Synthesis of High Molecular Weight Water-Soluble Polymers as Low-Viscosity Latex Particles by RAFT Aqueous Dispersion Polymerization in Highly Salty Media

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 (NH 4 ) 2 SO 4 ). 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. 1 H 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. 1 H 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.

Histidine‐Functionalized Diblock Copolymer Nanoparticles Exhibit Enhanced Adsorption onto Planar Stainless Steel

“…DMF GPC analysis indicated relatively high copolymer dispersities (Figure S3, Supporting Information), which are not uncommon for PISA formulations when targeting a relatively high DP for the core‐forming block. [ 40,56–58 ] Nevertheless, DLS analysis of the resulting series of PGEO5MA 46 ‐PIPGMA y nanoparticles indicated relatively narrow particle size distributions in each case (DLS polydispersity ≤ 0.06), see Figure . TEM analysis confirmed a spherical morphology for such nanoparticles ( Figure a,b).…”

Low-Viscosity Route to High-Molecular-Weight Water-Soluble Polymers: Exploiting the Salt Sensitivity of Poly(N-acryloylmorpholine)

“…In view of these observations, an ammonium sulfate concentration of 0.60 M was selected for the aqueous dispersion polymerization formulation explored in the present study. This salt concentration is significantly lower than that reported in the literature for a wide range of aqueous dispersion polymerization formulations conducted in the presence of ammonium sulfate. ,,− ,,,− …”

“…Each of these water-soluble polymers has been reported to exhibit salt-tolerant behavior. 22,24,26,35,38 The target PNAM DP was 3000 and 1 H NMR spectroscopy studies of the final reaction mixture confirmed that more than 99% NAM conversion is obtained in each case.…”

“…To complement the non-ionic salt-tolerant PHEAC 216 steric stabilizer, we selected a cationic polyelectrolyte (PATAC 242 ), an anionic polyelectrolyte (PAMPS 230 ), and a zwitterionic polyelectrolyte (PMPC 139 ), see Scheme . Each of these water-soluble polymers has been reported to exhibit salt-tolerant behavior. ,,,, The target PNAM DP was 3000 and 1 H NMR spectroscopy studies of the final reaction mixture confirmed that more than 99% NAM conversion is obtained in each case.…”

Ultra-High-Molecular-Weight, Narrow-Polydispersity Polyacrylamides Synthesized Using Photoiniferter Polymerization to Generate High-Performance Flocculants

“…Nevertheless, several articles using conventional RAFT polymerization technology have reported the synthesis of acrylamide-based, high-molecular-weight polymers . For example, CRP methods include low-temperature redox initiation in conventional gel polymerization, − enzyme-mediated RAFT solution polymerization, and under biphasic “water-in-water emulsion” high salt conditions . However, each report highlights the advantages and disadvantages of a selected technique, such as wide polydispersity values for the AB block copolymer flocculants synthesized by Dao et al Recently, photomediated or “photoiniferter” polymerization technology has been reported to be an effective tool to generate various acrylamide-based (co)­polymers with ultra-high molecular-weights and narrow polydispersity values. − Although similar to conventional RAFT polymerization technology through the use of either trithiocarbonate or xanthate chain transfer agents, the major difference is the lack of an external initiating radical source (e.g., thermal or redox initiation) .…”