Anionic living polymerization of macromonomers: Preparation of a particle-like purging reagent and characterization of poly(macromonomer)s

A cross-linked polystyrene particle (Merrifield resin, R-C₆H₅) was reacted with benzoyl chloride in nitrobenzene to produce R-C₆H₄-COC₆H₅ having a benzophenone group, and the R-C₆H₅-COC₆H₅ was reacted with a sodium mirror in THF under 10⁻⁵ mmHg to produce R-C₆H₅-CO⁻C₆H₅Na⁺ containing a benzophenone sodium as a particle-like purging reagent (PPBNa). (4-vinylbenzyl)Polystyrene macromonomers (PSM4: M_n=4.6₂×10³, M_w/M_n=1.0₃ and PSM7: M_n=7.1₀×10³, M_w/M_n=1.0₂) were dried under 10⁻⁶ mmHg for more than 72 h, purified by a special procedure using the PPBNa, and then were living anionically polymerized by sec-BuLi in benzene or n-BuLi in tetrahydrofuran to produce the corresponding poly(PSM)_n star polymers. The resultant star polymers were characterized by gel permeation chromatography equipped with low-angle laser light-scattering (GPC-LALLS), membrane osmometry (OSM), and light-scattering (LS). Anionic living polymerization of the PSM macromonomers was confirmed by the fact that the molecular weight of the poly(PSM)_n increased and by the fact that the initiation efficiency was constant despite an increase in the polymer yields. Some solution properties and specific dimensions characteristic to the poly(PSM)_n star polymers are discussed by comparing the GPC-LALLS, OSM, and LS results for those polymers with the results for linear polystyrenes.