Number-average Molecular Weight Research Articles

Bromine-containing copolymer polycarbonate for simultaneous thermal stability, transparency, and thin-wall flame-retardant polycarbonate

The incorporation of traditional low molecule bromine flame retardants can enhance the flame retardancy of polycarbonate (PC), yet their poor compatibility with PC impairs its transparency and mechanical properties. Here, brominated polycarbonate (B50PC) was synthesized by interfacial polycondensation method using bisphenol A, tetrabromobisphenol A, and triphosgene. The number average molecular weight (Mn) of B50PC reached 14,600, and compared to the low molecule bromine flame retardant tetrabromobisphenol A (TBBPA), its initial decomposition temperature increased by 38.7 % under air atmosphere. The PC composites containing 5 wt% B50PC achieved the V-0 rating in the UL-94 test, with LOI increased by 10.3 %. At the same time, the peak heat release rate (PHRR) was decreased by 28.6 % and the ignition time (TTI) was delayed by 21.3 %. Compared with that of samples with TBBPA, the composite with the same amount of B50PC maintained the original elongation at break of PC and the transmittance remained at 84.9 %. In summary, the composites with B50PC maintains outstanding transparency and mechanical properties while enhancing the flame retardancy. This work has developed a high molecular bromine flame retardant that combines flame retardancy and transparency, offering a strategy for expanding the application of PC in the electronics, construction, and aerospace sectors.

Use of commercial synthetic filament waste to reinforce biobased poly(butylene succinate) with the aid of compatibilizers

Since poly(butylene succinate) (PBS) has low rigidity for engineering application, this research attempted to reinforce PBS with poly(ethylene terephthalate) (PET) and polyamide-6 (nylon6) filaments with the reservation of polymer toughness. Filaments were chopped to be short fibers (length of 2 mm to 4 mm) and melt compounded with PBS pellets in the weight ratio of 1 wt%, 5 wt%, and 7 wt% using a twin-screw extruder that the temperature profile was set high enough for melting only PBS matrix. Two types of compatibilizers; hexamethylene diisocyanate (HMDI) or hexamethylene diamine (HMDA) of 0.05 wt% were used to treat fiber surface. It was found that tensile modulus of PBS increased with respect to fiber concentration, which untreated PET fibers provided higher tensile modulus about 2% to 7%. Surface treatment of fibers with either HMDI or HMDA increased rigidity of the composites, while elongation at break and impact strength were also improved with respect to fiber concentration. Also, shifting in glass transition temperature of PBS by DMA indicated improved interfacial interaction, which HMDA treatment gave the best benefit for mechanical properties. Number-average molecular weight of HMDI-treated composites was closed to extruded PBS, however, those of HMDA-treated composites were reduced dramatically implying chain scission highly occurred. SEM micrographs revealed good interfacial adhesion obtained after fiber treatment. Crystallization of PBS studied by XRD showed that the crystal form was not affected by the compatibilizer.

Controllable synthesis, characterization, and evaluation of poly (lauryl methacrylate-soybean oil) as a lubricant additive

Traditional free radical polymerization has poor controllability, and traditional petroleum-based lubricant additives have adverse effects on the environment. Poly (lauryl methacrylate (LMA)-soybean oil (SBO)) (P(LMA-SBO) was synthesized using Salen-Cu(II) complex as a catalyst and azodiisobutyronitrile (AIBN) as an initiator by the Schlenk techniques. The structure of P(LMA-SBO) was characterized by infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC) followed by evaluating the solidification point depression performance by the Chinese standard method GB/T 510-2018, and the wax crystal morphology was studied by optical microscopy. The results show the catalytic activity could be 22.88 × 104 g·mol−1·h−1 and the number average molecular weight (M n) of the copolymer is 8.71 × 104 with a low dispersity (Ɖ) of 1.37 under the optimal conditions, which indicates good controllability of the polymerization. Adding 1.0%(w) P(LMA-SBO) to the lubricating oil fraction (350–500 °C) could reduce the solidification point by 15 °C. Therefore, the Salen-Cu (II) catalyst was successfully applied to the controlled polymerization of LMA and SBO. The vegetable oil-based solidification point depressant of P(LMA-SBO) could be used as a potential alternative to replace the traditional solidification point depressant in the future.

