Poly(hydroxyalkanoate)s (PHAs) are natural or synthetic aliphatic polyesters that are biocompatible, degradable and recyclable thereby attracting considerable interest as circular engineering plastics, in particular as single-use plastics, packaging, or biomedical device with reduced environmental and societal impact [1].
In this presentation, our efforts focused on the design and development of new stereoregular polyester homo- and copolymers, thereby expanding the PHA family to original functional polyesters, will be discussed. Our recent highlights in the field include investigation of tunable catalytic systems for the ring-opening (co)polymerization (RO(CO)P) of functional β-propiolactones BPLFG (FG = (fluoro)alkyl, (di)methylene (thio)alkoxide, ester, diphenyl-phosphinate). The resulting stereoregular and sequence controlled/alternated PHA (co)polymers exhibit a high degree of control over molecular and microstructural characteristics. A close relationship between the catalytic system, the chemical structure, the composition, the topology of the macromolecules, and the thermal signature of the polyesters can thus be established. The fine-tuning of the PHA stereochemistry thus relies on the interplay between the stereoelectronic environment of the catalyst/active species and the β-lactone exocyclic functional group (FG) substituent, which serves as a crucial parameter [2-5].

Aliphatic polycarbonates and polyesters concentrate considerable attention not only in the medical field, due to their biodegradable character, but also for packaging and other commodity applications,1 as well as chemical recyclability.2 Further developments in these areas require reliable access to a broad range of polycarbonates / polyesters with different and well-controlled structures. A method to achieve this goal is the ring-opening (co)polymerization (ROP) of tailor-made monomers, which permits to tune the polymer properties by introducing new functional groups either on the polymer backbone or as a lateral group.
5-Methylene-1,3-dioxane-2-one (exTMC), a cyclic carbonate bearing an exocyclic methylene group, has been introduced as a comonomer for trimethylene carbonate (TMC) with the aim of preparing functionalized polycarbonates. Using methane sulfonic acid as organocatalyst, exTMC and TMC copolymerize in a controlled manner to lead to copolymers of adjusted composition and high randomness (reactivity ratios of 0.95-0.98 and 1.00-1.06 for exTMC and TMC, respectively).3 Subsequent thiol-ene reaction on the exomethylene group with non-protected thioglycolic acid or thioglycerol provides polycarbonates with adjustable amounts of COOH or OH groups randomly distributed along the polymer chains. The hydrophilicity and degradation rate of derived films can thus be tuned by adjusting the type and amount of functionalization. These functionalized polycarbonates can also be envisioned as a hydrophilic block, as an alternative to PEG,4 in combination with PTMC and/or polylactide (PLA) as hydrophobic blocks. Our objective is to develop an environmentally friendly and fully degradable amphiphilic block copolymers, offering a sustainable alternative to conventional PEGylated examples.

The enantioasymmetric ring opening polymerization (ROP) of racemic lactide (rac-LA) is a challenging route leading to the reaction of (predominantly) one enantiomer to provide a chiral PLA.¹ Organometallic catalysts based on aluminum or other metals working via a “coordination−insertion” mechanism have been by far the most investigated for the stereocontrolled ROP of rac-LA.²
To date, a limited number of studies have focused on the stereocontrolled organocatalytic ROP of rac-LA using either achiral or chiral organic catalysts,³ despite their potential advantages in sustainability and tunability.
In this presentation we employ density functional theory (DFT) calculations to compare the mechanistic pathways underlying enantioselective ROP catalyzed by both chiral organometallic⁴ and organocatalytic⁵ systems (Figure 1).
Our analysis highlights key factors influencing stereoselectivity, including (a) multiple competing mechanistic pathways, (b) the role of monomer enantiofaces, and (c) the shift in rate-determining steps -from nucleophilic addition to ring opening-depending on the chirality of the lactide monomer.
Furthermore, we explore the interplay between enantiomorphic site control and chain-end control, providing insights that align well with experimental stereoselectivity data.

Fig. 1 Stereoselective ROP behavior of organometallic (1A and 1B) and organocatalysts (2A) toward rac-LA.

Catalysis using main-group compounds featuring the most abundant aluminum and silicon elements is an attractive option but has been scarcely explored in literature [1]. Polymers can be regarded as ubiquitous components of material science that have impacted every facet of our daily lives [2]. The synthesis of polymers derived partially or fully from renewable feedstock using catalysts comprising of Earth-abundant elements is an appealing research goal for researchers [3]. Silylenes can be described as neutral dicoordinate species where the silicon atom exhibits an oxidation state of +II. In our work, we utilize silylene as a ligand to prepare a heterodinuclear compound with trimethyl aluminum (AlMe₃). The compound is used as a catalyst for synthesizing copolymers from cyclohexene oxide (CHO) and phthalic anhydride (PA) to produce polyesters and CHO and carbon dioxide (CO₂) to produce polycarbonates. An ideal catalyst should enable the sequential polymerization of cyclohexene oxide (CHO) with phthalic anhydride (PA) or CO₂, resulting in copolymers with predetermined chain lengths and molecular weight. Our catalyst exhibits high activity and a true-living nature for the production of polyester and polycarbonate materials with unprecedented microstructures. The full consumption of CHO equivalents occurs within minutes, producing polyester with the expected molecular weights. The one-pot sequential polymerization was successfully extended to achieve precise copolymers with CHO loading upto 10000 equivalents.

Vinyl polymers, despite their widespread application, are inherently limited by their non-degradable all-carbon backbone, raising significant concerns regarding their long-term environmental persistence. The demand for degradable polymers has intensified, particularly in fields such as environmental science and biomedicine. In this context, thionolactones have recently emerged as a promising class of monomers, enabling a unique polymerization mechanism known as Thiocarbonyl Addition–Ring-Opening (TARO) polymerization. This approach strategically incorporates cleavable thioester linkages into the vinyl copolymer backbone, facilitating enhanced degradability while preserving desirable polymer properties.[1]

Dibenzo[c,e]oxepine-5(7H)-thione (DOT) can successfully copolymerize with various monomers, introducing degradable units into the polymer backbone. Although homopolymerizing DOT is inherently challenging, this study demonstrates that incorporating a small amount of DEVP (diethyl vinyl phosphonate) enables the synthesis of DOT-rich copolymers. These DOT-co-DEVP copolymers contain ring-opened thioester linkages, making them susceptible to degradation upon exposure to ethylamine. This degradability was confirmed through gel permeation chromatography (GPC), which tracked changes in molecular weight before and after degradation. Thermal analysis and, infrared spectroscopy (IR) provided further structural insights. This approach presents a promising step towards developing degradable polymers with potential applications in environmental and biomedical fields.

Continuous flow chemistry has transformed polymer synthesis by offering superior control, safety, and scalability compared to traditional batch methods. While flow technology is well-suited for chain-growth polymerizations, applying it to step-growth polymerizations (SGP) presents challenges, including long reaction times, side reactions that hinder molar mass control, and concentration issues that impact viscosity and polymerization rates. In this study, we overcome these limitations by developing an efficient continuous process for producing CO₂-based poly(oxazolidone)s—an emerging class of non-isocyanate polyurethanes. Our approach streamlines SGP in flow reactors and integrates a sequential modification step within the same system. This telescoped process combines dehydration and cationic thiol–ene reactions in a continuous sequence, yielding highly functionalized poly(N,S-acetal oxazolidone)s without the need for intermediate purification. The ability to achieve rapid, high-yield production with precise functionalization highlights the transformative potential of flow chemistry for advancing functional polymer manufacturing through SGP.¹