Step-wise anionic polymerization

The data here related on the kinetics of the propylene polymerization and of the transfer processes and the studies of the catalysts carried out with C-labelled alkylaluminums, derive from a series of researches mostly carried out some time ago, when the knowledge of the mechanism of the considered catalytic processes was still rather limited. Nevertheless, it helped remarkably to know these new processes of anionic coordinated polymerization their true catalytic nature (which regard to a-TiCU) differentiates them from the more usual polymerization processes (radicalic) which, actually, are not catalytic. They substantially contributed to demonstrate that the anionic coordinated polymerization is a step-wise addition process in which each monomeric unit inserts itself into a metal carbon bond of the catalytic complex. 

Recently, efforts have been made to produce calibration standards of higher molecular weight that are chemically similar to lignins, by step-wise syntheses (12), anion-initiated polymerization of quinonemethides (13), and preparative HPSEC of acetylated lignins (14). Knowledge of the molecular weights of these materials is either built into the method of preparation or determined by absolute methods such as sedimentation equilibrium measurements. 

Chain-growth polymerization involves the sequential step-wise addition of monomer to a growing chain. Usually, the monomer is unsaturated, almost always a derivative of ethene, and most commonly vinylic, that is, a monosubstituted ethane, 1 particularly where the growing chain is a free radical. For such monomers, the polymerization process is classified by the way in which polymerization is initiated and thus the nature of the propagating chain, namely anionic, cationic, or free radical polymerization by coordination catalyst is generally considered separately as the nature of the growing chain-end may be less clear and coordination may bring about a substantial level of control not possible with other methods. ... 

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