All-Aqueous Multi-phase Systems and Emulsions Formed via Low-Concentration Ultra-high-Molar Mass Polyacrylamides

Abstract

Aqueous multi-phase systems have attracted a broad interest in recent years, which is mainly due to their applicability in biology for purification and isolation of biomolecules and also for separation of particles as well as environment for enzymatic reactions. Here, three polyacrylamides poly(N,N-dimethylacrylamide), poly(acrylamide), and poly(4-acryloylmorpholine) with ultrahigh molar mass were synthesized via photo-induced reversible addition−fragmentation chain-transfer polymerization (M n > 700,000 g•mol −1 ). The polymers were combined to form aqueous multi-phase systems with low total polymer concentration as low as 1.1 to 2.1 wt %. Furthermore, the aqueous multi-phase system could be transformed into water-in-water (w/w) emulsions, stabilized by layered double hydroxide nanoparticles. Due to the low polymer content, these aqueous multi-phase systems open up new pathways, for example, in the separation of biomolecules or the compartmentalization of aqueous environments in catalysis.

pH sensitive water-in-water emulsions based on the pullulan and poly(N,N-dimethylacrylamide) aqueous two-phase system

“…2-(((Ethylthio)carbonothioyl)thio)-2-methylpropanoic acid (EMP), 46,47 RITC-PDMA 17 and FITC-Pull 48,49 were synthesised according to the literature.…”

“…In recetn years, various studies showed a significant influence of the molar mass to the critical polymer concentration. 13,17,18 Due to the high biocompatibility, water-in-water (w/w) emulsions based on ATPS have received increased attention recently. 19,20 The dispersion of two thermodynamically incompatible aqueous solutions of macromolecules, e.g.…”

“…Different polymer mixtures were used in ATPS for w/w emulsion formation, for example, PEG and Dex 21 or different variations of polyacrylamides. 17 Nevertheless, the polymer combination PEG and Dex is most commonly utilised for the formation of w/w emulsions. Classic emulsions such as water-in-oil (w/o) or oil-in-water (o/w) emulsions can be stabilised by surfactants or larger particles.…”

“…40,41 These studies on block copolymer self-assembly are an indication that polyacrylamides such as PDMA might be a good choice for an ATPS and the formation of w/w emulsions in combination with Pull. 17,40,42 PDMA featuring different molar masses can be synthesised via reversible addition-fragmentation chain transfer (RAFT) polymerisation techniques e.g. photo-iniferter (PI)-RAFT polymerisation, 43,44 which gives a handle towards tailored ATPS and w/w emulsion formation.…”

Multicompartment Hydrogels

“…These emulsions are often based on two different immiscible polymers, e.g., dextran/PEG, [170][171][172] guar/ amylopectin/gelatin, [173] gelatin/dextran [174] or high molecular weight poly(acrylamides). [175] Commonly such emulsions are stabilized by nanoparticles, i.e., a Pickering emulsion approach is used, [176][177][178] which is required due to the low interfacial tension in an aqueous two-phase system (ATPS) as well as the broad interface of both phases. [179,180] W/W emulsions constitute an ideal option for compartmentalized hydrogels, as they are based on aqueous environments completely (Figure 7d).…”