Physically Crosslinked Acrylics with Enhanced Mechanical Strength and Processability: From DNA to Supramolecular Pressure Sensitive Adhesives

摘要

Supramolecular polymers are emerging as functional materials for many applications due to their unique reversibility and thermoresponsiveness.' There are two main types of supramolecular polymers: supramolecular polymers comprise of monomer units associated via noncova-lent interactions; or chemically linked polymer backbone bearing pendent groups that physical crosslink both inter-and intra-molecularly. The second type shows more potential in commercial application development, as it combines the benefit of traditional polymer synthesis and the unique reversibility from physical crosslinks. Noncovalent interactions, such as hydrogen bonding and pi-stacking, create supramolecular physical crosslinked network and significantly influence polymer properties. For adhesive materials, noncovalent interactions improve cohesive strength,2'3 enhance temperature dependence of melt viscosity,4 and drive self-assembly of phase separated morphology.5 Instead of covalently-crosslinked thermoset like epoxy, these supramolecular polymer networks regain their processibility when noncovalent interactions dissociate upon external stimuli, such as heat, pH, solvent, and salt (Figure 1). As a result, supramolecular adhesives have advantages over conventional adhesives on both mechanical performance and processibility.