Main Chain Structure Research Articles

Chemically Recyclable, Reprocessable, and Mechanically Robust Reversible Cross-Linked Polyurea Plastics for Fully Recyclable Aramid Fiber Reinforced Composites.

Aramid fiber reinforced composites (AFRCs) have received increasing attention because of their excellent comprehensive performance including high mechanical strength, high modulus, and light weight. However, full recycling of AFs from ARCFs is difficult to achieve. Herein, fully recyclable ARCFs are fabricated using reversible cross-linked polyurea plastics (PUHA) as the matrix. PUHA plastics are fabricated by cross-linking linear polyurea using hemiaminal groups. By changing the main chain structures, two types of PUHA plastics are prepared with excellent mechanical performance, which is comparable to that of traditional engineering plastics. PUHA plastics can be reprocessed at least five times without losing their original mechanical properties because of the dynamic exchangeability of the hemiaminal groups. Meanwhile, PUHA plastics can be rapidly depolymerized into linear polyurea under acidic conditions. When PUHA plastics are used as a matrix to fabricate AFRCs, the AFRCs exhibit excellent mechanical strength. Moreover, due to the simple chemical recycling ability of PUHA plastics, AFRCs can be fully decomposed into intact AFs and linear polyurea with high purity. This work presents the use of reversible cross-linked polyurea plastics in the fabrication of fully recyclable AFRCs and provides the future direction of developing fully recyclable and high-performance fiber-reinforced composites.

Synthesis and optical properties of fluorinated polyurethaneimide electro-optic waveguide polymer

Fluorinated polyurethaneimide (PUI) electro-optic waveguide polymer with polyurethane and polyimide chain segment structures was synthesized by stepwise polymerization using the synthesized amino ester oligomer pu and imide oligomer pi as monomers. Since the main chain structure of the synthesized PUI had the functionality of both polyurethane and polyimide chain segment structures, it combines the excellent thermal and film-forming properties of polyurethanes and polyimides, as well as lower optical transmission loss in the near-infrared wavelength band. The glass transition temperature (Tg) of PUI was 182 °C, and the 5% heat loss decomposition temperature was 325 °C. The PUI had good optical properties with an optical propagation loss of 1.10 dB/cm and an electro-optic (EO) coefficient (γ33) of 86 pm/V at a wavelength of 1550 nm. A Mach-Zehnder interferometric polymer waveguide EO modulator had been designed and fabricated by using the PUI as a waveguide electro-optic core layer. The prepared polymer waveguide EO modulator showed a good electro-optic modulation response at a wavelength of 1550 nm under an applied 1 kHz sinusoidal modulation signal. The results showed that the synthesized PUI met the performance requirements for the preparation of polymer optical waveguide devices and was a polymer electro-optic waveguide material with good overall performance.

Structural elucidation of a Acanthopanax senticosus polysaccharide CQ-1 and its hepatoprotective activity via gut health regulation and antioxidative defense

Acanthopanax senticosus has proven health benefits, particularly for liver damage. The objective of this study was to elucidate the protective effects and the underlying mechanisms of action of A. senticosus against metabolic dysfunction-associated fatty liver disease (MAFLD). A novel homogeneous water-soluble polysaccharide, CQ-1, was successfully isolated and purified from A. senticosus root. The main chain structure of CQ-1 was identified as →2)-α-L-Rha-(1 → 4)-α-D-GalAp-(1 → 6)-β-D-Galp-(1→. Additionally, branched chains comprising an arabinosyl residue, galactosyl residue, and galacturonic acidic residue were identified as being attached to →2,4)-α-L-Rha-(1→, →3,6)-β-D-Galp-(1→, and →3,4)-α-D-GalAp-(1→, respectively. CQ-1 exhibited antioxidant and prebiotic activities in vitro. CQ-1 increased antioxidant capacity and reduced serum pro-inflammatory cytokines in mice. Additionally, CQ-1 has been shown to enhance the diversity and composition of the gut microbiota, thereby facilitating the restoration of gut function. These include improving intestinal barrier function and increasing short-chain fatty acid levels in mice. Our study has shown that CQ-1 has a hepatoprotective effect in MAFLD mice, and we have proposed that CQ-1 may be a promising strategy for the treatment of MAFLD.

