C−H Functionalization and Allylic Amination for Post‐Polymerization Modification of Polynorbornenes

Abstract

Post-polymerization modification (PPM) via direct CÀ H functionalization is a powerful synthetic strategy to convert polymer feed-stocks into valueadded products. We found that a metal-free, Secatalyzed allylic CÀ H amination provided an efficient method for PPM of polynorbornenes (PNBs) produced via ring-opening metathesis polymerization. Inherent to the mechanism of the allylic amination, PPM on PNBs preserved the alkene functional groups along the polymer backbone, while also avoiding transposition of the double bonds. Amination using a series of aryl sulfonamides led to good control over the degree of functionalization, access to a range of functionalities, and tunable thermal properties from the resulting polymers.

Access to Functionalized Materials by Metal-Free Ring-Opening Metathesis Polymerization of Active Esters and Divergent Postpolymerization Modification

“…We also found that the material had a T g of −2 °C by differential scanning calorimetry (DSC, Figure 2e), which is lower than the reported value of 36−37 °C for polynorbornene. 20,39 This depression of T g is consistent with trends seen with polyalkylnorbornenes and is attributed to the flexible side chain. 39 With these results at hand, we began to investigate the PPM of poly-1b.…”

“…We targeted a postpolymerization modification (PPM) strategy to afford functionalized MF-ROMP polymers by circumventing deleterious side reactions with the high-energy, reactive intermediates generated during the polymerization. Collectively, strategies for PPM enable the synthesis of polymers with otherwise inaccessible architectures, − polymers whose (co)­monomers are synthetically inaccessible or are incompatible with polymerization conditions, ,− and materials libraries through late-stage diversification of pivotal polymeric building blocks. − Libraries that combine disparate functionality but identical backbone microstructures and degrees of polymerization are particularly relevant for biological and electronic applications in which materials properties are highly dependent on polymer microstructure. , Therefore, PPM of MF-ROMP polymers could lay a foundation for fully metal-free approaches to ROMP materials for a range of applications.…”

Dithiophosphoric Acids for Polymer Functionalization

“…using alkoxyamines. Similarly, Boydston et al [9] . demonstrated CH activation routes with Tos‐amides for polynorbornene (pNB) ring opening metathesis polymerization (ROMP).…”

Dithiophosphoric Acids for Polymer Functionalization

“…Novel CÀ H activation methods for polyethylene (PE) functionalization have elegantly been developed by Leibfarth and Einkensian et al [8] using alkoxyamines. Similarly, Boydston et al [9] demonstrated CH activation routes with Tos-amides for polynorbornene (pNB) ring opening metathesis polymerization (ROMP). Functionalization of backbone ROMPderived pNB has been historically challenging to due to steric constraints, with notable exceptions by Schrock et al and Mecking et al via addition bromination, or hydroxylation reactions, respectively.…”