Multivalency in healable supramolecular polymers: the effect of supramolecular cross-link density on the mechanical properties and healing of non- covalent polymer networks

Polymers with the ability to heal themselves could provide access to materials with extended lifetimes in a wide range of applications such as surface coatings, automotive components and aerospace composites. Here we describe the synthesis and characterisation of two novel, stimuli-responsive, supramolecular polymer blends based on p-electron-rich pyrenyl residues and p-electron-deficient, chain-folding aromatic diimides that interact through complementary p–p stacking interactions. Different degrees of supramolecular “cross-linking” were achieved by use of divalent or trivalent poly(ethylene glycol)-based polymers featuring pyrenyl end-groups, blended with a known diimide–ether copolymer. The mechanical properties of the resulting polymer blends revealed that higher degrees of supramolecular “cross-link density” yield materials with enhanced mechanical properties, such as increased tensile modulus, modulus of toughness, elasticity and yield point. After a number of break/heal cycles, these materials were found to retain the characteristics of the pristine polymer blend, and this new approach thus offers a simple route to mechanically robust yet healable materials

Thermoset Shape‐Memory Polyurethane with Intrinsic Plasticity Enabled by Transcarbamoylation

Thermoset polymers are known for their superior thermomechanical properties, but the chemical crosslinking typically leads to intractability. This is reflected in the great differences between thermoset and thermoplastic shape‐memory polymers; the former exhibit a robust shape memory but are not capable of redefining the permanent shape. Contrary to current knowledge, we reveal here that a classical thermoset shape‐memory polyurethane is readily capable of permanent reshaping (plasticity) after a topological network rearrangement that is induced by transcarbamoylation. By employing the Jianzhi technique (also known as kirigami), unexpected shape‐shifting versatility was observed for this otherwise classical material. As the essential carbamate moiety in polyurethanes is one of the most common polymer building units, we anticipate that our finding will have significant benefits beyond shape shifting.Thermoset polymers are known for their superior thermomechanical properties, but the chemical crosslinking typically leads to intractability. However, a classical thermoset shape‐memory polyurethane was now shown to be readily capable of permanent reshaping (plasticity) after a topological network rearrangement that is induced by transcarbamoylation.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137615/1/anie201602847.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137615/2/anie201602847-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137615/3/anie201602847_am.pd

Sustainable inverse-vulcanised sulfur polymers

We demonstrate two renewable crosslinkers that can stabilise sustainable high sulfur content polymers, via inverse-vulcanisation. With increasing levels of sulfur produced as a waste byproduct from hydrodesulfurisation of crude oil and gas, the need to find a method to utilise this abundant feedstock is pressing. The resulting sulfur copolymers can be synthesised relatively quickly, using a one-pot solvent free method, producing polymeric materials that are shape-persistent solids at room temperature and compare well to other inverse vulcanised polymers. The physical properties of these high sulfur polymeric materials, coupled with the ability to produce them sustainably, allow broad potential utility

