Co-reporter:Xiaoping Zeng, Zhonghui Sun, Hong Wang, Qin Wang, Yajiang Yang
Composites Science and Technology 2016 Volume 122() pp:149-154
Publication Date(Web):18 January 2016
DOI:10.1016/j.compscitech.2015.11.025
An inherent disadvantage of supramolecular gels is the lack of mechanical strength. In this work, we made an attempt to improve their mechanical strength through the adding hydrophobically modified halloysite nanotubes (HNTs) with in-situ formed Fe3O4 nanoparticles. Briefly, the magnetic supramolecular gel composites were prepared through adding 2 wt% benzyl sorbitol derivatives as the gelators into the solvents containing magnetic HNTs. It was found that the compressive strength of the reinforced supramolecular gel composites was remarkably increased from 19 kPa to 28 kPa by adding only 4 wt% of magnetic HNTs. The resultant magnetic supramolecular gel composites possess formability due to their sufficient mechanical strength and exhibit excellent properties for dye adsorption. Significantly, such magnetic supramolecular gel composites can be easily separated from the dye solutions by using an external magnet.
Co-reporter:Wan Li, Xiaoping Zeng, Hong Wang, Qin Wang and Yajiang Yang
New Journal of Chemistry 2016 vol. 40(Issue 5) pp:4528-4533
Publication Date(Web):01 Mar 2016
DOI:10.1039/C5NJ03430B
Glutathione–Ag (GSH–Ag) supramolecular hydrogels have almost no mechanical strength, and the disassembly of GSH–Ag complexes occurs very easily under UV irradiation. In this work, low molecular weight polyvinyl alcohol (PVA) was used to reinforce GSH–Ag gels. The phase transition temperature of GSH–Ag gels can be increased from 45 to 60 °C in the presence of only 0.8 wt% of PVA. Rheological studies indicated that the storage modulus of reinforced GSH–Ag gels was 6 times higher than that of unreinforced gels. SEM studies revealed that the macromolecular chains of PVA are intertwined with the GSH–Ag aggregates, leading to an increase of mechanical strength. The TEM studies and UV-vis spectra indicated that Ag+ within the GSH–Ag gels was in situ reduced to form Ag nanoparticles under UV irradiation. Meanwhile, gradual disassembly of GSH–Ag hydrogels can be induced through controlling the time of UV irradiation. Based on this feature, the controllable release of a loaded model drug (crystal violet) and Ag species can be realized from the reinforced GSH–Ag gels. The release media show a good inhibition effect on E. coli.
Co-reporter:Huabo Huang, Junlong Yao, Huiting Qin, Xiaoping Zeng, Hong Wang, Qin Wang, Yajiang Yang
Synthetic Metals 2016 Volume 221() pp:15-18
Publication Date(Web):November 2016
DOI:10.1016/j.synthmet.2016.10.002
•Conducting polyaniline/poly(vinyl alcohol) hydrogels.•High-pressure induced gelation of PVA solutions and in-situ polymerization of aniline.•One-pot to fabricate conducting PVA hydrogels.•Excellent electrochemical response.Conducting hydrogels were obtained through high-pressure induced gelation of poly(vinyl alcohol) aqueous solutions and subsequent in-situ polymerization of aniline (polyaniline). A study of scanning electron microscopy showed that polyaniline was homogeneously dispersed within the 3D nano-network matrix of the poly(vinyl alcohol) hydrogels. The UV–vis spectra and cyclic voltammetry of the hydrogels demonstrated that the high-pressure treatment had no influence on the in-situ polymerization and electrochemical feature of polyaniline. A study of electrochemical impedance indicated that the conducting hydrogels possessed electrical conductivity and potential application in the field of biomaterials and electrode materials of supercapacitors.Aniline and APS were dissolved in the acidic aqueous solution of PVA. The solution mixture was directly transformed into the hydrogels under high pressure. The pressure induced self-assembly of PVA chains acted as physically crosslinking junctions. After subsequent in-situ polymerization of aniline, the conducting PANI/PVA hydrogels with black color were obtained.
Co-reporter:Wan Li, Xiaoping Zeng, Hong Wang, Qin Wang, Yajiang Yang
European Polymer Journal 2015 Volume 66() pp:513-519
Publication Date(Web):May 2015
DOI:10.1016/j.eurpolymj.2015.03.020
•Supramolecular nanofibers formed by self-assembly of sorbitol derivatives.•Improve the mechanical strength of PANI-PSS conducting hydrogels.•Presence of nanofibers does not affect the electric properties of PANI-PSS hydrogels.•Reinforced PANI-PSS hydrogels can be used as drug carriers with electric-driven release.Due to the very poor mechanical strength of polyaniline-poly(styrene sulfonate) (PANI-PSS) conducting hydrogels, we explored the possibility to improve the strength of PANI-PSS hydrogels using supramolecular nanofibers formed by self-assembly of sorbitol derivatives (DBS). The compressive strength of these reinforced hydrogels was found to be 11 times higher than that of the unreinforced one. SEM studies indicated that the in-situ formed DBS nanofibers and PANI-PSS chains are entangled, leading to improvement of the hydrogel strength. The conductivity of reinforced hydrogels measured by impedance was found to be 10−4 S/cm, rather similar to that of the unreinforced hydrogels. In addition, the spectra of cyclic voltammetry for the reinforced and unreinforced hydrogels were almost the same. These results reveal that the presence of DBS nanofibers does not affect the electric properties of PANI-PSS hydrogels. As drug carriers with electric-driven release, the release rate of model drug Rhodamine B loaded within reinforced PANI-PSS hydrogels distinctly increased when an increase of voltage was applied. Furthermore, a pulse release could be realized when the voltage was alternatively applied.
Co-reporter:Hong Wang, Hao Wang, Xiaoqiong Yang, Qin Wang, and Yajiang Yang
Langmuir 2015 Volume 31(Issue 1) pp:486-491
Publication Date(Web):December 11, 2014
DOI:10.1021/la5040323
Ion-unquenchable and thermally on–off reversible room temperature phosphorescence (RTP) can be induced by entrapping 3-bromoquinoline (3-BrQ) into supramolecular gels formed by the self-assembly of a sorbitol derivative (DBS). In comparison with conventional substrates inducing RTP, the gel state 3-BrQ/DBS can produce strong RTP due to the efficient restriction of the vibration of 3-BrQ. Notably, the rather inconvenient deoxygenation is no longer necessary in the preparation of 3-BrQ/DBS gels. The produced RTP was found to be very fast to reach stable, not depending on the standing time. As a reference, in the liquid state of 3-BrQ/sodium deoxycholate (NaDC), stable RTP can be observed after standing for 5 h. The investigation of RTP quenching indicates that the mechanism of RTP induced by DBS gels mainly involves the microenvironment in which 3-BrQ is located. 3-BrQ was entrapped in the hydrophobic 3D network structure of DBS gels, thereby restricting the motion and collision of 3-BrQ and avoiding RTP quenching and additionally quenching by ions. Furthermore, the RTP of 3-BrQ/DBS gels show an excellent “on–off” effect at 10 or 80 °C. This indicates that the solid DBS gel is beneficial for the preparation of RTP sensor devices.
