Περίληψη:
High-cis polydicyclopentadiene (PDCPD) aerogels were synthesized using
ring opening metathesis polymerization (ROMP) of dicyclopentadiene
(DCPD) with a relatively air-stable ditungsten catalytic system,
Na[W-2(mu-Cl)(3)Cl-4(THF)(2)].(THF)(3) (W-2; ((WW)-W-3)(6+), a ‘(2)e
‘(4)), and norbornadiene (NBD)as a co-initiator. These aerogels are
compared in terms of chemical structure and material properties with
literature PDCPD aerogels obtained using well-established Ru-based
alkylidenes as catalysts. The use of NBD as a co-initiator enhances the
degree of crosslinking versus the more frequently used phenylacetylene
(PA), yielding materials with a controlled molecular structure that
would persist solvent swelling. Indeed, those PDCPD aerogels absorb
selected organic solvents (e.g., chloroform, tetrahydrofuran) and swell
rapidly, in some cases up to 4 times their original volume within 10
min, thus showing their potential for applications in chemical sensors
and solvent-responsive actuators. The advantage of aerogels versus
xerogels or dense polymers for these applications is their open
porosity, which provides rapid access of the solvent to their interior,
thus decreasing the diffusion distance inside the polymer itself, which
in turn accelerates the response to the solvents of interest.
