Influence of carboxymethylation on the gelling capacity,rheological properties,and antioxidant activity of feruloylated arabinoxylans from different sources

Feruloylated arabinoxylans (FAX) are gelling polysaccharides presenting antioxidant activity (AC) and potential application as delivery systems. The influence of carboxymethylation on the gelling capacity, rheological properties, and AC of FAX from wheat flour (FAX1) and maize distillers grains (FAX2) was analyzed. The degree of substitution of carboxymethyl groups was 0.27 and 1.77 for carboxymethylated FAX1 (CFAX1) and FAX2 (CFAX2), which presented a change in M _n from 446 to 362 kDa and from 120 to 180 kDa, and a loss in FA content from 1.05 to traces and from 10.13 to 0.12, respectively, after carboxymethylation. G′ value at the end of rheological tests for FAX1 (71 Pa) and FAX2 (726 Pa) was higher than the corresponding G″ value. In contrast, G″ value for CFAX1 (0.35 Pa) and CFAX2 (0.03 Pa) was higher than the respective G′ value, indicating that they do no form gels. The AC increased in CFAX1 in relation to FAX1 from 4.49 to 8.30 mmol Trolox equivalent antioxidant capacity (TEAC) kg⁻¹, respectively, while it decreased in CFAX2 with regard to FAX2 from 11.31 to 9.43 mmol TEAC kg⁻¹, respectively. Carboxymethylation could be a path to design FAX derivatives offering alternative potential applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48325.     

Enzymatic glycerolysis and transesterification of vegetable oil for enhanced production of feruloylated glycerols

Novel functional groups can be introduced into vegetable oils using enzymes, resulting in value-added products. The transesterification kinetics of ethyl ferulate with MAG, DAG, and TAG were examined. Transesterification was catalyzed by immobilized Candida antarctica lipase B in solventless batch and packed-bed reactors. Initial reaction rates with TAG were slightly sensitive to water activity, whereas rates with MAG and DAG were water activity independent. Transesterification was also three-to sixfold faster with MAG and DAG. These observations indicate that the reaction is rate limited by the acyl acceptor, and that oils with free hydroxyl groups are preferred acyl acceptors in comparison with TAG, which must undergo partial hydrolysis before becoming reactive.     

有机相酶促合成阿魏酸糖酯

利用酶促方法合成阿魏酸葡糖酯,对酶和有机溶剂进行了比较和筛选,并对影响阿魏酸葡糖酯产率的因素(酶量、反应时间、反应温度、底物比)进行了研究。结果表明,葡萄糖和阿魏酸乙烯酯(摩尔比4∶1)分别加入到体积比2∶1的无水吡啶和叔丁醇中,20 g/L Novozym 435脂肪酶,在220 r/min的空气振荡器中50℃反应72 h,产率能达到80.9%。     

Research on the rheological and flow characteristics of a supramolecular gel in fractures

Loss circulation is one of the major concerns in drilling and well construction. An effective way to control drilling fluid loss and strengthen the wellbore is to plug fractures and holes with loss circulation materials. In this work, a hydrophobic association supramolecular hydrogel GP-A developed by n-dodecylacrylamide, methacrylamide and 2-acrylamide-2-methylpropylsulfonic acid was proposed as a potential lost circulation material for malignant drilling fluid loss. The results show that the initial decomposition temperature of GP-A was 172°C, and the flow characteristics conform to the Herschel-Bulkley model with yield stress. Microstructural analysis shows that GP-A gel with a 3D spatial network, and hydrogen bonds between branched chains form a dynamically recoverable structure. Based on POLYFLOW, the Phan Thien–Tanner model with viscoelastic parameters was used to simulate the viscoelastic flow characteristics of the fluid in fractures. The higher the concentration is, the greater K, and the higher the inlet driving pressure, while the nonlinear relationship between the driving pressure and the gel slug length is evident. The introduction of supramolecular gel polymer as a loss circulation material is an innovative research topic, which provides a new method to simulate the flow of polymer fluid in fractures.     

