The conformation of ethylene oxide segments has been found to vary when they are incorporated into triblock oligomers [H(CH2)(m)(CH2CH2O)(n)(CH2)(m)H] or microblock copolymers [-(CH2)(m)-(CH2CH2O)(n)-](x) of ethylene (E) and ethylene oxide (EO) depending on the relative length (m vs n) of the sequences. Raman spectroscopy, wide-angle X-ray diffraction, and thermal analysis have been used to investigate these conformational variations. Since both segments crystallize, we have found a profound influence of intermolecular interactions on determining the conformation of the EO segment. In the regime where n < 7 (m = 12-20), the EO segment is found in the planar zigzag conformation similar to that observed in oriented poly(ethylene oxide) (PEO) held under tension. When n > 7 (m = 12-20), the EO segments are found to crystallize in the 7/2 helical conformation similar to that found in PEO. In the case where n = 7 (m = 12-20), both the helical and planar zigzag forms of EO are found depending on the thermal and solution processing history. The helical form can be induced by melt-quenching, but annealing at room temperature for several days produces a gradual return to the planar conformation. A conformational transition caused by solvents also occurs and will be discussed.