Kinetic study of the oligomerization of styrene in the presence of alpha-thioglycerol - comparison between batch and semi-batch processes

The oligomerization of styrene in the presence of alpha -thioglycerol, a fu nctionalized thiol, was studied in order to control the synthesis of omega -dihydroxylated polystyrene oligomers. Two different reaction processes wer e investigated: a batch process, where all the reactants are mixed together at the beginning of the reaction and a semi-batch process, where the thiol is slowly added to the reaction medium with a constant flow rate. A kineti c study performed by SEC indicated for a batch process an important drift o f the reaction medium composition. As far as the semi-batch process is conc erned, by adding the thiol with a controlled feed of thiol, monomodal oligo mers could be obtained resulting in an excellent yield and a functionality in the range of 0.8 even at high monomer conversion. Moreover, MALDI-TOF ma ss spectrometry of samples obtained by both processes allowed us to demonst rate the presence of very low molecular weight oligomers and of non-functio nalized oligomers. (C) 2001 Elsevier Science Ltd. All rights reserved.