Zwitterionic polysoaps with reduced density of surfactant side groups

Abstract

Several zwitterionic polymers were prepared by radical homopolymerization of surfactant monomers which bear diallyl, diene or vinylcyclopropane moieties. These polymer systems were complemented by alternating copolymers of appropriate zwitterionic vinyl compounds. Thus, polymers with reduced (as compared with simple vinylic homopolymers, or statistical copolymers) and well defined density of surfactant side groups are obtained. The solubilities found for these polymers are dominated by polymer geometry rather than by the balance of hydrophilic and hydrophobic fragments, thus corroborating a "main-chain spacer" model proposed recently. All water-soluble polymers exhibit characteristic features of classical polysoaps, as shown by surface tension measurements and by solubilization of hydrophobic dyes. In contrast, the water-insoluble copolymers are capable to form stable monolayers at the air-water interface.

Molecular concepts, self-organisation and properties of polysoaps

“…Either polymerizable surfactants are copolymerized with small, often polar or hydrophilic, comonomers, creating rather well defined surfactant fragments in the polysoaps [73,77,78,[156][157][158][159][160][161][162][163][164][165][166][167][168] (Fig. 3e).…”

“…The molecular architecture can be varied e.g. with respect to the polymer geometry [76,78,87,88,105,126,164,167,168,[223][224][225][226][227][228] the nature of the polymer backbone [76,78,84,167,168,229,230] and the incorporation of spacer groups [100-102, 157, 223, 231, 232] controlling the distance of the surfactant fragments from the polymer backbone (Fig. 5).…”

“…Similarly, zwitterionic polysoaps often exhibit low solubility in pure water [227]. But by minimizing these problems by proper design, a number of nonionic and zwitterionic polysoaps suited for systematic investigations have been prepared [78,167,168].…”

“…5c) are water-soluble and behave like polysoaps. The other isomers do not dissolve in water, but instead are soluble in less polar solvents, in which the water-soluble isomers are insoluble [76,78,85,86,126,156,164,167,168,225,231,279,280]. Hence in case of vinylic polymerized surfactants, no straight forward correlation between solubility and HLB exists: apparently more hydrophilic polymers of the poorly performing "head" geometry are less soluble in water than apparently more hydrophobic ones of the well behaving "tail end" geometry.…”

“…0.25 nm, and the minimal diameter of a hydrocarbon tail is ca. 0.5 nm [78, 167,168]: the backbone cannot offer enough space for an "amphiphilic conformation" of the surfactant fragments (Fig. 9a), independent of the shape of the hydrophobic aggregates.…”