Hypercrosslinked polystyrene network

BASIC PRINCIPLES OF FORMATION OF HYPERCROSSLINKED POLYSTYRENE NETWORKS... 

Preparation of Macronet Isoporous and Hypercrosslinked Polystyrene Networks... 

The following fundamental principles constitute the concept of hypercrosslinked polystyrene network formation. 

Synthesis conditions of macronet isoporous and hypercrosslinked polystyrene networks... 

Linear polymers are well known to dissolve only in solvents exhibiting strong affinity to the polymers, and traditional three-dimensional polymers can also swell with only such kind of media. Contrary to this rule hypercrosslinked polystyrene networks swell both with thermodynamically good solvents, such as toluene or methylene dichloride, and with typical precipitating media for linear polystyrene, such as methanol or -hexane (Fig. 7.5, Tables 7.1 and 7.2) [129-131]. 

The outstanding ability of hypercrosslinked polystyrene networks to increase several times their volume on contacting the dry polymer with non-solvents is a logical consequence of the main principle of network formation. The polymers have been obtained through the fixation of favorable unstressed chain conformations of the initially highly solvated polystyrene coils, by introducing numerous rigid crossHnks between them. 

The smaller values of the equilibrium swelling of hypercrosslinked hydro-phobic networks in water, as compared to organic solvents, arise from the disadvantageousness of replacing the strong interactions between water molecules in bulk liquid by extremely weak water-polystyrene dispersive interactions, if water would be placed into the numerous nano-sized compartments within the polystyrene network. Still, according to Fig. 7.8, even water does solvate the hypercrosslinked polystyrene network to a certain extent, causing an up to twofold expansion of the latter compared to its dry state. Naturally the internal strains of the dry network partially relax on this expansion. 

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