Swollen state polymer chain motion

Birr 156) finds that the reactions on supports like 1 % cross-linked polystyrene in suitable solvents are not strictly solid-phase reactions, even if the particles look solid. Under these loosely cross-linked conditions, the polymer exists in a quasi-dissolved gel state, and the reactivity of the chain molecule is not considerably reduced in any way by the gel character. The free motion of the large chain segments in the swollen state of the macromolecular gel phase — which is only very lightly cross-linked just to give macroscopic insolubility — guarantees reactivity which is not much different from the corresponding linear, soluble macromolecule. 

Polymer networks are conveniently characterized in the elastomeric state, which is exhibited at temperatures above the glass-to-rubber transition temperature T. In this state, the large ensemble of configurations accessible to flexible chain molecules by Brownian motion is very amenable to statistical mechanical analysis. Polymers with relatively high values of such as polystyrene or elastin are generally studied in the swollen state to lower their values of to below the temperature of investigation. It is also advantageous to study network behavior in the swollen state since this facilitates the approach to elastic equilibrium, which is required for application of rubber elasticity theories based on statistical thermodynamics. ... 

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