Raman structural analysis of lactide and ε-caprolactone linear oligomers and their blends

We present the Raman study of linear oligomers of L-lactide (L-OLA), D,L-lactide (D,L-OLA) and ε-caprolactone (OCL) with the degree of polymerization (DP) varied in the range of 10-100, and their blends. Two Raman methods, which were suggested earlier by our group for neat polylactide (PLA) and copolymers of L-lactide (L-LA) and ε-caprolactone (CL), were extended to analyze the oligomers and their blends. The Raman method of evaluating the crystallinity degree was proven for use for the L-OLA, while Raman method of evaluation of composition of the copolymers was extended to use for blends of the OLA and OCL and blends of PLA and poly(ε-caprolactone) (PCL). For the case of our way of synthesis, the ratios of intensities of the bands of 1,12-dodecanediol (co-initiator of the synthesis) and the bands of OLA can be used as a measure of the DP of the oligomers of up to 40-50. The obtained results can be very useful in development and testing of novel materials for 3D printing, targeted drug delivery systems and tissue-engineering constructions.