To achieve the full potential of covalent adaptable networks (CANs), it is essential to understand ─and control─ the underlying chemistry and physics of the dynamic covalent bonds that undergo exchange reactions in the network. In particular, understanding the network architecture that is assembled dynamically in a CAN is crucial, as exchange processes within the network will affect the material performance. In this context, the introduction of phase separation in different network hierarchies has recently been proposed as useful handle to control or improve the material properties of CANs.[1]

We present how to induce and visualise ─by various methods, including Raman confocal microscopy─ phase separation in imine-based CANs, on micrometer scale. Also, by modifying the CAN architecture, we could either suppress or enhance the phase separation, with associated effect on dynamic-mechanical material properties, and we propose that phase separation is driven by favourable π–π interactions.

The industrial implementation of covalent adaptable networks (CANs) hinges on the delicate task of achieving rapid bond exchange activation at specific temperatures while ensuring a sufficiently slow exchange at working temperatures to avoid irreversible deformation.[1] In this pursuit, latent catalysts offer a potential solution, allowing for spatio-temporal control of dynamic exchange in vitrimer networks. However, the irreversible nature of their activation has led to undesired creep deformation after multiple cycles of reprocessing.[2] In this work, we demonstrate that a tetraphenylborate tetramethyl guanidinium salt (TPB:TMG) undergoes a reversible thermal dissociation releasing free TMG.[3] This thermally-reversible organocatalyst can be readily introduced as an additive in industrially-relevant materials such as disulfide-containing polyurethane networks (PU) which undergo disulfide ex-change in the presence of a base catalyst. In contrast with a free-base catalyzed process, we demonstrate the dual benefit of adding the thermally-reversible TPB:TMG in preventing creep at lower temperatures and also enabling reprocessability of disulfide-containing PU networks at elevated temperatures. The remarkable reversibility of this thermally-activated catalyst allows for multiple reprocessing cycles, while effectively maintaining a creep-free state at service temperature.

Ionomers are defined as polymers having a few mole percent of ionic groups within their structure whose bulk properties are governed by ionic interactions in discrete regions of the material.[1] The covalent introduction of bonded ionic groups along a hydrophobic backbone, like the polyolefin one, deeply changes the physical and chemical behavior of the resulting material. The introduction of ionic forces to bound the polymer chains may lead to dynamic crosslinks, giving rise to complex viscoelastic behavior. Such dynamic bond feature leads to a structurally dynamic polymer architecture from which enhanced mechanical properties can be expected due to energy dissipative bond re-arrangement.[2] We present here a new type of ionomer obtained via high-pressure/high-temperature free radical copolymerization of ethylene in the presence of small amounts of ion-pair comonomers (IPCs) as shown in Figure 1.[3] This way, we can produce ionomers directly in the reactor, without any neutralization step which is typically used in incumbent technologies. The presence of ionic crosslinking groups induced by the IPC built in the polyethylene chains confer to the polymer specific properties that enable targeting applications that are normally not suited for PE materials. As a result, such ionomers can be used in a variety of applications, including areas where both crosslinked structure and melt processability are required,[4] as well as applications where material’ polarity is enhanced by the addition of ionic units, such as packaging and adhesives.[4]

Preparation and reprocessing of dynamic polymer networks in solventless conditions still face significant challenges in the design of suitable chemistry, (re)processing technology and applications.
Selected covalent associative networks may be prepared and processed in the melt state by extrusion, at limited crosslinking densities. For instance, the well-known catalyzed transesterification polyethylene terephthalate (PET) was exploited for the upcycling of recycled of low-grade PET from food trays [1]. Vinylogous urethane transamination was also exploited for the melt reactive compounding of covalent associative networks based on phonoxy resin for adhesives [2] and recently for the upcycling of polyvinylbutyral. On the other hand, thermoreversible networks based on dissociative bonds (i.e. Diels Alder or multiple H-bonds) are in principle easier to prepare via melt blending, provided processing temperature is low enough to prevent side reactions [3]. Furthermore, the incorporation of inorganic (nano)particles and fibres may be exploited to obtain a new class of hybrid organic-inorganic dynamic networks, as demonstrated by the inclusion of graphene-related materials or functionalized silica within thermoreversible rubbers [3,4].
Recent case studies on dynamic networks prepared by melt reactive processing with different polymers will be presented in this talk, by the discussion materials properties, limitations, challenges and possible applications.

With an increase in plastic production in the previous decade, the management of plastic waste has become an increasingly important topic for researchers to deal with. Plastic recycling, although a very prominent option has its drawbacks. Mechanical recycling, a preferred method for plastic recycling has limitations of poor mechanical integrity of recycled plastic compared to virgin plastic, which limits the applications of this recycled plastic [1]. Closed-loop recycling, which refers to the use of recycled plastic for the same application as that of virgin plastic demands that the mechanical integrity of the plastic should not be compromised during recycling [2]. To achieve this, scientists have increasingly turned to dynamic covalent bonds (DCB’s) as a potential solution. Incorporating DCB’s into thermoplastics to convert them into vitrimers improves the mechanical integrity of the plastics and preserves them during recycling which can enable the closed-loop recycling of various commercial thermoplastics [3,4]. In this study, we converted acrylonitrile-butadiene-styrene (ABS) into vitrimers via reactive extrusion which is a scalable and eco-friendly method widely employed in the polymer industry. The vitrimerization was carried out by crosslinking ABS with a commercial polyepoxide resin 4,4′ methylenebis-(N,N-diglycidylaniline) (TGDDM). The ABS vitrimers showed significant improvement in ultimate tensile strength (approximately 44%) and high retention of mechanical properties after three reprocessing runs. This strategy can potentially facilitate the closed-loop recycling of ABS and pave the way for a circular economy.

This research project focuses on a new generation of thermoplastic elastomers (TPEs) with tunable and scalable thermomechanical properties, addressing the growing demand for sustainable and high-performance polymeric materials. TPEs uniquely combine the elasticity of rubbers with the processability and recyclability of thermoplastics. Traditionally based on di- or tri-block copolymers, TPEs rely on a rubbery block for elasticity and one or two rigid blocks for thermal stability and stiffness1.
Our innovative approach involves side-chain-functionalized triblock copolymers, enabling independent, covalent, and reversible crosslinking of the blocks, as illustrated in Figure 1. This strategy allows precise fine-tuning of thermomechanical properties by exploiting orthogonal stimuli: the hard block undergoes thermal crosslinking, while the soft block is UV-crosslinkable. This dual-stimuli system not only facilitates local and selective property tuning but also enables the design of functionally graded materials. Furthermore, the TPEs are formed through self-assembly of the blocks via metallo-supramolecular chemistry, providing exceptional flexibility in macromolecular design and precise control over block synthesis. In addition, these heteroleptic Metal-Ligands Complexes (MLCs) are also thermally responsive and can be assembled/disassembled upon heating conferring to these TPEs a healing behavior.
This communication will focus on the synthesis, assembly, structure and thermomechanical characterizations of these materials, with a particular attention on the reversible crosslinking processes and their influence on thermal properties. Our results highlight the potential of this approach to expand the application scope of TPEs in advanced engineering and functional materials.