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Surface and interfacial chemistry of poly(vinylidene fluoride)
Abstract
Surface dehydrofluorinations of PVF$\sb2$ were examined to prepare "reactive handles" with which to effect further chemical transformations. Surfaces were analyzed by XPS, ATR IR, UV-vis, and contact angles. Using phase transfer catalysis and NaOH, modifications were surface-selective and autoinhibitive (at 40$\sp\circ$C and below), producing eliminated layers (PVF$\sb2$-E) containing some ketones and enols/alcohols. Reaction depths were determined gravimetrically and could be controlled from $\sim$40-100 A with temperature. PVF$\sb2$-E was reactive to nucleophiles, radicals, and electrophiles. The following surfaces were prepared: PVF$\sb2$-OH, PVF$\sb2$-(O)COOH, PVF$\sb2$-Br, PVF$\sb2$-Cl, PVF$\sb2$-NH$\sb2$, PVF$\sb2$-N$\sb3$, PVF$\sb2$-CN, PVF$\sb2$-SH, PVF$\sb2$-SCN, and PVF$\sb2$-Ag$\sp{\rm o}$. Alternatively, reaction of PVF$\sb2$ with DBU produced "patchy", hydrophobic, nearly oxygen-free eliminated surfaces; autoinhibitive kinetics were not observed. Reaction with LDA, KOt-Bu, t-BuLi, and KF/18-crown-6 yielded inferior eliminated substrates for studying surface transformations. Direct chlorination, bromination, or reduction of the PVF$\sb2$ surface was achieved via a cationic mechanism using aluminum chloride (or bromide). Reaction extent depended on the solvent, AlX$\sb3$ Lewis acid strength, temperature, and time. The PVF$\sb2$ surface was completely reduced using the aluminum halide in a heptane/cycloheptatriene mixture. The polyhydrocarbon-like/PVF$\sb2$ composites were oxidized with aqueous chromic acid to produce high surface energy substrates, similar to oxidized polyethylene. PVF$\sb2$ surfaces were modified via aluminum metal vapor deposition and subsequent metal dissolution in either sodium hydroxide or bromine to obtain thinly modified high energy substrates. XPS indicated the introduction of carboxylic acids and/or hydroxyl groups to the outer few angstroms of the substrate with NaOH; carbonyl and bromine groups were formed with net bromine. Surface modifications were used to regulate adsorption phenomena at soluble polystyrene-PVF$\sb2$ interfaces. At low concentrations and low molecular weights, neither polystyrene nor carboxylic acid-terminated polystyrene adsorbed from cyclohexane to PVF$\sb2$; however, adsorption did occur on PVF$\sb2$-NH$\sb2$ or PVF$\sb2$-OH substrates.
Subject Area
Polymers
Recommended Citation
Brennan, Joan Vivian, "Surface and interfacial chemistry of poly(vinylidene fluoride)" (1991). Doctoral Dissertations Available from Proquest. AAI9207366.
https://scholarworks.umass.edu/dissertations/AAI9207366