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

Wan Hafizi Wan Ishak,Oo Yong Jia,Ishak Ahmad

doi:10.3390/polym12091932

Abstract

A pH-sensitive poly(acrylic acid) composite hydrogel was successfully synthesized via gamma irradiation and reinforced with cellulosic materials of different sizes. Cellulose was extracted from rice husks via alkali and bleaching treatment, and an acid hydrolysis treatment was performed to extract cellulose nanocrystals (CNCs). Morphological observation of cellulose and CNCs using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed diameters of 22–123 μm and 5–16 nm, respectively. The swelling properties of the fabricated poly(acrylic acid)/cellulosic hydrogels were found to respond to changes in pH, and CNC-reinforced hydrogels performed better than cellulose-reinforced hydrogels. The highly crystalline CNC provided a greater storage modulus, hence acting as a better reinforcing material for poly(acrylic acid)-based hydrogels. SEM showed that hydrogels reinforced with the CNC nanofillers contained a homogeneous pore distribution and produced better interfacial interactions than those reinforced with the cellulose microfillers, thus performing better as hydrogels. These findings demonstrate that gamma-irradiated poly(acrylic acid) hydrogels reinforced with CNCs exhibit a better stimuli response toward pH than poly(acrylic acid) hydrogels reinforced with cellulose.

Highlights

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].hydrogels that simultaneously respond to several are desirable as more potential applications emerge [3]
The modification of cellulose fibers loaded during hydrogel production affects the hydrogel performance
The modification of cellulose fibers loaded during hydrogel production affects the hydrogel rigidity of the resulting poly(acrylic acid) (PAA) hydrogels increases owing to the formation of more pores and interfacial performance

Summary

Introduction

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].hydrogels that simultaneously respond to several are desirable as more potential applications emerge [3]. 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]. 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 needed for applications in numerous biomedical fields, including drug delivery, artificial organ development, wound dressing, and tissue engineering [1,2,7]. With the presence of carboxylic acid groups (COOH) in the PAA chains, the swelling ability largely depends on the surrounding pH, offering practical pharmaceutical applications, such as drug delivery [9].

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Conclusion