Thermotropic liquid crystalline properties of (hydroxypropyl)cellulose derivatives with butyryl and heptafluorobutyryl substituents

Abstract

(Hydroxypropyl)cellulose (HPC) derivatives with butyryl (Bu) and heptafluorobutyryl (7FBu) substituents were prepared in various proportions of the Bu/7FBu groups and at a fixed total DS (DSBu + DS7FBu) of 3.0. Thermotropic liquid crystallinity of the derivatives (Bu7FBu-HPC) was investigated to specify the effect of the fluoroacylation on the mesophase behavior. Thermal transition data were collected using differential scanning calorimetry and polarized light microscopy. The Bu7FBu-HPC samples formed a chiral nematic phase between their glass transition and isotropization temperatures, Tg and Ti-a, respectively; these transition temperatures rose moderately as the 7FBu proportion increased (Tg = −44-−27 °C and Ti-a = 158-190 °C for DS7FBu = 0.04-1.60). The structural property of the mesophase was examined at 70 °C by circular dichroism and other optical measurements. The chiral nematic pitch (P) sensitively increased with increasing 7FBu proportion, while the supramolecular helical arrangement remained right-handed. Selective light-reflection colors were observed for the samples of DS7FBu = 0.04-0.8, covering an entire spectrum range from violet to red. Temperature dependence of P was also examined for selected samples below Ti-a, and it was found to increase with increasing temperature; however, there was no indication of inversion in the handedness of the helical structure. Wide-angle X-ray diffractometry revealed that the increases of P responding to the increases in DS7FBu and temperature were attributable to the decrease of the twist angle between adjacent thin nematic layers.

Handedness Inversion in Chiral Nematic (Ethyl)cellulose Solutions: Effects of Substituents and Temperature

“…In the 3ClPC-EC/AA series, too, the distance d slightly fluctuated from 1.12 to 1.15 nm with the increase in DS PC from 0.07 to 0.30, whereas the angle φ changed more sensitively from −1.03° (3ClPC-EC 0.07 ) to +1.16° (3ClPC-EC 0.30 ) through ∼0° (3ClPC-EC 0.14 ). Evidently, the angle φ dominates the twisting power ( P –1 ∝ φ/ d ) of the chiral nematic arrangement; this item has also been confirmed in previous studies dealing with the DS and temperature dependences of P for similar mesophases of other cellulosic polymers. ,, …”

“…The apparatuses used were as follows: Olympus BX60F5 equipped with a hot stage Mettler FP82HT/FP90 (for POM); Hitachi U-4100 equipped with a thermo-regulated cell holder (for UV–vis–NIR); Jasco J-820DH equipped with a temperature controller PTC-423L (for CD and ORD); Atago Type-2T Abbé refractometer equipped with a rotatable polarizer (for refractometry); Rigaku Ultima IV (for WAXD with Cu Kα radiation). The measurement procedures were substantially similar to those described in our previous papers. , The following remarks should be made herein: (1) In the various optical measurements, lyotropic samples were usually spread in a layer of solution (100–200 μm thick) between two glass plates; however, in the WAXD measurement, the samples were loaded into a copper holder (0.50 mm high) and covered with a thin polyethylene (PE) film. (2) In POM photography, the observed images such as fingerprint textures were all taken under the condition of crossed polars.…”

Playing the blues, the greens and the reds with cellulose-based structural colours

“…A low average degree of substitution (DS $$$$ of the order of 0.15), of the fluor moiety, translated into a significant increase of the pitch value, compared with the pitch for the thermotropic with only butyryl substituents. The mixed esters presented selective reflection of RCP light and vivid colours from violet to red depending on the DS $$$$ of the substituents and on temperature 28 . Moreover, it has been reported in literature a sequence of colours, ranging from red to blue, such as in the rainbow, in thin solid films prepared from droplets of anisotropic cellulose nanocrystals (CNCs) aqueous solutions, after solvent evaporation.…”

Lyotropic Liquid Crystallinity of Linear and Cyclic Amylose Derivatives: Amylose Tris(n-octadecylcarbamate) in Tetrahydrofuran and 2-Octanone

“…Smallangle X-ray scattering (SAXS) measurement was also carried out for bulk and concentrated ATODC and cATODC solutions to determine the local alignment of polymer chains in the liquid crystalline phase since they may also have thermotropic liquid crystallinity as in the case of polysaccharide derivatives with alkyl side groups. [14][15][16] Chart 1. Chemical Structures of (a) ATODC and (b) cATODC.…”