Synthesis of block cationic polyacrylamide precursors using an aqueous RAFT dispersion polymerization

Bo Huang; Jie Jiang; Mutian Kang; Pingwei Liu; Hailong Sun; Bo-Geng Li; Wen-Jun Wang

doi:10.1039/c9ra02716e

Synthesis of block cationic polyacrylamide precursors using an aqueous RAFT dispersion polymerization

RSC Adv. 2019 Apr 23;9(22):12370-12383. doi: 10.1039/c9ra02716e. eCollection 2019 Apr 17.

Authors

Bo Huang¹, Jie Jiang¹, Mutian Kang¹, Pingwei Liu^{1

2}, Hailong Sun³, Bo-Geng Li¹, Wen-Jun Wang^{1

2}

Affiliations

¹ State Key Lab of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University 38 Zheda Road Hangzhou 310027 China wenjunwang@zju.edu.cn liupingwei@zju.edu.cn.
² Institute of Zhejiang University - Quzhou 78 Jiuhua Boulevard North Quzhou China 324000.
³ State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University 24 South Section 1, Yihuan Road Chengdu China 610064 sunhl@scu.edu.cn.

Abstract

Synthesis of cationic polyacrylamides (CPAMs) by introducing cationic polymer precursors followed by chain extension of acrylamide (AM) homopolymer blocks via RAFT polymerization is a promising approach for engineering high-performance CPAMs. However, the aqueous solution polymerization of AM usually leads to high viscosity, thus limiting the solid content in the polymerization system. Herein a novel approach is introduced that uses a random copolymer of AM and methacryloxyethyltrimethyl ammonium chloride (DMC) as a macro RAFT chain transfer agent (mCTA) and stabilizer for aqueous RAFT dispersion polymerization of AM. The AM/DMC random copolymers synthesized by RAFT solution polymerization, having narrow dispersities (Đ _s) at different molecular weights and cationic degrees (C _s), could serve as the mCTA, which was confirmed by mCTA chain extension in aqueous solution polymerization of AM under different C _s, solid contents, AM addition contents, extended PAM block lengths, and mCTA chain lengths. The block CPAMs had a Đ value of less than 1.2. A model was developed using the method of moments with consideration of the diffusion control effect, for further understanding the chain extension kinetics. Predicted polymerization kinetics provided an accurate fit of the experimental data. The AM/DMC random copolymers were further used for aqueous RAFT dispersion polymerization of AM under different polymerization temperatures, C _s, and mCTA chain lengths. The resulting products had a milky appearance, and the block copolymers had Đ _s of less than 1.3. Higher C _s and longer chain lengths on mCTAs were beneficial for stabilizing the polymerization systems and produced smaller particle sizes and less particle aggregation. The products remained stable at room temperature storage for more than a month. The results indicate that aqueous RAFT dispersion polymerization using random copolymers of AM and DMC at moderate cationic degrees as a stabilizer and mCTA is a suitable approach for synthesizing CPAM block precursors at an elevated solid content.