Molecular and mechanical properties of hydroxypropyl methylcellulose solutions during the sol:gel transition

This paper outlines the latest findings in our work to understand the fundamental interactions within hydrated hydroxypropyl methylcellulose (HPMC) at elevated temperature. ATR-FTIR spectroscopy was used to relate molecular interactions to the rheological changes in aqueous HPMC solutions during the sol:gel transition. Sol:gel transition temperatures determined using ATR-FTIR spectroscopy, oscillatory rheology and turbidimetry were in agreement to within experimental error. ATR-FTIR spectroscopy provided direct evidence of increased hydrophobic interactions within the gel network through a shift to lower wavenumber of ν_as(CH) vibrations observed during the gelation process. In addition, the FTIR spectra provide evidence that the structure of the polymer network is different in the thermo-formed gel, to that which exists in viscous solution. Both the rheological and ATR-FTIR data confirmed the supposition that thermal gelation is a two stage process. The first stage has been attributed to the disruption of native cellulosic bundles and this is supported by the changes in both the storage modulus and intensity of the ν(CO) band at low temperatures. The second stage corresponded to phase separation and gelation resulting from increased hydrophobic interactions between polymer chains at elevated temperatures.     

Effects of functionality and temperature on gel points in random polymerisation

First, the relationship between gel point and average functionality for an RA₂+R′B_f type polymerisation has been investigated by measuring the product of extents of reaction at gelation (α_c) for sebacoyl chloride (SC)/polyoxyproplyene (POP)diol/POP triol mixtures reacting at various initial dilutions in diglyme as solvent at 60°C. Intramolecular reaction always delays gelation and a generalisation of the Ahmad-Stepto gel point expression has been used to interpret the gelation data in terms of the ring-forming parameter λ′_ab. From the variation of λ′_ab with initial dilution, values of b, the effective bond length of the chain forming the smallest ring structure, have been derived. It is found that b decreases with average polyol functionality (f_w). This decrease apparently compensates for the increase in λ′_ab with f_w, so that ring formation is less sensitive to functionality than may have been expected. It is found that the Ahmad-Stepto expression does not predict a consistent relationship between λ′_ab, f_w and the gel dilution of reactive groups. Second, the effect of temperature on the gel point has been studied by measuring α_c for SC/POP triol mixtures reacting at various initial dilutions in diglyme as solvent at 27° C, 40° C and 60° C. At a given temperature, b decreases as triol molar mass increases, indicating that the POP residue of the chain forming the smallest ring structure is more flexible than the SC residue. This result is in keeping with those from previous investigations,^1,2 For a given triol, α_c decreases as temperature increases, indicating an increase in chain stiffness with temperature. Values of d In <r²>/dT are derived and found to be larger than those for linear chains.     

Thermal and rheological properties of poly(vinyl alcohol) gel with boric acid as a crosslinking agent

The gel of poly(vinyl alcohol) polymer with boric acid, added as a crosslinking agent, was made with a mixture of dimethyl sulfoxide and water. The thermal and dynamic modulus properties of poly(vinyl alcohol) gel were measured by a differential scanning calorimeter and a dynamic mechanical thermoanalyst. Results show that an increase of poly(vinyl alcohol) polymer or boric acid content to the gel makes an increasing of gel to sol transition temperature, endothermic enthalpy, and dynamic modulus. The maximum value of gel to sol transition temperature, endothermic enthalpy, and dynamic modulus happened at the volume ratio of 6 : 4 of dimethyl sulfoxide to water, which is independent on the poly(vinyl alcohol) and the boric acid content. According to the modified Eldridge–Ferry theory for thermoreversible gel, it is found that both the gel to sol transition temperature and the endothermic enthalpy versus poly(vinyl alcohol) content could be superimposed with respect to the boric acid content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2219–2226, 1999     

Identification of rheological and structural characteristics of foamable poly(ethylene terephthalate) by reactive extrusion