Synthesis, Structures, Thermal stability and optical spectroscopy of Pt(II) di‑yne and poly‑yne incorporating 2,2′-Bipyridine-4,4′-diyl spacer

In platinum(II) di-ynes and poly-ynes the optical properties are influenced by the pattern of conjugation in the functionalised acetylide linker groups. We report the synthesis and characterisation of new Pt(II) di‑yne trans-[(Ph)(Et₃P)₂Pt–CC–Ar–CC–Pt(PEt₃)₂(Ph)] (Pt-M) and Pt(II) poly‑yne trans-[Pt(nBu3P)2Pt–CC–Ar–CC–]n (Pt-P) (Ar = 2,2′-bipyridine-4,4′-diyl) materials using analytical and spectroscopic techniques. The solid-state structure of the protected ligand precursor 4,4′-bis(trimethylsilylethynyl)-2,2′-bipyridine (LP1) and the dinuclear Pt(II) di‑yne (Pt-M) have been determined by the single-crystal X-ray diffraction (SC-XRD) while the number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (PDI) of the Pt(II) poly‑yne (Pt-P) have been determined by the gel permeation chromatography/light-scattering (GPC/LS) methods (Mn/Mw/PDI = 55,210/88,560/1.6). The thermal stability of the protected and di-terminal alkynyl ligands, Pt(II) di‑yne (Pt-M) and Pt(II) poly‑yne (Pt-P) have been evaluated and are discussed. To delineate the impact of incorporating the heavy Pt(II) ion along the polymer backbone, optical absorption studies have been performed and are discussed in detail. The results of optical absorption studies, especially (Pt-M) have been compared to their 5,5′- and 6,6′-bis(ethynyl) substituted analogues to better understand the effect of ligand topology on the effective conjugation.

THE EFFECT OF CHEMICAL STRUCTURE OF VINYL CHLORIDE BASED POLYMERS ON ITS THE COMPATIBILITY WITH POLYURETHANEUREA ELASTOMER

The effect of the chemical structure of vinyl chloride-based polymers, such as poly(vinyl chloride) (PVC), chlorinated PVC (cPVC), vinyl chloride/vinylidene chloride copolymer VCVD-40TM, vinyl chloride/vinyl acetate copolymer А-15TM on its compatibility with poly(ether-urethane)urea elastomer (PUU) was studied by DSC and FTIR spectroscopy. The segmented PUU was synthesized by prepolymer approach in N,N-dimethylformamide (DMF) solution using poly(propylene glycol) of number-averaged molecular weight (Mn) of 1000 Da, 2,4-tolylenediisocyanate and tolylene 2,4-diamine as a chain extender at a molar ratio of 1:2:1. PUU/vinyl chloride-based polymer blends was prepared by solution casting technique vie DMF solution. It was found a compatibility of PUU based blends containing 30 % PVC (PUU/30PVC blend) or cPVC (PUU/30cPVC) were initiated by strong hydrogen bonding. As a result, the blends are characterized by single wide relaxation transition. A glass transition temperature (Тс) of PUU/30PVC composite is similar to the theoretical one (ТFс), which is calculated using the Flory-Fox equation, whereas Тс value of PUU/30cPVC composite is higher than ТFс. Introducing polar vinyl acetate or vinylidene chloride fragments into vinyl chloride-based polymer macrochains suppresses the compatibility of components of the polymer blends and initiates the formation of a biphase microheterogeneous structure. The formation of intermolecular hydrogen bonding network at the interface in polymer-polymer blends is confirmed by FTIR spectroscopy. Comparative analysis of experimental and theoretically calculated (additive) tensile characteristics of polymer blends demonstrates their substantial dependence on interface interactions between the constituents. The highest strengthening effect was observed for cPVC or PVC-containing nanocomposites.

