Copolyetheresteramides with bisesterdiamide units of a uniform length were synthesized in the current study, and the dynamic mechanical and elastic properties of the copolymers produced were studied. Diols are used to extend the length of uniform bisesterdiamide hard segments. Extenders have a twofold effect: increasing the lamellar thickness of the bisesterdiamide crystals and having the ability to independently adjust the ratio between the hard and soft segment. It was found that polymers containing 1,12-dodecanediol as an extender possess a multiphase structure. Two glass-transition temperatures (T-g) were observed along with a very broad melting transition. The T-g at about -70 degreesC was found to originate from the amorphous polyether phase, the T,at about 140-175 degreesC was attributed to a glassy aramid-1,12-dodecanediol phase. The broad melting transition was caused by the presence of the wide variety of lamellar sizes. This multiphase morphology is probably results from the liquid-liquid demixing of an aramid-polyether and from the aramid-extender phase. Polymers containing 1,12-dodecanediol and 13 wt % aramid had an improved elasticity compared to similar polymers without an extender. It is thought this is the result of large isolated, spherically shaped domains become less plastically deformed than the crystalline network of thin lamellae.