Self-assembled materials from cellulose nanocrystals conjugated with a thermotropic liquid crystalline moiety

Abstract

Manipulating molecular and supramolecular interactions within cellulose nanocrystals (CNCs) to introduce different levels of assemblies combined with multiple functionalities is required for the development of degradable smart materials from renewable...

Recent Advances and Opportunities for Cellulose Nanocrystal-Based Liquid Crystalline Polymer Hybrids and Composite Materials

“…However, the chemical functionalities available on cellulose and their solubility are different from CNCs. The topochemical modifications of the CNCs surfaces include esterification, oxidation, silylation, and etherification with small LCs molecules and liquid crystalline polymers (Figure , top). ,, Topochemical conjugations involve polymer grafting from CNC utilizing ring-opening polymerization (ROP), surface-initiated controlled radical polymerization (SI-CRP), free radical polymerization (FRP), surface reversible addition–fragmentation chain transfer (S-RAFT), or surface-initiated nitroxide-mediated polymerization (SI-NMP) (Figure , top) . CNCs grafted with LC or LCPs showed enhanced solubility in dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), N , N -dimethyl­formamide (DMF), 3-ethyl-1-ethylimidazolium acetate, and 3-butyl-1-ethylimidazolium acetate solvents at room temperature compared to native CNC materials. , …”

“…The increase of the elastic modulus of the modified CNC composites could be due to agglomeration, interlocking of the CNC network, and the introduction of the azobenzene’s hard segments . In other studies, it was observed that the presence of noncovalent bonds of hard segments of azobenzene in a liquid crystalline elastomer–CNC composite promoted an increase in both strength and elastic modulus of the materials (Figure d,e). , Similar mechanical behaviors were observed by our group when we grafted a 12-methylene spacer thermotropic LC molecule (12CB) onto a TEMPO-oxidized CNC (CNC-COO-CB12) via Steglich esterification (Figure f). A dynamic temperature ramp was performed on the modified CNC (CNC-COO-CB12) to determine its thermal transitions and mechanical properties.…”

“…44 CNCs grafted with LC or LCPs showed enhanced solubility in dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), N,N-dimethylformamide (DMF), 3ethyl-1-ethylimidazolium acetate, and 3-butyl-1-ethylimidazolium acetate solvents at room temperature compared to native CNC materials. 7,45 Selection of LCs or LCPs that have diverging orientational order from CNCs will enable technologies that cannot be obtained from the conventional N* mesophase of CNCs. While cholesteric and nematic mesophases have been reported from the self-assembly of CNCs grafted with LC of similar orientational order, smectic mesophases have been reported from the self-assembly of CNCs grafted with LCs of diverging orientational order during self-assembly, as described below.…”

“…While cholesteric and nematic mesophases have been reported from the self-assembly of CNCs grafted with LC of similar orientational order, smectic mesophases have been reported from the self-assembly of CNCs grafted with LCs of diverging orientational order during self-assembly, as described below. 7,11,46 2.1.1. Click Chemistry.…”

“…4,12,13 CNCs exhibit unique characteristics such as good mechanical strength, large surface area, high aspect ratio, low density, and high crystallinity that ranges from 54 to 88%. 6,7 These unique properties of CNC improve their colloidal stability in water. CNCs' aqueous suspensions showcase a rheological behavior, which can be described in terms of a sheardependent viscoelastic response (e.g., shear thinning), thus expanding the application of CNCs in industrial processes such as coatings, mixing, or pumping.…”