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

Abstract

International audienceThe 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 degrees 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 degrees 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

Well-defined and stable nanomicelles self-assembled from brush cyclic and tadpole copolymer amphiphiles: a versatile smart carrier platform

“…11,15,18,22,23 Their stabilities were relatively higher than those of their linear analogues but still limited to a certain extent. 1,11,13,15,18,22,23 Thus, they have not yet been fully understood in the aspect of structural characteristics (shape, size, size distribution, structural components, density gradient, stability and so on). In fact, micelles have great potent for applications as a carrier system in various fields, such as drug delivery, biomedical imaging, foods, cosmetics, coatings, photonics and molecular electronics.…”

“…[1][2][3][4][5][6][7][8][9][10] In addition, cyclic block copolymers have received interest due to selfassembly characteristics that deviate from the typical behaviours of their linear analogues. 3,5,[11][12][13][14][15][16][17][18][19][20][21][22][23][24] In the case of micelle formation in solution, cyclic block copolymers were reported to form relatively more compact micelles than their linear analogues. [11][12][13]15,16,18,23 The cyclic block copolymer micelles, however, were very often evaluated qualitatively.…”

“…3,5,[11][12][13][14][15][16][17][18][19][20][21][22][23][24] In the case of micelle formation in solution, cyclic block copolymers were reported to form relatively more compact micelles than their linear analogues. [11][12][13]15,16,18,23 The cyclic block copolymer micelles, however, were very often evaluated qualitatively. 11,15,18,22,23 Their stabilities were relatively higher than those of their linear analogues but still limited to a certain extent.…”

“…[11][12][13]15,16,18,23 The cyclic block copolymer micelles, however, were very often evaluated qualitatively. 11,15,18,22,23 Their stabilities were relatively higher than those of their linear analogues but still limited to a certain extent. 1,11,13,15,18,22,23 Thus, they have not yet been fully understood in the aspect of structural characteristics (shape, size, size distribution, structural components, density gradient, stability and so on).…”

Concentration dependent pathways in spontaneous self-assembly of unilamellar vesicles

“…1,2,8 Most well studied systems are surfactants 6,7,[10][11][12][14][15][16] and block copolymers [17][18][19] in selective solvents. The self-assembly process can be induced by rapid mixing of oppositely charged surfactant solutions, 6,10,15,20 temperature 19,21,22 or pH jumps.…”