Tactic styrene copolymers styrenic monomers

Polyethylene and polystyrene are two of the most commercially important and ubiquitous polymers, primarily because of their commercial value. Since the early days of polymer research there has been considerable interest to produce copolymers from ethylene (E) and styrene (S) because of both academic and business interests. Depending on the nature and type of polymerization chemistry, a variety of different molecular architectures can be produced. In addition to the different monomer distributions (random, alternating or blocky nature), there are possibilities for chain branching and tacticity in the chain microstructure. These molecular architectures have a profound influence on the melt and solid-state morphology and hence on the processability and material properties of the copolymers. 

Diene polymerization may involve either or both of the double bonds. Geometric and structural isomers of butadiene, for example, are indicated by using appropriate prefixes — cis or irons, 1,2 or 1,4 — before poly, as in cw-l,2-poly(l,3-butadiene). Tacticity of the polymer may be indicated by using the prefix i (isotactic), s (syndiotactic), or a (atactic) before poly, such as 5-polystyrene. Copolymers are identified by separating the monomers involved within parentheses by either alt (alternating), b (block), g (graft), or co (random), as in poly(styrene-g-butadiene). 

This unified volume explains the mechanistic basics of tactic polymerizations, beginning with an extensive survey of the most important classes of metallocene and post-metallocene catalysts used to make polypropylenes. It also focuses on tactic stereoblock and ethylene/propylene copolymers and catalyst active site models, followed by chapters discussing the structure of more stereochemically complex polymers and polymerizations that proceed via non-vinyl-addition mechanisms. Individual chapters thoroughly describe tactic polymerizations of a-olefins, styrene, dienes, acetylenes, lactides, epoxides, acrylates, and cyclic monomers, as well as cyclopolymerizations and ditactic structures, olefin/CO copolymers, and metathesis polyalkenamers. 

Van Doremaele and co-workers [22] applied H-NMR spectroscopy to the determination of monomer ratios in styrene methyl acrylate copolymers 400-MHz H-NMR spectra were obtained in CDCI3 solutions at 25 °C. Expansions of the methoxy region display additional fine splitting due to combined configurational (i.e., tacticity) and compositional sequence effects. Mean copolymer composition (mole fraction styrene, Fj) can be readily obtained by using absorbances, which represent the total peak areas of the aromatic and methoxy proton resonances, respectively. The initial feed (q = [S]/[M]), the average copolymer composition, and the conversion are summarised in Table 4.6, [S] = concentrated styrene in feed, [M] = concentration of methyl acrylate in feed. 

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