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.

SynopsisQuantitative determination of endgroups of poly(methy1 methacrylate), polystyrene and poly(viny1 acetate) obtained by aqueous initiation with KzSzOs under varied. conditions have been made by the application of two sensitive dye techniques, called the dye partition technique and the dye interaction technique. The description of the dye techniques are given in detail. Sulfate (OSOS-) and hydroxyl (OH) endgroups are generally found to be incorporated in the polymers to an average total of 1.5 to 2.5 endgroups per polymer chain. Hydroxyl endgroups are always present to a fairly large

SpopisA few redox systems containing thiourea as reductant have been found to be quite effective in initiating vinyl polymerization in aqueous media and polymers obtained in the process have all been found to contain amino endgroups to various extents by the application of dye techniques. Quite a few oxidants have so far been utilized for this purpose; among them are ferric chloride (Fe3+), ethylene dibiguanide complex salts of tripositive silver (Ag3+), hydrogen peroxide ( H z~z ) , persulfate (Se0g2-), bromate (Br-In jedem Falle wurden geeignete Startmechanismen vorgesehlagen.

Poly(methy1 methacrylate) samples obtained by aqueous redox initiation with reducing sulfoxy compounds such as HSO,-, SO:-, S,OG-, S,O:-, and S,O% in conjunction with different activators are analysed for endgroup content by the application of dye techniques, and limiting conditions for polymerization are reported in specific cases. Activators used are: (a) metal ions such as Cu2+, Fe3+, and Ag+ ion; (b) KClO, and KBrO,; (c) H,O,, and (d) oxygen. Endgroups incorporated are only nonhydrolysable sulfoxy in case of (a) and (b), and both nonhydrolysable sulfoxy and hydroxyl in case of (c) and (a). ZUSAMMENFASSUNG: An Polymethylmethacrylaten, durch Redoxinitiierung in wal3riger Losung dargestellt, wurden kolorimetrische Endgruppenbestimmungen durchgefiihrt. Die Redoxsysteme bestanden aus einer Sulfoxygruppe, HSO,-, SO;-, S,O;-, S, O:oder S,Ogals Reduktionsmittel und einem der folgenden Aktivatoren: (a) Metallionen: Cu2+, Fe3+ und Ag+; (b) Kaliumchlorat und -bromat ; (c) Wasserstoffperoxid und (d) Sauerstoff. Als Endgruppen werden im Falle (a) und (b) nur hydrolysebestandige Sulfoxygruppen eingebaut, bei (c) und (d) sowohl Sulfoxy-als auch Hydroxylgruppen.

Hydroxyl endgroups were incorporated in polymers of methyl methacrylate obtained by initiation with hydrogen peroxide with the monomer in bulk and in aqueous solution. Hydroxyl endgroups in the respective polymer samples were estimated by means of the dye interaction technique. Aqueous photoinitiation with hydrogen peroxide was found to incorporate an average of about 1–1.5 hydroxyl endgroups per polymer chain, depending on the concentration of the initiator used. Aqueous thermal (60°C.) polymerization leads to an average of nearly 1 hydroxyl endgroup per chain. Polymerization in the dark at room temperature was carried out by activation with Fe2+ and Fe3+ ions, and an average of nearly 1 hydroxyl endgroup per chain was obtained in both cases. Bulk polymerization (photo‐ and thermal) produces polymer having nearly 1.3–1.7 hydroxyl endgroups per chain.