Design, synthesis of novel bisazo disperse dyes: Structure analysis and dyeing performance on PET

Article abstract of DOI:10.1016/j.dyepig.2021.109761

To achieve bisazo disperse dyes with better dyeing performances, novel bisazo disperse dyes based on butane-1,4-diyl bis(ethyl(phenyl)carbamate) were synthesized by coupling with diazonium salts. Butane-1,4-diyl bis(ethyl(phenyl)carbamate) was prepared by condensation of 1,4-butanediol and N-ethyl-N-phenylglycinoyl chloride. N-ethyl-N-phenylglycinoyl chloride was achieved from N-ethyl-N-phenylglycine, which was hydrolyzed from ethyl N-ethyl-N-phenylglycinate. Compared with previously reported bisazo disperse dyes’ low exhaustion, poor fastness performance or monotone color, constructed symmetrical bisazo disperse dyes exhibited excellent dyeing performance on polyethylene terephthalate (PET) fabrics, by introducing 1,4-butanediol as soft chain to lessen structure hardness of dye molecule and stronger hydrophobicity. Enhanced affinity between dye molecular and fiber was achieved by ester groups existing both in dye molecular and fiber, increased molecular size also enhanced stronger Van der Waals force and hydrogen bonding. Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance techniques (¹H NMR) were used to confirm the structures of synthesized dyes. UV–Vis method was applied to estimate relationship between spectral properties and structures. Constructed bisazo disperse dyes were applied on polyethylene terephthalate (PET) fabric using conventional high temperature dyeing method under pressure, gave orange to blue shade with satisfying fastness properties. Quantum simulation was applied to provide a new guide line to evaluate structure-property relationship for dyestuffs.

Full text of DOI:10.1016/j.dyepig.2021.109761

Dyes and Pigments 196 (2021) 109761
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Design, synthesis of novel bisazo disperse dyes: Structure analysis and
dyeing performance on PET
a
a
b
b
a,b,*
Shengli Wang , Linbo Gao , Aiqin Hou , Kongliang Xie , Xiyu Song
a
Key Laboratory of Clean Dyeing and Finishing Technology of Zhejiang Province, Shaoxing University, Shaoxing, 312000, China
College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, 201620, China
b
A R T I C L E I N F O
A B S T R A C T
Keywords:
To achieve bisazo disperse dyes with better dyeing performances, novel bisazo disperse dyes based on butane-
Bisazo disperse dyes
Symmetrical
Soft chain
1
,4-diyl bis(ethyl(phenyl)carbamate) were synthesized by coupling with diazonium salts. Butane-1,4-diyl bis
(
ethyl(phenyl)carbamate) was prepared by condensation of 1,4-butanediol and N-ethyl-N-phenylglycinoyl
chloride. N-ethyl-N-phenylglycinoyl chloride was achieved from N-ethyl-N-phenylglycine, which was hydrolyzed
from ethyl N-ethyl-N-phenylglycinate. Compared with previously reported bisazo disperse dyes’ low exhaustion,
poor fastness performance or monotone color, constructed symmetrical bisazo disperse dyes exhibited excellent
dyeing performance on polyethylene terephthalate (PET) fabrics, by introducing 1,4-butanediol as soft chain to
lessen structure hardness of dye molecule and stronger hydrophobicity. Enhanced affinity between dye molecular
and fiber was achieved by ester groups existing both in dye molecular and fiber, increased molecular size also
enhanced stronger Van der Waals force and hydrogen bonding. Fourier transform infrared spectroscopy (FT-IR)
Quantum simulation
PET
1
and nuclear magnetic resonance techniques ( H NMR) were used to confirm the structures of synthesized dyes.
UV–Vis method was applied to estimate relationship between spectral properties and structures. Constructed
bisazo disperse dyes were applied on polyethylene terephthalate (PET) fabric using conventional high temper-
ature dyeing method under pressure, gave orange to blue shade with satisfying fastness properties. Quantum
simulation was applied to provide a new guide line to evaluate structure-property relationship for dyestuffs.
