Interaction Strength in Poly(4-vinylpyridine)-n-Alkylphenol Supramolecular Comb-Shaped Copolymers

The self-assembly of P4VP(3-PDP)(1.0) and P4VP(4-NDP)(1.0) supramolecular comb-shaped copolymers has previously been shown to have very interesting thermal properties, since besides crystallization of 3-PDP/4-NDPs alkyl tails, an additional order-disorder transition (ODT) was observed as well. In order to get a better insight into the processes involved and the parameters that determine this behavior, a library consisting of differently substituted n-alkylphenol surfactant molecules was synthesized. A general trend was found in the stoichiometric P4VP-based complexes. As expected, both the melting point and long period of the lamellar structure increased with a longer tail length, while surprisingly T-ODT only depended on the position of the hydroxyl group. Its magnitude is assumed to be directly related to the strength of hydrogen bonding, which is highest for the sterically least hindered surfactants (para). Additionally, critical behavior was discovered in meta-substituted complexes: a large reduction in both T-m and T-ODT was observed for a 13 methylene unit long amphiphile, while crystallization of the alkyl tails determined the self-assembly in P4VP(3-henicosylphenol)(1.0).