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排序方式: 共有121条查询结果,搜索用时 15 毫秒
1.
Matthew M. Malwitz Paul D. Butler Lionel Porcar Drew P. Angelette Gudrun Schmidt 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):3102-3112
The influence of shear on viscoelastic solutions of poly(ethylene oxide) (PEO) and clay [montmorillonite, i.e., Cloisite NA+ (CNA)] was investigated with rheology and small-angle neutron scattering (SANS). The steady-state viscosity and SANS were used to measure the shear-induced orientation and relaxation of the polymer and clay platelets. Anisotropic scattering patterns developed at much lower shear rates than in pure clay solutions. The scattering anisotropy saturated at low shear rates, and the CNA clay platelets aligned with the flow, with the surface normal parallel to the gradient direction. The cessation of shear led to partial and slow randomization of the CNA platelets, whereas extremely fast relaxation was observed for laponite (LRD) platelets. These PEO–CNA networklike solutions were compared with previously reported PEO–LRD networks, and the differences and similarities, with respect to the shear orientation, relaxation, and polymer–clay interactions, were examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3102–3112, 2004 相似文献
2.
Jon Samseth Richard J. Spontak Kell Mortensen 《Journal of Polymer Science.Polymer Physics》1993,31(4):467-474
Poly(siloxaneimide) (PSI) segmented copolymers exhibit organized microdomains if the blocks are sufficiently incompatible. As with neat diblock and triblock copolymers, the processing route employed to prepare films of PSI materials is expected to influence the dimensions and/or morphology of the resultant microstructure. In this work, small-angle neutron scattering (SANS) is utilized to characterize the disordered microstructure found in films of a series of PSI copolymers which are subjected to solvent casting and various thermal treatments. Microstructural dimensions such as the periodicity and correlation length are deduced from the Teubner-Strey (TS) model for disordered microemulsions. The scattering intensity of each copolymer up to q = 5.0 nm?1, where q is the scattering vector, is found to scale as q?2.8+?0.1. Results indicate that processing the materials as cast films or as melt-pressed films allowed to cool slowly has a small, but discernible, effect on microstructural characteristics. SANS profiles of films quenched from elevated temperatures reveal a clear transition in microdomain periodicity, which correlates well with the glass transition temperature of the imide microphase in these and other materials of similar chemical structure. © 1993 John Wiley & Sons, Inc. 相似文献
3.
Jeong Hwan Kim Ji Hoon Ko Byeong-Soo Bae 《Journal of Sol-Gel Science and Technology》2007,41(3):249-255
Multi-scale hybrid nanocomposites containing both ∼15 nm silica colloids and ∼2 nm oligosiloxanes in a methacryl polymer matrix
were newly designed and fabricated. Colloidal silica sols were dispersed in methacryl oligosiloxanes nano-hybrid resins synthesized
by sol-gel reaction of methacryloxypropylmethoxysilane and diphenylsilanediol. On the basis of TEM and SANS analyses, it was
confirmed that the silica colloids were compatibly dispersed and different sizes of colloidal silica and oligosiloxanes co-exist
in the solutions. Multi-scale hybrid nanocomposites fabricated by UV and thermal curing with incorporation of silica colloids
in the nano-hybrid materials show enhanced mechanical and thermal characteristics. 相似文献
4.
I. M. Miranda Salvado F. M. A. Margaça J. Teixeira 《Journal of Sol-Gel Science and Technology》1994,2(1-3):289-294
Silica-titania gels, prepared in acidic conditions, with contents of TiO2 up to 6 mol%, have been studied by small angle neutron scattering (SANS) as wet gel with increasing aging times. In all samples, small primary particles have been found with a diameter of about 3 nm. At the gel point, cylindrical clusters, ca. 10 nm long, were observed as well. These grow with aging time, becoming branched. The cluster-cluster diffusion limited aggregation model is found to be consistent with the SANS results. The growth process is independent of the TiO2 content. It is mainly influenced by the ratio of the aging time to the gelation time. 相似文献
5.
SANS data have been obtained for C12H25 (OC2H4)2SO4 Na. Results have been obtained for i) a series of solutions of variable concentration of the surfactant, ii) an approximately 0.07 M surfactant concentration to which variable amounts of NaCl were added, iii) a series of solutions 0.058M in surfactant but in different D2O-H2O mixtures. The SANS data can be described in terms of a model of monodispersed hard spheres interacting via a screened Coulombic potential. The micelles seem to be able to tolerate substantial amounts of salt without changing the internal structure. 相似文献
6.
