Orthogonal crystal orientation in double-crystalline block copolymer

Ming Champ Lin, Yi Chin Wang, Jean Hong Chen, Hsin Lung Chen*, Alejandro J. Müller, Chun Jen Su, U. Ser Jeng

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

23 Scopus citations


In this study, we explore the orientation of crystals formed within the lamellar domains of a diblock copolymer composed of two crystallizable blocks, that is, poly(l-lactide)-block-polyethylene (PLLA-b-PE). The orientation of both PLLA and PE crystals with respect to the lamellar interface was examined under two types of crystallization condition with a broad range of crystallization temperatures (Tc). The first type was the "two-stage crystallization", where the PLLA block was allowed to crystallize before PE. The second was the "one-stage crystallization", where PLLA and PE blocks competed to crystallize. A homeotropic crystal orientation was always observed for the PLLA crystals, with the crystalline stems lying parallel to the lamellar normal regardless of the crystallization condition, except when T c approached the glass-transition temperature of PLLA, where the orientation became random. A homogeneous crystal orientation with the PE crystalline stems oriented perpendicular to the lamellar normal was always identified at low-to-intermediate degree of undercooling, whereas at large undercooling, the crystals showed random orientation. The "orthogonal orientation" disclosed here was preserved over a broad range of undercooling. Our results further demonstrated that the orientation of both PLLA and PE crystals depended mainly on Tc but was independent of the competitiveness of the two crystallization processes. This was a consequence of the strong segregation that made the two blocks crystallize independently within their respective microdomains.

Original languageEnglish
Pages (from-to)6875-6884
Number of pages10
Issue number17
StatePublished - 13 09 2011
Externally publishedYes


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