Measurement and Modeling of Semi-Batch Solution Radical Copolymerization of N-tert-Butyl Acrylamide with Methyl Acrylate in Ethanol/Water

Abstract

The synthetic polymer industry is transitioning from the use of organic solvents to aqueous media in order to reduce environmental impact. However, with radical polymerization kinetics affected by hydrogen-bonding solvents, there is limited information regarding the use of water as a solvent for sparingly soluble monomers. Thus, in this paper, the radical polymerization of methyl acrylate (MA) and N-tert-butylacrylamide (t-BuAAm) is studied in water and ethanol (EtOH), as the copolymer product is of commercial interest. A series of semi-batch reactions are conducted under a range of operating conditions (i.e., reaction temperature, solvent-to-monomer ratio, and comonomer composition) to demonstrate that the copolymer can be successfully synthesized without significant drifts in product molar masses or composition. The experiments provide additional data to probe the influence of the solvent on the polymerization rate and copolymer properties, as the low monomer concentration maintained under starved-feed operation leads to a solvent-to-monomer ratio different from that in a batch system. A model that captures the influence of backbiting and solvent effects on rate, previously developed and tested against batch polymerizations, also provides an excellent description of semi-batch operation, validating the set of mechanisms and kinetic coefficients developed to represent the system.

A systematic study of tert‐butylacrylamide‐methyl acrylate‐acrylic acid radical solution terpolymerization

“…As for the batch experiments, f acrylates < F acrylates , indicating that AA and MA are preferentially incorporated into the terpolymer product relative to t-BuAAm, as also seen for the copolymerizations. [8] Furthermore, the model predicts a SCB level of 1.8% for the terpolymerization semi-batch experiment, in excellent For all experiments, the final reactor contents were w mon,total = 0.20, 2.0 wt.% AIBN, and α EtOH = 0.75. The copolymerization data and simulation profiles were taken from an earlier publication.…”

“…The kinetic mechanism used to describe AA homopolymerization in EtOH/H 2 O systems is based on a model developed to represent AA polymerized in water, as described by Wittenberg et al [ 19 ] PRT, the termination of an initiator fragment with a growing macroradical outside of the solvent cage, was considered, as also implemented in the MA and t ‐BuAAm polymerization models described by Agboluaje et al [ 4,6 ] While PRT has a negligible impact when simulating batch polymerization, the mechanism influences the simulation of semi‐batch monomer conversion and weight average molecular weight ( M w ) profiles. [ 4,8 ] The Table S1 values for AA with from 0.50 to 1 were acquired only at 25°C. [ 5 ] Since the of AA at was found to be of similar magnitude to that of MA in bulk, [ 5 ] its temperature dependency is assumed to also be the same, with an activation energy of 17.3 kJ ∙ mol −1 .…”

“…The terpolymerization was conducted at 70°C with w mon,total = 0.20 and 2.0 wt.% AIBN (based on a mixture at the end of feed time) in ethanol/water ( α EtOH = 0.75); a molar monomer ratio MA: t ‐BuAAm:AA = 45:45:10 was fed over 112 min, followed by a 1 h batch hold. Figure 12 compares the experimental and simulated profiles from the terpolymerization to those for 50:50 MA/ t ‐BuAAm semi‐batch copolymerizations conducted under identical reaction conditions presented in an earlier publication, [ 8 ] albeit with feed times of 75 and 150 min.…”

“…The semi‐batch procedures used for the terpolymerization experiment in the current work are as detailed by Kaur et al [ 8 ] The terpolymer experiment was conducted at 70°C under an N 2 blanket in a 250 mL three‐neck round bottom reactor flask attached to a Graham condenser. The total reaction mass of 120 g was partitioned between the room temperature feed vessel (containing only monomer and solvent) and the silicone oil heated reactor (consisting of AIBN and ethanol‐H6/H 2 O), with the monomer/solvent feed transferred to the reactor via a peristaltic pump.…”

“…These homopolymerization representations were then combined and extended to develop the model of MA/t-BuAAm copolymerization used to represent both batch [6] and semi-batch operation. [8] This systematic development follows the strategies pioneered by Archie Hamielec for the modelling of multicomponent radical polymerization. [9,10] Key kinetic coefficients needed to model the system were measured by a PLP-SEC study of how the t-BuAAm k p value varied with solvent composition and w mon , with additional experimentation demonstrating that the copolymerization system is well-represented by the terminal model of chain-growth in the EtOH-rich solvent mixtures of interest.…”