Polymeric Photoinitiators: A New Search toward High ...cheserv12.uwaterloo.ca/peml/resources/Publications/... · 2147 Polymeric Photoinitiators: A New Search toward High Performance

2145

Full PaperMacromolecularChemistry and Physics

wileyonlinelibrary.com© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/macp.201600260

Polymeric Photoinitiators: A New Search toward High Performance Visible Light Photoinitiating Systems Jing Zhang , Pu Xiao , Frédéric Dumur , * Chang Guo , Wei Hong , Yuning Li , Didier Gigmes , Bernadette Graff , Jean-Pierre Fouassier , Jacques Lalevée *

A series of conjugated polymers and oligomers previously used in organic photovoltaics and organic light-emitting diodes (OLEDs) have been examined for the fi rst time as photo-initiators of polymerization. They address the present and future challenges facing photopolymerization: require-ment of high extinction molar coeffi cients, absorption over the whole visible spectrum, ability to easily withdraw or release electrons. Interestingly, these compounds initiate the cationic polymerization of epoxides or the free radical polymerization of acrylates upon exposure of the photo-curable formulations to a LED emitting at 405 nm. Some of them can potentially operate under blue, green, or red laser diodes.

Dr. J. Zhang, Dr. P. Xiao, B. Graff, Prof. J. Lalevée Institut de Science des Matériaux de Mulhouse IS2M – UMR CNRS 7361 – UHA 15 rue Jean Starcky 68057 Mulhouse Cedex , France E-mail: [email protected] Dr. F. Dumur, Dr. D. Gigmes Aix-Marseille Université CNRS Institut de Chimie Radicalaire ICR UMR 7273, 13397 Marseille , France E-mail: [email protected] Dr. C. Guo, Dr. W. Hong, Prof. Y. Li Department of Chemical Engineering and Waterloo Institute for Nanotechnology (WIN) University of Waterloo 200 University Ave West Waterloo, Ontario N2L 3G1 , Canada Prof. J.-P. Fouassier UHA-ENSCMu 3 rue Alfred Werner, 68093 Mulhouse , France

growth of industrial applications. Notably, applications of photopolymers range from conventional areas such as coat-ings, inks, and adhesives to high-tech domains, e.g., opto-electronics, laser imaging, stereolithography, 3D-printing, or nanotechnology. [ 1 ] A light induced polymerization reac-tion requires the presence of a molecule, usually denoted as a photoinitiator (PI) (although it could sometimes exhibit a behavior of photosensitizer or photocatalyst) and having a strong absorption in the required wavelength range, which is incorporated into a photoinitiating system (PIS). [ 2 ] Recently, a major breakthrough has been achieved in the fi eld of PI operating under visible lights and low light intensity sources, providing a revival of interest for this polymerization technique known since decades. [ 3 ]

Presently, the search for new dyes acting as PIs (exhib-iting high molar extinction coeffi cients and visible light absorption spectra) together with suitable designed PISs still remains an active research fi eld facing the fact that all historical UV-operating PIs such as benzophenones, thioxanthones, or benzoin ethers can be clearly discarded for this purpose due to the lack of a suffi cient absorp-tion beyond 400 nm. If derivatives of these benchmark PIs and others PIs (e.g., camphorquinone, bis phosphine oxides, some dyes) have been proposed over the years, the chemical engineering required to develop novel

1. Introduction

During the past decade, the photopolymerization area has witnessed intense research efforts due to the constant

Macromol. Chem. Phys. 2016, 217, 2145−2153

2146

J. Zhang et al.

www.mcp-journal.de

MacromolecularChemistry and Physics

www.MaterialsViews.com© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

structures remains a hard work (see recent references, e.g., in refs. [ 4 ] and [ 5 ] ). Clearly, new innovative structures exhibiting naturally a strong absorption in the visible region have to be researched and tested in photopoly-merization reactions. With regards to the potential applica-tions of photopolymers, a second topic of current interest concerns the extractability of the residues issued from polymerization (unreacted PIs, side-products issued from the polymerization reactions). If a few examples of low-molecular weight PIs bearing a co-polymerizable moiety (e.g., acrylate group) have recently been proposed, [ 6 ] the low migration can also be ensured by means of PIs exhib-iting a high molecular weight. This strategy is particularly effi cient with polymeric PIs for which the intimate inter-play of the resulting polymer chains ensures a defi nitive immobilization of the PI into the polymer network.

