Frontal ring-opening metathesis

A. Mariani, S. Fiori, Y. Chekanov, and J. Pojman, Frontal ring-opening metathesis polymerization of dicyclop entadiene. Macromolecules, 34 (2001), pp. 6539-6541. 

Free-radical chemistry is the most widely used but not the only one. Frontal curing of epoxy resins has been studied (14-18). Begishev et al. studied anionic polymerization of e-caprolactam (19). Frontal Ring-Opening Metathesis Polymerization (FROMP) has been successfully achieved with dicyclopentadiene (20) and applied to making IPNs (21). Mariani et al. have achieved FP with urethane chemistry (22). 

Frontal polyurethane polymerization [13-15], frontal atom transfer radical polymerization [16], and frontal ring-opening metathesis polymerization (ROMP) [17] all suffer from short pot lives that is, bulk polymerization occurs in less than an hour. In some cases, the only way to avoid even faster bulk polymerization is to cool the reagents. For example, with frontal ring-opening metathesis polymerization of dicyclopentadiene with a Grubbs catalyst, the starting materials had to be frozen to prevent rapid bulk polymerization [17]. 

Most work has been with free-radical systems but other chemistries can be used. Begishev etal. studied frontal anionic polymerization of e-caprolactam [18, 19], and epoxy chemistry has been used as well [20-23]. Mariani ctal. demonstrated frontal ring-opening metathesis polymerization [17]. Fiori et al. produced polyacrylate-poly(dicydopentadiene) networks frontally [24], and Pojman etal. studied epoxy-acrylate binary systems [25]. Polyurethanes have been prepared frontally [13,14, 26]. Frontal atom transfer radical polymerization has been achieved [16] as well as FP with thiol-ene systems [27]. Recent work has been done using FP to prepare microporous polymers [28-30], polyurethane-nanosilica hybrid nanocomposites [31], and segmented polyurethanes [32]. 

Y., and Pojman, ).A. (2001) Frontal ring-opening metathesis polymerization of dicyclopentadiene. Macromckcules,... 

A problem with this system is that it has a relatively short pot life. The authors found that by using PPh3 the pot life was extended to 20 min. To overcome this drawback, they dissolved all components at 3 5 °C and quickly cooled them to 27 ° C. This means that frontal ring opening metathesis polymerization runs were performed on solid mktures, which melted immediately before being reached by the front. If stored at 7-8 ° C, the samples could support a front after 3 weeks. 

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