Simultaneously Enhancing the Thermal Stability,Mechanical Modulus,and Electrochemical Performance of Solid Polymer Electrolytes by Incorporating 2D Sheets

Solid state electrolytes are the key components for high energy density lithium ion batteries and especially for lithium metal batteries where lithium dendrite growth is an inevitable obstacle in liquid electrolytes. Solid polymer electrolytes based on a complex of polymers and lithium salts are intrinsically advantageous over inorganic electrolytes in terms of processability and film‐forming properties. But other properties such as ionic conductivity, thermal stability, mechanical modulus, and electrochemical stability need to be improved. Herein, for the first time, 2D additives using few‐layer vermiculite clay sheets as an example to comprehensively upgrade poly(ethylene oxide)‐based solid polymer electrolyte are introduced. With clay sheet additives, the polymer electrolyte exhibits improved thermal stability, mechanical modulus, ionic conductivity, and electrochemical stability along with reduced flammability and interface resistance. The composite polymer electrolyte can suppress the formation and growth of lithium dendrites in lithium metal batteries. It is anticipated that the clay sheets upgraded solid polymer electrolyte can be integrated to construct high performance solid state lithium ion and lithium metal batteries with higher energy and safety.     

Novel non-exfoliated clay-nanocomposite materials by in situ co-polymerisation of intercalated monomers: a combinatorial discovery approach

We report the synthesis and qualitative testing of a novel class of clay nanocomposite meterials made by the in situ copolymerisation of small intercalating monomer molecules using combinatorial-style diversity methods. Initial screening was undertaken by treating montmorillonite clay films with combinations of selected additives in aqueous solution. The treated films were assessed for their stability in a qualitative manner based on their response to water. The mechanical stength of these films was also assessed qualitatively. Promising “lead” formulations showed no signs of water-induced swelling and/or exfoliation, while also being flexible and hard. In addition, the interlamellar d-spacings in the treated clay films were measured using X-ray diffraction, where possible; the value of the d-spacing in the treated clays was found to vary significanlty, from 12.7–17.7?Å. The lead formulations were then tested on bulk montmorillonite clay, confirming that the thin film behaviour was representative of that of the bulk. Direct analysis of the treated clays by mass spectrometry using both FAB and MALDITOF did not provide any useful information. However, when the clays were subjected to extraction using chloroform, clear evidence of higher relative moleclar mass species was forthcoming, confirming that polymersation of the additives was occurring. Further supporting evidence was obtained by solid-state NMR anlaysis of treated iron-free (laponite) clay samples, which also revealed extensive polymerisation of the monomers used. Comparison of these data with the results of some simple molecular modelling studies indicates that polymerisation is indeed occurring within the clay galleries.     

Molecular Modelling of The Mechanism of Action of Organic Clay-Swelling Inhibitors

Abstract

It is well known that the sodium smectite class of clays swells macroscopically in contact with water, whereas under normal conditions the potassium form does not. In recent work using molecular simulation methods, we have provided a quantitative explanation both for the swelling behaviour of sodium smectite clays and the lack of swelling of potassium smectites [1]. In the present paper, we apply similar modelling methods to study the mechanism of inhibition of clay-swelling by a range of organic molecules.

Experimentally, it is known that polyalkylene glycols (polyethers) of intermediate to high relative molecular mass are effective inhibitors of smectite clay swelling. We use a range of atomistic simulation techniques, including Monte Carlo and molecular dynamics, to investigate the interactions between a selection of these compounds, water, and a model smectite clay mineral. These interactions occur by means of organised intercalation of water and organic molecules within the galleries between individual clay layers.

The atomic interaction potentials deployed in this work are not as highly optimised as those used in our clay-cation-water work [1]. Nevertheless, our simulations yield trends and results that are in qualitative and sometimes semi-quantitative agreement with experimental findings on similiar (but not identical) systems. The internal energy of adsorption of simple polyethers per unit mass on the model clay is not significantly different from that for water adsorption; our Monte Carlo studies indicate that entropy is the driving force for the sorption of the simpler organic molecules inside the clay layers: a single long chain polyethylene glycol can displace a large number of water molecules, each of whose translational entropy is greatly enhanced when outside the clay. Hydrophobically modified polyalkylene glycols also enjoy significant van der Waals interactions within the layers which they form within the clay galleries.

