CN-PPV is one of the important series of PPV and its derivatives

demonstrating very high quantum efficiency of over 4% in a two-layers device

ITO/PPV/CN-PPV/Al. It is widely known that the defects in the polymer backbone can affect the properties of the device. The main structural defects in PPV-type conjugated polymers involve the "tetrahedral" structural segments and the E-double bone configurations. In order to achieve a better understanding to the structure of MEH-CN-PPV

the model compound (8a) (Z

Z-configuration) was synthesized. The Z/E-isomerization of the vinylene moiety with cyano group happened easily under the influence of visible and UV light. (8a) dissolved in chloroform was irradiated in daylight for 2 days under purging nitrogen. Its NMR spectrum become more complex

which showed the occurrence of the Z/E-isomerization. Through a careful separation for this mixture by column chromatography (silica gel

cyclohexane/ dichloromethane 2:5) in the dark

two new compounds (8b) (a green solid) and (8c) (yellow oil) were obtained. According to the

1

H-NMR spectra

the configuration of (8b) was E

E and that of (8c) was Z

E. In the

1

H-NMR spectrum of the copolymer MEH-CN-PPV

the main signals were similar to (8a)

which indicated that the configuration of the copolymer MEH-CN-PPV was mainly Z. Some feeble signals at 6.47×10

-6

and 3.32 ×10

-6

were similar to the signals of the protons on the vinylene bond and OCH related with the E-configuration in (8b) and (8c). Hence these signals can prove the presence of the E-configuration in MEH-CN-PPV backbone. The ratio between the signal (d) and the signal (a) was 0.09. The contents of the Z/E-configuration could be estimated: for Z-configration was 85% and 15% for E-configration.