The hydrolytic degradation ofa series of poly-L-lactide (PLLA)-polyisobutylene (PIB) multiblock copolymerswas studied in phosphate buffer solution (pH = 7.4) at 37 �C.The multiblock copolymers were synthesized by chain extension of PLLA-b-PIB-b-PLLA triblock copolymers, which were obtained by ring-openingpolymerization of L-lactide initiated by hydroxyallyl telechelic PIB. Thedegradation strongly depended on the PLLA segment length. At constant PIBsegment length the multiblock copolymer with the shortest PLLA segment length(Mn = 700 g/mol) showed significant weight loss after 8 weeks,whereas copolymers with longest PLLA segment length (Mn = 2600g/mol) showed no weight loss up to 24 weeks. GPC analysis showed a decrease inthe number average molecular weight with time further supporting the weightloss data. A decrease in ultimate tensile stress and modulus with time wasobserved, the extent of which was dependent on the PLLA segment length.Differential scanning calorimetric analysis revealed additional meltingendotherms and changes in crystallinity with degradation time.

Hydrolytic degradation of polyisobutylene and poly-lactide based multiblock copolymers

240th National Meeting (2010)

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