Changes In Intrinsic Viscosity Research Articles

Intrinsic Viscosity and Reducing Sugar Profiles of Degraded Glucomannan using Cellulase

High viscosity of glucomannan has been limit its applications. Hence, the long polysaccharide glucomannan which consists of β-linked glucoses and mannoses needs to be degraded to broaden its utilizations. Enzymatic degradation is known as a safe method for food material treatment. Specifically targeting at 1,4-β-D-glycosidic linkages, cellulase has potential as a cleavage for glucomannan. This work aimed to study performance of cellulase in degrading glucomannan. The change in intrinsic viscosity and reducing sugar during degradation was observed. Degradation of 1% glucomannan by 20 ppm cellulase for 300 min decreased the viscosity from 12,420 to 353 cps. This degradation was also confirmed by the increase of reducing sugar amount from 1,238.57 to 8,510.00 µg/ml. This work showed the success of glucomannan degradation by cellulase.

Conformations of gelatin in trivalent chromium salt solutions: Viscosity and dynamic light scattering study

An investigation of the influences of pH, salt type, and salt concentration on the conformations of gelatin molecules in trivalent chromium salt solutions was performed by viscosity and dynamic light scattering (DLS) techniques. It was found that the viscosity behaviors as polyelectrolytes or polyampholytes depended on the charge distribution on the gelatin chains, which can be tuned by the value of pH of the gelatin solution. The intrinsic viscosity of gelatin in basic chromium sulfate aqueous solution at pH = 2.0 first decreased and then increased with increasing Cr(OH)SO4 concentration, while a monotonic decrease of the intrinsic viscosity of gelatin was observed in CrCl3 solution. However, the intrinsic viscosity of gelatin at pH = 5.0 was found to be increased first and then decreased with an increase in salt concentration in Cr(OH)SO4 solution, as well as in CrCl3 solution. We suggested that the observed viscosity behavior of gelatin in trivalent chromium salt solutions was attributed to the comprehensive effects of shielding, overcharging, and crosslinking (complexation) caused by the introduction of the different counterions. In addition, the average hydrodynamic radius (R h ) of gelatin molecules in various salt solutions was determined by DLS. It was found that the change trend of R h with salt concentration was the same as the change of intrinsic viscosity. Based on the results of the viscosity and DLS, a possible mechanism for the conformational transition of gelatin chains with external conditions including pH, salt concentration, and salt type is proposed.

Compressive stress relaxation modeling of butadiene rubber under thermo‐oxidative aging

ABSTRACTThe compressive stress relaxation tests of butadiene rubber (BR) at different thermo‐oxidative aging temperatures were carried out. Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR‐ATR) was used to observe the variations of internal groups before and after the thermo‐oxidative aging. Magnetic resonance‐crosslink density (MR‐XLD) spectroscopy was used to measure the crosslink densities. The results showed the compressive stress relaxation of BR during thermo‐oxidative aging was dominated by chemical reactions: crosslinking, chain scission, and oxidation. Then an empirical model and an amendatory standard linear solid (SLS) model were put forward to describe the compressive stress relaxation behavior of BR. Both models fitted the data well. The SLS model, based on the aging mechanism of BR, not only made up the disadvantages of the empirical model, but also considered the changes of intrinsic viscosity (η) during the thermo‐oxidative aging of BR. The SLS model showed that the thermo‐oxidative aging of BR was mainly dominated by the crosslinking and oxidation reactions. This research proposes the amendatory SLS model and has important significance for study the stress relaxation behavior of crosslinked rubbers during thermo‐oxidative aging. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44630.

Optical and chemical behaviors of CR-39 and Makrofol plastics under low-energy electron beam irradiation

In this study, CR-39 and Makrofol plastic nuclear track detectors were irradiated with low-energy electron beams to study the effect of the induced changes on their optical and chemical properties. Surface chemical changes were recorded by Fourier transform infrared (FTIR) spectroscopy, which showed successive degradation and crosslinking for CR-39 and decomposition for Makrofol. The optical band gap was determined by UV–vis spectroscopy. Also, the parameters of carbon cluster formation and disordering (Urbach’s energy) occurring on plastic surfaces were examined. The intrinsic viscosity changes were investigated as well. As a result, low-energy electron beams were found to be useful for the control of many properties of the surfaces of the investigated detectors.

