Co-reporter:Pengchong Li, Kun Xu, Ying Tan, Cuige Lu, Yangling Li, Pixin Wang
Polymer 2013 Volume 54(Issue 21) pp:5830-5838
Publication Date(Web):4 October 2013
DOI:10.1016/j.polymer.2013.08.019
High strength, stimuli-responsive poly(acrylamide) composite hydrogels (PAAm CH gels) were prepared by grafting polymerization of acrylamide (AAm) onto temperature-sensitive core–shell microgels. These microgels, composing of poly(N-isopropylacrylamide) as core and polyvinylamine (PVAm) as shell, were used as both initiator and crosslinker to form a robust three-dimensional network via bonding the poly(acrylamide) (PAAm) backbone. The CH gels exhibited a remarkably rapid shrinking rate and transmittance switch in response to the environmental temperature change, which the conventional chemically cross-linking PAAm hydrogels (PAAm OR) were short of. Even compared to the bulk PNIPAAm hydrogels (PNIPAAm OR) crosslinked with N,N′-methylenebisacrylamide (MBA), the CH gels were featured with faster responsive rate, which could be attributed to the formation of interconnected water transportation channels between the microspheres and PAAm gel matrix due to the fast shrinking of microgels. Moreover, the effects of microgel species and content on swelling and mechanical properties of CH gels were also systematically investigated. The results elaborated that the CH gels could be compressed almost 99% without breaking and completely recovered their original shape when the stress was removed. And the optimized compressive strength of CH gels could be up to 21.94 MPa. Based on the analysis of CH gel mechanical properties, the influence of microsphere content on effective network chains density of CH gels was discussed through rheology measurements. Finally, the essential reinforcement on mechanical properties was mainly contributed to the homogeneous microstructure of hydrogel network and the energy dissipation mechanism of microgels in gel matrix.
Co-reporter:Kun Xu, Huiyong An, Cuige Lu, Ying Tan, Pengchong Li, Pixin Wang
Polymer 2013 Volume 54(Issue 21) pp:5665-5672
Publication Date(Web):4 October 2013
DOI:10.1016/j.polymer.2013.07.079
A cationic surfactant monomer, dimethyldodecyl(2-acrylamidoethyl)ammonium bromide (AMQC12) was synthesized. A family of hydrophobic-associating cross-linking hydrogels (HAC-gels) fabricated via the self-assembly of amphiphilic multiblock copolymers of acrylamide and AMQC12 can be synthesized by free-radical aqueous solution micelle copolymerization in the absence of surfactants using the one-pot method. The HAC-gels possessed outstanding mechanical performance, with optimal tensile strength, compressive strength, and elongation at break of 250 kPa, 14 MPa, and 1850%, respectively. Meanwhile, the HAC-gels exhibited self-healing property, and tetrahydrofuran (THF) significantly accelerated their self-healing process. The recovery hysteresis of hydrophobic-associating hydrogels prepared in the presence of surfactants can be eliminated because of homogeneity of the hydrogel network and the dynamic and mobile properties of physical cross-linking junctions. Investigations on the mechanical property and structure evolution of hydrogels revealed that the hydrophobic-associating interaction was the driving force of self-assembly of amphiphilic multiblock copolymers. Furthermore, spherical micelles and macroscopic cross-linking network can be easily switched reversibly by regulating copolymers concentration.
Co-reporter:Ying Tan, Kun Xu, Chang Liu, Yangling Li, Cuige Lu, Pixin Wang
Carbohydrate Polymers 2012 Volume 88(Issue 4) pp:1358-1363
Publication Date(Web):16 May 2012
DOI:10.1016/j.carbpol.2012.02.018
Starch is successively modified by acetic anhydride and phthalic anhydride, and then starch-based nanospheres are fabricated by a simple nanoprecipitation procedure. These pH-responsive amphiphilic starch-based nanospheres of uniform size are used as particulate emulsifiers to stabilize Pickering emulsions. CLSM and SEM characterization find that starch-based nanospheres adsorbed at the interface between oil phase and water phase. Moreover, the catastrophic inversion and transitional inversion of such emulsions can be easily achieved by varied the water/oil volume ratio and pH of aqueous dispersion, respectively.Highlights► Starch-based nanospheres were used as solid particulate emulsifier. ► A amphiphilic group was introduced into the backbone of starch by a simple esterified reaction. ► Amphiphilic starch-based nanospheres were fabricated by a nanoprecipitation procedure. ► Nanospheres adsorbed at the interface between oil and water phase. ► The catastrophic inversion and transitional inversion could be easily achieved.
