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.

Fabrication of starch‐g‐poly(l‐lactic acid) biocomposite films: Effects of the shear‐mixing and reactive‐extrusion conditions

“…The dispersion in intercalated–exfoliated organoclay–LA matrix (reinforcement) and the amount of the added organoclay also affected the elongation at break. The highly increased mechanical properties in the St‐ g ‐PLA/organoclay nanocomposite compared to the St‐ g ‐PLA copolymers confirmed the unique interaction of the intercalated–exfoliated LA–MMT nanoclay and the polymer phase under high‐shear mixing and reactive extrusion; this led to the high intermolecular interactions with nanosized particle dispersion …”

“…Additionally, the bands at 1171, 1039, and 924‐cm −1 confirmed the SiOSi vibrations and SiO stretching from the delamination of the clay mineral layers [Figure (b)] . The peak at 1050 cm −1 confirmed the stretching and bending modes of the SiOSi groups [Figure (b)] . Finally, the most intense absorption peaks related to the graft copolymerization were obtained in the case of 5.0% LA–MMT intercalated–exfoliated nanofillers.…”

“…Furthermore, the incorporation of the nanoclays and the absorption of water by the hydrophilic part of the copolymer (starch and LA) effectively led to the reduction of the permeability. Moreover, other important parameters, such as the degree of dispersion of the clay in the polymer matrix, significantly reduced the solubility coefficient and finally WVP …”

“…At first, native starch was weighed and dried in an oven (Memmert, Germany) at 60 °C overnight. The LA–MMT organomodification was done by an intercalation–exfoliation technique with mechanical stirring for 24 h . Starch was transferred in a high‐shear mixer (Zeppelin, FML10, Germany) and lactic acid/LA–MMT was added slowly with a variable‐speed peristaltic pump feeder (Watson Marlow, England) while the starch was slowly mixed in (Figure S1, Supporting Information).…”

“…Actually, this study was a continuation of our previous studies presenting processing under a high shear rate to enhance the miscibility between starch and PLA for the fabrication of highly dispersed graft copolymers and their nanocomposites without the addition of any additives and conventional solvents by means of a high‐shear reactor and a twin‐screw extrusion system . The thermal stability, morphologies, and mechanical and permeability properties of the films were studied as a function of the starch–LA ratio and nanoclay content variations.…”