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Optical activity vinyl polymers

Recently, we found that the polymerization of TrMA with chiral anionic catalysts gave an optically active polymer the chirality of which is caused by helicity (12). This is the first example of optically active vinyl polymer the activity of which arises only from the helicity. This article describes the detailed results of the polymerization of TrMA by chiral anionic catalysts in addition to a brief review on our earlier studies described above. [Pg.353]

Several attempts were made to prepare optically active vinyl polymers, - CH2-CXY-)-g, which have chirality in the polymer chain (17-23). However, all the polymers obtained showed no or only small rotation which arose from the chiral terminal groups. It has been pointed out that even if an isotactic polymer composed of units of a single configuration is formed in the process of the polymerization, the polymer can not be optically active because the polymer becomes pseudo asymmetric (24, 25). [Pg.358]

The second method is the most widely used to prepare optically active vinyl polymers (poly-a-olefins, poly-vinyl-ethers, polyacrylic esters and amides etc.. ... [Pg.395]

Investigation of the conformational equilibria of the macromolecules in solution using optically active vinyl polymers... [Pg.443]

Analogous investigations yielded interesting results also in the field of optically active vinyl polymers. In some cases a remarkable dependence of the optical activity on stereoregularity was experimentally found and optical activity has been used to study the relationships between stereoregularity and conformation of the macromolecules in solution. [Pg.443]

Both in poly-a-olefins and in poly-vinyl-ethers, which are the most systematically investigated optically active vinyl polymers, the chromo-phoric systems responsible for the optical activity appear to be in the same spectral region of those of the low-molecular-weight models 66. 105,113a). [Pg.443]

Such a model is in agreement with all the experimental findings till now ascertained in the field of optically active vinyl-polymers in fact it explains, in the case of polymers having asymmetric carbon atoms in a or j position with respect to the principal chain, the relationships between absolute structure of monomers and sign of the rotatory power of polymers, and the high rotatory power observed in isotactic polymers. The rapid and reversible variation of the optical rotation with temperature (105) is probably connected with the existence of a conformational equilibrium that is rapidly attained at each temperature. [Pg.448]

Cationically Obtained Optically Active Vinyl Polymers.521... [Pg.508]

B. Photoresponsive Optically Active Vinyl Polymers with Configurational Chirality... [Pg.650]

Figure 13 shows several optically active vinyl polymers and copolymers with azobenzene or stilbene residues in the side groups. All these polymers were prepared by the conventional radical polymerization, so that the main chains should be atactic or syndiotactic and may not be able to take a helical conformation even in the presence of chiral pendants. The homopolymers (28-31) [83-85]... [Pg.652]

Actually, the successful synthesis of such polymers yielded the first example of an optically active vinyl polymer with main chain chirality [17]. In this case, templates used during polymerization control the composition, the stereochemistry, and the chirality of the polymer chains formed. [Pg.40]

The L-substiate was hydrolyzed 1.5—2 times faster than the D-substrate with either of the oligopeptides 11 or 12), and the flexible oligopeptide 12 was 2 to 3 times mote efficient than imidazole. The observed stereoselectivity is noteworthy, especially since there was no stereoselectivity in the solvolysis of some asymmetric phenyl esters 13,14,15 by an optically active vinyl-polymer containing imidazole group 16 134). [Pg.213]

However, it is possible to obtain an optically active vinyl polymer with main-chain configurational chirality if some higher-order tacticities are realized with asymmetric... [Pg.672]

According to the former procedure, optically active vinyl polymers containing carbazolyl moieties have been synthesized by polymerization of optically active monomers such as (S)-3-ycc-butyl-9-vinylcarbazole (1), (S)-9-(2-methylbutyl)-2-vinylcarbazole (2), and (S)-9-(2-methylbutyl)-3-vinylcarbazole The pre-... [Pg.147]