1
. Introduction
Azo disperse dyes play an important role in development of disperse
and soft alkane chains [12]. Those symmetric structure of biszao
disperse dyes are also good imitation of PET, which could help to boost
dyeing performance and fastness properties. Increased molecular weight
can enhance the fiber-dye intermolecular force to reduce the degree of
thermomigration of dyes [13]. A wide range of color can also be ach-
ieved by varying diazonium components [14]. Dyed PET fabrics exhibit
much better dyeing and fastness performance than previously reported
dyes for coloring synthetic fibers [1,2]. Many studies about bisazo
disperse dyes have been investigated to increase dye ability on PET
fabric [3,4]. Dye chemists have been focused on improving tinctorial
strength and fastness properties to fabrics over the years [5,6]. Low
fastness and poor dyeing performance were attributed to weak dye-fiber
affinity, disperse dyes containing multi-ester groups exhibited deeper
and brighter intense hues, eater groups can also enhance dye-fiber af-
finity [6]. Increased molecular mass can also facilitate dye-fiber inter-
action, which help to reduce thermomigration of disperse dyes on
hydrophobic fibers [7]. But Most developed bisazo disperse dyes are in
rigid construction, leading to lower affinity with fabrics, which would
increase burden of swage treatment [8,9].
.
bisazo disperse dyes [15–17] Quantum simulation was applied to
discuss relationship between dyeing performance and structures of
synthesized dyes [18]. Chromogenic moieties on both ends of symmet-
rical D1-D4 exhibited excellent coplanarity, which can enhance
dye-fiber interaction, as PET also showed good coplanarity.
2
. Experimental
In this context, butane-1,4-diyl bis(ethyl(phenyl)carbamate) was
designed as coupling compounds to enhance dye-fiber affinity and lessen
chemical hardness of dye molecular, by inserted ester groups [10,11]
2
.1. Materials and measurements
Polyester fabrics (plain weave, wrap/weft density 54/48 yarn/cm)
*
Corresponding author. Key Laboratory of Clean Dyeing and Finishing Technology of Zhejiang Province, Shaoxing University, Shaoxing, 312000, China.
E-mail address: xiaoyugemin@gmail.com (X. Song).
https://doi.org/10.1016/j.dyepig.2021.109761
Received 1 June 2021; Received in revised form 20 August 2021; Accepted 30 August 2021
Available online 1 September 2021
0
143-7208/© 2021 Published by Elsevier Ltd.

S. Wang et al.
Dyes and Pigments 196 (2021) 109761
Scheme 1. Synthsis route of ethyl N-ethyl-N-phenylglycinate.
were obtained from Zhejiang Xinfa Dyeing and Finishing Company,
Shaoxing, China. N-ethylaniline (98%), 4-nitroaniline (99%), 2-amino-
0.20 mol) was slowly added into the reaction mixture under constant
stirring. The reaction mixture was refluxed for 1 h. The same TLC
method was applied to estimate the reaction. The mixture was cooled to
RT after the end of the reaction, and hydrochloric acid was used to
6
-nitrobenzothiazole
(99%),
3-amino-5-nitro(2,1)benzisothiazole
(
98%) and 2-amino-3,5-binotro-thiophene (95%) were obtained from
Zhejiang Wanfeng Chemical Company, Shaoxing, China. Ethyl chlor-
oacetate (98%), Oxalyl chloride (98%) and 1,4-butanediol (99%) were
purchased from Shanghai Titan Scientific Co. Ltd., Shanghai, China. All
the other chemicals used were obtained from Shanghai Chemical Re-
agent Plant, Shanghai, China. All chemicals were used as received
without further purification.
2 2
regulate pH to 5. CH Cl (100 mL) and saturated brine (200 mL) was
added into and mixed completely. The mixture was transferred into
separating funnel and the organic liquid was kept. The organic layer was
yellowish and washed three times using 200 mL brine. The organic so-
lution was evaporated under vacuum to remove solvent. The N-ethyl-N-
phenylglycine (II, Scheme 2) was achieved as honey-like viscous liquid,
FT-IR spectra were measured using a Spectrum Two FT-IR spec-
trometer (PerkinElmer Perkin Elmer Inc, Liantrisant, UK) scanning be-
81.17% yield. 1H NMR (CDCl
6.56–6.62 (m, 3H, Ar–H), 4.11 (s, 2H, –CH
3
, δ , ppm): 7.12–7.16 (m, 2H, Ar–H),
H
2
-), 3.37–3.43 (q, 2H, –OCH
2
-
ꢀ 1 1
ꢀ 1
tween 4000 and 500 cm . H NMR (400 MHz) were recorded on a
), 1.17–1.20 (t, 3H, –CH
3
). Main FT-IR absorption peaks (v, cm ): 3050,
Bruker AV 400 (Bruker Co., Faellanden, Switzerland), using chloroform-
2973, 2929, 2881, 1726, 1598, 1502, 1382, 1352, 1193, 1263, 1127,
1074, 1029.
