Dynamic Rheological Behavior Research Articles

Synergistic effects of waste coral powder and metakaolin in cement pastes: Hydration, pore structure, rheology, and strength

Coral reefs are abundant in waste coral powder, and how to utilize coral powder efficiently to construct far-sea projects has become a major focus of research and engineering field, which is conducive to the development of green economy. However, existing research lacks a comprehensive and systematic investigation of the cement-coral powder-metakaolin ternary system. In this study, the hydration and rheological behavior, micromechanical and mechanical properties, and pore structure evolution of the ternary system are systematically investigated to uncover the synergistic mechanism between metakaolin and coral powder. The results indicated that, based on hydration, rheology, and mechanical properties, the recommended proportions of cement, coral powder, and metakaolin are 75 %, 10 %, and 15 %, respectively. The combination of coral powder and metakaolin effectively promotes hydration. Furthermore, it accelerates the aluminate reaction, resulting in a stronger aluminate exothermic peak immediately. In addition, metakaolin reacts with coral powder to form carboaluminate, activating the activity of the coral powder, which in turn improves the mechanical properties and pore structure of the ternary system. Moreover, metakaolin undergoes a pozzolanic reaction with calcium hydroxide, which contributes to optimizing the pore structure of the ternary system and enhancing its mechanical properties. Additionally, coral powder promotes the conversion of monosulfate to carboaluminate while inhibiting the transformation of ettringite into monosulfate. The Herschel-Bulkley model accurately simulates the dynamic rheological behavior of the ternary system. This study is highly significant and practically valuable for transforming waste coral powder into a supplementary cementitious material for the construction of the far-sea projects, providing a scientific basis for future related studies.

Study on the structure and γ‐ray shielding performance of polypropylene/PbO composites with heterogeneous networks

AbstractPolymer‐based radiation shielding materials are receiving more and more interests due to their desirable advantages in lightweight and maneuverability. Herein, we employ polypropylene (PP) as the matrix to construct γ‐ray shielding composites through the embedment of PbO particles with a wet reaction melt blending method. From the changes in dynamic rheological behaviors and fracture surface of PP/PbO composite, it can be found that the gradient addition of PbO particles facilitates the formation of heterogeneous network structure with, and high PbO content may make the composites undergo a “liquid–solid” transition. Rheological temperature and time scanning show that both PbO content and heterogeneous network structure greatly contribute to the storage modulus (G') and thermal stability. The γ‐ray (137Cs) shielding tests manifest that BPP/PbO‐4 has the best shielding performance, whose thicknesses of half value layer (HVL) and tenth value layer (TVL) are 0.32 and 1.05 cm, respectively, obviously smaller than those shielding materials ever reported. The analyses on effective atomic number (Zeff) and effective electron density (NE) reveal that the good shielding performance of BPP/PbO‐4 benefits from its proper content and dispersion of PbO particles.

Dynamic rheological behavior of high-amylose wheat dough during various heating stages: Insight from its starch characteristics

The objective of this study was to understand how the dynamic rheological behaviors of high-amylose wheat (HAW) dough during various heating stages measured using a mixolab were affected by the starch properties. At the heating stage of 30 °C - 90 °C, low minimum (C2) and peak (C3) torques were observed for HAW doughs, which resulted from their reduced starch granule swelling. During holding at 90 °C, HAW doughs had low minimum (C4) and C3 - C4 torques, indicating a good resistance to mechanical shear and endogenous enzyme degradation. HAW doughs also had low final (C5) and setback (C5 - C4) torques, consistent with their low starch swelling power and solubility. The increased amylose in HAW starch formed long-chain double-helical B-type polymorph and amylose-lipid complex, which resulted in high starch gelatinization-temperatures and enthalpy change, low swelling power and solubility, low pasting viscosity, and high resistance of swollen granules to mechanical shear and enzyme degradation. The overall patterns of dough-rheological behavior of HAW doughs during heating were similar to their respective starch pasting profiles, indicating that starch was the dominant contributor to the dough rheology during heating. This study provides useful information for food applications and manufacturing of HAW-based products, especially none-fermented products requiring firm texture and low viscosity.