Solvent-based synthesis, structural elucidation and thermal characterisation of free radical grafted PHBV

This study investigates the solvent-based free-radical graft copolymerization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with C11 (undecenoic acid, UDA), C12 (dodecene, DD), and C18 (octadecene, OD) alkene substrates using dicumyl peroxide as an initiator. Comprehensive Nuclear Magnetic Resonance (NMR) spectroscopy was employed to confirm and quantify grafting, which was achieved at up to 5.8 mol% of monomer units. Thermal analysis revealed a significant reduction in melting temperature for all modified PHBVs, ranging from 10-20°C decrease in comparison to virgin PHBV. A decrease in crystallisation temperature and a reduction in glass transition temperature was measured for the UDA and DD grafted PHBV. Additionally, molecular weight analysis showed a marked decrease in weight average molecular weight (M¯w) and number average molecular weight (M¯n) for PHBV grafted with UDA, which was attributed to the presence of carboxylic acid functionality, which accelerates chain scission. The molecular weight profiles of the dodecene and octadecene grafted PHBV were only marginally reduced (32% and 18% reductions in M¯w, respectively), which is a much less severe reduction than has been previously observed for similar chemistries. Overall, this work demonstrates that solvent-based free-radical graft copolymerization can reduce the melting temperature and disrupt the crystallinity of PHBV, hence improving its processability and progressing the field of PHA modification and application.

Synthesis of azelaic acid copolyester plasticizers and their application in PVC.

A series of 2-methyl-1,3-propanediol (MPO) modified azelaic acid and hexylene glycol copolyester (PHMAZ) plasticizers with varying contents were synthesized using a direct esterification melt polycondensation method, and their structures were characterized systematically. Analysis using infrared spectroscopy and nuclear magnetic resonance spectroscopy confirmed the synthesis of the designed copolyester structure. Gel permeation chromatography (GPC) tests indicated that the number average molecular weight of each copolyester sample ranged between 2000 and 3000. These copolyesters were used to plasticize polyvinyl chloride (PVC) resin, and the glass transition temperature of the plasticized PVC samples was tested using a differential scanning calorimeter (DSC). Further characterization of the plasticizing effects was conducted using an electronic universal testing machine. The research results showed that as the content of MPO increased, the plasticizing effect of the copolyester initially increased and then decreased. Specifically, the copolyester containing 45% MPO, PHMAZ-45, demonstrated the best plasticizing effect on PVC, with the glass transition temperature of the plasticized PVC system around -35 °C, elongation at break at 908.4%, and a plasticizing efficiency of 254.5%. Additionally, this new type of copolyester plasticizer uses bio-based raw materials, exhibits excellent plasticizing effects, and the preparation process is stable and controllable. It holds promising potential to replace traditional volatile and toxic phthalate esters, presenting significant industrial application value.

Rheological and microscopic characterization and correlation analysis of asphalt under high-intensity ultraviolet radiation

