Polymer Science and Polymer Chemistry

Macromolecular Polymeric Structure

Noncovalent interactions provide a flexible means of engineering new chemical entities with tailored properties. Specific interactions between functionalized small molecules and polymer chains bearing complementary binding sites can be used to engineer supramolecular complexes that display mesomorphic structure. This has been exploited to develop a range of functional materials including photonic band gap polymers, ionic conductors and donor-acceptor semiconducting polymers. Additionally, the deliberate association of polymers with surfactants in engineered, synthetic materials is increasingly motivated by the possibility of combining the stimuli-responsive self-assembly and solubilizing properties of surfactants with the intrinsic solution properties of polymers, such as rheology medication and facile coating of interfaces. In solution, the hydrophobic nature of the surfactant compared to a hydrophilic polymer backbone leads to coil-globule transitions on decreasing solvent quality, surfactants cluster and force small length scale intrachain associations, causing a sharp reduction in the end-end chain distance, i.e collapse. These transitions qualitatively mimic the behaviour of proteins in which there is an aggregation of hydrophobic side chains that occurs as a precursor to collapse and eventual folding. At higher concentrations, interchange associations drive supramolecular ordering, leading to larger characteristic length scales and in some cases to the formation of gels or networks. Overall, there is a compelling need to understand the physical chemistry, structure and dynamics of supramolecular polymers, both in solution and in the melt. Our work focuses on detailed examination of composition and temperature dependent molecular and supramolecular structures in solutions and melts. We quantitatively characterize the thermodynamics and kinetics of polymer-small molecule binding, elucidating the dependence on surfactant chemistry and environmental variables. We strive to formulate coherent frameworks describing structure-property relationships in the systems considered.