Thermogelling Behaviors of Aqueous Poly(N-Isopropylacrylamide-co-2-Hydroxyethyl Methacrylate) Microgel–Silica Nanoparticle Composite Dispersions

Abstract

Gelation behaviors of hydrogels have provided an outlook for the development of stimuli-responsive functional materials. Of these materials, the thermogelling behavior of poly(N-isopropylacrylamide) (p(NiPAm))-based microgels exhibits a unique, reverse sol–gel transition by bulk aggregation of microgels at the lower critical solution temperature (LCST). Despite its unique phase transition behaviors, the application of this material has been largely limited to the biomedical field, and the bulk gelation behavior of microgels in the presence of colloidal additives is still open for scrutinization. Here, we provide an in-depth investigation of the unique thermogelling behaviors of p(NiPAm)-based microgels through poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) microgel (p(NiPAm-co-HEMA))–silica nanoparticle composite to expand the application possibilities of the microgel system. Thermogelling behaviors of p(NiPAm-co-HEMA) microgel with different molar ratios of N-isopropylacrylamide (NiPAm) and 2-hydroxyethyl methacrylate (HEMA), their colloidal stability under various microgel concentrations, and the ionic strength of these aqueous solutions were investigated. In addition, sol–gel transition behaviors of various p(NiPAm-co-HEMA) microgel systems were compared by analyzing their rheological properties. Finally, we incorporated silica nanoparticles to the microgel system and investigated the thermogelling behaviors of the microgel–nanoparticle composite system. The composite system exhibited consistent thermogelling behaviors in moderate conditions, which was confirmed by an optical microscope. The composite demonstrated enhanced mechanical strength at gel state, which was confirmed by analyzing rheological properties.

Surface and Interface Engineering for Organic Device Applications

“…The diversity of contributions presented in this Special Issue exhibits the potential of organic materials in a variety of applications that are not limited to the fabrication of organic devices. This Special Issue contains eight featured original research papers as regards nanoarchitecture based on organic elements [ 1 ], physical behaviors of organic-based composite materials [ 2 ], surface exfoliation and device fabrication using functional polymers [ 3 , 4 ], performance enhancements of organic-based electronic devices [ 5 , 6 ], conductivity analysis of conducting polymers [ 7 ], and measurement system applicable to analysis of surface and interface engineering [ 8 ].…”

“…Byung Soo Hwang et al provided an outlook for the development of stimuli-responsive functional materials through their study of gelation behaviors of hydrogels in the contributed article entitled “Thermogelling Behaviors of Aqueous Poly(N-Isopropylacrylamide-co-2-Hydroxyethyl Methacrylate) Microgel–Silica Nano-particle Composite Dispersions” [ 2 ]. In this study, an in-depth investigation of the unique thermogelling behaviors of poly(N-isopropylacrylamide)-based microgels through poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) microgel (p(NiPAm-co-HEMA))-silica nanoparticle composite was performed with different molar ratios and various concentrations.…”

Surface and Interface Engineering for Organic Device Applications

“…Byung Soo Hwang et al provided an outlook for the development of stimuliresponsive functional materials through their study of gelation behaviors of hydrogels in the contributed article entitled "Thermogelling Behaviors of Aqueous Poly(N-Isopropylacrylamide-co-2-Hydroxyethyl Methacrylate) Microgel-Silica Nano-particle Composite Dispersions" [2]. In this study, an in-depth investigation of the unique thermogelling behaviors of poly(N-isopropylacrylamide)-based microgels through poly(Nisopropylacrylamide-co-2-hydroxyethyl methacrylate) microgel (p(NiPAm-co-HEMA))silica nanoparticle composite was performed with different molar ratios and various concentrations.…”