◦
d (CDCl
3
) as the solvents at room temperature (25 C). The visible ab-
sorption spectra were measured using UV–vis spectrometer (Hitachi
Limited, Japan). Melting points were measured by open capillary
method with a Mel-Temp capillary melting point apparatus (Shanghai
Precision and Scientific Instruments, China). Size distribution and zeta
potential of aqueous dispersions were measured with a Zetasizer Nano
2.2.3. Synthesis of N-ethyl-N-phenylglycinoyl chloride (III)
Oxalyl chloride (15.23 g/0.12 mol) was added dropwise to the
mixture of N-ethyl-N-phenylglycine (II, 1.79 g/0.10 mol) and DMF
◦
(0.73 g/0.01mol) in CH
2
Cl
2
at 0 C. Resulting solution was warmed to
◦
ZS90 instrument (Malvern Instruments Ltd., United Kingdom) at 25 C.
RT and continued stirred for 6.5 h. The same TLC method was applied to
confirm the reaction. Solvent and excessed oxalyl chloride were
removed under reduced pressure to afford N-ethyl-N-phenylglycinoyl
chloride (III, Scheme 3). The product was yellowish soft blocks, 98.73%
yield.
2
2
1
.2. Preparation of intermediates
.2.1. Synthesis of ethyl N-ethyl-N-phenylglycinate (I)
2 3
N-ethylaniline (24.40 g/0.20 mol) and sodium carbonate (Na CO ,
2
.2.4. Synthesis of butane-1,4-diyl bis(ethyl(phenyl)carbamate) (IV)
0.60 g/0.10 mol) were added in three-necked, round bottomed flask
1
,4-Butanediol (2.25 g/0.025 mol) and trimethylamine (Et
3
N, 8.10
containing 100 mL N,N-Dimethylformamide (DMF) at room tempera-
ture (RT). Ethyl chloroacetate (49.02 g/0.40 mol) was dropwise added
into reaction mixture under constant stirring. The reaction mixture was
◦
g/0.08 mmol) was dissolved in 100 mL CH Cl
2
2
at RT, and cooled to 0 C.
N-ethyl-N-phenylglycinoyl chloride (III, 19.80 g/0.1 mol) was slowly
added into reaction solution under constant stirring. Resulting suspen-
sion was warmed to RT and continued stirred overnight. TLC method
◦
heated to 110 C stirred for 1 h, thin layer chromatography (TLC)
method (toluene:acetone:acetic acid = 20:1:1 v/v) was applied to
monitor the reaction. After the end of the reaction, the reaction mixture
was added into ice slurry under stirring, then 100 mL dichloromethane
(
hexane:ethyl acetate: acetic acid = 2:1:1) was applied to detect the
reaction. Solvent and excessed Et N were removed under vacuum.
3
Acetone (40 mL) was added into mixture and disperse completely. The
mixture was filtered, and filtrate was evaporated under vacuum to
remove the solvent. The excessed N-ethyl-N-phenylglycinoyl chloride
(
2 2
CH Cl ) was added into mixture and fully mixed. The mixture was
transferred into separating funnel and the lower organic liquid was kept.
The organic layer was washed three times using 200 mL deionized (DI)
water. The organic solution was evaporated under vacuum to remove
solvent and excess ethyl chloroacetate. The ethyl N-ethyl-N-phenyl-
(
III) was separated out using DI water and chloroform extraction
method. The organic layer was evaporated under vacuum to give desired
1
product. Butane-1,4-diyl bis(ethyl(phenyl)carbamate) (IV, Scheme 4)
glycinate (I, Scheme 1) was obtained as yellow liquid, 98.87% yield. H
was brown viscous mucus, 77.45% yield. 1H NMR (CDCl
, δ
.22–7.26 (m, 4H, Ar–H), 6.74–6.78 (t, 2H, Ar–H), 6.67–6.72 (t, 4H,
Ar–H), 4.15–4.18 (t, 2H, –CH -), 4.04 (s, 2H, –CH -), 4.02 (s, 2H, –CH -),
3
H
, ppm):
NMR (CDCl
Ar–H), 6.60–6.65 (d, 2H, Ar–H), 4.16–4.22 (q, 2H, –CH
CH -), 1.24–1.27 (t, 3H, –CH
-), 3.44–3.49 (q, 2H, –OCH
). Main FT-IR absorption peaks (v, cm ): 2976, 2935, 1740,
600, 1504, 1383, 1361, 1183, 1266, 1129, 1030.
