Stijn Billiet

Plastic packaging has gained an increasing amount of attention in all aspects of society. Over the past several decades, plastics became the material of choice due to their excellent properties, performance, and economics, but the end of life of plastics is not well managed. This has led to plastic waste in our environment, especially the oceans, rivers, and estuaries, driving legislative, industrial, and voluntary initiatives to make the necessary pivot to circularity. While the plastics… Show more

Plastic packaging has gained an increasing amount of attention in all aspects of society. Over the past several decades, plastics became the material of choice due to their excellent properties, performance, and economics, but the end of life of plastics is not well managed. This has led to plastic waste in our environment, especially the oceans, rivers, and estuaries, driving legislative, industrial, and voluntary initiatives to make the necessary pivot to circularity. While the plastics recycling industry has made many advances in its relatively short life, there are still many technical and societal hurdles to be overcome. The goal of this work is not to provide a complete review of recycling as it pertains to circularity, but rather to highlight the technical gaps that need to be collaboratively addressed by the entire plastics community to achieve circularity. Each stage along the path, from design of packaging and materials of construction to sortation, recycling, and reprocessing are ripe for innovation. The most relevant issues are introduced to provide a starting point for research across all fields of polymer science to aid in reducing the environmental impact of plastic packaging waste. Show less

The reaction of triazolinediones (TADs) and indoles is of particular interest for polymer chemistry applications, as it is a very fast and irreversible additive-free process at room temperature, but can be turned into a dynamic covalent bond forming process at elevated temperatures, giving a reliable bond exchange or ‘transclick’ reaction. In this paper, we report an in-depth study aimed at controlling the TAD–indole reversible click reactions through rational design of modified indole reaction… Show more

The reaction of triazolinediones (TADs) and indoles is of particular interest for polymer chemistry applications, as it is a very fast and irreversible additive-free process at room temperature, but can be turned into a dynamic covalent bond forming process at elevated temperatures, giving a reliable bond exchange or ‘transclick’ reaction. In this paper, we report an in-depth study aimed at controlling the TAD–indole reversible click reactions through rational design of modified indole reaction partners. This has resulted in the identification of a novel class of easily accessible indole derivatives that give dynamic TAD-adduct formation at significantly lower temperatures. We further demonstrate that these new substrates can be used to design a directed cascade of click reactions of a functionalized TAD moiety from an initial indole reaction partner to a second indole, and finally to an irreversible reaction partner. This controlled sequence of click and transclick reactions of a single TAD reagent between three different substrates has been demonstrated both on small molecule and macromolecular level, and the factors that control the reversibility profiles have been rationalized and guided by mechanistic considerations supported by theoretical calculations. Show less

The ultrafast and additive-free triazolinedione-click reaction with electron rich (di)enes is a powerful method for the ultrafast ligation of polymer segments. A versatile method is described for the introduction of clickable TAD end groups in various polymer segments, using reversible addition–fragmentation chain transfer polymerization. These triazolinedione-functionalized prepolymers were subsequently used for macromolecular functionalization with a low molecular weight diene and block… Show more

The ultrafast and additive-free triazolinedione-click reaction with electron rich (di)enes is a powerful method for the ultrafast ligation of polymer segments. A versatile method is described for the introduction of clickable TAD end groups in various polymer segments, using reversible addition–fragmentation chain transfer polymerization. These triazolinedione-functionalized prepolymers were subsequently used for macromolecular functionalization with a low molecular weight diene and block copolymer synthesis of different types within seconds, at ambient conditions, through the coupling with diene-functionalized polymers such as poly(ethylene glycol) and poly(isobornyl acrylate). Show less

The ultrafast and additive-free triazolinedione-click reaction with electron rich (di)enes is a powerful method for the ultrafast ligation of polymer segments. A versatile method is described for the introduction of clickable TAD end groups in various polymer segments, using reversible addition–fragmentation chain transfer polymerization. These triazolinedione-functionalized prepolymers were subsequently used for macromolecular functionalization with a low molecular weight diene and block… Show more

The ultrafast and additive-free triazolinedione-click reaction with electron rich (di)enes is a powerful method for the ultrafast ligation of polymer segments. A versatile method is described for the introduction of clickable TAD end groups in various polymer segments, using reversible addition–fragmentation chain transfer polymerization. These triazolinedione-functionalized prepolymers were subsequently used for macromolecular functionalization with a low molecular weight diene and block copolymer synthesis of different types within seconds, at ambient conditions, through the coupling with diene-functionalized polymers such as poly(ethylene glycol) and poly(isobornyl acrylate). Show less

