共查询到20条相似文献,搜索用时 62 毫秒
1.
Badawi AM Fahmy AA Mohamed KA Noor El-Din MR Riad MG 《Applied biochemistry and biotechnology》2012,166(1):22-35
In this paper, four nonionic surfactants with different hydrophilic–lipophilic balance (HLB) based on sorbitan monolaurate
were synthesized by introducing ethylene oxide gas (n = 20, 40, 60, and 80 ethylene oxide units). The chemical structure of the prepared ethoxylated surfactants was confirmed
using Fourier transform-infrared and 1H NMR spectroscopes. The surface tension and thermodynamic properties of the prepared surfactants have been studied. The simultaneous
saccharification and fermentation (SSF) process for ethanol production from microwave/alkali pretreated wheat straw has been
assayed using nonionic surfactants have different ethylene oxide units. Ethanol yield was 82% and 61% for Kluyveromyces marxianus and Saccharomyces cerevisiae, respectively, with the addition of 2.5 g/l of the prepared nonionic surfactant (HLB = 18.2). Results show that the production
of ethanol from microwave/alkali pretreated wheat straw increased with increasing the (HLB) value of the nonionic surfactant. 相似文献
2.
Susan MA Ishibashi A Takeoka Y Watanabe M 《Colloids and surfaces. B, Biointerfaces》2004,38(3-4):167-173
A novel non-ionic surfactant, -(phenothiazinylhexyl)-ω-hydroxy-oligo(ethylene oxide) (PCPEG) containing phenothiazine as an electro-active group has been synthesized. Fundamental interfacial behavior of the surfactant at the air/water interface has been investigated by means of surface tensiometry to provide an insight into the relationship between the structure of the hydrophobic moiety and the surfactant properties. A comparison of diffusivity of PCPEG in the aqueous phase with that in the acetonitrile solution at high PCPEG concentrations shows that micellization has a pronounced effect on the redox behavior of PCPEG. The electrochemical responses for PCPEG aqueous solutions at the interface of a glassy carbon electrode are fairly dependent on the concentration of PCPEG. Above CMC, PCPEG molecules self-associate to form micellar aggregates and the formation and disruption of micelles can be reversibly controlled by change in the redox state of the phenothiazine group. The cyclic voltammetric responses for PCPEG aqueous solutions have been correlated with the dissolved states to explain the distinctive feature of the surfactant. 相似文献
3.
Silicone surfactants containing different pendant hydrophilic groups such as diethanol tertiary amine (SHE, nonionic), diethanol
methyl quaternary amine (cationic) and triethyl quaternary amine (cationic) have been synthesized and characterized by 1H and 13C NMR and gel permeation chromatography. The solution behavior of these novel surfactants has also been investigated by surface
tension measurement and a fluorescence method. It has been observed that the surface tension of these surfactants decreases
as a function of time at a very low polymer concentration (1 × 10−4 wt%). At higher concentration (0.1 wt%), the equilibrium surface tensions reached very low values compared to that of typical
polymer surfactants, for example, poly(ethylene oxide–propylene oxide) block copolymer (EPE0.8). In addition, the low I
1/I
3 values of these silicone surfactants indicate the formation of polymer aggregates in aqueous solution, and an extremely low
I
1/I
3 value of SHE (1.06) compared to other polymeric surfactants (EPE0.8) and conventional surfactants [poly(ethylene glycol n-nonyl phenyl ethers), cetyltrimethylammonium bromide, and sodium dodecyl sulfate] indicates its stronger hydrophobicity.
Received: 15 May 2000 Accepted: 18 October 2000 相似文献
4.
C. Lucas I. Eiroa M. R. Nunes P. A. Russo M. M. L. Ribeiro Carrott M. I. da Silva Pereira M. E. Melo Jorge 《Journal of Solid State Electrochemistry》2009,13(6):943-950
The electrochemical properties of Ca1 − x
Ce
x
MnO3 perovskite-type oxide electrode have been investigated by cyclic voltammetry in Na2SO4 aqueous solutions with pH 14. The structural and morphological characterizations have also been investigated and the information
used to interpret the electrochemical behavior. An estimation of the electrode’s capacitance and roughness factor has been
obtained by means of cyclic voltammetry. The specific capacitance and consequently the roughness factor values are affected
by the presence of Ce ions in the oxide. These findings are in agreement with the increase of the oxide-specific surface area
by the introduction of Ce ion. The open-circuit potential and the voltammetric patterns are dependent on the presence of Ce
ion in the electrodes and support that the surface electrochemistry of the perovskite oxide electrodes is governed by the
Mn4+–Mn3+ redox couple. 相似文献
5.