Asymmetric main-chain twisted small molecules for efficient polymer solar cells

Polymer solar cells (PSCs) based on small molecules with twisted backbones as electron acceptors, have many advantages over their planar counterparts, such as upshifted molecular energy levels, better charge extraction performance, enhanced extinction coefficient, extended carrier lifetime and reduced recombination rate, which are very helpful in improving the power conversion efficiencies (PCE). The present study was designed to synthesize two new small molecules with main-chain twisted structures that include an asymmetric electron donor core thiophene-phenylene-thieno[3,2-b]thiophene, namely i-T-TT and i-T-TT-4F, to investigate the “structure-property” correlation of main-chain twisted acceptors. Both asymmetric molecules exhibit bent geometric structures, and the fluorinated acceptor i-T-TT-4F possesses a more red-shifted spectrum, improved molar extinction coefficient, and deepened molecular energy levels. As a result, when combined with the middle bandgap polymer donor J52, there was a remarkable efficiency of 12.22 % for the device of i-T-TT-4F, higher than that of i-T-TT (9.51 %). Our research illustrates the importance of the main-chain twisted asymmetric electron-donating core and fluorinated end-capping group in the construction of efficient PSCs.

Controlled assembly and synthesis of oxygen-deficient W18O49 films based on solvent molecular strategy for electrochromic energy storage smart windows

18O49 is a promising electrochromic material with abundant oxygen vacancy and high carrier mobility. However, the electrochromism of W18O49 is not satisfactory, the regulation and synthesis of high-performance W18O49 have become the research hotspot. In this work, it is found that the main chain and side chain structure of solvent molecules can control the assembly and synthesis of W18O49 film, so as to achieve excellent electrochemical and electrochromic properties. The porous reticular W18O49 film synthesized in short-chain molecular solvent shows the excellent transmittance modulation (81.6 % at 633 nm, 77.0 % at 1050 nm), and exhibits the high energy storage of 41.7 mF cm−2 at 0.1 mA cm−2. Solvent molecular strategy provides a new way for the synthesis and regulation of W18O49 electrochromic films and promotes the further development of high-performance electrochromic materials.

Structural characterization and antioxidant activity mechanism of the ferulic acid-rich subfraction from sugar beet pectin

The feruloylated sugar chain in sugar beet pectin (SBP) is a natural polyphenol-polysaccharide complex. Its low abundance often leads to be neglected, thereby hindering its bioactivity and mechnism research. In this study, SBP-3 A, a novel feruloylated polysaccharide fragment, was isolated from sugar beet pectin utilizing enzymatic digestion. The presence of ferulic acid on SBP-3 A was confirmed through high-performance liquid chromatography (HPLC), with a mass fraction of 22.5 μg/mg. The average molecular weight was determined to be 33.31 kDa. Methylation analysis, and nuclear magnetic resonance (NMR) spectra revealed that SBP-3 A is a heteroglycan with the main chain structure of →2)-α-Rhap-(1 → 4)-α-GalpA-(1 → 2)-α-Rhap-(1→, and the branched chain structure of ferulic acid (FA) → 3,4)-β-Galp-(1 → 2,4)-α-Rhap-(1→. Subsequently, the antioxidant activity of SBP-3 A was evaluated using the Caenorhabditis elegans (C. elegans). SBP-3 A improved antioxidant enzymes and non-enzymatic defense system, decreased reactive oxygen species levels, and up-regulated the mRNA expression of sod-3, skn-1, and daf-16, while down-regulated the expression of age-1 in C. elegans. Moreover, SBP-3 A modulated the gut flora by favorably affecting the abundances of Lactobacillus, Ligilactobacillus, and Akkermansia, thereby enhancing antioxidant capacity in C. elegans. Consequently, the aforementioned findings support the potential application of SBP-3 A as a functional food for treating oxidative stress-related illnesses.

