Visible-light-sensitive Versatile Fluorescent Brightener-based Photoinitiating Systems †

doi:10.7503/cjcu20190596

Abstract

Abstract:

Five kinds of commercial fluorescent brighteners containing different fluorophores were investiga-ted, i.e. 4,4'-bis(2-benzoxazolyl)stilbene(BBS), diethylamino-4-methylcoumarin(C 1), bis-(triazinylamino)-stilbene disulphonic(CBUS 450), 4,4'-bis(2-sodium sulphonate styryl)biphenyl(CBS X) and 1,4-bis(2-benzoxazolyl)naphthalene(OB 7), the two-component photoinitiating systems including these fluorescent brighteners and diphenyliodonium hexafluorophosphate(IOD) and the three-component photoinitiating systems including these brighteners, IOD and optionally N-vinyl carbazole or amine were formed, respectively, both of them photoinitiated the free radical photopolymerization for the preparation of polyacrylates and the concomitant cationic/radical photopolymerization for the formation of an interpenetrating polymer network upon visible-light light-emitting diode(LED) exposure. The light absorption abilities of fluorescent brighteners were characterized by UV-visible spectrometer, the photochemical properties of them were analyzed by fluorescence spectrometer and electron spin resonance, the photoinitiation efficiencies of the photoinitiating systems were monitored by real-time Fourier transform infrared spectroscopy, meanwhile, the fracture surface morphology and surface morphology of the products obtained from the concomitant cationic/radical photopolymerization of epoxides/acrylates blends were observed and analyzed by scanning electron microscope and atomic force microscope, respectively. The results showed that fluorescent brighteners could be used as a versatile high-performance photoinitiator under visible-light LED, among them, the two-component and three-component photoinitiating systems based on naphthalene-benzoxazole OB 7, sulfonated triazinylstilbenes CBUS 450, sulfonated stilbene-biphenyl CBS X and coumarin C 1 exhibited quite excellent photoinitiating abilities even under air.

Key words: Visible-light light-emitting diode(LED), Fluorescent brightener, Interpenetrating polymer network, Free radical photopolymerization, Concomitant cationic/radical photopolymerization

CLC Number:

O631
TQ311

TrendMD:

ZUO Xiaoling, WU Chong, HUANG Anrong, LUO Jiaolian, LI Zhuyu, WANG Meng, ZHOU Ying, YU Hongna, GUO Jianbing. Visible-light-sensitive Versatile Fluorescent Brightener-based Photoinitiating Systems ^†[J]. Chem. J. Chinese Universities, 2020, 41(4): 811.

Figures/Tables 15

Fig.1 ε-λ curves of C 1(a), CBUS 450(b), CBS X(c) and OB 7(d) fluorescent brighteners

Fig.2 UV-Vis absorption spectra of DMSO(a) and BBS(b)

OBs	λ_max/nm	ε_max/(L·mol^-1·cm^-1)	ε_{420 nm}/(L·mol^-1·cm^-1)
BBS	376	Poor solubility	Poor solubility
C 1	373	32530±430	333±12
CBUS 450	361	39010±750	58±34
CBS X	357	75800±1020	80±13
OB 7	374	34290±1380	570±38

Fig.3 Stern-Volmer plots for the steady state fluorescence quenching in the presence of IODa. C 1; b. OB 7; c. BBS.

Fig.4 Fluorescence emission spectra of CBUS 450(A) and CBS X(B) in acetonitrile in the absence(a) and in the presence(b) of IOD (A) cIOD=1.0 mmol/L;(B) cIOD=4.3 mmol/L.

Fig.5 ESR-ST spectra of BBS/IOD(A) and OB 7/IOD(B) system

Fig.6 Photopolymerization profiles(acrylate function conversion vs time) of an Ebecryl 605/TMPTA(mass ratio, 70∶30) blends under air and in presence of BBS/IOD(a), OB 7/IOD(b), CBUS 450/IOD(c), CBS X/IOD(d), C 1/IOD(e), Ir369(1%, mass fraction, f) and Ir819(1%, mass fraction, g)

PIS	FC(%)	PR	PIS	FC(%)	PR
OBs alone	np*	np	CBS X/IOD(0.2%/1%)	50.7	0.71
IOD alone	np	np	C 1/IOD(0.2%/2%)	39.6	0.71
BBS/IOD(2%/3%)	np	np	Ir369(1%)	34.5	0.39
OB 7/IOD(1%/3%)	39.0	0.59	Ir819(1%)	38.0	0.82
CBUS 450/IOD(2%/3%)	19.2	0.05

Fig.7 Photopolymerization profiles(acrylate function conversion vs. time) of Ebecryl 605/TMPTA(mass ratio, 70/30) blends under air and exposure to LED@420 nm in the presence of BBS/IOD/NVK(a), BBS/IOD/EDB(b), OB 7/IOD(c), OB 7/IOD/NVK(d), and OB 7/IOD/EDB(e)

Fig.8 Photopolymerization profiles(acrylate function conversion vs. time) of Ebecryl 605/TMPTA(mass ratio, 70/30) blends under air and exposure to LED@420 nm in the presence of CBUS 450/IOD/NVK(a), CBUS 450/IOD/EDB(b), CBS X/IOD(c), CBS X/IOD/NVK(d) and CBS X/IOD/EDB(e)

Fig.9 Photopolymerization profiles(acrylate function conversion vs. time) of Ebecryl 605/TMPTA(mass ratio, 70/30) blends under air and exposure to LED@420 nm in the presence of C 1/IOD(a), C 1/IOD/NVK(b) and C 1/IOD/EDB(c)

PISs	None		2%NVK		2%EDB
PISs	FC	RP	FC	RP	FC	RP
OB alone			np*	np	np	np
BBS/IOD(2%/3%)	np	np	np	np	26.3	0.11
OB 7/IOD(1%/3%)	31.2	0.08	37.7	0.43	40.9	0.61
CBUS 450/IOD(2%/3%)	19.2	0.05	27.3	0.18	27.7	0.20
CBS X/IOD(0.2%/1%)	31.6	0.11	39.6	0.48	39.7	0.53
C 1/IOD(0.2%/2%)	32.7	0.09	40.6	0.54	44.0	0.63

Fig.10 SEM(A) and AFM(B) images of the product obtained from the EPOX/Ebecryl 605 hybrid monomers initiated by CBS X/IOD under LED@420 nm exposure

Fig.11 Photopolymerization profiles of an Ebecryl 605/EPOX blends under air(A) OB 7/IOD;(B) CBUS 450/IOD;(C) CBS X/IOD;(D) C 1/IOD.

Monomer	BBS/IOD (2%/3%)	OB 7/IOD (1%/3%)	CBUS 450/ IOD(2%/3%)	CBS X/ IOD(0.2%/1%)	C 1/IOD (0.2%/2%)
EPOX	np^*	29.7	25.7	36.4	29.5
Ebecryl 605	np	54.6	51.6	68.0	63.7

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