Ring-Opening Metathesis Polymerization as a Robust Platform to Bottlebrush Polymer Networks
Joel M. Sarapas, Edwin P. Chan, Emma M. Rettner, Kathryn L. Beers
To fully explore bottlebrush polymer networks as model entanglement-free materials, a robust and versatile synthetic platform is required. Ring-opening metathesis polymerization is a highly controlled, rapid, and functional group tolerant polymerization technique that has been used extensively for bottlebrush polymer generation, but to this point has not been used to synthesize bottlebrush polymer networks. Here, we polymerized a mono- and di-norbornene poly(n- butyl acrylate) macromonomer and crosslinker with Grubbs 3rd generation catalyst to achieve bottlebrush networks, and in turn demonstrate control over network properties as the ratio of macromonomer and crosslinker was varied. Macromonomer to crosslinker ratios ([MM]/[XL]) of 10 to 100 were investigated, of which all derivative networks yielded gel fractions over 90 %. Contact adhesion testing was used to quantify dry-state shear modulus G, which ranged from 1 kPa to 10 kPa, reinforcing that bottlebrush polymer networks, largely free of entanglements, can achieve low moduli in the dry state compared to other polymer network materials. A scaling relationship was found such that G ~ ([MM]/[XL])-0.81, indicating that macromonomer to crosslinker ratio is a good estimator of crosslinker density. Swelling ratio in toluene, Q, was compared to dry-state modulus to assess the universal scaling relationship for linear networks G ~ Q-1.75, and a measured exponent of -1.71 indicated good agreement. The synthetic platform outlined here represents a highly flexible route to a myriad of different bottlebrush networks, and will increase the accessibility of materials critical to applications ranging from fundamental to biomedical.
, Chan, E.
, Rettner, E.
and Beers, K.
Ring-Opening Metathesis Polymerization as a Robust Platform to Bottlebrush Polymer Networks, ACS Nano, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=924584
(Accessed December 3, 2023)