Synthetic polymers with conformational chirality have become a research field of widespread interest in recent years, and a wide range of polymers with conformational chirality have been synthesized from various types of monomers including vinyl monomers [9, 61-63, 128-136]. The existing examples of optically active vinyl polymers with conformational chirality include isotactic, helical polyolefins bearing asymmetric side chains [133-135] and isotactic, hehcal polymethacrylates bearing bulky, achiral side chains [61-63,136]. These polymers have stereocenters in the main and/or side chains. Optically active poly(PDBS) is the first vinyl polymer with conformational chirality bearing no stereocenters in the main and side chains whose chiroptical properties arise only from a chiral conformation. [Pg.38]

To summarize this section, asymmetric anionic polymerization afforded poly(PDBF)s showing signihcant CD absorptions in film although their intensity of chiroptical properties is below detectable level in solution. The polymers belong to a new class of optically active vinyl polymers whose chiroptical properties originate only from a chiral conformation in the absence of any configurational information. [Pg.44]

Marvel, Dec, and Cooke [J. Am. Chem. Soc., 62 (3499), 1940] have used optical rotation measurements to study the kinetics of the polymerization of certain optically active vinyl esters. The change in rotation during the polymerization may be used to determine the reaction order and reaction rate constant. The specific rotation angle in dioxane solution is a linear combination of the contributions of the monomer and of the polymerized mer units. The optical rotation due to each mer unit in the polymer chain is independent of the chain length. The following values of the optical rotation were recorded as a function of time for the polymerization of d-s-butyl a-chloroacrylate... [Pg.74]

The polymerization of monosubstituted vinyl compounds that give polymers like PS and PP produces polymer chains that possess chiral sites on every other carbon in the polymer backbone. Thus, the number of possible arrangements within a polymer chain is staggering since the number of possible isomers is 2" where n is the number of chiral sites. For a relatively short chain containing 50 propylene units the number of isomers is about 1 x lO. While the presence of such sites in smaller molecules can be the cause of optical activity, these polymers are not optically active since the combined interactions with light are negated by other similar, but not identical, sites contained on that particular and other polymer chains. Further, it is quite possible that no two polymer chains produced during a polymerization will be exactly identical because of chiral differences. [Pg.24]

Optically active vinyl ethers having different structure have been polymerized by different methods, particularly by Schmitt and Schuerch (126), by Liquori and co-workers (4, 11), by Pino and co-workers (65, 114, 117) and others. Table 11 reports some data on the monomers, on the corresponding polymers and on the polymerization conditions. [Pg.417]

As shown in Table 13, the sign of the optical activity of polymers of alkyl- or cycloalkyl-vinyl-ethers at 589 mp, in hydrocarbon solvent, can in general be foreseen on the basis of the absolute configuration of the asymmetric carbon atom that is the nearest to the ethereal group. A positive sign is observed when the asymmetric carbon atom of the monomer has absolute configuration (S), as in poly-a-olefins. [Pg.419]

Table 13. Relationship between the absolute configuration of the asymmetric carbon atom nearest to the vinyloxy group of some optically active vinyl-ethers and the sign of the optical activity of the corresponding polymers... Table 13. Relationship between the absolute configuration of the asymmetric carbon atom nearest to the vinyloxy group of some optically active vinyl-ethers and the sign of the optical activity of the corresponding polymers...
Cyclopolymerization of bifunctional monomers is an effective method of chirality induction. Optically active vinyl homopolymers and copolymers have been synthesized by using optically active distyrenic monomers (41) based on a readily removable chiral template moiety. Free-radical copolymerization of 41a with styrene and removal of the chiral template moiety from the obtained copolymer led to polystyrene, which showed optical activity ([Oc]365 -0.5-3.5°) (Scheme 11.6) [84], The optical activity was explained in terms of chiral (S,S)-diad units generated in the polymer chain through cyclopolymerization of 41a [85], Several different bifunctional monomers have been synthesized and used for this type of copolymerization [86-90]. [Pg.767]

Optically active vinyl sulfoxide was prepared by a combination of resolution and elimination reaction. Firstly, inclusion complexation of rac-2-chloroethyl m-tolyl- sulfoxide (118) and 14b in benzene gave, after two recrystallizations from benzene, a 1 1 complex of 14b and (+)-118 of 100% ee in 72% yield. Secondly, treatment of the complex with 10% NaOH gave optically pure (+)-m-tolyl vinyl sulfoxide (119) by HC1 elimination as colorless oil. Rapid polymerization of the (+)-119 proceeded by treatment with BuLi or BuMgBr at -78 °C to give optically active polymer (120). Oxidation of 120 with H2O2 gave optically active polysulfone (121).48... [Pg.27]

