Narrow Molecular Weight Distribution Research Articles

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.

Well-defined triphenylamine-containing polymers as hole-transporting layers in solution-processable organic light-emitting diodes via living anionic polymerization

In this study, we conducted anionic polymerization of N-[1,1′-biphenyl]-4-yl-N-(4′-ethenyl[1,1′-biphenyl]-4-yl)-9,9-dimethyl-9H-fluoren-2-amine (A) incorporating a triphenylamine group as a hole-transporting unit using sec-butyllithium and potassium naphthalenide as initiators in tetrahydrofuran at −30 ℃ for 10 min. The resultant poly(A)s exhibited controlled molecular weights (Mn = 20.9−126.3 kg/mol) and narrow molecular weight distributions (Mw/Mn ≤ 1.12). The living nature of the propagating chain end of poly(A) was confirmed by postpolymerization. Additionally, block copolymerization of A with styrene (St) and 2-vinylpyridine (2VP) was performed to assess its relative reactivity. Copolymerization resulted in the precise synthesis of well-defined block copolymers with poly(A) segments. Thermal properties of poly(A) were investigated using thermogravimetric analysis and differential scanning calorimetry. Notably, the thermal annealing of poly(A) film at 230 ℃ for 10 min made it insoluble in toluene, indicating its solvent resistance. Thus, poly(A) was used as the hole-transporting layer (HTL) in solution-processable organic light-emitting diodes (OLEDs). A comparative analysis against a reference device containing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) revealed an enhancement in the performance of the OLED comprising thermally annealed poly(A) as the HTL. These results strongly suggest that poly(A) is a promising HTL material for solution-processable OLEDs.

A Bio-Based Tackifier Synthesized by Room-Temperature Cationic Copolymerization of Isobutene and β-Pinene

Whereas the cationic homopolymerization of β-pinene and isobutene (IB) have been extensively studied, their copolymerization is still very scarce, and the conditions under which copolymerization can occur are limited to extremely low temperatures. Moreover, the application of the copolymer has not been reported. Here, a series of room-temperature copolymerizations of β-pinene and IB, using group 13 compounds as catalysts, were conducted. The copolymerizations yielded a low molecular weight (Mn ~ 103) and a narrow molecular weight distribution (Mw/Mn < 2.0) copolymer, with a satisfactory yield at various comonomer feeds, and their glass transition temperature was predictable from the comonomer composition. Furthermore, the tackifying property of the obtained copolymer was investigated using a 180° peel adhesion test. A blend polymer of the copolymer and a styrene-isoprene triblock copolymer showed a high peeling force (0.58 ± 0.14 N/10 mm) and a glass transition temperature low enough for its application as a pressure-sensitive adhesive.

Controlling reversible complexation-mediated polymerization (RCMP) via deep eutectic solvents: fast kinetics, narrow molecular weight distribution and mechanistic insights

Controlling reversible complexation-mediated polymerization (RCMP) via deep eutectic solvents: fast kinetics, narrow molecular weight distribution and mechanistic insights

Highly efficient dual photoredox/copper catalyzed atom transfer radical polymerization achieved through mechanism-driven photocatalyst design

Atom transfer radical polymerization (ATRP) with dual photoredox/copper catalysis combines the advantages of photo-ATRP and photoredox-mediated ATRP, utilizing visible light and ensuring broad monomer scope and solvent compatibility while minimizing side reactions. Despite its popularity, challenges include high photocatalyst (PC) loadings (10 to 1000 ppm), requiring additional purification and increasing costs. In this study, we discover a PC that functions at the sub-ppm level for ATRP through mechanism-driven PC design. Through studying polymerization mechanisms, we find that the efficient polymerizations are driven by PCs whose ground state oxidation potential—responsible for PC regeneration—play a more important role than their excited state reducing power, responsible for initiation. This is verified by screening PCs with varying redox potentials and triplet excited state generation capabilities. Based on these findings, we identify a highly efficient PC, 4DCDP-IPN, featuring moderate excited state reducing power and a maximized ground state oxidation potential. Employing this PC at 50 ppb, we synthesize poly(methyl methacrylate) with high conversion, narrow molecular weight distribution, and high chain-end fidelity. This system exhibits oxygen tolerance and supports large-scale reactions under ambient conditions. Our findings, driven by the systematic PC design, offer meaningful insights for controlled radical polymerizations and metallaphotoredox-mediated syntheses beyond ATRP.

