Synthesis and Characterization of Stiff, Self-Crosslinked Thermoresponsive DMAA Hydrogels

Abstract

Stiff thermosensitive hydrogels (HG) were synthesized by self-crosslinking free radical polymerization of N,N-dimethylacrylamide (DMAA) and N-isopropylacrylamide (NIPAAm), adjusting the degree of swelling by carboxylate-containing sodium acrylate (NaAc) or a 2-oxazoline macromonomer (MM). The formation of hydrogels was possible due to the self-crosslinking property of DMAA when polymerized with peroxodisulfate initiator type. The MM was synthetized by the ring-opening cationic polymerization of 2-methyl-2-oxazoline (MeOxa) and methyl-3-(oxazol-2-yl)-propionate (EsterOxa), and contained a polymerizable styryl endgroup. After ester hydrolysis of EsterOxa units, a carboxylate-containing MM was obtained. The structure of the hydrogels was confirmed by 1H high-resolution (HR)-MAS NMR spectroscopy. Suitable conditions and compositions of the comonomers have been found, which allowed efficient self-crosslinking as well as a thermoresponsive swelling in water. Incorporation of both the polar comonomer and the macromonomer, in small amounts furthermore allowed the adjustment of the degree of swelling. However, the macromonomer was better suited to retain the thermoresponsive behavior of the poly (NIPAAm) due to a phase separation of the tangling polyoxazoline side chains. Thermogravimetric analysis determined that the hydrogels were stable up to ~ 350 °C, and dynamic mechanical analysis characterized a viscoelastic behavior of the hydrogels, properties that are required, for example, for possible use as an actuator material.

Poly(2-Hydroxyethyl methacrylate-co-N,N-dimethylacrylamide)-Coated Quartz Crystal Microbalance Sensor: Membrane Characterization and Proof of Concept

“…Broadbands extending from ~3100 cm −1 to 3500 cm −1 are associated with -OH stretching vibrations; the broad absorp-tion band centered at ~3380 cm −1 found in all copolymers is related to the -OH functional group inherited from the chemical structure of the HEMA monomer. Meanwhile, the band centered at ~3450 cm −1 present on the homopolymer PDMAa spectrum comes from -OH's of the water molecules adsorbed by the hydrogel as moisture [38,40]. C=O deformation vibrations were found at ~1720 cm −1 or ~1610 cm −1 in the P(HEMA) and P(DMAa) spectra, respectively (Figure 1).…”

“…Consequently, the copolymerization of PHEMA with other nonionic acrylic monomers such as the N, N-dimethylacrylamide (DMAa) has been explored. DMAa is an interesting monomer; it is the simplest among the N,N-disubstituted self-crosslinking acrylamides, used in biological applications due to its superadsorbent properties (e.g., elongation up to 1350%) [40], with multiple applications [41][42][43]. As previously reported, poly(N,N-dimethylacrylamide-co-2-hydroxyethyl methacrylate) [P(DMAa-co-HEMA)], with a monomeric ratio of 1:1 mol%, was synthesized and studied; and it resulted in being an efficient hydrogel for adsorbing and removing methylene blue [44] and lead (II) [45] from aqueous solutions.…”

Síntesis Y Caracterización De Nuevos Copolímeros De Injerto Termosensibles a Partir De N-Isopropilacrilamida Y Macromonómeros De 2-Metil-2-Oxazolina

“…Sin embargo, una distribución aleatoria de unidades del acrilato de sodio dentro de la cadena de poliNIPAAm no permite obtener una fuerte intensidad de la respuesta térmica ni mantener la temperatura de transición LCST cercana a la temperatura del cuerpo humano 7 . Una posible solución a este problema podría ser que los grupos ácidos no estén en la cadena principal del PoliNIPAAm sino en cadenas laterales y esto se podría lograr copolimerizando el NIPAAm con macromonómeros que contengan grupos ácidos 8,9 . Los macromonómeros de poli(2-oxazolina), conteniendo grupos ácidos, podrían ser adecuados para lograr esta separación de fases y también pueden darles nuevas propiedades a los copolímeros injertados porque los grupos ácido pueden ser modificados posteriormente a diversas funciones químicas tales como aminas, tioles 9,10 .…”

pH-Responsive Gamma-Irradiated Poly(Acrylic Acid)-Cellulose-Nanocrystal-Reinforced Hydrogels

“…Recently, hydrogels that can inherently display dramatic changes in response to environmental stimuli such as temperature, pH, and certain chemicals have generated considerable research interest [ 1 , 2 ]. Furthermore, hydrogels that simultaneously respond to several are desirable as more potential applications emerge [ 3 ].…”

“…Current research is focused pH-sensitive hydrogels, as the parameter are fundamental in biomedical systems [ 4 , 5 , 6 ]. The development of unique stimuli-responsive hydrogels is therefore needed for applications in numerous biomedical fields, including drug delivery, artificial organ development, wound dressing, and tissue engineering [ 1 , 2 , 7 ].…”