Swelling cross-linked polymeric network

Studied. A cross-linked polymeric network was prepared in the presence of a given amount of diluent. When the gelation reaction was complete, the gel sample was transferred to a cell containing an excess of solvent. The cell was placed onto the stage of a profile projector. As the gel swelled to its equilibrium concentration, its size was recorded photographically. This method allowed an accurate measurement of the time evolution of the gel size during the swelling process. 

As mentioned earlier, the discrete microgels are colloidal stable cross-linked polymeric networks on the nanometre to micrometre size scale. The de-swelling process of microgels is controlled by diffusion, where the rate of the collapsing of the macromolecule is correlated to the dimensions of the pores in the polymeric matrix. 

Polymer-supported Wittig reagents were first prepared more than 20 years ago [32]. It has been shown that the success of the reaction depends strongly upon (i) the preparation of the reagent by bromination and phosphination of cross-linked polystyrene rather than by co-polymerization using styryldi-phenyl phosphine, and (ii) the generation of the phosphorane with a base/ solvent system that swells the phosphonium sites in the polymer network (Scheme 6) [33]. Thus, bromination of polystyrene 1 yielded phenyl bromide 32, and this was followed by phosphination with n-butyUithium and chlor-odiphenylphosphine or with Hthium diphenylphosphide to give 33, a compound which is commercially available (Scheme 6). 

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