Co-reporter:Huabo Huang, Xiaoping Zeng, Wan Li, Hong Wang, Qin Wang and Yajiang Yang
Journal of Materials Chemistry A 2014 vol. 2(Issue 39) pp:16516-16522
Publication Date(Web):2014/08/05
DOI:10.1039/C4TA03332A
By using the in situ polymerization of aniline in an aqueous solution of sodium alginate, we prepared reinforced conducting hydrogels (PANI–SA) with good conductivity (∼10−3 S cm−1). SEM images indicated that the microstructure of PANI–SA hydrogels was a typical 3D nano-fiber network formed by the entanglement of the PANI and SA molecular chains, leading to a good compressive strength (∼41 kPa). Because the system does not contain any adhesives and conducting fillers, the PANI–SA conducting hydrogels with self-supported structures can be directly employed as electrode materials for supercapacitors. A study of cyclic voltammograms indicated that the currents of the cathodic peak significantly increased with an increase in the scan rate, indicating that the electrode materials possess good responsiveness. As a reference, traditional compressive tablet electrodes were also prepared by mixing the powder of PANI–SA xerogels, adhesive and conducting filler. The results of galvanostatic charge/discharge and impedance show that PANI–SA hydrogels possess longer discharge times, higher specific capacitance and lower electronic resistance in comparison with compressive tablet electrodes. After 1000 cycles of charge/discharge, there is almost no difference in the retained specific capacitance between PANI–SA hydrogels electrodes and compressive tablet electrodes. The easily fabricated PANI–SA conducting hydrogels show great potential as electrode materials for supercapacitors.
Co-reporter:Huabo Huang, Wan Li, Hong Wang, Xiaoping Zeng, Qin Wang, and Yajiang Yang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 3) pp:1595
Publication Date(Web):January 20, 2014
DOI:10.1021/am4043799
Novel conducting hydrogels (PVA-TA) with dual network structures were synthesized by the grafting reaction of tetraaniline (TA) into the main chains of poly(vinyl alcohol) and in situ reinforced by self-assembly of a sorbitol derivative as the gelator. The chemical structure of the PVA-TA hydrogels was characterized by using FT-IR and NMR. The mechanical strength of the PVA-TA hydrogels was strongly improved due to the presence of supramolecular nanofibers. For instance, the compressive and tensile strengths of supramolecular nanofiber-reinforced hydrogels were, respectively, 10 times and 5 times higher than those of PVA-TA hydrogels. Their storage modulus (G′) and loss modulus (G″) were 5 times and 21 times higher than those of PVA-TA hydrogels, respectively. Cyclic voltammetry and conductivity measurements indicated that the electroactivity of reinforced hydrogels is not influenced by the presence of supramolecular nanofibers.Keywords: conducting hydrogels; in situ reinforce; poly(vinyl alcohol); supramolecular nanofibers; tetraaniline;
Co-reporter:Wan Li, Hong Wang and Yajiang Yang
RSC Advances 2014 vol. 4(Issue 5) pp:2109-2114
Publication Date(Web):20 Nov 2013
DOI:10.1039/C3RA45868G
Microemulsions were prepared by using Tween 80 as a surfactant, 1,2-propylene glycol as a co-surfactant, isopropyl myristate as an oil phase and phosphate-buffered saline as an aqueous phase. The resultant microemulsions possess a bicontinuous-phase structure which was characterized by pseudo-ternary phase diagrams and dye solubility tests. The microemulsions were gelled by the self-assembly of sorbitol derivatives as a gelator to form novel supramolecularly gelled microemulsions that can be used as the carrier of a dual-drug, such as hydrophilic 5-aminosalicylic acid and lipophilic curcumin. The effect of bovine serum albumin (BSA) on their release behavior depends upon the pH of the release media. In the case of pH 7.4, BSA inhibits the release of both drugs, but promotes their release if the pH is less than 7.4. We conclude that protein-modulated release is a promising strategy for dual-drug loading in the supramolecularly gelled microemulsions.
Co-reporter:Qin Wang, Xiao Xiao, Yuandu Hu, Hong Wang and Yajiang Yang
RSC Advances 2014 vol. 4(Issue 43) pp:22380-22386
Publication Date(Web):12 May 2014
DOI:10.1039/C4RA03357D
In an aqueous solution of an L-phenylalanine derivative-based gelator, the addition of a suitable amount of thermosensitive poly(N-isopropylacrylamide) nanogel particles leads to the formation of hybridized supramolecular hydrogels. Due to the presence of the nanogel particles, the gelation ability of the gelator can be improved as shown by the decrease of the critical gelation concentration (CGC) of the gelator from 2.5 wt% to 0.8 wt% when 1 wt% of nanogels was employed. Meanwhile, the thermostability of the hybridized system was also improved. For instance, the phase transition temperature (TGS) increased from 48 °C to 61 °C. Rheological studies indicated that the supramolecular hydrogels can be significantly reinforced by hybridizing 0.6 wt% nanogels. When used as a drug carrier, the drug release behavior from the hybridized system can be controlled by changing the content of nanogels as well as the temperature.
Co-reporter:Lei Jin, Hong Wang, Yajiang Yang
Composites Science and Technology 2013 Volume 79() pp:58-63
Publication Date(Web):18 April 2013
DOI:10.1016/j.compscitech.2013.02.017
1,3:2,4-di-O-benzylidene-D-sorbitol (DBS) can self-assemble into supramolecular nanofibers in the precursor of polyurethane followed by gelation. After UV-initiated polymerization, in situ supramolecular nanofibers reinforced polyurethane composites can be obtained. SEM studies indicate that the in situ formed supramolecular nanofibers can induce the composite interface at the molecular level, greatly improving interface compatibility of the fibers and matrices. Static and dynamic mechanical analysis indicated that the tensile strength of 12 wt% DBS nanofibers reinforced polyurethane was 2.8 times higher than that of pure polyurethane. Their breaking elongation was 2.5 times higher than that of conventional glass fibers reinforced polyurethane. In comparison with conventional fiber reinforced polymers, the utilizing of in situ formed supramolecular nanofibers not only reinforce, but also toughen the polymer matrices, and show the advantage of reducing the weight and maintaining transparency of the polymers.
