Intrinsic Viscosity Research Articles

Elongated Rodlike Particle Formation of Methyl Cellulose in Aqueous Solution.

The conformation and structure of methyl cellulose (MC) ether samples dissolved in pure water under dilute conditions were carefully reconsidered based on the results obtained using small-to-wide-angle neutron scattering (S-WANS), static light scattering (SLS), dynamic light scattering (DLS), and viscometric techniques. The examined MC samples possessed an average degree of substitution by methyl groups per glucose unit of ca 1.8 and weight average molar masses (Mw), ranging from 23 to 790 kg mol–1. S-WANS experiments clearly demonstrated that the samples possess highly elongated rigid rodlike local structures in deuterium oxide solutions with weak periodicities of ca 0.4 and 1.0 nm on a length scale, which correspond to the average intermolecular distance between molecular chain portions facing each other in the formed rodlike structure and the repeating length of the monomeric cellobiose unit of molecular chains, respectively. Ratios of the particle length (L) to the radius of gyration (Rg) determined by SLS techniques approximately showed the relationship LRg–1 = holding in rigid rods over the entire Mw range examined in this study. However, the folding number, defined as the ratio of the average molecular contour length (l) to L, remained at the value of lL–1 ∼ 2, representing an elongated one-folded hairpin structure, until Mw ∼ 300 kg mol–1 and increased substantially up to ca 4.9 at the highest Mw of 790 kg mol–1. The observed increase in the lL–1 value corresponded well with an increase in the diameter of the formed rod with increasing Mw observed in the S-WANS data. The Mw dependencies of the translational diffusion coefficient determined via DLS measurements and that of the intrinsic viscosity detected via viscometric techniques also distinctly demonstrated that particles formed by the MC samples dissolved in aqueous solution behave as elongated rigid rods irrespective of Mw.

Microwave assisted synthesis of guar gum based biopolymeric macromolecule optimized as a flocculant for mineral ore processing

The research endeavour to synthesize a novel, non-toxic, eco-friendly guar gum based biopolymeric macromolecule, [2-(methacryloyloxy) ethyl] trimethyl ammonium chloride grafted guar gum (GG-g-P (MAETMAC)) that has been optimized as a flocculant for mineral ore processing. The synthesis was performed using non-radiation and microwave assisted technique to compare and ensure the superiority of the latter. The intended grafting of monomer[2-(methacryloyloxy) ethyl] trimethyl ammonium chloride on to the biological macromolecule (guar gum) was confirmed through standard physico-chemical characterization techniques namely X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV–visible) spectroscopy, intrinsic viscosity study, etc. The flocculation efficacy of the synthesized novel graft copolymer was thoroughly investigated in kaolin, coal fine, and iron ore suspensions. We have explored a graft copolymer, [2-(methacryloyloxy) ethyl] trimethyl ammonium chloride grafted guar gum that has not been studied yet to the best of our knowledge. To establish the superiority of the synthesized biomaterial, the flocculation study revealed that the best grade of the synthesized novel graft copolymer showed flocculation efficacy of 90 % in kaolin, 69 % in Iron ore, and 29 % in coal fine suspensions which was significantly higher than using alum as a coagulant which provided 36 % efficacy in kaolin, 29 % in iron ore and 10 % in coal fine suspensions.

Hydrophobic association copolymer as viscosifier for high‐temperature high‐pressure anti‐sedimentation performance of water‐based drilling fluid

AbstractIn this study, a new type of amphiphilic copolymer SPXFJ, with amide and sulfonate functional groups, was synthesized via the free radical polymerization method. And the chemical structure and properties of this new polymer were characterized by elemental analysis (EA), X‐ray photoelectron spectroscopy (XPS), intrinsic viscosity tests, and thermogravimetric analysis (TGA). The hydrophobic association and thermo‐thickening properties of SPXFJ copolymer were investigated through viscometer, contact angle tester, high‐resolution scanning electron microscope analysis, and X‐ray laser static scattering (XLSS) test. The test results indicated that SPXFJ copolymer showed superior amphiphilic properties, especially in the solution condition. Furthermore, a thermo‐associative behavior was found in the solution that aged at 180°C. Thus, SPXFJ‐based drilling fluid showed a higher temperature resistance. The test results, in both high‐temperature aging tests and high‐temperature high‐pressure (HTHP) downhole simulation tests, showed that the water‐based drilling fluid showed excellent anti‐sedimentation properties with the use of SPXFJ polymer and can be improved significantly, especially in the high‐pressure condition. The water‐based drilling fluid of 2.0 g/cm3 showed no sedimentation of barite powders at 180°C/100 MPa, of which the density deviation just reached approximately 0.06 g/cm3.

