A number of acrylamideaery late copolymers were synthesized in which the acrylate (CH2=CHC00(CH2CH20)"R) is hydrophobic on account of the presence of a 1,1-dihydroperfluorooctyl group or a dodecyl group connected to the acrylate via a -(CH2CH20)" hydrophilic spacer ( = 0-3).Copolymerization of these monomers was initiated by sodium metabisulfite and ammonium persulfate at 60 °C in aqueous media in the presence of surfactants and acetone. The low shear viscosities of 0.5 wt % solutions of these copolymers as a function of comonomer molar content gave bell-shaped curves having maxima at 0.10-0.60 mol % comonomer, consistent with competitive interand intramolecular hydrophobic association. The copolymers having perfluorocarbon pendent groups gave higher viscosities at lower comonomer content. Furthermore, for both the hydrocarbon-and perfluorocarbon-containing copolymers the viscosities increased, and the comonomer content at the viscosity maximum decreased, with increasing spacer length. The increased effectiveness of the longer spacers is attributed to entropy effects in the formation of polymer assemblies.
dihydroperfluorooctyl, and octyl derivatives of (hydroxyethyl)cellulose (HEC) were prepared by reaction of the Na salt of HEC in aqueous isopropyl alcohol with 1,1dihydroperfluorobutyl or octyl p-toluenesulfonate (4 or 5), with 1,1-dihydroperfluorobutyl or octyl glycidyl ether or (8 or 9), and with octyl glycidyl ether (12). The degrees of substitution of HEC were determined using 19F NMR and varied between 0.023 and 1.20 mol % of anhydroglucose units (AGU). The HEC derivatives modified with 4,5, and 8 were sparingly soluble or insoluble, and their aqueous solutions were generally low in viscosity. In contrast solutions of HEC modified with 9 did have significantly enhanced viscosities with respect to unmodified HEC or compared to HEC modified with the octyl glycidyl ether, having the same chain length as 9. The Brookfield viscosity plotted against perfluorocarbon content of aqueous solutions of HEC modified with 9 was shown to go through a maximum at about 0.42 mol % (0.92 wt %) with respect to AGU's. The solutions of this and similar polymers were shown to be highly pseudoplastic. Furthermore, increases in viscosity were observed upon addition to NaCl. These observations are consistent with the very strong intermolecular hydrophobic association of the perfluorocarbon groups.
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