Poly S>4-methyl-l-hexene

An independent proof of this finding was recently obtained by Ciardelli, Benedetti, Pieroni and Pino (23, 24) who prepared an atactic poly-(S)-4-xnethyl-1-hexene having [M] >5 = +190 from a poly-(S)-4-methyl-l-hexyne having an optical purity of about 89.5% as demonstrated by the optical purity of (S)-3-methyl-pentanoic acid obtained by ozonization of the unsaturated polymer. The rotatory power of the polymer thus prepared is very near to the rotatory power of the non crystallizable poly-(S)-4-methyl-l-hexene obtained from a monomer having a 93% optical purity (see Table 8). 

The conformational analysis, according to Brewster, of isotactic poly-a-olefins demonstrates that, in the case of poly-(S)-3-methyl-1-pentene and poly-(S)-4-methyl-l-hexene, only 3 conformations are allowed for each monomeric unit two of them correspond to a left-handed helix conformation of the principal chain and one to a right-handed helix conformation (Table 25). 

Figure 4-24. Dependence of the reciprocal molar optical rotaton,, with tacticity content of isotactic, x, and syndiotactic, Xs, diads for poly (S)-4-methyl-l-hexene. Optical purity of initial monomer was 93% (according to measurements by P. Pino et al).

In these isotactic polymers, the optical purity of the monomer affected the optical activity via the relationship to the excess helical sense of the polymer (Figure 1). ° In the case of isotactic poly((S)-4-methyl-l-hexene) (2) and poly((i )-3,7-dimethyl-l-octene) (3), an increase in the optical purity of the monomers resulted in an increase in the optical activity of the polymers in a nonlinear fashion the optical activity of the polymers leveled off when the optical purity of the monomer reached -80%. By contrast, in the case of isotactic poly((S)-5-methyl-l-heptene) (4), the relation was linear. These findings imply that the side-chain chiral centers of 4, which are separated from the main chain by three covalent bonds, may be too far from the main chain to affect the helical conformation. 

Figure 4-21. Molar optical rotation per monomeric unit [< )] as a function of optical purity % of the monomer for poly[(S)-4-methyl-l-hexene] (top curve) poly[(S)-5-methyl-l-heptene], and poly[(R)-3,7-dimethyl-l-octene] (bottom curve) (after P. Pino, F. Ciardelli, G. Montagnoli, and O. Pieroni).

Second virial coefi cient of poly[(S)-4-methyl-l-hexen-3-one]... 

Poly(R)-4-methyl-l-hexen und Poly(R)(S)-4-methyl-l-hexen bestatigt (77). Die verwendeten Katalysatoren — es handelte sich um Mischungen aus Trialkylaluminium und Titan-(III)- bzw.Titan-(IV)-chlorid — muBten also neben ihrer Fahigkeit, stereospezifisch zu polymerisieren, auch die Eigenschaft besitzen, den einen Oder anderen Antipoden selektiv in die Molekulkette einzubauen. 

S)-MHO) poly(4-methyl-1 -penten-3 -one-co-(S)-4-methyl-l-hexen-3-one) (22 mol% 54000 trichloromethane 309.15 13 1983THI1... 

The polymers of the optically active and racemic 4-methyl-1-hexene and the poly-(S)-5-methyl-l-heptene have isotactic structure (115) the same structure seems probable also in the case of the other polymers prepared till now from optically active or racemic a-olefins. 

Poly-4-methyl-l-hexene Acetone sol. Poly-(S)-3-methyl-l-pentene 1.7... 

Fig. 7 DSC melting and crystallization curves of isotactic poly(S)-4-methyl-hexene-l. Note the two melting peaks (at 193.5 and 227.4 °C, respectively, AH 2.5 and 1.5cal/gram) and two crystallization peaks (at 201 and 120 °C, respectively same AH), as well as the significant temperature gap ( 74 °C) between the lower crystallization and melting processes. (From [44])...

In other optically active polymers, as well as in some polymers from achiral monomers, chiral structures, characterized by all isomorphous helical chains in the unit cell, have been found. For instance, in isotactic poly(5-methyl-l-hexene) [94], isotactic poly(ubutylacrylate) [95], and optically active isotactic poly((S)-5-methyl-l-heptene) [94b,c], chiral pseudo-hexagonal or tetragonal packing with isomorphous 3/1 or 4/1 helical chains have been found. 

Poly-4-methyl- 1-hexene Poly-3-methyl-l-pentene (S) (R) (106)... 

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