Co-reporter:Wenbo Li, Huiyong An, Ying Tan, Cuige Lu, Chang Liu, Pengchong Li, Kun Xu and Pixin Wang
Soft Matter 2012 vol. 8(Issue 18) pp:5078-5086
Publication Date(Web):23 Mar 2012
DOI:10.1039/C2SM07200A
In this work, a physically cross-linked hydrogel (HA gels) with high mechanical strength is synthesized via micellar copolymerization of acrylamide (AAm) and an anionic surface active monomer (surfmer), sodium 9 or 10-acrylamidostearic acid (NaAAS) without any adscititious surfactant or chemical cross-linkers. SEM and DLS characterizations indicate that the surfmer formed multi-micellar aggregates with 80–90 nm diameters above its critical micelle concentration, and serve as a crosslinked-center to endow the obtained hydrogel a robust three-dimensional architecture. Compared with the chemically cross-linked hydrogel, HA gels exhibit unusual swelling–deswelling behavior in water and a pulsatile swelling–deswelling behavior is exhibited with alternating pH changes from 5 to 10 because the presence of carboxyl in the surfmer, demonstrating a smart characteristic of the hydrogel. Moreover, the presence of the surfmer greatly improve the mechanical properties of HA gels. A hydrogel containing 20% (mol/mol) surfmer shows a compression strength of 22.50 MPa at a strain of 90% and can be elongated to 13 times its original length. Furthermore, the HA gels show a significant hysteresis recovery after large deformation, underlying a serious energy-dissipation mechanism. This uncommon swelling behavior and mechanical properties of the HA gels result from its special characteristic of cross-linked units. A self-healing ability is expected for this physical hydrogel in future applications in biotechnology.
Co-reporter:Yang Li, Ying Tan, Zhigang Ning, Sumiao Sun, Yuan Gao, Pixin Wang
Carbohydrate Polymers 2011 Volume 86(Issue 1) pp:291-295
Publication Date(Web):1 August 2011
DOI:10.1016/j.carbpol.2011.04.049
Fluorescein isothiocyanate (FITC) is covalently attached onto the starch acetate, and the fluorescein-labeled starch acetate can self-assemble to form uniform nanospheres in water. The size of the fluorescent nanospheres can be easily controlled by adjusting the polymer concentration in acetone and the proportions of the water and organic phases. The fluorescent intensity of the nanospheres increases with increasing pH, and its fluorescent intensity has no major effect in the physiologically relevant range from pH 5.7 to pH 8 compared with free FITC. Fluorescence quenching studies prove that the fluorescent nanospheres showed a super fluorescent stability without self-association. The fluorescent nanospheres are degradable and can be potential applied for pH-sensing in biological samples.
Co-reporter:Chunlei Song;Huiyong An;Qingbo Yang;Wenbo Li;Chang Liu;Pixin Wang
Polymer Bulletin 2011 Volume 67( Issue 9) pp:1917-1934
Publication Date(Web):2011 December
DOI:10.1007/s00289-011-0587-8
A new water-soluble monomer of sodium 10-Acryloyloxydecanoate (NaAD), which possesses a hydrophobic group and an ionizable group, was synthesized from acryloyl chloride and 10-hydroxydecanoic acid, and the series of copolymers of NaAD with acrylamide (AM) were prepared by the free radical polymerization in aqueous solution using ammonium persulfate as the initiator. The feed ratio of NaAD:AM was varied from 5:95 to 70:30 mol%, with the total monomer concentration held constant at 0.5 M. The copolymer compositions were determined from elemental analysis. The molecular weights of the copolymers were determined by gel permeation chromatography ranged from 0.76 × 106 to 1.37 × 106 g/mol. All copolymers were soluble in deionized water and salt solutions at pH > 5. The dilute and semidilute solution behavior of the copolymers was studied as a function of composition, pH, and added electrolytes, and the results indicated that NaAD30 exhibited much higher viscosity values. At moderate pH values, the copolymers coils become slightly more expanded and intermolecular association interactions occur, which was indicated by fluorescence and apparent viscosity measurements. Upon the addition of NaCl and in low pH, viscosities tended to decrease because of the disruption of the intermolecular associations.
Co-reporter:Huiyong An;Cuige Lu;Pixin Wang;Wenbo Li;Ying Tan;Kun Xu;Chang Liu
Polymer Bulletin 2011 Volume 67( Issue 1) pp:141-158
Publication Date(Web):2011 June
DOI:10.1007/s00289-011-0465-4
A novel hydrophobically associating polyampholytes of poly(AM/AA/AMQC12) were synthesized by the free radical copolymerization of acrylamide (AM), acrylic acid (AA), and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide (AMQC12) in water without any surfactants (named AAQ series). The structures of polymers were confirmed by 1H NMR and 13C NMR. The molecular weight and polydispersity were obtained using gel permeation chromatography (GPC). The hydrophobically associated properties of polymer solution were characterized by rheology, steady-state fluorescence probe, and 1H NMR relaxation time (T2). Isoelectric points (IEPs) of polymer solution were determined by the effect of pH on viscosity below critical association concentrations (cac), and the reduced viscosities of samples at IEPs were increased in the presence of NaCl. Moreover, the steady-shear viscosity of sample at IEP was also greatly enhanced in NaCl solutions when the polymer concentration is above the cac. Meantime, the storage modulus and the loss modulus of copolymers showed that the sample behaved as gel in salt media.
