Effect of degradation on thermotropic cholesteric optical properties of (2‐hydroxypropyl) cellulose (HPC) esters

Rusig, I.; Dedier, J.; Filliatre, C.; Godhino, M. H.; Varichon, L.; Sixou, P.

doi:10.1002/pola.1992.080300521

Cited by 15 publications

(7 citation statements)

References 18 publications

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“…The esters presented in Table I were prepared without solvent at room temperature from the corresponding acid chlorid and ( 2-hydroxypropyl) cellulose [Hercules Klucel E, = 120,000 g/mol, with a degree of substitution (m) of 2.5 and a molar substitution (m) of 3.751 according to the procedure described previously. 12 In the case of BPC, two different procedures were used. To obtain different extents of esterification, we used different amounts of acid chloride for 10 g ( 3 equiv) of HPC.…”

Section: Methodsmentioning

confidence: 99%

Optical properties of cholesteric (2‐hydroxypropyl) cellulose (HPC) esters

Rusig

Godinho

Varichon

et al. 1994

J Polym Sci B Polym Phys

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Acetoxypropylcellulose (APC) and propionic, n‐butyric, isobutyric, valeric, isovaleric, hexanionic, and heptanionic acid esters of hydroxypropylcellulose (HPC) (respectively PPC, BPC, iBPC, VPC, iVPC, HexPc, and HepPc) were prepared and characterized by differential scanning calorimetry, chromatography, polarizing microscopy, chemical methods, and spectroscopy. All these esters form thermotropic cholesteric liquid crystalline phases. The glass (Tg) and clearing (Tc) transition temperatures were determined. The stability interval of the mesophases appears to be greater in the case of longer‐linear side chains. The mesophases of APC, PPC, iBPC, VPC, and iVPC exhibit reflection bands in the visible region, at wavelengths that depend on temperature, moisture content, size and number of substituents, and degree of polymerization ( \[ \overline {{\rm DP}} \] ). The pitch of the cholesteric helical structure increases with side chain length and with increasing temperature. At room temperature, a fingerprint‐like pattern can be observed for HepPc. No reversal in the sense of the pitch with temperature variations was observed. The pitch of BPC increases with moisture content and with decreasing values of the degree of esterification ( \[ \overline {{\rm DE}} \] ) and \[ \overline {{\rm DP}} \] . A theory for cholesteric mesophases composed of helical rod‐like species and a model of elastic bend chain have been compared to the experimentally observed changes in the pitch with temperature and with the length of the side chain substituents (for iBPC, iVPC, BPC, PPC, and APC) and \[ \overline {{\rm DE}} \] and \[ \overline {{\rm DP}} \] (for BPC). © 1994 John Wiley & Sons, Inc.

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Section: Methodsmentioning

confidence: 99%

Optical properties of cholesteric (2‐hydroxypropyl) cellulose (HPC) esters

Rusig

Godinho

Varichon

et al. 1994

J Polym Sci B Polym Phys

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“…The generic synthesis of (Acetoxypropyl)cellulose is described in detail in Rusig et al (1992), Tseng et al (1981), and Costa et al (2007). In our case we had the following modifications: acetilation of (hydroxypropyl)cellulose (HPC) (Aldrich, nominal M w = 100,000, molar substitution equal to 4 as determined by 1 H NMR) (50 g) was performed by adding the HPC to acetic anhydride (160 g).…”

Section: Experimental Partmentioning

confidence: 99%

Liquid crystalline cellulose derivative elastomer films under uniaxial strain

Godinho¹,

Filip²,

Costa³

et al. 2008

Cellulose

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Mesogenic cellulose derivative chains cross-linked into free-standing thin films were prepared by a shear-casting technique from anisotropic precursor solutions of thermotropic (acetoxypropyl) cellulose. After shear cessation a macroscopically oriented serpentine structure with the director in average along the shear direction is locked resulting in anisotropic optical and mechanical properties of the material. These films were submitted to an external uniaxial mechanical field perpendicular and parallel to the shear direction. Stretching perpendicular to the shear direction produced significant director rotations and a reset of order of the director order parameter for a deformation in the range 2-3 as detected by X-rays and optical microscopy. The different response found for strains imposed parallel and perpendicular to the initial average director orientation indicates that even though our system shows a serpentine director modulation that is either attenuated or reinforced by deformations parallel or perpendicular to the shear direction, its behaviour is similar to theoretical predictions for monodomain nematic elastomers described in the literature.

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“…The rheological behavior of HPC derivatives possessing acyl groups is interesting. Previous studies reported that sticky products are obtained by acylation of HPC [3,4,[8][9][10]. This phenomenon is quite strange in that sticky polymer melts are produced from a powdery raw material of pristine HPC after the simple acylation.…”

Section: Introductionmentioning

confidence: 99%