Co-reporter:Lei Jin, Hong Wang, Yajiang Yang
Journal of Colloid and Interface Science 2013 Volume 393() pp:53-57
Publication Date(Web):1 March 2013
DOI:10.1016/j.jcis.2012.10.030
Triblock copolymer PE6200 (PEO10.5–PPO30–PEO10.5) in aqueous solution can undergo a transition from an isotropic micellar phase to an anisotropic lamellar phase at a specific temperature. Based on this feature, the self-assembly behavior of a benzenetetracarboxylic acid based hydrogelator in aqueous solutions of PE6200 has been investigated. The results of small angle X-ray scattering (SAXS) measurements indicated that the hydrogelator self-assembled into stable three-dimensional network structures below 50 °C. In the range of 50–60 °C, a transition from three-dimensional to two-dimensional self-assembly was observed, which can be attributed to the fact that PE6200 undergoes a transition from an isotropic micellar phase to an anisotropic lamellar phase. Differential scanning calorimetry (DSC) and varying temperature laser Raman spectroscopy further confirmed the thermodynamically controllable transition of 3D to 2D self-assembly. Controlling the self-assembly by utilizing the phase behavior of triblock copolymers is a novel strategy.Graphical abstractHighlights► Thermodynamically controllable. ► 3D/2D supramolecular self-assembly. ► Based on the phase behaviors of triblock polymer.
Co-reporter:Huabo Huang, Xiang Zhu, Lei Su, Hong Wang and Yajiang Yang
RSC Advances 2013 vol. 3(Issue 29) pp:11854-11859
Publication Date(Web):17 May 2013
DOI:10.1039/C3RA41540F
Using 1-methyl-2,4-bis(N′-octadecaneureido)benzene (MBB-18) as a gelator and chlorobenzene (CB) as the solvent, supramolecular gels were prepared. Their phase behaviors were investigated under high pressure using a diamond anvil cell with in situ Raman spectroscopy and optical microscopy at a range of temperatures. As a reference, the phase transition of CB was also examined under corresponding conditions. Unlike the single-component system, the phase behavior of the MBB-18/CB gels, being a dual-components system, involves both phase transition of CB and transition of the supramolecular self-assembly/disassembly. The results indicated that the observed phase transition of the gels at 23 °C and 1.07 GPa can be attributed to a transition from liquid CB to solid CB. Similar results were found at 60 °C and 1.44 GPa. At 150 °C and 0.85 GPa, the phase transition of the gels should be attributed to self-assembly transition of MBB-18 because CB remains in the liquid state in this case. This is a significant result. MBB-18 cannot self-assemble at 150 °C and at normal pressure because the temperature is too high. However, an increase of the pressure to 0.85 GPa enables the self-assembly to occur at the same temperature.
Co-reporter:Qingyao Liu, Xiangliang Yang, Huibi Xu, Kaijin Pan, Yajiang Yang
European Polymer Journal 2013 Volume 49(Issue 11) pp:3522-3529
Publication Date(Web):November 2013
DOI:10.1016/j.eurpolymj.2013.08.012
•Synthesis of hydroxyethyl starch grafted polylactides as a novel drug carrier.•Formation and characterization of HES-g-PLA nanomicelles.•Lipophilic docetaxel loaded HES-g-PLA nanomicelles.•Controllable release by changing length of PLA chains.A novel drug carrier was synthesized through grafting polymerization of hydroxyethyl starch (HES) and d,l-lactide. By changing the molar ratio of HES and d,l-lactide, HES-g-PLA copolymers with different chain lengths of PLA can be obtained. Their chemical structures were characterized by FT-IR and 1H NMR. Through self-emulsification combined with solvent evaporation, HES-g-PLAs self-assembled into micelles with uniform sizes ranging from 65 to 130 nm, depending upon the chain length of PLA. In vitro release profiles of docetaxel-loaded HES-g-PLAs meet first-order release kinetics via a mechanism of diffusion and polymer chain relaxation. The size of the micelles and the amount of drug loading can be controlled by varying the chain length of PLA. Another significant result is that release rates of docetaxel can be also modulated by changing the chain lengths of the PLA segments.Amphiphilic hydroxyethyl starch-grafted polylactides with a varied chain length of the PLA segments self-assemble into nanomicelles. The lipophilic docetaxel (DTX) was loaded within the micelles. The release rates of docetaxel can be modulated by changing the chain length of the PLA segment.
Co-reporter:Yuandu Hu, Jianying Wang, Chengnian Li, Qin Wang, Hong Wang, Jintao Zhu, and Yajiang Yang
Langmuir 2013 Volume 29(Issue 50) pp:15529-15534
Publication Date(Web):2017-2-22
DOI:10.1021/la404082y
A new strategy to prepare core/shell Janus photonic crystal (PC) microspheres with reversible optical spectrum property is demonstrated. The microfluidic technique was employed to generate the uniform core/shell PC microspheres containing nanogels aqueous suspension. Under centrifugal force, the nanogel particles homogeneously dispersed in the core of microspheres would aggregate in the half of the microspheres, leading to Janus PC microspheres with varied reflection spectra at the different side of the spheres. More interestingly, such Janus structure of PC microspheres and their reflection spectrum were significantly reversible when the centrifugation was employed and removed alternatively. In addition, due to the soft and thermal-responsive nature of the building blocks (e.g., nanogels), Janus structures and optical properties of the PC microspheres are highly influenced by the temperature, centrifugal speed, and time, providing the other parameters on the manipulation of properties of the PC microspheres. This strategy provides a new concept for the preparation of Janus PC microspheres with tunable structures and optical properties, which will find potential applications in the field of sensors, optical devices, barcodes, etc.
Co-reporter:Hong Wang, Liang He, Bogumil E. Brycki, Iwona H. Kowalczyk, Edyta Kuliszewska, Yajiang Yang
Electrochimica Acta 2013 90() pp: 326-331
Publication Date(Web):
DOI:10.1016/j.electacta.2012.11.130
Co-reporter:Qin Wang, Di Zhang, Huibi Xu, Xiangliang Yang, Amy Q. Shen and Yajiang Yang
Lab on a Chip 2012 vol. 12(Issue 22) pp:4781-4786
Publication Date(Web):31 Aug 2012
DOI:10.1039/C2LC40740J
In this work, we report a new strategy to fabricate monodispersed radiopaque alginate (Ba–alginate) microgels by a one-step microfluidic method. Alginate droplets containing sulfate ions are first formed by a flow focusing microfluidic setup. These alginate droplets are subsequently solidified by barium ions in a collection bath. During the solidification process, excessive barium ions in the collection bath also react with sulfate ions in the alginate droplet, resulting in barium sulfate (BaSO4) nanoparticles in situ synthesized (acting as radiopaque imaging agents) within the Ba–alginate microgels. Scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX) illustrate that 800 nm BaSO4 nanoparticles are uniformly distributed inside the 30 μm Ba–alginate microgels, with 62 wt% of elemental barium (Ba). In addition, X-ray diffraction (XRD) measurements indicate that the BaSO4 nanoparticles consist of 10 nm in situ synthesized BaSO4 crystallites. The alginate microgels act as a soft and porous template to prevent the precipitation and aggregation of BaSO4 nanoparticles. The Ba–alginate microgels are also visible under X-ray radiation. The facile route to fabricate alginate microgels as radiopaque embolic materials is of particular importance for endovascular embolization and localized diagnostic imaging applications. Similar approaches can also be adopted for synthesizing other inorganic nanoparticles in microgels.
