Structure and anisotropy in polycarbonate III. Study of elastic and optical properties of oriented samples with the method of high resolution Brillouin spectroscopy

Abstract

High resolution Brillouin spectroscopy (BS) has been used to investigate elastic and optical properties of uniaxially drawn samples ofpolycarbonate (PC). The results are discussed in the framework of the single phase aggregate model (SPAM) of Ward. According to a recently developed evaluation technique, the SPAM parameters of PC are determined, resulting in the following elastic constants of the structural units: r = 33 GPa, c~1 = 7 GPa, c~3 = 9.7 GPa, c~4 = 1.4 GPa, and r = 1 GPa. A nearly quadratic dependence of the orientation parameter P4 on P2 results, which can be explained by a modified pseudoaffine deformation scheme.

Orientation of the diphenylene propane unit in stretched polycarbonate from two-dimensional magic-angle-spinning NMR

“…For both values of P~, the aggregate model overestimates the orientation parameter of PC stretched at T = 403 K. In fact, deformation schemes different from the aggregate model have successfully been used to describe the deformation behavior of PC stretched at high drawing temperatures [8,11,12]. These generally take into account non-orientational components of deformation and are, therefore, consistent with the lower values of P2 observed.…”

“…However, these models are generally applicable only for certain ranges of temperature and strain rate. At temperatures sufficiently below Tg, the deformation of glassy polymers has frequently been discussed on the basis of the aggregate model [1,2,4,5,11] which only takes into account the orientational component. In this model it is assumed that the polymer consists of an aggregate of transversely isotropic units whose axes rotate on drawing in the same manner as lines joining pairs of points in a body which deforms affinely.…”

“…The fact (5) that PC stretched at T = 403 K to high extension ratios exhibits a somewhat lower orientation parameter than at T = 295 K can be attributed to the existence of a nonorientational component. Various deformation schemes [1,2,[4][5][6][7]11,12,20,21] have been used to describe the deformation and orientation behavior of glassy polymers. However, these models are generally applicable only for certain ranges of temperature and strain rate.…”

The problem of intrinsic birefringence and chain conformation in polycarbonate from bisphenol-A

“…The anisotropic heat conduction [5], and the elastic anisotropy [6] do not have such a well-defined monomer related reference frame. They refer, more or less, to the average local chain direction.…”

“…v) uncertainty of ,4o~a m due to dispersion effects. The polarizabilities were measured at ,~ = 632 nm, whereas An is usually measured at ~, = 546 nm, giving a 3 % higher value than at the former wavelength [6].…”