3
, δ
H
, ppm): 7.19–7.23 (m, 2H, Ar–H), 6.69–6.73 (t, 1H,
-), 4.01 (s, 2H,
) 1.19–1.22
7
2
2
2
2
–
(
2
2
3
ꢀ 1
3.58–3.61 (t, 2H, –CH -), 3.44–3.51 (m, 4H, –CH -), 1.69–1.71 (t, 2H,
2
2
t, 3H, –CH
3
–
CH
2
-), 1.56–1.60 (t, 2H, –CH
2
-), 1.51–1.55 (t, 2H, –CH -), 1.22–1.24 (t,
2
1
3
1
1
H, –CH
3
), 1.19–1.21 (t, 3H, –CH
3
). Main FT-IR absorption peaks (v, cm-
): 2966, 2928, 1737, 1662, 1599, 1503, 1386, 1347, 1271, 1180, 1125,
038.
2
.2.2. Synthesis of N-ethyl-N-phenylglycine (II)
Sodium hydroxide (NaOH, 12 g/0.30 mol) was dissolved into
mixture of ethanol (80 mL) and DI water (100 ml) at RT in a three-
necked, round-bottomed flask. N-ethyl-N-phenylglycine (I, 41.40 g/
Scheme 2. Synthsis route of N-ethyl-N-phenylglycine.
2

S. Wang et al.
Dyes and Pigments 196 (2021) 109761
Scheme 3. Synthsis route of N-ethyl-N-phenylglycinoyl chloride.
Scheme 4. Synthsis route of butane-1,4-diyl bis(ethyl(phenyl)carbamate).
Scheme 5. Chemical structures of the synthesized bisazo disperse dyes.
2
.3. Preparation of bisazo disperse dyes
Ar–H), 4.39 (s, 2H, –CH
CH
2
-), 4.23–4.27 (t, 2H, –CH
2
-), 3.71–3.75 (t, 2H,
). Main FT-IR
–
2
-), 3.66–3.70 (t, 2H, –CH
2
-), 1.35–1.38 (t, 3H, –CH
3
ꢀ 1
Aromatic amines were diazotized according to previously reported
absorption peaks (v, cm ): 2968, 2931, 1736, 1593, 1511, 1384,
methods [6,13]. Diazonium salts were coupled with coupling compo-
nents to achieve desired bisazo disperse dyes. The chemical structures of
the designed bisazo disperse dyes are shown in Scheme 5.
1327, 1249, 1188, 1131.
2.3.2. Synthesis of bisazo disperse dye D2
2
-amino-6-nitrobenzothiazole was diazotized using nitrosylsulfuric
2
.3.1. Synthesis of bisazo disperse dye D1
-nitroaniline (0.56 g/4 mmol) was disperse in 1.50 mL water and
.75 ml HCl (36%, v/v) at RT under constant stirring. After fully mixed
acid (41%, w/w) as diazotization reagent in strong acid medium at
◦
4
0–5 C. The resulting diazonium salt was used in the coupling reaction
0
with butane-1,4-diyl bis(ethyl(phenyl)carbamate) in the same condition
as D1. Reaction mixture was added into water, then filtered to get crude
product. Ethanol recrystallization method was applied to get purified
for 30 min, sodium nitrite solution (0.5 g, 30%, w/w) was quickly added
◦
into the cooled suspension at 0–5 C. The mixture was stirred for 1 h at
0
◦
◦
1
–5 C. Sulphamic acid was added to eliminate excessed nitrous acid.
3 H
D2, 83.65% yield. Mp: 102–104 C. H NMR (CDCl , δ , ppm):
The resulting diazonium salt solution was dropwise added into cooled
8.75–8.77 (m, 1H, Ar–H), 8.33–8.36 (m, 1H, Ar–H), 8.12–8.16 (t, 1H,
Ar–H), 7.99–8.04 (t, 2H, Ar–H), 6.72–6.77 (t, 2H, Ar–H), 4.23–4.26 (t,
butane-1,4-diyl bis(ethyl(phenyl)carbamate) (IV, 0.79 g/2 mmol) so-
◦
lution in ethanol at 0–5 C. The reaction mixture was warmed to
1
2H, –CH
2H, –CH
2
-), 4.19 (s, 2H, –CH
-), 1.31–1.35 (t, 3H, –CH
2
-), 3.63–3.68 (m, 2H, –CH
2
-), 1.75–1.79 (t,
◦
0–15 C and stirred for 4 h. The reaction mixture was dispersed thor-
2
3
). Main FT-IR absorption peaks (v,
ꢀ
1
oughly in water and filtered to obtain the precipitate. The crude product
cm ): 2969, 2872, 1738, 1597, 1552, 1512, 1406, 1363, 1326, 1273,
1188, 1140, 1108, 1073.
was recrystallized from ethanol to get D1, 89.40% yield. Mp:
82–184 ◦C. H NMR (CDCl
1
, δ , ppm): 8.44–8.48 (m, 2H, Ar–H),
1
8
3
H
.31–8.34 (m, 2H, Ar–H), 8.25–8.27 (m, 2H, Ar–H), 6.85–6.90 (m, 2H,
3

S. Wang et al.
Dyes and Pigments 196 (2021) 109761
Fig. 1. Dyeing procedure of polyester using the synthesized dye.