In this paper, a series of new dyes developed for organic electronics and still not investigated as PIs yet are pro-posed (Scheme 1 ) and tested for the fi rst time in the photopolymerization of acrylates and epoxides upon light emitting diode (LEDs) irradiations. Notably, poly[[4.8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fl uoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b] thiophenediyl]] (PTB7), [ 7 ] poly[N-9″-heptadecanyl-2,

7-carbazole-alt-5,5- (4′,7′-di-2-thienyl-2′,1′,3′-benzothi-adiazole) (PCDTBT), [ 8 ] and poly[4,8-bis[(2-ethylhexyl)-oxy] benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-(1,3-(5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione))] (PBDTBO-TPDO) [ 9 ] stand out as electron-donating co-polymers of high interest for polymer solar cells. PTB7 is an electron-donating semi-conducting co-polymer often associated with poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′]dithio-phene-2,6-diyl]] (PCPDTBT) in ternary solar cells whereby PTB7 (which exhibits a low energy bandgap, E g = 1.6 eV) (the energy band gap is a good indicator of the visible light absorption properties) is added in complement of PCPDTBT ( E g = 1.8 eV). [ 10 ] In parallel, PCDTBT is one of the latest generation of conjugated polymers that have been designed for organic photovoltaics (OPV) applica-tions. [ 11 ] High power conversion effi ciencies were also reported with PBDTBO-TPDO ( E g = 1.73 eV) characterized by a π-conjugated backbone structure and designed with a linear alkyl substituent appended to N -alkylthieno[3,4- c ]pyrrole-4,6-dione to provide a planarization of the conjugated backbone. [ 9 ] Conversely, DTS(FBTTh 2 ) 2 [ 12 ] ( E g = 1.78 eV) is not a conjugated polymer but a small-molecule donor compound. Apart from this important


Scheme 1. The different compounds investigated in this study.

2147

Polymeric Photoinitiators: A New Search toward High Performance Visible Light Photoinitiating Systems

www.mcp-journal.de


www.MaterialsViews.com © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

distinction, DTS(FBTTh 2 ) 2 that benefi ts the inclusion of the [1,2,5]-thiadiazolo-[3,4- c ]-pyridine heterocycle [ 13 ] exhibits a similar ability than PBDTBO-TPDO to harvest sunlight and comprises one of the most successful OPV molecular framework. [ 14 ] Another material is the conju-gated polymer ADS109GE which was notably developed to act as active material for solution-processed green light-emitting organic light-emitting diodes. [ 15 ] These different compounds proposed here as PIs are appealing candidates due to their well-adapted absorption spectra, their electroactivities and their high molecular weights. Parallel to these fi ve materials, two other dyes (IDG2 and PBBTZ20) have been examined as PIs due to the similarity of their absorption spectra with those of the aforemen-tioned compounds. For comparison, IDG1 previously used in photopolymerization [ 16 ] has been also revisited in this study.

All these dyes will be mixed either with diphenyli-odonium hexafl uorophosphate (Iod) and N -vinylcarbazole (NVK) for the development of new high performance photoinitiating systems (PISs). The corresponding PISs operate as observed in other Dye/Iod or Dye/Iod/NVK sys-tems already described by us. Briefl y (Scheme 2 ), the dye reacts with Iod and generates a dye cation radical (Dye •+ ) and a phenyl radical (Ph • ). This radical adds to the NVK double bond and forms a Ph-NVK • radical. Both radicals initiate a free radical polymerization (FRP). The produced Ph-NVK • radical is oxidized by Iod to form a Ph-NVK + cation suitable for a free radical promoted cationic poly-merization (FRPCP). The cationic polymerization (CP) is initiated by Dye +• .

The polymerization initiating ability of all these Dye/Iod and Dye/Iod/NVK PISs will be checked by real-time Fourier transform infrared (FTIR) spectroscopy. FRP, CP, and FRPCP will be conducted under exposure to a LED emitting at 405 nm so that the relative effi ciencies can be easily evaluated.

2. Experimental Section

2.1. The Compounds Used as PIs

The different compounds investigated in this study are presented in the Scheme 1 . Poly[[4.8- bis [(2-ethylhexyl)oxy]-benzo [1,2- b :4,5- b ′ ]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl) carbonyl] thieno[3,4- b ] thiophenediyl]] PTB7, poly[ N -9″-heptadecanyl-2,7-carbazole- alt -5,5- (4′,7′-di-2-thienyl-2′,1′,3′-benzothi adiazole) PCDTBT, 7,7′-(4,4- bis (2-ethylhexyl)-4 H -silolo-[3,2- b :4,5- b′ ]dithio phene-2,6-diyl) bis (6-fluoro-4-(5′-hexyl-[2,2′-bithiophen]-5-yl) benzo[ c ] [1,2,5] thiadiazole) DTS(FBTTh 2 ) 2 , and poly[4,8- bis [(2-ethylhexyl) oxy]benzo[1,2- b :4,5- b′ ]dithiophene-2,6-diyl- alt -(1,3-(5-octyl-4 H -thieno[3,4- c ]pyrrole-4,6(5 H )-dione))] PBDTBO-TPDO (also named PBDTTPD) were purchased from Lumtec, whereas poly[(9,9-dioctyl-2,7-divinylene-fl uoreny lene)- alt - co -{2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene}] ADS109GE was supplied from American Dye Source, Inc. All dyes were used with the highest purity available. IDG1 and IDG2 (Supporting Information) were synthesized as previously reported. [ 16 ] Synthesis of PBBTZ20 was described in Supporting Information.

