Poly(ethylene glycol)-poly(epsilon-caprolactone) block oligomers as injectable materials

A family of segmented low MW poly(ethylene glycol)-poly(epsilon-caprolactone) (PEG-PCL) oligomers was synthesized by reacting PCL-based macrodiisocyanates and diblocks comprising MPEG and PCL short segments. The oligomers have the following general structure: MPEG350-(CL)n-HDI-PCL530-HDI-(CL)n-MPEG350. The composition of the oligomers and their molecular weight was determined by 1H and 13C-NMR, FT-IR and GPC. Depending on the length of the (CL)n block, soft waxes to hard solids were produced. The isothermal crystallization process was performed at various temperatures and investigated by DSC, FT-IR and WAXS, while the mechanical behavior was determined using a compression test. All the oligomers investigated were able to crystallize at low temperatures (4 and 25 °C), while at body temperature, only oligomers comprising longer (CL)n blocks (n=5 and above), were able to crystallize.