<title>Time-resolved SAXS/WAXS study of polymer blend crystallization</title>

Abstract

Time-resolved SAXS and SAXS/WAXS experiments were exploited to monitor the development of lamellar microstructure and crystallinity in neat poly(ethylene oxide) (PEO) and its blends with melt-miscible amorphous poly(methyl methacrylate) (PMMA). The low-molecular-weight fractions of PEO (Mw 3000) and of PMMA (Mw 1170, 3100, 3950) were used. Such PEO fraction crystallizes in the lamellae with extended (EC) or integrally folded (IF) chains. It has been found that in early stages of crystallization, transient NIF lamellae of PEO were formed in a wide range of compositions and temperatures similarly to the situation in neat PEO. Subsequent transformation of these lamellae into the lamellae with once-folded chains (1F) or EC occurred through isothermal thickening and thinning. The amorphous diluent has played a decisive role in structure development. The thickening prevailed in blends with high contents and high molecular weight of PMMA and at high crystallization temperature, the induction time of crystal formation increased, whereas the rates of NIF, 1F and EC crystallization and at the start and rate of the NIF structure recrystallization decreased. The retardation effect of amorphous diluent on the kinetics of these processes resulted in tendency to form gradually more stable and more perfectly ordered lamellar structures.