Transformation of polyethylene into a vitrimer by nitroxide radical coupling of a bis-dioxaborolane

Caffy, Florent; Nicolaÿ, Renaud

doi:10.1039/c9py00253g

“…As previously observed, 15,21,56 PE vitrimer relinquishes an insoluble portion when placed in a good solvent. The insoluble portion of PE-v (PE-v-insol) was isolated using a method based on the ISO 10147 standard procedure.…”

Section: Isolation Of Insoluble and Soluble Portions Of Polyethylene supporting

confidence: 73%

Linear Viscoelasticity and Flow of Self-Assembled Vitrimers: The Case of a Polyethylene/Dioxaborolane System

Ricarte

¹

,

Tournilhac

²

,

Cloître

³

et al. 2020

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For vitrimer systems obtained by dynamic cross-linking of polymer chains, incompatibility effects between the cross-links and polymer backbone can lead to microphase separation, resulting in a network made of cross-linked aggregates. Additionally, when there is a wide distribution of the number of cross-links per chain, macrophase separation can occur, mostly due to entropic effects.Here, we investigate the linear viscoelasticity and flow of a polyethylene (PE) vitrimer that has cross-linkable dioxaborolane maleimide grafts, which self-assemble into a hierarchical nanostructure. To elucidate the role of self-assembly, we first studied dioxaborolane graft functionalized PE that was non-cross-linked. It had a terminal relaxation time that was orders of magnitude larger than both neat PE and partially peroxide cross-linked PE. When dioxaborolane cross-linker was added to form the vitrimer, the resulting material could not achieve terminal relaxation within 8 h. The soluble and insoluble portions of the PE vitrimer were then isolated and characterized. The soluble portion, which was graft-poor, expressed similar flow behavior as neat PE, while the insoluble portion -which was a graft-rich network of cross-linked aggregatesrelaxed very little over 8 h. When the insoluble and soluble portions were blended, the rheological behavior of the original vitrimer was basically recovered, showing that the soluble portion acts as a lubricant. When the insoluble portion was blended with neat PE, the material relaxed much more stress, but still did not reach steady-state flow within 8 h. When high stresses were applied, however, PE vitrimer flowed. Nonlinear rheology experiments revealed melt fracture at high strains and suggested that flow is enabled by rapid healing, which follows fracture events. The presence of macroscopic phase separation facilitated flow. IntroductionVitrimers are covalent networks that engage in thermoactivated associative exchange reactions. 1,2,3 Under cooling, they undergo a reversible topology freezing transition, analogous to the glass transition of amorphous silica. In contrast to dissociative cross-links, the associative cross-links of vitrimers preserve network connectivity at all times and temperatures below degradation conditions, yet still enable the network topology to fluctuate. 1,2,3 The consequences of the topology freezing transition on materials properties were investigated for epoxy/acid systems that underwent catalyst-driven transesterification. 1 Since then, the literature has focused on altering the exchange reaction (either catalytically controlled or catalyst-free) and adapting chemistries to different polymer backbones. Other studies explored the properties of vitrimer composites and the addition of nondynamic cross-links to the network. 14,28,29,30,31,32,33,34,35 These research efforts established that modifying vitrimer chemistry provides a pathway for tuning mechanical properties, 36,37,38 stress relaxation, 39,40,41,42 shape memory, 43,44,45 and the ability to self-heal and adher...

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“…Determined by FTIR spectroscopy. b Error bars are the standard deviation of measurements from three different pieces of the sample.Isolation of insoluble and soluble portions of polyethylene vitrimer.As previously observed,15,21,56 PE vitrimer relinquishes an insoluble portion when placed in a good solvent. The insoluble portion of PE-v (PE-v-insol) was isolated using a method based on the ISO 10147 standard procedure.…”

supporting

confidence: 70%

“…The cross-links rearrange by engaging in a dioxaborolane metathesis exchange reaction. 15,21,56 Previously, we observed that strong interactions between the polymer backbone and cross-links induce PE vitrimer to adopt hierarchical meso-and nanostructures ( Figure 1). Essentially, PE vitrimer may be described as a phase separated blend with two distinct macrophases.…”

Section: Introductionmentioning

confidence: 91%

“…1 Since then, the literature has focused on altering the exchange reaction (either catalytically controlled or catalyst-free) and adapting chemistries to different polymer backbones. 2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27 Other studies explored the properties of vitrimer composites and the addition of nondynamic cross-links to the network. 14,28,29,30,31,32,33,34,35 These research efforts established that modifying vitrimer chemistry provides a pathway for tuning mechanical properties, 36,37,38 stress relaxation, 39,40,41,42 shape memory, 43,44,45 and the ability to self-heal and adhere to other materials.…”

