Morphology and molecular miscibility of segmented copoly(ether ester)s with improved elastic properties as studied by solid state NMR

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Gabrielse, Wouter ; van Guldener, Viola ; Schmalz, Holger ; Abetz, Volker ; Lange, Ronald:
Morphology and molecular miscibility of segmented copoly(ether ester)s with improved elastic properties as studied by solid state NMR.
In: Macromolecules. Bd. 35 (2002) Heft 18 . - S. 6946-6952.
ISSN 1520-5835
DOI: https://doi.org/10.1021/ma020029i

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Abstract

The morphology of copoly(ether ester) elastomers, based on poly(butylene terephthalate) (PBT) hard blocks and poly(ethylene oxide)-block-poly(ethylene-stat-butylene)-block-poly(ethylene oxide) (PEO-b-PEB-b-PEO) soft blocks, has been investigated by various solid-state NMR methods. C-13 IRCP and H-1 T-1p NMR experiments show a heterogeneity, in molecular motions for the PEO and PBT segments, indicating the presence of a PEO-rich phase and a PEO/PBT mixed phase. In contrast, for the PEB segments a homogeneous NMR relaxation behavior is observed, indicating the presence of a separate pure PEB phase.. Deuterium NMR spectra recorded of block copolymers with selectively deuterated PBT clearly show at least two distinct motional environments of PBT already at room temperature: a broad peak which is assigned to PBT segments in a crystalline phase and an extremely narrow peak which is assigned to highly mobile PBT segments embedded in an amorphous matrix (PBT/PEO mixed phase). For copoly(ether ester)s with a relatively high PBT content (45%. (w/w)), (HT1)-H-1 inversion-recovery experiments even reveal the presence of a ``pure'' amorphous PBT phase next to the PBT/PEO mixed phase. Hysteresis experiments show that copoly(ether ester)s based on PEO-b-PEB-b-PEO soft blocks have a significantly improved elastic behavior, i.e. lower plastic set, compared to that of PTMO-based copoly(ether ester)s.