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The heterogeneous structure of lignocellulosic biomass makes it difficult to dissolve its main components (cellulose, hemicelluloses, and lignin) by solvent action with the aim of further applying the mixture of the biological macromolecules generated in the solvent medium. In the present study, the dissolution efficiency (DE) of lignocellulosic sisal fibers in the lithium chloride/dimethylacetamide solvent system (LiCl/DMAc) was evaluated for further application in the formation of hydrogels. Catalytic amounts of trifluoroacetic acid (TFA) were used in some experiments, which increased the DE from 40% to 90%. The regeneration of the solutions, either previously filtered or not, led to hydrogels based on sisal lignocellulosic biomass. In brief, the properties of the hydrogels were influenced by the content of the lignocellulosic components in the hydrogels, present both in the dissolved fraction and in the incorporated undissolved fraction (when nonfiltered solutions were used). Hydrogels presented water absorption up to 7479% and resorption content in the lyophilized hydrogel up to 2133%. Extracts obtained from preselected hydrogels exhibited cell viability up to 127% compared to the control group when in contact with fibroblast cultures, exhibiting their noncytotoxic properties. This attribute increased the range of possible applications of these hydrogels, ranging from agriculture to biocompatible materials.

Cellulose nanocrystals (CNCs), castor oil (CO), and recycled poly(ethylene terephthalate) (rPET), were used to add value to renewable raw materials and to a recycled polymer produced worldwide, producing mats composed of fibers on the nano- and submicrometric (ultrathin) scales through a sustainable process. Bio-based electrospun mats composed of aligned (rotary collector) and nonaligned (static collector) nanofibers/ultrathin fibers were produced from the electrospinning of solutions prepared from rPET (mixed with CO, CNCs, or CNCs/CO). The contact angle results showed that the CNC mat surfaces composed of nonaligned fibers were hydrophilic, and in contrast, these surfaces were hydrophobic when composed of aligned fibers. Among the mats composed of nonaligned fibers, PET/CO/CNC exhibited storage and Young's moduli approximately eleven and ten times, respectively, better than those of neat rPET. The PET/CO/CNC mat showed both modulus and tensile strength values higher than those of PET/CNC, when characterized in the preferential direction of fiber alignment. Electrospun mats were obtained from environmentally sound raw materials with diversified properties, which were modulated by the type of collector used, as well as whether CO and CNC were mixed with rPET, and have the potential for use in applications such as membrane separation processes and biomedical applications.

Properties of cellulosic materials, such as average molar mass (MMvis), crystallinity index and hemicelluloses content may influence the efficiency of the enzymatic conversion of cellulose to glucose. Studies on the simultaneous influence of these parameters have been scarcely found in the literature. In the present study, the conversion of cellulose to glucose was investigated using cellulosic materials with different MMvis, crystallinity, and hemicelluloses content: microcrystalline cellulose (MCC, MMvis = 22104 g mol−1, CI = 79%, no hemicelluloses detected), sisal pulp (SP, MMvis = 94618 g mol−1, CI = 66%, hemicelluloses content = 2.6%) and filter paper (FP, MMvis = 98530 g mol−1, CI = 63%, hemicelluloses content = 19.2%). During the reactions, aliquots were withdrawn and, in addition to the liquors, the unreacted cellulosic materials were evaluated by MMvis, CI, SEM, length and thickness, which can help further understand the reaction as a whole. The liquors were characterized by high-performance liquid chromatography (HPLC) and Miller's method (or DNS). The highest yield for the conversion of cellulose to glucose was observed for SP (88%), followed by MCC (64%) and FP (52%). The results indicated that the presence of high hemicelluloses content (FP) had a more significant interference effect than high crystallinity (MCC).

Blend solutions of poly(e-caprolactone) (PCL) and N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride (QCh) were successfully electrospun. The weight ratio PCL/QCh ranged in the interval 95/5–70/30 while two QCh samples were used, namely QCh1 ( D Q ¯ = 47.3%; D P v ¯ = 2218) and QCh2 ( D Q ¯ = 71.1%; D P v ¯ = 1427). According to the characteristics of QCh derivative and to the QCh content on the resulting PCL/QCh nonwoven, the nanofibers displayed different average diameter (175 nm–415 nm), and the nonwovens exhibited variable porosity (57.0%–81.6%), swelling capacity (175%–425%) and water vapor transmission rate (1600 g m−2 24 h–2500 g m−2 24 h). The surface hydrophilicity of nonwovens increases with increasing QCh content, favoring fibroblast (HDFn) adhesion and spreading. Tensile tests revealed that the nonwovens present a good balance between elasticity and strength under both dry and hydrated state. Results indicate that the PCL/QCh electrospun nonwovens are new nanofibers-based biomaterials potentially useful as wound dressings.

