A Layered Polydiacetylene Containing Hydrogen‐Bonding 4,4′‐Bipyridyl Guests: Reversible Color Changes with a Wide‐Range Temperature Response

Abstract

Layered organic polymers have intercalation capabilities and dynamic properties. In classical intercalation chemistry, the interlayer guests are intercalated in the host layers via electrostatic interaction. The present work shows the organic layered materials with the host-guest interlayer interaction via hydrogen bond. Polydiacetylene (PDA) exhibits color changes from blue to red with the application of external stimuli, such as thermal and mechanical stresses. Here we report on a layered PDA containing 4,4'-bipyridyl in the interlayer space as a hydrogen-bonding guest. Whereas the layered PDA without interlayer guest shows the color transition at 65 °C, gradual color changes with two-stage reversibility are observed in the temperature range of À 20-240 °C by the introduction of the hydrogen-bonding guest. The weaker interlayer interaction via the hydrogen bond promotes the dynamic motion directing the thermoresponsive color changes in a wide temperature range.

Imaging of Accumulated Mechanical Stresses Using Self-Assembled Layered Conjugated Polymer

“…The molecular motion of the alkyl side chain induces the distortion of the PDA main chain with shortening the effective conjugation length. In our previous works, 47,53,55,57 the intercalated guests in the interlayer space and matrix polymer outside of the PDA domain have effects on the molecular motion leading to the color change. In the present work, the thermoresponsivity of PDA is enhanced by the intercalated PEG-PEI and matrix PU.…”

“…PDA shows visible color changes in response to external stimuli, such as thermal and chemical stresses. − The blue-to-red color change has potential for visible and colorimetric sensing. PDA-based materials and devices have been designed for sensing chemical and thermal stresses. − Although the frictional stresses induce the color changes of PDA, − the color is not changed by the other mechanical stresses, such as compression and tensile stresses. A recent study using atomic force microscopy indicates that a layered PDA based on self-assembled amphiphilic diacetylene (DA) molecules has responsiveness only to shear stress applied in the lateral direction to the lamellar .…”

Stimuli‐Responsive Sponge for Imaging and Measuring Weak Compression Stresses

“…The stimuli responsivity of PDA is controlled by molecular design and intercalation approaches. [ 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ] In general, PDA is synthesized by topochemical polymerization of diacetylene (DA) monomers in condensed states, such as layered structures and vesicles. [ 61 ] Whereas color changes in response to thermal and chemical stresses were extensively studied, responsiveness to mechanical stress was limited in previous works.…”