SURFACE MODIFICATION OF POLY(CHLOROTRIFLUOROETHYLENE) - INTRODUCTION OF REACTIVE CARBOXYLIC-ACID FUNCTIONALITY

The reaction of poly(chlorotrifluoroethylene) (PCTFE) film with trimethyl 4-lithioorthobutyrate in THF/heptane at -78 to -17-degrees-C produces a modified (PCTFE) surface containing orthobutyrate functionality in the outer approximately 25- approximately 100 angstrom (PCTFE-(CH2)3C(OCH3)3). Quantitative X-ray photoelectron spectroscopy (XPS) indicates that the modified surface layer contains orthobutyrate groups attached to approximately 80% of the original PCTFE repeat units; the other approximately 20% of virign repeat units has been converted to difluoroolefins. Hydrolysis of the orthobutyrate surface renders carboxylic acids and produces a very hydrophilic polymer film sample (PCTFE-(CH2)3CO2H). The advancing water contact angle (theta(A)) of PCTFE-(CH2)3CO2H is dependent on pH and is approximately 56-degrees at low pH and approximately 30-degrees at high pH. The receding water contact angle (theta(R)) is 0-degrees at all pH values. PCTFE-(CH2)3CO2H forms esters in high yields using three standard esterification conditions: The n-octyl ester was prepared by acid-catalyzed esterification, through the intermediate acid chloride (prepared with thionyl chloride) and through the intermediate acyl imidazolide (prepared with carbonyldiimidazole). PCTFE-(CH2)3CO2H is reduced to the alcohol, PCTFE-(CH2)4OH, with borane/THF complex. The surface-chemical transformations reported have been monitored by a combination of XPS, ATR, IR, contact angle, UV-vis, and gravimetric analyses.