following data: Young’s modulus, 316 kgf/cm
2 ; tensile strength, 33.7 kgf/cm
2 ; and
elongation at break, 496.1%. These results suggest that the copolymers can be
applied for coatings, soft films, etc. [41, 42].
On the other hand, using BMA as comonomer the PLA-Graft copolymer (I)
(Macro, m ¼ 6.0) having M n ¼ 37,600 with biomass content of 53 wt% showed a
T g value of 27.0
C. The copolymer composition was in a molar ratio Macro:BMA
¼ 1.0:2.9. The copolymer sample was very hard and very brittle, as shown by
elongation at break of 101.3%. It is understandable from the monomer structure that
both the Macro and BMA have an α,α-disubstituted structure of CH 2 ¼CRR
0 and,
moreover, that the Macro contains a bulky PLA group of R¼CH 2 C(¼O)PLA. Thus,
the resulting copolymer should have a main chain with condensed packing,
resulting in non-flexible polymeric materials. Therefore, the copolymers from
BMA may find applications in hard plastic materials requiring a tough nature,
which can probably be accomplished via further crosslinking reactions. Graft
copolymers (I) and (II) possess a –CO 2 H group in the main chain and, hence,
they are derivative polymers of methacrylic acid. Their applications are also
conceivable in this direction.
2.2.2 Copolymer Approach
The other way to produce PLA-graft copolymers is shown as reactions (4) and (5) in
Scheme 2 [43]. First, IAn-BMA copolymer was prepared via radical copolymerization of IAn and BMA. IAn-BMA copolymers were obtained in good yields, with M n
reaching 1.1 Â 10
5 . The next step was grafting the PLA chain onto IAn-BMA
copolymer by Sn-catalyzed reaction of PLA to afford PLA-Graft copolymer (II)
according to reaction (5) in Scheme 2. In one case, the value of M n ¼ 5.76 Â 10
4
for IAn-BMA copolymer was increased slightly to 5.88 Â 10
4 after the grafting.
The grafting reaction is a polymer–polymer reaction, which is generally harder than
a polymer–monomer reaction and it is not easy to achieve a high conversion.
Therefore, some portions of the anhydride group of the main chain remained
unreacted. In this respect, the macromolecular approach seems more effective.
2.3 Comb Polymers via Macromonomer
Comb polymers are those having a graft chain at every repeating unit. Such copolymers
can be derived by homopolymerization of a macromonomer (Scheme 3) [41].
Some results of the radical homopolymerization of MMm are given in Table 2 [41].
Normally, the radical polymerization of macromonomers needs a large amount of
initiator and, hence, AIBN was employed at 10 mol%. But, regardless of the amount
(1 or 5 mol%), polymer yield was relatively high and M n was between 2.19 Â 10
4 and
9.00 Â 10
4 (M w was between 2.67 Â 10
4 and 11.0 Â 10
4
), showing a high molecular
weight of the product comb polymers.
148
S. Kobayashi
2 ; tensile strength, 33.7 kgf/cm
2 ; and
elongation at break, 496.1%. These results suggest that the copolymers can be
applied for coatings, soft films, etc. [41, 42].
On the other hand, using BMA as comonomer the PLA-Graft copolymer (I)
(Macro, m ¼ 6.0) having M n ¼ 37,600 with biomass content of 53 wt% showed a
T g value of 27.0
C. The copolymer composition was in a molar ratio Macro:BMA
¼ 1.0:2.9. The copolymer sample was very hard and very brittle, as shown by
elongation at break of 101.3%. It is understandable from the monomer structure that
both the Macro and BMA have an α,α-disubstituted structure of CH 2 ¼CRR
0 and,
moreover, that the Macro contains a bulky PLA group of R¼CH 2 C(¼O)PLA. Thus,
the resulting copolymer should have a main chain with condensed packing,
resulting in non-flexible polymeric materials. Therefore, the copolymers from
BMA may find applications in hard plastic materials requiring a tough nature,
which can probably be accomplished via further crosslinking reactions. Graft
copolymers (I) and (II) possess a –CO 2 H group in the main chain and, hence,
they are derivative polymers of methacrylic acid. Their applications are also
conceivable in this direction.
2.2.2 Copolymer Approach
The other way to produce PLA-graft copolymers is shown as reactions (4) and (5) in
Scheme 2 [43]. First, IAn-BMA copolymer was prepared via radical copolymerization of IAn and BMA. IAn-BMA copolymers were obtained in good yields, with M n
reaching 1.1 Â 10
5 . The next step was grafting the PLA chain onto IAn-BMA
copolymer by Sn-catalyzed reaction of PLA to afford PLA-Graft copolymer (II)
according to reaction (5) in Scheme 2. In one case, the value of M n ¼ 5.76 Â 10
4
for IAn-BMA copolymer was increased slightly to 5.88 Â 10
4 after the grafting.
The grafting reaction is a polymer–polymer reaction, which is generally harder than
a polymer–monomer reaction and it is not easy to achieve a high conversion.
Therefore, some portions of the anhydride group of the main chain remained
unreacted. In this respect, the macromolecular approach seems more effective.
2.3 Comb Polymers via Macromonomer
Comb polymers are those having a graft chain at every repeating unit. Such copolymers
can be derived by homopolymerization of a macromonomer (Scheme 3) [41].
Some results of the radical homopolymerization of MMm are given in Table 2 [41].
Normally, the radical polymerization of macromonomers needs a large amount of
initiator and, hence, AIBN was employed at 10 mol%. But, regardless of the amount
(1 or 5 mol%), polymer yield was relatively high and M n was between 2.19 Â 10
4 and
9.00 Â 10
4 (M w was between 2.67 Â 10
4 and 11.0 Â 10
4
), showing a high molecular
weight of the product comb polymers.
148
S. Kobayashi