Highly Porous Cationic Polyelectrolytes via Oil-in-Water Concentrated Emulsions: Synthesis and Adsorption Kinetic Study

Abstract

This work merges the fields of highly porous polymers (polymerized high internal phase emulsions, polyHIPEs) and synthetic cationic polyelectrolytes and introduces a new approach toward the synthesis of highly porous cationic polyelectrolytes. Cationic polyelectrolytes based on (3-acrylamidopropyl)-trimethylammonium chloride (AMPTMA) were synthesized directly through the oil-in-water HIPEs. The resulting polyelectrolyte-based polyHIPEs are distinguished by the highly porous morphology as well as high concentration and accessibility of the cationic N-quaternized functional groups. The most efficient AMPTMA-based polyelectrolyte polyHIPE exhibits the total ion-exchange capacity of 3.53 mmol of AgNO per gram of dry resin and the water uptake of up to 95 g·g, which is a great improvement as compared to the state-of-the-art of polyHIPE absorbents bearing cationic moieties. Results of erythrosine dye adsorption show that chemisorption is a rate-determining step because adsorption follows the pseudo-second-order kinetic model. Multilinearity of the Weber and Morris plots assumes that more than one regime is involved in the diffusion of the erythrosine dye molecules into the polyHIPE structure with the diffusion in between the swollen polymer chains as a rate-limiting step.

Recent advances in separation applications of polymerized high internal phase emulsions

“…Organic dyes are one kind of the most hazardous pollutants in environmental samples, and thus, their selective adsorption and separations are an attractive research area in polyHIPEs applications. At present, many polyHIPEs have been tested for the dye separation and displayed high separation performance in adsorption capacity, selectivity, and robustness [12, 26, 102–109]. EHA/DVB/methyl methacrylate [MMA] polyHIPE monoliths offered a maximum column capacity of 24.01, 24.33, 21.59, 21.98, and 22.68 μg/g for Para Red, Sudan I, Sudan II, Sudan III, and Sudan IV, respectively, suggesting that the polyHIPE monolith possessed great extraction ability for separation of Para Red and Sudan from chilli samples [12].…”

“…The results of Zhao et al [106] indicated that the high porosity and consequent small foam density resulted in the high adsorption capacity (454.2 mg/g calculated by Langmuir model) and faster adsorption rate. On the other hand, the adsorption processes of dyes onto the porous polyHIPEs were probably controlled by chemical adsorption process and physical adsorption process simultaneously [106–108]. At high concentrations of methyl blue, the chemical adsorption played a more important role than the physical adsorption with the chitosan‐g‐polyacrylamide polyHIPEs [106].…”

“…At high concentrations of methyl blue, the chemical adsorption played a more important role than the physical adsorption with the chitosan‐g‐polyacrylamide polyHIPEs [106]. During the adsorption process of erythrosine dye with polyelectrolyte‐based polyHIPEs, Kovačič et al [107] found that the chemical adsorption was a rate‐determining step and more than one regime was involved in the diffusion of the erythrosine dye molecules into the polyHIPE structure with the diffusion in‐between the swollen polymer chains as a rate limiting step.…”

Porous, bicontinuous, and cationic polyelectrolyte obtained by high internal phase emulsion polymerization

“…This work aims to synthesize cationic polyelectrolyte poly (HIPE)‐bearing quaternary ammonium groups (‐N + R 3 ) through an oil‐in‐water high internal phase emulsion. To date, this type of cationic polymer has been poorly explored, and only one recent publication presented a study of an ammonium‐based polyelectrolyte . Usually, to introduce positive charges to the poly (HIPE) (or bestow hydrophilic characteristic), the procedure starts with the preparation of the poly (HIPE) using a monomer able to be subsequently modified (ie, 4‐vinylbenzyl chloride and glycidyl methacrylate) followed by the functionalization of the already formed porous polymers; however, this strategy requires additional experimental steps and reagents such as solvents and alkylating reagents.…”

“…To date, this type of cationic polymer has been poorly explored, and only one recent publication presented a study of an ammonium-based polyelectrolyte. 21 Usually, to introduce positive charges to the poly (HIPE) (or bestow hydrophilic characteristic), the procedure starts with the preparation of the poly (HIPE) using a monomer able to be subsequently modified (ie, 4vinylbenzyl chloride and glycidyl methacrylate) followed by the functionalization of the already formed porous polymers [22][23][24] ; however, this strategy requires additional experimental steps and reagents such as solvents and alkylating reagents. The cationic poly (HIPE) was obtained using a monomer that contained an ammonium group such as (4-vinylbenzyl)trimethyl ammonium chloride and crosslinked with N,N-methylene-bis-acrylamide, ensuring that the cationic functional groups are incorporated into the polymer during the polymerization and not in a postsynthesis step.…”