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Digital archive of theses discussed at the University of Pisa


Thesis etd-02082018-103524

Thesis type
Tesi di dottorato di ricerca
Thesis title
Designed amphiphilic polymers: self-assembly and nanostructure in solution and in thin film
Academic discipline
Course of study
tutor Prof. Galli, Giancarlo
relatore Dott.ssa Martinelli, Elisa
  • amphiphilic polymers
  • antifouling
  • ATRP
  • fluorescent molecular rotors
  • fluoropolymers
  • fouling release
  • hydrolyzable polymers
  • RAFT
  • self-assembly
  • single-chain folding
  • thermoresponsive polymers
  • unimer micelles
Graduation session start date
Different classes of amphiphilic copolymers were designed to incorporate both hydrophilic and hydrophobic components which could enable investigation of their distinct self-assembly and nanostructure over various states from solution in selective solvents to surface of thin solid films. By taking advantage of the controlled nature of the reversible-deactivation radical polymerisation methods, namely ATRP and RAFT, copolymers with diverse chemical architectures and structures were prepared with a tailored and varied philic/phobic balance. Comonomers, such as those based on a hydrophilic polyethyleneglycol methacrylate, a hydrophobic and lipophobic fluoroalkyl acrylate, a hydrophobic polysiloxane methacrylate, and two hydrolysable trialkylsilyl methacrylates, were selected in order to provide the materials with functional and responsive characters in addition to the capacity of self-assembling and structuring over length scales.
Amphiphilic ATRP random copolymers of polyethyleneglycol methacrylate and either fluoroalkyl acrylate or polysiloxane methacrylate were identified as single-chain folding polymers, where hydrophobic intramolecular interactions led to the copolymer self-assembly in solution to form unimer micelles. Dynamic light scattering (DLS) and small angle neutron scattering (SANS) experiments confirmed the formation of nanosized, unimer micelles at room temperature which turned into collective nano-to-microsized aggregates above a critical transition temperature. Fluorescent molecular probes were used to further investigate the properties of the nanostructures obtained. Molecular dynamics (MD) simulations were carried out to evaluate folding trajectories of the amphiphilic copolymers and supported the single-chain folding model proposed with conformational details. The interaction and self-assembly of hydrophobic side chains in the solid state were evidenced by NMR relaxometry studies of 1H and 19F nuclei. Moreover, the nanostructured, outer surface of thin copolymer films was shown to be preferentially populated by perfluoralkyl chains by angle-resolved X-ray photoemission spectroscopy (AR-XPS) analyses.
Amphiphilic hydrolysable RAFT block copolymers were synthesised with the aim to develop surface-active materials for new marine antifouling/fouling release coatings. Low elastic modulus and low surface energy were key parameters of the coating envisaged to combat fouling in a way to interfere with aquatic foulant adhesion and favour the biomass removal. These two features were combined in a silicone matrix-based coating that contained the surface-active amphiphilic copolymer carrying labile trialkylsilyl ester moieties at the surface of the film. The responsiveness to the outer environment mediated the reconstruction of the surface at the polymer-water interface to gradually renovate the surface and sustain high efficacy over time without the use of any toxic biocide. Wettability of model coatings was investigated with sessile drop and captive air bubble contact angle measurements. Antifouling and fouling release properties were assessed during a campaign of field immersion tests in natural seawater in Toulon (France) bay by regular and periodic inspections of coatings during seventeen weeks. Adhesion of different foulants, including biofilm, soft foulants and hard foulants, was evaluated which permitted to identify an intensity factor (I) and a severity factor (S) with a corresponding efficacy factor (N) to estimate the bounty of the antifouling potential. Removal of adhered biomass was also evaluated by sponge cleaning the coatings, which pointed to the effectiveness of the fouling-release performance.