Preparation of Uniaxially Aligned Nanoporous Polymer Films via Photopolymerization Using Self-Assembling Molecular Templates

Abstract

The phase structures of hydrogen-bonded benzene-1,3,5-tricarboxamide (BTA) derivatives in divinylbenzene (DVB) solutions were examined together with the template effects of these derivatives during photopolymerization to make nanoporous polymers. BTA derivatives with linear or branched alkyl chains were found to form hydrogen-bonded supramolecular chains, solid crystalline nanofibers, or mesophase aggregates in DVB. These self-assembled structures caused the DVB/BTA molecular composites to adopt viscous liquid, nematic columnar liquid crystal, or physical gel states. The photopolymerization of DVB in homogeneous mixtures containing hydrogen-bonded supramolecular BTA chains resulted in macro-phase separation of the photo-cross-linked DVB and the BTA derivatives. In contrast, hydrogen-bonded crystalline BTA derivatives or mesophase nanofiber aggregates of these derivatives dispersed in DVB functioned as templates to produce nanoporous polymers after removal of the derivatives. A mesomorphic mixture exhibiting a structural transition from a homogeneous nematic columnar liquid crystal to a heterogeneous gel state enabled the preparation of uniaxially aligned nanoporous polymers. Horizontally- and vertically aligned nanoporous films were synthesized through shear-induced and electric-field-induced alignment of a nematic columnar phase. The use of self-assembled molecular additives provides a potential approach to controlling the nanostructures and improving the optical and electrical properties and functionalities of conventional polymeric materials and composites.