Dithiolanes, such as the naturally occurring lipoic acid and asparagusic acid and their respective derivatives, exhibit many advantages as monomers and crosslinkers in the development of stimuli-responsive materials. Polymerizable via anionically or radically mediated mechanisms, these functional groups form polydisulfide chains amenable to multiple modes of dynamic behavior.

Covalent adaptable networks produced from dithiolane polymerizations may undergo thermally induced plasticity via reversible addition as linear disulfides undergo cyclization to regenerate their initial reactive groups. Alternatively, and at lower temperatures, these same linear disulfides can undergo disulfide exchange (e.g. via radically-mediated photoinitiation).

In addition to the homopolymerization of dithiolanes, the moieties also readily react, radically, with various alkenes (e.g. norbornenes, vinyl ethers) and alkynes (e.g. phenylacetylenes, aliphatic alkynes), providing a methodology to simultaneously introduce additional functional groups within polymers as well as to fine-tune the dynamic character of the resulting material. The versatility of the dithiolane polymerization and copolymerization as well as that of their polymers portend a broad range of potential applications within the realm of smart materials.

Sulfur is a waste product generated on the scale of 60 million tonnes per annum. Efforts to use this sulfur as a feedstock for functional polymer materials have resulted in the process of inverse vulcanisation and the products of this process. These polymers have been used in applications such as Li-S batteries, 2 mercury sequestration from wastewater, and as antibacterial surfaces. Problems arise in this process however, including polymer solubility in only organic solvents, the high temperatures (>120 °C) required for the synthesis, and the production of hydrogen sulfide as a by-product of the reaction. A new synthesis involving the nucleophilic decomposition of sodium polysulfides by a carbanion generated from the common surfactant sodium allyl sulfide yielded a linear sulfur polymer with exceptional water solubility. This process occurs at mild reaction temperatures and generates no hazardous hydrogen sulfide. This polymer demonstrated a high capacity for atmospheric water harvesting with a capacity of 345 W/w%, and the ability to act as a flocculant to remove up to 87% of mercury ions from a 1 ppm solution.

Elemental sulfur, a byproduct of the oil refining process, represents a promising raw material for the synthesis of degradable polymers. Utilizing an emerging approach called sequence-selective terpolymerization, we show that simple lithium alkoxides can catalyze the polymerization of elemental sulfur (S₈) with industrially relevant propylene oxide (PO) to yield poly(monothiocarbonate-alt-Sₓ) or poly(ester-alt-Sₓ), where x can be controlled by the amount of sulfur supplied. The in situ generation of thiolate intermediates, formed through a rearrangement, enables the integration of S₈ and epoxides into a single polymer sequence—something otherwise not achievable.
The mechanistic basis for sequence selectivity is discussed, with both kinetic and thermodynamic factors facilitating this novel catalysis. Due to the dynamic nature of sulfur–sulfur bonds, the polymer can undergo skeletal editing and, after crosslinking, can function as a dynamic covalent network useful in thermally reprocessable adhesives. This study illustrates how mechanistic insights can allow the combination of intrinsically incompatible building blocks, advancing sulfur waste utilization.

The widespread use of polymers in modern applications demands the development of effective and efficient polymerization techniques. The emergence of new functional polymers and innovative polymerization methods has become a significant area of research in material science, with the potential to yield advanced materials exhibiting enhanced properties and opening avenues for new applications. In this context, "click" polymerization between activated alkynes and heteronucleophile groups offers a promising strategy, as it eliminates the need for transition-metal catalysts and enables reactions to proceed under mild conditions. In this presentation, we discuss our work in harnessing the activated alkyne-hydroxyl reactivity to develop degradable and self-healable polyureas (PUs). The presence of urea groups in the resulting polymers facilitates interchain hydrogen bonding, contributing to the self-healing behavior of the material. Furthermore, the polymerization process generates vinyl ether functionalities along the polymer backbone, rendering the polymers degradable under acidic conditions. We will also explore our efforts to extend this synthetic strategy to other commodity polymers, highlighting the versatility and potential of this approach in polymer design and functionalization.

Over the past few years, crosslinking has been widely investigated in order to improve the mechanical performance of coatings made using emulsion polymers. One of the most common crosslinking systems in commercial products is based on the reaction of diacetone acrylamide (DAAM) and adipic acid dihydrazide (ADH) [1]. Nevertheless, due to a recent classification as toxic to the aquatic environment, the European Eco Label [2] limits the use of ADH up to 1% (w/w). The aim of this study is to find an alternative to ADH as crosslinker for aqueous acrylic emulsions.
For this purpose, various dynamic crosslinking chemistries involving reactions between DAAM and alternative compounds such as oximes, hydrazides and amines have been investigated to gather insights into bond formation and hydrolysis that occurs during film formation. Hydrolysis is a crucial factor as it provides an insight into the potential release of hydrazine into the environment. As a step toward the substitution of ADH, novel crosslinkers have been synthesized by tailoring both their chemistry and structure, ranging from functionalized latexes to the development of bifunctional molecules. These alternative crosslinking technologies are capable of displaying mechanical properties that approach the ones of conventional ADH systems but with an improved environmental profile.

Several applications of polymer materials rely on a convenient polymerization process at room temperature and ambient atmosphere. This is where two-component (2K) systems based on redox-initiated radical polymerization excel. However, these initiation systems often come with drawbacks of toxicity and thermal lability.
Herein, we present a newly developed 2K redox initiation system for polymerization of difunctional methacrylic monomers. To that end, diboranes were used as labile bonds for a copper catalyzed cleaving, resulting in the generation of initiating radical species.[1]

This radical initiation system proved to be a powerful tool for adjustable reactivity towards polymerization between one and twenty minutes, depending on the diborane and copper compound used. Furthermore, mechanistic insights into the initiation reaction are presented in detail.[2] In addition, the yielded polymers were characterized with focus on their (thermo)mechanical properties, resulting in the development of a new platform for radical 2K initiation with well adjustable polymerization reactivity and polymer properties.