CRYSTALLIZATION OF ALCOHOL ETHOXYLATE DIBLOCK COPOLYMERS FROM BODY-CENTERED-CUBIC MICELLAR PHASES FORMED IN CONCENTRATED AQUEOUS-SOLUTIONS

Crystallization in concentrated aqueous solutions of the alcohol ethox ylate diblock copolymers C11E40, C15E39 and C17E40 (where C = methylen e or methyl and E = oxyethylene) has been investigated using small-ang le X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS) and rhe ology. It is shown that the gel phase formed in these materials has bo dy-centred cubic (bcc) symmetry, and that the bcc structure can be mac roscopically oriented by large amplitude oscillatory shear. At concent rations above about 55 wt.-% copolymer, crystallization of the poly(ox yethylene) block occurs at low temperatures, and the effect of crystal lization from the oriented bcc structure of a 70 wt.-% solution is exa mined using SAXS/WAXS. Crystallization induces a second phase separati on, i.e. the semicrystalline lamellar structure resulting from poly(ox yethylene)-block crystallization is incommensurate with the oriented b ce structure, with which it coexists at low temperatures. However, cry stallization produces an unoriented lamellar structure. WAXS indicates that the poly(oxyethylene) in the diblock copolymer crystallizes in i ts usual (helical) form.