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Biobased polymers: synthesis of graft copolymers and comb polymers using lactic acid macromonomer and properties of the product polymers.

Biomacromolecules (2012-09-19)
Kiyoaki Ishimoto, Maho Arimoto, Tomoya Okuda, Syuhei Yamaguchi, Yuji Aso, Hitomi Ohara, Shiro Kobayashi, Masahiko Ishii, Koji Morita, Hirofumi Yamashita, Naoya Yabuuchi
ABSTRACT

For developing broader application of biobased polymers, graft copolymers and comb polymers having poly(lactic acid) (PLA) side chains have been synthesized by using a macromonomer technique. PLA macromonomers (MMm) having a methacryloyl polymerizable group with different PLA chain length with an average length m = 4, 6, 8, 12, 18, and 30 were prepared via ring-opening polymerization of l-lactide using hydroxyethyl methacrylate (HEMA) initiator catalyzed by Sn(Oct)(2). Radical polymerization behaviors of these macromonomers were examined. Radical copolymerization of MMm (m = 4, 6, and 8), with vinyl monomers like n-butyl methacrylate (BMA) and n-butyl acrylate (BA) in water as the reaction medium, gave stable miniemulsions of poly[n-butyl (meth)acrylate-graft-lactic acid]s [PB(M)A-g-PLAm]. MMm with m value higher than 12, however, gave aggregate products in a minor amount besides miniemulsions in a major amount, producing not a stable emulsion system of graft copolymers. The solution copolymerization, on the other hand, produced a wider variety of the graft copolymers, where a wider range of MMm (even m ≥ 12) can be employed. In a 1,4-dioxane solution, the radical copolymerization of MMm with BMA and methyl methacrylate (MMA) gave various graft copolymers [PB(M)MA-g-PLAm]. A new type of comb polymers (PMMm) having PLAm as pendant side chains were obtained by radical homopolymerization of MMm in a 1,4-dioxane solution. The graft copolymers and comb polymers obtained here are amorphous. Physical properties of the polymers from miniemulsions suggested them to be applicable for coatings or elastic materials which are environmentally desirable as a new class of biobased polymers. In addition, the present approach provided fundamental information on relationships between the length of PLA side chain and the bulk properties of the product polymers.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
1,4-Dioxane, anhydrous, 99.8%
Sigma-Aldrich
Butyl acrylate, ≥99%, contains 10-60 ppm monomethyl ether hydroquinone as inhibitor
Sigma-Aldrich
1,4-Dioxane, ACS reagent, ≥99.0%
Sigma-Aldrich
1,4-Dioxane, suitable for HPLC, ≥99.5%
Supelco
1,4-Dioxane, analytical standard
Sigma-Aldrich
1,4-Dioxane, ReagentPlus®, ≥99%
Supelco
1,4-Dioxane solution, certified reference material, 2000 μg/mL in methanol, ampule of 1 mL
Supelco
Butyl acrylate, analytical standard
Sigma-Aldrich
1,4-Dioxane, ACS reagent, ≥99.0%
Sigma-Aldrich
1,4-Dioxane, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥99.5% (GC)
Sigma-Aldrich
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D)
Supelco
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), NMR tube size 5 mm × 8 in.
Sigma-Aldrich
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), chromium(III) acetylacetonate 5 mg/mL, NMR tube size 5 mm × 8 in.
Sigma-Aldrich
1,4-Dioxane solution, NMR reference standard, 10 mM in D2O ("100%", 99.96 atom % D), NMR tube size 5 mm × 7 in.
Sigma-Aldrich
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), NMR tube size 10 mm × 8 in.
Supelco
1,4-Dioxane solution, NMR reference standard, 5 mM in chloroform-d (99.8 atom % D), NMR tube size 3 mm × 8 in.
Supelco
1,4-Dioxane solution, NMR reference standard, 5 mM in benzene-d6 (99.6 atom % D), NMR tube size 3 mm × 8 in.
Sigma-Aldrich
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), chromium(III) acetylacetonate 5 mg/mL, NMR tube size 3 mm × 8 in.
Supelco
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), NMR tube size 3 mm × 8 in.