2.2. Other Chemical Compounds

Iod and NVK (Scheme 3 ) were purchased from Sigma-Aldrich and used as received without further purifi cation. Trimethylol-propane triacrylate (TMPTA) and (3,4-epoxy-cyclohexane)methyl 3,4-epoxycyclohexylcarboxylate (EPOX) were obtained from Allnex and used as benchmark monomers for radical and cati-onic photopolymerization reactions.

2.3. Irradiation Sources

A LED at 405 nm (M405L2 – ThorLabs; ≈110 mW cm −2 ) was used for the irradiation of the photocurable samples.

2.4. Computational Procedure

Molecular orbital calculations were carried out with the Gaussian 03 package. The electronic absorption spectra for the FM deriva-tives were calculated from the time-dependent density func-tional theory at B3LYP/6-31G* level on the relaxed geometries calculated at this latter level; the molecular orbitals involved in these electronic transitions were also extracted.

2.5. Photopolymerization Experiments

For photopolymerization experiments, the conditions are given in the fi gure captions. The photosensitive formulations (25 μm thick) were deposited on a BaF 2 pellet in laminate (the


Scheme 2. Chemical mechanisms in the Dye/Iod/NVK systems. Scheme 3. Chemical structures of the additives and the monomers.

2148

J. Zhang et al.

www.mcp-journal.de



formulation is sandwiched between two polypropylene fi lms to avoid the re-oxygenation during the photopolymerization) or under air and irradiated with the different light sources. The evolution of the TMPTA double bond content or the EPOX epoxy group content were continuously followed by real time FTIR spectroscopy (JASCO FTIR 4100) at about 1630 and 790 cm −1 , respectively. [ 17 ] TMPTA and EPOX being multifunctional mono-mers, the conversion indicated in the present paper correspond to the conversion in the polymerizable functions (acrylate and epoxy functions, respectively).

2.6. Redox Potentials

The oxidation potentials ( E ox vs standard calomel electrode (SCE)) of the investigated compounds used as PIs were measured in acetonitrile by cyclic voltammetry with tetrabutylammonium hexafl uorophosphate (0.1 M ) as a supporting electrolyte (Voltalab 6 Radiometer). The procedure has been presented in detail in ref. [ 17 ] . The free energy change Δ G et of the electron transfer reac-tion between 1 PIs and Iod can be calculated from the classical Rehm–Weller equation: Δ G = E ox – E red – E S (or E T ) + C ; where E ox , E red , E S (or E T ), and C are the oxidation potential of the studied photoinitiators, the reduction potential of Iod, the excited singlet state energy of the studied PIs, and the electrostatic interaction energy for the initially formed ion pair (this latter parameter is generally considered as negligible in polar solvents). [ 18 ]

3. Results and Discussion

3.1. Absorption Properties of the New Dyes

The ground state absorption spectra of the new proposed dyes are depicted in Figure 1 and the relevant photophys-ical characteristics of the different compounds are gath-ered in Table 1 . The absorption maxima λ max are located at 671, 554, 580, 589, and 481 nm for PTB7, PCDTBT, DTS(FBTTh 2 ) 2 , PBDTBO-TPDO, and ADS109GE, respec-tively. Considering their initial use as chromophores for

solar cells, the different dyes exhibit absorption spectra largely covering the visible range (see Figure 1 ). Notice-ably, PTB7, PCDTBT, PBDTBO-TPDO, and DTS(FBTTh 2 ) 2 share in common thiophene units as electron-donating groups, ensuring low oxidation potentials. On the oppo-site, the low band gap polymer ADS109GE is charac-terized by two electron-donating units (fl uorene and dialkoxybenzene) connected to the accepting cyano groups. Due to the weak electron-accepting ability of this group, the absorption spectrum of the light-emitting polymer is less extended than those observed for the materials devoted to photovoltaics applications and only ranges in the 350–550 nm region. Still based on push–pull structures, IDG1, IDG2, and PBBTZ20 are respectively based on the indigo and the 5 H -pyrrolo- bis -thiazine scaf-folds. Absorption maxima corresponding to the positions of the intramolecular charge transfer band are respec-tively determined at 591, 540, and 450/480 nm for IDG1, IDG2, and PBBTZ20. Interestingly, most of the compounds examined in this study are soluble in common organic solvents: this is directly related to the primary use of these materials, i.e., the optoelectronic devices (OLEDs, solar cells, transistors) by solution process. From this specifi city, a suffi cient solubility of the dyes in the dif-ferent envisioned formulations is observed, except for PTB7 and PBDTBO-TPDO that are insoluble in EPOX and TMPTA. Beyond the solubility, all dyes, thanks to their absorption spectra clearly centered in the visible range, are suitable for irradiations with LED bulbs emitting at 405 nm and other devices such as laser diodes emitting at 457 and 532 nm and even in the red.

