Functional organo-Mt/copolymer nanoarchitectures. XXII. Interlamellar graft copolymerisation of l-lactic acid onto poly(maleic anhydride-alt-1-octadecene) in the presence of different clays as catalyst-nanofillers

In this work, novel functional copolymer-g-biopolymer layered silicate nanocomposites were prepared by in situ graft copolymerisation of l-lactic acid (LA) onto poly(maleic anhydride-alt-1-octadecene) in the presence of Na+-montmorillonite (Mt), Ag+-Mt and octadecyl amine-Mt (ODA) nanofillers using a specially constructed vacuum micro-reactor with Dean-Stark unit at 80 °C. It was observed that inorganic and organic clays executed the dual functions as catalyst of interlamellar graft copolymerisation and nano-filler in formation of clay polymer nanocomposites (CPNs). This new approach allow us to realise the grafting and graft copolymerisation without use of hazardous tin(oct)2 catalyst. The surfactant matrix copolymer provides the first step of grafting via ring opening monoesterification of anhydride units with LA monomer. The catalytic activity of the positively charged clays and their LA preintercalated complexes as a function of phase separation time, strongly depends on the particle parameters (zeta-size and zeta-potential) of the used clay systems and changed in the following range: organoclay < Na+-Mt < Ag+-Mt. The obtained graft copolymer/clay nanohybrids were characterised by FTIR, 1H and 13C NMR, DSC-TGA-DTG, XRD and SEM-TEM analysis methods. These observed that type of the clays significantly influences the chemical and physical structures, thermal properties, surface and internal core–shell morphology of the copolymer-g-PLA layered silicate nanocomposites. Better results were obtained for the copolymer-g-biopolymer/reactive organoclay nanocomposites. It was concluded that this versatile and green synthetic method can utilise for a wide range of anhydride-containing alternating, random, graft and block functional copolymers as matrix polymers and their silicate layered nanocomposites.