Enzymatic Ring-Opening Copolymerizations

An ester-amide polymer was prepared by ROP, catalyzed by Porcine pancreatic lipase (5 wt %) of a six-membered cyclic depsipeptide, 3(S)-isopropylmorpholine-2,5-dione (IPDM), in bulk at 100°C, with M = 17500, M = 18500, and 66% yield [103]. 

A compilation of cyclic ester related polymers, the enzymes used, and the corresponding citation(s) is given in Table 4.2. 

Copolymerization of 8-VL with e-CL using lipase from Pseudomonas Jluorescens, and copolymerization of 8-OL with e-CL and DDL using immobilized form of CALB, were reported by Kobayashi and coworkers [80]. In this later report, copolymerization was performed in isooctane at 60 °C for 48 h, and, according to 13C NMR analysis, random-structured copolymers were obtained with Mn values up to 9000 and yields up to 97%. 

Furthermore, using Novozym 435 as catalyst, 2-oxo-12-crown-4-ether (OC) was copolymerized with PDL giving copolyesters with random sequence distributions [106]. 

Biodegradable polyesters were synthesized via ring-opening copolymerizations of various oxiranes (glycidyl phenyl ether, benzyl glycidate, glycidyl methyl ether, styrene oxide) and various dicarboxylic anhydrides (succinic anhydride, phthalic 

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Also, the novel enzymatic ring-opening copolymerization of ethyl ethylene phosphate (EEP) and TMC was performed in bulk at 100 °C using PPL or C. rugosa lipase to yield random copolymers having molecular weights ranging from 3200 to... 

Scheme 90 Copolymerization of TMC with TMP in the presence of Al(/Bu)3 as a cataiyst (a) enzymatic ring-opening copolymerization of EEP and TMC in the presence of PPL or C. rugosa iipase.

Uyama H, Takeya K, Kobayashi S (1993) Synthesis of polyesters by enzymatic ring-opening copolymerization using lipase catalyst. Proc Jpn Acad B 69 203—207... 

Enzymatic ring-opening polymerization and copolymerization of 8-octanolide by lipase catalyst. Macromolecules, 31 (17), 5655-5659. 

Thermoplastic poly(lactic acid) (PLA) is obtained by polycondensation of the acid or by ring-opening of the lactide. Its mechanical performance is similar to that of PS. Lactic acid (LA) can be produced by fermentation of coal, petroleum or namral gas. PLA is sensitive to enzymatic and chemical hydrolysis. It has been used for medical implants, dmg delivery, packaging and consumer goods. LA can be copolymerized with ethylene glycol into highly hydrophilic poly(ether-ester) block copolymers. Similarly, LA was copolymerized... 

The lack of reactivity of the alcohol moiety of lactic acid when using Novozym 435 as catalyst would imply that lactide is not a good substrate in enzymatic ROP, as propagation requires an active chain end. Indeed, copolymerizations of lactide with CL showed a dramatic decrease in CL consumption after an initial rapid consumption of lactide, which appeared to be the better substrate. Indeed, many weeks were required in order to observe the formation of random copolymers [74]. Clearly, the lack of nucleophilicity of the secondary alcohol of ring-opened lactide is primarily responsible for the dramatic reduction in polymerization rate. 

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