| Abstract: | Real-time SAXS and WAXS patterns have been simultaneously obtained during isothermal melt-crystallization of blends of low-molecular-weight poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA). The analysis of results shows that the originally homogeneous, single-phase polymer blend separates into two phases. The PMMA molecules diffuse from the blend and form completely segregated regions while PEO starts to crystallize. The first and dominating effect at the beginning of crystallization is the formation of unstable lamellae of nonintegrally folded chains (NIF). The real-time crystallinity and density of the PEO crystalline phase in absolute units were obtained from the time-resolved SAXS/WAXS results. The structure development proceeds in two steps. A very fast evolution of PEO crystals from the melt starts to crystallize in disordered NIF lamellae with thick amorphous interlayers and with a lower density of crystalline phase. The steep growth of crystallinity and crystalline density mean quick thickening of crystalline part of lamellae and improvement of their crystalline structure. In the second step, the structure of the crystalline phase gradually improves and crystallinity grows very slowly. The recrystallization of NIF lamellae into extended chain lamellae (EC) and lamellae with once folded chains (1F) proceeds during both stages of crystallization. |
