Random copolyester formed from

The copolymerization of lactones took place through enzyme catalysis [92]. The copolymerization of e-CL with d-VL catalyzed by lipase PF affords the corresponding copolymer having a molecular weight of several thousand. From 13C NMR analysis, the copolymer was found to be of random structure having both units, suggesting the frequent occurrence of transesterifications between the polyesters. In the copolymerization of 8-OL with e-CL or DDL, random copolyesters were also formed [84], whereas the copolymer from e-CL and PDL was not statistically random [88]. 

There is a further very important class of main-chain liquid-crystal polymers that differ from those discussed above by being random copolyesters based on polymers such as poly(hydroxybenzoic acid) -fO— —C=0), where — — represents a para-disubstituted benzene ring (para-phenylene unit). The random copolymers include units of various other forms containing phenylene or naphthylene rings and their introduction reduces the crystallinity and melting point considerably without necessarily lowering the value of Polymers of these types have... 

The melting peak Tmi arises from the original crystals, which are formed at the crystallization temperature T. Figure 4 shows the dependence of Tml on Tc for P(3HB-co-3HH) copolyesters with different 3HH contents. Tm increases linearly with Tc for all the samples, and this temperature decreases with increasing 3HH contents at the same crystallization temperature. The decrease of the melting temperature can be attributed to the random distribution of 3HH units, which are excluded from the P(3HB) sequence crystals and hence reduce the lamellar thickness. 

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