2
.3.3. Synthesis of bisazo disperse dye D3
-amino-5-nitro(2,1)benzisothiazole was diazotized using nitro-
n
0
A
0
ꢀ n
1
A
1
3
E% =
× 100%
(1)
n
0
A
0
sylsulfuric acid (41%, w/w) as diazotization reagent in concentrated
sulfuric acid at RT. The resulting diazonium salt was used in the
coupling reaction with butane-1,4-diyl bis(ethyl(phenyl)carbamate) in
the same condition as D1. Water was added to precipitate the crude
product. Pure D3 was derived from ethanol recrystallization method,
Where A
DMF solution and n
after dyeing, respectively.
0
and A
1
are the absorptions before and after dyeing in their
0
and n are dilution ratios for dye liquor before and
1
The levelness of dyed samples was evaluated by comparing color
differences. Five points on the dyed samples at 1% o.w.f. were measured.
The first point was taken as the standard, the other four points were
compared to give the ΔE values and averaged.
◦
1
9
3 H
0.93% yield. Mp: 142–144 C. H NMR (CDCl , δ , ppm): 9.22 (s, 1H,
Ar–H), 8.22–8.24 (t, 1H, Ar–H), 8.00–8.02 (m, 2H, Ar–H), 7.79–7.81 (t,
1
2
H, Ar–H), 6.76–6.79 (m, 2H, Ar–H), 4.23–4.26 (t, 2H, –CH
2
-), 4.21 (s,
). Main
H, –CH -), 3.64–3.69 (m, 4H, –CH -), 1.32–1.35 (t, 3H, –CH
2
2
3
ꢀ 1
FT-IR absorption peaks (v, cm ): 2967, 2930, 1735, 1591, 1506, 1401,
2
.6. Fastness performance
1
309, 1242, 1196, 1111, 1065.
Color fastness was evaluated according to the respective interna-
2
.3.4. Synthesis of bisazo disperse dye D4
tional standard methods. The fastness to rubbing was performed in a
crockmeter (CM-5, Atlas Co., USA) with dry and wet samples according
to ISO 105-X12 (2003), the staining on the white test cloth was assessed
according to the gray scale. The fastness to washing was carried out by
using a washing fastness apparatus (SW-12AII, Wenzhou Darong Textile
The same diazotization condition and coupling method as D3 to
achieve D4 using 2-amino-3,5-binotro-thiophene as raw material,
◦
1
9
3 H
5.47% yield. Mp: 108–110 C. H NMR (CDCl , δ , ppm): 8.38 (s, 1H, H
of thiazole ring), 7.97–7.99 (d, 2H, Ar–H), 6.74–6.76 (d, 2H, Ar–H),
4
3
.24–4.28 (t, 2H, –CH
.64–3.66 (t, 2H, –CH
2
-), 4.22 (s, 2H, –CH
2
2
-), 3.67–3.69 (t, 2H, –CH
2
-),
◦
Techology Co., Ltd, China) at 60 C for 30 min according to ISO 105-C03
-), 1.32–1.36 (t, 3H, –CH
3
). Main FT-IR absorp-
ꢀ 1
(2010), and staining on adjacent fabrics (Multifibre DW, Shanghai
Textile Industry Institute of Technical Supercision, China) were applied
to for the assessment of staining fastness, treated samples were also
compared with original samples to evaluate their shade change. The
sublimation fastness test was processed by using a sublimation tester
tion peaks (v, cm ): 3104, 2970, 2929, 1735, 1595, 1538, 1499, 1389,
1
326, 1233, 1112, 1058, 1018.
2
.4. Dyeing of PET using synthesized bisazo disperse dyes
(
YG(B)605D, Wenzhou Darong Textile Techology Co., Ltd, China) to
PET fabrics were dyed using formulated dye, 0.5 g synthesized bisazo
◦
◦
heat the samples at 180 C and 210 C for 30 s according to ISO105/P01
1993), and adjacent fabrics of Multifibre DW were applied for assess-
dye grinded with 0.5 g dispersant (Dispersant MF, anionic type) thor-
oughly, in a STARLET DL-6000 IR dyeing machine (Daelim Starlet Co.,
Ltd, South Korea) at a liquor ratio of 1:20. The dyeing profile was shown
as Fig. 1.
