ED Sciences Chimiques
From Secondary Structure to Mesoscale Order in Polypeptide-based Films
by Yupei MA (Laboratoire de Chimie des Polymères Organiques)
The defense will take place at 14h00 - Amphithéâtre 1 Université de Bordeaux, 16 avenue Pey Berland, 33600 Pessac
in front of the jury composed of
- Colin BONDUELLE - Directeur de recherche - CNRS / Université de Bordeaux / LCPO - Directeur de these
- Blanca MARTIN-VACA - Professeure des universités - Université de Toulouse-Paul-Sabatier / Laboratoire Hétérochimie Fondamentale Et Appliquée, Toulouse - Examinateur
- Fouzia BOULMEDAIS - Directrice de recherche - CNRS / Institut Charles Sadron - Rapporteur
- Guillaume FLEURY - Professeur des universités - Université de Bordeaux / LCPO - CoDirecteur de these
- Esma ISMAILOVA - Professeure des universités - École des Mines de Saint-Étienne - Rapporteur
- Olivier MONDAIN-MONVAL - Professeur des universités - Université de Bordeaux / Centre de recherche Paul Pascal - Examinateur
Polypeptides are a distinctive family of synthetic polymers whose chains fold into well-defined secondary structures. Along the α-helix axis the dipole of every peptide bond accumulates into a macrodipole, giving an intrinsic polarity that underlies dielectric and electromechanical behavior, and in the solid state these rigid helices pack laterally into hexagonal columnar arrays. Polypeptide films have recently been developed to exploit this hierarchical organization in functional coatings and responsive interfaces. The quantitative rules relating chain length and side-chain chemistry to molecular packing have nevertheless been established almost exclusively in bulk, and their transposition to thin film geometry remains uninvestigated. The objective of this project was to establish the relationships between processing, structure and properties in polypeptide thin films. The materials were obtained by ring-opening polymerization of N-carboxyanhydrides, which gives access to protein-like polymers of controlled length, and comprised protected lysine homopolymers, fluorinated homopolymers and polypeptide-based block copolymers. The degree of polymerization governed the secondary structure, whereas side-chain chemistry influenced thermal stability, molecular packing and dielectric response. A coil block further introduced mesoscale periodic organization absent in the homopolymer systems and allowed otherwise poorly processable fluorinated polypeptides to be processed into thin films. Structural studies from the molecular to the mesoscale reveal these films as nanostructured platforms for dielectric and electromechanical applications.