Liquid crystalline dispersions of complexes formed by chitosan with double-stranded nucleic acids

Double-stranded molecules of nucleic acids (NAs) were shown to interact with chitosans to form under certain conditions (chitosan molecular mass, content of amino groups, distance between amino groups, pH of solution, etc.) multiple types of liquid crystalline dispersions. The dispersions formed are different in their spatial structures, and hence in the sense and magnitude of the abnormal optical activity. The physicochemical properties of these dispersions were investigated. Time- and temperature-stabilization of dispersions that possess abnormal optical activity were achieved by chemical crosslinking of chitosan molecules in the liquid crystalline dispersions formed from NA-chitosan complexes. The accessibility of these 'NA-liquid crystalline elastomers' with respect to enzyme and drug action was tested. The multiplicity of liquid crystalline forms of DNA-chitosan complexes was possibly explained by the influence of the character of the dipole distribution over the surface DNA molecules on the sense of the spatial twist of the cholesteric liquid crystalline dispersions resulting from these complexes.     

A novel type of microscopic size chip based on double-stranded nucleic acids

The double-stranded molecules of nucleic acids (NA) of B- and A-families fixed in the structure of cholesteric liquid-crystalline dispersions, formed as a result of phase exclusion of these molecules from polymer-containing solution, have been used as 'building blocks' for the molecular design. Using the formation of polymeric chelate bridges between NA molecules, three-dimensional structures consisting of alternating NA, anthracycline and copper ions, were created. The formation of the polymeric chelate bridges allows one to stabilize the initial spatial mode of ordering of neighboring NA molecules in a form of so-called 'molecular constructions', immobilize these constructions onto supporting film and evaluate their sizes and shape. The creation of NA molecular constructions is accompanied by an 'extra-increase' in the amplitude of the bands in the CD spectra, despite the initial sense of cholesteric twisting characteristic of liquid-crystalline dispersions. Destroying of polymeric chelate bridges between NA molecules by action of biologically relevant compounds results in disintegration of NA liquid-crystalline molecular constructions. Three-dimensional NA molecular construction can be used as a microscopic size multifunctional chemical unit (chip) for biological or chemical needs.     

Liquid-crystalline phases of circular superhelical plasmid DNA and their modification by the action of nuclease enzymes

CD spectra of liquid-crystalline dispersions, X-ray diffraction patterns and optical textures of liquid crystals prepared from native superhelical DNA in poly(ethyleneglycol)-containing water-salt solutions before and after treatment of DNA with micrococcal nuclease have been obtained. It was found that condensation of native superhelical DNA is accompanied by the formation of liquid crystals with a non-specific optical texture. After treatment of the DNA, liquid-crystalline dispersions, with Micrococcal nuclease the DNA is able to form two similar types of liquid crystals with abnormal optical activity which differ in the peculiarities of their textures. The data obtained demonstrate the formation of multiple types of liquid crystals from high molar mass double-stranded optically active DNA molecules.     

Kinetic peculiarities of <Emphasis Type="Italic">Quillaja Saponaria Molina</Emphasis> saponin sorption by chitosan

A relationship between adsorption layer structure at different stages of sorbent filling, hydrophilicity, and spatial orientation of saponin in chitosan phase is revealed by joint analysis of the kinetic curves of saponin sorption, IR spectra of chitosan and saponin samples, and computer-simulation data. The sorbent–sorbate complex is formed due to electrostatic interactions between protonated amino groups in chitosan and carboanions of glucuronic acid in saponin, as well as hydrogen bonding between NH₂ and OH groups in chitosan molecules and OH groups in the carbohydrate moiety of saponin molecules.     

Comparison of calculated and observed CD spectra of liquid crystalline dispersions formed from double-stranded DNA and from DNA complexes with coloured compounds

The CD spectra of dispersions of DNA, in the form of cholesteric liquid crystalline droplets, in an aqueous continuum have been studied. Calculated curves have been fitted to experimental spectra. The amplitude and the sign of the intense absorption band of the purine and pyrimidine bases vary with the droplet size, the pitch and the twist sense of the cholesteric phase. The CD spectra of dispersions of the complex formed by DNA and a coloured intercalating antibiotic have been similarly studied. A general satisfactory level of fitting between observed and calculated CD spectra was found.     

Restructuring space ordering of (DNA-protamine) complexes in liquid crystalline dispersions under proteolytic enzyme treatment

Complexes of DNA with the protamines stellin A and stellin B, in polymer-containing solutions, form both liquid crystalline phases and liquid crystalline dispersions. The 'non-specific' organization of the (DNA-protamine) phase is determined by the presence of protamine 'cross links' between the DNA molecules and not by the inherent anisotropy (cholesteric) double-stranded DNA molecules. Elimination of these 'cross links' by proteolytic enzyme action causes an increase in the distance between the DNA molecules which results in the appearance of an intense band in the CD spectrum and a 'fingerprint' (cholesteric) texture.     

