ABSTRACT
Figure 5.2 Representative chemical reactions to link the maltooligosaccharide to polymer backbones or polymerizable groups.
In the research field of the synthetic polymer chemistry, polystyrene and its derivatives are the most representative synthetic polymers because of some unique properties that make them useful in a wide range of products [11]. The commercial success of polystyrene is due to transparency, ease of fabrication, thermal stability, relative high modulus, and low cost. Hybridization between polystyrene and amylose is a promising research topic from the viewpoints of not only preparation of new hybrid materials but also fusion of two symbolic polymers in both synthetic and natural polymer chemistries. However, it may be difficult to hybridize the polystyrene and amylose by blend method of these two polymers because of the immiscibility of these polymeric chains caused by quite different polarities. Therefore, the chemoenzymatic method according to the following reaction manners was investigated to provide such a polystyrene-amylose hybrid material, i.e., an amylose-grafted polystyrene. The amylose-grafted polystyrene was prepared by two different approaches from a styrene-type macromonomer having a maltooligosaccharide chain, which was obtained by the reaction of a Glc5 lactone with 4-vinylbenzylamine (Fig. 5.3) [12,13]. In route I, the phosphorylase-catalyzed enzymatic polymerization of Glc-1-P from the macromonomer was first performed to give a styrene-type macromonomer having an amylose chain. The radical polymerization of the product gave the desired amylose-grafted polystyrene. This is indicated as the synthetic route (ii)→(v)→(vii) in Fig. 5.1. In route II, however, the radical polymerization of the macromonomer having a maltooligosaccharide chain was first carried out, followed by the phosphorylase-catalyzed enzymatic polymerization, giving rise to the amylose-grafted polystyrene. This is explained as the synthetic route (ii)→(iv)→(vi) in Fig. 5.1. Every repeating unit in the produced polystyrene derivative by route I has the amylose chains, whereas the amylose chains are probably present partially in the repeating units of the polystyrene derivative obtained by route II because of the probable occurrence of the enzymatic polymerization from a part of the maltooligosaccharide primers on the polystyrene main chain due to steric hindrance in the latter case.
