Narrow Molecular Weight Distribution Research Articles

PH-Switchable Surfactant-Based Microemulsions: Reversible Transition between Microemulsification and Demulsification Triggered by Suitable Acids and Bases.

pH-switchable surfactant-based microemulsions (SBMEs) are those that can switch reversibly between a monophasic state and a fully phase-separated state under the alternation of acids and bases, which is rarely reported. By using an equimolar mixture of sodium dodecyl sulfate and N,N-dimethyldodecylamine (SDS-C12A) as a pH-switchable surfactant, a pH-switchable SDS-C12A-based microemulsion (SDS-C12A-ME) has been fabricated for the first time. The main principles of the reversible switching are the reversible destruction/formation of the emulsifier, SDS-C12A-n-butanol, film at the oil-water interface due to the alternating protonation/deprotonation of C12A caused by acids and bases. The byproducts, H2O and salt, had an adverse effect on the reversibility of SDS-C12A-ME, with salt having a greater adverse effect than H2O. However, the reversibility of SDS-C12A-ME could be enhanced by suitable acids and bases. For example, for the same oil-in-water (O/W) SDS-C12A-ME, the number of switching cycles with HCl-choline hydroxide (ChOH) as a stimulus can be as large as 11, but only 3 with HCl-NaOH as a stimulus. By using the methyl methacrylate photochemical polymerization as a model, such a pH-switchable SBME can function as a recyclable reaction medium, while the resultant poly(methyl methacrylate) has a considerably reproducible molecular weight and narrow molecular weight distribution (polydispersity index is around 1.2) over three cycles. It is anticipated that the results presented in this work will serve as a reference for the design and fabrication of pH-switched SBMEs and also that such pH-switched SBMEs may have potential applications in practical technological areas such as industrial reaction media, drug delivery, microreactors, etc.

Disassembly of catechyl lignin from castor shells by maleic acid aqueous and production of single catechols

Catechyl lignin (C-lignin) is recognized as a uniform and straight biopolymer that stands out as an exemplary archetype of what is often referred to as "ideal lignin." This difference is due to its unique ability to efficiently depolymerize into a single catechol product. This remarkable property makes C-lignin suitable for further applications and highlights its potential for the production of chemicals. In this study, a protocol utilizing maleic acid aqueous (MAA) was developed for the effective disassembly of coexisting C-lignin and G/S-lignin in castor shells under mild conditions. Thioacidolysis combined with nuclear magnetic resonance (NMR) spectroscopic analyses revealed a significant enrichment of benzodioxane units, without observation of β-O-4 structures from G/S-lignin. The mechanism underlying selective disassembly of coexisting C-lignin and G/S-lignin in castor shells was comprehensive elucidated by analyzing the chemical structure change of benzodioxane and β-O-4 lignin model compounds. Furthermore, the structural characteristics of the disassembled C-lignin were synthetically evaluated, highlighting its narrow molecular weight distribution (Mw = 2432–2763 Da) and high hydroxyl content (aliphatic OH = 7.7–8.4 mmol/g; catechol OH = 5.7–7.5 mmol/g). Compared with the feedstock containing C-lignin and G/S-lignin, the extracted C-lignin sample showed exceptional catalytic activity and selectivity. The results show that the Pd/C-catalyzed hydrogenation reaction mainly produces catechylpropanol compounds (selectivity as high as 97 %).

New insights into the catalyst and cocatalyst pre‐contact process in ethylene copolymerization

AbstractThe influence of pre‐contacting time and temperature as well as mixing intensity on polyethylene copolymerization has been investigated employing DSC, rotational rheometry tests, as well as particle size distribution analysis. For this purpose, a commercial‐supported Ziegler–Natta catalyst has been pre‐contacted with Teal as cocatalyst under different time, temperature, and stirring speed followed by similar polymerization process. It was found that the increase in mixing intensity has no impact on rheological properties; it causes increase in crystallinity percentage of polymer due to better distribution of active centers. Moreover, the pre‐contacting time represents the most impact on catalyst activity and rheology of polymer powder while the pre‐contacting temperature changes is mostly effective on controlling the morphology of polymer. Additionally, the results reveal that 10‐min pre‐contacting of catalyst and Teal under 10°C and stirring speed of 500 rpm was accompanied by highest catalyst activity and lowest content of fine particles.Highlights Pre‐activation was studied under different time and temperature. Adjusting pre‐contacting time influences the polymer morphology. Pre‐contacting under lower temperature results in narrower molecular weight distribution.

