Co-reporter:Zhixiang Cai, Hongbin Zhang, Yue Wei, and Fengsong Cong
Biomacromolecules June 12, 2017 Volume 18(Issue 6) pp:1677-1677
Publication Date(Web):May 9, 2017
DOI:10.1021/acs.biomac.7b00424
Nanomaterials, including gold, silver, and magnetic nanoparticles, carbon, and mesoporous materials, possess unique physiochemical and biological properties, thus offering promising applications in biomedicine, such as in drug delivery, biosensing, molecular imaging, and therapy. Recent advances in nanotechnology have improved the features and properties of nanomaterials. However, these nanomaterials are potentially cytotoxic and demonstrate a lack of cell-specific function. Thus, they have been functionalized with various polymers, especially polysaccharides, to reduce toxicity and improve biocompatibility and stability under physiological conditions. In particular, nanomaterials have been widely functionalized with hyaluronan (HA) to enhance their distribution in specific cells and tissues. This review highlights the most recent advances on HA-functionalized nanomaterials for biotechnological and biomedical applications, as nanocarriers in drug delivery, contrast agents in molecular imaging, and diagnostic agents in cancer therapy. A critical evaluation of barriers affecting the use of HA-functionalized nanomaterials is also discussed, and insights into the outlook of the field are explored.
Co-reporter:Qiangwei Jin, Zhixiang Cai, Xiaobei Li, Madhav P. Yadav, Hongbin Zhang
Food Hydrocolloids 2017 Volume 64(Volume 64) pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.foodhyd.2016.11.002
•Bulk and air/liquid interfacial rheology are compared for high Mw branched gums.•Distinguished difference in viscoelasticity is found for the four gum solutions.•Two gums exhibit Newtonian fluid behavior forming viscos interfacial layers.•The others show shear thinning and thixotropy forming elastic interfacial layers.•Viscoelastic disparities reflect the influence of chain structures and conformation.A comparative study of both the bulk and air/liquid interfacial rheological responses was carried out by using four kinds of representative high molecular weight and highly branched polysaccharide emulsifiers, (a) corn fiber gum (CFG), (b) octenyl succinate anhydride-modified starch (OSA-s), (c) gum arabic (GA) and (d) soybean soluble polysaccharides (SSPS), spanning the concentration range of 1–15 wt%. We found that the bulk and interfacial rheological properties of their aqueous solutions were significantly different. While both CFG and OSA-s showed Newtonian flow behavior at higher concentrations, both GA and SSPS exhibited obviously shear thinning behavior or thixotropy even at a low concentration of 1 wt%. The time-dependent flow behavior for CFG, GA and SSPS reflected microstructural breakdown and rebuilding in solutions under shear, indicated that their proteinaceous portion was strongly bound to their polysaccharide part. This phenomenon was not observed for the almost protein-free OSA-s. The interfacial rheology responses showed that the layers formed by CFG and OSA-s were viscously predominant with faster formation kinetics while they were elastically predominant for GA and SSPS with slower formation kinetics. Interfacial viscoelastic responses of CFG and OSA-s were weaker than those of GA and SSPS. By comparison, the interfacial layer for OSA-s showed pure viscous responses whereas SSPS showed the highest elastic responses. These significant disparities in bulk and interfacial viscoelasticity of the four polysaccharide emulsifiers reflect the influence of different fine chain structures on the dissimilarity in the intermolecular associations and the architectures of the interfacial layers.Download high-res image (226KB)Download full-size image
Co-reporter:Zhixiang Cai, Hongbin Zhang
Food Hydrocolloids 2017 Volume 68(Volume 68) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.foodhyd.2016.09.014