The reactivity and efficiency of five low molecular weight multifunctional anhydride and epoxy compounds as chemical modifiers of a bottle grade poly(ethylene terephthalate) (PET) resin were evaluated by reactive extrusion under controlled conditions. The two dianhydrides and the three epoxy compounds were used at concentrations based on stoichiometry derived from the measured carboxyl and hydroxyl end group contents of the base resin. Measures of melt viscosity, melt strength, intrinsic viscosity and carboxyl group content were used as criteria of the extent of the modification. Correlations of die pressure with extrudate swell during extrusion, and melt flow index (MFI) with melt strength by off‐line testing of the extrudates permitted the ranking of the modifiers according to their chain‐extending/branching efficiency. For some systems molecular weight increases (related to die pressure/MFI/intrinsic viscosity) accompanied by broadening of the molecular weight distribution (related to die swell/melt strength) were considered excessive. Extrusion foaming experiments with one particular dianhydride modifier that increased the intrinsic viscosity of the resin from 0.71 to 0.9 dl g^?1 indicate that production of low‐density foams by a process involving one‐step reactive modification/gas injection foaming is feasible, at conditions not significantly different from those employed in the simple reactive modification of the PET resin. The rheological and structural parameters determined in this work may be used as criteria to specify PET foamable compositions in terms of types and concentrations of modifiers. Copyright © 2004 Society of Chemical Industry     

The rheological and structural behavior of silylcellulosics derivatives

The trimethylsilylcellulose (TMSC) samples were characterized in solution by osmometry, viscometry, and gel permeation chromatography. The Mark-Houwink-Sakurada (M-H-S) equation coefficients were determined in chloroform, 1,1,1-trichloroethane, and o-xylene, in all cases the exponent “a” being higher than unit, this indicating a great stiffness of the macromolecules in solution. Also, the temperature dependence of the limiting viscosity number and M-H-S coefficients respectively for TMSC in o-xylene were studied. The exponent from M-H-S equation is also higher than unit, and increases linearly with the temperature. The GPC studies indicates a relative high polydispersity of the studied samples; the polydispersity index being situated between 2 and 3. The change of the crystalline structure as the result of silylation reaction was evidenced, the crystallinity of silyl derivatives depending on the substitution degree (DS), and the molecular weight. The viscous flow parameters for dilute solutions of trimethylsilylcellulose in o-xylene were determined in the temperature range 30–70°C. The temperature dependence of the dynamic viscosity of the solutions obeys an Arrhenius-type equation in which the apparent activation energy is linearly dependent on both the solution's concentration and molecular weight. For preexponential factor no significant dependence on concentration and molecular weight was found. This behavior was attributed to the very great stiffness of the macromolecular chains. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2277–2285, 2001     

Preparation of gelatin fiber by gel spinning and its mechanical properties

A gel‐spinning process was used in an attempt to prepare a gelatin fiber with a high level of drawability. A gel fiber prepared by extrusion of 15 wt % gelatin in dimethyl sulfoxide into methanol at ?20°C was drawn to sixteen times the original length. After extraction of the dispersion medium, the mechanical strength of the fiber increased markedly with the draw ratio, and the fiber exhibited a tensile strength of 146 MPa and a Young's modulus of 2.3 GPa when drawn to the maximum. A gelatin fiber with greater mechanical strength was obtained when ethylene glycol was used as the spinning solvent. The X‐ray diffraction profile indicated the formation of triple‐helical structures and their lateral association, which is responsible for the mechanical strength of the fiber. Heat‐treatment improved the water‐resistance of the prepared fiber. γ‐Irradiation and treatment with glutaraldehyde improved the mechanical strength of the fiber. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Viscoelastic sol–gel state of the chitosan and alginate solution mixture