Influence of high cis-1,4-liquid polydienes on properties of carbon-black filled composites

High cis-1,4 liquid polybutadiene (cLBR) and polyisoprene (cLIR) with narrow molecular weight distribution were prepared by the chain-transfer coordination polymerization. The effects of cLBR and cLIR on the physical and dynamic mechanical properties of carbon-black filled composites containing single polybutadiene (PBR) or a blend of PBR/polyisoprene (PIR), were investigated. The results showed that cLBR and cLIR effectively ameliorated filler dispersion compared with the treated distillate aromatic extract (TDAE) oil. The wet skid resistance and rolling resistance of vulcanized PBR/PIR composites plasticized with 5 phr cis-1,4 liquid rubbers were significantly improved. Therefore, a new type of plasticizers cLBR and cLIR that are environmental benign and highly compatible with matrix rubbers, has been discovered to replace the conventional TDAE oil used in fabricating the “green” tyres.

Clean and Complete Protein Digestion with an Autolysis Resistant Trypsin for Peptide Mapping.

Peptide mapping requires cleavage of proteins in a predictable fashion so that target protein-specific peptides can be reliably identified and quantified. Trypsin, a commonly used protease in this process, can also undergo self-cleavage or autolysis, thereby reducing the effectivity and even cleavage specificity at lysine and arginine residues. Here, we report highly efficient and reproducible peptide mapping of biotherapeutic monoclonal antibodies. We highlight the properties of a homogeneous chemically modified trypsin on thermal stability, a 54% increase in melting temperature with an 84% increase in energy required for unfolding, an indication of more thermally stable trypsin, >90% retained intact mass peak area after exposure to digestion conditions confirming autolysis resistance, 10× more intensity for intact enzyme compared to trypsin of similar source and narrower molecular weight distribution with LC-MS indicative of low degradation compared to 3 other types of trypsin. Finally, we show the utility of this autolysis-resistant trypsin in characterizing biotherapeutic monoclonal antibodies consistently and reliably showing a >30% reduction in missed cleavage for a short-duration protein digestion time of 30 min compared to heterogeneously modified trypsin of a similar source.

ATRP with ppb Concentrations of Photocatalysts.

In atom transfer radical polymerization (ATRP), dormant alkyl halides are intermittently activated to form growing radicals in the presence of a CuI/L/X-CuII/L (activator/deactivator) catalytic system. Recently developed very active copper complexes could decrease the catalyst concentration to ppm level. However, unavoidable radical termination results in irreversible oxidation of the activator to the deactivator species, leading to limited monomer conversions. Therefore, successful ATRP at a low catalyst loading requires continuous regeneration of the activators. Such a regenerative ATRP can be performed with various reducing agents under milder reaction conditions and with catalyst concentrations diminished in comparison to conventional ATRP. Photoinduced ATRP (PhotoATRP) is one of the most efficient methods of activator regeneration. It initially employed UV irradiation to reduce the air-stable excited X-CuII/L deactivators to the activators in the presence of sacrificial electron donors. Photocatalysts (PCs) can be excited after absorbing light at longer wavelengths and, due to their favorable redox potentials, can reduce X-CuII/L to CuI/L. Herein, we present the application of three commercially available xanthene dyes as ATRP PCs: rose bengal (RB), rhodamine B (RD), and rhodamine 6G (RD-6G). Even at very low Cu catalyst concentrations (50 ppm), they successfully controlled PhotoATRP. Well-defined polymers with preserved livingness were prepared under green LED irradiation, with subppm concentrations ([PC] ≥ 10 ppb) of RB and RD-6G or 5 ppm of RD. Interestingly, these PCs efficiently controlled ATRP at wavelengths longer than their absorption maxima but required higher loadings. Polymerizations proceeded with high initiation efficiencies, yielding polymers with narrow molecular weight distributions and high chain-end fidelity. UV-vis, fluorescence, and laser flash photolysis studies helped to elucidate the mechanism of the processes involved in the dual-catalytic systems, comprising parts per million of Cu complexes and parts per billion of PCs.

Helical Star-Shaped Bottlebrush Polymers: From Controlled Synthesis to Tunable Photoluminescence and Circularly Polarized Luminescence.