•Recent progresses for curdlan and its derivatives have been summarized.•Gelation mechanism, chemical modification and functionalization are emphasized.•Chemical modifications are based on improving water solubility and bioactivity.•Curdlan and derivatives have shown promise for food and biomedical applications.Curdlan, a high molecular weight 1,3-β-D-glucan, is a natural biomaterial that has shown practical applications in food industry as a gelling agent and texture modifier. Simultaneously curdlan and chemically modified curdlan have also shown promise for biomedical applications. Although this exopolysaccharide possesses many advantages, such as unique gelling properties, mild conditions of processing, non-digestibility and non-cytotoxicity, the poor water solubility, the lack of specific attachment sites for anchorage-dependent cells and processability of curdlan are not totally satisfactory in different biomedical contexts. However, the multiple hydroxyl groups in repeating unit of curdlan can be used for chemical modification and functionalization in order to optimize its physicochemical and biological properties. A number of chemical modification approaches have been employed. This review outlines the recent progresses for curdlan and its derivatives, and identifies the new challenges in the gelation mechanism and chemical modifications.Download high-res image (226KB)Download full-size image
Co-reporter:Qiangwei Jin, Xiaobei Li, Zhixiang Cai, Fei Zhang, Madhav P. Yadav, Hongbin Zhang
Food Hydrocolloids 2017 Volume 70(Volume 70) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.foodhyd.2017.03.005
•The interfacial rheology of four high Mw branched polymer emulsifiers is compared.•Distinct dynamics and viscoelastic responses are revealed at O/W interface.•CFG adsorbed layer is predominantly viscous while OSA-s layer is pure viscous.•Elastic layers of GA and SSPS show shear-thinning and yielding behavior.•Interfacial dynamics and stability mechanisms are discussed.The interfacial rheology of polysaccharide adsorption layers of corn fiber gum (CFG), octenyl succinate anhydride-modified starch (OSA-s), gum arabic (GA) and soybean soluble polysaccharides (SSPS) at the oil/water interface and their emulsifying properties in oil-in-water (O/W) emulsions were compared. All four amphiphilic polymers contain different amounts of protein and they are of high molecular weight with highly branched structure. Based on the obtained interfacial shear rheological information such as a number of influence factor dependence (time, concentration, temperature, strain dependency) of interfacial dynamic moduli, creep or relaxation response, and steady/dynamic flow behavior of the interfacial layers, we found pronounced differences in the viscoelastic response of the four hybrid polyelectrolytes in shear flow. The adsorbed film of CFG is unique because it exhibits a predominantly viscous showing an apparently increasing storage modulus throughout the whole test without a saturated value whereas OSA-s produces a pure viscous layer at interface with a very low viscosity and quick forming kinetics; in contrast, both GA and SSPS form more rigid, solid–like layers. Models to describe the distinct interfacial dynamics and stabilizing mechanism of the four emulsifiers involving steric repulsion and electrostatic repulsion are proposed. Emulsifying properties of the four polymers are evaluated in terms of the emulsion physical properties, droplet-size distribution and optical microscopy observation. The effect of concentration and storage temperature on the interfacial viscoelastic response and the corresponding emulsion stability of each biopolymer are also compared.Download high-res image (241KB)Download full-size image
Co-reporter:Ding Kang, Zhixiang Cai, Yue Wei, Hongbin Zhang
Polymer 2017 Volume 128(Volume 128) pp:
Publication Date(Web):16 October 2017
DOI:10.1016/j.polymer.2017.09.035
•High-acyl gellan (HG) fractions obtained by ultrasound show very similar structures.•Molecular parameters of HG in DMSO were determined by using viscometry and GPC.•Conformation characteristics of HG were deduced by the unperturbed chain model.•HG macromolecules behave as semi-flexible chains in NaNO3/DMSO solution.High acyl gellan gums have been widely considered using as gelling biopolymers in colloidal products although their structure and chain conformation characteristics have been poorly understood. Five fractions of high acyl gellan gum (HG) with a molecular weight (Mw) ranging from 4.2 × 105 to 10.1 × 105, obtained by ultrasonic depolymerization from a native gellan, have been used to determine their molecular parameters and conformation characteristics in the good solvent of 50 mM NaNO3 dimethyl sulphoxide solution by using capillary viscometry and laser light scattering. The influence of ultrasound on the chemical structure and Mw of HG is investigated by GPC, FT-IR and NMR. The chain architectures of HG fractions are confirmed to be very similar to that of the native one without either deacylation or