Synthesis And Characterization Of Novel Ionically Crosslinked Polymers

Author : Guodong Deng
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (141 download)

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Download or read book Synthesis and Characterization of Ionically Cross-linked Networks Through the Use of Ion-pair Comonomers written by Guodong Deng and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Structurally dynamic polymer networks, which can break and reform under external stimuli (e.g. heat, mechanical stress, light, etc.) have emerged as a useful approach to fabricate stimuli-responsive polymers (SRPs). One general route to introduce dynamic bonds is through non-covalent supramolecular interactions. Ion-pairing, is another potential non-covalent dynamic bond distinct from other interactions like hydrogen bonding and metal-ligand interactions. In this study, we demonstrate a new route to prepare structurally dynamic polymer networks by direct copolymerization of organic ion-pair comonomers (IPCs) with n-butyl acrylate (BA). A series of these copolymers were prepared and their results of rheological, mechanical, thermal and morphological behaviors will be comprehensively studied to understand the structure-property relationships. Firstly, a phosphonium-based IPC was synthesized and copolymerized with BA to prepare polyampholyte ionomers. Evidence of microphase separation of the ion-pairs to produce vitrified ion-rich domains acting as physical cross-links was found in polyampholyte ionomers by rheological and atomic force microscopy measurements. Comparison to analogous cationic and anionic ionomers with pendant counter-ions demonstrated the strong impact of direct ion-pair cross-linking on the material's viscoelastic properties. Characterization of the corresponding polyelectrolytes showed a ca. 125 oC increase in the glass transition temperature (Tg) from the cationic to the polyampholytic polyelectrolyte. This elevated Tg allowed the vitrification of the ion-rich domains at ambient temperatures in the polyampholyte networks over a range of ion-pair concentrations. An increase in molecular weight could lead to highly entangled samples, which displayed an improved mechanical properties. Secondly, the copolymers of the ion-pair co-monomer and cationic monomer were found to effectively plasticize the synthesized polyampholytic polyelectrolyte and tune their Tg. This plasticizing effect could also be applied to the polyampholyte ionomers through the copolymerization of BA and ionic monomers blends. In this way, the Tg of vitrified ion-rich domains in polyampholyte ionomers can be approximately predicted with IPC concentration, which opens up the toolbox for designing SPRs with varying transition temperature. Thirdly, an analogous ammonium-based IPC was also synthesized and used to prepare polyampholyte ionomers. Comparison to analogous phosphonium-based polyampholyte ionomers demonstrated a stronger ion-pair interaction and weaker thermal stability in ammonium/sulfonate than phosphonium/sulfonate. This novel IPC can expand the IPCs' library and fine tune viscoelastic behavior of polyampholyte ionomers systems with less expensive starting materials.