Preparation of Poly(ether ketone) Dendrons with Graded Structures

New highly branched poly(ether ketone) dendrons, with graded structures, were synthesized by the convergent approach using aromatic nucleophilic substitution reactions. Four kinds of compounds3,5-bis(4-fluorobenzoyl)anisole, 1; 4-methoxy-3‘,5‘-bis(4-fluorobenzoyl)-biphenyl, 2; 4-methoxy-3‘ ‘,5‘ ‘-bis(4-fluorobenzoyl)-p-terphenyl, 3; and 4-methoxy-3‘ ‘‘,5‘ ‘‘-bis(4-fluorobenzoyl)-p-quaterphenyl, 4(numberedin the order of the phenylene length) were used as the building blocks, where the methoxy groups were the protected form of hydroxy groups. The reactions of 1 with phenol gave the first generation dendron, G1. Next, after the methoxy group of G1 was converted to the hydroxy derivative, G1 − OH by the reaction with aluminum chloride, the resultant phenol functionality of G1 − OH was allowed to react with 2 to yield the second generation dendron: G2. By repeating the procedure, further generations G3 and G4, were prepared using 3 and 4 as the building block, respectively. The 1H and 13C NMR spectra were consistent with the structure of these dendrons. The molecular weight and molecular weight distribution determined by gel permeation chromatography indicated that the dendron posessed remarkably narrow molecular weight distribution after purification by silica gel chromatography. The analysis of these structurally unambiguous dendrons by matrix-assisted laser desorption ionization time of flight is described. The structure of the dendrons were demonstrated with a gradient of phenylene chain lengths from the periphery to the core.