Cyanine dyes (1a–d) with the 5,5′,6,6′‐tetrachloro‐1,1′‐dialkyl‐3,3′‐di‐(3‐carboxypropyl)‐benzimidocarbocyanine chromophore differing only in the chain length of their alkyl groups in 1,1′‐position have been synthesized, spectroscopically characterized, and compared with 5,5′6,6′‐tetrachloro‐1,1′‐diethyl‐3,3′‐di‐(4‐sulfobutyl)‐benzimidocarbocyanine(TDBC). In aqueous solution the dyes form J‐aggregates which, depending on the alkyl group chain length, exhibit J‐bands differing in spectral positions, bandwidth, and in the number of peaks.

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Control over both color and transparency is reported for the thermochromic materials presented here. Dyes such as Bromothymol Blue (BB) can reversibly change color with temperature when embedded in aqueous polyether/LiCl gel networks. The Figure shows a gel containing BB at room temperature (green, transparent) and at 33 °C (yellow, transparent). At 36 °C the gel becomes milky.

On the basis of a generalized Frumkin-Damaskin isotherm, synergistic interactions between mixed surfactants adsorbed at fluid interfaces are discussed in terms of a mutual interaction parameter. By use of experimental -logc curves of sodium dodecyl sulfate, oxethylated decanol (5EO), and two homologous (N-n-alkyl-AT^V-dimethylammonio)acetic acid bromides (at pH = 7 predominantly betains), the adsorption parameters of these surfactants were determined, including their self-interaction parameters. By use of these adsorption parameters, an additional interaction parameter was determined, which characterizes the interaction between two different surfactants. This additional interaction parameter is small for mixtures of sodium dodecyl sulfate and the nonionic surfactant. It becomes considerable for mixtures of sodium dodecyl sulfate and CZV-n-alkyl-iV,jV-dimethylammonio)acetic acid bromides, which indicates an additional synergistic attraction between the interacting molecules in the adsorption layer. The additional interaction parameters depend remarkably on the mixing ratio and correlate to the depression of the critical micelle concentration of these mixtures. ch3 R-NH-CH2-COO-CH3 and SDS, the shift of the o-log c curves was found to be

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