeation chromatography (GPC), and thermal analysis (DSC and TGA) techniques. (C) 2002 Wiley Periodicals, Inc. J Appl Polyra Sci 85: 965-973, 2002 Daha fazlası Daha az

Kul, Dilek | Volga, Cüneyt | Yılmaz-Savaşkan, Sevil | Hazer, Baki

Article | 2002 | POLYMER BULLETIN49 ( 1 ) , pp.25 - 32

WOS: 000178013300004

Kopaç, Türkan | Kocabaş, Sefa

Article | 2002 | Chemical Engineering and Processing41 ( 3 ) , pp.223 - 230

In this work, the adsorption equilibrium and adsorption rate of sulfur dioxide were investigated on silica gel. A packed bed adsorber 0.1 m in length and 0.0095 m in diameter was used for the adsorption experiments. The adsorption equilibrium experiments were carried out at 473 K constant temperature with an initial sulfur dioxide concentration in the range 430-3400 p.p.m. in nitrogen carrier gas. The experimental adsorption isotherms were compared with the Freundlich, Langmuir, and the linearized form of the Brunauer-Emmett-Teller and the Dubinin-Radushkevitch-Kaganer models by the nonlinear least-squares estimate method. The Freun . . .dlich model gave the best fit with a correlation coefficient greater than 0.98, suggesting a surface adsorption mechanism for sulfur dioxide adsorption on silica gel. The deactivation model was applied to the adsorption rate data. It was found that the adsorption rate data fitted well with the deactivation model. Observed adsorption rate constants and the first-order deactivation rate constants were obtained from the model. The nonlinear least-squares analysis technique was used to estimate the parameters appearing in the deactivation model. The breakthrough experiments were repeated at 1610 p.p.m. constant initial sulfur dioxide concentration in a temperature range of 323-473 K, and the effect of initial sulfur dioxide concentration and the effect of temperature were investigated on the model results. © 2002 Elsevier Science B.V. All rights reserved Daha fazlası Daha az

Arkın, Ali Hakan | Hazer, Baki

Article | 2002 | Biomacromolecules3 ( 6 ) , pp.1327 - 1335

Chlorination of microbial polyesters poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxyoctanoate) (PHO) was carried out by passing chlorine gas through their solutions. The chlorine contents in chlorinated PHB (PHB-Cl) and chlorinated PHO (PHO-Cl) were between 5.45 and 23.81 wt % and 28.09 and 39.09 wt %, respectively. Molecular weights of the chlorinated samples were in the range of between one-half to one-fourth of the original values because of hydrolysis during the chlorination process. Thermal properties of the PHO-Cl were dramatically changed with an increase in its glass transition (Tg = 2 °C) and the melting transition (Tm). T . . .he Tg of PHB-Cl varied from -20 to 10 °C, and its Tm decreased to 148 °C. The chlorinated poly(3-hydroxyalkanoate)s (PHA-Cl) were converted to their corresponding quaternary ammonium salts (PHA-N+R3), sodium sulfate salts (PHA-S), and phenyl derivatives (PHA-Ph). Cross-linked polymers were also formed by a Friedel-Crafts reaction between benzene and PHA-Cl. The modified PHO derivatives were characterized by 1H NMR and 13C NMR spectrometry, Fourier transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry techniques Daha fazlası Daha az