The rheological behavior of chitosan/alginate solutions was investigated in relation to gelation and polyelectrolyte complex (PEC) formation. Before mixing, the chitosan and the alginate solutions were both homogeneous fluids. However, heterogeneity developed after mixing, accompanied by a serious increase of viscosity. To determine the sol–gel state of the solutions, the viscoelastic variables, such as the dynamic storage modulus (G′) and loss modulus (G″), the loss tangent, and the viscoelastic exponents for G′ and G″, were obtained. Depending on the concentration, the chitosan/alginate solutions revealed unexpected rheological behavior. At a polymer concentration of 1.0 wt %, the chitosan/alginate solution was in a viscoelastic gel state, whereas, at higher concentrations, viscoelastic sol properties were dominant. A viscoelastic gel state for the chitosan/alginate solution was induced based on the weak formation of fiber‐shaped precipitates of a PEC at a low polymer concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1408–1414, 2007     

一种耐温耐盐类凝胶调剖剂封堵性能的研究

高温高盐复杂油藏由于地层温度高,矿化度高,一般堵水剂的可泵时间和长期稳定性达不到使用要求。在实验室研究了一种适用于高温高矿化度复杂油藏深部调剖的凝胶调驱体系,该体系优于传统的凝胶体系,在高温高盐的复杂地层环境下达到了延缓交联和提高凝胶热稳定性的目的。     

Dynamic rheological behavior and microcrystalline structure of dioctyl phthalate plasticized poly(vinyl chloride)

The dynamic rheological behavior of poly(vinyl chloride) (PVC)/dioctyl phthalate (DOP) systems were studied as a function of DOP content and melting temperature. The dynamic rheological behavior of the PVC/DOP systems was found to be remarkably affected by the DOP content. The observed curves of storage modulus (G′) versus frequency were well fitted to an empirical equation (G′ = G′₀ + Kωⁿ, where G′₀ is the low‐frequency yield value of the storage modulus, the exponent n is a dependent index of frequency, K is a constant coefficient, and ω is the angular frequency). The loss tangent and/or phase angle increased remarkably at a higher DOP content. There was an apparent critical DOP content transition where the dynamic rheological behavior of the PVC/DOP systems changed greatly. Scanning electron microscopy observations revealed the existence of a multiscale particle structure in the PVC/DOP systems. For the PVC/DOP (100/70) system, with increasing melting temperature, its dynamic rheological behavior showed an apparent mutation at about 190°C. Differential scanning calorimetry (DSC) analysis confirmed that the high elastic networks in the PVC/DOP systems were closely related to the microcrystalline structure of PVC. The transitions in the curves of the gelation degree and crystallinity versus the DOP content corresponded well to the DOP content transition in the dynamic rheological behavior. DOP could inhibit the secondary crystallite of PVC and almost had no effect on the primary crystallite of PVC. The coexistence of the microcrystalline structure of PVC and the plasticizer (DOP) resulted in high elastic networks in the PVC/DOP systems. The DSC results explained the DOP content transition and the temperature transition in the dynamic rheological behavior of the PVC/DOP systems well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

阿魏酸衍生物的应用及合成

综述了阿魏酸和阿魏酸衍生物在医药、化妆品、食品等方面的广泛应用及阿魏酸酯类、酰胺类、酮类、醚类等衍生物的合成研究进展。通过同传统的化学合成方法的比较说明了生物催化合成方法的优势。     

Influence of surfactant properties on thermal behavior and sol–gel transitions in surfactant‐HPMC mixtures

Four surfactants, namely, sodium n‐decyl sulfate (SDeS), sodium n‐hexadecyl sulfate (SHS), sodium n‐dodecyl sulfate (SDS), and Triton X‐100, were used as additives to study thermal behavior and sol–gel transformations in dilute aqueous hydroxypropyl methyl cellulose (HPMC)/surfactant mixtures using micro‐differential scanning calorimetry. The influence of anionic surfactant, SDS on the gelation varied with SDS concentration where the sol–gel transition started at a higher temperature. Shape of the thermograms changed from single mode to dual mode at the SDS concentration of 6 mM and higher. SDeS and SHS, however, resulted in “salt‐in” effect of a different magnitude during gelation. Triton X‐100, being a non‐ionic surfactant, showed a minor “salt‐out” effect on the thermo‐gelation process. On the basis of different thermal behavior of anionic and non‐ionic surfactant/HPMC systems, a mechanism is proposed explaining how the chemical structure and electro‐charge of the surfactants affect the polymer/surfactant binding and polymer/polymer aggregation because of hydrophobic interaction during the sol–gel transition. © 2009 Wiley Periodicals, Inc. Journal of Applied Polymer Science, 2009     