The molecular orbitals (MO) involved in the lowest HOMO → LUMO energy transition (where HOMO and LUMO stand for the highest occupied and lowest unoc-cupied molecular orbitals, respectively) are depicted in Figure 2 . The calculations were restricted to a single monomer unit to reduce the computational cost. As anticipated, all dyes (PTB7, PCDTBT, PBDTBO-TPDO, DTS(FBTTh 2 ) 2 ) possessing thiophene units as electron-donating groups showed a HOMO level centered on this group, the LUMO level being located on the electron-accepting part. Due to the presence of a HOMO and a LUMO level spatially well-separated on these compounds, a clear distinction between the electron withdrawing and electron-releasing part can be established. On the oppo-site, for the four other dyes (ADS109GE, IDG1, IDG2, and PBBTZ20) exhibiting weak electron donor and acceptor properties, this separation could not be detected and a contribution of the whole molecule to the two orbitals could be evidenced. Theoretical investigation of their respective HOMO and LUMO energy values revealed these latter to be highly dependent of the co-monomers used. Differences of reactivity can already be anticipated for these photoinitiators.


Figure 1. Normalized UV–visible absorption spectra of the different dyes in THF (except for IDG2 in acetonitrile).

2149


www.mcp-journal.de


www.MaterialsViews.com © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimMacromol. Chem. Phys. 2016, 217, 2145−2153

Table 1. Ground state absorption maxima (nm).

Dyes λ max (Abs) [nm]

E HOMO a) [eV]

E LUMO a) [eV]

E HOMO b) [eV]

E LUMO b) [eV]

E ox c) (V vs SCE) Δ G d) ( 1 dye/Iod) [eV]

PTB7 622, 671 −5.15 [ 20 ] −3.31 [ 20 ] −5.25 −2.18 – –

PCDTBT 391, 554 −5.45 [ 21 ] −3.60 [ 22 ] −4.90 −2.61 – –

DTS(FBTTh 2 ) 2 372, 580 −5.12 [ 23 ] −3.34 [ 23 ] −4.65 −2.78 – –

PBDTBO-TPDO 408, 589 −5.40 [ 9 ] – −5.33 −2.20 0.88 [ 9 ] –

ADS109GE 455, 481 – – −5.52 −2.01 – –

IDG1 548 (s), 591 – – −6.10 −3.16 – –

IDG2 500 (s), 540 – – −6.04 −2.94 – –

PBBTZ20 450, 480 – – −4.98 −2.10 1.25 −1.09

a) Energy levels reported in the literature; b) Energy levels determined by theoretical calculations; c) Oxydation potential determined exper-imentally; d) The free energy change Δ G , calculated from the classical Rehm–Weller equation: [ 18 ] Δ G = E ox – E red – E S (or E T ) + C ; where E ox , E red , E S (or E T ), and C are the oxidation potential of the studied photoinitiators, the reduction potential of Iod, the excited singlet (or triplet) state energy of the studied photoinitiators, and the electrostatic interaction energy for the initially formed ion pair. This latter parameter is generally considered as negligible in polar solvents. [ 19 ]

Figure 2. Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the different dyes at UB3LYP/6-31G* level; for the MO calculations, an ethyl group instead of the alkyl chain was considered for IDG1 and a propyl group instead of the alkyl chain for PCDTBT, PBBTZ20, and PBDTBO-TPDO.

2150

J. Zhang et al.

www.mcp-journal.de



3.2. Cationic Photopolymerization of Epoxides

The cationic photopolymerization of EPOX was car-ried out under air upon exposure of the different dyes/Iod combinations to a low consumption LED emitting at 405 nm (≈110 mW cm −2 ) (see Figures 3 – 6 ). As evi-denced in Figure 3 , in the presence of PCDTBT/Iod or DTS(FBTTh 2 ) 2 /Iod, a moderate fi nal conversion (FC) of 20% was obtained with PCDTBT/Iod after 800 s of irradiation with the LED@405 nm (see Table 2 ); no polymerization occurred with DTS(FBTTh 2 ) 2 /Iod as likely resulting from its insolubility in EPOX. While adding NVK, comparable FCs were obtained: FCs = 46 and 49% using PCDTBT/Iod/NVK and DTS(FBTTh 2 ) 2 /Iod/NVK, respectively. The polymeriza-tion ability of DTS(FBTTh 2 ) 2 /Iod/NVK can be confi dently assigned to an improved solubility of the dye in the formu-lation, resulting from the presence of NVK.

Considering that ADS109GE does not exhibit a suffi cient absorption at 405 nm, the cationic poly-merization of EPOX was carried out upon irradiation with the LED@455 nm (M455L3 – ThorLabs; ≈80 mW cm −2 ) or the halogen lamp (intensity = 12 mW cm −2 ). Good poly-merization profi les were obtained upon the halogen lamp exposure (e.g., FC = 29 and 36% respectively after 800 s of irradiation using ADS109GE/Iod and ADS109GE/Iod/NVK, respectively (see Figure 4 ). On the opposite, only a low fi nal conversion (FC ≈ 16%) was obtained upon the LED@455 nm exposure, these counter-performances being directly related to the lower light intensity of the LED bulb compared to the halogen lamp.