Co-reporter:Dr. Ying Tan;Dr. Kun Xu;Dr. Cuige Lu;Dr. Chang Liu ;Dr. Pixin Wang
Chemistry - A European Journal 2011 Volume 17( Issue 30) pp:8277-8280
Publication Date(Web):
DOI:10.1002/chem.201101060
Co-reporter:Ying Tan, Kun Xu, Yang Li, Sumiao Sun and Pixin Wang
Chemical Communications 2010 vol. 46(Issue 25) pp:4523-4525
Publication Date(Web):22 Apr 2010
DOI:10.1039/C000471E
Starch-based vesicles with controlled size have been successfully achieved by a simple nanoprecipitation procedure from starch mixed ester.
Co-reporter:Ying Tan, Kun Xu, Pixin Wang, Wenbo Li, Shumiao Sun and LiSong Dong
Soft Matter 2010 vol. 6(Issue 7) pp:1467-1471
Publication Date(Web):09 Feb 2010
DOI:10.1039/B916942C
A novel approach is presented for fabricating the thermo-responsive poly(N-isopropylacrylamide) hydrogels (TPHs) using starch-based nanospheres with derivable allyl groups as nanoscale crosslinkers. The obtained hydrogels possess an extremely high mechanical strength and a remarkably rapid shrinking time, which is much shorter than the time it will take for a conventional hydrogel (CH). Moreover, the effects of the crosslink density on the swelling, deswelling, and mechanical properties are also systematically studied. The results show that TPHs can sustain strength two hundred times more than the CH, and the characteristic time of deswelling is almost eight times shorter than that of CH. These excellent properties of the TPH gels can be attributed to their special microstructure and the even distribution of the starch-based nanospheres in the hydrogel network.
Co-reporter:Kun Xu, Ying Tan, Qiang Chen, Huiyong An, Wenbo Li, Lisong Dong, Pixin Wang
Journal of Colloid and Interface Science 2010 Volume 345(Issue 2) pp:360-368
Publication Date(Web):15 May 2010
DOI:10.1016/j.jcis.2010.01.058
Series of hydrophilic core–shell microgels with cross-linked poly(N-isopropylacrylamide) (PNIPAAm) as core and poly(vinyl amine) (PVAm) as shell are synthesized via surfactant-free emulsion polymerization. Then, the microgels are treated with a small amount of potassium persulfate (KPS) to generate free radicals on the amine nitrogens of PVAm, which subsequently initiate the graft copolymerization of acrylic acid (AA), acryloyloxyethyl trimethyl ammonium chloride (DAC), and acrylamide (AAm) onto microgels to prepare multi-responsive composite hydrogels. The composite hydrogels consist of cross-linked ungrafted polyampholyte chains as the first network and microgels with grafted polyampholyte chains as graft point and second network and show surprising mechanical strength and rapid response rate. The investigation shows the compress strength of composite hydrogels is up to 17–30 MPa, which is 60–100 times higher than that of the hydrogel matrix. The composite hydrogel shows reversible switch of transmittance when traveling the lowest critical temperature (LCST) of microgels. When the composite hydrogel swollen in pH 2.86 solution at ambient condition is immersed into the pH 7.00 solution at 45 °C, a rapid dynamic shrinking can be observed. And the character time (τ) of shrinking dynamic of composite hydrogel is 251.9 min, which is less than that of hydrogel matrix (τ = 2273.7 min).The composite hydrogels consist of cross-linked ungrafted polyampholyte chains as the first network and microgels with graft polyampholyte chains as graft points and second network and show surprising mechanical strength and rapid response rate. The investigation shows the compress strength of composite hydrogels is up to 17–30 MPa, which is 60–100 times higher than that of hydrogel matrix. The composite hydrogel shows reversible switch of transmittance without any volume change when traveling the lowest critical temperature (LCST) of microgels.
