Viscosity Average Molar Mass Research Articles

New Quaternary Ammonium Derivatives Based on Citrus Pectin.

New citrus pectin derivatives carrying pendant N,N-dimethyl-N-alkyl-N-(2-hydroxy propyl) ammonium chloride groups were achieved via polysaccharide derivatization with a mixture of N,N-dimethyl-N-alkyl amine (alkyl = ethyl, butyl, benzyl, octyl, dodecyl) and epichlorohydrin in aqueous solution. The structural characteristics of the polymers were examined via elemental analysis, conductometric titration, Fourier Transform Infrared spectroscopy (FTIR) and 1D (1H and 13C) nuclear magnetic resonance (NMR). Capillary viscosity measurements allowed for the study of viscometric behavior as well as the determination of viscosity-average molar mass for pristine polysaccharide and intrinsic viscosity ([η]) values for pectin and its derivatives. Dynamic light scattering measurements (DLS) showed that pectin-based polymers formed aggregates in aqueous solution with a unimodal distribution. Critical aggregation concentration (cac) for the hydrophobic pectin derivatives were determined using fluorescence spectroscopy. Atom force microscopy (AFM) images allowed for the investigation of the morphology of polymeric populations obtained in aqueous solution, consisting of flocs and aggregates for crude pectin and its hydrophilic derivatives and well-organized aggregates for lipophilic pectin derivatives. Antimicrobial activity, examined using the disc diffusion method, proved that all polymers were active against Staphylococcus aureus bacterium and Candida albicans yeast.

Special Aspects of Nitrocellulose Molar Mass Determination by Dynamic Light Scattering.

The dynamic light scattering method was successfully applied to determine the molar mass of nitrocellulose. The methodology of nitrocellulose fractionation in acetonic solutions is described in detail; six polymer fractions with monomodal distribution were obtained. It was shown that the unfractionated colloxylin with polymodal molar mass distribution had mass average molecular mass values of 87.3 ± 14.1, 28.3 ± 7.3, and 0.54 ± 0.17 kDa when investigated by the dynamic light scattering method. The viscometric method only provided integral viscosity average molar mass equal to 56.7 ± 5.8 kDa.

Determination of viscosity average molar masses of polyethylene in a wide range using rheological measurements with a harmless solvent

Rheological measurements of polyethylene solutions in a novel nontoxic solvent were used to determine the Mark-Houwink parameters for PE of widely different molecular weights to assess the viscosity average molar mass for PE of several millions of g.mol−1. Solutions of high density polyethylene that had been previously characterized by size exclusion chromatography were prepared in a harmless naphthenic oil. The intrinsic viscosities were obtained by varying the concentrations of the different calibration samples solutions using a rotational rheometer equipped with a Couette cell. The intrinsic viscosities were determined by both Huggins and Kraemer descriptions of the viscosity variations with concentration. Subsequently, a calibration curve of intrinsic viscosities versus the molar mass was plotted, and the parameters of the Mark-Houwink-Sakurada equation were obtained for polyethylene in naphthenic oil. Using this equation and the newly estimated parameters, the viscosity average molar mass of a high molar mass polyethylene and a commercial ultra high molar mass polyethylene were been determined by measuring their respective intrinsic viscosities. Finally, the method has been validated by comparing these results to values obtained by standard viscosimetry in 1,2,4-trichlorobenzene and to the values given by the supplier, obtained by other methods.

On the Formation and Stability of Chitosan/Hyaluronan-Based Complex Coacervates.

