Direct Measurement of Chain Stretching in Diblock Copolymers at the Microphase Separation Transition

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Abstract
The microphase separation transition (MST) in poly(styrene-b-paramethylstyrene) diblock copolymers is investigated by small-angle neutron scattering. In a blend of fully deuterated and protonated chains the conformation of single chains as a function of temperature is obtained. We observe chain stretching at MST of approximately 5% going from the disordered to the ordered regime. Directly determined radii of gyration are compared to calculated ones, which are obtained from an analysis of the Leibler-peak position. Results are discussed in the context of recent theories and computer simulations.