Tris(hydroxyphenyl)ethane Benzotriazole:  A Copolymerizable UV Light Stabilizer^,1a

Abstract

A novel UV-light stabilizer (UVLS), 3′-(2H-benzotriazol-2′′-yl)-1,1,1-tris(4′-hydroxyphenyl)-ethane or simply tris(hydroxyphenyl)ethane benzotriazole (THPE-BZT), that can be copolymerized with engineering plastic monomers has been synthesized in three steps. The compound has two solid forms, a hydrate and an anhydrous form. Surprisingly, the hydrated form is more soluble in organic solvents such as acetone. Infrared spectra reveal that the hydrated form loses water of hydration upon heating and then forms a coplanar ring structure with a strong intramolecular hydrogen bond (IMHB) between one benzotriazole nitrogen and the adjacent phenolic OH. The NMR and UV-vis spectra in less polar organic solvents are also in accordance with the IMHB structure of THPE-BZT. In polar organic solvents such as DMSO and DMF and in MeOH/water at pH >10, the IMHB is disrupted, and the disrupted form exists in equilibrium with the planar or nondisrupted form. However, THPE-BZT copolymerized into low molecular weight polysulfones and polycarbonates retains the planar IMHB structure, as indicated by the UV absorption peak at ∼335 nm. These copolymers have greater UV stability than those without any THPE-BZT because of dissipation of photon energy by molecular vibrational relaxation in the planar form. Also, polysulfone copolymers containing THPE-BZT in the range of 0.25-1.5 mol % have greater UV light stability than polysulfone containing additive-type UVLS such as 2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole (Cyasorb 5411). For polycarbonates, preliminary results show that copolymers of THPE-BZT have UV-light stability comparable to or only slightly less than that of polycarbonates blended with Cyasorb 5411 or THPE-BZT as additives. But the copolymers should escape the problems of surface "blooming" and leaching by extraction experienced by noncopolymerized UVLS additives. Thermogravimetric analysis indicates that THPE-BZT is more stable than the commercial benzotriazoles 2-(2′-hydroxy-5′-methylphenyl)benzotriazole (Tinuvin P), Cyasorb 5411, and the industrial standards2-[2′-hydroxy-3′,5′-bis (1-methyl-1-phenylethyl)phenyl]benzotriazole (Tinuvin 900)sand therefore might offer superior performance, even as an additive.

Excited state intramolecular proton transfer in amino 2-(2′-hydroxyphenyl)benzazole derivatives: Effects of the solvent and the amino group position

“…Compounds emitting fluorescence through the excitedstate intramolecular proton transfer (ESIPT) mechanism [1][2][3][4][5][6] have become a very attractive field of research by virtue of the widespread applications that can be envisaged for these dyes, such as UV-light polymer stabilizers [7,8], sensors [9] and laser dyes [10]. Particular interest has recently been shown in a new class of ESIPT amino benzazole derivatives, where applications such as fluorescent probes to label proteins and DNA [11] and new polymeric materials [12,13] were also reported.…”

Novel ESIPT fluorescent benzazolyl-4-quinolones: Synthesis, spectroscopic characterization and photophysical properties

“…Intramolecular proton transfer occurs when a molecule contains both an acidic and a basic site which, upon electronic excitation, experience enhanced acidity or basicity, respectively [21] The excited keto tautomer (K 1 ) decays, therby emitting fluorescence as the fundamental keto tautomer (K 0 ), and the initial enol form (E 0 ) is regenerated [22,23]. Since most ESIPT processes are reversible, these systems have found application as UV-light stabilizers [24,25], laser dyes [26], sensors [27], DNA probes [28,29], in drug delivery systems [30], hybrid materials [31] and also as fluorescent probes [32][33][34][35].…”

A Novel Synthetic Method for Well‐Defined Polymers Containing Benzotriazole and Diazobenzene Chromophores

“…On the other hand, benzotriazole and its derivatives have been widely used as UV-light stabilizer to diminish the photodegradation of polymers, dyes, and pigments. [40][41][42] Therefore, the functional precursor polymer, poly{2-[3-(2H-Benzotriazol-2-yl)-4-hydroxyphenyl]ethylmethacrylate} (PBHEMA), was further modified through the substitution reaction between the hydroxyl group of PBHEMA and bromide of bromo-nitrodiazobenzene, which finally resulted in a benzotriazole functionalized polymer. Through this strategy, the well-designed double functional polymers containing benzotriazole and azobenzene group with narrow molecular weight distributions, controllable molecular weights and adjustable degree of functionalities were obtained.…”