The lower radiation intensity (2–20 W/m2) was widely used for asphalt ultraviolet (UV) aging. The effect of high-intensity radiation on asphalt properties and microscopic morphology is unknown. This study investigated the rheological behavior, microscopic characterization, and correlation analysis of SBS modified asphalt under high-intensity UV radiation. Rheological properties tests encompassed temperature sweep (TS), multiple stress creep recovery (MSCR), and frequency sweep (FS). Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Gel Permeation Chromatography (GPC) tests were performed to reveal the microscopic characterization. In the early stages of UV aging, the rutting factor of asphalt was increased. The increment decreased as the UV aging time increased. The UV aging process did not alter the temperature sensitivity of asphalt. The complex shear modulus was influenced by UV radiation duration and loading frequency. Extended exposure to high-intensity UV radiation resulted in the formation of microcracks on the surface of the asphalt. The maximum molecular weight of the UV-aged asphalt was higher than that of the original asphalt. The degraded SBS modifier deteriorated the homogeneity of asphalt. The sulfoxide aging index, carbonyl aging index, number-average molecular weight (Mn), weight average molecular weight (Mw), and polymer dispersity index (PDI) presented a better correlation with rheological behavior indexes. The correlation between small molecule size (SMS), medium molecule size (MMS), and large molecule size (LMS) with rutting factor and complex shear modulus was poor. It was worth mentioning that the correlation between the MSCR test results and microscopic performance indicators was the best. Especially for the recovery rate and Jnr at 3.2 kPa, the mean absolute value of the correlation coefficient was 0.953.

Surface pre-treatment of aluminum alloy for mechanical improvement of adhesive bonding by maple-assisted pulsed laser evaporation technique.

Adhesive joints are widely used for structural bonding in various industrial sectors. The performance of bonded joints is commonly attributed to the cleanliness of the substrate and the pre-treatment of the surfaces to be bonded. In this study, the Matrix Assisted Pulsed Laser Evaporation (MAPLE) deposition technique was used for surface modification of aluminum (Al) plates by the deposition of poly(propylene glycol) bis(2-aminopropyl ether) (PPG-NH2) of different number average molecular weights (Mn) of 400 g mol-1, 2000 g mol-1, and 4000 g mol-1, respectively. Fourier-transformed infrared spectroscopy (FT-IR) analysis indicated the characteristic peaks for the deposited layers of PPG-NH2 of different molecular weights in all cases while scanning electron microscopy (SEM) revealed continuous layers on the surface of Al plates. In order to demonstrate alterations in the wettability of Al substrates, a crucial aspect in surface treatment and adhesive bonding, measurements of contact angles, surface free energies (SFE), and adhesion work (W a) were conducted. The tensile strength measurements were performed using the lap-joint test after applying the commercial silyl-based polymer adhesive Bison Max Repair Extreme Adhesive®. It was evidenced that at higher values of the SFE and W a, the tensile strength was almost 3 times higher for PPG-NH2 with Mn = 4000 g mol-1 compared with the untreated Al sample. This study provides valuable insights into the successful application of the MAPLE technique as a pre-treatment method for reinforcing adhesive bonding of Al plates, which can lead to improved mechanical performance in various industrial applications.

Investigation of Peroxidase-Like Activity of Flower-Shaped Nanobiocatalyst from Viburnum Opulus L. Extract on the Polymerization Reactions

Here, we report the effects of peroxidase-mimicking activity of flower shaped hybrid nanobiocatalyst obtained from Viburnum-Opulus L. (Gilaburu) extract and Cu2+ ions on the polymerization of phenol and its derivatives (guaiacol and salicylic acid). The obtained nanoflowers exhibited quite high catalytic activity upon the polymerization of phenol and guaiacol. The yields and the number average molecular weights of the obtained polymers were significantly high. Due to solubility issue of salicylic acid in aqueous media, polymerization of salicylic acid resulted in very low yields. Free-horseradish peroxidase (HRP) enzyme is known to be losing its catalytic activity at 60 °C and above temperatures. However, the synthesized nanoflowers exhibited quite high catalytic activity even at 60 °C and above reaction temperatures. This provides notable benefits for reactions needed at high temperatures, and it is very important to use these kinds of nanobiocatalysts for both scientific studies and industrial applications.

