Characterization of Ultrathin Films of Cellulose Esters

The adsorption of cellulose acetate (CA), cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) from solutions prepared in acetone onto silicon wafers led to ultrathin films, which were characterized by ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The polysaccharides films were characterized in the air just after their formation and after annealing at temperatures higher than their glass transition temperature or melt temperature. The films thickness close to 2 nm and surface roughness did not vary significantly upon annealing. AFM images revealed the presence of small clumps dispersed on a homogeneous layer, which covered completely the Si wafers. Such topographic details were also observed after annealing. However, upon annealing the films surfaces changed from hydrophilic to hydrophobic, evidencing molecular re-orientation at the solid–air interface. The adhesion of bovine serum albumin (BSA) and lipase onto the cellulose esters films was quantified in order to evaluate the possibility of applying such films as selective support for biomolecules.     

Synthesis and Opto-Electronic Properties of Cholesteric Cellulose Esters

Cholesteric materials display unique optical properties which can be exploited in opto-electronic applications such as light emitting diodes. The key feature is the position of the wavelength of the emitted light relative to the one of the selective reflection band. We have synthesized a set of cellulose derivatives displaying the cholesteric phase with the aim to investigate the correlation between chemical structure and properties. Phase transition temperatures, the chain packing, the wavelength of selective reflection but also absorption and fluorescence spectra were investigated as a function of the degree of substitution (DS), the nature of lateral substituents, the composition of doped systems and blends of different cellulose derivatives. Investigated were furthermore the degree of circular polarization of the emitted light for guest–host systems and for cellulose systems with chromophores linked by covalent bonds to the cellulose backbone as well as their performance in light emitting diodes. The conclusion is that the optical properties can be accounted for on the basis of the model of a one-dimensional photonic crystal. The limiting factor with respect to opto-electronic applications is the poor control of the uniformity of the helix formation and orientation.     

Determination of the Content of Bound Carboxylic Acids in Mixed Cellulose Esters

A method was proposed for differential determination of bound carboxylic acids in mixed cellulose esters containing residues of acetic and higher carboxylic (capric, lauric, myristic, palmitic) acids.     

Sorption Properties of Gel Films of Bacterial Cellulose

The structure and sorption properties of gel films of bacterial cellulose were studied in its interaction with polyvinylpyrrolidone and silver nanoparticles stabilized by this compound.     

Cluster Structure of the Surface of Plasticized Cellulose Triacetate Films

The influence of plasticizers, dibutyl phthalate and triphenyl phosphate, on the structure of the surface of cellulose triacetate films was studied. The parameters of an infinite cluster of the cellulose triacetate molecules on the film surface, the correlation radius ξ of the spatial distribution of density, the degree ρ_s of surface filling of the cluster, and the fractal dimensionality D, were calculated from the electron-microscopic data, using the cluster model.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 306–309.Original Russian Text Copyright © 2005 by Novikov, Varlamov, Mnatsakanov.     

阳离子化纳米纤维素晶体增强壳聚糖复合膜的制备及性能

利用水相连续法实现了纳米纤维素晶体(NCC)的高碘酸钠氧化及阳离子化,然后将阳离子化纳米纤维素晶体(CDAC)悬浮液与壳聚糖(CTS)醋酸溶液混合,并采用流延法制得壳聚糖-纳米纤维素(CTS-CDAC)复合膜。采用红外光谱(FT-IR)、透射电镜(TEM)、X射线衍射(XRD)、Zeta电位及粒径分析表征了改性前后NCC的结构与性能,并研究了制得的CDAC悬浮液与CTS醋酸溶液混合时的相容性及CTS-CDAC复合膜中CDAC质量分数对复合膜力学性能、水溶胀性的影响。结果表明:CDAC悬浮液与CTS醋酸溶液混合时相容性良好,CDAC在CTS基质中分散均匀,CTS-CDAC复合膜的力学性能较纯CTS膜明显提高。当复合膜中CDAC的质量分数为12%时,拉伸强度达到最高。另外,CTS-CDAC复合膜在水中的溶胀度较纯CTS膜明显降低,稳定性变好。     

Properties of Mixed Aqueous Solutions of Polyethylene Oxide and Carboxymethyl Cellulose with Different Degrees of Ionization and of Composite Films Prepared from Them

Russian Journal of Applied Chemistry - Rheological properties of mixtures of dilute and moderately concentrated aqueous solutions of carboxymethyl cellulose with various degrees of ionization and...     

Properties of Flax Cellulose Solutions in Tertiary Amine N-Oxides and of Films Thereof

The solubility of flax fibers differing in the degree of purity in triethylamine N-oxide monohydrate was studied. The size and amount of the associates in equiconcentrated solutions were estimated from the turbidity spectra. Rheological properties of solutions of cotton and flax cellulose were compared. Hydrated cellulose films were obtained from solutions, and their physicomechanical properties were studied. The films were characterized by IR spectroscopy.     

