Poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate): influence of stereochemistry of 1,4-cyclohexylene units on the thermal properties

A series of poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) (PCCD) samples, characterized by different cis/trans ratio of the 1,4-cyclohexanedicarbonyl unit, have been synthesized and analyzed by thermogravimetry (TGA), calorimetry (DSC), and X-ray diffraction (WAXD). The thermal stability results are good and are not affected by the stereochemistry of the 1,4-cyclohexylene units. On the other hand, the thermal transitions are notably influenced by the cis/trans content. With the increment of the trans content the polymer changes from completely amorphous to semicrystalline material. Tg, Tm, and crystallinity increase. These results suggest that the trans configuration induces a better chain packing and higher symmetry, improving the crystallizability of the samples. The effect of the molecular structure on the thermal properties is analyzed by using a statistical approach. From the effective correlations found between stereochemistry of the C6 rings and transition temperatures it is possible to extrapolate that the configuration of 1,4-cyclohexylene ring deriving from 1,4-cyclohexanedicarboxylic acid or dimethyl 1,4-cyclohexanedicarboxylate results to be the main element responsible for the thermal properties. This is due to the high rigidity of the 1,4-cyclohexanedicarbonyl unit with respect to 1,4-cyclohexanedimethyleneoxy unit, deriving from the diol.