Abstract
Commercial metathesis polynorbornene is used for the fabrication of high-damping coatings and bulk materials that dissipate vibration and impact energies. Functionalization of this non-polar polymer can improve its adhesive, gas barrier, and other properties, thereby potentially expanding its application area. With this aim, the post-modification of polynorbornene was carried out by inserting ethylene–vinyl acetate–vinyl alcohol blocks into its backbone via the cross-metathesis of polynorbornene with poly(5-acetoxy-1-octenylene) and subsequent deacetylation and hydrogenation of the obtained multiblock copolymers. For the first time, epoxy groups were introduced into the main chains of these copolymers, followed by the oxirane ring opening reaction. The influence of post-modification on the thermal, gas separation, and mechanical properties of the new copolymers was studied. It was shown that the gas permeability of the copolymer significantly depends on its composition, as well as on the amounts of hydroxyl and epoxy groups. The developed methods efficiently improve the barrier properties, reducing the oxygen permeability by 15–33 times in comparison with polynorbornene. The obtained results are promising for various applications and can be extended to a broader family of polydienes and other polymers containing backbone double bonds.
Highlights
The development of new polymer materials heavily relies on the possibility to impart new properties to known polymers
The main approaches in the chemistry of polynorbornenes include: (i) tailoring the repeating unit at the stage of monomer synthesis by introducing the desired substituents or choosing the type of norbornene-containing fragment; (ii) the design of the monomer unit sequence via polymerization according to the metathesis (ROMP), addition (AP), or catalytic arene–norbornene annulation (CANAL) schemes
It was shown that the epoxidation led to a significant decrease in gas permeability of metathesis polynorbornenes due decreases in diffusion and solubility coefficients for almost all gases [3]
Summary
The development of new polymer materials heavily relies on the possibility to impart new properties to known polymers. An efficient approach was used to obtain copolymers containing the fragments of polysiloxane and substituted polynorbornenes, cross-linked in situ through norbornene units [6,7,8,9,10] Some of these copolymers demonstrated the gas permeability values above the Robeson upper bound [7,9,10]. We have recently shown that new multiblock norbornene–ethylene–vinyl acetate/vinyl alcohol copolymers can be synthesized via the macromolecular cross-metathesis of polynorbornene with poly(5-acetoxy-1-octenylene) followed by hydrogenation and deacetylation [20]. Interest in such copolymers is associated with the possibility of obtaining materials that combine the properties of original homopolymers. The copolymer characterization is focused on measuring the gas permeability parameters and discussing their relations with the copolymer structure and method of modification
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