Ultra-high-molecular weight cyclic olefin copolymers with excellent all-round performance prepared via highly effective quasi-living copolymerization

Cyclic olefin copolymers (COCs) are a type of engineering thermoplastics that have excellent transparency, high heat deflection temperature, high tensile modulus, and rigidity, but low elongation (usually below 5 %). Achieving COCs with better mechanical performance, particularly toughness, while maintaining their other properties, is a critical goal that remains a significant challenge. Herein, COCs with an ultra-high-molecular weight (UHMW)—an average molecular weight of up to 2046 kDa—and a relatively narrow molecular weight distribution (Mw/Mn < 1.66), were prepared via a highly efficient, quasi-living catalytic system under mild polymerization conditions. The dependence of the tensile properties, impact properties, wear rate, mean friction coefficient, water vapor transmission rate, and oxygen permeability of the newly obtained COCs on their molecular weight was studied in-depth and compared with those of a commercial COC (Topas 6013, with a molecular weight of 144 kDa). As clearly shown, the obtained UHMW-COCs not only provided satisfactory heat resistance and excellent optical transparency but also demonstrated excellent mechanical performance, tribology behaviors, and barrier properties. Compared with the COCs with lower molecular weight but similar norbornene (NBE) incorporation and optical transmittance, these UHMW-COC samples possessed a higher glass transition temperature, higher tensile strength (up to 73.5 MPa), better elongation at break (6.8 %), better impact strength (4.0 kJ/m2), and a lower wear rate (2 × 10−5 mm3/mN), as well as a lower mean friction coefficient (0.48), lower water vapor transmission rate (0.68 g·mm·m−2·day−1), and lower oxygen permeability (1.60 Barrer). These all-round properties, together with their original advantages, make the UHMW-COCs promising for a broad range of high-end applications.

Particle size effects on silyl‐chromate/VOx/silica bimetallic catalyst for UHMWPE/HDPE in‐reactor blends

AbstractIn this work, four kinds of silica with similar textural properties but different particle size (PS) from 6 to 60 μm were selected as support to prepare silyl‐chromate/VOx/silica bimetallic catalysts for ethylene polymerization, thus making it possible to conduct convincing investigation on the effects of catalyst PS over catalytic behaviors and polymer properties. It is found, owing to mass‐ and heat‐transfer limitations, the catalysts with smaller PS showed higher initial activity, while the deactivation in the later stage was more remarkable. Meanwhile, catalysts with smaller PS synthesized bimodal ultrahigh molecular weight polyethylene/high‐density polyethylene in‐reactor blends (UHMWPE/HDPE IRBs) with higher molecular weight (MW) and narrower molecular weight distribution (MWD). Four PE sample couples with MW increasing from 5 × 105 to 10 × 105 g mol−1 and PS from 40 to 460 μm were selected for tensile and rheological tests. For each couple with similar MW and MWD, the sample with smaller PS always had larger tensile strength and breaking elongation. The cryogenically fractured surface of the samples made by smaller PE particles showed fewer delamination defects and unfused small particles. The rheological results indicate that higher homogeneity was achieved for the sample with smaller PS, which was reflected by the unexpected higher viscosity and storage modulus.

Tri(phenylethynyl)Bismuth: A promising and low-toxic pre-catalyst for stereoselective ring-opening polymerization of rac-lactide

Bismuth-based catalysts have gained attention for their low toxicity and remarkable catalytic activity in the production of biodegradable polyesters. This study introduces, for the first time, the synthesis and thorough characterization of tri (phenylethynyl) bismuth (BiAK3), achieved through 1H and 13C NMR and FTIR spectroscopic analysis. Subsequently, BiAK3 was employed in the ring-opening polymerization (ROP) of rac-lactide (rac-LA). Notably, the addition of alcohol as a co-catalyst facilitated polymerization via a coordination-insertion mechanism, yielding partially isotactic-enriched poly (lactide) (PLA) with a tacticity index of up to 0.67. The kinetic profile of this polymerization was explored through various experimental conditions, highlighting not only the catalyst's performance but also its remarkable control over the polymerization process. Significantly, a linear relationship between molecular weight (Mn) and LA conversion was observed, accompanied by narrow molecular weight distributions (Ɖ). Therefore, our findings highlight the potential of BiAK3 as a bismuth-based pre-catalyst for the control synthesis of biodegradable polyesters, shedding light on its catalytic efficacy and precision in controlling the polymerization.

Effect of tetrahydrofuran on the anionic copolymerization of 4‐trimethylsilylstyrene with isoprene

AbstractThe statistical anionic copolymerization of 4‐trimethylsilylstyrene (TMSS) with isoprene (I) in cyclohexane was investigated using in situ near‐infrared (NIR) spectroscopy in the presence of various amounts of the polar modifier tetrahydrofuran (THF). Polymers with narrow molecular weight distribution of 85–138 kg/mol and dispersities of 1.09–1.22 were obtained. By increasing modifier content, the reactivity ratios can be adjusted over a wide range from rTMSS &lt; rI to rTMSS &gt;&gt; rI. Compared to the system styrene/isoprene (S/I) only a minute amount of modifier (0.5 eq THF relative to lithium) is sufficient to alter the reactivity ratios, resulting in an ideally random copolymerization, which validates the higher reactivity of TMSS compared to styrene. Using these reactivity ratios, molar and volume composition gradients were calculated. Additionally, the glass transition temperature and microstructure of the polyisoprene units were investigated via differential scanning calorimetry and proton nuclear magnetic resonance. The results are encouraging for the use of these materials in high‐end applications like membranes.

