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Synthesis and characterization of multiblock copolymers poly[poly( L ‐lactide)‐ block ‐polydimethylsiloxane]
Author(s) -
Bachari Abdelkrim,
Bélorgey Georges,
Hélary Gérard,
Sauvet Georges
Publication year - 1995
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1995.021960130
Subject(s) - polymer chemistry , lactide , copolymer , hydrosilylation , polydimethylsiloxane , cationic polymerization , ring opening polymerization , polymerization , materials science , bifunctional , ethylene glycol , thermoplastic elastomer , condensation polymer , telechelic polymer , chemistry , end group , polymer , catalysis , organic chemistry
The preparation of multiblock copolymers poly[poly( L ‐lactide)‐ block ‐polydimethylsiloxane] by polycondensation of bifunctional oligomers via hydrosilylation is described. The procedure consists first to synthesize the two bifunctional oligomers α,ω‐disilyl‐polydimethylsiloxane and α,ω‐diallyl‐poly( L ‐lactide). The former is prepared in one step by cationic polymerization of octamethylcyclotetrasiloxane in the presence of 1,1,3,3‐tetramethyldisiloxane as end‐blocker. Two steps are necessary to prepare α,ω‐diallyl‐poly( L ‐lactide). The first one is the polymerization of L‐lactide initiated by the system ethylene glycol/tin 2‐ethylhexanoate. In a second step, the hydroxyl end‐groups of the resulting α,ω‐dihydroxy‐poly( L ‐lactide) are transformed, by reaction with allyl isocyanate, into terminal allylic functions. Different multiblock copolymers were prepared by hydrosilylation (catalyzed by hexachloroplatinic acid) using the same α,ω‐diallyl‐poly( L ‐lactide) (M̄ n = 2000 g · mol −1 ) and various α,ω‐disilyl‐polydimethylsiloxanes (M̄ n from 1 750 to 9 000 g · mol −1 ). The influence of parameters such as temperature, stoichiometry of reactive end‐groups and catalyst concentration on the molecular weight of the copolymers was studied. High molecular weight copolymers were obtained (DP n > 12 by SEC). In addition to the biodegradability of the lactic acid units, the immiscibility of the polydimethylsiloxane and poly( L ‐lactide) blocks imparts thermoplastic elastomer properties to these copolymers. The crystallinity of the poly( L ‐lactide) phase is dependent on the molecular weight of the polydimethylsiloxane blocks.