Syndiotactic structures styrene/substituted styrenes

Mean-square unperturbed dimensions and dipole moments are calculated for propylene-vinyl chloride copolymers by means of RIS theory. The calculations indicate that for these chain molecules is much more sensitive to chemical sequence distribution than is 0, a conclusion in agreement with results of previous studies of ethylene-propylene copolymers and styrene-substituted styrene copolymers. In the case of propylene-vinyl chloride chains, both 0 and are most strongly dependent on chemical sequence distribution in the case of copolymers which are significantly syndiotactic in stereochemical structure. 

Styrene and ring-substituted styrenes also form copolymers with carbon monoxide, similarly to ethylene and a-olefins. These styrene/carbon monoxide copolymers are of alternating, highly regioregular head-to-tail structure and are characterised by different stereoregularity (syndiotactic, isotactic) [115-117]. 

Configuration also refers to structural regularity with respect to the substituted carbon within the polymer chain (Figure 1.9). For linear homopolymers derived from monomers of the form H2C = CHX, such as styrene and vinyl chloride, configuration from monomeric unit to monomeric unit can vary somewhat randomly (atactic abbreviated at) with respect to the geometry and configuration about the carbon to which the X is attached, or can vary alternately (syndiotactic st), or can be uniform (isotactic it) when all the X groups can be placed on the same side of a backbone plane. 

Trichloro cyclopenta[l]phenanthrene titanium complexes (Scheme 183) have been synthesized. The crystal structure of the 2-methyl-substituted derivative has been determined by X-ray diffraction. In the presence of MAO, these complexes are highly active pre-catalysts for the syndiotactic polymerization of styrene. The 2-phenyl-substituted complex exhibits especially high catalytic activity.416... 

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