This contribution is aimed at extending our previous findings on the formation and stability of chitosan/hyaluronan-based complex coacervates. Colloids are herewith formed by harnessing electrostatic interactions between the two polyelectrolytes. The presence of tiny amounts of the multivalent anion tripolyphosphate (TPP) in the protocol synthesis serves as an adjuvant “point-like” cross-linker for chitosan. Hydrochloride chitosans at different viscosity average molar mass, , in the range 10,000–400,000 g/mol, and fraction of acetylated units, FA, (0.16, 0.46 and 0.63) were selected to fabricate a large library of formulations. Concepts such as coacervate size, surface charge and homogeneity in relation to chitosan variables are herein disclosed. The stability of coacervates in Phosphate Buffered Saline (PBS) was verified by means of scattering techniques, i.e., Dynamic Light Scattering (DLS) and Small-Angle X-ray Scattering (SAXS). The conclusions from this set of experiments are the following: (i) a subtle equilibrium between chitosan FA and does exist in ensuring colloidal stability; (ii) once diluted in PBS, osmotic swelling-driven forces trigger the enlargement of the polymeric mesh with an ensuing increase of coacervate size and porosity.

Size-exclusion chromatography with on-line viscometry of various celluloses with branched and linear structures

We analyzed softwood and hardwood bleached kraft pulps (SBKP and HBKP, respectively), and Japanese cedar (Cryptomeria japonica) celluloses prepared from wood powders using delignification, hemicellulose removal, and dilute acid hydrolysis. For sample preparation, each sample was dissolved in 8% (w/w) lithium chloride/N,N-dimethylacetamide (LiCl/DMAc), after the sample was soaked in ethylenediamine (EDA) and the EDA was exchanged with DMAc through methanol. These solutions were diluted to 1% (w/v) LiCl/DMAc and subjected to size-exclusion chromatography (SEC) combined with multiangle laser light scattering and viscometry analyses. SEC/multiangle laser light scattering and SEC/viscometry use different principles to determine the molecular structures of polymers dissolved in LiCl/DMAc. Both methods showed that SBKP celluloses with high molar masses had branched structures, whereas HBKP celluloses had linear structures as like cotton, bacterial, tunicate, and algal celluloses. Conventionally, viscosity-average molar masses or viscosity-average degrees of polymerization of SBKP and HBKP are obtained by capillary viscometry using a 0.5 M copper ethylenediamine hydroxide (cuen) solution. Because SBKP and HBKP have different cellulose structures (branched and linear molecules, respectively), their viscosity-average molar masses and viscosity-average degrees of polymerization should not be calculated using the same Mark–Houwink–Sakurada equation.

Molar mass dependence of structure of xanthan thermally denatured and renatured in dilute solution

Double helical polysaccharide, xanthan samples with varying molar mass were thermally denatured and renatured in dilute solutions. Both the weight average molar mass, which was determined by size exclusion chromatography (SEC), and viscosity average molar mass decreased after denaturation and renaturation for samples with an initial molar mass of 106 g mol−1, but those for the samples with an initial molar mass of 105 or 107 g mol−1 decreased only slightly. Although the double helices of xanthan only partially dissociated into single chains, the molar mass distribution estimated by SEC did not broaden drastically by the denaturation and renaturation. These results can be explained by the formation of hairpin structures by the single chains, which are restricted to xanthan with a molar mass of 105 g mol−1 by the strain of the hairpin loop, and for xanthan molar masses of 107 g mol−1 by the incomplete dissociation of its long polymer chains. Double helical polysaccharide, xanthan samples with varying molar mass were thermally denatured and renatured in dilute solutions. The molar mass decreased after denaturation and renaturation for samples with an initial molar mass of 106 g mol−1, but those for the samples with an initial molar mass of 105 or 107 g mol−1 decreased only slightly. A model explaining this molar mass dependence of the denaturation and renaturation behaviors was proposed based on the experimental results.

Determination of average molecular weight of guar gum by a simple twice headspace extraction gas chromatographic technique

This paper proposed a new method for the determination of the viscosity average molar mass of guar gum, based on a volatile tracer assisted twice headspace extraction gas chromatographic technique. The feasibility study showed that n-butanol was a suitable tracer to be used in this method. The results showed that the present method had a good precision (with the relative standard deviation < 0.86%) and good accuracy (in which the relative differences were within 7.94% when compared with the reference method). The present method is simple and practical. It can conduct an automated measurement when a batch sample testing is required.

