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An Extreme Case of Swelling of Mostly cis-Polydicyclopentadiene by Selective Solvent AbsorptionApplication in Decontamination and Environmental Remediation

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journal contribution
posted on 22.05.2019, 00:00 by Despoina Chriti, Grigorios Raptopoulos, George C. Anyfantis, Patrina Paraskevopoulou
Polydicyclopentadiene (PDCPD) xerogels (W2-PDCPD) consisting of mostly cis-polymer were prepared using a catalytic system based on the ditungsten cluster Na­[W2(μ-Cl)3Cl4(THF)2]·(THF)3 (W2, {WW}6+, a′2e′4). W2-PDCPD xerogels have shown extreme swelling in various organic solvents, mainly aromatic, chlorinated, and brominated hydrocarbons. For instance, in toluene or in chloroform, the volume of the swollen gels exceeds by more than 100 or 50 times the volume of the parent xerogel, respectively. Because of that extreme swelling, the volume of material required for the uptake of a given volume of solvent is very small (1/100 or even less versus other absorbents reported in the literature including organic polymers or carbon-based materials). In addition, the competitiveness of the technology for preparing W2-PDCPD xerogels (i.e., inexpensive starting materials and catalyst, room temperature reaction, ambient drying) renders those xerogels superior materials in terms of solvent uptake. Their swelling behavior was studied with the Hansen solubility parameters (HSP) theory and the Flory theory, each of which provided valuable insight into the swelling mechanism and the parameters that affected it. On the basis of 44 different aliphatic and aromatic organic solvents, a correlation was made between the swelling behavior of the xerogels in each solvent and the solvent HSP, leading to an estimation of the HSP of mostly-cis PDCPD and, subsequently, to the calculation of the Flory–Huggins parameter χ12. On the basis of our findings, W2-PDCPD xerogels were used to separate organic solvents from water.