The Effect of Hydrogen-Bonds of Amino Acid-Derived Diacetylene by Photopolymerization in Supramolecular Hydrogels

Abstract

Amino acids derived diacetylene hydrogelators 1 and 2 which have glycine or alanine moiety as head group were synthesized by several steps. The influences on the hydrogen-bonding interaction between amino acids moieties of hydrogelators in the polymerization by UV irradiation were investigated. The glycine-based hydrogel 1 resulted in the generation of stronger absorption peak at 540 nm at room temperature by UV-irradiation. Interestingly, the red color of the glycine-based diacetylene hydrogel 1 was gradually changed into blue color by decreasing temperature. Finally, the absorption band with 640 nm of glycine-based diacetylene hydrogel 1 showed at 77 K. On the other hand, the alanine-based hydrogel 2 had no significant color change at 77 K. These different color changes between the hydrogels 1 and 2 are attributed to the strong intermolecular hydrogen-bonding interaction between glycine moieties of the hydrogelator 1, as confirmed by FTIR observation. These results indicate that the hydrogen-bonding strength of the self-assembled hydrogel is a strong influence on the degree of polymerization.

Selective Chirality-Driven Photopolymerization of Diacetylene Crystals

“…As expected, the conjugated backbone follows the direction of the hydrogen-bond (HB) network in the resulting crystal structure of PDA5 (Figure ). It is noteworthy that literature indicates that the presence of a HB network close and placed parallel to the PDA backbone sometimes hinders the polymerization of DA precursor monomers in the solid state, − which is fortunately not the case here as evidenced by the well-resolved XRD structure as well as Raman analyses. The unit-cell volume of the monomeric crystal is reduced (from 1068.0 Å 3 for DA4 to 1044.6 Å 3 for PDA5 ), and consequently the density is increased (from 1.258 g cm –3 for DA4 to 1.286 g cm –3 for PDA5 ).…”

Rapid Access to Polychlorodiacetylene Single Crystals through H-Bond Templating and Computations on Helical PDA Oligomers

“…An important feature of the resulting crystal structure of the PClDA 5 (Figure c) is the direction of the hydrogen bonds (HBs) network, which is parallel to the PDA skeleton. A search of crystallographic databases shows that, even if groups forming HBs are often considered to promote the optimal stacking of reactive DAs, the direction of chain propagation in polymerization is not always parallel to the hydrogen bonded chains. , In fact, single crystal elucidations of PDA with HBs parallel to the π-conjugated backbone are scarce. , Furthermore, if HBs are too strong and too close to the DA group, they may inhibit the polymerization. − As a consequence, spacers of various lengths are widely used to bring enough flexibility for the reactive monomers and to increase the solubility of the polymer, or to control the odd/even effect of the alkyl chain side groups . To the best of our knowledge, a clear SCXRD structure determination of a PDA with an HBs network as close (such as the one reported here with 14 membered rings) to the PDA backbone and that coincides with the polymerization direction has not been reported, since these kinds of systems involved DA monomers which are only partially reactive in the solid state. ,− However, noncovalent backbone rigidification strategies, as well as the development of novel HB-constrained conjugated polymers, ,− may have considerable impact on the optoelectronic properties, since it can induce “conformational control and enhanced planarity along a conjugated polymer” …”

Carbohydrate Derived Organogelators and the Corresponding Functional Gels Developed in Recent Time

“…Supramolecular gels can be sensitized to external stimuli such as temperature, pH, light, or chemicals, to undergo a reversible sol-gel phase transition [5,27,88]. A blue to red color transition in response to environmental changes, and also, in the presence of biomolecules is exhibited by polydiacetylenes (PDAs) [89,90,91,92,93]. PDAs have nonlinear optical properties and show other optical effects [94,95,96,97,98]; these properties make PDAs more attractive for further study in scientific communities.…”