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Tesi etd-01282014-164423

Thesis type
Tesi di laurea magistrale
email address
Synthesis and characterization of thermoreponsive multiblock copolymer brushes via confined atom transfer radical polymerizations
Corso di studi
relatore Dott. Pucci, Andrea
correlatore Dott. Benetti, Edmondo Maria
controrelatore Dott. Di Francesco, Fabio
Parole chiave
  • ATRP
  • AFM
  • Ellipsometry
Data inizio appello
Riassunto analitico
With the primal aim of controlling the atom transfer radical polymerization of N-isopropyl acrylamide from surface-initiated silicon oxide substrates the first project of this thesis concerns on the study of the ATRP kinetic. We report the synthesis of poly(N-isopropylacrylamide) brush layers grafted onto the silicon oxide substrates at room temperature via surface-initiated atom transfer radical polymerization using different global polymerization ratios. The effective modification of the silicon oxide surfaces were verified by contact angle and Fourier transform infrared spectroscopy techniques, and the chain length of the polymer chains were measured through ellipsometry analysis. Moreover, the influence of the polarity of the polymerization solution and the relative concentration of activator, deactivator and ligand were studied. <br>The reproducibility of the surface-initiated atom transfer radical polymerization of N-isopropylacrylamide grafted from silicon oxide surfaces was studied comparing the dry thicknesses measured with ellipsometry. In addition, we investigated the swelling behaviour of the poly(N-isopropylacrylamide) brushes and the thermoresponsive property by determining the lower critical solution temperature with in-situ ellipsometry. <br>Finally the surface-tethered triblock copolymers composed of poly(N-isopropylacrylamide), poly(Hydroxyethyl methacrylate-co-ethylene glycol di(metha)acrylate) and poly(N-isopropylacrylamide) were grown from silicon oxide substrates by a series of atom transfer radical polymerization at room temperature. After the synthesis of the first block the growing chains were quenched transferring a quenching solution composed of a large excess of deactivator and ligand, CuBr2 and N, N, N&#39;, N&#39;, N&#39;-pentmethyldiethylentriamine. Comparing the thicknesses of the multiblock copolymers films with the thicknesses of the respective homopolymer films using a surface-initiated silicon oxide substrate, the efficiency of the quenching approach was evaluated. The swelling and the thermoresponsive properties were studied using ellipsometry and atomic force microscopy techniques. The mechanical properties of the surfaces were studied through indentation atomic force microscopy experiments and the topographical images were obtained through tapping mode atomic force microscopy. Independently from the architecture of the multiblock copolymers, the swelling and thermoresponsive properties of the materials were preserved, while the mechanical properties of the hydrogel changed dramatically when it was grafted onto the thermoresponsive brush layer. <br>