Dendrimer-like miktoarm star terpolymers: A(3)-(B-C)(3) via click reaction strategy

Abstract

Two samples of dendrimer-like miktoarm star terpolymers: (poly(tertbutyl acrylate))(3)-(polystyrene-poly(epsilon-caprolactone))(3) (PtBA)(3)-(PS-PCL)(3), and (PS)(3)-(PtBA-poly(ethylene glycol)(3) were prepared using efficient Cu catalyzed Huisgen cycloaddition (click reaction). As a first step, azido-terminated 3-arm star polymers PtBA and PS as core (A) were synthesized by atom transfer radical polymerization (ATRP) of tBA and St, respectively, followed by the conversion of bromide end group to azide. Secondly, PS-PCL and PtBA-PEG block copolymers with alkyne group at the junction as peripheral arms (B-C) were obtained via multiple living polymerization mechanisms such as nitroxide mediated radical polymerization (NMP) of St, ring opening polymerization (ROP) of epsilon-CL, ATRP of tBA. Thus obtained core and peripheral arms were linked via click reaction to give target (A)(3)-(B-C)(3) dendrimer-like miktoarm star terpolymers. (PtBA)(3)-(PS-PCL)(3) and (PS)(3)-(PEG-PtBA)(3) have been characterized by GPC, DSC, AFM, and SAXS measurements. (PtBA)(3)-(PS-PCL)(3) did not show any self-organization with annealing due to the miscibility of the peripheral arm segments. In contrast, the micro-phase separation of the peripheral arm segments in (PS)(3)-(PtBA-PEG)(3) resulted in self-organized phase-separated morphology with a long period of similar to 13 nm.