Turbidity and small-angle neutron scattering (SANS) measurements have been carried out over an extended temperature range (10-60 °C) on thermoreversible gelling and non-gelling semidilute aqueous systems of ethyl(hydroxyethyl)cellulose (EHEC) in the presence of various amounts of sodium dodecyl sulfate (SDS). EHEC dissolved in D2O exhibits a lower consolute solution temperature with an abrupt change of the turbidity upon heating the sample. The turbidity transformation is shifted toward higher temperatures (the cloud point temperature rises) and it becomes gradually gentler as the level of surfactant addition increases. Precision turbidity measurements demonstrate the existence of hysteresis effects when heating and cooling scans are conducted. This effect is reduced with SDS addition and disappears at a sufficiently high SDS concentration where most aggregates are disrupted. It is shown from temperature quench turbidity experiments that it takes a very long time for the temperature-induced complexes to disintegrate. The scattered intensity results from SANS at low values of the scattering vector (q) disclose that elevated temperature and low SDS concentration promote the formation of large-scale associations, and at higher levels of surfactant addition the tendency to form aggregates is suppressed. At high surfactant concentrations (8 and 16 mm), an interaction peak appears in the spectrum at intermediate values of q. For the EHEC sample with 8 mm SDS, the peak disappears at higher temperatures because of enhanced hydrophobicity of the polymer. The analysis of the SANS data for the gelling sample (EHEC with 4 mm SDS) reveals that the inhomogeneity of the gel becomes more pronounced in the post-gel region. 相似文献
7.
The analysis of the interaction of micelles formed by a blockcopolymer is given by means of small-angle X-ray (SAXS) and
small-angle neutron scattering (SANS). The blockcopolymer consists of poly(styrene) and poly(ethylene oxide) (molecular weight
of each block: 1000 g/mol) and forms well-defined micelles (weight-association number: 400, weight-average diameter: 15.4 nm)
in water. The internal structure has been studied previously (Macromolecules 29:4006 (1996)) by SAXS. There it has been shown
that the micelles are spherical objects. The structure factor S(q) as a function of the scattering vector q (q=(4π/λ) sin (θ/2); λ: wavelength of the radiation in the medium; θ: scattering angle) can be extracted from both sets of small-angle
scattering data (SANS: q≤0.4 nm-1; SAXS: q≤0.6 nm-1). It is shown that particle interaction in the present system can be described by assuming soft interaction which is modeled
by a square-step potential.
Received: 12 May 1997 Accepted: 9 July 1997 相似文献
8.
Griffiths PC Fallis IA Willock DJ Paul A Barrie CL Griffiths PM Williams GM King SM Heenan RK Görgl R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(8):2022-2028
The morphology of micelles formed by two novel metallosurfactants has been studied by small-angle neutron scattering (SANS) and small-angle-X-ray scattering (SAXS). The two surfactants both contain a dodecyl chain as the hydrophobic moiety, but differ in the structure of the head group. The surfactants are Cu(II) complexes of monopendant alcohol derivatives of a) the face-capping macrocycle 1,4,7-triazacyclanonane (tacn), and b) an analogue based upon the tetraazamacrocycle 1,4,7,10-tetraazacyclododecane. Here, neutron scattering has been used to study the overall size and shape of the surfactant micelles, in conjunction with X-ray scattering to locate the metal ions. For the 1,4,7,10-tetraazacyclododecane-based surfactant, oblate micelles are observed, which are smaller to the prolate micelles formed by the 1,4,7-triazacyclononane analogue. The X-ray scattering analysis shows that the metal ions are distributed throughout the polar head-group region, rather than at a well-defined radius; this is in good agreement with the SANS-derived dimensions of the micelle. Indeed, the same model for micelle morphology can be used to fit both the SANS and SAXS data. 相似文献
9.
H. Etori H. Hirata Y. Yamada H. Okabayashi M. Furusaka 《Colloid and polymer science》1997,275(3):263-273
Potassium salts of N-decanoylglycine and N-decanoyl-L-alanine oligopeptides (monomer, dimer and trimer) were synthesized.
For these oligomer salts in aqueous solutions, the microstructures of micelles have been investigated by small-angle neutron-scattering
(SANS). In the calculation of SANS intensity data, the thickness of the hydrophilic layer was altered by changing the conformation
of the oligomer moiety (helical and β-sheet structures). For micelles of the trimer salts, the helical structure models provide
the best fit to the observed SANS intensity data. For micelles of the monomer-and dimer-salts, the β-sheet model provides
the best fit to the observed data. For the monomer-and dimer-micelles, the aggregation number (n) is not dependent on the species of amino acid residue, imply-ing that the decanoyl group plays a critical role in micelle
formation. However, for the trimer micelles, the n value is dependent on the species of amino acid residue.
Received: 11 July 1996 Accepted: 11 September 1996 相似文献
10.