The surfactant effect on the lower critical solution temperature (LCST) of thermosensitive poly(organophosphazenes) with
methoxy-poly(ethylene glycol) and amino acid esters as side groups was examined in terms of molecular interactions between
the polyphosphazenes and surfactants including various anionic, cationic, and nonionic surfactants in aqueous solution. Most
of the anionic and cationic surfactants increased the LCST of the polymers: the LCST increased more sharply with increasing
length and hydrophobicity of the hydrophobic part of the surfactant molecule. The ΔLCSTs (T
0.03M − T
0M), the change in the LCST by addition of 0 and 0.03 M sodium dodecyl sulfate (SDS), were found to be 7.0 and 14.5 °C for the
polymers bearing ethyl esters of glycine and aspartic acid, respectively. The LCST increase of poly(organophosphazene) having
a more hydrophobic aspartic acid ethyl ester was 2 times larger compared with that of the polymer having glycine ethyl ester
as a side group. The binding behavior of SDS to the polymer bearing glycine ethyl ester as a hydrophobic group was explained
from the results of titration of the polymer solutions containing SDS with tetrapropylammonium bromide. Graphic models for
the molecular interactions of polymer/surfactant and polymer/surfactant/salt in aqueous solutions were proposed.
Received: 17 February 2000/Accepted: 25 April 2000 相似文献
6.
Avinash Bhadani Takeshi Endo Kenichi Sakai Hideki Sakai Masahiko Abe 《Colloid and polymer science》2014,292(7):1685-1692
New series of ester functionalized quaternary ammonium gemini surfactants having different ethylene oxide units as spacer have been synthesized and investigated for their aggregation behavior and thermodynamic properties of micellization by surface tension, conductivity, and fluorescence methods. The critical micelle concentration (cmc) of these gemini surfactants increases with the increase in the length of polar hydrophilic ethylene oxide spacer. The micellization process has been found to be entropy-driven and dependent on both the tendency of the hydrophobic group of the surfactants to transfer from aqueous environment to interior of micelle as well as the rearrangement of flexible ester-linked ethylene oxide units (hydrophilic spacer) into aqueous phase. The polar ester functional groups and pairs of nonbonding electrons on oxygen atom of ethylene oxide spacer form hydrogen bonding with water molecules enhancing their solubility in aqueous system. 相似文献
7.
This paper reports the adsorption and interfacial viscoelasticity of gemini surfactants with a hydroxyl-substituted spacer,
2-hydroxyl-propanediyl-α,ω-bis(dimethyldodecylammonium bromide), 2-hydroxyl-butanediyl-α,ω-bis(dimethyldodecylammonium bromide),
and 2,3-hydroxyl-butanediyl-α,ω-bis(dimethyldodecylammonium bromide), referred to as 12-3(OH)-12, 12-4(OH)-12, and 12-4(OH)2-12, respectively, at the air/water interface using dropping shape and interface dilational rheology measurements. For comparison,
the unsubstituted surfactants were also examined at identical conditions. The results showed that substituted surfactants
produced a remarkably higher interfacial elasticity than the corresponding unsubstituted ones. This was attributed to the
effect of the intermolecular hydrogen bonding occurring between the hydroxyl-substituted spacers of adsorbed molecules, which
resulted in tighter packing of the molecules in the monolayer. Besides, we measured foam stability. The foam produced by the
substituted geminis was found to have higher stability than that by the unsubstituted geminis. It was suggested that the foam
stability may be related to the limit elasticity of interfacial film at the level of identical surface excesses. 相似文献
8.
Cyclic voltammetry (CV) and viscosity measurements have been employed to study the aggregation behavior of mixed micellar
systems of anionic surfactant (dioctyl sulfosuccinate sodium salt, AOT) with conventional nonionic surfactants such as Brij
35/TritonX-100/Tween 20/Tween 80/Myrj 45 and two triblock copolymers (L64 and F68). Critical micelle concentration (cmc) values
have been determined for various micellar systems from CV measurements using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)
as an electroactive probe at 25 °C. Diffusion coefficient (D) has been evaluated from Randles–Sevcik equation which showed an overall decrease for most of the binary systems. The negative
values of interaction parameters (β) obtained from regular solution theory suggest the synergistic behavior in all the binary systems except AOT + Tween 80 mixtures.
