Morphology And Molecular Miscibility Of Segmented Copoly(Ether Ester)S With Improved Elastic Properties As Studied By Solid State Nmr

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.