In conjunction with experimental studies, our work furnishes valuable insights into the relative effectiveness of the compounds considered and reveals the generic features that high performance clay-swelling inhibitors should possess. For optimal inhibitory activity, these compounds should be reasonably long chain linear organic molecules with localised hydrophobic and hydrophilic regions along the chain. On intercalation of these molecules within the clay layers, the hydrophobic regions provide an effective seal against ingress of water, while the hydrophilic ones enhance the binding of the sodium cations to the clay surface, preventing their hydration and the ensuing clay swelling.     

Preparation of phenylalanine imprinted polymer by the sol–gel transition method

A phenylalanine (Phe) imprinted polymer was prepared by the wet-phase inversion and sol–gel transition method to endow a copolymer matrix with a large uptake capacity of template molecules and prominent adsorption selectivity at the high concentration of the racemate solution. A copolymer bead prepared by wet-phase inversion was shrunken in a hydrochloric acid solution containing a large amount of template molecules after swelling in a sodium hydroxide solution. Template molecules were effectively implanted in the polymer matrix during shrinking after swelling. The adsorption selectivities of Phe-imprinted copolymer bead were 2.1 and 1.33 at 1 g and 10 g Phe/l racemate solution, respectively, and the Phe uptake capacity reached about 1 g Phe/g dry weight of the copolymer. The adsorption selectivity of the copolymer was retained after five batches of adsorption/desorption in 1 g Phe/l solution composed of 5% D-Phe and 95% L-Phe.     

Effect of clay,organic matter and CaCO3 content on zinc adsorption by soils

Summary Zinc adsorption was studied in suspensions of six soils of different physicochemical characteristics in dilute ZnSO₄ solutions. At low concentrations, Zn²⁺ adsorption was described by the Langmuir adsorption equation. The calculated Langmuir adsorption maxima were related positively to clay and carbonate content and negatively with organic matter content of soils. Multiple regression analysis revealed that zinc adsorption maxima can be predicted with good precision from information in soil survey reports. When the added Zn²⁺ exceeded the adsorption maximum, the solid phase of zinc controlling its concentration in solution was either zinc hydroxide or carbonate so long as soil carbonates were present. The values of zinc potential also indicated that soils retain Zn²⁺ more strongly than Zn(OH)₂ or carbonate. Postgraduate student Professor of Soils. Professor of Soils.     

The chemical fractionation of soil zinc and its specific and total adsorption by Egyptian alluvial soils

Summary The Zn contents of twenty-nine alluvial soils from Egypt were chemically fractionated into: water soluble+exchangeable, weakly bound to inorganic sites, organically bound, occluded as free oxide material, and residual mainly in the mineral structure. On the average these fractions constituted about 0.01, 1.20, 28.6, 21.5 and 45.5% of the total soil Zn respectively which averaged 76.25 ppm. Significant correlations were obtained between each individual Zn-fraction and some soil variable.Zinc adsorption isotherms were developed for seven soils suspended in dilute ZnCl₂ solution in the presence of either 0.05M CaCl₂ solution (Specific adsorption) or deionized water (Total adsorption). The Langmuir constants (adsorption maximum and bonding energy) were calculated. The average value of specific adsorption maximum was 1.94 mg Zn/g soil and of total adsorption maxima was 11.54 mg Zn/g soil. Correlation analysis showed that CEC, free Fe₂O₃ and clay content were the dominant soil variables contributing towards specific Zn adsorption. The (Zn) (OH)₂ ion concentration products in the solutions when Zn adsorption corresponded to the Langmuir adsorption maxima were 0.92×10^–17 in the specific adsorption treatment, and 1.35×10^–15 in the total adsorption treatment. These values are within the solubility range of Zn (OH)₂ and ZnCO₃. The values of Langmuir bonding energy constants showed that Zn was more strongly adsorbed by low carbonate or carbonate-free soils than by carbonate-rich soils.     

