Radical polymerization publication rate

Figure 1.1 Publication rate of journal papers on radical polymerization and on living, controlled or mediated radical polymerization for period 1975-2002 based on SeiFinder search (as of Mar 2005).

In a recent publication Okamura et ah (12) describe similar results in a different system. It is believed that the unusual rate increase observed in these various systems which are chemically so different is caused by the physical state of the reaction medium at temperatures a few degrees above Tg. The high viscosity of this gel-like medium presumably favors chain propagation in its competition with termination. This effect, which is kinetically similar to the "gel-effect in free radical polymerizations, can only arise if the termination step (charge recombination) becomes diffusion controlled. The latter process would arise if both ionic species involved in the reaction were of macromolecular size. This is undoubtedly true for the growing chain, but the mobility of the counter ion should only be significantly reduced in such a medium if it is of a polymolecular structure, involving perhaps a voluminous solvation cluster. 

At the time of the first edition of this book (1995), this field was still very much in its infancy. NMP was described, though little had been published in the open literature, and methods such as ATRP and RAFT had not been reported. Since 1995, the area has expanded dramatically and by themselves living/ controllcd/mcdiatcd processes now account for a very substantial fraction of all research on radical polymerization (Chapter 1). The development of this field over this period can be followed in the publications following successful ACS symposia held in 1997/ 2000 and 2002 and SML meetings held in 1996 and 2001. Publications continue to appear at a rapid rate. Matyjaszewski has provided an overview of the history and development of living radical polymerization through 2001 in the Handbook of Radical Polymerization ... 

Anionic polymerization of styrene has attracted much attention during recent years and several publications and patents have been published on this issue. The main reason for this interest is the high rate of polymerization which can be achieved compared to free-radical polymerization, and the low content of residual styrene and oligomers in the final polymer [145-147]. 

Figure 1 Publication rate of journal papers on radical polymerization and on living, controlled, or mediated radical polymerization for the period 1975-2008 based on SciFinder search (as of March 2010). It does not distinguish forms of controlled radical polymerization. It includes most papers on ATRP, RAFT, and NMP and would also include conventional, non-RDRP, controlled radical polymerizations. It would not include papers, which do not mention the terms living , controlled , or mediated .

Systems Where Radical Desorption is Negligible. Styrene and methyl methacrylate emulsion polymerization are examples of systems where radical desorption can be neglected. In Figures 4 and 5 are shown comparisons between experimental and theoretical conversion histories in methyl methacrylate and styrene polymerization. The solid curves represent the model, and it appears that there is excellent agreement between theory and experiment. The values of the rate constants used for the theoretical simulations are reported in previous publications (, 3). The dashed curves represent the corresponding theoretical curves in the calculation of which gel-effect has been neglected, that is, ktp is kept constant at a value for low viscosity solutions. It appears that neglecting gel-effect in the simulation of styrene... 

It is worth noting that the dimer and trimer generated in reactions (8) and (9) can react with polymeric radicals as a chain transfer agent, and therefore their effect on the polymer molecular weight should not be neglected the quantitative estimation of the concentration of these byproducts depends on the fact that whether the rate of thermal initiation is a second- or third-order reaction of monomer concentration. More kinetic information for such transfer reactions can be found in a number of publications [14-19]. Nevertheless, detailed kinetic studies on such Diels-Alder byproducts remain scarce. Katzenmayer [20], Olaj et al. [21,22], and Kirchner and Riederle [23] have published some quantitative results on this matter. 

These results point to two processes, premature radical chain termination and film shrinkage, which compete in determining the ultimate polymerization conversion efficient of multifunctional acrylates. It is obvious that critical attention must be paid to the pulse repetition rate, photoinitiator concentration, and acrylate functionality in developing any photopolymerizable system for laser-initiated polymerization. Future publications on laser-initiated polymerization of multifunctional acrylates will deal with monomer extraction of partially polymerized films, mechanical properties of laser polymerized films, and the Idnetics of single-pulsed systems. 

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