One‐Step Ring Opening Metathesis Block‐Like Copolymers and their Compositional Analysis by a Novel Retardation Technique

Abstract

Using a one‐step synthetic route for block copolymers avoids the repeated addition of monomers to the polymerization mixture, which can easily lead to contamination and, therefore, to the unwanted termination of chain growth. For this purpose, monomers (M1–M5) with different steric hindrances and different propagation rates are explored. Copolymerization of M1 (propagating rapidly) with M2 (propagating slowly), M1 with M3 (propagating extremely slowly) and M4 (propagating rapidly) with M5 (propagating slowly) yielded diblock‐like copolymers using Grubbs’ first (G1) or third generation catalyst (G3). The monomer consumption was followed by 1H NMR spectroscopy, which revealed vastly different reactivity ratios for M1 and M2. In the case of M1 and M3, we observed the highest difference in reactivity ratios (r1=324 and r2=0.003) ever reported for a copolymerization method. A triblock‐like copolymer was also synthesized using G3 by first allowing the consumption of the mixture of M1 and M2 and then adding M1 again. In addition, in order to measure the fast reaction rates of the G3 catalyst with M1, we report a novel retardation technique based on an unusual reversible G3 Fischer‐carbene to G3 benzylidene/alkylidene transformation.

Fast Ring-Opening Metathesis Polymerization of Tricyclic Oxanorbornene Derivatives

“…This was totally contradictory to the block-like copolymer synthesized in one step using a mixture of fast and slow monomers reported by us previously. 36 From this observation we conclude that our initial hypothesis was correct and that the cross-propagations of monomers 11a and 10f must be virtually identical. In other words, both 10f and 11a are initiated equally quickly and hence statistically and, therefore, the retarded propagation of 10f can slow down the entire copolymerization.…”

Synthesis of poly-α/β-peptides with tunable sequence via the copolymerization on N-carboxyanhydride and N-thiocarboxyanhydride

“…When THF was used as the solvent for copolymerization on a mixture of a-NCA and b-NTA, using Boc-a-L-Lys NCA and Bn-b 3 -LCHG NTA as the model, we found no significant gradient separation in compositional profile of two amino acid subunits within the poly-a/b-peptide chain, though Boc-a-L-Lys NCA have a slightly higher reactivity than Bn-b 3 -LCHG NTA according to the kinetic plot of residual monomer (Figures 3A-3C) and instantaneous copolymer composition F a-NCA (Figures 3C and S19). (Gleede et al, 2019) This copolymerization proceeded close to ''ideal copolymerization'' (r a-NCA 3 r b-NTA = 0.93, r a-NCA 3 r b-NTA = 1 means ideal copolymerization) (Yasir et al, 2020), which in combination with the instantaneous copolymer composition F a-NCA revealed that the resulting poly-a/b-peptide was a random-like copolymer and the b-amino acid residue has a nearly even distribution along poly-a/b-peptide chain (Figure 3C) (Yasir et al, 2020). Poly-a/b-peptides have proven to be important mimics and modifications of nature polypeptides, such as host defense peptide (HDP), to effectively improve the stability upon enzymatic degradation and therapeutic potential (Konai et al, 2018;Schmitt et al, 2004Schmitt et al, , 2007.…”

“…However, the synthesis of sequence-controlled polypeptides via polymerization is a long-lasting challenge (Jones, 2008;Lutz, 2010;Lutz et al, 2013). Therefore, a breakthrough in sequence-controlled poly-a/b-peptide synthesis is highly desired, though sequence-controlled polymerizations are reported recently on the synthesis of polyacrylates, polynorbornene, poly(styrene-b-maleimide) and polyesters (Jia et al, 2021;McGraw et al, 2020;Pfeifer and Lutz, 2007;Yasir et al, 2020). ll OPEN…”