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NICCOLÒ BRAIDI

Dottorando
Dipartimento di Scienze Chimiche e Geologiche

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Pubblicazioni

2023 - A PETase enzyme synthesised in the chloroplast of the microalga Chlamydomonas reinhardtii is active against post-consumer plastics [Articolo su rivista]
Di Rocco, G.; Taunt, H. N.; Berto, M.; Jackson, H. O.; Piccinini, D.; Carletti, A.; Scurani, G.; Braidi, N.; Purton, S.
abstract

Polyethylene terephthalate hydrolases (PETases) are a newly discovered and industrially important class of enzymes that catalyze the enzymatic degradation of polyethylene terephatalate (PET), one of the most abundant plastics in the world. The greater enzymatic efficiencies of PETases compared to close relatives from the cutinase and lipase families have resulted in increasing research interest. Despite this, further characterization of PETases is essential, particularly regarding their possible activity against other kinds of plastic. In this study, we exploited for the first time the use of the microalgal chloroplast for more sustainable synthesis of a PETase enzyme. A photosynthetic-restoration strategy was used to generate a marker-free transformant line of the green microalga Chlamydomonas reinhardtii in which the PETase from Ideonella sakaiensis was constitutively expressed in the chloroplast. Subsequently, the activity of the PETase against both PET and post-consumer plastics was investigated via atomic force microscopy, revealing evidence of degradation of the plastics.

2023 - A Trifunctional ATRP Initiator Bearing Adaptable Bonds [Poster]
Scurani, Giulia; Braidi, Niccolo'; Porcelli, Nicola; Tassinari, Francesco; Parenti, Francesca
abstract

Atom Transfer Radical Polymerization (ATRP) allows for the production of polymers with precise control over molecular weight, dispersity, topology, composition, and functionality. Functional groups can be introduced into the polymer through post-functionalization of chain ends, or on the alkyl residue of the initiator, or by introducing functionalized (co)monomers, greatly greatly enhancing the targetable applications. In addition, the desired functional group can also be carried by the ATRP initiator. Some researchers have explored initiators with hydrolysis- or heat-sensitive functionalities to impart self-healing properties to the final polymer. However, the commonly used aliphatic halide ester initiators have shown poor thermal stability. To address this issue, we recently developed a novel bifunctional benzamide-containing initiator employed in ARGET ATRP of styrene, demonstrating enhanced thermal stability. Covalent Adaptable Networks (CANs) have emerged as a solution for improving the recyclability of thermoset materials. CANs can reorganize connectivity between chains upon thermal treatment, enabling reprocessing. Our goal is to modify the structure of the benzamide-containing initiator to develop a trifunctional initiator bearing adaptable bonds.

2023 - Influences of nitrogen base excess on ARGET ATRP of styrene with ascorbic acid acetonide and traces of oxygen and water [Articolo su rivista]
Braidi, N; Parenti, F; Scurani, G; Tassinari, F; Buffagni, M; Bonifaci, L; Cavalca, G; Pettenuzzo, N; Ghelfi, F
abstract

Ascorbic acid is a promising regenerating agent for Activators ReGenerated by Electron Transfer Atom Transfer Radical Polymerization (ARGET ATRP) thanks to its sustainability and environmental friendlyness. The ascorbate anion has even more potential because it has a higher kinetic rate constant of reduction toward the copper catalyst than its protonated counterpart. Although ascorbic acid can be easily neutralized with inorganic bases, the resulting heterogeneous system in the polymerization of hydrophobic monomers (such as styrene) is not well-suited for industrial applications. To overcome this problem, in this study we investigate the use of ascorbic acid acetonide, a more lipophilic derivative, together with soluble nitrogen bases of different basicity. The results show how the pK(a) of the protonated form of the nitrogen base affects the process, especially in the presence of traces of water and/or oxygen. Additionally, we report that milder bases yield better results in terms of dispersity and chain-end fidelity, while high pK(a) bases lead to a complete loss of control.