Co-reporter:Yuandu Hu, Jianying Wang, Hong Wang, Qin Wang, Jintao Zhu, and Yajiang Yang
Langmuir 2012 Volume 28(Issue 49) pp:17186-17192
Publication Date(Web):November 15, 2012
DOI:10.1021/la304058j
Soft photonic crystals (PC) are more appealing due to the responsiveness of the building blocking-deformable nanoparticles to the external stimuli. In this report, we demonstrate, for the first time, the generation of soft core/shell PC microspheres through a combination of a microfluidic technique, encapsulation of well-ordered temperature responsive polymer nanogels suspension, and photopolymerization of a transparent shell resin. This strategy not only ensures the monodispersity of core/shell PC microspheres, but also precisely controls their size, shell thickness, and optical properties by simply adjusting the flow rate ratio and mass fraction of the nanogels. More interestingly, the intensity of the reflection spectra of the crystalline nanogel arrays in the core can be modulated reversibly by controlling the shell thickness or the temperature. As a result of their symmetric structure, the resulting PC microspheres exhibited excellent structural colors and photonic band gaps for normal incident light independent of the position on the spherical surface. Multifunctional PC microspheres can also be generated by simply dispersing functional species together with the nanogels. This core/shell PC microsphere with tunable shell thickness and reversible thermoresponse could be significant for potential applications in the fields of chemical/biological sensors, display, encoding, and optical switching.
Co-reporter:Hong Wang;Fang Fang;Xue Li;Cheng Fu
Science Bulletin 2012 Volume 57( Issue 33) pp:4257-4263
Publication Date(Web):2012 November
DOI:10.1007/s11434-012-5451-1
Retinyl palmitate (RP) is a derivative of Vitamin A and widely applied as the active component in the fields of cosmetic and pharmaceutics. RP can easily lose its physiological activity under UV irradiation due to its photosensitivity. In this work, it was found that the activity of RP remained 75% after 80 min of UVA irradiation when RP was entrapped in supramolecular gels formed by self-assembly of sorbitol-based gelators. By contrast, the activity of RP in conventional hydroxyethyl cellulose gels only remained 10% under the same conditions. These results showed that the supramolecular gels exhibited a significant protective effect on the photostability of RP. UV spectra of RP in supramolecular gels and corresponding solutions showed no distinct differences, indicating no change of the physicochemical properties of RP. The images of field-emission scanning electron microscopy and fluorescent optical microscopy suggested that the protection by supramolecular gels on the photostability of RP may be attributed to the three-dimensional network structure formed by the self-assembly of the gelators, which reduced the molecular collisions and the degradation process of the photoactivated RP. The present results showed that this protection can be influenced by the structures and the concentration of gelators as well as by the solvent composition.
Co-reporter:Hong Wang, Cheng Fu, Xue Li, Liang He and Yajiang Yang
Soft Matter 2011 vol. 7(Issue 19) pp:8892-8897
Publication Date(Web):08 Aug 2011
DOI:10.1039/C1SM05568B
A new strategy was proposed to monitor transition behavior involved in F−- and H+-triggered reversible supramolecular self-assembly/disassembly by using a Ru2+ complex (Ru(Phen)32+) as a fluorescent probe. N,N-Dibenzoyl-L-cystine (DBC) was used as gelator to form supramolecular gels. Fluorescent images of the fluorescent-labelled DBC gels indicate that Ru(Phen)32+ is dispersed in the gapping place of three-dimensional networks formed by fibrillar DBC aggregates. In a certain range of F− concentrations, it was found that there is a good linear relationship (R2 = 0.999) between F− concentrations and the fluorescent intensity difference between the DBC gels and corresponding solutions. The phase transition temperature of DBC gels is increased with a decrease of F− concentration. Interestingly, the addition of H+ to disassembled systems results in reassembly of DBC. The rate of H+-triggered reassembly is increased with an increase of the H+ concentration. SEM images of reassembled aggregates show no substantial difference in comparison with that of original DBC aggregates, indicating that the F−- and H+-triggered disassembly/reassembly is completely reversible. Time-dependent fluorescent spectra indicate that monitoring self-assembly/disassembly transitions by using the Ru2+ complex as a fluorescent probe is a fast and precise strategy.
Co-reporter:Hong Wang, Chongyue Yi, Xue Li, Fang Fang, Yajiang Yang
Journal of Luminescence 2011 Volume 131(Issue 4) pp:603-607
Publication Date(Web):April 2011
DOI:10.1016/j.jlumin.2010.10.040
Luminescence enhancement of terbium-ion prulifloxacin complexes (Tb(III)–PUFX) in supramolecular hydrogels formed by assembly of 1,3:2,4-di-O-benzylidene-D-sorbitol (DBS) was investigated by steady-state fluorescence, varying temperature fluorescence and time-resolved fluorescence. The luminescence images show that Tb(III)–PUFX were dispersed in the DBS gels. The luminescence intensity of Tb(III)–PUFX in the DBS gels was significantly increased in comparison with that in corresponding aqueous solutions. The varying temperature fluorescent spectra show that the luminescence intensity of Tb(III)–PUFX decreased with an increase in the temperature. This implies that the luminescence enhancement of Tb(III)–PUFX is related to the dissociation and the formation of the DBS assemblies. Time-resolved fluorescence measurements show slower rotational motion in DBS gels in comparison with that in the corresponding aqueous solutions. This may be ascribed to a unique microstructure of three-dimensional network formed by DBC aggregates, resulting in deactivation of the nonradiative relaxation. The images of field emission scanning electron microscopy and polarized optical microscopy indicate that the morphology of the DBS assemblies was not influenced upon addition of Tb(III)–PUFX to the DBS gels.
Co-reporter:Xuelin Dong, Hong Wang, Fang Fang, Xue Li, Yajiang Yang
Electrochimica Acta 2010 Volume 55(Issue 7) pp:2275-2279
Publication Date(Web):28 February 2010
DOI:10.1016/j.electacta.2009.11.042
Bis(4-acylaminophenyl)methane (G1) and bis(4-acylaminophenyl)ether (G2) with varied acyl chains were found to be efficient gelators for the gelation of imidazole-based ionic liquids. The supramolecular gel electrolytes were formed via the self-assembly of these gelators in ionic liquids. The minimum gelator concentrations (MGCs) for the gelation of ionic liquids depend on the chemical structures of the gelators. The longer the acyl chains, the lower the MGCs. Polarized optical microscopy images of the ionic-liquid gels reveal the formation of spherical crystallites resulting from the fibrillar aggregates of the gelators. In addition, the phase transition temperatures of the ionic-liquid gels increase with an increase of the acyl chain length of the gelators. The impedance spectra of the ionic-liquid gels indicate that the temperature dependence of the conductivity follows the classical Arrhenius equation. The conductivities of ionic-liquid gels also decrease with an increase of the acyl chain length, but the differences in conductivities between the gels and corresponding ionic liquids are in one order of magnitude. The ionic-liquid gels possess a stable electrochemical window.
