Towards chiral polystyrene based materials: controlled polymerization of p-(2,2′-diphenylethyl)styrene

Abstract

p-(2,2′-Diphenylethyl)styrene (DPES) was polymerized in an atactic, syndiotactic, and isospecific fashion. Atactic polymerization was initiated by 2,2′-azobis(2-methylpropionitrile) (AIBN). Syndiotactic polymer was obtained using the catalyst system TiCp^*Cl₃/MAO. Isospecific polymerization was performed with the homochiral postmetallocene catalystdichloro{trans-1,2-dithiocyclohexanediyl-2,2′-bis(4,6-di-tert-butylphenolato)}titanium/MAO. Optically active isotactic polymers were obtained by a controlled reduction of the molecular weight, employing two different chain transfer methodologies. In addition to 1-hexene as a chain transfer agent (CTA), the use of diethylzinc as a CTA for DPES oligomerization was introduced. Polymers with molecular weights below M_n of 50,000 g mol⁻¹ showed specific rotation values ([α]²³_D) between ±0.2 and 2.2.