The Photo-Induced Anisotropy Properties Of Azopolymer And Its Application

The dissertation includes two parts. Part I is the investigation about effect of molecule structure on photo-induced alignment of azo-containing polymer film. Part II is fabrication of axially-symmetric phase retardation plate by use of azobenzene-containing copolymer. The contents of these parts are as follow。1. The introduction of properties of azobenzene and some basic knowledge of optics.2. The AzoNO2-co-HEMA and biAzoNO2-co-HEMA were prepared. A device for measuring birefringence was set up.Photo-induced alignment process of the prepolarized film and unprepolarized film were performed,using this device under irradiation of linearly polarized light at 442nm.It was found from the work that the birefringence of biAzoNO2-co-HEMA in our experiment was 5 times of the AzoNO2-co-HEMA. Furthermore,the birefringence of the two material was found became larger when the material was had been prepolarized.Supramolecular bisazopolymers was prepared basing on the experiment result of AzoNO2-co-HEMA and biAzoNO2-co-HEMA by connection of two azobenzene groups via hydrogen bonding.The supramolecular bisazopolymers contain poly(6-(4-(pyridin-4-yldiazenyl)phenoxy)hexyl methacrylate) (pAzopy) as a hydrogen bonding acceptor and 4-((4-hydroxyphenyl)diazenyl)benzonitrile (AzoCN) as a hydrogen bonding donor . High quality films of the supramolecular bisazopolymers with different molar ratios of donor/acceptor from 0.25 to 1 are prepared .The induced birefringence and relaxation curve of the azobenzene containing copolymer with different molar ratio(0,0.25,0.5,0.75,1)was measured。The results showed the birefringence of this series increase from 0.0265 to 0.1 , respectively, as molar ratio in the samples increases, which indicates a larger proportion of AzoCN enhances both the birefringence and its stability. We also use an azopolymer without pyridine groups (pAzoCH3) and AzoCN to do a control experiment, which shows that pAzoCH3/(AzoCN)1.0 do not show significant enhanced birefringence and its stability. The enhancements in pAzopy/(AzoCN)x are because of the unique structure of the supramolecular bisazopolymers.Cross-linked azobenzene containing copolymer was synthesized and utilized to fabricate axially-symmetric phase retardation plate. Based on the photo-isomerization characteristics of azobenzene copolymer, a linearly polarized light inducing device was set up. The device consists of three parts:the fabrication part,the detection part and the computer software.Placed on a rotating stage which was controlled by a five phase stepping motor, the azobenzene film was irradiated by the linearly polarized light to form molecule alignment of axially-symmetric distribution. During the fabrication process,the light beam kept still, the sample was rotated with the rotating stage. Meanwhile,the detection part recorded the birefringence of the sample.When the birefringence reached the number which we needed, we stop the process.The experimental results show the induced birefringence of the sample is 0.0205. Its thickness is 3um and the phase retardation is 65°. The axially-symmetric phase retardation films have a wide application in many domains such as high-resolution measurement, materials processing and optical waveguides.