 Solution

Taking the printed reference to part(iii) literally, measure an equilibrium water contact angle with a calibrated sessile-drop goniometer on a smooth homogeneous surface. With independently constrained interfacial tensions, test ${\gamma }_{SV}-{\gamma }_{SL}={\gamma }_{LV}\cos {\theta }_C$. Advancing and receding measurements reveal pinning and hysteresis; contact angle alone cannot independently determine both unknown solid-interface energies.

If the intended reference was instead the polymer-size prediction in the preceding part, use static light scattering or small-angle neutron scattering at both temperatures on appropriately dilute solutions. At small scattering wave number $q$, the Guinier approximationgives $R_g$ from the slope of $\ln I$ against $q^2$. Control concentration, aggregation and scattering contrast, and compare the extracted radii. Dynamic light scattering normally measures a hydrodynamic size rather than directly the same radius of gyration. Answering both readings avoids silently correcting the printed cross-reference.