Optical anisotropies of model analogs of polycarbonates

Abstract

Depolarized light scattering and electric birefringence have been used to evaluate the optical anisotropy tensors for dimethyl carbonate, methyl phenyl carbonate, diphenyl carbonate, and 2,2-diphenylpropane. Rotational potentials about the phenyl axes in diphenyl carbonate and in diphenylpropane are estimated from force field calculations of interactions between nonbonded atoms. Rotations of the same sign » |46°| of the phenyl groups in diphenylpropane and uncorrelated rotations ~|46°| about carbonate bonds are indicated. By combination of the information on structure, anisotropy, and conformation of these model compounds, the optical anisotropy tensors for carbonate and phenyl groups are estimated for these analogues of units occurring in the polycarbonate chain.

Conformational features of bisphenol-A polycarbonate

“…However, the above' experimental values for the activation energy can perhaps be accounted for by combining the energy barrier of -2 kcal mol-' mentioned above for the carbonate group at [ = 90" and the barrier for the phenyl rotation discussed in the next section. The results reported by Flory and co-workers (15) show that with the same geometrical parameters (Set II), and the Hill's function, the minimum occurs at [ = 45" with B = 2 kcal mol-I. However, according to our calculations shown in Although intuitively one would expect the minimum to occur at (+,$) = (60°,600), the shifts of the minima from such a position in Figs.…”

“…The geometrical parameters derived by Dulmage et al (14) are not used here. Comparing them with the parameters reported by Erman et al (15), it is found that there are appreciable differences in the bond angles of the carbonate group as well as the 2,2-diphenyl propane segment. The bond angles in the phenyl group, for example, vary from 120" to as small as 1 1 1.8", and a pronounced nonplanarity of the phenyl is indicated.…”

“…Also included (Set 11) are the values used by Erman et al (15) based on a crystal structure analysis of diphenyl carbonate. ' Both sets of parameters have been used in the present calculations.…”

“…While this work was in progress, a paper on the optical anisotropy of polycarbonate analogs was published by Flory and co-workers (15). The calculations of optical anisotropy were based on the conformations of the carbonate and the diphenyl segments.…”

The effect of annealing on the local structure of glassy polycarbonate

“…Figure 3 shows the chemical configuration of a polycarbonate segment and identifies the rotation angles. Analyses are available [15,[21][22][23][24][25]] based on energy calculations and diffraction analysis of the glass and of the crystalline form of both the polymer and of low molecular weight analogues. They indicate that the carbonate group is trans-cis and that the chain, considering virtual phenylene bonds, is essentially a planar zig-zag.…”