We report biomass-derived, shape-memory materials prepared via simple reactions, including “grafting from” ATRP and TAD click chemistry. Although the biomass, including plant oils and cellulose nanocrystals, has heterogeneous chemical structures in nature, these materials exhibit excellent multiple shape-memory properties toward temperature, water, and organic solvents, which are comparable to petroleum counterparts. The work presented herein provides burgeoning opportunities to design the… Show more

We report biomass-derived, shape-memory materials prepared via simple reactions, including “grafting from” ATRP and TAD click chemistry. Although the biomass, including plant oils and cellulose nanocrystals, has heterogeneous chemical structures in nature, these materials exhibit excellent multiple shape-memory properties toward temperature, water, and organic solvents, which are comparable to petroleum counterparts. The work presented herein provides burgeoning opportunities to design the next-generation, low-cost, biomass-prevalent, green materials for niche applications. Show less

Triazolinediones (TADs) are unique reagents in organic synthesis that have also found wide applications in different research disciplines, in spite of their somewhat “exotic” reputation. In this review, we offer two case studies that demonstrate the possibilities of these versatile and reliable synthetic tools, namely, in the field of polymer science as well as in more recently emerging applications in the field of click chemistry. As the general use of triazolinediones has always been hampered… Show more

Triazolinediones (TADs) are unique reagents in organic synthesis that have also found wide applications in different research disciplines, in spite of their somewhat “exotic” reputation. In this review, we offer two case studies that demonstrate the possibilities of these versatile and reliable synthetic tools, namely, in the field of polymer science as well as in more recently emerging applications in the field of click chemistry. As the general use of triazolinediones has always been hampered by the limited commercial and synthetic availability of such reagents, we also offer a review of the available TAD reagents, together with a detailed discussion of their synthesis and reactivity. This review thus aims to serve as a practical guide for researchers that are interested in exploiting and further developing the exceptional click-like reactivity of triazolinediones in various applications. Show less

We report the preparation of plant oil based triblock copolymers based on soybean oil monomers. The monomers were polymerized via atom transfer radical polymerization with subsequent chain extension, resulting in poly(styrene-b-soybean oil acrylate-b-styrene) (PS-b-PSBA-b-PS) and poly(styrene-b-soybean oil methacrylate-b-styrene) (PS-b-PSBMA-b-PS) triblock copolymers. These polymers, ranging from thermoplastics to thermoplastic elastomers (TPEs), were obtained by tuning molecular structures. We… Show more

We report the preparation of plant oil based triblock copolymers based on soybean oil monomers. The monomers were polymerized via atom transfer radical polymerization with subsequent chain extension, resulting in poly(styrene-b-soybean oil acrylate-b-styrene) (PS-b-PSBA-b-PS) and poly(styrene-b-soybean oil methacrylate-b-styrene) (PS-b-PSBMA-b-PS) triblock copolymers. These polymers, ranging from thermoplastics to thermoplastic elastomers (TPEs), were obtained by tuning molecular structures. We employed a “click coupling” strategy using triazolinedione (TAD) chemistry to create chemical junctions between the soft middle blocks of the triblock copolymers, which behave similar to physical chain entanglements. This method helps to overcome the drawbacks of plant oil based polymers, allowing for increase of tensile strength without sacrificing elongation. Cyclic tensile tests show that the “click coupled” triblock copolymers exhibit excellent elastic recovery characteristics. Show less

With the aid of triazolinedione (TAD) chemistry, an additive-free, straightforward functionalization and crosslinking strategy for numerous plant oils was developed. In a first step, model studies on the most common natural fatty acids were performed with the aid of monofunctional TAD moieties. These equimolar functionalization reactions were readily monitored by NMR and MS analysis, further facilitated by the disappearance of the characteristic red colour of the TAD molecule. Then, a series of… Show more