Photo-degradable and recyclable starch/Fe3O4/TiO2 nanocomposites: feasibility of an approach to reduce the recycling labor cost in plastic waste management.

In this research, a biodegradable starch/Fe3O4/TiO2 bio-nanocomposites (SFT) were produced using different nano Fe3O4/TiO2 (FT) (3, 5, and 10 (wt% dry based)) contents. Mechanical properties, visual properties, moisture-sensitive parameters, magnetic properties, and physical properties of the film specimens were investigated. Photodegradability of film specimens was also evaluated under UV-A irradiation. The FT content increased the hydrophobicity of the film specimens. Tensile strength (TS) of SFT films was increased by increasing FT up to 3%. Elongation at break (EB) and tensile energy to break (TEB) were decreased by adding FT content up to 3% simultaneously. The film specimens’ water vapor permeability (WVP) was decreased with increasing FT content. The intrinsic viscosity of SFT was decreased by increasing FT content. It confirms the enhancement of photodegradability of the specimens by increasing FT content. It seems the compatibility of FT with biopolymer has had great effects on these properties. Use of FT-based nanocomposites is an appropriate approach to developing magnetic-recyclable and photodegradable packaging materials.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-022-22049-1.

The unusual rheological behaviors of poly(acrylamide-co-acrylonitrile)s with UCST features in aqueous solutions

The polymer with the upper critical solution temperature (UCST) in aqueous solution exhibits temperature sensitivity, whose solvation is more sensitive to temperature than that of ordinary polymer in aqueous solution. However, the rheological behavior of UCST-type polymer in aqueous solution with temperature has not been definitively concluded. In this work, the rheological behaviors of poly(acrylamide-co-acrylonitrile) with UCST features in dilute and semi-dilute aqueous solutions at different temperatures were investigated. Our results showed that the viscosities of both the dilute and semi-dilute aqueous solutions increase when temperature rises. To understand this unusual observation of rheological behavior, related dynamic and thermodynamic properties were studied. The intrinsic viscosity ([η]), viscometric radius (Rη), hydrodynamic size (Rh), friction coefficient (ζ), relaxation time(τ) and correlation length(▪) of the solution were quantitatively investigated at different temperatures. Based on experimental data, the theta temperature was determined, and the change rate of excluded volume with temperature was also obtained. The interaction parameter χ and intermolecular interactions of polymer were analyzed at different temperatures. The unusual rheological behavior of UCST-type polymer in aqueous solution is analyzed according to classical polymer physics based upon our experimental observations. We envisage that this work will provide an insight and benefit for the design of thermoviscosifying UCST-type polymers which is urgently needed in both petroleum and chemical industries.

Thermal Stability of Cationic Poly(3-methacryloylamino Propyl Trimethyl Ammonium Chloride) in Salt Solution

