排序方式: 共有11条查询结果,搜索用时 15 毫秒
1.
V. V. A. Fernandez N. Tepale J. C. Sánchez-Díaz E. Mendizábal J. E. Puig J. F. A. Soltero 《Colloid and polymer science》2006,284(4):387-395
The synthesis of nanostructured poly(N-isopropylacrylamide) (polyNIPA) hydrogels by a two-stage polymerization process is reported here. The process involves the
synthesis of slightly crosslinked polyNIPA nanoparticles by inverse (w/o) microemulsion polymerization; then, these particles
are dried, cleaned and dispersed in an aqueous solution of NIPA and a crosslinking agent (N,N-methylene-bis-acrylamide or NMBA) and polymerized to produce the nanostructured hydrogels. Their swelling and de-swelling
kinetics, volume phase transition temperatures (T
VPT) and mechanical properties at the equilibrium swollen state are investigated as a function of the weight ratio of polyNIPA
particles to monomer (NIPA). The nanostructured gels exhibit larger equilibrium water uptake, faster swelling and de-swelling
rates and similar T
VPT than those of the conventional ones; moreover, the elastic and Young moduli are larger than those of the conventional hydrogels
at similar swelling ratios. The fast swelling and de-swelling kinetics are explained in terms of the controlled inhomogeneities
introduced by the method of synthesis. 相似文献
2.
Bolognesi M Sánchez-Díaz A Ajuria J Pacios R Palomares E 《Physical chemistry chemical physics : PCCP》2011,13(13):6105-6109
Organic polymer solar cells (OPSCs) have been prepared using TiO(x) metal oxides as selective electrodes for electron collection. The interfacial charge transfer reactions, under working conditions, that limit the energy conversion efficiency of these devices have been measured and compared to the standard OPSC geometry which collects the electrons through a low work function metal contact. 相似文献
3.
V. V. A. Fernandez J. Aguilar J. F. A. Soltero F. J. Moscoso-Sánchez J. C. Sánchez-Díaz 《高分子科学杂志,A辑:纯化学与应用化学》2016,53(3):152-159
Here we report the preparation and characterization of nanostructured thermo-responsive poly(acrylamide) (PAM)-based hydrogels. The addition of slightly crosslinked poly(N-isopropylacrylamide) (PNIPA) nanogels to AM reactive aqueous solution produces nanostructured hydrogels that exhibit a volume phase transition temperature (TVPT). Their swelling kinetics, TVPT's and mechanical properties at the equilibrium-swollen state (Heq) are investigated as a function of the concentration of PNIPA nanogels in the nanostructured hydrogels. Nanostructured hydrogels with PNIPA nanogels/AM mass ratios of 20/80 and above exhibit higher Heq and longer time to reach the equilibrium swelling than those of the conventional PAM hydrogels. However, the PNIPA nanogels possess thermo-responsive character missing in conventional PAM hydrogels. The TVPT of nanostructured hydrogels depends on PNIPA nanogel content but their elastic and Young moduli are larger than those of conventional hydrogels at similar swelling ratios. Swelling kinetics, TVPT, and mechanical properties are explained in terms of the controlled in-homogeneities introduced by the PNIPA nanogels during the polymerization. 相似文献
4.
Sánchez-Díaz LE Mendez-Maldonado GA González-Melchor M Ruiz-Estrada H Medina-Noyola M 《The Journal of chemical physics》2011,135(1):014504
The generalized mean spherical approximation of the structural properties of the binary charge-symmetric fluid of screened charged hard-spheres of the same diameter, i.e., the screened restricted primitive model, is extended to include binary charge-asymmetric and multi-component fluids. Molecular dynamics simulation data are generated to assess the accuracy of the corresponding theoretical predictions. 相似文献
5.
Reynal A Forneli A Martinez-Ferrero E Sánchez-Díaz A Vidal-Ferran A O'Regan BC Palomares E 《Journal of the American Chemical Society》2008,130(41):13558-13567
A series of heteroleptic ruthenium(II) polypyridyl complexes containing phenanthroline ligands have been designed, synthesized, and characterized. The spectroscopic and electrochemical properties of the complexes have been studied in solution and adsorbed onto semiconductor nanocrystalline metal oxide particles. The results show that for two of the ruthenium complexes, bearing electron-donating (-NH2) or electron-withdrawing (-NO2) groups, the presence of the redox-active I(-)/I3(-) electrolyte produces important changes in the interfacial charge transfer processes that limit the device performance. For example, those dyes enhanced the electron recombination reaction between the photoinjected electrons at TiO2 and the oxidized redox electrolyte. In an effort to understand the details of such striking observations, we have monitored the charge transfer reactions taking place at the different interfaces of the devices using time-resolved single photon counting, laser transient spectroscopy, and light-induced photovoltage measurements. 相似文献
6.
