Nineteen oxybutylene/oxyethylene/oxybutylene triblock copolymers [B n /2 E m B n /2, E = oxyethylene, OCH 2 CH 2; B = oxybutylene, OCH 2 CH(CH 2 CH 3 )] were prepared and characterized. Twelve of the copolymers microphase-separated in the melt. Investigation of this microphase-separation behavior using small-angle X-ray scattering (SAXS) yielded values of the domain spacing ( d -spacings) in the ordered phases and of the temperature of the order−disorder transition ( T ODT ). In several cases the ordered phase structure was deduced from a combination of 1D and 2D SAXS and rheology. Values of T ODT for the triblock copolymers were ca. 100 °C lower than those for E m B n diblock copolymers of identical composition and chain length but 30 °C higher if compared with diblock copolymers of half the triblock length. Values of the d -spacings indicated that the triblock copolymers were 10% more stretched than corresponding diblock copolymers. Determination of the Flory−Huggins parameter ( χ ) for the diblock and triblock systems gave identical results. The experimental results are compared with the prediction of mean-field theory.
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Mai et al. (2000) studied this question.
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