共查询到20条相似文献,搜索用时 11 毫秒
1.
R. H. Ottewill E. Sinagra I. P. MacDonald J. F. Marsh R. K. Heenan 《Colloid and polymer science》1992,270(6):602-608
A method is described for the preparation of magnesium carbonate particles in a nonaqueous hydrocarbon environment. The particles were stabilised in the colloidal sense by the adsorption of an alkyl-aryl sulphonic acid. The particle morphology and particle-size distribution were examined by small-angle neutron scattering. It was concluded that the particle structure was of the coreshell type, with a core particle of basic magnesium carbonate, radius ca. 40 Å, and a shell of thickness ca. 13 Å. The results suggested that the latter was predominantly that of the alkyl-aryl part of the stabilising moiety. 相似文献
2.
J Santhanalakshmi P S Goyal V K Aswal G Vijayalakshmi 《Journal of Chemical Sciences》1999,111(5):651-658
Small-angle neutron scattering cross-section distributions of sodium dodecyl sulphate (SDS) and dodecyl trimethyl ammonium
bromide (DTAB), each 0·3 M in D2O were obtained in the absence and presence of 0·1 M 1-pentanol, 1-hexanol, and 1-octanol at 25°C. The Hayter-Penfold type
analysis was adopted. An ellipsoidal model with semiminor axis (a=16·5 ?) and semimajor axes (b=40·7 ? and 29·8 ?) for pure SDS and DTAB micelles has produced best fits. On increasing alkanol chain lengths an increase
inb values was found. Micellar parameters like effective radius (R), (a, b), fraction of counterions per micelle, and intermicellar distances were obtained. Surfactant aggregation number, additive
aggregation number intermicellar interaction potentials and values of Debye screening length were obtained for SDS and DTAB
in the presence of alkanols. Implications of partitioning effect, surfactant ionicity and intermicellar potentials on the
microstructures are rationalised. 相似文献
3.
SANS data on micellar solutions of C12E6 as a function of temperature have been reanalysed using a cylinder growth model. Reasonably good fits to the experimental curves were obtained using only the rod length as an adjustable parameter. The effect of polydispersity in the micelle size on the scattering profile was also investigated. Our main conclusion is that SANS is not a sufficiently sensitive technique to allow a clear identification of the micelle structure(s) at elevated temperatures. 相似文献
4.
Emmanuel Beaudoin Oleg Borisov Alain Lapp Jeanne François 《Macromolecular Symposia》2003,191(1):89-98
The effect of temperature on the structure of aqueous dispersions of hydrophobically end-capped poly(ethylene oxide) (PEOM) was investigated by small angle neutron scattering (SANS). Polymers with hydrogenated or deuterated n-octadecyl end-groups were studied in heavy water or in a mixture heavy water / water, respectively. In the latter case the PEO chains were selectively matched. In all the cases, the scattering curves were characterised by a main peak which revealed organisation of polymers into micelles consisting of hydrophobic cores surrounded by repulsive PEO coronae. Measurements were performed in the semi-dilute regime where micelles coronae overlap. At constant polymer concentration, an increase in temperature leads to decreasing solvent strength of water for the PEO chains and decreasing repulsion between the PEO coronae. As a result, the intensity of the peak in a mixture of water /heavy water decreases with temperature On the contrary, in heavy water, the peak of the scattered intensity increases with increasing temperature. This scattering behaviour is interpreted on the basis of a scaling theory of the semi-dilute solutions of star-like polymer micelles. 相似文献
5.
