共查询到20条相似文献,搜索用时 15 毫秒
1.
Jae Hyeung Park Hyun Woo Lee Dong Keun Chae Weontae Oh Jae Deuk Yun Yulin Deng Jeong Hyun Yeum 《Colloid and polymer science》2009,287(8):943-950
Submicron fibers of the composite of poly(vinyl alcohol) (PVA), chitosan oligosaccharide [COS, (1→4)2-amino-2-deoxy-β-d-glucose], and montmorillonite clay (MMT) were prepared using electrospinning method with aqueous solutions. Scanning electron
microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), thermal gravimetric analyzer, and tensile strength
testing machine (Zwick) were utilized to characterize the PVA/COS/MMT nanofiber mats morphology and properties. The PVA/COS
ratio and MMT concentration play important roles in nanofiber mat properties. XRD and TEM data demonstrated that exfoliated
MMT layers were well-distributed within nanofiber. It was also found that the mechanical property and thermal stability were
increased with COS and MMT contents. 相似文献
2.
壳聚糖/聚乙烯醇共混超细纤维的制备及紫外光交联研究 总被引:4,自引:0,他引:4
用静电纺丝法制备壳聚糖/聚乙烯醇的共混超细纤维,采用扫描电镜考察了纺丝液浓度、共混物配比、喷丝口内径对纤维形貌的影响.此外,为减少壳聚糖/聚乙烯醇纤维膜的溶胀变形,在上述体系中加入可光交联的单体二缩三乙二醇双甲基丙烯酸酯(TEGDMA)、引发剂2-羟基-2-甲基-1苯基丙酮(1173),对电纺纤维进行紫外光交联.结果表明,当壳聚糖与聚乙烯醇质量比为8:2的共混体系中加入占混合溶液质量分数4%的TEGDMA、0.12%的1173作为交联剂时,所得的无纺布纤维直径比较均一,平均约为200 nm,经光交联处理后其耐水性能得到提高. 相似文献
3.
Mário A. P. Nunes Hélder Vila-Real Pedro C. B. Fernandes Maria H. L. Ribeiro 《Applied biochemistry and biotechnology》2010,160(7):2129-2147
A synthetic polymer, polyvinyl alcohol (PVA), a cheap and nontoxic synthetic polymer to organism, has been ascribed for biocatalyst
immobilization. In this work PVA–alginate beads were developed with thermal, mechanical, and chemical stability to high temperatures
(<80 °C). The combination of alginate and bead treatment with sodium sulfate not only prevented agglomeration but produced
beads of high gel strength and conferred enzyme protection from inactivation by boric acid. Naringinase from Penicillium decumbens was immobilized in PVA (10%)–alginate beads with three different sizes (1–3 mm), at three different alginate concentrations
(0.2–1.0%), and these features were investigated in terms of swelling ratio within the beads, enzyme activity, and immobilization
yield during hydrolysis of naringin. The pH and temperature optimum were 4.0 and 70 °C for the PVA–alginate-immobilized naringinase.
The highest naringinase activity yield in PVA (10%)–alginate (1%) beads of 2 mm was 80%, at pH 4.0 and 70 °C. The Michaelis
constant (K
Mapp) and the maximum reaction velocity (V
maxapp) were evaluated for both free (K
Mapp = 0.233 mM; V
maxapp = 0.13 mM min−1) and immobilized naringinase (K
Mapp = 0.349 mM; V
maxapp = 0.08 mM min−1). The residual activity of the immobilized enzyme was followed in eight consecutive batch runs with a retention activity
of 70%. After 6 weeks, upon storage in acetate buffer pH 4 at 4 °C, the immobilized biocatalyst retained 90% of the initial
activity. These promising results are illustrative of the potential of this immobilization strategy for the system evaluated
and suggest that its application may be effectively performed for the entrapment of other biocatalysts. 相似文献
4.
