Lyotropic Mesophases of Poly(ethylene oxide)-b-poly(butadiene) Diblock Copolymers and Their Cross-Linking To Generate Ordered Gels

Abstract

This study reports the lyotropic phase behavior of two poly(ethylene oxide)-b-poly(butadiene) diblock copolymers and their cross-linking in the mesophase under retention of the mesoscopic order. The lyotropic phase behavior in water was characterized by polarized light microscopy and small-angle X-ray scattering (SAXS) in the concentration range from 0 to 100 wt % and in a temperature range between 20 and 100 °C. Depending on polymer composition and concentration micellar, hexagonal, lamellar, and cubic phases are found. Their ranges as well as pronounced coexisting phase regions were determined. Several of these mesophases were cross-linked via γ-irradiation to form mesostructured hydrogels. It is shown that the cross-linked polymer gel essentially maintains the parental lyotropic order, as proven by SAXS, polarized light microscopy, and transmission electron microscopy (TEM). TEM enables imaging of the polymer gel structure and thereby the visualization of the liquid-crystalline mesophase morphologies in themselves. The lyotropic mesophases as well as the lyotropic gels were used as templates for the synthesis of mesoporous silica, which is expected to give a negative solid copy of the ordered soft matter structure. The influence of the different templates on the silica structure formation is discussed.

Block Copolymer Assemblies as Templates for the Generation of Mesoporous Inorganic Materials and Crystalline Films

“…[11] An unusual case is shown in Figure 4, where a branched lamellar phase is replicated and compared with the original phase. The two TEM images show the original lyotropic phase (Figure 4, A) and the templated, porous silica (Figure 4, B), and it is nicely seen that one is the "negative" of the other.…”

Porous materials via nanocasting procedures: innovative materials and learning about soft-matter organization

“…6). 58 The solid silica imprint had the inverted structure of the organic template, but the template structure was not affected by the casting process itself, as seen by the direct relationship. Because of these advantages, a whole variety of amphiphilic block copolymers has been used.…”

“…22 The approach of imprinting molecules (molecular imprinting) on all It can be seen that the pore system ('inverse matter') has exactly the size and shape expected under the assumption of a 1+1 transformation process. 58 The term nanocasting is justified. sorts of networks is now widely in use also for polymeric materials.…”

Amphiphilic single and double networks: a small-angle X-ray scattering investigation

“…This is the subject of the present work, where we focus on the structural characterization of the first APCN and the corresponding DN gels with SAXS. SAXS has been used to study the mesoscopic structures of amphiphilic hydrogels [2,7,25], as an alternative to small-angle neutron scattering (SANS) [9, 22-24, 28, 29].…”