SYNTHESIS OF POLYMER NANO PARTICLES FOR STRUCTURAL COLOR APPLICATIONS

Abstract

Colors are the evolution's most beautiful accident. The color of the paint in general is attributed to the pigments present in it. Pigments exhibit color by absorbing defined portion of the wavelength of light, leaving the reflected portion of light which is being perceived by human as color. 1-lowever. nature offers us with various examples such as butterfly wings, peacock feathers, beetle shells which exhibit color based on physical interaction of light with biological structures rather than pigments. Research focus has been shifted from pigment based colors to structural based colors in the recent years. The color of the Morpho butterfly wings originates from the Bragg diffraction and scattering of light in the visible spectrum which is termed as structural color. Many researchers have laid focus on the bio-mimicry of the biological structures to obtain structural color. Mimicking the structural color through synthetic means has been partially successful. The concept of structural color through bio-mimicking has motivated us to explore the feasibility of achieving color of the paint without pigments. Herein, we report a preliminary method to obtain color from the proper alignment of synthetic polymer nanoparticles. We have synthesised polystyrene, poly(slyrene-co-methyl melhacrylate-co-aciylic acid), poly(styrene-co-niethyl methacry late -co-2-hydroxy ethyl meihacrylate) and poly(styrcne-co-mcthyl methacrylate-co-EDM) nanoparticles with particle size varying from 200-350 nm via emulsion polymerization. The resultant nanoparticles exhibited different colors like violet, blue and green depending on the particle size, refractive index of the particles and spacing between the particles, when coated upon an aluminium substrate. The color of the IlIms obtained from nanoparticle coated panels was further conlirmed by UV-Vis-NIR spectroscopy measurements. An increase in adhesion of nanoparticles on aluminium substrate was observed with films obtained from poly(styrene-co-methyl mcthacrylate-co-EDM) nanoparticles compared to acrylic acid and l-lEMA based nanoparticles. Overall the concept of structural color was established and made efforts to -5- achieve good adhesion over aluminium substrate. Finally, proposed few routes to improve the 41 adhesion of polymer nanoparticles on aluminium substrate.