Nanoscale Order and Crystallization in POSS-PCL Shape Memory Molecular Networks

Bonifacio Alvarado-Tenorio, Angel Romo-Uribe, Patrick T. Mather

Research output: Contribution to journalArticle

33 Scopus citations

Abstract

The angstrom- and nanometer-scale crystallization and long-range ordering behavior of polyhedral oligosilsesquioxane-poly(ε-caprolactone) (POSS-PCL) shape memory nanocomposites under thermomechanical shape memory cycles and uniaxial stretching were studied by simultaneous wide-angle and small-angle X-ray scattering (WAXS/SAXS). POSS/PCL cross-linked molecular networks featuring a single POSS moiety centered between two PCL network chains, previously reported [ Alvarado-Tenorio et al. Macromolecules 2011, 44, 5682-5692 ], with molecular weight of 2600 g/mol and exhibiting shape memory behavior, were synthesized with variation of cross-linking molar ratio (POSS-PCL diacrylate/tetrathiol cross-linker, 2:1, 2:1.5, and 2:2). The photocured networks exhibited a morphology consisting of POSS crystals embedded in an amorphous PCL matrix, and the POSS crystals were ordered in a cubic nanostructure. However, under tensile stress afforded by a shape memory cycle, the networks yielded a double-induced orientation (90° and 180°) of the POSS crystals, as indicated by the 101 reflection. Moreover, we detected stretch-induced crystallization of the otherwise amorphous PCL chains. Investigation of nanometer-scale structure by SAXS revealed long periods along the meridional and equatorial axes corresponding to a lamellar nanostructure of PCL chains coexisting with the cubic POSS superstructure. We conclude that the shape memory cycles promoted crystallization and highly ordered nanostructures. (Graph Presented).

Original languageEnglish (US)
Pages (from-to)5770-5779
Number of pages10
JournalMacromolecules
Volume48
Issue number16
DOIs
StatePublished - Aug 25 2015

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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