Effects of aging on some anionic initiators

The effects of aging on sodium naphthalene and sodium α‐methylstyrene initiators, prepared in 1957, were investigated. The green sodium naphthalene had turned brown and faded; the aged sample failed to initiate the polymerization of α‐methylstyrene at low temperature. Naphthalene had been completely converted into dihydronaphthalene; the retention of the brown color reflected a relative stability of anions of the latter. The freshly prepared brown sodium‐dihydronaphthalene complex was also ineffective for polymerization of α‐methylstyrene. No evidence for the cleavage of the ether solvent (tetrahydrofuran) on aging was obtained. The aged sodium α‐methylstyrene initiator retained its vivid red color and effectiveness in the polymerization of α‐methylstyrene. The inherent better stability of dianions than of radical anions was thus confirmed. Since the sodium α‐methylstyrene initiator was actually a low molecular weight “living” polymer, the 7‐yr. aging test demonstrated, in effect, the “longevity” of living polymers. The structure of the “living tetramer” of α‐methylstyrene was discussed in the light of previous studies and present results. Apparent discrepancies were pointed out, and the necessity of more comprehensive studies was indicated.