PHOTOCHEMICAL ALTERATIONS IN DNA REVEALED BY DNA-BASED LIQUID CRYSTALS

Abstract The preparations of chicken erythrocyte linear double-stranded DNA and superhelical plasmid pBR322 DNA were irradiated by continuous low-intensity UV radiation (I = 25-50 W/m², λ= 254 nm) as well as by highintensity picosecond laser UV radiation (I = 10¹¹-10¹³ W/m², λ= 266 nm). The effect of DNA secondary structure alterations on the formation of liquid-crystalline dispersions from UV-irradiated DNA preparations was studied. It was shown that in the case of linear DNA, watching the disappearance of abnormal optical activity characteristic for cholesteric liquid crystal we managed to detect the presence of photochemical alterations in DNA irradiated by low-intensity UV radiation at an absorbed energy of more than 20 quanta per nucleotide. In the case of superhelical DNA using enzyme treatment of liquid-crystalline dispersions and monitoring the appearance of abnormal optical activity, we detected the presence of photochemical alterations in DNA molecules after low-intensity UV irradiation at an absorbed energy of less than 4 quanta per nucleotide. Under the latter approach using picosecond UV laser irradiation at three different light intensities we were able to distinguish the different mechanisms of fine alterations in DNA secondary structure at an absorbed energy value of about 3 quanta per nucleotide.     

A new reverse mode light shutter from silica-dispersed liquid crystals

Nanoparticle dispersions in liquid crystalline materials at low concentrations allow both investigating the formation of defects in liquid crystal (LC) and enhancing the light-scattering properties of LC optical devices. Reverse mode LC dispersions are LC devices, which look like transparent in their OFF state, when no electric field is applied, and opaque in their ON state. In this paper, a new reverse mode device, formed by a dispersion of a LC mixture in a silica nanoparticle crosslinked network, is presented. The morphology and the electro-optical properties of these silica nanoparticle/LC composites were investigated for two different LC mixtures with a negative dielectric anisotropy. The observed transmittances and relaxation times were found to depend strongly on the silica amount and chemical–physical properties of LC used in the sample preparation.     

Nanoorganization and Phase Behavior of Mixtures of Nicotinic Acid with Dodecylbenzenesulfonic Acid

Abstract

Mesomorphically ordered structures and phase behavior of the mixtures of nicotinic acid (NICA) and dodecylbenzenesulfonic acid (DBSA) were investigated by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and polarized optical microscopy (POM). The POM observations revealed that the NICA–DBSA mixtures spontaneously formed liquid crystalline phases, although both NICA and DBSA were not liquid crystalline molecules. The NICA–DBSA mixtures formed ordered lamellar structures in DBSA‐rich mixtures and hexagonal cylinder structure in NICA‐rich mixtures. The mesomorphically ordered structures and optical anisotropy were caused by hierarchical interactions in the NICA–DBSA mixtures. The phase diagram divided into five regions—optically isotropic disordered phase, optically isotropic lamellar phase, optically anisotropic lamellar phase, optically anisotropic cylinder phase, and crystalline solid phase—is drawn by summarizing the XRD and POM results.     

Chitosan-cellulose sulfate acetate complexation in acetic acid solutions

Colloidal and optical properties of dispersions of chitosan-cellulose sulfate acetate interpolyelectrolyte complexes resultant from mixing dilute solutions of the polymers in acetic acid and in acetic acid-based buffer mixtures are investigated. It is established that, in acetic acid, an insoluble complex is formed whose composition corresponds to the unit ratio [chitosan]: [cellulose sulfate acetate] = 1: 1.5, mol/mol. Particle size and concentration are independent of the order of mixing of the solutions of the polymers. In buffer solvents, the particle size is larger and the particle concentration is lower than those in acetic acid. Excess chitosan causes the dissolution of the complex. The addition of low-molecular-weight electrolytes to ionic strengths of 0.2–0.3 also promotes the dissolution of the interpolyelectrolyte complex. The complex becomes completely soluble at ionic strengths of 1.5–2.0.     