(
ment of staining fastness. The light fastness was performed by employ-
ing a light fastness tester (150S+, Altas Co. USA) with xenon lamps for a
certain period of time according to ISO I05–B02 (2013), and blue scale
was used for light fastness assessment.
The pH value of dye bath was adjusted to 4–5 using acetic acid so-
lution (10%, v/v), and dye dosage was 1% (o.w.f.). Dyeing processes
◦
◦
◦
were commenced at 30 C and raised at a rate of 2 C/min to 130 C,
maintained for 60 min. Reduction cleaning of dyed PET fabrics were
processed in an aqueous solution containing sodium dithionite (2 g/L)
2
.7. Stability of dispersion and pH stability assessment
Stability of dispersion was determined by particle size distribution
◦
and sodium carbonate (2 g/L) at 85 C for 15 min.
and zeta potential of bisazo disperse dye suspensions. Dye dispersions at
g/L were processed according to dyeing profile of Fig. 1 without PET,
1
2
.5. Color yield and levelness assessment
which was compared with milled bisazo disperse dyes bath without
dyeing process. Particle size distribution and zeta potential of diluted
dye suspensions at 0.2 g/L, before and after dyeing process, were
measured to estimate stability of dispersion.
The colorimetric parameters of dyed polyester fabrics were deter-
mined by Datacolor SP 600
+
spectrophotometer (Datacolor,
◦
Switzerland), under illuminant D65 using10 standard observer in the
visible spectrum region 380–720 nm. The measurements of the dyed
samples were taken at least four different positions and averaged to
achieve the final K/S value.
pH stability of dyeing bath was evaluated by adjust pH of dyeing bath
according to dyeing profile of Fig. 1 at 1% o.w.f. The pH-value of the dye
3
liquor was adjusted to 5.5 with CH COOH solution, 7 without other
additives, 9, 11 and 13 using NaOH solution. Dyed fabric samples were
reductive cleared and compared to evaluate pH stability of synthesized
bisazo disperse dyes.
The dye exhaustion (E %) on PET was measured and calculated using
equation (1):
4

S. Wang et al.
Dyes and Pigments 196 (2021) 109761
Fig. 2. The optimized geometries for D1-D4 and PET (front and side view).
. Results and discussions
3
As an attempt to generate disazo disperse dyes containing both ester
group and soft chain in their structures, butane-1,4-diyl bis(ethyl
phenyl)carbamate) was designed and synthesized. Chloroactic acid was
(
proposed as raw material to react with N-ethylaniline to obtain N-ethyl-
N-phenylglycine (II). But carboxyl group of chloroactic acid exhibited
much stronger polarity than ester group of ethylchloroacetate, leading
to incomplete reaction with N-ethylaniline. Ethylchloroacetate was
reacted with N-ethylaniline thoroughly, and product I was hydrolyzed
into N-ethyl-N-phenylglycine (II) with acidification. Oxalyl chloride was
applied as acylation reagent to give N-ethyl-N-phenylglycinoyl chloride
(
III), which is much easier to react with alcohol than carboxyl com-
pounds. Diazonium was reacted with symmetrical butane-1,4-diyl bis
ethyl(phenyl)carbamate) (IV) to achieve novel bisazo disperse dyes.
(
3
.1. Spectral properties of synthesized bisazo disperse dyes
Relationship between structure and color is an important part in both
dye development and its commercialization. The absorption spectra of
bisazo disperse dyes in their DMF solutions were shown in Fig. 3.
The color of the dye is correlated with both coupling component and
diazo component. In this paper, synthesized bisazo disperse dyes’ color
was influenced by diazo compounds with fixed coupling component.
The wavelength of absorption maxima (λmax) and molar extinction co-
Fig. 3. UV–Vis absorption for D1-D4 in their DMF solution.
.8. Computational methods
2
The optimized geometries (Fig. 2) at ground state of designed disazo
disperse dyes have been computed with DFT method at B3LYP/6-31G
d) level by Gaussian 16 program. It can be indicated that chromo-
efficients ( ) of the four dyes were also compared to illustrate relation-
ε
(
ship between color and structure (Table 1).
genic moieties on both ends of symmetrical D1-D4 exhibited excellent
coplanarity, which can enhance dye-fiber interaction, as PET also
The synthesized bisazo disperse dyes are symmetrical D- -A (Donor-
π
π
-acceptor) structures. The λmax of the bisazo disperse dyes ranged from
78 to 629 nm. Bathochromic shifts of the visible absorption band were
showed good coplanarity. The
π
electron distribution of dyes were
4
analyzed with wavefunction analysis code Multiwfn to evaluate dyeing
performance of synthesized dyes.
observed, which was attributed to electronic transitions of whole con-
jugated structures in solvent. The bisazo disperse dyes also exhibited
marvelous much higher
ε
values than reported bisazo disperse dyes [5,
Table 1
λ
max and
ε of the synthesized bisazo disperse dyes in solvents.