The mixed systems of AOT with triblock copolymers showed stronger synergistic interactions than that of mixed systems of AOT
with nonionic surfactants. A comparative evaluation of mixed systems of anionic surfactants AOT and sodium dodecyl sulfate
with Myrj 45 and AOT + L64 and F68 has been made on the basis of different micellar parameters and structural properties of
surfactants. Viscosity measurements also show similar type of interactions in the mixed micelles. 相似文献
9.
Self-assembled monolayer gold electrode for surfactant analysis 总被引:2,自引:0,他引:2
Marc Gerlache Zühre Senturk Guy Quarin Jean-Michel Kauffmann 《Journal of Solid State Electrochemistry》1997,1(2):155-160
A gold electrode coated with a self-assembled monolayer of octane-thiol (SAM/Au) has been used as an amperometric detector
for the determination of surfactants. This detector operated in the presence of a high percentage of organic solvent and was
adapted to an HPLC System. At the SAM/Au, the electrochemical response of an electroactive tracer (potassium ferricyanide)
was completely inhibited, but, in the presence of a cationic surfactant, the electrochemical reduction was progressively restored.
In flow injection analysis, using the SAM/Au in an amperometric flow-through detector polarised at 0.0 V vs Ag/AgCl, a linear
response (i=f{[surfactant]}) was observed for cationic surfactants e.g. cetylpyridinium chloride in the concentration range 2 × 10−6–1 × 10−3 M. The electrochemical data along with the determination of the ion pair stoichiometry between the redox tracer and the surfactant
suggest an electrochemical response related to ion pair formation and governed by electron transfer by tunneling effect.
Received: 28 January 1997 / Accepted: 7 March 1997 相似文献
10.
Ramesh Kumar Banjare Manoj Kumar Banjare Sandhyarani Panda 《Journal of solution chemistry》2020,49(1):34-51
A comprehensive study the effect of acetonitrile (ACN) with four cationic surfactants, viz. tetradecyltrimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC) and cetylpyridinium bromide (CPB) was made by using the conductivity, surface tension, fluorescence and FTIR techniques. Significant micellar, interfacial and thermodynamic properties were studied by the tensiometeric and conductivity methods. The critical micelle concentration (CMC), aggregation number (Nagg), and Stern–Volmer constants (Ksv) have also been studied by the steady state fluorescence method using pyrene as probe. The fluorescence study also supports the CMC results obtained from conductivity and surface tension. FTIR was used to ascertain that the strength of intermolecular interactions such as hydrogen bonding, ion–ion pair interactions and induced dipole interactions between the surfactants and ACN depend upon the head-group of the surfactants. The interaction of surfactants with ACN is energetically favorable and occurs via direct interactions between the surfactants and ACN. The results further revealed that the strength of interactions between the surfactants and ACN follows the order: TTAB > CTAB > CPC > CPB. 相似文献
11.
Katsuhiro Inomata Reina Doi Erina Yamada Hideki Sugimoto Eiji Nakanishi 《Colloid and polymer science》2007,285(10):1129-1137
Amphiphilic polymers Cn-PHEG consisting of water-soluble poly[N
5-2-(hydroxyethyl) l-glutamine] (PHEG) and hydrophobic alkyl chain (carbon number n = 12, 14, 16, or 18) attached at the PHEG terminal was prepared, and association behavior and structure of associate for
Cn-PHEG in selective solvent (water/ethylene glycol mixed solvent) have been investigated. α-Helix content of PHEG block for
all the polymers increased with weight fraction of ethylene glycol in the mixed solvent (W
EG). By light scattering measurements, formation of a small micelle was suggested for C14-, C16-, and C18-PHEG when W
EG = 0. With the increase in W
EG, appearance of a larger associate was revealed for C16- and C18-PHEG. Evaluated molecular weight and radius of gyration suggested
that the micelle is star-like sphere when W
EG = 0 and worm-like cylinder when W
EG = 0.7. C12-PHEG did not demonstrate any distinct micellization behavior because of the weak hydrophobicity of C12 chain. 相似文献
12.
A sequence-ordered, periodic copolymer of ethylene, ethylene, and acrylic acid, poly (ethylene-per-ethylene-per-acrylic acid) (PEEA), with M
w=1.44×105 has been synthesized by alternating copolymerization of 1,3-butadiene and methyl acrylate, followed by hydrogenation and
hydrolysis. Aqueous solution and dissociation properties of the alkali-soluble PEEA were explored by potentiometric titration
and intrinsic viscosity at 25 °C. The pH values of PEEA were almost constant (pH = 6.48 ∼ 6.55) with an increasing degree
of dissociation (α) from 0.3 to 0.8 at C
s=50 mN NaCl. Correspondingly, the plots of negative logarithm of apparent dissociation constant (pK
a) against α showed a reversed S-shape curve over the whole α, indicating an extensive precipitation and subsequent tran-sition
from compact to coiled conformation. The intrinsic viscosity steeply increased with α above 0.4 up to 9.97 dl/g at α = 1.0.
