Study On New Photochromic Materials

In the past few years,spiropyran has emerged as the molecule-of-choice for the construction of novel dynamic photochromic materials.This special molecular switch undergoes structural isomerisation in response to a variety of orthogonal stimuli,e.g.light,temperature,p H,metal ions,and mechanical stress.In addition,spiropyran compounds are of great significance in the field of optical information storage and biology.Therefore,our group envisage to embed two kinds of spiropyran photochromic in polysiloxane,aiming at the development of spiropyan-based smart materials that can response to multiple stimuli and can serve as unique,highly sensitive and selective,and reversible sensor system.Herein,we successfully synthesized a type of spiropyran-grafted polysiloxane based on the former research of our group and investigation on the multiple responsive behavior of the polymer.The research contents include two parts:In the first part,we have synthesized two kinds of novel spiropyran compounds,and grafted onto poly?methylhydrosiloxane?via hydrosilylation by using H2 Pt Cl6·6H2O as catalyst.And the yield of two spiropyran compounds?1-allyl-6-nitro[2H]-1-benzopyran-2,2'-indoline?;1-allyl-6chloride-[2H]-1-benzopyran-2,2'-indoline)was 49% and 57%,respectively.Two kinds of new photochromic materials?SP1-Si,SP2-Si?were obtained by grafting onto poly?methylhydrosiloxane?.First and foremost,the synthesized target polymer?SP1-Si and SP2-Si?was characterized by the FT?IR Spectroscopy and GPC measurements.Through comparing the difference of SP-Si and poly?methylhydrosiloxane?,there are obvious changes of absorption peak at 2100cm-1 in the FT?IR spectrum,the characteristic peak belongs to the stretching vibration of Si-H bonds,both two kind of target polymer and poly?methylhydrosiloxane?have a same absorption at 1100 cm-1 due to the characteristic peak that attribute to Si?O?Si bonds,the results show that the Si?H bonds had bonded with carbon-carbon double bond which from spiropyran monomers.Therefore,we can preliminary infer that spiropyran monomers had grafted onto poly?methylhydrosiloxane?.In this paper,the molecular weight of two kinds of target polymers was determined by GPC;SP1-Si;Mw: 21660,Mn: 19410,PDI: 1.116;SP2-Si;Mw: 59094,Mn:41482,PDI: 1.425.The structures of spiropyran monomers and two target polymers were confirmed by IR and GPC.In the second part,we studied the properties of two kinds of new photochromic materials.Firstly,the thermal stability of the target polymer through TGA measurement was studied.22.1%weight loss measured form 190.3°C to 309.1 °C of SP1-Si;quality lost only 22.1%;and the78.72% weight loss of SP2-Si was measured from 245.3°C to 552.4°C.and the mass loss was78.72%.It can be concluded that the two target polymers have good thermal stability.The property of photoluminescence of the polymer was discussed by UV spectra.We dissolved SP1-Si into ethanol,and its stable as a type of yellow solution under dark conditions or UV light,the solution became colorless when exposure to the visible light.While the SP2-Si was stable as a type of yellow solution under dark conditions,but it became light yellow when exposure to the visible light and UV light which showing the inverse photochromes phenomenon.The results further strengthens that target polymer,which also maintained photochromic properties while not affect by grafting onto poly?methylhydrosiloxane?.It was found that the polymer SP1-Si and SP2-Si could respond to external stimulus,such as p H,Ag⁺ and Fe³⁺.The polymer solution will become orange and yellow after the addition of Ag⁺ and Fe³⁺,the color of solution became deeper with the increase of time after addition of the Ag⁺,it also has good sensitivity,interference immunity to Ag⁺ and Fe³⁺.And LOD?The limit of detection?for Ag⁺ ions were 1.06 × 10-5M?SP1-Si?: 1.45 ×10-6M?SP2-Si?,respectively.For Fe³⁺ ions were 1.25 × 10-5M?SP1-Si?and 3.52 × 10-6M?SP2-Si?,respectively.