Polymer drying. VII. 1H-NMR studies of evaporation from liquid saturated poly(styrene-co-divinylbenzene)

Composition-studies were carried out in which samples of films composed of poly(styrene-co-divinylbenzene) particles enmeshed by poly(tetrafluoroethylene) fibers were saturated with dichloromethane and then allowed to evaporate at 23°C to virtual dryness as the ¹H-NMR signals and residual weight of sorbed liquid were monitored. The correlations, of ¹H-NMR line-widths with the corresponding log of the number, α_t of residual sorbed molecules per monomer unit show that sharp changes occur as α_t passes through α_G the composition that exists when all the liquid not sorbed (i.e., not present within the liquid-saturated particles), has been eliminated, and again as α_t passes through α_g the composition that exists when the particles attain the rigidity characteristic of the glassy state. Correlation of the corresponding T₁ relaxation times with log α_t show that sharp changes occur when α_t becomes equal first to α′_s and then to α′_g the compositions that exist respectively when, firstly, all the sorbed liquid not immobilized by adsorption to the polymer chains within the particles has been eliminated, and then when the desorption of immobilized liquid from the chains causes the composition to begin to undergo transition from its rubbery state to its glassy state.