The increased awareness about environmental issues has resulted in developing novel materials and sustainable solutions to reduce the dependence on fossil-based products. Herein, cellulose from sisal was derivatized into carboxylic esters (acetate, Ac; butyrate, Bu; and hexanoate, Hx); the produced materials were “shaped” into mats composed of nano- and ultrathin fibers. Our objective was to assess the effects of cellulose ester degree of substitution (DS), low- and high DS, ca. 0.2 and 2.6; the length of the acyl group and the electrospinning flow rate, 45.5 and 65.5 μL/min on the morphology of the fibrous material obtained therefrom. Cellulose was converted into its carboxylic esters under homogeneous conditions using LiCl/N,N-dimethylacetamide solvent, and acid anhydrides as acylating agents. The obtained cellulose- acetate, Cel-Ac, butyrate, Cel-Bu, and hexanoate, Cel-Hx were dissolved in trifluoracetic acid. The solutions of esters were subjected to electrospinning, under positive voltage of 25 kV, and needle-collector distance of 4 cm. Scanning Electron Microscopy of the electrospun mats showed the formation of ultrathin- (100 nm > diameter

The present investigation addressed the use of treated and untreated sisal fibers (3 cm, 30 wt%, randomly distributed) as a reinforcement in bio-based composites. Sodium lignosulfonate (NaLS) was used to physically treat the sisal fibers and also as a macromonomer to prepare phenolic-type thermosets, namely, the matrices (LCs). The introduction of NaLS moieties on the surface of the fibers and in the chemical structure of the matrix aimed to increase the affinity of the fiber-matrix interface in addition to increasing the bio-sourced character of the final material. Sisal fibers were treated (and subsequently characterized) with aqueous 5 wt% NaLS solutions via heating (70 °C/1 h, SFT1), ultrasound irradiation (1 and 2 h, SFT2 and SFT3, respectively), and room temperature treatment at 24 h followed by ultrasound (1 h, SFT4). Briefly, considering only some properties of the composites, the following results can be highlighted: all the phenolic composites (PC, control samples) exhibited impact and flexural strengths considerably greater than the unreinforced phenolic thermoset (PT). The phenolic composite reinforced with untreated sisal fiber (PC-UF) and PC-SFT4 exhibited an impact strength of approximately 435 Jm −1 , and the others, PC-SFT1 and PC-SFT2, had a tendency to have a greater impact strength, with the exception of PC-SFT3 when compared with PC-UF. Based on the results exhibited by the PC-treated fibers, only LC-SFT1 and LC-SFT2 were prepared among the LC-treated fibers besides LC-UF. The set of PCs exhibited a lower impact strength than their LC composite counterparts. For example, the impact strength of LC-UF was approximately 1000 Jm −1 (compared to approximately 435 Jm −1 for PC-UF). This is a very good result for a thermoset matrix reinforced with natural fibers and clearly shows that the fiber-matrix interaction at the interface was favored when the thermoset was prepared from NaLS, and then, the load received during the impact was more efficiently transferred to the sisal fibers. SEM images showed good adhesion at the fiber-matrix interface of LC-treated fibers due to the similarity of the chemical structure of the matrix and treated sisal fiber. Concerning the assessment of the thermal conductivity (at 10, 25 and 50 °C), only the thermosets (phenolic, PT, lignosulfonate-based, and LT), the composites reinforced with untreated fibers (PC-UF and LC-UF), and PC-SFT2 (due to its high impact strength) were evaluated. The results showed no significant variation in the thermal conductivity as a function of temperature. There was no significant variation in the thermal conductivity of both thermosets (the thermal conductivity of PT and LT at 25 °C, for instance, were 0.30 and 0.28 Wm −1 K −1 , respectively) to their respective composites (at 25 °C, the thermal conductivity was 0.40 and 0.36 Wm −1 K − 1 for PC–UF and PC–SFT2, respectively, and 0.24 Wm −1 K −1 for LC–UF). A tendency towards lower conductivities (at 10, 25 and 50 °C) was observed for LC-UF when compared with PC-UF. Overall, these results meet the current expectations concerning the production of materials prepared from a high percentage of raw materials from renewable sources with good properties.