How to develop globular proteins into adhesives

To make globular proteins suitable for application in adhesives, the specific bonds and interactions which shape their structure have to broken. Only then, a layer of relatively large, flexible and interwoven polymer chains, which are firmly attached to the solid surface by adsorption, can be created. Such a network layer is essential to save the adhesive bond under an applied force, because it can distribute the concentration of stresses generated at the interface into the bulk. Unfolding and swelling of a protein can be achieved by changing the solvent quality. For the globular whey protein beta-lactoglobulin, the optimal conditions for unfolding and swelling is found with 98% formic acid as a solvent. In formic acid, beta-lactoglobulin looses its amphoteric character (it is protonated, probably for approximately 20%). In addition, formic acid is less polar than water and thus a better solvent for the apolar parts of the protein. The swelling and unfolding behaviour of beta-lactoglobulin is studied by viscosity and CD-spectroscopy measurements. For the interpretation of the results we apply the Kuhn formalism that the conformation of a protein can be described in terms of a statistical chain which consists of segments of an average persistence length P. The statistical segment length P, which varies with the experimental conditions, is directly related to the adsorption energy required for a strong adhesion between coil and surface. It determines the depletion energy kT P(-2) m(-2) which must be overcome by specific attraction between side groups of the protein chain and the surface. For beta-lactoglobulin in 98% formic acid, we find a P value of approximately 2.2 nm, pointing at a relatively flexible chain. The minimum net adsorption energy kT P(-2) is then approximately 1 mJ m(-2), a relatively small value to be exceeded. Preliminary results of destructive adhesion tests on beech wood lap-shear joints reveal promising tensile strengths of approximately 2.9+/-1.1 N mm(-2), indeed.     

Optical absorption investigations for efficient crystal violet dye removal from wastewater via carbon nanotubes:Montmorillonite-based nanocomposite

The current study reports a facile method to fabricate functionalized multi-walled carbon nanotubes and montmorillonite clay mineral-based nanocomposite matrix and its detailed characterization using spectroscopic and morphological techniques. The nanocomposites have been studied for their potential applications in the treatment of contaminated water using batch adsorption studies. The investigations conducted using optical absorption spectroscopic measurements for the adsorption process indicate that the nanocomposite matrix can effectively remove almost 98% of the dye from aqueous solution. The nanocomposites have showed fast and strong adsorption behaviour for the dye with the maximum adsorption capacity (q_m) of ~467.3 mg g⁻¹ in 25 min. The experimental data at equilibrium were also correlated with the theoretical adsorption isotherm and kinetic models. The results demonstrate that the experimental data fits well to the Freundlich adsorption isotherm model and conforms to second-order kinetics. Furthermore, the nanocomposite exhibits good recyclability without any marked decrease in the adsorption performance even after five adsorption cycles of usage which indicates its potential application as reusable adsorbent for the efficient removal of hazardous dyes from contaminated water.     

Cations as Mediators of the Adsorption of Nucleic Acids on Clay Surfaces in Prebiotic Environments

Monovalent ([Na⁺] > 10 mM) and divalent ([Ca²⁺], [Mg²⁺] > 1.0 mM) cations induced the precipitationof nucleic acid molecules. In the presence of clay minerals (montmorillonite and kaolinite), there was adsorption instead of precipitation. The cation concentration needed for adsorption depended on both the valence of the cations and the chemical nature of the nucleic acid molecules. Double-stranded nucleic acids needed higher cation concentrations than single-stranded ones to be adsorbed to the same extent on clay. Divalent cations were more efficient than monovalent ones in mediating adsorption. Adsorption to the clay occurred only when both nucleic acids and cations were present. However, once the complexes were formed, the cations could not be removed from the system by washing, indicating that they are directly involved in the association between nucleic acids and mineral surfaces.These observations indicate that cations take part directly in the formation of nucleic acid-clay complexes, acting as a `bridge' between the negative charges on the mineral surface and those of the phosphate groups of the genetic polymer. The relatively low cation concentrations needed for adsorption and the ubiquitous presence of clay minerals in the environment suggest that the adsorption of nucleic acids on mineral surfaces could have taken place in prebiotic habitats. This may have played an important role in the formation and preservation of nucleic acids and/or their precursor polymers.     