In this paper the thermal stability properties of poly(3-methacryloylamino propyl trimethyl ammonium chloride) (PMAPTAC) with a series of molecular weights in various salt solutions were investigated by monitoring the apparent viscosity and viscosity retention rate with aging time, for the first time to our knowledge. Secondly, the thermal stability properties of poly(methacryloyloxy ethyl trimethyl ammonium chloride) (PDMC) solution was studied and compared with that of the PMAPTAC solution under the same conditions. The results showed that the viscosity retention rate of PMAPTAC/salt solutions with salinities from 40 g/L to 200 g/L at 85 °C were about 60%, indicating that PMAPTAC had good temperature and salt resistance. Besides, the temperature and salt resistance of PMAPTAC with 0.62 dL/g was better than that of PMAPTAC with 7.55 dL/g under the conditions of this study. In addition, the viscosity retention rate of PDMC/salt solution with the same intrinsic viscosity as PMAPTAC/salt solution was 45%, indicating that compared with PDMC, the PMAPTAC with viscosity retention rate of 60% had better temperature and salt resistance. We suggest the results obtained in this study will not only fill the current gaps in the research of the temperature and salt tolerance properties of PMAPTAC, but also provide support for the potential application of PMAPTAC products in high-temperature and high-salt environments.

Complex viscous behaviour of a hydrophilic fumed silica suspension: Temperature and particle concentration influence

• Shear-thickening dependence on temperature and solid concentration. • New criteria for shear-thickening intensity. • Variation of the shear-thickening microstructure with shear stress. • Intrinsic viscosity and activation entropy for the viscous flow increasing with shear stress. Shear-thickening (ST) is a non-Newtonian viscous behaviour characterized by the increase of the steady viscosity by shearing. It is well known that applied stress better than shear rate is the source of fluid inner microstructure changes which lead to non-Newtonian behaviours. Therefore, the influence of temperature and solid concentration on the stress-induced complex steady viscous behaviour shown by a hydrophilic fumed silica suspension (A200PPG400) has been studied. Previous works have demonstrated that hydroclusters model is the appropriate approach justifying the ST behaviour of A200PPG400 suspensions. In this work, more detailed description of this ST mechanism has been proposed based upon the analysis of intrinsic viscosity and activation energy for the viscous flow experimental data.

Sepiolite organic modifiers effect on pet/sepiolite nanocomposites degradation

In this paper the effect of different organosepiolites on PET matrix was evaluated through the analyses of Melt Flow Index (MFI) and Intrinsic Viscosity (IV) of the nanocomposites. PET/sepiolite nanocomposites were produced through a two-stage process. The masterbatch production was done in a melt compounding extruder, and then these were taken to an injection machine, where different specimens were obtained for characterization purposes. Two types of organomodifiers were tested, silanes in one hand and a quaternary ammonium salt on the other. Thermal analyses were done to determine thermal stability of the organomodifiers. Then, different experiments were carried out increasing the concentration of coupling agents to analyse its effect on PET matrix degradation. As results indicate a high degree of degradation of the nanocomposites matrix, pyromellitic dianhydride (PMDA) was added as chain extender to react with PET molecular chains, with the aim of increasing its molecular weight (Mw).

Alkalization of Kraft Pulps from Pine and Eucalyptus and Its Effect on Enzymatic Saccharification and Viscosity Control of Cellulose.

Bleached kraft pulps from eucalyptus and pine were subjected to cold caustic extraction (CCE) with NaOH (5, 10, 17.5, and 35%) for hemicelluloses removal and to increase cellulose accessibility. The effect of these changes was evaluated in enzymatic saccharification with the multicomponent Cellic CTec3 enzyme cocktail, and in viscosity reduction of pulps with the monocomponent Trichoderma reesei endoglucanase (EG). After CCE with 10% NaOH (CCE10) and 17.5% NaOH (CCE17.5), hemicellulose content lower than 1% was achieved in eucalyptus and pine pulps, respectively. At these concentrations, cellulose I started to be converted into cellulose II. NaOH concentrations higher than 17.5% decreased the intrinsic viscosity (from 730 to 420 mL/g in eucalyptus and from 510 to 410 mL/g in pine). Cellulose crystallinity was reduced from 60% to 44% in eucalyptus and from 71% to 44% in pine, as the NaOH concentration increased. Enzymatic multicomponent saccharification showed higher glucose yields in all CCE-treated eucalyptus samples (up to 93%) while only CCE17.5 and CCE35 pine pulps achieved 90% after 40 h of incubation. Untreated bleached pulps of both species presented saccharification yields lower than 70%. When monocomponent EG was used to treat the same pulps, depending on enzyme charge and incubation time, a wide range of intrinsic viscosity reduction was obtained (up to 74%). Results showed that eucalyptus pulps are more accessible and easier to hydrolyze by enzymes than pine pulps and that the conversion of cellulose I to cellulose II hydrate only has the effect of increasing saccharification of CCE pine samples. Viscosity reduction of CCE pulps and EG treated pulps were obtained in a wide range indicating that pulps presented characteristics suitable for cellulose derivatives production.

