(49d) Novel Hyperbranched Cationic Polyacrylamide: Tailoring and Flocculation Properties

Polyacrylamides (PAMs) and its derivatives play an important role in sewage treatment, oil recovery, and within the mining and paper industries. Most commercial PAMs flocculants are linear random copolymers. It is unclear if flocculation performances of PAMs could be improved by offering them with 3-D topological structures and their structure effects on flocculation performances. Herein, a cationic hyperbranched PAM having a core-shell structure with a hyperbranched acrylamide homopolymer core and [2-(methacryloxy) ethyl]trimethyl ammonium chloride (DMC) block arms locating at polymer chain end was synthesized via aqueous reversible addition-fragmentation chain transfer (RAFT) polymerization using a core-first semi-batch strategy. Hyperbranched polyacrylamides (b-PAM) were prepared by adding N,N’-Methylenebisacrylamide (BisAM) into acrylamide solutions at a constant speed, using 3-(((benzylthio) carbonthioy) thio) propanoic acid (BCPA) as a chain-transfer agent and ammonium persulfate (APS) as initiator. Cationic hyperbranched polyacrylamides (b-CPAMs) were prepared by RAFT polymerization of DMC using b-PAM as a multi-functional macro-RAFT agent. The b-CPAMs having branching densities (BDs) of 7.2-11.7 C/1000Cs and length of cationic chain terminals of 40-134 DMC units were produced. The products, whose molecule weight ranged from 2400-4300 kg/mol, were then used as flocculants in the flocculation of titanium dioxide suspensions. The flocculation performance was superior to commercial cationic linear random copolymer flocculants with both high molecular weight and cationic degree. The b-CPAMs had an excellent flocculation performance even at very low polymer dosages. It was found that higher BD and longer cationic blocks would help to promote its flocculation performance.