Phase relationships of an equivalent mixture of sulfated polyvinyl alcohol and aminoacetalyzed polyvinyl alcohol in microsalt aqueous solution

A new type of polymer salt was prepared from an equivalent mixture of partly sulfated polyvinyl alcohol (polyanion, Q^?) and partly aminoacetalyzed polyvinyl alcohol (polycation, P⁺). With respect to a three-component system composed of this polymer salt (P⁺Q^?), water, and a microsalt (K⁺A^?), phase relationships, as represented by complex coacervation, were investigated. Experimental results were discussed according to a theoretical equation for the free energy of mixing derived by taking into account the entropy and enthalpy contributions as ascribed for non-ionic polymer solution, and the electrostatic free energy expression as derived by Voorn.     

Biosynthesis of an amphiphilic silk-like polymer

An amphiphilic silk-like protein polymer was efficiently produced in the yeast Pichia pastoris. The secreted product was fully intact and was purified by solubilization in formic acid and subsequent precipitation of denatured host proteins upon dilution with water. In aqueous alkaline solution, the negatively charged acidic polymer assumed extended helical (silk III-like) and unordered conformations. Upon subsequent drying, it assumed a conformation rich in beta-turns. In water at low pH, the uncharged polymer aggregated and the solution became turbid. Concentrated solutions in 70% (v/v) formic acid slowly formed gels. Replacement of the formic acid-water mixture with methanol and subsequent drying resulted in beta-sheets, which stacked into fibril-like structures. The novel polymer instantaneously lowered the air-water interfacial tension under neutral to alkaline conditions and reversed the polarity of hydrophobic and hydrophilic solid surfaces upon adsorption.     

Adsorption and separation of proteins by a smectitic clay mineral

The adsorption of proteins by a smectitic clay mineral was investigated. The clay used in this study is a mixture of montmorillonite and amorphous SiO₂. Due to the high porosity the montmorillonite units are accessible for protein adsorption. The amorphous silica prevents the montmorillonite from swelling and allows column packing. Protein adsorption was performed at different pH under static conditions. Furthermore, static capacities were determined. The material reveals high adsorption capacities for proteins under static conditions (270–408 mg/g), whereby proteins are mainly adsorbed via electrostatic interactions. The Freundlich isotherm is suggested as an adsorption model. For desorption a pH shift was found to be most effective. Binding and elution of human serum albumin and ovalbumin were tested under dynamic conditions. Dynamic capacities of about 40 mg/g for ovalbumin at 764 cm/h were found. The clay mineral provides suitable properties for the application as cost-efficient, alternative separation material.     

Concentration and composition of dissolved organic carbon in streams in relation to catchment soil properties

Two adjacent catchments in the Otway Ranges of Victoria, Australia (Redwater and Clearwater) produce water with markedly different concentrations of dissolved organic carbon (DOC) during summer. Water from Redwater Creek had a DOC concentration of 32 mg L^–1, while water from Clearwater Creek had a DOC concentration of 3.8 mg L^–1. Examination of the catchments revealed that while climate, topography, vegetation and land use were similar, the soils were different. The objective of this study was to examine the relationship between the concentration and chemical composition of DOC in stream waters and the nature of soils in the two catchments. Soil mapping determined that clayey soils formed on Cretaceous sediments (Cretaceous soils) occurred throughout both catchments, but that Redwater Catchment also contained a large area (39%) of sandy soils formed on Tertiary sediments (Tertiary soils). The concentration of DOC in forest floor leachate was high in both the Tertiary and Cretaceous areas; however, the concentration of DOC in water draining areas dominated by Tertiary soils was greater than that in water draining areas dominated by Cretaceous soils. Laboratory experiments showed that the Cretaceous soils had higher adsorption capacities for forest floor leachate DOC than the Tertiary soils. The difference in DOC concentrations of the streams was therefore attributed to the difference in adsorption capacity of catchment soils for DOC. Adsorption capacities of the soils were found to be a function of their clay contents and specific surface areas.Solid-state³C nuclear magnetic resonance spectroscopy and pyrolysis-mass spectrometry were used to determine the chemical structure of DOC found in streams and forest floor leachate samples and that remaining in solution after interaction with soil. Chemistry of DOC in forest floor leachate was similar before and after interaction with soil, indicating no preferential adsorption of a particular type of carbon. Thus, differences between the chemical structure of stream DOC and forest floor leachate DOC could be attributed to microbial modifications during its movement through soils and into the streams, rather than losses by adsorption.     

