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A model set of 1,4-polybutadiene-l,2-polybutadiene diblock copolymers has been prepared and molecularly characterized. Physical characterization by differential scanning calorimetry (DSC) and qualitative identification of the flow behavior (liquidvs. solid-like) over a period of several days have established die critical degree of polymerization for this system as Nc = 1.20 (± 0.14) X 103. Below the microphase separation transition the polymers exhibit a single broad glass transition, as measured by DSC, which has been attributed to local segment density fluctuations. This effect was found to be dependent on the degree of polymerization, as predicted from theory.

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