An IPN is a polymeric system consisting of at least two independently crosslinked polymer networks that are solely physically entangled without any chemical bond formation between the individual networks. IPNs can inherent unique combinations of materials properties like high toughness combined with great stretchability which makes them ideal candidates for high demanding material applications. We aim to design IPNs trough a knowledge-based straightforward blending approach. The underlying mechanisms of IPN formation and involved driving forces (thermodynamic driven de-mixing and kinetic entrapped entanglement) are investigated via comprehensive material characterization, property testing, and imaging methods. The resulting structure-property relation will be translated into physical models and predictions of material behavior for unknown systems. The knowledge gained will be applied to develop design strategies for application in flexible electronics and sustainable plastic design. By understanding the underlying mechanism of IPN formation and the structure of the material, a broad spectrum of properties and applications can be envisaged.
We incorporated styrylpyrene - a reversible photo-crosslinking moiety - in polymer network. Styrylpyrene can crosslink with visible light and reverses with UV light. When crosslinked films were irradiated with UV light, only 17% of the crosslinks reopened compared to nearly full reversal in solution, due to limited mobility of the chromophores. The network retains its mechanical integrity after UV irradiation because of the confinement effect limiting the photostationary state. By applying an additional stimulus like mechanical force or solvation during UV irradiation the photostationary state can be further perturbed and a higher degree of reverse reaction can be seen. This dynamic change of chemical equilibrium for de-crosslinking can lead to new design approaches for recyclable crosslinked polymer networks.
We incorporated styrylpyrene - a reversible photo-crosslinking moiety - in polymer network. Styrylpyrene can crosslink with visible light and reverses with UV light. When crosslinked films were irradiated with UV light, only 17% of the crosslinks reopened compared to nearly full reversal in solution, due to limited mobility of the chromophores. The network retains its mechanical integrity after UV irradiation because of the confinement effect limiting the photostationary state. By applying an additional stimulus like mechanical force or solvation during UV irradiation the photostationary state can be further perturbed and a higher degree of reverse reaction can be seen. This dynamic change of chemical equilibrium for de-crosslinking can lead to new design approaches for recyclable crosslinked polymer networks.
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