Co-reporter:Lei Tan, Xuelin Dong, Hong Wang, Yajiang Yang
Electrochemistry Communications 2009 Volume 11(Issue 5) pp:933-936
Publication Date(Web):May 2009
DOI:10.1016/j.elecom.2009.02.025
Three types of gelators, bis(4-octanoylaminophenyl) ether (BODE), bis(4-octanoylaminophenyl) methane (BODM) and 2,4′-bis(octanureido) toluene (BOUT) were utilized as gelators for the gelation of ionic liquid 1-butyl-3-menthyl-imidazolium hexafluorophosphate ([C4mim]PF6). The mean minimum gelator concentrations (MGCs) for the [C4mim]PF6 were found to be less than 2 wt%. The polarized optical microscopy image of [C4mim]PF6 gels reveals the formation of spherical crystallites resulting from the fibrillar aggregates of the gelators. The cyclic voltammograms of the [C4mim]PF6 gels indicate a good electrochemical stability over the range from −3.0 to 3.0 V. The impedance spectra of the [C4mim]PF6 gels show good linear relationships between ion conductivity and temperature, indicating that the temperature dependence of the conductivity follows the classical Arrhenius equation.
Co-reporter:Qin Wang;Yanbing Zhao;Huibi Xu;Xiangliang Yang
Journal of Applied Polymer Science 2009 Volume 113( Issue 1) pp:321-326
Publication Date(Web):
DOI:10.1002/app.29642
Abstract
Thermosensitive poly(N-isopropylacrylamide-co-acrylamide) microgel particles were prepared through precipitation polymerization. The diameters of the microgel particles were in the range of 220–270 nm and showed a monodispersion. The lower critical solution temperatures (LCST) of the microgel dispersions were measured by dynamic light scattering and turbidimetric analysis. The results indicated that the LCST increased with an increase of acrylamide (AAm) content in the copolymer composition. The kinetics of the thermosensitive phase transitions of the microgel particles were investigated by time-course UV–vis spectroscopy. The results indicated that the higher the content of AAm in copolymer composition, the more time is required for equilibrium deswelling and the less time required for equilibrium swelling. In addition, the time required for equilibrium deswelling decreased with an increase of the content of the microgel particles in dispersions. By contrast, the time required for equilibrium swelling increased slightly. Thus, a suitable LCST and time required for equilibrium of phase transition can be achieved by adjusting the molar ratio of the comonomers in the microgels and the content of the microgel particles in dispersions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Qin Wang;Huibi Xu;Xiangliang Yang
Polymer Engineering & Science 2009 Volume 49( Issue 1) pp:177-181
Publication Date(Web):
DOI:10.1002/pen.21237
Abstract
Thermosensitive poly(N-isopropylacrylamide-co-acrylamide) nanogels with varied monomer compositions were prepared by precipitation polymerization. The aqueous dispersions of these thermosensitive nanogels (9 wt% of nanogel particles in phosphate-buffered saline solution) exhibited in situ gelable characteristics. A steady-state and dynamic rheological analysis demonstrated that the nanogel dispersions were typical pseudoplastic liquids at room temperature. The viscosity of the nanogel dispersions at a constant shear rate increased with an increase of the acrylamide content. When the temperature was increased to 37°C, the pseudoplastic liquid turned into an elastic solid, as the result of a sol–gel phase transition of the nanogel aqueous dispersion during the raise of the temperature. Dynamic temperature ramp circle curves suggest that the sol–gel transition was reversible but with a clear hysteresis. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
Co-reporter:Hong Wang, Weiping Zhang, Xueling Dong, Yajiang Yang
Talanta 2009 Volume 77(Issue 5) pp:1864-1868
Publication Date(Web):15 March 2009
DOI:10.1016/j.talanta.2008.10.040
Fluorescence enhancement of acridine orange (AO) in supramolecular hydrogels formed by self-assembly of the gelators 3-{[(2R)-2-(octadecylamino)-3-phenylpropanoyl]amino}butyrate (TC18PheBu) and 1,3:2,4-di-O-benzylidene-d-sorbitol (DBS) was investigated by steady-state and varying temperature fluorescence, polarized fluorescence and time-resolved fluorescence techniques. The results showed that the fluorescence intensities of AO in the gels remarkably increased in comparison with AO aqueous solutions, and increased with an increase of the gelator concentrations. The varying temperature fluorescence analysis indicated that fluorescence intensities of AO in the gels decreased upon an increase of temperature, and vice versa. This can be attributed to aggregation and dissociation of the gelators in the systems, since the fluorescence enhancement of AO was induced by self-assembly of the gelators. Polarized fluorescence analysis indicated that the values of anisotropy (r) of AO are significantly higher than that in water. This further confirmed that the three-dimensional network formed by the gelator aggregates constrained the rotation of AO entrapped within the gels, resulting in high values of anisotropy. Time-resolved fluorescence analysis indicated that the rates of fluorescence decay in the gels are lower than that in water. These results reveal thermo-reversibility of the fluorescence enhancement of AO in supramolecular hydrogels.
Co-reporter:Yun Xiong, Zifu Li, Guilong Feng, Hong Wang, Huibi Xu, Xiangliang Yang and Yajiang Yang
Physical Chemistry Chemical Physics 2008 vol. 10(Issue 43) pp:6479-6482
Publication Date(Web):25 Sep 2008
DOI:10.1039/B813525H
The self-assembly of low molecular weight gelators confined within the nano-scale interlayer space of organo-montmorillonite is likely to be different from that under normal conditions (bulk space). Four kinds of gelators, 1-methyl-2,4-bis(N′-n-octadecylureido) benzene (MBB18), 1-methyl-2,4-bis(N′-n-dodecylureido)benzene (MBB12), bis(4′-stearamido phenyl) methane (BSM18) and bis(4′-octanamido phenyl)methane (BOM8), were used to investigate gelation of organic solvents confined within the nano-scale interlayer space of organo-montmorillonite. The possible morphologies of these gelators aggregates confined within the nano-scale space of organo-montmorillonite will be discussed in comparison with that in bulk space by employing differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Herein, two types of organogels were prepared under the same conditions. One of them was formed within the interlayer space of organo-montmorillonite and another was formed in bulk space. The XRD patterns confirm that self-assembly of gelators takes place via an unusual pathway within the confined interlayer space of organo-montmorillonite, indicating that the alkyl chains of gelators adopt a parallel arrangement and do not insert into each other. This unusual arrangement of gelators confined within the interlayer space of organo-montmorillonite does lead to the different thermal effect observed by the DSC measurements. These features ultimately strengthen the thermodynamic stability of gelator aggregates, for example MBB18, and raise the gel-to-sol transition temperature, which jumps from 60 to 123 °C.
