Thermodynamics of Self-Healing in Polymeric Materials
Inspired by biological systems, the self-healing of polymers represents an array of events involving conformational and configurational changes of macromolecular segments, associated with covalent, supramolecular or coordination bond reformations and usually induced by external stimuli. This chapter discusses recent advances in self-healing of thermoplastic and thermosetting polymers in the context of physico-chemical events responsible for repair processes. The first part focuses on thermodynamic considerations of self-healing and the role of entropic and enthalpic contributions to the Gibbs free energy during self-healing events. The proposed recoupling self-healing lattice model allows an estimate of the contributions of configurational changes, as well as chemical reactions occurring during self-healing, to the Gibbs free energy. As chains undergo transitions from non-equilibrium to equilibrium Gaussian states during self-healing, the magnitude of entropic and enthalpic contributions undergoes dynamic changes that lead to equilibrium at which Gibbs free energy reaches the minimum. The second part reviews recent advances in chemical reactions that involve remolding of thermoplastic and thermosetting polymers by reforming covalent bonding, coordination and supramolecular chemistries. Although the field of self-healing materials is still in its early stages, the combination of multi-faceted reactions offers significant promises in the development of new self-healing thermoplastic and thermosetting polymers.