Synthesis And Characterization Of Photorefractive Polymers Based On Polyphosphazene

Nonlinear optical (NLO) materials have been widely researched. The development of NLO materials is very rapid in both synthesis and applications. They have been obtained great applications in the fields of national defence, industries and commodities. However, their applications are restricted due to the nonlinearity-transparency trade-off especially. Polyphosphazenes present a number of useful features for practical devices, such as the excellent flexibility of the backbone, high thermal and oxidative stability, optical transparency from 220 nm to the near-IR region. And controlled incorporation of covalently chromophores can be easily accomplished over a broad concentration range. They have been the focus of much recent research.Polyphosphazenes are inorganic-backbone polymers resulting from the repetition of the–P=N- monomer unit and with two side groups linked to the phosphorus atoms. Because the backbone has no–C-C- bonding or conjugatedπbonding, they are flexible; the backbone has good optical transparency. The chlorine atoms are highly reactive and they can be easily replaced by different groups. The ratio of different groups can be easily tailed. The photorefractivity can be enforced due to the intercourse between backbone and side groups and can get better features by forming network polymers. They combine the advantages of organic and inorganic materials and present some unique performance.A series innovative research works have been carried out and based on synthesis of a new type of photorefractive polyphosphazene polymers at the first time. The work is depicted as follows.A new kind of chromophore intermediate that has brand new chemical structure was synthesized by designing multi-dipolar chromophores. The chromophore intermediate was characterized by means of 1H NMR, 31P NMR, FT-IR, UV-Vis, Elemental Analyses, DSC, TGA and GPC. It presents high thermal stability and glass-transition temperature Tg (>120℃), good transparency. The intermediate was proved to be a competitive candidate.The chlorine atoms of backbone can be replaced by chromophore intermediate through nucleophilic substitution. Some photorefractive polymers with different terminal groups are synthesized and characterized by means of 1H NMR, 31P NMR, FT-IR, UV-Vis, Elemental Analyses, DSC, TGA and GPC.Birefringence of the polymers are about 10-2, silimar to that of other materials coming recently. At the same time, the plymers'transparency is good enough: the maximum absorptionλmax are between 354-375nm, the absence of absorption between 425-465. They provide a wide transparent window and dozens of blueshift compared to other materials which have excellent photorefractivity. The polymers'Tg are between150-180℃, which ensure the stability when the polymers are in metastable state. It is the first time that polyphosphazene polymers were observed to present photorefractivity without adscititious electric field or advanced polarization in room temperature. According to previous research, the presentation of organic materials'photorefractivity usually needs adscititious electric field or advanced polarization. These polyphosphazene polymers are a new kind of materials which are called all-optical photorefractive materials. To these materials, possible damage to the materials causing by adscititious electric field or advanced polarization does not need to be considered. Membrane of the polymers could be made thicker to get better performance when there is no restriction of adscititious electric field or advanced polarization.