The relationship between silane hydrolysis and polymer adhesion to glass as studied by 13C solid state NMR

Solid state¹³C-NMR has been used to follow the hydrolysis of ¹³C methoxy labeled phenylaminopropyltrimethoxysilane in a PVC thermoplastic polymer film as a function of polymer process history. The relative adhesion level of the polymer to glass was observed to increase with the in-situ hydrolysis of the silane as monitored by the disappearance of the ¹³C labeled methoxy group from the solid polymer matrix. Silane hydrolysis was found to depend on both the atmospheric conditioning of the polymer matrix (relative humidity), and its exposure to heat during processing. High levels of hydrolysis (90%) occurred only with a combination of heat and moisture. Variable contact time cross polarization experiments were also used to show that the methoxy groups existed in multiple spin environments, and that the total fraction of nuclei in solid-like environments increased with increasing hydrolysis (as measured from the ratio of cross polarization and single excitation intensities). These data collectively show that process history influences the degree of hydrolysis and the final state of the silane, both of which can influence macroscopic adhesion.