Optical Activity in Polymers Stereoisomerism in polymers is formally similar to the optical isomerism of organic chemistry. In a vinyl polymer with the general structure shown in (XIH) every other carbon atom in the chain, labeled C, is a site of steric isomerism, because it has four different substituents, namely, X, Y, and two sections of the main chain that differ in length (Rudin, 1982). [Pg.55]

DMPMA (32), an optically active monomer, also affords an optically active helical polymer whose helicity is mainly controlled not by the chirality of the ligand used for the polymerization but by the chirality of the monomer itself. Poly (DMPMA) exhibited reversible helix-helix transition where excess helix sense is determined by solvent properties. This is the first example of a reversible helix-helix transition of a vinyl polymer. [Pg.638]

Also, in studies with optically active vinyl ethers it was observed [104] that trimethyl vinyl silane, which is bulky and non-chiral forms highly syndiotactic polymers. Equally bulky, but chiral (—)-menthyl vinyl ether, however, produces isotactic polymers in polar solvents. This suggests that isotactic propagation is preferred in a polar medium because of helical conformation of the polymer... [Pg.171]

This asymmetric oxidation is the first example of introduction of chirality in good enantioselectivity into the main chain of a polymer hy the polymer reaction, that is, the first example of the control of tacticit hy polsrmer reaction. An earlier paper (282) described the synthesis of the liquid crystalhne polymers having sulfoxide groups with low enantiomeric excess (25% ee). Another synthetic route to optical active poly sulfoxides is the polymerization of optically active vinyl sulfoxides (283,284). [Pg.8004]

Optically-active vinyl carbazole derivatives can be polymerized cationically to yield polymers whose optical rotation depends upon the initiator system employed. In contrast cationic polymerization of a series of 2-phenylvinylalkyl thioethers produced polymers of optical rotations identical to those of the corresponding mode compounds. ... [Pg.30]

Circular dichroism is extensively employed in the stmctural study of biological polymers, but not in the study of synthetic polymers. This is because most biological polymers are optically active, whereas most synthetic polymers are not. However, if the optically active vinyl or vinylidene monomers are incorporated in a synthetic polymer, the synthetic polymr could become optically active. [Pg.275]

Arcus [8] discussed the conditions of the optical activity of polymers in alternate copolymerizations and underlined that an asymmetry was brought into main chains in the polymerization between vinyl monomers and a,j3-substituted monomers. Accordingly, the main chains of the polymers obtained by vinyl homopolymerizations do not have optical activities since they are pseudo-asymmetric. [Pg.162]

The synthetic approach to optically active polymers based on the copolymerization of prochiral carbazole containing monomers with easily available optically active vinyl or vinylidenic comonomers is by far the most convenient route to a large variety of optically active polymers. Accordingly, N-vinylcarbazole and spaced-carbazole containing vinyl monomers 11-14 have been copolymerized with different optically active monomers 15-20. [Pg.149]

It is known that vinyl aromatic monomers when inserted in copolymer macromolecules with optically active vinyl or vinylidenic monomers become optically active and may or may not contribute to the optical rotation of the whole polymer measured at the sodium D line In particular, by mvestigating the electronic transitions of the aromatic chromophores, it is general found that both symmetry forbidden and... [Pg.159]


See other pages where Optical activity vinyl polymers is mentioned: [Pg.97]    [Pg.393]    [Pg.521]    [Pg.521]    [Pg.80]    [Pg.648]    [Pg.97]    [Pg.393]    [Pg.521]    [Pg.521]    [Pg.80]    [Pg.648]    [Pg.665]    [Pg.73]    [Pg.782]    [Pg.53]    [Pg.98]    [Pg.146]   
See also in sourсe #XX -- [ Pg.161 , Pg.162 , Pg.163 , Pg.164 , Pg.165 ]




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