title: Transition from star-like to crew-cut micelles induced by UV radiation.
abstract: In the present article, the effect of UV on PS-b-PMMA micelles in solution is discussed. Micellar solutions of the amphiphilic poly(styrene-b-methylmethacrylate) block copolymer in selective solvent (methanol for the PMMA block) were exposed to UV radiation, which has simultaneously led to cross linking of the micellar core (PS) and degradation of the micellar corona (PMMA). The kinetics of such process were investigated in situ by means of dynamic light scattering, allowing the measurement of hydrodynamic radius as a function of UV exposure time. Results indicate that the size of micelles has decreased with UV exposure time down to a minimum value. Such reduced size resulted from PMMA degradation, which later promoted aggregation and coagulation because the micellar core was no longer well protected by PMMA. Addition of good solvent for both blocks (toluene) to non-UV exposed micelles has led to core swelling (PS) and, ultimately, system disassembly (free copolymer chain). The effect of adding toluene on the UV-exposed micelles has only caused core swelling as a consequence of the PS cross-linking.
authors.affiliation: Centre de Recherches sur les Macromolécules Végétales CERMAV-CNRS), Affiliated with Grenoble Alpes University and Member of the Institut de Chimie Moléculaire de Grenoble, BP 53, F-38041 Grenoble Cedex 9, France; Department of Chemistry, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, Brazil.
authors.forename: Samira Jamil
authors.initials: SJ
authors.lastname: Fayad
authors.affiliation: Department of Chemistry, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, Brazil.
authors.forename: Edson
authors.initials: E
authors.lastname: Minatti
authors.affiliation: Department of Chemistry, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, Brazil.
authors.forename: Valdir
authors.initials: V
authors.lastname: Soldi
authors.affiliation: Centre de Recherches sur les Macromolécules Végétales CERMAV-CNRS), Affiliated with Grenoble Alpes University and Member of the Institut de Chimie Moléculaire de Grenoble, BP 53, F-38041 Grenoble Cedex 9, France. Electronic address: borsali@cermav.cnrs.fr.
authors.forename: Redouane
authors.initials: R
authors.lastname: Borsali
mesh_terms: D007700:Kinetics; D008689:Methacrylates / Q000737:chemistry* / Q000528:radiation effects; D000432:Methanol / Q000737:chemistry*; D008823:Micelles; D053758:Nanoparticles / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry* / Q000528:radiation effects; D012996:Solutions; D012997:Solvents / Q000737:chemistry*; D013499:Surface Properties; D014050:Toluene / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D008689:Methacrylates; D008823:Micelles; D011137:Polystyrenes; D012996:Solutions; D012997:Solvents; C522509:polystyrene-block-poly(methyl methacrylate); D014050:Toluene; D000432:Methanol
keywords: Block copolymer; Dynamic light scattering; Micelles; Self-assembly; UV-radiation