NEW POLYMER SYNTHESES - 90 - A-B-A-TRIBLOCK COPOLYMERS WITH HYPERBRANCHED POLYESTER A-BLOCKS

Telechelic oligo(ether-ketone)s containing two trimethylsiloxy end gro ups and one methyl group per repeating unit were prepared by polyconde nsation of -fluoro-2'-methyl-4'-(trimethylsiloxy)benzophenon. The tele chelic character was achieved by cocondensation of a small amount of s ilylated bisphenol-P. The end groups of the silylated oligo(ether-keto ne)s were acetylated by means of acetyl chloride. On the basis of H-1- NMR end group analyses two samples of alpha,omega-bis(acetoxy) oligo(e ther-ketone)s with DP = 14 and DP similar to 28 were obtained. These o ligo(ether-ketone)s and a 70 or 140 fold molar amount of silylated 3,5 -bis(acetoxy) benzoic acid were polycondensed at 270 degrees C in bulk . The resulting A-B-A triblock copolymers were fractionated by dissolu tion in tetrahydrofuran. In three out of four experiments a small frac tion of precipitated material rich in oligo(ether-ketone) was isolated . The purified triblock copolymers were characterized by inherent visc osities and NMR spectra. For those samples containing the long oligo(e ther-ketone) block a low degree of crystallinity was observed after an nealing. Four additional polycondensations were conducted with an init ial reaction temperature of 290 degrees C. In this way a completely so luble and amorphous triblock copolymer was obtained. (C) 1998 John Wil ey & Sons, Inc.