By means of encapsulation method

poly(vinyl alcohol) (PVA) dispersed liquid crystal films (PDLCs) have been prepared with 4-pentyl-4'-cyanobiphenyl (5CB) as a liquid crystal (LC) phase and N

N'-didodecyl-N

N

N'

N'

N- pentamethyl-1

4

7-triazaheptane diiodide as a Gemini surfactant.The effects of Gemini surfactant with a concentration slightly larger than its critical micelle concentration (CMC) on the microstructures and electro-optical properties of PDLCs have also been investigated.The addition of Gemini surfactant slightly enhances the compatibility between PVA and LC.The PDLC films still retain high degree of phase separation

i.e.

0.85

in comparison with 0.92 for PDLCs without any surfactant.The LC phases are uniformly dispersed in PVA matrix

but the size of LC droplets decreases greatly from 2~30 m without surfactant to 2~5 m with the addition of Gemini surfactant.Moreover

the configuration of LC director changes to be radial from bipolar.Additionally

the addition of Gemini surfactant increases the contrast and the response speed of PDLCs

and retains a low driving voltage of 4.6 V.The transparency under zero voltage

switch-on time and switch-off time are 51.8%

18 ms and 14.2 ms for the PDLCs without surfactant

10.2%

1.5 ms and 10.5 ms for the PDLCs with Gemini surfactant

respectively.