Molecular Weight Mn Research Articles

Integration of Neural Networks and First-Principles Model for Optimizing l-Lactide Branched Polymerization.

Addressing the growing demand for sustainable materials, this research paves the way for the efficient consumption and sustainable production of branched polylactide (PLA). A novel hybrid modeling approach combines first-principles (FP) model with artificial neural network (ANN) for ring-opening polymerization (ROP). The hybrid ANN, trained with FP model data, demonstrated optimal performance with a hidden layer of 20 neurons, achieving a root mean square error (RMSE) of 0.004 and a regression coefficient (R2) of 0.99. The hybrid model accurately predicted key polymer properties, including average molecular weights (Mn and Mw), polydispersity index (PDI), degree of branching (DB), monomer conversion, and polymerization time. Validation was performed on various branched PLA compositions (PLLH80, PLLH94, and PLLH97). Multiobjective optimization (MOO) using NSGA-II showed strong agreement between FP model and hybrid ANN across six case studies, highlighting their effectiveness in predicting polymerization outcomes.

Study on the Mechanical and Thermal Properties and Shape Memory Behaviors of Blends of Bio-Based Polybenzoxazine and Polycaprolactone with Different Molecular Weights

In this research, blends of bio-based polybenzoxazine (V-fa) and polycaprolactone (PCL) with different molecular weights (Mn) (14,000, 45,000, and 80,000 Da) were prepared with varying PCL content from 10 to 95 wt%. The spectra measured using Fourier Transform Infrared Spectroscopy (FTIR) may indicate the presence of hydrogen bonding between two polymeric components. The thermograms obtained using a Differential Scanning Calorimeter (DSC) and dynamic mechanical analyzer (DMA) exhibited a shift in glass transition temperature (Tg), which indicated partial miscibility between V-fa and PCL. The thermograms obtained using a thermogravimetric analyzer (TGA) revealed that the addition of PCL led to an increase in the maximum decomposition temperature (Tdmax). The tensile strength and modulus decreased with an increase in PCL, thus indicating a decrease in brittleness. Interestingly, only the samples with an Mn of 80,000 Da were bendable. The blends with 80 wt% PCL were revealed to have shape memory behaviors with a shape fixity of approximately 81%. The shape recovery ratio of the blends with 95 wt% PCL was approximately 78%.

Synthesis Characterization and Physicochemical Properties of Rigid Alicyclic Polyimide Films Based on Bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic Dianhydride.

Four polyimides based on bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTD), BTD-MIMA, BTD-HFA, BTD-FND, and BTD-TPM, with different rigid substituted diamines were synthesized. The chemical structure of the polyimides was corroborated by 1H NMR spectroscopy. These polyimides were soluble in organic solvents and presented molecular weights (Mn) between 39 and 70 KDa. BTD-MIMA, BTD-HFA, BTD-FND, and BTD-TPM showed thermal stability above 400 °C. These polyimides also presented high glass transition temperatures between 272 and 355 °C. The alicyclic moiety increased solubility compared with other rigid polyimides. Membrane films from BTD-MIMA and BTD-HFA exhibited the highest gas permeability compared to BTD-FND and BTD-TPM. The introduction of ortho-substituents in BTD-MIMA or bulky -CF3 groups in BTD-HFA, in combination with the alicyclic dianhydride fragment, prevented chain packing and enhanced macromolecular chain rigidity. In turn, there was a shift toward higher gas permeability coefficients for BTD-MIMA and BTD-HFA, with a moderate loss of CO2/N2 and CO2/CH4 selectivity, and they presented similar selectivities to those of other reported polyimides with alicyclic BTD moieties containing asymmetric fragments.

