Masakatsu Kochi

Isomeric Biphenyl Polyimides. (II) Glass Transitions and Secondary Relaxation Processes

Dynamic mechanical analysis was performed on a series of the isomeric polyimides (PIs) made from the reaction of s-, a-, and i-BPDA each with 4,4′-ODA, 3,3′-ODA, 1,3,3-APB and 1,4,4-APB. The glass transitions (T g s) moved towards higher temperatures in the order of s-, a-, and i-BPDA for the para diamine-based PIs whereas the T g values showed little change for meta diamine-based PI regardless of the BPDA isomer. Conversely, the temperature of the β relaxation process increased in the order of i-, a-, and s-BPDA with any diamine. These behaviors can be interpreted in terms of the steric hindrance effects due to the configuration of BPDA isomers and diamines.

Photoluminescence of solid aromatic polymers—I. Poly(p-xylylene)

Abstract The fluorescence emission spectrum of poly( p -xylylene) (PPX) film has been studied in detail. The structured strong emission peaking at 370 nm, which had been incorrectly attributed to the associated ground state complexes, was reasonably explained in terms of a small amount of CHCH unsaturation in the main chains. The distribution of intensity among the vibrational progression of this emission band was found to be very sensitive to the crystalline phase transitions and molecular motions of PPX.