Step-growth Polymerization Research Articles

Generalization of the Carothers equation for linear step growth polymers

In the synthesis of linear step-growth polymers molecular weight control is accomplished through the addition of a controlled amount of monomer carrying the functional group B in excess (B-B or H-B types). The Carothers equation is used to calculate average chain lengths. This paper extends the analysis of chain lengths to include the effect of monofunctional monomers carrying the limiting group A (H-A), allowing the systematic analysis of complex systems containing both bifunctional and monofunctional species of any type (A-A, B-B, H-B and H-A). This refinement is particularly relevant for the synthesis of oligomers from systems with complex feed composition.

Understanding Broad Polydispersity in Step-growth Polymerization via Catalyst Competition Mechanism

Understanding Broad Polydispersity in Step-growth Polymerization via Catalyst Competition Mechanism

Self-promoted Controlled Ring-opening Polymerization via Side Chain-mediated Proton Transfer for the Synthesis of Tertiary Amine-pendant Polypeptoids.

Proton transfer is essential in virtually all biochemical processes, with enzymes facilitating this transfer by optimizing the proximity and orientation of reactants through site-specific hydrogen bonds. Proton transfer is also crucial in the rate-determining step for the ring-opening polymerization of N-carboxyanhydrides (NCAs), widely used to prepare various peptidomimetic materials. This study utilizes side chain-assisted strategy to accelerate the rate of chain propagation by using NCAs with tertiary amine pendants. This moiety enables hydrogen bond formation between the incoming NCA and the polymer amino growing end. The tertiary amine side chain of the NCA forms a proton shuttle, via a less constrained transition state, to facilitate the proton transfer process. Moreover, the tertiary amine side chains enable the precipitation of NCA monomers through in situ protonation during the monomer synthesis. This greatly facilitates the synthesis of these unreported monomers, allowing the direct controlled synthesis of tertiary amine-pendant polypeptoids. This side chain-promoted polymerization has rarely been reported. Additionally, the tertiary amine side chains, as widely used functional groups, endow the polymers with unique properties including pH- and thermo-responsiveness, tunable pKas, and siRNA transfection capability. The self-promoted synthesis, facile monomer preparation, and attractive properties make tertiary amine-pendant polypeptoids promising materials for various applications.

Optimizing Tubulin Yield from Porcine Brain Tissue.

Neural tissue from any source is an excellent material for tubulin isolation, as the dendrites and axons of neurons are rich in microtubules. Here, we present a procedure for extracting tubulin that can be employed, with minor modifications, for neural tissue from multiple sources. In the presented protocol, a new clarification step of the crude lysate has been introduced, which led to a significant reduction in the initial amount of insoluble debris before the first polymerization step occurred. This additional step allowed the processing of additional tissue while using the same instrumentation and, thus, increasing the relative volume of the processed homogenate. The newly introduced step has no significant effect on the quality of purified tubulin, as confirmed by in vitro activity assays and transmission electron microscopy. The described procedure contains all crucial steps, including tissue collection, transport, tissue homogenization, tubulin isolation cycles, and final polishing by ion exchange chromatography using FPLC and subsequent activity measurement assays. The homogeneity of purified tubulin was more than 97%, as confirmed by MS/MS analysis utilizing electrospray ionization and MALDI-TOF.

Kinetic and Mechanistic Studies of Human Oligoadenylate Synthetase 1.

