Simultaneous ROP and Polycondensation

Simultaneous ROP and Polycondensation Table 15.1 Nucleophilic and nonnucleophilic polar solvents... 

It was shown that lipases can catalyze enzymatic ROP and polycondensation simultaneously. This lipase ability was employed in order to obtain various polyesters. 

Uyama and co-workers [126,127] utilised PFL in the single-step ROP of DDL and acylation of hydroxy termini with different vinyl esters to produce polymers containing polymerisable groups only at one terminus of the polymer chain. Kobayashi and coworkers [128] have reported that the lipase-catalysed (CAL and PCL) polymerisation of lactones (12-, 13- and 16-membered), divinyl esters of adipic and sebacic acid and a,(o-glycols using one-pot synthesis produced the corresponding ester copolymers in which two different types of polymerisation, ROP and polycondensation as well as transesterification, simultaneously occurred via the same enzyme intermediate to provide random copolymers. Polymerisation of macrolides (DDL and PDL) in the presence of preformed polyester (polycaprolactone) produced the corresponding copolyesters [129]. 

In a KCP, cyclics cannot be formed by back-biting , and thus the formation of cyclic oligomers and polymers is indicative for the intermediate formation of linear chains having two reactive end groups. In other words, the formation of cyclics is indicative for simultaneous ROP and (poly)condensation steps. If side reactions are absent, and if the linear chains are mobile enough for cyclization, cyclics will be the only reaction products, and combined ROP and polycondensation is an eflhcient strategy for the preparation of cyclic polymers in high yields. 

The copolymerization of 12-, 13-and 16-membered lactones, divinyl esters of adipic and sebacic acid and a,co-glycols by using Candida antartica and Pseudomonas cepacia lipases yielded copolymers of high molecular weight, in moderate yields (Scheme 11.8). Taken together, these results indicated that ROP and polycondensation can occur simultaneously in a one-pot reaction to yield copolyesters [67]. 

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