5. Polyaniline PAN
In the same year, PolyVaniline film was successfully developed in foreign countries in 1980. Due to its many advantages, it has always been at the forefront of international research. It has become a new hot spot in conducting polymer research. Polyaniline can usually be prepared by electrochemical polymerization and chemical polymerization. The conductivity, morphology and properties of polyaniline obtained by selecting different synthesis methods and process conditions are quite different. Since Diaz succeeded in preparing active polyaniline films by electrochemical polymerization, the electrochemical polymerization and electrochemical properties of polyaniline have been studied in depth. According to different conditions, polyaniline prepared by electrochemical method, It can be a thin film or a powder deposited on the electrode surface. Compared with other conductive polymers, PAN has the following characteristics: 1 Diversified structure. Different molecular structures, their color and conductivity also change accordingly; 2 good electrical conductivity. After the PAN is doped, the conductivity can be as high as 10 square s/cm; 3 the stability is good. The oxidation resistance and heat resistance of PAN are good, the decomposition of eigenstate PAN occurs at 360°C, and 4 special doping mechanism. PAN is completely different from other conductive polymers in that it is electrically conductive by proton acid doping. The same as PAN performance, the application has been very extensive.
6. Poly-p-phenylene acetylene PPV
Poly-Phenylene Vinylene (PPV), a conductive polymer developed in the 1980s, is a typical conductive polymer composed of π-π conjugated bonds. It has not only higher conductivity, but also It also has a glowing display function. Greatly expanded the prospect of application in the packaging field. Because PPV can only be made into prepolymers and then heated in vacuum to make the advantages of conductive films, it has become one of the most studied conductive polymers in the world since the 1990s. There are two methods for the modification of PPV: one is to introduce a substituent on the benzene ring; the other is to modify the vinyl group. Among the substituents introduced on the benzene ring in the former, the alkoxy (RO-) studies are more detailed. The alkoxy-substituted poly-p-phenylene acetylene has the advantages of being soluble and the like, but such substituents have an excessive influence on its electrical conductivity and deteriorate its own characteristics. Therefore, alkyl-substituted PPVs have been developed, such as PPV derivatives such as poly(2,5-diheptyl)-p-phenylene acetylene (HP-PPV), so that the PPV can be dissolved and the PPV's good electrical conductivity is ensured. The conductivity can be as high as 10 3 S/cm. Applications have also been expanded.
7. Packaging of Conductive Polymers The first application of antistatic conductive polymers started with antistatic. Various antistatic and electrostatic shielding materials based on PTY, PTP, PPP, and PAN have been introduced one after another. U.S. UNIX company took the lead in blending polyaniline doped with organic sulfonic acid and commercial high polymer to make antistatic plastic materials of various colors; AS company also made antistatic products using organic phosphate human dopants. . S. PArmes et al. added a small amount of a water-soluble polymer (such as a small amount of styryl-pyrrolidone containing amine) grafted with a strong interaction with PPY, PTP, and PAN synthesis systems. Dispersible aqueous emulsions are used as anticorrosive coatings and antistatic coatings. Japan also produced a transparent PPY, PAN anti-static coating, and was used for computer floppy disk, anti-static packaging, electrostatic shielding and other effects are very good. China's Luoyang Ship Institute uses Pan anti-fouling anti-fouling anti-static multifunctional paint for hull painting. Even if the paint is partially peeled off in seawater, the hull material is still bright as new. The protection function is quite good.
8. Anti-electromagnetic conductive polymer as an anti-electromagnetic material in the ascendant. The conventional electromagnetic shielding material is composed of copper or aluminum. Although it has a good shielding effect, it is very expensive and expensive, thus limiting its application range. People have also used carbon black added to polymer materials, but this often leads to a decrease in the mechanical properties of the material. Electromagnetic screen materials based on PPV, PTP, and PAN make up for these deficiencies. The United States, Germany, Japan, and other countries have begun research in this area and have made breakthrough progress. In addition, there have been many studies on the combination of a conductive polymer with a polymer having high optical or mechanical properties to obtain a compound having excellent properties. U.S. UNIX company prepared a transparent conductive coating with excellent performance through solution blending. The transmittance is about 80%, and the surface resistivity is only 190Ω. It is expected to be used in electromagnetically transparent packaging. In addition, PAN, PPY and other materials such as PET, LPES, etc., have been reported at home and abroad as a composite film, which laid the foundation for the extensive application of anti-electromagnetic materials in the technology.
