Lyotropic mesophases of poly(ethylene oxide)-b-poly(butadiene) diblock copolymers and their cross-linking to generate ordered gels

This study reports the lyotropic phase behavior of two poly(ethylene oxide) -b-poly(butadiene) diblock copolymers and their cross-linking in the mesoph ase under retention of the mesoscopic order. The lyotropic phase behavior i n water was characterized by polarized light microscopy and small-angle X-r ay scattering (SAXS) in the concentration range from 0 to 100 wt % and in a temperature range between 20 and 100 degrees C. Depending on polymer compo sition and concentration micellar, hexagonal, lamellar, and cubic phases ar e found. Their ranges as well as pronounced coexisting phase regions were d etermined. Several of these mesophases were cross-linked via gamma-irradiat ion to form mesostructured hydrogels. It is shown that the cross-linked pol ymer gel essentially maintains the parental lyotropic order, as proven by S AXS, polarized light microscopy, and transmission electron microscopy (TEM) . TEM enables imaging of the polymer gel structure and thereby the visualiz ation of the Liquid-crystalline mesophase morphologies in themselves. The l yotropic mesophases as well as the lyotropic gels were used as templates fo r the synthesis of mesoporous silica, which is expected to give a negative solid copy of the ordered soft matter structure. The influence of the diffe rent templates on the silica structure formation is discussed.