We studied the adsorption of two neutral polymers [poly(vinyl pyrrolidone) and poly(vinyl alcohol) (PVA)] on negatively charged
liposomes composed of 25:2:3 (molar ratio) soy lecithin/dicetyl phosphate/cholesterol.The liposomes were prepared in buffered
solution at pH 7.4 and were mixed with the solution of the polymers in the desired polymer/lipid ratios. Adsorption was measured
by determination of the equilibrium bulk concentration of the polymer. Protamine hydrochloride was used to aggregate the liposomes
with polymers adsorbed on their surface and to facilitate their separation from the equilibrium bulk solution. In the case
of PVA, quantitative adsorption measurements with a specific reagent were possible. Adsorption isotherms were recorded at
25 ± 0.2 °C. It was concluded that adsorbed and nonadsorbed PVA molecules are in equilibrium even at low polymer/lipide ratios.
The results were confirmed by dynamic laser light scattering, X-ray diffraction and thermal activity monitoring experiments.
Received: 13 October 2000 Accepted: 8 March 2001 相似文献
5.
Morphology and mechanical properties of poly(vinyl alcohol) and starch blends prepared by gelation/crystallization from solutions 总被引:1,自引:0,他引:1
In an attempt to produce biodegradation materials, poly(vinyl alcohol) (PVA)–starch (ST) blends were prepared by gelation/crystallization
from semidilute solutions in dimethyl sulfoxide (Me2SO) and water mixtures and elongated up to 8 times. The content of mixed solvent represented as Me2SO/H2O (volume percent) was set to be 60/40 assuring the greatest drawability of PVA homopolymer films. The PVA/ST compositions
chosen were 1/1, 1/3, and 1/5. The elongation up to 8 times could be done for the 1/1 blend but any elongation was impossible
for blends whose ST content was beyond 50%. When the blends were immersed in water at 20 or 83 °C, the solubility became considerable
for an undrawn blend with 1/5 composition and a drawn 1/1 blend with λ=8. To avoid this phenomenon, cross-linking of PVA chains
was carried out by formalization under formaldehyde vapor. Significant improvement could be established by the cross-linking
of PVA chains. For the 1/1 blend, the amount of ST dissolved in water at 23 °C was less than 3% for the undrawn state and
25% for the drawn film. The decrease in the ST content was enough for use as biodegradation materials. Namely, the water content
relating to the biodegradation in soil is obviously different from such a serious experimental condition that a piece of blend
film was immersed in a water bath. At temperatures above 0 °C, the storage modulus of the formalization blends became slightly
higher than those of the nonformalization blends. The Young's modulus of the drawn films with a draw ratio of 8 times was
2 GPa at 20 °C.
Received: 23 June 2000 Accepted: 30 October 2000 相似文献
6.
Submicron poly(vinyl alcohol) (PVA) fiber mats were prepared by electrospinning of aqueous PVA solutions in 6-8% concentration. Fiber morphology was observed under a scanning electron microscope and effects of instrument parameters including electric voltage, tip-target distance, flow rate and solution parameters such as concentration on the morphology of electrospun PVA fibers were evaluated. Results showed that, when PVA with higher degree of hydrolysis (DH) of 98% was used, tip-target distance exhibited no significant effect on the fiber morphology, however the morphological structure can be slightly changed by changing the solution flow rate. At high voltages above 10 kV, electrospun PVA fibers exhibited a broad diameter distribution. With increasing solution concentration, the morphology was changed from beaded fiber to uniform fiber and the average fiber diameter could be increased from 87 ± 14 nm to 246 ± 50 nm. It was also found that additions of sodium chloride and ethanol had significant effects on the fiber diameter and the morphology of electrospun PVA fibers because of the different solution conductivity, surface tension and viscosity. When the DH value of PVA was increased from 80% to 99%, the morphology electrospun PVA fibers was changed from ribbon-like fibers to uniform fibers and then to beaded fibers. The addition of aspirin and bovine serum albumin also resulted in the appearance of beads. 相似文献
7.