From the series of dyes investigated in this study, PBBTZ20/Iod/NVK led to the best polymerization profi les, with FC = 58% after 800 s of irradiation (LED@405 nm; see Figure 5 ). A comparison established with the previously reported IDG1/

Iod/NVK [ 16 ] evidenced that PBBTZ20 outperformed IDG1 (FC = 52% in the same experimental conditions). The high FCs are in line with the good absorption of PBBTZ20 at 405 nm.

In the IDG1 and IDG2 indigo derivatives, the chromo-phores possess the same central core but differ by the length of the alkyl chains. As shown in Figure 6 , the new IDG2/Iod/NVK system led to a fi nal reduced conversion of ≈30% compared to IDG1/Iod/NVK. Considering that the two dyes exhibit the same scaffold, the lower performance of IDG2 can be assigned to the lower solubility resulting from the presence of shorter alkyl chains. Once again, the practical photoinitiating ability of a molecule is intimately linked to its solubility in the photocurable formulation.


Figure 3. Photopolymerization profi les of EPOX under air in the presence of (1) PCDTBT/Iod (0.5%/2%, w/w), (2) PCDTBT/Iod/NVK (0.5%/2%/3%, w/w/w), and (3) DTS(FBTTh 2 ) 2 /Iod/NVK (0.5%/2%/3%, w/w/w) upon the laser diode at 405 nm exposure.

Figure 4. Photopolymerization profi les of EPOX under air in the presence of (1) ADS109GE/Iod (0.5%/2%, w/w) and (2) ADS109GE/Iod/NVK (0.5%/2%/3%, w/w/w) upon the halogen lamp exposure, (3) ADS109GE/Iod/NVK (0.5%/2%/3%, w/w/w) upon the 457 nm laser diode exposure.

Figure 5. Photopolymerization profi les of EPOX under air in the presence of (1) PBBTZ20/Iod (0.5%/2%, w/w), (2) PBBTZ20/Iod/NVK (0.5%/2%/3%, w/w/w), or (3) IDG1 / Iod / NVK (0.5%/2%/3%, w/w/w). LED@405 nm exposure.

2151


www.mcp-journal.de


www.MaterialsViews.com © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

3.3. Free Radical Photopolymerization of Acrylates

In light of the above results and its remarkable photoiniti-ating ability, only PBBTZ20 was selected for the radical poly-merization of a trifunctional acrylate monomer (TMPTA) at 405 nm (see Figure 7 and Table 3 ). A fi nal conversion of 32% was achieved with PBBTZ20/Iod/NVK (Figure 7 curve 1) versus FC = 42% with IDG1/Iod/NVK (Figure 7 , curve 2). The IDG1/MEDA/R-Cl three-component system (that works through a reduction cycle as in ref. [ 1 ] ) led to a less effi cient polymerization profi le (FC = 37% after 400 s).

4. Conclusions

Seven new dyes have been examined as photoinitiators for the polymerization of acrylate and/or epoxide mono-mers. Among all chromophores, PBBTZ20/Iod/NVK proved to be the most effi cient for the cationic polymerization of epoxides. Indeed, especially, for the polymerization of EPOX, this 5 H -pyrrolo- bis -thiazine derivative could outper-form the IDG1/Iod/NVK reference system which is already better than similar Eosin or camphorquinone based combi-nations. PBBTZ20 belongs to an unknown class of photoini-tiators so far and the preliminary results presented in this work make this new family a promising scaffold for future developments. For radical polymerization, IDG1 is found a good photoinitiator. Most of the experimental work has been carried out here on the ability of the Dye/Iod/NVK systems to work at 405 nm where their relative effi ciency can be evaluated. The excited state reactivity being not wavelength dependent in such systems (as observed with many other similar PISs), it is obvious that an effi cient


Figure 6. Photopolymerization profi les of EPOX under air in the presence of IDGs/Iod/NVK upon the LED@405 nm (IDG1 (1) and IDG2 (2): 0.5 wt%; Iod: 2 wt%; NVK: 3 wt%).

Figure 7. Photopolymerization profi les of TMPTA in laminate in the presence of (1) PBBTZ20/Iod/NVK (0.5%/2%/3%, w/w/w), (2)IDG1/Iod/NVK (0.5%/2%/3%, w/w/w), or (3) IDG1/MDEA/R-Cl (0.5%/2%/3%, w/w/w) upon the LED at 405 nm exposure.

Table 2. EPOX conversions obtained under air upon exposure to the LED@405 nm for 800 s in the presence of Dye/Iod (0.5%/2%, w/w) or Dye/Iod/NVK (0.5%/2%/3%, w/w/w).

LED (405 nm)

PCDTBT/Iod 20%

PCDTBT/Iod/NVK 46%

DTS(FBTTh 2 ) 2 /Iod np a)

DTS(FBTTh 2 ) 2 /Iod/NVK 49%

ADS109GE/Iod –

ADS109GE/Iod/NVK a) –

PBBTZ20/Iod 34%

PBBTZ20/Iod/NVK 58%

IDG1/Iod np a)

IDG1/Iod/NVK 52%

IDG2/Iod –

IDG2/Iod/NVK 35%

a) FC = 17% using ADS109GE/Iod/NVK under the 457 nm laser diode exposure.