Co-reporter:Shengzu Zhang;Xinjian Fu;Hong Wang
Journal of Separation Science 2008 Volume 31( Issue 21) pp:
Publication Date(Web):
DOI:10.1002/jssc.200800349
Abstract
The polymerizable gelator N-octadecyl maleamic acid (ODMA) can self-assemble in selected polymerizable organic solvents, such as 2-hydroxyethyl methacrylate (HEMA) and methylacrylic acid (MAA) to form thermally stable polymerizable organogels. A mixture consisting of HEMA and MAA as the monomer and functional monomer, PEG dimethacrylates (PEG200DMA) as the crosslinker, BOC-L-phenylalanine (BPA) or L-phenylalanine ethyl ester (PEE) as the chiral templates, was gelatinized by ODMA firstly and subsequently polymerized by in situ UV irradiation or thermal initiation. The molecularly imprinted polymerized organogels were obtained after the removal of the templates through ethanol extraction. Selective adsorption of D- and L-phenylalanine was performed on the polymerized organogels. The results indicate rather high adsorption efficiency obtained for L-phenylalanine compared with that for D-phenylalanine, which was found to be dependent on the concentrations of ODMA, content of template, and the method of polymerization. Herein, the concentration of ODMA in the organogels played an important role for the adsorption efficiency of D- and L-phenylalanine.
Co-reporter:Wanyu Chen, Yajiang Yang, Chang H. Lee and Amy Q. Shen
Langmuir 2008 Volume 24(Issue 18) pp:10432-10436
Publication Date(Web):August 13, 2008
DOI:10.1021/la801734x
1,3:2,4-di-p-methylbenzylidene sorbitol (MDBS) is a small organic molecule that is capable of inducing self-assembly in a wide variety of organic solvents and of forming organogels. In this paper, we present a novel approach to tune the network architectures of organogels by utilizing geometric confinement while varying the gelator concentration. Self-assembly of MDBS in propylene carbonate (PC) is investigated in a series of microchannels with widths varying from 20 to 80 μm and the gelator concentration varying from 2 to 7 wt %. We demonstrate by optical microscopy and scanning electron microscopy (SEM) that a transition from fibrillar structure to sheaflike spherulite structure occurs when (a) the channel width is increased for fixed gelator concentrations and (b) gelator concentration is increased for fixed channel widths. A phase diagram is built based on these observations. Polarized microscopy and transmission electron microscopy (TEM) images are also obtained for organogel under unconfined condition to display the spherulite structures viewed under different length scales. The thermal properties of the organogel are measured by differential scanning calorimetry (DSC) to verify the structural difference obtained under confined and unconfined conditions and the structure stability. Our results provide a novel strategy to control the topological structure of self-assembled systems and to modify their thermal properties via geometric confinement.
Co-reporter:Xinjian Fu, Ningxia Wang, Shengzu Zhang, Hong Wang, Yajiang Yang
Journal of Colloid and Interface Science 2007 Volume 315(Issue 1) pp:376-381
Publication Date(Web):1 November 2007
DOI:10.1016/j.jcis.2007.06.013
A novel chiral hydrogelator, l-phenylalanine derivative can self-assemble in aqueous media at different pH values to form supramolecular hydrogels. The images of the FE-SEM indicate that different aggregates of TC18PheBu in morphology were formed, which further lead to the formation of spherical crystallites as observed by polarized optical microscope (POM). The FT-IR spectra of the supramolecular hydrogels reveal that intermolecular hydrogen-bonding and hydrophobic interactions are the driving forces for the self-assembly of TC18PheBu. Fluorescence spectra of TC18PheBu in aqueous solutions in the presence of pyrene as a probe further confirm the importance of hydrophobic interactions for the self-assembly. The circular dichroism (CD) spectra of TC18PheBu in supramolecular hydrogels in the presence of KF indicate that the hydrogen-bonding interaction can be disrupted by fluoride ions, which further confirm the importance of hydrogen bonding for the self-assembly of TC18PheBu.A novel chiral hydrogelator, l-phenylalanine derivative (TC18PheBu) can self-assemble in aqueous media to form supramolecular hydrogels. Investigation of the formation mechanism of the supramolecular hydrogel indicates that hydrogen bonding and hydrophobic interactions are driving forces through the characterization of POM, FT-IR, fluorescence, and CD.
Co-reporter:Shengfang Li;Xiangliang Yang;Huibi Xu
Journal of Applied Polymer Science 2007 Volume 105(Issue 6) pp:3432-3438
Publication Date(Web):30 MAY 2007
DOI:10.1002/app.26389
The enzymatic degradation mechanism of semi-interpenetrating network (semi-IPN) hydrogel of poly (acrylic acid-acrylamide-methacrylate) crosslinked by azocompound and amylose in vitro was investigated in the presence of Fungamyl 800L (α-amylase) and rat cecum content (cecum bacteria). The degradation mechanism involves degradable competition, i.e., reduction of azo crosslinkage is dominant in the earlier period of degradation. Subsequently, the degradation of gels is continued by combination of reduction of azo crosslinkage and hydrolysis of amylose. The cumulative release ratios of Bovine serum albumin (BSA, as a model drug) loaded semi-IPN gels are 25% in pH 2.2 buffer solutions and 74% in pH 7.4 buffer solutions within 48 h. Moreover, the release behavior of BSA from the semi-IPN gels indicates that it follows Fickian diffusion mechanism in pH 2.2 media and non-Fickian diffusion and polymer chains relaxation mechanism in pH 7.4 media. The results indicate that the release of BSA from the semi-IPN gels was controlled via a combined mechanism of pH dependent swelling and specificity to enzymatic degradation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Co-reporter:Xinjian Fu;Ningxia Wang;Yang Yang;Hong Wang
Journal of Molecular Recognition 2007 Volume 20(Issue 4) pp:238-244
Publication Date(Web):11 JUL 2007
DOI:10.1002/jmr.831
N-Stearine-N′-stearyl-L-phenylalanine, a chiral compound, was synthesized and used as a gelator for the gelation of polymerizable solvents, such as ß-hydroxyethyl methacrylate (HEMA), styrene, etc. The scanning electron microscope (SEM) images of the gelator aggregates show fibril-like helices, typical chiral aggregates with diameters of 100–200 nm. The solvent molecules were immobilized by capillary forces in the three-dimensional network structures of the organogels. The HEMA organogels containing crosslinker polyethylene glycol dimethacrylates (PEG200DMA) were subsequently polymerized by in situ UV irradiation. A porous polymerized organogels were obtained after removal of gelator aggregates through ethanol extraction. The chiral separation of D- and L-phenylalanine was carried out by the adsorption of the polymerized organogels. The adsorption efficiency of L-phenylalanine on the polymerized organogels was found to be dependent on the concentration of the gelator and crosslinker. Copyright © 2007 John Wiley & Sons, Ltd.
