Abstract
AbstractThe unperturbed dimensions of block copolymers of polystyrene and polyisoprene in dilute solution have been determined from measurements made under theta conditions, by application of the FLORY‐FOX theory to viscosity data. In solvents, where theta temperatures preclude direct evaluation, the STOCKMAYER‐FIXMAN method has been applied. The results show that unperturbed dimension determined under theta conditions, whether measured directly or by appropriate extrapolation procedures, vary linearly with composition. Thus the characteristic ratio for the block copolymer may be calculated from homopolymer data according to the relation where x is the mole fraction and superscripts PS and PI refer to polystyrene and polyisoprene respectively. The steric factor σ = rr obeys a similar relation.Short range interaction parameters have also been determined by application of equations relating osmotic second virial coefficients with the excluded volume and which have been shown to be reasonably successful when applied to homopolymers. Data from viscosity and osmometry methods are compared and discussed.
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