Highly thermostable and crystalline poly(butylene adipate) bionanocomposites prepared by in situ polycondensation with organically modified Moroccan Beidellite clay

Bionancomposites from bioplastics and nanoclays are of great interest for packaging, agricultural, and other large volume and niche applications due to their enhanced physical, thermal, mechanical, and processing characteristics compared to the parent polymer. In this study, the biodegradable polyester poly(butylene adipate) (PBA) was synthesized by in situ polycondensation catalyzed by titanium tetrabutoxide in the presence of the natural Moroccan clay Beidellite (BDT). Optimisation of the nanoclay exfoliation in the bionanocomposite was achieved by cation exchange of BDT with cetyltrimethylammonium bromide, CTA, and by selecting the most effective among a range of organically modified xCTA-BDT (x=CTA/BDT equivalent feed ratio). FT-IR, 1H NMR, and SEC analyses confirmed the effectiveness of the in situ polymerization, yielding structurally regular PBA with narrow molecular weight polydispersity and 7750>M ̅_n>30360 g/mol, depending on the organoclay load. XRD and TEM analyses showed best clay dispersion and homogeneous distribution at 2 wt% 3CTA-BDT. From TGA and DSC results the thermal stability of PBA is greatly improved even at 1 wt% 3CTA-BDT, its glass transition temperature is nearly unaffected while crystallinity is increased by the organoclay nucleating action. These results, along with a bionanocomposite hydrophilicity only moderately higher than that of PBA, make this preparation approach particularly promising.