Effect of Different Sterilization Methods on Biodegradation of Biomedical Polypropylene

The aim of the present work is to study the effect of different sterilization methods on the biodegradation of biomedical polypropylene (PP) under the same biotic conditions. Three different sterilization techniques; γ-irradiation, steam sterilization and UV-irradiation were used to compare the effect of different sterilization methods on the biodegradability of PP. Neat and sterilized samples were incubated in compost and fungal culture environments. The changes in functional groups, mechanical properties, surface morphology and intrinsic viscosity in polymer were characterized by FT-IR spectroscopy, Instron, SEM and viscometric measurements, respectively. It was observed that the biodegradation of γ-sterilized samples in composting and microbial culture environments was higher than UVirradiated samples, while UV-irradiated more than steam-sterilized and neat samples. The results showed that the radio and photo-oxidative pretreatment directly enhanced the biodegradability of PP as the increase in fungal growth rate and weight loss during composting was found. The biodegradation rate of PP at the same biotic conditions mainly depends on the rate of degradation that initially occurred during sterilization. Overall, this study demonstrated that the biodegradation of sterilized PP in biotic conditions significantly depends on the nature of sterilization method.

Effects of gamma irradiation and moist heat for sterilization on sodium alginate.

Polysaccharides, such as alginates, are already being used as carriers for drug delivery. The physicochemical and biological properties of alginates may be affected via irradiation and thermal treatments. To explore and compare effects of two kinds of sterilization methods, gamma irradiation and moist heat, on sodium alginate (SA), physicochemical and biological properties of SA powder and solutions were investigated after sterilization. Human umbilical vein endothelial cells (HUVEC) was used to assess the cytotoxicity of the SA after sterilization. The research showed that 25 kGy gamma ray can effectively sterilize microorganism. Both gamma irradiation and moist heat hardly affect the native pH of SA. Compared to irradiation sterilization, moist heat sterilization showed smaller changes in intrinsic viscosity for all SA samples and lead to less glycosidic bond breaking of SA powders. The moist heat sterilization can cause the main chain scission and double bonds formation of the SA solutions. Cytotoxicity studies demonstrated that sterilized SA powers and SA solutions treated by gamma ray sterilization can increase the viability of HUVEC. However, SA solutions treated by moist heat sterilization were found to present severe cytotoxicity. The research results may provide interesting future advancements toward the development of SA-based products for biomedical applications.

Enhanced degradation stability of poly(p‐dioxanone) under different temperature and humidity with bis‐(2,6‐diisopropylphenyl) carbodiimide

ABSTRACTThe influences on the degradation of poly(p‐dioxanone) (PPDO) under different temperature and relatively humidity is initially investigated by adding bis‐(2,6‐diisopropylphenyl) carbodiimide (commercial name: stabaxol®‐1). The changes of intrinsic viscosity, mechanical properties, crystallinity, surface morphologies, and microstructure of PPDO and PPDO containing stabaxol®‐1 for 6 weeks are monitored. With increasing the degradation time, the intrinsic viscosity and mechanical properties of PPDO decrease much faster than those of PPDO containing 0.6 wt % stabaxol®‐1. During the degradation, PPDO containing 0.6 wt % stabaxol®‐1 shows a better physical integrity than PPDO. It has been shown that stabaxol®‐1 can retard the hydrolysis degradation of PPDO and enhance its hydrolytic stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40026.

Degradation behavior of hydroxyapatite/poly(lactic-co-glycolic) acid nanocomposite in simulated body fluid

To investigate the effect of hydroxyapatite(HA) on the degradation behavior of hydroxyapatite/poly(lactic-co-glycolic) acid (HA/PLGA) nanocomposite, the degradation experiment of n-HA/PLGA composite and pure PLGA were carried out by soaking in simulated body fluid(SBF) at 37°C for 1, 2, 4 and 6 months. The change of intrinsic viscosity, thermal properties, inner structure, bending strength reduction, surface morphology and the surface deposit of n-HA/PLGA composite and pure PLGA with respect to the soaking time were investigated by means of UbbeloHde Viscometer, differential scanning calorimeter (DSC), scanning electron microscope(SEM), electromechanical universal tester, a conventional camera and X-ray diffraction (XRD). The results showed that n-HA played an important role in improving the degradation behavior of n-HA/PLGA composite, which can accelerate the degradation PLGA and endow it with bioactivity, after n-HA was detached from PLGA during the degradation, so that n-HA/PLGA composite may have a more promising prospect of the clinical application than pure PLGA as bone fracture internal fixation materials.