Abraham G. Alvarado Jorge Cortés Lourdes A. Pérez-Carrillo Martin Rabelero Jesús Arellano Juan Carlos Sánchez-Díaz 《Journal of Macromolecular Science: Physics》2016,55(11):1086-1098
The synthesis, by two sequential inverse microemulsion polymerizations, of interpenetrating polymer networks (IPN) formed by polyacrylamide (PAM) and poly(acrylic acid) (PAA) and their response to changes in pH and temperature are reported here. The temperature and pH responses of the IPN nanoparticles are compared with those of polyacrylamide and random copolymers of polyacrylamide and poly(acrylic acid) P(AM-co-AA) nanoparticles also made by inverse microemulsion polymerization. We found that only the IPN nanogels exhibited a sharp swelling increase with temperature associated with its Upper Consolute Solution Temperature, driven by hydrogen bonding interactions, and with pH, driven by electrostatic repulsions of the PAA carboxylic groups, especially at pHs larger than the pKa of the PAA. The ?-potentials of the PAM, P(AM-co-AA) and IPN nanogels were measured as a function of pH and temperature, to determine the effects of these two variables, which in turn, affected the swelling of the nanogels. Field emission scanning electron microscopy revealed that the IPN nanogels were spheroidal with sizes similar to those determined by dynamic light scattering. 相似文献
7.
V. V. A. Fernández J. Aguilar F. Becerra J. C. Sánchez-Díaz J. F. A. Soltero P. Ortega-Gudiño E. Hernandez F. Bautista J. E. Puig 《Colloid and polymer science》2013,291(8):1829-1842
The thermoresponsive behavior and mechanical properties of nanostructured hydrogels, which consist of poly(acrylamide) nanoparticles embedded in a cross-linked poly(N-isopropylacrylamide) hydrogel matrix, are reported here. Nanostructured hydrogels exhibit a tuned volume phase transition temperature (T VPT), which varies with nanoparticle content in the range from 32 up to 39–40 °C. Moreover, larger equilibrium water uptake, faster swelling and de-swelling rates, and larger equilibrium swelling at 25 °C were obtained with nanostructured hydrogels compared with those of conventional ones. Elastic and Young’s moduli were larger than those of conventional hydrogels at similar swelling ratios. The tuned T VPT and the de-swelling rate were predicted with a modified Flory–Rehner equation coupled with a mixing rule that considers the contribution of both polymers. These behaviors are explained by a combination of hydrophilic/hydrophobic interactions and by the controlled inhomogeneities (nanoparticles) introduced by the method of synthesis. 相似文献
8.
Nuño-Donlucas SM Sánchez-Díaz JC Rabelero M Cortés-Ortega J Luhrs-Olmos CC Fernández-Escamilla VV Mendizábal E Puig JE 《Journal of colloid and interface science》2004,270(1):94-98
Poly(methyl methacrylate) nanosize particles, made by microemulsion polymerization, were dispersed in an acrylamide aqueous solution, which was polymerized in the presence of a cross-linking agent to yield microstructured hydrogels. The kinetics of swelling and the mechanical properties of these hydrogels were investigated as a function of concentration of particles. The microstructured hydrogels exhibit higher equilibrium swelling and larger Young modulus than conventional (that is, without particles) polyacrylamide hydrogel. The morphology of the microstructured hydrogels was examined by transmission electron microscopy. 相似文献
9.
Puig LJ Sánchez-Díaz JC Villacampa M Mendizábal E Puig JE Aguiar A Katime I 《Journal of colloid and interface science》2001,235(2):278-282
The synthesis by a two-stage polymerization process of microstructured polyacrylamide hydrogels with large swelling capacity and improved mechanical properties is reported. First, crosslinked polyacrylamide particles of nanosize scale are made by inverse microemulsion polymerization. These particles are then dried and redispersed in an aqueous solution of acrylamide and polymerized in the presence of a crosslinking agent. The microstructured hydrogels, in contrast to transparent conventional polyacrylamide hydrogels, are translucid due to the presence of the dispersed particles. The swelling capacity of these hydrogels increases as the particle content increases and their Young and elastic moduli (at equilibrium swelling) diminish only slightly. Mechanical tests disclose that the microstructured hydrogels have larger Young moduli than conventional hydrogels with an identical degree of swelling. Copyright 2001 Academic Press. 相似文献
10.
Gorka Garay Josebe Hurtado Manuel Pedrón Lorena García Dr. Efraim Reyes Eduardo Sánchez-Díez Prof. Dr. Tomás Tejero Prof. Dr. Luisa Carrillo Prof. Dr. Pedro Merino Prof. Dr. Jose L. Vicario 《Angewandte Chemie (International ed. in English)》2023,62(22):e202302416
We have demonstrated that the catalytic and enantioselective vinylcyclopropane-cyclopentene rearrangement can be carried out on (vinylcyclopropyl)acetaldehydes through activation via enamine intermediates. The reaction makes use of racemic starting materials that, upon ring opening facilitated by the catalytic generation of a donor-acceptor cyclopropane, deliver an acyclic iminium ion/dienolate intermediate in which all stereochemical information has been deleted. The final cyclization step forms the rearrangement product, showing that chirality transfer from the catalyst to the final compound is highly effective and leads to the stereocontrolled formation of a variety of structurally different cyclopentenes. 相似文献