Temperature-sensitive fragrance-releasing polymeric microcapsules

This research aimed to control release of fragrance using thermally-actuated microcapsules so that the release rate shows a considerable change at a certain temperature. Accordingly, four different polymers, namely, two grades of poly(methyl methacrylate) having different molecular weight as well as two poly[(methyl methacrylate)–co-(2-ethylhexyl acrylate)] copolymers, which were synthesized in this work, were designated as capsules’ shell. Number-average molecular weight of the copolymers and one of the two used PMMA grades was in the range of 47 to 56 kDa while that of the other PMMA grade was 344 kDa. Furthermore, Tg of the lower molecular weight grade PMMA and the two copolymers was determined as 119.3, 72.2 and 66.3 °C, respectively, using DSC experiments. Subsequently, R-Limonene as a model fragrance, was encapsulated by either of the polymers using solvent evaporation method. Effect of various parameters, including molecular weight and Tg of the shell polymer and concentration of emulsifier, on morphological characteristics of the microcapsules were investigated. Using two microscopic techniques, it was observed that increment of molecular weight of shell polymer enhances microcapsules’ size, shell thickness and porosity. Moreover, elevation of emulsifier concentration to a certain value of 1.5 wt% was shown to lessen size and porosity of microcapsules. The fragrance release profiles were determined and fitted to several mathematical models, proving that at least one more mechanism, in addition to diffusion, is involved in the release, which was attributed to capillary effects in the shell pores. Moreover, a pronounced increase in release rate upon elevation of temperature from 5 to 15 °C was observed for either of the copolymer shells. The effect was ascribed to remarkable strengthening of segmental mobility of the copolymers due to elevation of temperature and can be regarded as a promising way for the fabrication of smart microcapsules capable of thermal controlling fragrance release.

Biodegradable polybutylene adipate terephthalate foams: Investigating sustainability via reprocessing and green solvent

AbstractIncorporating reprocessing, recycling, and sustainable processes and materials is essential for a circular economy. Reprocessing and recycling are related since both help minimize wastage and produce a sustainable regenerative economy. However, polymers might undergo degradation depending on the recycling process, reducing their lifespan. In this study, polybutylene adipate terephthalate (PBAT) undergoes repetitive reprocessing under varied temperatures, times, and shear rates to investigate the evolution of mechanical, chemical, and thermal properties. Furthermore, foaming experiments are conducted using supercritical carbon dioxide (scCO2) on reprocessed samples to examine changes in the properties and morphology of the foam. The significance of reprocessing PBAT is divided into environmental, temperature, and processing effects. Environmental conditions impact the results where no oxidation effects are noticed in the 2‐hour test, while 7 days of humidity exposure lead to a tenfold reduction in polymer viscosity. Different processing techniques reduce the molecular weight of PBAT and alter its polydispersity. Specifically, the number average molecular weight (Mn) decreases from an initial 53 to 37 kDa after processes like extrusion or mixing. However, elongation at break and ultimate strength of PBAT remain unchanged after high‐shear extrusion processing. Additionally, PBAT foam morphology evolves over 5 cycles, leading to smaller pores and reducing compressive modulus.

Isolation and characterization of a hepatoprotective polysaccharide from Lonicera caerulea L. var. edulis Turcz. ex Herd. fruit against APAP-induced acute liver injury mice

The structure and bioactivities of a novel polysaccharide from Lonicera caerulea L. var. edulis Turcz. ex Herd. fruit (THP-3) were investigated. The crude polysaccharides of Turcz. ex Herd. (THP) were extracted by hot water extraction. After purification, the chemical structure of polysaccharides was identified. Then, a mouse model of acute drug-induced liver injury was constructed using 4-acetamidophenol (APAP) and pretreated with THP. The number-average molecular weight of THP-3 was 48.89 kDa and the mass average molar mass was 97.87 kDa. THP-3 was mainly composed of arabinose (42.54 %), glucose (27.62 %), galacturonic acid and galactose (29.84 %). The main linkage types of THP-3 were 1-linked Araf, 1,4-linked Glcp, and 1,3,6-linked Galp. In addition, after THP treatment, serum Alanine aminotransferase (ALT), Aspartate aminotransferase (AST) and γ-glutamyl transpeptidase (γGT) in AILI mice were successfully down-regulated. The results showed that THP could prevent the characteristic morphological changes of hepatic lobular injury and lipid depletion caused by APAP, reduced the level of oxidative damage in mice, increased the expression of APAP-induced hypolipidemia and related inflammatory indicators, and improved the detoxification function of liver. In general, the newly extracted THP polysaccharide has a good liver protection effect and is an ideal natural medicine for the treatment of liver diseases.