Activation thermodynamics of virus adsorption to solids.

The kinetics of bacteriophage MS2, T2, and f2 adsorption to powdered nitrocellulose and disrupted Seitz S1 filters at pH 7 were determined as a function of temperature. Data from these studies were combined with data produced in a previous study on MS2 adsorption to clay by Stagg et al. (Appl. Environ. Microbiol. 33:385-391, 1977). These workers studied the adsorption of MS2 to bentonite clay as a function of temperature. Data from both this previous study and the current one were used to calculate the thermodynamic parameters of virus adsorption. The results show that adsorption of bacteriophages to the solids tested is a physical process (energy of activation, less than 40 kcal [168 J]/mol) rather than a chemical process (energy of activation, greater than 40 kcal/mol). The free energy of activation showed a high negative correlation (r = -0.904, r2 = 0.817) with the percentage of virus adsorption to the solids tested. The energy of activation was highly negatively correlated with the percentage of virus adsorption to nitrocellulose and clay (r = -0.913, r2 = 0.834) but poorly correlated with the percentage of virus adsorption to disrupted Seitz S1 filters (r = -0.348, r2 = 0.121). In general, under conditions in which the percentage of virus adsorption was low, the energy of activation, the free energy of activation, and the entropy of activation were high. Increasing the percentage of virus adsorbed by changing the adsorbing conditions or changing the adsorbing solid decreased the energy of activation, the free energy of activation, and the entropy of activation.     

First-principles study of water desorption from montmorillonite surface

Knowledge about water desorption is important to give a full picture of water diffusion in montmorillonites (MMT), which is a driving factor in MMT swelling. The desorption paths and energetics of water molecules from the surface of MMT with trapped Li⁺, Na⁺ or K⁺ counterions were studied using periodic density functional theory calculations. Two paths—surface and vacuum desorption—were designed for water desorption starting from a stationary structure in which water bonds with both the counterion and the MMT surface. Surface desorption is energetically more favorable than vacuum desorption due to water–surface hydrogen bonds that help stabilize the intermediate structure of water released from the counterion. The energy barriers of water desorption are in the order of Li⁺?>?Na⁺?>?K⁺, which can be attributed to the short ionic radius of Li⁺, which favors strong binding with the water molecule. The temperature dependence of water adsorption and desorption rates were compared based on the computed activation energies. Our calculations reveal that the water desorption on the MMT surface has a different mechanism from water adsorption, which results from surface effects favoring stabilization of water conformers during the desorption process.     

DONNAN EQUILIBRIUM AND THE PHYSICAL PROPERTIES OF PROTEINS : IV. VISCOSITY—Continued.