Preparation and luminescence properties of polypyrrole-thiophene derivatives

Four kinds of polypyrrole-thiophene derivatives (PPy-Th) are prepared via solution polycondensation using pyrrole, 3-acylpyrrole, and 2-thenaldehyde as monomers. The structure, molecular weight, micromorphology, thermal degradation, ultraviolet-visible absorption, and luminescence performance of the derivatives are investigated by fourier transform infrared (FTIR), hydrogen nuclear magnetic resonance (1HNMR) spectroscopy, gel permeation chromatography (GPC), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis), and fluorescence spectra. FTIR and 1HNMR confirm that the derivatives have been successfully fabricated, and GPC indicates that the derivatives belong to oligomers with narrow molecular weight distribution. For acyl-substituted derivatives, the microstructures are mainly lamellar accumulation. Furthermore, under ultraviolet excitation, the derivatives can produce blue or green light emission, corresponding to the transitions of large π electrons in the conjugated structure of the molecular chains. Especially, the maximum emission wavelengths and Stokes shifts of the acyl-substituted derivatives are markedly larger than that of the non-acyl-substituted derivatives. The fluorescence quantum yield and band gap of the PVT are 4.46% and 2.01 eV, respectively. The fabricated PPy-Th can be used as luminescent materials in the development and application of polymer light-emitting diodes.

Synergy of metallic Co and oxygen vacancy sites in Co/Ce-MOF catalysts for efficiently promoting lignin derived phenols and macromolecular lignin hydrodeoxygenation

The enhanced utilization of biomass-derived chemicals for the generation of high value aromatics through an advanced catalytic strategy has captured considerable attention within the realm of eco-friendly manufacturing. This work presented four innovative three-dimensional rod-shaped mesoporous Ce-based MOF materials, which were coupled with a H-donor solvent to facilitate vanillin hydrodeoxygenation and macromolecular lignin. Under the optimized conditions (30 mg CoCe@C catalyst, 2 MPa N2 pressure, 15 mL isopropanol, 190 °C, and 5 h), the CoCe@C catalyst achieved nearly complete conversion of vanillin and demonstrated 87.8 % selectivity in the hydrogen-donor solvent. The characterization findings suggested that the synergy between metallic Co and oxygen vacancy sites enabled the effective activation of CHO group in vanillin, leading to formation of reactive product MMP. In addition, the optimal CoCe@C catalyst could also achieve macromolecular lignin hydrodeoxygenation to obtain high yield of lignin oil products with narrower molecular weight distribution. This study presented a viable approach for the concurrent utilization of lignin derivatives in the generation of high value fuels and chemicals.

Inorganic polymers as drug carriers: opportunities and challenges

Innovative methods and significant developments in designing new synthetic inorganic materials have been used to overcome limitations of current drug delivery systems. Inorganic polymers are widely used in the field of biomedicine, imaging, tissue engineering and drug delivery because of their bioactivity, biocompatibility, and stability. A few of the more well-known wholly inorganic polymers are portland cement, silicon dioxide, polyanionic glasses (including titania- and aluminosilicate glasses), poly(sulphur nitride), polycrystalline diamond, graphite, poly(sulphur nitride), and alumi¬num-silicate materials. Inorganic polymers, especially those possessing significant porosity, are good potential candi¬dates for the delivery of several drugs (anticancer, antibiotics, and anti-inflammatories), providing advantages such as encapsulation, controlled delivery, and improved targeting of drugs. Choosing a suitable drug carrier with a selec¬tive targeting potential also seems to be a very promising way for improving stability as well as selectivity. Despite all the advances, developing homogeneous inorganic polymers with narrow molecular weight distributions is a multidis¬ciplinary challenge. The current keynote speech provides a review of the opportunities and challenges of using inor¬ganic polymers as drug carriers.

Efficient synthesis of high vinyl polybutadiene based on continuous flow microchannel reactor

AbstractThe traditional batch synthesis of liquid rubber faces issues such as low monomer polymerization concentration, poor uniformity of the reaction system, and inadequate heat dissipation, resulting in an unsatisfactory synthesis efficiency. This study presents a method for the rapid and efficient synthesis of high vinyl 1,2‐polybutadiene liquid rubber using butadiene as the monomer and n‐butyllithium as the initiator. By applying continuous flow microchannel reactors, the limitation of traditional synthesis method can be overcome. The addition of a modifier in the raw material promotes the formation of high vinyl structure. The preparation of liquid rubber requires the addition of a large amount of metal lithium initiator. However, for aerospace sealants, there is a requirement for low metal ion content. To address this, we employed different methods to reduce the metal ion content in the liquid rubber and increase its purity. Ultimately, we achieved the synthesis of high‐purity polybutadiene liquid rubber with 1,2‐vinyl content exceeding 88%, narrow molecular weight distribution, and tunable molecular weights. This research will provide technical guidance for the industrial application of polybutadiene synthesis in continuous flow microchannel reactors.

