**5.2 Spirooxazines**

The chemical structure is similar to spiropyrans, the difference exit that instead of pyron core, it has oxazine group [ 30, 31] (**Figure 4**). The spirooxazines has very good resistance to photo degradation. The spirooxazines produces fast fading blue

**Figure 3.** *Photochromic reaction of spiropyrans (from closed ring structure to open ring structure).*

#### **Figure 4.**

*Photochromic reaction of spirooxazines (from closed ring structure to open ring structure).*

ophthalmic lenses were manufactured using spirooxazines. Other applications are

*Photochromic reactions of napthopyrans (TT trans-trans, CT cis-trans,TC trans-cis, CC cis-cis).*

It has wide commercial applications such as in plastic photochromic lenses. The photochromism mechanism of benzo and naphthopyron are similar to spiropyrans [33]. They all have breaking of C—O bond in the pyron core. The photochromic reactions of napthopyrans/benzochromenes by the light induced ring opening is shown in **Figure 6**. The ring opening of molecular structure produces more planer structure with greater conjugation of bonds. The planer conjugated structure are capable to absorb visible region wavelength and produces color. The naphthopyrans

The p type photochromic materials have applications in computing, optical circuitry, memory technology and in ultra high density storage devices. The p type photochromic materials are of two types such as fulgides and diarylethenes. In p type photochromic molecules, the open ring structures are colorless and closed ring

The fulgides and fulgimide family belong to P type photochromic materials (**Figure 7**). In 1905 Stobbe synthesized some photochromic fulgides named as phenyl substituted bismethylene succinic anhdides. Heller et al. [37] developed a compound succinimide called fulgimide. It exhibit good photochromic properties. It has shows absorption spectrum of both forms with efficient photoreaction, thermal and photochemical stability. The application of fulgides are In optical switches,

photochromic inks, dyes and various cosmetics items.

**5.3 Napthopyrans/benzochromenes**

*Photochromic Dyes for Smart Textiles*

*DOI: http://dx.doi.org/10.5772/intechopen.96055*

are less sensitive to temperature.

structures are colored [34–36].

sensors, dye inks and memory disks.

**6.1 Fulgides**

**87**

**Figure 6.**

**6. P type photochromic materials**

#### **Figure 5.**

*Different structures of photochromic oxazine (R = alkyl group, X = H, amino, hetaryl Y = H, halogen, a = electron acceptor.*

photo coloration. The different chemical structure of spirooxazines are shown in **Figure 5**. The presence of different alkyl groups R at nitrogen atom decide the fading and color strength of molecules [32]. In 1990s, plastic photochromic

**Figure 6.** *Photochromic reactions of napthopyrans (TT trans-trans, CT cis-trans,TC trans-cis, CC cis-cis).*

ophthalmic lenses were manufactured using spirooxazines. Other applications are photochromic inks, dyes and various cosmetics items.

### **5.3 Napthopyrans/benzochromenes**

It has wide commercial applications such as in plastic photochromic lenses. The photochromism mechanism of benzo and naphthopyron are similar to spiropyrans [33]. They all have breaking of C—O bond in the pyron core. The photochromic reactions of napthopyrans/benzochromenes by the light induced ring opening is shown in **Figure 6**. The ring opening of molecular structure produces more planer structure with greater conjugation of bonds. The planer conjugated structure are capable to absorb visible region wavelength and produces color. The naphthopyrans are less sensitive to temperature.

#### **6. P type photochromic materials**

The p type photochromic materials have applications in computing, optical circuitry, memory technology and in ultra high density storage devices. The p type photochromic materials are of two types such as fulgides and diarylethenes. In p type photochromic molecules, the open ring structures are colorless and closed ring structures are colored [34–36].

#### **6.1 Fulgides**

The fulgides and fulgimide family belong to P type photochromic materials (**Figure 7**). In 1905 Stobbe synthesized some photochromic fulgides named as phenyl substituted bismethylene succinic anhdides. Heller et al. [37] developed a compound succinimide called fulgimide. It exhibit good photochromic properties. It has shows absorption spectrum of both forms with efficient photoreaction, thermal and photochemical stability. The application of fulgides are In optical switches, sensors, dye inks and memory disks.

photo coloration. The different chemical structure of spirooxazines are shown in **Figure 5**. The presence of different alkyl groups R at nitrogen atom decide the fading and color strength of molecules [32]. In 1990s, plastic photochromic

*Different structures of photochromic oxazine (R = alkyl group, X = H, amino, hetaryl Y = H, halogen,*

*Photochromic reaction of spirooxazines (from closed ring structure to open ring structure).*

*Dyes and Pigments - Novel Applications and Waste Treatment*

**Figure 4.**

**Figure 5.**

**86**

*a = electron acceptor.*

• In nitro substituted chromenes, it was observed that temperature variations influenced the coloration which developed due to substitution in the molecular

In this method the photochromic dyes are dispersed with dispersing agent [42] and dissolved in water keeping the M:L ratio of dyeing 1:50. The dyebath pH is maintained between 4.5–5.5. The dyebath temperature raised from 40 <sup>0</sup> C to 60 °C with 20 C/min gradient and then after it is reduced 1<sup>0</sup> C/min and final dyeing temperature is maintained at 90 <sup>0</sup> C and dyeing is continued at this temperature for 60 min. After completion of dyeing, soaping, rinsing and washing are done to

In this method the photochromic dyes can be applied as a disperse dye on polyester fabrics by exhaust method of dyeing [43]. The dye is pasted with acetone and then stirred in water with dispersing agent (1%) keeping the M:L ratio of dyeing 1:50.The pH of the dyebath is maintained between 4.5–5.5.The aqueous dyebath is boiled to evaporate acetone, subsequently temperature is raised to 120°C and dyeing is done at this temperature for 45 minute. After dyeing reduction clearing treatment is given at 70 °C for 20 min. and finally sample is soaped,

In this method photochromic dyes are dissolved in acetone and then mixed with binder solution and padded with padding mangle at appropriate pressure. After padding fabric is dried at 80 C and cured at 140 C for 3.0 minute in hot air oven or

Photochromic dyes can be used as a disperse dyes which are insoluble in water. The photochromic dyes are disperse with dispersing agent and wetting agent of anionic nature. The dye dispersion is milled on a roller mill by using ceramic balls in glass jar. The dye dispersion is mixed with sodium alginate thickener solution to get printing paste. The polyester or nylon fabric can be printed with printing paste. The fabric is dried at 100 °C and cured at 140 °C for 5 minute. After reduction clearing treatment, printed samples were soaped with nonionic detergent and finally

• A combination of photochromic and thermochromic materials possess synergistic effect and give superior performance at high temperature.

structure.

**8. Applications in textiles**

*Photochromic Dyes for Smart Textiles*

*DOI: http://dx.doi.org/10.5772/intechopen.96055*

improve fastness properties.

**8.1 By exhaust dyeing**

*8.1.1 Method 1*

*8.1.2 Method 2*

rinsed and washed.

stenter machine [44].

neutralization is done.

**89**

*8.2.1 As a disperse dyes in printing*

**8.2 By continuous dyeing**

**Figure 7.** *Photochromic reaction of fulgides.*
