Περίληψη:
Polydicyclopentadiene (PDCPD) xerogels (W-2-PDCPD) consisting of mostly
cis-polymer were prepared using a catalytic system based on the
ditungsten cluster Na[W-2(mu-Cl)(3)Cl-4(THF)(2)]center dot(THF)(3)
(W-2, W W(6+), a’(2)e’(4)) W-2-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 W-2-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 chi(12). On the basis of our findings,
W-2-PDCPD xerogels were used to separate organic solvents from water.