Conjugated polymers side chains

To overcome the above mentioned problems, we developed a self-assembly DNA-conjugated polymer for novel DNA chip fabrication [66-68]. The system developed uses ssDNA as a probe and disulfide bridges located in the polymer side chain for self-assembly immobilization. This polymer can be immobilized on gold substrate with the self-assembly technique. On the surface, DNA (hydrophilic) is exposed to a solution site without lying due to the hydrophobic polymer main chain (Fig. 4). Finally, we have discriminated differential of one base mismatched sequences using DNA-conjugated polymer. 

A self-assembly DNA-conjugated polymer-based DNA detection method was previously mentioned. This study showed specific immobilization to a gold substrate with the self-assembly technique, not physical adsorption and great selectivity to fully matched DNA instead of nonspecific adsorption due to self-assembly DNA-conjugated polyallylamine and PAA coating [67,68]. However, a major problem was that we needed to prepare many kinds of DNA-conjugated polymer to analyze many kinds of target DNA due to direct modification of probe DNA to the polymer side chain. 

Table 11 Recognition of binding sites conjugated as side chains to polymers...

Liquid crystals (LCs) are described as a fluid phase that flows like a liquid and is oriented in a crystalline manner. LCs are divided into two types thermotropic LCs, where the LC phase transition is dependent on temperature or lyotropic LCs, where the LC phase transition occurs as a function of solvent concentration. To introduce liquid crystallinity to conjugated polymers, LC moieties can be introduced to the polymer side chains for side chain-type liquid crystallinity. On the other hand, designing conjugated polymers with rigid main chain structures with flexible alkyl side chains for solubility enables main chain-type liquid crystallinity. 

In addition to investigating ferroelectric liquid crystalline conjugated polymers with dynamic switching functionahties under an electric field, our group has also developed photoresponsive liquid crystalline conjugated polymers with dynamic switching of linearly and circularly polarized luminescence. This was accomplished through the use of a photoisomerizable moiety in the polymer side chain. 

The polymers exhibit a good thermal stability and film-forming ability. The absorption spectra show a broader absorption band from 300 to 580 nm in comparison to a PPV type without conjugated thiophene side chains. 

Cyclic voltammetry revealed that the band gap was reduced effectively by attaching the conjugated thiophene side chains. Therefore, these polymers have been proposed for solar-cell applications [20]. 

Fig. 1.9 a First isoindigo-based polymer FETs. b Impact of poliuner symmetry and backbone curvature, c Branching position effects of polymer side chains, d Ambipolar transport in lluorinated isoindigo-based polymers, e Chlorination as a useful method to modulate charge transport in conjugated polymers... 

Recently, polyimines include the synthesis of long alkoxy (Cg-Cig) side chain derivatives [188,189], which are presumably soluble to some extent in organic solvents and derivatives containing fluorene cardo unit [190]. Trifluoromethyl groups [191] in the polymer backbone provide solubility in organic solvents. Studies of the electrical conductivity of doped conjugated aromatic polyimines and alkoxy derivatives have been reported [188], and the values are in the range of 10 to 10 S/ cm. 

For copolymers of structure I, for both types of side-chains, there is a striking similarity with the optical properties of the corresponding models the absorption and photoluminescence maxima of the polymers arc only 0.08-0.09 eV red-shifted relative to those of the models, as shown in Figure 16-9 (left) for the octyloxy-substituted compounds. The small shift can be readily explained by the fact that in the copolymers the chromophorcs are actually substituted by silylene units, which have a weakly electron-donating character. The shifts between absorption and luminescence maxima are exactly the same for polymers and models and the width of the emission bands is almost identical. The quantum yields are only slightly reduced in the polymers. These results confirm that the active chro-mophores are the PPV-type blocks and that the silylene unit is an efficient re-conjugation interrupter. 

The sulfonium precursor route may also be applied to alkoxy-substituted PPVs, but a dehydrohalogenation-condensation polymerization route, pioneered by Gilch, is favored 37]. The polymerization again proceeds via a quinomethide intermediate, but die syndicsis of the conjugated polymer requires only two steps and proceeds often in improved yields. The synthesis of the much-studied poly 2-methoxy-5-(2-ethylhexyloxy)-l,4-phenylene vinylene], MEH-PPV 15 is outlined in Scheme 1-5 33, 35]. The solubility of MEH-PPV is believed to be enhanced by the branched nature of its side-chain. 

Both the main chain and side chains can greatly influence die properties of polymers. By varying the side chains and using different linkers, properties of polymers such as die solubility and conjugation along the polymer backbone can be greatly altered. 

Introduction of side chains will generally increase the solubility of the polymers but usually disrupt the conjugation along the polymer backbone. By properly choosing the side chains and linker, it is possible to prepare polymers with desired conjugation and solubilities.40... 

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