The controlled synthesis of star-shaped bottlebrush polymers with tunable topologies is a challenge. However, such materials may exhibit distinct photoluminescence properties. Bottlebrush polymers have polymerization-induced emission (PIE) properties due to their aggregated side chains, and aggregation-induced emission (AIE) is also a unique luminescent property. In this work, we prepared a variety of highly active alkyne Pd catalysts and polymerized poly(L/D-lactic acid) macromonomers containing polymerizable phenylisocyanide groups as end groups to obtain a variety of topologically structured bottlebrush polymers with controllable molecular weights and narrow molecular weight distributions. Bottlebrush polymers with tetraphenyl ethylene (TPE) units as the core exhibit tunable photoluminescence and circularly polarized luminescence properties. We propose that such properties are due to the unique AIE characteristics of the TPE unit combined with the PIE characteristics of the bottlebrush polymer.

Synthesis of well-defined poly(p-alkoxystyrene) by anionic polymerization in the presence of di-n-butylmagnesium

This study demonstrates the necessity of introducing di-n-butylmagnesium (n-Bu2Mg) additives to synthesize precisely controlled polymers through anionic polymerization of p-alkoxystyrene monomers at -40°C. Without additives, 4-tert-butoxystyrene (BSt) and 4-(1-ethoxy ethoxy)styrene (EESt) are polymerized using sec-butyllithium (s-BuLi) in tetrahydrofuran (THF) solvent, yielding a molecular weight distribution (MWD) of 1.36. However, the MWD is strictly controlled to 1.05–1.06 after adding n-Bu2Mg in more than 30 times the amount of s-BuLi, resulting in an accurately designed molecular weight. Therefore, n-Bu2Mg effectively suppresses side reactions that could occur at the polymerization temperature of -40°C in the Schlenk reactor. Interestingly, the polymerization reaction of styrene monomer proceeds when n-Bu2Mg is mixed in THF solvent at -40°C for an extended period, even without s-BuLi. This result suggests that, despite being a weak anionic initiator, n-Bu2Mg can initiate polymerization due to the lower electron density of the styrene double bond compared to BSt or EESt. Based on these results, a precise copolymer with a narrow molecular weight distribution can be synthesized by initiating polymerization with s-BuLi within 20 seconds of adding n-Bu2Mg to the mixed monomers of styrene and EESt.

Miktoarm Star-polypept(o)ide-Based Polyion Complex Micelles for the Delivery of Large Nucleic Acids.

Miktoarm star polymers exhibit a captivating range of physicochemical properties, setting them apart from their linear counterparts. This study devised a synthetic pathway to synthesize cationic miktoarm stars utilizing polypept(o)ides (PeptoMiktoStars), comprising 3 or 6 polysarcosine (pSar) arms (AB3×100, AB6×50, overall 300) for shielding and a cross-linkable poly(S-ethylsulfonyl-l-homocysteine) (pHcy(SO2Et)20) block and a poly(l-lysine) ((pLys)20) block for nucleic acid complexation. Precise control over the DPn and narrow molecular weight distributions (D̵ ≈ 1.2) were achieved for both structures. Both PeptoMiktoStars efficiently complexed mRNA and pDNA into polyion complex micelles (PICMs). AB6-PICMs provided modest (mRNA) to high (pDNA) stability against glutathione and heparin sulfate (HS), while even cross-linked AB3-PICMs were susceptible to HS. All PICMs delivered pDNA and mRNA into D1 cells (over 80%) and Jurkat T cells (over 50%) in vitro. Despite payload- and cell-dependency, AB3 showed overall higher transfection efficiency, while AB6 demonstrated better shielding and enhanced stability.

Silver-Mediated ARGET-ATRP of Reactive Acrylates Using TPMANMe2 Ligand: A Universal Strategy for Controlled Copolymerization.

A controlled polymerization using activated acrylate monomers via ARGET-ATRP is developed with a tris[(4-dimethylamino pyridyl)methyl]amine ligand to address issues with weaker ligands and monomers that can undergo postpolymerization functionalization. This catalyst system enables the polymerization of N-acryloxy succinimide, fluorinated monomers, and isocyanato ethyl acrylate under controlled homogeneous conditions, ensuring linear molecular-weight growth and low polydispersity. Two block copolymerization strategies produce amphiphilic copolymers with narrow molecular-weight distributions and customizable compositions, allowing for various postpolymerization functionalizations.

