A composite polymer based on vinylogous urethane vitrimer bonding with both photodimerizable and thermally exchangeable functionalities is described. Polymers containing various ratios of photodimerizable diaminoanthracene monomers and thermally exchangeable diaminoalkyl monomers linked by a common bisacetoacetate group are studied. It is demonstrated that alkyl amines undergo the necessary thermal exchange reactions for vinylogous urethane vitrimers, while aromatic amines do not. UV-induced dimerization of the anthracene units results in changes to the rheological properties and the glass transition temperature due to polymer cross-linking. Rapid and near-complete scratch healing upon heating is demonstrated, with a tunable onset temperature for healing controlled by UV irradiation. The viability of a composite vitrimeric system, wherein vitrimeric monomers are combined with non-vitrimeric, stimuli-responsive monomers to generate random copolymers with new properties, is demonstrated.

The chemical functionalization of polyolefins to access responsive materials is a long-standing challenge in materials science. Current protocols do not typically tolerate polar functional groups, and postpolymerization modification often leads to material defects. Here the catalytic synthesis of amine-functionalized polyolefins has been achieved using a two-step catalytic combination of hydroaminoalkylation and ring-opening metathesis polymerization (ROMP). Furthermore, reduction was used to obtain an aminated polyethylene analogue. This preparation transforms simple starting materials into polar-functionalized polymers with complete atom economy. Utilizing dynamic associative interactions, including hydrogen bonding, these materials demonstrate tunable rheological properties, autonomous self-healing, and unexpected adhesion to polytetrafluoroethylene (PTFE).

Amine-functionalized polymeric materials have a wide variety of applications; however, the preparation of these materials is often plagued by laborious, multistep synthetic routes. Herein, a modified and improved synthetic protocol utilizes the hydroaminoalkylation reaction to catalytically assemble amine-functionalized monomers on a gram scale with 100% atom economy. Combined with ring-opening metathesis polymerization (ROMP), amine-functionalized polymers with varying electronic properties have been synthesized. Extensive rheological characterizations show that modification of the electronic properties of the amine substituent influences the bulk material properties through modification of hydrogen bonding and π-stacking interactions to afford dynamic cross-linking within the polymeric material. Tertiary amine-containing polymers display distinct rheological properties that differ from those of polymers with pendant hydrogen-bond-donating secondary amines. The profound viscoelastic effects that result from the incorporation of tunable dynamic interactions are presented.

Cationic indium complexes were used as catalysts for the copolymerization of epoxides and racemic lactide (rac-LA) via sequential addition to form high-molecular weight block copolymers. Mechanistic studies and control experiments indicate that the epoxide is polymerized by a cationic mechanism to yield a neutral alkoxide indium species that subsequently polymerizes the lactide by a coordination-insertion mechanism with no significant interference of the two mechanisms under polymerization conditions. The thermal and tensile properties of different block copolymers were studied, revealing mostly amorphous materials. We were able to control the ductility and stiffness of the copolymers by tuning the nature and chain length of the blocks.

Using a parallel-plate rheometer equipped with a partitioned plate, and the Sentmanat extensional rheometer fixture, a full rheological characterization of several commercial ionomers and their corresponding parent copolymers has been carried out. Particular emphasis has been placed on the distribution of the relaxation times to identify the characteristic times, such as reptation, Rouse, and sticky-Rouse, that are associated with the characteristic lifetime of the ionic and hydrogen bonding associations. As such, scaling laws have been used to calculate the order of magnitude of the lifetimes of associations and the association energy that are important parameters to gain a better understanding of their rheological behavior. To study the effects of ionic associations, the commercial ionomers were completely unneutralized and their rheological behavior was compared directly with their associative counterparts. The rheological comparison included the linear viscoelastic moduli, the damping function, steady shear, and extensional rheology demonstrating the significant effects of ionic interactions.