Air-stable and recoverable catalyst for copper-catalyzed controlled/living radical polymerization of styrene; in situ generation of Cu(I) species via electron transfer reaction

Copper-catalyzed controlled/living radical polymerization (LRP) of styrene (St) was conducted using the silica gel-supported CuCl₂/N, N, N′, N′, N″-pentamethyl-diethylenetriamine (SG-CuCl ₂/PMDETA) complex as catalyst at 110°C in the presence of a definite amount of air. This novel approach is based on in situ generation and regeneration of Cu(I) via electron transfer reaction between phenols and Cu(II). Sodium phenoxide or p-methoxyphenol was used as a reducing agent of Cu(II) complexes in LRP. The number-average molecular weight, M_n,GPC, increases linearly with monomer conversion and agrees well with the theoretical values up to 85% conversion The molecular weight distribution, M _w/M_n, decreases as the conversion increases and reaches values below 1.2. The catalyst was recovered in aerobic condition and reused in copper-catalyzed LRP of St. For the second run, the number-average molecular weights increased with monomer conversion and the polydispersities decreased as the polymerization proceeded and reached to the value <1.3 at 81% conversion. The recycled catalyst retained 90% of its original activity in the subsequent polymerization.