Underlying the mechanisms of incorporation of κ-carrageenan on the formation of low-salt myofibrillar protein gels during heating process: Perspective on the dynamic changes of protein structures and molecular interactions

This study aimed to systematacially investigate the effects of κ-carrageenan (KC) concentration on the formation of myofibrillar protein (MP) gels under low-salt condition based on the dynamic changes of protein structures and molecular interactions during heating process. The results indicated that incorporating KC markedly improved the water holding capacity (WHC) and gel strength of MP gels (P < 0.05). Those properties were most improved by adding 0.4% KC with WHC of 71.44% and gel strength of 1.62 N. During the heating process, when the temperature was above 50 °C, KC addition significantly increased the turbidity and particle size and decreased solubility of MP in a concentration-dependent manner, as well as exhibiting higher surface hydrophobicity at 0.2% KC concentration (P < 0.05), indicating that KC accelerated the rate of aggregation of MP during heating process. The dynamic rheological behaviors indicated that the addition of KC promoted the early unfolding and aggregation of MP at a relatively lower temperature, which was verified by the fluorescence denaturation mechanism results. Moreover, the addition of KC significantly promoted the heat-induced conformational transition of MP from α-helix companied with β-sheet and β-turn, which was due to the interaction between MP and KC accelerating the formation of MP gels during the heating process. Intermolecular forces results revealed that the aggregation of myosin head and cross-linking of myosin tail of MP added KC was enhanced by ionic bonds, hydrophobic interactions, and disulfide bonds, which facilitated the better gel performance. Our present results provided a comprehensive understanding of gelation mechanism of MP-KC mixed gels under low-salt condition, with implications for the practical application of KC in meat processing.

Synergistic compatibilization effect on phase morphology evolution and properties of poly(ether-block-amide)/ethylene-vinyl acetate blends

We investigate the synergistic effect of ethylene-vinyl acetate grafted maleic anhydride (EVA-g-MAH) and styrene-ethylene-butene-styrene grafted maleic anhydride (SEBS-g-MAH) compatibilizers on the phase morphology evolution, thermal and mechanical properties of polyether-block-amide/ethylene-vinyl acetate (PEBA/EVA) blends. Phase morphology of PEBA/EVA blends shows that the size of dispersed phase decreases in the presence of either EVA-g-MAH or SEBS-g-MAH compatibilizer. The simultaneous use of these two compatibilizers further reduces the dispersed phase size, indicating the synergistic effect of compatibilization. Thermal behavior analysis of PEBA/EVA blends reveals that the crystallization temperature (Tc), the enthalpy of fusion (ΔHm) and the crystallinity of PEBA decrease, the melting point (Tm) remains relatively unchanged with increasing EVA content. Tc and ΔHm increase for PEBA/EVA blends in the presence of compatibilizer. The tensile strength and elongation at break of PEBA/EVA blends decrease first and then increase with increasing EVA content. The simultaneous addition of EVA-g-MAH and SEBS-g-MAH compatibilizers is efficient to significantly improve the mechanical properties of PEBA/EVA blends. For instance, the tensile strength increases from 5.7 to 11.4 MPa, and the elongation at break increases from 73.5% to 600.9% for PEBA/EVA (50/50) blend in the presence of dual compatibilizers compared to the uncompatibilized blend. Dynamic mechanical analysis and rheological behaviors demonstrate that the modulus and complex viscosity are higher in PEBA/EVA blends by the simultaneous addition of two compatibilizers compared with the blends in the presence of one compatibilizer, suggesting the enhancement of interfacial interactions between PEBA and EVA, and further confirming the synergistic effect of compatibilization.

