(475c) Layered Morphologies in Precise Acid-Containing Polyethylenes: Hierarchical Structures and the Implications on Properties
Acid-containing polymers have specific interactions that produce both hierarchical nanoscale morphologies containing acid-rich aggregates and remarkable bulk properties. Untangling the correlations between the primary structure of such associating polymers and their morphologies and properties has long been a challenge in polymer physics, because most associating polymers have random sequences of polar and non-polar monomeric units. New synthetic methods can increasingly produce polymers with greater molecular precision that provide greater uniformity of and control over the hierarchical structure morphologies and even yield new morphologies. The talk will focus on precise polyethylenes with acid groups evenly spaced along linear chains and with spacer lengths of 21 carbons such that the polymers produce hierarchical structures with acid layers. Using a combination of atomistic molecular dynamics, X-ray scattering and FTIR, the chain conformations near the acid groups have been determined to be hairpins. Moreover, this acid-layer motif with hairpin chain conformations packs into a semi-crystalline morphology with the acid-layers perpendicular to the crystalline lamellae. The implications of this morphology will be explored for tensile deformation and proton transport.