Impact of polymer modulus/chain mobility on water accumulation at polymer/metal oxide interfaces

Moisture is known to accumulate at the interface between polymers and metal oxides, leading to detrimental effects on physical properties such as modulus and adhesion. Direct measurement of the interfacial moisture profile has been carried out with neutron reflectivity, while thickness dependent swelling of a thin film series has also been also utilized to indirectly assess the interfacial moisture content. In this work, the moisture adsorption on the clean surfaces is compared to that observed when the surface is coated with a series of polymer films. The mechanical properties of the polymer appear to impact the quantity of moisture adsorbed at the interface; surprisingly less moisture accumulates at the interface if the coating is rubbery (larger intrinsic mobility of polymer chains). For glassy polymers, the total accumulation at the interface is identical to the adsorption on the clean metal oxide surface. This result potentially provides an understanding of solvent distribution in glassy nanocomposites by measuring moisture adsorption onto the bare filler materials prior to incorporation into the polymer matrix.