Fine tuning the color-transition temperature of thermoreversible polydiacetylene/zinc oxide nanocomposites: The effect of photopolymerization time

Effect of UV Irradiation Time and Headgroup Interactions on the Reversible Colorimetric pH Response of Polydiacetylene Assemblies

Polydiacetylenes are chromatic conjugated polymers formed upon the photopolymerization of self-assembled diacetylenes. They exhibit conformation-dependent colorimetric responses, usually irreversible, to external triggers. Here, we presented an approach to obtain a reversible colorimetric response to a pH change through structural modifications on the monomer and extended photopolymerization time. Both factors, enhanced hydrogen bond forming headgroups and longer UV exposure, impacted the rotational freedom of polydiacetylene conformation. Such a restricted conformation state reduced colorimetric response efficiency but enabled reversible colorimetric response to a pH change. These results highlight the possibility of obtaining a reversible colorimetric pH response of polydiacetylenes for customized sensing applications through monomer-level tailoring combined with tuning the photopolymerization time.

Hydrogen bonding reversibility in poly(10,12-pentacosadiynoic acid)/titanium dioxide composite analyzed by infrared spectroscopy

In this work, the chromatic behavior of a poly(10,12-pentacosadiinoic acid)/titanium dioxide (TiO₂) nanocomposite was studied. Infrared spectroscopy showed that above 55 °C the peak of the carboxyl groups undergoes a shift from 1690 cm^-1 (25-55° C) to 1710 cm^-1 (≥60 °C), which is reversible after cooling regardless of whether the sample was in the blue or red phase prior to heating. This indicates that the thermochromic behavior and the hydrogen bond shifting are not completely related, since the signal of the hydrogen bond is influenced by temperature, but is reversible; however, the color change is not. Importantly, TiO2 does favor thermochromic reversibility, unlike that indicated in previous reports. Computational chemistry showed that the effect of temperature on a polydiacetylene oligomer with three repeating units produces torsion, which directly impacts the strength of the hydrogen bonds between the carboxyl groups, coinciding with the experimental work.

Polydiacetylene and its composites with long effective conjugation lengths and tunable third-order nonlinear optical absorption

Through the deliberate annealing of suspensions, bluish-green phase polydiacetylene and polydiacetylene composites that have remarkably extended ECLs were effectively fabricated that exhibit different nonlinear optical absorption types.

Tuning chromatic response, sensitivity, and specificity of polydiacetylene-based sensors

In this review, we provide an overview of six major techniques to tune the sensitivity and specificity of polydiacetylene-based sensors.

Flexible electrochromic materials based on CNT/PDA hybrids

Materials that change color in response to external stimuli can cater to diverse applications from sensing to art. If made flexible, stretchable and weavable, they may even be directly integrated with advanced technologies such as smart textiles. A new class of engineered composite based on polydiacetylene (PDA) functionalized carbon nanotubes (CNT) shows tremendous potential in this regard. While the inherent multi stimuli chromatic response of the polymer (blue to red) is retained, the underlying conducting CNTs invoke electrochromism in PDA. Further, the fiber form factor of dry-spun CNT yarns facilitate direct weaving of large scale electrochromic fabrics, where current flow and thus color change can be accurately controlled. This review summarizes the fundamental aspects of CNT yarns and PDAs, focusing especially on their interaction chemistry which results in the scientifically and commercially appealing electrochromic transition in these hybrids.

Advances in polydiacetylene development for the design of side chain groups in smart material applications – a mini review

This review focuses on various side chain groups based on PDAs published over the last 3 years, covering urea, melamine, ferriferous oxide and coumarin. Perspectives on the remaining challenges and future developments are also proposed.