Facile synthesis of poly(hydroxyethyl acrylate) by frontal free-radical polymerization

We report the first synthesis of poly(hydroxyethyl acrylate) (PHEA) without solvent by free-radical frontal polymerization (FP) at ambient pressure. In a typical run, the appropriate amounts of reactant (hydroxyethyl acrylate) and initiator (1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane) (Luperox 231) were mixed together at ambient pressure. FP was initiated by heating the wall of the tube with a soldering iron, and the resultant hot fronts were allowed to self-propagate throughout the reaction vessel. Once initiated, no further energy was required for polymerization to occur. To study the macrokinetics, we also produced PHEA frontally with ammonium persulfate as initiator and dimethyl sulfoxide as the solvent. The dependences of the front velocity and front temperature on the initiator concentration and reactant dilution were investigated. The front temperatures were between 124 and 157 °C, depending on the ammonium persulfate concentration. Thermogravimetric analysis indicates that PHEA prepared by FP with ammonium persulfate as initiator had higher thermal stability than solvent-free frontally prepared PHEA with Luperox 231 as initiator.