Cellulose Esters Prepared by Wood Esterification

Trends in the yields and properties of cellulose esters are studied as a function of wood esterification conditions. The yield, total extent of cellulose ester substitution, and degree of conversion depend on the duration and acylation temperature     

Water Sorption Properties and Antimicrobial Action of Zinc Oxide Nanoparticles-Loaded Cellulose Acetate Films

In this work, ZnO nanoparticles loaded cellulose acetate (ZOLCA) films have been prepared and characterized by XRD, SPR and SEM analysis. The moisture permeation properties of the films have been investigated. The GAB isotherm model has been found to fit well on the moisture uptake data obtained at different temperatures. The monolayer sorption capacity χ_m was found to decrease from 0.059 to 0.0079 g water/g dry film with increase in temperature from 20 to 37°C. The isosteric heat of sorption, when studied in the lower water activity range of 0.04 to 0.10, was evaluated to be 46.55 to 87.29 kJ/mol. The water vapor permeability across the ZOLCA films was found to increase with temperature and activation energy of moisture sorption process was found to be 48.57 kJ/mol. These films have shown excellent antibacterial action against model bacteria E-Coli when investigated by qualitative and quantitative methods. Films exhibit great potential to be used as edible films to protect food stuff against microbial infections.     

Aluminum Antimonide Thin Films: Structure and Properties

Protocols for sputtering stoichiometric aluminum antimonide thin films were developed by calculating aluminum and antimony vapor condensation flux densities. Aluminum and antimony were sputtered separately. The high chemical reactivity of nanosized aluminum and antimony films made it possible to reduce the synthesis temperature considerably (far below the melting point of the compound). The synthesis involved thermal annealing. The reaction between aluminum and antimony films started at 470°С. Optimal AlSb formation parameters comprise annealing at 540°С for at least 10 h. Film synthesis steps were studied by X-ray powder diffraction, optical, electron, and atomic force microscopy. The composition was monitored by energy dispersive X-ray spectra. The films were found to have hole conductivity; the 300-K charge density and charge mobility in the films are 1 × 10¹⁹ cm^–3 and 1 × 10² cm²/(V s), respectively.     

Tensile Properties and Morphology of Oil Palm Empty Fruit Bunch Regenerated Cellulose Biocomposite Films

The regenerated cellulose (RC)biocomposite films were prepared using casting method where oil palm empty fruit bunch (OPEFB) and microcrystalline cellulose (MCC) were dissolved in N-dimethylacetamide/lithium chloride (DMAc/LiCl)solution. The increasing of OPEFB contents up to 2 wt% increased the tensile strength and modulus of elasticity of RC biocomposite films while the elongation at break decreased. However, at 3 and 4 wt% of OPEFB content, the tensile strength and modulus of elasticity decreased with increases OPEFB content, but elongation at break increased. The increment of tensile strength and modulus of elasticity at 2 wt% is due to the OPEFB fiber that partially dissolved and dispersed with the OPEFB matrix. The morphology studies illustrate that at 2 wt% of OPEFB content of biocomposite films surface consists less voids and agglomerations than at 4 wt%. This can be considered the RC filler was partially dispersed with the RC matrix in the biocomposite films.     

Effect of Butyl Methacrylate on Properties of Regenerated Cellulose Coconut Shell Biocomposite Films

In this study, butyl methacrylate acid (BMA) is used as chemical modifier of regenerated cellulose (RC) coconut shell (CS) biocomposite films. The effect of CS content and BMA on tensile properties and crystallinity index (CrI) of RCCSbiocomposite films were investigated. It is found that the increasing of CS content up to 3 wt% increased the tensile strength and modulus of elasticity but decreased at higher content of CS. Elongation at break decreased with increasing of CS content and increased at 4 wt% of CS. Cystallinity index (CrI) of biocomposite films also increased with increasing CS up to 3 wt% content. At similar CS content, treated RC CS biocomposite films with BMA were found to have higher tensile properties and crystallinity index (CrI) than the untreated biocomposite films. The modification by BMA improved interfacial interaction and dispersion of CS in RC biocomposite films.     