An analytical ultracentrifugation based study on the conformation of lambda carrageenan in aqueous solution

The conformation and heterogeneity of lambda-carrageenan, a sulphonated galactan from red seaweed, solubilised in aqueous solvent with the assistance of microwave irradiation, has been assessed by a combination of analytical ultracentrifugation, size-exclusion chromatography, light scattering and capillary viscometry. Preparations appeared generally unimodal on the basis of sedimentation coefficient distributions from sedimentation velocity although at the highest concentrations a shoulder appears with a sedimentation coefficient approximately 1.1 times greater than that of the main component. Even under conditions commensurate with charge suppression simple linear regression was insufficient to represent non-ideal concentration dependence and the extraction of the Grálen concentration dependence parameter ks. A more general fitting algorithm was therefore employed. Mark-Houwink-Kuhn-Sakurada analysis of the change in intrinsic viscosity [η] with molecular weight, together with the Wales-van Holde ratio (combination of ks with [η]) point to an extended flexible conformation for lambda-carrageenan in the (weight average) molecular weight range Mw=340,000-870,000g/mol. The origin of the larger sedimentation coefficient component appearing at the higher concentrations is considered.

Degradation of Imidazolium- and Quaternary Ammonium-Functionalized Poly(fluorenyl ether ketone sulfone) Anion Exchange Membranes

Imidazolium and quaternary ammonium-functionalized poly(fluorenyl ether ketone sulfone)s were synthesized successfully with the same degree of cationic functionalization and identical polymer backbones for a comparative study of anion exchange membranes (AEMs) for solid-state alkaline membrane fuel cells (AMFCs). Both anion exchange membranes were synthesized using a new methyl-containing monomer that avoided the use of toxic chloromethylation reagents. The polymer chemical structures were confirmed by ¹H NMR and FTIR. The derived AEMs were fully characterized by water uptake, anion conductivity, stability under aqueous basic conditions, and thermal stability. Interestingly, both the cationic groups and the polymer backbone were found to be degraded in 1 M NaOH solution at 60 °C over 48 h as measured by changes of ion exchange capacity and intrinsic viscosity. Imidazolium-functionalized poly(fluorenyl ether ketone sulfone)s had similar aqueous alkaline stability to quaternary ammonium-functionalized materials at 60 °C but much lower stability at 80 °C. This work demonstrates that quaternary ammonium and imidazolium cationic groups are not stable on poly(arylene ether sulfone) backbones under relatively mild conditions. Additionally, the poly(arylene ether sulfone) backbone, which is one of the most common polymers used in ion exchange membrane applications, is not stable in the types of molecular configurations analyzed.

Study on the changing regularity of structure and properties of PC aged outdoor in western areas of China

AbstractAs an important engineering material, polycarbonate (PC) has been used widely. When exposed to the environment, PC will have aging process, which will reduce its performance and efficiency. This article studies the changing regularities of PCs structure and properties of ageing in western areas of China by measuring the change of intrinsic viscosity (IV), thermal decomposition temperature, glass transition temperature, and the groups within PC. The analysis of its IV, DSC, and thermo gravimetric analysis exhibited the same changing regularity, i.e., the aged PC (in Lasa, Yuli, and Jiangjin) experienced degradation and crosslinking, while degradation occurred earlier in the process of ageing, crosslinking predominated in later period. In addition, the results of UV absorption spectra and infrared absorption spectra showed the evidence of decomposition of the ester groups, resulting in the production of alcohol and phenol. And the results of mechanical tests indicated that the ductility disappeared mainly in the first year of outdoor aging. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Acetaldehyde scavengers and their effects on thermal stability and physical properties of poly(ethylene terephthalate)

AbstractThe acetaldehyde (AA) scavenging abilities of poly(ethylene terephthalate) (PET) blends containing various concentrations of anthranilamide, meta‐xylenediamine (MXDA), or alpha‐cyclodextrin have been evaluated. It was found that higher AA scavenger concentrations generally resulted in greater reductions in detectable AA in terms of both the AA generation rates and residual AA contents. As little as 100 ppm, by weight, of anthranilamide and MXDA were respectively shown to reduce residual AA detected in PET preforms by 46% and 36%. Melt‐blending 500 ppm of alpha‐cyclodextrin, into PET, reduced preform residual AA concentration by 42%. The scavengers acted as PET nucleating agents causing more rapid crystallization while heating the blends from the glassy state and when cooling from the melt; however, they caused no changes in the glass transitions, melting characteristics, or oxygen permeation behaviors of the blends. Addition of optimal scavenger concentrations had minimal effects on preform intrinsic viscosity and color changes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Comparison of polysaccharide degradations by dynamic high-pressure homogenization

