Dilute solutions of poly(methyl methacrylate) (PMMA) in a mixed solvent (r-butyl alcohol (TBA), containing 2.5 vol% water) were studied by static and dynamic light scattering at temperatures below the Θ-temperature. The temperature-dependence of the second virial coefficient A 2 with a minimum and a maximum below the Θ-temperature was compared with curves calculated based on different theoretical models. The collapse process of PMMA chains due to the coil-globule transition was measured by static and dynamic light scattering; after the temperature jump below the Θtemperature, both the mean-square radius of gyration and the hydrodynamic radius of PMMA chains continued to decrease for several days, and the ratio ρ of the radius of gyration to the hydrodynamic radius decreased from 1.4 to 0.87, indicating a conformational change from a random coil to a globular state. In order to measure the chain expansion process from globule to coil by static light scattering, dilute solutions of PMMA were quenched below the Θ-temperature and preserved at the temperature for a time period Θ, followed by a temperature jump to Θ. The radius of gyration of PMMA was measured as a function of time after the temperature rise and its value reached unity in several hours. Furthermore, the chain expansion was shown to become slower with increasing t w.
All Science Journal Classification (ASJC) codes
- Polymers and Plastics
- Environmental Science(all)
- Materials Science (miscellaneous)
- Chemical Engineering (miscellaneous)