New highly phenylated bis(phthalic) and bis(naphthalic) anhydrides and polyimides therefrom - Polyimides and Other High Temperature Polymers - page 106

Table 4.
Maxima of absorption and fluorescence spectra of phenylated polymers

VA-VG

Polymer

a max , nm f max , nm

λ λ

A 390 490

B 392 550

380 500

C

D 410 560

E 395 500

389 500, 540

F

G 384 480

', of the phenylated PIs. These values
vary from 2.72 to 3.10 and 2.89 to 3.44 at relative humidities of 0 and 50%,
respectively, with an electric field frequency of 1 kHz. Phenylated PIs

Table 3 also shows the dielectric constant, ε

containing trifluoromethyl and hexafluoroisopropylidene groups have the smallest
dielectric constants (2.75 and 2.72, respectively, at the zero humidity). At a humid-
ity of 50%, the dielectric constant of these polymers varies from 2.89 to 3.44; i.e.,
these values are 0.3 higher than those of the corresponding phenylated PIs measured
at zero humidity. The reduced moisture absorption of fluoro-containing phenylated
PIs ensures the long-term stability of their dielectric parameters.
Table 4 shows some photophysical characteristics of the phenylated PIs exam-
ined (for the corresponding polymer films under similar experimental conditions).
For phenylated PIs, the maxima in the absorption spectra,

VC and VG

a max appear in the 380-
410 nm range. All the studied polymers fluoresce in the red region with maxima
at

λ

f max = 480-560 nm. The fluorescence spectra of

ex-
hibit similar profiles with maxima at 490 nm. Unlike these polymers, the poly-
mers

λ VA , VB , VC , VE and VG

VD and VF fluoresce strongly. The VF polyimide shows two maxima at

f max of the

500 and 540 nm, whereas the λ VD polymer (560 nm) is shifted by 20

nm to longer wavelengths.
Phenylated PNIs were synthesized by high-temperature polycyclocondensation
in p-chlorophenol via the reaction of compound III with the equimolar amounts

of various aromatic diamines (Scheme 2). All the reactions proceeded

under homogeneous conditions. This enabled us to synthesize polymers with a re-
duced viscosity of 0.52-0.78 dl/g. The yields of the phenylated PNIs were close to
the theoretical value.
The structures of phenylated PNIs were confirmed by FTIR, Raman, and 1 H
and 13 C NMR spectroscopies. Carbonyl peaks were observed in the IR spectra of
phenylated PNIs at 1713 and 1673 cm -1 . The 13 C NMR spectra of

IVA-IVG

poly-
mers exhibited two signals at -164.0 and -164.2 ppm, which were assigned to
two nonequivalent carbons of naphthalimide carbonyl and a triplet at 200 ppm,
corresponding to the carbonyl of the benzophenone moiety of the three isomers.

VIA-VIG