The rational valorization of lignin and its derivatives is a challenge in biorefinery because this biopolymer is one of the major source of aromatic moieties. Lignosulfonates are used to a lesser extent than lignin to prepare macromolecular materials. In the current study, sodium lignosulfonate (NaLS), which was either blended or not blended with OH-containing vegetable oil (i.e., castor oil (CO)), was reacted with diphenylmethane diisocyanate (MDI) to prepare polyurethane-type materials, such as lignopolyurethanes (i.e., CO/NaLS/MDI and NaLS/MDI, respectively). NaLS was oxypropylated (LS-Oxy) to increase its reactivity towards MDI. LS-Oxy was characterized and then used after being blended or not blended with CO to prepare lignopolyurethanes CO/LS-Oxy/MDI and LS-Oxy/MDI, respectively. These materials were characterized by infrared spectroscopy, thermogravimetry (TG), and dynamic mechanical thermoanalysis (DMA). The Tg values obtained from DMA (loss modulus peak) indicated that the lignopolyurethanes with an intermediate degree of cross-linking were obtained. In a final set of experiments and due to their potential application, the obtained lignopolyurethanes were reinforced with sisal fibers, and the impact strength, flexural properties and scanning electron microscopy (SEM) images of the materials were obtained. The results indicated that the presence of sisal fibers led to a significant improvement in the impact strength of the lignopolyurethanes, especially in those prepared from LS-Oxy [CO/LS-Oxy/MDI: approximately from 40 J m −1 (without sisal) to 370 J m −1 (with sisal); LS-Oxy/MDI: from 15 J m −1 (without sisal) to 459 J m −1 (with sisal)]. The flexural properties of CO/LS-Oxy/MDI (with or without sisal) corresponded to a less rigid material compared to the other material. The results indicated that the characteristics of the lignopolyurethanes could be tuned by oxypropylation of NaLS and/or blending with CO as well as by the addition of sisal fibers, which enables the production of materials with a wide range of properties.

Biocomposites based on a polymer with good biodegradability, poly(butylene succinate) (PBS), and reinforced with different lignocellulosic fibers (coconut, sugarcane bagasse, curaua, sisal) were prepared through the traditional thermo-pressed molding technique. The fibers were characterized in terms of chemical composition, thermal stability (TGA), cristallinity (XRD) and surface morphology (SEM). The polymer thermal properties were evaluated by TGA and DSC. The composite characteristics were investigated by mechanical tests (Izod impact strength, flexural resistance), thermal stability (TGA), water uptake and SEM micrographs of the fractured surfaces. The results showed that sisal and curaua fibers feature a huge potential as reinforcing agents of PBS due to their superior chemical compatibility with the aliphatic matrix as well as to their surface morphology. Both factors contributed to the formation of a strong interface capable to effectively transfer the load from the matrix to the fibers. Sisal/PBS and curaua/PBS composites also showed greater resistance against water absorption if compared to coconut/PBS and sugarcane bagasse/PBS composites. Novel biocomposites with good properties were produced from fibers and polymer that can obtained from renewable raw materials.

Composites of high-density biopolyethylene (HDBPE) obtained from ethylene derived from sugarcane ethanol and curaua fibers were formed by first mixing in an internal mixer followed by thermopressing. Additionally, hydroxyl-terminated polybutadiene (LHPB), which is usually used as an impact modifier, was mainly used in this study as a compatibilizer agent. The fibers, HDBPE and LHPB were also compounded using an inter-meshing twin-screw extruder and, subsequently, injection molded. The presence of the curaua fibers enhanced some of the properties of the HDBPE, such as its flexural strength and storage modulus. SEM images showed that the addition of LHPB improved the adhesion of the fiber/matrix at the interface, which increased the impact strength of the composite. The higher shear experienced during processing probably led to a more homogeneous distribution of fibers, making the composite that was prepared through extruder/injection molding more resistant to impact than the composite processed by the internal mixer/thermopressing.