Co-reporter:Qin Wang;Yanbing Zhao;Huibi Xu
Colloid and Polymer Science 2007 Volume 285( Issue 5) pp:515-521
Publication Date(Web):2007 February
DOI:10.1007/s00396-006-1592-6
In situ gelable poly(N-isopropylacrylamide-co-acrylamide) microgels were prepared by precipitation polymerization in the presence of various amounts of N,N′-methlenebisacrylamide as a crosslinker. The diameters of microgels were in the range of 200–300 nm with narrow distributions as determined by photo correlation spectroscopy. The equilibrium swelling ratio and thermosensitive properties of the microgels increased with decreasing crosslinker content. The volume phase transition of microgels dispersions at high concentrations were investigated by phase diagrams. The microgels dispersions experienced four phases when the temperature was increased: semitranslucent swollen gel, clear flowable suspension, cloud flowable suspension, and white shrunken gel. The related phase transition temperatures were influenced by crosslinker content and the concentration of the microgel dispersions. Herein, the gelation temperature was changed by more than 20 °C, shrinking temperatures were slightly changed by about 3 °C, and cloud point temperatures showed almost no change. The three phase transition temperatures of microgels dispersed in phosphate-buffered saline solutions were lower than that in water. As drug carriers, the release rates of bleomycin from bleomycin-loaded microgel dispersions exhibited diffusion control at human body temperature.
Co-reporter:Yanbing Zhao;Wanyu Chen;Xiangliang Yang
Colloid and Polymer Science 2007 Volume 285( Issue 12) pp:1395-1400
Publication Date(Web):2007 September
DOI:10.1007/s00396-007-1710-0
Ionically cross-linked polyampholytic hydrogels were synthesized by redox copolymerization of acrylamide and an ionic complex of (N,N-diethylamino)ethyl methacrylate and acrylic acid (designated as PADA hydrogel). The swelling behavior of the hydrogels in water indicated that a minimal equilibrium swelling ratio is found when the molar ratio of anionic/cationic monomers was 1.55. In NaCl solution, the hydrogels exhibited the typical swelling behavior of conventional polyampholytic gels. Their equilibrium swelling ratios increased with an increase in the NaCl concentration. In solutions of multivalent ions (CaCl2 and trisodium citrate solutions), the equilibrium swelling ratios of the hydrogels increased first and were then followed by a decrease with an increase in salt concentration. Interestingly, an unexpected abrupt swelling phenomenon was observed when the fully swollen hydrogels in salt solution were transmitted to pure water. The unique swelling behavior of PADA hydrogels depends not only on the molar ratio of the anionic/cationic monomers but also on the valency of the ions.
Co-reporter:Chang Xueling, Li Wang, Yajiang Yang, Xiangliang Yang, Huibi Xu
Materials Chemistry and Physics 2006 Volume 99(Issue 1) pp:61-65
Publication Date(Web):10 September 2006
DOI:10.1016/j.matchemphys.2005.09.081
Gelator, bis-(4-stearoylaminophenyl)methane (BSAPM), can be used to gelatinize some organic solvents, such as benzene and n-butanol and so on. TEM images of n-butanol gel indicate that BSAPM can self-assembled at lower concentration (less than 3 wt.%) into fiber-like aggregates, which in turn form an extended three-dimensional network structure. The driving force for BSAPM assembling in organic solvent is mainly hydrogen bonding, π–π stack interaction and other non-covalent intermolecular interaction. Using the fiber-like aggregates assembled by BSAPM as templates, tetraethoxysilane (TEOS) can be adsorbed onto the surfaces of fiber-like aggregates and then polymerized by sol–gel polymerization. SiO2 nanowires were formed after calcinations. SEM and AFM images indicate that silica consisted of nanowires structures with diameters of 200–500 nm and lengths of 2–18 μm.
Co-reporter:Yanbing Zhao;Huibi Xu;Xiangliang Yang
Journal of Applied Polymer Science 2006 Volume 102(Issue 4) pp:3857-3861
Publication Date(Web):29 AUG 2006
DOI:10.1002/app.24877
A novel polyampholyte hydrogels were prepared by free radical aqueous copolymerization of ionic complex consisting of acrylic acid (AAc), (N,N-diethylamino) ethyl methacrylate (DEAEM), and acrylamide (designated as PADA). Without any chemical crosslinker, the formation of PADA network structures was mainly attributed to the electrostatic interaction of AAc (anionic monomer) and DEAEM (cationic monomer). The PADA gels exhibited a typical swelling behavior of polyampholyte gels in buffer solutions. The hysteresis of isoelectric point (pI) for PADA gels was observed after preswollen in alkaline solutions. The swelling behavior of PADA gels in response to change of pH was investigated. It was found that the equilibrium swelling ratio orderly decreased in buffer solutions with alternating pH between 2.2 and 5. An abrupt swelling was observed for the hydrogels at the pH near isoelectric point in the earlier stage of swelling process. The study of swelling kinetics of the hydrogels showed that the swelling process was in agreement with the second-order swelling kinetics. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3857–3861, 2006
Co-reporter:Yanbing Zhao;Wanyu Chen;Wei Liu;Jianjun Xia;Xiangliang Yang;Huibi Xu
Macromolecular Chemistry and Physics 2006 Volume 207(Issue 18) pp:1674-1679
Publication Date(Web):18 SEP 2006
DOI:10.1002/macp.200600116
Summary: An ionic complex of anionic and cationic monomers was obtained when (N,N-diethylamino)ethylmethacrylate (DEAEM) was protonated with acrylic acid (AAc). Through the free radical copolymerization of the ionic complex and acrylamide (AAm) in aqueous solution, a novel ionically crosslinked polyampholyte gel (poly(AAc-DEAEM-AAm), designated PADA) was prepared without chemical crosslinker. An investigation of swelling behavior indicated that PADA gels exhibited peculiar erosion phenomena under contact and non-contact DC electric fields. Under contact DC electric fields, PADA gels of swollen equilibrium experienced a dual response to DC fields, i.e., swelling first and then erosion. This phenomenon has not been described elsewhere. In contrast to with the contact DC electric fields, PADA gels did not undergo a swelling process, but eroded completely within 20 min under non-contact DC fields. The NaCl concentration in electrolyte solutions greatly influenced the swelling/eroding behavior of PADA gels because the ionic crosslinkages of PADA gels could be weakened and screened by salt ions. The combined effects of higher NaCl concentration and local pH change near the electrode under DC electric fields resulted in crosslinkages quickly dissociating into cationic and anionic groups. In this case, PADA gels did not experience the swelling process, but directly eroded. Moreover, the erosion rate of PADA gels was related to the voltage of the electric field. The swelling/eroding rate for the gels in contact with the cathode was faster than that for the gels in contact with the anode. This difference can be attributed to varying local pH near different electrodes.