Effect of Epoxy Chain Extender on the Properties of Polylactic Acid

Modification of polylactic acid (PLA) by chain extension is a method used to improve its melt strength and heat resistance. In this study, the chemical structure, viscosity average molecular weight, thermal properties, melt viscosity, mechanical properties and Vicat softening temperature of PLA before and after the modification were measured by Fourier-transform infrared spectroscopy (FTIR), a viscometer (Mv), differential scanning calorimetry (DSC), a melt index instrument (MI), a rotary rheometer, a universal material testing machine, and a Vicat softening temperature tester, respectively, to characterize the effect of chemically modifying PLA with KL-E4370. The experimental results showed that the epoxy group contained in KL-E4370 reacted with the carboxyl group of PLA. In addition, the modified PLA showed increased molecular weight, enhanced melt strength, decreased melt fluidity, a significantly decreased melt index, significantly increased complex viscosity and modulus, enhanced impact and tensile strengths, and an increased Vicat softening temperature. When the content of KL-E4370 was 0.1%, the viscosity average molar mass increased from 2.88×103 g/mol (that of neat PLA) to 4.02×103 g/mol, the crystallinity increased from 17.0% (that of neat PLA) to 32.5%, the melt index decreased from 6.0 g/10 min (that of neat PLA) to 2.2 g/10 min, the Vicat softening temperature increased from 67.9 °C (that of neat PLA) to 160.1 °C, and the heat resistance of PLA was improved significantly

ZnS Nanocrystals as an Additive for Gamma-Irradiated Poly (Vinyl Chloride)

Zinc sulfide (ZnS) was synthesized by sonochemical method and nanoparticles with crystallite size around 2 nm were obtained. PVC containing ZnS nanoparticles at concentrations of 0.10; 0.30; 0.50; 0.7 and 1.00 wt% were gamma irradiated (60Co) at room temperature in air. No appreciable decrease in PVC Viscosity-Average Molar Mass (Mv) was observed for samples containing 0.7 wt% of ZnS nanocrystals. It was demonstrated that the addition of ZnS nanocrystals imparted molecular protection to the polymer matrix while improving flexibility, by decreasing the Young Modulus of PVC films. These results suggest the use of sonochemically synthesized ZnS nanocrystals as a new additive for radiation-grade PVC materials.

Effect of Copper Sulfide Nanoparticles in Poly(vinyl chloride) Exposed to Gamma Irradiation

Hybrid organic–inorganic materials combine both typical inorganic and organic material properties, allowing them to be applied in a wide range of areas, including radiation-resistant polymers. In this study, Copper sulfide (CuS) is presented as an unprecedented inorganic radiolytic stabilizer for Poly(vinyl chloride). CuS nanoparticles were synthesized from copper (II) chloride (CuCl2) and thioacetamide (CH3CSNH2) by sonochemical route. TEM image showed the size of CuS nanoparticle ranging around 50 nm in diameter. Commercial PVC containing CuS nanoparticles in concentrations of 0.10; 0.30; 0.50 and 0.70 wt% were irradiated with gamma radiation (60Co) at room temperature in air. Samples containing 0.5 wt% of CuS nanoparticles showed no detectable decrease in viscosity-average molar mass (Mv), while appreciable degradation was seen in the remaining samples. These results suggest that the addition of CuS nanoparticles imparted molecular protection to the polymer matrix. The observed FTIR band shifts indicate the intermolecular interactions between the CuS and the PVC matrix. These interactions favored the action of nanoparticles as a plasticizer in PVC matrix. In addition, the CuS act as thermal stabilizer because an increase in PVC thermal degradation onset temperature was evidenced. Our findings pave the way to the use of CuS as a nanostructured multifunctional stabilizer for PVC.

