A5084821034- Liquid Crystal Research Advancements
- Nonlinear Dynamics and Pattern Formation
- Material Dynamics and Properties
- Molecular spectroscopy and chirality
- Surfactants and Colloidal Systems
- Advanced Materials and Mechanics
- Rheology and Fluid Dynamics Studies
- Advanced Cellulose Research Studies
- Photonic Crystals and Applications
- Theoretical and Computational Physics
- Micro and Nano Robotics
- Adsorption, diffusion, and thermodynamic properties of materials
- Block Copolymer Self-Assembly
- Material Properties and Processing
- Luminescence Properties of Advanced Materials
- Polymer composites and self-healing
- ZnO doping and properties
- Plant Reproductive Biology
- Force Microscopy Techniques and Applications
- Spectroscopy and Quantum Chemical Studies
- Photochemistry and Electron Transfer Studies
- Insect and Arachnid Ecology and Behavior
- Polydiacetylene-based materials and applications
- Inflammatory Biomarkers in Disease Prognosis
- Fullerene Chemistry and Applications
Universidade Nova de Lisboa
2004-2023
Hospital Curry Cabral
2022
University of Lisbon
1990-2022
University of Aveiro
2016-2018
Centro Hospitalar de Lisboa Central
2017
University of Padua
2000
Département de Chimie Moléculaire
1981-1986
CEA Grenoble
1971-1986
Fundação para a Ciência e Tecnologia
1985
Instituto de Investigação Científica Tropical
1980-1981
We propose a simple NMR technique, and the underlying theory, to evaluate, with high accuracy, four out of five viscosity coefficients ratio $\frac{{k}_{33}}{{k}_{11}}$ bend splay Frank elastic constants, in nematic polymers. Quantitative data on viscosities ${\ensuremath{\gamma}}_{1}$, ${\ensuremath{\alpha}}_{1}$, ${\ensuremath{\alpha}}_{2}$, ${\ensuremath{\eta}}_{c}$ are given for first time thermotropic polymer. The material studied is poly...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNMR study of some thermotropic nematic polyesters with mesogenic elements and flexible spacers in the main chainAssis F. Martins, J. B. Ferreira, Volino, A. Blumstein, R. BlumsteinCite this: Macromolecules 1983, 16, 2, 279–287Publication Date (Print):February 1, 1983Publication History Published online1 May 2002Published inissue 1 February 1983https://pubs.acs.org/doi/10.1021/ma00236a023https://doi.org/10.1021/ma00236a023research-articleACS...
ZnO tetrapods–C<sub>60</sub> based hybrid materials show interesting defect mediated optical and electrical responses which could be suitable for various applications.
Abstract We have measured the twist viscosity Y′(T) by rotating field method, over entire nematic range of 4,4′-di-n-alkoxyazoxybenznes (mOAB) from m = 2 to 7. The results these measurements are presented here together with a new development our previous theory γ1(T) which accounts for free volume variation temperature and gives following main result: where S is order parameter, ϵS height Maier-Saupe potential, TO motional “freezing” director, g ø nearly constant parameters may be either...
Abstract The reorientational behaviour of a nematic monodomain, in static magnetic field, following the rotation mean director through an angle α ≈ π/2 to field direction, is investigated by optical polarizing microscopy and proton NMR spectroscopy. Optical evidence supporting reorientation process pure bend transient distortion reported for poly (4,4′-dioxy-2,2′-dimethylazoxybenzene nonanediyl), main-chain thermotropic polymer. time evolution flow patterns are deduced from detailed analysis...
Simulations of nematic and smectic mesophases based on a dissipative particle dynamics approach are discussed. Mesogenic units built in the form standard semirigid bead-spring chains. It is shown that phases can be formed for chains containing at least eight beads, provided conservative soft-repulsive potential between nonconnected beads sufficiently strong. Smectic observed only by modifying repulsive interaction main-chain terminal beads. The simulations indicate smectic-nematic...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation J. B. Riti, M. T. Cidade, H. Godinho, A. F. Martins, P. Navard; Shear induced textures of thermotropic acetoxypropylcellulose. Rheol. 1 November 1997; 41 (6): 1247–1260. https://doi.org/10.1122/1.550842 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks...
