Hyperbranched poly(ethyleneimine) derivatives as modifiers in epoxy networks

Identifier:  TDX:2380

Handle: https://hdl.handle.net/20.500.11797/TDX2380

Authors:  Acebo Gorostiza, Cristina

Abstract:
In the present thesis the chemical modification of commercial hyperbranched poly(ethyleneimine) (PEI) to prepare new dendritic structures, able to act as modifiers has been done. These modifiers have been added to diglycidylether of bisphenol A (DGEBA) formulations to improve thermosets characteristics. The use of PEI modified with long alkyl chains in epoxy/anhydride formulations allowed the preparation of new thermosets with high impact resistance and nanograined morphologies. A series of star polymers was prepared from poly(ethyleneimine) core and poly(lactide) (PLLA) or poly(ε-caprolactone) (PCL) arms. The addition of PCL stars to the epoxy formulations improved toughness characteristics, while the processability of the reactive mixtures was maintained. In addition, the final hydroxyl groups of the star were blocked by reaction with acetic anhydride. In this way, a notable improvement in impact resistance was achieved for the modified thermosets. At last, using PLLA stars as modifiers thermally reworkable thermosets were obtained. The synthesis of poly(ethyleneimine) with akoxysilyl groups as chain ends allowed us to obtain new hybrid organic-inorganic materials by sol-gel methodology with an epoxy matrix. These materials presented a high scratch resistance and even a self-repairing character was observed. It was also studied the effect of adding other inorganic precursors in the properties of the hybrid materials previously developed. In the last part, through the combination of click reactions, different organic hybrid materials were prepared. 1,3-Cycloaddition reaction of alkynyl units with organic azides allowed us to prepare poly(ethyleneimine) decorated with triazole groups. Its ability as macroinitiator in the anionic homopolymerization of DGEBA could be confirmed. By combining different thiol-click reactions. New materials were obtained from PEI modified with allyl and propargyl terminal groups as macromonomers with DGEBA in thiol-ene/thiol-epoxy and thiol-yne/thiol-epoxy dual curing systems.