Properties of polymerized cyclic butylene terephthalate and its composites via ring-opening polymerization

Continuous glass fiber (GF)-reinforced polymerized cyclic butylene terephthalate (pCBT) composites were prepared via vacuum-assisted resin transfer molding using butyltin tris(2-ethylhexanoate) as the catalyst. The relationship between melt viscosity and polymerization time was examined in the ring-opening polymerization of CBT resin. The effects of polymerization conditions such as catalyst content and polymerization temperature on viscosity average molar mass ( Mv), crystallization, mechanical properties, and microstructure of GF/pCBT composites were also investigated in detail. It is found that both high molecular weight and high degree of crystallinity of resin matrix can lead to high mechanical properties of composites. The composites prepared with 0.5% catalyst at 190°C show the best mechanical properties with tensile strength of 549 MPa, flexural strength of 585.2 MPa, and interlaminar shear strength of 47.1 MPa. The scanning electron microscopy analysis also demonstrates that good interfacial adhesion exists between fiber and resin, which agrees very well with experimental results.

Time-dependent viscometry study of endoglucanase action on xyloglucan: A real-time approach

Hydrolysis of xyloglucan from Tamarindus indica and Hymenaea courbaril seeds with endoglucanase (EGII), which randomly breaks the (1→4)-linked β-glycosidic bonds of the polymer chain, was monitored in real time using time-dependent viscometry analysis (TDV). For both samples there was a decrease in the intrinsic viscosity ([η]), viscosity average molar mass (Mv), radius de gyration (Rg) and persistence length (Lp) immediately after the addition of the enzyme. It was observed the formation of oligosaccharides and oligomers composed of ∼2 units, up to 140min. Galactose-containing side chains two positions away from the non-substituted glucose, modulated the action of EGII, and the complete hydrolysis of the XG oligomers occurred after 24h. The results demonstrate for the first time the real-time degradation of xyloglucan as well the macromolecular and oligosaccharide composition during the EGII hydrolysis process.

Use of Lead (II) Sulfide Nanoparticles as Stabilizer for PMMA Exposed to Gamma Irradiation

Lead (II) sulfide (PbS) were synthesized by sonochemical method and crystals with cubic structure exhibit aggregated nanoparticles with size in the range of 50-100 nm. Commercial Poly(methyl methacrylate) (PMMA) containing the PbS nanoparticles (PbS-NP) exposed to gamma irradiation were investigated and both the viscosity-average molar mass (Mv) and degradation index (DI) values were measured. Ours results showed decreases in molar mass when the systems were gamma irradiated, i. e., random scission effects that take place in the main chain. On the other hand, DI results showed that the addition of PbS-NP at 0.3 wt% into the PMMA matrix decreased 100% the number of main chain scissions. Results about the free radical scavenger action of the PbS-NP were obtained by use of 2,2-diphenyl-1-(2,4,6-trinitrophenyl)-hydrazyl radical (DPPH) and are discussed in this study. Analysis of infrared spectra, refraction index, mechanical, and thermal properties showed influence of the PbS-NP in the physical behavior of PMMA.

Synthesis, characterisation and thermal study of composite of polyaniline doped with multiligand urea complex of cobalt(II)

In the present communication, doping of polyaniline (PANI) has been carried out with multiligand urea complex of cobalt(II) via in situ oxidative polymerisation by ammonium persulphate. The dopant has been synthesised and characterised using elemental analysis, Fourier transform infrared (FTIR), X-ray diffraction (XRD) and thermogravimetric (TG) analysis. The composite based on the synthesised dopant has been subjected to FTIR and XRD techniques. Thermal analysis has been performed using TG and differential scanning calorimetry technique. Viscosity average molar mass has been determined by viscosity method using Ostawald’s viscometer and Mark–Houwink–Sakurada polymer equation. Various parameters like crystallite size, interplanar distance, microstrain and dislocation density have been calculated using Bragg’s and other related equations. Moreover, lattice parameters a, b, c, α, β and γ have also been calculated for the dopant as well as the composite using powder X software. Thermal stability of PANI composite is better than that of pure PANI.

