Synthesis and characterization of poly(ethylene glycol) bottlebrush networks via ring‐opening metathesis polymerization

Abstract

Herein it is reported how the overlap concentration (C*) can be used to overcome crosslinking due to diol impurities in commercial poly(ethylene glycol) (PEG), allowing for the synthesize of bottlebrush polymers with good control over molecular weight. Additionally, PEG‐based bottlebrush networks are synthesized via ring‐opening metathesis polymerization, attaining high conversions with minimal sol fractions (<2%). The crystallinity and mechanical properties of these networks are then further altered by solvent swelling with phosphate buffer solution and 1‐ethyl‐3‐methylimidazolium ethyl sulfate/dichloromethane cosolvents. The syntheses reported here highlight the potential of the bottlebrush network architecture for use in the rational design of new materials.

Radical–radical coupling effects in the direct-growth grafting-through synthesis of bottlebrush polymers using RAFT and ROMP

“…44 Characterization NMR spectra were measured on Bruker 500 MHz or Agilent 400 MHz spectrometers. 1 H and 13 C NMR chemical shifts are reported in ppm relative to internal solvent resonances of CDCl 3 . Yields refer to spectroscopically and chromatographically pure compounds unless otherwise stated.…”

“…Bisnorbornenyl species can also form even when radical polymerizations are not employed in the MM synthesis; for example, the diol impurity present in commercial monofunctionalized polyethylene glycol (PEG) can affect the synthesis of bottlebrush polymers. 13 Thus, synthetic methods to reduce the presence of bisnorbornenyl species in MMs are needed to achieve well-defined bottlebrush polymers, which are under investigation for the synthesis of complex polymer topologies [14][15][16][17][18] and applications including biomedicine, [19][20][21][22][23][24][25] electronic and transport materials, 26,27 elastomers, 6,[28][29][30][31][32] photonic crystals, [33][34][35][36][37] and nanoporous materials. [38][39][40][41] Two approaches are typically used to synthesize MMs monofunctionalized with a norbornene.…”

Bottlebrush Amphiphilic Polymer Co-Networks

“…The values for each variable are compiled in Table . While the ϕ PEG = 0.80 sample was as crystalline as neat PEG, our previous work demonstrated PEG bottlebrush networks that were actually less crystalline despite containing a higher volume fraction of PEG ( X c = 0.824) . This indicates that the inclusion of low amounts of PDMS helps to sequester PEG into segregated domains, resulting in increased crystallinity compared to the analogous homopolymer PEG networks.…”

“…While the ϕ PEG = 0.80 sample was as crystalline as neat PEG, our previous work demonstrated PEG bottlebrush networks that were actually less crystalline despite containing a higher volume fraction of PEG (X c = 0.824). 72 This indicates that the inclusion of low amounts of PDMS helps to sequester PEG into segregated domains, resulting in increased crystallinity compared to the analogous homopolymer PEG networks. Additionally, the X c drops from 0.718 to 0 between ϕ PEG = 0.40 and ϕ PEG = 0.35, suggesting that ϕ PEG < 0.40 samples are comprised of only amorphous PEG.…”

Bioinspired Bottlebrush Polymers for Aqueous Boundary Lubrication

“…The conformation of the backbone and the length and the density of the side chains in bottlebrush polymers play significant roles in the lubrication properties. Inspired by bottlebrush bio-lubricants, synthetic bottlebrush polymers have been designed and prepared [91][92][93][94][95][96][97]. Conventional radical polymerization methods including atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT), and nitroxide-mediated radical polymerization (NMP)) have been used to prepare precisely designed bottlebrush polymers [98][99][100][101][102][103].…”