Homopolymer, chiroptical properties

Angiolini L, Caretti D, Carlini C, SalateUi E. 1995. Optically active polymers bearing side chain photochromic moieties synthesis and chiroptical properties of methacrylic and acrylic homopolymers with pendant l lactic acid or l alanine residues connected to trans 4 aminoazobenzene. Macromol Chem Phys 196(9) 2737 2750. 

The cooperative effect anticipated by the asymptotic dependence of chiroptical properties on the degree of tacticity is further evidenced by the study of the chiroptical properties of copolymers between optically active a-olefins and achiral comonomers. i Co-isotactic copolymers of (5)-4-methyl-l-hexene with 4-methyl-1-pentene show, at any composition, an optical rotation higher than the two homopolymer mixtures, thus indicating that 4-methyl-1-pentene (4MP) units in the copolymer contribute to optical rotation, the contribution being of the same sign as that of the (5)-4-methyl-l-hexene (4MH) units. By assuming that (Od )4mh is the same in the copolymer and in the homopolymer, the values of ( )4mp can be derived at each composition by the equation ... 

L. Angiolini, T. Benelli, L. Gioigini, E. Salatelli, R. Bozio, A. Dauru, D. Pedron, Synthesis, chiroptical properties and photoinduced linear birefringence of the homopolymer of (R)-3-methacryloyloxy-l-(4 -cyano-4-azobenzene) pyrrolidine and of the copolymers with the enantiomeric monomer. Europ. Poly. J. 41, 2045-2054 (2005)... 

With the asymmetric site in the position to the double bond (monomer LXVIb) the polymerization occurs easily with good yield but without any stereoselectivity in contrast the polymerization of monomer LXVIa yields crystalline polymers, with a low yield due to steric interactions between active sites and the side chain as for jS-branched-a-olefins [168]. The chiroptical properties of these stereoregular copolymers compared to those of OA phenylalkanes (LXVlc, d) [169b] show that the homopolymer of (LXVl) as well as its copolymer contain block sequences in helical conformation with a predominant direction of the screw, which seems to be the right handed one. 

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