1,2-syndiotactic poly

It is typical, for instance, of syndiotactic polystyrene (s-PS) [7-9] and syndiotactic poly- p-methylstyrene (s-PPMS) [10] to present crystalline forms with a transplant conformation of the chains (shown for s-PS in Fig. 1) as well as crystalline forms with sequences of dihedral angles of the kind TTG+G+ (or the equivalent G G TT), corresponding to a s(2/l)2 helical symmetry of the chains (shown for s-PS in Fig. 1). 

Horinaka, J., Ono, K. and Yamamoto, M. (1995) Local chain dynamics of syndiotactic poly(methyl methacrylate) studied by the fluorescence depolarization method. Polym. J., 27, 429-435. 

Preparation of Block Copolymers. Poly(styrene-b-methyl methacrylate) and poly(styrene-b-t-butyl methacrylate) were prepared by procedures similar to those reported for poly(styrene-b-methyl methacrylate (12,13). Poly(methyl methacrylate-b-t-butyl methacrylate) was synthesized by adaptation of the method published (14) for syndiotactic poly(methyl methacrylate) polymerization of methyl methacrylate was initiated with fluorenyllithium, and prior to termination, t-butyl methacrylate was added to give the block copolymer. Pertinent analytical data are as follows. 

Crystalline samples of syndiotactic poly(methyl methacrylate) (st-PMMA) may be obtained from chloroacetone 178). This guest could be completely replaced by a variety of other guest molecules such as acetone, 1,3-dichloroacetone, bromoacetone, pinacolone, cyclohexanone, acetophenone and benzene. The X-ray diffraction patterns for these inclusion compounds were similar. These data indicate that the st-PMMA chains adopt a helical conformation of radius about 8 A and pitch 8.85 A. The guest molecules are located both inside the helical canals and in interhelix interstitial sites. 

Table 1 IR peak assignments (cm ) for isotactic and syndiotactic poly(methyl methacrylate)...

The synthesis of monodisperse high molecular weight syndiotactic poly(methyl methacrylate) mentioned above was possible at a polymerization temperature as low as — 95 °C [3]. However, methods to synthesize it at a relatively high temperature or to synthesize its isotactic counterpart remain to be found. When the latter is made available, the synthesis of stereo-complexes of poly(methyl methacrylate) will become the focus of considerable interest. 

Mesomorphic forms characterized by conformationally ordered polymer chains packed in lattices with different kinds of lateral disorder have been described for various isotactic and syndiotactic polymers. For instance, for iPP,706 sPP,201 sPS,202 syndiotactic poly(p-methylstyrene) (sPPMS),203 and syndiotactic poly(m -methylstyrene),204 mesomorphic forms have been found. In all of these cases the X-ray fiber diffraction patterns show diffraction confined in well-defined layer lines, indicating order in the conformation of the chains, but broad reflections and diffuse haloes on the equator and on the other layer lines, indicating the presence of disorder in the arrangement of the chain axes as well as the absence of long-range lateral correlations between the chains. 

Poly(l,4-benzamide) (PBA), 13 371 Poly(1-butene) (PB), 4 429. See also Blown PB film Isotactic PB resins Isotactic poly(l- butene) (PB) PB entries Pipe-grade PB resin Syndiotactic poly(1-butene) (PB) mechanical properties of, 20 418 polymerization processes for, 20 424-425 uses of, 20 430-431 commercial manufacture of, 20 429 Poly-1-olefins, regioregular, 26 513 Poly(l,4-butylene terephthalate) (PBT), 10 188... 

Note Structure-based names of tactic polymers are formed before the application of adjectives designating tacticity thus, syndiotactic poly(methylmethylene) is preferred to syndiotactic poly(l,2-dimethylethane-l,2-diyl) because a shorter repeating unit is identified, in conformity with the rules in Ref. 3. 

Preparation of Isotactic and Syndiotactic Poly(Methyl Methacrylate) with Bu llithium in Solution... 

Because of acid-catalyzed hydrolysis of N-vinylpyrrolidone in water, polymerization was carried out in organic solvent - DMF. Three types of samples of poly(methacrylic acid) were used syndiotactic - obtained by radiation polymerization, atactic - obtained by radical polymerization, and isotactic - obtained by hydrolysis of isotactic poly(methyl methacrylate). It was found that in all cases the rate enhancement appeared in comparison with the blank polymerization (without template). The rate enhancement became more pronounced with increasing chain length and syndiotacticity of the template. According to the authors, the rate enhancement is connected with the stronger complex formation between poly(vinyl pyrrolidone) and syndiotactic poly(methacrylic acid) then with isotactic template. This conclusion was supported by turbimetric titration in DMF/DMSO system and by model considerations. It is worth noting, however, that... 

Figure 29-8 Configuration of atactic, isotactic, and syndiotactic poly-propene. These configurations are drawn here to show the stereochemical relationships of the substituent groups and are not meant to represent necessarily the stable conformations of the polymer chains.

Figure 8. X-ray diagrams of syndiotactic poly (methyl methacrylate)(39)...

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