macromonomer was radically copolymerized with BMA, n-butyl acrylate (BA),
MMA, and ethyl methacrylate (EMA) to efficiently give graft copolymers
[PLA-Graft copolymer (I)] with M n up to 1.61 Â 10
5 and a biomass content higher
than 34 wt%. Second, the copolymer approach employed first IAn as comonomer
for radical copolymerization with BMA, giving rise to IAn-BMA copolymer with
M n higher than 5.76 Â 10
4 . Then, Sn-catalyzed grafting of PLA onto the IAn
moiety of the copolymer produced PLA-Graft copolymer (II) with M n higher than
5.88 Â 10
4 and a biomass content !29 wt%.
By using these two approaches employing IAn as a starting reactive material,
PLA-graft copolymers were obtained as biomass plastics. The properties of
PLA-Graft copolymers (I) were also examined, which revealed possible
applications for coatings and plastics. Furthermore, the IAn-containing graft
copolymers are a convenient starting biomass polymer, having a reactive IAn
moiety in the main chain for further grafting or various functional groupintroducing reactions.
2.2.1 Macromonomer Approach
IAn was employed for the first time to prepare an IAn-PLA macromonomer
by utilizing the reactive nature of IAn with ring-opening. The macromonomer
(IAn-PLA Macro) was prepared via a one-pot two-stage method [reactions
(1) and (2) in Scheme 2]. IAn is an unsymmetrical anhydride, and the structure of
IAn-PLA Macro given in reaction (2) was the major product, at around 90%. By
varying the feed ratio of BuOH and L-lactide, it was possible to tune m values
(m ¼ 5, 6 and 12). The reaction yields were almost quantitative and the functionality of IAn-PLA Macro was realized at ~100% in all cases.
Radical copolymerization of IAn-PLA Macro with a vinyl monomer yielded
PLA-Graft copolymer (I) according to reaction (3) in Scheme 2. Copolymerization
using BMA as comonomer by AIBN initiator gave PLA-Graft copolymer (I) in high
yields in bulk or in toluene, with M n , up to 1.1 Â 10
5 . In 1,4-dioxane, lower
copolymer yields with lower molecular weight were obtained. Both IAn-PLA
Macro and BMA are of methacryloyl-type structure; the former showed a little
less radical copolymerization reactivity toward BMA. The biomass content of
PLA-Graft copolymers was in the range of 34–70 wt%, indicating the biomass
plastic nature of the graft copolymers.
Likewise, radical copolymerization of IAn-PLA Macro (I) with other three vinyl
monomers (BA, MMA, and EMA) produced PLA-Graft copolymers (I) as shown in
reaction (3) of Scheme 2. All these product copolymers are biomass plastics
(biomass content 46–75 wt%).
Regarding the graft copolymer properties, a PLA-Graft copolymer (I) sample
(Macro, m ¼ 6.0) derived from BA typically gave a transparent film by casting
from a chloroform solution. The sample had a molar ratio Macro:BA ¼ 1.0:2.4,
was of high molecular weight (M n ¼ 161,000), had a T g value of 11.2
, and a high
biomass content of 59 wt%. It showed a very good elastic property, as shown by the
Green Polymer Chemistry: Recent Developments
147
MMA, and ethyl methacrylate (EMA) to efficiently give graft copolymers
[PLA-Graft copolymer (I)] with M n up to 1.61 Â 10
5 and a biomass content higher
than 34 wt%. Second, the copolymer approach employed first IAn as comonomer
for radical copolymerization with BMA, giving rise to IAn-BMA copolymer with
M n higher than 5.76 Â 10
4 . Then, Sn-catalyzed grafting of PLA onto the IAn
moiety of the copolymer produced PLA-Graft copolymer (II) with M n higher than
5.88 Â 10
4 and a biomass content !29 wt%.
By using these two approaches employing IAn as a starting reactive material,
PLA-graft copolymers were obtained as biomass plastics. The properties of
PLA-Graft copolymers (I) were also examined, which revealed possible
applications for coatings and plastics. Furthermore, the IAn-containing graft
copolymers are a convenient starting biomass polymer, having a reactive IAn
moiety in the main chain for further grafting or various functional groupintroducing reactions.
2.2.1 Macromonomer Approach
IAn was employed for the first time to prepare an IAn-PLA macromonomer
by utilizing the reactive nature of IAn with ring-opening. The macromonomer
(IAn-PLA Macro) was prepared via a one-pot two-stage method [reactions
(1) and (2) in Scheme 2]. IAn is an unsymmetrical anhydride, and the structure of
IAn-PLA Macro given in reaction (2) was the major product, at around 90%. By
varying the feed ratio of BuOH and L-lactide, it was possible to tune m values
(m ¼ 5, 6 and 12). The reaction yields were almost quantitative and the functionality of IAn-PLA Macro was realized at ~100% in all cases.
Radical copolymerization of IAn-PLA Macro with a vinyl monomer yielded
PLA-Graft copolymer (I) according to reaction (3) in Scheme 2. Copolymerization
using BMA as comonomer by AIBN initiator gave PLA-Graft copolymer (I) in high
yields in bulk or in toluene, with M n , up to 1.1 Â 10
5 . In 1,4-dioxane, lower
copolymer yields with lower molecular weight were obtained. Both IAn-PLA
Macro and BMA are of methacryloyl-type structure; the former showed a little
less radical copolymerization reactivity toward BMA. The biomass content of
PLA-Graft copolymers was in the range of 34–70 wt%, indicating the biomass
plastic nature of the graft copolymers.
Likewise, radical copolymerization of IAn-PLA Macro (I) with other three vinyl
monomers (BA, MMA, and EMA) produced PLA-Graft copolymers (I) as shown in
reaction (3) of Scheme 2. All these product copolymers are biomass plastics
(biomass content 46–75 wt%).
Regarding the graft copolymer properties, a PLA-Graft copolymer (I) sample
(Macro, m ¼ 6.0) derived from BA typically gave a transparent film by casting
from a chloroform solution. The sample had a molar ratio Macro:BA ¼ 1.0:2.4,
was of high molecular weight (M n ¼ 161,000), had a T g value of 11.2
, and a high
biomass content of 59 wt%. It showed a very good elastic property, as shown by the
Green Polymer Chemistry: Recent Developments
147