Good agreement between the observed electrostatic potential and that calculated from the rod model with a smeared charge density
was observed in the region of α higher than 0.9. The dissociation and dissolution processes of PEEA with neutralization in
water were described.
Received: 14 April 1998 Accepted: 3 June 1998 相似文献
13.
Poly(ethylene oxide) macromonomers carrying methoxy group on the one (α-) end and methacryloyloxyhexyl or methacryloyloxydecyl
group on the other (ω-) end were prepared, homopolymerized in water, and dispersion-copolymer-ized with styrene or methyl
methacrylate in a methanol–water mixture. They were found to polymerize more rapidly and to produce stable polystyrene dispersions
more effectively, as compared to the corresponding macromonomers carrying either α-methoxy and or α-dodecyloxy and ω-methacryloyloxy
end groups. Thus, the amphiphilic constitution of the macromonomers such that favors the polymerizing methacrylate end groups
to locally concentrate into the micelle core or to the particle surface while the poly(ethylene oxide) chains extending to
the medium appears to be most important in enhancing their polymerizability and effectiveness as reactive steric stabilizers.
On the other hand, stable poly(methyl methacry-late) particles with a number of craters or pleats on the surface were produced
with a PEO macromono-mer with α-methoxy and ω-methacryl-oyloxy end groups.
Received: 4 September 1996 Accepted: 18 October 1996 相似文献
14.
Inclusion complexes of poly(ethylene oxide) with α-cyclodextrin are the key compounds in the synthesis of polyrotaxanes. These
complexes prepared in aqueous solutions contain free cyclodextrin, which cocrystallizes with the major reaction product. These
complexes dissociate upon dissolution in DMF and DMSO to form cyclodextrin and pseudopolyrotaxanes with a low cyclodextrin
content. Polyrotaxane was synthesized with the use of poly(ethylene oxide)-α,ω-bis-amine as a linear component. The end-groups
of the polymer in the inclusion complex were modified by the reaction with 2,4-dinitrofluorobenzene. A procedure was developed
for purification of a polyrotaxane with high cyclodextrin content.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1914–1918, August, 2005. 相似文献
15.
The pH dependence of an anionic surfactant, sodium N-dodecanoylsarcosinate (SLAS), has been studied by measuring interfacial tension, fluorescence, dynamic light scattering,
etc., in aqueous solutions with phosphate and borate buffers. The interfacial tension (γ) of SLAS decreases remarkably with a pH decrease and is constant at pH > 7.3. The observed values for the critical micelle
concentration (cmc) and the surfactant concentration at which its γ value is reduced by 20 mN/m from that of pure water (C
20) decrease with a pH decrease, while those also become constant at pH > 6.5 and >7.3, respectively. On the other hand, the
interfacial excess of SLAS increases at pH < 7.3. These interfacial behaviors have been further investigated by the addition
of Tl+ which replaces Na+ of SLAS. The observed γ values of LAS− with the different counter cations are in the order of H+ < Tl+ < Na+. In order to reveal aggregation properties of SLAS, the aggregation number (N
agg), the micropolarity, the hydrodynamic radius (R
h) of micelle, and the fluorescence anisotropy of Rhodamine B (r) have been evaluated at various pHs. The N
agg value shows a decreasing tendency with a pH increase. The I
1/I
3 ratio and the R
h values do not strongly depend on pH. The r value decreases until pH 7 and remains constant at pH > 7.0. These interfacial and micelle properties have been discussed
in detail considering the electrostatic interaction and the molecular structures of the hydrophilic headgroup. 相似文献
16.
Amphiphilic diblock copolymers consisting of a hydrophobic polystyrene block (PS) and a hydrophilic poly(ethylene oxide)
block (PEO) with block sizes of 1000 or 3000 g/mol for both blocks were studied at the air/water and toluene/water interface.
