Concentration and temperature dependence of the helical twisting power of poly(γ‐benzyl <scp>L</scp>‐glutamate) liquid crystals in m‐cresol

Toriumi, Hirokazu; Minakuchi, Sadaomi; Uematsu, Ichitaro; Uematsu, Yoshiko

doi:10.1002/pol.1981.180190715

Cited by 16 publications

(13 citation statements)

References 6 publications

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“…Similar results have been reported for (hydroxypropyl) cellulose in water and (acetoxypropyl) cellulose in acetone [38]. Experimental results for the variation of the pitch with concentration for polypeptides can also be fitted by a general power lawWhere x has a value between 1 and 2 [39]. The magnitude of x depends on the solvent, temperature and molecular weight.…”

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2017

MSEIJ

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Chitosan is a biopolymer used in biomedical applications which has the ability to form lyotropic mesophases (chiral nematic) in several solvents. Currently, chitosan liquid crystalline phase is only observed at high polymer concentrations where the system has already transitioned to a gel-like state. Due to the non-homogenous mechanical behavior of a gel, it would be preferable to obtain a liquid crystalline phase while at solution state. Therefore, the formation of chitosan liquid-crystalline at solution state was investigated. Malic and hydrochloric aqueous solutions with different concentrations of chitosan were prepared and the gel formation was followed by rheological measurements. The concentration, C Gel , at which the gel is formed, was found to be dependent on the acid used, the malic aqueous solutions presenting higher C Gel . For the chitosan/malic acid system the chiral nematic mesophase appeared in solution and was preserved in the gel (for C>C Gel ) while for the chitosan/hydrochloric acid system, mesophase was only observed in gel. Using Polarized Optical Microscopy (POM) Swirl-like fingerprint textures typical of cholesteric mesophases were observed and the helical pitch was determined. The existence of mesophases in the gel, in both chitosan aqueous solutions, was also confirmed by rheometry.Keywords: Morphology; Rheology; Cholesteric; Liquid-crystals; Gels IntroductionChitin and chitosan are glycosaminoglycans with the rare property of bioactivity. These polysaccharides are in fact copolymers of β-(1→4)-linked 2-acetamido-2-deoxy-Dglucopyranose and 2-amino-2-deoxy-D-glucopyranose. The difference between the two is determined by the DA, the degree of acetylation, corresponding to the molar fraction of acetyl units constituting the polymer chains. It is considered that chitosan refers to polymers with DAs below 50 % (more commonly 10-30 %) [1]. Chitin is considered the second most abundant polymer in nature but due to its low solubility has limited applications and therefore is mostly used in the deacetylated form, as chitosan. Chitosan is the product of the alkali hydrolysis of chitin and is soluble in dilute acidic solutions [2]. The reason why chitosan presents a higher solubility than chitin is the presence of protonated free amine groups below pH 6.2 [3] and this polycation material has several applications in different fields, from agriculture, waste and water treatment, food and beverages, cosmetic and toiletries, biopharmaceuticals to biomedical applications [4,5]. In biomedical and pharmaceutical applications chitosan is used to produce hydrogels, due to its gelation properties. Several reports on literature can be found concerning the production of chemical [6,7] and physical [8,9] hydrogels from chitosan. Hamdine [10,11] reported an extensive work regarding chitosan gelation in different acids and concluded that chitosan has different behaviours when dissolved in acid malic and in hydrochloric acid. In the first case, due to the considerable volume of the acid molecule, that ...

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“…Where x has a value between 1 and 2 [39]. The magnitude of x depends on the solvent, temperature and molecular weight.…”

Section: Polarized Optical Microscopy (Pom)mentioning

confidence: 99%

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“…In general, experimental results for single-stranded polypeptides may be fitted to the relationship l/P oc fa (10) where x has a value between 1 and 2. 39 Iizuka found x to be 1.1 for doubleand triple-stranded polyribonucleotide liquid crystals. 40 Cellulose-based liquid crystals display a somewhat steeper inverse dependence of pitch on concentration.…”

Section: Resultsmentioning

confidence: 99%

Optical properties of hydroxypropyl cellulose liquid crystals. I. Cholesteric pitch and polymer concentration

Werbowyj¹,

Gray²

1984

Macromolecules

150

107

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“…Up to now experimental studies on lyotropic polymer cholesteric liquid crystals have been limited to the very few macromolecular systems which are available for such work. [16][17][18][19][20][21][22][23][24] Moreover, no quantitative comparisons with theory for the cholesteric liquid crystal state have been made except for poly(7-benzyl L-glutamate) (l).14 '15 Since progress in this area has involved the interplay of experiment and theory, the small numbers of experimental models make it difficult to define the boundaries of understanding of the fundamental forces controlling the lyotropic cholesteric state formed by macromolecules.…”

Section: Introductionmentioning

confidence: 99%

Polyisocyanates and the interplay of experiment and theory in the formation of lyotropic cholesteric states

Sato¹,

Sato²,

Umemura³

et al. 1993

Macromolecules

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We have made the first observations of the lyotropic cholesteric liquid crystal state of polyisocyanates, in which a synthetically controlled range of the dynamic excesses of one helical sense offer new opportunities for study in the area. In poly((R)-2,6-dimethylheptyl isocyanate) we have generated the cholesteric lyotropic state and studied the pitch as a function of solvent, temperature, and concentration. These data were broken down into entropic, Sq, and enthalpic, Hq, terms and were compared to theoretical predictions. The data for the polyisocyanate were compared to those already known for poly(7-benzyl L-glutamate) and schizophyllail. For all three helical polymers, the sign of S, agrees with Straley's screw model, allowing an absolute assignment of macromolecular helical sense from liquid crystal properties. The nematic phase of the dynamically racemic poly(n-hexyl isocyanate) was doped with a derivative of a steroid and of menthol, and the resulting cholesteric pitch was studied as a function of temperature and dope concentration. The failure to fit these data to theoretical expectations applicable to intrinsically chiral polymers may be due to a sensitivity of the helix sense ratio of the macromolecule to the chiral characteristics of the cholesteric phase.

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Concentration and temperature dependence of the helical twisting power of poly(γ‐benzyl L‐glutamate) liquid crystals in m‐cresol

Cited by 16 publications

References 6 publications

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Optical properties of hydroxypropyl cellulose liquid crystals. I. Cholesteric pitch and polymer concentration

Polyisocyanates and the interplay of experiment and theory in the formation of lyotropic cholesteric states

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