Highly Active and Stereoselective Ring‐Opening Polymerization of Racemic Lactide Over HTGCP Catalysts

ABSTRACTDespite the extraordinary success has been achieved in metal catalyst‐promoted stereoselective ring‐opening polymerization (ROP) of rac‐lactide (rac‐LA), well‐controlled stereoselective rac‐LA ROP by organic catalyst still remains a scientific challenge. In this study, we showcase the remarkable ability of the phosphazene base 2,2,4,4,6,6‐hexa(tetramethyl‐guanidyl)‐1,3,5,2λ5,4λ5,6λ5‐cyclictri(phosphazene) (HTGCP) to facilitate the stereoselective ROP of rac‐LA at low temperatures, yielding isotactic stereoblock poly (lactic acid) (PLA) with a stereoselectivity index (Pm) up to 0.86. Furthermore, by harnessing the synergy between HTGCP and a (thio)urea, both high stereoselectivity (Pm up to 0.85) and remarkable catalytic activity (> 99% monomer conversion within an hour) can be achieved at ambient temperature. Notably, upon decreasing the temperature to −20°C, an even higher degree of regularity is attained (Pm up to 0.91). The direct linear correlation between molecular weights (Mn), monomer conversions, and the narrow dispersity (Đ) of the resulting polymers, coupled with their high end‐group fidelity, underscores the meticulous control exerted over the polymerization. Based on these findings, we propose that the chain end control mechanism underlies the synthesis of isotactic stereoblock PLA from rac‐LA in the presence of HTGCP, offering a novel and efficient pathway to produce high‐performance PLA materials.

Antibacterial, Transparency, and Mechanical Properties of Cationic Radical Initiator Triggered Polystyrene Sheets Obtained by Thermal Blending.

Polystyrene (PS) is widely used because of its transparency, mechanical strength, and ease of production. With rising health concerns, antibacterial PS is increasingly sought after, but few polymer-based antibacterial agents have been prepared to date. In this study, polystyrene was synthesized using a cationic radical initiator, 2,2'-azobis-[2-(1,3-dimethyl-4,5-dihydro-1H-imidazol-3-ium-2-yl)] propane triflate (ADIP), and evaluated as an antibacterial additive. The PS polymerized with ADIP (ADIP-PS) was prepared with number-average molecular weights (Mn) from 15,000 to 40,000. Further, blending 5-10% ADIP-PS with an Mn of 23,000 into general-purpose polystyrene (GPPS) provided antibacterial activity against Staphylococcus aureus while maintaining the transparency and strength of GPPS. Surface analysis revealed hydrophilic properties and exposed cationic groups, as confirmed by contact angle measurement and anionic dye titration, respectively. In addition, the antibacterial activity increased with higher cationic group concentrations, particularly at lower molecular weights. This method presents a promising approach to introducing antibacterial properties to PS products.

Regulating Entanglement Networks of Fibrillatable Binders for Sub-20-µm Thick, Robust, Dry-Processed Solid Electrolyte Membranes in All-Solid-State Batteries.

Despite significant advancements in all-solid-state batteries (ASSBs), the reliance on thick solid electrolyte (SE) membranes hinders their commercial viability. Although the dry process using polytetrafluoroethylene (PTFE) binder is proposed for thin SE membranes, a comprehensive understanding of the correlation between PTFE fibrillation and SE membrane quality remains lacking. Here an important guidance is provided for producing durable SE membranes that can be reduced to sub-20-µm thickness by regulating the entanglement networks of PTFE. While establishing fabrication parameters; shear time and shear temperature, a dominant effect of the number-average molecular weight (Mn) on PTFE fibrillation is revealed for the first time. Moreover, the degree of PTFE fibrillation is quantified using systematic X-ray diffraction (XRD) analysis. The SE membrane utilizing the high-Mn PTFE binder that achieves a maximum fibrillation degree (≈98%) and thus forms highly entangled fibrous PTFE network interweaving SE particles, exhibited superior toughness. Consequently, the 18 µm thick SE membrane with 0.5wt% high-Mn PTFE shows a considerably higher areal conductance. The ASSB using this durable, ultrathin SE membrane outperforms its counterparts that used flimsy SE membranes or pure SE pellets. Finally, uniquely thin ASSBs demonstrate significantly improved cell-level energy densities, showcasing the promising potential for practical ASSB fabrication.