Living anionic copolymerization of 1,3-pentadiene isomers with alpha-methylstyrene in the presence of 2,2-di(2-tetrahydrofuryl)propane

The synthesis of statistical copolymers of alpha-methylstyrene (AMS) and 1,3-pentadiene (PD) isomers in the presence of 2,2-di(2-tetrahydrofuryl)propane (DTHFP) by living carbanionic polymerization was investigated in this paper. To the best of our knowledge, either AMS or PD monomer was rather difficult to homopolymerize in non-polar solvents without the help of polar additives even at high temperature due to its low ceiling temperature or relatively high electron cloud density of the conjugated CC double bond. However, the combination of RLi initiator and DTHFP regulator (0.1<DTHFP/Li < 0.5) allowed the rapid synthesis of the well-defined poly(AMS-stat-PD) with controlled molar masses (up to 32.5 kDa) and relatively narrow molecular weight distributions (1.10 < ĐMs < 1.52). Calculation of reactivity ratios by the Kelen–Tüdos method suggested that AMS copolymerized much more readily to with (Z)-1,3-pentadiene (ZP) than with (E)-1,3-pentadiene (EP) under the same conditions, whereas the EP/AMS copolymer exhibited much lower dispersity. 1H NMR results indicated that the polymer chain was found to be a mixture of 1,2-addition and 1,4-addition units, in the absence of 3,4-units. Kinetic experiments also showed that the apparent activation energy of EP/AMS copolymerization was slightly higher than that of the ZP/AMS case. To ensure complete conversion of the monomer, the feed ratio of AMS (fAMS) must be controlled to be within 0.3. In addition, the incorporation rate of AMS into the polymer chain increased with the increase in the feed ratio of AMS monomer. DSC curves showed that the Tg of the resulting copolymers increased gradually and could reach up to 25 °C (FAMS = 47). Based on the observation of the anionic statistical copolymerization behavior, an interpretation of the formation mechanism is presented here.

Multi-functional RAFT reagent to prepare fluorescent hyper-branched macromolecular probes for the detection of Fe3+ ions

Reversible addition-fragmentation chain transfer (RAFT) polymerization has the advantages of precise control, high yield, and narrow molecular weight distribution. These merits make it an ideal method for the preparation of hyper-branched fluorescent polymers (FL-HBPs). In this work, a multi-functional RAFT reagent (AVCT-NLP) was prepared for the synthesis of monodisperse FL-HBPs. Firstly, dithionate compound (CN1) containing a CC double bond was synthesized by the reaction of 4-nitrophenol with 1-(bromomethyl)-4-vinylbenzene. Subsequently, the NO2 group on CN1 was reduced to NH2, and the −Br on the 4-bromo-1,8-naphthalic anhydride was substituted to emit fluorescence. Finally, the fluorophore was introduced by the reaction of NH2 with the anhydride on the naphthalene ring to obtain AVCT-NLP which contains fluorophore, dithionate, and CC double bond in one molecule. AVCT-NLP was then used to synthesize the homopolymer (PAVCT-NLP) as both monomer and RAFT reagent. Moreover, PAVCT-NLP served as a macromolecular RAFT reagent, and hydrophilic monomer methacrylic acid (MAA) or 3-butene-1,2-diol were polymerized to obtain amphiphilic hyper-branched polymers (FL-AHBP-1, FL-AHBP-2). All the as-prepared macromolecules (PAVCT-NLP, FL-AHBP-1, and FL-AHBP-2) exhibited specific recognition and high sensitivity for Fe3+. The fluorescence quenching reached up to 74.4 %, with the limit of detection (LOD) as low as 1.82 nM. Additionally, the probe demonstrated pH stability and environmental adaptability. Due to the multi-functional structures of AVCT-NLP, it could be subjected to RAFT polymerization to obtain a monodisperse hyper-branched polymer. All polymers have a high fluorophore density and the polydispersity index (PDI) of the polymer is close to 1.00. This paper provided an effective approach for synthesizing polymer fluorescent probes with versatile structure and fluorescence properties in future applications.

Effect of branch length of cluster dextrin on the textural and rheological properties of κ-carrageenan emulsion gels

In this paper, a range of novel cluster dextrins (CDs) with high molecular weight (∼105 g/mol) and narrow molecular weight distribution were fabricated by α-amylase and branching enzyme (BE, EC 2.4.1.18). The influence of CDs on the physicochemical properties of κ-carrageenan (KC) emulsion gels was investigated. The average particle size of the composite emulsion gels containing CD was decreased by 7.85–12.66 μm, and the gel network was more uniform and denser, owing to stronger non-covalent interactions in the composite sample system. Textural results demonstrated that the composite emulsion gels exhibited higher hardness and springiness, but lower cohesiveness. CDs hindered the formation and aggregation of KC double helices, as evidenced by reducing the intensity of the sulfate group peak at 1223 cm−1. Furthermore, CDs increased the apparent viscosity, storage modulus (G'), and melting temperature (Tm) of emulsion gels, based on rheological results. CDs with longer branch lengths were more prone to entangle with KC chains to optimize the gel structure, exhibiting a more significant effect on the physicochemical properties of emulsion gels. The present study provided a new insight for constructing a new energy delivery system.

