Enzyme Mediated Polymerization

A number of recent papers have explored enzyme-mediated polymerization. Monomers polymerized include MMA, S, AM and derivatives. The area has been 

One of the most used systems involves use of horseradish peroxidase, a (3-dikelone (most commonly 2,4-peniandione), and hydrogen peroxide. Since these enzymes contain iron(II), initiation may involve decomposition of hydrogen peroxide by a redox reaction with formation of hydroxy radicals. However, the proposed initiation mechanism involves a catalytic cycle with enzyme activation by hydrogen peroxide and oxidation of the 3-diketone to give a species which initiates polymerization. Some influence of the enzyme on tacticity and molecular 

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Further discussion on the effects of the reaction media and Lewis acids on lacticily appears in Section 7.2. Attempts to control laciicily by template polymerization and by enzyme mediated polymerization are described in Section 7.3. Devising effective means for achieving stereochemical control over propagation in radical polymerization remains an important challenge in the field. 

Perry et al. [56] found little or no catechins in 402 soil samples from eleven C. maculosa sites. These authors were less firm in their hypothesis that (-)-catechin plays a role in allelopathy. In fact, molecules such as catechins, catechol, and l-DOPA are quite unstable in soil, especially at high pH [57]. In a more recent paper [58] those who previously strongly supported an allelopathic role of (-)-catechin indicate that because of the instability of catechin in soil and its ability to form complexes in soil, it is extremely difficult to conclusively attribute allelopathic significance to catechins without improved methods. Tharayil et al. [5] found the presence ofphenohc acids in soil to increase the half life of ( )-catechin (50 50 racemic mixture). But, they also found ( )-catechin to polymerize in soil to form a procyanidin dimer that has a short soil half life. They found ( )-catechin to be essentially non-phytotoxic in their bioassays with both monocots and dicots, even though they observed the same root browning that Bais et al. [46] attributed to necrosis. Tharayil et al. [5] attributed the root browning to enzyme-mediated polymerization of catechin to brown polymers, rather than to necrosis. 

Abstract The in vitro enzyme-mediated polymerization of vinyl monomers is reviewed with a scope covering enzymatic polymerization of vitamin C functionalized vinyl monomers, styrene, derivatives of styrene, acrylates, and acrylamide in water and water-miscible cosolvents. Vitamin C functionalized polymers were synthesized via a two-step biocatalytic approach where vitamin C was first regioselectively coupled to vinyl monomers and then subsequently polymerized. The analysis of this enzymatic cascade approach to functionalized vinyl polymers showed that the vitamin C in polymeric form retained its antioxidant property. Kinetic and mechanistic studies revealed that a ternary system (horseradish peroxidase, H2O2, initiator fS-diketone) was required for efficient polymerization and that the initiator controls the characteristics of the polymer. The main attributes of enzymatic approaches to vinyl polymerization when compared with more traditional synthetic approaches include facile ambient reaction environments of temperature and pressure, aqueous conditions, and direct control of selectivity to generate functionalized materials as described for the ascorbic acid modified polymers. 

Ayyagari, M., Akkara, J. A., and Kaplan, D. L. (1996). Enzyme-Mediated Polymerization Reactions Peroxidase-Catalyzed Polyphenol Synthesis, Acta Polym., 47,193—203. 

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