关键词: 染色, 苯并[a]吩恶嗪, 功能染料, 阳离子可染改性涤纶, 荧光, 光动力

Abstract:

Objective Functionally modified polyester textiles with high added value have significant development value in the fields of both domestic and industrial textiles. Cationic dyeable modified polyester fabrics are often endowed with enhanced functionality by coating and cross-linking with polymers. However, these modifications can compromise their breathability and adversely affect their apparent color and luster. This study aims to synthesize a novel photo-functional benzo[a]phenoxazine cationic dye, aim to achieve an integrated construction of both color and functionality on cationic dyeable modified polyester fabrics via a streamlined dyeing process.

Method Two dyes, 5-ethylenediamino-9-(diethylamino)benzo[a]phenoxazine ammonium chloride (N1) and 5-propylamino-9-(diethylamino)benzo[a]phenoxazine ammonium chloride (N2), were synthesized via nucleophilic substitution reactions. The structural characterizations of these dyes were accomplished using proton nuclear magnetic resonance (¹H NMR) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. Additionally, 5-amino-9-(diethylamino)benzo[a]phenoxazine ammonium sulfate (Nile Blue sulfate, N3) was selected as the comparative dye. The photophysical and chemical properties of these dyes, along with their dyeing performance on cationic dyeable modified polyester fabrics, were investigated using a color matching instrument, UV-visible spectrophotometer, and fluorescence spectrophotometer. The fluorescence emission and photodynamic properties of the dyed fabrics were also examined.

Results This study was focused on two photo-functional benzo[a]phenoxazine cationic dyes for dyeing cationic dyeable modified polyester fabrics.¹H NMR and FT-IR confirmed the successful synthesis of 5-ethylenediamino-9-(diethylamino)benzo[a]phenoxazine ammonium chloride (N1) and 5-propylamino-9-(diethylamino)benzo[a]phenoxazine ammonium chloride (N2). The maximum absorption wavelengths (λ_max) of the three dyes in water were 648 nm, 639 nm, and 635 nm, respectively, presenting a blue color. In DMF, both λ_max and the maximum emission wavelengths (λ_em) of the three dyes exhibited a blue shift, with the solution color changing from blue to red and displaying orange-yellow fluorescence under a 365 nm ultraviolet lamp, which may be caused by the molecular deprotonation. Dye N2, with a propyl amino group at the 5-position, achieved a dye-uptake of 99.65% on cationic dyeable modified polyester fabric, demonstrating rapid dye uptake with good levelness. The a^*(green-red axis) and b^*(blue-yellow axis) values of the fabrics dyed with these dyes were all negative, while the lightness (L^*) values were positive, indicating that the dyed fabric exhibited a bright blue with a greenish tint. Due to the enhanced π-π^* transition caused by the propyl amino group in dye N2, fabric dyed with 1% (o.w.f) dosage exhibited strong red fluorescence, while the increasing dye dosage led to fluorescence self-quenching on the fabric. The photodynamic properties of the dyed fabrics were investigated. The bleaching rate of 1,3-diphenylisobenzofuran on fabric dyed with N3 (6%, o.w.f) reached over 80% after 40 min of red-light exposure. Under the same condition, the bleaching rate for fabric dyed with N1 was 63.5%, demonstrating that these dyed fabrics have the ability of photoinduced singlet oxygen generation. Additionally, color fastness tests indicated that the fabrics dyed with these three dyes (1%, o.w.f) achieved excellent rubbing and washing fastness which is over level 4, and the light fastness were in the range of levels 3 to 4.

Conclusion In this work, two benzo[a]phenoxazine-based functional dyes (N1 and N2) were developed and characterized. N1 and N2 exhibit solvatochromic behaviors, and they have excellent dyeing performance on cationic dyeable modified polyester fabrics with high dye-uptake rate and good color fastness. The dyed fabrics show red fluorescence emission and photodynamic¹O₂ generation ability. Dye N1 with an ethylenediamine group at the 5-position has better photodynamic¹O₂ generation performance than the dye N2. This offers a novel approach to the development of multicolor textiles for health and safety protection. In future research on benzo[a]phenoxazine cationic dyes, further modulation of molecular structure could enhance the photodynamic generation of reactive oxygen species by the dyes and the antibacterial activity of the dyed fabrics, thereby enriching the color palette and functional versatility of health protection textiles.

Key words: dyeing, benzo[a]phenoxazine, functional dye, cationic dyeable modified polyester, fluorescence, photodynamic