Co-reporter:Ying Tan, Kun Xu, Linglu Li, Chang Liu, Chunlei Song and Pixin Wang
ACS Applied Materials & Interfaces 2009 Volume 1(Issue 4) pp:956
Publication Date(Web):March 31, 2009
DOI:10.1021/am900054f
Nanometric and monodisperse starch acetate nanospheres can be prepared through a simple procedure of nanoprecipitation, by the dropwise addition of water to an acetone solution of starch acetate, without any stabilizing agent. This is the first report of the preparation of starch-based nanospheres by this method. The size of the nanospheres obtained can be easily controlled by a number of simple and efficient modifications, i.e., through regulation of the polymer concentration in acetone, the proportions of the water and organic phases, and the molecular weight and degree of substitution of the starch esters. A number of reasons are suggested to explain the observed transitions in the particle size. Fluorescence spectroscopic studies proved that these types of nanospheres could be potentially used for the encapsulation of hydrophobic drugs.Keywords: biopolymers; encapsulation; nanoprecipitation; nanospheres; size-controlled; starch acetate
Co-reporter:Yumei Yue, Xiang Sheng, Pixin Wang
European Polymer Journal 2009 Volume 45(Issue 2) pp:309-315
Publication Date(Web):February 2009
DOI:10.1016/j.eurpolymj.2008.10.038
Novel microstructured and pH sensitive poly(acryliac acid-co-2-hydroxyethyl methacrylate)/poly(vinyl alcohol) (P(AA-co-HEMA)/PVA) interpenetrating network (IPN) hydrogel films were prepared by radical precipitation copolymerization and sequential IPN technology. The first P(AA-co-HEMA) network was synthesized in the present of PVA aqueous solution by radical initiating, then followed by condensation reaction (Glutaraldehyde as crosslinking agent) within the resultant latex, it formed multiple IPN microstructured hydrogel film. The film samples were characterized by IR, SEM and DSC. Swelling and deswelling behaviors and mechanical property showed the novel multiple IPN nanostuctured film had rapid response and good mechanical property. The IPN films were studied as controlled drug delivery material in different pH buffer solution using cationic compound, crystal violet as a model drug. The drug release followed different release mechanism at pH 4.0 and pH 7.4, respectively.
Co-reporter:Ying Tan;Pixin Wang;Kun Xu;Wenbo Li;Huiyong An;Linglu Li;Chang Liu;Lisong Dong
Macromolecular Materials and Engineering 2009 Volume 294( Issue 12) pp:855-859
Publication Date(Web):
DOI:10.1002/mame.200900182
Co-reporter:Wang Pi-xin, Wu Xiu-li, Dong-hua Xue, Kun Xu, Ying Tan, Xi-bing Du, Wen-bo Li
Carbohydrate Research 2009 Volume 344(Issue 7) pp:851-855
Publication Date(Web):12 May 2009
DOI:10.1016/j.carres.2009.02.023
Cationic corn starch derivatives with a high degree of substitution are prepared in alkaline solution or in mixed media of organic solvent and water with different levels of the cationic reagent, 2,3-epoxypropyltrimethylammonium chloride. The starch cationization yield is investigated, and the results indicate that the degree of substitution (DS) of the samples depends on the reaction conditions and reaction media. The maximum DS values are up to 1.37 in 1,4-dioxane alkaline–aqueous solution. Meanwhile, the structures of the cationic starch derivatives are characterized by elemental analyses, FTIR spectroscopy, X-ray diffraction, and 13C NMR spectroscopy, as well as by SEM techniques.
Co-reporter:Yumei Yue;Pixin Wang;Qiang Chen;Xiao Guang Liu
Journal of Applied Polymer Science 2009 Volume 112( Issue 4) pp:2261-2269
Publication Date(Web):
DOI:10.1002/app.29773
Abstract
Novel nanostructured, high transparent, and pH sensitive poly(2-hydroxyethyl methacrylate-co-methacryliac acid)/poly(vinyl alcohol) (P(HEMA-co-MA)/PVA) interpenetrating polymer network (IPN) hydrogel films were prepared by precipitation copolymerization of aqueous phase and sequential IPN technology. The first P(HEMA-co-MA) network was synthesized in aqueous solution of PVA, then followed by aldol condensation reaction, it formed multiple IPN nanostructured hydrogel film. The film samples were characterized by IR, SEM, DSC, and UV-vis spectrum. The transmittance arrived at 93%. Swelling and deswelling behaviors showed the multiple IPN nanostuctured film had rapid response. The mechanical properties of all the IPN films improved than that of PVA film. Using crystal violet as a model drug, the release behaviors of the films were studied. The results showed that compared with PVA, which had low drug loading and exhibited high and burst release, the three IPN films had high drug loading and exhibited sustained release. Besides, the release followed different release mechanism at pH = 4.0 and pH = 7.4, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Xiaoguang Liu;Qiang Chen;Kun Xu;Wende Zhang;Pixin Wang
Journal of Applied Polymer Science 2009 Volume 113( Issue 4) pp:2693-2701
Publication Date(Web):
DOI:10.1002/app.30372
Abstract
