title: QCM studies of gel spreading: Kraton gels on polystyrene surfaces.
abstract: Contact of a polymer gel made from a styrene/ethylene-butene/styrene triblock copolymer in mineral oil was investigated by bringing the gel into contact with the coated surface of a quartz crystal microbalance (QCM). The experimental apparatus enabled simultaneous measurement of the load, displacement, and contact area, in addition to the resonant frequency and dissipation of the oscillating quartz crystal. The QCM response was determined by the linear viscoelastic properties of the gel at the frequency of oscillation. A geometric correction factor involving the contact area provided a means for quantitatively determining these viscoelastic parameters as the gel spread over the QCM surface. When the gel was removed from the surface, a thin solvent layer was left behind. The thickness of this solvent layer was determined from the QCM response and was compared to predictions from a simple model involving the disjoining pressure of the film and the osmotic pressure of the gel. Qualitative agreement with the model required that tensile, adhesive forces at the perimeter of the gel/QCM contact area were taken into account when calculating the film thickness.
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, USA.
authors.forename: F Nelson
authors.initials: FN
authors.lastname: Nunalee
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Shull
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004548:Elasticity; D005030:Ethylenes / Q000737:chemistry; D005782:Gels; D011137:Polystyrenes / Q000737:chemistry*; D012997:Solvents; D013499:Surface Properties
chemical_list: D005030:Ethylenes; D005782:Gels; D011137:Polystyrenes; D012997:Solvents; C036216:ethylene