Microwave‐modified xanthan gum: Alterations in steady and dynamic rheological behaviors

AbstractIn this study, microwave modification of xanthan gum (XG) powder under various power and time settings was aimed at achieving diversity for different applications requiring different flow behaviors. Microwave treatment for 6 min at various powers showed no noticeable effect on the properties of XG. The apparent viscosity, consistency coefficient and viscoelastic properties (G′–G″) increased as powders were subjected to microwave treatment for up to 8 min and the highest increase was observed in XGs with 720 W application. The increasing power to 1200 W resulted in a decrease in consistency at 8 min. At all levels of power, a prolonged microwave treatment (10 min) resulted in the degradation of the molecules, leading to a decrease in the mentioned rheological properties of XG. The values for intercepts (K′ and K″) began to increase at 960 W‐6 min, with the largest increase occurring at 720 W‐8 min. Fourier transform infrared (FTIR) analysis revealed that the primary structure and repeated units were not negatively impacted by the use of microwave treatment. Therefore, with adjustable modification, microwaves may be employed to produce xanthan gum with a high economic value that is suitable for a variety of applications, while maintaining the gum's color properties.Practical applicationsOur research demonstrated that the use of microwave technology as a non‐thermal physical process to modify xanthan gum powder without dissolving it in water is a highly effective technique. This approach enables the flow characteristics of xanthan gum to be conveniently modified, regardless of its concentration, and increases its economic value by diversifying its techno‐functional properties. The increase in apparent viscosity and viscoelastic properties by increasing the interaction of polymer molecules or the adaptation of xanthan gum to different purposes by polymer degradation can be adjusted depending on the power and time of the microwave.

Rheological and radioactive decontamination properties of ethyl cellulose sols in green solvents at a temperature below 0 °C.

Strippable film decontamination has been considered one of the best prospects for radioactive surface decontamination due to its high decontamination effect and less secondary pollution. However, research into strippable films has until now focused on radioactive decontamination at room temperature. Therefore, it is vital to seek a suitable degradable material for preparing strippable films in removing contaminants in an extremely cold region, as it will face the problem of the freezing of the detergent. Ethyl cellulose (EC) is a kind of degradable biopolymer which is easily dissolved in volatile green organic solvents to form a sol below 0 °C which is advantageous for forming a film. Therefore, it would be the best choice for preparing a strippable film detergent. In this study, EC sols were obtained by placing EC powder into the green solvents anhydrous ethanol and ethyl acetate. The steady and dynamic rheological behavior of EC sols was investigated with a rotary rheometer with the temperature ranging from -10 °C to 0 °C to disclose their spraying performance. Moreover, the radioactive decontamination effect of EC sols and the mechanism were also investigated. The results showed that the EC sols were pseudoplastic fluids which obeyed the Ostwald-de Waele power law below 0 °C. Furthermore, the viscosity of EC sols could be reduced by stirring, which is convenient for large-area spraying during decontamination below 0 °C. At -10 °C, the comprehensive decontamination rates of all plates were over 85%. Therefore, EC sols could be used as a basic material for strippable film decontamination below 0 °C.

Synergistic functionality of transglutaminase and protease on modulating texture of pea protein based yogurt alternative: From rheological and tribological characterizations to sensory perception

Although the general mechanism of transglutaminase (TGase) and protease on texturizing protein gels has been known, their synergistic functionalities on modulating the textural and sensory attributes of pea protein based yogurt alternative (PPBYA) are still not clear. In this work, 9 PPBYA gels treated by the mentioned enzymes were manufactured to investigate their texturizing functionality. By treating PPBYA milk (emulsion) with TGase (0.47 U/g protein), the resultant PPBYA gel had an increased strain resilience by ∼1.8-fold compared to blank control (γ-LVE); however, the brittleness of the gel was also increased by ∼4.8-fold (Index-FT). Co-application of TGase (0.47 U/g protein) and protease (0.1 U/g protein) seemed not to cause changes in some conventional rheological parameters as compared to the PPBYA control, for instance the referred parameters were strain resistance, hardness, and brittleness. However, the impact of mentioned synergistic enzymatic treatment on PPBYA gel may be clearly demonstrated by nonlinear rheological parameters; the Pipkin diagrams showed that co-application of TGase and protease resulted in PPBYA gels with higher homogeneity of dynamic rheology behavior in response to large deformation. Overall, the enzymatic treatments were able to result in significant changes in structure, rheology, tribology, and sensory attributes. Sensory textural attributes e.g. smoothness-in-mouth and astringency were both correlated with flow strain, whereas lubrication transition behavior was correlated with astringency. The obtained results demonstrated that the difference of textural characteristics between PPBYA and yogurt can be reduced by the co-application of TGase and protease at an optimized ratio and dosage rate.

