CuBr/N

N

N′

N″

N″-pentamethyldiethylenetriamine-catalyzed self-condensing atom transfer radical polymerization (SCATRP) of N-［4-(α-bromoisobutyryloxy)phenyl］ maleimide (BiBPM) with a large excess of (N

N-dimethylamino)ethyl methacrylate (DMAEMA) was carried out

in which the conversion

relative molecular weight (MW) and its distribution

absolute MW and specific viscosity of the PDMAEMA were monitored by gas chromatography

gel-permeation chromatography coupled with multi-angle laser light scattering and online visometry.The results showed that with the increase of the monomer conversion

the MW and polydispersity of the PDMAEMA increases gradually.The specific viscosity of the so-obtained PDMAEMA in tetrahydrofuran (THF) was significantly lower than that of the linear analogues with comparable MW

indicating the presence of the branched structure.The contraction factor (g′)

as a function of the MW of the branched PDMAEMA

decreases with increasing MW

suggesting that the degree of branching (OB) decreased slowly.The above results suggested that the SCATRP with a large comonomer/inimer feed ratio is a multi-step process: the inimer-initiated ATRP of comonomers forms the primary chains of several repeating units and the SCATRP of the primary chains forms low-MW and high-degree of branching PDMAEMA during the early stage

and the ATRP of DMAEMA initiated by branched PDMAEMA during the later period

gives rise to the high-MW and low-degree of branching PDMAEMA.