阿魏酸的合成及抗氧化性能的研究

以香草醛和丙二酸为原料、乙酸铵为催化剂、DMF为溶剂、苯为带水剂,合成了阿魏酸。在V（苯）∶V（DMF）=2∶1、乙酸铵用量为6%（以香草醛质量计）、n（香草醛）∶n（丙二酸）=1∶1.4、反应时间为4h的优化条件下,阿魏酸产率达到71.02%。阿魏酸的抗氧化性实验结果表明,阿魏酸对食用油脂有一定的抗氧化能力,其在油脂中的抗氧化能力优于维生素E。     

Chemorheology and thermomechanical characteristics of benzoxazine‐urethane copolymers

In this research, processability and some important thermomechanical properties of polybenzoxazine (BA‐a) modified with a highly flexible urethane elastomer (PU) are discussed. This copolymer has been reported to show synergy in its glass transition temperature and some mechanical properties thus provides a fascinating group of high temperature polymers with enhanced flexibility. The results reveal that a processing window of the BA‐a/PU mixtures is widened with the increasing urethane prepolymer fraction, that is, the liquefying temperature is lowered and the gel point shifted to higher temperature with the amount of the PU. Synergism in glass transition temperature (T_g) of this copolymer was clearly confirmed, i.e., T_g's of the BA‐a/PU alloys were significantly greater than those of the parent resins, i.e., BA‐a (T_g = 166°C) and PU (T_g = ? 70°C). In addition, flexural modulus was found to systemically decrease from 5.4 GPa of the neat polybenzoxazine to 2.1 GPa at 40% by weight of the PU. Flexural strength of the alloys also shows a synergistic behavior at the BA‐a/PU ratio of 90/10. Coefficient of thermal expansion of the polymer alloys were also found to show a minimum value at BA‐a/PU = 90/10. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

电场对黄孢原毛平革菌生长、细胞通透性及其胞外酶反应的影响

研究了交、直流电场对黄孢原毛平革菌Phanerochaete chrysosporuim的生长、细胞通透性及其所分泌的漆酶、木质素过氧化物酶及锰型过氧化物酶活力的影响. 结果表明,施加50 Hz, 50 mA交流电可显著地促进Phanerochaete chrysosporium的生长,经过10 d的培养,其干菌重为对照组的1.72倍;施加交、直流电都能够使细胞的通透性增强;施加交、直流电场在短时间内可显著提高3种胞外酶的活力,而时间过长则导致活力降低,电流强度为10 mA时的适宜加电时间为10 h.     

甘油预处理蔗渣的木质素分离提取及结构表征

以甘油分别对甘蔗渣进行常压甘油自催化（AGO）预处理和常压甘油碱催化（al-AGO）预处理。利用酸沉法分别从预处理液中得到自催化甘油木质素（AGOL）和碱催化甘油木质素（al-AGOL）。利用单因素实验和正交实验得到最佳木质素提取工艺为转速8000r/min、离心时间15min、甘油混合液pH为3、甘油混合液浓度10%,在该条件下木质素AGOL和al-AGOL提取率分别达到72%和76%。采用扫描电镜（SEM）、元素分析、紫外光谱（UV）、凝胶色谱（GPC）、核磁共振¹H谱、热重分析以及抗氧化活性分析等技术手段对提取得到的木质素进行结构表征。结果表明：从甘蔗渣中提取的球磨甘蔗木质素（MBL）、AGOL和al-AGOL主要呈现出球形特征;AGOL和al-AGOL具有相似的活性特点,与MBL相比,AGOL和al-AGOL的分子量更小、分布更窄、均一性更好,热稳定性和抗氧化活性更高,有望成为重要的工业原料。