Azobenzene-decorated cellulose nanocrystals as photo-switchable chiral solutes in nematic liquid crystals

Abstract

In this work, we validate that cellulose nanocrystals (CNCs), surface-functionalized with pro-mesogenic azobenzen pendants, can act as photoswitchable chiral solutes in a nematic liquid crystal (N-LC). Upon UV illumination, the...

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

“…chirality transfer from the CNC chiral core to the achiral N-LC bulk. 52 Exploration of achiral molecules that diminish the inherent chirality transfer from the CNC chiral core to the achiral molecules needs to be conducted. In addition, more studies on the CNC surface grafting concept should be undertaken to synthesize CNCs functionalized with structurally different azobenzene derivatives to afford compatibility of UV-responsive materials in various solvent media, thus diversifying research on functional materials.…”

“…63,64 To overcome the fast and smooth relaxation dynamics, CNCs are tagged with stimuli-responsive, nematogenic, or smectogenic liquid crystals. 7,52 The introduction of LCs onto the topographical surface of the CNCs will, theoretically, decrease the role of bending fluctuations and the simultaneous increase of the energy barrier separating the chiral nematic ordering of the CNCs and the nematic or smectic mesophases from individual LC pedants. 63,65,66 Additionally, by initially achieving an order parameter that is less than the critical order parameter, S c = 0.25, the self-assembly of appended CNCs will predominantly be controlled by LC motifs; thus, different mesophases can be achieved.…”

“…7 CNCs surface-functionalized with pro-mesogenic azobenzene pendants are used as photoswitchable chiral solutes in a nematic liquid crystal (N-LC) (Figure 4). 52 The azo pendant allows the alteration of the CNC helical pitch and the helical twisting power (βw) based on the trans−cis photoisomerization upon UV illumination. 52 The results also show textural characteristics of the induced N*-LC phase, thereby providing evidence of The first step involves the immobilization of the ATRP initiator on the filter paper, and the second step depicts the actual grafting of 11-(4cyanophenyl-4-phenoxy)undecyl acrylate using ATRP.…”

“…52 The azo pendant allows the alteration of the CNC helical pitch and the helical twisting power (βw) based on the trans−cis photoisomerization upon UV illumination. 52 The results also show textural characteristics of the induced N*-LC phase, thereby providing evidence of The first step involves the immobilization of the ATRP initiator on the filter paper, and the second step depicts the actual grafting of 11-(4cyanophenyl-4-phenoxy)undecyl acrylate using ATRP. The first step involves the immobilization of the initiator on the CNC surface, and the second step depicts the grafting of PMMAZO using ATRP.…”

“…The neat or surface modification of CNCs with mesogenic motifs has also been accomplished through Steglich esterification at the primary hydroxyl group (C6). ,, For instance, Hegmann et al tagged pro-mesogenic chiral molecules, 6-[(4′-cyano­{1,1′-biphenyl}-4-yl)­oxy]­hexanoic acid (6OCB) and 6-[[4′-(heptyloxy)-[1,1′-biphenyl]-4-yl]­oxy]­hexanoic acid (BiPh), and an achiral molecule, cholest-5-en-3-ol-(3β),3-(hydrogen pentanedioate) (Chol), on the surface of CNCs (specifically the primary hydroxyl group at carbon C6) with an average width of about 20 nm and a length varying from about 100 to 150 nm with an aspect ratio of ∼6.5, to elucidate the role of core chirality from CNC (Figure ). Prior to esterification, the sodium sulfonate groups, despite their overall low degree of sulfonation, were converted into sulfonic acid groups to render the resulting CNCs more soluble in organic solvents .…”