Osamu Urakawa Hiroyoshi Ikuta Shogo Nobukawa Toshiyuki Shikata 《Journal of polymer science. Part A, Polymer chemistry》2008,46(23):2556-2565
Thermal concentration fluctuation in the blends of deuterated poly(ethylene oxide) (dPEO) and poly(vinyl acetate-co-vinyl alcohol) [P(VAc-VOH)] with various VOH contents fOH were examined by small angle neutron scattering techniques at a fixed blend composition, dPEO/P(VAc-VOH) = 20/80 which is close to the critical composition. Blends at the highest fOH (=0.35) showed a non-Lorentzian scattering profile: specifically the scattering intensities at the low q (angle) region were suppressed compared to those expected from the random phase approximation (RPA) theory. However, for the blends at lower fOH (≤0.28), the profiles could be represented by the RPA. Using the RPA we determined effective values of the Flory-Huggins interaction parameter χeff as a function of fOH (=0–0.28). The χeff showed the minimum around fOH = 0.1–0.18 meaning the highest miscibility of the blend at these fOH. On the basis of the random copolymer theory, we evaluated the three interaction parameters χAc–EO, χEO–OH, and χAc–OH separately from the χeff(fOH) and found the order of magnitude; χAc–EO < 0 < χEO–OH < χAc–OH. The largest positive χAc–OH showing intrachain interaction in the P(VAc-VOH) copolymer was concluded to be the origin of the enhanced miscibility at around fOH = 0.1–0.18. On the basis of the Coleman and Painter's theory, the effects of hydrogen bonding on these three χA-B were discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2556–2565, 2008 相似文献
6.
The structure of a microemulsion mixed with polymer networks was investigated by means of small-angle neutron scattering (SANS). The system consists of nonionic surfactant, polymer network, oil, and water. The microemulsion and the polymer network employed in this work are known to undergo temperature-induced structural transition and volume phase transition, respectively. Polymer solutions and gels were made by polymerizing monomer solutions in the presence of microemulsion droplets. In the case of a mixture of an N-isopropylacrylamide (NIPA) monomer solution and a microemulsion, the NIPA monomer was found to behave as a cosurfactant. However, polymerization resulted in a phase separation to polymer-rich and -poor phases. Interestingly, SANS results indicated that a well-developed ordered structure of oil domains was formed in polymer network and the structure was very different from its parent systems. Furthermore, the system underwent two different types of structural transitions with respect to temperature. One was originated from the structural transition of microemulsion due to the change of the spontaneous curvature and the other from the volume phase transition of the NIPA gel. 相似文献
7.
Small-angle neutron scattering from micelles of alkylpolyoxyethylene sulfate: Effect of chain length
Small-angle neutron scattering (SANS) data have been obtained for (i) a series of solutions of C
m
H2m+1(OCH2–CH2)2SO4Na, for m=18, 16, and 14; (ii) an approximately 0.07M solution of C14H29(OCH2–CH2)2SO4Na to which different amounts of NaCl were added; and (iii) a series of solutions of variable concentration of C12H25(OCH2–CH2)SO4Na. The increase of the number of carbon atoms of the hydrocarbon chain produces a noticeable increase of the aggregation number of the micelles, while the salt tolerance decreases with increasing m. All the data can be described in terms of a monodispersed, charged, hard-spheres model interacting via a screened Coulombic potential, except the run at highest salt concentration, for which an ellipsoid model gives better results. 相似文献
8.
V. T. Lebedev Yu. V. Kul’velis D. N. Orlova V. V. Shamanin L. V. Vinogradova 《Polymer Science Series A》2016,58(5):697-709
The structuring of films based on regular six-arm and twelve-arm polystyrenes with the arm characteristics Mn = 118 × 103 and Mw/Mn = 1.06 and a fullerene (С60) branching center in a weakly swollen state in a mixture of deuterated solvents (90 vol % D-methanol and 10 vol % D-toluene) is studied by small-angle neutron scattering. Analogous studies are performed for films based on linear polystyrene (Mn = 280 × 103, Mw/Mn = 1.07) and its composites with fullerene С60 (0.5 wt %). It is shown that, during saturation of the samples with the solvent D-toluene, filling of the free volume that forms chain-transport channels that have gyration radii of the order of diameters of macromolecules and unite to form submicron and micron structures occurs. The degree of filling of the free volume, which is maximum for the linear polymer, becomes minimum for polystyrene with the inserted free fullerene. In addition, the transition from the linear polymer to the six-arm polymer is related to a smaller degree of filling of the free volume due to the formation of thinner migration channels. As the amount of arms in macromolecules is increased to 12, permeability of the polymer matrix improves because molecular order partially appears in accordance with the model of the densest packing of solid spheres. 相似文献
9.
