High molecular weight lipase-catalyzed polymerization

Alkyl esters often show low reactivity for lipase-catalyzed transesterifications with alcohols. Therefore, it is difficult to obtain high molecular weight polyesters by lipase-catalyzed polycondensation of dialkyl esters with glycols. The molecular weight greatly improved by polymerization under vacuum to remove the formed alcohols, leading to a shift of equilibrium toward the product polymer the polyester with molecular weight of 2 x 10" was obtained by the lipase MM-catalyzed polymerization of sebacic acid and 1,4-butanediol in diphenyl ether or veratrole under reduced pressure. ... 

Lipase-catalyzed polymerization of divinyl adipate or divinyl sebacate with a, co-glycols with different chain length has been reported [40]. Lipases CA, MM, PC, and PF showed high catalytic activity toward the polymerization. A combination of divinyl adipate, 1,4-butanediol, and lipase PC afforded the polymer with number-average molecular weight (Mn) of 2.1 x 104. The yield of the polymer from divinyl sebacate was higher than that from divinyl adipate, whereas the opposite tendency was observed in the polymer molecular weight. 

Detailed studies on the lipase-catalyzed polymerization of divinyl adipate and 1,4-butanediol were performed [41-44]. Bulk polymerization increased the reaction rate and molecular weight of the polymer however, the hydrolysis of the terminal vinyl ester significantly limited the formation of the polyester with high molecular weight. A mathematical model describing the kinetics of this polymerization was proposed, which effectively predicts the composition (terminal structure) of the polyester. 

Aromatic polyesters were enzymatically synthesized under mild reaction conditions. Divinyl esters of isophthalic acid, terephthalic acid, and p-phen-ylene diacetic acid were polymerized with glycols by lipase CA catalyst to give polyesters containing an aromatic moiety in the main chain.208 In the lipase-catalyzed polymerization of dimethyl isophthalate and 1,6-hexanediol in toluene with nitrogen bubbling, a mixture of linear and cyclic polymers was formed.209 High molecular weight aromatic polyester (Mw 5.5 x 104) was synthesized by the lipase CA-catalyzed polymerization of isophthalic acid and 1,6-hexanediol under vacuum.210 Enzymatic polymerization of divinyl esters and aromatic diols also afforded the aromatic polyesters.211... 

PPL catalyzed the polymerization of methyl esters of 5-hydroxypentanoic and 6-hydroxyhexanoic acids.149 In the polymerization of the latter in hexane at 69 °C for more than 50 days, the polymer with DP up to 100 was formed. Relationships between solvent type and polymerization behaviors were systematically investigated hydrophobic solvents such as hydrocarbons and diisopropyl ether were suitable for the enzymatic production of high molecular weight polymer. Pseudomonas sp. lipase catalyzed the polymerization of ethyl esters of 3- and 4-hydroxybu-tyric acids, 5- and 6-hydroxyhexanoic acids, 5-hy-droxydodecanoic acid, and 15-hydroxypentadecanoic acid.157 Oxyacid vinyl esters were demonstrated as new monomers for polyester production under mild reaction conditions, yielding the corresponding polyesters with A/n of several thousands.276... 

For instance an epoxy-functionalized polyester from the suberin monomer cis-9,10-epoxy-18-hydroxyoctadecanoic acid (see also Chapter 1) was synthesized by Olsson et al. [30]. The lipase-catalyzed polymerization was performed in toluene in the presence of 4A molecular sieves for 68 h and high molecular weight of epoxy-functionalized polyester was obtained (M , =20000 M JMn =2.2). 

The synthesis of chiral poly(depsipeptides), polymers with alternating amide and ester bonds, by lipase-catalyzed ring opening of 3-isopropyl morpholino-2,5-dione (19) was shown by Hocker and coworkers (Scheme 11.5) [26], Various lipases were tested for the bulk polymerization of these heterocyclic monomers at temperatures of 100 °C or above. PPL and lipase type III from a pseudomonas species were shown to be effective catalysts. The isolated polymers showed Mn values of 3.5-17.5 kgmol-1. The influence of reaction temperature, the amount of enzyme and the presence of water in the reaction medium were shown to be important factors on the high molecular weight fraction and were investigated in detail [26b]. Comparison of optical rotation values for polymers prepared by... 

The lipase catalysis was effective for the ROP of macrolides such as 11-undecanolide (UDL 12-membered) [92], 12-dodecanolide (DDL 13-membered) [93], 15-pentadecanolide (PDL 16-membered) [94-96], and 16-hexadecanolide (17-membered) [97]. Various lipases catalyzed the polymerization of these macrolides. For the polymerization of DDL, the activity order of the catalyst was lipase BC > lipase PF > lipase CR > PPL. The lipase CA-catalyzed polymerization of PDL proceeded rapidly in toluene to produce a high-molecular-weight polymer... 

Feng, J., He, F., Zhuo, R, 2002. Polymerization of trimethylene carbonate with high molecular weight catalyzed by immobilized lipase on silica microparticles. Macromolecules 35, 7175-7177. 

Medium size lactones, 3-valerolactone (5-VL, six-membered) and e-caprolactone (e-CL, seven-membered), were subjected to lipase-catalyzed polymerizations. Lipases CC, PF, and PPL showed high catalytic activity for the polymerization of S-VL (149,150). The molecular weight of enzymatically obtained... 

As the characteristic features of lipase-catalyzed ring-opening polymerization, macrolides were readily polymerized to produce high-molecular-weight polyesters that were not easily obtained by the conventional chemical catalysts. Uyama et al. first reported the lipase-catalyzed polymerization of... 

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