Propagation Kinetics of the Radical Polymerization of Methylated Acrylamides in Aqueous Solution

Abstract

Propagation rate coeffi cients, k p , of the radical polymerization of N , N -dimethylacrylamide ( N , N -dimethylprop-2-enamide), N -methylmethacrylamide ( N ,2-dimethylprop-2-enamide), and methacrylamide (2-methylprop-2-enamide) in aqueous solution are measured via pulsed-laser polymerization in conjunction with size-exclusion chromatography within wide ranges of monomer concentration, temperature, and pressure. As observed for aqueous solutions of other monomers, k p decreases signifi cantly towards higher monomer concentration. For methacrylamide, a higher activation energy and a larger volume of activation are found as compared with N , N -dimethylacrylamide. These two activation parameters are almost identical for N -methylmethacrylamide and for N , N -dimethylacrylamide. radical polymerization processes. Among them, the propagation rate coeffi cient, k p , is of particular relevance. For k p measurement, pulsed-laser polymerization (PLP) in conjunction with polymer analysis by size-exclusion chromatography (SEC) is the well-established method recommended by the IUPAC Subcommittee on "Modeling of Polymerization Kinetics and Processes". [ 5 ] By PLP-SEC, k p is determined via Equation 1 :where X b is the degree of polymerization at the point of infl ection (POI) of the molar-mass distribution (MMD), which may be found from maxima in the fi rst-derivative curve of the logarithmic MMD. [ 6 ] X 1 is obtained from the position of the fi rst such maximum on the low-molar-mass side of the MMD and is identifi ed with the number of propagation steps occurring in the preselected time interval t 0 between two successively applied laser pulses. Monomer concentration, c M , is determined as the arithmetic mean of monomer concentrations before and after application of the sequence of laser pulses required for generating the PLP sample for SEC analysis. The degree of monomer conversion should not exceed a few percent to avoid signifi cant changes in monomer concentration, which would

Termination and Transfer Kinetics of Acrylamide Homopolymerization in Aqueous Solution

“…53,58 For methacrylamide, an increase in k p s by 32% has been observed in passing from 20 to 10 wt % monomer in aqueous solution. 62 Since SPR and MCR propagation are subject to the same effects of molecular environment, k p t may well reflect the same dependence on monomer concentration as does k Table 4 shows that k p t of AAm polymerization is much closer to the associated numbers for AA and BA than are the backbiting rate coefficients of these monomers (see Table 3). The k p t /k p s ratio for AAm, e.g., at 75°C is 0.35× 10 −3 , which is not too dissimilar from k p t /k p s = 1.0 × 10 −3 for AA (10 wt % in H 2 O) and k p t /k p s = 1.1 × 10 −3 for BA in 1.5 M in toluene.…”

EPR Study of Backbiting in the Aqueous‐Solution Polymerization of Acrylamide

“…On the other hand, the similarity between AAm and other acrylic monomers suggests that backbiting may occur, perhaps at higher temperatures than with acrylates and acrylic acid. This assumption is supported by the loss of overtone components in PLP–SEC experiments on DM‐AAm and AAm at higher temperatures . No similar loss is seen with acrylamides bearing an α ‐methyl group on the backbone .…”

“…Pulsed laser polymerization investigations accompanied by size‐exclusion‐chromatography (PLP–SEC) into AAm and N , N ‐dimethylacrylamide (DM‐AAm) polymerizations resulted in a pronounced laser‐pulse‐induced structure of the molar‐mass distribution even at low laser pulse repetition rates and temperatures up to 50 °C. This may be interpreted as an indication of backbiting either being absent or of only minor significance . On the other hand, the similarity between AAm and other acrylic monomers suggests that backbiting may occur, perhaps at higher temperatures than with acrylates and acrylic acid.…”

Determination of Homopolymerization Kinetics of 10‐(N‐Methylacrylamido)‐decylphosphonic acid, Its Diethyl ester, and 10‐(Methacryloyloxy)‐decylphosphonic acid, and Their Copolymerization with Methyl methacrylate

“…Most studies of polar monomer polymerization activity concerned acrylic acid, acrylamide, and their derivatives . The propagating chain growth and termination rate constants may be varied by changing the polymerization batch composition …”