AbstractThe chain modulus of poly(ethylene oxide) is determined by the Raman longitudinal acoustic mode method with the aid of a normal coordinate analysis and found to be 1.3 × 1011dyn/cm2. Our normal mode calculations provide a clear basis for explaining the discrepancy between chain moduli determined from Raman and x‐ray experiments. They show that the uncorrected Raman modulus of helical polymers reflects the presence of interchain interactions and therefore should not be taken as the correct elastic modulus of a single cha