Synthesis of Highly Stretchable, Mechanically Tough, Zwitterionic Sulfobetaine Nanocomposite Gels with Controlled Thermosensitivities

Abstract

Novel nanocomposite (NC) gels with zwitterionic characteristics were prepared by in situ free-radical polymerization of sulfobetaine monomers in the presence of exfoliated clay platelets in aqueous media. Two specific sulfobetaine monomers, N,N-dimethyl(acrylamidopropyl)ammonium propanesulfonate and butanesulfonate, were selected on the basis of the interactions between the monomers and clay, which result in uniform aqueous solutions of low viscosity and gel formation without using an organic cross-linker. The resulting NC gels with polymer–clay network structures were insoluble in NaCl solution or hot water, unlike conventional physically cross-linked gels. Also, NC gels with high mechanical properties and well-controlled thermosensitivities were effectively prepared by copolymerization with a small amount of N,N-dimethylacrylamide. The copolymer NC gels were uniform and simultaneously showed high stretchability, tough mechanical properties, and well-defined upper critical solution temperature (UCST) phase-transitions. Furthermore, the tensile mechanical properties and UCST were controlled over a wide range by altering the clay concentration and copolymerization ratio.

Changes in the Properties and Self‐Healing Behaviors of Zwitterionic Nanocomposite Gels Across Their UCST Transition

“…The transparencies at 20 and 5 C for A 3 Dx-NC3 gels with different x (0-100) are shown in Table 1. As reported previously, [21] when x ¼ 0, the resulting as-prepared gel ( A 3 -NC3 gel) was structurally uniform and transparent at 20 C but became opaque (white) at 5 C, owing to UCST type thermosensitivity (UCST ¼ 16.5 C), whereas when x ¼ 100 ( D-NC3 gel), the gel was transparent regardless of temperature. [22] When the value of x is equal to or greater than 30 (30À90), the A 3 Dx-NC3 gels are always transparent and do not exhibit thermosensitivity.…”

“…[21] Briefly, the initial reaction solutions consisting of water (20 mL), clay (Laponite XLG), two monomers (DMAA and A 3 ), an initiator (KPS: 7.4 Â 10 À2 mmol), and an accelerator (TEMED: 1.07 Â 10 À1 mmol)…”

“…To overcome these problems, we developed zwitterionic nanocomposite gels (A 3 -NC gels) consisting of a sulfobetaine A 3 polymer and inorganic clay by in situ free-radical polymerization in aqueous media in the presence of exfoliated clay platelets. [21] In analogy with normal NC gels consisting of a neutral polymer, [22][23][24] the resulting zwitterionic A 3 -NC gels exhibited good mechanical properties as well as high structural uniformity (transparency) and a well-defined thermoresponsive transition. Furthermore, we developed zwitterionic copolymer NC gels (A 3 D-NC gels) with high stretchability and tough mechanical properties by in situ copolymerization of two monomers, A 3 and N,N-dimethylacrylamide (DMAA).…”

“…Furthermore, we developed zwitterionic copolymer NC gels (A 3 D-NC gels) with high stretchability and tough mechanical properties by in situ copolymerization of two monomers, A 3 and N,N-dimethylacrylamide (DMAA). [21,25] The thermosensitivity and transition temperature (UCST) of the A 3 D-NC gels could be controlled over a wide range by altering the monomer ratio and clay and monomer concentrations. In the present paper, we demonstrate the changes in the properties of thermoresponsive A 3 D-NC gels, such as optical transmittance, gel volume, dynamic viscoelasticity, and tensile mechanical response, by varying the temperature across the UCST.…”

Synthesis of Amphiphilic Polymer Gels Containing Poly(trimethylene carbonate) Segments and Evaluation of Its Molecular Incorporation Properties

“…High mechanical strength, drug loading ability, and biocompatibility are required for advanced materials. Moreover, amphiphilic hydrogels can incorporate hydrophobic drug molecules for application in drug delivery systems [5][6][7][8].…”