Tuning Cationic Block Copolymer Micelle Size by pH and Ionic Strength

Dustin Sprouse, Yaming Jiang, Jennifer E. Laaser, Timothy P. Lodge, Theresa M. Reineke

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


The formation, morphology, and pH and ionic strength responses of cationic block copolymer micelles in aqueous solutions have been examined in detail to provide insight into the future development of cationic micelles for complexation with polyanions such as DNA. Diblock polymers composed of a hydrophilic/cationic block of N,N-dimethylaminoethyl methacrylate (DMAEMA) and a hydrophobic/nonionic block of n-butyl methacrylate (BMA) were synthesized [denoted as DMAEMA-b-BMA (X-Y), where X = DMAEMA molecular weight and Y = molecular weight of BMA in kDa]. Four variants were created with block molecular weights of 14-13, 14-23, 27-14, 27-29 kDa and low dispersities less than 1.10. The amphiphilic polymers self-assembled in aqueous conditions into core-shell micelles that ranged in size from 25-80 nm. These cationic micelles were extensively characterized in terms of size and net charge in different buffers over a wide range of ionic strength (0.02-1 M) and pH (5-10) conditions. The micelle core is kinetically trapped, and the corona contracts with increasing pH and ionic strength, consistent with previous work on micelles with glassy polystyrene cores, indicating that the corona properties are independent of the dynamics of the micelle core. The contraction and extension of the corona scales with solution ionic strength and charge fraction of the amine groups. The aggregation numbers of the micelles were obtained by static light scattering, and the Rg/Rh ratios are close to that of a hard sphere. The zeta potentials of the micelles were positive up to two pH units above the corona pKa, suggesting that applications relying on micelle charge for stability should be viable over a wide range of solution conditions.

Original languageEnglish (US)
Pages (from-to)2849-2859
Number of pages11
Issue number9
StatePublished - Sep 12 2016

Bibliographical note

Funding Information:
This project was partially funded by the National Institutes of Health (NIH) Directors New Innovator Award program (1 DP2 OD00666901) and partially funded by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-1420013.

Publisher Copyright:
© 2016 American Chemical Society.

MRSEC Support

  • Primary

PubMed: MeSH publication types

  • Journal Article
  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.


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