Oligoadenylate synthetase 1 (OAS1) catalyzes the dsRNA-dependent polymerization of ATP to form oligoadenylate, a second messenger of the innate immunity system. This paper reports kinetic and mechanistic studies of OAS1-catalyzed dimerization of ATP to form 2'-5'-diadenylate and pyrophosphate (PPi), the first step in ATP polymerization. Major findings include the following: (1) Reaction progress curves for the production of PPi are biphasic, characterized by a presteady-state lag followed by the linear, steady-state production of PPi. (2) The dependence of steady-state velocity on ATP concentration is sigmoidal and can be described by a rate law derived for a mechanism involving enzyme-catalyzed substrate dimerization. (3) Steady-state velocities were determined as a function of ATP concentration at fixed concentrations of poly(I:C), a synthetic dsRNA activator of OAS1. The data suggest a random mechanism in which either ATP or poly(I:C) can add first to the enzyme. (4) The dependence of klag on poly(I:C) and ATP concentration requires expansion of this mechanism to include slow conformational isomerization of various poly(I:C)- and ATP-bound complexes of inactive OAS1 to form complexes comprising an active enzyme, to ultimately form the reactive Michaelis complex of active OAS1, poly(I:C), and two molecules of ATP. Finally, within this complex, the two molecules of ATP dimerize to form 2'-5'-diadenylate and pyrophosphate. (5) The pH dependence and solvent deuterium isotope effect for kcat suggests that proton transfer occurs in the rate-limiting transition state, which likely involves proton abstraction from the 2'-hydroxyl of the adenylate acceptor ATP as the oxygen of this hydroxyl attacks the a-phosphate of the adenylate donor ATP in an SN2 fashion.

Versatile and reliable extraction of phytosterols employing sonochemical synthesized molecularly imprinted polymer

Phytosterols (PSs) are bioactive compounds in the sterol family, present in numerous complex food and plant matrices in free and conjugated forms. The interest in these compounds arises for phytotherapeutic purposes, particularly for their action on cholesterol metabolism and impact on cardiovascular diseases. There is a need to develop approaches that can selectively extract target analytes and accurately identify and quantify them with high precision. This work proposed the synthesis of molecularly imprinted polymers (MIPs) for PSs with a sonochemical approach, enabling a rapid polymerization step (5 min). This proposed MIP was able to extract 8 PSs (brassicasterol, stigmastanol, campesterol, campestanol, stigmasterol, β-sitosterol, Δ5-avenasterol, α-spinasterol) from a wide range of plant and food matrices belonging to different classes (Brassicaceae, dried fruits and Leguminosae) and was coupled to ultra-high liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS). MIP based on dispersed solid phase extraction (dSPE-MIP) and targeted analysis has proven to be particularly effective in addressing the challenges associated with the complexity of plant-derived matrices, minimising interferences. This was demonstrated by the excellent control of the matrix effect, which was within ±15 %, ensuring the robustness and reliability of the method. The identification and quantification of 8 different PSs was successfully achieved with satisfactory recovery values ranging from 65 % to 100 %. The proposed strategy offers an affordable alternative to classical methods, providing enhanced sensitivity, selectivity and overall performance.

A Systematic Study on Biobased Epoxy-Alcohol Networks: Highlighting the Advantage of Step-Growth Polyaddition over Chain-Growth Cationic Photopolymerization.

Vanillyl alcohol has emerged as a widely used building block for the development of biobased monomers. More specifically, the cationic (photo-)polymerization of the respective diglycidyl ether (DGEVA) is known to produce materials of outstanding thermomechanical performance. Generally, chain transfer agents (CTAs) are of interest in cationic resins not only because they lead to more homogeneous polymer networks but also because they strikingly improve the polymerization speed. Herein, the aim is to compare the cationic chain-growth photopolymerization with the thermally initiated anionic step-growth polymerization, with and without the addition of CTAs. Indeed, CTAs lead to faster polymerization reactions as well as the formation of more homogeneous networks, especially in the case of the thermal anionic step-growth polymerization. Resulting from curing above the TG of the respective anionic step-growth polymer, materials with outstanding tensile toughness (>5MJ cm-3) are obtained that result in the manufacture of potential shape-memory polymers.