The mechanical degradation of polysaccharides was investigated using dynamic high and ultra-high-pressure homogenization (HPH). The objectives were to reduce the molar mass of polymer chains, and simultaneously, the apparent and intrinsic viscosity of polysaccharides in solution. The influence of homogenization pressure (up to 200 MPa) and cycles was compared on polysaccharides with different physical and structure properties: namely, guar gum, hydroxyethylcellulose (HEC), sodium carboxymethylcellulose (Na-CMC), sodium alginate (Na-alginate) and gum arabic. HPH was applied on semi-dilute solutions. The apparent changes in molar mass, gyration radius and intrinsic viscosity were deduced from size exclusion chromatography coupled on-line with multi-angle laser light scattering, differential viscometer detector and differential refractive index detector (SEC/MALS/DV/DRI), while the evolution of the critical overlap concentration ( C ∗) was obtained by viscosimetry. A method based on a succession of homogenization cycles and polymer pre-concentration steps was developed to determine the minimum molar mass achieved at constant pressure. Molar mass, and intrinsic viscosity were shown to fall simultaneously while logically C ∗ increased during HPH for all polysaccharides, except gum arabic, probably because of its globular and branched structure. This highlights that the differences of polysaccharide structures and conformation (linear, branched…) exhibit a stronger impact on HPH treatments than polymer charge or molar mass. Finally, via an empirical approach linking the decrease of both molar masses and viscosities, we have evidenced a specific scaling exponent that should characterize the flexibility of the treated polymer (i.e. its ability to be degraded by HPH).

Calcium-induced Folding of Intrinsically Disordered Repeat-in-Toxin (RTX) Motifs via Changes of Protein Charges and Oligomerization States

Ligand-induced disorder-to-order transition plays a key role in the biological functions of many proteins that contain intrinsically disordered regions. This trait is exhibited by so-called RTX (repeat-in-toxin) motifs found in many virulence factors secreted by numerous gram-negative pathogenic bacteria: RTX proteins are natively disordered in the absence of calcium but fold upon calcium binding. The adenylate cyclase toxin (CyaA) produced by Bordetella pertussis, the causative agent of whooping cough, contains ∼40 RTX motifs organized in five successive blocks separated by non-RTX flanking regions. This RTX domain mediates toxin binding to its eukaryotic cell receptor. We previously showed that the last block of the RTX domain, block V, which is critical for CyaA toxicity, exhibits the hallmarks of intrinsically disordered proteins in the absence of calcium. Moreover, the C-terminal flanking region of CyaA block V is required for its calcium-induced folding. Here, we describe a comprehensive analysis of the hydrodynamic and electrophoretic properties of several block V RTX polypeptides that differ in the presence and/or length of the flanking regions. Our results indicate that the length of the C-terminal flanking region not only controls the calcium-induced folding but also the calcium-induced multimerization of the RTX polypeptides. Moreover, we showed that calcium binding is accompanied by a strong reduction of the net charge of the RTX polypeptides. These data indicate that the disorder-to-order transition in RTX proteins is controlled by a calcium-induced change of the polypeptide charges and stabilized by multimerization.

Effect of UV irradiation on mechanical properties and structure of poly(1,3,4-oxadiazole) fibers

The accelerated ultraviolet aging behavior of poly(1,3,4-oxadiazole) fibers (POD fibers) exposed to artificial environment for different durations were studied. The influence of ultraviolet light on the intrinsic viscosity, structure, appearance and morphology, mechanical properties of POD fibers were investigated during aging by ATR-FTIR and UV-spectra, XPS, WXRD, SEM and tensile strength tester. The results revealed that the structure and properties of POD fibers were affected by UV light. Tensile strength and breaking elongation of POD fibers were severely decreased after 48 h UV light irradiation, and the change of intrinsic viscosity indicated that only degradation but not crosslink occurred. Disruption of oxadiazole rings and formation of carbonyl and amide were observed. UV aging process in nitrogen atmosphere suggested that the oxygen was indispensable and the essence of POD UV aging was photo-oxidation process. POD was amorphous and the recrystallization on surface was present after UV aging due to degradation. Morphology of POD fiber surface was damaged after UV aging.

