Ring-opening polymerization ©Substituted lactones

Various cyclic esters have been subjected to hpase-catalyzed ring-opening polymerization. Lipase catalyzed the ring-opening polymerization of 4- to 17-membered non-substituted lactones.In 1993, it was first demonstrated that medium-size lactones, 8-valerolactone (8-VL, six-membered) and e-caprolactone (e-CL, seven-membered), were polymerized by lipases derived from Candida cylindracea, Burkholderia cepacia (lipase BC), Pseudomonas fluorescens (lipase PF), and porcine pancreas (PPL). °... 

Ring-opening polymerization of a-methyl-substituted medium-size lactones, a-methyl-y-valerolactone and a-methyl-c-caprolactone, proceeded by using lipase CA catalyst in bulk [82]. As to (R)- and (S)-3-methyl-4-oxa-6-hexa-nolides (MOHELs), lipase PC induced the polymerization of both isomers. The apparent initial rate of the S-isomer was seven times larger than that of the R-isomer, indicating that the enantioselective polymerization of MOHEL took place through lipase catalysis [83]. 

Poly(3-hydroxyalkanoate)s have potential for application to engineering plastics endowed with biodegradable nature. One of the synthetic approaches to the polyesters is the ring-opening polymerization of -substituted /3-lactones which can be effectively produced by ring-expansion carbonylation of epox-... 

Enantioselective Ring-Opening Polymerizations of Substituted Lactones Using Lipases... 

Cationic organozinc compounds are expected to be good catalysts for ring opening polymerization reactions of epoxides and lactones because the enhanced Lewis acidity (see Lewis Acids Bases) of the zinc center favors its coordination to the monomer. For example, Walker and coworkers have found that the cationic zinc substituted cyclopentadienyl complex [3,5-Me2C6H3CH2CMe2C5H4Zn(TMEDA)]+ [EtB(C6F5)3] is an active initiator species for the polymerization of cyclohexene oxide and e-caprolactone. ... 

Lewis acid-assisted high-speed living anionic polymerization can be applied not only to the accelerated synthesis of naiTOw MWD poly(methacrylic esters) but also to the synthesis of polyethers from epoxides (11) and polyesters from lactones (14 and 15) with aluminum porphyrins as initiators. Furthermore, ring-opening polymerization of episulfides (18) with zinc AT-substituted porphyrins (5) can also be accelerated by Lewis acids. 

S, (2002) lipase-catalyzed ring-opening polymerization of substituted lactones. Polymer Journal, 34(11), 835-40,... 

Ring-openTng polymerizations involve a variety of the ionic growing species. Moreover, some of the heterocyclic monomers may react ambidently and, therefore, produce chemically isomeric structures of active centers. Polymerization of lactones or polymerization of substituted a-oxides, both with two possible ways of ring-opening, are the typical examples. 

To date, many investigations have been conducted on the (non)-substituted-four-membered lactone polymerizations using enzymes as catalysts. The ratedetermining step in the overall polymerization scheme corresponds to the formation of the enzyme-activated monomer (EAM), which itself is obtained by reaction of the monomer with the catalytic site of the lipase (serine residue), followed by ring-opening cleavage [80]. 

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