We present evidence for a change in electron–phonon coupling across a bulk phase transition. Below the lattice stiffening transition at around 160K, there is a change in the diffracted peak width observed by neutron and X-ray scattering techniques. Also, the electronic band structure of the copolymer is shifting in binding energy below 160K, decreasing the density of states near the Fermi level. The value of the effective Debye temperature above the transition temperature is approximately 50K, while below 160K, the value of the Debye parameter is 245K. We postulate that the coupling between electrons and phonons results in a static distortion of the lattice (below 160K), and this distortion “melts” above 160K.