Investigation on the Dynamic Rheological Behavior of the Highly Elastic Organohydrogel

Investigation on the Dynamic Rheological Behavior of the Highly Elastic Organohydrogel

The Effect of Multistage Refinement on the Bio-Physico-Chemical Properties and Gel-Forming Ability of Fish Protein Isolates from Mackerel (Rastrelliger kanagurta).

The objective of this research was to improve the protein extraction processes of Rastrelliger kanagurta (Indian mackerel) to generate protein isolate with enhanced bio-physico-chemical properties and gel-forming ability. To achieve this, two novel approaches were designed that utilized an additional alkaline separation step and were compared to a conventional process: acid solubilization → alkaline solubilization → pI and acid solubilization → pI → alkaline solubilization. The novel extraction designs resulted in a lower lipid content, lipid oxidation, and TCA-soluble peptides, as well as improving the color and sensory features of the refined proteins, which corresponded to the lowest total heme pigments (p < 0.05). Furthermore, the protein isolate recovered with the modified processes showed significant changes in biochemical properties (decreases in Ca2+-ATPase activity/reactive sulfhydryl content and an increase in surface hydrophobicity) and dynamic rheological behavior. As a result, by altering the extraction procedure it was possible to obtain improved gel characteristics such as gel strength, color, expelled moisture, and improved gel microstructure. Moreover, this study demonstrated that the gel network was partly stabilized by disulfide bonds, according to SDS-PAGE. Overall, this study demonstrates that by optimizing protein extraction procedures a considerable improvement in quality can be achieved and that an additional alkaline extraction after isoelectric point precipitation results in the optimized gel-forming ability of mackerel proteins.

Comparative effects of micro vs. submicron emulsions on textural properties of myofibrillar protein composite gels

This study aimed to investigate the impact of emulsion particle size (micro vs. submicron) on the physicochemical and rheological properties of myofibrillar protein (MP) gels. MP-based oil-in-water micro-emulsions (∼2,091 nm) and submicron-emulsions (∼522 nm) were compared with each other and with lecithin-stabilized micro-emulsions (∼1,330 nm) and submicron-emulsions (∼543 nm). Emulsion particle size, ζ-potential, and morphological properties using transmission and confocal microscopies) were measured. Additionally, dynamic rheological behavior, mechanical strength, water-holding capacity (WHC), water mobility, and protein secondary structures of the emulsion gels containing 2.5% protein and 5% oil) were analyzed. The results showed that emulsion droplet size had no significant effect on gel strength and storage modulus, regardless of the surfactants used. However, the MP-coated submicron-emulsion exhibited a greater improvement in gel WHC (p < 0.05) compared to its micro-emulsion counterpart. Overall, emulsion gels displayed greater strength than oil-free control gels. MP-based emulsions proved more effective than lecithin-stabilized emulsions in modifying the gelling properties, primarily due to the formation of a visible interfacial protein film that prevented oil droplet aggregation. Based on these findings, protein-based emulsions were preferred over lecithin-based emulsions, with MP submicron-emulsions offering the advantage of enhanced moisture retention in cooked MP gels.