Atsushi Suzuki Motoyasu Fujiwara Masahiko Nishijima 《Colloid and polymer science》2008,286(5):525-534
We have studied the magnetic properties of an Fe(II) spin-crossover complex near its high spin/low spin (HS/LS) phase transition
in the emulsion polymerization of trifluoroethylmethacrylate (TFEMA) using poly(vinyl alcohol) (PVA) as a protective colloid,
in comparison with sodium lauryl sulfate (SLS). Morphological analysis was used to establish that the nanodispersed spin-crossover
complex was incorporated into the cores of polymer particles covered with PVA shells. The obvious bi-stability of the HS/LS
phase transition was considered by the identification of multiplet states such as the triplet (S = 1) and quintet (S = 2) states, and the paramagnetic state (S = 1/2), by noting a gradual shift of g-value anisotropy in the electron spin resonance (ESR) spectrum at 5 K. This was thought to have arisen from the exchange
interaction as a Jahn–Teller effect in the emulsion particles. Chemical modifications such as ligand substitution, and the
nature of the central metal atom in the emulsion particle, especially influenced the HS/LS phase transition. 相似文献
8.
<正>The stability ofpoly(vinyl alcohol)(PVA) nanofibrous mats in water media was improved by post-electrospinning treatments.Bifunctional glutaraldehyde(GA) in methanol was used as a crosslinking agent to stabilize PVA nanofiber,but fiber twinning was observed frequently,and the highly porous structure of PVA nanofibrous mats was destroyed when the crosslinked fiber was soaked in water.To overcome this shortcoming,chitosan(CS) was introduced into the PVA spinning solution to prepare PVA/CS composite nanofibers.Their treatment in GA/methanol solution could retain the fiber morphology of PVA/CS nanofibers and porous structure of PVA/CS nanofibrous mats even if they were soaked in aqueous solutions for 1 month.Scanning electron microscopy(SEM),X-ray diffraction(XRD),thermal gravimetric analysis(TGA) and differential scanning calorimetry(DSC) were applied to characterize the physicochemical structure and thermal properties of PVA nanofibers.It was found that the water resistance of PVA nanofibrous mats was enhanced because of the improvement of the degree of crosslinking and crystallinity in the electrospun PVA fibers after soaking in GA/methanol solution. 相似文献
9.
The reentrant behavior of Poly(vinyl alcohol) (PVA)–borax aqueous semidilute solutions with a PVA concentration of 20 g/l
and borax concentrations varies from 0.0 to 0.20 M was investigated using dynamic light scattering (DLS) and dynamic viscoelastic
measurements. Two (fast and slow modes) and three (fast, middle, and slow) relaxation modes of PVA semidilute aqueous solutions
without and with the presence of borax, respectively, were observed from DLS measurements. The fast and middle relaxation
modes were q
2-dependent (q is the scattering vector) characteristic of diffusive behavior; however, the slow modes were q
3-dependent, characteristic of intraparticle dynamics. The experimental results showed that the slow relaxation mode dominates
the DLS relaxation. The DLS slow mode relaxation time, τs, and the viscoelastic modulus G′(ω) and G′′(ω) data had a similar trend and demonstrated reentrant behavior as the borax concentration was increased from 0.0 to 0.20 M,
i.e. τs, G′(ω), and G′′(ω) fluctuated with increasing borax concentration. The excluded-volume effect of polymers, charge repulsion among borate
ions bound on PVA molecules, and intermolecular cross-linking didiol–borate complexation caused an expansion of the polymer
chain; however, the screening effect of free Na+ ions on the negative charge of the borate ions bound on PVA and intramolecular cross-linking didiol–borate complexation led
to a shrinkage of the polymer chain. The reentrant behavior was the consequence of the balance between expansion and shrinkage
of the PVA–borate complex.
Received: 26 March 1999/Accepted in revised form: 3 September 1999 相似文献
10.
