Promoting self-assembly and synthesis of color-responsive polydiacetylenes using mixed water-organic solvents: Effects of solvent composition, structure, and incubation temperature

A conventional method for the synthesis of color-responsive polydiacetylene (PDA) materials normally involves the dispersion of amphiphilic diacetylene (DA) monomers in water, incubation at low temperature, and then photopolymerization. This time-consuming process produces relatively low PDA yield, limiting the utilization in industrial applications. Recently, we introduced a solution-mixing method (SMM) that significantly improved the synthetic process of PDA/Zn(II)/ZnO nanocomposites (Chanakul et al. (2021) [54]). Our previous report focused on the self-assembly and synthesis of the nanocomposites in mixed water-organic solvents containing ~5%vol/vol organic solvents. In this continuing study, we further explore the SMM for improving the synthesis of pure PDAs. The addition of organic solvents at various concentrations (0–70%vol/vol) into water alters physicochemical properties of solvent media. At suitable solvent compositions, the self-assembly of amphiphilic DA monomers is drastically enhanced, leading to the increase of PDA yield after photopolymerization. The PDA yield in this study is ~5 times higher than those obtained from the conventional thin film hydration method and solvent injection method. The addition of organic solvents also causes the increase of particle size and induces morphological transition. We have found that the dielectric constant and structure of organic solvents are important parameters, dictating the self-assembly of amphiphilic DA monomers. The incubation temperature also plays an important role. Interestingly, the self-assembly can be promoted by increasing the incubation temperature during the synthetic process. Our study presents a simple approach for promoting the self-assembly of DA monomers and hence increasing PDA yield. The resultant PDAs still exhibits colorimetric response to heat and various solvents, allowing the utilization in sensing applications.