deglycerylation. Mark−Houwink equation and the relationship between radius of gyration (Rg) and Mw are established to be [η] = 1.16 × 10−3Mw0.67 (dl/g) and Rg = 2.06 × 10−2Mw0.61 (nm) for HG with a ratio of geometric to hydrodynamic radius (Rh) of 1.67 that is independent of the Mw of HG. In term of Zimm model, a relationship among these molecular parameters is founded as [η]≈4NARg2Rh/Mw. On the basis of unperturbed chain models, the conformation parameters of HG are also calculated and compared. The results indicate that HG macromolecules with an estimate of about 9 nm for persistence length Lp take the conformation of relatively extended semi-flexible chains in solution.Download high-res image (82KB)Download full-size image
Co-reporter:Ding Kang, Fei Zhang, Hongbin Zhang
Materials Chemistry and Physics 2015 s 149–150() pp: 129-139
Publication Date(Web):
DOI:10.1016/j.matchemphys.2014.09.055
Co-reporter:Zinan Zhang;Fengyuan Yu;Wei Yu
Journal of Polymer Research 2015 Volume 22( Issue 10) pp:
Publication Date(Web):2015 October
DOI:10.1007/s10965-015-0845-9
The non-isothermal crystallization behaviors of long chain branched isotactic polypropylene (LCB PP), dynamically vulcanized LCB PP/ethylene-propylene-diene monomer (EPDM) blends at various weight ratios were investigated by DSC, rheology and optical microscopy. LCB PP/EPDM blends were found to show a different crystallization behavior in comparison with linear PP/EPDM blends, showing a minimum in the peak temperature of crystallization with increasing the content of EPDM while the latter showing a maximum. The nucleation and the crystallization kinetics of PP were induced and accelerated by long chain branches and EPDM. The acceleration of crystallization kinetics of LCB PP induced by LCB structures was attributed to the grafted efficient nucleation agent. The influence of EDPM on the crystallization combines the effects of enhancement and retardation, depending on its content in the blends. Based on the thermodynamics theory of crystallization, a modified crystallization model was developed to reveal the crystallization mechanism of LCB PP/EPDM blends.
Co-reporter:Zinan Zhang;Bin Lin;Ning Zhou;Fengyuan Yu
Journal of Applied Polymer Science 2014 Volume 131( Issue 7) pp:
Publication Date(Web):
DOI:10.1002/app.40066
ABSTRACT
A series of halogen-free intumescent flame retardants (IFR) based on home-made melamine phosphate and pentaerythritol system (MPPER) including polyamid 12, basic nickel carbonate (NiCO3·2Ni(OH)2·4H2O), lanthanum oxide (La2O3), and expandable graphite compounding with MPPER, were adopted for flame retarding olefin block copolymers (OBC). Flame-retardant effects and thermal stabilities of OBC-IFR composites were investigated by limiting oxygen index, vertical burning test (UL-94), and thermogravimetry analysis along with the analysis of morphological structures of the char residue by scanning electron microscopy. The mechanical properties and the flame-retardant mechanism of the final composited materials have been also discussed. The loading of suitable amount of IFR can improve effectively the flame retardancy of the OBC with tolerable decrease in mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40066.
Co-reporter:Fengyuan Yu, Fei Zhang, Tu Luan, Zinan Zhang, Hongbin Zhang
Polymer 2014 Volume 55(Issue 1) pp:295-301
Publication Date(Web):14 January 2014
DOI:10.1016/j.polymer.2013.11.047
We have investigated the scaling relationship between rheological behavior and concentration for both salt-free and saline solutions of hyaluronan (HA), and adopted three viscoelastic constitutive models to predict the linear/non-linear viscoelastic behavior of these aqueous solutions of HA with different molecular weights at different concentrations up to 20 mg/ml. A series of concentration equations are obtained to describe the influence of HA concentration on solution viscosity. Corresponding to dilute and semi-dilute concentration region, salt-free HA solutions have scaling relationship between specific viscosity and HA concentration as ηsp ∼ c1.0 and ηsp ∼ c3.5, respectively, while for 0.15 M NaCl HA solutions, the scaling exponents are 1.5 and 4.2, respectively. Simulation results indicate that these constitutive models have good applicability to describe quantitatively the rheological properties of HA entangled solutions under either dynamic or steady shear flow. In addition, the plateau modulus scaling of HA solutions can be well described by the concentration-dependent length scale.
