Polymer Micro- and Nanocapsules: Current Status, Challenges and Opportunities

Dear Colleagues,

Inspired by the remarkable wound-healing functionality of living organisms, a self-healing material/structure can repair small or medium-scale damage; thus, restoring the impaired functionalities, potentially being capable of significantly increasing the lifetime of a structure, paving the way for a more sustainable and smart future.

Self-healing materials and, more specifically, polymers, can be categorized into three conceptual approaches: the intrinsic, the vascular and the capsule-based. The intrinsic self-healing approach exploits the inherent ability of a composite to restore its initial properties at the molecular level through physical or chemical reversible bonding. An alternative, extrinsic route towards developing self-healing polymers is by mimicking the blood vessels of living organisms. This approach involves the fabrication of a vascular network composed of micro-channels or hollow fibres, whereby the healing agent is manually or automatically introduced into the material. Finally, the capsule-based self-healing strategy concept is of high importance, involving the embedment of micro- or nano-capsules containing an active liquid, i.e., the healing agent, within the host material. When the polymer sustains damage, the capsules rupture, releasing the liquid agent at the damage site; thus, healing the polymer.

Capsule-based self-healing systems, incorporating micro- or nano-sized capsules, have attracted considerable attention in the research society due to their minimal reduction in mechanical properties after the incorporation of self-healing, the potential for mass production and high healing efficiency values. Numerous attempts have been presented every year, focusing on the development of different capsule-based self-healing systems (healing agent chemistry, encapsulation methods, etc.), as well as their integration to large-scale production with the best possible property–cost relationship, indicating the increased interest of the research community towards this filed.

The scope of this Special Issue is to present and discuss the recent advancements, healing fundamentals and mechanisms in self-healing polymers which utilise micro- or nano-sized capsules, with emphasis given to developments in encapsulation methods and novel functional materials related to capsule-based self-healing polymers.

With great pleasure, we would like to invite you to submit a manuscript for publication in this Special Issue, full papers, communications and reviews all being welcome. In addition, the list of keywords is not exhaustive, but it may help prepare your submission. If you would like to go beyond it, please submit a paper whose topic is not mentioned in this list.

Dr. Dimitrios Bekas
Prof. Sotirios Grammatikos
Guest Editors

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