Phase Separation and Lamellae Assembly below UCST in Poly(l-lactic acid)/Poly(1,4-butylene adipate) Blend Induced by Crystallization

Abstract

The crystalline/crystalline poly(l-lactic acid)/poly(1,4-butylene adipate) (PLLA/PBA) blend system exhibits upper critical solution temperature (UCST) behavior below the melting temperature of PLLA. When the PLLA/PBA (50/50) blend is cooled to crystallize below UCST, phase-separated domains appear prior to crystallization of PLLA, resulting in PLLA spherulites being overlapped with the phase-separated domains. However, phase-separated domains only appear in blends when they are crystallized after being subjected to maximum melting temperature (Tmax) for a short melting time (Δtmax 5 min). When PLLA/PBA (50/50) blend is melted for short Δtmax, the chain entanglement density is less; thus, the PBA chains are easy to be mutually expelled from the PLLA chains during crystallization of PLLA, resulting in PLLA-rich and PBA-rich separate domains. Apparently, phase separation in the PLLA/PBA blends is initiated by the ...