Co-reporter:Fei Zhang, Xianjue Chen, Ramiz A. Boulos, Faizah Md Yasin, Haibo Lu, Colin Raston and Hongbin Zhang
Chemical Communications 2013 vol. 49(Issue 42) pp:4845-4847
Publication Date(Web):11 Apr 2013
DOI:10.1039/C3CC41973H
Pyrene-conjugated hyaluronan (Py-HA) facilitates the exfoliation of low-dimensional nanomaterials including graphite, hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2), and the dispersion of carbon nanotubes (CNTs) and carbon nano-onions (CNOs) in water (and PBS solutions), with the assistance of sonication.
Co-reporter:Fei Zhang, Faizah Md Yasin, Xianjue Chen, Jingxin Mo, Colin L. Raston and Hongbin Zhang
RSC Advances 2013 vol. 3(Issue 47) pp:25166-25174
Publication Date(Web):14 Oct 2013
DOI:10.1039/C3RA45037F
Pyrene-conjugated-hyaluronan (Py–HA) stabilises reduced graphene oxide (Py–HA–RGO) in water, with the composite material providing a substrate for building up nanostructures of Au, Ag, Pd and Pt, of varying sizes, shape, and surface properties. Formation of the metal is effective using in situ UV irradiation (Au and Ag) or hydrogen gas at ambient pressure (Pd and Pt). The Py–HA is multifunctional in stabilising Py–HA–RGO in water and controlling the nature of the resulting metal nanostructures. The hybrid Au nanomaterials have been tested as a sensor material for hydrogen peroxide, using electrocatalysis, and the Pd nanomaterials are readily incorporated into hydrogen gas sensors using a drop casting technique, with both systems having nanostructured-dependent detecting responses.
Co-reporter:Hongbin Zhang, Fei Zhang, Juan Wu
Reactive and Functional Polymers 2013 73(7) pp: 923-928
Publication Date(Web):July 2013
DOI:10.1016/j.reactfunctpolym.2012.12.014
Co-reporter:Tu Luan, Lijiao Wu, Hongbin Zhang, You Wang
Carbohydrate Polymers 2012 Volume 87(Issue 3) pp:2076-2085
Publication Date(Web):14 February 2012
DOI:10.1016/j.carbpol.2011.10.029
In this study, the influence of acidification and salting effect on the properties of hyaluronan (HA) aqueous solutions and cryotropic weak gels were investigated by dynamic rheometry, polarizing and optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and FTIR spectroscopy. The forming mechanism of HA cryotropic weak gels was also discussed. Experimental results indicated that the HA weak gel showing a thermoreversible property was constructed by entangled bundle-like structures that could be melted at elevated temperature above 70 °C, and that the junction knots of three-dimensional polymeric network were not the ordinary microcrystalline zones that are generally of detectable crystallinity and thermal effect. The intermolecular hydrogen bonding induced from –COOH and –NHCOCH3 in HA chains played a predominant role in respect to the network formation and stabilization of HA weak gel.Highlights► Hydrogen bonding rather than microcrystallization in HA cryotropic weak gel is verified. ► Protonation of the polyanion of HA is indispensable to the association of HA chains. ► Hydrogen bonding between –COOH and –NHCOCH3 plays a crucial role on such bridging.
