Supporting data for "Physical Aging of Polylactide Based Graft Block Polymers"

Abstract

These files contain primary data along with associated output from instrumentation supporting all results reported in Haugan et al. Physical Aging of Polylactide Based Graft Block Polymers. In Haugan et al. we found: Graft block polymers (BCPs) with poly(4-methylcaprolactone)-block-poly(lactide) (P4MCL-PLA) side chains containing 80 to 100% PLA content were synthesized with the aim of producing tough and sustainable plastics. These graft BCPs experience physical aging and become brittle over time. For short aging times, ta, the samples are ductile and shear yielding is the primary deformation mechanism. A double yield phenomenon emerges at intermediate ta where the materials deform by crazing followed by shear yielding. At long ta the samples become brittle and fail after crazing. PLA content strongly governs the time to brittle failure, where a 100% PLA graft polymer embrittles in 1 day, an 86% PLA graft BCP embrittles in 35 days, and at 80% PLA the material remains ductile after 210 days. Molecular architecture is also a factor in increasing the persistence of ductility with time; a linear triblock ages three times faster than a graft BCP with the same PLA content. SAXS and TEM analysis reveal the role of the rubbery P4MCL domains in initiating crazing by cavitation. Pre-straining the graft BCPs also significantly toughens these glassy materials. Physical aging induced embrittlement is eliminated in all the pre-strained polymers, which remain ductile after aging for 60 days. The pre-strained graft BCPs also demonstrate shape memory properties. When heated above Tg the stretched polymer within seconds returns to its original shape and recovers the original mechanical properties of the unstrained material. These results demonstrate that graft BCPs can be used to make tough, durable, and sustainable plastics and highlight the importance of understanding the mechanical performance of sustainable plastics over extended periods of time following processing.