Sprecher
Beschreibung
Abstract: Understanding the structural development and stereocomplex (SC) formation in polylactide (PLA)based block copolymer systems has garnered significant interest for tailoring material properties and expanding potential applications. In this study, we investigate the structural and morphological evolution of melt-quenched diblock copolymers, poly(isoprene‑b‑ʟ‑lactide) (PI-b-PLLA) and poly(styrene‑b‑ᴅ‑lactide) (PS-b-PDLA), and their equimolar blend, which promotes the formation of a non-covalent triblock terpolymer, polystyrene-SCPLA-polyisoprene (PS-SC-PI) during controlled heating. For PI-b-PLLA, fractional crystallization of the PLLA block occurs under soft confinement. Specifically: (i) PLLA initially crystallizes into metastable β and forms, which subsequently transform into the stable form; (ii) persistent microphase separation is observed between 70–110 °C, accompanied by significant thickening of microdomains; and (iii) above 110 °C, breakout crystallization indicates a transition beyond the soft confinement regime[1]. In contrast, PDLA in PS-b-PDLA crystallizes directly into the form, constrained by the microphase-separated morphology. In melt-quenched blends, PLA crystallizes above the glass transition temperature into the SC form, along with metastable intermediates such as the SC mesophase, (), β, and form within the microphase-separated framework, which gradually evolve into the stable SC structure. Above 200 °C, a new reflection at 2 = 21.7° appears, indicating altered SC lattice packing. Microphase separation is retained below 180 °C, whereas breakout crystallization above this temperature signifies the breakdown of confinement. These findings shed light on the confined crystallization behavior and SC formation pathways in PLA-based block copolymers, offering valuable insights for the design of high-performance biodegradable materials.