Doping polyaniline with copper bisglycinate[Cu(gly)2]—Synthesis, characterization and thermal study

The present paper deals with the synthesis of polyaniline (PANI) composite with dopant copper bisglycinate (Cu(gly)2) via in situ oxidative polymerization by ammonium persulphate. The dopant has been synthesized by the known method and characterized by using elemental analysis, FTIR, XRD and thermogravimetric (TG) analysis. The composite based on the synthesized dopant has been subjected to FTIR, X-ray diffraction and SEM characterization techniques. Thermal analysis has been done by using TG and DSC technique. Viscosity average molar mass of the composite has been determined by viscosity method using Ostawald's viscometer and Mark–Houwink Sakaruda polymer equation. FTIR absorption peaks confirm the insertion of dopant in the backbone of PANI. The FTIR spectrum of composite shows that it is rich in both quinoid and benzenoid rings, hence showing partitial oxidation of PANI base. SEM of the composite also supports its successful synthesis. The XRD of dopant shows crystalline structure, which has remained dominant in the composite, hence proving the successful synthesis of PANI composite with dopant. Various parameters like crystallite size (L), interplanar distance (d), micro strain (ε) and dislocation density (ρ) have been calculated by using Bragg's and other related equations. Moreover lattice parameters a, b, c, α, β and γ have also been calculated for the dopant as well as the composite using powder X software. The calculated d spacing values are in agreement with the experimental d spacing values. Thermal analysis shows high thermal stability of dopant which in turn has improved the thermal stability of PANI composite, therefore, shows the potential of composite for high temperature application purposes.

Propriedades e Características da Quitosana Obtida a Partir do Exoesqueleto de Caranguejo-Uçá Utilizando Radiação de Micro-Ondas

Neste trabalho, obteve-se quitosana a partir do exoesqueleto de Ucides cordatus cordatus, comumente denominado caranguejo-uca, em um processo no qual a conversao da quitina em quitosana foi feita via reacao convencional (QV) e tambem usando radiacao de microondas (QP). Caracterizaram-se as quitosanas produzidas em funcao do grau de desacetilacao (GD), viscosidade intrinseca (η) e massa molar viscosimetrica media (Mz), avaliando-se as propriedades em comparacao com uma amostra de quitosana de caranguejo comercial (QC). A quitosana produzida por radiacao de microondas apresentou grau de desacetilacao maior do que a produzida via reacao convencional e a quitosana comercial, com valores obtidos por titulacao de 77%, 65% e 71% para QP, QV e QC, respectivamente. No teste de solubilidade, a amostra QP dissolveu mais facilmente em solucao de acido acetico diluido do que a QC, enquanto que a amostra QV nao apresentou boa solubilidade em solucao de acido acetico 2%, devido ao seu baixo grau de desacetilacao. A massa molar viscosimetrica das amostras QP e QC foi 412.600 g/mol e 336.100 g/mol, respectivamente, situando-se dentro dos padroes reportados na literatura. Em suma, pode-se afirmar que a conversao de quitina em quitosana por radiacao com microondas e um metodo vantajoso, pois houve reducao consideravel de consumo de energia e de tempo em relacao ao processo convencional, sendo que a amostra QP mostrou propriedades superiores a amostra QV, e propriedades equivalentes a amostra comercial QC. Alem disso, o metodo empregado pode ser ajustado para producao de quitosana em escala industrial.

The effect of gamma radiation on mechanical properties of biodegradable polymers poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Brazilian poly(3-hydroxybutyrate), P(3-HB), and its copolymer, poly (3-hydroxybutyrate-co-3-hydroxyvalerate), P(3-HB-co-3-HV) were irradiated with gamma radiation (60Co) at room temperature and in the presence of oxygen. The viscosity-average molar mass (Mv) was analyzed by viscometry using an Ostwald-type capillary viscometer. Both polymers showed a decrease in molar mass with the increase in dose, reflecting that random main chain scissions occurred. The value G (scissions/100 eV of energy transferred to the system) and the parameter α (scissions per original molecule) were also determined. Mechanical properties decrease with the increase in dose, revealing that P(3-HB) underwent significant changes, especially at doses higher than 50 kGy. Tensile at break and impact resistance properties were the most affected by radiation, while the elastic modulus remained virtually unaltered up to 100 kGy dose.