High-solids, low-viscosity, stable polyacrylamide (PAM) aqueous dispersions were prepared by dispersion polymerization of acrylamide in aqueous solution of ammonium sulfate (AS) using poly (sodium acrylic acid) (PAANa) as the stabilizer, ammonium persulfate (APS) or 2,2′-Azobis (N,N′-dimethyleneisobutyramidine) dihydrochloride (VA-044) as the initiator. The molecular weight of the formed PAM, ranged from 710, 000 g/mol to 4,330,000 g/mol, was controlled by the addition of sodium formate as a conventional chain-transfer agent. The progress of a typical AM dispersion polymerization was monitored with aqueous size exclusion chromatography. The influences of the AS concentration, the poly(sodium acrylic acid) concentration, the initiator type and concentration, the chain-transfer agent concentration and temperature on the monomer conversion, the dispersion viscosity, the PAM molecular weight and distribution, the particle size and morphology were systematically investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Qiang Chen;Kun Xu;Wende Zhang;Chunlei Song;Pixin Wang
Colloid and Polymer Science 2009 Volume 287( Issue 11) pp:
Publication Date(Web):2009 November
DOI:10.1007/s00396-009-2095-z
In this paper, well-defined temperature- and pH-sensitive core-shell microgels were synthesized by graft copolymerization in the absence of surfactant and stabilizer. The microgel particles consisted of poly (N-isopropylacrylamide (NIPAm)) core crosslinked with N, N′-methylene-bisacrylamide (MBA) and polyvinylamine (PVAm) shell. The effect of MBA content and NIPAm/PVAm ratio on microgel size was investigated. SEM showed that the microgels were spherical and had narrow particle-size distribution. TEM images of the microgels clearly displayed well-defined core-shell morphologies. Zeta-potential measurement further elucidated that the microgels possessed positively charged PVAm molecules on the microgel surface. Turbidity measurement and 1H-nuclear magnetic resonance (NMR) experiments indicated that the VPTT of microgels was the same as the LCST of PNIPAm. 1H-NMR experiments also inferred that the methyl proton of N-isopropylacrylamide appeared three peaks and responded to hydrogen-bonding interaction including polymer chain with water molecular, intramolecular interaction and intermolecular interaction, respectively.
Co-reporter:Hui Chi, Kun Xu, Xiuli Wu, Qiang Chen, Donghua Xue, Chunlei Song, Wende Zhang, Pixin Wang
Food Chemistry 2008 Volume 106(Issue 3) pp:923-928
Publication Date(Web):1 February 2008
DOI:10.1016/j.foodchem.2007.07.002
Acetylated corn starches with different degrees of substitution (DS 0.85, DS 1.78, DS 2.89) were synthesized by the reaction of corn starch with acetic anhydride in the presence of acetic acid under varying reaction temperatures. The product was characterized by FTIR spectroscopy, 1H NMR, X-ray diffraction and contact angle measurement. Acid-base titration and 1H NMR methods were employed to determine the degree of substitution of product. FTIR spectroscopic analysis showed that the characteristic absorption intensities of esterified starch increased with increase in the degree of substitution, and the characterized peak of hydroxyl group almost disappeared in the spectrum of DS 2.89 acetylated starch. The detailed chemical microstructure of native starch and acetylated starch was confirmed by 1H NMR, 13C NMR and 13C–1H COSY spectra. Analysis of 1H NMR spectra of acetylated starches was assigned accurately. Strong peaks in X-ray diffraction of acetylated starch revealed that new crystalline regions were formed. Compared with native starch, the hydrophobic performance of acetylated starch esters was increased. The contact angle of acetylated starch with DS 2.89 was 68.2°.
Co-reporter:Yu-Mei Yue;Kun Xu;Xiao-Guang Liu;Qiang Chen;Xiang Sheng
Journal of Applied Polymer Science 2008 Volume 108( Issue 6) pp:3836-3842
Publication Date(Web):
DOI:10.1002/app.28023
Abstract
A series of full interpenetrating polymer network (full-IPN) films of poly(acrylic acid) (PAA)/poly (vinyl alcohol) (PVA) were prepared by radical solution polymerization and sequential IPN technology. Attenuated total reflectance-Fourier transform infrared spectroscopy, swelling properties, mechanical properties, morphology, and glass transition temperature of the films were investigated. FTIR spectra analysis showed that new interaction hydrogen bonds between PVA and PAA were formed. Swelling property of the films in distilled water and different pH buffer solution was studied. Swelling ratio increased with increasing PAA content of IPN films in all media, and swelling ratio decreased with increasing PVA crosslink degree. Tensile strength and elongation at break related not only to the constitution of IPNs but also to the swelling ratio of IPNs. Mechanical property of glutaraldehyde (0.5%) for poly(vinyl alcohol) crosslinking was better than that of glutaraldehyde (1.0%). DSC of the IPN films showed only a single glass transition temperature (Tg) for each sample, and Tg data showed a linear relationship with network composition. Morphology was observed a homogeneous structure, indicating the good compatibility and miscibility between PAA and PVA. Potential application of the IPN films in controlled drug delivery was also examined using crystal violet as a model drug. The release rate of the drug was higher at 37°C than 25°C for all IPNs and also increased slightly with decreasing of poly(acrylic acid) content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Qiang Chen;Xiaoguang Liu;Kun Xu;Chunlei Song;Wende Zhang;Pixin Wang
