Cellulose liquid crystalline properties

An effort to combine the thermotropic liquid-crystalline properties of selected cellulose derivatives with the ion-conductive characteristics of poly(ethylene oxide) (PEO) has currently been pursued [234,235]. TPEO-CELL shown in Scheme 7 is a representative sample. 

Wang, N., Ding, E., Cheng, R. Preparation and liquid crystalline properties of spherical cellulose nanocrystals. Langmuir 24, 5 (2008)... 

Many cellulose derivatives form lyotropic liquid crystals in suitable solvents and several thermotropic cellulose derivatives have been reported (1-3) Cellulosic liquid crystalline systems reported prior to early 1982 have been tabulated (1). Since then, some new substituted cellulosic derivatives which form thermotropic cholesteric phases have been prepared (4), and much effort has been devoted to investigating the previously-reported systems. Anisotropic solutions of cellulose acetate and triacetate in tri-fluoroacetic acid have attracted the attention of several groups. Chiroptical properties (5,6), refractive index (7), phase boundaries (8), nuclear magnetic resonance spectra (9,10) and differential scanning calorimetry (11,12) have been reported for this system. However, trifluoroacetic acid causes degradation of cellulosic polymers this calls into question some of the physical measurements on these mesophases, because time is required for the mesophase solutions to achieve their equilibrium order. Mixtures of trifluoroacetic acid with chlorinated solvents have been employed to minimize this problem (13), and anisotropic solutions of cellulose acetate and triacetate in other solvents have been examined (14,15). The mesophase formed by (hydroxypropyl)cellulose (HPC) in water (16) is stable and easy to handle, and has thus attracted further attention (10,11,17-19), as has the thermotropic mesophase of HPC (20). Detailed studies of mesophase formation and chain rigidity for HPC in dimethyl acetamide (21) and for the benzoic acid ester of HPC in acetone and benzene (22) have been published. Anisotropic solutions of methylol cellulose in dimethyl sulfoxide (23) and of cellulose in dimethyl acetamide/ LiCl (24) were reported. Cellulose tricarbanilate in methyl ethyl ketone forms a liquid crystalline solution (25) with optical properties which are quite distinct from those of previously reported cholesteric cellulosic mesophases (26). 

Pawlowski W.P, Gilbert R.D., Pomes R.E., Purrington S.T., The liquid-crystalline properties of selected cellulose derivatives, J. Polym. Sci. B Polym. Phys., 26, 1988, 1101-1110. 

Liquid crystalline properties of cellulose and its derivatives can be exploited to produce biomimetic materials or all-cellulosic-based composites with enhanced mechanical properties. These materials will be the focus of this chapter. 

W. P. Pawlowski, R. D. Gilbert, R. E. Formes, and S. T. Purrington, The thermotropic and lyotropic liquid-crystalline properties of acetoacetoxypropyl cellulose. /. Polym. Sci. PartB Polym. Phys. 25, 2293-2301 (1987). 

Pawiowski WP, Gilbert RD, Fomes RE, Purrington ST (1987) The thermotropic and lyotropic liquid-crystalline properties of acetoacetoxypropyl cellulose. J Polym Sci B 25(11) 2293-2301 Perez S, Mazeau K (2005) ConfiMmations, structures, and morphologies of celluloses. In Dumitriu S (ed) Polysaccharides stmctural diversity and fimctional versatility, 2nd edn. Marcel... 

Chemical modification of natural polymers such as starch, dextran, cellulose and proteins represents an attractive alternative route to totally synthetic polymers for producing biodegradable polymers. Early modification of polysaccharides resulted in hydrophobic materials such as cellulose acetate and cellulose nitrate. Both are degradable by microorganisms. Hydroxyalkylcelluloses should be of interest because of their liquid crystalline properties.The only question is whether their biodegradability is unified. Polysaccharides react with small carboxylic acids to produce derivatives that are biodegradable. " ... 

Liquid crystal display technology, 15 113 Liquid crystalline cellulose, 5 384-386 cellulose esters, 5 418 Liquid crystalline conducting polymers (LCCPs), 7 523-524 Liquid crystalline compounds, 15 118 central linkages found in, 15 103 Liquid crystalline materials, 15 81-120 applications of, 15 113-117 availability and safety of, 15 118 in biological systems, 15 111-113 blue phases of, 15 96 bond orientational order of, 15 85 columnar phase of, 15 96 lyotropic liquid crystals, 15 98-101 orientational distribution function and order parameter of, 15 82-85 polymer liquid crystals, 15 107-111 polymorphism in, 15 101-102 positional distribution function and order parameter of, 15 85 structure-property relations in,... 

Organic cellulose esters, 5 412—439 analysis, 5 430—434 economic aspects, 5 427—430 health and safety factors, 5 434—435 liquid crystalline, 5 418 manufacture and processing, 5 418—427 physical properties, 5 415—418, 416t, 417t... 

Liquid-crystalline solutions and melts of cellulosic polymers are often colored due to the selective reflection of visible fight, originating from the cholesteric helical periodicity. As a typical example, hydroxypropyl cellulose (HPC) is known to exhibit this optical property in aqueous solutions at polymer concentrations of 50-70 wt%. The aqueous solution system is also known to show an LCST-type of phase diagram and therefore becomes turbid at an elevated temperature [184]. 

