Research On Arene-Cyclopentadienyl Iron Salts As Cationic Photoinitiators

In order to obtain novel cationic photoinitiators with high photosensitivities under high pressure Hg lamp, ten arene-Cp iron salts([Cp-Fe-arene]PF6/BF4) and a ferrocenium salt (FcBF4) were synthesized using ferrocene(Fc), including [Cp-Fe-benzene]+ ( I ) , [Cp-Fe-toluenef( II ), [Cp-Fe-p-xylenef( III ), [Cp-Fe-naphthalenef(IV), [Cp-Fe-biphenylH V), [Cp-Fe-(2,5-dimethylhypnone)]+(VI), [(acyl-Cp)-Fe-(p-xylene)]+( VD ), [Cp-Fe-anisole]+( VI), [Cp-Fe-diphenyletherH IX ). [Cp-Fe-p-diethoxybenzene]+( X). Among them, VI, Vfl and X are new compounds. At the same time, to increase the yield, the reaction conditions and the purification process were optimized.The UV-Vis absorption spectra and photolysis of arene-Cp iron salts in CHaCb which irradiated by high pressure Hg lamp were studied. The light absorption above 350nm caused by d-d transition of arene-Cp iron salts are more efficient than that of iodonium salts and sulfonium salts when they are irradiated with high-pressure Hg lamp as light source. By structure changes in the ligands, the absorption can be varied over a wide range. Compared with [Cp-Fe-benzene] ( I ) , the molar extinction coefficients of IV, V, VI and YD at 350-400nm in CH2C12 raise 8 times, 4 times,14 times and 6 times respectively, that of Vffl, DC and X raise 2 times.The kinetics of photolysis under high pressure Hg lamp has been determined. The results show that the photolysis of arene-Cp iron salts results arene release reaction and the reaction is the first order. The absorptions both at 200-300nm and 300-400nm are effective on the photolysis. The rate of photolysis can be raised by replacing benzene in the molecule with naphthalene, biphenyl, hypnone, anisole, diphenylether anddiethoxybenzene.Arene-Cp iron salts are capable of initiate the polymerization of epoxide effectively under high pressure Hg lamp. Their photoinitiated activities are different. The photosensitivity value of [Cp-Fe-biphenylJPFeV is approximately on the equal level with that of the same system photoinitiated by SR1012(S=342mJ.cm"2); The photosensitivity value ofVIKD(%VIIUIV>X.,I is lower than that of 1-261. The values of photosensitivity of arene-Cp iron salts when they initiate the polymerization of epoxide oligomer ERL4221+EPON812 (2: 1) , have the following order that is: V (340 mJ.cm'2) < Vfl (410 mJ.cm'2) < IX (432 mJ.crn'2) < Vffl(446 mJ.cm'2) < IV (451 mJ.cm'2) < X (464 mJ.cm'2) < I (486 mJ.cm'2) < IK VI (554 mJ.cnV2) < III (602 mJ.cm"2). Compared with SR1012, the exposure time for 100% curing of epoxide oligomer photoinitiated by [Cp-Fe-arene]PF6 V\ VDK DC and IV is shorter.Some organic peroxides, such as cumene hydro peroxide CHP and benzoyl peroxide BPO could promote the photopolymerization of epoxide oligomer initiated by arene-Cp iron salts significantly, in accordance with the oxidability and concentration of the peroxides. The photosensitivity value of the same system photoinitiated by [Cp-Fe-arene]PF6 with BPO is less than that of by SR1012 and the difference of photosensitivities among different arene-Cp iron salts is small. The photosensitivity of [Cp-Fe-areneJPFe + BPO(1:1) in the photopolymerization of epoxide oligomer ERL4221+EPON812 (2: 1) is: I + BPO (162 mJ.cm'2) , III+BPO (270mJ.crn2) , IV+BPO (lOSmJ.cm'2) , V+BPO (162 mJ.cm'2) , VI+BPO (176 mJ.cm'2) , V1D+ BPO (162mJ.cm'2) , DC+BPO (216mJ.cm"2) , X+BPO (149mJ.cnV2) .With the absorptions at 358nm( e =1.23 X 103 L.mor'.cm"1) and 620nm( c =221 L.mor'.cm"1), FcBF4 not only can match with the high pressure Hg lamp, but also may photoinitiate the polymerization of epoxide oligomer by visible light. For the iron ion with three valence in FcBF4 is more active than that in some arene-Cp iron salts under high pressure Hg lamp. Heating the photosensitive compositions which have been irradiated by nature light can make the photopolymerization quicker. Owing the process of post-curing, the exposure time can be shorted and the amount of photoinitiator FcBF4 can be reduced.The conditions of photopolymerization have been discussed, including differe...