Hexaarylbiimidazoles as visible light thiol-ene photoinitiators.
Hexaarylbiimidazoles as visible light thiol-ene photoinitiators.
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DOI：
10.1016/j.dental.2015.06.005
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发表时间：
2015-09
期刊：
影响因子：
--
通讯作者：
Scott TF
中科院分区：
文献类型：
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作者：
Ahn D;Sathe SS;Clarkson BH;Scott TF
本研究的目的是确定六芳基联咪唑（HABI）是否是有效的，可见光活性的硫醇-烯体系的光引发剂。我们假设，由于碘苯自由基与硫醇的反应性和硫醇-烯制剂中硫醇的必要高浓度，HABI将在可见光照射下有效地引发硫醇-烯聚合。使用UV-vis光谱法获得光引发剂溶液的UV-vis吸收光谱，而EPR光谱法用于确认HABI光解后的自由基物质产生。使用FTIR光谱法监测光聚合过程中的官能团转化率，并使用动态力学分析确定热机械性能。研究的HABI衍生物在469 nm处表现出比邻苯二酚更低的吸收率;然而，与双（2，4，6-三甲基苯甲酰基）-苯基氧化膦相比，它们在该波长处提供了更高的灵敏度。光解的调查HABI提供洛菲自由基。将羟基己基官能团附接至HABI核显著改善了溶解度。用HABI光引发剂配制的硫醇-烯树脂在469 nm照射下迅速聚合。用双（羟己基）官能化HABI配制并在室温和体温下光聚合的硫醇-烯树脂的玻璃化转变温度分别为49.5±0.5°C和52.2±0.1°C。虽然硫醇-烯显示出作为复合牙科修复材料的连续相的前景，但它们与传统的邻苯二酚/叔胺光引发体系的反应性差。相反，尽管它们的可见光吸收率相对较低，但HABI光引发剂提供快速的硫醇-烯光聚合速率。此外，微小的结构修饰表明了改善HABI溶解度和可见光吸收的途径。
The aim of this study is to determine if hexaarylbiimidazoles (HABIs) are efficient, visible light-active photoinitiators for thiol–ene systems. We hypothesize that, owing to the reactivity of lophyl radicals with thiols and the necessarily high concentration of thiol in thiol–ene formulations, HABIs will effectively initiate thiol–ene polymerization upon visible light irradiation. UV-vis absorption spectra of photoinitiator solutions were obtained using UV-vis spectroscopy, while EPR spectroscopy was used to confirm radical species generation upon HABI photolysis. Functional group conversions during photopolymerization were monitored using FTIR spectroscopy, and thermomechanical properties were determined using dynamic mechanical analysis. The HABI derivatives investigated exhibit less absorptivity than camphorquinone at 469 nm; however, they afford increased sensitivity at this wavelength when compared with bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide. Photolysis of the investigated HABIs affords lophyl radicals. Affixing hydroxyhexyl functional groups to the HABI core significantly improved solubility. Thiol–ene resins formulated with HABI photoinitiators polymerized rapidly upon irradiation with 469 nm. The glass transition temperatures of the thiol–ene resin formulated with a bis(hydroxyhexyl)-functionalized HABI and photopolymerized at room and body temperature were 49.5±0.5°C and 52.2±0.1°C, respectively. Although thiol–enes show promise as continuous phases for composite dental restorative materials, they show poor reactivity with the conventional camphorquinone/tertiary amine photoinitiation system. Conversely, despite their relatively low visible light absorptivity, HABI photoinitiators afford rapid thiol–ene photopolymerization rates. Moreover, minor structural modifications suggest pathways for improved HABI solubility and visible light absorption.