Functional copolymer/organo-MMT nanoarchitectures. XIX. Nanofabrication and characterization of poly(MA-alt -1-octadecene)-g -PLA layered silicate nanocomposites with nanoporous core-shell morphology

Abstract

Novel bioengineering functional copolymer-g-biopolymer-based layered silicate nanocomposites were fabricated by catalytic interlamellar bulk graft copolymerization of L-lactic acid (LA) monomer onto alternating copolymer of maleic anhydride (MA) with 1-octadecene as a reactive matrix polymer in the presence of preintercalated LA…organo-MMT clay (reactive ODA-MMT and non-reactive DMDA-MMT) complexes as nanofillers and tin(oct)2 as a catalyst under vacuum at 80°C. To characterize the functional copolymer layered silicate nanocomposites and understand the mechanism of in situ processing, interfacial interactions and nanostructure formation in these nanosystems, we have utilized a combination of variuous methods such as FT-IR spectroscopy, X-ray diffraction (XRD), dynamic mechanical (DMA), thermal (DSC and TGA-DTG), SEM and TEM morphology. It was found that in situ graft copolymerization occurred through the following steps: (i) esterification of anhydride units of copolymer with LA; (ii) intercalation of LA between silicate galleries; (iii) intercalation of matrix copolymer into silicate layers through in situ amidization of anhydride units with octadecyl amine intercalant; and (iv) interlamellar graft copolymerization via in situ intercalating/exfoliating processing. The main properties and observed micro- and nanoporous surface and internal core–shell morphology of the nanocomposites significantly depend on the origin of MMT clays and type of in situ processing (ion exchanging, amidization reaction, strong H-bonding and self-organized hydrophobic/hydrophilic interfacial interactions). This developed approach can be applied to a wide range of anhydride-containing copolymers such as random, alternating and graft copolymers of MA to synthesize new generation of polymer-g-biopolymer silicate layered nanocomposites and nanofibers for nanoengineering and nanomedicine applications. Copyright © 2014 John Wiley & Sons, Ltd.