Screening of a readily selenium-enriched Spirulina polysaccharide and characterization of its structure and bioactivity

The potential of selenium-containing polysaccharides as organic selenium nutritional supplements has attracted considerable interest; however, they also encounter obstacles, including the presence of impurities and a low selenium binding efficiency. In this study, a novel method combining Q-Sepharose Fast-Flow (QFF) column chromatography with the HNO3–Na2SeO3 method was proposed. Through the application of this methodology, the selenium binding efficiency of polysaccharides was enhanced by a factor of 3.41. The selenium binding capacities of rhamnose and glucose were the highest among the monosaccharides, reaching 770.7 mg/L and 955.3 mg/L, respectively. Spirulina polysaccharide-3 (SPS-3) was selected for further investigation because of its elevated total rhamnose and glucose contents and optimal selenium binding efficiency. Employing common assays, a comparative analysis of selenium-containing Spirulina polysaccharide-3 (SeCSPS) and SPS-3 is presented. Upon selenium binding, the surface morphology of the monosaccharides changed, whereas the main chain structure remained unaltered. The antihyperglycemic activity of SeCSPS was enhanced by selenium binding. Furthermore, both SeCSPS and SPS-3 can be degraded by the simulated digestive system. In conclusion, SeCSPS can be employed as an organic selenium supplement in food or nutraceuticals while also resulting in a high selenium content. The findings of this study will provide a viable avenue for the high-value utilization of Spirulina, which will help resolve the selenium deficiency issue faced by populations with low selenium intake globally.

Single‐step preparation of intrinsic solid–solid phase change materials with excellent anti‐leakage and form‐stable performance

AbstractPhase change materials (PCM) often encounter severe problems of leakage and shape collapse concerns. Chemical modification methods, utilizing chemical bonds to bind phase change molecular chains, have the potential to address the above‐mentioned problems radically. However, this approach often entails the use of expensive raw materials and complex processes. Therefore, a simple one‐pot preparation method had been reported using earth‐abundant and inexpensive octadecyl methacrylate (OMA) and 1,6‐hexanediol diacrylate (HD) as raw materials to prepare PCM with a molecular structure of cross‐linked polymer main chains and phase change side chains through free radical polymerization. Owing to the three‐dimensional polymer main chain structure, it exhibited excellent leakage‐proof performance, maintaining its form‐stable nature at 70°C with no obvious leakage observed during the phase change process, confirming it to be an excellent intrinsic solid–solid PCM (SSPCM). Additionally, the introduction of the cross linking segment significantly improves its thermal stability, and the 50% degradation temperature increased significantly from 228.8 to 355.9°C. Moreover, the latent heat increased with the decrease of the crosslinking density until the molar ratio of HD/OMA was reduced to 1/40 and then tended to reach constant. At the optimal ratio the latent heat of SSPCM can reach 88.23 J g−1. Excessive crosslinking density will affect the stacking tightness of molecular chains during the crystallization process, thereby reducing the latent heat.

Essential oil-derived robust and heat-resistant polybenzoxazine-POSS composites as low dielectric matrixes

Polybenzoxazines (PBozs) are regarded as prime candidates as low dielectric matrixes. However, the fabrication of high-performance PBozs that combines low dielectric property with high thermal stability using sustainable resources as the starting raw materials remains a significant challenge. In this work, we constructed a novel main-chain benzoxazine (Boz) oligomer from natural essential oil-derived compounds (eugenol and p-menthane diamine) to fulfill the principles of green chemistry. To enhance their low dielectric properties, polar C-Si unit on the main-chain and cellular structure of polyoctahedral silsesquioxanes (POSS) as the cross-linkers were introduced in PBoz-POSS composites. The obtained composites demonstrated excellent thermal stability, mechanical property, and with remarkable low dielectric constants. Coupled with their exceptional hydrophobicity and heat resistance, these materials are promising matrixes for low dielectric application in contemporary electronic industries.

Radical Homopolymerization of Linear α‐Olefins Enabled by 1,4‐Cyano Group Migration

Abstractα‐Olefins are valued and abundant building blocks from fossil resources. They are widely used to provide small‐molecule or polymeric products. Despite numerous advantages of radical polymerization, it has been well‐documented as textbook knowledge that α‐olefins and their functionalized derivatives cannot be radically homopolymerized because of the degradative chain transfer side reactions. Herein, we report our studies on the homopolymerization of thiocyanate functionalized α‐olefins enabled by 1,4‐cyano group migration under radical conditions. By this approach, a library of ABC sequence‐controlled polymers with high molecular weights can be prepared. We can also extend this strategy to the homopolymerization of α‐substituted styrenic and acylate monomers which are known to be challenging to achieve. Overall, the demonstrated functional group migration radical polymerization could provide new possibilities to synthesize polymers with unprecedented main chain sequences and structures. These polymers are promising candidates for novel polymeric materials.

