Study On Modification Of Organic Pigments By Photochromic Materials

Photochromic materials are widely used in the fields of optical instrument materials,image display,variable optical density filtering,optical information storage,photographic templates and optical control switches.Currently,researches on organic photochromic materials mainly focus on spiropyran,spirooxazine,fulgide,diaryl ethylene and other related organic heterocyclic compounds.Microencapsulation technology are widely used in food,printing and dyeing,coating,ink,flame retardant,petrochemical,biological medicine and other fields.In this paper,the preparation of photochromic organic pigment microcapsules by microencapsulation technology after combining organic pigments with photochromic materials was studied.The study is divided into three parts:In the first part,the synthesis and characterization of hexaarylbiimidazole and spiropyran.The photochromic materials of hexaarylbiimidazole were prepared by cyclization reaction of imidazole and oxidation reaction.The yield of 2,2'-bis(4-methoxyphenyl)-4,4',5,5'-tetraphenyl-2'H-1,2'-biimidazole and 2,2'-bis(2-chlorobenzyl)-4,4',5,5'-tetraphenyl-2'H-1,2'-biimidazole,named HABI1 and HABI2,was 89.8% and 85.9%,respectively.The photochromic materials of spiropyran were prepared respectively through fischer indole synthesis reaction,which were 1-chloro-3-(6-chloro-3',3'-dimethylspiro[chromene-2,2'-indolin]-1'-yl)propan-2-ol and 1-(6-bromo-3',3'-dimethyl-8-nitrospiro[chromene-2,2'-indolin]-1'-yl)-3-chloropropan-2-ol,named SP1 and SP2,with the yield of 48.0% and 59.1% respectively.Four photochromic materials were characterized by infrared absorption spectra and nuclear magnetic resonance spectra of hydrogen.In the second part,two different emulsion polymerization methods,interfacial polymerization and in-situ polymerization,were used to explore the technological conditions for the preparation of organic pigment microcapsules modified by photochromic materials.For photochromic compounds of spiropyran,in-situ polymerization was usually used with melamine resin as the capsule wall material of the microcapsule,with phthalate dioctyl as the capsule core material of the microcapsule and with the OP-10 as emulsifier to form the structure of microcapsules.The homogeneous speed and emulsifying time together with ratio of core and wall materials were mainly studied during emulsification.For compounds of hexaarylbiimidazole,interfacial polymerization was mainly used with isophorone diisocyanate and diethylenetriamine as monomer,and with phthalic acid dioctyl ester and butyl acetate as the core material.The influences on the performance of microcapsule were studied with the core material type,ratio of photochromic materials and organic pigments and the selection of emulsifying agent.The relative optimum technological conditions for the preparation of photochromic organic pigment microcapsules were determined by exploratory experiments.In the third part,study was based on the determination of optimum technological conditions for the preparation of photochromic organic pigment microcapsules.Other organic pigments such as phthalocyanine blue,phthalocyanine green and diphenylamine yellow were selected for the synthesis of twenty-two kinds of photochromic materials modified organic pigment microcapsules,and the structure and composition together with performance of microcapsule were characterized and tested.The performance which includes the infrared absorption spectra,core content,particle size distribution and photochromic properties of organic pigment microcapsules were tested.Experimental results show that the properties of microcapsules obtained by different microencapsulation processes are very different.The average particle size of microcapsules obtained by interphase polymerization is 124.1 microns with a narrow distribution and the core content is 60.6%.While the average particle size of microcapsules obtained by in-site polymerization is 153.7 microns with a wide distribution and the core content is 40.8%.