Stimulus-responsive non-ionic diblock copolymers: protonation of a tertiary amine end-group induces vesicle-to-worm or vesicle-to-sphere transitions

摘要: A well-defined poly(glycerol monomethacrylate) (PGMA) macromolecular chain transfer agent (macro-CTA) with a mean degree of polymerisation (DP) 43 was prepared by reversible addition–fragmentation (RAFT) using morpholine-functionalised trithiocarbonate-based (MPETTC). Chain extension this macro-CTA RAFT aqueous dispersion 2-hydroxypropyl methacrylate (HPMA) at pH 7.0–7.5 produced series four MPETTC-PGMA43-PHPMAy vesicles (where y = 190, 200, 220 or 230). Protonation the morpholine end-group increases hydrophilic character PGMA stabiliser block, which leads to reduction in packing parameter for diblock copolymer chains. However, such pH-responsive behaviour critically depends on value y. For 190 lowering solution 3 induces vesicle-to-worm transition 20 °C according dynamic light scattering, electrophoresis, transmission electron microscopy and turbidimetry studies. This order–order is suppressed presence added electrolyte, screens cationic end-groups. In addition, no change morphology observed temperature neutral pH, regardless value. The nano-objects obtained were also cooled 4 examine their dual stimulus-responsive both triggers. all cases, from either worms afford spheres (or plus relatively short worms) observed. Temperature-dependent oscillatory rheology experiments performed indicated worm-to-sphere cooling °C, degelation. summary, spheres, can be MPETTC-PGMA-PHPMA copolymers first 3, followed °C.