Radical Homopolymerization of Linear α-Olefins Enabled by 1,4-Cyano Group Migration.

α-Olefins are valued and abundant building blocks from fossil resources. They are widely used to provide small-molecule or polymeric products. Despite numerous advantages of radical polymerization, it has been well-documented as textbook knowledge that α-olefins and their functionalized derivatives cannot be radically homopolymerized because of the degradative chain transfer side reactions. Herein, we report our studies on the homopolymerization of thiocyanate functionalized α-olefins enabled by 1,4-cyano group migration under radical conditions. By this approach, a library of ABC sequence-controlled polymers with high molecular weights can be prepared. We can also extend this strategy to the homopolymerization of α-substituted styrenic and acylate monomers which are known to be challenging to achieve. Overall, the demonstrated functional group migration radical polymerization could provide new possibilities to synthesize polymers with unprecedented main chain sequences and structures. These polymers are promising candidates for novel polymeric materials.

L-PTMI-co-L-PEI copolymers obtained through copolymerization of cyclic imino ethers and their chain modification: Antibacterial properties and cytotoxicity

Polymeric antimicrobial agents are intensively investigated as potential novel antibiotics. In this work we use copolymerization of 2-propyl-2-oxazine (PrOzi) and 2-methyl-2-oxazoline (MeOx) combined with hydrolysis of the polymer side chains as a tool to obtain various linear polymeric derivatives of polytrimethylenimines (L-PTMI) and polyethylenimine (L-PEI). To obtain well-defined polymers, initially we determined copolymerization rates, and subsequently, we investigated the hydrolytic rates of various repeating units, namely PrOzi, MeOx, and 2-methyl-2-oxazine (MeOzi) in both homo- and copolymers. We observed that the structure of the polymeric main chain significantly influences the rate of acidic hydrolysis. In particular, the protonated L–PEI repeating unit (r.u.) accelerates the hydrolytic cleavage of the amide bond more than the protonated L-PTMI r.u., due to the shorter distance between amine centers.The biological activity of the polymers was assessed against three model microorganisms, namely Escherichia coli, Staphylococcus aureus and Candida albicans, and benchmarked in toxicity test against human lung fibroblast cell line. The antibacterial activity of L-PTMI-co-L–PEI increases monotonically with the increasing content of PTMI r.u., indicating an additive effect of covalently bonded L-PTMI and L-PEI. The antimicrobial activity of the copolymers is almost identical to that of the tested polymer blends in the corresponding ratios.The introduction of up to 40 % of PrOzi r.u. into the polyamine structure of PTMI (PPrOzi–co-L-PTMI copolymer) does not decrease the antimicrobial activity, compared to L–PTMI. The molecule remains active, particularly against Staphylococcus aureus (MIC = 4 μg/mL). At the same time, the presence of amide r.u. reduces toxicity. The highest observable selectivity index can reach values as high as 20 (PPrOzi40%–co-L-PTMI60%).

Sulfated Polysaccharides with Anticoagulant Potential: A Review Focusing on Structure-Activity Relationship and Action Mechanism.

Thromboembolism is the culprit of cardiovascular diseases, leading to the highest global mortality rate. Anticoagulation emerges as the primary approach for managing thrombotic conditions. Notably, sulfated polysaccharides exhibit favorable anticoagulant efficacy with reduced side effects. This review focuses on the structure-anticoagulant activity relationship of sulfated polysaccharides and the underlying action mechanisms. It is concluded that chlorosulfonicacid-pyridine method serves as the preferred technique to synthesize sulfated polysaccharides. The anticoagulant activity of sulfated polysaccharides is linked to the substitution site of sulfate groups, degree of substitution, molecular weight, main side chain structure, and glycosidic bond conformation. Moreover, sulfated polysaccharides exert anticoagulant activity via various pathways, including the inhibition of blood coagulation factors, activation of antithrombin III and heparin cofactor II, antiplatelet aggregation, and promotion of the fibrinolytic system.

