The rod−coil polymer of ethyl 4-[4‘-oxy-4-biphenylylcarbonyloxy]-4‘-biphenylcarboxylate with poly(ethylene oxide) with a degree of polymerization of 12 (12-4) was observed to exhibit a microphase-separated lamellar structure with nanoscale dimension and to melt into a layered smectic A mesophase. The complexes of 12-4 with 0.05−0.8 mol of LiCF3SO3 per ethylene oxide unit of a molecule were also prepared in order to investigate mesomorphic phase changes of 12-4 upon complexation. An abrupt mesophase change was observed for the entire range of salt concentrations. The complexes with 0.05−0.2 mol of LiCF3SO3 display an enantiotropic smectic A phase as their highest temperature mesophase. From the complex with 0.2 mol of LiCF3SO3, an enantiotropic cubic phase is induced and a smectic A phase disappears at the complex with 0.25 mol of LiCF3SO3, which displays a cubic mesophase only. The complex with 0.3 mol of LiCF3SO3 also exhibits an enantiotropic cubic phase; however, it exhibits a cylindrical micellar mesophase as its highest temperature mesophase, contrary to the complexes with up to 0.25 mol of LiCF3SO3. The complexes with 0.4−0.7 mol of LiCF3SO3 exhibit only a cylindrical micellar mesophase, and the complex with higher salt concentration becomes amorphous. These results, characterized by a combination of differential scanning calorimetry, optical polarized microscopy, and X-ray scattering experiments, are discussed.

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The phase diagram of the blends of a diblock copolymer (A-B) and a random copolymer (ABR) is constructed by the modified confined-chain model developed earlier where the morphology of A-B block copolymer is lamellae and the composition of ABR random copolymer is close to that of A-B. These theoretical results predict a relatively simple phase behavior for the A-B/ABR blends in comparison to the A-B/A blends, A being a homopolymer, studied previously. Unlike in A-B/A blends, the orderdisorder transition temperature in A-B/ABR blends is lowered by the addition of the random copolymer regardless of its molecular weight. It is also found that the fraction of ABR solubilized into the A-B is very limited due to the endothermic mixing interaction between ABR and each block of A-B.

The change in the order−disorder transition temperature (T ODT) of a diblock copolymer, induced by the addition of a random copolymer, was investigated with synchrotron small-angle X-ray scattering and differential scanning calorimetry techniques. The studied block copolymer was poly(styrene-b-butadiene) containing 52 wt % styrene, and the added random copolymer was a small amount of poly(styrene-r-butadiene) containing 50 wt % styrene. The observed transition from the isotropic melt to the lamellar ordered structure appeared as a pronounced discontinuity in the peak's height and shape, and the estimated T ODT was found to decrease as the fraction of a random copolymer increased within the solubility limit (about 15 wt %). It was noted that the interdomain distance (D) decreased slightly upon the addition of a random copolymer, suggesting that the added random copolymer may have dissolved into the interfacial region of the microdomain. The plot of the reciprocal scattering maximum S-1(q*) as a function of the reciprocal absolute temperature T -1 can be fitted satisfactorily to the theoretical prediction based on the work of Fredrickson and Helfand. Also, the shift of T ODT in the blend is calculated with the theoretical prediction developed by Whitmore and Noolandi. The spinodal temperature (T S) and the T ODT decreased along a similar slope with the addition of a random copolymer.