Suitability of Flours and Gels From Crops Affected by Climate Change in Honduras: Crystallinity, Thermal, Dynamic Rheological and Textural Behavior

In Honduras, various tubers, roots, and cereals are cultivated as starchy crops. The current climatic crisis affects these crops' productivity, leading to an increase in agricultural residue, resulting in food insecurity. Agricultural residues from these crops have the potential to be processed, marketed, and contribute to the regular diets of consumers. In addition to serving as an essential source of carbohydrates, these crops provide several nutrients and health benefits. This study aimed to characterize the flours and gels of Colocasia esculenta (taro), Manihot esculenta (cassava), and Zea mays (maize) in terms of crystallinity and thermal parameters for flours and dynamic rheological, firmness, and color behavior of gels. The relative crystallinity of the selected crop samples is reported. There were considerable variations in the thermal parameters among the three cultivars. All flour suspensions at different concentrations led to gels with solid-like behavior (G′ &gt; G″) at 25 °C, with the highest consistency for maize gels at the same concentration. The Avrami mathematical model was effectively applied to analyze the firmness kinetics of taro, cassava, and maize gels stored at 4 °C. All properties characterized suggest that flours from these crops affected by climate change would be suitable ingredients in different food formulations. Keywords: Food security; Climate change; Crystallinity; Thermal properties; Gel rheology.

Synergistic effect of compound rubber and SiO2 nanoparticles on low-temperature toughening and balanced stiffness-toughness of random copolymer polypropylene nanocomposites

Random copolymer polypropylene (PPR)/rubber/silica nanocomposites with excellent low-temperature toughness and balanced rigidity-toughness were prepared by using compound rubber composed of ethylene propylene rubber (EPR) and isoprene rubber (IR). Effects of compound rubber on reinforcement and toughening of PPR were systematically investigated through mechanical properties, dynamic mechanical behavior, morphologies and rheological behavior. Mechanical results showed compound rubber had higher efficiency in both reinforcement and toughening than single rubber. According to morphological analysis and rheological results, it was found that the EPR/IR compound rubber had a better distribution in PPR matrix due to the close viscosity to PPR matrix and maintained the characteristics of silica distribution at the interface between rubber and matrix. Dynamic mechanical results revealed PPR/compound rubber blends showed larger area of loss factor. Consequently, the better toughening effect and achieving good rigidity-toughness balance of compound rubber in PPR nanocomposites was ascribed to the synergistic effect of compound rubber and SiO2 nanoparticles, which results in smaller particle spacing and larger loss factor area of rubber phase in nanocomposites without changing preferential loading of nanoparticles at polymeric interface.

Influence of chemical modifications on dynamic rheological behaviour, thermal techno-functionalities, morpho-structural characteristics and prebiotic activity of banana starches

Banana starch is explored for its use in food and pharmaceutical applications. In this study, in order to improve the techno-functional properties of native banana starch (NS), different chemical modifications namely acid thinning (AT), oxidation (OX), sodium-trimetaphosphate method (STMP), cross linking phosphorylation (CLP), hydroxypropylation (HYP) were employed. Among the modified starches, amylose content was higher in CLP starch and the least was observed in AT. Resistant starch (RS) of HYP (65.38 %) and CLP starches (62.76 %) were significantly higher than other modified starches. Lesser amylose, higher water solubility and lower swelling of AT starch resulted in inferior paste clarity and inability to make a firm gel. Non-Newtonian behaviour of starch gels were observed from static viscosity observations. The dynamic rheological behaviour of the starch gels affirmed the higher gel strength of STMP (0.46) and CLP (0.56) starches. Imperfection and exo-corrosion in starch morphology was observed through SEM and influence of chemicals on the starch structure was elucidated through FTIR and XRD analyses. Except AT starch, modified starches with higher RS resulted in lowering glycemic index (57–69 %). STMP starches recorded highest prebiotic activity score of 0.88. Chemical modifications enable to enhance the functionalities of banana starch and offers potential industrial uses.