Preparation of Lipid–Polymer Conjugates by Photoiniferter Polymerization and Application to Cell Surface Modification

ABSTRACTThe growing demand for lipid–polymer conjugates (LPCs) in biomedicine highlights the need for efficient synthesis methods. This study presents a novel Y‐type photoiniferter reagent (Lipid‐PIT) with a diethyldithiocarbamate group and a diacylglycerol group. Lipid‐PIT efficiently initiated the polymerization of vinyl monomers such as oligo(ethylene glycol) methacrylate (OEGMA), N,N‐dimethylacrylamide (DMA), tert‐butyl acrylate (tBA), and n‐butyl acrylate (nBA) under UV irradiation at room temperature, yielding LPCs. Proton NMR confirmed the presence of diethyldithiocarbamate and diacylglycerol moieties at the chain ends. The polymerization kinetics of DMA showed a linear increase in molecular weight (Mn) with time, with a polydispersity (Đ) below 1.50, demonstrating high controllability. Moreover, Lipid‐PIT allows for the creation of block copolymers via secondary chain extension. In vitro assays revealed that LPCs synthesized from OEGMA monomers successfully modified L929 and HeLa cell surfaces and exhibited good biocompatibility. This study offers a rapid, efficient method for LPC synthesis with promising biomedical applications.

Impact of molecular architecture and draw ratio on enhancement of targeted mechanical properties of machine direction oriented polyethylene films produced after blown film extrusion

Conventional multi-material multi-layer flexible packaging offers excellent properties. However, it has recycling challenges, necessitating a shift to mono-material multi-layer flexible packaging for example all-polyethylene (PE) packaging which can be tailored through various synthesis and processing methods for different layers. In this work, we study how the key molecular properties (number-average molecular weight ( Mn), weight-average molecular weight ( M w), molecular weight distribution (MWD), comonomer content (short chain branching)) and machine direction orientation (MDO) process draw ratio (MDX) influence the final morphology and mechanical properties of MDO-PE films which are intended as the outer layer of mono-material all-polyethylene multi-layer flexible packaging. Five PE grades and various blends were extruded and blown into films. Selected blown films were machine direction oriented to obtain the final MDO-PE films. Furthermore, one selected PE blown film was processed at different MDO process draw ratios while keeping other process parameters constant. From the molecular properties point of view, the higher molecular weight fractions provide a higher possibility for uniform stretching whereas lower molecular weight fractions provide a higher natural draw ratio and therefore higher modulus and stiffness enhancement. Further, the results show that increasing MDO process draw ratio leads to more fibrillation and increased crystallinity. Consequently, the tensile modulus and stiffness at the higher draw ratios increase as well and are comparable to conventionally used polymers in outer layers of multilayer flexible packaging. Thus, this work demonstrates that MDO-PE films with enhanced modulus can provide sufficient stiffness for the design of outer layer of mono-material multi-layer all-PE packaging which presents higher potential for mechanical recyclability.

Comparison and Optimization of Three Extraction Methods for Epimedium polysaccharides

Epimedium is used in traditional Chinese medicine. Epimedium polysaccharides have a variety of physiological properties. This study compared three different processes for the extraction of polysaccharides from Epimedium spp., including ultrasonic, aqueous enzymatic, and microwave extraction, to optimize the extraction conditions and determine the optimal extraction method. The optimal parameters for each method were analyzed. The results showed that the optimal process for ultrasonic extraction was an ultrasonic power of 250 W, an extraction time of 60 min, a temperature of 50 °C, and a solid–liquid ratio of 1:35. The optimal conditions for the aqueous enzymatic method were a papain concentration of 70 U/mL, extraction time of 70 min, a temperature of 50 °C, and a material-to-liquid ratio of 1:30, while those for microwave extraction were a microwave power of 650 W, an extraction time of 50 min, a temperature of 40 °C, and a material-to-liquid ratio of 1:25. The polysaccharide yields were 4.85%, 4.72%, and 3.98% for the three methods, respectively, indicating that ultrasonic extraction resulted in the highest yield of polysaccharides from Epimedium brevicornum. After purification with DEAE-cellulose, the polysaccharide yields were 4.13%, 3.67%, and 3.12%, respectively. A comprehensive comparison demonstrated the superiority of the ultrasonic extraction method in terms of both extraction yield and purification efficiency. Characterization of the extracted Epimedium polysaccharides showed the presence of five monosaccharides, i.e., glucose, galactose, mannose, galacturonic acid, and rhamnose, and a number average molecular weight Mn of 1.65 × 105 Da and weight average molecular weight Mw of 6.61 × 105 Da. These results provide a scientific basis for the in-depth study and application of Epimedium polysaccharides.

