AVS 50th International Symposium
    Biomaterial Interfaces Monday Sessions
       Session BI-MoA

Paper BI-MoA4
Use of QCM-D to Analyze Thin Polymer Films at Interfaces

Monday, November 3, 2003, 3:00 pm, Room 307

Session: Non-fouling Surfaces and Biolubrication
Presenter: E.F. Irwin, University of California, Berkeley
Authors: E.F. Irwin, University of California, Berkeley
J Ho, University of California, Berkeley
K.E. Healy, University of California, Berkeley
Correspondent: Click to Email
An interpenetrating polymer network (IPN) of acrylamide (AAm) and poly(ethylene glycol) (pEG) was designed that can be covalently bound directly onto metal oxide and polymer surfaces via photoinitiated free radical polymerization. A p(AAm-co-EG) with acrylic acid (AA) was also designed to allow further functionalization of the IPN surface with a diamino pEG spacer arm (pEG-NH@sub 2@).@footnote 1@ In this study, we are employing a quartz crystal microbalance with dissipation (QCM-D) (qsense) to monitor the IPN swelling and protein adsorption behavior in phosphate buffered saline (PBS), pH 7.4. QCM-D crystals coated with SiO@sub 2@ and TiO@sub 2@/Ti were modified with IPNs of p(AAm-co-EG), p(AAm-co-EG/AA), and p(AAm-co-EG/AA) + pEG-NH@sub 2@. The Sauerbrey relationship was used to calculate a thickness of 48nm for a dry film of p(AAm-co-EG/AA). QCM-D thickness data can be compared to a dry IPN thickness of 17nm determined previously by spectroscopic ellipsometry.@footnote 1@ A Kelvin-Voight model of viscoelasticity was used to interpret frequency and dissipation data of the hydrated films over the swelling period. Modeling the swelling data of a p(AAm-co-EG/AAc) IPN gave an initial hydrated thickness of 101nm (after 2 minutes) and a final swollen thickness of 150nm. The shear modulus of the film ranged from 285 to 365kPa and the viscosity ranged from 6.7E-3 to 8.6E-3kg/ms according to the model. One limitation of this model is that one single density of the IPN surface is assumed (in this case a density of 1.1g/cm@super 3@) over the entire swelling period. These IPN surfaces minimize the adsorption of the protein fibrinogen that has a role in thrombosis. The QCM-D provides unique and complementary information to other surface analytical techniques (i.e. AFM, XPS) for understanding the behavior of thin polymer films at interfaces. @FootnoteText@ @footnote 1@ Bearinger, JP, et al., J. Biomat. Sci. Polym. Ed., 9 (7) 1998.