Application of a novel surface-active green demulsifier for demulsification of field crude oil emulsion

ABSTRACT In the petroleum industry, generally surface-active chemicals are used to break the crude oil emulsion. But these chemicals are toxic and less biodegradable, which can cause environmental pollution. Therefore, in this paper, eco-friendly demulsifiers (LA1 and LA2) were synthesized by esterification based on fatty acid having low cost and biodegradability. It was characterized by FTIR, NMR, DLS analysis, and TGA. The synthesized demulsifiers were comprehensively characterized by evaluating the micellization parameters such as CMC, Amin, etc. The demulsification performance of synthesized demulsifiers was studied through the static bottle test method. The effect of temperature, demulsifier concentration, pH, settling time, and water content on the demulsification efficiency was thoroughly examined. The result shows that both demulsifiers have excellent surface-active properties. The demulsification mechanism of demulsifiers was elucidated by measuring dynamic interfacial tension and rheological behavior. The bottle test results indicated that the LA1 demulsifier gave 100% separation efficiency at 70°C in 90 min, which performed better than the commercial demulsifier. The present study will give a new route for the eco-friendly and cost-effective treatment of asphaltene-based crude oil emulsion.

Polyglycerol‐modified polyvinyl alcohol with improved stability during thermoplastic processing

AbstractPolyvinyl alcohol (PVA), which can be synthesized via a non‐petroleum route, is a multi‐hydroxyl polymer with good comprehensive properties and environmental friendliness. However, poor thermal processability impedes its development. Herein, polyglycerol (PGL) was firstly adopted to substitute parts of glycerin as one of the plasticizers to prepare modified PVA with greater thermal stability. FTIR spectra revealed the strong hydrogen‐bonding interaction between PGL and PVA which would be destroyed during heating, indicating that PGL was suitable for plasticizing PVA. The introduction of PGL weakened the volatilization of plasticizer as T5% of modified PVA was remarkably improved from 174.7°C to 245.8°C with the addition of 20 wt% PGL. The effects of PGL content on the crystallization behaviors, melting characteristics, dynamic rheological behaviors, and mechanical properties of PVA were investigated. It revealed that the substitution of PGL for glycerin did not influence the final crystalline structure and crystallinity of PVA, but shortened the crystallization time, improved the tensile strength and decreased the melt index owing to the entanglement between PVA and PGL molecules. Dynamic oscillatory rheological measurement showed that the lowest complex viscosity was obtained when 10 wt% PGL was incorporated, which is beneficial for practical processing and film forming. Under proper processing conditions, the production and application of this hot‐blown PVA film were realized at an experimental scale. This work sheds light on the exploitation of new plasticizers with high plasticizing efficiency and thermal stability during processing of PVA.

Reinforcement of polyamide 6 with carbon fiber surface modified by a polar cross-linked network interfacial phase

Carbon fiber-reinforced polyamide 6 (CF/PA6) composite materials have low relative density, high specific strength, and high specific modulus. However, the surface of the CF is smooth and chemically inert, resulting in poor interfacial adhesion in CF/PA6 composites, thereby limiting its application range. Herein, an epoxy resin emulsifier with hydrophilic ends and lipophilic middle was synthesized. After sizing, the surface chemical activity and roughness of the CF were higher. The tensile strength of the prepared CF/PA6 composite material was increased by 38.6%, and the impact strength was increased by 26.4%. By testing the tensile strength and wettability of the CF, as well as the dynamic thermomechanical properties and rheological behavior of the CF/PA6 composites, the influence of the sizing agent on the properties of CF and the interfacial properties of CF/PA6 composites was evaluated, and its mechanism of action is discussed herein.

