The preparation of stimuli-responsive aminomethyl functionalized poly(p-xylylene) coatings by chemical vapor deposition polymerization is reported. Modification of the paracyclophane precursor with ionizable aminomethyl groups leads to polymer coatings with pH-responsive swelling properties. The swelling behavior is monitored in situ using spectroscopic ellipsometry and additional streaming potential measurements are performed. With decreasing pH-value, the coating becomes increasingly charged and reversibly swells to several times its dry thickness. The swelling ratio is sensitive to the ionic strength of the solution. By using a mixture of unfunctionalized and functionalized precursors in the chemical vapor deposition process, the number of charges in the polymer layer can be tuned and with it the swelling ratio of the coating. As a proof-of-concept for possible applications, a commercial paper filter is coated. This results in a pH-dependent wetting behavior and pH-dependent transport through the capillaries of the paper. (Figure presented.).
Bibliographical noteFunding Information:
The authors acknowledge funding from the Helmholtz Association within the BioInterfaces Program of the KIT. The K-Alpha+ instrument was financially supported by the Federal Ministry of Economics and Technology on the basis of a decision by the German Bundestag. The authors thank the Institute of Nanotechnology at KIT for use of the SEM. C.H., L.B., and J.L. thank the German Science Foundation (DFG) for financial support within the frame of the collaborative research center SFB 1176 (Project B3). J.L. and R.K. acknowledge support from the Defense Threat Reduction Agency (DTRA) through Grant HDTRA1-12-1- 0039 as a part of the interfacial dynamics and reactivity program. J.L. and R.K. are also grateful to the Army Research Office (ARO) for funding provided under Grant W911NF-11-1-0251.
- chemical vapor deposition polymerization
- hydrogel coatings
- responsive coatings