Enzymatic synthesis of aromatic biobased polymers in green, low-boiling solvents

Given the urge to accelerate the substitution of petrol-derived solvents not only in more traditional fields like pharmaceuticals, personal care, or electronics but also in innovative research processes, this work focuses on the utilisation of four biobased solvents as media for the enzymatic synthesis of aliphatic-aromatic polyesters. As building blocks, the lignin-derived diethyl-2,4-pyridinedicarboxylate was selected as the potentially biobased, aromatic component while more classical diols such as 1,4-butanediol and 1,8-octanediol were used as the aliphatic portion. Results show that among the tested green solvents (cyclohexanone, phenetole, anisole and eucalyptol), the most suitable medium for lipase B from Candida antarctica-catalysed polycondensation reactions was eucalyptol that allowed reach monomer conversions >95 % and number average molecular weights up to 3500 g·mol−1. On the other hand, cyclohexanone led to the lowest monomer conversions (<80 %) and molecular weights (Mn<500 g·mol−1) confirming once again the unsuitability of ketone-containing solvents for enzymatic esterification and transesterification reactions. The lipase could be used up to three times, in eucalyptol as a solvent, without a significant decrease in monomer conversion or molecular weight.

Influence of Molecular Weight and End Groups on Ion Transport in Weakly and Strongly Coordinating Polymer Electrolytes

AbstractIn the development of polymer electrolytes, the understanding of the complex interplay of factors that affect ion transport is of importance. In this study, the strongly coordinating and flexible poly (ethylene oxide) (PEO) is compared to the weakly coordinating and stiff poly (trimethylene carbonate) (PTMC) as opposing model systems. The effect of molecular weight (Mn) and end group chemistry on the physical properties: glass transition temperature (Tg) and viscosity (η) and ion transport properties: transference number (T+), ion coordination strength and ionic conductivities were investigated. The cation transference number (T+) showed the opposite dependence on Mn for PEO and PTMC, decreasing at low Mn for PTMC and increasing for PEO. This was shown to be highly dependent on the ion coordination strength of the system regardless of whether the end group was OH or if the chains were end‐capped. Although the coordination is mainly of the cations in the systems, the differences in T+ were due to differences in anion rather than cation conductivity, with a similar Li+ conductivity across the polymer series when accounting for the differences in segmental mobility.

Exploring the impact of poly(sodium styrene sulfonate) dispersants’ architecture on their performance in coal water slurry preparation

In this work, the architecture of poly(sodium styrene sulfonate) (PSSNa) dispersants were flexibly tailored by various strategies. Three categories of PSSNa dispersants with different topologies were obtained, namely, linear structured PSSNa (1-A-PSSNa), three-arm star PSSNa (3-AS-PSSNa) and six-arm star PSSNa (6-AS-PSSNa). The molecular weights (Mn) of these dispersants were adjusted in the range of 3200–26,200 g/mol by varying the feeding ratio of monomer to initiator. In addition, the polydispersity index (PDI) of resultant dispersants were also varied by using different polymerization technologies, such as atom transfer radical polymerization (ATRP) and conventional free radical polymerization technique (RP). Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) verified these architecture parameters of resultant PSSNa dispersants. Afterwards, the impact of these architectural factors on the performance of PSSNa dispersants in coal water slurry (CWS) preparation were evaluated. The results revealed that with the Mn of dispersants increased from 9800 to 26,200 g/mol, the apparent viscosity of CWS increased by around 11 %. The comparison between dispersants with approximate Mn (26,200 and 26,900 g/mol) and very different PDI (1.27 and 2.25) indicated that wide PDI are favourable for the performance. This work also confirmed that the topology of dispersants has a significant impact on their performance. The maximum coal loaded can increase from 63.9 % to 64.3 % when 1-A-PSSNa dispersant was replaced by 6-AS-PSSNa. Meanwhile, these architectural factors have a limited impact on the fluid type of CWSs, as all CWSs obtained in this work were pseudoplastic fluids regardless of the used dispersants. The potential mechanism was investigated using various technologies, such as the measurements of zeta potentials, contact angles, and low-field nuclear magnetic resonance spectra. The results revealed that topologizing did not alter the interaction between dispersant and coal surface. However, due to the special features of topological polymers, they can grant adsorbed coal particles with enhanced electrostatic repulsion and steric hindrance, which facilitated the dispersion of coal particles.

