Confined Nucleation and Crystallization Kinetics in Lamellar Crystalline-Amorphous Diblock Copolymer Poly(ε-caprolactone)-b-poly(4-vinylpyridine)

The nucleation and crystallization kinetics of lamellar crystallineamorphous diblock copolymer poly(e-caprolactone)-b-poly(4-vinylpyridine) (PCLP4VP) was investigated by ultrafast differential scanning calorimetry (UFDSC) with temperature scanning rates up to 10 000 K/s and compared with that of poly(e-caprolactone) (PCL) homopolymer. We found that the critical cooling rate (ccr) to get the fully amorphous PCL is 1 order of magnitude slower than that for PCL homopolymer with the similar molecular weight. Isothermal nucleation and crystallization of PCL block in the PCL-P4VP copolymer and PCL homopolymer were studied covering times from 10(-2) to 10(-3) s and temperatures from 200 K (10 K below the glass transition temperature of PCL) to 300 K (about 40 K below the equilibrium melt temperature of PCL). It was found that the PCL block in PCL-P4VP copolymer experienced a slower homogeneous nucleation rate as well as crystallization rate than PCL homopolymer, indicating that even the local nucleation events of PCL chains is affected by the long-range glassy P4VP in copolymer. The confinement also hinders the long-range diffusion of PCL chains and becomes more effective once the chains get the mobility from the glassy state at crystallization temperatures above the T-g. Another effect of the confinement is the lower Avrami index in copolymer than that in homopolymer attributed to the restricted growth dimension under confinement. The results reported here might enhance the understanding of confinement effect on crystallization and give new details on the nucleation kinetics under nanoscale confinement.