Self-healing Properties Of Dynamic Polymer Gels

Self-healing materials imitate the principle of biological damage healing. They are thesubject of increasing interest, because they can repair the internal and external damagethereby extending the life time of the material in numerous applications, and they can reduceproduction costs. It is a new method for polymers employ the reversible covalent bonds tocomplete self-healing through controlling the exchange reaction.Acylhydrazone as one of dynamic covalent bonds, in weak acid or neutral condition canundergo reversible breaking and reformation. So it is stronger than molecular forces such ashydrogen bond. Gels which are cross-linked with this bond may have good stability andmechanical strength like chemical gels and have the self-healing property as well as physicalgels. On the basis of previous work, in this paper we synthesize new Gelators to formdynamic hydrogels and organic gels containing acylhydrazone. Polymer gel is formed bychemical cross-linking and has the self-healing performance.The main contents and results of this paper are as follows:1. Glators’ synthesis: Through esterification, nucleophilic substitution and acylation,aldehydeterminated3-armed PEO and acylhydrazine-terminated PEO were obtained withalmost100%degree of terminal functionality.2. Gels’ synthesis and its properties: Intelligent gels were synthesized by two glatorscontaining aldehyde and hydrazide reacting. In weak acid or neutral condition, hydrogels andorganic gels can repair through exchange reaction of acylhydrazone bonds. Tensile testsindicate that after48h of self-healing; the break stress and strain can reach94%of the originalgel. Rheological test and tensile test indicate gels have good mechanical properties.3. Fast healing property of hydrogel and anisole gel: Two glators form gels in water(with lemon yellow) and anisole, respectively. Hydrogel and anisole gel can healing within5minutes without external interferences. After healing, break stress and strain values are notconsistent with original hydrogel’s, they are not consistent with anisole gel’s either, and theyare actually in between. Make preliminary exploration of fast healing property.