Thermodynamic and Kinetic Polymerizability

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). 

The chemical, thermodynamic, and kinetic aspects of lactam polymerizability have been the subjects of many papers mainly published in the 1960s and 1970s. " Remarkably elegant has been the study of Korshak et who intended to... 

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-... 

Because of the general lack of quantitative thermodynamic (ceiling temperature Tc) and kinetic (kp, kp/k[J 5) data for the polymerization of the captodative olefins, it is impossible to draw firm conclusions about the importance of electronic factors on their polymerizability. If we compare them with other 1,1-disubstituted olefins by replacing the heteroatom O, S, or N by a CH2 and check the polymerizability of the resulting olefins, we find that the latter are in fact also difficult to polymerize as shown in Table 8 [77], Only methyl acrylates and methacrylates give high polymers easily. The polymerizability decreases rapidly with the steric hindrance of the substituent. 

According to Astle (4o) et al. trioxocane can be obtained by condensation of diethylene glycol with paraformaldehyde it is easily polymerizable by cationic catalysts or by electrochemical initiation (41). Copolymerization with e.g. trioxane or dioxolane are possible, too (41). Kinetics, thermodynamics and mechanism of homopolymerization have been studied in detail by several authors. According to the analytic results of Weichert (42) the structure of the polymers of /2/... 

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. ... 

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. 

Shea [13] and Shea and Sasaki [41,51] used ketals (entry f) for imprinting synthetic polymers. Diketones with various distances between the keto groups were treated with polymerizable diols, to obtain template monomers. After polymerization and removal of the template, these polymers showed considerable selectivity for the original template when the imprinted polymers were reloaded with a mixture of diketones. Unlike the reloading experiments mentioned earlier, this bond formation takes place slowly, and therefore it seems to be kinetically controlled in contrast to the bonding reactions described so far, which are thermodynamically controlled. If the arrangement of functional groups is the same, the size and shape of the rest of the... 

Although the thermodynamics of the products of multistage polymeriz.ation determine which structure will be the most stable, it is possible, and frequently necessary, to produce particle structures that appear nominally to be thermodynamically forbidden. This is achieved either by changing the surface characteristics of a polymer phase from those of the bulk material or by employing kinetic factors to produce and anchor energetically unfavored morphologies. Both types of methods are summarized below. 

Thus cationic polymerizability could only be related to the entropy of activation as desaibed in this chapter for cyclic esters of phosphoric acid. Most probably substituents and the related polymer linear units are getting enhanced statistical probability of states in the transition state. One could expect dependence on basicity, but the known basicities are almost the same and do not change monotonically (given in ADy (m )) OX 103 MOX 106 DMOX 99. Thus, like in polymerization of cyclic esters of phosphoric acid, where the thermodynamic reactivity is governed by entropy change, this is the kinetic reactivity depending on the change of entropy of activation. 

Duda et al. [41] have investigated the kinetics of ROP of lactones of different ring sizes by using a nonenzymatic (zinc-2-ethylhexanoate/butyl alcohol) system at 100 °C, and compared the results to those with enzymatic methods. The decreasing order of rates for nonenzymatic methods showed a reverse trend to that of enzymatic polymerization. The 17-membered lactone was most reactive towards enzymatic polymerization, a fact attributed to thermodynamic factors in chemical polymerization, while the hydrophobicity of the large-ring lactones was seen as the major contributory factor for enzymatic polymerization. The introduction of an a-methyl substituent reduced the polymerizability of 13- and 16-membered lactones, and a reduction in monomer conversion as well as M was observed [59]. 

---