Kyu-Oh Kim Yun-A Seo Byoung-Suhk Kim Kee-Jong Yoon Myung-Seob Khil Hak-Yong Kim Ick-Soo Kim 《Colloid and polymer science》2011,289(8):863-870
We report solution properties of the blend solutions of poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG)–POSS telechelic
and its corresponding hybrid nanofibers prepared by electrospinning. The morphologies, microstructures, and wettability of
the resulting PVA/PEG3.4k–POSS hybrid nanofibers are studied. The morphologies of the resultant PVA/PEG3.4k–POSS nanofibers
are regular with the fiber diameter ranging from 610 ± 110 to 810 ± 280 nm. When the content of PEG3.4k–POSS telechelic increases
above 20 wt.%, the beaded fiber morphologies are observed due to severe aggregations of the PEG3.4k–POSS telechelics as well
as increased viscosity at higher concentration. In addition, the solution properties of pure PEG3.4k–POSS telechelic solution
(ca. 3–5 wt.%) and PVA/PEG3.4k–POSS solutions blended with PVA are explored, and found to show the reversible turbid-to-transparent
transition behavior with respect to the solution temperature. Water contact angle measurement of the PVA/PEG3.4k–POSS nanofiber
membranes demonstrates an enhanced hydrophobic nature due to the incorporated POSS moieties. 相似文献
11.
二氧化硅/聚乙烯醇杂化电纺纤维膜的制备与结构形态 总被引:3,自引:0,他引:3
用溶胶-凝胶(Sol-Gel)法制备了不同二氧化硅含量的PVA/SiO2杂化纺丝液,将其电纺成纤维膜.XRD结果表明,杂化电纺纤维膜的结晶度较纯PVA电纺纤维膜小;FTIR证实了PVA的羟基与正硅酸乙酯水解后的羟基发生了缩合反应,杂化电纺纤维膜是以网络结构形式相结合的;FESEM表明,PVA/SiO2质量比为4∶1时,纤维光滑,分散比较均匀.随着二氧化硅含量的增加,纤维直径变细,纺锤形珠节结构增多.加入金属盐NaCl和MgCl2后,纤维直径变细,圆形珠节增多.从理论上分析了纤维膜结构形态的形成机理. 相似文献
12.
Caglar P Tuncel SA Malcik N Landers JP Ferrance JP 《Analytical and bioanalytical chemistry》2006,386(5):1303-1312
A newly designed glass-PDMS microchip-based sensor for use in the determination of Ca2+ ions has been developed, utilizing reflectance measurements from arsenazo III (1,8-dihydroxynaphthalene-3,6-disulfonic acid-2,7-bis[(azo-2)-phenyl
arsenic acid]) immobilized on the surface of polymer beads. The beads, produced from cross-linked poly(p-chloromethylstyrene) (PCMS), were covalently modified with polyethylenimine (PEI) to which the Arsenazo III could be adsorbed.
The maximum amount of Arsenazo III which could be immobilized onto the PEI-attached PCMS beads was found to be 373.71 mg g−1 polymer at pH 1. Once fabricated, the beads were utilized at the detection point of the microfluidic sensor device with a
fiber optic assembly for reflectance measurements. Samples were mobilized past the detection point in the sensor where they
interact with the immobilized dye. The sensor could be regenerated and re-used by rinsing with HCl solution. The pH, voltage,
linear range, and the effect of interfering ions were evaluated for Ca2+ determination using this microchip sensor. At the optimum potential, 0.8 kV, and pH 9.0, the linear range of the microchip
sensor was 3.57 × 10−5 – 5.71 × 10−4 M Ca2+, with a limit of detection (LOD) of 2.68 × 10−5 M. The microchip biosensor was then applied for clinical analysis of calcium ions in serum with good results.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
13.
Lingzhi Liu Yaming Niu Xiaoliang Zhu XiaoBo Sun Guibin Wang Zhenhua Jiang 《Colloid and polymer science》2006,284(5):556-561
The self-assembly of a rod-like polymer [hydroxyl-terminated trifluoromethylphenyl-substituted fluorinated poly(ether ether
ketone) (FPEEK)] and a coil-like polymer (polyvinyl alcohol, PVA) in water has been studied. It was found that this polymer
pair could form micelle-like particles. Hydrogen bonding between the hydroxy groups of rod-like FPEEK and coil-like PVA, and
parallel packing of the rod-like FPEEK are the main factors affecting the formation of micelle-like particles. Over a broad
range, when the FPEEK/PVA mass ratio or the tetrahydrofolate/H2O volume ratio is decreased, the diameter of micelle-like particles is decreased. The diameters (around 250 nm) of micelle-like
particles measured by scanning electron microscopy and dynamic light scattering are similar, but are different from that measured
by transmission electron microscopy (around 150 nm). Thus, it can be concluded that micelle-like particles have a core–shell
structure and the cores of micelles are composed of FPEEK, and that the shells of micelles are composed of PVA. When polyethylene
glycol was used instead of PVA, micelle-like particles were also formed, but the average diameter was bigger than that of
the particles formed by PVA and FPEEK.
