OUARTI, Nadia; VIVILLE, Pascal; LAZZARONI, Roberto; MINATTI, Edson; SCHAPPACHER, Michel; DEFFIEUX, Alain; PUTAUX, Jean-Luc; BORSALI, Redouane

doi:10.1021/la050935z

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OUARTI, Nadia
Univ Mons, Belgique, Serv Chim Mat Nouveaux

VIVILLE, Pascal
Univ Mons, Belgique, Serv Chim Mat Nouveaux

LAZZARONI, Roberto
Univ Mons, Belgique, Serv Chim Mat Nouveaux

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Langmuir. 2005, vol. 21, n° 20, p. 9085-9090

American Chemical Society

Résumé en anglais

The morphology of micelles formed from blends of linear and cyclic poly(styrene-b-isoprene) (PS-b-PI) block copolymers has been investigated in solution using dynamic light scattering (DLS) and in thin solid deposits by atomic force microscopy (AFM) and transmission electron microscopy under cryogenic conditions (cryo-TEM). Micelles of the pure cyclic PS290-b-PI110 copolymers are wormlike cylindrical objects built by unidirectional aggregation of 33 nm wide sunflower micelles, while the linear block copolymer having the same volume fraction and molar mass forms spherical micelles 40 nm in diameter. The DLS, AFM, and cryo-TEM results consistently show that the addition of the linear copolymer (even for amounts as low as 5% w/w) to the cyclic copolymer rather favors the formation of spherical micelles at the expense of the cylindrical aggregates. Those results clearly show that the linear block copolymer chains can be used to stabilize the thermodynamically unstable elementary sunflower micelle. The thermal stability of the micelles (from the pure copolymers and from the blends) has been examined in solid deposits with in situ AFM measurements. Coalescence starts at about 70 degrees C, and the surface roughness shows a two-step decrease toward a fully homogeneous and flat structure.< Réduire

Mots clés en anglais

WORMLIKE MICELLES

FORMING COPOLYMERS

HOMOPOLYMER BLENDS

SELECTIVE SOLVENTS

EXCLUDED-VOLUME INTERACTIONS

SMALL-ANGLE NEUTRON

BLOCK-COPOLYMER

ORDERED STRUCTURE

PHASE-EQUILIBRIA

LIGHT-SCATTERING

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Micellar aggregation in blends of linear and cyclic poly(styrene-b-isoprene) diblock copolymers

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