Semiconducting Polymers Based on Asymmetric Thiadiazoloquinoxaline for Augmented In Vivo NIR-II Photoacoustic Imaging.

A photoacoustic (PA) imaging technique using the second near-infrared (NIR-II) window has attracted more and more attention because of its merits of deeper penetration depth and higher signal-to-noise (S/N) ratio than that using the first near-infrared (NIR-I) one. However, the design and development of high-performance PA imaging contrast agents in the NIR-II window is still a challenge. A semiconducting polymer, constructed by asymmetric units, exhibits regiorandom characteristics that effectively increase the distortion of the backbone. This increase in the degree of twist can regulate the twisted intramolecular charge transfer (TICT) effect, resulting in an enhancement of the PA signal. In this paper, an asymmetric structural acceptor strategy is developed to improve the PA signals of the resulting semiconducting polymer (PATQ-MP) in the NIR-II window with improved brightness, higher S/N ratio, and better photothermal conversion efficiency compared to polymers with the same main-chain structure containing a symmetric acceptor. DFT analysis showed that PATQ-MP containing an asymmetric acceptor monomer had a larger dihedral angle, which effectively improved the PA signal intensity by enhancing the TICT effect. The PEG-encapsulated PATQ-MP nanoparticles exhibit promising performance in the PA imaging of mouse tumors in vivo, demonstrating the clear identification of microvessels as small as 100 μm along with rapid metabolism within a span of 5 h. Therefore, this work provides a unique molecular design strategy for improving the signal intensity of PA imaging in the NIR-II window.

Design of Multi-Chain Traceability Model for Pepper Products Based on Traceability Code

In the specific application scenario of pepper product supply chain traceability, with the advancement of pepper product production, the expansion of links, and the increase of nodes, the quantity of data will become more and more enormous. The single-chain model is less efficient for querying if the data are all stored into the same blockchain. In order to improve the efficiency of blockchain data querying, this paper proposes a traceability model with one main chain and multiple side chain structures, which separate the uplinked data from each link and use multi-chain transactions to improve the efficiency of data queries. This model builds an indexing mechanism with a product traceability code, using one main chain and multiple side chains. The main and side chains form a one-to-many mapping relationship, storing the mapping relationship between the traceability code and the transaction address of the side chain traceability information in the main chain. This enables information to travel through the main chain traversal query based on the mapping relationship and then query the direct index out of the side chain, to achieve fast traceability query and improve the efficiency of querying.

Preparation and performance of polyimide lithium‐ion battery separator based on benzonorbornene main chain structure

Preparation and performance of polyimide lithium‐ion battery separator based on benzonorbornene main chain structure

Essential dextrin structure as donor substrate for 4-α-glucanotransferase in glycogen debranching enzyme.

Glycogen debranching enzyme is a single polypeptide with distinct catalytic sites for 4-α-glucanotransferase and amylo-α-1,6-glucosidase. To allow phosphorylase to degrade the inner tiers of highly branched glycogen, 4-α-glucanotransferase converts the phosphorylase-limit biantennary branch G-G-G-G-(G-G-G-G↔)G-G- (G: d-glucose, hyphens: α-1,4-linkages; double-headed arrow: α-1,6-linkage) into the G-G-G-G-(G↔)G-G- residue, which is then subjected to amylo-α-1,6-glucosidase to release the remaining G↔ residue. However, while the essential side-chain structure of the 4-α-glucanotransferase donor substrate has been determined to be the G-G-G-G↔ residue (Watanabe, Y., etal. (2008) J. Biochem.143, 435-440), its essential main-chain structure remains to be investigated. In this study, we probed the 4-α-glucanotransferase donor-binding region using novel fluorogenic dextrins Gm-(G4↔)G-Gn-F (F: 1-deoxy-1-[(2-pyridyl)amino]-d-glucitol) and maltohexaose (G6) as the donor and acceptor substrates, respectively. 4-α-Glucanotransferase exhibited maximum activity towards G4-(G4↔)G-F and G4-(G4↔)G-G-F, indicating that recognition of the G4-(G4↔)G-moiety was essential for full enzyme function. Notably, when the 4-α-glucanotransferase activity towards G4-(G4↔)G-G-F was taken as unity, those towards nonbranching dextrins were < 0.001. This indicated that the disproportionation activities towards maltooligosaccharides (Gm) are abnormal behaviours of 4-α-glucanotransferase. Notably, however, these activities have been traditionally measured to identify the 4-α-glucanotransferase mutations causing glycogen storage disease type III. This study provides a basis for more accurate identification.