Chimie de Polycondensation, Polymères Supramoléculaires et Vitrimères

The aim of this thesis was the design and synthesis of polymer materials that exhibit unusual combinations of properties. To this end, we used step-growth polymerization and simple and up-scalable chemical reactions. First, we described chemically cross-linked networks that are permanent and insoluble, yet malleable, weldable and processable at high temperatures. To achieve this, we synthesized epoxy networks that can rearrange their topology by transesterification reactions without modification of the numbers of links. The versatility of the chemistry allows for an easy adjustment of the network structure, and thus the thermomechanical properties, by changing the monomers that are used. Catalysis brings control over the malleability properties. We called these networks "vitrimers" because, unlike almost all known organic and inorganic glass formers, their viscosity gradually decreases with temperature, in a very similar way to silica. Then, using crystallizable moieties inspired by supramolecular chemistry, we obtained nanophase-segregated oligoamides. These materials exhibit mechanical properties similar to those of conventional thermoplastics, but with a remarkably lower melt viscosity. This feature permits to consider new applications for thermoplastics, that are generally formed of high molecular weight polymer chains.Au cours de cette thèse, à l'aide de réactions chimiques simples et industrialisables, nous avons tenté d'élaborer par polycondensation des matériaux polymères possédant des combinaisons de propriétés inhabituelles. Dans un premier temps, nous décrivons des réseaux chimiques qui sont insolubles mais pourtant malléables, soudables sans apport de matière et recyclables à haute température. Pour obtenir ces matériaux originaux, des réactions de transestérification, capables de réorganiser la topologie du réseau sans modification du nombre de liens chimiques, ont été induites dans des résines époxy grâce à des catalyseurs adaptés. Le choix des monomères permet de moduler très facilement la structure du réseau, et donc ses propriétés mécaniques ou la température de transition vitreuse. La nature et la quantité de catalyseur permettent un contrôle des réactions d'échanges, et jouent ainsi sur la malléabilité. Nous nommons ces réseaux " vitrimères " puisque, contrairement à la quasi-totalité des composés vitreux, ces matériaux se ramollissent très progressivement avec la température, de manière similaire à un matériau jusque-là unique : la silice. Dans un second temps, en utilisant des motifs cristallisables inspirés de la chimie supramoléculaire, nous avons obtenu des oligoamides organisés en nanophases. Ces matériaux présentent des propriétés mécaniques approchant celles de thermoplastiques usuels, mais avec une viscosité en fondu remarquablement faible. Cette particularité permet d'envisager de nouvelles applications pour les thermoplastiques, qui sont en général des polymères de grande masse, et donc de viscosité élevée

Chimie de Polycondensation, Polymères Supramoléculaires et Vitrimères

The aim of this thesis was the design and synthesis of polymer materials that exhibit unusual combinations of properties. To this end, we used step-growth polymerization and simple and up-scalable chemical reactions. First, we described chemically cross-linked networks that are permanent and insoluble, yet malleable, weldable and processable at high temperatures. To achieve this, we synthesized epoxy networks that can rearrange their topology by transesterification reactions without modification of the numbers of links. The versatility of the chemistry allows for an easy adjustment of the network structure, and thus the thermomechanical properties, by changing the monomers that are used. Catalysis brings control over the malleability properties. We called these networks "vitrimers" because, unlike almost all known organic and inorganic glass formers, their viscosity gradually decreases with temperature, in a very similar way to silica. Then, using crystallizable moieties inspired by supramolecular chemistry, we obtained nanophase-segregated oligoamides. These materials exhibit mechanical properties similar to those of conventional thermoplastics, but with a remarkably lower melt viscosity. This feature permits to consider new applications for thermoplastics, that are generally formed of high molecular weight polymer chains.Au cours de cette thèse, à l'aide de réactions chimiques simples et industrialisables, nous avons tenté d'élaborer par polycondensation des matériaux polymères possédant des combinaisons de propriétés inhabituelles. Dans un premier temps, nous décrivons des réseaux chimiques qui sont insolubles mais pourtant malléables, soudables sans apport de matière et recyclables à haute température. Pour obtenir ces matériaux originaux, des réactions de transestérification, capables de réorganiser la topologie du réseau sans modification du nombre de liens chimiques, ont été induites dans des résines époxy grâce à des catalyseurs adaptés. Le choix des monomères permet de moduler très facilement la structure du réseau, et donc ses propriétés mécaniques ou la température de transition vitreuse. La nature et la quantité de catalyseur permettent un contrôle des réactions d'échanges, et jouent ainsi sur la malléabilité. Nous nommons ces réseaux " vitrimères " puisque, contrairement à la quasi-totalité des composés vitreux, ces matériaux se ramollissent très progressivement avec la température, de manière similaire à un matériau jusque-là unique : la silice. Dans un second temps, en utilisant des motifs cristallisables inspirés de la chimie supramoléculaire, nous avons obtenu des oligoamides organisés en nanophases. Ces matériaux présentent des propriétés mécaniques approchant celles de thermoplastiques usuels, mais avec une viscosité en fondu remarquablement faible. Cette particularité permet d'envisager de nouvelles applications pour les thermoplastiques, qui sont en général des polymères de grande masse, et donc de viscosité élevée

La obra quirúrgica de Martín Martínez

Separata da "Revista Portuguèsa de Medicina", Lisboa, V, Decembro, 195

Metal-Catalyzed Transesterification for Healing and Assembling of Thermosets

International audienc

Silica-Like Malleable Materials from Permanent Organic Networks

A polymer shows thermoset-like stability while displaying melt processability like that of a thermopolymer.</jats:p