Complex formation of cyclodextrins with poly(propylene glycol) derivatives

The complex formation between cyclodextrins (CDs) and poly(propylene glycol) (PPG) derivatives is described. β‐CD and γ‐CD formed complexes with PPG derivatives such as 1‐naphthyl (1NA), 2‐naphthyl (2NA), 3,5‐dinitrobenzoyl, and 2,4‐dinitrophenyl PPG. α‐CD did not form complexes with these PPG derivatives. Although γ‐CD gave complexes with 9‐anthryl PPG (PPG9An), β‐CD did not efficiently form complexes with PPG9An. β‐CD did not form complexes with trityl PPG, demonstrating that trityl groups were too bulky to thread a β‐CD cavity. The emission spectra of the complexes showed that β‐CD bound a single 2NA moiety in its cavity and that γ‐CD included two 2NA moieties. In contrast, γ‐CD bound a single 1NA moiety in the cavity. X‐ray diffraction studies and ¹H NMR analysis showed that the CD molecules were stacked along a PPG chain to form a channel structure. The inclusion modes are discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4839–4849, 2000     

Supramolecular main chain liquid crystalline polymers utilizing azopyridine derivatives

A series of main chain liquid crystalline polymers were formed through intermolecular hydrogen bonding between a functionalized bisazopyridine phenol and aromatic bisacids. The behaviour of these complexes was studied through differential scanning calorimetry and thermal polarizing optical microscopy. The presence of the hydrogen bonds was confirmed through infrared spectroscopy. These complexes formed thermotropic mesophases. The phases were determined to be nematic in nature from the schlieren textures of the optical micrographs. As the length of flexible spacer groups separating the mesogenic portions increased, the clearing temperatures of the mesophases decreased. As the length of the rigid component increased, the clearing temperature increased. A new bisacid species based on 2-hydroxy-6-naphthoic acid was used to increase clearing temperatures while remaining within an acceptable temperature window.     

Effects of liquid crystalline and shear alignment on the optical properties of cellulose nanocrystal films

Rheo-optics, microspectrophotometry, and optical contrast measurements were used to gain new insights into the interrelated effects of liquid crystalline phase behavior, flow alignment, and microstructural relaxation on cellulose nanocrystal (CNC) films’ alignment and optical properties. Optical contrast measurements were found to be an effective and facile way of determining changes in anisotropy directly from cross-polarized microscopy images. This method was used to continuously measure microstructural relaxation after the cessation of shear as well as the anisotropy of dried CNC films. Aqueous liquid crystalline CNC dispersions showed greater alignment after shear than isotropic or biphasic dispersions. However, CNC gels exhibited lower alignment at equivalent shear rates. The combination of greater initial alignment and slower relaxation of sheared liquid crystalline dispersions resulted in the most optically anisotropic films. Depending on their thickness, the CNC films were optically transparent in the visible regime or exhibited tunable interference colors. The results of this work highlight the tunability of CNC dispersion processing for producing color filters and other optical materials with controlled properties.     

THE STRUCTURE AND PROPERTIES OF CHITOSAN/PPLYETHYLENE GLYCOL/SILICA TERNARY HYBRID ORGANIC-NORGANIC FILMS

The ternary hybrid films consisting of chitosan(CS),polyethylene glycol(PEG)and nano-sized silica which was surface-modified by amino groups(RNSA)were prepared.The structures of the blend membranes were characterized by attenuation total reflection-infrared spectroscopy(ATR-IR),X-ray diffraction(XRD),optical microscopy(OM)and differential scanning calorimetry (DSC).The results showed that the addition of silica affected not only the distribution and crystallinity of PEG on the sample surface.but also the phase coarseness and the crystalline structure of chitosan in the blend system.Moreover,PEG changed the crystalline structure of chitosan.Upon annealing(at 100℃ for 1 h),the blends would show the altered crystalline structure of chitosan,the reinforced phase coarseness.as well as the decreased miscibility and interaction between chitosan and PEG.     

A series of azo-type side-chain liquid crystalline polysiloxane–palladium complexes

A series of azo-type side-chain liquid crystalline polysiloxanes (AZLCPs) were synthesized, starting from organic polysiloxane and azo-type mesogenic compounds having an end allyl group. The AZLCPs were further used to coordinate with palladium dichloride and potassium chloride, by which a series of palladium complexes of AZLCPs (Pd–AZLCPs) were prepared. The mesogenic properties of all of the liquid crystalline polymers were characterized by using differential scanning calorimetry, polarized microscope and wide-angle X-ray diffraction. It was found that all of the polymer ligands and their palladium complexes showed thermotropic liquid crystallinity and that the incorporation of the palladium ions gave positive effects to the mesogenic properties of their polymer ligand counterpart. Compared with the corresponding AZLCPs, the Pd–AZLCPs have higher isotropization temperatures and a broader mesophase temperature range. The mesogenic properties of the liquid crystalline polymer ligands and their palladium complexes were also varied gradually by changing the length of the alkoxy groups on the side chain. The polymers that have a color emissive group and a highly flexible polysiloxane main chain may potentially be used as nonlinear optical materials.     