Switchable Coacervate Formation via Amino Acid Functionalization of Poly(dehydroalanine).

Our group recently developed a family of side-chain amino acid-functionalized poly(S-alkyl-l-homocysteines), Xaa-CH (Xaa = generic amino acid), which possess the ability to form environmentally responsive coacervates in water. In an effort to further study how the molecular structure affects polypeptide coacervate formation, we prepared side-chain amino acid-functionalized poly(S-alkyl-rac-cysteines), Xaa-rac-C, via post-polymerization modification of poly(dehydroalanine), ADH. The use of the ADH platform allowed straightforward synthesis of a diverse range of side-chain amino acid-functionalized polypeptides via direct reaction of unprotected l-amino acid 2-mercaptoethylamides with ADH. Despite their differences in the main-chain structure, we found that Xaa-rac-C can form coacervates with properties similar to those seen with Xaa-CH. These results suggest that the incorporation of side-chain amino acids onto polypeptides may be a way to generally favor coacervation. The incorporation of l-methionine in Met-rac-C allowed the preparation of coacervates with improved stability against high ionic strength media. Further, the presence of additional thioether groups in Met-rac-C resulted in an increased solubility change upon oxidation allowing facile reversible redox switching of coacervate formation in aqueous media.

Novel hydrophobic butyl rubber damping composites modified with bio-based PF/DBA via the construction of a three-dimensional network

It is of interest to develop wide-temperature domain damped hydrophobic materials. In this paper, we designed incorporating bio-based phenolic resin into the IIR matrix and introducing dibenzyl fork acetone (DBA) into the main chain structure with sodium hydroxide activation to construct three-dimensional network. In this paper, we designed incorporating bio-based phenolic resin into the IIR matrix and introducing dibenzyl fork acetone (DBA) into the main chain structure with sodium hydroxide activation to construct three-dimensional network. The added bio-based phenolic resin has reticulated structure blended with butyl rubber, combined with sodium hydride activation-modified IIR. The results show that sodium hydride activated modification of DBA is introduced into the main chain structure of IIR by infrared and 1H NMR analysis. The material hydrophobic is realized by the introduction of DBA with static water contact angle of 103.5°. The addition of 10phr lignin-based phenolic resin (LPF) is compatible with IIR, and the torque can reach 7.0 N-m. The tensile elongation of the modified butyl rubber composite can reach 2400% with tensile strength up to 11.43 MPa, while the damping factor can reach 0.37 even at 70 °C. The thermal stability of the composites is enhanced with mass retention rate of 28%. The bio-based PF/NaH activation-modified butyl rubber damping material has potential applications in damping hydrophobicity with wide temperature range.

Monomer Dependence of Colorless and Transparent Polyimide Films: Thermomechanical Properties, Optical Transparency, and Solubility.

Six poly(amic acid)s (PAAs) were synthesized by reacting bis(3-aminophenyl) sulfone with various dianhydride monomers such as pyromellitic dianhydride, 4,4'-biphthalic anhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, 4,4'-oxidiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 4,4'-(hexafluoroisopropylidene) diphthalic anhydride. These PAAs were then converted to polyimide (PI) films by thermal imidization at various temperatures. To obtain colorless and transparent PI (CPI), the dianhydride monomer used in this study had an overall bent structure, a structure containing a strong electron-withdrawing -CF3 substituent or an alicyclic ring. In addition, some monomers contained ether or ketone functional groups in their bent structures. The thermomechanical properties, optical transparency, and solubility of CPI films with six different dianhydride monomer structures were investigated, and the correlation between the monomer structure and CPI film properties was clarified. Overall, CPI with an aromatic main chain structure or a linear structure had excellent thermal and mechanical properties. In contrast, CPI with a bent structure containing functional groups or substituents in the main chain exhibited excellent optical transparency and solubility.