Stress-optical behavior of poly(cis/trans-1, 4-cyclohexane dimethanol-alt-formaldehyde) (PCDO) networks

Two samples of poly(cis/trans-1,4-cyclohexane dimethanol-alt-formaldehyde), having fractions of trans configuration of cyclohexylene rings F_t = 0.1 and 0.7, were synthesized by polycondensation of the appropriate mixtures of glycols with paraformaldehyde. These two samples were crosslinked by a chemical reaction using 2,4-bis(p-isocyanatebenzyl) phenylisocyanate as the crosslinking agent. The stress-optical behavior of the resulting networks was studied at several temperatures in the range 10–80°C. The values of the optical configuration parameter Δα were 9.9 and 7.2 in units of 10^?24 cm³ for F_t = 0.7 and 0.1, respectively. The temperature coefficient of this quantity was roughly zero. Theoretical analysis, performed using the rotational isomeric state model, proved that the only parameters that have an appreciable effect on the calculated values of Δα are those concerning the cyclohexane ring (i.e., F_t and the optical parameter Γ_CC = Δα_CC ? 2Δα_CH). Conformational energies, geometrical parameters, and contributions to the optical anisotropies from the oxymethylene oxide have no noticeable effect on the value of Δα calculated for the polymer. In fact, values of Δα calculated for the polymer at F_t = 0 and 1 are very close to those obtained, respectively, for cis and trans cyclohexane dimethylene. The theoretical values of Δα are roughly one order of magnitude lower than the experimental results; however, the theory reproduces satisfactorily both the variation of Δα with F_t and its temperature coefficient.