ABSTRACTA sample of propargyl dehydroabietic ester grafted to α-azide substituted poly(ϵ-caprolactone) (PCL-g-DAPE) in THF was characterized at 24°C, 30°C, 40°C, 50°C by a combination of on-line measurement of intrinsic viscosity, refractive index and two-angle light scattering in a size exclusion chromatograph. The weight average molecular weight (w), intrinsic viscosity ([η]), hydrodynamic radius (RH), and concentration of the polymer fractions were obtained from corresponding traces of the chromatograms. The data were used to construct double logarithmic plots of w versus [η], and w versus RH, as well as Stockmayer-Fixman plots, to scale the intrinsic viscosity, hydrodynamic radii and dimensions of the PCL-g-DAPE chains to molar mass. The results indicated that PCL-g-DAPE was more rigid than the parent PCL; however, PCL-g-DAPE can be classified as a flexible-coil polymer, similar to poly(methyl acrylate). The PCL-g-DAPE stiffness was related to the chemical structure of the bulky side chains that induced preferential conformation correlations of the polymer backbones in solution. The PCL-g-DAPE –THF system behaved as a lower critical consolute solution system with highest miscibility around 30°C, judged based on the slope of double logarithmic plots of molecular weight and intrinsic viscosity. Moreover, a transition in the conformation of the PCL-g-DAPE in THF at 30°C was observed.