Study on the synthesis and properties of a new fluorine‐containing copolyarylate

AbstractA range of new fluorine‐containing copolyarylates were successfully produced through interfacial polymerization using hexafluorobisphenol A (BPAF) featuring a symmetric trifluoromethyl group structure, bisphenol B (BPB), and two acyl chloride monomers as raw materials. The results indicated that the synthesized amorphous copolyarylates exhibited good solubility, with number average molecular weights (Mn) of 19,000–44,000 g/mol, weight average molecular weights (Mw) of 66,000–159,000 g/mol, and intrinsic viscosities of 0.66–1.19 dL/g. The thermal stability of copolyarylates increased with the increase of BPAF monomer content (0~100%), which was manifested by the linear increase of glass transition temperature (Tg) from 201.6 to 237.1°C, and the increase of 5% thermogravimetric weight loss temperature (T5%) from 474.1 to 491.5°C. The tensile strength of copolyarylates ranged from 52.63 to 59.93 MPa, the tensile modulus ranged from 1102.08 to 1502.84 MPa, and the elongation at break ranged from 32.0 to 75.5%. In addition, the copolyarylates had good dielectric properties with a dielectric constant of 2.58–3.75 at 107 Hz and a dielectric loss tangent of 0.021–0.028.

An asymmetric polymerized small molecular acceptor with temperature-dependent aggregation and superior batch-to-batch reproducibility for efficient all-polymer solar cells

Polymerized small molecular acceptors (PSMAs) have been instrumental in driving the advancements in power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs). However, PSMAs commonly face challenges such as low molecular weights and notable batch-to-batch variation, posing significant obstacles to the transition of all-PSCs from lab to fab. Herein, a novel PSMA, which we refer to PAY-IT with an asymmetric conjugated skeleton is reported. The A–D1A'D2–A-type asymmetric monomer endows PAY-IT a random conjugated backbone, thus offering a desired temperature dependent aggregation behavior, which is hardly observed in conventional PSMAs. This characteristic facilitates chain growth during polymerization, thus yielding high molecular weights and low batch-to-batch sensitivity for the polymer. Moreover, the “S-shape” configuration of the asymmetric monomer endows PAY-IT good planarity and excellent charge transport property. As a result, the all-PSC consisted of PAY-IT and PM6 showcased a remarkable PCE of 14.9 %. More importantly, three batches of PAY-IT with number-average molecular weights ranging from 18.3 to 26.2 kDa exhibited nearly identical PCE (14.4–14.9 %), demonstrating superior batch-to-batch reproducibility of this polymer acceptor. This work explored PSMAs with asymmetric skeleton for the first time, and the results demonstrated a new design concept for the development of state-of-the-art PSMAs with minimal batch-to-batch variation.

Biodegradable composites fabricated using recycled poly(lactic acid)-based single-use coffee cup and regenerated cellulose fiber

ABSTRACT A series of biodegradable composites, including maleic acid-grafted recycled poly(lactic acid) (g-rPLA) and chemically modified lyocell (m-lyocell), were successfully synthesized. The rPLA was obtained from waste PLA-based single-use coffee cups. The storage modulus at −20°C of g-rPLA was increased from 1920 MPa for pure PLA to 3370 MPa for 5 wt% g-rPLA/m-lyocell composites, which is more than 75% enhancement. The number-average molecular weight after photodegradation for 60 days of g-rPLA and 5 wt% g-rPLA/m-lyocell composites was decreased by about 67.12% and 26.17% as compared to the samples before photodegradation, respectively. The results of photodegradations for composites indicate that the change of number-average molecular weight after photodegradation decreased by increasing the loading of m-lyocell. This result suggests that the existence of m-lyocell improved the UV protection ability of the g-rPLA. With the enhancement of mechanical properties and UV protection ability, this work provides an appropriate approach for the applications to reuse the waste PLA-based single-use coffee cups.

