stretchable polymeric materials include the use of double networks, [4][5][6] nanocomposites, [7] and dynamic polymer networks. [8][9][10][11][12][13][14][15][16][17] Among these strategies, dynamic polymer networks based on dynamic crosslinks such as hydrophobic association, [8] metal-ligand interactions, [9,10] host-guest interactions, [11] dynamic covalent bonds, [12] ion-dipole interactions, [13] hydrogen bonds, [14][15][16] and ion bonds [17] have attracted much attention. Compared with traditional covalent bonds, these dynamic crosslinks can effectively dissipate energy via reversible bond formation/scission or exchange reactions, [9,12,18] resulting in highly stretchable polymeric materials. Despite this progress, the construction of dynamic polymer networks with a stretching ratio beyond 1000× remains a great challenge. Here, we report the preparation of superstretchable polymer networks by using two types of dynamic bonds. We utilize a small number of strong crosslinks to maintain the network integrity during stretching and a large number of weak crosslinks to dissipate energy. We found that the synergetic interplay between these two mechanisms resulted in a superstretchable polymer network that could be stretched to more than 10 000× its original length.Specifically, polybutadiene (PB) networks crosslinked by ionic hydrogen bonds and imine bonds were prepared and examined. PB oligomers (liquid state, M w = 9400) were functionalized by amine and carboxyl groups via a thiol-ene reaction to obtain PB-NH 2 -9.8% and PB-COOH-5%, respectively (the number indicates the degree of functionalization; Figure S1 and Table S1, Supporting Information). Oligomeric PB was chosen because of the abundant vinyl double bonds (90% 1,2-addition) available for amine and carboxyl modification. PB-NH 2 -9.8% and PB-COOH-5% could be completely dissolved, and gel permeation chromatography (GPC) analysis showed that M w of the functionalized PB was similar to that of the original PB, revealing that no chemical crosslinking occurred during the thiol-ene reaction ( Figure S2, Supporting Information). Then, PB-NH 2 -9.8%, PB-COOH-5%, and benezene-1,3,5-tricarbaldehyde were mixed at different ratios. In this formulation, crosslinked polymer networks were constructed via the weak ionic hydrogen bonds between the amine and carboxyl groups and the strong imine bonds from the reaction of amine and aldehyde groups (Figure 1; Movie S1, Supporting Information). [19,20] PB networks with fixed crosslink degrees at 9.8%, but varied ratios and different orders of formation of the ionic hydrogen bonds and imine bonds, were prepared. The resultant networks were labeled PB-ion-imine-x-y and PB-imine-ion-y-x, where x and y indicate the concentration Superstretchable materials have many applications in advanced technological fields but are difficult to stretch to more than 1000× their original length. A superstretchable dynamic polymer network that can be stretched to 13 000× its original length is designed. It is revealed that superstretchability of...

Combined computational and experimental techniques were employed to investigate at the microscopic level the structural and dynamic properties of ferro- and ferricyanide ions in aqueous solution. The characterization of the structural patterns and multiscale dynamics taking place within the first solvation spheres in water and heavy water solvents was first achieved through extensive molecular dynamics simulations, performed with refined force fields, specifically parametrized for the cyanide ions under investigation. The information gained about the solute-solvent interactions is then validated through the successful comparison of computed and measured waiting-time-dependent 2D IR spectra. The vibrational patterns resulting from 2D IR measurements were rationalized in terms of the interaction between the ion and the neighboring water molecules described by simulation. It was found that, within the first solvation sphere, the stronger interactions of the solvent with the ferro species are responsible for a delay in the relaxation dynamics, which becomes more and more evident on longer time scales.

In this work, we carried out steady-state IR absorption, transient IR pump-probe, and waiting-time-dependent two-dimensional (2D) IR measurements on ferrocyanide and ferricyanide ions solvated in water and deuterated water. These two anions are highly symmetric and have distributed cyano groups with IR-active stretching modes in the 5 μm wavelength region. The line width of their linear IR spectra and the initial value of the vibrational frequency-frequency correlation function extracted from their 2D IR spectra indicate water molecules in the hydration shell of the ferro-species are more inhomogeneously distributed but more tightly bound to the cyano groups than those of the ferri-species. Different charges and their distributions in the two anions cause different hydrogen bonding strengths with solvent. The frequency correlation relaxes somewhat slower in ferrocyanide, agreeing with stronger solute-solvent hydrogen-bonding interaction in this case. Mechanisms of the solvent isotope effect on the vibrational relaxation dynamics of the cyano stretching mode are discussed. These results also suggest that in the hydration shell the ferro-species breaks more water structure than the ferri-species, which is opposite to the situation of the bulk water region (beyond the hydration shell) reported previously. This work demonstrated that combined IR methods can be very useful for understanding the molecular details of the structure and dynamics of the hydrated ions.