A series of polyether esters thermoplastic elastomer

based on polyethylene glycol (PEG) as the soft segment and poly(butylene terephthalate)(PBT) as the hard segment

are synthesized by molten polycondensation and characterized by means of NMR

IR

DSC and mechanical testing．The influence of hard segment lengths on the properies of the copolymer is investigated in the case of the soft segment length remaining constant．It is observed that

first

the lenghth of hard segments calculated from 1H-NMR spectra is increased with the decrease of PEG content；secondly

four phases corresponding to the amorphous and the crystal phases of soft and hard segments coexist at certain temperatures；thirdly

the glass transition temperature (Tg) of the soft segment is increased

at the same time its molten point (Tm) and the degree of crystal (Wc) are decreased with the increase of the PBT segment length．Moreover

the inherent viscosity changes from 1.34 dL／g to 1.72 dL／g

and water uptake increases from 29.4％ to 104.4％ as the PEG content changes from 30％ to 80％(wt)．Although all copolymers are distinguished by a high elastic and plastic deformation and break at very high relative deformations

the sample of high PEG content displays the typical high elastic state

while the sample of low PEG centent exhibits neck-formation characteristics in the stress-strain curve．Obviously

the material’s properties under constant soft segment length can be tailored conveniently by changing the weight ratio of two components in formula.