1. The proof is completed that the influence of electrolytes on the viscosity of suspensions of powdered particles of gelatin in water is similar to the influence of electrolytes on the viscosity of solutions of gelatin in water. 2. It has been suggested that the high viscosity of proteins is due to the existence of a different type of viscosity from that existing in crystalloids. It is shown that such an assumption is unnecessary and that the high viscosity of solutions of isoelectric gelatin can be accounted for quantitatively on the assumption that the relative volume of the gelatin in solution is comparatively high. 3. Since isoelectric gelatin is not ionized, the large volume cannot be due to a hydration of gelatin ions. It is suggested that this high volume of gelatin solutions is caused by the existence in the gelatin solution of submicroscopic pieces of solid gelatin occluding water, the relative quantity of which is regulated by the Donnan equilibrium. This would also explain why the influence of electrolytes on the viscosity of gelatin solutions is similar to the influence of electrolytes on the viscosity of suspensions of particles of gelatin. 4. This idea is supported by experiments on solutions and suspensions of casein chloride in which it is shown that their viscosity is chiefly due to the swelling of solid particles of casein, occluding quantities of water regulated by the Donnan equilibrium; and that the breaking up of these solid particles into smaller particles, no longer capable of swelling, diminishes the viscosity. 5. This leads to the idea that proteins form true solutions in water which in certain cases, however, contain, side by side with isolated ions and molecules, submicroscopic solid particles capable of occluding water whereby the relative volume and the viscosity of the solution is considerably increased. This accounts not only for the high order of magnitude of the viscosity of such protein solutions but also for the fact that the viscosity is influenced by electrolytes in a similar way as is the swelling of protein particles. 6. We therefore reach the conclusion that there are two sources for the viscosity of protein solutions; one due to the isolated protein ions and molecules, and the other to the submicroscopic solid particles contained in the solution. The viscosity due to the isolated molecules and ions of proteins we will call the general viscosity since it is of a similar low order of magnitude as that of crystalloids in solution; while the high viscosity due to the submicroscopic solid protein particles capable of occluding water and of swelling we will call the special viscosity of protein solutions. Under ordinary conditions of hydrogen ion concentration and temperature (and in not too high a concentration of the protein in solution) the general viscosity due to isolated ions and molecules prevails in solutions of crystalline egg albumin and in solutions of metal caseinates (where the metal is monovalent) while under the same conditions the second type of viscosity prevails in solutions of gelatin and in solutions of acid-salts of casein; and also in solutions of crystalline egg albumin at a pH below 1.0 and at higher temperatures. The special viscosity is higher in solutions of gelatin than of casein salts for the probable reason that the amount of water occluded by the submicroscopic solid gel particles in a gelatin solution is, as a rule, considerably higher than that occluded by the corresponding particles of casein.     

Activation thermodynamics of virus adsorption to solids

The kinetics of bacteriophage MS2, T2, and f2 adsorption to powdered nitrocellulose and disrupted Seitz S1 filters at pH 7 were determined as a function of temperature. Data from these studies were combined with data produced in a previous study on MS2 adsorption to clay by Stagg et al. (Appl. Environ. Microbiol. 33:385-391, 1977). These workers studied the adsorption of MS2 to bentonite clay as a function of temperature. Data from both this previous study and the current one were used to calculate the thermodynamic parameters of virus adsorption. The results show that adsorption of bacteriophages to the solids tested is a physical process (energy of activation, less than 40 kcal [168 J]/mol) rather than a chemical process (energy of activation, greater than 40 kcal/mol). The free energy of activation showed a high negative correlation (r = -0.904, r2 = 0.817) with the percentage of virus adsorption to the solids tested. The energy of activation was highly negatively correlated with the percentage of virus adsorption to nitrocellulose and clay (r = -0.913, r2 = 0.834) but poorly correlated with the percentage of virus adsorption to disrupted Seitz S1 filters (r = -0.348, r2 = 0.121). In general, under conditions in which the percentage of virus adsorption was low, the energy of activation, the free energy of activation, and the entropy of activation were high. Increasing the percentage of virus adsorbed by changing the adsorbing conditions or changing the adsorbing solid decreased the energy of activation, the free energy of activation, and the entropy of activation.     

