POLY 381-Advanced amorphous porous polymer networks:understanding molecular level structure and dynamics using solid-state NMR

2 /g. Likewise, "polymers of intrinsic microporosity" (PIMs) are rigid, contorted polymers which display permanent microporosity. Neither approach, however, has demonstrated systematic control over micropore size distribution by varying the structure of the monomers. Recently we have used several synthetic approaches for the preparation of microporous polymeric frameworks - for example, polyynes, poly(phenylenev inylene)s, poly(phenylene butadiynylene)s and hypercrosslinked polymers. These materials exhibit large surface area and the possibility of tuning pore size by synthesis. However, the frameworks are amorphous and their structural characterization at molecular level is therefore challenging. Solid-state NMR is the method of choice for such materials. Relying on short-range magnetic interactions, this method can yield information on molecular level connectivities even for solids with very limited long-range ordering. Moreover, dynamic properties of amorphous networks can be correlated to their host-guest properties. We have assessed several types of porous polymeric frameworks. The combination of NMR information with molecular simulations has enabled us to construct structural models of these networks consistent with their textural properties and explaining the location of gaseous guests in the structure (e.g., H2). Results and Discussion Porous poly(aryleneethynylene) networks have been synthesised using palladium-catalyzed Sonogashira-Hagihara cross-coupling chemistry, 1 as exploited previously in the preparation of polymers, molecular wires, shape- persistent macrocycles, and ligands for coordination polymer synthesis. Each network is based on a 1,3,5-substituted benzene node connected by rigid phenyleneethynylene struts. 2 For example, network CMP-1 consists of 1,3,5- substituted benzene nodes connected by struts containing one phenylene moiety and two ethynylene groups. A series of three networks, CMP-1, CMP- 2, and CMP-3, was synthesized, each possessing two ethynyl groups per strut while the number of phenylene moieties in the linker increases from one (CMP-1) to three (CMP-3). The networks were observed to precipitate from solution during polymerization as brown-coloured powders which were totally insoluble in all solvents tested. The materials exhibited high thermal stability (decomposition temperature >400 °C) and were chemically stable, for example, to acids and bases.