Synthesis and Characterization of Fluorinated Chitosan Polymers

Fluorinated methacrylamide chitosan (MACF) and methacrylamide chitosan were synthesized (Fig. 1) and characterized as previously described.^{25 (link), 38 (link)} Briefly, to prepare MACF first 3 wt% chitosan (ChitoClear 43010, Primex, Siglufjordur, Iceland) was dissolved in 2 vol% acetic acid:water. Fluorinated groups were added to chitosan by adding 0.14 M pentadecafluorooctanoyl chloride (Sigma-Aldrich, Saint Louis, MO, USA). Next, the resulting polymer was modified with methacrylic anhydride (Sigma-Aldrich) to add methacrylate groups to the polymer to create MACF. For purification, MACF or MAC solutions were placed in dialysis membranes (12,000–14,000 Da MW cut-off; Spectra/Por, Spectrum Labs, Rancho Dominguez, CA, USA) and dialyzed against deionized water for 3 d with 3 changes of water each day followed by lyophilizing (Labconco, Kansas City, MO, USA) to yield dry MACF or MAC polymer.^{38 (link)} Finally, small samples of each were dissolved in 2 vol% deuterated acetic acid/D₂O and ¹H and ¹⁹F nuclear magnetic resonance (NMR; Varian 500 MHz, Varian, Inc., Palo Alto, CA, USA) were conducted to find percent methacrylation and percent fluorination respectively as previously described. ^{25 (link), 38 (link)}