Random Copolymer Effect in Self-Assembled Hydrogen-Bonded P(S-co-4VP)(PDP) Side-Chain Polymers

Random copolymers of styrene and 4-vinylpyridine P(S(1-x)-co-4VP(x)) were synthesized to study the effect of the random copolymer "repulsion" on the self-assembly in hydrogen-bonded complexes with pentadecylphenol (one PDP molecule per 4VP group). The major trends observed as a function of the fraction of styrene monomers 1 - x in the random copolymer are a decrease in order-disorder transition temperature, T(ODT), and a decrease in the periodic length scale of the ordered lamellar state. The lower T(ODT) results from a partial shielding in the disordered state of the highly unfavorable styrene/4-vinylpyridine interactions by the PDP alkyl tails. The reduced layer thickness in the ordered state is due to the relaxation into a more coil-like conformation of the alkyl tails of the PDP amphiphiles, made possible by the presence of styrene units. The self-assembly properties of P(S(1-x)-co-4VP(x))(PDP)(1.0) are compared with those of the lamellar self-assembled homopolymer-based P4VP(PDP)(x) system, where x denotes the number of PDP molecules per 4VP repeat unit. As in P(S(1-x)-co-4VP(x))(PDP)(1.0), in P4VP(PDP)(x) also only a fraction x of the total number of monomers of the macromolecule may potentially hydrogen bond with PDP molecules at any given instant. In contrast to P(S(1-x)-co-4VP(x))(PDP)(1.0), for P4VP(PDP),, however, the long period is found to increase for decreasing values of x.