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A series of three nonionic surfactants which undergo acid-catalyzed hydrolysis, O -[(2,2-dialkyl-1,3-dioxolan-4-yl) methoxy] – O ′-methoxy poly(ethylene glycol), or cyclic ketal (CK), were synthesized. The surfactants shared similar HLB values (9.2–9.8) but differed in the relative length of their two alkyl tails. Water/CK/isooctane microemulsion systems formed by each of the three surfactants also shared similar phase behavior, physical properties, and surfactant hydrolysis kinetics. The apparent critical microemulsion concentration for three CK surfactants, 0.060–0.075 g g −1 (in both water and isooctane), and the efficiency, the minimum amount of surfactant required to totally mix water and oil into single microemulsion phase, 0.35–0.40 g g −1 , are significantly higher than values possessed by regular, linear, alkyl ethoxylate surfactants. The underlying causes for the high values were investigated. Due to the broad distribution of its ethoxylate head group size, CK surfactants were distributed among all phases within two- and three-phases systems, with CKs possessing shorter ethoxylate groups partitioning to the oil phase and CKs with larger ethoxylate groups to the aqueous phase. Small-angle neutron scattering experiments suggest that CK exists as monomers or very small pre-micellar aggregates in isooctane at 12% and as ellipsoidal aggregates in water at 2.5–25%. Surface pressure versus surface area measurements of CK surfactant monolayers at the water-air interface demonstrate two differences from linear alkyl ethoxylate monolayers: the occurrence of a collapse at moderately low surface pressure (30 mN m −1 ) and high surface area per molecule (0.59 nm 2 ) and the inability to undergo dissolution when subjected to a constant, moderately high surface pressure (25 mN m −1 ). The results suggest that CK molecules are not able to pack as efficiently as linear alkyl ethoxylates at interfaces, and are strongly anchored to monolayers in aqueous media.

There has been much recent interest in the use of poly(ethylene glycol)s (PEGs) for a variety of biotechnical applications. In the present work we have immobilized several cellulose derivatives and dextran on polystyrene surfaces and have measured the extent of fibrinogen adsorption onto the coated surfaces. Immobilization was achieved by adsorption onto clean polystyrene and by covalent linkage of oxidized polysaccharides to polyethylenimine which was ionically bound to polystyrene. Covalently bound polysaccharides, and adsorbed polysaccharides that are strongly held, compare well with poly(ethylene glycol) in preventing fibrinogen adsorption. The same polymers were coupled to polystyrene latex particles to permit examination by analytical microparticle electrophoresis. This investigation suggests that adsorbed polysaccharides form thicker layers than do covalently bound polysaccharides. Despite the polysaccharides being bound at many points along the polymer chain while PEG is bound only at the polymer terminus, the functional equivalence of polysaccharide and PEG coatings is of significance in interpreting the protein-rejecting ability of polymer-modified surfaces.

Analytical microparticle electrophoresis was used to characterize various polymer coatings known to control protein adsorption and related phenomena of biotechnical significance. The electrophoretic mobility of polystyrene latex microspheres and the electro-osmosis associated with quartz capillaries were characterized over the pH range 2–11. Such characterization provides information related to surface modification. Aminopropylsilane and mercaptopropylsilane were shown to be effective sublayers for covalent attachment of hydrophilic polymers to quartz glass surfaces. Poly(ethylenimine) was similarly verified as an effective sublayer for polystyrene latex. Polymer coatings based on poly(ethylene glycol) and three polysaccharides, dextran, ethyl(hydroxyethyl)cellulose, and hydroxypropylcellulose, were found to reduce capillary electro-osmosis and microsphere electrophoretic mobility significantly over a broad pH range. This reduction corresponds to the ability of these coatings to reduce protein adsorption and control surface wetting by aqueous polymer two-phase systems.