Organic solgel synthesis of microporous molecular networks containing spirobifluorene and tetraphenylmethane nodes

Abstract

The microporous molecular networks based on rigid tetrafunctional units are synthesized via organic solgel polymerization of 2,2,7,7-tetraamino-9,9-spirobifluorene (TASBF) and/or tetrakis(4-aminophenyl)methane (TAPM) with a diisocyanate, hexamethylene diisocyanate (HDI), or p-phenylene diisocyanate. This study is performed as an extension of our previous report on the first organic solgel method, which enabled the synthesis of microporous molecular networks via a two-stage mechanism involving the formation of colloidal dispersions of the nanoparticulate molecular networks and their subsequent growth to monolithic networks on solvent evaporation. The solgel-synthesized molecular networks obtained by incorporating TASBF as a network former show improved porosity, processability, and thermal stability than the TAPM-based system. The improved porosity of TASBF-based networks is attributed to higher rigidity of the spirobifluorene compared with the tetraphenylmethane units. We also demonstrate the synthesis of mixed organic molecular networks by solgel copolymerization of the two network formers, TASBF and TAPM, and a diisocyanate monomer. The solgel transformation of TASBF/TAPM/HDI occurred at longer reaction times with increasing the amount of TASBF in the TASBF/TAPM/HDI mixture. The results indicate that the organic solgel method can be further optimized by adjusting various synthesis parameters to create new functional organic molecular network materials. (c) 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013. 51, 1758-1766