Yuri Y. Svirkin

Bio: Yuri Y. Svirkin is an academic researcher from University of Massachusetts Lowell. The author has contributed to research in topics: Ring-opening polymerization & Polymerization. The author has an hindex of 4, co-authored 4 publications receiving 523 citations.

Enzyme-Catalyzed .epsilon.-Caprolactone Ring-Opening Polymerization

Abstract: The polymerization of e-caprolactone, (e-CL) using porcine pancreatic lipase (PPL) as the catalyst was studied Polymerization reactions (4 days, 65°C) of e-CL at ∼10% (w/v) concentrations in dioxane, toluene, and heptane using butanol as an initiating species (monomer/butanol ratio= 147)gave poly(e-caprolactone) (PCL) with M n values (by GPC) of 313, 753, and 1600, respectively Monomer conversion to PCL for these polymerizations was 33, 55, and 100%, respectively M n measurements of PCL products by 1 H NMR end group analyses were slightly lower (by a factor of -09) than the values obtained by GPC Polymerizations conducted in heptane at 37, 45, 55, and 65°C showed the highest extent of monomer conversion at 65)C Therefore, subsequent studies were conducted at 65°C in heptane For a polymerization carried out with a 15/1 monomer/butanol ratio and -029 mmol of water, -70 and -100% of the monomer had been converted to PCL by reaction times of 24 and 96 h, respectively Polymer molecular weight increased slowly with conversion, suggesting that this is a chain polymerization with rapid initiation and slow propagation Increases in the e-CL/butanol ratio from 15/1 up to where no butanol was added showed only a modest increase in product molecular weight from 1600 to 2700 This was explained by the fact that the water present in polymerizations was active in chain initiation Variation in the monomer/butanol ratio at constant water concentration resulted in PCL chains with 0-065 mol fraction of butyl ester and 033-086 mol fraction of carboxylic acid chain end groups (by 1 H NMR analyses) The presence of water concentrations in polymerization reactions above that which is strongly enzyme bound is believed to be an important factor which limited the formation of PCL chains of significantly higher molecular weight

Lipase-Catalyzed Ring-Opening Polymerization of Trimethylene Carbonate†

Abstract: This work was directed at extending the use of lipase-catalyzed ring-opening polymerizations to cyclic carbonate monomers. Of the seven lipases screened for bulk trimethylene carbonate (TMC) polymerization (70 °C, 120 h), Novozym-435 from Candida antarctica gave almost quantitative monomer conversion (97%) and poly(TMC) with a Mn = 15 000 (Mw/Mn = 2.2) with no apparent decarboxylation during propagation. The lipases from Pseudomonas species (AK and PS-30) and porcine pancreas (PPL) also exhibited high monomer conversions (>80%, 120 h) but gave lower molecular weight polymers with broad polydispersity. Analyses by 1H-NMR spectroscopy suggested that poly(TMC) prepared by Novozym-435-catalyzed polymerization had terminal −CH2OH functionalities at both chain ends. A monotonic increase in monomer conversion with time and the rapid increase in Mn as a function of monomer conversion for Novozym-435-catalyzed TMC bulk polymerization at 70 °C suggest that the polymerization has chain-type propagation kinetics. An ...

Enzyme-Catalyzed Polymerizations of ε-Caprolactone: Effects of Initiator on Product Structure, Propagation Kinetics, and Mechanism

Abstract: Studies were undertaken to gain mechanistic information on lactone ring-opening polymerization reactions using porcine pancreatic lipase (PPL) as the catalyst and e-caprolactone (e-CL) as the monomer. Polymerizations were carried out at low water levels (0.13 mmol) and supplemented with either butanol or butylamine. Rates of monomer conversion, product molecular weight, total chain number, and chain end structure were determined by 1H NMR. In the presence of water alone, a maximum Mn of 7600 g/mol was obtained at 85% conversion, which decreased to 4200 g/mol as the reaction continued to 98% conversion. Reactions with butanol and butylamine at 100% conversion gave polymers with Mn values of 1900 and 1200 g/mol, respectively. For these three polymerizations, the total number of polymer chains increased with conversion due to a simultaneous increase in carboxylic acid chain ends. Within 4 h (∼26% monomer conversion), butylamine was completely consumed but only 37% of butanol reacted. Reactions with butylamin...

