Optimization of poly(1,4-cyclohexylidene cyclohexane-1,4-dicarboxylate) (PCCD) preparation for increased crystallinity

A key factor, which affects the crystallization temperature on cooling (T-c) of PCCD is the cis/trans isomer ratio of the cyclohexyl diester in the polymer. Isomerization of pure dimethyl-trans-1,4-cyclohexanedicarboxy late can occur during the polymerization, and the T. on cooling decreases along with the trans content. The isomerization reaction is enhanced with temperature, time and catalyst amount, and these variables should be minimized to prepare PCCD polymers with high T-c. However, these same variables also control the molecular weight growth of the polymer, and so a compromise between the best conditions for high T-c and those for high M-w must be made. A set of optimized conditions were obtained leading to PCCD polymers with M-w of 75,000-80,000 and T-c on cooling of 164-167 degrees C. Solid state polymerization was used to prepare high molecular weight PCCD with a high level of crystallinity (T-c on cooling similar to 193 degrees C). It was also shown that adding small amounts of supplementary diols facilitates PCCD preparation by ensuring that high molecular weight PCCD polymers will be obtained even when the stoichiometry of monomer feed is off by > 3%, i.e. conditions which would otherwise lead to low Mw. Finally, less crystalline PCCD's have been prepared via either incorporation of diethylene glycol or increasing the cis-diester amount in the polymer. (c) 2006 Elsevier Ltd. All rights reserved.