Kinetic polymerizability

The kinetic polymerizability of monomers belonging to the same class of compounds and studied at similar conditions could be compared using thermodynamic activation parameters. Actually, these parameters are determined from the dependence of the rate constants of elementary reactions (In fep) on 1/T in several instances comparison of fep could be sufficient. Comparison of and A S is more subtle since it provides information on the genuine source of differences in kp and therefore on kinetic polymerizabilities. A good example of such a comparison for CROP of oxetane, 3-methyloxetane, and 3,3-dimethyloxetane is given in a classical work by Saegusa and Kobayashi. ... 

The thermodynamics of trioxane polymerization is discussed in more detail in the chapter on Thermodynamic and Kinetic Polymerizability (Chapter 4.02) (by S. Penczek and K. Kaluzyhski). 

A few attempts have been made to describe the kinetic polymerizability of lactams, but rather poor results have been obtained and contradictory conclusions on reactivities and, in particular, on substituent effects have been published. Sekiguchi and Coutin proposed a... 

Thermodynamically speaking, 2-piperidone is slightly more polymerizable than 2-pyrrolidone, but kinetically less reactive. The low kinetic polymerizability has been attributed to the concurrent crystallization of the growing chains and consequent physical termination as well as the relevance of side reactions, allowed to extensively occur because of the slowness of the polymerization. Activators have been found to be always essential for the polymerization of 2-piperidone. Relatively high molar masses of poly(2-piperidone) have been achieved only when quaternary ammonium salts have been used as initiators. The resultant polyamide has a Tm of 283°C, higher than that of poly(2-pyrrolidone), 260 °C, and is thermally much more stable than the latter. Therefore, melt spinning can be safely carried out and fibers with good characteristics are obtained. 

Surfactants provide temporary emulsion droplet stabilization of monomer droplets in tire two-phase reaction mixture obtained in emulsion polymerization. A cartoon of tliis process is given in figure C2.3.11. There we see tliat a reservoir of polymerizable monomer exists in a relatively large droplet (of tire order of tire size of tire wavelengtli of light or larger) kinetically stabilized by surfactant. 

In this section, we consider the kinetics of propagation and the features of the propagating radical (Pn ) and the monomer (M) structure that render the monomer polymerizable by radical homopolymerization (Section 4.5.1). The reactivities of monomers towards initiator-derived species (Section 3.3) and in copolymerizalion (Chapter 6) arc considered elsewhere. 

From the kinetic viewpoint the polymerizability of 61 is considered to be higher than that of e-caprolactam, which is polymerized usually at temperatures above 135 °C63,64 Thermodynamically, the polymerization of 61 appears to be more favored than that of a-pyrrolidone, for which no polymerization is observed in THF63-65 The higher polymerizability of 61 may be attributed not only to its highly strained bicyclic structure but also to the activation of the anion 66 by the... 

On the other hand, the macrolides showed unusual enzymatic reactivity. Lipase PF-catalyzed polymerization of the macrolides proceeded much faster than that of 8-CL. The lipase-catalyzed polymerizability of lactones was quantitatively evaluated by Michaelis-Menten kinetics. For all monomers, linearity was observed in the Hanes-Woolf plot, indicating that the polymerization followed Michaehs-Menten kinetics. The V, (iaotone) and K,ax(iaotone)/ m(iaotone) values increased with the ring size of lactone, whereas the A (iactone) values scarcely changed. These data imply that the enzymatic polymerizability increased as a function of the ring size, and the large enzymatic polymerizability is governed mainly by the reachon rate hut not to the binding abilities, i.e., the reaction process of... 

Organic peroxides and hydroperoxides decompose in part by a self-induced radical chain mechanism whereby radicals released in spontaneous decomposition attack other molecules of the peroxide.The attacking radical combines with one part of the peroxide molecule and simultaneously releases another radical. The net result is the wastage of a molecule of peroxide since the number of primary radicals available for initiation is unchanged. The velocity constant ka we require refers to the spontaneous decomposition only and not to the total decomposition rate which includes the contribution of the chain, or induced, decomposition. Induced decomposition usually is indicated by deviation of the decomposition process from first-order kinetics and by a dependence of the rate on the solvent, especially when it consists of a polymerizable monomer. The constant kd may be separately evaluated through kinetic measurements carried out in the presence of inhibitors which destroy the radical chain carriers. The aliphatic azo-bis-nitriles offer a real advantage over benzoyl peroxide in that they are not susceptible to induced decomposition. 

Several applications of hyperbranched polymers as precursors for synthesis of crosslinked materials have been reported [91-97] but systematic studies of crosslinking kinetics, gelation, network formation and network properties are still missing. These studies include application of hyperbranched aliphatic polyesters as hydroxy group containing precursors in alkyd resins by which the hardness of alkyd films was improved [94], Several studies involved the modification of hyperbranched polyesters to introduce polymerizable unsaturated C=C double bonds (maleate or acrylic groups). A crosslinked network was formed by free-radical homopolymerization or copolymerization. 

Thus, room-temperature ionic liquids have the potential to provide environmentally friendly solvents for the chemical and pharmaceutical industries. The ionic liquid environment is very different from normal polar and nonpolar organic solvents both the thermodynamics and the kinetics of chemical reactions are different, and so the outcome of a reaction may also be different. Organic reactions that have been successfully studied in ionic liquids include Friedel-Crafts, Diels-Alder,Heck catalysis, chlorination, enzyme catalysis,polymeriz-... 

The polymerization kinetics of propylene, 3-methyl-l-butene, and 4-methyl-l-pentene can be described by Eq. (12) and it is felt that this scheme may be generally valid for cationic polymerization of olefins as there is no reason to suspect that a fundamental difference in polymerization mechanism exists in the case of the three monomers cited above as compared with other cationically polymerizable olefins. 

---