title: Thermoresponsive PDMAEMA Brushes: Effect of Gold Nanoparticle Deposition.
abstract: The paper addresses the effect of gold nanoparticle (Au-NP) deposition on the thermoresponsive volume phase transition of the weak polyelectrolyte poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. PDMAEMA brushes were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP). The PDMAEMA/Au-NP composite brushes were fabricated by immersing the brush modified wafer in the Au-NP suspension. Atomic force microscopy (AFM), ellipsometry, and scanning electron microscopy (SEM) have been employed to characterize the neat PDMAEMA brushes and PDMAEMA/Au-NP composite brushes. All neat PDMAEMA brushes swelled below the volume phase transition temperature and collapsed with increasing temperature over a broad temperature range independent of the initial brush thickness. Water uptake of the brushes is also independent of initial brush thickness. The adsorption of the charged Au-NPs significantly affects the degree of swelling and the thermoresponsive properties of the brushes. PDMAEMA/Au-NP composite brushes do not exhibit any noticeable phase transition at the experimental temperature range irrespective of the initial brush thickness. The reason for this behavior is attributed to a combination of the following: the decreased conformational entropy of the Au-NP adsorbed polymer chains, the increased hydrophilicity of the system due to the charged Au-NPs, and the ≈13 nm diameter Au-NPs causing steric hindrance. We have also shown that the AFM full-indentation method can be successfully applied to determine the polymer brush thicknesses.
authors.forename: Zuleyha
authors.initials: Z
authors.lastname: Yenice
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schön
authors.forename: Hakan
authors.initials: H
authors.lastname: Bildirir
authors.affiliation: §Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, United States.
authors.forename: Jan
authors.initials: J
authors.lastname: Genzer
authors.forename: Regine
authors.initials: R
authors.lastname: von Klitzing
mesh_terms: D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008689:Methacrylates / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D009757:Nylons / Q000737:chemistry*; D044367:Phase Transition; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D008689:Methacrylates; D009757:Nylons; C407037:poly(2-(dimethylamino)ethyl methacrylate); D014867:Water; D006046:Gold