Electro-initiated Polymerization Based On Cationic Photopolymerization

Cationic photopolymerization has been widely used in coating, ink, adhesive, photo etching and electronic integrated circuits due to its advantage of economy, environment, efficient, low volume shrinkage and high adhesion force. For the cationic photopymerization system using iodonium salt and sulfonium salt as initiators, after UV exposure, iodonium salt and sulfonium salt were photo-reduced to generate free radical and strong Bronsted acid, then cationic polymerization of vinyl ether and epoxy monomers was initiated by the strong Bronsted acid. In this way, the +3 state iodonium salt was reduced to +1 state during the photolysis. As we all known, electrochemical reduction was one of the most common methods of reduction. So, the iodonium salts and sulfonium salts could be electrochemical reduced to generate active center which initiate the cationic polymerization of vinyl ether and epoxy monomer. However, almost no papers were reported about electropolymerization of vinyl ether and epoxy monomers by using iodonium salts or sulfonium salts as initiators.Most of the systems for electro-polymerization contain electrodes, monomer, electrolyte solution and a lot of solvents. Until now, the mechanism of electro-polymerization was not confirmed yet, mainly because the existence of electrolyte solution and solvents made it complicated to study the mechanism. It’s very important to find a electro-polymerization system without electrolyte solution and solvents for investigating the mechanism. In this subject, the electro-initiated polymerization of vinyl ether and epoxy monomers was investigated by using the cationic polymerization system without electrolyte solution and solvents. For the system that not only can be initiated by UV light, but also can be initiated by electric field, comparative studies were made for the kinetics of these two polymerizations. After that, the optimal conditions of electro-initiated polymerization were found out, which could provide a theoretical basis for the practical industrial production. The initiator systems were expanded for non-solvent electroinitiated polymerization, the materials with non-nucleophilicity anions were found out to be efficient initiators for electroinitiated polymerization of vinyl ether and epoxy monomers. Anti-corrosive epoxy coatings were fabricated on the conductive mental pipe, and the properties of the epoxy coatings were also investigated. The main research contents of the subject include:1. ITO conductive glasses which allowed the transmission of near infrared spectroscopy were used as the electrodes. After that, real time FT-NIR was used to investigate the kinetics of electroinitiated polymerization. It’s graveness by using real time FT-NIR with accuracy and high efficiency to substitute for the complicated and time consuming methods like weighing, GC and NMR to study the mechanism of electro-initiated polymerization.2. For the system that could be initiated by UV light or electric field, comparative studies were made for the kinetics of these two polymerizations by using real time FT-NIR. The influence of different UV intensity/voltage, different initiator content, different water content, different KOH content on the electro-initiated and photo-initiated polymerization was investigated in detail. The post curing behavior was also investigated. The results showed that the electroinitiated polymerization of vinyl ethers by using iodonium salt or sulfonium salt as initiator also followed a cationic profile.3. The initiator systems were expanded for non-solvent electroinitiated polymerization, the materials with non-nucleophilicity anions were found out to be efficient initiators for electroinitiated polymerization of vinyl ether and epoxy monomers. The results showed that KSbF6 could be efficient initiator for the electroinitiated polymerization of vinyl ether and epoxy monomers. The influence of different voltage, different monomers and different KOH content on the electroinitiated polymerization was investigated in detail. The post curing behavior was also investigated. What’s more, proper mechanism was also postulated.4. The initiator system needed to be further expanded due to the poor solubility of KSbF6. Therefore, ionic liquid (BMIMBF4) with non-nucleophlic anion was used as initiator for electro-initiated cationic polymerization of vinyl ether and epoxy monomers in the subject. The kinetics of electroinitiated polymerization was investigated by real time FT-NIR. The results showed that BMIMBF4 had higher initiation efficiency than KBF4 at the same condition. The proper mechanism was also postulated here. What’s more, the fact that vinyl ether and epoxy monomers could be electroinitiated by using BMIMBF4 as initiator reminded people to consider the initiation effect when using ionic liquid with non-nucleophlic anion as reaction medium.5. Epoxy coatings were fabricated on the conductive metal pipes by electropolymerization. Stainless steel plates were used to substitute the conductive metal pipe for the convenience of test, then epoxy coatings were fabricated on the stainless steel plates. The properties of the coating were tested in accordance with Guo Biao. The results showed that uniform coatings could be fabricated, and the thickness of the coatings could be adjusted by controlling the voltage and reactive time. The epoxy coatings fabricated by electropolymerization possessed good adhesion force, great harness and excellent liquid resistance.