Phase separations and self-assembly of hydrophilic polymers and double hydrophilic block copolymers

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 an environment for enzymatic reactions. Furthermore, the self-assembly of block copolymers constitutes a timely research area in polymer science with implications for applications like sensing or drug-delivery. Here, the phase separation and formation of water-in-water emulsions of different ultra-high molar mass poly(acrylamides) and pullulan was investigated. The ultra-high molar mass poly(acrylamides) were synthesised via photo iniferter reversible addition–fragmentation chain-transfer (PI RAFT) polymerisation (Mn > 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, stabilised by different stabilisers. Confocal laser scanning microscopy (CLSM) imaging showed that at first polymer-containing droplets in water were formed directly after dispersion and water droplets in polymer matrix after phase separation. Furthermore, a pH sensitive w/w emulsion was observed using pullulan ultra-high molar mass poly(acrylamides). Additionally, the self-assembly of double hydrophilic block copolymers (DHBC), based on poly(acrylamides) in organic and aqueous environment was investigated. The hydrophilic block copolymer induced phase separation at high concentration in aqueous solution leading to giant droplets. However, the mesoscale phase separation at high concentration (>20 wt%) was reversible upon dilution. In order to stabilise the giant droplets during dilution crosslinking via oxime formation was applied. However, the successful crosslinked block copolymer droplets were not stable upon dilution. Additionally, the block copolymer displayed aggregates at lower concentration in aqueous and organic solution. Furthermore, the unprecedented aggregation behaviour of high molar mass block copolymer poly(N,N-diethylacrylamide)-b-poly(4-acryloylmorpholine) (PDEA-b-PAM) (Mn > 400 kg mol−1) in organic solvent tetrahydrofuran (THF) was investigated. The aggregate formation was assigned to the unprecedented upper critical solution temperature behaviour of PAM in THF at elevated concentrations (> 6 wt.%) and high molar masses. With adequate stability and required concentration, aggregates formed via DHBC or w/w emulsion open pathways for potential biomedical applications in the future