Leveraging the water electrolysis reaction in bipolar electrophoresis to form robust and defectless chitosan films

Bo-Han Huang; Shih-Yuan Li; Tze-Ting Chiang; Pu-Wei Wu

doi:10.1016/j.carbpol.2020.116912

Leveraging the water electrolysis reaction in bipolar electrophoresis to form robust and defectless chitosan films

Carbohydr Polym. 2020 Dec 15:250:116912. doi: 10.1016/j.carbpol.2020.116912. Epub 2020 Aug 15.

Authors

Bo-Han Huang¹, Shih-Yuan Li¹, Tze-Ting Chiang¹, Pu-Wei Wu²

Affiliations

¹ Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan, ROC.
² Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan, ROC. Electronic address: ppwu@mail.nctu.edu.tw.

PMID: 33049832
DOI: 10.1016/j.carbpol.2020.116912

Abstract

Electrophoresis of chitosan and its composites are widely used to form a coating on selective substrates, but the parasitic water electrolysis causes structural defects that weaken the resulting film. In this work, we demonstrate a bipolar electrophoresis technique that leverages the water electrolysis to produce a chitosan film with less porosity and surface cavities. The process involves a negative bias to deposit the protonated chitosan molecules from the solution, followed by a positive bias to remove the entrapped hydrogen bubbles via the re-protonation of chitosan deposit. Since water electrolysis occurs for both positive and negative bias, the bipolar profile is designed to engender pH changeup near the electrode for "surface conditioning" of chitosan film. The bipolar electrophoresis route demonstrates better coulomb efficiency than that of conventional potentiostatic electrophoresis, resulting in a free-standing chitosan film with sufficient mechanical strength and large area.

Keywords: Bipolar pulses; Chitosan; Electrophoresis; Free-standing; Mechanical properties; Water electrolysis.