Tuning Biocompatible Block Copolymer Micelles by Varying Solvent Composition: Core/Corona Structure and Solvent Uptake

Published

May 4, 2017

Author(s)

Tyler J. Cooksey, Avantika Singh, Kim Mai Le, Shu Wang, Elizabeth Kelley, Lilin He, Sameer Vajjala Kesava, Enrique D. Gomez, Bryce E. Kidd, Louis A. Madsen, Megan L. Robertson

Abstract

The structural properties and solvent uptake of biocompatible poly(ethylene oxide-b/}-ε-caprolactone) (PEO-PCL) diblock copolymers in deuterated water (D₂O)/tetrahydrofuran (THF_d8) mixtures were investigated with a combination of small-angle neutron scattering, nuclear magnetic resonance, and transmission electron microscopy. PEO-PCO block copolymers, of varying molecular weight yet constant block ratio, formed spherical micelles through a wide range of solvent compositions. Varying the solvent composition from 10 - 60 vol% THF_d8 in THF_d8/D₂O mixtures was a convenient means of varying the interfacial tension in the micelle system. An increase in THF_d8 content in the bulk solvent increased the solvent uptake within the micelle core, which was comparable for the two series, irrespective of the polymer molecular weight. The two micelle series showed remarkably different behavior in the aggregation number N_agg: in the low molecular weight series N_agg was relatively constant. Differences in the behaviors of the micelle size parameters (core radius and overall micelle radius) as the solvent composition varied originated from the differing trends N_agg for the two micelle series. Incorporation of the known unimer content determined from NMR into the SANS analysis had little impact on the characterized micelle size parameters, yet resulted in an increase in N_agg and decrease in solvent uptake of the core. In summary, the two micelle series showed similar solvent uptake that was independent of the polymer weight, yet significantly different dependencies of their aggregation number and size parameters on the solvent composition.

Citation

Macromolecules

Volume

50

Pub Type

Journals

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Keywords

block copolymer micelles, co-solvent additives, micelle core and solvent interaction, small-angle neutron scattering (SANS), dynamic light scattering (DLS)

Citation

Cooksey, T. , Singh, A. , Le, K. , Wang, S. , Kelley, E. , He, L. , Kesava, S. , Gomez, E. , Kidd, B. , Madsen, L. and Robertson, M. (2017), Tuning Biocompatible Block Copolymer Micelles by Varying Solvent Composition: Core/Corona Structure and Solvent Uptake, Macromolecules, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=922121 (Accessed March 13, 2025)