Extraction and Isolation of Two Polysaccharides from Chloranthus japonicus Sieb. and Evaluation of Their Anti-Gastric Cancer Activities.

Two unreported heteropolysaccharides, denoted as YCJP-1 and YCJP-2, were isolated from the herbs of Chloranthus japonicus. YCJP-1 was a heteropolysaccharide composed of glucose, galactose, arabinose, mannose, rhamnose, and a minor proportion of uronic acids, with the molecular weight mainly distributed in the 74,475-228,443 Da range. YCJP-2 was mainly composed of glucose, mannose, and galactose, with the molecular weights ranging from 848 to 5810 Da. To further evaluate the anti-gastric cancer effects of C. japonicus, the inhibitory effects of the crude polysaccharide (YCJP) and the purified polysaccharides (YCJP-1 and YCJP-2) were determined using a CCK-8 assay and colon-forming assay on MGC-803 and AGS gastric cancer cell lines. Our results showed that YCJP, YCJP-1, and YCJP-2 possess prominent inhibitory effects on the proliferation of MGC-803 and AGS cells, and the AGS cell was more sensitive to YCJP, YCJP-1, and YCJP-2. Moreover, YCJP-2 demonstrated superior anti-gastric cancer effects compared to YCJP-1. This could potentially be attributed to YCJP-2's higher glucose content and narrower molecular weight distribution.

Easy Synthetic Access to High‐Melting Sulfurated Copolymers and their Self‐Assembling Diblock Copolymers from Phenylisothiocyanate and Oxetane

AbstractAlthough sulfurated polymers promise unique properties, their controlled synthesis, particularly when it comes to complex and functional architectures, remains challenging. Here, we show that the copolymerization of oxetane and phenyl isothiocyanate selectively yields polythioimidocarbonates as a new class of sulfur containing polymers, with narrow molecular weight distributions (Mn=5–80 kg/mol with Đ≤1.2; Mn,max=124 kg/mol) and high melting points of up to 181 °C. The method tolerates different substituent patterns on both the oxetane and the isothiocyanate. Self‐nucleation experiments reveal that π‐stacking of phenyl substituents, the presence of unsubstituted polymer backbones, and the kinetically controlled linkage selectivity are key factors in maximising melting points. The increased tolerance to macro‐chain transfer agents and the controlled propagation allows the synthesis of double crystalline and amphiphilic diblock copolymers, which can be assembled into micellar‐ and worm‐like structures with amorphous cores in water. In contrast, crystallization driven self‐assembly in ethanol gives cylindrical micelles or platelets.

Easy Synthetic Access to High-Melting Sulfurated Copolymers and their Self-Assembling Diblock Copolymers from Phenylisothiocyanate and Oxetane.

Although sulfurated polymers promise unique properties, their controlled synthesis, particularly when it comes to complex and functional architectures, remains challenging. Here, we show that the copolymerization of oxetane and phenyl isothiocyanate selectively yields polythioimidocarbonates as a new class of sulfur containing polymers, with narrow molecular weight distributions (Mn=5-80 kg/mol with Đ≤1.2; Mn,max=124 kg/mol) and high melting points of up to 181 °C. The method tolerates different substituent patterns on both the oxetane and the isothiocyanate. Self-nucleation experiments reveal that π-stacking of phenyl substituents, the presence of unsubstituted polymer backbones, and the kinetically controlled linkage selectivity are key factors in maximising melting points. The increased tolerance to macro-chain transfer agents and the controlled propagation allows the synthesis of double crystalline and amphiphilic diblock copolymers, which can be assembled into micellar- and worm-like structures with amorphous cores in water. In contrast, crystallization driven self-assembly in ethanol gives cylindrical micelles or platelets.

A new radical initiation for the ring-opening polymerization of tetrahydrofuran with a radical substitution mechanism

A new radical-Lewis acid system has been discovered to achieve the ring-opening polymerization of tetrahydrofuran. Different types of reaction mechanisms were discovered for the initiation and polymerization processes. The proposed initiation mechanism was studied by MALDI-TOF and ESI-MS as a radical substitution mechanism and polymerization was a coordination-insertion mechanism. And polytetrahydrofuran with high molecular weight (Mn = 14.6 × 104 g mol−1) and narrow molecular weight distribution (PDI = 1.44) could be obtained.