Electroactive self-standing polyester membranes prepared using magnetite/poly(3,4-ethylenedioxythiophene) core-shell particles

In this work hybrid magnetite (Fe3O4)/poly(3,4-ethylenedioxythiophene) (PEDOT) core-shell particles are used to produce electro-responsive self-standing polycaprolactone (PCL) membranes with many potential applications. For this purpose, Fe3O4/PEDOT core-shell particles with different magnetite contents are prepared by combining chemical precipitation and emulsion polymerization. After chemical, morphological and physical characterization, the electrochemical response of the hybrid particles is analyzed and compared with that of PEDOT nanoparticles. In all cases, Fe3O4/PEDOT core-shell particles are more electroactive than PEDOT particles, with the electrochemical response of the former increasing with the content of magnetite. Composite membranes were prepared by spin-coating a mixture of polycaprolactone (PCL) and Fe3O4/PEDOT particles. The resulting Fe3O4/PEDOT-PCL membranes, which maintained the magnetic behavior, were transformed into electro-responsive by incorporating a PEDOT surface layer through anodic polymerization, which was possible thanks to the role of Fe3O4/PEDOT particles as polymerization nuclei. One of the potential applications of self-supported electro-responsive Fe3O4/PEDOT-PCL/PEDOT membranes was illustrated through a proof-of-concept. Specifically, a wide-spectrum antibiotic, chloramphenicol, was loaded into the membranes during the anodic polymerization step promoted by the hybrid Fe3O4/PEDOT particles and, subsequently, completely released by electrical stimulation. Overall, Fe3O4/PEDOT core-shell particles allowed us to obtain self-standing membranes with electric and magnetic properties, as promising candidates for many technological applications.

Catalyst free PET and PEF polyesters using a new traceless oxalate chain extender.

Plastic material performance is strongly correlated to the polymer's molecular weight. Obtaining a sufficiently high molecular weight is therefore a key goal of polymerization processes. The most important polyester polyethylene terephthalate (PET) and the new polyethylene furanoate (PEF) require metal catalysts and time-consuming production processes to reach sufficiently high molecular weights. Metal catalysts, which are typically antimony or tin for polyesters, end up in the plastic products which may result in sustainability and ecological challenges. When the less reactive comonomer isosorbide is introduced to produce (partly) biobased materials with enhanced thermal properties, such as polyethylene-co-isosorbide furanoate (PEIF), reaching high enough molecular weight becomes even more challenging. This study presents an easily implementable approach to produce high molecular weight PET and PEF polyesters and their isosorbide copolyesters PEIT and PEIF by coupling lower molecular weight polymer chains by the reactive diguaiacyl oxalate (DGO) chain extender. DGO is so reactive, that the use of metal catalysts can be completely avoided and it helps avoiding an extra solid-state polymerization step. In addition, DGO distinguishes itself from typical chain extenders by its ability to be completely removed from the resulting polymer, thereby avoiding the inherent drawbacks associated with typical chain extenders.

Coupling atomization, emulsification, and polymerization steps for creating gel microspheres

Coupling atomization, emulsification, and polymerization steps for creating gel microspheres

Robust Multifunctional Ultrathin 2 Nanometer Organic Nanofibers.

Ultrathin organic nanofibers (UTONFs) represent an emerging class of nanomaterials as they carry a set of favorable attributes, including ultrahigh specific surface area, lightweight, and mechanical flexibility, over inorganic counterparts, for use in biomedicine and nanotechnology. However, precise synthesis of uniform UTONFs (diameter ≤ 2 nm) with tailored functionalities remained challenging. Herein, we report robust multifunctional UTONFs using hydrophobic interaction-driven self-assembly of amphiphilic alternating peptoids containing hydrophobic photoresponsive azobenzene and hydrophilic hydroxyl moieties periodically arranged along the peptoid backbone. Notably, the as-crafted UTONFs are approximately 2 nm in diameter and tens of micrometers in length (an aspect ratio, AR, of ∼10000), exemplifying the UTONFs with the smallest diameter yielded via self-assembly. Intriguingly, UTONFs were disassembled into short-segmented nanofibers and controllably reassembled into UTONFs, resembling "step-growth polymerization". Photoisomerization of azobenzene moieties leads to reversible transformation between UTONFs and spherical micelles. Such meticulously engineered UTONFs demonstrate potential for catalysis, bioimaging, and antibacterial therapeutics. Our study highlights the significance of the rational design of amphiphiles containing alternating hydrophobic and hydrophilic moieties in constructing otherwise unattainable extremely thin UTONFs with ultrahigh AR and stimuli-responsive functionalities for energy and bionanotechnology.

