Thermal properties of a new class of block copolymers based on segments of poly(D,L-lactic-glycolic acid) and poly(e-caprolactone)

The results of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic-mechanical thermal analysis (DMTA) investigations performed on a new class of multi-block copolymers based on poly(d,l-lactic-glycolic acid) (PLGA) and diol-terminated poly(ε-caprolactone) (PCDT) segments are reported. The synthesis and molecular weight characterisation of these materials, having a structure of poly(ester-carbonate)s, were described in a recent paper. In the present work the influence of the length of PCDT segments and of the molar ratio between the d,l-lactic acid (LA) and glycolic acid (GA) residues on thermal stability, degree of crystallinity and glass transition temperature (Tg) has been investigated. Materials completely amorphous or having variable degrees of crystallinity have been obtained modulating the above parameters. The TGA traces run under nitrogen atmosphere exhibit two degradation processes that can be ascribed to the PLGA and PCDT segments, respectively. In addition, the thermal-stability increases with the LA content in the PLGA blocks.