Section: Introductionmentioning

confidence: 99%

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Linear Viscoelasticity and Flow of Self-Assembled Vitrimers: The Case of a Polyethylene/dioxaborolane System

Ricarte

¹

,

Tournilhac²,

Cloître³

et al. 2019

Preprint

0

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For vitrimer systems obtained by dynamic cross-linking of polymer chains, incompatibility effects between the cross-links and polymer backbone can lead to microphase separation, resulting in a network made of cross-linked aggregates. Additionally, when there is a wide distribution of the number of cross-links per chain, macrophase separation can occur. Here, we investigate the linear viscoelasticity and flow of a polyethylene (PE) vitrimer that has cross-linkable dioxaborolane maleimide grafts, which aggregate into a hierarchical nanostructure. To elucidate the role of selfassembly, noncross-linked graft functionalized PE was first studied. It had a terminal relaxation time that was orders of magnitude larger than both neat PE and partially peroxide cross-linked PE.When dioxaborolane cross-linker was added to form the vitrimer, the resulting material could not achieve terminal relaxation within 8 hr. The graft-poor soluble and graft-rich insoluble portions of the PE vitrimer were then isolated and characterized. The soluble portion expressed similar flow behavior as neat PE, while the insoluble portion -which is a network of cross-linked aggregatesrelaxed very little over 8 hr. When the insoluble and soluble portions were blended, the rheological behavior of the original vitrimer was basically recovered, showing that the soluble portion acts as a lubricant. When the insoluble portion was blended with neat PE, the material relaxed much more stress, but still did not reach steady-state flow within 8 hr. When high stresses were applied, however, PE vitrimer flowed. Nonlinear rheology experiments revealed melt fracture at high strains and suggested that flow is enabled by rapid healing, which follows fracture events. The presence of macroscopic phase separation facilitated flow.

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“…[14] Recently,N icolaþ, Leibler, and co-workers disclosed fascinating covalent exchangeable vitrimers crosslinked by dynamic exchange of boronate ester linkages,a lthough the actual exchange mechanism still remains unsolved. [24][25][26] To the best of our knowledge,n one of the dynamically crosslinked materials described so far reach the very high glass transition temperatures (T g above 200 8 8C) required for adhesives,p rotective coatings,l ow-wear,o rl ow-friction materials when exposed to high temperatures (contact with hot parts,c omposites for aerospace,e lectronics,b earings). Fors uch demanding applications,o nly af ew thermoplastics constituted of very rigid segments,w ith various degrees of solubility and processability are commercially available (for example,p olyaryletherketones,p olyethersulfones,p olyaramides,p olyetherimides,o rp olybenzimidazoles).…”

Section: Introductionmentioning

confidence: 99%

High Glass‐Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates

Brunet

¹

,

Collas²,

Humbert

³

et al. 2019

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Differential scanning calorimetry of high molar mass poly(4-vinylphenylboronic acid, pinacol ester)s evidenced unusual reactive events above 120 8 8C, resulting in ahigh glass-transition temperature of 220 8 8C. Areversible ringopening reactivity of pinacol boronates is proposed, involving anucleophilic attackonthe sp 2 boron and subsequent bridging between boron atoms by interconnected pinacol moieties to form adensely crosslinked network with high T g .FTIR, solidstate NMR investigations,and rheology studies on the polymer as well as double-tagging analyses on molecular model structures and theoretical calculations further support this hypothesis and indicate ar ing-opening inducing crosslinking. When diluted in an apolar solvent such as toluene,the polymer network can be resolubilized via ring closing,t hus recovering the entropically favored linear chains featuring cyclic boronate esters.

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Transformation of polyethylene into a vitrimer by nitroxide radical coupling of a bis-dioxaborolane

Abstract: This work reports the synthesis and characterization of HDPE vitrimers obtained via reactive extrusion in the presence of bis-nitroxide dioxaborolanes.

Cited by 117 publications

References 35 publications

Linear Viscoelasticity and Flow of Self-Assembled Vitrimers: The Case of a Polyethylene/Dioxaborolane System

Linear Viscoelasticity and Flow of Self-Assembled Vitrimers: The Case of a Polyethylene/Dioxaborolane System

Linear Viscoelasticity and Flow of Self-Assembled Vitrimers: The Case of a Polyethylene/dioxaborolane System

High Glass‐Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates

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