Development of Supramolecular Polysiloxanes as Functional Coating for Catalytic Applications

開發超分子聚矽氧烷材料作為功能塗層應用於催化

Student thesis: Doctoral Thesis

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Award date18 Aug 2021

Abstract

Siloxane-based materials show a wide range of applications in daily life and industry due to their exceptional physicochemical and mechanical properties. As the emerging technologies require high-performance polymeric materials, the inherent characteristics of traditional silicones led them to insufficient mechanical toughness, limited interfacial adhesion, and lacking recyclability. Such problems have recently been tackled by the implementation of a supramolecular design into siloxane-based materials. Based on diverse non-covalent interactions, the derived supramolecular siloxane materials demonstrate mechanical tunability, stimuli-responsiveness, self-healing ability, and reprocessability, making them promising for a range of applications from wearable electronics to energy devices.

Despite the advances achieved in supramolecular polysiloxanes, the research interest largely focuses on their bulk properties and the application as substrate materials. Here we developed supramolecular polysiloxanes as functional coating with damage-healing nature and special wettability, and explored their potential application in catalysis. Specifically, there are three parts in this thesis.

In the first part, a dual-crosslinked supramolecular polysiloxane has been designed to apply as functional coating with ion-controlled mechanical property, damage-healing and oil-sliding properties. Due to the formation of non-covalent bonding between the supramolecular polysiloxane and substrates, the coating shows high interfacial adhesion to various substrates. The mechanical property of the supramolecular polysiloxane coatings can be tuned by alteration of the coordinated metal ions or the molecular weight of polydimethylsiloxane macromonomers. In addition, the coating can repeatedly heal form severe damages due to the dense and dynamic bonds in the polymer network. Moreover, homogeneously distributed siloxane motifs on the extremely smooth surface contribute to the oil sliding/dewetting abilities of the silicone coating.

In the second part, a superhydrophobic and catalytically active coating that integrate the catechol-terminated supramolecular polysiloxane and metal-organic framework (MOF) nanoparticles has been developed by the coordination-driven assembly of the two components. During the curing process of the coating, the strong coordination between MOF nanoparticles and the supramolecular polysiloxane not only enabled the fast surface functionalization of MOFs and the superhydrophobicity of the coating, but also endowed the coating with good mechanical stability. The coating can show superior catalytic activity toward Knoevenagel condensation with the synergistic effect of retained porosity of MOFs and hydrophobicity of supramolecular polysiloxane.

In the third part, we fabricated a series of supramolecular polysiloxane coated MOF heterogeneous catalysts by postsynthetic modification of the Zr-based UiO-66 MOFs with ureidopyrimidinone (UPy)-terminated supramolecular polysiloxanes. The supramolecular polysiloxane coated MOFs showed remarkable catalytic performance in Knoevenagel condensation reactions, with much higher reaction activity relative to pristine UiO-66-NH2 powders. In addition, the recycling test indicated the long-term stability of the modified MOFs for cycle use. Moreover, the gram-scale tandem catalytic reactions for the chromene product demonstrate the application potential of the supramolecular polysiloxane-coated MOF material.