The mechanism of acid curing of epoxy resins catalyzed with tertiary amines was investigated by using model systems composed of phenylglycidyl ether and benzoic acid or acetic acid anhydrides in the presence of benzyldimethylamine. The reaction was studied by NMR spectrometry, liquid chromatography, and ozone absorption. The main findings are that (1) the tert‐amine is bound chemically and irreversibly during the reaction under the formation of a quaternary ammonium salt magnified image and (2) 1‐phenyloxypropanediol‐2,3‐dibenzoate or diacetate is the main reaction product. The suggested reaction mechanism involves initiation in which the tertiary amine reacts with the epoxy group, giving rise to a zwitterion that contains a quaternary nitrogen atom and an alkoxide anion; the latter immediately reacts with the anhydride and quaternary salt is formed. In a later stage the carboxy anion of the quaternary salt reacts first with the epoxy group, then with the anhydride. By this reaction diester is formed and the carboxy anion is regenerated.

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A series of ionic networks were prepared by copolymerization of acrylamide, methylenebis-(acrylamide), and A/-[2-(alkyldimethylammonio)ethyl]acrylamide with Cl, C4, C6, C8, C12, and C16 straight-chain alkyls (mole fraction of the last comonomer xi = 0-0.15). Small-angle X-ray scattering, swelling, and mechanical behavior of the networks were investigated in water-ethanol mixtures. For the gels with C1-C8 alkyls collapse was found; both the volume jump and the critical ethanol concentration at which the transition takes place, ec, increase with increasing content of the ionic component, xj.Increasing the alkyl length stabilizes the expanded state of the gel and increases the ec values, probably due to preferential sorption of ethanol by hydrophobic regions. Different swelling behavior was found for gels with C12 and C16 alkyls, where mostly a decrease in swelling in water at low ethanol concentrations was observed with increasing xi. This is caused by a distinct amphiphilic character of salts with the two longest alkyls; in networks with the C16 alkyl formation of micelles was proved by SAXS. Mechanical behavior of the networks is predominantly determined by the degree of swelling; a jumpwise change in the gel volume is accompanied by a similar change in the equilibrium modulus. amide)14 and polyCZV-isopropylacrylamide)4'15 hydrogels.

The effect of dilution at network formation (polymer volume fraction do) = 1 -0,4) on the fraction and equilibrium photoelastic behaviour of polyurethane networks was investigated. The networks were prepared from poly(oxypropy1ene)triol and 4,4'-methylenedi(phenyl isocyanate) with various mole ratios of reactive groups 1 < rH = [OH]/[NCO] < I ,5. From a comparison between the experiments and the theory of branching processes we find that: a) with both increasing ratio rH and increasing dilution the fraction of bonds lost in elastically inactive cycles increases from 0,02 to 0,06; b) the experimental reduced equilibrium moduli G, of the predominant majority of samples are higher than those theoretically predicted by the Flory junction-fluctuation theory for the front factor A = 1. Also the decrease of G, with dilution (expressed as volume fraction of diluent during network formation do)) is very steep, thus supporting the contribution of permanent interchain constraints to the overall G, value.

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