Soutenance de thèse : Valentina CAVALLO

Tailoring intermolecular interactions in methacrylate-based copolymers and nanocomposites: Effect on molecular dynamics and thermal properties

Doctorante : Valentina CAVALLO 

Laboratoire INSA : IMP
Ecole doctorale : ED34 : Matériaux de Lyon

A correlation between the strength of the intermolecular interactions and physical properties has been reported for amorphous polymers. In particular, an increment of thermal conductivity has been associated to the addition of stronger interactions compared with weak van der Walls, i.e. hydrogen and ionic bonds. In this work, an attempt to tailor thermal conductivity in amorphous polymers has been made by engineering intermolecular interactions. Poly(methylmethacrylate) PMMA was used as standard and poly(methylmethacrylate-co-methacrylic acid) (PMMA-co-MAA) copolymers were synthesised by free radical copolymerization in order to introduce inter-chain hydrogen bonds and, after neutralisation, ionic bonds. Copolymers were successfully obtained up to 30%wt of MAA and characterized. Also, different comonomers were used to evaluate the impact of a flexible unit bringing H-bonds, 2-hydroxyethylmethacrylate (HEMA) or 2-carboxyethylacrylate (CEA). Thermal conductivity slightly increased increasing MAA and HEMA content, while for CEA copolymers the presence of defects prevented the measurement.
Later, PMMA-co-MAA was used as a matrix for cellulose-based nanocomposites to tailor filler compatibility, thanks to the presence of H-bonds between MAA unit and cellulose surface. Cellulose nanofibers (CNFs) up to 15%wt were efficiently dispersed by solvent casting in a mixture of two solvents (tetrahydrofuran/methanol). Thermal conduction showed no significant changes following the introduction of CNFs.
Dynamic mechanical analysis (DMA) and broadband dielectric spectroscopy (BDS) were used in combination to fully characterize the macromolecular mobility of PMMA-co-MAA following the introduction of inter-chain H-bonds and the subsequent addition of CNFs.