Synthesis of reactive and stimuli-responsive polymer thin films by initiated chemical vapor deposition and their sensor applications

摘要

Stimuli-responsive polymer thin films provide the ability to control the interaction of a surface with its environment. Synthetic techniques with fine compositional control are required to engineer specific responses to stimuli. Initiated chemical vapor deposition (iCVD) is a novel vacuum deposition technique in which polymer films are synthesized bottom-up as monomer and initiator vapors are introduced into a vacuum coating chamber. iCVD can conformally coat nanoscale, three-dimensional geometries with a high level of compositional control. Such coating capabilities are difficult by solution-based film synthesis techniques, and compositional control is difficult by other CVD techniques. In this thesis work, the synthesis and application of stimuli-responsive and reactive polymer thin films by iCVD have been studied. First, functionally versatile alternating copolymers of poly(styrene-alt-maleic anhydride) were synthesized. This was the first demonstration of alternating copolymer synthesis by CVD. Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and 13C NMR characterization verified that well-defined alternating structure was present, as predicted from standard solution phase polymerizations. Next, polymer crosslinking was tuned in the synthesis of pH-responsive hydrogel thin films composed of poly(maleic anhydride-co-dimethylacrylamide-co-di(ethylene glycol) divinyl ether). These films had swelling ratios, defined as the thickness in the water-swollen state over the thickness in the dry state, in excess of 11. These films were employed as ultrathin permeable, size-selective skin layers in composite membranes.