Ring-opening polymerization immobilized lipase

Enzyme activity for the polymerization of lactones was improved by the immobilization on Celite [93]. Immobilized lipase PF adsorbed on a Celite showed much higher catalytic activity than that before the immobilization. The catalytic activity was further enhanced by the addition of a sugar or poly(ethylene glycol) in the immobilization. Surfactant-coated lipase efficiently polymerized the ring-opening polymerization of lactones in organic solvents [94]. 

In our study (6), porcine pancreas lipase (PPL) immobilized on silica particles (narrow distributed micron particles) was employed for ring-opening polymerization of TMC. No evidence of decarboxylation occurring during the polymerization. The results showed that silica microparticles improved immobilization efficiency much more. The most preferable polymerization temperature of TMC was 100 °C during 24h polymerization. The M of the resulting polymers was significantly increased compared with that catalyzed by... 

In recent years, the enzymatic synthesis of biodegradable polyesters was focused on the polycondensation method (22,23). Among the very few successful example of enzymatic ring-opening polymerization for polyesters synthesis, Novozyme-435 (immobilized lipase B from Candida antartica) has been proved an effective catalyst for polycaprolactone (PCL) synthesis in toluene (24). Considering the low cost and high recyclablity of IPPL, we also... 

MNPHP is a well-known irreversible inhibitor of lipases that is highly specific for reaction with active-site serine residues. Thus, MNPHP was selected as the inhibitor to determine, by titration, the fraction of catalytic sites that are accessible and active. Since we are concerned with CALB activity in organic media, inhibition was studied in heptane. LC-MS was used to determine the release of p-nitrophenol (pNP) which corresponds with accessible active sites. To ensure that adsorption of pNP by resins was taken into consideration, pNP concentration was corrected as follows. A fixed quantity of enzyme-free resin was incubated overnight in acetonitrile with different concentrations of j NP. Standard curves of pNP adsorption by each resin as a function of pNP concentration were constructed from LC-MS measurements. MNPHP-inhibited immobilized enzymes were used for e-caprolactone ring-opening polymerizations in toluene (70 C). No conversion of monomer was observed in 30 minutes. Hence, MNPHP titration resulted in complete inhibition of CALB activity. 

Typical diol-diacid type biodegradable aliphatic polyesters, PBA and PBS, were degraded in a diluted toluene solution by the immobilized lipase CA which exclusively formed the cyclic oligomers. Their composition was partially dependent on the degradation conditions, such as the enzyme concentration and temperature. On the other hand, in a more concentrated condition, the cyclic oligomer was readily repolymerized by the ring-opening polymerization. 

Hiroshi et al. reported [46] a high-performance immobilized lipase catalyst for polyester synthesis. A porous polypropylene was found to be a good support for immobilization of Candida antarctica lipase (enzyme). The immobilized lipase on polypropylene efficiently catalyzes ring opening polymerization of 15-pentadecanolide, polycondensation of divinyl sebacate, and 1,8-octanediol. 

Fujioka et al. [100] conducted the ring-opening polymerization of L-lactide by using immobilized lipase Candida Antarctica (Novozym 435) as a catalyst at a... 

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. 

Furthermore, the ring-opening co-polymerization of BTMC with 5,5-dimethyl-trimethylene carbonate (DTC) by immobilized porcine pancreatic lipase (0.1 wt%) catalyzed in bulk copolymerization at 150°C for 24h [117]. Under these conditions, the highest molecular weight of poly(BTMC-co-DTC) of M =26 400 was obtained, with 83% monomer conversion. 

---