(Invited) Electrochemical Engineering Approaches for High-Performing Electrosynthesis of Polymer Precursors

The chemical industry accounts for ~5% of the US energy utilization and >30% of the US energy-derived industrial CO2 emissions. Amongst these processes, the production of organic chemical commodities, many of which are used as polymer precursors, account for the majority of the energy utilization (>1200 TBTU/y). The electrification of these processes via the implementation of electro-organic reactions could accelerate the decarbonization of the chemical industry, and bring additional sustainability advantages over their thermo-chemical counterparts. Currently, however, two major challenges prevent the deployment of electro-organic reactions: their low selectivity and their low production rates. To circumvent these barriers, our group deploys electrochemical reaction engineering principles to engineer electrode/electrolyte interfaces and design high-performing electro-organic processes. In this presentation, I will discuss how we implement this approach to understand and improve the performance of electro-organic reactions for the production of large-scale precursors for the production of Nylon 6,6 and polyethylene.The production of Nylon 6,6 involves the step-growth polymerization of 1,6-hexanediamine (HMDA) with adipic acid. HMDA is currently produced by the hydrogenation of adiponitrile (ADN). Here, I will present our insights into the electrohydrodimerization of acrylonitrile (AN) to adiponitrile (ADN). This is one of the largest electro-organic reaction deployed in industry and serves as a model process for the development of practical organic electrochemical processes. Our investigations on ADN uncovered relationships between the microenvironment at and near the electrical double layer (EDL) and reaction performance metrics (i.e., selectivity, efficiency, and productivity). I will discuss general guidelines for electrolyte formulation, dynamic electrochemical operation, the implementation of convective forces to mitigate transport limitations, ultimately leading in the conversion of AN to ADN at Faradaic efficiencies >80% and current densities of 100’s mA/cm2. Our learnings on ADN electrosynthesis helped us to engineer the electrocatalytic hydrogenation of ADN to HMDA, achieving the highest reported selectivity to date for this reaction (>95%). I will also show how similar electrochemical engineering approaches allowed us to elucidate factors that control performance in the electrochemical production of ADN from glutamic acid, an abundant and inexpensive bio-based feedstock, and of ethylene from bio-derived propionic acid. Through our studies, we aim to electrify and bring sustainability to chemical manufacturing, one reaction at a time.

Exploration of the rapid growth of high-molecular-weight oligomers in the later stage of diisocyanate self-polymerization

Diisocyanate trimers are important products in the polyurethane industry. Large amounts of high-molecular-weight oligomers, which change the physical and chemical properties of the final products, are generated in the later stages of the synthesis process. It is important to understand the self-polymerization of high-molecular-weight oligomers. The relationship between this phenomenon and the PDI monomer concentration was first experimentally demonstrated. Then the self-polymerization of pentamethylene diisocyanate (PDI) was investigated via Dmol3 calculations using the linear synchronous transition (LST) and quadratic synchronous transition (QST) methods. Calculations revealed a new synthesis pathway with a reaction energy barrier of 31.548 kcal/mol, leading to the conversion of pentamers into decamers. In the initial stage of the polymerization reaction, the PDI monomer concentration was high, and the reaction followed a step-growth polymerization. However, as the PDI monomer concentration decreased and the PDI pentamer concentration increased in the later stage of the reaction, a new synthesis pathway emerged, leading to the direct synthesis of high-molecular-weight oligomers from the available oligomers. This study further demonstrates the self-polymerization of diisocyanate and provides a comprehensive understanding of its synthesis process. By inhibiting this new pathway can reduce the content of high-molecular-weight oligomers, increase yields, and reduce the product viscosity, all of which are beneficial for chemical process optimization.

