Self Healing of Polymer Systems

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The majority of the processes developed for self healing make use of chemical reactions for surface protection or structure restoration. Polymers undergo far more degradation due to damage events and fatigue as compared to inorganic materials, and thus self healing is truly essential for them. However, for the same reasons that they degrade, they can be self healed, as they do not resist reversible or responsive chemical reactions.

Some of the techniques used for self healing via chemical reactions are: -

- restoration of broken bonds by using catalytic additives (Takeda et al., 2003)

- supramolecular chemistry - creation of excess hydrogen bonds at fractured surfaces

- polymeric nanogels (Lieber et al., 2008)

- microencapsulation of the monomer and the catalyst in the polymer matrix (single damage event) (White et al., 2001)

- three-dimensional microvascular channel network inside a polymer matrix (multiple damage events) (Toohey et al., 2007)

IV. Conclusions

Self healing is essential for nanoscale systems because of the large number of defects which it inherits due to the sheer number of atoms present on its surface. Natural, biological systems provide us with infinite processes and techniques which nature has intricately designed to achieve self healing both microscopically and macroscopically.

What we can learn from nature and integrate into our own self healing systems is, specific damage recognition, isolation of the damaged component and transportation to the repair site, and a hierarchical structure with multi-scale repairing mechanisms. Man-made self healing systems are primitive as compared to those found in nature, and advance research in this field is required for nanosystems to be used commercially, because of their inherent defects, which would lead to failure is self healing properties are not imparted to them.

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