Near-Monodisperse Poly(2-(methacryloyloxy)ethyl phosphorylcholine)-Based Macromonomers Prepared by Atom Transfer Radical Polymerization and Thiol鈥揈ne Click Chemistry: Novel Reactive Steric Stabilizers
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- 作者：Nicholas J. Warren ; Carl Muise ; Alex Stephens ; Steven P. Armes ; Andrew L. Lewis
- 刊名：Langmuir
- 出版年：2012
- 出版时间：February 7, 2012
- 年：2012
- 卷：28
- 期：5
- 页码：2928-2936
- 全文大小：469K
- 年卷期：v.28,no.5(February 7, 2012)
- ISSN：1520-5827
文摘
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鈥?00 nm in diameter. As a comparison, the disulfide-containing PMPC homopolymer precursor and the intermediate thiol-functional PMPC homopolymer (PMPC鈥揝H) 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鈥揝H homopolymer as a reactive steric stabilizer, remained colloidally stable after both freeze鈥搕haw 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鈥搕haw cycle or the addition of an electrolyte, as expected.