This work was supported by the National Nature Science Foundation of China (50203004). 相似文献
14.
The polyvinyl acetal sponge modified by chitosan was prepared by adding chitosan/polyvinyl alcohol (PVA) solution during the
acetalation reaction of PVA and formaldehyde. The effect of vesicant and chitosan to the pore morphology, water absorption
ratio, water absorption rate, expansion time and mechanical properties were studied. The polyvinyl acetal sponge modified
by chitosan was used as a hemostatic packing material for the injured rabbit nasal tissue. The hemostatic effect and the healing
effect of the modified sponge on the nasal mucosa after nasal surgery were studied. The results indicated that the polyvinyl
acetal sponge modified by chitosan has an interconnected pore structure and the wall between large pores also has small pores.
The chitosan adhered on the inner surface of the pores. The increased content of vesicant led to an increase in pore diameter,
in the water absorption ratio and in expansion time. However, there was only a small change in the water absorption rate and
a decrease in tensile strength and compression strength were noted. With an increase in chitosan content, the pore diameter
and interconnection of the sponge was reduced. Water absorption ratio, expansion time and water absorption rate decreased,
but tensile strength and compression strength improved. Observation of the rabbit nasal tissue after surgical operation suggested
that polyvinyl acetal sponge modified by chitosan has an anti-inflammatory, hemostatic and anti-adherent characteristic and
could promote the healing and functional recovery of rabbit nasal mucosa.
__________
Translated from Journal of Jinan University (Natural Science & Medicine Edition), 2007, 28(3): 283–287 [译自: 暨南大学学报(自然科学与医学版)] 相似文献
15.
Yeong-Tarng Shieh Hong-Mao Wu Yawo-Kuo Twu Yi-Chang Chung 《Colloid and polymer science》2010,288(4):377-385
The dispersion of carbon nanotubes (CNT) in water of different pH and in chitosan aqueous solution of three acids, acetic
acid, formic acid, and hydrochloric acid, was investigated. Chitosan was soluble in water of pH ≤3 and could well disperse
untreated CNT and acid-treated CNT, both of which had poor dispersion in water of pH ≤3. With the presence of 0.1 wt% chitosan
in solution, particle sizes of the CNT dispersion were found to decrease with increasing COOH contents on the CNT. Particle
sizes of CNT, untreated and acid-treated, in the three acidic aqueous solutions were found to increase with increasing chitosan
contents in solutions. Among the three acids, hydrochloric acid gave the smallest particle size of the CNT dispersion. Without
chitosan, the dispersibility of the acid-treated CNT in aqueous solutions of three acids was in the order of acetic acid >
formic acid > hydrochloric acid. 相似文献
16.
17.
Quan Shi Narendiran Vitchuli Joshua Nowak Zhan Lin Bingkun Guo Marian Mccord Mohamed Bourham Xiangwu Zhang 《Journal of Polymer Science.Polymer Physics》2011,49(2):115-122
The electrospinnability of polyethylene oxide (PEO) was manipulated by atmospheric plasma treatment of pre‐electrospinning solutions. Conductivity, viscosity, and surface tension of PEO solutions increased after plasma treatment, and the plasma effect remained longer when the solution concentrate increased. Both untreated and treated solutions were then electrospun, and the morphology of the resultant nanofibers was observed by SEM. Atmospheric plasma treatment improved the electrospinnability of PEO solutions and led to less beads and finer diameter distribution in the resultant nanofibers. Additionally, plasma treatment of the pre‐electrospinning solutions affected the crystal structure of resultant nanofibers. These results suggest that atmospheric plasma treatment is a feasible approach to improve the electrospinnability of polymer solutions and can used to control the structure of electrospun nanofibers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献
18.
