The structure of water in PEO-based segmented block copolymers and its effect on transition temperatures

The effect of water on block copolymers that contain hydrophilic PEO flexible segments is studied. The polyether phase consisted of either PEO or mixtures of PEO and hydrophobic PTMO, monodisperse crystallisable T6T6T was used as hard segments. Water absorption as a function of relative humidity and PEO content were studied. The PEO melting temperature and crystallinity were strongly reduced when the copolymer absorbed water, while the PTMO phase remained unaffected by its presence. Freezing water was present in the PEO-based copolymers when the PEO phase contained 30 vol.-% water, its relative amount being almost independent of PEO concentration and molecular weight and the presence of hydrophobic PTMO segments.