Smart, Reconfigurable Polymer Networks

Smart, crosslinked polymers with the ability to reconfigure the underlying network on command and respond to changes in their immediate environment have recently received attention in enabling applications that range from data storage to tissue engineering to 3D prototyping.  Here, two independent underlying approaches, Dual-Cure (two-stage reactive) networks and Addition-Fragmentation Chain Transfer (AFCT)-based networks, are used to form crosslinked polymeric materials.  These networks function as smart, reconfigurable materials with the ability to control the shape, modulus and behavior of the underlying polymer network with both spatial and temporal control.

 In one approach, a dual-cure (two-stage reactive) polymer system is used to create an initial polymer network via a self-limiting click thiol-Michael addition reaction. This stable material can then be reacted further to achieve a second, final and independent set of material properties via a photoinduced reaction, enabling the achievement of material properties and performance that are necessary for multiple stages in the life-cycle of applications such as shape memory polymers (SMP) and optical materials. In a second approach, a photochemically initiated mechanism that gives rise to network rearrangement within a crosslinked polymer network via addition-fragmentation chain transfer (AFCT) will be discussed. Such materials can be designed to exhibit self-healing characteristics, where fractured pieces of material reform upon irradiation. In addition to the ability to induce a reduction in external stresses applied post-polymerization via photo-induced creep and the ability to form photochemically defined lithographic features formed on materials, the ability of AFCT materials to be stretched and irradiated in a patterned manner to impart 3D shape changes and  alter the surface topography of materials is also demonstrated.