Metal-free anionic polymerization of methyl methacrylate

Abstract

Abstract�Results on the metal-free anionic polymerization of methyl methacrylate (MMA) are presented. MMA was polymerized in tetrahydrofuran, using tetrabutylammonium diethyl 2-ethylmalonate and tetrabutylammonium 2-nitropropanate as initiators. Immediate polymerization was observed only in cases where the initators did not contain traces of their precursor molecules, the presence of which causes an appreciable inhibition period. This is attributed to the transfer reaction between active species and the precursor molecules. Only after their consumption can the major polymerization start. Using very pure initiators, no inhibition period was observed. Curves from dilatometric measurements showed the existence of an induction period. As usual, this is attributed to an initiation reaction which is slower than the propagation reaction. It is more clearly marked for tetrabutylammonium diethyl 2-ethylmalonate than for tetrabutylammonium 2-nitropropanate as initiator. All polymerizations of MMA usually go to complete consumption of the monomer. However, termination reactions have to be taken into account as well. The well-known intramolecular cyclization reaction was not observed in the MMA system. Here, a Hofmann elimination reaction terminates the growing of chains, which is due to the butyl ligands of the ammonium cation, where a β-hydrogen atom can be transferred to the growing chain under the formation of tri-n-butylamine and 1-butene. To eliminate this termination step, tetramethylammonium diethyl 2-ethylmalonate was synthesized and used as the initiator for the polymerization of MMA. Now transalkylation under the formation of a methyl group terminated the saturated chain end and trimethyl amine could be detected as a second termination reaction. Neither of the termination reactions seems to be very fast. The molecular weight distributions of the synthesized polymers are relatively broad.

Anionic polymerization of methyl methacrylate using tetrakis[tris(dimethylamino)phosphoranylidenamino] phosphonium (P5+) as counterion in tetrahydrofuran

“…Bidinger and Quirk 32) used TBA + 9-methylfluorenide at low concentration as an initiator for the polymerization of MMA at ambient temperature resulting in polymers with rather broad MWD. Bandermann et al 33) also reported induction periods and broad MWD's as well as the presence of residual initiator in MMA polymerization using TBA malonate as initiator. They also found evidence for Hofmann elimination as a termination reaction.…”

Anionic Polymerization of Butadiene Initiated by Tributyltin Sodium. Kinetic Analysis of Induction Periods Generated by Transfer to Initiator Precursor

“…In the metalfree anionic polymerization of methyl methacrylate (MMA) initiated by tetrabutylammonium diethyl ethyl malonate in THF (obtained from the reaction of tetrabutylammonium hydroxide with diethyl ethyl malonate), Fieberg et al [14] also reported very long induction periods similar to those shown in Figure 1 and 2. It was concluded that the more nucleophilic oligo-MMA anion reacts with unreacted initiator precursor, diethyl ethyl malonate.…”

“…A similar behavior has also been observed in some other anionic and group transfer polymerizations. [14,15] Therefore, the explanation and kinetic analysis of this phenomenon is also included in this communication.…”

Metal-free anionic polymerization of methyl methacrylate in tetrahydrofuran using bis(triphenylphosphoranilydene)ammonium (PNP+) as counterion

“…Bidinger and Quirk 3) used TBA + 9-methylfluorenide as initiator for the polymerization of MMA, obtaining PMMA with broad MWDs. Bandermann et al 4) also reported broad MWDs, residual initiator and Hoffmann elimination as termination reaction when using TBA + malonate as initiator. Baskaran et al 5) reported similar results and explained these observations by a reversible initiation step when using initiators with low pK a values like malonates and fluorenides.…”