ESR study of MMA polymerization by a peroxide/amine system: Bone cement formation

Abstract

Electron spin resonance (ESR) spectroscopy was used to gain insight at the molecular level into the curing of bone cement. Methyl methacrylate was polymerized using a N,N-dimethyl-p-toluidine (TD)/benzoyl peroxide (BPO) redox system in the presence of polymethyl methacrylate (PMMA) powder. The conventional nine-line ESR spectrum for the growing polymer radical was detected at the gel stage of polymerization. While the optimum free radical concentration was observed near the equimolar amine/BPO concentration, excess amine led to a change in the chemical structure of the trapped radical and inhibited the polymerization process. At a high amine/BPO ratio the nine-line signal disappeared and a three-line nitroxide-based radical appeared. The appearance of this nitroxide signal seems to depend on the amine/BPO molar ratio and on the presence of PMMA. An excess amount of amine with respect to BPO was found to inhibit the polymerization process. When BPO was removed, the system still polymerized but with a longer gelation time and a lower radical concentration. These results demonstrate that trapped free radicals in the bulk polymerization of MMA convert to polymeric peroxides that act as initiators in bone cement. When the accelerator 4-dimethylamino phenethyl alcohol (TDOH) was used, a higher radical concentration was observed in the polymerizing system. TDOH shows potential for being a more effective accelerator than TD for bone cement curing.

Poly(ethylene terephthalate) foams: Correlation between the polymer properties and the foaming process

“…The significant increase in k ′ with increase in PLMR is explained in terms of the fact that, with increase in PLMR, there is an increase in the amount of free radicals in the cement, because there is an increase in the amounts of the initiator of the polymerization reaction (benzoyl peroxide)37 as well as of the powder per se , which, it has been said, may play a role as additional initiator 38…”

Study of the Effect of Two Bpo/Amine Initiation Systems on the Free-Radical Polymerization of Mma Used in Dental Resins and Bone Cements

“…[2] The side reactions of BPO and amine influence the optimum BPO to amine ratio, which seems to depend on their individual concentrations; that is, for a fixed BPO concentration there will be an Table 1 presents the number-average molecular weight M n , weightaverage molecular weight M w , and polydispersity index ( M w = M n ) of the prepared PMMA. [12] The effect of the reaction temperature on the polymerization of MMA initiated by BPO=DMPOH or BPO=DMT (molar ratio 1.12) is shown, respectively in Figs. A clear dependence of M n on the molar ratio BPO=amine used is observed, which is shown more clearly in Fig.…”

“…Furthermore, it can cause prosthesis failure in hypersensitive patients that develop a florid tissue reaction at the interface between cement and the bone, and can induce contact dermatitis. [12] They found that DMPOH shows potential for being a more effective accelerator than DMT for bone cement curing and that optimum free macroradical concentration can be obtained by using equimolar BPO=amine concentration. With low amine concentration, nearly colorless restorations, having good color stability, were obtained.…”

Redox initiation of bulk thiol–ene polymerizations

“…In particular, the benzoyl peroxide (BPO) and N,N-dimethyl-p-toluidine (DMT) redox pair has been used for decades to initiate the free radical polymerization of methacrylate monomers in bone cements and dental resins. 29, 30 More recently, the same redox pair has been applied to the fabrication of microfluidic chips and hydrogels, again through the network formation of multifunctional methacrylate monomers. 31, 32 In contrast, little work has been conducted on the use of BPO/DMT or similar redox initiating systems in neat thiol-ene formulations despite the abundant advantages of thiol-ene copolymerizations over methacrylate homopolymerizations.…”