Effects of malting process on molecular weight distribution and content of total and water-extractable arabinoxylan in barley

This work aims to evaluate the effects of the malting process on the malt total and water-extractable (WE) arabinoxylan (AX), also considering the barley cultivar and year of cultivation. The WEAX molecular properties were characterized by high-pressure size exclusion chromatography (HPSEC) - triple detector array (TDA). Most of the barley malt WEAX showed a molecular weight over 4.0 × 105 Da with a random coil conformation. Compared to raw barley, the malts show analogous content of AX and WEAX, similar intrinsic viscosity, less rigid conformation, and higher polydispersity. The WEAX content of malt was highly and negatively related to the common quality parameters, resulting in a useful indicator of malt modification, even more representative than the total AX content. WEAX is highly positively related to the Congress wort viscosity, and thus, lautering could be more significantly affected by WEAX rather than total AX content.

Pelletizing ultra-high molecular weight polyethylene (UHMWPE) powders with a novel tapered die and addition of high density polyethylene (HDPE): Processing, morphology, and properties

The extremely high molecular weight and molecular entanglement have rendered ultra-high molecular weight polyethylene (UHMWPE) superior properties. However, poor inter-particle diffusion makes it difficult to pelletize UHMWPE powders for easy processing/handling. A novel tapered die with air cooling was proposed to pelletize UHMWPE and a UHMWPE blend with 5 wt% high-density polyethylene (HDPE) for compression molding and material characterization. The tensile strength of samples prepared with the tapered die outperformed those by the regular die or from virgin powders. The addition of HDPE further improved the tensile strength. Fourier transform infrared spectroscopy (FTIR) revealed little chain scission and the lowest amount of oxidation from the tapered die. Intrinsic viscosity (IV) measurements confirmed the negligible chain scission and showed an increment in IV for the UHMWPE/HDPE blend. Multi-angle light scattering with size-exclusion chromatography (SEC-MALS) indicated no change in the UHMWPE molecular weight distribution, but some crosslinking in the blend. Polarized optical microscopy (POM) showed that the HDPE and extrusion led to a finer UHMWPE domain size and better fusion between UHMWPE and HDPE. The combined effect of enhanced molecular chain diffusion, improved consolidation, and lower oxidation using the tapered die led to 40% improvement of tensile strength for the UHMWPE/HDPE blend.

Rheology and molecular interactions in polyacrylonitrile solutions: Role of a solvent

We examined the rheological properties of polyacrylonitrile (PAN) solutions in seven solvents over a wide range of shear rates. These solutions were characterized using the Hansen solubility parameter. The viscosity of these dilute solutions was primarily determined by this parameter. However, above the crossover point (at c[η] > 0.7) not only viscosity but also nature of the solvents was found to be an important factor. At high polymer concentrations, certain solutions showed gelation tendency.This study aims to determine a correlation between the rheological properties of the solutions and the affinity of the solvent with PAN. These correlations are present for an intrinsic viscosity (or the Huggins constant), a second virial coefficient, and solubility parameter. However, in certain cases, experimental points do not correspond to general dependence. This is also observed for these solutions when presenting the data of viscoelastic measurements in G′–G″ coordinates: certain points deviate from the general dependence.A detailed infrared spectroscopy analysis has been used for examining these experimental results. It has been shown the water presence in the solvents and polymer solutions even than anhydrous solvents were used. Water presence tend to a solvent–water associate formation in the solutions. The solubility of PAN in these solvents and the gelation tendency depends on the polymer concentration, in addition to the structure and stability of the polymer–water associates. The experimental results obtained and the reported correlation made it possible to develop a subsequence of solvents used as per their affinity with PAN. The charactristics of dilute solutions were compared with the rheological properties of moderately concentrated solution.