Co-reporter:Juan Wu, Fei Zhang, Hongbin Zhang
Carbohydrate Polymers 2012 Volume 90(Issue 1) pp:261-269
Publication Date(Web):1 September 2012
DOI:10.1016/j.carbpol.2012.05.033
Carboxymethyl curdlan (CMc), a β-d-glucan derivative, was used in the photoinduced synthesis of Ag nanoparticles. The size, size distribution, morphology and structure of the as-prepared Ag nanoparticles were investigated with UV–vis spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The experimental results indicated that the particle size increased and the size distribution became broader with increasing the concentrations of both AgNO3 and CMc, and the effect of the latter was more pronounced. With the CMc concentration increasing, the diversity of morphology was obtained as a result of the plasmon excitation and the role of CMc. It was found that CMc played an important role in the synthesis and stabilization of Ag nanoparticles through a series of contrastive experiments. The enhancement effect of the produced Ag nanoparticles in surface enhanced Raman scattering (SERS) was also investigated.Highlights► A green and simple route was proposed to synthesize Ag nanoparticles. ► Ag particles were formed by using carboxymethyl curdlan (CMc) under UV irradiation. ► CMc played an important role in the synthesis and stabilization of Ag nanoparticles. ► Size dispersity and morphology of Ag particles related to the concentration of CMc. ► Enhancement effect of Ag particles in surface enhanced Raman scattering was found.
Co-reporter:Renliang Lv;Yinyi Sun;Fengyuan Yu
Journal of Applied Polymer Science 2012 Volume 124( Issue 1) pp:855-863
Publication Date(Web):
DOI:10.1002/app.35117
Abstract
Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with a series of anionic polysaccharides such as carboxymethyl cellulose, sodium hyaluronate, xanthan gum, pectin, gellan gum were prepared by electropolymerization in aqueous solutions. Some other dopants of potassium nitrate, potassium sulfate, sodium poly(styrenesulfonate), and sodium polyacrylate were used in comparison with the anionic polysaccharides. The electrochemical properties and stability of the obtained PEDOT films were also investigated. It was found that indium tin oxide (ITO) conductive glass could be used as the working electrode of the electropolymerization of EDOT and that the dopant had a great influence on polymerization potential and overoxidation potential. These charged biomolecules of anionic polysaccharides were found to facilitate electropolymerization of EDOT instead of common doping anions as counterion. The electroactive PEDOT films doped with anionic polysaccharides showed stable electrochemical properties, good texture, and adhesion properties to the ITO conductive glass. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:Fengyuan Yu;Zinan Zhang;Wei Yu;Chixing Zhou
Polymer International 2012 Volume 61( Issue 9) pp:1389-1393
Publication Date(Web):
DOI:10.1002/pi.4220
Abstract
Poly(ethylene-co-octene) (PEOc) has been shown to provide a high toughening contribution to isotactic polypropylene (iPP). The theoretical modeling of flow-induced crystallization (FIC) of blends of iPP and PEOc is not much reported in the literature. The aim of the present work is to clarify the FIC of iPP upon addition of PEOc in terms of theoretical modeling. The crystallization of iPP and PEOc blends in flow is simulated by a modified FIC model based on the conformation tensor theory. Two kinds of flow fields, shear flow and elongational flow, are considered in the prediction to analyze the influence of flow field on the crystallization kinetics of the polymer. The simulation results show that the elongation flow is much more effective than shear flow in reducing the dimensionless induction time of polymer crystallization. In addition, the induction time of crystallization in the blends is sensitive to the change of shear rate. In comparison with experimental data, the modified model shows its validity for the prediction of the induction time of crystallization of iPP in the blends. Moreover, the simulated relaxation time for the blends becomes longer with increasing percentage of PEOc in the blends. Copyright © 2012 Society of Chemical Industry
Co-reporter:Renliang Lv, Tu Luan, Fengyuan Yu, Hongbin Zhang
Carbohydrate Polymers 2011 Volume 85(Issue 4) pp:862-868
Publication Date(Web):1 July 2011
DOI:10.1016/j.carbpol.2011.04.009
In the present work aqueous mixtures of polysaccharide of methylcellulose (MC) and conductive polymer of ammonium poly(3-thiophene acetic acid) (PTAA-NH4) were prepared and the effect of PTAA-NH4 on the rheological and thermal properties of MC solution were investigated. Significant viscous synergism depending on shear rate and concentration of PTAA-NH4 was found for the mixtures, indicating a special interaction between the two amphiphilic polymers of MC and PTAA-NH4. In comparison with pure MC solutions, the mixtures showed much more evident shear thinning characteristics. When the concentration of PTAA-NH4 added was higher than 0.15%, weak gel-like behavior of the mixtures was also observed at low temperatures. In addition, though the gelation and degelation patterns of MC were not changed by the addition of PTAA-NH4, both rheological and calorimetric measurements showed that the presence of PTAA-NH4 shifted the sol–gel transition temperature of MC solution to higher temperature with increasing of the concentration of PTAA-NH4.