Journal of Applied Polymer Science 2008 Volume 109( Issue 5) pp:2802-2807
Publication Date(Web):
DOI:10.1002/app.28271
Abstract
Copolymers of N-vinylformamide and acrylic acid were synthesized by conventional aqueous free-radical polymerization. The phase behavior of the copolymer solutions was investigated through the addition of hydrochloric acid and the variation of the temperature. With a moderate content of N-vinylformamide, the copolymers showed complex phase behaviors. Under low-acidity conditions, a suspending liquid was formed, whereas under high-acidity conditions, the random copolymers could assemble into round nanoparticles with a broad particle size distribution. When the temperature was reduced, a much less cloudy solution that contained nanoparticles became a milk-like suspending liquid, and this temperature-responsive phenomenon was reversible. This indicated that the formamide group was protonated under highly acidic conditions; the repulsive electrostatic forces compelled the aggregates to disperse. The amount of salt and excess acid influenced the particle size as well as the temperature-responsive behavior of the copolymers under highly acidic conditions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Qingbo Yang;Chunlei Song;Qiang Chen;Pingping Zhang;Pixin Wang
Journal of Polymer Science Part B: Polymer Physics 2008 Volume 46( Issue 22) pp:2465-2474
Publication Date(Web):
DOI:10.1002/polb.21577
Abstract
In this investigation, hydrophobically modified polyacrylamide with low amounts of anionic long-chain alkyl was synthesized by the free radical polymerization in deionized water. This water-soluble copolymerization method is more convenient compared with the traditional micellar copolymerization methods. The copolymers were characterized using Fourier transform infrared, 1H NMR, and the molecular weight and polydispersity were determined using gel permeation chromatography. The solution behavior of the copolymers was studied as a function of composition, pH, and added electrolytes. As NaCl was added to solutions of AM/C11AM copolymers or pH was lowered, the shielding or elimination of electrostatic repulsions between carboxylate groups of the C11AM unit lead to coil shrinkage. The steady shear viscosity and dynamic shear viscoelastic properties in semidilute, salt-free aqueous solutions were conducted to examine the concentration effects on copolymers. In addition, the shear superimposed oscillation technique was used to probe the structural changes of the network under various stresses or shear conditions. We prepared hydrophobically modified polyacrylamide with N-alkyl groups in the aqueous medium. The advantage of this method is that the production is pure without surfactants. These results suggest that the unique aqueous solution behavior of the copolymers is different from conventional hydrophobically associating acrylamide. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2465–2474, 2008
Co-reporter:Qiang Chen;Xiaoguang Liu;Qingbo Yang;Kun Xu;Wende Zhang
Polymer Bulletin 2008 Volume 60( Issue 4) pp:545-554
Publication Date(Web):2008 April
DOI:10.1007/s00289-007-0885-3
Novel ampholytic terpolymer of N-vinylformamide (NVF), vinylamine (VAm) and sodium acrylate (NA) with
low cationic proportion was obtained by hydrolyzing copolymer of NVF and NA (PNVFNA). Solution properties
of the polymer were investigated by methods of turbidity and viscosity experiment. The effect of sodium
dodecyl sulfate (SDS) on solution viscosity was also investigated. The results showed that the turbidity
curves were bimodal, and pH 3.0 was determined as the isoelectric point (IEP). At high salt concentration,
polyampholyte effect was noticeable at IEP in viscosity experiment. Although the proportion of VAm in polyampholyte
was lower, the solution properties were influenced markedly in the presence of SDS. At IEP, the viscosity
increased more rapidly as salt concentration increased when 10-3 mol/L SDS contained
in solution. A mechanism of SDS bound to positive sites on the collapsed globule surface was suggested.
Co-reporter:Xuefeng Su;Guo Zhang;Kun Xu;Jihua Wang;Chunlei Song;Pixin Wang
Polymer Bulletin 2008 Volume 60( Issue 1) pp:69-78
Publication Date(Web):2008 February
DOI:10.1007/s00289-007-0843-0
A series of superabsorbent composites containing Montmorillonite (MMT), modified- Montmorillonite (OMMT) and sodium acrylate were synthesized by free-radical polymerization in aqueous solution. The structure of composites was characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and X-ray diffraction (XRD), and the results showed that the polymer chains were grafted onto the edge and the surface of MMT or OMMT. At the same time, the equilibrium swelling ratio of the composites was investigated as a function of the clay content and the results showed that the equilibrium swelling ratio of composites was improved by the introduction of clay. The maximum equilibrium swelling ratio of composite in distilled water and 0.9 wt% sodium chloride solutions were up to 2450 g/g and 118 g/g, respectively. Finally, the result of thermogravimetric analysis (TGA) suggested that the introduction of clay and modified clay could improve the thermal stability of superabsorbent composites.
