Collapse of a single polystyrene chain in dioctyl phthalate: Effect of molecular weight

The use of a viscous solvent (dioctyl phthalate) made possible an investigation of the whole coil-globule transition of polystyrene chains in dilute solution. For values of the reduced temperature variable τ√M lower than - 230 the globular polymer region was observed in which the radius R and the molecular weight M are related by R ~ M1/3. The range of the Θ region where the expansion factor α is a linear function of τ√M was determined as -50 < τ√M < 50. It was shown that within the whole temperature range investigated the expansion factor is a universal function of the variable τ√M. The polymer dimensions at the Θ temperature are higher by some 15% in this solvent than in cyclohexane; also, the width of the transition region is much larger.