Co-reporter:Tu Luan, Yapeng Fang, Saphwan Al-Assaf, Glyn O. Phillips, Hongbin Zhang
Polymer 2011 Volume 52(Issue 24) pp:5648-5658
Publication Date(Web):10 November 2011
DOI:10.1016/j.polymer.2011.10.024
The biological functions as well as physico-chemical properties of hyaluronan (HA), one of the most important and ubiquitous glycosaminoglycan in various organisms, are closely related to its molecular weight, molecular weight distribution and chain conformation. For this reason it is crucially important to make a reliable characterization of these parameters for HA in both chemical and clinical fields. The present work compared the application of different techniques including capillary viscometry, concentration gradient multiangle laser light scattering (CG-MALLS), size exclusion chromatography-multiangle laser light scattering (SEC-MALLS), asymmetric flow field flow fractionation-multiangle laser light scattering (AFlFFF-MALLS) and horizontal agarose gel electrophoresis (AGE), to the characterization of a range of HA samples of bacterial and animal sources. The advantage and limitation of these techniques were discussed in terms of producing accurate and reliable molecular parameters.
Co-reporter:Fengyuan Yu, Hongbin Zhang, Ruogu Liao, Hong Zheng, Wei Yu, Chixing Zhou
European Polymer Journal 2009 Volume 45(Issue 7) pp:2110-2118
Publication Date(Web):July 2009
DOI:10.1016/j.eurpolymj.2009.03.011
In the present work long chain branched polypropylene (LCB PP) polymers were prepared by linear polypropylene and multi-functional monomer through melt grafting reaction. A quantitative rheological method was adopted to analysis the structure parameters of LCB PP. The effects of chain branched level on the crystallization kinetics of PP were investigated by rheology, differential scanning calorimetry, polarized optical microscope and wide-angle X-ray diffraction. The dynamic viscoelastic properties of LCB PP showed that the increase in the chain branched level caused a typical deviation from the terminal behavior and a different distribution of the melt relaxation spectrum in the long relaxation time regime. It was found that the chain branched level had a significant effect on the flow induced crystallization (FIC) process of PP melts. The crystallization of LCB PP was more sensitive to shear flow than that of linear PP during induced period at low shear rates. This result also indicated that the longer relaxation time of the polymer chains played an important role in the nucleation of PP under shear flow fields. LCB PP with high chain branched level showed accelerated crystallization kinetics in comparison with that with low chain branched level.
Co-reporter:Fengyuan Yu;Zhigang Wang;Wei Yu;Chixing Zhou
Journal of Polymer Science Part B: Polymer Physics 2009 Volume 47( Issue 5) pp:531-538
Publication Date(Web):
DOI:10.1002/polb.21660
Abstract
In this work, the isothermal flow-induced crystallization (FIC) of high-density polyethylene (HDPE) under a simple shear flow was investigated. Two experimental modes, including steady shear and preshear treatment, were performed on the polymer melt. Based on the nonequilibrium thermodynamic theory, the FIC process of HDPE was predicted through the modification of a continuum FIC model. The theoretical predictions of the evolution of both the viscosity in steady shear flow and the complex modulus under preshear treatment were essentially related to the crystallinity of HDPE, in agreement with the experimental findings. Both experimental and predicted results showed that the applied flow field could accelerate the crystallization kinetics of HDPE significantly. However, the effect of the intensity of shear flow on the crystallization of HDPE was finite, showing a saturation phenomenon, namely, the accelerated degree of crystallization tending to level off when the shear rate was large enough. In additional, it was found that the predicted crystallinity of HDPE was very low in induction period either in steady shear flow or by preshear treatment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 531–538, 2009
Co-reporter:Wanchun Yin, Hongbin Zhang, Long Huang, Katsuyoshi Nishinari
Carbohydrate Polymers 2008 Volume 74(Issue 1) pp:68-78
Publication Date(Web):1 October 2008
DOI:10.1016/j.carbpol.2008.01.016
Effects of Lyotropic series salts on the gelation behavior of konjac glucomannan (KGM) in aqueous solutions were studied by means of rheometry and electron spin resonance (ESR). Rheological measurements showed that sulfate alone, heretofore never reported, was capable of inducing KGM form a thermally irreversible gel rather than via deacetylation that has been the approbatory origin when the commonly alkaline coagulant of Na2CO3 is used. The increase in rotational correlation time that scales with the microviscosity indicated reduced mobilities of KGM chains upon addition of Na2SO4, in agreement with the rheological results. In the presence of Na2CO3, salting-out salts facilitated the gelation, whereas salting-in salts assisted the gelation at low salt concentrations but suppressed it at high salt concentrations. It was suggested that the Na2CO3 be also of salting-out effect in addition to facilitating the deacetylation of KGM chains.
