Controlled Radical Photopolymerization Of Isobutyl Methacrylate Mediated By DEPN

Nitroxide-mediated thermal polymerization, which could gain well-defined expected polymer, has the obvious advantage in the field. Recently, with the appearance of nitroxide radical or photosensitive nitroxide radical applied in photopolymerization increasing attention has been paid to it by overseas scholars. In this paper, firstly, the recent achievements of control radical polymerization(CRP) at the presence of SGI was reviewed in these systems such as bulk, solution, emulsion, miniemulsion and dispersion polymerization, as well as active monomers for styrene(St), methyl methacrylate (MMA), n-butyl methacrylate (n-BMA), acrylamide (AM), macromonomer in the thermal polymerization have got many results as plots of ln([M]0/[M]) vs. time and conversion vs. number-average molecular weight (Mn).Second, at the given expriment conditons, the influence of the bluk photopolymerization of i-BMA in kinetic factors such as light intensity, kinds of photo initiator, concentration of photo initiators, mole ratios of initiator and SGI has been investigated, The third, the photopolymerization of i-BMA was successful performed in the bulk, solution, and microemulsion. Structure and component of the product has been characterized by FTIR and 1H NMR spectrum, Mn and polydispersity index (PDI) of the product has been measured by GPC. Finally water soulable photo initiators and synthesis of SGI were reported.(1) At the given experiment conditons, using Irgaure907 as a photo initiator, the influence of different concentration of initiator and mole ratio of [SG1]/[initiator] research on the reaction kinetics of photopolymerization of i-BMA in bulk was investgated. The results showed that the polymerization rate increased more quickly with concentration of i-BMA increasing. Although, when [SG1]/[Irgaure 907] was 1.0, plots of Mn vs. conversion and ln([M]0/[M]) vs. time were linear respectively, but the polymeizarzion progress of the i-BMA homopolymerization not controlled with higher PDI (1.8-2.0). When [SGl]/[Irgaure 907] was 2.0, plot of ln([M]0/[M]) vs. time still kept linear, but Mn increasing with conversion was not regular. It was possible reason that the termination such as chain-transferring and coupled termination was occurred to form gel-effect at the higher conversion stage. At last higher PDI was not the expected result.(2) The photopolymerization of i-BMA in benzene solution was performed with SG1 used as a mediator at ambient temperature. When [SGl]/[Irgaure 907] was 1.1, plots of conversion vs. Mn and ln([M]o/[M]) vs. time were linear respectively, whereas the the rage of polydispersity indexes was 1.2-13 that we expected. Then the conclusion that because in soultion polymerization, benzene was enough to make polymer and monomer soulable for the balance of reactive-deactive presistented, was a better contolled effect. At the same time, compared with SG1/initiator and H-TEMPO/initiator, the polymerization appearred longer induced time about 40 minutes in H-TEMPO/initiator system, however not in SG1/initiator. Because the balance constant K of reactive-deactive for the polymerization of i-BMA with SGI is 100 times than i-BMA with H-TEMPO, the system at the presence of SGI needed addition energy by heating to complete the balance at lower (room) temperature.(3) Polymerization reaction in the water in oil (W/O) micoemulsion had only been on the oil continuous phase; however the water phase as a heat disspartional container. In the oil in water (O/W) micoemulsion, initiate-polymerization was in the common oil phase, which was a nanometer leveled monomer storage. When the mole ratio of [SG1]/[Irgacure 907] is 1.0, the system kept transparent apearance, but the conversion was up to 47% after 100 minutes and polymerization rate was lower than in bulk and soultion system. Although, ln([M]0/[M]) vs. time was well linear with a lower PDI(1.3～1.5), but the plot of Mn vs. conversion decreased progressively. Because the heat of polymerization dissipated, propagating chain radical was caught to being dead chain by SG1. But propagating chain radical in the initial polymerization was less and instantly completed. At the mid-term or final-term, radical numbers of initator, propagating chain were so more that SGI carried them to terminational chains at once. Polymer of different chain length for chain more length in the pre-polymerization and chain shorter in mid or final polymerization explained number-average molecular weight decreased gradually. When the mole ratio of [SG1]/[Irgacure 907] was 2.0 in the O/W microemulsion system, plots of Mn vs. conversion and ln([M]o/[M]) vs. time were linear respectively and PDI had limited between 1.1～1.5. After 100 minutes, conversion had arrived up to 45% just as the nomal phase. The phase structure of the microemulsion system had destroyed in the mid-term of the polymerization, it was due to the monomer was not enough soluable so as to produce the polymeric partical precipatited. If light insentity increased from 3.3 to 5.0 mW/cm2, conversion had increased up to about two times in 100 minutes from 45% to 90%. But when light insentity was 5.0 mW/cm2, the gel-effect in progress of polymerization had emerged, and the reaction kinetics showed conventional radical polymerization with the reversed "S"curve.