Ultrasonic-assisted extraction, structural analysis and antioxidative mechanism of polysaccharide from sunflower disc

The crude sunflower disc polysaccharide (SDP) was obtained by using ultrasonic assist hot water extraction. Homogeneous SDP was separated by DEAE-cellulose column and Sephacryl S-400 HR column. Its physical properties and antioxidant mechanism was studied. Results showed that extraction yield of SDP was 15.3 %, total sugar was 91.3 %, weight molecular weight (Mw) was7.46 × 103 Da, number-average molecular weight (Mn) was 6.16 × 103 Da and polydispersion coefficient (Mw/Mn) was 1.21. SDP was composed of galactose (Gal), fucose (Fuc), xylose (Xyl), glucose (Glc), arabinose (Ara), rhamnose (Rha), glucuronic acid (Gle-UA) and galacturonic acid (Ga-UA), and the ratio of substance were 1.77∶2.00∶4.55∶8.44∶9.57∶14.26∶2.13∶57.28. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results showed that smooth surface and structure of SDP was relatively dense, and some crystallization existed, but the crystallization was weak. Two-dimensional structure of SDP showed that the main chain →4)-α-d-GalpA-(1→, →3)-α-l-Araf-(1→, →2)-α-l-Rhap-(1→, →2, 4)-α-l-Rhap-(1→, →2, 4)-α-d-GlcpA-(1→ and →3, 6)-β-d-Galp-(1→ interconnection form. Results of in vitro and in vivo of SDP and its derivatives showed that a good antioxidant activity. In vitro antioxidant activity, the scavenging rates of ABTS+, ·OH, DPPH and superoxide anions were 95.8 %, 93.9 %, 93.6 % and 92.1 %, respectively, when treated with 3.2 mg/mL of SDP solution. The preliminary antioxidative mechanism results showed that SDP had a regulatory effects on the down-regulation of Nrf2, HO-1 and NQO1 proteins in RAW264.7 cells. Preliminary pharmacokinetic analysis showed that the SDP could be absorbed orally and reached its peak concentration in the blood at about 2 h. The content of polysaccharide in blood reached the peak value at 30 min and reached the lowest value at 8 h after intravenous injection.

Synthesis of renewable and seawater-degradable polyesters based on a fully biobased diester

The design and development of biobased plastics that can degrade in seawater is a potential approach to address the seawater pollution of fossil plastics. Herein, N,N'-pentamethylene-bis(pyrrolidone-4-methyl carboxylate) (PBPC), a biobased diester with two pyrrolidone rings, was synthesized from renewable 1,5-pentanediamine and dimethyl itaconate. PBPC was polymerized with three α,ω-diols to prepare biobased homopolyesters with number-average molecular weight (Mn) around 25 kDa. These amorphous homopolyesters presented remarkable UV shielding abilities compared with poly(lactic acid) (PLA) and poly(butylene succinate) (PBS). Incubation experiments in artificial seawater for 150 days indicated that the homopolyesters based on PBPC exhibited rapid seawater-degradability. Then, PBPC was copolymerized with 1,4-butanediol and terephthalic acid to prepare a series of copolyesters with Mn around 20 kDa. The introduction of PBPC into poly(butylene terephthalate) (PBT) resulted in the elevated toughness and sensitivity to seawater degradation. Depending on the composition of PBPC, the thermal, mechanical, and degradation rate of the copolyesters were adjustable. Overall, the PBPC-based polyesters are promising alternatives to commercial packaging materials in improving the renewability of raw materials and achieving seawater degradation.

Structural characterization and hypolipidemic activity of a natural polysaccharide from Suaeda salsa L.

