Side-chain liquid crystalline polyelectrolytes containing terminal (cyanobiphenylyl)oxy moieties were obtained through hydrolysis of the corresponding poly(maleic anhydride-co-alkyl vinyl ether)s with spacer lengths of 6-12 methylene groups. All polymers display a liquid crystalline phase. The transition temperatures are lower for the more rigid polyimaleic anhydride-co-alkyl vinyl ether)s. The enthalpy gain associated with the phase transition decreases with increasing rigidity of the polymeric backbone and with decreasing spacer lengths. In aqueous solution all polyelectrolytes have two distinct apparent pvalues, 3.3 and 6.5, indicative for strong nearest neighbor interactions within a maleic acid moiety. At neutral pH a blue shift of the absorbance maximum is observed which increases with increasing spacer length. Above pH 8 the blue shift decreases, indicating a conformational transition of the polyelectrolytes from more compact microdomains to a more extended chain conformation.

Poly(sulfonylethylmaleic acid monoamide-co-alkyl vinyl ether)s carrying both a sulfonic acid and a carboxylic acid moiety are obtained by reacting the corresponding poly(maleic anhydride-co-alkyl vinyl ether)s with 2-aminoethanesulfonic acid. The alkyl vinyl ethers have a n-hexyl or n-dodecyl group or the alkyl groups have a terminal (cyanobiphenylyl)oxy chromophore and spacer lengths of 6−12 methylene units. Dynamic light scattering experiments show that all polymers form large aggregates in water in which the polymer chains are entangled. The formed aggregates are highly ordered as can be deduced from the blue shift of the absorption maxima of the chromophores by UV spectroscopy. When the charge density on the polyelectrolyte backbones is increased by varying the pH or the hydrophobicity of the polyelectrolyte is decreased by variation of the spacer length, the aggregates become more open and less ordered. The interaction between the polyelectrolytes and n-dodecyltrimethylammonium bromide (DTAB) has been investigated by potentiometry using a DTAB-selective electrode and surface tension measurements. The binding already has begun at very low DTAB concentrations and has been shown to be noncooperative. This is caused by the presence of hydrophobic microdomains formed by the polyelectrolytes. With small amounts of DTAB the polyelectrolytes form highly surface active complexes. These complexes are more hydrophobic than the individual components, resulting in an accumulation of the complexes at the air−solution interface. UV spectroscopy was used to investigate the interactions between the polyelectrolytes and DTAB, n-hexadecyltrimethylammonium bromide, poly(oxyethylene(4)lauryl ether), and sodium dodecyl sulfate.

The formation and transfer of ordered layers of poly(maleic anhydride-alt-alkyl vinyl ether)s and poly(maleic acid-alt-alkyl vinyl ether)s with and without (cyanobiphenylyl)oxy moieties on aqueous subphases is studied by use of the Langmuir−Blodgett technique. The length of the spacers, flexibility of the polyelectrolyte backbone, pH of the subphase, and the presence of counterions determine the orientation of the polymers at the air−water interface. As counterions Cu2+, Mg2+, tetrabutylammonium, n-dodecyltrimethylammonium, and n-dodecyl sulfate are used. The increase in lift-off area proves the interaction of both cationic and anionic surfactants with the maleic acid copolymers. This is due to electrostatic interactions between the charged groups and hydrophobic interactions between the side chains of the polymer and surfactant tail. The π−A isotherms and Brewster angle microscopy of the maleic acid copolymers on water and on a 1 mM n-dodecyltrimethylammonium solution show the formation of a triple layer upon compression of the monolayer. Monolayers of the maleic acid copolymers on both subphases could be transferred onto hydrophilic glass and quartz slides in a Z-type fashion. However, second harmonic generation (SHG) measurements showed that the noncentrosymmetry is not maintained in the deposited multilayers.

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The binding of n- dodecyl-, n-hexadecyl-and N-(ω-(4′-cyanoazobenz-4-oxy)decyl)-N,N,N-trimethylammonium bromide to poly(maleic acid-co-alkyl vinyl ether)s with n-butyl, n-dodecyl, n-[(4-cyano-4′-biphenylyl)oxy]hexyl and n- [(4-cyano-4′-biphenylyl)oxy]dodecyl side chains has been investigated by UV spectroscopy. Results from dynamic light scattering studies of the polyelectrolytes in the absence of surfactants are in agreement with the presence of the extended conformation for the butyl copolymer between pH 7 and 11. For the other polyelectrolytes an increase in hydrodynamic radius is observed upon increasing the pH. By UV spectroscopy the shifts in absorption maxima of the (cyanobiphenylyl)oxy and cyanoazobenzoxy chromophores, due to mutual π-π stacking interactions, were monitored to provide information on the interaction between polyelectrolytes and surfactants. Changes on both polyelectrolyte and surfactant could be studied upon addition of surfactant to polyelectrolyte in aqueous solution. For the butyl polyelectrolyte, cooperative interaction is observed (pH > 7), whereas for the other copolymers no cooperativity is observed. A model for the different interactions is proposed.