New polymer synthesis 99. Hyperbranched poly(ester-imide)s derived from 4,5-dichlorophthalic acid

A new trifunctional monomer was prepared from ethyl-4-(4,5-dichlorophthalimido) benzoate and 4-mercaptophenol. The phenolic OH groups were acetylated,and the carboxylic group was silylated to reduce the melting temperature. A successful homopolycondensation yielding a completely soluble hyperbranched poly(ester-imide) was only obtained when the silylated monomer was used. This branching monomer was polycondensed with a difunctional imide monomer to yield co(polyester-imide)s having a variable degree of branching. Furthermore, copolycondensations with 3-acetoxybenzoic acid or 3,5-bisacetoxybenzoic acid (and their trimethylsilyl esters) were studied. The composition of the resulting copolyesters were checked by elemental analyses and H-1 NMR spectra. The glass transition temperatures (TgS) showed a systematic variation between the values of the parent homopolyesters.