2022 - Basicity Can Choregraph Regeneration in Homogeneous ARGET ATRP of Styrene [Poster]
Braidi, Niccolo'; Galanti, Marco; Scurani, Giulia; Parenti, Francesca
abstract

There are two drawbacks in the use of H2AA when polymerizing a hydrophobic monomer such as styrene. First, the low solubility of the reducing agent in non-aqueous solvents. Second, the reduction kinetic rate constant of the catalyst by H2AA is around two-orders of magnitude lower than that of ascorbate (HAA–). In non-dissociating solvents this means that the polymerization is much slower since it is strictly related to the amount of reduced catalyst. To overcome this, we employed for the first time a more lipophilic ascorbic acid derivative (5,6-isopropylidene ascorbic acid) in place of H2AA, complemented by nitrogen bases of varying basicity: trimethylpyridine (TMP), diisopropylethylamine (DIPEA), and 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU). The resulting system is an efficient and effective, homogeneous ARGET ATRP of styrene. Furthermore, it highlighted how basicity influences the concentration of radicals, and thus control over the final product.

2022 - EVALUATION OF α,ω UNSATURED POLYSTIRENE VS DIVINYLBENZENE AS CROSSLINKING AGENT IN STYRENE FREE RADICAL POLYMERIZATION [Poster]
Bedogni, Elena; Braidi, Niccolo'; Bonifaci, Luisa; Cavalca, Gianfranco; Ghelfi, Franco; Longo, Aldo; Morandini, Ida; Parenti, Francesca; Pettenuzzo, Nicolò; Piccinini, Sofia
abstract

Telechelic polymers have grown in interest over the past decade thanks also to the evaluation of vitrimers and their properties with high added value (e.g.: recycling efficiency). In this context we propose an evaluation study of replacing a component such as divinylbenzene with a short telechelic alkene-ended polystyrene (α,ω-dienePS). This can be produced by dehydrochlorination of a dihalide-terminated precursor obtained by Atom Transfer Radical Polymerization (ATRP)

2022 - MAY POST-ARGET ATRP FUNCTIONALIZATION BE A GOOD WAY FOR POLYSTYRENE UP-CYCLING? [Poster]
Braidi, Niccolo'; Bedogni, Elena; Bonifaci, Luisa; Cavalca, Gianfranco; Ghelfi, Franco; Longo, Aldo; Morandini, Ida; Parenti, Francesca; Pettenuzzo, Nicolò; Piccinini, Sofia
abstract

The notoriously poor (bio)degradability of vinyl polymers is due to their chemically stable backbone. To lower their environmental impact, it is strategic to intercalate labile bonds along the backbone. These weaker bonds could then be broken faster under environmental conditions, releasing more easily (bio)degradable fragments. By intercalation of disulfide bonds, chemical upcycling is also made possible since the released fragments have the same functionality at both ends (thiol-terminated telechelic shorter chains). These fragments can thus undergo polycondensation, either to reform the starting polymer or to be copolymerized into a novel material. The pursue of sustainability in polymers should show both in the final product as well as in the employed synthetic route. Meaning that, a sensible procedure to intercalate said labile bonds should be employed.

2022 - Novel Bifunctional Amide-Based Initiator for the Atom Transfer Radical Polymerization of Styrene with Ascorbic Acid Acetonide as Reducing Agent [Poster]
Scurani, Giulia; Braidi, Niccolo'; Tassinari, Francesco; Parenti, Francesca
abstract

This study focuses on the synthesis and characterization of a new bifunctional benzamide initiator, CMB2HexDA, for the production of thermostable α,ω-dichloropolystyrene via ARGET ATRP. The motivation behind this research is the need to obtain functionalized polystyrene that can withstand the high temperatures used in industrial extrusion processes, as well as the previous development of a method to obtain α,ω-dialkenepolystyrene by solventless thermal dehydrohalogenation. The commonly used initiators in ATRP undergo thermal fragmentation, leading to chain length reduction and loss of telechelicity. The synthesized initiator was purified and characterized, and the resulting α,ω-dichloropolystyrenes were analyzed through GPC and NMR. The telechelic polystyrene produced with the new initiator exhibited enhanced thermal stability compared to aliphatic-halide ester initiators. Although the specific diamine used does not confer specific functionality, the developed synthetic pathway allows for the introduction of other functionalities into thermostable polystyrenes. Furthermore, the benzamidic function could be exploited to achieve controlled chemical degradation of polystyrene, resulting in more readly degradable oligomeric fragments.

