Synthesis and cellular compatibility of multi-block biodegradable poly(ε-caprolactone)-based polyurethanes

A library of block copolymers was synthesized by varying the molecular weight of the poly(epsilon-caprolactone) (PCL)-diol soft segment (M-w = 850, 3050, 3700 or 7000), which was reacted with methylene diphenyl diisocyanate (MDI), 1,4-phenylene diisocyanate (PDI), 1,1'-methylenebis(4-isocyanatocyclohexane) (HMDI), or 2,4-toluene diisocyanate (TDI) with 1,4-butanediol (BD) or ethylene glycol (EG) added as chain extenders. Thermal and X-ray measurements indicated that the crystalline structure of the copolymers was largely dependent on the chain length of the PCL-diol, with no crystallization taking place with the smallest diol (M-w = 850) using MDI, TDI or HMDI. However, the copolymers produced from a PCL-diol (M-w = 850) and PDI and chain extenders (BD or EG) showed resolved crystalline peaks while no peaks appeared with other diisocyanates. Hydrolytic degradation studies demonstrated a faster degradation rate in the case of more amorphous copolymers than semi-crystalline copolymers. The cellular compatibility of the copolymers was evaluated by fabricating the entire library of polymers in a microarray format and in vitro cell culture, demonstrating that all the 57 copolymers supported cellular attachment and growth.