Structure of PEP-PEO block copolymer micelles: exploiting the complementarity of small-angle X-ray scattering and static light scattering

The structure of large block copolymer micelles is traditionally determined by small‐angle neutron scattering (SANS), covering a large range of scattering vectors and employing contrast variation to determine the overall micelle morphology as well as the internal structure on shorter length scales....

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Bibliographic Details
Published in:	Journal of applied crystallography Vol. 44; no. 3; pp. 473 - 482
Main Authors:	Jensen, Grethe Vestergaard, Shi, Qing, Hernansanz, María J., Oliveira, Cristiano L. P., Deen, G. Roshan, Almdal, Kristoffer, Pedersen, Jan Skov
Format:	Journal Article
Language:	English
Published:	5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01-06-2011 Blackwell Publishing Ltd
Subjects:	Block copolymers Blocking contrast variation Copolymers Crystal structure Crystallography Ethyl alcohol Light scattering Micelles Morphology SAXS Scattering Small angle X ray scattering static light scattering
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Summary:	The structure of large block copolymer micelles is traditionally determined by small‐angle neutron scattering (SANS), covering a large range of scattering vectors and employing contrast variation to determine the overall micelle morphology as well as the internal structure on shorter length scales. The present work shows that the same information can be obtained by combining static light scattering (SLS) and small‐angle X‐ray scattering (SAXS), which provide information on, respectively, large and short length scales. Micelles of a series of block copolymers of poly(ethylene propylene)‐b‐poly(ethylene oxide) (PEP–PEO) in a 70% ethanol solution are investigated. The polymers have identical PEP blocks of 5.0 kDa and varying PEO blocks of 2.8–49 kDa. The SLS contrasts of PEP and PEO are similar, providing a homogeneous contrast, making SLS ideal for determining the overall micelle morphology. The SAXS contrasts of the two components are very different, allowing for resolution of the internal micelle structure. A core–shell model with a PEP core and PEO corona is fitted simultaneously to the SAXS and SLS data using the different contrasts of the two blocks for each technique. With increasing PEO molecular weight, a transition from cylindrical to spherical micelles is observed. This transition cannot be identified from the SAXS data alone, but only from the SLS data.
Bibliography:	istex:4D0FCBC2F7634D93A72DA996969BA9669BD12D70 ark:/67375/WNG-6087MBTJ-0 ArticleID:JCRCE5100 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1600-5767 0021-8898 1600-5767
DOI:	10.1107/S0021889811013343