Hyperbranched Conductive Polymers Constituted of Triphenylamine
- PDF / 262,215 Bytes
- 5 Pages / 420.48 x 639 pts Page_size
- 66 Downloads / 212 Views
structure, it usually requires extensive intermediate purification of the products at every protection-deprotection step of the growth process. This makes dendritic polymers expensive and difficult to produce on a large scale. Hyperbranched polymers can be obtained by a one-
~
N-0L-
--
M
gWr
Arý
Scheme 1 179 Mat. Res. Soc. Symp. Proc. Vol. 600 © 2000 Materials Research Society
step process, where an ABx-type monomer undergoes self-condensation polymerization as first discussed theoretically by Flory in 19525. The advantage of this one-pot ABx approach lies in its potential for greater general applicability. It is important to produce hyperbranched polymers on a large scale at a reasonable cost. But this method involves the loss of control in molecular weight, accompanied by a broad molecular weight distribution. We report here the preparation of a hyperbranched conjugated polymer containing triphenylamine by the Grignard reaction of tris(4-bromophenyl)amine 1 (Scheme 1). Polymer 3 was also obtained via the Pd-catalyzed coupling of N,N-bis(4-bromophenyl)-4animobenzeneboronic acid 4. Oligomeric and polymeric materials based on triphenylamine have been attracted much attention because of their stability and useful properties such as electrical conductivity and electroluminesence 6 8 . EXPERIMENTAL Polymerization of tris(4-bromophenyl)amine 1 to polymer 3 via a Grignard route To tris(4-bromophenyl)amine 1 in dry THF was added a 1.6 M n-BuLi solution at -78°C under argon. The mixture was stirred for 10 min. To the lithiate was added MgBr 2 "Et2O in dry diethyl ether at -78 0 C. The yellow solution was warmed to room temperature and was added to Ni(acac)2 in THF. The dark green mixture was refluxed for 24 h, and then water was added at room temperature. The solution was concentrated in vacuo, and the polymer was precipitated from petroleum ether. After washing with a dilute HCl solution, water, and methanol and drying, a light yellow powder was obtained. M.p. 192-199 0 C. N,N-Bis(4-bromophenyl)-4-aminobenzeneboronic acid 4 To a solution of amine 1 in dry diethyl ether was added n-BuLi at -78 0 C under argon. The mixture was stirred for 15 min and then added to trimethyl borate in diethyl ether at -780 C. The solution was stirred for 15 min and then allowed to warm to room temperature. After stirred for 20 h, the solution was treated with 2 N HCl. The ether layer was extracted with a KOH solution. The combined aqueous solution was washed with ether and then acidified with 6 N HCI to pH 3 at 0°C. A gray powder was obtained by filtration, washed with water and dried in vacuo. M.p. 186-198 0 C. Preparation of hyperbranched polymer 3 via Pd-catalyzed coupping To a mixture of benzene, a 2 M Na 2 CO 3 solution, and Pd(PPh3 )4 was added acid 4 under argon. The mixture was refluxed for 20 h and then cooled to room temperature. The whole mixture was poured into acetone. The solid material was collected by filtration, washed with 1 N HCI. After drying in vavuo, the hyperbranched polymer 3 was obtained. M.p.> 5001C. Measure
Data Loading...