4
ꢀ 1
ꢀ 1
Dye
λ
max (nm)
ε
( × 10 L mol cm
)
DMF
CH
3
OH
3
CH CN
CHCl
3
DMF
3
CH OH
CH
3
CN
CHCl
3
D1
D2
D3
D4
478
540
592
629
460
530
575
615
460
525
575
605
460
523
569
605
4.55
7.44
4.77
5.21
4.43
6.99
4.57
5.43
4.42
7.29
4.51
5.17
4.33
7.15
4.45
5.03
5

S. Wang et al.
Dyes and Pigments 196 (2021) 109761
than 0.5, the levelness was considered to be excellent. The exhaustion
for synthesized bisazo disperse dyes was more than 94% using tradi-
tional high temperature dyeing under pressure. The high exhaustion of
the dyes was attributed to enhanced dye-fiber affinity by stronger
hydrogen bond and van der Waals force between fiber and synthesized
dyes. Ester groups and larger molecular mass were the main factor to
afford high exhaustion, soft hydrophobic alkyl chain also help to pene-
trate into fibers to achieve high exhaustion. The high exhaustion of those
dyes can be attributed to chromogenic skeleton. As shown in Fig. 5, both
PET and chromogenic skeleton exhibited coplanar structure, which
facilitated
π
-π interaction between PET and dyes.
As shown in Fig. 6, synthesized bisazo exhibited different color yield
with increased dye concentration. Heterocylic bisazo disperse dyes
showed satisfying K/S values with increased dye concentration. D1
showed lower color yield than those heterocylic-containing bisazo
disperse dyes.
Fig. 4. Effect of dyeing time on the K/S value on PET fabrics.
Table 2
Dye exhaustion and levelness of bisazo disperse dyes.
Dye
D1
D2
D3
D4
E%
94.26
0.46
96.70
0.32
99.45
0.21
99.88
0.30
ΔE
8
]. The higher
ε
values, the stronger chromophore, makes dyes more
values, 70000, than
other heterocylic bisazo disperse dyes. Carbocyclic D1 also achieved
value at 45000, higher than reported carbocyclic bisazo disperse dyes
16,17].
cost effective [19]. D2 exhibited much higher
ε
ε
[
3
.2. Dyeing properties on PET fabrics
The synthesized bisazo dispersed dyes were applied at 1% (o.w.f)
depth on polyester fabric. K/S was used to represent color depth of dyed
PET fabrics, and data was curved in Fig. 4.
Fig. 6. Build-up curves of bisazo disperse dyes.
It can be indicated from Table 2 that ΔE of the dyed samples was less
Fig. 5.
π
electronic structure of D1-D4, and PET (front and side view).
6

S. Wang et al.
Dyes and Pigments 196 (2021) 109761
Table 3
As shown in Fig. 7, the bisazo disperse dyes showed poor dyeing
performance under alkaline condition, which was attributed to ester
groups in dye molecular structures. Ester groups can be hydrolyzed
under high temperature and alkaline condition. D1-D3 showed different
degrees of shade reduction with increased pH-value. D4 containing
thiophene rings can be easily decomposed under alkaline condition [20,
21], showed the worst alkaline-resistance.
Particle size, Zeta potential of aqueous suspensions of bisazo disperse dyes.
Samples
D1
average particle size (nm)
Zeta Potential (mV)
before
after
588
420
594
539
357
294
220
216
ꢀ 39.13
ꢀ 35.50
ꢀ 38.40
ꢀ 35.10
ꢀ 50.80
ꢀ 47.17
ꢀ 50.3
D2
D3
D4
before
after
before
after
before
after
3
.4. Fastness properties of dyed PET fabrics
ꢀ 46.60
Synthesized bisazo disperse dyes endowed a wide range of color
ranging from orange to blue shade with good levelness, brightness and
depth on the fabric. All the fastness properties of dyed PET fabrics using
synthesized bisazo disperse dyes are shown in Table 4. Samples applied
to estimate their rubbing, washing and sublimation fastness were 1% o.
w.f. dyed PET fabrics, and 0.5% o.w.f. for light fastness.