Controlling the Processability and Stability of Supramolecular Polymers Using the Interplay of Intra- and Intermolecular Interactions.

Polymer networks crosslinked via non-covalent interactions afford interesting materials for a wide range of applications due to their self-healing capability, recyclability, and tunable material properties. However, when strong non-covalent binding motifs in combination with high crosslink density are used, processing of the materials becomes troublesome because of high viscosities and the formation of insoluble gels. Here, we present an approach to control the processability of grafted polymers containing strong non-covalent interactions by balancing the interplay of intra- and intermolecular hydrogen bonding. A library of copolymers with different degrees of polymerization and content of protected ureido-pyrimidinone-urea (UPy-urea) grafts was prepared. Photo-deprotection in a good solvent like tetrahydrofuran (THF) at low concentrations (≤1 mg mL–1) created intramolecularly assembled nanoparticles. Remarkably, the intrinsic viscosity of these nanoparticle solutions was an order of magnitude lower compared to solutions of the intermolecularly assembled analogues, highlighting the crucial role of intra- versus intermolecular interactions. Due to the strong hydrogen bonds between UPy dimers, the intramolecularly assembled structures were kinetically trapped. As a result, the polymer nanoparticles were readily processed into a bulk material, without causing major changes in the morphology as verified by atomic force microscopy. Subsequent intermolecular crosslinking of the nanoparticle film, by heating to temperatures where the hydrogen-bond exchange becomes fast, resulted in a crosslinked network. The reversibility of the hereby obtained polymer networks was shown by retrieving the intramolecularly assembled nanoparticles via redissolution and sonication of the intermolecularly crosslinked film in THF with a small amount of acid. Our results highlight that the stability and processability of highly supramolecularly crosslinked polymers can be controlled both in solution and in bulk by using the interplay of intra- and intermolecular non-covalent interactions in grafted polymers.

Study on the impact of temperature, salts, sugars and pH on dilute solution properties of Lepidium perfoliatum seed gum.

The functional properties of food gums are remarkably affected by the quality of solvent/cosolutes and temperature in a food system. In this work, for the first time, the chemical characterizations and dilute solution properties of Lepidium perfoliatum seed gum (LPSG), as an emerging carbohydrate polymer, were investigated. It was found that xylose (14.27%), galacturonic acid (10.70%), arabinose (9.07%) and galactose (8.80%) were the main monosaccharaide components in the LPSG samples. The uronic acid content of LPSG samples was obtained to be 14.83%. The average molecular weight and polydispersity index of LPSG were to be 2.34 × 105 g/mol and 3.3, respectively. As the temperature was increased and the pH was decreased and the concentration of cosolutes (Na+, Ca2+, sucrose and lactose) presented in the LPSG solutions was enhanced, the intrinsic viscosity [η] and coil dimension (R coil , V coil , υ s ) of LPSG molecular chains decreased. Activation energy and chain flexibility of LPSG were estimated to be 0.46 × 107 J/kg.mol and 553.08 K, respectively. The relative stiffness parameter (B) of LPSG in the presence of Ca2+ (0.079) was more than that of Na+ (0.032). Incorporation of LPSG into deionized water (0.2%, w/v) diminished the surface activity from 76.75 mN/m to 75.70 mN/m. Zeta potential (ζ) values (-46.85 mV--19.63 mV) demonstrated that dilute solutions of LPSG had strong anionic nature in the pH range of 3-11. The molecular conformation of LPSG was random coil in all the selected solution conditions. It can be concluded that temperature and presence of cosolutes can significantly influence on the LPSG properties in the dilute systems.

The Preparation of Hydroxyl-Terminated Deproteinized Natural Rubber Latex by Photochemical Reaction Utilizing Nanometric TiO2 Depositing on Quartz Substrate as a Photocatalyst.

