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Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Synthesis and properties of the polythiourethanes obtained by the cationic ring-opening polymerization of cyclic thiourethanes

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2006
Daisuke Nagai
Abstract The cationic ring-opening polymerization of a five-membered thiourethane [3-benzyl-1,3-oxazolidine-2-thione (BOT)] with boron trifluoride etherate afforded the corresponding polythiourethane with a narrow molecular weight distribution in an excellent yield. The molecular weight of the polymers could be controlled by the feed ratio of the monomer to the initiator. A kinetic study of the polymerization revealed that the polymerization rate of BOT (1.3 × 10,2 L mol,1 min,1) was two times larger than that of the six-membered thiourethane [3-benzyltetrahydro-1,3-oxazolidine-2-thione (BTOT); 6.8 × 10,3 L mol,1 min,1], and the monomer conversion obeyed the first-order kinetic equation. These observations, along with the successful results in the two-stage polymerization, supported the idea that this polymerization proceeded in a controlled manner. Block copolymerizations of BOT with BTOT were also carried out to afford the corresponding di- and triblock copolymers with narrow molecular weight distributions. The order of the 5% weight loss temperatures was as follows: poly(3-benzyltetrahydro-1,3-oxazolidine-2-thione) [poly(BTOT)] > poly(BTOT54 - b -BOT46) > poly(3-benzyl-1,3-oxazolidine-2-thione) [poly(BOT)]. This indicated that an increase in the BTOT unit content raised the decomposition temperature. The order of the refractive indices was poly(BOT) > poly(BTOT54 - b -BOT46) > poly(BTOT54 - b -BOT46 - b -BTOT50) > poly(BTOT); this was in accord with the order of the sulfur content in the polymer chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4795,4803, 2006 [source]

Synthesis of poly(L -lactide)-grafted pullulan through coupling reaction between amino group end-capped poly(L -lactide) and carboxymethyl pullulan and its aggregation behavior in water

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2004
Tatsuro Ouchi
Abstract Poly(L -lactide) (PLLA) with terminal primary amino groups (PLLA-NH2) was synthesized and used to construct PLLA-grafted pullulan (Pul- g -PLLA). It consisted of a hydrophilic carboxymethyl Pul (CM-Pul) main chain and hydrophobic PLLA graft chains that were created through a direct coupling reaction between PLLA-NH2 and CM-Pul using 2-ethoxy-1-(ethoxycarbonyl)-1,2-dihydroquinoline as a condensation reagent. Pul- g -PLLAs with over 78 wt % sugar unit content were found to form nanometer-sized aggregates in water. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5482,5487, 2004 [source]

Miscibility and Physical Properties of Poly(3-hydroxybutyrate -co- 3-hydroxyhexanoate)/Poly(ethylene oxide) Binary Blends

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 12 2009
Fang Yu
Abstract In order to improve some inferior physical properties of bacterial poly(3-hydroxybutyrate -co- 3-hydroxyhexanoate) [P(3HB -co- 3HHx)] by blending with PEO, the miscibility, spherulite morphology, crystallization behavior and mechanical properties of P(3HB -co- 3HHx)/PEO binary biodegradable polymer blends were investigated. A good miscibility between P(3HB -co- 3HHx) with a 3HHx unit content of 11 mol-% and PEO in the amorphous state was found when the PEO weight fraction was 10,wt.-%, while the miscibility decreased dramatically when the PEO weight fraction exceeded 20,wt.-%. Strongly depending on the blend composition, the mechanical properties of P(3HB -co- 3HHx) was found to be significantly improved by blending with PEO with a weight fraction of ,5,17.5,wt.-%. [source]

Melting behavior and crystallization kinetics of sulfonated poly(butylene isophthalate)

POLYMER ENGINEERING & SCIENCE, Issue 7 2002
Nadia Lotti
The melting behavior and the crystallization kinetics of sulfonated poly(butylene isophthalate) random copolymers were investigated by means of differential scanning calorimetry. The multiple endotherms, commonly observed in polyesters, were found to be influenced both by composition and crystallization temperature. By applying the Hoffman-Weeks method, the equilibrium melting temperatures of the copolymers under investigation were obtained. The presence of a crystal-amorphous interphase was evidenced and its amount was found to increase as the sulfonated unit content was increased. Isothermal melt crystallization kinetics of the sample containing the lowest amount of sulfonated units was analyzed according to the Avrami treatment. The introduction of such units was found to decrease the overall crystallization rate of poly(butylene isophthalate). Values of Avrami's exponent n close to 3 were obtained, independently of crystallization temperature, in agreement with a crystallization process originating from predetermined nuclei and characterized by three-dimensional spherulitic growth. [source]