Co-reporter:Qiang Zhang;Kun Xu;Pixin Wang
Fibers and Polymers 2008 Volume 9( Issue 3) pp:271-275
Publication Date(Web):2008 June
DOI:10.1007/s12221-008-0043-z
The domain-structure of samples containing a series of starch/poly(sodium acrylate)-grafted superabsorbents, pure starch, pure poly(sodium acrylate), and blend of starch/poly(sodium acrylate) has been studied by high-resolution solid-state 13C NMR spectroscopy at room temperature. The result shows that the crystallinity of starch decreases greatly in the grafted and blended samples. The values of 1H spin-lattice relaxation time in rotating frame T1ρ and 1H spin-lattice relaxation time T1 shows that starch and poly(sodium acrylate) components in both grafted and blended samples have good compatibility in nanometer scale. In the 13C cross-polarization/magic-angle-spinning (CP/MAS) spectra, the chemical shift of the carbonyl group of poly(sodium acrylate) depends on the composition of the grafting samples, which indicates that the starch and the poly(sodium acrylate) components of the grafting samples exhibit better compatibility with each other than that of blended samples at molecular level.
Co-reporter:Kun Xu, Jihua Wang, Sheng Xiang, Qiang Chen, Yumei Yue, Xuefeng Su, Chunlei Song, Pixin Wang
Composites Science and Technology 2007 Volume 67(15–16) pp:3480-3486
Publication Date(Web):December 2007
DOI:10.1016/j.compscitech.2007.02.009
A series of novel polyampholyte superabsorbent nanocomposites with excellent gel strength were synthesized by in situ solution polymerization in aqueous solution. Acrylic acid and acryloyloxyethyl trimethyl ammonium chloride (DAC) were employed as ionic monomers and montmorillonite (MMT) was used as inorganic component. The addition of cationic component could supply the positive charge in the network of nanocomposite and promote the formation of nanostructure of composites due to the interaction between DAC and clay platelets. The performance of polyampholyte nanocomposites were investigated and the result showed that the gel strength of nanocomposite hydrogel in distilled water and 0.9 wt% NaCl solution could reach 198.85 and 204.23 mJ/g, respectively, which were 13 times of the gel strength of matrix. The investigation of swelling behaviors showed that the nanocomposites had particular swelling behaviors of polyampholytes hydrogel in solution with different pH values and concentration of NaCl.
Co-reporter:Xiaoguang Liu, Sheng Xiang, Yumei Yue, Xuefeng Su, Wende Zhang, Chunlei Song, Pixin Wang
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2007 Volume 311(1–3) pp:131-139
Publication Date(Web):1 December 2007
DOI:10.1016/j.colsurfa.2007.06.007
High-solids, low-viscosity, stable poly(acrylamide-co-acrylic acid) aqueous latex dispersions were prepared by the dispersion polymerization of acrylamide (AM) and acrylic acid (AA) in an aqueous solution of ammonium sulfate (AS) medium using anionic polyelectrolytes as stabilizers. The anionic polyelectrolytes employed include poly(2-acrylamido-2-methylpropanesulfonic acid sodium) (PAMPSNa) homopolymer and random copolymers of 2-acrylamido-2-methylpropanesulfonic acid sodium (AMPSNa) with methacrylic acid sodium (MAANa), acrylic acid sodium (AANa) or acrylamide (AM). The influences of stabilizer's structure, composition, molecular weight and concentration, AA/AM molar feed ratio, total monomer, initiator and aqueous solution of AS concentration, and stirring speed on the monomer conversion, the particle size and distribution, the bulk viscosity and stability of the dispersions, and the intrinsic viscosity of the resulting copolymer were systematically investigated. Polydisperse spherical as well as ellipsoidal particles were formed in the system. The broad particle size distributions indicated that coalescence of the particles takes place to a greater extent. The chemical structures of the final formed copolymers were characterized by FTIR and 13C NMR. The result obtained by 13C NMR was excellent agreement between the feed monomer compositions and the final copolymer compositions.
Co-reporter:Dongnian Chen, Xiaoguang Liu, Yumei Yue, Wende Zhang, Pixin Wang
European Polymer Journal 2006 Volume 42(Issue 6) pp:1284-1297
Publication Date(Web):June 2006
DOI:10.1016/j.eurpolymj.2005.12.007
Dispersion copolymerization of acrylamide (AM) with 2-methylacryloylxyethyl trimethyl ammonium chloride (DMC) has been carried out in aqueous salts solution containing ammonium sulfate and sodium chloride with poly(acryloylxyethyl trimethyl ammonium chloride) (PDAC) as the stabilizer and 2,2′-azobis[2-(2-inidazolin-2-yl)propane]-dihydro chloride (VA-044) as the initiator. A new particle formation mechanism of the dispersion polymerization for the present system has been proposed. The effects of inorganic salts and stabilizer concentration on dispersion polymerization have been investigated. The results show that varying the salt concentration could affect the morphology and molecular weight of the resultant copolymer particles significantly. With increasing the stabilizer concentration, the particle size decreased at first and then increased, meanwhile the effect on the copolymer molecular weight was the contrary. These results had been rationalized based on the proposed mechanism.
