SAXS and DSC studies of the crystallization and melting phenomena of poly(epsilon-caprolactone)

Abstract

The relationships between the crystallization temperature, T,, the crystal thickness, d(c) and the melting peak temperature, T-m of poly(epsilon -caprolactone)have been determined by carrying out time- and temperature-dependent small angle x-ray scattering experiments. A two-step melting has been suggested, resulting in the occurrence of two well defined independent boundary lines, indicating the transformation from melt into the partially crystalline state. For crystallization temperatures lower than 40 degreesC, during heating, more pronounced peak shifts are observed with the final melting of the crystallites having the same thickness of d(c) approximate to 7 nm. In this region, it is evident that crystals have relatively good stabilities, since they have fairly uniform thickness. At higher temperatures, above 40 degreesC, T-m increases with T-c, together with the thickness. The transformation of the melt into the partially crystalline state depicts a two-step process, beginning with the formation of a well defined initial structure with lower order, which is subsequently stabilized.