Individual artificial polymers are usually capable of fulfilling only a narrow set of requirements in terms of strength, toughness, elasticity, modulus, etc. The vast majority of them are not adaptive to different stimuli, do not self-heal, and do not possess shape-memory. In contrast, many natural biopolymers combine all of these properties into one material. Researchers have recently mimicked a skeletal muscle protein, titin, to produce a synthetic polymer that shares these characteristics by taking advantage of bioinspired molecular interactions. The titin polymer is composed of linear tandem units of beta sheet forming subunits. When stress is applied axially to the strand, the hydrogen bonds holding the beta sheets together break then reform and return to their original state. Researchers mimicked this tendency by polymerizing a chain of cyclic, modular subunits (ureidopyrimidinone functionality or UPy) that each contain four hydrogen bond-forming units. In their most stable state, the hydrogen bonds encourage the subunits to fold into biomimetic beta sheets. The polymer was found to closely mimic both the architecture of titin, its physical properties, and its adaptability. Although quite strong, the material was also extremely elastic. In artificial polymers designed to be strong, hyperextension produces necking and crazing which are types of permanent damage. The biomimetic polymer, however, was able to return to its original state after some time had elapsed (self-healing and memory). Moreover, the healing rate and temporary memory states could be modulated by changing the temperature. This modular biopolymer combines some extraordinary characteristics that make it extremely useful for certain applications that require specialized materials. Recently, the Dutch company SupraPolix BV has developed a commercial UPy polymer called SupraB®. This material is marketed as a strong, elastic, memory forming plastic that can be modified by varying temperatures.
UPy based plastics like SupraB® could be more durable than conventional plastics because of their self-healing, memory, and stress-absorbing properties.
Conventional polymers are relatively simple from an intramolecular physics point of view. They are usually quite well designed to be either strong or elastic but not both. Moreover, few show adaptable stress-strain properties and even fewer demonstrate self-healing or shape-memory. UPy based polymers like SupraB® can combine all of these properties by mimicking the molecular design of titin.Edit Summary