Conjugated polymers chiral

Incorporation of chiral units into polymers generates optically active polymers.27 Two types of optically active polymers could be obtained according to where the chiral units reside optically active polymers with chirality derived from chiral side chains and optically active polymers with chirality derived from tire chiral main chain. The circular dichroism (CD) measurement of 32, an optically active polymer with chiral side chains, showed that the chiral substituents have induced main-chain chirality. The induced main-chain chirality disappeared at higher temperature and appeared upon cooling. This type of chiral conjugated polymer is potentially useful in reversing optical recording28 ... 

Chemistry (Continued) polyimide, 287-300 polyurethane, 222-236, 546 transition metal coupling, 483-490 Chiral conjugated polymers, 479-480 Chlorinated solvents, 91 Chlorofluorocarbons (CFCs), 201, 205 Chloroformate endgroups, 87 Chloromethylation, 354 Church, A. Cameron, 431 Circular dichroism, 490 Classical catalysts, 433 Clean Air Act of 1990, 201, 205 Clearcoat, 240... 

Poly(iV-substituted dithieno[3,2-3 2, 3 -rf pyrroles (PDTPs) 167a,b) <2005MM4545>, a class of soluble (chiral) conjugated polymers with a stable oxidized state, were prepared by an oxidative coupling by FeClj in chloroform under an argon atmosphere. The crude material was reduced with hydrazine to afford compound 167 (Scheme 19) <2005MM4545>. 

Another approach to CPL is the synthesis of conjugated polymers with intrinsic chiro-optical properties. A variety of polymers with CPPL have been synthesized so far. Most of them are based upon well-known conjugated polymers such as poly(thiophene)s [4,111], polyphenylene vinylene)s [123], poly(thienylene vinylene)s [124], ladder polymers [125], PPPs [126], polyphenylene ethynylene)s, [127] and poly(fluorenes) [128]. All of them have been modified with chiral side-chains, which induce the chiro-optical properties. 

Zahn S, Swager TM (2002) Three-dimensional electronic delocalization in chiral conjugated polymers. Angew Chem Int Ed 41 4225 -230... 

The methods that have been examined for producing polarised EL include the use of liquid crystalline chiral oligomers and polymers. - Promising results have been obtained using conjugated polymers where fluorene makes up the backbone, e.g. (5.6), which was synthesised from the dibromo monomer via Yamamoto coupling. These types of material exhibit LC behaviour at transition temperatures of 100-200 °C, and produce blue polarised EL (425 nm) from thin flhns. °... 

Pu reported the synthesis of axially chiral-conjugated polymer 82 bearing a chiral binaphthyl moiety in the main chain by the cross-coupling polymerization of chiral bifunctional boronic acid 80 with dibromide 81 (Equation (39)). The polymer is soluble in common organic solvents, such as THE, benzene, toluene, pyridine, chlorobenzene, dichloromethane, chloroform, and 1,2-dichloroethane. The polymer composed of racemic 80 was also synthesized, and the difference of characteristics was examined. Optically active polymer 82 was shown to enhance fluorescence quantum yield up to = 0.8 compared with the racemic 82 ( = 0.5). Morphologies of the optically active and racemic polymers were also compared with a systematic atomic-force microscopy (AEM). 

However, the particular synthetic requirements in the preparation of conjugated polymers have thus far severely limited the number of similarly hierarchically structured examples. Pu et al. reported different types of conjugated polymers with fixed main-chain chirality containing binaphthyl units in their backbone which exhibited, for example, nonlinear optical activity or were used as enantioselective fluorescent sensors [42—46]. Some chirally substituted poly(thiophene)s were observed to form helical superstructures in solution [47-51], Okamoto and coworkers reported excess helicity in nonchiral, functional poly(phenyl acetylenejs upon supramolecular interactions with chiral additives, and they were able to induce a switch between unordered forms as well as helical forms with opposite helical senses [37, 52, 53]. 

S. Zahn, T. M. Swager, Three-dimensional Electronic Delocalization in Chiral Conjugated Polymers, Angew. Chem. Int. Ed. 2002, 41, 4225-4230. 

H. Goto, K. Akagi, Optically Active Conjugated Polymers Prepared from Achiral Monomers by Polycondensation in a Chiral Nematic Solvent, Angetv. Chem. Int. Ed. 2005, 44, 4322-4328. 

Chiral conjugate polymers such as polythiophenes with an optically active substituent in the 3 position have been studied for use in optoelectronic devices, sensors, and catalysis (Nilsson et al., 2004). These materials show activity based on their chiral behaviors, which can be influenced by solvent or temperature. Flelical biomolecules can be used to induce chirality in optically inactive polythiophenes (Ewbank et al., 2001). Nilsson et al. (2004) extended this to use a positively charged random-coil peptide conjugated with a... 

Harlev, E. Wudl, F. Synthesis and Optical properties of Chiral Poly [2,5-bis (3,7-dimethyl-6-octenoxy)-l,4-phenylenevinylene], In Conjugated Polymers and Related materials, The Connection of Chemical and Electronic Structure, Proceedings of the 81st Nobel Symposium Salaneck, W. R., Lundstrom, I., Ranby, B., Eds. Oxford University Press Oxford, U.K., 1993 p 139. 

---