Microporous hyper-cross-linked polyacetylene networks: Covalent structure and texture modification by reversible Schiff-base chemistry
Abstract
We present controlled de-cross-linking and detemplating for modifying the porosity and covalent structure of porous organic polymers. HCΞC-C6H4-CH=N-C6H4-N=CH-C6H4-CΞCH and HCΞC-C6H4-N=CH-C6H4-CH=N-C6H4-CΞCH monomers (-C6H4- is meta- and para-phenylene) having two polymerizable ethynyl groups and two hydrolysable azomethine groups per molecule were copolymerized with 4,4-diethynylbiphenyl and tetrakis (4-ethynylphenyl)methane into porous polyacetylene-type hyper-cross-linked networks.
Two types of cross-links were involved in cross-linking: hydrolysable Schiff-base-type cross-links and stable non-hydrolysable cross-links. Postpolymerization hydrolysis caused cleavage of the azomethine groups and release of phenylenediamine or diformylbenzene template segments from the Schiff-base-type cross-links.
Although hydrolysis resulted in partial de-cross-linking, stable cross-links remaining in the networks prevented the collapse of the porous texture. Partial de-cross-linking led to an increase in the micropore diameter and, moreover, -HC = O or -NH2 groups were introduced into the networks in this way.
Modified networks decorated with above groups acted as chemisorbents for trapping aldehydes or primary amines under formation of azomethine links between the network and adsorptive.