Analysis of poly(ethyl methacrylate)s by on line hyphenation of liquid chromatography at the critical adsorption point and nuclear magnetic resonance spectroscopy

Liquid chromatography at the critical adsorption point (LC CAP) with on-line NMR detection (on-line LC CAP NMR) was utilized for analysis of tacticity distribution of stereo-regular poly(ethyl methacrylate)s (PEMAs). The separation of a model PEMA sample composed of four constituents with similar molar masses (M-w = (14-16) x 10(3) g mol(-1)) differing in their tacticity (rr triad content = 0, 33, 68, and 89%) was achieved by LC CAP with a mixed eluent composed of acetone, acetone-d(6), and cyclohexane. The tacticity composition within each peak eluted from the LC CAP column was directly determined by a 750-MHz H-1 NMR spectrometer that was used as a real-time detector in the continuous-flow mode. Tacticity distribution in a particular PEMA sample with mm/mr/rr = 2/45/53 and narrow molar mass distribution of M-w/M-n, = 1.05 has been revealed by the LC CAP NMR technique.