title: Association of a multifunctional ionic block copolymer in a selective solvent.
abstract: The self-assembly of multiblock copolymers in solutions is controlled by a delicate balance between inherent phase segregation due to incompatibility of the blocks and the interaction of the individual blocks with the solvent. The current study elucidates the association of pentablock copolymers in a mixture of selective solvents which are good for the hydrophobic segments and poor for the hydrophilic blocks using small angle neutron scattering (SANS). The pentablock consists of a center block of randomly sulfonated polystyrene, designed for transport, tethered to poly-ethylene-r-propylene and end-capped by poly-t-butyl styrene, for mechanical stability. We find that the pentablock forms ellipsoidal core-shell micelles with the sulfonated polystyrene in the core and Gaussian decaying chains of swollen poly-ethylene-r-propylene and poly-t-butyl styrene tertiary in the corona. With increasing solution concentration, the size of the micelle, the thickness of the corona, and the aggregation number increase, while the solvent fraction in the core decreases. In dilute solution the micelle increases in size as the temperature is increased, however, temperature effects dissipate with increasing solution concentration.
authors.affiliation: Department of Chemistry, Clemson University, Clemson, South Carolina 29634, USA.
authors.forename: Thusitha N
authors.initials: TN
authors.lastname: Etampawala
authors.affiliation: Department of Chemistry, Clemson University, Clemson, South Carolina 29634, USA.
authors.forename: Dipak
authors.initials: D
authors.lastname: Aryal
authors.affiliation: Department of Chemistry, Clemson University, Clemson, South Carolina 29634, USA.
authors.forename: Naresh C
authors.initials: NC
authors.lastname: Osti
authors.affiliation: Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Lilin
authors.initials: L
authors.lastname: He
authors.affiliation: Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: William T
authors.initials: WT
authors.lastname: Heller
authors.affiliation: Kraton Polymers US LLC, 16400 Park Row, Houston, Texas 77084, USA.
authors.forename: Carl L
authors.initials: CL
authors.lastname: Willis
authors.affiliation: Sandia National Laboratories, Albuquerque, New Mexico 87185, USA.
authors.forename: Gary S
authors.initials: GS
authors.lastname: Grest
authors.affiliation: Department of Chemistry, Clemson University, Clemson, South Carolina 29634, USA.
authors.forename: Dvora
authors.initials: D
authors.lastname: Perahia