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 1 H 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 (Me 6 TREN) ligand and tin(II) 2‐ethylhexanoate [Sn(EH) 2 ] reducing agent at 90 °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 ( β ‐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 _ n,NMR = 11 600 g · mol −1 , M _ n,theor. = 9 600 g · mol −1 ) and narrow molecular weight distribution ( M w / M 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 successfully prepared ( M _ n,GPC = 185 000 g · mol −1 , M w / M ₙ = 1.35). magnified image
No takes yet. Share an insight, caveat, or question.
Jakubowski et al. (2007) studied this question.