ABSOLUTE, ONLINE MONITORING OF MOLAR-MASS DURING POLYMERIZATION REACTIONS

To perform on-line monitoring of the absolute weight-averaged mass, M- W, of the polymers produced in a polymerization reaction, refractomete r (RI), ultraviolet absorbance (UV), and time-dependent static light s cattering (TDSLS) detectors were placed in series, and a diluted strea m of reactant solution was made to flow through them. The technique al lows rapid determination of time-dependent reaction ''signatures'' and end-product masses. Hence the effects of changing reaction conditions such as reactant concentrations, temperature, and initiators can be q uickly assessed. Such a technique is expected to be of wide utility in characterizing polymerization reactions, both on the laboratory scale , where new polymers are synthesized and conditions optimized, as well as on the industrial scale, where on-line quality control can be perf ormed. For stepwise reactions, the RI and TDSLS detectors are sufficie nt for determination of M-W, whereas for free radical reactions, the p olymer concentration must be measured in order to obtain the tradition ally defined M-W (i.e. without monomer taken into consideration). The latter was achieved for poly(vinyl pyrrolidinone) polymerization by me asuring the monomer concentration with the UV detector. As a further m easure of characterization, a single capillary viscometer was also pla ced in series with the other instruments. This allowed the reduced vis cosity to be monitored simultaneously.