PIVALOLACTONE .2. COPOLYESTER SYNTHESIS VIA INTERCHANGE REACTIONS WITH POLYPIVALOLACTONE

The synthesis of copolyesters via interchange reactions of polypivalol actone (PPVL) with several compounds was studied. The synthetical proc edures are two-stage melt processes: in the first stage ester bonds in the polymer chain are cleaved and new groups are incorporated in the polymer chain, while in the second step condensation of the end-groups formed occurs. For the synthesis of copolymers, three procedures were used, with tetrabutyl orthotitanate as a catalyst. PPVL was heated wi th equimolar mixtures of bisphenol-A diacetate (BPAac) and terephthali c acid (TA), but no copolymers were formed; instead, polycondensation of BPAac with TA occurred, leaving the PPVL unaffected. From PPVL and mixtures of BPAac and dimethyl terephthalate (DMT) polymers were obtai ned which contained a significant amount of copolymeric sequences. How ever, most of the polymeric chains consisted of PPVL and poly(bispheno l-A terephthalate) blocks. Random copolymers with thermal stability we re obtained after heating PPVL with bisphenol-A polycarbonate and DMT. The latter process was studied in detail by IR, DSC, and solubility a nd selective degradation tests. Based on the results of these studies, the reactions occurring during the three procedures were discussed.