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.