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Synthesis and adsorption of polymers: Control of polymer and surface structure
Abstract
Polymer surface modification can be accomplished by several techniques including chemical reaction and adsorption. In Chapter I, a simple and versatile technique to introduce carboxylic acid functionality to the surfaces of three fluoropolymer film samples is described. In Chapter II, the adsorption of neutral poly(scL-lysine) (PLL) from solution to the water-fluoropolymer interface is described. Chapter III combines the methods of surface modification described in Chapters I and II and discusses the adsorption of charged PLL to a carboxylic acid-functionalized fluoropolymer film surface. The hydrophobic interaction as a driving force for adsorption is further studied in Chapter IV where the synthesis and adsorption of poly(ethylene oxide) (PEO) and its derivatives are discussed. The syntheses of carboxylic acid-functionalized fluoropolymer films rely upon a two step mechanism where unsaturation, introduced in the first step, is oxidatively removed in the second step; one acidic group per twelve to sixteen repeat units was introduced to the surface. Contact angles ($\theta\sb{\rm A}$/$\theta\sb{\rm R}$) of the acid-functionalized fluoropolymer films decrease with increasing pH: PVF$\sb2$-CO$\sb2$H (77$\sp\circ$/39$\sp\circ$ decreases to 68$\sp\circ$/25$\sp\circ$); PCTFE-CO$\sb2$H (93$\sp\circ$/55$\sp\circ$ decreases to 93$\sp\circ$/43$\sp\circ$); and FEP-CO$\sb2$H (101$\sp\circ$/78$\sp\circ$ decreases to 97$\sp\circ$/61$\sp\circ$). The adsorption of poly(scL-lysine) (PLL) to the water-FEP interface was controlled by pH of the aqueous solution and PLL solution conformation. Only neutral, $\alpha$-helical PLL adsorbed to FEP (FEP-PLL). The adsorption of PLL to carboxylic acid-functionalized FEP, FEP-CO$\sb2$H, was controlled by an electrostatic interaction; both a hydrogen bonding interaction between FEP-carboxylic acid and PLL backbone and an ionic interaction between FEP-carboxylate and PLL-ammonium enhanced adsorption. Both FEP-PLL (80$\sp\circ$/16$\sp\circ$) and FEP-CO$\sb2$H-PLL (78$\sp\circ$/29$\sp\circ$) are more hydrophilic than FEP. FEP-PLL-$\varepsilon$-amine reacts with 3,5-dinitrobenzoyl chloride in 65% yield whereas FEP-CO$\sb2$H-PLL-$\varepsilon$-amine reacts in 100% yield. Adsorption of PLL to FEP and FEP-CO$\sb2$H improves the peel strength of adhesive joints prepared with these substrates and the adhesion and growth of biological cells on these film samples. PEO (5,000 to 50,000 g/mole and polydispersity indices of 1.07 to 1.17) was synthesized by anionic ring opening polymerization of ethylene oxide in THF with triethylene glycol monomethyl ether potassium initiation. PEO was end-capped (PEO-R) by reaction with a (perfluoro)alkyl acid chloride in THF with pyridine catalysis. A polar interaction between substrate and segment controlled adsorption at the fluoropolymer-water interface; PEO adsorbed preferentially to PVF$\sb2$ over PCTFE and FEP. Both PEO and PEO-R adsorbed to the polystyrene latex-water interface; the latter formed a thicker adsorbed layer. PEO-R showed increased surface activity over PEO at the air-water interface; PEO-perfluorodecanoate decreased the surface tension of water to 35 dyn/cm.
Subject Area
Polymer chemistry|Materials science
Recommended Citation
Shoichet, Molly Sandra, "Synthesis and adsorption of polymers: Control of polymer and surface structure" (1992). Doctoral Dissertations Available from Proquest. AAI9305896.
https://scholarworks.umass.edu/dissertations/AAI9305896