Using conductive polymers to absorb microwaves, the United States has developed stealth aircraft, stealth intercontinental missiles, France has developed stealth submarines, and so on; the United States will also be used as a long-distance heating material for plastic welding and maintenance in the space shuttle.
9. In the observation window conductive polymer, PTP, PPY, PAN and other high polymers have stable properties and significant discoloration effects, and can be used as intelligent observation windows. Both Toyota of Japan and Chronar of the United States used polyaniline to try smart windows. Toyota's PAN/WO3 smart window has a response time of approximately 1 s, and the number of discoloration cycles is 1 million times, and the light transmittance can be as high as 80%. Chronar's polyaniline smart window optical response time is less than 1s, the number of cycles of color change also reached tens of thousands of times. The relevant person at the US Natick Institute pointed out that if the response speed and cycle life of conductive polymers can be further improved, the conductive polymer smart window will soon enter the military stage. This will be very beneficial to the long-term packaging and storage of defense military products, which will save many manpower, material resources, and time for inventory.
10. Soft batteries Among the conductive polymers, polyanilines in particular have good redox properties, and the most used ones are secondary batteries. Polyaniline as a positive full-plastic battery is a research hotspot in recent years. Research on polyaniline as a material for secondary batteries began in 1970. Studies have shown that the specific energy of all-plastic batteries can reach as high as 560 Wh/kg, which is the highest among the existing polymerization actives.
According to reports, in 2001 the United States packaging giant - the International Paper Company launched a smart new packaging, so that commodity packaging and decoration become alive, but also to revolutionize the entire packaging industry. This new package uses an ultra-thin flexible battery made of conductive polymer developed by Israel Energy Paper. This new type of battery can be “printed†on the product packaging like ink. International paper companies and energy paper companies hope that this kind of disposable battery can enable manufacturers to more effectively attract consumers through product packaging and enhance the competitiveness of their products.
11. Light-Emitting Diodes Since 1990, all-plastic light-emitting diodes have been the goal of scientists and conductive polymers have created the conditions for this goal. In 1992, the U.S. UNIX company made a flexible and flexible conductive polymer light emitting diode. The first layer of the diode is polyethylene terephthalate PET, the second layer is a polyaniline PAN film (positive electrode), and the third layer is a luminescent film (MEH-PPV) and an upper layer of a calcium film negative electrode. The light-emitting diode thus produced emits orange light at a voltage of 2-3V. If a different light emitting layer (PPV) is used, light of different colors can also be obtained, the lightness is moderate, and it is easily observed under normal indoor light. It creates the conditions for the quantity or time of the luminous packaging label or special instructions.
12. Optical devices In addition to electrical conductivity, conductive polymers also have excellent optical and electrical properties. For example, when polyaniline is irradiated with light, photocurrent can be generated, which has remarkable photoelectric conversion characteristics. Volkov et al. pointed out that polyaniline is a P-type semiconductor and that a negative quadratic photocurrent of 0.25 μAcm can be recorded under a 80 nm polyaniline film. The photo-response of polyaniline is very complex under different light sources, and is related to the oxidation state of the polymer. Polyaniline responds very quickly to light. Under the action of laser, polyaniline also exhibits prominent nonlinear optical properties, microseconds of light conversion. Studies have shown that polyaniline has a higher second-order optical nonlinear coefficient -10 negative 11th power esu. Some experts pointed out that the use of their photoelectric characteristics, supermarket packaging bar code information processing will undergo a tremendous transformation.
13. Conclusion In conclusion, conductive polymers have many excellent properties and broad application prospects. However, we must also point out that the properties of the polymers obtained by the different synthesis methods are not the same. Although there are some typical applications in the packaging field today, there are still a lot of distances from widespread application. Just like nanotechnology, scientists and packaging workers still need to work together and all kinds of new packaging will shine in the new century. . (Finish)