Co-reporter:Xiaoguang Liu;Dongnian Chen;Yumei Yue;Wende Zhang;Pixin Wang
Journal of Applied Polymer Science 2006 Volume 102(Issue 4) pp:3685-3690
Publication Date(Web):29 AUG 2006
DOI:10.1002/app.24259
Dispersion copolymerization of acrylamide with acrylic acid in an aqueous solution of ammonium sulfate using poly(2-acrylamido-2-methylpropanesulfonic acid sodium) as the stabilizer and ammonium persulfate (APS) as the initiator was investigated. The influence of initiator concentration, stabilizer concentration, ammonium sulfate concentration, chain-transfer agent concentration, and polymerization temperature on the copolymerization was discussed. The results showed that varying the ammonium sulfate concentration could affect the particle size and the intrinsic viscosity of the copolymer significantly. With increasing the stabilizer concentration, the particle size of the copolymer decreased first, and then increased, meanwhile the intrinsic viscosity of the copolymer decreased. The increase of initiator concentration, chain-transfer agent concentration, and polymerization temperature resulted in the increase in the particle size. Polydisperse spherical particles were formed in the system, and the kinetics for the dispersion copolymerization were discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3685–3690, 2006
Co-reporter:K. Xu;W. D. Zhang;P. X. Wang;Y. M. Yue
Journal of Applied Polymer Science 2005 Volume 98(Issue 3) pp:1050-1054
Publication Date(Web):4 AUG 2005
DOI:10.1002/app.22234
A superabsorbent of starch, 2-acrylamido-2-methyl-propanosulfonic acid (AMPS), and sodium acrylate was synthesized by microwave irradiation, and the effect of AMPS on the performance of the polymer was investigated. The best mass fraction of the three components was determined (starch/acrylic acid/AMPS = 2 : 5 : 3). The structure of the polymer was characterized by Fourier transform infrared, 13C cross-polarization/magic-angle spinning NMR, and scanning electron microscopy, and the morphology of the surface of the sample was studied. The results showed that the morphology of the polymer was changed to some extent under microwave irradiation, and the swelling rate of the polymer synthesized by microwave polymerization was faster than the swelling rate of a polymer synthesized by a traditional method. The best absorbent capacities of the product in distilled water and a 0.9% sodium chloride solution were 450 and 53 g/g, respectively. Meanwhile, the introduction of AMPS to a superabsorbent resin was an effective method for improving the performance of the polymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1050–1054, 2005
Co-reporter:Kun Xu, Jihua Wang, Sheng Xiang, Qiang Chen, Wende Zhang, Pixin Wang
Applied Clay Science (December 2007) Volume 38(Issues 1–2) pp:139-145
Publication Date(Web):December 2007
DOI:10.1016/j.clay.2007.02.009
Co-reporter:Kun Xu, Jihua Wang, Qiang Chen, Yumei Yue, Wende Zhang, Pixin Wang
Journal of Colloid and Interface Science (15 May 2008) Volume 321(Issue 2) pp:272-278
Publication Date(Web):15 May 2008
DOI:10.1016/j.jcis.2008.02.024
A circular system is employed in this paper to investigate the swelling behaviors of polyampholyte hydrogels; this circular system can effectively eliminate the disturbance of various factors and keep the surrounding environment constant. It is found that there exists a spontaneous volume transition to the collapsed state of polyampholyte hydrogels, which is attributed to the overshooting effect, and the transition can occur repeatedly under certain conditions. 13C NMR is employed to investigate the swelling behavior of polyampholyte hydrogels. The swelling kinetics of polyampholyte hydrogels under various circular media and various circular runs are also investigated in this paper. All the results suggest that the spontaneous volume transition to the collapsed state of polyampholyte hydrogels is dominated by pure electrostatic interaction between different charges in polymer chains.A polyampholyte nanocomposite hydrogel shows a spontaneous volume transition to the collapsed state based on a pure electrostatic interaction.Download full-size image
Co-reporter:Ying Tan, Kun Xu, Yang Li, Sumiao Sun and Pixin Wang
Chemical Communications 2010 - vol. 46(Issue 25) pp:NaN4525-4525
Publication Date(Web):2010/04/22
DOI:10.1039/C000471E
Starch-based vesicles with controlled size have been successfully achieved by a simple nanoprecipitation procedure from starch mixed ester.
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4.png)
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4_b.png)
