Abstract
Hoveyda-Grubbs 2nd generation catalyst that has the alkylidene functionalized with pyrene (HG2pyrene) was synthesized and characterized. This catalyst can be bound to carbonaceous filler (graphite, graphene or carbon nanotubes) by π-stacking interaction, but, since the catalytic site become poorly accessible to the incoming monomer, its activity in the ROMP (Ring Opening Metathesis Polymerization) is reduced. This is due to the fact that the above interaction also occurs with the aryl groups of NHC ligand of the ruthenium, as demonstrated by nuclear magnetic resonance and by fluorescence analysis of a solution of the catalyst with a molecule that simulated the structure of graphene. Very interesting results were obtained using HG2pyrene as a catalyst in the ROMP of 2-norbornene and 1,5-cyclooctadiene. The activity of this catalyst was the same as that obtained with the classical commercial HG2. Obviously, the polymers obtained with catalyst HG2pyrene have a pyrene as a chain end group. This group can give a strong π-stacking interaction with carbonaceous filler, producing a material that is able to promote the dispersion of other materials such as graphite in the polymer matrix.
Highlights
Polyolefins are widely used materials in many applications such as industrial and food packaging, cling-film and agricultural film, crates, boxes, carrier bags, electrical cable, bottles, pipes, houseware, toys, petrol tanks, carpet fibers, medical appliances, etc., because of their low cost and intrinsic properties of low density, high stiffness, good tensile strength, recyclability, good workability, non-toxicity, and biocompatibility [1]
Synthesis of Ruthenium-Based Metathesis Catalyst Having the Alkylidene Functionalized with a Pyrene
The modified Hoveyda-Grubbs second-generation ruthenium catalyst (HG2pyrene ) was obtained using the synthetic strategy reported in Scheme 1, by reacting the suitable pyrene derivative with the classic second-generation Hoveyda-Grubbs catalyst [43,44]
Summary
Polyolefins are widely used materials in many applications such as industrial and food packaging, cling-film and agricultural film, crates, boxes, carrier bags, electrical cable, bottles, pipes, houseware, toys, petrol tanks, carpet fibers, medical appliances, etc., because of their low cost and intrinsic properties of low density, high stiffness, good tensile strength, recyclability, good workability, non-toxicity, and biocompatibility [1]. It is important to note that process techniques that are useful for increasing a property could reduce another one, e.g.,: oxygenated functionalities are introduced into the graphite structure by strong oxidizing agents to produce GO, giving rise to a filler that can disperse in organic solvents, water, and different matrices. This is a great advantage when using this filler in polymeric matrices to improve their mechanical properties, but compromises the electrical properties of the nanocomposite [41,42]. The employment of the non-oxidized filler may allow all of the previously mentioned interesting carbonaceous material applications [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]
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