|472. Arslan, H.; Pfaff, A.; Lu, Y.; Stepánek, P.; Müller, A.H.E.: 472. Stimuli-Responsive Spherical Brushes Based on D Galactopyranose and 2-(Dimethylamino)ethyl Methacrylate, Macromol. Biosci. 14(13), 81-91 (2014) -- DOI: 10.1002/mabi.201300290|
Stimuli-responsive spherical brushes composed of 6-O-methacryloyl-1,2:3,4-di-O-isopropylidene-D-galactopyranose (MAIGal) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) are prepared via atom transfer radical polymerization (ATRP) using cross-linked polystyrene nanoparticles covered with a thin layer of 2-(2-bromoisobutyryloxy)ethyl methacrylate (BIEM) as ATRP initiator by the ‘‘grafting from’’ approach. The stimuli-responsive behavior of the deprotected spherical PMAGal-b-PDMAEMA block copolymer brushes is investigated by dynamic light scattering and cryogenic transmission electron microscopy. A brush with arms containing160MAGaland170DMAEMAmonomer unitsshowsasignificantcontractionofthe hydrodynamicradiusfrom20to70 8 CatpH ¼ 8withacloudpointat 40 8 C,whereasnoLCSTis detected at pH ¼ 6 and 7 due to the protonation of the DMAEMA units. Aggregates occur at low temperatures and pH 8 due to intermolecular interactions between the chains of different brushes, which disappear above LCST, when the PDMAEMA chains fold back to the core of the brushes, exposing the glycopolymer chains to the outside.