Within the proposed project nanoparticles based on carbon or cellulose will be modified with polymer brushes made of 2-hydroxyethyl/2-aminoethyl methacrylate (HEMA/AEMA) as well as tulipalin A via a surface-initiated reversible addition and fragmentation chain transfer (RAFT) polymerization. These nanoparticles will be used as fillers for mechanical property improvement of biodegradable PLA foils. Prior to the polymerization, a suitable RAFT agent will be immobilized onto the nanoparticle surface by common synthetic methods. HEMA as well as AEMA will be used as (co)monomers for RAFT polymerization and also as initiators for the subsequent ring opening polymerization of lactide. Provided that, the poly(tulipalin) side butyrolactone rings will active participate in ring opening polymerization of lactide and in this way will mediate the polymerization on the particles surface. For nanoparticles it is planned to investigate different types, starting with cellulose, which can be easier modified with the RAFT agent due to its abundant hydroxyl groups on the surface. Nevertheless, also carbon black, graphene oxide, as well as multiwalled carbon nanotubes (MWCNTs) should be investigated for RAFT agent immobilization and preparation of core-shell nanostructures. Covalent metal carboxylates like tin (II) compounds as well as organo-catalyst based on dimethyl-4-aminopyridine will be used as catalysts for ring opening polymerization of lactide. The molar masses of prepared brushes will be characterized by gel permeation chromatography (GPC) and monomer conversion will be verified using nuclear magnetic resonance (1H NMR). The thermal properties of prepared particles will be investigated by the thermal gravimetric analysis (TGA).
The proposed process is innovative and was not used so far for production of degradable composites. The big advantage of using masterbatch/PLA hybrids in comparison with unmodified fillers will be easier distribution in the polymer matrix resulting in better exfoliation process. Well dispersed PLA hybrids allow for tuning the required properties of the composites at low hybrids loading.