Pr-Ce-Zr复合氧化物的结构与储氧性能研究

采用氨水共沉淀方法制备了PrxCe0.3－xZr0.7O2（x=0,0．1,0．2,0．3）复合氧化物,对样品进行了X光衍射、比表面积等表征及动态和静态储氧性能测试。结果表明,Pr进入铈锆的晶格,形成了良好的固溶体,并有效地阻止了水热老化处理造成铈锆的分相。在富锆复合氧化物中,Pr本身的氧化还原能力较弱,对固溶体的总储氧能力贡献不大;而适量Pr掺杂（10％,原子分数）可以对铈锆样品的表面改性,提高动态储放氧能力。     

纳米纤维素/聚3,4-乙撑二氧噻吩复合薄膜的制备及电致变色性能

以棉浆粕为原料,采用硫酸溶胀结合超声波处理的方法制备了纳米纤维素(NC).在纳米纤维素的水分散液中加入3,4-乙撑二氧噻吩单体,以过硫酸铵为氧化剂,采用原位化学氧化法制得了纳米纤维素/聚3,4-乙撑二氧噻吩(NC/PEDOT)纳米复合物.对NC和NC/PEDOT复合物进行扫描电镜、透射电镜和红外光谱分析.将纳米复合物的水分散液滴涂在氧化铟锡(ITO)玻璃表面形成复合薄膜,考察不同纳米纤维素含量对NC/PEDOT复合薄膜电致变色性能的影响.结果表明,NC呈棒状,平均直径为20 nm,长度为100~300nm;NC/PEDOT复合物中PEDOT均匀包覆在NC表面形成核壳结构,平均直径为30 nm;复合薄膜中当NC含量为60%时,其电致变色性能最好,具有最高的对比度(24.4%),最短的响应时间(1 s),最高的着色效率(51.8 cm~2/C).     

Study of the Structure and Sorption Properties of Some Types of Cellulose

The pulsed NMR, isopiestic and pycnometric methods are applied to investigate the physicochemical properties of softwood [GOST (State Standard) 9571-89] and hardwood [GOST 28172-89] celluloses, as well as flax cellulose [GOST 10330-76, 9394-76], both in the initial state and subjected to chemical treatment. Possible changes occurring in the supramolecular structure of a polymer are analyzed. The structural and sorption characteristics of the investigated samples are calculated. Their water absorption capacities are determined.     

Structure and Properties of Bacterial Cellulose Produced Using a Trickling Bed Reactor

Structure and properties of bacterial cellulose (BC) produced by trickling fermentation were studied. The following indexes, such as extrinsic shapes, microstructure, chemical structure, purity, water holding capacity, porosity, and thermogravimetric characteristics, are recommended for assessing the structure and properties of bacterial cellulose. With the comparison to bacterial cellulose produced by static fermentation and shaking fermentation, the results showed that for different BC cultivation methods, the extrinsic shapes, synthetic mode, and microstructure were different. The basic consistency of the infrared spectrogram from three kinds of bacterial cellulose reflected that the chemical structures were very similar. But the –OH associating degree of trickling fermentation BC was higher, and the polymerization degree, purity, water holding capacity, porosity, and thermal stability of trickling fermentation BC were also higher than those of static fermentation BC and shaking fermentation BC. But the crystallinity and crystal grain size of trickling fermentation BC were less than those of static fermentation BC and greater than those of shaking fermentation BC and plant fiber. These above structure and properties of trickling fermentation BC could reference bacterial cellulose’s application in food and material field.     

水可分散体羧甲基纤维素醋酸丁酸酯结构与性能研究

采用大浴比碱化、醚化与半均相酯化的合成方式,制备出纤维素混合醚酯——羧甲基纤维素醋酸丁酸酯（CMCAB）。利用^1H—NMR、FTIR、XRD、TG和DSC等技术对CMCAB结构与热性能进行分析与表征,并对其溶液表面性能、水分散体流变性能进行了研究。结果表明,CMCAB分子链上亲水性羧基分布均匀;CMCAB结晶度低、热...     

海藻酸钠/水性聚氨酯共混膜的结构表征和性能测试

本文将海藻酸钠与聚酯型水性聚氨酯共混制膜，并通过红外光谱（FTIR）、X射线衍射（XRD）、扫描电镜（SEM）、紫外光谱（UV）、力学性能测试对共混膜的结构和性能进行了表征与测试。结果表明，共混膜中两种分子间存在着强烈的相互作用和良好的相容性，与纯海藻酸钠膜相比共混膜有较高的抗水性和断裂伸长率。     

A Study on the Preparation,Structure, and Properties of Microcrystalline Cellulose

Abstract

The preparation, structure, and properties of microcrystalline cellulose (MCC) from rice straw were investigated by IR, x-ray, viscometry, polarizing microscope, SEM, etc. The results are as follows:

1. The leveling-off degree of polymerization (LODP) obtained from rice straw is about 80–150. The dimensions of MCC granules are 20–30 μm length, 0.5–0.8 μm thick, and the crystallinity is about 80%.

2. The aqueous suspension of a certain concentration of MCC can form a gel under the effect of shear force. The viscosity of MCC gel increased with an increasing content of MCC in water. A sharper increase of viscosity occurred in the 3–6% range.

3. The addition of one or two valence salts into the MCC gel increased the viscosity.

4. The viscosity of MCC gel has its maximum value at pH 8.

5. The MCC gel as an emulsifying agent can form a stable emulsion in the oil/water system when the ratio of oil/water is below 6/4.