Atomic force microscopy studies of hydration of fluorinated amide/urethane copolymer film surfaces

A poly(amide urethane) block copolymer has been studied using atomic force microscopy and infrared spectroscopy to examine the effects on the surface of immersion underwater. A film initially prepared in air and annealed above the glass transition temperature undergoes significant surface morphology change upon immersion, with noteworthy formation of surface particles. The particles are compliant and reduce surface friction probed by atomic force microscopy. The pH dependence of the force of adhesion of the atomic force microscope tip to the polymer is examined and found to vary with surface morphology and with tip functionality. Double layer forces as well as tip-induced extensions of the polymeric particle are identified. The infrared measurements indicate that both hydrophobic and hydrophilic blocks are partially hydrated within minutes and undergo further hydration on longer time scales, up to days.