Surface Interaction Parameter Measurement of Solvated Polymers via Model End-Tethered Chains

We present a method
for the direct measurement of the relative
energy of interaction between a solvated polymer and a solid interface.
By tethering linear chains covalently to the surface, we ensured the
idealized and constant configuration of polymer molecules for measurement,
modeling, and parameter estimation. For the case of amine-terminated
polystyrene bound to a glycidoxy­propylsilane film submerged
in cyclohexane-d12, we estimated the χ
parameter for the temperature range 10.7–52.0 °C and found
a downward sloping trend that crosses the χ = 0.5 threshold
at 37–40 °C, in agreement with solution estimates for
the same system. We simultaneously estimated the surface interaction
parameter χs at each temperature, finding a decreasing
affinity of the chains for the surface with increasing temperature,
consistent with empirical observations. The theoretical model shows
some limitations in a stronger solvent (toluene-d8) that prevent rigorous parameter estimation, but we
demonstrate a qualitative change in χ and χs toward stronger solvency and weaker surface interaction with increasing
temperature.