Synthesis and Morphology of High-Molecular-Weight Polyisobutylene-Polystyrene Block Copolymers Containing Dynamic Covalent Bonds.

Incorporating dynamic covalent bonds into block copolymers provides useful molecular level information during mechanical testing, but it is currently unknown how the incorporation of these units affects the resultant polymer morphology. High-molecular-weight polyisobutylene-b-polystyrene block copolymers containing an anthracene/maleimide dynamic covalent bond are synthesized through a combination of postpolymerization modification, reversible addition-fragmentation chain-transfer polymerization, and Diels-Alder coupling. The bulk morphologies with and without dynamic covalent bond are characterized by atomic force microscopy  and small-angle X-ray scattering, which reveal a strong dependence on annealing time and casting solvent. Morphology is largely unaffected by the inclusion of the mechanophore. The high-molecular-weight polymers synthesized allow interrogation of a large range of polymer domain sizes.

Gold-Catalyzed Post-Polymerization Modification of Commodity Aromatic Polymers.

Synthetic aromatic polymers are ubiquitous and indispensable to modern life, industry, and the global economy. The direct functionalization of these materials remains a considerable challenge on account of their unreactive aromatic C-H bonds and robust physical properties. Here, we demonstrate that homogeneous gold catalysis offers a mild, chemoselective, and practical approach to functionalize high-volume commodity aromatic polymers. Utilizing a gold-catalyzed intermolecular hydroarylation between a methyl ester functionalized alkyne, methyl propiolate, and nucleophilic arenes within polystyrene (PS) results in direct functionalization of phenyl rings with 1,2-substituted methyl acrylate functional groups. The reactivity and functionalization depend on the steric and electronic environment of the catalyst, counterion pairing, and method of activation. The reactivity is broad in scope, enabling the functionalization of arenes within commercial polysulfone (PSU) and waste polyethylene terephthalate (PET). These reactions open new opportunities to chemically transform aromatic polymers and modify their physical properties.