A highly efficient oxygen tolerant visible-light mediated RAFT polymerization

Recently, oxygen-tolerant reversible addition-fragmentation chain transfer (RAFT) polymerization has attracted increasing attention in polymer chemistry. Inspired by the monomers containing glycol ethers group have high polymerization rates and even achieved a desirable oxygen tolerance. Herein, we proposed a simple, effective, low-cost, and eco-friendly strategy to accomplish the oxygen-tolerant visible-light activated RAFT polymerization of acrylates and acrylamides in a mixed solution of glycol ether and water at ambient temperature. This photo-mediated RAFT polymerization does not require additives, prior deoxygenation, or inert gas protection. The acrylates and acrylamides with high conversion under irradiation for 2 h, and the resulting polymers were narrow unimodal and narrow molecular weight distributions (PDI<1.3). In addition, the “living” and well-controlled behaviors of this oxygen-tolerant photo-mediated RAFT polymerization were demonstrated through water content in solvents, headspace, initial concentration of monomers, various monomers, chain lengths, light ON/OFF experiment, and high-end group fidelity of block copolymers. This RAFT polymerization also opens up a wide avenue for the industrial production of functional polymeric materials via an in situ chain extension strategy. These results indicate that the mixed solution of glycol ethers and water are effective green media for promoting photo-mediated RAFT polymerization without additives or tedious degassing processes.

RAFT copolymerization of methyl methacrylate and di(ethylene glycol) methyl ether methacrylate in a hexylpyridinium ionic liquid

AbstractSmart polymers undergo significant physical or chemical changes in response to stimuli like temperature and pH. Achieving a narrow molecular weight distribution is crucial for their sensitivity. Reversible addition–fragmentation chain transfer (RAFT) in ionic liquids is an effective method for synthesizing such polymers due to its favorable kinetics and environmental benefits. Most studies use imidazolium ionic liquids, while pyridinium ionic liquids are less common despite their easy synthesis. This study reports the first successful RAFT copolymerization of di(ethylene glycol) methyl ether methacrylate (DEGMEMA) and methyl methacrylate in N‐hexylpyridinium hexafluorophosphate ([HPY][PF6]). Both linear and hyperbranched copolymers (Mn &gt; 25,000) with narrow molecular weight distribution were synthesized, showing observable temperature responses and biocompatibility. The linear copolymers had a desirable dispersity (Ð) of less than 1.10, while the hyperbranched copolymer had a Ð of 2.034. The lower critical solution temperatures (LCSTs) of the copolymers were close to or below the LCST of PDEGMEMA (26°C). This study indicates that pyridinium ionic liquids can be explored as a suitable solvent for synthesizing methacrylate‐based smart polymers.

Jeffamine-based diblock copolymer nanoparticles via reverse sequence polymerization-induced self-assembly in aqueous media

Jeffamines® are commercially available amine-capped poly (alkylene oxides) that have been used for various applications. In this study, a weakly hydrophobic monoamine-capped propylene oxide-rich Jeffamine® (M2005) is derivatized to introduce a trithiocarbonate end-group via amidation. This precursor is then dissolved using N,N′-dimethylacrylamide (DMAC), 2-(N-acryloyloxy)ethyl pyrrolidone (NAEP) or N-acryloylmorpholine (NAM) as a co-solvent to produce a concentrated aqueous reaction mixture containing 20 % w/w water. Subsequently, reversible addition-fragmentation chain transfer (RAFT) polymerization is used to prepare Jeffamine®-core diblock copolymer nanoparticles by reverse sequence polymerization-induced self-assembly (PISA). At intermediate conversion, additional degassed water is added and each polymerization continues to almost full conversion (>99 %) within 4 h at 60 °C, resulting in a 10–20 % w/w aqueous dispersion of sterically-stabilized Jeffamine®-core nanoparticles. Efficient chain extension of the Jeffamine® precursor is achieved in most cases and relatively narrow molecular weight distributions are obtained (Mw/Mn < 1.30) as judged by GPC analysis. Transmission electron microscopy studies confirm a polydisperse spherical morphology and dynamic light scattering studies report hydrodynamic diameters ranging from 145 to 312 nm. Finally, aqueous electrophoresis studies indicate essentially neutral nanoparticles over a wide range of solution pH, as expected for the three types of non-ionic steric stabilizer chains selected for this study.

