Mesomorphic structures in flexible polymer-surfactant systems due to hydrogen bonding: Poly(4-vinylpyridine)-pentadecylphenol

Properly selected hydrogen bonding suffices to induce mesomorphic structures in mixtures of flexible polymers and nonmesogenic surfactants. For poy(4-vinylpyridine)-3-pentadecylphenol (P4VP-(PDP)_x) complexes, the long period of the lemellar structure decreases as x^-1 (x is the number of PDP molecules per P4VP repeat unit) in complete contrast to similar polyelectrolyte systems. Upon cooling from 80 °C to the room temperature, the long period gradually increases and levels off at around 30 °C at a value which is approximately 4 Å above the starting value. After an induction time, a structural transformation occurs in the highly complexed samples, due to the crystallization of the alkyl side chains. It is accompanied by a sudden decrease in the long period of approximately 5 Å. However, the structure is not stable and after an additional induction time both structures are present in the samples. Arguments to explain most of the observed phenomena will be given.