title: Design and use of organic nanoparticles prepared from star-shaped polymers with reactive end groups.
abstract: Star-shaped poly(isobornyl acrylate) (PiBA) was prepared by atom transfer radical polymerization (ATRP) using multifunctional initiators. The optimal ATRP conditions were determined to minimize star-star coupling and to preserve high end group functionality (>90%). Star-shaped PiBA with a narrow polydispersity index was synthesized with 4, 6, and 12 arms and of varying molecular weight (10,000 to 100,000 g x mol(-1)) using 4 equiv of a Cu(I)Br/PMDETA catalyst system in acetone. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) analysis, NMR spectroscopy, and size exclusion chromatography (SEC) confirmed their controlled synthesis. The bromine end group of each arm was then transformed to a reactive end group by a nucleophilic substitution with methacrylic acid or cinnamic acid (conversion >90%). These reactive star polymers were used to prepare PiBA nanoparticles by intramolecular polymerization of the end groups. The successful preparation of this new type of organic nanoparticles on a multigram scale was proven by NMR spectroscopy and SEC. Subsequently, they have been used as additives for linear, rubbery poly(n-butyl acrylate). Rheology measurements indicated that the viscoelastic properties of the resulting materials can be fine-tuned by changing the amount of incorporated nanoparticles (1-20 wt %), as a result of the entanglements between the nanoparticles and the linear polymers.
authors.affiliation: Department of Organic Chemistry, Polymer Chemistry Research Group, Ghent University, Krijgslaan 281 S4-bis, B-9000 Ghent, Belgium.
authors.forename: Lieven M
authors.initials: LM
authors.lastname: Van Renterghem
authors.forename: Mieke
authors.initials: M
authors.lastname: Lammens
authors.forename: Bart
authors.initials: B
authors.lastname: Dervaux
authors.forename: Pascal
authors.initials: P
authors.lastname: Viville
authors.forename: Roberto
authors.initials: R
authors.lastname: Lazzaroni
authors.forename: Filip E
authors.initials: FE
authors.lastname: Du Prez