Polystyrene networks mobility

Macroporous and isoporous polystyrene supports have been used for onium ion catalysts in attempts to overcome intraparticle diffusional limitations on catalyst activity. A macroporous polymer may be defined as one which retains significant porosity in the dry state68-71 . The terms macroporous and macroreticular are synonomous in this review. Macroreticular is the term used by the Rohm and Haas Company to describe macroporous ion exchange resins and adsorbents 108). The terms microporous and gel have been used for cross-linked polymers which have no macropores. Both terms can be confusing. The micropores are the solvent-filled spaces between polymer chains in a swollen network. They have dimensions of one or a few molecular diameters. When swollen by solvent a macroporous polymer has both solvent-filled macropores and micropores created by the solvent within the network. A gel is defined as a solvent-swollen polymer network. It is a macroscopic solid, since it does not flow, and a microscopic liquid, since the solvent molecules and polymer chains are mobile within the network. Thus a solvent-swollen macroporous polymer is also microporous and is a gel. Non-macroporous is a better term for the polymers usually called microporous or gels. A sample of 200/400 mesh spherical non-macroporous polystyrene beads has a surface area of about 0.1 m2/g. Macroporous polystyrenes can have surface areas up to 1000 m2/g. 

The most rigid networks form when the polystyrene chains are crosslinked with tris-(chloromethyl)-mesitylene (CMM) [12], since one molecule of this compound connects in space with not two but three polystyrene chains at one junction point. Contrary to this, four subsequent methylene groups in the CMB molecule should strongly contribute to the conformational mobility of cross-bridges and the network as a whole. 

ABSTRACT - Fluorescence polarization and its application to orientation measurements of uniaxially stretched polymers are described. Results obtained on anthracene labelled polystyrene chains embedded in normal polystyrene and stretched at various temperatures and strain rates are presented and discussed. An improvement of the Doi-Edwards slip-link model is required to account for the results and a modified model is proposed. Finally, an illustration of fluorescence polarization measurements on mobile and oriented polyisoprene networks is shown. 

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