Hydrolases in Polymer Chemistry: Chemoenzymatic Approaches to Polymeric Materials - Enzymatic Polymerisation - page 84

transesterification leads to a mixture of functional (meth)acrylate monomers, which
can be polymerized by free-radical polymerization without further workup to yield
multifunctional poly(meth)acrylates.

2.3 Block Copolymers

Enzymatic polymerization has been combined with various chemical polymeriza-
tions for the synthesis of block copolymers. The choice of chemical polymerization
generally depends on the applied strategy for the block copolymer synthesis. These
can be divided into three main approaches, as shown in Fig. 4 for the example of en-
zymatic ROP. It has to be noted that some of these strategies have also been applied
for enzymatic polycondensations.
Initial reports on chemoenzymatic block copolymer synthesis focus on the enzy-
matic macroinitiation from chemically obtained hydroxy-functional polymers (route
AinFig. 4 ) . The first report on enzymatic macroinitiation was published by Kumar
et al., who used anionically synthesized hydroxy-functional polybutadiene of vari-
ous molecular weights ranging from 2600 to 19,000 Da (Fig. 5 ) [ 16 ] . In a systematic
study, the authors investigated the efficiency of the macroinitiation of CL and PDL
by Novozym 435 as a function of the polybutadiene macroinitiator. The reaction
profile showed that polybutadiene consumption steadily increased with the reaction

O

O

a

OH

OH

chemical

enzymatic

O

b

R-OH

X-COOR

O

X

R OH R X R

enzymatic

chemical

O

c

X-OH

O

X OH X

enzymatic HO

chemical

O

OH
O
O

Cl Cl

O

O OH O

X-OH:

HO Br

O

HO Cl

O

Br

Br

ATRP-1 ATRP-2 ATRP-3 ATRP-4

S

N

O OH SH

S S HO

OH

NMP-1 RAFT-1 FRP-1

X-COOR:

O

O

Br

Cl

Br

Cl

Cl

ATRP-5

ATRP-6

Fig. 4 Chemoenzymatic strategies ( a-c ) for the synthesis of block copolymers employing enzy-
matic ROP and radical polymerization techniques