Synthesis of End-Functionalized Poly(norbornenes) and Poly(ethylidene norbornenes) Using a Pd(II) Catalyst in Combination with Chain Transfer Agents

Abstract

Synthesis of end-functionalized poly­(norbornenes) (PNBs) and poly­(ethylidenenorbornenes) (PENBs) were prepared using the palladium catalyst t Bu3PPdMeCl/NaBArf in combination with the chain transfer agents (CTAs) 4-penten-1-ol and 10-undecenal. These CTAs produce polymers end-capped with −OH and −CHO groups, respectively, in high yields with M n values in the range of 6–17K, depending on the CTA:monomer molar ratio. End-functionalized PNBs and PENBs with precisely controlled M n values and very narrow molecular weight distributions were accessed by using 4-penten-1-ol and 10-undecenal as chain-terminating agents following living polymerizations in which the monomer is completely consumed. The utility of the aldehyde-functionalized polymers is illustrated via coupling to a dye molecule and by the synthesis of ambiphilic diblock copolymers, PNB-b-PEG and PENB-b-PEG.

Polymerization of Terminal Acetylenes by a Bulky Monophosphine-Palladium Catalyst

“…Furthermore, palladium-catalyzed alkyne oligomerization often leads to stereoisomer mixtures or cyclic oligomerization. ,,,, Consequently, we decided to explore well-defined monodentate phosphine palladium catalysts for the polymerization of functionalized terminal acetylenes. Such bulky monophosphine palladium complexes play an important role in cross-coupling methodology and polymer synthesis. , Specifically attractive are Buchwald’s bulky diarylphosphine ligands, in which weak palladium–arene interactions between the metal center and the ligand aromatic ring may result in better catalyst stability while allowing access of the substrate to the catalyst “vacant site”. We report here the preparation of a new Pd complex 1 ligated with the bulky diarylphosphine (tBuXPhos), which polymerizes a wide scope of terminal acetylenes affording head-to-tail and cis–transoidal polymers (Scheme ).…”

Norbornene Monomer Effects and Mechanistic Insights in Binuclear Nickel-Catalyzed Olefin Chain Walking Copolymerizations

“…The M n, NMR of most low-molecular-weight samples agree with the corresponding M n, GPC (see Table S1 for more details), confirming β-H elimination and chain transfer as the chain termination pathway. There have been several studies of Ni/Pd-catalyzed NBE or NBE derivative copolymerizations, in which ethylene, ,,, α-olefin, , 4-penten-1-ol, or 10-undecenal plays the role of chain transfer agent (CTA). Meanwhile, these Ni/Pd catalysts show either no activity or no oligomerization capability when used in reactions with ethylene, α-olefin, or functionalized α-olefins.…”

Aldehyde end-capped CO2-based polycarbonates: a green synthetic platform for site-specific functionalization

“…[11][12][13][14][15][16] Based on these advantages, aldehyde end-capped polymers are promising for the applications of drug delivery, diagnosis, surface modification and construction of supramolecular architectures. [17][18][19] For instance, Haddleton et al demonstrated the synthesis of aldehyde end-capped methacrylic polymers by living radical polymerization for protein conjugation. 13 Brookhart et al developed a strategy to prepare aldehyde endfunctionalized polyolefins using an unsaturated alcohol as the chain-transfer agent (CTA).…”