Examples of amphitropic polymers: monolayer film, Langmuir–Blodgett film and liquid-crystalline properties of some polymeric amphiphiles containing cholestanol moieties and those of some closely related non-polymeric amphiphiles

Abstract

A range of alternating copolymers were prepared by free-radical-initiated copolymerizations of maleic anhydride with a series of α-alkenes containing cholestanyl moieties. Derivatives of these copolymers were prepared by reacting the anhydride residues with methanol, water, dimethylamine and/or morpholine. A related series of non-polymeric amphiphiles containing steroid moieties was also prepared. Isotherms were measured for monolayers of the various polymers and the various non-polymeric amphiphiles on water and, where possible, Langmuir–Blodgett (LB) multilayers were prepared. The majority of the materials gave good isotherms (relatively steep with collapse pressures >40 nM m^–1) indicating that the monolayers were ordered and, as determined by the detection of Bragg peaks by X-ray diffraction, Y-type LB films with regular layer structures. Appropriate materials were also examined, by optical microscopy and differential scanning calorimetry (DSC), for possible liquid-crystalline properties. Four polymers and one non-polymeric amphiphile exhibited smectic A mesophases. Another non-polymeric amphiphile exhibited a cholesteric mesophase. Thus, examples were found of amphitropic polymers and non-polymeric amphiphiles which can form organised molecular arrangements both because they are amphiphilic and because they contain mesogens.