A tannin–phenolic resin (40 wt% of tannin, characterized by 1 H nuclear magnetic resonance (NMR) and 13 C NMR, Fourier transform infrared, thermogravimetry, differential scanning calorimetry) was used to prepare composites reinforced with sisal fibers (30–70 wt%). Inverse gas chromatography results showed that the sisal fibers and the tannin–phenolic thermoset have close values of the dispersive component and also have predominance of acid sites (acid character) at the surface, confirming the favoring of interaction between the sisal fibers and the tannin–phenolic matrix at the interface. The Izod impact strength increased up to 50 wt% of sisal fibers. This composite also showed high storage modulus, and the lower loss modulus, confirming its good fiber/matrix interface, also observed by SEM images. A composite with good properties was prepared from high content of raw material obtained from renewable sources (40 wt% of tannin substituted the phenol in the preparation of the matrix and 50 wt% of matrix was replaced by sisal fibers).

Tannin–phenolic polymers prepared using tannin, a macromolecule obtained from natural sources, were used in the preparation of composites reinforced with coir fibers. The composites based on tannin–phenolic polymers (50% (w/w) of tannin as substitute of the phenol) were prepared using the coir fibers as reinforcement (30–70% (w/w), 3.0–6.0 cm, randomly distributed). The Izod impact strength of the composites showed an improvement in this property due to the incorporation of coir fibers in the tannin–phenolic matrices. The SEM images showed excellent adhesion at the fiber/matrix interface. The coir fiber had bundles regularly spaced, which enhanced the diffusion of the resin into the fiber. In addition, the high lignin content of this fiber results in a high concentration of aromatic rings, which increased the compatibility with the matrix. The values of the diffusion coefficient of water, determined using Fick's laws, show that there was no correlation between the fiber percentage and the water diffusion. The DMTA curves showed that the storage moduli of the composites reinforced with coir fibers were considerably higher than that of the thermoset, and the increase in the proportion of fibers led to a proportional increase in the storage moduli of these materials. The biobased composites obtained have potential for non-structural applications, such as in the internal parts of automotives vehicles. To our knowledge, this is the first study on this kind of biobased composites.

The aim of the present work was to investigate the toughening of phenolic thermoset and its composites reinforced with sisal fibers, using hydroxyl-terminated polybutadiene rubber (HTPB) as both impact modifier and coupling agent. Substantial increase in the impact strength of the thermoset was achieved by the addition 10% of HTPB. Scanning electron microscopy (SEM) images of the material with 15% HTPB content revealed the formation of some rubber aggregates that reduced the efficiency of the toughening mechanism. In composites, the toughening effect was observed only when 2.5% of HTPB was added. The rubber aggregates were found located mainly at the matrix–fiber interface suggesting that HTPB could be used as coupling agent between the sisal fibers and the phenolic matrix. A composite reinforced with sisal fibers pre-impregnated with HTPB was then prepared; its SEM images showed the formation of a thin coating of HTPB on the surface of the fibers. The ability of HTBP as coupling agent between sisal fibers and phenolic matrix was then investigated by preparing a composite reinforced with sisal fibers pre-treated with HTPB. As revealed by its SEM images, the HTPB pre-treatment of the fibers resulted on the formation of a thin coating of HTPB on the surface of the fibers, which provided better compatibility between the fibers and the matrix at their interface, resulting in a material with low water absorption capacity and no loss of impact strength.

The (bio)degradation of polyolefins can be accelerated by modifying the level of crystallinity or by incorporation of carbonyl groups by adding pro-oxidants to masterbatches or through exposure to ultraviolet irradiation. In this work, we sought to improve the degradation of PP by adding cobalt, calcium or magnesium stearate to Ecoflex ® , PP or Ecoflex ® /PP blends. The effect of the pro-oxidants on biodegradability was assessed by examining the mechanical properties and fluidity of the polymers. PP had higher values for tensile strength at break and Young's modulus than Ecoflex ® , and the latter had little influence on the properties of PP in Ecoflex ® /PP blends. However, the presence of pro-oxidants (except for calcium) reduced these properties. All of the pro-oxidants enhanced the fluidity of PP, a phenomenon that facilitated polymer degradation at high temperatures.

Thermoset phenolic composites reinforced with sisal fibers were prepared to optimize the cure step. In the present study, processing parameters such as pressure, temperature, and time interval were varied to control the vaporization of the water generated as a byproduct during the crosslinking reaction. These molecules can vaporize forming voids, which in turn affect the final material properties. The set of results on impact strength revealed that the application of higher pressure before the gel point of the phenolic matrix produced composites with better properties. The SEM images showed that the cure cycle corresponding to the application of higher values of molding pressure at the gel point of the phenolic resin led to the reduction of voids in the matrix. In addition, the increase in the molding pressure during the cure step increased the resin interdiffusion. Better filling of the fiber channels decreased the possibility of water molecules diffusing through the internal spaces of the fibers. These molecules then diffused mainly through the bulk of the thermoset matrix, which led to a decrease in the water diffusion coefficient (D) at all three temperatures (25, 55 and 70 °C) considered in the experiments.

