Polymérisation radicalaire du pentadiène‐1,3. IV. Détermination de la composition et du “run number” des copolymères de cis‐ ou trans‐pentadiène‐1,3 et d'acrylonitrile par pyrolyse éclair couplée à la chromatographie en phase gazeuse

Abstract

AbstractThis paper investigates the possibility of using the method of flash pyrolysis‐gas chromatography for the quantitative determination of the composition of free‐radically prepared cis‐ or trans‐1,3‐pentadiene–acrylonitrile copolymers and for evaluation of their comonomer sequence distributions in terms of the run numbers. The experiments (sample weight: 50 μg, pyrolysis time: 4 s) were carried out, under a flow of helium, at a thermolysis temperature ranging from 450 to 900°C with a Curie‐point pyrolyzer. After discussion of the respective thermal behaviors of the poly(1,3‐pentadiene), polyacrylonitrile, mixtures of these homopolymers, and various kinds of copolymers (radically or fully alternating samples), the pyrolysis–gas chromatographic characterization of the primary structure of copolymers was studied, between 500 and 800°C, through the quantitative treatment of the corresponding liberated monomers which appeared on the pyrograms. By applying the both‐side boundary effect theory on the molar amounts of these degradation products, which depend both upon copolymer composition and triad sequence distributions in the chain, the relative values of the monomer formation probability constants were calculated. The composition and the run number of each pyrolyzed sample were then determined using these parameters. The analytical data obtained by means of the procedure suggested are in very good agreement with those predicted, from reactivity ratios, by the usual theory of copolymerization (terminal‐unit model) and with the evaluations provided by the 13C‐NMR spectroscopy.