Effect of PGMA-saponite brushes on the rheology, crystallization and supercritical CO2 foaming behavior of poly(lactic acid)

In this work, poly(glycidyl methacrylate) (PGMA) were grafted onto the surface of saponite to form polymer brushes (m@g-Sap) via surface-initiated atom transfer radical polymerization (SI-ATRP). Moreover, PLA/m@g-Sap nanocomposites foams were prepared by supercritical carbon dioxide foaming with m@g-Sap as fillers. And its comprehensive performance, structure-properties relationship were investigated. It was shown that m@g-Sap as an efficient nucleating agent enhanced the rheological properties, crystallization behavior and foamability of PLA. The pore density of PLA4 (PLA/m@g-Sap (0.7 wt%) nanocomposites foams) is increased by 3 orders of magnitude and its average pore size is reduced by 84.94%. Furthermore, the unique intercalation structure and branched interpenetration network structure of m@g-Sap effectively improved the compression resistance of PLA based nanocomposites foams. Compared with pure PLA foam, the compressive strength of PLA4 platform region increased by 282%. Finally, what's more, the results of simultaneous rheological and in situ IR, molecular dy-namics simulations indicate that there was a significant interaction between m@g-Sap and PLA and CO2, which in turn enhanced the melt strength of PLA based nanocomposites and induced the rapid crystallization of PLA. The above results demonstrated that m@g-Sap had great potential to improve the foaming behavior of PLA.