The effect of different storage temperatures on the physical properties of pectin solutions and gels

The stability (in terms of viscosity and gel strength) of pectin solutions and gels potentially plays an important role in their behaviour and functional properties in a wide range of applications and therefore any changes over time must be understood. The gel strength of pectin gels and intrinsic viscosity of pectin solutions at different temperatures (4 °C, 25 °C and 40 °C) have been investigated using a “rolling ball” viscometer and a texture analyser respectively. Both the intrinsic viscosity ([η]) and gel strength decrease with increased storage time, although this more pronounced at elevated temperatures. The changes in intrinsic viscosity with storage time and temperature were used to determine the depolymerisation constant ( k). Pectin storage conditions and particularly temperature have an influence on depolymerisation, particularly elevated storage temperatures, but whether or not this will be detrimental to its intended application will depend on the functional significance of the changes that occur. In this case based on the previous diffusion studies on a model drug (paracetamol) we conclude that the decreases in viscosity and gel strength within the range observed have no detrimental effect on the drug release properties.

Yellow dextrins: Evaluating changes in structure and colour during processing

AbstractThe preparation of a yellow dextrin is thoroughly characterized during different stages of its production process with a SEC system equipped with four detectors (light scattering, viscosity, UV and RI). With this system, also referred to as SEC‐4D, it was shown that the changes in characteristics are only in line with initial expectations up to 5 h after initiation of the reaction. After 5 h, changes in molar mass, intrinsic viscosity and colour point to the presence of significantly different structures. The combined results of the SEC‐4D measurements indicate the formation of aggregate like structures made of small starch fragments which are intensely coloured and physically linked. The obtained results also indicate that the aggregate like structures are probably still susceptible to repolymerization and transglycosylation. The newly derived parameter YI‐400 nm played an important role in defining a plausible cause for the observed changes in characteristics.

Study on degradation reactions in polyethylene terephthalate containing 5-sulpho isophthalyl moieties

Kinetics of thermal degradation occurring on polyester containing cationic dyeable comonomer units viz. 5-sulphoisophthalate moieties are studied by measurement of changes in intrinsic viscosity and carboxyl values on the polymer after subjecting the polymer chips to temperatures in the range 275–285°C for different residence times ranging from 5 to 60 min and comparing with the homopolymer. The activation energy values for degradation are estimated from the kinetic data. Mechanical properties of the textured yarns produced from the partially oriented yarns (POY) spun under different residence times are measured. Yarn produced with higher residence time has poor mechanical properties. The SEM images of the POY show presence of particles at the surface of the yarn due to polymer degradation. The size of the particles as seen on the surface increase with increase of retention time. Addition of thermal stabilizer helps in controlling the thermal degradation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effect of γ-Dose rate on Biodegradation of γ-Sterilized Biomedical Polyolefins

The aim of the present study is to study the effect of γ-dose rate on the biodegradation of γ-sterilized polyolefins. Films of isotactic polypropylene, high density polyethylene and ethylene-propylene (EP) copolymer were sterilized under γ-radiation with doses of 10 and 25 kGy. Two different 60Co sources were used with dose rate 600 and 780 Gy h−1. Neat and sterilized samples were incubated in compost and fungal culture environments. The changes in functional groups, surface morphology and intrinsic viscosity in polymer chains were characterized by FT-IR spectroscopy, SEM and viscometric measurements, respectively. It was observed that both γ-degradation and biodegradation processes depend on the dose rate of γ-source. It was found that the biodegradation of γ-sterilized polyolefins in composting and microbial culture environments increased with decreasing the γ-dose rate.

Kinetics of degradation of Lycium barbarum polysaccharide by ultrasonication

AbstractLycium barbarum polysaccharide (LBP) was subjected to ultrasonic degradation under the controlled conditions, such as, temperature, irradiation time, initial pH value, and concentration of solution. The ultrasonic degradation of LBP was demonstrated by the changes of intrinsic viscosity. Viscometry was used to study the degradation behavior and a kinetic model was developed to estimate the degradation rate. The results showed that the degradation rate was reduced with the increase of solution concentration and pH, and increased with increase of temperature. The relationship between the number average molar mass (Mn) and intrinsic viscosities as interpreted using the Mark‐Houwink equation suggested that LBP adopted a flexible coil conformation in aqueous solution. The activation energy of ultrasonic degradation of LBP is 26.5 kJ/mol, which indicates that the ultrasonic degradation is a convenient, time saving, and cost‐efficient method for obtaining a desired molecular weight. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 509–513, 2010