title: Aggregation behavior of poly(ethylene glycol-bl-propylene sulfide) di- and triblock copolymers in aqueous solution.
abstract: Block copolymers of poly(ethylene glycol)-bl-poly(propylene sulfide) (PEG-PPS) have recently emerged as a new macromolecular amphiphile capable of forming a wide range of morphologies when dispersed in water. To understand better the relationship between stability and morphology in terms of the relative and absolute block compositions, we have synthesized a collection of PEG-PPS block copolymers and quantified their critical aggregation concentration and observed their morphology using cryogenic transmission electron microscopy after thin film hydration with extrusion and after solvent dispersion from tetrahydrofuran, a solvent for both blocks. By understanding the relationship between aggregate character and block copolymer architecture, we have observed that whereas the relative block lengths control morphology, the stability of the aggregates upon dilution is determined by the absolute block length of the hydrophobic PPS block. We have compared results obtained with PEG-PPS to those obtained with poly(ethylene glycol)-bl-poly(propylene oxide)-bl-poly(ethylene glycol) block copolymers (Pluronics). The results reveal that the PEG-PPS aggregates are substantially more stable than Pluronic aggregates, by more than an order of magnitude. PEG-PPS can form a wide variety of stable or metastable morphologies in dilute solution within normal time and temperature ranges, whereas Pluronics can generally form only spherical micelles under the same conditions. On the basis of these results, block copolymers of PEG with poly(propylene sulfide) may present distinct advantages over those with poly(propylene glycol) for a number of applications.
authors.affiliation: Institute for Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 15, CH-1015 Lausanne, Switzerland.
authors.forename: Simona
authors.initials: S
authors.lastname: Cerritelli
authors.forename: Conlin P
authors.initials: CP
authors.lastname: O'Neil
authors.forename: Diana
authors.initials: D
authors.lastname: Velluto
authors.forename: Antonella
authors.initials: A
authors.lastname: Fontana
authors.forename: Marc
authors.initials: M
authors.lastname: Adrian
authors.forename: Jacques
authors.initials: J
authors.lastname: Dubochet
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Hubbell
mesh_terms: D004337:Drug Carriers / Q000737:chemistry; D031541:Fluorescence Resonance Energy Transfer; D057927:Hydrophobic and Hydrophilic Interactions; D046529:Microscopy, Electron, Transmission; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D012996:Solutions; D013440:Sulfides / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D004337:Drug Carriers; D011108:Polymers; D012996:Solutions; D013440:Sulfides; C522256:poly(propylene sulfide); D014867:Water; D011092:Polyethylene Glycols