Enzyme-Catalyzed Stereoelective Ring-Opening Polymerization of α-Methyl-β-propiolactone

Abstract: The lipase-catalyzed stereoelective ring-opening polymerization of racemic α-methyl-β-propiolactone (MPL) was investigated. Using the lipase PS-30 from Pseudomonas fluorescens, a direct route to optically active (S)-enriched poly(α-methyl-β-propiolactone), PMPL, was demonstrated. From a comparative study of different organic media, polymerizations conducted in toluene and heptane proceeded more rapidly than those carried out in dioxane. The enantiomeric ratios E in toluene, heptane, and dioxane were 4.1 ± 0.2, 0.9, and 2.0, respectively. Thus, from the point of view of reaction rates and enantioselectivity, toluene was found to be the preferred solvent. PMPL products prepared in toluene by PS-30 catalysis had Mn values from 2600 to 2900 g/mol and [α]25D +12.2° to +19.0° (c 0.9 g/dL, CHCl3). Analysis of the polymer chain end structure by 1H and 13C NMR showed that these products have hydroxyl and carboxylic acid termini. Based on the analysis of chain stereosequence distributions by 13C NMR, it was conclud...

Synthesis of polycaprolactone: a review

Abstract: Polycaprolactone (PCL) is an important polymer due to its mechanical properties, miscibility with a large range of other polymers and biodegradability. Two main pathways to produce polycaprolactone have been described in the literature: the polycondensation of a hydroxycarboxylic acid: 6-hydroxyhexanoic acid, and the ring-opening polymerisation (ROP) of a lactone: e-caprolactone (e-CL). This critical review summarises the different conditions which have been described to synthesise PCL, and gives a broad overview of the different catalytic systems that were used (enzymatic, organic and metal catalyst systems). A surprising variety of catalytic systems have been studied, touching on virtually every section of the periodic table. A detailed list of reaction conditions and catalysts/initiators is given and reaction mechanisms are presented where known. Emphasis is put on the ROP pathway due to its prevalence in the literature and the superior polymer that is obtained. In addition, ineffective systems that have been tried to catalyse the production of PCL are included in the electronic supplementary information for completeness (141 references).

Polymer Synthesis by In Vitro Enzyme Catalysis

Abstract: In nature, living organisms are constantly producing different macromolecules for their metabolic needs. These macromolecules, such as polysaccharides, polynucleotides, proteins, or polyesters, are essential to organism survival. Their synthesis generally involves in vivo enzyme-catalyzed chaingrowth polymerization reactions of activated monomers, which are generally formed within the cells by complex metabolic processes. Because of their diversity and renewability, microbial polymers such as polysaccharides, bacterial polyhydroxyalkanoates (1) and polyanions such as poly(γ-glutamic acid) (2) have received increasing attention as candidates for industrial applications. In many cases, microorganisms carry out polymer syntheses that are impractical or impossible to accomplish with conventional chemistry. Thus, microbial catalysts enable the production of materials that might otherwise be unavailable. Microbial polymers are synthesized from renewable low-cost feedstocks, and the polymerizations operate under mild process conditions with minimal environmental impact. In addition, microbial polymers provide products that, when disposed, can degrade to nontoxic products.

Aliphatic Polyesters: Synthesis, Properties and Applications

Abstract: The synthesis of aliphatic polyesters by polycondensation and ring-opening polymerization is reviewed. This includes homopolyesters, random, block, graft, star, and hyper-branched (co)polyesters. Recent progress in the synthesis of high molecular weight aliphatic polyesters is described. Specific properties of these polymers are also given. The biomedical and ecological applications of these biodegradable polymers show their technological importance and relevance.

Enzymatic polymer synthesis: an opportunity for green polymer chemistry.

Abstract: Polymeric materials, natural and unnatural, are indispensable to the modern society. They are widely used from everyday life usages as commodity materials to industry and technology usages in the fields such as electronics, machinery, communications, transportations, pharmacy, and medicine as highly advanced materials. Today, it is hard to think of the present society without polymeric materials. Developments of various polymeric materials have been owed to epoch-making innovative works as exemplified typically by the discovery of Ziegler-Natta catalyst,1-3 the concept of living polymerization,4 the discovery of conducting polymers,5 and the discovery of metathesis catalyst.6,7 These observations demonstrate that new polymeric materials are often brought about by new production methods including polymerization catalysts. Historically, polymerization catalysts utilized classical catalysts of acids (Brønsted acids, Lewis acids, and various cations), bases (Lewis bases and various anions), and radical generating compounds since the 1920s, the early stage of polymer chemistry. In the following * To whom correspondence should be addressed. Fax/Tel: (+81)-75-7247688. E-mail: kobayash@kit.ac.jp. † Kyoto Institute of Technology and Emeritus Professor of Kyoto University. ‡ Kyoto University. Chem. Rev. 2009, 109, 5288–5353 5288