Abstract
A simple-structured polymeric colorimetric thermometer with selective colorimetric changes over a specific temperature range was developed. Thermo-responsive poly(N-isopropylacrylamide-co-Dicyanodihydrofuran hydrazone) [Poly(NIPAM-co-DCDHFH)] organogel imprinted with DCDHFH chromophoric probe was prepared via free radical polymerization. The DCDHFH chromophore bearing a vinyl group was prepared by azo-coupling of DCDHF with a diazonium salt of 2-amino-5-nitrophenol bearing a vinyl substituent. The poly(NIPAM-co-DCDHFH) consists of DCDHFH chromophore and N-isopropylacrylamide (NIPAM) monomers. The chemical structure of DCDHFH probe was verified by H-1 NMR and FT-IR. The thermochromic property can be attributed to a heat-stimulated polymer self-assembly process controlling the inner hydrophobicity leading to charge delocalization on the molecular system of the DCDHFH chromophore. Poly(NIPAM-co-DCDHFH) functioned as a thermochromic detector displaying colorful shifts between yellow (422 nm) and blue (580 nm) with raising the temperature of the aqueous poly(NIPAM-co-DCDHFH). These color shifts were correlated to the temperature increment from 28 to 46 degrees C owing to the phase changes of the poly(NIPAM-co-DCDHFH) copolymer in aqueous media. The morphological features of the organogel nanofibers were studied by transmission electron microscope (TEM) and scanning electron microscopy (SEM). The working mechanism accounting for the thermochromic performance of poly(NIPAM-co-DCDHFH) was explored. The cytotoxicity of the poly(NIPAM-co-DCDHFH) hydrogel was also evaluated. This is a significant study for a variety of potential applications, such as functional apparel and medicinal applications.