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joined together at temperature higher than the T g since the latter has larger flat segmental distribution.Due to unavailability of a universal method to obtain the healing thereby varied healing times along withnon-autonomous nature of the process, motivation for this approach almost ended by the beginning of1990s. However the theory of interdiffusion and the models presented have been used to study anddesign encapsulation and microsvascular based healing approaches.Figure – 1.20: Mechanisms involved in self healing via molecular interdiffusion.1.4.2 Dynamic Covalent BondingMuch like dynamic non-covalent bonding, dynamic covalent bond chemistry has also been extensivelyexplored. Polymers incorporating these bonds do not suffer from low mechanical properties as theircounterparts with non-covalent bonds. However again, this comes with less impressive self-healingability and lower healing efficiencies. Moreover, most of these systems require a particular stimuli likeheat, light, mechanical stress, pH fluctuations specific to the inherent dynamic chemistry of the material.In most of the cases, these materials have been designed in such a fashion that the required stimulus forthe healing is encountered as a part of the sought application. Nevertheless, human intervention is stillrequired in some way or another; hence these systems are categorized as non-autonomous self-healingsystems.1.4.2.1 Diels-Alder Chemistry26