2021 - ARGET ATRP of styrene in EtOAc/EtOH using only Na2CO3 to promote the copper catalyst regeneration [Articolo su rivista]
Braidi, Niccolo'; Buffagni, Mirko; Ghelfi, Franco; Parenti, Francesca; Gennaro, Armando; Isse, Abdirisak A.; Bedogni, Elena; Bonifaci, Luisa; Cavalca, Gianfranco; Ferrando, Angelo; Longo, Aldo; Ida Morandini, And
abstract

“Activator regenerated by electron transfer” “atom transfer radical polymerization” (ARGET ATRP) process catalyzed by CuCl /tris(2-pyridylmethyl)amine (TPMA) (1/1) in ethyl acetate/ethanol (EtOAc/EtOH) for the polymerization of styrene from ethyl 2,2-dichloropropanoate (EDCP) is described. The (re)generation of the activating Cu complex is accomplished by Na CO without the addition of any explicit reducing agent. Differently from the analogous process operating in the presence of ascorbic acid/carbonate as the reducing system, branching is not present and control over polymerization is improved. The activation mechanism should follow a composite route, where both EtOH and TPMA contribute to the regeneration of the catalyst. The oxidation of TPMA is suggested by the absence of the ligand in the final reaction mixture and by the reduction of Cu even in t-BuOAc/t-BuOH, notwithstanding the very poor ability of t-BuOH as a reducing agent. Oxidative degradation of TPMA causes a progressive malfunctioning of the redox catalyst. Consequently, the polymerization rate, after a prompt start, becomes slower and slower, fixing conversions at around 50% (4.5 h). This means a gradual decrease of the free radical concentration, which develops unfavorable conditions for the reductive coupling (termination) between the bifunctional growing chains, preserving a controlled growth of the polymer.

2021 - Copper-catalyzed ARGET ATRP of styrene from ethyl α-haloisobutyrate in EtOAc/EtOH, using ascorbic acid/Na2CO3 as reducing system [Articolo su rivista]
Borsari, M.; Braidi, N.; Buffagni, M.; Ghelfi, F.; Parenti, F.; Porcelli, N.; Serafini, G.; Isse, A. A.; Bonifaci, L.; Cavalca, G.; Longo, A.; Morandini, I.; Pettenuzzo, N.
abstract

Atom transfer radical polymerization (ATRP) is one of the most powerful techniques to synthesize precisely tailored polymers and macrostructures. Activators regenerated by electron transfer (ARGET) ATRP was developed as a “green” strategy to decrease the load of the metal catalyst. However, ARGET ATRP usually uses not-so-green reducing agents (e.g. Sn2+) or expensive and industrially impractical procedures. For these reasons, we report an ARGET ATRP of styrene with various carbonates as reducing agents, both alone and paired with ascorbic acid (AA), using monofunctional initiators and Cl or Br as exchanging atoms. The solvent mixture is composed of the green combination of EtOAc and EtOH, even in the presence of modest amounts of H2O. Cyclic voltammetry was used to evaluate the effect of H2O on the catalyst, as well as the absence of AA. The system returned high yields and low dispersities with low amounts of catalyst (~60 ppm) and moderate reaction times. Excellent results were obtained only with the Cl-ATRP system. NMR spectroscopy and kinetic analyses proved the livingness of the final polymer chains.

2021 - Unusual Cross-Linked Polystyrene by Copper-Catalyzed ARGET ATRP Using a Bifunctional Initiator and No Cross-Linking Agent [Articolo su rivista]
Braidi, Niccolò; Buffagni, Mirko; Buzzoni, Valentina; Ghelfi, Franco; Parenti, Francesca; Focarete, Maria Letizia; Gualandi, Chiara; Bedogni, Elena; Bonifaci, Luisa; Cavalca, Gianfranco; Ferrando, Angelo; Longo, Aldo; Morandini, Ida; Pettenuzzo, Nicolò
abstract

2020 - Copper-Catalysed “Activators Regenerated by Electron Transfer” “Atom Transfer Radical Polymerisation” of Styrene from a Bifunctional Initiator in Ethyl Acetate/Ethanol, Using Ascorbic Acid/Sodium Carbonate as Reducing System [Articolo su rivista]
Braidi, Niccolo'; Buffagni, Mirko; Ghelfi, Franco; Imperato, Manuel; Menabue, Alberto; Parenti, Francesca; Gennaro, Armando; Isse, Abdirisak A.; Bedogni, Elena; Bonifaci, Luisa; Cavalca, Gianfranco; Ferrando, Angelo; Longo, Aldo; Morandini, Ida
abstract