Herein, the identification and analysis of a newly discovered hypolipidemic polysaccharide extracted from Suaeda salsa L., SS3-N1, is reported. The weight-average molecular weight (Mw), number-average molecular weight (Mn), and dispersity (Ð) of SS3-N1 were determined to be 45.50 kDa, 34.21 kDa, and 1.33, respectively. This polysaccharide primarily consists of galactose (50.80 %) and arabinose (30.70 %), with lower proportions of xylose, mannose, guluronic acid, rhamnose, glucuronic acid, ribose, and fucose. Methylation and NMR analyses indicated that its backbone was primarily composed of R → 3,6)-β-D-Galp-(1 → R and R → 5)-α-L-Araf-(1→ residues. The sugar units at the reducing and nonreducing ends were identified as R → 4)-β-D-Xylp-(1 → R and R → 3)-β-D-Galp-(1 → R, respectively. In addition, α-L-Araf (1 → R side branches were incorporated at the C-3 position of R → 3,6)-β-D-Galp-(1 → R. At 100 μg/mL, SS3-N1 surpassed the lipid-lowering efficacy of the positive control, atorvastatin (0.4 μM), in an egg yolk powder (EYP)-induced hyperlipidemic zebrafish model. This effect may be attributed to the modulation of cholesterol metabolism due to the upregulation of nrf2, ho-1, ampk, ppara, and cyp7a1 gene expression and the downregulation of acaca and hmgcr gene expression. Such dual gene regulation inhibits fatty acid and cholesterol synthesis, suggesting potential applications for the natural hypolipidemic polysaccharide derived from S. salsa L.

Design of flexible polyethylene glycol-based phase change materials by crystal structure regulation

The design of flexible phase change materials (FPCMs) with polyethylene glycol (PEG) as phase change components remains a great challenge due to high crystalline structure makes for high thermal energy storage ability yet deteriorates mechanical toughness. Herein, the preparation strategy of FPCMs was developed by introducing crystal structure regulators (CSRs) in PEG-based FPCM networks in a form of covalent linkages. The hydroquinone CSR had the strongest ability of crystal structure regulation over FPCMs compared to the three other used CSRs. The FPCMs had tuneable phase change temperatures (−2.0 °C–49.7 °C) and enthalpies (40.7 J g−1 to 109.3 J g−1) depending on the number-average molecular weight (Mn = 4000 Da, 6000 Da) of PEGs used as well as the content and type of CSRs, further enabling tuneable mechanical stress (0.59–15.61 MPa) and strain (5.74%–505.86 %). Compared with the pristine PEGs, the FPCMs yielded excellent shape stability, thermal stability and thermal reliability. The flexibility and phase change properties endowed the FPCMs with excellent self-adaptability and shape memory function. The innovative strategy towards FPCMs highlights the application potential on individual wearable temperature-controlled devices.

Recyclable Polythioesters and Poly(thioester-co-peptoid)s via Ring-Opening Cascade Polymerization of Amino Acid N-Carboxyanhydrides.

Polythioesters (PTEs) are emerging sustainable polymers for their degradability and recyclability. However, low polymerizability of monomers and extensive side reactions often hampered the polymerization process. Moreover, copolymers containing both thioester and other types of functional groups in the backbone are highly desirable but rarely accomplished owing to several synthetic challenges. Here, we report the ring-opening cascade polymerization (ROCAP) of N-(2-(acetylthio)ethyl)-glycine N-carboxyanhydrides (TE-NCA) to afford recyclable PTEs and unprecedented poly(thioester-co-peptoid)s (P(TE-co-PP)s) in a controlled manner. By developing appropriated carboxylic acid-tertiary amine dual catalysts, intramolecular S-to-N acyl shift is coupled into the ROCAP process of TE-NCA to yield products with dispersity below 1.10, molecular weight (Mn) up to 84.5 kDa, and precisely controlled ratio of thioester to peptoids. Random copolymerization of sarcosine NCA (Sar-NCA) and TE-NCA gives thioester-embedded polysarcosine with facile backbone degradation while maintaining the water solubility. This work represents a paradigm shift for the ROP of NCAs, enriches the realm of cascade polymerizations, and provides a powerful synthetic approach to functional PTEs and P(TE-co-PP)s that are otherwise difficult or impossible to make.

Alteration of the upper critical solution temperature (UCST) behavior of the nonionic polymer poly(N-acryloyl-nipecotamide) by its terminal group

