Synthesis of polyamide-imide-montmorillonite-nanocomposites via new approach of in situ polymerization and solvent casting

•In situ polymerization for synthesis of PAI-MMT-nanocomposites was investigated.•Swelling process of MMT was realized through blocked MDI.•Following polymerization of MDI and TMA to PAI resulted in exfoliation of MMT.•Exfoliation via in situ polymerization was compared to solvent casting method. Due to the inherent importance of nanostructuring in coatings the present article provides a new approach for exfoliation of montmorillonite via in situ polymerization in comparison to solvent casting method. The new in situ polymerization with PAI was realized by swelling MMT's intergallery with p-chlorphenole blocked 4,4′-methylene diphenyl diisocyanate and 1,2,4-benzenetricarboxylic acid anhydride followed by polymerization within MMT's intergalleries. XRD-measurements and SEM analysis at cross-sections revealed nanocomposites with exfoliated sheet structure up to 2.0wt% MMT while for solvent casting 1.2wt% was determined as limiting concentration. Therefore, this novel approach provides synthesis of higher concentrated exfoliated PAI-MMT-nanocomposites. Despite its disadvantage in lower limiting concentration, when it comes to application, the solvent casting method turned out to be superior to in situ polymerization as it is much faster and economically more feasible.