Lipases copolymers Polymer

Ester-thioester copolymers were enzymatically synthesized (Scheme 7). ° The lipase CA-catalyzed copolymerization of e-caprolactone with 11-mercaptoundecanoic acid or 3-mercaptopropionic acid under reduced pressure produced the polymer with molecular weight higher than 2 x 10". The thioester unit of the resulting polymer was lower than the feed ratio. The transesterification between poly(8-caprolactone) and 11-mercaptoundecanoic acid or 3-mercaptopropionic acid also took place by lipase CA catalyst. Recently, aliphatic polythioesters were synthesized by lipase CA-catalyzed polycondensation of diesters with 1,6-hexanedithiol. ... 

The enzymatic polymerization of lactones could be initiated at the hydroxy group of the polymer, which expanded to enzymatic synthesis of graft copolymers. The polymerization of c-CL using thermophilic lipase as catalyst in the presence of hydroxyethyl cellulose (HEC) film produced HEC-gra/f-poly( -CL) with degree of substitution from 0.10 to 0.32 [102]. 

Use of Pseudomonas cepacia lipase (lipase PS) or Porcine pancreatic lipase does allow for the enzymatic ROP of lactide. Matsumura and coworkers reported polymers with extraordinarily high molecular weights (Mw up to 270 kDa) and very narrow PDI (<1.3) [135-137]. However, high temperatures (130°C) were needed to achieve good conversions, and polymerizations proceeded only when conducted in bulk. It is conceivable that another non-enzymatic mechanism contributed in these polymerizations. In fact, Koning and coworkers synthesized copolymers... 

Naka K., Nakamura T., Okhi A., Maeda S. Aggregates of amphiphilic block copolymers derived from poly((A-acylimido)ethylene) and their complexes with lipase in water. Polymer J. 1995 27(11) 1071-1078. 

Immobilized CALB has frequently been applied in the literature as a catalyst for polymerization of aliphatic polyesters, polycarbonates, polyurethanes and their copolymers. In the present work on CALB catalyzed polymerization, the ring opening of e-caprolactone to polycaprolactone was selected as the model polymerization reaction (Figure 3.3). This model reaction has been well established in the literature [24-27] as an example of a polymerization reaction that can be successfully catalyzed by immobilized lipases (see also Chapter 4). Polymer synthesis and characterization was performed in four steps (i) polymerization (ii) separation (iii) purification and (iv) characterization. 

Li, G., Yao, D., and Zong, M. (2008) Lipase-catalyzed synthesis of biodegradable copolymer containing malic acid units in solvent-free system. Eur. Polym.J., 44 (4), 1123-1129. 

Enzymes are perfectly equipped to convert substrates into products in high enantio-, regio-, or chemoselectivity, a property that is commonly used in industry to prepare optically active fine-chemical intermediates [5]. More specifically, lipases appeared as ideal catalysts as a result of their high enantioselectivity, broad substrate scope and stability. In addition, lipases are powerful catalysts for the preparation of polyesters, polycarbonates and even polyamides, as is reviewed in Chapters 4 and 5 of this book. Moreover, a variety of different polymer architectures such as block copolymers, graft copolymers etc have been prepared using lipases as the catalyst (see Chapter 12). 

In the previous section, chiral (co)polymers were prepared using a one-pot system that is, all reactants and catalysts are present at the start of the reaction and both catalysts work simultaneously. This section will deal with the synthesis of chiral block copolymers (i) using a chiral polymer as the initiator or (ii) using different catalysts in sequence. Furthermore, some examples are highlighted in which the polymer properties are determined by the chirality of the polymer. The latter is introduced via lipase catalysis, before or after polymerization of the monomer. 

Porcine Pancreas Lipase (PPL), a common lipase with low cost, could be immobilized on silica particles with good stability and recyclablity. Then the immoblized lipase (IPPL) was employed as the catalyst for polymer synthesis, such as polyesters, polycarbonates, polyphosphates, and their copolymers. Here we present a mini-review of some works in our lab within this area. 

More recently, Lopez-Luna et al. [54] reported the successful enzyme-mediated syntheses of polyester structures in SCCO2 and R-134a. Lipase-mediated synthesis of relatively high molecular weight poly(S-valerolactone) (PVL) was reported in SCCO2 and liquid R-134a solvent media. However, they found that polymers and copolymers... 

Lipase catalysis is often used for the enantioselective production of chiral compounds indeed, lipase has been known to induce an enantioselective ROP of racemic lactones. In the lipase-catalyzed polymerization of racemic j8-butyrolactone (/3-BL), the enantioselectivity was low rather, an enantioselective polymerization of /3-BL occurred by employing a thermophilic lipase to yield the (R)-enriched polymer with 20-37% enantiomeric excess (e.e.) [101]. The enantioselectivity was greatly improved by copolymerization with seven- or 13-membered nonsubstituted lactones, using the lipase CA catalyst, whereby the e.e.-value reached almost 70% for the copolymerization of /3-BL with DDL [102]. It should be noted that, in the case of the lipase CA catalyst, the (S)-isomer was reacted preferentially to produce the (S)-enriched, optically active copolymer. The lipase CA-catalyzed copolymerization of i5-CL (six-membered) with DDL proceeded enantioselectively, to yield the (R)-enriched optically active polyester with an e.e.-value of 76%. 

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