Sisal fibers have been chemically modified by reaction with lignins, extracted from sugarcane bagasse and Pinus-type wood and then hydroxymethylated, to increase adhesion in resol-type phenolic thermoset matrices. Inverse gas chromatography (IGC) results showed that acidic sites predominate for unmodified/modified sisal fibers and for phenolic thermoset, indicating that the phenolic matrix has properties that favor the interaction with sisal fibers. The IGC results also showed that the phenolic thermoset has a dispersive component closer to those of the modified fibers suggesting that thermoset interactions with the less polar modified fibers are favored. Surface SEM images of the modified fibers showed that the fiber bundle deaggregation increased after the treatment, making the interfibrillar structure less dense in comparison with that of unmodified fibers, which increased the contact area and encouraged microbial biodegradation in simulated soil. Water diffusion was observed to be faster for composites reinforced with modified fibers, since the phenolic resin penetrated better into modified fibers, thereby blocking water passage through their channels. Overall, composites' properties showed that modified fibers promote a significant reduction in the hydrophilic character, and consequently of the reinforced composite without a major effect on impact strength and with increased storage modulus.

We report the acetylation of celluloses from sisal (untreated and alkali treated) and cotton linters (alkali treated), under homogeneous solution conditions, using DMAc/LiCl as solvent system. Our target was to evaluate the effects of cellulose dissolution and reactions conditions on the product properties. The products were characterized in terms of degree of substitution (DS) by 1H NMR, and molar weight distribution (MWD) by size exclusion chromatography. Changes in the DS of the products were correlated with reaction conditions and solution properties. It was found that the dissolution of celluloses and degree of substitution of cellulose derivatives depends on a fine adjustment of the dissolution/derivatization conditions, as well as on the origin (sisal or linters) of celluloses.

This study used infrared spectroscopy to compare the degree of conversion (DC) of Z250 resin composite at different depths, using a variety of light-curing sources. Photo-activation was performed with: plasma arc (PAC) light, a blue light emitting diode (LED) and four different exposure scenarios using quartz–tungsten–halogen (QTH) light. Cured composite cylinders were transversally cut into 300 μm-thick slices corresponding to surface, 1–5 mm depths. Each disc was finely pulverized, incorporated into KBr pellets, and analyzed by FTIR. Results demonstrated that for the surface and depths of 1 and 2 mm, conversion values did not differ significantly between lights or exposure treatments. At 3 and 4 mm depths, the LED source showed significantly higher DC than did the PAC light. All QTH methods were not significantly different to either LED or PAC. At 5 mm, there was no significant difference in DC between methods, except that PAC was not able to cure the composite.

Linters cellulose was subjected to different treatments (mercerization and ionized air) before acetylation with acetic anhydride, in homogeneous medium, using DMAc/LiCl as solvent system. Before derivatization, the treated fibres were characterized by Scanning Electron Microscopy, X-ray diffraction, alpha-cellulose content, Inverse Gas Chromatography and viscosimetry. It was shown that except a decrease in the dispersive surface energy, the treatments induced small changes in the cellulose. The degree of acetylation of these fibers was found to follow a linear behavior with the stoichiometry between acetic anhydride and glucose unit, but this linearity obeyed high rate up to a DS of 2.0. The order of reactivity observed for all samples, C6>>C2>C3, confirms the higher reactivity of OH in C6 position, because this group is the least sterically hindered of the anhydroglucose unity.

This study evaluated the degree of conversion (DC) by FTIR spectroscopy and Knoop hardness (KHN) of Z250 composite, using seven photo-activation methods: continuous light (800 mW/cm 2 −40 s); exponential light (0–800 mW/cm 2 -40 s); intermittent light (2 s-600 mW/cm 2 ; 2 s without light-80 s); stepped light (10 s-150 mW/cm 2 ; 30 s-650 mW/cm 2 ); PAC (1320 mW/cm 2 −3 s); LED1 (100 mW/cm 2 -40 s); LED2 (350 mW/cm 2 −40 s). For FTIR analysis, the specimens were finely pulverized and, after 24±1 h, pressed with KBr and analyzed. For Knoop hardness tests, the specimens were measured on the surface and at 1 and 2 mm depth. The results showed that there was no statistical difference in DC values between the photo-activation methods. The highest Knoop hardness value was obtained for continuous light, followed by stepped, exponential and LED2 with no difference between them. For intermittent light, no difference was observed compared with stepped, exponential LED2 and PAC. The KHN for PAC was lower than those of stepped and exponential light. LED1 demonstrated the lowest KHN, which was statistically different to the other methods.

