Inverse Gas Chromatography Studies of Poly(dimethylsiloxane)-Polycarbonate Copolymers and Blends

Abstract

The specific retention volumes of a series of volatile probes on stationary phases consisting of homopolymers of poly(dimethylsiloxane) (PDMS) and bisphenol A polycarbonate (PC) as well as block copolymers and blends of these substances were evaluated in terms of the Flory-Huggins approximation. The polymer-solvent, 12, and normalized polymer-polymer, X23', noncombinatorial free energies of mixing were determined in each case, X23’ was studied as a function of block length of PC in the copolymer, the chemical structure of the probes, and the copolymer or blend composition. In addition, the morphologies of phaseseparated copolymers were analyzed from the specific retention volumes of n-decane, a solvent for PDMS and a nonsolvent for PC, at temperatures below the polycarbonate glass transition. The data obtained were compared to morphological information obtained from differential scanning calorimetry, electron microscopy, and small-angle X-ray scattering. Measured X23’ values reflected in all cases the known incompatibility of PDMS and PC in the copolymers and blends. Also, useful information on the copolymers' morphology was obtained by studying the retention behavior of the n-decane probe below the PC glass transition. The specific retention volume for the microphase-separated copolymers under these conditions indicated whether the PDMS phase was continuous or not and, in some cases, the actual surface area of the PC domains. Diameters of domains (assuming rod or lamellar geometry) ranging from 180 to 700 Á were calculated from the results. © 1981, American Chemical Society. All rights reserved.