Influences of the terminal group of non-ionic polymer with upper critical solution temperature on cloud points (CPs) has been one of curious research topics, however, detailed investigation has not been conducted so far. This study investigates the effect of the terminal group of poly(N-acryloyl-nipecotamide)s (PNANAms) on their CPs in aqueous solution. PNANAms with different molecular weights (Mn) ranging from 4,100 to 34,300 and different terminal end groups were successfully synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. The temperature-dependent optical transmittance of aqueous solutions of the PNANAms revealed that their CP was influenced by their terminal group, in addition to their Mn and polymer concentration. PNANAms with low Mn (Mn ≥ 7,500) and a hydrophobic (dodecyl) terminal group exhibited poor solubility, whereas PNANAms with a moderate Mn (Mn ≤ 10,200) and hydrophilic (maleimide or carboxylic) terminal groups were readily soluble in aqueous solution. However, PNANAms with a high Mn (Mn = 34,300) were hardly soluble in aqueous solution. The poor solubility of such PNANAms suggests that strong inter- and intramolecular hydrogen bonds were formed among the polymer chains, increasing their CP. PNANAm with a low Mn (Mn = 4,100) and the hydrophobic terminal and that with a moderate Mn (13,200 ≤ Mn ≤ 18,200) and hydrophilic terminal groups exhibited CPs in aqueous solution. The CP of PNANAms with carboxylic terminal groups was also influenced by the solution pH owing to the deprotonation of these groups. The size of polymeric aggregates was directly observed using phase-contrast microscopy, and the temperature-dependent aggregation and dispersion of the polymers were described in terms of the inter- and intramolecular hydrogen bonds formed among PNANAm chains. Finally, a cell viability assay was conducted to explore the possibility of the applications of PNANAm in the fields of biomaterials and regenerative therapy.

Preparation and characterization of crystalline poly(L‐lactic acid)/silica nanocomposite films with high ductility and gas barrier properties

AbstractIncorporating inorganic particles is a common approach to preparing polymeric materials with desirable physical properties and processability. However, this often results in increased brittleness, necessitating methods to improve melt strength and toughness. In this study, in situ polymerization was employed to functionalize silica nanoparticles with the silane coupling agent (3‐aminopropyl) triethoxysilane (APTES) as a core. A flexible chain segment, poly(butylene itaconate) (PBI), was then introduced as a “rubbery” intermediate layer, resulting in a core‐shell structure of poly(L‐lactic‐co‐butanediol itaconate) nano‐silica copolymer films (PLBISiO2) with both branched and “rubbery” structures. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) confirmed the formation of macromolecular chains, with the molecular weight (Mn) of PLBI increasing from 59,638 to 74,306 g/mol. This significant increase supports the “rubbery” core‐shell structure. When 0.5% SiO2 was added, the T5% of the film increased by 40°C, significantly improving thermal stability. Additionally, the elongation at break increased to 265.7%, while retaining the original tensile strength. Dynamic rheology experiments further confirmed the generation of branched or “rubbery” core‐shell structures, and a doubling of gas barrier properties was observed with increased silica nanoparticles, suggesting potential applications in food packaging or biopharmaceuticals.Highlights Nanocomposites with core‐shell structure and improved mechanical properties. Dynamic rheology experiments confirmed the formation of the core‐shell structure. Significantly improved gas barrier properties due to core‐shell structure.

Recent Trends on Zinc Complexes Bearing Bi‐, Tri‐ and Tetra‐Dentate Schiff Base Ligands for Catalytic Ring‐Opening Polymerization of Lactides

AbstractNumerous zinc complexes based on N‐ and O‐donor Schiff‐base ligands have shown great promise in the ring‐opening polymerization (ROP) of lactides, which are cyclic dimers of lactic acid, to produce poly(lactic acid) (PLA). This is primarily because zinc is a borderline metal, making it non‐cytotoxic, inexpensive, abundant, biocompatible, and environmentally safe. Additionally, Schiff‐based ligands offer stability, stereoselectivity, desirable electronic and steric environments, and resistance to impurities. As a result, zinc complexes are easy to synthesize, colourless, have high reactivity and solubility in organic solvents, and are manageable under typical circumstances. Furthermore, these complexes are free to adopt a variety of coordination numbers since zinc does not have ligand field stabilization energy (LFSC). Zinc complexes possess high catalytic activity due to their distinctive properties, including high Lewis acidity, high electron transfer ability, stability concerning the reactive intermediate, and the ability to monitor polymerization by nuclear magnetic resonance (NMR) spectroscopy. Moreover, these complexes also have reasonable control over stereochemistry, number‐average molecular weight (Mn), and dispersity index (Ð). These advantages make it possible to produce colourless PLA with a high yield, high molecular weight, and narrow dispersity index in bulk and solvent‐based conditions.