Hydrophobically Associating Hydrogels with Microphase-Separated Morphologies
Hydrophobically associating hydrogels based on copolymers of a water-soluble monomer with a fluoroacrylate or fluoromethacrylate possess microphase-separated morphologies that provide unique properties. Physical crosslinks in these hydrogels involve hydro
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Hydrophobically Associating Hydrogels with Microphase-Separated Morphologies Bryan D. Vogt and R. A. Weiss
Contents 1 Introduction 2 Fluorinated Amphiphilic Copolymers 2.1 Synthesis of Fluorinated Amphiphilic Copolymers 2.2 Preparation of Hydrophobically Associating Supramolecular Hydrogels 2.3 Hydrogel Microstructure 2.4 Direct Extrusion of Hydrogels 2.5 Self-Healing Behavior 2.6 Mechanical Behavior 3 Applications 3.1 Injectable Hydrogels 3.2 Electrospinning Hydrogel Fiber Mats for Potential Tissue Scaffolds 3.3 Controlled Drug Release 3.4 Antifreeze Hydrogel 3.5 Shape Memory Hydrogels 4 Summary References
Abstract Hydrophobically associating hydrogels based on copolymers of a watersoluble monomer with a fluoroacrylate or fluoromethacrylate possess microphaseseparated morphologies that provide unique properties. Physical crosslinks in these
B. D. Vogt Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA e-mail: [email protected] R. A. Weiss (*) Department of Polymer Engineering, University of Akron, Lenox, MA, USA e-mail: [email protected]
B. D. Vogt and R. A. Weiss
hydrogels involve hydrophobic bonds between fluoro(meth)acrylate groups that associate into 2–6-nm-diameter core–shell nanodomains that represent multifunctional crosslinks. These hydrogels exhibit exceptional mechanical properties and fracture toughness values approaching 104 J/m2, are extrudable, and show self-healing behavior of the microstructure. This chapter reviews the characteristics of these microphase-separated, hydrophobically associating hydrogels and discusses potential applications of these materials as injectable in situ forming hydrogels, electrospun fiber mats suitable for tissue scaffolds, controlled drug release, antifreeze materials, and shape memory hydrogels. Keywords Amphiphilic copolymers · Microphase separation · Physical hydrogels · Supramolecular hydrogels
1 Introduction Supramolecular hydrogels (SMHs) are of contemporary interest due to the reversibility of the polymer network from which they are derived and properties such as processability, toughness, and self-healing that result from having reversible crosslinks. SMHs have been developed from a variety of non-covalent chemistries, including hydrogen bonds, ionic bonds, ligand–receptor complexation, and hydrophobic interactions [1, 2]. This chapter concerns SMHs based on hydrophobic interactions, specifically those based on fluorinated monomers. Hydrophobically modified hydrogels have been primarily derived from hydrocarbon-containing monomers [3]. The motivation for synthesizing and studying the fluorocarbon-based hydrogels discussed in this chapter was the work of Hogen-Esch and coworkers [4–7], who studied aqueous solutions of water-soluble copolymers containing fluorinated co-monomers. The objective of their work was to compare the viscosity enhancement of fluorocarbon hydrophobically associating water-soluble polymers to that of hydrocarbon hydrophobically associating watersoluble polymers. The greater viscosification effect of the
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