研究比较线型聚酯胺和超支化聚酯胺作为添加剂用于静电纺丝时,对低浓度聚甲基丙烯酸甲酯溶液可纺性的改善效果及其机理.结果表明,只需加入1wt%的添加剂,无论是线型的还是超支化聚酯胺均能够提高低浓度聚甲基丙烯酸甲酯溶液的可纺性,得到无"串珠"结构的均匀纤维,其直径比不加添加剂而在高浓度纺丝时得到的均匀纤维细很多.通过溶液性能的测试,发现提高可纺性的原因均是由于溶液电导率的提高.超支化聚酯胺因其多枝的结构而含有较多的极性端基,致使本身电导率较高,因而对可纺性的改善效果好于线型聚酯胺. 相似文献
19.
Different Strategies of Covalent Attachment of Oligonucleotide Probe onto Glass Beads and the Hybridization Properties 总被引:1,自引:0,他引:1
The glass bead is a new biochip support material for immobilization biomolecules, due to its independence and convenient rearrangement.
In order to optimize the immobilization efficiency of oligonucleotides onto glass beads and obtain the highest hybridization
efficiency, three commonly used coupling strategies have been studied for covalently attaching oligonucleotides onto large
glass beads. Glass beads with 250 μm diameter were amino-silaned with 2% 3-aminopropyltrimethoxysilane (APTMS) and then reacted
separately with glutaraldehyde, succinic anhydride and 1,4-phenylene diisothiocyanate (PDITC) to derive CHO beads, COOH beads
and isothiocyanate-modified beads (NCS-Beads) accordingly. Afterwards, amino-terminal oligonucleotides were covalently attached
onto the surface of beads achieved by three strategies mentioned above. The immobilization efficiency were studied to compare
the three strategies, which turned out 2.55 × 1013 probes/cm2 for CHO-Beads, 3.21 × 1013 probes/cm2 for COOH beads and 6.68 × 1013 probes/cm2 for NCS beads. It meant that the immobilization efficiency based on NCS beads was most acceptable. And the method, developed
by attaching amino-terminal oligonucleotides onto these cyanate active beads, could be regarded as an efficient one for immobilizing
oligonucleotides onto a solid surface. Moreover, in this paper, the hybridization properties of NCS bead-based oligonucleotides
have been studied by employing Cy5-tagged complementary oligonucleotides. It was found that the high probe density NCS beads
led to low hybridization efficiency possibly due to the existence of steric crowding. In addition, the equilibrium binding
constant K
A was determined by employing Langmuir isotherm model, which was 7.0 × 106 M−1 for NCS beads with the density of 6.7 × 1013 probes/cm2. Furthermore, it only took 60 min to reach hybridization equilibrium. These large microspheres (>100 μm) can be employed
in the mesofluidic systems for automated heterogeneous assays. 相似文献
20.
Cui Pang Yunhai Liu Xiaohong Cao Rong Hua Caixia Wang Chunqing Li 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):185-193
Chitosan-coated attapulgite beads were prepared by coating chitosan on naturally and abundantly available attapulgite, and
made into spherical beads to adsorb uranium from aqueous solutions. The beads were characterized by SEM, EDS and FT-IR. The
characteristics of beads of adsorbing uranium(VI) from aqueous solutions were studied at different conditions of pH, initial
uranium concentration, contact time, biomass dosage and temperature. The pseudo-second order rate equation was used to describe
the kinetic data, and isotherm data were fitted to Langmuir and Freundlich adsorption models. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) of the biosorption were also calculated. Thermodynamic parameters of the CAAB, viz., ΔG°(308 K), ΔH°, and ΔS° were determined to be −21.59, 6.29l and 90.51 J/mol K, respectively. The experimental results demonstrate that the beads
of chitosan coated onto attapulgite exhibit considerable potential for application in both adsorption and removal of uranium
from aqueous solutions. 相似文献