Abstract
A series of ten block copolymers of poly(isoprene:styrene) have been examined by osmometry over a range of temperatures. Several solvents were used; one was a good solvent for both sequences (toluene), another was a bad solvent for both sequences (methyl iso-butyl ketone) and another was a preferential solvent (cyclohexane) which is a good solvent for the polyisoprene sequence but a poor solvent for polystyrene. Flory (or theta) temperatures have been determined for all polymers in the three solvents; a comparison is made with values of θ determined by cloud point methods using methyl ethyl ketone as solvent. The interaction parameter χ 1 is separated into its enthalpic and entropic parts and examined in relation to composition and molecular weight. The molecular weight dependence of the second virial coefficient is also discussed. The inclusion of the composition parameter, in addition to those normally used for homopolymers in these systems, is not adequate for a complete description of solution properties of block copolymers, particularly in the case of preferential solvents where there is ample evidence for intramolecular phase separation.
Published Version
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