Cadmium(II) sorption from water samples by powdered marble wastes

Abstract

A series of batch adsorption experiments were carried out, with the aim of removing cadmium ions from aqueous solutions and water samples using powdered marble wastes (PMW) as an effective inorganic sorbent. PMW is inexpensive, widespread, and may be considered as environmental problem. The main parameters (i.e. solution pH, sorbent and cadmium concentrations, stirring time, and temperature) influencing the sorption process were investigated. The results obtained for sorption of cadmium ions onto PMW are well described by the Freundlich and Langmuir models. The Dubinin-Radushkevick (D–R) isotherm model was applied to describe the nature of the adsorption of the metal ion; it was found that the adsorption process was chemical in nature. The thermodynamic parameters were also calculated from the Gibbs free energy change (ΔG°), enthalpy (AH°) and entropy (ΔS°). These parameters indicated that the adsorption process of cadmium(II) ions on PMW was spontaneous and endothermic in nature. Under the optimum experimental conditions employed the removal of ca ~100% of Cd²⁺ ions was attained. The procedure was successfully applied to removal of the cadmium ions from aqueous and various natural water samples. The adsorption mechanism is discussed.     

Chiral bio-nanocomposites based on thermally stable poly(amide-imide) having phenylalanine linkages and reactive organoclay containing tyrosine amino acid

Montmorillonite clay modified with the bio-active trifunctional l-tyrosine amino acid salt was used as a reactive organoclay (OC) for the preparation of poly(amide-imide) (PAI)/OC hybrid films. One of the functional groups of the l-tyrosine as the swelling agent formed an ionic bond with the negatively charged silicates, whereas the remaining functional groups were available for further reaction with polymer matrix. The soluble PAI with amine end groups including phenylalanine amino acid was synthesised under green condition using molten tetra-butylammonium bromide by direct polymerization reaction of chiral diacid and 2-(3,5-diaminophenyl)benzimidazole. PAI/OC bio-nanocomposites films containing different contents of OC were prepared via solution intercalation method through blending of OC with the PAI solution. X-ray diffraction and transmission electron microscopy revealed that the dispersion of silicate layers in the PAI created an exfoliated structure as a result of using the trifunctional groups of the swelling agent. The structure and thermal behavior of the synthesised materials were characterized by a range of methods, including X-ray diffraction, Fourier transform infrared spectroscopy, ¹H-NMR, electron microscopy, elemental and thermogravimetric analysis techniques. Thermogravimetric analysis results indicated that the addition of OC into the PAI matrix was increased in the thermal decomposition temperatures of the resulted bio-nanocomposites.     

Swelling of Root Cell Walls as an Indicator of Their Functional State

The swelling capacity of cell walls isolated from different parts of lupine root was investigated. The water content in fragments of intact roots (Q) and swelling coefficient of standardized samples of cell walls (K^cw) were determined, and the dependences of Q and Kcw on the distance from the root tip (L) were plotted. It was shown that the change in Q value along the stretch of the lupine root reaches its maximum at distances of 1.5-6 cm or 7-12 cm from the root tip in 7-day-old and 14-day-old seedlings, respectively, whereas the K^cw value distribution over the root length is virtually invariable. In the radial direction, both the Q and K^cw values in cortex tissues are about twice higher than in the central cylinder. In our opinion, the changes of both Q and K^cw in the radial direction are associated with different degrees of cross-linking between polymer chains in cell wall structures of root cortex and central cylinder. The results of measurement of the K^cw value are consistent with the widely accepted mechanisms of water transport in roots in the radial direction. These data show that water transport through apoplast to the border between the cortex and central cylinder is accompanied by an increase in the resistance to water flow. Among other factors, this increase is due to a greater degree of cross-linking between cell wall polymers in the central cylinder. The results of measurement of the swelling coefficient of standardized cell wall samples in water and in 10 mM KCl at different pH values show that the swelling capacity of root cell walls varies according to the physicochemical properties of synthetic ion exchangers. Cell walls shrink (cell wall volume decreases) as ion concentration in solution increases and pH decreases. This causes an increase in the hydraulic resistance (or a decrease in the hydraulic conductivity) of apoplast. It was concluded that swelling is determined by the physicochemical properties of the cell wall, whereas the change in the swelling capacity induced by variation of external or internal conditions is an element of the mechanism of regulation of volume water flow in roots.