Ipso-Arylative polymerization as a route to π-conjugated polymers: synthesis of poly(3-hexylthiophene). Issue 23 (29th May 2018) - Shih, Feng-Yang
Abstract : Palladium-catalyzed ipso -arylative polymerization of diphenylcarbinol-substituted thiophene derivatives proceeds to reasonably high molecular weights, but is limited by side reactions. Abstract : ipso -Arylative cross-coupling with two 3-hexylthiophene derivatives, (5-bromo-4-hexylthiophen-2-yl)diphenylmethanol and 2-(5-bromo-4-hexylthiophen-2-yl)propan-2-ol, has been used to prepare poly(3-hexylhiophene) (P3HT) as a model conjugated polymer. P3HT with number-average molecular weights ranging from 8–20 kg mol −1 ( Đ 1.4–2.2) was prepared from 5-bromo-4-hexylthiophen-2-yl)diphenylmethanol with a Pd(OAc)2 /PCy3 /Cs2 CO3 catalyst system. Only oligomerization of 2-(5-bromo-4-hexylthiophen-2-yl)propan-2-ol ( M n ≈ 3 kg mol −1 ) was observed under similar conditions. Studies with model compounds suggest that side reactions involving end-group loss limit ultimate molecular weights.