Nanoporous Thermosets with Percolating Pores from Block Polymers Chemically Fixed above the Order–Disorder Transition

Abstract

A lamellar diblock polymer combining a cross-linkable segment with a chemically etchable segment was cross-linked above its order–disorder temperature (TODT) to kinetically trap the morphology associated with the fluctuating disordered state. After removal of the etchable block, evaluation of the resulting porous thermoset allows for an unprecedented experimental characterization of the trapped disordered phase. Through a combination of small-angle X-ray scattering, nitrogen sorption, scanning electron microscopy, and electron tomography experiments we demonstrate that the nanoporous structure exhibits a narrow pore size distribution and a high surface to volume ratio and is bicontinuous over a large sample area. Together with the processability of the polymeric starting material, the proposed system combines attractive attributes for many advanced applications. In particular, it was used to design new composite membranes for the ultrafiltration of water.

Mechanical and Structural Consequences of Associative Dynamic Cross-Linking in Acrylic Diblock Copolymers

“…Lightly cross-linked block copolymer networks re-assemble into organized morphologies upon cooling or solvent removal, but over a critical cross-link density, the networks are trapped in a disordered or disordered-like state. [73][74][75][76] Dynamic cross-links can also interfere with long-range order;…”

Block Copolymer Membranes

“…Crosslinking strategies would be important to secure solvent resistance. Crosslinking examples have been reported [108][109][110] for membrane systems requiring block etching for pore formation and for microgels. [111] Pyrolysis of block copolymer films [112,113] could be extended to membranes.…”

Network Model of the Disordered Phase in Symmetric Diblock Copolymer Melts

“…Within the experimentally relevant range of molecular weights, however, both experiments and simulations have shown that the ordered and disordered phases are both rather strongly segregated near the ODT, and contain nearly pure domains of A and B monomers [3][4][5]. In this regime, the disordered phase near the ODT appears to have a disordered bicontinuous network structure qualitatively similar to that of the bicontinuous microemulsion phase of some ternary systems [3,[6][7][8]. To describe this regime, one should use a theoretical approach that can describe strongly segregated structures.…”