Advanced Synthesis, Structural Characterization, and Functional Applications of Precision Polymers.

In the realm of biological macromolecules, entities such as nucleic acids and proteins are distinguished by their homochirality, consistently defined chain lengths, and integral sequence-dependent functionalities. Historically, these refined attributes have eluded traditional synthetic polymers, which often exhibit wide variabilities in chain lengths, limited batch-to-batch reproducibility, and stochastic monomer arrangements. Bridging this divide represents a pivotal challenge within the domain of polymer science - a challenge that the burgeoning discipline of precision polymer chemistry is poised to address. Recent advancements have yielded precision polymers that boast prescribed monomer sequences and narrow molecular weight distributions, heralding a new era for developing model systems to decipher structure-property correlations within functional polymers, analogous to those within biological matrices. This review discusses the innovative liquid-phase and solid-phase synthesis techniques for creating precision polymers and the advanced characterization tools essential for dissecting their structure and properties. We highlight potential applications in self-assembly, catalysis, data storage, imaging, and therapy, and provide insights into the future challenges and directions of precision polymers.

Isolation of Polyethylene Glycol with Larger Molecular Weights via Metal-Organic Frameworks.

Polymer products typically present as mixtures with a range of molecular weights, which notably influence the expression of their properties. In this study, a technique is proposed to separate polyethylene glycol (PEG) mixtures of varying molecular weights using metal-organic frameworks (MOFs), thereby narrowing down their molecular weight distribution. Due to the hydrogen bond interactions between PEG and -OH groups in the pores of NU-1000, NU-1000 can selectively adsorb PEG with larger molecular weights from PEG mixture. This separation method consistently yields with narrower molecular weight distribution across multiple cycles. This is the first application of MOFs in regulating the dispersity (Ð) of polymers in solution, providing a novel approach for separating and purifying mixed molecular weight polymers.

Chemically Recyclable Pseudo-Polysaccharides from Living Ring-Opening Polymerization of Glucurono-1,6-lactones.

Recent advances in synthetic methods and monomer design have given access to precision carbohydrate polymers that extend beyond native polysaccharides. In this article, we present the synthesis of a class of chemically recyclable ester-linked pseudo-polysaccharides via the living anionic ring-opening polymerization of glucurono-1,6-lactones. Notably, the pseudo-polysaccharides exhibited defined chain-end groups, well-controlled molecular weights, and narrow molecular weight distributions, all hallmarks of living polymerization. Furthermore, we demonstrate that our approach is modular, as evidenced by tunable glass transition temperatures (Tg) and the ability to produce both amorphous and semicrystalline polymers by adjusting the monomer side chain structure. Lastly, we showcased the complete catalytic chemical recycling of these pseudo-polysaccharides back to the monomers. The flexibility of the polymerization and the recyclability of these pseudo-polysaccharides promote a sustainable circular economy while offering the potential to access polysaccharide-like materials with tunable thermal and mechanical properties.

Fractionation and refining of pectic oligosaccharides derived from onion skins through continuous feed diafiltration

In this work, a diafiltration-based process was investigated for the recovery of pectic oligosaccharides produced by subcritical water hydrolysis from onion skin waste. Four tubular ceramic membranes from 100 to 1 kDa were selected based on the molecular weight of the different galacturonic acid species present in the onion skin hydrolysate. All these membranes showed high selectivity towards pectic oligosaccharides, with low retention for free galacturonic acid, monosaccharides, organic acids, and other impurities. The 50 and 100 kDa membranes completely retained pectic oligosaccharides with a molecular weight exceeding 80 kDa, accounting for approximately 30 % of the initial pectic oligosaccharides in the hydrolysate. However, the purification rate was significantly slower using the 50 kDa membrane due to the increased cake layer resistance. Furthermore, it was examined a fractionation/purification cascade involving sequential diafiltration stages using 100, 10, and 1 kDa membranes at 25 °C, TMP = 1 bar, and a crossflow velocity of 1.5 m s−1. Approximately 87 % of the initial pectic oligosaccharides were successfully recovered and purified in the retentates, highlighting their potential for diverse applications due to their narrow molecular weight distribution, while phenolic compounds and other valuable low molecular weight molecules were recovered in the final permeate.