A sample of disubstituted poly(acetylene), poly[1-(trimethylgermyl)-1-propyne], containing, on average, 90% trans double C=C bonds was fractionated, and birefringence induced by a pulsed electric field (the Kerr effect) in dilute solutions of the as-obtained fractions was studied. It was discovered that, in the Gaussian region, fractions with similar molecular masses have different electrooptical properties. The trans chain of the polymer was analyzed by the quantum-chemical semiempirical PM-3 method, and the helix of type 4₁ was found to be the most optimum conformation. The presence of more polar (compared to irregular fragments) and optically anisotropic trans helical fragments with various lengths in the polymer macromolecular chains (stereoblocks) is responsible for the different electrooptical behavior of the studied fractions.