Table 3. TMPTA conversions obtained in laminate upon expo-sure to the LED@405 nm for 400 s in the presence of Dye/Iod (0.5%/2%, w/w) or Dye/Iod/NVK (0.5%/2%/3%, w/w/w).

LED (405 nm)

PBBTZ20/Iod <10%

PBBTZ20/Iod/NVK 32%

IDG1/Iod np a)

IDG1/Iod/NVK 42%

IDG1/MDEA/R-Cl 37%

IDG2/Iod –

IDG2/Iod/NVK –

a) np: no polymerization.

2152

J. Zhang et al.

www.mcp-journal.de


www.MaterialsViews.com© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimMacromol. Chem. Phys. 2016, 217, 2145−2153

system at 405 nm will remain effi cient under exposure to other visible light sources providing a good matching with the absorption spectra: this is the case for, e.g., PBBTZ20 at 470 nm, PCDTBT at 532 nm or DTS(FBTTh 2 ) 2 at 532 or 605 nm. If the examination of compounds developed for organic electronics is unusual for the polymer com-munity and mostly developed by our research groups, it can offer the possibility to propose new highly reactive scaffolds.

Supporting Information

Supporting Information is available from the Wiley Online Library or from the author.

Acknowledgements : Jacques Lalevée thanks the Institut Universitaire de France.

Received: May 30, 2016 ; Revised: July 6, 2016 ; Published online: August 3, 2016; DOI: 10.1002/macp.201600260

Keywords: acrylate ; epoxide ; LED ; photoinitiator ; polymer

[1] a) J.-P. Fouassier , J. Lalevée , Photoinitiators for Poly mer Synthesis-Scope, Reactivity, and Effi ciency , Wiley-VCH Verlag GmbH & Co. KGaA , Weinheim 2012 ; b) J. Lalevée , M. A. Tehfe , N. Blanchard , F. Morlet-Savary , J.-P. Fouassier , Radical Polymerization: New Developments , Nova Science Publishers, Inc. , Hauppauge, N.Y. 2011 , ch. 7; c) J.-P. Fouassier , J. Lalevée , in New Developments in Chromophore Research , Nova Science Publishers, Haup-pauge , NY, USA 2013 ; d) J. V. Crivello , Photoinitiators for Free Radical, Cationic and Anionic Photo-Polymerization , 2nd ed. , John Wiley & Sons , Chichester 1998 ; e) J.-P. Fouassier , Photoinitiator, Photopolymerization and Photocuring: Fun-damentals and Applications , Hanser Publishers , Munich 1995 ; f) N. S. Allen , Photochemistry and Photophysics of Polymer Materials , Wiley , NY, USA 2010 ; g) J. F. Rabek , Mechanisms of Photophysical Processes and Photochemical Reactions in Polymers: Theory and Applications , Wiley , New York 1987 ; h) S. Davidson , Exploring the Science, Technology and Application of UV and EB Curing , Sita Technology Ltd , London 1999 ; i) K. Dietliker , A Compilation of Photoinitiators Commercially Available for UV Today , Sita Technology Ltd , Edinburgh, London 2002 .

[2] a) Photoinitiated Polymerization (Eds: K. D. Belfi ed , J. V. Crivello) , ACS Symposium series 847 , Washington, DC 2003 ; b) Photochemistry and UV Curing (Ed: J.-P. Fouassier) , Research Signpost, Trivandrum , India 2006 ; c) Photochemistry and Photophysics of Polymer Materials (Ed: N. S. Allen) , Wiley , USA 2010 ; d) Basics of Photopolymerization Reactions (Eds: J.-P. Fouassier , X. Allonas) , Research Signpost , Trivandrum, India 2010 ; e) W. A. Green , Industrial Photoinitiators , CRC Press , Boca Raton 2010 .

[3] P. Xiao , J. Zhang , F. Dumur , M. A. Tehfe , F. Morlet-Savary , B. Graff , D. Gigmes , J.-P. Fouassier , J. Lalevée , Prog. Polym. Sci. 2015 , 41 , 32 .