Characteristics of Interactions in the Pectin–Chitosan System

Interpolymeric complexes have been obtained from citric pectin and chitosan, the latter synthesized from crab chitin. The composition and structure of complexes obtained from different ratios of the components were studied by IR spectroscopy, rheological investigation of gel structure, and mathematical modelling of system properties. Rheological investigation of the processes involved in the formation of interpolymeric complexes with gel structures from citric pectin and chitosan was conducted in moderately concentrated solutions containing different ratios of the components. It was shown that the toughness of the gel structures was determined by the ratio of the amounts of the heterogeneous polymers. The toughest product (τ=121.4 Pa) was obtained by use of equimolar quantities of pectin and chitosan. With deviation of the composition of the mixture from equimolar the toughness of the gel decreased. It is proposed that the polyelectrolyte pectin–chitosan complex with a network structure is formed at the expense of electrostatic interaction between positively charged amino groups at C-2 of the chitosan pyranose ring and negatively charged carboxyl groups at the C-5 of the pectin pyranose ring.     

Hexagonal columnar mesophases in oxygen-bridged dicopper complexes

The synthesis of a series of bidentate Schiff 's bases; 3,5-bis(3 ,4 ,5-trialkoxybenzyloxy)phenyl2- N -(3-hydroxypropy)iminopropyl ketone, and their dicopper complexes are reported. The liquid crystalline behaviour of these dicopper complexes was studied by DSC, polarized optical microscopy and X-ray diffraction. The phases were characterized and identified as hexagonal columnar (D ) phases, which are typical of disc-like molecules. h     

Preparation of some chitosan heavy metal complexes and study of its properties

The chitosan was prepared and mixed with some metal salts (FeCl₃, Co(OAc)₂ and NiCl₂) by different concentrations to form chitosan-metal complexes. The metal ions which strongly complexed to the amino groups of chitosan like Fe showed a smooth surface product, amorphous phase, thermally more stable and high electrical conductivity than other complexes, while the Co ions which the weakly complexed with chitosan showed a rough surface product, crystalline phase, thermally less stable and low electrical conductivity. The chitosan-metal complexes have a higher electrical conductivity than chitosan pure at room temperature.     

Supramolecular hydrogel formation based on inclusion complexation between poly(ethylene glycol)-modified chitosan and alpha-cyclodextrin

Supramolecular hydrogels have been prepared on the basis of polymer inclusion complex (PIC) formation between poly(ethylene glycol) (PEG)-modified chitosans and alpha-cyclodextrin (alpha-CD). A series of PEG-modified chitosans were synthesized by coupling reactions between chitosan and monocarboxylated PEG using water-soluble carbodiimide (EDC) as coupling agent. With simple mixing, the resultant supramolecular assembly of the polymers and alpha-CD molecules led to hydrogel formation in aqueous media. The supramolecular structure of the PIC hydrogels was confirmed by differential scanning calorimetry (DSC), X-ray diffraction, and (13)C cross-polarized/magic-angle spinning (CP/MAS) NMR characterization. The PEG side-chains on the chitosan backbones were found to form inclusion complexes (ICs) with alpha-CD molecules, resulting in the formation of channel-type crystalline micro-domains. The IC domains play an important role in holding together hydrated chitosan chains as physical junctions. The gelation property was affected by several factors including the PEG content in the polymers, the solution concentration, the mixing ratio of host and guest molecules, temperature, pH, etc. All the hydrogels in acidic conditions exhibited thermo-reversible gel-sol transitions under appropriate conditions of mixing ratio and PEG content in the mixing process. The transitions were induced by supramolecular association and dissociation. These supramolecular hydrogels were found to have phase-separated structures that consist of hydrophobic crystalline PIC domains, which were formed by the host-guest interaction between alpha-CD and PEG, and hydrated chitosan matrices below the pK(a).The formation of inclusion complexes between alpha-cyclodextrin and PEG-modified chitosan leads to the formation of hydrogels that can undergo thermo-reversible supramolecular dissociation.     

Recent developments in polymeric charge transfer complexes

The recent literature on polymeric charge transfer complexes is reviewed with emphasis on the author's own work. After a definition of the area and a survey of investigations on the spatial arrangement of donor and acceptor sites in the solid state, a variety of applications of these complexes is presented. Electrically conductive polymers are excluded. These applications are: compatibilization of polymer blends, liquid crystalline supramolecular organization, new developments in photo-conductivity, electroluminescence, nonlinear optical properties, photorefractivity and reversible optical storage.