Ringed spherulite morphology and compatibility in the binary blends of poly(ε-caprolactone) with ethyl cellulose

Ringed spherulite morphology of poly(ε-caprolactone) (PCL) in PCL/ethyl cellulose (EC) blends has been observed by polarizing microscopy. When EC content was less than 40% the clear and regular ringed spherulites can form at crystallization temperatures around 313 K. Differential scanning calorimetry measurements showed the melting temperatures (Tm) and the thermal crystallization temperatures (Tc) of PCL in the blends decreased while the supercooling ΔT (ΔT=Tm0−Tc) increased comparing with those of pure PCL. Such results mean that PCL and EC are partially compatible. Fourier transform infrared measurements showed that the absorption bands of hydroxyl groups in EC shift to the lower frequencies when PCL content increases, and a specific interaction exists between the carbonyl groups of PCL and the hydroxyl groups. Just the existence of a specific interaction and partial compatibility between PCL and amorphous EC improved the formation of PCL ringed spherulites in the blends.