title: Cross-linking of cationic block copolymer micelles by silica deposition.
abstract: Diblock copolymer micelles comprising cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMA) coronas and hydrophobic poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) cores are used as nanosized templates for the deposition of silica from aqueous solution at pH 7.2 and 20 degrees C. Both noncross-linked and shell cross-linked (SCL) micelles can be coated with silica without loss of colloid stability. Under optimized conditions, the silica deposition is confined to the partially quaternized cationic PDMA chains, leading to hybrid copolymer-silica particles of around 35 nm diameter with well-defined core-shell morphologies. 1H NMR studies confirmed that the PDPA cores of these copolymer-silica particles became protonated at low pH and deprotonated at high pH, which suggests possible encapsulation and controlled release applications. Moreover, in situ silica deposition effectively stabilizes the PDPA-PDMA micelles, which remain intact on lowering the solution pH (whereas the original noncross-linked PDPA-PDMA micelles dissociate in acidic solution). This suggests a convenient route to silica-stabilized SCL micelles under mild conditions.
authors.affiliation: Department of Chemistry, The University of Sheffield, Brook Hill, Sheffield S3 7HF, UK.
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: Yuan
authors.forename: Oleksandr O
authors.initials: OO
authors.lastname: Mykhaylyk
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Ryan
authors.forename: Steven P
authors.initials: SP
authors.lastname: Armes
mesh_terms: D002412:Cations; D003432:Cross-Linking Reagents / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008689:Methacrylates / Q000737:chemistry*; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D009757:Nylons / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D002412:Cations; D003432:Cross-Linking Reagents; D008689:Methacrylates; D008823:Micelles; D009757:Nylons; D011109:Polymethacrylic Acids; C511861:poly(2-(diisopropylamino)ethyl methacrylate); C407037:poly(2-(dimethylamino)ethyl methacrylate); D012822:Silicon Dioxide