title: Near-monodisperse poly(2-(methacryloyloxy)ethyl phosphorylcholine)-based macromonomers prepared by atom transfer radical polymerization and thiol-ene click chemistry: novel reactive steric stabilizers for aqueous emulsion polymerization.
abstract: Poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) macromonomers have been prepared by the atom transfer radical polymerization (ATRP) of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) using a bifunctional disulfide-based initiator. To attach a terminal polymerizable methacrylate group, the central disulfide bond was cleaved and the resulting thiols were conjugated to 3-(acryloyloxy)-2-hydroxypropyl methacrylate using tris(2-carboxyethyl)phosphine (TCEP) in water. Here TCEP serves as both the disulfide cleavage agent and also the catalyst for the subsequent Michael addition, which is highly selective for the acrylate group. The resulting methacrylate-terminated macromonomers were used as a reactive steric stabilizer for the aqueous emulsion polymerization of styrene, yielding near-monodisperse PMPC-stabilized polystyrene (PS) latexes of around 100-200 nm in diameter. As a comparison, the disulfide-containing PMPC homopolymer precursor and the intermediate thiol-functional PMPC homopolymer (PMPC-SH) were also evaluated as potential steric stabilizers. Interestingly, near-monodisperse latexes were also obtained in each case. These three sterically-stabilized latexes, prepared using either PMPC macromonomer, disulfide-based PMPC homopolymer, or PMPC-SH homopolymer as a reactive steric stabilizer, remained colloidally stable after both freeze-thaw experiments and the addition of an electrolyte, indicating that a coronal layer of PMPC chains prevented flocculation in each case. In contrast, both a charge-stabilized PS latex prepared in the absence of any steric stabilizer and a PS latex prepared in the presence of a nonfunctional PMPC homopolymer exhibited very poor colloidal stability when subjected to a freeze-thaw cycle or the addition of an electrolyte, as expected.
authors.affiliation: Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Warren
authors.forename: Carl
authors.initials: C
authors.lastname: Muise
authors.forename: Alex
authors.initials: A
authors.lastname: Stephens
authors.forename: Steven P
authors.initials: SP
authors.lastname: Armes
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Lewis
mesh_terms: D057930:Click Chemistry; D004655:Emulsions / Q000737:chemistry; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D046911:Macromolecular Substances / Q000138:chemical synthesis / Q000737:chemistry; D008689:Methacrylates / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D010316:Particle Size; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids; D011137:Polystyrenes / Q000138:chemical synthesis* / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D004655:Emulsions; D005609:Free Radicals; D046911:Macromolecular Substances; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011137:Polystyrenes; D013438:Sulfhydryl Compounds; C115766:poly(2-methacryloyloxyethyl-phosphorylcholine); D014867:Water; D010767:Phosphorylcholine