(1) renewable biobased materials, (2) nontoxic, and (3) environmentally benign.
Green synthetic reactions involve (4) efficient catalytic reactions (not a molar
reaction), (5) selective reactions to minimize side-products, (6) reactions under
mild conditions at a lower temperature to save energy, and (7) reactions in a green
solvent like water. From this viewpoint, we have recently conducted green polymer
chemistry, e.g., synthesis of polyester-containing polymers by using biobased
renewable starting materials and employing nontoxic, environmentally benign
lipase enzyme as green catalyst. It should be mentioned that very recently “green
polymer chemistry” has become a well-known keyword [20, 24, 25]. In view of the
character of this special volume, the present review focuses mainly on our recent
results together with the developments of related studies.
2 Green Starting Materials: Biobased Renewable
Resources for Polymer Production
There are twelve important platform chemicals listed that are derived from biomass [26].
They include succinic acid, itaconic acid, and glycerol. Some other important
biobased renewable chemicals such as lactic acid and 1,4-butanediol are produced via
fermentation and/or chemo-enzymatic processes from various biomass sources like
corn, sugarcane, wheat, etc. These platform chemicals have been used as starting
materials for the production of polymers.
2.1 Lactic Acid-Derived Graft Copolymers Using
the Macromonomer Method
Aliphatic polyesters like poly(ε-caprolactone), poly(butylene succinate), and poly
(hydroxyalkanoate)s are widely used. An aromatic polyester of poly(ethylene
terephthalate) is much more utilized practically. Poly(lactic acid) (PLA) is an
aliphatic polyester and has recently attracted major attention. So far, PLA has
been a leading polymer produced from biobased resources. High molecular weight
PLA is already produced in various ways and used as a green plastic for electronic
products, automobile parts, and in biomedical applications [27–40].
PLA has a drawback in its properties, however, which is due to breaking of the
PLA chain through ester bond hydrolysis. Until now, various efforts have been
made to decrease the bond breaking damage but so far it has been very difficult to
suppress the hydrolysis completely. A possible solution to mitigate the damage is
not to use PLA as a main chain, but to employ PLA as side chains. Figure 1
illustrates the concept [41].
The macromonomer technique is a practical and convenient method for preparing graft copolymers. So far, PLA has been prepared mainly via two ways:
ring-opening polymerization (ROP) of lactide (a six-membered cyclic dimer of
Green Polymer Chemistry: Recent Developments
143
Green synthetic reactions involve (4) efficient catalytic reactions (not a molar
reaction), (5) selective reactions to minimize side-products, (6) reactions under
mild conditions at a lower temperature to save energy, and (7) reactions in a green
solvent like water. From this viewpoint, we have recently conducted green polymer
chemistry, e.g., synthesis of polyester-containing polymers by using biobased
renewable starting materials and employing nontoxic, environmentally benign
lipase enzyme as green catalyst. It should be mentioned that very recently “green
polymer chemistry” has become a well-known keyword [20, 24, 25]. In view of the
character of this special volume, the present review focuses mainly on our recent
results together with the developments of related studies.
2 Green Starting Materials: Biobased Renewable
Resources for Polymer Production
There are twelve important platform chemicals listed that are derived from biomass [26].
They include succinic acid, itaconic acid, and glycerol. Some other important
biobased renewable chemicals such as lactic acid and 1,4-butanediol are produced via
fermentation and/or chemo-enzymatic processes from various biomass sources like
corn, sugarcane, wheat, etc. These platform chemicals have been used as starting
materials for the production of polymers.
2.1 Lactic Acid-Derived Graft Copolymers Using
the Macromonomer Method
Aliphatic polyesters like poly(ε-caprolactone), poly(butylene succinate), and poly
(hydroxyalkanoate)s are widely used. An aromatic polyester of poly(ethylene
terephthalate) is much more utilized practically. Poly(lactic acid) (PLA) is an
aliphatic polyester and has recently attracted major attention. So far, PLA has
been a leading polymer produced from biobased resources. High molecular weight
PLA is already produced in various ways and used as a green plastic for electronic
products, automobile parts, and in biomedical applications [27–40].
PLA has a drawback in its properties, however, which is due to breaking of the
PLA chain through ester bond hydrolysis. Until now, various efforts have been
made to decrease the bond breaking damage but so far it has been very difficult to
suppress the hydrolysis completely. A possible solution to mitigate the damage is
not to use PLA as a main chain, but to employ PLA as side chains. Figure 1
illustrates the concept [41].
The macromonomer technique is a practical and convenient method for preparing graft copolymers. So far, PLA has been prepared mainly via two ways:
ring-opening polymerization (ROP) of lactide (a six-membered cyclic dimer of
Green Polymer Chemistry: Recent Developments
143