Hydroxyl-terminated natural rubber (HTNR) is a product of interest for making natural rubber (NR) easy and versatile for use in a wide range of applications. Photochemical degradation using a TiO2 film that has been deposited on a glass substrate is one of the fascinating methods of producing HTNR. Nevertheless, light energy is wasted during the photodegradation process because a glass substrate has a cutoff for ultraviolet light. To enhance the effectiveness of the process, a quartz substrate was coated with the TiO2 film for photochemical breakdown. X-ray diffraction (XRD) spectroscopy and atomic force microscopy (AFM) were applied to investigate the TiO2 deposited on glass and quartz substrates. In addition, the influence of several factors, such as rubber and surfactant concentrations, on the reaction was investigated. After the reaction, the properties of the rubber products, including intrinsic viscosity, molecular weight, and microstructure, were determined. A unique diffraction peak for the anatase (101) phase could be observed in the TiO2 film deposited on the quartz substrate, resulting in photochemical activity and photocatalytic efficiency significantly higher than those of the substrate made of glass. In the scenario of deproteinized NR (DPNR) latex containing 10% DRC, 20% w/w H2O2, and TiO2 film coated on a quartz substrate, the HTNR could be manufactured effectively.

Study on Hydrolysis Properties and Mechanism of Poly(3-Methacrylamido Propyl Trimethyl Ammonium Chloride) Solution.

Poly(3-methacrylamido propyl trimethyl ammonium chloride) (PMAPTAC) is a typical cationic water-soluble polyelectrolyte, which has been widely used in petroleum, papermaking, daily cosmetics and other fields in the form of an aqueous solution. However, the acid–base and thermal stability of PMAPTAC in aqueous solution have not been reported yet, which hinders its further application in high-temperature and acid–base environments. To address these deficiencies, the effects of temperature and pH of PMAPTAC with different intrinsic viscosities on its hydrolysis stability were investigated qualitatively and quantitatively, and the hydrolysis mechanism was studied. Firstly, the qualitative analysis showed that the apparent viscosity of the PMAPTAC solution decreased with hydrolysis time at different temperatures and pH. The higher the temperature and the lower the pH, the greater the viscosity loss of PMAPTAC. The quantitative analysis showed that the hydrolysis rate of the PMAPTAC sample solution increased with the increase in temperature and pH. In addition, the intrinsic viscosity of PMAPTAC samples had little effect on the hydrolytic stability of PMAPTAC. Secondly, by analyzing the viscosity curves at different pH and temperatures by Arrhenius analysis, the Arrhenius equations were found to be 1/τ = 200.34e^((−25.04)/RT), 1/τ = 9127.07e^((−38.90)/RT) and 1/τ = 4683.03e^((−39.89)/RT) for pH 3, pH 7 and pH 11, respectively. Thirdly, the hydrolysis rate of PDMC was the fastest under alkaline conditions. In addition, compared with PDMC, PMAPTAC had better hydrolysis stability under the same conditions. Finally, the mechanism of the hydrolyzed polymer was studied by FTIR and 13CNMR, which showed that the carbonyl group of PMAPTAC was hydrolyzed into a carboxyl group, and the small molecule (3-aminopropyl) trimethylammonium chloride was generated, while the ester group of PDMC was hydrolyzed into a carboxyl group, and choline chloride was released. The above results can provide a theoretical basis for the application of PMAPTAC in some high-temperature and acid–base environments.

Structural and Rheological Properties of Yanang Gum (Tiliacora triandra).

Plant polysaccharides are used in the food industry to improve the texture and stability of food. The viscosity of polysaccharides, which includes both thickening and gelling, is an important characteristic. Yanang, Tilaicora triandra (Colebr.) Diels., composed of polysaccharide gum in its leaves. In this research, Yanang gum’s structural and rheological properties were investigated. The gum’s structure is xylan, with a backbone made up mostly of mixed (1,3)- and (1,4)-D-xylan. The average molecular weight of Yanang gum is 3819 kDa, with a gyration radius of 120.4 nm and an intrinsic viscosity of 14.6 dL/g. The power-law model was found to be the best fit for Yanang gum flow curves. The consistency coefficient, k, increases significantly with concentration in both the forward and the reverse measurements, whereas the flow behavior index, n, decreased as concentration increased. Yanang gum exhibited shear-thinning flow behavior. Increasing the concentration results in heightened G′ and G″, and the cross-over point shifts toward lower frequencies. The results of this study show that Yanang gum may be beneficial as other natural gums for food products.

