PH and Salt Effects on Surface Activity and Self-Assembly of Copolymers Containing a Weak Polybase

Neta Cohen, Lana Binyamin, Yael Levi-Kalisman, Geoffrey Y. Berguig, Anthony Convertine, Patrick Stayton, Rachel Yerushalmi-Rozen

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Copolymers with well-defined architectures, controlled molecular weights, and narrow molar mass dispersities (A) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The resultant polymers contain different combinations of the pH-responsive monomer 2-(diethylaminoethyl) methacrylate (DEAEMA), the hydrophobic comonomer butyl methacrylate (BMA), and a neutral hydrophilic stabilizing monomer polyethylene glycol monomethyl ether methacrylate (designated O950). Surface tension and cryo-TEM measurements of native and heavy-atom stained samples were used to characterize the pH and salt responsiveness of the different polymers as a function of their composition. These studies indicate that while the polymers predominately self-assemble to form spherical micelles, a narrow size distribution is observed in aqueous solutions of poly(O950)-b-(BMA) and poly(O950)-b-(DEAEMA-co-BMA), whereas a broad size distribution characterizes the assemblies of poly(O950)-b-(DEAEMA) and poly(DEAEMA-co-BMA). In the latter case, micelles having diameters around 15-25 nm are found along with smaller aggregates (about 10 nm) mostly arranged in elongated necklace-like structures. The pH and salt-responsiveness of the DEAEMA residue, as indicated by the surface activity of the copolymers, was found to depend on the nature of the additional components: covalently linked hydrophobic groups (BMA) moderated the pH response of the copolymer as compared to nonionic and hydrophilic groups as in poly(O950)-b-(DEAEMA). These results suggest that mutual interactions among the building blocks of self-assembling copolymers should be taken into account when designing responsive copolymers.

Original languageEnglish
Pages (from-to)9286-9292
Number of pages7
JournalLangmuir
Volume32
Issue number36
DOIs
StatePublished - 13 Sep 2016

ASJC Scopus subject areas

  • Materials Science (all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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