Co-reporter:Fengyuan Yu, Hongbin Zhang, Hong Zheng, Wei Yu, Chixing Zhou
European Polymer Journal 2008 Volume 44(Issue 1) pp:79-86
Publication Date(Web):January 2008
DOI:10.1016/j.eurpolymj.2007.10.022
The crystallization behavior of the blends of isotactic polypropylene (iPP) and poly(ethylene-co-octene) (PEOc) under quiescent condition and shear flow were studied by differential scanning calorimetry (DSC) and rheology, respectively. The DSC curves of the iPP phase in the blends showed similar crystallization exothermic peaks to that of pure iPP itself, indicating that the addition of PEOc up to a percentage of 30 in weight almost had no influence on the crystallization behavior of iPP at quiescent condition. The rheological results of isothermal flow-induced crystallization (FIC) of iPP in the blends showed that the crystallization kinetics of iPP was enhanced with the increase of shear rate, similar to that of pure iPP, but the presence of PEOc enhanced the effect of shear on the crystallization kinetics of iPP significantly in the cases of shear rates larger than 0.2 s−1, which was due to that PEOc played an important role to promote the nucleation of iPP. The rheological results also implied that the characteristic relaxation times of blends were longer than that of pure iPP during the FIC process, indicating a different relaxation mechanism which might be related to the occurrence of interface relaxation and chain relaxation of the PEOc phase in the blends.
Co-reporter:Wanchun Yin;Long Huang;Katsuyoshi Nishinari
Colloid and Polymer Science 2008 Volume 286( Issue 6-7) pp:663-672
Publication Date(Web):2008 June
DOI:10.1007/s00396-007-1810-x
The interaction between konjac glucomannan (KGM) and an anionic surfactant, sodium dodecyl sulfate (SDS) is studied by rheological, circular dichroism (CD), conductivity, electron spin resonance (ESR), and FT-IR measurements. Since KGM is a neutral polysaccharide and has no significant hydrophobic side groups, the critical micelle concentration value of SDS is not influenced with the addition of KGM, and no marked binding occurs between them. SDS makes no conformational changes of KGM with or without heat treatment. The weak alkaline character of SDS induces the deacetylation of KGM chains and makes it form gels with heat treatment. At the same pH value, the gelation time needed for KGM by using SDS as the coagulant is shorter than that by using Na2CO3. The addition of SDS promotes the gelation process of KGM, indicating that although the interaction is weak, SDS micelles seem to play an important role in the gelation of KGM.
Co-reporter:Takahiro Funami;Katsuyoshi Nishinari;Yimei Yin
Macromolecular Rapid Communications 2006 Volume 27(Issue 12) pp:971-975
Publication Date(Web):19 JUN 2006
DOI:10.1002/marc.200600099
Summary: The existence of liquid-crystalline (LC) phases in dilute methylcellulose solutions is demonstrated by exothermic peaks in differential scanning calorimetry (DSC) curves upon heating and is evidenced by a discontinuity of the dynamic storage modulus when the concentration of methylcellulose increases. This crystalline phenomenon is further confirmed by polarized light microscopy and optical rotatory dispersion measurements. It is found that the appearance of the LC formation is related to the temperature, concentration, and molecular weight of methylcellulose.
