CHEMICAL MODIFICATION OF POLY(ETHER ETHER KETONE) FOR SIZE-EXCLUSION CHROMATOGRAPHY AT ROOM-TEMPERATURE .1. ABSOLUTE MOLECULAR-MASS DETERMINATION FOR SULFONATED PEEK

A new method for poly(ether ether ketone) (PEEK) molecular-mass charac terization by room-temperature (r.t.) size (steric) exclusion chromato graphy (s.e.c.) based on a derivatization procedure that improves the polymer solubility is described. Upon dissolution in 99.5% sulfuric ac id at room temperature, PEEK is chemically modified by sulfonation of phenyl rings without polymer degradation. As complete sulfonation is a chieved, the reproducibility of the chemical modification is ensured a s well as the increase of molecular mass. Sulfonated PEEK is soluble a t room temperature in different solvents suitable for s.e.c. N-Methyl- 2-pyrrolidine (NMP) is selected as PEEK s.e.c. solvent. Owing to the p olyelectrolyte nature of sulfonated PEEK, a salt (0.1 M LiBr) is added to NMP. Various broad-dispersity PEEK standards are used to establish specific and universal calibrations. The viscosity laws of sulfonated PEEK in NMP + LiBr (0.1 M), in methanesulfonic acid (MSA) and in 99.5 % H2SO4 are determined. As sulfonated PEEK is a hygroscopic polymer, s ome spectroscopic methods are developed to determine the absolute conc entration of the standards in order to perform accurate viscometric ex periments giving the Mark-Houwink-Sakurada parameters in NMP-salt and in MSA. The s.e.c. universal calibration curve is constructed with pol y(methyl methacrylate) narrow-dispersity standards.