Dual Light- and pH-Responsive Composite of Polyazo-Derivative Grafted Cellulose Nanocrystals

Abstract

As a type of functional group, azo-derivatives are commonly used to synthesize responsive materials. Cellulose nanocrystals (CNCs), prepared by acid hydrolysis of cotton, were dewatered and reacted with 2-bromoisobuturyl bromide to form a macro-initiator, which grafted 6-[4-(4-methoxyphenyl-azo) phenoxy] hexyl methacrylate (MMAZO) via atom transfer radical polymerization. The successful grafting was supported by Fourier transform infrared spectroscopy (FT-IR) and Solid magnetic resonance carbon spectrum (MAS 13C-NMR). The morphology and surface composition of the poly{6-[4-(4-methoxyphenylazo) phenoxy] hexyl methacrylate} (PMMAZO)-grafted CNCs were confirmed with Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The grafting rate on the macro-initiator of CNCs was over 870%, and the polydispersities of branched polymers were narrow. The crystal structure of CNCs did not change after grafting, as determined by X-ray diffraction (XRD). The polymer PMMAZO improved the thermal stability of cellulose nanocrystals, as shown by thermogravimetry analysis (TGA). Then the PMMAZO-grafted CNCs were mixed with polyurethane and casted to form a composite film. The film showed a significant light and pH response, which may be suitable for visual acid-alkali measurement and reversible optical storage.

Stimulus-responsive sequential release systems for drug and gene delivery

“…There are several different types of these dual responsive systems including, light/pHresponsive [156], pH/temperature-responsive [157], magnetic field/pH-responsive [158,159], pH/redox-responsive, light/temperature [160], magnetic field/temperature [161], etc.…”

Azo-Dyes-Grafted Oligosaccharides—From Synthesis to Applications

“…In this context, exploring photochromic cellulose nanocrystals (CNCs) functi ized thanks to poly {6-[4-(4-methoxyphenylazo) phenoxy]hexyl methacr (PMMAZO) can lead to a changing of color in UV irradiation or pH, and thus to a probe related to these stimuli (Figure 15). It is also noticeable that for UV/Vis illumin the process was claimed to be fully reversible without fatigue [95]. Smart responsive nanomaterials have received much attention over the last decade for their functional properties in response to environmental variables and especially light [93,94].…”

“…In this context, exploring photochromic cellulose nanocrystals (CNCs) functionalized thanks to poly {6-[4-(4-methoxyphenylazo) phenoxy]hexyl methacrylate} (PMMAZO) can lead to a changing of color in UV irradiation or pH, and thus to a great probe related to these stimuli ( Figure 15 ). It is also noticeable that for UV/Vis illumination, the process was claimed to be fully reversible without fatigue [ 95 ].…”

Extending Cellulose-Based Polymers Application in Additive Manufacturing Technology: A Review of Recent Approaches

“…The coating can be applied onto papers and allow the production of paper-based fluid timers [ 162 ]. The incorporation of CNC and 2-bromoisobuuturyl bromide into 6-[4-(4-methoxyphenyl-azo) phenoxy] hexyl methacrylate produced a photo-responsive composite that changes in color through the irradiation to light with the wavelength of 350 nm [ 163 ].…”