Poly optically active polymer

Preparation of addition polymers having the oxolene (dihydrofuran) functionality can be envisioned to occur in two possible ways (Scheme 13). Both, in fact, have been observed (77MI11102). Whereas furan (53) or its derivatives do not homopolymerize under free radical conditions, 1 1 alternating copolymers possessing the 1,4-structure are produced with maleic anhydride (50). Intermediate formation of a CT complex between monomers (50) and (53) is believed to be necessary before polymerization can occur. On the other hand, cationic polymerization is quite facile. The outcome is straightforward with benzo[f>]furan derivatives, producing 1,2-polymers. Optically active poly(benzofurans) are formed when the cationic polymerizations are conducted in the presence of a chiral anion. 

An interesting aspect of the benzofuran cationic polymerization was uncovered by Natta, Farina, Peraldo and Bressan who reported in 196160,61 that an asymmetric synthesis of an optically active poly(benzofuran) could be achieved by using AlCl2Et coupled with (-)j3-phenylalanine, (+)camphorsulphonic acid or with (-)brucine. The optical activity was definitely due to the asymmetric carbon atoms in the polymer chain, indicating that at least some of the polymer s macromolecules possessed a di-isotactic structure, v/ z.62 ... 

Optically active polymers, 473, 479-480 synthesis of, 509 Optically active poly(phenylene-ethynylene), synthesis of,... 

In this section, we comprehensively focused on the controlled synthesis, chiroptical characterization, and manipulation of optically active poly(dialkyl-silane)s. Although many artificial polymers adopting preferential screw sense... 

It is considered that, if ideal, optically active poly(alkyl(aryl)silane) homopolymer and copolymer systems could be obtained which had stiffer main-chain structures with longer persistence lengths, it should be possible to clarify the relationship between the gabs value and the chiral molar composition. The magnitude of the chirality of the polyisocyanates allowed precise correlations with the cooperativity models.18q In the theory of the cooperative helical order in polyisocyanates, the polymers are characterized by the chiral order parameter M, which is the fraction of the main chain twisting in one helical sense minus the fraction of the main chain twisting in the opposing sense. This order parameter is equal to the optical activity normalized by the value for an entirely one-handed helical polymer. The theory predicts... 

Yashima et al. showed an example where the polymer helicity was controlled by enzymatic enantioselective acylation of the monomers [109]. Optically active phenylacetylenes containing hydroxyl or ester groups were obtained by the kinetic resolution of the corresponding racemic hydroxy-functional phenylacetylene (see Scheme 16). Polymerization of the phenylacetylenes afforded an optically active poly(phenylacetylene) with a high molecular weight (Mn = 89kDa PDI = 2.0) and... 

Scheme 68 illustrates cyclopolymerization of 1,5-hexadiene catalyzed by a homogeneous chiral zirconocene complex to form optically active poly(methylenecyclopentane), whose chirality derives from configurational main-chain stereochemistry (757). This polymer is predominantly isotactic and contains predominantly trans cyclopentane rings. 

The most widely investigated optically active poly-acrylic-esters are the polymers of bomyl and menthyl acrylate and methacrylate in this case the monomers have been polymerized by radical polymerization using benzoyl-peroxide (135), A. I. B. N. (134, 135), y-rays (131, 135), U. V. rays (4) in the presence of benzoin (134), and by anionic polymerization using LiC4H9 (4, 135) or C6H5MgBr (134, 135) as catalyst. 

According to the above data and to preliminary determinations of the polymers optical activity in the solid state (112) it was suggested (105) that the principal chain of optically active poly-a-olefins, which in general posses a helix type conformation in the solid state, consists of sections having helix conformation also in the molten state or in dilute solution. Most sections of the principal chain are spiraled in one screw sense only, depending on the absolute configuration of the asymmetric carbon atom of the lateral chains. 

