Mechanics, adhesion and fracture of dynamic polymers.

Dynamic polymers are made of molecular networks with transient connections, which makes then visco-elastic, self-healing and potentially recyclable. While omnipresent in biology, their synthetic counterparts have only been recently made in labs (such as vitrimers or covalent adaptable networks for instance). Due to their high energy dissipation, dynamic polymers can exhibit controllable flow and elasticity, exceptional toughness and self-healing properties. We study how molecular architecture and dynamics can be tuned to tame the mechanical response of these wild materials. We now focus on several aspect of their response:

  1. Competition between flow and fracture in dynamic networks. This phenomenon, that is still poorly understood is at the origin of cavitation and fracture in dynamic polymer, and thus at the origin of their resistance to fracture. We aim to elucidate the mechanisms at play and identify molecular networks (multiple networks, hybrid networks, ...) that yield polymers and gels with high fracture toughness.This work is in collaboration with the Cai group (UCSD), with dynamic polymers based on living exchange reactions of disulfide bonds.
  2. Dynamic liquid crystal elastomers.  Number of biological materials are made of a combination of rigid filaments, linked by flexible chains. Inspired by the structure of fungi cell walls and muscles, we study the time-dependent actuation patterns (helical/extensional) of these networks. We seek applications into actuators whose motion is controlled by a dynamic molecular structure that can be reprogrammed over time. This work is in collaboration with the Cai group (UCSD) using disulfide liquid crystal elastomer as a model system and with the Bruns group (CU Boulder) using polyrotaxane gels. 
  3. Failure and fracture in adhesives. We study the complex mechanisms and pattern formation during the failure of adhesives on soft and rigid substrates. This work, in collaboration with 3M corporation aims to develop smart adhesives under various conditions.

dynamic polymers