Efficient production of polyhydroxybutyrate using lignocellulosic biomass derived from oil palm trunks by the inhibitor-tolerant strain Burkholderia ambifaria E5-3.

Lignocellulosic biomass is a valuable, renewable substrate for the synthesis of polyhydroxybutyrate (PHB), an ecofriendly biopolymer. In this study, bacterial strain E5-3 was isolated from soil in Japan; it was identified as Burkholderia ambifaria strain E5-3 by 16S rRNA gene sequencing. The strain showed optimal growth at 37°C with an initial pH of 9. It demonstrated diverse metabolic ability, processing a broad range of carbon substrates, including xylose, glucose, sucrose, glycerol, cellobiose, and, notably, palm oil. Palm oil induced the highest cellular growth, with a PHB content of 65% wt. The strain exhibited inherent tolerance to potential fermentation inhibitors derived from lignocellulosic hydrolysate, withstanding 3g/L 5-hydroxymethylfurfural and 1.25g/L acetic acid. Employing a fed-batch fermentation strategy with a combination of glucose, xylose, and cellobiose resulted in PHB production 2.7-times that in traditional batch fermentation. The use of oil palm trunk hydrolysate, without inhibitor pretreatment, in a fed-batch fermentation setup led to significant cell growth with a PHB content of 45% wt, equivalent to 10g/L. The physicochemical attributes of xylose-derived PHB produced by strain E5-3 included a molecular weight of 722kDa, a number-average molecular weight of 191kDa, and a polydispersity index of 3.78. The amorphous structure of this PHB displayed a glass transition temperature of 4.59°C, while its crystalline counterpart had a melting point of 171.03°C. This research highlights the potential of lignocellulosic feedstocks, especially oil palm trunk hydrolysate, for PHB production through fed-batch fermentation by B. ambifaria strain E5-3, which has high inhibitor tolerance.

From Facile One-Pot Synthesis of Semi-Degradable Amphiphilic Miktoarm Polymers to Unique Degradation Properties.

We report a one-pot synthesis of well-defined A5B and A8B miktoarm star-shaped polymers where N,N-dimethylaminoethyl methacrylate (DMAEMA) and various cyclic esters such as ε-caprolactone (ε-CL), lactide (LA) and glycolide (GA) were used for the synthesis. Miktopolymers were obtained by simultaneously carrying out atom transfer radical polymerization (ATRP) of DMAEMA, ring-opening polymerization (ROP) of cyclic esters, and click reaction between the azide group in gluconamide-based (GLBr5-Az) or lactonamide-based (GLBr8-Az) ATRP initiators and 4-pentyn-1-ol. The relatively low dispersity indices of the obtained miktoarm stars (Đ = 1.2-1.6) indicate that control over the polymerization processes was sustained despite almost complete monomers conversions (83-99%). The presence of salts from phosphate-buffered saline (PBS) in polymer solutions affects the phase transition, increasing cloud point temperatures (TCP) values. The critical aggregation concentration (CAC) values increased with a decreasing number of average molecular weights of the hydrophobic fraction. Hydrolytic degradation studies revealed that the highest reduction of molecular weight was observed for polymers with PCL and PLGCL arm. The influence of the composition on the miktopolymers hydrophilicity was investigated via water contact angle (WCA) measurement. Thermogravimetric analysis (TGA) disclosed that the number of arms and their composition in the miktopolymer affects its weight loss under the influence of temperature.

