COMPOSITIONAL SEQUENCE DISTRIBUTION IN UNSATURATED POLYESTERS AS REVEALED BY C-13 NMR-SPECTROSCOPY

A series of model unsaturated polyesters derived from maleic anhydride and various diols were synthesized and a study of their structures wa s carried out by means of C-13 n.m.r. spectroscopy. The n.m.r. spectra of polyesters produced by different procedures are reported and inter preted in terms of variety in the arrangement of diol components. Both fumarate and ester carbon atoms were found to be sensitive to composi tional differences in the polyester chains. Diversity of the diol-fuma rate-diol sequences was evidenced to account for the observed splittin g of the resonances. Assignment of the peaks to different compositiona l sequences was accomplished through systematic alterations in polyest er composition. The contributions of individual sequences were calcula ted assuming random and block distribution of diol units and compared with the experimental results. The comparison confirmed the validity o f the assignment as well as the efficiency of the approach in the desc ription of diol unit distribution in unsaturated polyesters.