Segmented blockcopolymers based on poly(tetramethylene oxide) (PTMO) soft segments and uniform crystallisable tetra-amide segments (TxTxT) are made via polycondensation. The PTMO soft segments, with a molecular weight of 1000 g/mol, are extended with terephthalic groups to a molecular weight of 6000 g/mol. The crystallisable segment is uniform of length and is based on a tetra-amide with terephthalamide groups. The length of the aliphatic diamine (x) in the tetra-amide segment is varied from x = 2 to 8. The thermal properties 9 of the blockcopolymers were studied with dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Due to the use of uniform TxTxT segments a fast and almost complete crystallization of the hard segments is obtained. The melting temperature of the blockpolymers increases with decreasing diamine length and the well-known odd-even effect is observed. The elastic behavior of the blockcopolymer was studied by compression set. All the blockcopolymers had a low compression set and were highly elastic. (C) 2004 Elsevier Ltd. All rights reserved.