Structural characteristics, immune-activating mechanisms in vitro, and immunomodulatory effects in vivo of the exopolysaccharide EPS53 from Streptococcus thermophilus XJ53

Our previous investigations have successfully identified the repeating structural units of EPS53, an exopolysaccharide derived from Streptococcus thermophilus XJ53 fermented milk, and substantiated its potential immunomodulatory properties. The present study further elucidated the structural characteristics of EPS53 and investigated the underlying mechanisms governing its in vitro immunoreactivity as well as its in vivo immunoreactivity. The results obtained from multi-detector high performance gel filtration chromatography revealed that EPS53 adopted a rigid rod conformation in aqueous solution, with the weight-average molecular weight of 1464 kDa, the number-average molecular weight of 694 kDa, and the polydispersity index of 2.11. Congo red experiment confirmed the absence of a triple helix conformation. Scanning electron microscopy showed that EPS53 displayed a three-dimensional fibrous structure covered with flakes. The in vitro findings indicated that EPS53 enhanced phagocytosis ability, reactive oxygen species (ROS) production, and cytokine levels of macrophages via the TLR4-mediated NF-κB/MAPK signaling pathways as confirmed by immunofluorescence staining experiments, inhibition blocking experiments, and Western blot assay. Additionally, the in vivo experiments demonstrated that EPS53 significantly increased macrophage and neutrophil number while enhancing NO and ROS levels in zebrafish larvae; thus, providing further evidence for the immunomodulatory efficacy of EPS53.

Interpenetrating polymer networks of polyurethane and polytriazole: Effect of the composition and number average molecular weight of glycidyl azide polymer on the mechanical properties and morphology

AbstractOn account of some special advantages of interpenetrating polymer networks (IPNs), the preparation of IPNs with excellent properties may be a promising way to strengthen the polyurethanes (PUs) and toughen the glycidyl azide polymer (GAP) based polytriazoles (PTAs). This work provides the effect of composition and number average molecular weight (Mn) of GAP on the mechanical properties and morphology of full‐IPNs. A series of IPNs based on the crosslinked Ace‐terminated GAP (Ace‐GAP) as polytriazole phase and crosslinked hydroxy‐terminated liquid fluorinated polymer (HTLF‐1500) as polyurethane phase (namely, GAP‐HTLF‐X full‐IPNs) were successfully fabricated via in situ polymerization without any catalysts at 80°C by azide–alkynyl click chemistry and hydroxyl‐isocyanate urethane reaction. These IPNs were characterized using attenuated total reflectance/Fourier‐transform infrared spectroscopy (ATR/FTIR), uniaxial tensile testing, swelling measurement, and scanning electron microscopy (SEM). The tensile strength of GAP‐HTLF full‐IPNs gradually increased by increasing the weight ratio of Ace‐GAP, but the breaking elongation dramatically decreased compared with elongation at break of HTLF polyurethane. In addition, a small Mn of GAP is beneficial in enhancing the tensile strength, elongation at break and toughness of the IPNs. However, a small Mn of GAP corresponds to increased difficulty of preparing GAP‐HTLF full‐IPNs. GAP1k‐HTLF full‐IPN was not successfully prepared. When the Mn of GAP was 2000 g/mol, the GAP2k‐HTLF‐80 full‐IPN exhibited prominent mechanical performance with a tensile strength of 83.1 MPa, elongation at break of 28.5% and fracture energy of 99.1 kJ/m3. Swelling measurement showed that when the weight ratio of GAP with larger Mn (5, 3, and 2 k) increased to more than 70%, the molecular interpenetration existed in the IPNs, demonstrating the presence of additional physical crosslinks and entanglement for full‐IPNs. SEM studies revealed that highly formed interpenetration and few microphase separations can be observed on the fracture surface of the IPNs with optimal mechanical properties. Combined with the results of mechanical properties, swelling measurement, and SEM studies, the degree of molecular interpenetration and microphase separation were beneficial to improve the mechanical properties of elastomers. This work can provide a certain guiding significance for the preparation of IPN with excellent properties.