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Thermal concentration fluctuation in the blends of deuterated poly(ethyl- ene oxide) (dPEO) and poly(vinyl acetate-co-vinyl alcohol) (P(VAc-VOH)) with various VOH contents fOH were examined by small angle neutron scattering techniques at a fixed blend composition, dPEO/P(VAc-VOH) ¼ 20/80 which is close to the critical com- position. Blends at the highest fOH (¼0.35) showed a non-Lorentzian scattering pro- file: specifically the scattering intensities at the low q (angle) region were suppressed compared to those expected from the random phase approximation (RPA) theory. However, for the blends at lower fOH (� 0.28), the profiles could be represented by the RPA. Using the RPA we determined effective values of the Flory-Huggins interaction parameter veff as a function of fOH (¼0-0.28). The veff showed the minimum around fOH ¼ 0.1-0.18 meaning the highest miscibility of the blend at these fOH. On the ba- sis of the random copolymer theory, we evaluated the three interaction parameters vAc-EO, vEO-OH, and vAc-OH separately from the veff(fOH) and found the order of mag- nitude; vAc-EO \ 0 \ vEO-OH \ vAc-OH. The largest positive vAc-OH showing intra- chain interaction in the P(VAc-VOH) copolymer was concluded to be the origin of the enhanced miscibility at around fOH ¼ 0.1-0.18. On the basis of the Coleman and Painter's theory, the effects of hydrogen bonding on these three vA-B were discussed.

We studied the dielectric relaxation behavior of low mass compounds (LMC) mixed in polystyrene (PS). Specifically, LMCs that are used are alkyl-cyanobenzene (nCBz, n = 0), alkyl-cyanobiphenyl (nCB, n = 0, 1, 3, 5, and 7), and alkyl-cyanoterphenyl (nCT, n = 5), where n represents the number of carbon atoms of the normal alkyl groups of the LMCs. Owing to a much larger dipole moment of the cyano group than that of PS, only motions of the LMCs were observed. In a blend of 5CT (5 wt %)/PS, single relaxation process designated as α was observed. On the other hand, in nCB (5 wt %)/PS, partially overlapped two relaxation processes (α and β) were observed in the order of decreasing temperature. We assigned the α process to cooperative motions between the LMC molecules and the PS segments, and the β process to spatially restricted motions of the LMC molecules in the glassy state. In 0CBz (8 wt %)/PS, the α and β processes were observed in distinct temperature regions and the intensity of the α peak was comparable to that of pure PS, indicating that the 0CBz molecules do not move cooperatively with the PS segments. We conclude the existence of two critical sizes (I and II) of LMC in relation to cooperativity: when an LMC molecule is smaller than the size-I, the motions of the LMCs and PS segments decouple each other, but above the size-I, they become cooperative. Above the size-II, the spatially restricted motion (β-process) of LMC does not occur. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 967–974, 2006

We investigated the segmental and terminal relaxation dynamics of a well-characterized disordered diblock copolymer, poly(isoprene-b-vinyl ethylene) (PI-PVE), and miscible blends of polyisoprene (PI)/poly(vinyl ethylene) (PVE), using dielectric and viscoelastic spectroscopies. Generally, the concentration fluctuation (CF) amplitude of a disordered diblock copolymer is smaller than that of the miscible blend, especially in a length scale longer than the size of the whole block chain. To test whether the difference in the CF amplitudes causes the difference in the segmental relaxation spectra, we compared the shape of the dielectric loss curves between PI-PVE and PI/PVE with the same composition (PI/PVE ratio = 17:83). However, no appreciable difference was observed, indicating that the CF amplitudes in PI-PVE and PI/PVE are not so different in the length scale of the segmental motions. We also examined the effect of distinct friction coefficients of the PI and PVE chains on the terminal relaxation dynamics by comparisons of the viscoelastic and dielectric normal mode relaxations in PI-PVE. The former probes the whole chain motion and the latter probes motions of the PI block. Shift factors (aT) for the viscoelastic and dielectric relaxations were compared. The dielectric normal mode aT was found to have weaker temperature dependence than the viscoelastic aT, which indicates that the friction for the PI block chain is lower than the average friction for the PI-PVE chain. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4084–4094, 2004

The oxidation of monoalkyl 2-(9H-xanthenyl)malonates 1 with Mn(OAc)3 gave the 9- or 10-dibenz[b,f]oxepincarboxylates 2 in good yields. The reaction proceeds with high regioselectivity except for the case of (1-methoxyxanthenyl)malonate 1 (R1 = Me, R2 = 1-MeO), which gave two regioisomers. It was proposed that the process for the formation of 2 must include the 1,2-aryl radical rearrangement followed by oxidative decarboxylation.