[4] a) P. Xiao , F. Dumur , B. Graff , D. Gigmes , J.-P. Fouassier , J. Lalevée , Macromolecules 2013 , 46 , 7661 ; b) J. Zhang , N. Zivic , F. Dumur , P. Xiao , B. Graff , D. Gigmes , J.-P. Fouassier , J. Lalevée , J. Polym. Sci. A Polym. Chem. 2015 , 53 , 445 ; c) M.-A. Tehfe , F. Dumur , B. Graff , J.-L. Clément , D. Gigmes , F. Morlet-Savary , J.-P. Fouassier , J. Lalevée , Macromolecules 2013 , 46 , 736 ; d) M.-A. Tehfe , F. Dumur , E. Contal , B. Graff , D. Gigmes , F. Morlet-Savary , J.-P. Fouassier , J. Lalevée , Polym. Chem. 2013 , 4 , 1625 ; e) J. Lalevée , M.-A. Tehfe , F. Dumur , D. Gigmes , B. Graff , F. Morlet-Savary , J.-P. Fouassier , Macromol. Rapid. Commun. 2013 , 34 , 239 ; f) M.-A. Tehfe , F. Dumur , B. Graff , F. Morlet-Savary , J.-P. Fouassier , D. Gigmes , J. Lalevée , Macromolecules 2012 , 45 , 8639 ; g) S. Telitel , F. Dumur , D. Gigmes , B. Graff , J.-P. Fouassier , J. Lalevée , Polymer 2013 , 54 , 2857 ; h) S. Telitel , F. Dumur , T. Faury , B. Graff , M.-A. Tehfe , D. Gigmes , J.-P. Fouassier , J. Lalevée , Beilstein J. Org. Chem. 2013 , 9 , 877 ; i) M.-A. Tehfe , F. Dumur , B. Graff , F. Morlet-Savary , D. Gigmes , J.-P. Fouassier , J. Lalevée , Polym. Chem. 2013 , 4 , 2313 ; j) P. Xiao , F. Dumur , B. Graff , D. Gigmes , J.-P. Fouassier , J. Lalevée , Macromole-cules 2014 , 47 , 601 ; k) P. Xiao , F. Dumur , B. Graff , D. Gigmes , J.-P. Fouassier , J. Lalevée , Macromolecules 2014 , 47 , 973 ; l) J. Zhang , F. Dumur , P. Xiao , B. Graff , D. Bardelang , D. Gigmes , J.-P. Fouassier , J. Lalevée , Macromolecules 2015 , 48 , 2054 .

[5] a) J. Crivello , Dyes and Chromophores in Polymer Science (Eds: J. Lalevée , J.-P. Fouassier) , ISTE Wiley , London 2015 ; b) A. E. Allen , D. W. C. MacMillan , Chem. Sci. 2012 , 3 , 633 ; c) J. M. R. Narayanam , C. R. J. Stephenson , Chem. Soc. Rev. 2011 , 40 , 102 ; d) B. P. Fors , C. J. Hawker , Angew. Chem. Int. Ed. 2012 , 51 , 8850 ; e) D. Konkolewicz , K. Schroder , J. Buback , S. Bernhard , K. Matyjaszewski , ACS Macro Lett. 2012 , 1 , 1219 ; f) X. Pan , C. Fang , M. Fantin , N. Malhotra , W. Y. So , L. A. Peteanu , A. A. Isse , A. Gennaro , P. Liu , K. Matyjaszewski , J. Am. Chem. Soc. 2016 , 138 , 2411 ; g) K. Kaastrup , A. Aguirre-Soto , C. Wang , C. N. Bowman , J. W. Stansbury , H. D. Sikes , Polym. Chem. 2016 , 7 , 592 ; h) T. Brömme , D. Oprych , J. Horst , P. S. Pinto , B. Strehmel , RSC Adv. 2015 , 5 , 69915 ; i) A. Aguirre-Soto , C.-H. Lim , A. T. Hwang , C. B. Musgrave , J. W. Stansbury , J. Am. Chem. Soc. 2014 , 136 , 7418 ; j) G. Müller , M. Zalibera , G. Gescheidt , A. Rosenthal , G. Santiso-Quinones , K. Dietliker , H. Grützmacher , Macromol. Rapid Commun. 2015 , 36 , 553 .

[6] a) P. Xiao , F. Dumur , M. Frigoli , M.-A. Tehfe , D. Gigmes , J.-P. Fouassier , J. Lalevée , Polym. Chem. 2013 , 4 , 5440 ; b) Z. Raad , E. Ay , O. Dautel , F. Dumur , G. Wantz , D. Gigmes , J.-P. Fouassier , J. Lalevée , Macromolecules 2016 , 49 , 2124 .

[7] a) C. H. To , A. Ng , Q. Dong , A. B. Djuriš ic , J. A. Zapien , W. K. Chan , C. Surya , ACS Appl. Mater. Interf. 2015 , 7 , 13198 ; b) S. Das , J. K. Keum , J. F. Browning , G. Gu , B. Yang , O. Dyck , C. Do , W. Chen , J. Chen , I. N. Ivanov , K. Hong , A. J. Rondinone , P. C. Joshi , D. B. Geohegan , G. Duscher , K. Xiao , Nanoscale 2015 , 7 , 15576 ; c) L. Lu , L. Yu , Adv. Mater. 2014 , 26 , 4413 ; d) Z. He , C. Zhong , S. Su , M. Xu , H. Wu , Y. Cao , Nat. Photon. 2012 , 6 , 593 .