The new cellulose solvent dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride (TBAF) was applied as reaction medium for the carboxymethylation of mercerized cellulose from sisal and cotton linters. The reaction parameters studied were the molar ratio of reagent and NaOH to anhydroglucose unit (AGU) and the addition of the NaOH either as an aqueous solution or as solid particles. Size Exclusion Chromatography results (SEC) indicated that the dissolution medium and/or derivatizing method used in the present work causes a certain depolymerization on the cellulose chains The pattern of substitution within the AGU and along the polymer chains of the carboxymethylcellulose (CMC), which was analyzed by 1H NMR spectroscopy and HPLC after acidic depolymerization of the CMC, is in the order O-6>O-2≥O-3. With regard to the mole fractions of the different repeating units, samples prepared using aqueous NaOH possess a statistic content, while by using solid NaOH a deviation from statistically calculated values was observed. As a consequence of the non-statistics, the solubility in water of these samples starts at a DS 0.85, while conventionally prepared CMC are water-soluble at a DS as low as 0.4.

Sugar cane bagasse and curaua acidolysis lignins were used to get a better understanding of the mechanism involved in a new chemical modification of sugar cane bagasse and curaua fibres, consisting in a selective oxidation of lignin by chlorine dioxide and reacting some of the created unsaturated units (quinones or muconic derivatives) with furfuryl alcohol (FA). The objective of the treatment was to create a fibre coating increasing compatibility between fibres and phenolic resins in composites. The lignins were reacted with chlorine dioxide to oxidize the phenolic units of the polymer and then treated with furfuryl alcohol. Weight percent gain of 14% and 10% were obtained for sugar cane bagasse and curaua, respectively. 1 H and 31 P NMR, as well as FT-IR results showed that bagasse lignin had more guaiacyl than syringyl units and the reverse for curaua lignin. 1 H NMR of oxidized lignins revealed a decrease of the aromatic and methoxy content after the ClO 2 oxidation, due to partial degradation of the macromolecule. Thermal analysis showed that sugar cane lignin decomposes at lower temperature than curaua lignin, partly due to the high content of condensed structural units present in curaua lignin. Condensed units decompose at higher temperatures than uncondensed ones. The reaction of oxidized lignin with FA shifted the decomposition exotherm to lower temperature for both curaua and sugar cane bagasse lignins, due to the modification introduced into their structures.

The purpose of this paper is to draw a general picture for viscometric behaviour of polyelectrolytes. The polymers tested are hyaluronan (λ=0.7) and sodium polystyrene sulfonate (λ=2.8) with different molecular weights. The viscometric behaviour in isoionic dilution is examined and one demonstrates that k′[η]∼Cs−3/2. Dilution in water or with solvent of low salt concentration causes the reduced viscosity to pass through a maximum for a given polymer concentration. The position of the maximum and the amplitude of this maximum is analyzed for the low molecular weight samples in the dilute regime. The electrostatic contribution dominates and the treatment adopted gives good agreement between calculated and experimental data.

The aim of this work was to study the properties of the carboxylated polyelectrolyte obtained from guar gum. The C-6 alcohol functions of galactose units side chains were oxidized first by GO-ase to aldehyde groups and then to carboxylic groups by halogen oxidation. The enzymic oxidation step was followed by the Dische method, by viscosity and light scattering measurements. With regard to previous reports, some changes were introduced in the two-step reaction, in order to prevent polymer degradation. Several characteristics of the carboxylated polyelectrolyte have been studied, such as molecular weight distribution, degree of substitution, viscosity, intrinsic viscosity determined by the isoionic method, radius of gyration, charge parameter and apparent intrinsic persistence length. The charged macromolecule formed from native guar showed all the typical characteristics of a polyelectrolyte. The viscometry results indicate that carboxylated guar has a much higher viscosity in low salt content than the native polymer, which improves its thickening properties.