Co-reporter:Mingxing Liu, Jing Dong, Yajiang Yang, Xiangliang Yang, Huibi Xu
European Polymer Journal 2005 Volume 41(Issue 2) pp:375-382
Publication Date(Web):February 2005
DOI:10.1016/j.eurpolymj.2004.09.015
Triptolide (TP), which has immunosuppressive effect, anti-neoplastic activity, anti-fertility function and severe toxicities on digestive, urogenital, blood circulatory system, was used as a model drug in this study. TP-loaded poly (d,l-lactic acid) (PLA) nanoparticles were prepared by the modified spontaneous emulsification solvent diffusion method (modified-SESD method). Dynamic light scattering system (DLS), transmission electron microscope (TEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), X-ray powder diffractometry and Fourier transform infra-red spectroscopy (FT-IR) were employed to characterize the nanoparticles fabricated for size and size distribution, surface morphology, the physical state of drug in nanoparticles, and the interaction between the drug and polymer. Encapsulation efficiency (EE) and the in vitro release of TP in nanoparticles were measured by the reverse phase high-performance liquid chromatography (RP-HPLC). The produced nanoparticles exhibited a narrow size distribution with a mean size of approximately 150 nm and polydispersity index of 0.088. The morphology of the nanoparticles exhibited a fine spherical shape with smooth surfaces without aggregation or adhesion. TP-entrapped in nanoparticles was found in the form of amorphous or semicrystalline. It was found that a weak interaction existed between the drug and polymer. In all experiments, more than 65% of EE were obtained. The in vitro release profile of TP from nanoparticles exhibited a typical biphasic release phenomenon, namely initial burst release and consequently sustained release. In this case, the particle size played an important role for the drug release. The modified-SESD method was a potential and advantage method to produce an ideal polymer nanoparticles for drug delivery system (DDS).
Co-reporter:Yihua Yin;Huibi Xu;Yihua Yin;Huibi Xu
Journal of Applied Polymer Science 2002 Volume 83(Issue 13) pp:2835-2842
Publication Date(Web):10 JAN 2002
DOI:10.1002/app.10259
Hydrogels based on n-alkyl methacrylate esters (n-AMA), acrylic acid, and acrylamide crosslinked with 4,4′-di(methacryloylamino)azobenzene were prepared. Swelling behavior of the hydrogels was studied by the immersion of slabs in buffered solutions at pH 2.2–7.4. The diffusion of water into the slabs was discussed on the stress relaxation model of polymer chains. The results obtained are in good agreement with Schott's second-order diffusion kinetics. The constants A and B of Schott's kinetics equation depend on the balance of hydrophobicity/hydrophilicity, the rigidity/flexibility, and the degree of crosslinking. The factors that exert the greatest influence on the swelling behavior of the gels include the degree of crosslinking, the lengths of the n-AMA side chains, and pH values. By adjusting these factors, the degree of swelling of the hydrogels in the small intestine can be controlled, and consequently the drugs may avoid being released before arriving in the colon. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2835–2842, 2002; DOI 10.1002/app.10259
Co-reporter:Yun Xiong, Zifu Li, Guilong Feng, Hong Wang, Huibi Xu, Xiangliang Yang and Yajiang Yang
Physical Chemistry Chemical Physics 2008 - vol. 10(Issue 43) pp:NaN6482-6482
Publication Date(Web):2008/09/25
DOI:10.1039/B813525H
The self-assembly of low molecular weight gelators confined within the nano-scale interlayer space of organo-montmorillonite is likely to be different from that under normal conditions (bulk space). Four kinds of gelators, 1-methyl-2,4-bis(N′-n-octadecylureido) benzene (MBB18), 1-methyl-2,4-bis(N′-n-dodecylureido)benzene (MBB12), bis(4′-stearamido phenyl) methane (BSM18) and bis(4′-octanamido phenyl)methane (BOM8), were used to investigate gelation of organic solvents confined within the nano-scale interlayer space of organo-montmorillonite. The possible morphologies of these gelators aggregates confined within the nano-scale space of organo-montmorillonite will be discussed in comparison with that in bulk space by employing differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Herein, two types of organogels were prepared under the same conditions. One of them was formed within the interlayer space of organo-montmorillonite and another was formed in bulk space. The XRD patterns confirm that self-assembly of gelators takes place via an unusual pathway within the confined interlayer space of organo-montmorillonite, indicating that the alkyl chains of gelators adopt a parallel arrangement and do not insert into each other. This unusual arrangement of gelators confined within the interlayer space of organo-montmorillonite does lead to the different thermal effect observed by the DSC measurements. These features ultimately strengthen the thermodynamic stability of gelator aggregates, for example MBB18, and raise the gel-to-sol transition temperature, which jumps from 60 to 123 °C.
Co-reporter:Huabo Huang, Xiaoping Zeng, Wan Li, Hong Wang, Qin Wang and Yajiang Yang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 39) pp:NaN16522-16522
Publication Date(Web):2014/08/05
DOI:10.1039/C4TA03332A
By using the in situ polymerization of aniline in an aqueous solution of sodium alginate, we prepared reinforced conducting hydrogels (PANI–SA) with good conductivity (∼10−3 S cm−1). SEM images indicated that the microstructure of PANI–SA hydrogels was a typical 3D nano-fiber network formed by the entanglement of the PANI and SA molecular chains, leading to a good compressive strength (∼41 kPa). Because the system does not contain any adhesives and conducting fillers, the PANI–SA conducting hydrogels with self-supported structures can be directly employed as electrode materials for supercapacitors. A study of cyclic voltammograms indicated that the currents of the cathodic peak significantly increased with an increase in the scan rate, indicating that the electrode materials possess good responsiveness. As a reference, traditional compressive tablet electrodes were also prepared by mixing the powder of PANI–SA xerogels, adhesive and conducting filler. The results of galvanostatic charge/discharge and impedance show that PANI–SA hydrogels possess longer discharge times, higher specific capacitance and lower electronic resistance in comparison with compressive tablet electrodes. After 1000 cycles of charge/discharge, there is almost no difference in the retained specific capacitance between PANI–SA hydrogels electrodes and compressive tablet electrodes. The easily fabricated PANI–SA conducting hydrogels show great potential as electrode materials for supercapacitors.
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