Doped polymer matrices

Many of the linear conjugated tricyclic systems have interesting fluorescence or other electrophysical properties. Bis-pyrazolepyridines such as compound 30 have been incorporated into polymers as fluorescent chromophores <1999JMC339>, and used in doped polymer matrices <1997JMC2323>. They are electroluminescent at 425 nm and photoluminescent at 427 and 430 nm in a poly(vinylcarbazole) matrix with a quantum efficiency of 0.8. 

A study of the comparative rates of triplet exciton migration has been carried out on molecularly doped polymers and on vinyl aromatic polymers. In both cases specific rate constants for triplet exciton migration were estimated from rate constants for triplet-triplet annihilation. The rate data were obtained by using a laser pulse-optical probe method to determine triplet concentrations directly by triplet-triplet absorption. It is found that triplet exciton migration rates for polymers are ten-fold to one-hundred-fold larger than those for doped polymer matrices probably due to the more dense local chromophore concentrations in the former. 

Z. He, A. Danel, and G. H. W. Milbum. Thin-layer photoluminescence and electroluminescence observed from pyrazoloquinoline-doped polymer matrices. J. Lumin., 122-123 605-609, January-April 2007. 

One of the drawbacks of doping polymer matrices with azobenzenes that exhibit photoinduced motions is that at higher concentration levels, phase separation... 

The volatility of a particular stabilizer is certainly related to its molecular weight. It is however difficult to define unambiguously the limit value of the molecular weight of a stabilizer assuring a low volatility under specific conditions of application. Substituent effects in the stabilizer molecule and physical relations in the particular doped polymer matrix affect the volatility very seriously. The borderline between volatile and nonvolatile stabilizers is therefore rather diffuse. Values of molecular weights from 400 to 650 were reported to be satisfactory for solving volatility problems [31]. 

In recent years there has been an interest in the development of polymer-supported supramolecules for sensor arrays. Such arrays include electronic noses to sense vapour analytes. There are many polymer supports that have been used to create sensor arrays, for example, conductive polymers, polymer composites, dye-doped polymer matrixes and surface acoustic wave sensors (SAWs). 

Li-HPE is a hybrid plastic electrolyte which is a two-component mixture of a Li salt-doped polymer matrix swollen with a liquid electrolyte. 

These conjugated polymers can be chemically and electrochemically reduced and reoxidized in a reversible manner. In all cases the charges on the polymer backbone must be compensated by ions from the reaction medium which are then incorporated into the polymer lattice. The rate of the doping process is dependent on the mobiHty of these charge compensating ions into and out of the polymer matrix. 

Conduction in the raw doped polymer can be improved by devices such as compression and stretching and judicious after-synthesis dopant ion exchange. Matrix-guided electropolymerization also yields superior products. 

Further modification of the above nanostructures is useful for obtaining new functional materials. Thirdly, we apply the dopant-induced laser ablation technique to site-selectively doped thin diblock copolymer films with spheres (sea-island), cylinders (hole-network), and wormlike structures on the nanoscale [19, 20]. When the dye-doped component parts are ablated away by laser light, the films are modified selectively. Concerning the laser ablation of diblock copolymer films, Lengl et al. carried out the excimer laser ablation of diblock copolymer monolayer films, forming spherical micelles loaded with an Au salt to obtain metallic Au nanodots [21]. They used the laser ablation to remove the polymer matrix. In our experiment, however, the laser ablation is used to remove one component of block copolymers. Thereby, we can expect to obtain new functional materials with novel nanostmctures. 

Later on a lot of research into the photosensitivity of the polymer matrix with various inserted molecules was carried out. A great deal of attention was focused on molecule doped polycarbonates. The photoconduction mechanism in such systems has many common features with the same mechanism for doped PVC. 

Triphenylamine (TPA) and isopropylcarbazole (IPC) were used at the beginning as a model doping molecules [287-289]. The introduction into the polymer matrix IPC molecules with a concentration of 102Ocm-3 leads to the clearly seen photogeneration and charge transfer. 

The effective carrier mobilities and their dependence on concentration for benztriazole derivatives embedded in polycarbonate were explained by the percolative aspects in photoconductivity [296]. The observed field dependence of the mobility for polycarbonate films doped with diethynylaminobenzaldehy-de-diphenyl hydrazone cannot be accounted for by any known hopping model [297]. The influence of the nature of the polymer matrix on photogeneration and transport properties of the molecule doped polymers was investigated in some papers [57, 58, 298, 299],... 

The susceptibility tensors measure the macroscopic compliance of the electrons. Since the second order polarization is a second rank tensor, SHG is zero in a centrosymmetric or randomly oriented system. To make the material capable of SHG, the NLO dopants must be oriented noncentrosymmetricaly in the polymer matrix (2-3). When modeling the poled, doped films using a free gas approximation, the poled second order susceptibilities are given by (2.19)... 

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