Bulk polymerization of styrene and methyl methacrylate using tetraphenylbisphosphine as an initiator

In this study a controlled polymerization of styrene (S) and methyl methacr ylate (MMA) with tetraphenylbisphosphine (TPhBP) as the initiator in bulk w as carried out, using UV light as the energy source. The yield of polymeriz ation was up to 15% for PS and up to 62% for PMMA. TPhBP is decomposed to f orm 'PPh2 radicals, or is oxidized to form bisphosphine oxide. Only non-oxi dized TPhBP initiates the photo-poly merization. For S and MMA an insignifi cant portion of photo- and thermal-polymerization was detected. In the pres ence of oxygen the phosphine end-groups of the polymer are oxidized to -PO( Ph)(2) groups. The molecular weights of PMMA were determined from H-1 NMR s pectra and the molecular weights of PMMA and PS were determined by gel perm eation chromatography (GPC) measurements. With increasing concentration of the initiator the molecular weight decreases and at a high concentration of the initiator the molecular weight decreases with conversion. The polydisp ersity decreases with increasing concentration of TPhBP. Termination occurs by combination of primary radicals (PPh2)-P-., by combination of macroradi cals, and by chain transfer to the initiator. Because of different types of termination the ratio between the tail -CH2P(Ph)(2) and the head -C(CK3,CO OCH3)P(Ph)(2) groups is about 4 to 1, and decreases with increasing concent ration of the initiator.