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.
Highlights
Smart responsive nanomaterials have received much attention over the last decade for their functional properties in response to environmental variables, such as temperature [1,2], humidity [3,4], light [5,6], and pH [7,8]
We explored cellulose nanocrystals functionalized with poly{6-[4-(4-methoxyphenylazo)
We explored cellulose nanocrystals functionalized with poly{6-[4-(4-methoxyphenylazo) or changing pH conditions
Summary
Smart responsive nanomaterials have received much attention over the last decade for their functional properties in response to environmental variables, such as temperature [1,2], humidity [3,4], light [5,6], and pH [7,8]. Developing such smart nanomaterials from widely available natural resources provides an opportunity for high value-added for natural polymers, such as cellulose. Light-activated or pH-responsive functional groups can be introduced to certain places on the surface of the CNCs [12]
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