Biology Reference
In-Depth Information
5.3
Chemoenzymatic Synthesis of Amylose-
Grated Polystyrene
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 Glc
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)
5
→
→
(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)
(v)
→
→
(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.
(iv)