[8] a) S. Alem , T.-Y. Chu , S. C. Tse , S. Wakim , J. Lu , R. Movileanu , Y. Tao , F. Bélanger , D. Désilets , S. Beaupré , M. Leclerc , S. Rodman , D. Waller , R. Gaudiana , Org. Electron. 2011 , 12 , 1788 ; b) S. Beaupré , M. Leclerc , J. Mater. Chem. A 2013 , 1 , 11097 ; c) Y. Zhang , E. Bovill , J. Kingsley , A. R. Buckley , H. Yi , A. Iraqi , T. Wang , D. G. Lidzey , Sci. Report 2016 , DOI: 10.1038/srep21632 .

2153


www.mcp-journal.de


www.MaterialsViews.com © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimMacromol. Chem. Phys. 2016, 217, 2145−2153

[9] C. Piliego , T. W. Holcombe , J. D. Douglas , C. H. Woo , P. M. Beaujuge , J. M. J. Fréchet , J. Am. Chem. Soc. 2010 , 132 , 7595 .

[10] R. Lin , M. Wright , B. P. Veettil , A. Uddin , Synth. Met. 2014 , 192 , 113 .

[11] a) S. H. Park , A. Roy , S. Beaupré , S. Cho , N. Coates , J. S. Moon , D. Moses , M. Leclerc , K. Lee , A. J. Heeger , Nat. Photon 2009 , 3 , 297 ; b) T.-Y. Chu , S. Alem , S.-W. Tsang , S.-C. Tse , S. Wakim , J. Lu , G. Dennler , D. Waller , R. Gaudiana , Y. Tao , Appl. Phys. Lett. 2011 , 98 , 25301 .

[12] a) Y. J. Kim , D. S. Chung , C. E. Park , Nano Energy 2015 , 15 , 343 ; b) A. K. K. Kyaw , D. Gehrig , J. Zhang , Y. Huang , G. C. Bazan , F. Laquai , T.-Q. Nguyen , J. Mater. Chem. A 2015 , 3 , 1530 ; c) T. S. van der Poll , J. A. Love , T.-Q. Nguyen , G. C. Bazan , Adv. Mater. 2012 , 24 , 3646 ; d) Y. Sun , J. Seifter , L. Huo , Y. Yang , B. B. Y. Hsu , H. Zhou , X. Sun , S. Xiao , L. Jiang , A. J. Heeger , Adv. Energy Mater. 2014 , 1400987 .

[13] a) N. Blouin , A. Michaud , D. Gendron , S. Wakim , E. Blair , R. Neagu-Plesu , M. Belletête , G. Durocher , Y. Toa , M. Leclerc , J. Am. Chem. Soc. 2008 , 130 , 732 ; b) Z. B. Henson , G. C. Welch , T. S. van der Poll , G. C. Bazan , J. Am. Chem. Soc. 2012 , 134 , 3766 .

[14] G. C. Welch , L. Perez , C. V. Hoven , Y. Zhang , X.-D. Dang , A. Sharenko , M. F. Toney , E. J. Kramer , T.-Q. Nguyen , G. C. Bazan , J. Mater. Chem. 2011 , 21 , 12700 .

[15] a) G. Wantz , B. Gautier , F. Dumur , T. N. T Phan , D. Gigmes , L. Hirsch , J. Gao , Org. Electron. 2012 , 13 , 1859 ; b) M. Ben Khalifa , G. Wantz , J. Parneix , L. Hirsch , Eur. Phys. J. Appl. Phys. 2008 , 41 , 29 .

[16] J. Zhang , N. Zivic , F. Dumur , C. Guo , Y. Li , P. Xiao , B. Graff , D. Gigmes , J.-P. Fouassier , J. Lalevée , Mater. Today Commun. 2015 , 4 , 101 .

[17] M. A. Tehfe , J. Lalevée , S. Telitel , E. Contal , F. Dumur , D. Gigmes , D. Bertin , M. Nechab , B. Graff , F. Morlet-Savary , J.-P. Fouassier , Macromolecules 2012 , 45 , 4454 .

[18] D. Rehm , A. Weller , Isr. J. Chem. 1970 , 8 , 259 . [19] J. Lalevée , A. Dirani , M. El Roz , B. Graff , X. Allonas ,

J.-P. Fouassier , Macromolecules 2008 , 41 , 2003 . [20] R. Lin , M. Wright , B. P. Veettil , A. Uddin , Synth. Met. 2014 ,

192 , 113 . [21] S. Alem , T.-Y. Chu , S. C. Tse , S. Wakim , J. Lu , R. Movileanu ,

Y. Tao , F. Bélanger , D. Désilets , S. Beaupré , M. Leclerc , S. Rodman , D. Waller , R. Gaudiana , Org. Electron. 2011 , 12 , 1788 .

[22] Y. Zhu , L. Yang , S. Zhao , Y. Huang , Z. Xu , Q. Yang , P. Wang , Y. Li , X. Xu , Phys. Chem. Chem. Phys. 2015 , 17 , 26777 .

[23] Y. J. Kim , D. S. Chung , C. E. Park , Nano Energy 2015 , 15 , 343 .

Documents

Polymeric Photoinitiators: A New Search toward High ...cheserv12.uwaterloo.ca/peml/resources/Publications/... · 2147 Polymeric Photoinitiators: A New Search toward High Performance