Abstract A novel type of PDLC display utilizing solid films obtained from the cellulose derivative hydroxypropylcellulose (HPC) with molecular weights 60000 (HPC60000) and 100000 (HPC100000), cross-linked two different di-isocyanates, 1,4-di-isocyanatobutane (BDI) 1,6-di-isocyanatohexane (HDI), is presented. This kind (optical cell) composed a porous elastomeric film (20–60 μm thick) HPC-BDI or HPC-HDI, impregnated nematic liquid crystal contained between transparent conducting substrates....
Abstract The tensile properties of cross‐linked and uncross‐linked composite films (thickness ∼20–35 μm) prepared from Hydroxypropylcellulose (HPC) with incorporation microcrystalline cellulose fibers (Avicel) were studied. concentration in the composites ranged 0 to 30 w/w% obtained by reaction HPC‐Avicel mixtures 1,4‐butyldiisocyanate. It was demonstrated that inclusion a HPC matrix produces enhanced mechanical are improved cross‐linking. Mechanical results seem indicate elastic...
from teaching and research institutions in France or abroad, public private centers.L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques niveau recherche, publiés ou non, émanant des établissements d'enseignement recherche français étrangers, laboratoires publics privés.Evidence by proton NMR of the alignment a thermotropic nematic polymer magnetic field ∼ 1 tesla
We give a coherent quantitative interpretation of both the frequency and temperature behavior proton spin-lattice relaxation time ${T}_{1}$ in nematic phase $p$-azoxyanisole. The dependence is dominated by long-wavelength thermal fluctuations orientational order. has an important contribution from short-range phenomena involved motion methyl protons. activation energy for this $W\ensuremath{\approx}9$ kcal/mole.
Abstract Acetoxypropylcellulose (APC) and propionic, n ‐butyric, isobutyric, valeric, isovaleric, hexanionic, heptanionic acid esters of hydroxypropylcellulose (HPC) (respectively PPC, BPC, iBPC, VPC, iVPC, HexPc, HepPc) were prepared characterized by differential scanning calorimetry, chromatography, polarizing microscopy, chemical methods, spectroscopy. All these form thermotropic cholesteric liquid crystalline phases. The glass ( T g ) clearing c transition temperatures determined....
ZnO nanorod arrays have been grown by potentiostatic pulse electrodeposition between a reduction potential and "rest" potential. The effect of the duty cycle frequency as well heat-treatment in air on properties electrodeposits has studied. Surface morphology, structural, optical electrical were evaluated. Absorption spectra reveal high energy bandgap Burstein-Moss shift for as-grown nanorods, line with donor density (1.1 × 1019 9.5 cm−3) determined from electrochemical impedance...
Abstract Deuterium and proton magnetic resonance data of fully deuterated, partially deuterated on the rings methyl groups, protonated nematic para-azoxy-anisole (PAA) are analysed self-consistently in terms molecular structure, conformation orientational order using a single parameter model. The values temperature dependences some conformational averages deduced. These results discussed light obtained by other methods: X-ray diffraction, quantum chemistry calculations, macroscopic...
We investigate the director reorientation in a nematic liquid crystal confined between two parallel plates and subjected to both magnetic an electric field. The permanent field is used first align and, subsequently, allow nuclear resonance (NMR) observation of response following application For sufficiently strong fields, reorients aligns In this work we focus on geometry where fields are orthogonal each other. configuration state system, immediately after applying field, steady unstable, at...
This work describes an investigation of the static (or quasistatic) nuclear magnetic resonance (NMR) response in a nematic liquid crystal confined between two planar conducting plates and subject to field electric produced by difference voltage applied on plates. Deuterium NMR spectroscopy 4-pentyl-d(2)-4'-cyanobiphenyl (5CB-d(2)) under these conditions has revealed dependent inhomogeneous director distribution for particular narrow range voltages fixed (that spectrometer). In ideal setup...
Abstract The magnetic field reorientation of an initially aligned sample a nematic polymer liquid crystal was followed by proton NMR. Evolution to metastable (banded) state considered using Rheo-NMR technique developed previously. Late stage studied taking into account the dynamics defects following formation splay–bend walls. NMR spectra simulation allowed us obtain wall density as function time. This result, together with defect-controlled dissolution model proposed Rey [1], used...