N. Hattori H. Hirata H. Okabayashi M. Furusaka C. J. O'Connor R. Zana 《Colloid and polymer science》1999,277(1):95-100
The microstructure of the normal micelles formed by dimeric surfactants with long spacers, [Br−(CH3)2N+(C
m
H2
m
+1)-(CH2)
S
-(C
m
H2
m
+1)N+(CH3)2Br−, m = 10 and s = 8, 10 and 12], has been investigated by small-angle neutron scattering and compared with previously reported results for
micelles of the same dimeric surfactants with shorter spacers (m = 10 and s = 2, 3, 4 and 6). It was found that for dimeric surfactants with long spacers (s = 8 and 10), both micellar growth and variation in shape occur to only a small extent, if at all, compared with dimeric surfactants
with short spacers. However, for the dimeric surfactant with the longest spacer, s = 12, the extent of micellar growth and shape variation is also large. These results are due to the differences in conformation
of dimeric surfactants with short spacers (s = 2–6) compared with that of the surfactants with long spacers (s = 8–12).
Received: 15 June 1998 Accepted: 22 July 1998 相似文献
10.
Chil-Hung Cheng Daniel F. Shantz 《Current Opinion in Colloid & Interface Science》2005,10(5-6):188-194
This review summarizes recent small-angle X-ray scattering investigations of the initial stages of zeolite formation and growth. These studies have increased the zeolite science community's understanding of the structures present at the earliest stages of growth, particularly in the case of silicalite-1 formed from so-called ‘clear solution’ syntheses. 相似文献
11.
Motokawa R Annaka M Nakahira T Koizumi S 《Colloids and surfaces. B, Biointerfaces》2004,38(3-4):213-219
By employing small-angle neutron scattering (SANS), we investigated the microstructures of, poly(N-isopropylacrylamide) (PNIPA)-block-poly(ethylene glycol) (PEG) (NE) in deuterated water D2O, as related to macroscopic behaviors of fluidity, turbidity and synerisis. SANS revealed following results: (i) microphase separation occurs at around above 17 °C in a temperature range of transparent sol below 30 °C. In the microdomain appeared in the transparent sol state, both block chains of PNIPA and PEG are swollen by water; (ii) for the NE solution of polymer concentration Wp > 3.5% (w/v), corresponding to opaque gel above 30 °C, a percolated structure, i.e., network-like domain is formed by NE as a result of macrophase separation due to dehydration of the PNIPA chains. As the temperature increases toward 40 °C, the network domain is squeezed along a direction parallel to the NE interface, which leads to increase of the interfacial thickness given by swollen PEG chains and to the macroscopic synerisis behavior. 相似文献
12.
S. Borbély L. Cser Sz. Vass V. Yu. Bezzabotho Yu. M. Ostanevich 《Colloid and polymer science》1993,271(8):786-792
Micelle formation in aqueous sodium hexadecyl sulfate solutions is studied by small-angle neutron scattering. Measurements are carried out at different concentrations (1.1, 2.2, 3.2, 5.4, 10.9 and 32.8 mM/dm3) and at different temperatures (40°, 50°, and 60°C). The monotonous evolution of interparticle correlation can be observed on the measured scattering patterns. At high concentrations (10.9 and 32.8 mM/dm3) scattering patterns are described by interacting ellipsoids, but at low concentrations by non-interacting ellipsoids. Computation of the distance distribution function proved the ellipsoidal shape at 10.9 and 32.8 mM/dm3, but showed an unexpectedly large particle dimension and elongation of the micelles at lower concentrations. 相似文献
13.
Summary The shear orientation of a micellar hexagonal liquid crystalline phase was investigated by small-angle neutron scattering. The hexagonal phase in the quiescent state showed a symmetrical scattering pattern typical of a polydomain structure. Enhanced scattering along the flow direction was observed during shear and the anisotropy of scattering intensity became stronger with increasing shear rate. The anisotropic scattering pattern corresponds to an orientation perpendicular to the flow direction and can be interpreted as a log-rolling state. The oriented sample did not relax after cessation of shear. The results from small-angle neutron scattering confirm data obtained previously from rheo-small angle light scattering measurements and are discussed in comparison to shear alignment of lyotropic liquid crystalline polymer solutions. 相似文献
14.
Yu. V. Kulvelis V. T. Lebedev D. Torok A. B. Melnikov 《Journal of Structural Chemistry》2007,48(4):740-746
Interaction of sulfonated scandium diphthalocyanine ScPc2(SO3)4(NH4)4 with DNA in water salt solutions was studied by small-angle neutron scattering, dynamic light scattering, and atomic force microscopy. The results provide evidence about packaging of DNA molecules and agree with previous viscosimetry and spectrophotometry data. 相似文献
15.
