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| - Interfacial Properties of a Diblock Amphiphilic Copolymer: Poly(isobutylvinyl ether-b-2-methyl-2-oxazoline)
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| - Novel amphiphilic diblock copolymers, poly(isobutylvinyl ether-b-2-methyl-2-oxazoline)(PIBVE-b-POXZ), were synthesized by cationic polymerization. The molar ratio of IBVE in the copolymerswas varied from 20% to 50%. Their molecular weights were over the range from 1000 to 4000. Theassociations of these copolymers have been studied by small-angle neutron scattering (SANS) in twoselective solvents: water which solubilizes the POXZ block and cyclohexane which solubilizes the PIBVEblock. In 1% solutions, all the soluble copolymers formed micellar aggregates. The copolymers have beenadsorbed on porous silica particles from selective and nonselective solvents. The adsorbed layers havebeen studied by SANS. In the case of a nonselective solvent of the two sequences (dichloromethane)copolymers have shown comparable adsorption as the homopolymers. Influence of concentration ofsolutions has been studied in adsorption from aqueous solutions. For dilute watery solutions, the adsorbedchains were in mushroom configuration and the adsorbed amounts were low. On the opposite, stable andvery dense copolymer layers corresponding to extended brushes have been obtained in the presence ofconcentrated watery solutions. The copolymer chains are anchored by the PIBVE blocks which arecollapsed on the surface while the POXZ blocks are in a very extended conformation. The influence of thehydrophilic/lipophilic balance has been studied by varying the chemical composition. The amounts ofadsorbed polymer were increased with amount of IBVE in the copolymer. The thicknesses of the adsorbedlayers have been found to follow qualitatively the theoretical model of Marques and Joanny for theadsorption of diblock copolymers in selective solvents. Adsorption from cyclohexane which is a selectivesolvent of the PIBVE block at different copolymer compositions has shown thick adsorbed layers whichcould correspond to direct adsorption of the micelles on the surface.
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