Guest-host polymer systems

We mentioned in the previous section that the bulk NLO properties of a poled-polymer host-guest system might be expected to be proportional to the chromophore fi/3 multiplied by the number density of chromophores. However, for high loadings of molecules with large pi, the d33 and r33 coefficients do not continue to increase linearly with chromophore loading, but exhibit maxima these are attributed to competition between the interaction of the chromophores and the poling... 

G. Vamvounis and S. Holdcroft, Enhancing solid-state emission from conjugated polymers via self-forming host-guest systems, Adv. Mater., 16 716-719, 2004. 

In this review, the synthesis, properties, and applications in optoelectronic fields of polyfluorenes with on-chain metal centers have been briefly summarized. Metal complexes involving iridium(III), platinum(II), europium(III), rhenium(I), and ruthenium(II) complex coupled with polyfluorene are surveyed. Efficient energy transfer from polymer main-chain to metal-centers can occur in these host-guest systems. These kinds of novel polymers are usually applied in the fields of phosphorescent OLEDs, memory devices, and sensors. In particular, the realization of efficient energy transfer and phosphorescence offers a huge potential for future optoelectronic devices based on these kinds of materials. 

It is not necessary to use only dyes to take advantage of the energy transfer blends of two polymers can also be used as host-guest systems (Lee et al 2002). The guest molecules can be florescent or phosphorescent in nature. However, phosphorescent dyes based on Ir and Pt complexes have provided significantly higher efficiency of OLEDs because of their ability to emit from both singlet and triplet excitons of the host molecule (Kamata et al 2002),... 

Kato T, Hirota N, Fujishima A, Frechet JMJ. 1996. Supramolecular hydrogen bonded liquid crystalline polymer complexes. Design of side chain polymers and a host guest system by noncovalent interaction. J Polym Sci A 3 57 62. 

The Ae representation is often impractical for supra-molecular samples whose molar concentration is poorly defined (e.g., polymers) and for those of multicomponent systems (e.g., host-guest systems). Therefore, it is common for such samples to present CD spectra in ellipticity 9 (mdeg), which is normally the raw output of CD instruments. Ellipticity is correlated with AA by (9). 

Three host-guest systems were buUt and their structural and physical features were simulated. The model hybrid materials consist of PMMA/nc-SiC, PC/nc-SiC, and PVK/nc-SiC composites. For each system, the starting structure was generated using Hyper-Chem program package. The imit cell of each structure consists of one SiC cluster surrounded by one polymer chain of... 

Irradiation of cinnamate derivatives in chiral host environments has long attracted attention as a gateway to asymmetric photochemical synthesis. The use of a nonchiral host induced to crystallize in a chiral space group represents an example of absolute asymmetric synthesis, as described by Vaida et al. for the cinnamamide/cinnamic acid host/guest system and by Hasegawa et al. - for the cross dimerization of 5 (which spontaneously crystallizes in a chiral space group). It should be noted that even apparently minor modifications, at times, have a profound impact on the outcome of sohd-state reactions. In the previous example, the methyl ester derivative of 5 gives, upon irradiation, hnear polymers. 

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