Coil-globule transition of poly(methyl methacrylate) in isoamyl acetate

Abstract

The coil-globule transition was studied by static light scattering measurements on poly(methyl methacrylate) with the molecular weight [Formula Presented] and 4.4 in isoamyl acetate. Since the phase separation of the dilute solution occurred very slowly, the measurements could be made in the broad temperature range from near the Θ temperature 61 °C to 0 °C 30 min after a quench of the solution. The observed expansion factor [Formula Presented] for the radius of gyration was represented as a function only of [Formula Presented] and showed a constant value at large [Formula Presented] with τ being [Formula Presented] A quantitative comparison between a recent theory for a contracted coil and the data of [Formula Presented] revealed the coil-globule crossover phenomena. The behavior of plot of [Formula Presented] versus [Formula Presented] was distinctly different in the three ranges, i.e., coil range, globule range, and range of a constant α. The plot of the observed second virial coefficient [Formula Presented] against temperature yielded a minimum as predicted from a theory of [Formula Presented] below the Θ temperature. © 1997 The American Physical Society.