Swelling characteristics of poly(N‐isopropylmethacrylamide‐co‐itaconic acid) gels prepared in various conditions

Abstract

Thermo-and pH-sensitive gels composed of N-isopropylmethacrylamide (NIPMA) and itaconic acid (IA) were prepared by free-radical crosslinking copolymerization in poly(ethylene glycol) (PEG) solution at 22 C and in water at À22 C and at 22 C, which were called as the macroporous gel (MGel), the cryogel (CGel), and the conventional gel (NGel), respectively. The gels were characterized by the equilibrium swelling, interior morphology, and deswelling kinetics. With increasing temperature in water, the gels exhibit reentrant conformational phase transition. During this transition, the gels first deswell in the range of temperature between 5 and 29 C, then drastically reswell if temperature is monotonically increased. The reswelling of the collapsed gels occurs above 45 C. It was shown that the reentrant transition in poly(N-isopropylmethacrylamideco-itaconic acid) [poly(NIPMA-co-IA)] gels requires moderate temperature, so that the hydrophobic interactions between chains dominate the swelling process. Scanning electron micrographs revealed that the interior network structure of MGel is more porous compared with those of CGel and NGel. This more porous structure provided numerous water channels for water diffusion out of the matrix and, therefore, an improved response rate to the external temperature and pH changes during the deswelling process.

Intelligent Poly(N-Isopropylmethacrylamide) Hydrogels: Synthesis, Structure Characterization, Stimuli-Responsive Swelling Properties, and Their Radiation Decomposition

“…They are known as "intelligent" or "smart" hydrogels, because when environmental factors change (e.g., pH-value, temperature, light, glucose concentration, pressure, and magnetic or electric fields), they can respond with the changes of some physicochemical property (e.g., swelling capacity) [2]. Their syntheses can be designed to vary swelling ability, porosity, physical structure, etc., in order to provide an adequate response to the external stimuli changes [3]. All changes that occur in the hydrogels are reversible, and they can return to their original state upon the removal of the stimulus.…”

Thermoresponsive behavior and rheology of SiO2–hyaluronic acid/poly(N‐isopropylacrylamide) (NaHA/PNIPAm) core–shell structured microparticles

“…A comparison of microparticles with similar DMs shows that the microparticles prepared using longer NaHA chains have larger Δd values. This may be interpreted as the longer NaHA chains forming a looser adsorption layer, and a higher swelling rate resulting from the higher porosity. The d values depend mainly on the amount of NaHA adsorption which cannot be measured directly here.…”

Preparation of a gel‐coated liposome and its application in drug release

“…Apparently, their reductions in diameter Δ d are also different, thought to be related to the crosslink density of the HA/PNIPAM gel shell. Pure PNIPAM gel having lower crosslink density was reported to show a higher swelling/deswelling rate because of its porous and loose network structure. Besides the reaction conditions, such as the amount of reactants, reaction period, crosslink density of HA/PNIPAM gel is determined by the amount of unsaturated linkage on the HA backbone, i.e.…”