Flame retarded poly(lactic acid) using POSS-modified cellulose. 1. Thermal and combustion properties of intumescing composites

POSS-modified nanofibrillated cellulose (PNFC) was used as a carbon source in intumescing flame retardants (IFRs) for melt-blended poly(lactic acid) (PLA) composites. The POSS moeities were found to inhibit reactions between ammonium polyphosphate (APP) and cellulose during extrusion. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) indicated this was due to cross-linking between the silanol groups on PNFC and phosphate groups on APP. Composite properties were assessed using viscometry, thermogravimetric analysis (TGA), pyrolysis combustion flow calorimetry (PCFC), cone calorimetry, and dynamic mechanical analysis (DMA). Viscosity average molar masses of PLA decreased during extrusion, which was accelerated in the presence of APP based flame retardants. The use of PNFC resulted in the highest PLA molar mass of all flame retarded composites. Extruding the neat PLA lowered onset and peak decompositions, but the addition of APP based flame retardants modestly increased these temperatures. PCFC was found to be inconclusive in assessing beneficial flammability characteristics of the composites. The addition of 15% by mass IFR reduced the peak heat release rate by 45% and the total heat released by 20%, regardless of the carbon source. PNFC led to reduced smoke production compared to unmodified nanofibrillated cellulose (NFC) or pentaerythritol (PER). Use of APP–PER reduced composite stiffness and the glass transition temperature. The use of APP–NFC and APP–PNFC slightly increased composite stiffness, and did not significantly affect the glass transition temperature.

Preparation and properties of continuous glass fiber reinforced anionic polyamide-6 thermoplastic composites

Continuous glass fiber (GF) reinforced anionic polyamide-6 (APA6) composites were prepared via in situ ring-opening polymerization of caprolactam monomers. The effects of catalyst content, polymerization temperature and time on the viscosity average molar mass (Mv) and degree of crystallinity (Xc) were investigated in detail. The final mechanical properties of GF/APA6 composites were also studied. The results indicated that both high molecular weight and the high degree of crystallinity of resin matrix lead to the high mechanical properties of composites. Furthermore, the mechanical test results showed that the composites of plain woven fabric had tensile strength of 434MPa and flexural strength of 407MPa. The morphologies of tensile fracture surfaces of the composites specimens were observed through Scanning Electron Microscope (SEM). The SEM analysis showed that many disorganized nano-fiber crystals appear in the tensile fracture surfaces, which improve the mechanical properties of the matrix resin. The mechanical properties of the composites with different post-heat treatments were further investigated. The mechanical properties of the composites are significantly reduced after quenching treatment, but hardly improved after annealing.

Synthesis, characterization, and thermal study of polyaniline composite with the photoadduct of potassium hexacyanoferrate (II) involving hexamine ligand

The present paper involves the synthesis of polyaniline (PANI) composite with photoadduct of potassium hexacyanoferrate (II) involving hexamine as a ligand and cobalt chloride as a complexing agent via in situ oxidative polymerization by ammonium persulphate. The photoadduct has been synthesized by photoirradiation followed by substitution with the hexamine ligand. The final product has been isolated by using CoCl2 as complexing agent. Viscosity average molar mass has been determined by viscosity method using Ostwald’s viscometer. The photoirradiation, substitution, and successful synthesis have been proved by recording pH, UV–visible spectra before and after irradiation, and FTIR of the photoadduct. The composite based on the synthesized photoadduct has been subjected to FTIR, X-ray diffraction, and SEM characterization techniques. Thermal analysis has been done by using TG and DSC technique. FTIR absorption peaks confirm the insertion of photoadduct in the backbone of PANI. SEM of the composite also supports its successful synthesis. The XRD of photoadduct shows crystalline structure, which has remained dominant in the composite, hence proving the successful synthesis of PANI composite with photoadduct. Thermal analysis shows high thermal stability of photoadduct which in turn has improved the thermal stability of PANI composite, therefore, shows the potential of composite for high-temperature application purposes.