Polymerized Carbon Dots with Broad Emission and Suppressed Aggregation‐Caused Quenching Effect Toward Electroluminescent White Light‐Emitting Diodes

AbstractCarbon dots (CDs) possess intrinsically broad emission spectra, making them suitable for modulating high‐quality white light‐emitting diodes (WLEDs). However, the chief technical challenge in applying CDs to WLEDs is the aggregation‐caused quenching (ACQ) effect. A common solution is polymer post‐modification on the surface of CDs, which is a low‐yield, hard‐to‐purified, and complicated process. Herein, polymerized CDs with broad emission (full width at half maxima, FWHM = 187 nm) are synthesized via a one‐step solvothermal method. The obtained polymerized CDs display excellent solution‐processed and film‐forming capabilities, with absolute photoluminescence quantum yield as high as 4.7% in thin film state, creating a firm foundation for assembling solution‐processed WLEDs. Moreover, the polymerization steps of CDs are analyzed and described in detail. The polymer chains prevent ACQ and create new energy levels, resulting in the broad emission of CDs in an aggregated state. Subsequently, WLEDs are fabricated using polymerized CDs as the single active emitting material. The optimal device achieves the maximum brightness of 337.50 cd m−2 and FWHM of 242 nm, covering nearly the entire visible spectral window. The results present a new approach to obtaining polymerized CDs and further fabricating WLED with a straightforward, cost‐effective method.

ROS-responsive thioketal nanoparticles delivering system for targeted ulcerative colitis therapy with potent HDAC6 inhibitor, tubastatin A

Ulcerative colitis (UC) is a common gastrointestinal problem characterized by the mucosal injury primarily affecting the large intestine. Currently available therapies are not satisfactory as evidenced by high relapse rate and adverse effects. In this study we aimed to develop an effective drug delivery system using reactive oxygen species (ROS)-responsive thioketal nanoparticles (TKNP), to deliver tubastatin A, a potent HDAC6 inhibitor, to the inflamed colon in mice with ulcerative colitis (UC). TKNPs were synthesized by step-growth polymerization from an acetal exchange reaction while TUBA-TKNP was prepared using the single emulsion solvent evaporation technique. Our developed nanoparticle showed release of tubastatin A only in presence of ROS which is found to be highly present at the site of inflamed colon. Oral administration of TUBA-TKNP resulted in the higher accumulation of tubastatin A at the inflamed colon site and decreased the inflammation as evidenced by reduced infiltration of immune cells and decreased level of pro-inflammatory cytokines in TUBA-TKNP treated mice. In summary, our results show the successful localization of tubastatin A at the site of colon inflammation through TUBA-TKNP delivery, as well as resolution of clinical features of UC in mice.

Chemical Recycling of Step-Growth Polymers Guided by Le Chatelier’s Principle

Chemical Recycling of Step-Growth Polymers Guided by Le Chatelier’s Principle

Step-growth irreversible deactivation radical polymerization: synergistic developments with chain-growth reversible deactivation radical polymerization

Abstract Recent advances in chain-growth reversible deactivation radical polymerization (CG-RDRP), i.e. the so-called “living radical polymerization”, have synergistically developed step-growth radical polymerizations via controlled formation of radical species from covalent bonds followed by irreversible deactivation of the resulting radical species. The monomers for radical polyaddition are thus designed to possess carbon–halogen or thioester bonds, which can generate radical species in the presence of transition metal catalysts and radical initiators, as well as carbon‒carbon double bonds, which will irreversibly form carbon–halogen or thioester bonds. Radical polycondensations are achievable via radical coupling reactions of carbon-centered radicals generated from carbon–halogen bonds or radical quenching reactions with nitroxides. Furthermore, radical addition-condensation polymerizations are achieved by a sequence of reactions, i.e. the formation of radical species from carbon–halogen bonds, radical addition to nitroso or thiocarbonylthio compounds, and coupling or quenching reactions with the resulting stable radical. These step-growth irreversible deactivation radical polymerizations (SG-IDRP) enable the synthesis of a variety of polymers, such as polyethers, polyesters, polyamides, and polyimides, which have aliphatic, aromatic, polar, and degradable groups in their main chains. Sequence-regulated vinyl polymer structures can also be constructed by designing monomers. Combinations with CG-RDRPs further lead to unique hybrid block, multiblock, graft, hyperbranched, and network polymers.