Effects of Abelmoschus manihot gum content, heating temperature and salt ions on the texture and rheology properties of konjac gum/Abelmoschus manihot gum composite gel

To improve the gelling property of konjac gum (KGM) and enhance the application value of Abelmoschus manihot (L.) medic gum (AMG), a novel type of gel was prepared using KGM and AMG in this study. The effects of AMG content, heating temperature and salt ions on the characteristics of KGM/AMG composite gels were studied by Fourier transform infrared spectroscopy (FTIR), zeta potential, texture analysis and dynamic rheological behavior analysis. The results indicated that the AMG content, heating temperature and salt ions could affect the gel strength of KGM/AMG composite gels. Hardness, springiness, resilience, G′, G* and η* of KGM/AMG composite gels increased when AMG content increased from 0 to 2.0 %, but they decreased when AMG increased from 2.0 % to 3.5 %. High-temperature treatment significantly enhanced the texture and rheological properties of KGM/AMG composite gels. The addition of salt ions reduced the zeta potential absolute value and weakened the texture and rheological properties of KGM/AMG composite gels. Furthermore, the KGM/AMG composite gels could be classified as non-covalent gels. The non-covalent linkages included hydrogen bonding and electrostatic interactions. These findings would help understand the properties and formation mechanism of KGM/AMG composite gels and help improve the application value of KGM and AMG.

Graphene quantum dot doped viscoelastic lyotropic liquid crystal nanocolloids for antibacterial applications.

Graphene quantum dots (GQDs) are prepared and characterized via X-ray diffraction (XRD), UV-Visible spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL). GQDs are doped (5 mg and 10 mg) in the lyotropic liquid crystalline (LLC) lamellar and hexagonal phases to prepare GQD/LLC nanocolloids. Polarizing optical microscopy and X-ray diffraction measurement reveals that GQDs do not affect the lamellar and hexagonal LLC structures and may organize on their interface. Pure LLC phases and nanocolloids are studied for steady and dynamic rheological behavior. LLC phases and GQD/LLC nanocolloids possess shear thinning and frequency dependent liquid viscoelastic behavior. A complex moduli study of LLCs and GQD/LLC nanocolloids is carried out which indicates the gel to viscous transition in LLCs and GQD/LLC nanocolloids as a function of frequency. LLC phases and GQD/LLC nanocolloids are tested for antibacterial activity against Listeria ivanovii. The effect of surfactant concentration, LLC phase geometry and GQD concentration has been studied and discussed. A probable mechanism for the strong antimicrobial activity of LLCs and GQD/LLC nanocolloids is presented considering intermolecular interactions. The viscoelastic behavior and strong antibacterial activity (inhibition zone 49.2 mm) of LLCs and GQD/LLC nanocolloids make them valuable candidates for lubrication, cleaning, cosmetics and pharmaceutical applications.

Doping of γ -Fe3O4 magnetic nanoparticles in Pluronic F127/ DMF LLCs phases to tune the structural transitions and rheological behavior

ABSTRACT A new rapid microwave-assisted approach has been employed to prepare the γ-Fe3O4 magnetic nanoparticles (γ-Fe3O4 MNPs). The formation of spherical γ-Fe3O4 MNPs with an average size of 45 nm and bandgap of 2.3 eV is confirmed by FESEM and UV–Visible spectroscopy. γ-Fe3O4 is doped (0.01 wt% and 0.02 wt%) in the lyotropic liquid crystalline (LLC) lamellar phases of Pluronic F127/N,N dimethylformamide (DMF) to prepare the LLC nanocolloids. Polarizing optical microscopy measurement reveals that γ-Fe3O4 doping does not affect the lamellar LLC structures except 0.02 wt% at 10:90 wt%:wt% system where lamellar to nematic LLC phase transition is observed. Pure LLC phases and nanocolloids are studied for steady and dynamic rheological behavior. LLC phases and LLC nanocolloids possess shear thinning and solid viscoelastic behavior. A complex moduli study of LLCs and LLC nanocolloids is done which indicates the highly elastic strength-based lamellar and nematic phases. Shear-thinning and highly viscoelastic nature of LLCs and LLC nanocolloids have future applications in lubrication, cleaning, cosmetics, and pharmaceutical.