Studies on polymer solutions, gels and grafted layers using the quartz crystal microbalance technique

The oscillation behaviour of a piezoelectric crystal in contact with polymer solutions and the crystal grafted with polymer ‘brushes’ in contact with solvents was studied. It was found that currently used theories of the piezoelectric crystal oscillation cannot be applied for viscoelastic media; the discrepancies between experimental and theoretical values increase with an increase in the concentration and the molecular weight of polymers and the degree of cross-linking. The quartz crystal microbalance (QCM) technique seems to be an extremely sensitive experimental technique to study viscoelastic properties of the parts of polymer molecules which have relaxation times comparable with the reverse fundamental frequency of the QCM. Graft polymerization onto the gold electrodes modified with self-assembled monolayers of organosulfide and trichlorosilane surfactant showed that the QCM technique is also sensitive to properties of the polymer ‘brushes’, such as density of the grafted polymer chains, thickness of the grafted layer, and to their behaviour in various solvents.