Abstract
Poly(sodium2-(acrylamido)-2-methylpropanesulfonate)-block-poly(sodium11-(acrylamido)undecanoate) (PAMPS–PAaU) was synthesized via reversible addition-fragmentation chain transfer (RAFT)-controlled radical polymerization. The “living” polymerization of PAaU was evidenced by the fact that the molecular weight distribution was narrow (Mw/Mn = 1.23). The pH-induced association behavior of PAMPS–PAaU in 0.1 M NaCl aqueous solutions as a function of solution pH was investigated by 1H NMR spin-spin relaxation time, dynamic light scattering (DLS), static light scattering (SLS), and fluorescence probe techniques. These results indicated that PAMPS–PAaU formed polymer micelles in 0.1 M NaCl aqueous solutions at pH < 9. At pH = 8–9, the polymer formed the micelles intramolecularly due to hydrophobic self-association of the PAaU block within the single polymer chain. On the other hand, at pH < 8, micellization occurred intermolecularly to form polymer micelles comprising hydrophobic PAaU cores and hydrophilic PAMPS shells.
Highlights
Amphiphilic diblock copolymers form micelles in water in which hydrophobic blocks constitute a core and hydrophilic blocks form shells [1]
All measurements were made with 0.1 M NaCl aqueous solutions to avoid an effect of a small change in the ion strength resulting from a small amount of NaOH or HCl added to the solutions
Gel-permeation chromatography (GPC), was 75, because the terminal phenyl protons in PAMPS macro-CTA were overlapped with the pendant amide groups
Summary
Amphiphilic diblock copolymers form micelles in water in which hydrophobic blocks constitute a core and hydrophilic blocks form shells [1]. We previously synthesized poly(sodium2-(acrylamido)-2-methylpropanesulfonate)-blockpoly(sodium6-(acrylamido)hexanoate) (PAMPS–PAaH) via RAFT radical polymerization, and investigated its pH-induced association behavior in 0.1 M NaCl aqueous solutions with dynamic light scattering (DLS), static light scattering (SLS), 1 H NMR relaxation, and fluorescence probe techniques [11]. Paper, we report on the pH-induced self-association behavior of a diblock copolymer hysteresis (PAMPS–PAaU). In this paper,of wepoly(sodium2-(acrylamido)-2-methylpropanesulfonate) report on the pH-induced self-association behavior(PAMPS). (PAaU), which has a longer pendant alkyl chain than and that copolymer (PAMPS–PAaU) of poly(sodium2-(acrylamido)-2-methylpropanesulfonate). (PAaU), which using has a longer pendant alkyl chain than that of (Chart in1).anThe diblock copolymer will exhibit pH-induced self-association due toagent the The diblock of copolymer will exhibit pH-induced due focused to the selective protonation of association and residues dissociation behavior of PAMPS–PAaU aqueous as characterized using the carboxylate at low pH values.
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