Inversion of crystallization rates in miscible block copolymers of poly(lactide)-: Block -poly(2-isopropyl-2-oxazoline)

Research output: Contribution to journalArticleScientificpeer-review

Researchers

  • Fabian Pooch
  • Marjolein Sliepen
  • Kirsi J. Svedström
  • Antti Korpi

  • Françoise M. Winnik
  • Heikki Tenhu

Research units

  • University of Helsinki
  • National Institute for Materials Science Tsukuba
  • University of Montreal

Abstract

Miscible block copolymers (BCPs) are rarely studied. When one or both components of such BCPs are semi-crystalline polymers, strong effects on the crystallization behavior can be expected. We present a study of 18 miscible BCPs comprised of poly(lactide) (PLLA, semi-crystalline and PDLLA, amorphous) and poly(2-isopropyl-2-oxazoline) (PiPOx, semi-crystalline) with PiPOx volume fractions of 0.14 < φPiPOx < 0.82. All BCPs exhibit a single glass transition and form a homogeneous melt. Mixing has a plasticizing effect on PiPOx and increases its crystallization rates (DSC). In contrast, the crystallization rates of PLLA are dramatically reduced, or in most cases entirely prevented. During isothermal crystallization at 130 °C, the crystallization rates of the BCPs were inverted in comparison with those of the parent homopolymers. Crystallization drives the BCPs to phase separate and the formed crystalline structure is that of the parent homopolymers. The fast crystallization of PiPOx confines the observed superstructure. The BCPs were studied on multiple length scales-from the atomic level (WAXS, IR spectroscopy) to the meso level (AFM, SAXS) and the macroscopic superstructure (polarized optical microscopy). A mechanism of the structure evolution is presented.

Details

Original languageEnglish
Pages (from-to)1848-1856
Number of pages9
JournalPolymer Chemistry
Volume9
Issue number14
Publication statusPublished - 14 Apr 2018
MoE publication typeA1 Journal article-refereed

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