Effect of the side chain structure on the glass transition temperature. Part 3. Molecular weight dependence of T_g in some poly(thiocarbonates)

Different T_g-^-M_n (number-average molecular weight) relationships for poly(oxythio-carbonyloxy-1, 4-phenylene-2,2-propyl-1,4-phenylene) (PMMT), poly(oxythiocarbonyloxy-1, 4-phenylene-2,2-butyl-1,4-phenylene) (PMET), poly(oxythiocarbonyloxy-1,4-phenylene-(4-methyl)-2, 2-pentyl-1,4-phenylene) (PMiBT), and poly(oxythiocarbonyloxy-1,4-phenylene-(methyl) phenylmethylene-1,4-phenylene) (PMPhT) have been established in order to obtain the glass transition temperature in the limit of high molecular weight T_g∞. Non linear dependence between T_g and ^-M_n^-1 is found, for PMMT and PMPhT, but the relationship between T_g and log M shows a linear dependence. The variations of the values of T_g∞ and the values of the conformational parameter σ with the polymer structure are compared for the different polymers.