The reversible addition-fragmentation chain transfer (RAFT) polymerization technique has been employed to synthesize linear ␣, -telechelic polymers with either hydroxyl or carboxyl end groups. Methyl methacrylate, butyl methacrylate, and butyl acrylate were polymerized with RAFT polymerization. The polymerizations exhibited the usual characteristics of living processes. Telechelic polymethacrylates were obtained from a hydroxyl monofunctional RAFT polymer with a two-step chain-end modification procedure of the dithioester end group. The procedure consisted of an aminolysis followed by a Michael addition on the resulting thiol. The different steps of the procedure were followed by detailed analysis. It was found that this route was always accompanied by side reactions, resulting in disulfides and hydrogen-terminated polymer chains as side products next to the hydroxyl-terminated telechelic polymers. Telechelic poly(butyl acrylates) with carboxyl end groups were produced in a single step procedure with difunctional trithiocarbonates as RAFT agents. The high yield in terms of end group functionality was confirmed by a new critical-liquid-chromatography method, in which the polymers were separated based on acid-functionality and by mass spectrometry analysis. Scheme 1. Synthesis of hydroxyl-telechelic polymethacrylates.

State-of-the-art techniques for the mass spectrometric characterization of synthetic polymers have been applied to functional poly(methyl methacrylate), synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization. The polymers were first separated effectively according to functionality by liquid chromatography (LC) at the critical conditions (i.e., almost no influence of molecular weight on retention). The separated polymers were characterized off-line by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), and both off-line and on-line by LC-electrospray-ionization-quadrupole-TOF-MS (LC-ESI-QTOF- MS). The on-line ESI experiments confirmed a clear baseline separation of the hydroxyl-functional prepolymers according to the number of hydroxyl groups. Labile end groups of PMMA, such as the dithioester group, were lost in the MALDI-TOF-MS experiments, while they were observed intact in the ESI-QTOF-MS spectra. This indicates that in the present case ESI is a much softer ionization technique than is MALDI. The ESI-MS experiments provided direct evidence that the RAFT polymers still exhibited living characteristics in the form of the dithio moiety.

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