Polystyrene with improved chain-end functionality and higher molecular weight by ARGET ATRP

The bromine chain-end functionality of polystyrene (PSt) prepared by activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) was analyzed using 500 MHz H-1 nuclear magnetic resonance (NMR). Bulk polymerization of styrene (St) was carried out with 50 ppm of copper in the presence of tris[2-(dimethylamino)ethyl]amine (Me6TREN) ligand and tin(II) 2-ethylhexanoate [Sn(EH)(2)] reducing agent at 90 degrees C. Due to the use of a low concentration of an active Cu/ligand catalyst complex, it was possible to significantly decrease the occurrence of catalyst-based side reactions (beta-H elimination). As a result, compared to PSt prepared via normal ATRP, PSt with improved chain-end functionality was obtained. For example, at 92% monomer conversion in normal ATRP only 48% of chains retained chain-end functionality, whereas 87% of the chains in an ARGET ATRP still contained halogen functionality. PSt with controlled molecular weight ((M) over bar (n,NMR) = 11600 g.mol(-1), (M) over bar (n,theor.) = 9600 g.mol(-1)) and narrow molecular weight distribution ((M) over bar (w)/(M) over bar (n) =1.14) was prepared under these conditions. In addition, as a result of decreased frequency of side reactions in ARGET ATRP, PSt with relatively high molecular weight was success fully prepared ((M) over bar (n,GPC) = 185000 g.mol(-1), (M) over bar (w)/(M) over bar (n) =1.35).