Ring-opening metathesis polymerization of norbornene–benzoladderene (macro)monomers

Abstract

We report high kp (macro)monomer structures for use in grafting-through ring-opening metathesis polymerization to make linear and bottlebrush polymers.

Tricyclononenes and tricyclononadienes as efficient monomers for controlled ROMP: understanding structure–propagation rate relationships and enabling facile post-polymerization modification

“…The HOMO energies ranged from −183 kcal mol −1 to −194 kcal mol −1 , which falls within the range reported for other ROMP monomers (−174 kcal mol −1 to −197 kcal mol −1 ) calculated with the same functional and basis set. 5,6,8 In agreement with Matson and coworkers, a positive correlation between k p values and HOMO energies was observed; however, NB-CO 2 Me stands out as having a much larger k p value than its HOMO energy would predict. Notably, NB-CO 2 Me is the only monosubstituted norbornene (only one of the two exo positions is substituted) of the monomers studied here.…”

“…Density functional theory (DFT) calculations of monomer electronic and steric parameters to predict k p Matson and coworkers have proposed that the DFT-calculated HOMO energy levels of exo-NB monomers correlate well with their k p values in G3-initiated ROMP. [5][6][7][8] To determine if TCNs and TCNDs follow this trend, the HOMO energies for each monomer shown in Fig. 2b were calculated using the M06-2X functional and dev2-TZVP basis set (with a conductor-like polarizable continuum model for chloroform) and plotted against the measured ln(k p ) values (Fig.…”

“…2,3 Exo-NBs are, however, oen more difficult to synthesize and more expensive than their endo isomers. Recent detailed studies of the mechanism 4 and the effects of the exo-norbornene monomer structure on the rate of propagation and degree of "livingness" of these polymerizations [5][6][7][8] have led to new insights that may guide the design of next-generation initiator and monomer classes. For example, Matson and coworkers [5][6][7][8] have suggested that the HOMO energy levels of exo-NBs correlate with their G3-initiated ROMP propagation rates.…”

“…TCNs and TCNDs are tricyclic, strained olens with fused cyclobutane and cyclobutene rings, respectively, connected to the two exo positions of the NB skeleton. Compared to other exo-substituted NB monomers, which oen require high temperatures [9][10][11] and/or precious metal catalysts 8,12 for their synthesis, exo-TCNs and TCNDs can be conveniently assembled by thermal cycloadditions of activated olens and quadricyclane with perfect exo selectivity. 13,14 While TCN and TCNDbased polymers have been synthesized using Mo (Schrock-type initiators) 15 and Ru (Grubbs 1st and 2nd generation initiators) initiated ROMP 16,17 and studied for applications in gas separations, [18][19][20][21][22][23][24][25] no studies of their performance under "living" ROMP conditions initiated by G3 or post-polymerization functionalization have been reported.…”

“…Recent detailed studies of the mechanism 4 and the effects of the exo-norbornene monomer structure on the rate of propagation and degree of "livingness" of these polymerizations [5][6][7][8] have led to new insights that may guide the design of next-generation initiator and monomer classes. For example, Matson and coworkers [5][6][7][8] have suggested that the HOMO energy levels of exo-NBs correlate with their G3-initiated ROMP propagation rates. Inspired by this work, and seeking synthetically accessible, functional monomers that do not compromise polymerization kinetics and controlled polymerization behavior, we identied tricyclononenes (TCN) and tricyclononadienes (TCND) as monomers ripe for further study (Fig.…”