1334532-10-3Relevant articles and documents
Synthesis of sterically-stabilized polystyrene latexes using well-defined thermoresponsive poly(N-isopropylacrylamide) macromonomers
McKee,Ladmiral,Niskanen,Tenhu,Armes
, p. 7692 - 7703 (2011)
A series of well-defined thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) macromonomers was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization followed by aminolysis and nucleophilic Michael addition. 2-(Dodecylthiocarbonothioylthio)-2-methylpropanoic-2-phenoxyethyl ester (CTA) was used as the RAFT chain transfer agent to prepare six PNIPAM-CTA precursors with target degrees of polymerization of 20, 30, 40, 50, 60, and 75. These NIPAM polymerizations were conducted in 1,4-dioxane and proceeded with good control and low polydispersities (Mw/Mn a one-pot reaction. The resulting PNIPAM macromonomers were evaluated as reactive steric stabilizers for latex syntheses. Near-monodisperse submicrometer-sized latexes were obtained by alcoholic dispersion polymerization of styrene in methanol, as judged by scanning electron microscopy (SEM) and dynamic light scattering (DLS). In contrast, a latex synthesized in the presence of a PNIPAM-CTA had a bimodal size distribution, while thiol-capped PNIPAM chains produced ill-defined nonspherical particles and styrene polymerization conducted in the absence of any stabilizer led to macroscopic precipitation. These control experiments confirm that using the methacrylate-capped macromonomers is essential for successful latex syntheses. 1H NMR analysis confirm the presence of PNIPAM chains in the latex particles and XPS measurements indicate that the stabilizer is located on the particle surface, as expected. The well-known thermo-responsive nature of the stabilizer was successfully transferred to these latexes, which exhibit reversible flocculation upon heating above the LCST of the PNIPAM chains.
