(45h) Compositionally Versatile Polymer Thin Films for pH-Responsive Properties and Metal Capture

Polymer thin films with versatile functionality are important in the modification of surfaces for applications in adhesion, lubrication, biocompatibility, corrosion protection, and extreme wettability. Among the techniques of preparation for polymer thin films, surface-initiated polymerization (SIP) is an approach that offers stable adhesion, high grafting density, advanced thickness control, independence of substrate geometric shape, and straightforward separation processes. Surface-initiated ring-opening metathesis polymerization (SiROMP) is one of the most powerful methods in polymer coating preparation due to its rapid kinetics, mild reaction conditions, and relatively high functional group tolerance. Here, we report the rapid preparation of poly(trans-5-norbornene-2,3-dicarbonyl chloride) (pNBDAC) by SiROMP from the vapor phase to produce polymer thin films with versatile acid chloride functionality throughout. The instability of the acyl chloride groups in the polymer make pNBDAC an excellent intermediate to obtain polymer films with many other functional groups via simple post-polymerization modification with a host of common reagents. We show that pNBDAC can react with water, alcohols, amines, and phenols to prepare polymer coatings with carboxylic acid, ester, amide and other functional groups to dramatically alter the interfacial and barrier properties of the films. Through these modifications, we have designed pH-responsive films with dramatic sensitivity to pH, as well as hydrophobic coatings that impede the transfer of water and ions. By modification of pNBDAC with hydroxyl amine, we have successfully prepared thin films that have hydroxamic acid functionality throughout. These pendant hydroxamic acids are able to chelate transition metal ions such as Fe²⁺, Fe³⁺, and Cu²⁺, which yields a tremendous change in the mechanical properties and stability of the film. We show that these chelating films can be loaded with metal ions even at solution concentrations of < 10 micromolar to yield an effective sensing and detection platform.