J Santhanalakshmi G Shantha Lakshmi V K Aswal P S Goyal 《Journal of Chemical Sciences》2001,113(1):55-62
Small angle neutron scattering (SANS) measurements of D2O solutions (0.1 M) of sodium cholate (NaC) and sodium deoxycholate (NaDC) were carried out atT= 298 K. Under compositions very much above the critical micelle concentration (CMC), the bile salt micelle size growths were
monitored by adopting Hayter-Penfold type analysis of the scattering data. NaC and NaDC solutions show presence of correlation
peaks atQ = 0.12 and 0.1 ?-1 respectively. Monodisperse ellipsoids of the micelles produce best fits. For NaC and NaDC systems, aggregation number (9.0,
16.0), fraction of the free counterions per micelle (0.79, 0.62), semi-minor (8.0 ?) and semi-major axes (18.4, 31.7 ?) values
for the micelles were deduced. Extent of micellar growth was studied using ESR correlation time measurements on a suitable
probe incorporating NaC and NaDC micelles. The growth parameter (axial ratio) values were found to be 2.3 and 4.0 for NaC
and NaDC systems respectively. The values agree with those of SANS. 相似文献
16.
Small angle neutron scattering studies have been made on solutions of dodecylhexaoxyethylene glycol in D2O above the critical micelle concentration and as a function of temperature. It was possible to fit the experimental data at low values of scattering vector using a cylindrical model for the micelle shape. 相似文献
17.
Aurel Radulescu Dietmar Schwahn Michael Monkenbusch Lewis J. Fetters Dieter Richter 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):3113-3132
Random crystalline–amorphous copolymers containing ethylene and butene segments, yielded from dilute-solution, and self-assembled to one-dimensional, needle-shaped aggregates, can modify wax crystal structures through the cocrystallization of the copolymer and wax molecules into hairy platelets. These copolymers show selectivity in their wax crystal modification capacities that depends on the ethylene content of the backbone. Thus, it has been qualitatively established that a copolymer containing larger crystallizable polyethylene sections [poly(ethylene butene) with 7.5 ethyl branches per 100 backbone carbons (PEB-7.5)] is very efficient for longer wax molecules (C36), whereas for shorter waxes (C24), its efficacy diminishes. Here we present a quantitative evaluation of the small-angle neutron scattering results obtained in a complex study of the self-assembling behavior of PEB-7.5 and paraffin waxes (C24 and C36) in decane and of cocrystallization for different polymer–paraffin combinations and solution conditions. The richness of the morphologies was evaluated with a contrast variation technique and the application of structural models. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3113–3132, 2004 相似文献
18.
R. M. Clapperton R. H. Ottewill A. R. Rennie B. T. Ingram 《Colloid and polymer science》1999,277(1):15-24
The size and shape of ammonium decanoate and ammonium dodecanoate micelles as functions of micellar concentration have been
studied using the techniques of small-angle neutron scattering and time-averaged light scattering. The results indicate that
the micellar mass of ammonium dodecanoate increases with surfactant concentration. This behaviour can be attributed to the
formation of rod-like micelles. A comparison is made with the homologous surface active agent, ammonium decanoate.
Received: 27 July 1998 Accepted: 18 August 1998 相似文献
19.
The existence of attractive interaction between CMC and BSA was evidenced in solution at pH higher than the protein isoelectric point by means of SAXS. Mixtures of BSA at 10 x 10(-3) g . mL(-1) and CMC at the concentration range of 1 x 10(-3) g . mL(-1) to 10 x 10(-3) g . mL(-1) were investigated. Upturns in the very low q range revealed the presence of aggregates when the CMC concentration was higher than 2 x 10(-3) g . mL(-1). The comparison between the calculated form factor with the experimental curves at intermediate and long q values indicated that the BSA molecules keep their native form in mixtures with CMC concentrations lower than 5 x 10(-3) g . mL(-1). Therefore, for CMC concentrations higher than 2 x 10(-3) g . mL(-1) the mixtures start to present aggregates and free BSA molecules coexisting in solution. 相似文献