Isocyanide Polymers Bulky isocyanides give polymers having a 4 1 helical conformation (115) [154]. An optically active polyisocyanide was first obtained by chromatographic resolution of poly(f-butyl isocyanide) (poly-116) using optically active poly((S)-sec-butyl isocyanide) as a stationary phase and the polymer showing positive rotation was found to possess an M-helical conformation on the basis of CD spectral analysis [155,156]. Polymerization of bulky isocyanides with chiral catalysts also leads to optically active polymers. 

Okamoto, Y., Mohri, H., Ishikura, M., Hatada, K., and Yuki, H., Optically active poly(diphenyl-2-pyridylmethyl methacrylate) asymmetric synthesis, stability of helix, and chiral recognition ability, J. Polymer Sci. Polymer Symp., 74, 125, 1986. 

In addition to this we have several examples of which the polymer conformation of the polymeric complex leads the asymmetrical selectivity Hydrogenation reactions of 1-methylcinnamic acid and 1-acetamidocinnamic acid by several poly(L-amino acid)-Pd complexes are observed (142-144). Poly(L-valine) (/3-form) and poly(/3-benzyl-L-aspartate) (a-helix, sinistral) give dextrorotative products, and poly(L-leucine) and poly( 3-benzyl-L-aspartate) (a-helix, dextral) do levo-rotatory products. Also, optical active poly-/3-hydroxyl esters-Raney Ni catalyst (145) and Ion-exchange resin modified by optical active amino acid-metal complex (146,147) are observed in asymmetrically selective hydrogenations. 

The H and 13C NMR spectra of azo compounds incorporated into monomers and polymers have been measured.67-73 Chiral methacrylic polymers containing azobenzene chromophore,67,68 epoxy-based polymers functionalized with tricyanivinylphenylazo chromophores,69 4-vinylazobenzene and homo- and copolymers,70 microstructure of trans-4-acrylooyloxyazo-benzene/methyl methacrylate copolymers,71 optically active poly[(S)-4-(2-methacryloyloxypropanoyloxy)azobenzene]72 and polyetherurethane pendant with azo dye by TV-substitution73 have been studied. 

The asymmetric oxidation reaction of prochiral poly(ester 0-sulfide)s to optically active poly(ester 0-sulfoxide)s can be accomplished with almost theoretical chemoselactivity and moderate to high enantioselectivity degrees. While the asymmetric oxidation of prochiral sulfides should not be a preparative method for chiral sulfoxides, we expect that the structure of the parent polymers might be specifically designed for the preparation of chiral thermotropic poly(ester 0-sulfoxi-de)s. 

A new type of enantioselective diene polymerization is found with cyclopolymerization of 1,5-hexadiene which leads to polymers with a saturated chiral main chain28,58>109. As catalyst, (—)-(7 )-[l,T-ethylenebis(4,5,6,7-tetrahydro-l-indenyl)]zirconium (/ )-binaphtholate is used in the presence of methylalumoxane to give optically active poly(methylene-1,3-cyclopentane) (3) with 68% trans configuration in the five-membered ring (diisotacticity). If the (S)-enantiomer of the ansa-metallocene with (ft)-binaphthol is used as catalyst then the opposite rotation of the polymer is observed58. 

Proportions of these isomers were correlated with the microstructure of the starting polymers. This was proved by degradation studies of the optically active poly(ds-DMT) the higher the optical activity, the higher the corresponding ratios (I/II and III/IV). 

Optically active poly meth(acryl) amides were synthesized under solvent-free conditions by microwave heating of a mixture of meth(acrytic) add and (R)-l-phenylethylamine in the presence of 2,2 -azoisobutyronitrile (AIBN) as a free radical initiator (Scheme 3.7). Characterization of the prepared materials revealed the presence of imide moieties, presumably due to the high reaction temperatures achieved and, as a result, facile intramolecular dehydration. Interestingly, in the case of the acrylic acid derivatives, the molecular weight of the obtained polymers was found to be inversely proportional to the applied microwave power. 

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