The apparent specific volume of polymers in dilute solution

Apparent specific volumes φ 2 of polymers in dilute solution (<5%) have been obtained with a magnetic float type densitometer for the following systems: polyvinyl acetate–chlorobenzene, polyisobutylene–benzene and –chlorobenzene, and polystyrene–chlorobenzene and –chloroform. Large variations of φ 2 with concentration in very dilute solution have been reported in the literature, but could not be detected; preliminary results did show a variation, but this was found to be a nonequilibrium effect. The difference between φ 2 and the specific volume of the pure polymeric liquid is found to be roughly proportional to the calorimetrically determined heat of mixing of polymer and solvent.