Tuning the Solubility of Copper Complex in Atom Transfer Radical Self-Condensing Vinyl Polymerizations to Control Polymer Topology via One-Pot to the Synthesis of Hyperbranched Core Star Polymers

摘要

In this paper, we propose a simple one-pot methodology for proceeding from atom transfer reaction-induced conventional free radical polymerization (AT-FRP) to atom transfer self-condensing vinyl polymerization (AT-SCVP) through manipulation of the catalyst phase homogeneity (i.e., CuBr/2,2'-bipyridine (CuBr/Bpy)) in a mixture of styrene (St), 4-vinyl benzyl chloride (VBC), and ethyl 2-bromoisobutyrate. Tests of the solubilities of CuBr/Bpy and CuBr₂/Bpy under various conditions revealed that both temperature and solvent polarity were factors affecting the solubility of these copper complexes. Accordingly, we obtained different polymer topologies when performing AT-SCVP in different single solvents. We investigated two different strategies to control the polymer topology in one-pot: varying temperature and varying solvent polarity. In both cases, different fractions of branching revealed the efficacy of varying the polymer topology. To diversify the functionality of the peripheral space, we performed chain extensions of the resulting hyperbranched poly(St-co-VBC) macroinitiator (name as: hbPSt MI) with either St or tBA (tert-butyl acrylate). The resulting hyperbranched core star polymer had high molecular weights (hbPSt-g-PSt: M_n = 25,000, Đ = 1.77; hbPSt-g-PtBA: M_n = 27,000, Đ = 1.98); hydrolysis of the tert-butyl groups of the later provided a hyperbranched core star polymer featuring hydrophilic poly(acrylic acid) segments.