Coil–globule transition of poly(methyl methacrylate) by intrinsic viscosity

The coil–globule transition for poly(methyl methacrylate) has been studied in the mixed solvent tert-butyl alcohol+water system. Two polymeric samples having molecular weights Mw=2.55×106 and Mw=4.73×106 were used. The contraction and expansion of the molecular chains were determined by viscometric measurements. The results were compared with light scattering data obtained recently for the same system. A smooth and continuous contraction was observed below the θ temperature (41.5 °C). The temperature dependence of [η] can be represented by a master curve in αη3|τ|Mw1/2 vs |τ|Mw1/2 plot, where αη3=[η(T)]/[η(θ)] is a viscosity expansion factor and τ=(T−θ)/T is the reduced temperature. A comparison of the observed globular radius with a theory for contracted coil confirmed the coil–globule transition for this system.