Structural Aspects of the Thermochromic Transition in Urethane-Substituted Polydiacetylenes

Abstract

Thermochromic transitions of the polydiacetylenes (PDAs) of the bis(ethyl)-and bis-(isopropyl)urethanes of 5,7-dodecadiyne-1,12-diol (poly(ETCD) and poly(IPUDO)) were investigated by solid-state 13 C cross-polarization and magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry (DSC). Side group conformational changes resulting from the polymerization and thermochromic transition were monitored by solid-state 13 C CP/MAS NMR. Consecutive heating/cooling cycles in DSC experiments in the temperature range that includes the thermochromic transition reveal that poly(IPUDO) displays better reversibility than poly(ETCD). In solidstate 13 C CP/MAS NMR spectra, poly(IPUDO) showed more restricted side group movement during the transition than poly(ETCD), which may be the major factor for better reversibility. A nonthermochromic form of poly(ETCD) was prepared and compared to its thermochromic counterpart by means of X-ray powder diffraction, DSC, Fourier transform infrared spectroscopy (FT-IR), and solid-state 13 C CP/MAS NMR spectroscopy. Nonthermochromic poly(ETCD) maintains intramolecular hydrogen bonding between neighboring urethane functions as in thermochromic poly(ETCD). The 13 C NMR chemical shifts, sensitive to mechanical strain, of nonthermochromic poly(ETCD) showed an upfield shift of 2 ppm from the red phase alkyne carbon resonance of thermochromic poly(ETCD), which may be an indicator of the removal of thermochromic interactions.

Optical Chirality Induced in Evaporated Poly(diacetylene) Film by Circularly Polarized Light

“…It is known that the phasetransition of PDA is taken place by the strain of the backbone owing to the reorientation of the side chains. [11] Therefore, we may expect that the optical induced chirality we study here will also be dependent on the strain of backbone. Interestingly, our previous study showed that the thermochromic phase transition never broke the chirality of PDA induced by CPL, [6] and topochemical reaction was probable at high substrate temperature.…”

Role of Gel to Fluid Transition Temperatures of Polydiacetylene Vesicles with 10,12-Pentacosadiynoic Acid and Cholesterol in Their Thermochromisms

“…It was suggested that the change in the conformation of the conjugated ene-yne backbone or the conjugated p-orbital arrays (from planar to partially distorted) varied the conjugation length, which was primarily responsible for the color change of the polydiacetylenes. [36][37][38][39] Regarding factors affecting conformation change in the π-bond, head group interactions, arising from hydrogen bonds/lateral stacking between aromatic rings or the flexibility of head groups, were suggested to play important roles. 30,[33][34][35]40 Meanwhile, melting of the unreacted monomers was also suggested to be a factor for the conformation change of the backbone.…”

A Polydiacetylenes-Based Sensor for Discriminating Oleic Acid from Stearic Acid and Elaidic Acid

“…When oleic acid are added, the disruption of hydrogen bonding and π-π stacking formation can allow the release of the strain energy imposed on the alkyl side chains generated during polymerization. 12 The release of side-chain strain can cause partial distortion of the arrayed p orbitals, which can lead to the observed change in optical properties. Both anionic head group and appropriate long hydrophobic moiety are required.…”