As shown in Table 4, the dyed PET fabrics exhibited excellent
◦
washing fastness and good to excellent sublimation fastness at 180 C,
which was attributed to enhanced dye-fiber affinity. Sublimation fast-
◦
ness tested at 210 C showed obvious decreased level for staining on
polyester. Rubbing fastness was designed to determine the amount of
color transferred from surface of dyed PET to another surface under
rubbing. Synthesized dyes exhibited a moderate (3) to excellent (5)
rubbing fastness, which was attributed to inadequate diffusion of dye
into fibers. Commercial azo disperse dyes showed poor light fastness
(
≤3), which was attributed to diazo components were prone to photo-
fading. The prepared dyes showed better light fastness, which might
be ascribed to less prone to fading. Ester groups, polar group (-NO
2
)
existed in dye and large molecular mass help to reinforce hydrogen bond
and van der Waals force between bisazo disperse dyes and PET. The
dyed fabrics showed excellent washing fastness, no staining on adjacent
fabrics, as well as barely shade change after treatment.
Fig. 7. K/S for D1-D4 dyed PET fabrics at different pH-values.
3
.3. Stability of dispersion and pH stability
4
. Conclusion
The stability of the bisazo dye dispersions were evaluated by
The novel symmetrical coupling component, butane-1,4-diyl bis
measuring their particle size and Zeta potential (Table 3). The pH sta-
bility of dyeing bath was evaluated using dyed fabric samples dyed at
pH = 5.5, 7, 9, 11, 13. K/S was used to represent color depth of dyed PET
fabrics and compared to express pH stability of bisazo disperse dyes, as
curved in Fig. 7.
(
ethyl(phenyl)carbamate), has been synthesized using 1,4-butanediol as
linker to react with synthesized N-ethyl-N-phenylglycinoyl chloride.
Bisazo disperse dyes are synthesized using synthesized butane-1,4-diyl
bis(ethyl(phenyl)carbamate) and characterized. These dyes give or-
ange, red, purple and blue shades on PET fabrics having good fastness
performance. The visible absorption and the shade of the dyed fabric are
correlated with diazo components. Excellent levelness and exhaustion
indicates the good penetration and affinity of these dyes to fabric. The
high color yield is attributed to instrinsic conjugation structure of the
bisazo disperse dyes.
As shown in Table 3, the bisazo dye bath exhibited good disperse
stability, dye suspensions showed slightly decreased average particle
size after high temperature and high pressure dyeing process. The
average particle size of aqueous suspensions were at the range of
2
20–594 nm before dyeing, and 216–539 nm after dyeing process.
Carbocyclic D1 showed the most obvious decreased average particle
size, form 588 nm–420 nm. Heterocyclic D2-D4 showed relative less
decreased average particle size. Zeta potentials of aqueous suspensions
were around ꢀ 38 ~ ꢀ 50 mV, showed slightly change after dyeing
process. The dye dispersions exhibited excellent disperse stability even
processed by severe dyeing environment, average particle size <600 nm,
CRediT authorship contribution statement
Shengli Wang: Synthesis of dyes, Data curation, Writing – original
draft, preparation. Linbo Gao: Samples testing, Analysis. Aiqin Hou:
Dyeing application. Kongliang Xie: Validation, Supervision, Reviewing.
Xiyu Song: Quantum simulation, Writing – review & editing.
far below 1 m.
μ
Table 4
Fastness properties of dyed PET fabrics.
Samples
Fastness to rubbing
Fastness to washing
Fastness to light
Fastness to sublimation
◦
◦
C
Change
Staining
180
SP
C
210
SP
Dry
Wet
SP
SC
SC
SC
D1
D2
D3
D4
5
4
4–5
4–5
4–5
4–5
5
5
5
5
5
5
5
5
3–4
4
4
4–5
5
2–3
3
3–4
4
3–4
4
4
4–5
4–5
4
4–5
4
4
4–5
4–5
4
4–5
4
3
4
2–3
SC = staining on cotton; SP = staining on polyester.
7

S. Wang et al.
Dyes and Pigments 196 (2021) 109761
Declaration of competing interest
[10] Cui ZH, Xia G, Gao JR, et al. Synthesis and properties of alkali-clearable azo
disperse dyes containing a carboxylic ethyl ester group. Fibers Polym 2017;18(9):
1
708–17.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
[
[
11] Zhang Z, Hong X, Zheng C. Synthesis of single azo disperse dye containing double
ester and determination of crystal structure. Kor J Chem Eng 2013;30(12):
2
19–2222.
12] Wessig P, Matthes A. Preparation of strained axially chiral (1,5)naphthalenophanes
by photo-dehydro-Diels-Alder reaction. J Am Chem Soc 2011;133(8):2642–50.
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