Rapid additive‐free TEMPO‐mediated stable free radical polymerizations of styrene

Abstract

The stable free radical polymerization (SFRP) of styrene, initiated with benzoyl peroxide in the presence of TEMPO, under bulk conditions, is demonstrated to proceed rapidly without the need for any rate enhancing additives such as camphorsulfonic acid, 2‐fluoro‐1‐methyl pyridinium p‐toluenesulfonate, or acetic anhydride. Monomer conversions as high as 70% can be achieved in 5 h or less while maintaining polydispersity indexes of 1.15. These results stand in stark contrast to earlier reactions that required 70 h to achieve similar conversions. This study demonstrates that the single largest factor governing the rates of polymerization is the molar concentration of excess TEMPO remaining in solution after initiation. A reduction in the TEMPO to BPO ratio is required when large amounts of BPO are used to target low molecular weight polystyrenes. However, when a lower molar amount of BPO is used to obtain high molecular weight polystyrenes, a higher TEMPO to BPO ratio is required. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5487–5493, 2007

A Homogeneous, Recyclable Polymer Support for Rh(I)-Catalyzed C–C Bond Formation

“…Ultimately, we have been able to synthesize a polymer having comparatively low molecular weight and a narrow molecular weight distribution by utilizing nitroxyl radical-mediated living radical polymerization (Figure 3). 11 To do so, comonomer 2 was subjected to copolymerization with styrene (1:10) at 123 °C for 4 hours in the presence of catalytic TEMPO and benzoyl peroxide initiator. Of note, further heating improves yield of the polymer but leads to the formation of partially insoluble polymer.…”

A replicated investigation of nitroxide‐mediated radical polymerization of styrene over a range of reaction conditions

“…Although at first glance the system seems relatively well studied, no detailed/reliable experimental results (over the whole range of polymerization) are available in the literature. For instance, the conversion versus time data points reported in the past only capture the first few hours of the experiment and low to medium conversion (see, e.g., Veregin et al, 1996a,b; Dollin et al, 2007). Average molecular weight data are usually not readily available (Veregin et al, 1996a,b) and, if available, are presented as number‐average molecular weight points evaluated at a limited number of conversion levels (usually, low‐medium‐high conversion; see, e.g., MacLeod et al 1997; Dollin et al, 2007).…”

Application of Stable Radicals as Mediators in Living‐Radical Polymerization

“…60 An alternative to primary initiators are alkoxyamines, 33 -36 adducts of an initiator fragment (optional), a monomer, and a nitroxide (for example 3-5). The C-O bond of the alkoxyamine is labile and upon heating dissociates to form an initiating species and a stable radical mediator in a 1 : 1 ratio, although this is not necessarily the right ratio of the propagating chain to nitroxide for a well controlled polymerization.…”

“…82 It was subsequently shown that polymerizations of styrene can proceed quickly and efficiently using a primary initiator, such as BPO, in the absence of an additive, if the ratio of TEMPO to BPO is varied according to the targeted molecular weight. 60 …”