Filters

2020 - 20222

More filters

2021 - 20232
Reset filters

Settings

DDC: 540 × Subject: PNIPAM ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Dual Stimuli-Responsive Self-Assembly Behavior of a Tailor-Made ABC-Type Amphiphilic Tri-Block Copolymer
    (Hoboken, NJ [u.a.] : Wiley, 2020) Pal, Sanjay; Kather, Michael; Banerjee, Sovan Lal; Saha, Pabitra; Pich, Andrij; Singha, Nikhil K.
    This investigation describes the synthesis of a dual stimuli-responsive, amphiphilic ABC tri-block copolymer (BCP) based on the functional monomers via RAFT polymerization. In this case, ABC-type BCP was prepared based on N-isopropylacrylamide, n-butyl acrylate, and 4-vinylpyridine in DMF solvent using cyanomethyl dodecyl trithiocarbonate as the RAFT agent and azobisisobutyronitrile as a thermal initiator in a subsequent macro-RAFT approach, respectively. The BCPs were characterized by SEC, 1H-NMR, FTIR spectroscopy, and DSC analyses. Temperature and pH-dependent properties of the smart BCP micelles in aqueous medium were investigated using dynamic light scattering. Transmission electron microscopic images were taken at cryogenic and dry conditions to study the morphology of molecular assemblies of block copolymers in an aqueous medium. The phase and topographical images were captured by atomic force microscopy to understand the assembly of block copolymers in solvents of different polarities. The morphology of BCP micelles was transformed from flower-like to spherical in the presence of solvents with different polarities (H2O or CHCl3). © 2020 The Authors. Journal of Polymer Science published by Wiley Periodicals, Inc.
  • Thumbnail Image
    Item
    Cononsolvency of the responsive polymer poly(N-isopropylacrylamide) in water/methanol mixtures: a dynamic light scattering study of the effect of pressure on the collective dynamics
    (Berlin ; Heidelberg : Springer, 2022) Niebuur, Bart-Jan; Deyerling, André; Höfer, Nicole; Schulte, Alfons; Papadakis, Christine M.
    The collective dynamics of 25 wt% poly(N-isopropylacrylamide) (PNIPAM) solutions in water or an 80:20 v/v water/methanol mixture are investigated in the one-phase region in dependence on pressure and temperature using dynamic light scattering. Throughout, two dynamic modes are observed, the fast one corresponding to the relaxation of the chain segments within the polymer blobs and the slow one to the relaxation of the blobs. A pressure scan in the one-phase region on an aqueous solution at 34.0 °C, i.e., slightly below the maximum of the coexistence line, reveals that the dynamic correlation length of the fast mode increases when the left and the right branch of the coexistence line are approached. Thus, the chains are rather swollen far away from the coexistence line, but contracted near the phase transition. Temperature scans of solutions in neat H2O or in H2O/CD3OD at 0.1, 130, and 200 MPa reveal that the dynamic correlation length of the fast mode shows critical behavior. However, the critical exponents are significantly larger than the value predicted by mean-field theory for the static correlation length, ν = 0.5, and the exponent is significantly larger for the solution in the H2O/CD3OD mixture than in neat H2O.