Liquid Polymer Matrix Research Articles

ゾル‐ゲル法を用いた微粒子充填エラストマーの調製と諸物性

Rheological and mechanical properties of silicone resins filled with various silica particles were investigated before and after crosslinking. Both hydrophilic and hydrophobic particles were prepared from tetraethoxysilane and vinyltriethoxysilane, respectively in a liquid silicone matrix through a sol-gel process. Vinyl groups on the surface of the hydrophobic particles react with silicone resin. Rheological investigation for the uncrosslinked resin filled with particles revealed that the liquid polymer matrix containing hydrophilic particles has a strong three-dimensional structure. While the hydrophilic particle tends to form a three-dimensional structure, the hydrophobic particle in the liquid silicone matrix suppressed such tendency. Once matrix is crosslinked, although the three-dimensional structure of the hydrophilic particles gives rise to the slight increase in tensile modulus, the tensile strength and the elongation at break decrease. However, adhesion between hydrophobic particles and the matrix enhances the mechanical properties significantly.

Deformation of liquid crystal droplets under the action of an external ac electric field.

Deformation of liquid crystal droplets suspended in liquid polymer matrix under the action of external electric field was observed in dependence of ion concentration in such system. Experimental dependence of droplet elongation vs electric field demonstrates nonmonotonous character with increase of ion concentration. The theory that provides the basic agreement with experimental observation is developed.

Fluorescent nanosensors for intracellular chemical analysis: decyl methacrylate liquid polymer matrix and ion-exchange-based potassium PEBBLE sensors with real-time application to viable rat C6 glioma cells.

Fluorescent spherical nanosensors, or PEBBLEs (probes encapsulated by biologically localized embedding), in the 500 nm-1 microm size range have been developed using decyl methacrylate as a matrix. A general scheme for the polymerization and introduction of sensing components creates a matrix that allows for the utilization of the highly selective ionophores used in poly(vinyl chloride) and decyl methacrylate ion-selective electrodes. We have applied these optically silent ionophores to fluorescence-based sensing by using ion-exchange and highly selective pH chromoionophores. This allows the tailoring of selective submicrometer sensors for use in intracellular measurements of important analytes for which selective enough fluorescent probes do not exist. The protocol for sensor development has been worked out for potassium sensing. It is based on the BME-44 ionophore (2-dodecyl-2-methyl-1,3-propanediylbis[N-[5'nitro(benzo-15-crown-5)-4'-yl]carbamate]). The general scheme should work for any available ionophore used in PVC or decyl methacrylate ion-selective electrodes, with minor adjustments to account for differences in ionophore charge and analyte binding constant. The reversible and highly selective sensors developed have a subsecond response time and an adjustable dynamic range. Applications to live C6 glioma cells demonstrate their utility; the intracellular potassium activity is followed in real time upon extracellular administration of kainic acid.

Second-order nonlinear optical properties and relaxation dynamics of aligned cross-linked polyurethanes with hemicyanine-type chromophores

Three types of different cross-linked polyurethane were prepared by the reaction of poly[(phenylisocyanate)-co-formaldehyde] with three different hydroxy-functionalized nonlinear optical chromophores. For poled and cured polymers the χ(2) values were between 16.8 and 37.4 pm/V, measured at a wavelength of 1.064 μm. Thermal stability studies performed on a sample having bonding sites of vertical–parallel structure between the chromophore and the liquid polymer matrix indicated, by second-harmonic-generation activity, a minimum decay of the χ(2) value owing to lattice hardening of the polyurethane matrix with three bonding sites. The relaxation times of aligned dipoles in vertical–parallel polyurethane were measured by variation of poling and cross-linking conditions. Three decay modes were found to exist: the mode that corresponds to partially bonded or free unbonded chromophores, the mode of thermal relaxation of bonded chromophores, and the mode that is due to the relaxation of an elastically stressed main chain induced by the poling elastic field.

Optical studies on some dyes for liquid solar concentrators

Spectral characteristics of some luminescent dyes, derivatives of xanthene and benzoxazinone groups, in a liquid polymer matrix, Triton x-100, have been studied. It is seen that Triton x-100 could serve as a suitable liquid matrix for the luminescent solar concentrators (LSCs).

Liquid crystal polymer‐carbon fiber composites. Molecular orientation

AbstractThe objective of this work has been to study composite systems in which carbon fibers are dispersed in a liquid crystal polymer matrix. The fundamental point of interest here has been the interfacial response that fiber surfaces can potentially induce in self‐ordering polymers. The matrix material used was a thermotropic liquid crystal polyester synthesized in our laboratory from the monomers p‐acetoxybenzoic acid, diacetoxyhydroquinone, and pimelic acid. The aromatic‐aliphatic polymer was characterized by NMR as a chemically disordered polymer of the three structural units which exhibits a nematic phase at temperatures above 150°C. Breadline proton NMR above the solid to liquid crystal transition was used to measure the rate of magnetic alignment of molecules in the matrix and polarized optical microscopy was used to analyze interfacial zones in composite samples. Fiber surfaces were found to influence the orientation and orientational dynamics of a liquid crystal polymer matrix. This was revealed by enhanced rates of magnetic orientation in the polymer melt when carbon fibers are dispersed in the medium. Fiber surfaces were also found to stabilize nematic ordering of the polymer as the melt was heated towards complete isotropization. The phenomena discovered here may originate in the development of zones around fibers with a common molecular orientation anchored by the carbon surface.

Wear performance of a bulk liquid crystal polymer and its short-fibre composites

The wear behaviour of short-fibre reinforced composites having a liquid crystal polymer (LCP) matrix was investigated under two extremely different types of wear loading. Sliding wear tests against smooth steel at different values of sliding speed v and contact pressure p revealed that reinforcing LCP with carbon fibres, or glass fibres plus mineral filler and graphite flake, was much more effective in improving the composites' wear resistance than a reinforcement with glass fibres only. The same trend holds as far as the limiting pv factor was concerned. No improvement in wear resistance due to fibre reinforcement could be found under abrasive wear conditions. The layered structure of the unfilled LCP gave rise to a large anisotropy in wear rate in different sliding directions, but this was almost eliminated by the addition of short fibres under sliding wear conditions.