Stiff rod-like helical polymers are expected to spontaneously form a thermotropic cholesteric liquid crystalline (TChLC) phase under specific conditions as well as a lyotropic liquid crystal phase. A certain rod-like poly(f-glutamate) with long alkyl side chains was recently reported to form a TChLC phase in addition to hexagonal columnar and/or smectic phases [97,98]. These properties have already been observed in other organic polymers such as cellulose and aromatic polymers. 

The first part of the book discusses formation and characterization of the microemulsions aspect of polymer association structures in water-in-oil, middle-phase, and oil-in-water systems. Polymerization in microemulsions is covered by a review chapter and a chapter on preparation of polymers. The second part of the book discusses the liquid crystalline phase of polymer association structures. Discussed are meso-phase formation of a polypeptide, cellulose, and its derivatives in various solvents, emphasizing theory, novel systems, characterization, and properties. Applications such as fibers and polymer formation are described. The third part of the book treats polymer association structures other than microemulsions and liquid crystals such as polymer-polymer and polymer-surfactant, microemulsion, or rigid sphere interactions. 

Discovery of the formation of liquid crystalline solutions by cellulosics in the mid-1970s has resulted in attempts to develop new cellulosics products with properties superior to those of conventional cellulosic. Following the first observation of mesophases formed in aqueous solutions of hydroxypropyl cellulose (HPC), a variety of other cellulose derivatives have been reported to form liquid crystals. Liquid crystalline solutions of cellulose and its derivatives provide a potential route to high-modulus and high-tenacity cellulosic fibers, films, and other high-performance products. 

Lyotropic liquid crystalline cellulose derivatives exhibit unique optical properties because of their helicoidal supramolecular structure.The chiro-optical properties of the helicoidal structure can be described by a pitch p (or its inverse, the twist p ) p = 2o/fi, where is the reflection wavelength and h is the mean refractive index of a sheet, and the corresponding handedness of the twist right-handed helicoidal structure being assigned to a positive pitch p > 0) and left-handed helicoidal structures to a negative pitch p < The nematic mesophase can be... 

The values of pitch for lyotropic AEC solutions in AA (50% w/w) are given in Table 1, where AEC-2 is a pure AEC with medium DA and AEC-3 is the mixture of EC and fully acetated AEC, which has the same average DA as AEC-2. However, in the liquid crystalline solutions, even at the same concentration, AEC-2 and AEC-3 have different pitch and handedness. This phenomenon was also observed in the lyotropic AEC/chloroform system. The difference in chiro-optical properties may come from the complex interactions of multiple chiral centers present in each repeating unit of the cellulose chain, not from simple racemic mixtures as in the PBG system. 

Dai, Q.G. Gilbert, R.D. Khan, S.A. Kadla, J.F. Relaxation behaviors of lyotropic (acetyl)(ethyl) cellulose/acrylic acid solutions with different chiro-optical properties. Polym. Preprints (ACS, Div Polym. Chem.) 2004, 45 (1), 824-825. Shimamoto, S. Uraki, Y. Sano, Y. Optical properties and photopolymerization of liquid crystalline (acetyl) (ethyl) cellulose/acrylic acid system. Cellulose 2000, 7 (4), 347-358. 

The formation of liquid-crystalline phases of cellulosics, especially of the lyotropic kind, has yet to be explained. Certainly the chain stiffness may have to be taken into account as one of the factors in question, but the solvent-polymer interaetion may have to be considered as well. In the next section, models for the description of the pitch as a chiral property and models to... 

Fink, H.-R, Ebeling, H. and Rihm, R. (2006) Fibre Formation from Liquid Crystalline Solutions of Cellulose Carbamate in NMMO. Proceedings of the 7th Int. Symp. Alternative Cellulose-Manufacturing, Forming, Properties , September 6-7, 2006, Rudolstadt, pp. 13-23. 

Noishiki Y, Nishiyama Y, Wada M et al (2002) Mechanical properties of silk fibroin-microcrys-talline cellulose composite films. J Appl Polym Sci 86 3425-3429 O Sullivan AC (1997) Cellulose the structure slowly unravels. Cellulose 4 173-207 Oksman K, Mathew AP, Bondeson D et al (2006) Manufacturing process of cellulose whiskers/ polylactic acid nanocomposites. Compos Sci Technol 66 2776-2784 Orts WJ, Godbout L, Marchessault RH et al (1998) Enhanced ordering of liquid crystalline suspensions of cellulose microfibrils a small-angle neutron scattering study. Macromolecules 31 5717-5725... 

In this section the mechanical properties (Young s modulus) and the strength of the fiber-matrix interface (quality of the interface) of isotropic all-cellulosic based composites will be analyzed using theoretical models existing in literature. For the anisotropic composites such an approach was not performed. The anisotropy in these composites arises mainly from the liquid crystalline character of the matrix. 

The length of the cellulose molecules, especially its relation to the length of the elementary crystals or fused fibrillar aggregations. Recent studies favour the idea that the cellulosic material is dispersed in a matrix of non-cellulosic material. The ordered cellulosic fibres are organized in a pseudo-liquid crystalline form. This type of model is consistent with many physical properties of these materials (Figure 12.6b). 

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