Flavone/Tertiary Amine as Free Radical Photoinitiator for UV Photopolymerization of Tripropylene Glycol Diacrylate(TPGDA)†

doi:10.7503/cjcu20130700

Abstract

Abstract:

The polymerization kinetics of tripropylene glycol diacrylate(TPGDA) was monitored by real time near infrared(RTIR) with favone(FL) as photosensitizer and different hydrogen donor as coinitiator. The commercial photosensitizer benzophenone(BP) was used as control. The results showed that the molar extinction coefficient(ε_max) of FL was much higher than that of BP. When FL was used in combination with tertiary amine hydrogen donor ethyl 4-N,N'-dimethylaminobenzoate(EDAB), the rate of polymerization(R_p) and final double bond conversion(DC_f) could reach 0.58 s^-1 and 97%, respectively, which was very close to that of commercial BP/EDAB system. However, using sesamin(SM) and benzodioxole(BDO) as coinitiator for FL, the R_p and DC_f were both very low, which indicated that the excited FL and tertiary amine could generate aminoalkyl free radical species via electron/proton transfer process and initiate the efficient photopolymerization of TPGDA. More importantly, when the co-polymerizable tertiary amines such as EBERYL P115 and dimethy-laminoethyl methacrylate(DMEM) are used, the natural component characteristics of FL make it a promising photoinitiator in biomedical and food-packaging fields.

Key words: Flavone, Photoinitiator, Hydrogen donor, Acrylate, Photopolymerization

CLC Number:

O631

TrendMD:

SHI Suqing, YANG Yang, CAI Tianyuan, GAO Na, GONG Yongkuan, NIE Jun. Flavone/Tertiary Amine as Free Radical Photoinitiator for UV Photopolymerization of Tripropylene Glycol Diacrylate(TPGDA)^†[J]. Chem. J. Chinese Universities, 2014, 35(3): 660.

Figures/Tables 10

Fig.1 Chemical structures of TPGDA, photosensitizer(FL, EDAB, DMEM) and hydrogen donors(BP, BDO, SM)

Fig.2 UV-Vis absorption spectra of FL(a)and BP(b, c) in cyclohexanea. cFL=5×10-5 mol/L; b. cBP=5×10-5 mol/L; c. cBP=5×10-3 mol/L.

Table 1 UV spectra data of FL and BP in cyclohexane

Material	λ_max/nm	ε_max/(L·mol^-1·cm^-1)
BP	250	21580
	346	154
	258	22480
FL	293	28980
	310	23780

Fig.3 Fluorescence spectra of FL at different concentrations EDAB in cyclohexane (A)λex=354 nm, cFL=5×10-5 mol/L, PMT voltage 950 V; (B) plot of I0/I vs. cEDAB.

Fig.4 Effects of concentrations of EDAB on DC(A) and Rp(B) of TPGDA with 1.0%(mass fraction) FL as photosensitizer

Fig.5 Effects of concentrations of FL on DC(A) and Rp(B) of TPGDA with 1.0%(mass fraction) EDAB as photosensitizer

Fig.6 Effects of hydrogen donors(1.0%) on photo-polymerization kinetics of TPGDA with 1.0%FL as photosensitizer

Fig.7 Photoinitiating process of FL/EDAB system

Table 2 Rp,max and DCf of TPGDA photopolymerization by 1.0%FL in combination with 1.0%hydrogen donor

Hydrogen donor	R_{p, max}/s^-1	DC_f(%)
Without hydrogen donor		27±2
BDO		32±1
SM		38±2
DMEM	0.31±0.01	93±1
EBERYL P115	0.37±0.02	95±1
EDAB	0.58±0.01	97±1

Fig.8 Comparison of FL/EDAB(a) and BP/EDAB(b) on photopolymerization kinetics of TPGDA

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