Controlled Free‐Radical Copolymerization Kinetics of Styrene and Divinylbenzene by Bimolecular NMRP using TEMPO and Dibenzoyl Peroxide

Effect of the addition of inert or TEMPO‐capped prepolymer on polymerization rate and molecular weight development in the nitroxide‐mediated radical polymerization of styrene

“…Because DC effects seemed to be weak in NMRP, physical means to promote them were also attempted. The first approach was to add small amounts of crosslinker (divinylbenzene, DVB) with the idea of promoting higher molecular weights and thus, higher viscosities, from early on in the reaction 25. The second approach, reported herein, consisted of carrying out NMRP experiments in the presence of prepolymer, also with the idea of promoting high viscosities from early on in the reaction, but avoiding the formation of a polymer network.…”

Modeling of the Production of Hydrogels from Hydroxyethyl Methacrylate and (Di)Ethylene Glycol Dimethacrylate in the Presence of RAFT Agents

“…Figure shows a decrease in Ð at very low conversions for both cases, and then a gradual increase up to the gelation point. As with other controlled systems, the divergence in Ð at the gelation point is rather sudden, which means that the polymer molecules grow in a controlled manner until close to the gelation point.…”

Gel Formation in Aqueous Suspension Nitroxide‐Mediated Radical Co‐Polymerization of Styrene/Divinylbenzene

“…These features make the CRP techniques advantageous, comparatively to FRP, to synthesize hyperbranched polymers and gels with an improved control of the molecular architecture. Thus, CRP has been recently exploited to increase the homogeneity of these products, namely using atom‐transfer radical polymerization (ATRP),32–38 reversible addition–fragmentation chain transfer polymerization (RAFT)31, 39–45 and also nitroxide‐mediated radical polymerization (NMRP, see27, 37, 38, 46–56 and references therein). “Living” radical polymerization through the use of iniferter molecules was also considered in past works with similar goals 13, 57.…”

“…Expected differences between CRP and FRP crosslinking systems include (among others) the delay in the onset of gelation, a steady increase of gel fraction, and higher swelling ratios of the synthesized gels 45. These issues were studied in past works dealing with NMRP crosslinking using different synthesis approaches: 4,4′‐divinylbiphenyl/S bulk copolymerization (in sealed tubes) mediated by 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (PS‐TEMPO) adduct at 125 °C,46, 47 t ‐butylstyrene/DVB microgels preparation in benzene solution (sealed tubes) at 130 °C,48, 49 production of S/DVB monoliths directly in stainless columns (sonicated monomer/porogen mixture) at 130 °C considering different TEMPO‐based mediators,50, 51 miniemulsion/micro‐suspension of TEMPO mediated S/DVB copolymerization in shake ampoules at 125 °C52–55 and bulk S/DVB copolymerization at 120 °C mediated by TEMPO in sealed ampoules 56…”

“…This work reports experimental studies concerning the synthesis of S/DVB networks using NMRP in aqueous suspension. Compared with the above described works dealing with NMRP of S/DVB,46–56 a different synthesis approach is also considered in the present work where the NMRP aqueous suspension copolymerization of S/DVB was performed using an one‐pot stirred reactor, allowing the direct measurement of the dynamics of gelation. Kinetic data on the polymerization were collected and the molecular architecture of the products was probed using size exclusion chromatography with refractive index (RI) and multi‐angle laser light scattering (MALLS) detection.…”