Effects of epoxy resin crosslinking networks on stereocomplexation of poly(l-lactic acid)/poly(d-lactic acid) racemic blends

In contrast to existing methods that add specific substances to poly(l-lactic acid)/poly(d-lactic acid) racemic blends to enhance stereocomplexation, in this study, a crosslinkable epoxy resin (EP) was introduced into a racemic blend. The results showed that, when the mass ratio of EP to racemic blend was 0.2:1 (EP:racemic blend = 0.2), regardless of the amount of diethylenetriamine (DETA) curing agent, homo-crystals in the racemic blend were essentially inhibited. With a fixed EP content, a 0.05:1 DETA to EP mass ratio resulted in a homogeneous poly(l-lactic acid)/poly(d-lactic acid)/EP/DETA mixture. Uniformly dispersed EP network promoted the stereocomplexation of the racemic blend from the melt, but delayed the lamellar thickening of the stereocomplex crystals during heating. Thus, the constrained chain diffusion caused by the uniformly dispersed EP network was likely responsible for these contradictory results. Introducing uniformly dispersed network into poly(l-lactic acid)/poly(d-lactic acid) racemic blends is presumably a promising approach for gaining more insight into poly(lactic acid) stereocomplexation. (c) 2020 Society of Industrial Chemistry