Co-reporter:Yang Jin, Hongbin Zhang, Yimei Yin, Katsuyoshi Nishinari
Carbohydrate Research 2006 Volume 341(Issue 1) pp:90-99
Publication Date(Web):16 January 2006
DOI:10.1016/j.carres.2005.11.003
Curdlan was carboxymethylated in an aqueous alkaline medium using monochloroacetic acid as the etherifying agent. The structure of carboxymethylated curdlan (CMc) was analyzed by FT-IR and NMR spectroscopy, which revealed that the carboxymethyl group was introduced mainly at the C-6 position as well as at the C-2 and C-4 positions. Furthermore, CMc was compared with the native curdlan by using rheology and DSC methods. It was found that in water, both polysaccharides behaved as pseudoplastic fluids and fit the power law and Herschel–Bulkley rheological models well. Both the storage shear modulus G′ and the loss shear modulus G″ of CMc aqueous solutions decreased and became more frequency dependent with decreasing concentration in comparison with the curdlan aqueous suspensions. The modulus–temperature curve also suggested that the gel characteristic of curdlan has been lost after chemical modification, which is consistent with the DSC results. AFM images revealed differences in the conformation of native and carboxymethylated curdlan, which changed from the aggregation of macromolecules to triple helices. All the experimental results suggest that the hydrogen bonds that bind curdlan with interstitial water to form the micelles have been destroyed completely and that the hydrophobic interactions related to the methylene groups at C-6 formed above 55 °C disappeared due to the introduction of the hydrophilic carboxymethyl group.For the temperature dependence of G′ and G″ of carboxymethylated curdlan, the moduli did not increase markedly above 55 °C and no gel formation occurred indicating that the intrinsic hydrophobic structure related to the methylene groups at C-6 position for the native curdlan had been influenced by the carboxymethylated modification.
Co-reporter:Juan Wu, Junliang Liu, Qiaoyu Dai, Hongbin Zhang
International Dairy Journal (January 2013) Volume 28(Issue 1) pp:40-42
Publication Date(Web):1 January 2013
DOI:10.1016/j.idairyj.2012.05.005
Carboxymethylcellulose (CMC) was used as a stabiliser for acidified whole milk drinks. The stability of the acidified whole milk drinks was investigated by observation of the evolution of size and zeta potential of colloidal particles during acidification along with sedimentation measurement and was compared with the stability of acidified skim milk drinks. It was found that the presence of fat resulted in larger particle sizes, but it did not disturb the absorption of CMC onto casein micelles below pH 5.2. The absorption of CMC endows the casein micelles with electrostatic and steric repulsions, essential to the stability of the acidified milk drinks. Acidified whole milk drinks can be stabilised by CMC, which is capable of effectively preventing the unwanted creaming of fat embedded in the clusters of CMC and caseins as well as preventing the aggregation of casein micelles as it did in skim milk drinks.
Co-reporter:Fei Zhang, Xianjue Chen, Ramiz A. Boulos, Faizah Md Yasin, Haibo Lu, Colin Raston and Hongbin Zhang
Chemical Communications 2013 - vol. 49(Issue 42) pp:NaN4847-4847
Publication Date(Web):2013/04/11
DOI:10.1039/C3CC41973H
Pyrene-conjugated hyaluronan (Py-HA) facilitates the exfoliation of low-dimensional nanomaterials including graphite, hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2), and the dispersion of carbon nanotubes (CNTs) and carbon nano-onions (CNOs) in water (and PBS solutions), with the assistance of sonication.
![Poly[imino(2-methyl-1,4-cyclohexanediyl)methylene(3-methyl-1,4-cyclohexanediyl)imino(1,12-dioxo-1,12-dodecanediyl)]](http://img.cochemist.com/ccimg/163900/163800-67-7.png)
![Poly[imino(2-methyl-1,4-cyclohexanediyl)methylene(3-methyl-1,4-cyclohexanediyl)imino(1,12-dioxo-1,12-dodecanediyl)]](http://img.cochemist.com/ccimg/163900/163800-67-7_b.png)