Measurements of the film pressure π of spread monolayers at the water surface reveal two limiting regimes of the π−a
m isotherms, in which the mean molecular area a
m is determined either by the size of the hydrophilic or the hydrophobic blocks of the PS-PEO molecules. The interfacial activity
of the block copolymers at the toluene/water interface was studied by measuring the interfacial tension σ over a wide range
of concentrations. Pronounced differences in the temperature dependence of the interfacial tension were observed, depending
mostly on the block length of the hydrophilic PEO block. From the temperature dependence of σ it is inferred that for the
block copolymers with the PEO block size of 3000 g/mol the phase inversion temperature (PIT) is well above 60 °C while for
those with a PEO block size of 1000 g/mol the PIT is below or near 25 °C in the toluene/water system.
Received: 5 February 1998 Accepted: 16 February 1998 相似文献
17.
K. Fukada M. Kawasaki T. Seimiya Y. Abe M. Fujiwara K. Ohbu 《Colloid and polymer science》2000,278(6):576-580
The apparent molar volume and the apparent molar adiabatic compressibility of the sugar-based surfactants methyl 6-O-octanoyl-α-d-glucopyranoside (α-MOnG), methyl 6-O-octanoyl-β-d-glucopyranoside (β-MOnG), and octyl β-d-glucoside were measured over a wide concentration range. Also, the aggregation number of their micelles was determined from
the Debye plot using static light scattering data. It was found that the micellar aggregation number for α-MOnG is 179 at
35 °C, which is 1.5 times larger than that for β-MOnG, suggesting that the anomerism of the head group influences the packing
of the monomers during micelle formation.
Received: 30 September 1999 Accepted: 15 December 1999 相似文献
18.
The micellar aggregation of two fluorocarbon surfactants bearing a polymerizable acrylamido group and differing only in the
degree of amido substitution (CONH or CONC2H5) has been investigated by viscometry. The two surfactants exhibit distinct solution properties with a micellar growth occurring
at a much lower concentration for the N-monosubstituted sample which shows in addition a shear thickening and rheopectic behavior. The ability of the latter surfactant
to form hydrogen bonding is responsible for this difference in behavior. Micellar copolymerization of acrylamide with these
surfactants or with a hydrocarbon analogue gives copolymers with a polysoap-like behavior. The copolymers in aqueous solution
show a pronounced intramolecular hydrophobic aggregation expressed by relatively low-viscosity values when compared with those
of other hydrophobically modified water-soluble polymers reported in the literature. Surfactant–polymer mixed systems do not
show a strong incompatibility between fluorocarbon and hydrocarbon moieties.
Received: 24 March 1998 Accepted: 30 June 1998 相似文献
19.
Weifeng Song 《Journal of Dispersion Science and Technology》2016,37(12):1700-1709
The interfacial tensions and dilational properties of adsorbed films of two non-ionic surfactants with different hydrophobic groups, polyoxy-ethylene sorbitan stearate (Tween 60) and polyoxy-ethylene sorbitan monooleate (Tween 80), at the water–decane interface have been investigated by the drop-shape analysis method. The effects of dilational frequency and bulk concentration on the interfacial properties were expounded. The influence of low temperature on the interfacial tensions and dilational properties have also been researched. The experiment results show that the interfacial activity of Tween 80 is rather large compared with Tween 60. The minimum area per molecule at the water–decane interface (Amin) value of Tween 80 is little large than that of Tween 60, which is due to the steric effect of unsaturated double bond in Tween 80 molecule. The dilational data show that the ethylene oxide groups of non-ionic surfactant form a stable sub-layer, which results in the increase of modulus and the decrease of phase angle for both Tween 60 and Tween 80 than those of common ionic surfactants. Moreover, the unsaturated hydrophobic group of Tween 80 is much flexible, which is easily crosslinked and entangled. Therefore, dilational modulus of Tween 80 is higher and phase angle is lower than that of Tween 60. Low temperature decreases the flexibility of unsaturated hydrophobic group and lessens the influence on the interaction of saturated hydrophobic group. Saturated surfactant molecules of Tween 60 almost lose temperature response. 相似文献
20.
Jürgen Heinze Peter Tschuncky Andreas Smie 《Journal of Solid State Electrochemistry》1998,2(2):102-109
Electrochemical investigations on oligomeric model compounds (β-carotenoids) of polyacetylene varying the chain length in
the range between 5 and 23 double bonds provide deeper insights into the redox properties of such systems. Furthermore, cyclic
voltammetric studies of α,ω-diphenylpolyenes and phenylenevinylenes give clear evidence that the formation of the radical
ions is followed by a rapid reversible dimerization between the oligomeric chains. The thermodynamic and kinetic parameters
of the chemical reaction are presented. Applying these results to the properties of conducting polymers opens up new perspectives
for interpreting charge storage and conductivity.
Received: 27 May 1997 / Accepted: 6 October 1997 相似文献