Micellar transformations of poly(styrene-b-isoprene) block copolymers in selective solvents

The morphology of micelles formed from linear and cyclic poly(styrene-b-isoprene) copolymers (PS166-b-PI278) has been studied in solvents with different selectivity for the two block components: heptane and decane, good solvents for the PI block, and DMF, a good solvent for the PS block. Using small and ultra small angle X-ray scattering experiments, SAXS and USAXS, respectively, morphological changes were monitored as a function of the temperature. While micelles formed in DMF were stable and no morphological changes occurred as a function of the temperature, transformations from cylinder-like micelles to vesicles-like objects were observed in both decane and heptane above 60 °C for the linear PS-b-PI copolymer. The transition occurred through intermediate steps, where the coexistence between different micellar morphologies was observed. On the contrary, the morphology of the block copolymers with the cyclic architecture was found to be independent of temperature and concentration. For linear blocks, a demicellization was detected at higher temperatures (above 80 °C) and the process was fully reversible when the solution was cooled down to ambient temperature. These results are consistent with complementary dynamic light scattering (DLS) observations.

[1]  T. Weiss,et al.  Dynamics of spontaneous vesicle formation in fluorocarbon and hydrocarbon surfactant mixtures. , 2008, Langmuir : the ACS journal of surfaces and colloids.

[2]  F. Schmid,et al.  Spontaneous formation of complex micelles from a homogeneous solution. , 2007, Physical review letters.

[3]  Anja Kroeger,et al.  Dendrimer-influenced supramolecular structure formation of block copolymers. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[4]  Takashi Uneyama,et al.  Density functional simulation of spontaneous formation of vesicle in block copolymer solutions. , 2007, The Journal of chemical physics.

[5]  T. Narayanan,et al.  Development of an ultra-small-angle X-ray scattering instrument for probing the microstructure and the dynamics of soft matter , 2006 .

[6]  Hiroshi Noguchi,et al.  Dynamics of vesicle self-assembly and dissolution. , 2006, The Journal of chemical physics.

[7]  A. Ryan,et al.  Pathways of polymeric vesicle formation. , 2006, The journal of physical chemistry. B.

[8]  M. Pitsikalis,et al.  Reversible morphological transitions of polystyrene-b-polyisoprene micelles , 2006 .

[9]  F. Schmid,et al.  Dynamics of Spontaneous Vesicle Formation in Dilute Solutions of Amphiphilic Diblock Copolymers , 2006 .

[10]  T. Lodge,et al.  Sphere, cylinder, and vesicle nanoaggregates in poly(styrene-b-isoprene) diblock copolymer solutions , 2006 .

[11]  E. Minatti,et al.  Vesicles made of PS-PI cyclic diblock copolymers: in situ freeze-drying cryo-TEM and dynamic light scattering experiments. , 2005, Faraday discussions.

[12]  M. Hillmyer,et al.  Strategies for controlling intra- and intermicellar packing in block copolymer solutions: illustrating the flexibility of the self-assembly toolbox. , 2005, Faraday discussions.

[13]  T. Weiss,et al.  Dynamics of the self-assembly of unilamellar vesicles. , 2005, Physical review letters.

[14]  V. Abetz,et al.  Phase behaviour and morphologies of block copolymers , 2005 .

[15]  Moon Jeong Park,et al.  Temperature-dependent micellar structures in poly(styrene-b-isoprene) diblock copolymer solutions near the critical micelle temperature. , 2004, The Journal of chemical physics.

[16]  Ian W. Hamley,et al.  Small-angle scattering of block copolymers: in the melt, solution and crystal states , 2004 .

[17]  G. Beaucage,et al.  Particle size distributions from small-angle scattering using global scattering functions , 2004 .

[18]  T. Narayanan,et al.  Microphase Separation of Linear and Cyclic Block Copolymers Poly(styrene-b-isoprene): SAXS Experiments , 2004 .

[19]  M. Gradzielski.  TOPICAL REVIEW: Vesicles and vesicle gels - structure and dynamics of formation , 2003 .

[20]  T. Lodge,et al.  Origins of Anomalous Micellization in Diblock Copolymer Solutions , 2003 .

[21]  T. Narayanan,et al.  From “Sunflower-like” Assemblies toward Giant Wormlike Micelles , 2003 .

[22]  Nikos Hadjichristidis,et al.  Block Copolymers: Synthetic Strategies, Physical Properties, and Applications , 2002 .

[23]  T. Narayanan,et al.  Effect of cyclization of polystyrene/polyisoprene block copolymers on their micellar morphology , 2002 .

[24]  T. A. Hatton,et al.  Model for Formation and Growth of Vesicles in Mixed Anionic/Cationic (SOS/CTAB) Surfactant Systems , 2002 .

[25]  Dennis E. Discher,et al.  Polymer vesicles : Materials science: Soft surfaces , 2002 .

[26]  T. Narayanan,et al.  SAXS and USAXS on the high brilliance beamline at the ESRF , 2001 .

[27]  D. Danino,et al.  Cryo-TEM of thread-like micelles: on-the-grid microstructural transformations induced during specimen preparation , 2000 .

[28]  J. L. Zakin,et al.  Cryo-TEM Imaging the Flow-Induced Transition from Vesicles to Threadlike Micelles , 2000 .

[29]  W. Burchard.  Solution Properties of Branched Macromolecules , 1999 .

[30]  Ian W. Hamley,et al.  The physics of block copolymers , 1998 .

[31]  Jan Skov Pedersen,et al.  Analysis of small-angle scattering data from colloids and polymer solutions: modeling and least-squares fitting , 1997 .

[32]  H. Brumberger.  Modern aspects of small-angle scattering , 1995 .

[33]  W. Brown.  Dynamic light scattering : the method and some applications , 1993 .

[34]  Sow-Hsin Chen,et al.  Analysis of small angle neutron scattering spectra from polydisperse interacting colloids , 1983 .

[35]  L. Leibler.  Theory of Microphase Separation in Block Copolymers , 1980 .

[36]  B. Berne,et al.  Dynamic Light Scattering: With Applications to Chemistry, Biology, and Physics , 1976 .

[37]  H. R. Anderson,et al.  Scattering by an Inhomogeneous Solid. II. The Correlation Function and Its Application , 1957 .