CRYSTALLINITY AND FUSION OF LOW-MOLECULAR WEIGHT ALPHA, OMEGA-ALKOXY-POLY (ETHYLENE-OXIDE) - OCTADECOXY TO TRIACONTANOXY END-GROUPS

Samples of α, ω-alkoxy-poly(ethylene oxide) with an average oxyethylene chain length of 45 units and with C18, C26, and C30 end-groups have been prepared and characterized. Several experimental methods have been used to investigate the crystalline structure and the melting behaviour of the solids produced by crystallization in the range Tc = 25° to 45°C. The oxyethylene chains crystallize in folded-chain conformation in all samples. The methylene chains also crystallize in samples with C26 (low Tc) and C30 end-groups. The extent of crystallinity is low in the solids in which both types of chain crystallize. The melting points of the oxyethylene lamelae increase markedly as the methylene chain length is increased. This is explained by the high free energy change on mixing oxyethylene and methylene chains when the solid is transformed to a random melt, especially as unlike segments are more effectively segregated in the layer structure of the solid when the methylene chain is long. © 1979.