Construction of a CRISPR/nCas9-assisted genome editing system for exopolysaccharide biosynthesis in Streptococcus thermophilus

Streptococcus thermophilus is an economically prominent starter for common dairy products due to its potential health and nutritional benefits. However, lack of precise genetic manipulation approaches has greatly hampered the industrial application of S. thermophilus.. Herein, we developed an efficient genome editing toolbox (pKLH353) based on CRISPR/nCas9 (Cas9 nickase) in S. thermophilus to seamlessly edit single or multiple genes. A native constitutive promoter library was used to optimize the nCas9 and sgRNA expression with gene deletion efficiencies of 14–60%. The epsA, epsB and epsE were identified as key genes affecting exopolysaccharide (EPS) biosynthesis in S. thermophilus S-3 using the CRISPR/nCas9 toolbox. Moreover, compared to the wild-type, knockout of epsC, epsE or epsG led to a decrease of EPS titer with reducing in its molecular weight (>2.5-fold) and intrinsic viscosity (>19.8-fold). The ratio of monosaccharide composition of the mutants has also changed, suggesting that these eps genes are involved in the chain length synthesis and repeat unit assembly. Taken together, this CRISPR/nCas9 system can serve as a basic toolkit for precise genetic engineering of S. thermophilus and facilitate strain engineering to produce bio-based products.

Estimation of the rheological curve of HPAM solutions from measurements using the Brookfield viscometer

In recent studies, Jouenne and Levache (2020) proposed a rheological model for polymeric solutions used in enhanced oil recovery, based essentially on a variable obtained as the product of the intrinsic viscosity of the solution and the concentration of the polymer. Using this variable, the authors propose expressions in which is possible to predict the coefficients of Carreau–Yasuda’s law that are of interest: the viscosity under zero shear regime η0, the power index n, and the relaxation time λ. In this work, the robustness of this model is improved using a machine learning technique and a larger database than the one previously considered. Based on this enhanced model, a technique is proposed to estimate the intrinsic viscosity of the solutions and the parameters of Carreau–Yasuda’s law using only the measurement of viscosity at a shear rate of 7.3 s−1. The results obtained with this approach are compared to those issued from experimental data finding satisfactory results. The use of this strategy is of particular interest for field studies or laboratories that only have as available instruments the Brookfield viscometer.

Synthesis and structural characterization of elastin-based polypentapeptide/hydroxypropylmethylcellulose blend films: Assessment of miscibility, thermal stability and surface characteristics

This work portrays the synthesis of Elastin-based polymer poly(GVGIP) (where; G-Glycine, V-Valine, I-Isoleucine, P-Proline) through the solution-phase strategy by stepwise approach followed by characterization with modern analytical tools. The miscibility attributes of the polypeptide were explored with hydroxypropylmethylcellulose (HPMC) using dilute solution viscometry method, spectroscopic, thermal, SEM, and XRD analysis. Explicitly the Huggins coefficient [KH], the intrinsic viscosity [η], parameters such as α by Sun, ∆[η]m by Garcia ∆B, and µ suggested by Chee, ∆K, and β advocated by Jiang and Han, recommend the miscibility up to 50% of the polypeptide. In the solid phase, DSC and TGA analysis showed that miscible blends possessed a higher glass transition temperature (Tg) and thermal stability, respectively. The Scanning Electron Microscopy (SEM) evinced the smooth morphology for miscible blends. Besides, XRD showed broadening of the diffraction pattern ratified the miscibility. The change in frequency and intensity of FTIR peaks demonstrated the existence of intermolecular interchanges between two polymers. Overall, the approach successfully synthesized poly(GVGIP)/HPMC miscible blends up to 50%, make it an excellent choice for biomedical and pharmaceutical purposes.