Abstract
In this work we rationalize the relationship between polymer architecture, energy stored during scratch damage, entropy release during healing and gap closure of scratches.
Highlights
IntroductionEnvironmental concerns related to material overconsumption and the ineffective life cycle of commodity polymers are valuable drivers for the development of alternative and more sustainable solutions to current materials and design rules.[1,2,3,4] Among the various strategies explored by polymer scientists, the development of self-healing polymers is one of the promising routes to extend the life-time of polymers.[5,6,7,8,9] Autonomous selfhealing polymers rely on the incorporation of a fraction of reversible bonds that allow the temporary de-construction of the network, while permanent crosslinks, main chain entanglements or microphase separation ensure mechanical robustness and network integrity.[10]
The current study tests the hypothesis that different levels of released entropy during the shape memory transition can be accessed by controlling the damage and healing temperatures, which can be quantitatively assessed in terms of the released entropy that contributes to the scratch closure
In general terms, enhanced closure will be obtained in polymers with a high junction density and combinations of sufficient local deformation during damage and healing temperatures which lead to an optimal release of the stored energy
Summary
Environmental concerns related to material overconsumption and the ineffective life cycle of commodity polymers are valuable drivers for the development of alternative and more sustainable solutions to current materials and design rules.[1,2,3,4] Among the various strategies explored by polymer scientists, the development of self-healing polymers is one of the promising routes to extend the life-time of polymers.[5,6,7,8,9] Autonomous selfhealing polymers rely on the incorporation of a fraction of reversible bonds that allow the temporary de-construction of the network, while permanent crosslinks, main chain entanglements or microphase separation ensure mechanical robustness and network integrity.[10]. The current study tests the hypothesis that different levels of released entropy during the shape memory transition can be accessed by controlling the damage and healing temperatures, which can be quantitatively assessed in terms of the released entropy that contributes to the scratch closure. Using this approach empirical relations between released entropy, junction density, and scratch closure displacement for thermoplastic healing polyurethanes with known and variable healing kinetics can be developed. The VLT values used in this study are obtained as the algebraic mean of the set of DMA tests
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