Through a well-targeted design, vitrimers are able to reorganise their three-dimensional covalently crosslinked network structure by associative exchange reactions when the so-called topology freezing transition temperature (T-v) is exceeded. Although in the past decade a vast number of vitrimers have been developed, there is only a very limited number of elaborate strategies for enabling a controlled and spatially resolved onset of the exchange reactions above T-v. Herein, we describe a convenient approach for a locally controllable photoactivation of vitrimeric properties in a covalently crosslinked thiol-epoxy network by the UV-mediated release of a strong amidine base acting as an efficient transesterification catalyst. In contrast to previous work, the applied photolatent catalysts benefit from superior solubility properties, adequate curing characteristics in the non-activated state (the addition of a supplementary catalyst is not required) and an excellent thermal stability. The spatially controlled activation of vitrimeric properties in terms of dynamic transesterification, macroscopically visible as a viscoelastic flow, is demonstrated by stress relaxation studies and a reshaping experiment. Moreover, we confirm that an undesired purely thermally induced catalyst release can be entirely excluded.
Streamlined concept towards spatially resolved photoactivation of dynamic transesterification in vitrimeric polymers by applying thermally stable photolatent bases / Reisinger, David; Dietliker, Kurt; Sangermano, Marco; Schlögl, Sandra. - In: POLYMER CHEMISTRY. - ISSN 1759-9954. - ELETTRONICO. - 13:9(2022), pp. 1169-1176. [10.1039/D1PY01722E]
Streamlined concept towards spatially resolved photoactivation of dynamic transesterification in vitrimeric polymers by applying thermally stable photolatent bases
Sangermano, Marco;
2022
Abstract
Through a well-targeted design, vitrimers are able to reorganise their three-dimensional covalently crosslinked network structure by associative exchange reactions when the so-called topology freezing transition temperature (T-v) is exceeded. Although in the past decade a vast number of vitrimers have been developed, there is only a very limited number of elaborate strategies for enabling a controlled and spatially resolved onset of the exchange reactions above T-v. Herein, we describe a convenient approach for a locally controllable photoactivation of vitrimeric properties in a covalently crosslinked thiol-epoxy network by the UV-mediated release of a strong amidine base acting as an efficient transesterification catalyst. In contrast to previous work, the applied photolatent catalysts benefit from superior solubility properties, adequate curing characteristics in the non-activated state (the addition of a supplementary catalyst is not required) and an excellent thermal stability. The spatially controlled activation of vitrimeric properties in terms of dynamic transesterification, macroscopically visible as a viscoelastic flow, is demonstrated by stress relaxation studies and a reshaping experiment. Moreover, we confirm that an undesired purely thermally induced catalyst release can be entirely excluded.File | Dimensione | Formato | |
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https://hdl.handle.net/11583/2957138