A novel reactive phosphonium-containing polyelectrolyte with multiple reactivities: monomer synthesis, RAFT polymerization and post-polymerization modifications

Abstract

A reactive polyelectrolyte can be defined as a kind of functional polymer which possesses not only the basic properties of a polyelectrolyte but also wide post-polymerization modification possibilities, which can be achieved via various reactions. In this study, we first introduce a well-defined phosphonium polyelectrolyte containing three reactive hydroxymethyl groups which are bonded directly to a phosphorus atom. First, a novel phosphonium-containing monomer, namely 4-vinylbenzyl-(trihydroxymethylphosphonium) chloride (VBzTHPC), was designed and synthesized from tetrakis(hydroxymethyl) chloride (THPC), a commercial product from phosphine (PH₃) tail gas. The efficient, controlled polymerization of VBzTHPC was achieved by using reversible addition–fragmentation chain transfer (RAFT) polymerization in N,N′-dimethylformamide (DMF). First-order linear kinetic plots were observed with different molecular weights and narrow molecular weight distributions (M_w/M_n typically below 1.30) by adjusting the polymerization conditions. These adjustments included the temperature (60 and 70 °C), monomer concentration (20, 25 and 33 wt%), types of initiator (AIBN and AIVN) and chain transfer agent. The hydroxymethyl-containing polyelectrolyte was readily converted to the corresponding non-electrolytic linear polymer with alkali treatment under mild conditions, and underwent a substitution reaction with secondary amine compounds without any catalysts. In addition, the water-soluble polyelectrolyte shows high reactivity with metal ions, and silver particles (D_h = 104 nm) can be efficiently obtained with PVBzTHPC as a reducing agent.