Temperature Dependence of the Surface and Volume Hydrophilicity of Hydrophilic Polymer Brushes

• DOI: 10.1021/acs.langmuir.6b00448
• Publication Date: 2016-03-22T20:54:50Z
• Authors: Pengyu Zhuang; Ali Dirani; Karine Glinel; Alain M. Jonas
• Keywords: Quartz Crystal Microbalance; Atom-transfer radical-polymerization; Ellipsometry

The temperature-dependence of the volume and surface hydrophilicity a series water-swollen dense polymer brushes is measured by contact angle measurements in captive bubble configuration, ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D). Thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) poly(di(methoxyethoxy)ethyl methacrylate) (PMEO2MA), strongly hydrophilic poly(N,N-dimethylacrylamide) (PDMA) poly(oligo(ethylene glycol) (POEGMA), weakly poly(2-hydroxyethyl (PHEMA) were synthesized surface-initiated atom-transfer radical polymerization (SI-ATRP). Conditions leading to reproducible are first provided, giving access hydrophilicity. Volume quantified measuring swelling brushes, either QCM-D or ellipsometry. A model-free methodology proposed analyze data. Comparison between acoustic optical coefficients shows that sensitive maximal thickness swollen while ellipsometry provides an integral thickness. Diagrams versus finally lead identify two types behavior: exhibit progressive decrease temperature, changes moderately; have close-to-constant hydrophilicity, decreases temperature. abruptly switch from one behavior other, do not abrupt change across their collapse transition contrarily common erroneous belief. In general, there no direct correlation because properties dependent on details conformation composition at surface, whereas averaged over finite region within brush.