Abstract
A silicone-thioxanthone (STX) visible light photoinitiator was prepared by the nucleophilic substitution reaction of 2-[(4-hydroxybenzyl)-(methyl)-amino]-9H-thioxanthen-9-one (TX-HB) and γ-chloropropylmethylpolysiloxane-co-dimethyl-polysiloxane (PSO-Cl). Its structure was confirmed by 1H NMR, 13C NMR, FTIR, UV-vis and GPC. The photopolymerization kinetics of 1, 6-Hexanedioldiacrylate (HDDA) and trimethylolpropane triacrylate (TMPTA) initiated by STX confirmed that STX is an efficient photoinitiator. Its visible light photolysis experiment and the photopolymerization kinetics studies implied that a possible synergistic effect existed between two adjacent thioxanthone groups. Moreover, a higher migration stability was revealed in STX than 2-benzyl (methyl) amino-9H-thioxanthen-9-one (TX-B). STX could change the surface property of the cured film of polyurethane diacrylate prepolymer (PUA) from hydrophilic to hydrophobic, as well as change the thermal stability of the polymer network. Meanwhile, it could improve the resistance against water and acid. Thus, STX is an effective multifunctionalized photoinitiator.
Highlights
In recent years, photopolymerization has been widely recognized for its many applications in coatings, printing ink, adhesives, 3D print, and optoelectronic products [1,2,3]
We have reported a series of one-component aminothioxanthone (ATX) visible light photoinitiators, such as small molecular (TX-A, TX-B, TX-C and TX-Ac in Chart 1) [37], waterborne (TX-MPEG in Chart 1) [38], and polymerizable (TX-PA, TX-EA and TX-BDA in Chart 1) [36,37,38,39,40,41] TXs
The thermal behaviors of the cured polyurethane films initiated by TX-B and STX were measured by differential scanning calorimeter (DSC) (Table 1 and Figure S9)
Summary
Photopolymerization has been widely recognized for its many applications in coatings, printing ink, adhesives, 3D print, and optoelectronic products [1,2,3]. Silicone has been known as an inorganic–organic hybrid polymer material featured with a series of properties such as good chemical and thermal ability, weather-resistance, low friction coefficient, low surface energy, and nonstick behavior [20,21,22,23,24]. We reported on a series of silicone-naphthalimide visible photoinitiator for free radical polymerization They showed very good photoinitiating properties, and brought about the desired modification to the cured-materials, such as improved resistance against water and ethanol, and better thermal stability [9,10]. The surface properties of the cured film of PUA films changes from hydrophilic to hydrophobic after the photocuring process This multifunctionalized photoinitiator STX improves the thermal stability of the cured polyurethane diacrylate (PUA) films and effectively increases waterand acid-resistance abilities.
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