Catalyst-Free synthesis of sulfonamide-functionalized Poly(phosphonate)s and Poly(phosphate)s using Bis(aziridine)s

We present an efficient step-growth polymerization method for synthesizing sulfonamide-functionalized poly(phosphonate)s and poly(phosphate)s. The polymerization process involves treating bis(aziridine) with organophosphorus acid in toluene, without the need for any catalyst, yielding the desired polymers in high yields. Six different types of organophosphorus acids and inorganic phosphoric acid were found to be suitable for this method. Thermal analysis of the resulting poly(phosphonate)s and poly(phosphate)s revealed a decomposition temperature (Td,5%) of up to 330 °C at 5 % weight loss, while differential scanning calorimetry (DSC) analysis showed glass transition temperatures (Tg) ranging from 54 to 98 °C. Microscale combustion calorimetry (MCC) analysis demonstrated that the cross-linked poly(phosphate) derived from inorganic phosphoric acid exhibited the lowest peak heat release rate (HRR) and total heat release (THR) compared to the linear ones. These findings are expected to provide a straightforward approach for synthesizing novel phosphorus-containing polymers.

Multishell Silver Indium Selenide-Based Quantum Dots and Their Poly(methyl methacrylate) Composites for Application in Red-Light-Emitting Diodes.

In this work, the production of novel multishell silver indium selenide quantum dots (QDs) shelled with zinc selenide and zinc sulfide through a multistep synthesis precisely designed to develop high-quality red-emitting QDs is explored. The formation of the multishell nanoheterostructure significantly improves the photoluminescence quantum yield of the nanocrystals from 3% observed for the silver indium selenide core to 27 and 46% after the deposition of the zinc selenide and zinc sulfide layers, respectively. Moreover, the incorporation of the multishelled QDs in a poly(methyl methacrylate) (PMMA) matrix via in situ radical polymerization is investigated, and the role of thiol ligand passivation is proven to be fundamental for the stabilization of the QDs during the polymerization step, preventing their decomposition and the relative luminescence quenching. In particular, the role of interface chemistry is investigated by considering both surface passivation by inorganic zinc chalcogenide layers, which allows us to improve the optical properties, and organic thiol ligand passivation, which is fundamental to ensuring the chemical stability of the nanocrystals during in situ radical polymerization. In this way, it is possible to produce silver-indium selenide QD-PMMA composites that exhibit bright red luminescence and high transparency, making them promising for potential applications in photonics. Finally, it is demonstrated that the new silver indium selenide QD-PMMA composites can serve as an efficient color conversion layer for the production of red light-emitting diodes.

Thermal behaviors and DC conductivity of linker spacer influence on polymerized ionic liquids with bis-imidazolium embedding in the backbone chain

A series of polymerized ionic liquids (PILs) with bis-imidazolium embedding into the backbone was designed to study the effect of linker spacers (C-2, C-4, C-6, and C-8) on their ionic conductivity and thermal behaviors. All PILs were prepared by step-growth polymerization using a modified Menshutkin reaction, where 1,1′-(1,4-butadiyl) bisimidazole (Bbim), was structurally modified by a series of bis-bromoacetates (1,1-(1,n-alkanediyl) bis(bromoacetate) (n = 2, 4, 6, and 8 correspond to 1,2-EBA, 1,4-BBA, 1,6-HBA, and 1,8-OBA, respectively). Interestingly, the density function theory (DFT)-derived complexation energy exhibits a correlation with spacer length, decreasing as the linker spacer increases. Moreover, shorter linker chains notably elevate the glass transition temperature (Tg). The room temperature dc-conductivity of C-8 is the highest (2.2 × 10–5 S/cm) among PILs with shorter linker chain lengths. These results indicate that PILs 1–4 have the potential to yield substantial ionic conductivity in a chain of flexible segments (low Tg), while exhibiting a decrease in complexation energy.