PLP-SEC Investigation of the Influence of Electrostatic Interactions on the Radical Propagation Rate Coefficients of Cationic Monomers TMAEMC and MAPTAC

Abstract

The decisive role of counterions on the propagation mechanism in the radical polymerization of ionized monomers is comprehensively studied. Propagation rate coefficients, k p, were obtained for cationic monomers [2-(methacryloyloxyethyl)]­trimethylammonium chloride (TMAEMC) and [3-(methacryloylaminopropyl)]­trimethylammonium chloride (MAPTAC) in aqueous solution by pulsed-laser polymerization combined with size-exclusion chromatography over broad ranges of monomer concentration (1–40 wt %), temperature (5–90 °C), pH (2–12), and salts selected to provide a molar counterion concentration, c counterion, between 0.05 and 3 mol·L–1. Both monomers behave similarly under conditions at which repulsive electrostatic interactions between a polymer chain and a reacting monomer dominate (c counterion < 0.2 mol·L–1). The k p values increase linearly with c counterion above this value due to screening of the repulsive interactions and follow the family behavior of nonionized methacrylate and methacrylamide monomers manifested by a higher k p for TMAEMC than for MAPTAC. The hydration of the polyelectrolyte chain is considered as an additional factor contributing to higher k p values for cationic TMAEMC at high c counterion values compared to its nonionized analogue 2-dimethylaminoethyl methacrylate. The extensive set of k p data can be represented using average activation energies of 14.4 ± 2.7 and 14.7 ± 2.0 kJ·mol–1 for TMAEMC and MAPTAC, respectively, and a preexponential factor that increases with c counterion. The batch polymerization of MAPTAC compared to that of TMAEMC reflects the differences in k p behavior for these monomers.

Effect of Ionization on Aqueous Phase Radical Copolymerization of Acrylic Acid and Cationic Monomers

“…PLP-SEC investigations on k p of NaMA and NaA have highlighted the importance of counterions in the screening of monomer-radical electrostatic interactions, with an increase in k p observed with an increased concentration of counterions. Similar findings were recently reported by the group of Lacı́k for TMAEMC and MAPTAC . The propagation behavior of ionized monomers under the conditions providing effective screening of repulsive electrostatic interactions reveals family-type behavior consistent with their nonionized counterparts. , On the other hand, the information available regarding termination rate coefficients ( k t ) for fully ionized systems in aqueous phase is more limited.…”

“…Similar findings were recently reported by the group of Lacı ́k for TMAEMC and MAPTAC. 17 The propagation behavior of ionized monomers under the conditions providing effective screening of repulsive electrostatic interactions reveals family-type behavior consistent with their nonionized counterparts. 18,19 On the other hand, the information available regarding termination rate coefficients (k t ) for fully ionized systems in aqueous phase is more limited.…”

“…It was hypothesized and later verified experimentally that addition of NaCl to increase the counterion concentration in systems containing ionized monomers enhances the homopropagation rate. While previous studies demonstrated that salt addition enhanced the relative incorporation of either cationic ,, or anionic comonomers when copolymerized with a neutral monomer, the influence of added salt on the copolymerization of cationic with anionic monomers is unknown.…”

“…As seen from the comparison of comonomer composition drifts with AA and NaA as comonomer (Figure e,f), the cationic comonomer (both TMAEMC and MAPTAC) is incorporated at faster relative rates when copolymerized with NaA than AA, suggesting that higher values for r TMAEMC and r MAPTAC are needed to represent the data. However, as the relative consumption rates of the cationic comonomers are found to vary with total monomer concentration in a similar fashion (Figure d for NaA-TMAEMC and Figure S4d for NaA-MAPTAC), the functional form established in previous studies , is used with values for b set to 1.0 for TMAEMC and 0.5 for MAPTAC, based on the dependence of homopolymerization k p values on counterion concentration ( C Cl – ) from PLP-SEC studies …”

Research Progress on Typical Quaternary Ammonium Salt Polymers

“…This method has effectively solved the mass and heat transfer in the reaction process, and the post-treatment of the crude product is relatively simple. The product quality was significantly better than the products obtained by direct reaction of DMAEA (or DMAEMA) with CH 3 Cl or reaction in organic solvents [24][25][26]. Because DAC (or DMC) is highly active and easy to self-polymerize, a certain amount of some polymerization inhibitor, such as phenothiazine, hydroquinone or p-hydroxyanisole, is usually added to prevent self-polymerization.…”