Bisulfite‐initiated vinyl polymerization in aqueous media

Abstract

Bisulfite initiates aqueous polymerization of certain vinyl monomers such as methyl methacrylate, ethyl methacrylate, methacrylic acid and styrene but it fails in case of acrylonitrile, vinyl acetate, methylacrylate, and acrylic acid under identical conditions. The mechanism of initiation has been discussed. Catalyst exponent of this initiator with respect to methyl methacrylate is near about 0.5. Quantitative determination of endgroup by dye techniques of the polymers obtained show that about 2 sulfonate (‐SO3H) endgroups are present per chain in almost all cases. No sulphate endgroup (‐OSO3H) is ever found. In case of very low initiator concentration ( < 0.005 mole/1.), some hydroxyl endgroups are also found in general but the total (sulfonate and hydroxyl combined) amounts to about 2 per polymer chain.

Synthesis of cationic flocculants by the inverse microemulsion copolymerization of acrylamide with 60% 2‐acryloxyethyltrimethyl ammonium chloride in the monomer feed. I. Initiation by ammonium persulfate/sodium disulfite redox system

“…They also proposed that both radicals do not recombine just after formed because of steric hindrance imposed by the methyl group attached to vinyl group. But in our case, neither of both monomers have a methyl group that could avoid recombination and, therefore, this lack should be counteracted by resonance stabilization of Figure 9 Initiation mechanism proposed by Mukherjee et al 21 applied to both monomers. Figure 10 Resonance stabilization of both radicals allowing initiation reaction.…”

“…Initiation by sodium bisulfite might be explained by a mechanism based on that proposed by Mukherjee et al 21 for monomers containing a methyl group attached to vinyl group. These authors proposed that bisulfite ion resulting from sodium disulfite dissociation in water attacks the vinyl group producing radicals in both species (see Fig.…”

Some observations in the aqueous and emulsion polymerizations of common vinyl monomers initiated by sodium metabisulfite (Na2S2O5) at 50°C

“…Kim also noted the fall in the rate of polymerization at higher bisulfite although Mukherjee et al 4 did not observe such effects at 35OC when the concentration of NaHS03 was as high as 0.20 (m/l). Statistical treatment of the average rate data indicates that the average rate of polymerization is approximately inversely proportional to the 0.62 f 0.06 power of the metabisulfite concentrations.…”

“…Konar and Palit2 reported that potassium or sodium bisulfite (HSO,) could initiate the aqueous polymerization of MMA at a pH of about 4-5 (due to the bisulfite alone) in the presence of nitrogen. They suggested that trace of air in the media might have generated the initiating free radicals by the known redox reaction3 H-SO, + 0 2 -+ SO, + HOa Mukherjee et al 4 later on reported that NaHS03 alone could initiate the aqueous and emulsion polymerizations of MMA, EMA, styrene, etc., but failed to initiate the polymerizations of AN, MA, acrylic acid, and vinyl acetate in the presence of nitrogen. They postulated an overall reaction for the initiating radical: Kim et al [5][6][7][8] reported recently that NaHS03 could initiate the aqueous polymerization of MMA and acrylamide easily, but the emulsion polymerizations of MA and AN could take place only in the presence of a cationic detergent micelles and in the presence of oxygen only.…”

Synthesis of cationic flocculants by the inverse microemulsion copolymerization of acrylamide with 60% 2‐acryloxyethyltrimethyl ammonium chloride in the monomer feed. II. Influence of the formulation composition, hydrophilic‐lipophilic balance, starting polymerization temperature, and reaction time

“…In that work, we proved that DS could initiate AM/ADQUAT copolymerization itself, contrary to what was expected. Mukherjee et al 3 determined that sodium bisulfite (produced by the dissociation of DS in water) was able to produce radicals by a reaction with vinyl monomers having a methyl group on the double-bond carbon, avoiding radical recombination. In fact, no monomer used in that work had this methyl group contributing to steric hindrance, but the radical that formed was stabilized by resonance through the carbonyl group next to the double bond.…”