Microencapsulation of leuco dye based thermochromic system by complex coacervation method for thermochromic, thermoregulating and antibacterial composite cotton fabric

The main focus of the study is to produce the natural, environmentally friendly and biodegradable polymeric shell-structured thermochromic microcapsules for textile applications. Three-component thermochromic system (TCTS) which consists of crystal violet lactone dye, phenolphthalein and 1-tetradecanol was microencapsulated into gelatin/gum arabic (G/GA) by complex coacervation method. Sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) were used as surfactants with different ionic character. In the study, the effect of core and wall material ratio, and ionic character of the surfactant on morphology and thermochromic properties of microcapsules was also investigated. The microcapsules with spherical morphology produced in the study had a melting enthalpy ranging from 57.4 to 129.2 J/g and good thermal stability. The CTAB allowed better capsule formation with a spherical morphology and excellent thermochromic performance compared to SDS surfactant. It was determined that decreasing amount of wall polymer made the color change more pronounced, but did not significantly affect morphology. Microcapsules with core/shell of 1/0.5 ratio that offered the most pronounced color change were applied to cotton fabrics by impregnation method. The color measurements based on CIELab system confirmed the reversible color change of the composite fabric from blue to colorless. The fabrics exhibited antibacterial activity (99.49% bacterial decrease) besides the thermochromic and thermoregulating properties. However, the water vapour permeability of the fabrics decreased despite the increased hydrophilicity. Microcapsule application significantly affected air permeability, the bending rigidity and warp tear strength of the fabric.