With the aid of triazolinedione (TAD) chemistry, an additive-free, straightforward functionalization and crosslinking strategy for numerous plant oils was developed. In a first step, model studies on the most common natural fatty acids were performed with the aid of monofunctional TAD moieties. These equimolar functionalization reactions were readily monitored by NMR and MS analysis, further facilitated by the disappearance of the characteristic red colour of the TAD molecule. Then, a series of synthesized, bifunctional TAD molecules were used for the chemical crosslinking of crude plant oils, a process that was typically finished within minutes. In this way, a large variety of polymer networks could be obtained, such as plant oil-based foils, showing a wide range of thermal properties, which can be tuned and rationalized by the chemical structure of the different plant oils. Show less

With its focus on synthetic reactions that are highly specific and reliable, ‘click’ chemistry has become a valuable tool for many scientific research areas and applications. Combining the modular, covalently bonded nature of click-chemistry linkages with an ability to reverse these linkages and reuse the constituent reactants in another click reaction, however, is a feature that is not found in most click reactions. Here we show that triazolinedione compounds can be used in click-chemistry… Show more

With its focus on synthetic reactions that are highly specific and reliable, ‘click’ chemistry has become a valuable tool for many scientific research areas and applications. Combining the modular, covalently bonded nature of click-chemistry linkages with an ability to reverse these linkages and reuse the constituent reactants in another click reaction, however, is a feature that is not found in most click reactions. Here we show that triazolinedione compounds can be used in click-chemistry applications. We present examples of simple and ultrafast macromolecular functionalization, polymer–polymer linking and polymer crosslinking under ambient conditions without the need for a catalyst. Moreover, when triazolinediones are combined with indole reaction partners, the reverse reaction can also be induced at elevated temperatures, and the triazolinedione reacted with a different reaction partner, reversibly or irreversibly dependent on its exact nature. We have used this ‘transclick’ reaction to introduce thermoreversible links into polyurethane and polymethacrylate materials, which allows dynamic polymer-network healing, reshaping and recycling. Show less

In this self-contained reference, the team of renowned international authors systematically covers all important aspects of designing self-healing polymers from concepts to applications - transferring lessons learnt from nature to materials science.

Recent developments in material design have seen an exponential increase of polymers and polymer composites that can repair themselves in response to damage. In this review, a distinction is made between extrinsic materials, where the self-healing property is obtained by adding healing agents to the material to be repaired, and intrinsic materials, where self-healing is achieved by the
material itself through its chemical nature. An overview of the crosslinking chemistries used in… Show more

Recent developments in material design have seen an exponential increase of polymers and polymer composites that can repair themselves in response to damage. In this review, a distinction is made between extrinsic materials, where the self-healing property is obtained by adding healing agents to the material to be repaired, and intrinsic materials, where self-healing is achieved by the
material itself through its chemical nature. An overview of the crosslinking chemistries used in self-healing materials will be given, discussing the advantages and drawbacks of each system. The review is not only aiming to enable researchers to compare their ongoing research with the state-of-the-art but also to serve as a guide for the newcomers, which allows for a selection of the most promising self-healing chemistries. Show less

Maleimide chemistry involving amines and thiols is presented and evaluated for the design of autonomous self-healing epoxy materials. Model reactions show that amines react rapidly with maleimide compounds at room temperature via the Michael addition reaction. Moreover, thiols and maleimides react readily in the presence of tertiary amines that are present in the epoxy material. The maleimide conjugation reaction with residual amines in the epoxy material ensures chemical bonding of the newly… Show more

Maleimide chemistry involving amines and thiols is presented and evaluated for the design of autonomous self-healing epoxy materials. Model reactions show that amines react rapidly with maleimide compounds at room temperature via the Michael addition reaction. Moreover, thiols and maleimides react readily in the presence of tertiary amines that are present in the epoxy material. The maleimide conjugation reaction with residual amines in the epoxy material ensures chemical bonding of the newly formed network with the original materials during crack healing, while in the crack plane, multifunctional thiols react with difunctional maleimides to fill the crack area. Healing efficiencies are evaluated using the tapered double cantilever beam (TDCB) test method with manual injection of the healing agents, revealing a maximum healing efficiency up to 121% for EPON 828 epoxy material. Furthermore, the use of maleimide chemistry has also been evaluated for self-healing applications towards a cold-curing resin that is currently used for infusion of wind turbine blades (RIM resin). While the healing efficiency is strongly dependent on the type of epoxy material, the average maximum peak load for fracture after healing is roughly the same for all tested epoxy materials. Show less