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Synthesis of high molecular weight water-soluble polymers as low-viscosity latex particles by RAFT aqueous dispersion polymerization in highly salty media

DOI: 10.1021/acs.macromol.2c01071 DOI Help

Authors: Rory J. Mcbride (University of Sheffield) , John F. Miller (Enlighten Scientific LLC) , Adam Blanazs (BASF SE) , Hans-Joachim Hähnle (BASF SE) , Steven P. Armes (University of Sheffield)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Macromolecules , VOL 268

State: Published (Approved)
Published: August 2022
Diamond Proposal Number(s): 28667

Open Access Open Access

Abstract: We report the synthesis of sterically-stabilized diblock copolymer particles at 20% w/w solids via reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization of N,N′-dimethylacrylamide (DMAC) in highly salty media (2.0 M (NH4)2SO4). This is achieved by selecting a well-known zwitterionic water-soluble polymer, poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC), to act as the salt-tolerant soluble precursor block. A relatively high degree of polymerization (DP) can be targeted for the salt-insoluble PDMAC block, which leads to the formation of a turbid free-flowing dispersion of PDMAC-core particles by a steric stabilization mechanism. 1H NMR spectroscopy studies indicate that relatively high DMAC conversions (>99%) can be achieved within a few hours at 30 °C. Aqueous GPC analysis indicates high blocking efficiencies and unimodal molecular weight distributions, although dispersities increase monotonically as higher degrees of polymerization (DPs) are targeted for the PDMAC block. Particle characterization techniques include dynamic light scattering (DLS) and electrophoretic light scattering (ELS) using a state-of-the-art instrument that enables accurate ζ potential measurements in a concentrated salt solution. 1H NMR spectroscopy studies confirm that dilution of the as-synthesized dispersions using deionized water lowers the background salt concentration and hence causes in situ molecular dissolution of the salt-intolerant PDMAC chains, which leads to a substantial thickening effect and the formation of transparent gels. Thus, this new polymerization-induced self-assembly (PISA) formulation enables high molecular weight water-soluble polymers to be prepared in a highly convenient, low-viscosity form. In principle, such aqueous PISA formulations are highly attractive: there are various commercial applications for high molecular weight water-soluble polymers, while the well-known negative aspects of using a RAFT agent (i.e., its cost, color, and malodor) are minimized when targeting such high DPs.

Journal Keywords: Anions; Cations; Colloids; RAFT polymerization; Solution chemistry

Subject Areas: Materials, Chemistry

Instruments: I22-Small angle scattering & Diffraction

Added On: 31/08/2022 09:22


Discipline Tags:

Soft condensed matter physics Chemistry Materials Science Polymer Science

Technical Tags:

Scattering Small Angle X-ray Scattering (SAXS)