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The basic "hydrolysis" of ethylene-vinyl acetate copolymers (EVA) leads to ethylene-vinyl alcohol copolymers (EVOH) or ethylene-vinyl acetate-vinyl alcohol terpolymers which can be used for their surface properties or for further chemical modification. The controlled basic solvolysis of EVA takes place via a complicated nonstoichiometric mechanism. The solvolysis by anhydrous methanol catalyzed by sodium methoxide has been investigated thoroughly. This reaction is capable of fully converting acetate groups; the solvolysis of an acetate group next to another acetate (in EVV triads) is faster than that for isolated vinyl acetate (EVE triads) and proceeds immediately to the neighboring acetate group. The rate constants of each elementary step have been determined with the help of numerical simulations of kinetics data. In particular, the forward rate constant, k +, of the SN2 attack of the methoxide ion on vinyl acetate strongly depends on solvent quality (methanol content), i.e., on polymer coil expansion. When sodium hydroxide is used as a base, the reaction system is more complex because of the additional steps and equilibria involving water. The most prominent difference with respect to anhydrous conditions is partial solvolysis of acetate groups, even when fully converted. Indeed, the reaction stops when the reactive species have been fully converted into acetate ions of low reactivity. The numerical simulation of the kinetics agreed with the experimental data, but the large number of reaction steps and equilibria did not allow reliable determination of the rate constants.

No abstract

Zwitterionic amphiphiles of the general formula H(CH2)y +N(CH3)2(CH2)n PO2C6H~-, where the number of intercharge methylenes n is varied, were studied in dilute aqueous solution. Their critical micellar concentrations show a peculiar variation with n, first increasing as n varies from 1 to 4 and then slowly decreasing as methylenes are added up to 10. This behavior is interpreted as being the consequence of two opposite contributions. The first is the classical CMC lowering due to the increase of hydrophobic character with the total number of methylene groups in the surfactant molecule. The second contribution is the increase in the dipole moment of the zwitterionic headgroup with n, leading to stronger dipole-dipole repulsions between headgroups at the micellar surface. Experimental results suggest that the dipole moment does not increase linearly with n because of the polymethylene chain flexibility. This is supported by 13C NMR relaxation experiments.

Neutral phosphonato-, phosphinato-, and carboxybeta'ine moieties linked to various polymer supports, poly(styrene-co-4-vinylpyridine) and poly(styrene-co4dimethylaminomethylstyrene), were synthesized by a two step sequence. These products were characterized by means of FTIR analysis. Complexing properties towards transition metal salts are outlined. 0025-1 16X/86/%03.00