Configurational properties of polyesters with cyclohexane rings incorporated in the main chain

Abstract

Poly(oxymethylene-l,4-czs-cyclohexylenemethyleneoxysebacoyl) (PCCS) and poly(oxymethylene-l,4-irazis-cyclohexylenemethyleneoxysebacoyl) (PTCS) were synthesized by condensation of the corresponding cis and trans isomers of 1,4-cyclohexanedimethanol with sebacic acid. Values of the mean-square dipole moments (µ2) of both polyesters were determined from dielectric constant measurements on dilute solutions of the polymers in benzene. The values of the dipole moment ratio (µ2) ¡nrr? at 30 °C were found to be 0.983 and 0.631 for PCCS and PTCS, respectively, and the temperature coefficient of the dipole moments for the former was significantly lower than for the latter. The values of the temperature coefficient of the unperturbed dimensions 103d In (r2)0/dT of the polyesters, determined from thermoelastic experiments carried out on networks obtained by cross-linking hydroxyl-terminated polymers with an aromatic triisocyanate, were -0.93 ± 0.25 and -1.26 ± 0.34 K"1 for PCCS and PTCS, respectively. Theoretical calculations carried out with the rotational isomeric state model gave values of d In (r2)0/dT in very good agreement with the experimental results. Fair agreement between theory and experiment was also found in the case of the dipole moments of the chains.

RIS Models and Unperturbed Chain Properties of Polyesters Containing 1,3‐Cyclobutylene and 1,4‐Cyclohexylene Linkages

“…For f 6 , it is found that the g þ (g À ) states are preferred over the t states by 0.7 kcal Á mol À1 while the reported value from Lennard-Jones potential calculations is 0.55 kcal Á mol À1 . [7] The second order interaction energy for the tg þ and tg À states is found to be 1.4 kcal Á mol À1 and those for the g þ g À and g À g þ states is 0.94 kcal Á mol À1 . In the earlier reported statistical weight matrix for this bond pair, the tg þ and tg À states were taken to be at the same energy as the tt state and the g þ g À and g À g þ states were neglected.…”

“…The statistical weight matrices for these specific bond pairs in the terephthalate linkage in PCT are also the same as those given for CBDO. Conformational calculations about bond pair (f 4 , f 5 ) (Figure 2) [7] The energy barrier for interconversion from the t to the g þ (or g À ) state is found to be 2.3 kcal Á mol À1 . Rotations about the bond pair (f 5 , f 6 ) are highly interdependent (where f 6 is equatorially oriented) and the minimum energy states corresponding to the f 6 bond are 08 (trans, t), 1208 (gauche þ , g þ ), and À1208 (gauche À , g À ) wherein these are defined with respect to the virtual bond across the cyclohexylene group.…”

“…RIS models developed for various polyesters have been summarized by Rehahn et al [5] Here we will be discussing only those RIS models pertaining to the polyester structures chosen in the present work. The only RIS models reported in the literature for polyesters with cyclohexane rings in the main chain are those by Riande et al [6][7][8][9] Experimental measurements and RIS calculations were performed on polyformals synthesized from transcyclohexane-1,4-dimethanol and paraformaldehyde to determine the mean-square dipole moment and its temperature coefficient. [6] Agreement between the experimental and calculated values was satisfactory.…”

“…RIS models have also been formulated for polyesters of sebacic acid with cis-cyclohexane-1,4-dimethanol (PCCS) and transcyclohexane-1,4-dimethanol (PTCS). [7] Calculations of the intramolecular interactions between the various bonds in that work was carried out with Lennard-Jones potentials and conformational energies were also derived. RIS method was then used to calculate the dipole moment and its temperature coefficient along with the temperature coefficient of the unperturbed dimensions, dlnhr 2 i 0 /dT.…”

“…Unperturbed dimensions of PCCS and PTCS exhibit negative temperature dependence and the absolute value of dlnhr 2 i 0 / dT is found to be larger for the trans than the cis isomer. [7] Experimentally, the quantity was determined from thermoelastic experiments carried out on networks obtained by crosslinking the polyesters with an aromatic triisocyanate. Fair agreement was found between the calculated and the experimental value of dlnhr 2 i 0 /dT (within 8-13% of the experimental value).…”