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The Effect of Polymerization of Ionic Liquid [C4Vim]Br on Phase Behavior and Partitioning of L-Tryptophan: Experimental and Molecular Dynamics Study Enhanced Publication
Abstract：In recent decades, there is growing interest in various applications of polymerized ionic liquids (PILs), particularly in the aqueous biphasic systems (ABSs) used as media for extraction of solutes. In this work, we report new experimental data on the binodal curve and tie lines in the ABSs containing PIL and non-polymerized ionic liquid (IL): poly-[C4Vim]Br-K3PO4-H2O and [C4Vim]Br-K3PO4-H2O at 298.15 K. For the ABS with PIL, the partition coefficient of L-tryptophan between the liquid phases is obtained from experiment and compared with our previous data on ABS [C4mim]Br-K3PO4-H2O containing non-polymerized IL. We conclude that the ABS containing poly-[C4Vim]Br has a lower extraction efficiency than the ABS based on non-polymerized ILs. To elucidate the mechanism underlying such behavior of the PIL-containing mixture, we performed MD simulations of PIL-rich aqueous mixtures in presence of K3PO4 and L-tryptophan. We obtained diffusion coefficients of low molecular mass ions and water, and data on the distribution of these species around polycation over a range of mixture compositions. MD data show that poly-[C4Vim]Br exhibits no favorable selectivity towards L-tryptophan anions in the presence of phosphate background. This confirms unfavorable combination of poly-[C4Vim]Br with phosphate for the extraction of L-tryptophan, in accord with our experimental findings.Keywords：Aqueous biphasic systems;Molecular dynamics;Partitioning of L-tryptophan;Phase diagrams;Polymerized ionic liquids16|2|0
Updated：2026-04-15 -
Experimental Investigation of Graphene and TiO2 Reinforced PVA-Based Fiber Metal Laminates Enhanced Publication
Abstract：This study investigates the mechanical performance of hybrid fiber-metal laminates (FMLs) fabricated using a polyvinyl alcohol (PVA) matrix reinforced with woven glass and carbon fibers, further enhanced with titanium dioxide (TiO2) and graphene fillers. The composites were fabricated using the vacuum bag molding process, and to optimize the mechanical behavior, different filler loadings were incorporated as graphene at (0.5, 1, and 3 wt.%), and TiO2 (0.5, 1, 2, and 3 wt.%). Mechanical tests revealed that the inclusion of filler particles significantly enhanced tensile, flexural, and toughness properties. The optimal graphene loading was found to be 0.5 wt.%, resulting in an 83.4% increase in Young’s modulus and a 127% improvement in tensile strength compared to PVA composites without filler. Optimal loading for TiO2 was 2% by weight, which resulted in a 102.3% increase in Young's modulus and an 81.5% increase in ultimate tensile strength. The maximum flexural properties were achieved for 0.5 wt.% graphene-loaded composites, with a flexural strength of 56.6 MPa and a flexural modulus of 19.3 GPa, while the highest toughness value of 4.2 MPa was also observed at this loading. Density analysis showed a slight increase in composite density with filler addition and minimum porosity at 0.5 wt.% graphene and 2 wt.% TiO2, consistent with improved mechanical performance. XRD and FTIR analysis confirmed successful filler incorporation, enhanced crystallinity for TiO2-filled composites, and the SEM analysis confirmed the strong interfacial interactions without altering the PVA matrix chemistry, while higher filler loadings led to property degradation due to particle agglomeration and stress concentration effects.Keywords：Metal Laminated Composites, Fiber Reinforcement, Filler Concentration,Mechanical Characterization62|7|0Updated：2026-04-07 -
Molecular Weight Distribution Effects on the Structural and Mechanical Performance of Conjugated Polymers Incorporating Flexible Spacers: A Simulation Study Enhanced Publication
Abstract： Conjugated polymers incorporating flexible spacers (CP-FSs) offer a promising route to mechanically robust active layers for flexible organic solar cells. However, the influence of molecular weight distribution (MWD)—a fundamental polymer characteristic—on structural and mechanical performance remains poorly understood due to synthetic challenges. Here, we employ dissipative particle dynamics and coarse-grained molecular dynamics simulations to elucidate how MWD, quantified by polydispersity index (PDI), governs structure-property relationships in CP-FSs. Our results reveal that PDI acts as a molecular switch controlling phase morphology: increasing PDI drives transitions from lamellar to perforated lamellar structures at intermediate rigid segment lengths. At the molecular level, higher PDI significantly increases the fraction of bridging conformations ( ), strengthening a load-bearing network. During tensile deformation, this enhanced load-bearing network suppresses destructive fibrillation and instead promotes reconstructive strengthening through dynamic loop-to-bridge transitions. These findings demonstrate that controlled MWD offers a composition-independent strategy for developing mechanically robust active layers, providing practical guidelines for flexible organic solar cell design.Keywords：Conjugated polymers incorporating flexible spacers;Molecular weight distribution;Structural performance;Mechanical performance56|1|0Updated：2026-03-31 -
Modulating Molecular Electrostatic Potential Unlocks Efficient Exciton Dissociation in A-D-A-Type Narrow Bandgap Acceptors-Based Organic Solar Cells Enhanced Publication
Abstract：Multithiophene-based fused-ring electron acceptors (MFREAs) have demonstrated remarkable performance not only in organic solar cells, but also in other optoelectronic devices owing to their extended near-infrared absorption. However, an insufficient electrostatic potential (ESP) difference with the donor results in a weak intermolecular electric field (IEF), which leads to low exciton dissociation efficiency. In addition, the narrow bandgap causes substantial energy loss (Eloss), thereby restricting the open-circuit voltage. To address these problems, we developed two novel MFREAs, 6TFIC-C11-4F and 6TFIC-C11-4Cl, which were developed from the typical molecule 6TIC-4F via central-core side-chain fluorination and terminal chlorination. Although core fluorination slightly attenuated the intramolecular charge transfer (ICT) effect, this strategy significantly increased the overall average ESP value, strengthening the donor-acceptor IEF, thereby facilitating exciton dissociation. Terminal chlorination enhanced the ICT effect, resulting in a red-shifted absorption spectrum and stronger IEF. Notably, 6TFIC-C11-4F exhibited increased intermolecular interactions and reduced π–π stacking distances, leading to better charge transport. As a result, the PM6:6TFIC-C11-4F device achieved a decent power conversion efficiency of 13.32%, significantly outperforming the PM6:6TIC-4F device (10.52%). In addition, the PM6:6TFIC-C11-4Cl device demonstrated reduced Eloss and a higher short-circuit current density, validating the potential of central-core side-chain fluorination and terminal chlorination in designing high-performance MFREAs.Keywords：multithiophene fused-ring electron acceptors, organic solar cells, central-core side-chain fluorination, electrostatic potential, exciton dissociation107|6|0Updated：2026-03-26 -
Microenvironment Responsive Polymeric NO Releasing Micelles for Enhancing Eradication of Methicillin-resistant Staphylococcus aureus Biofilm Enhanced Publication
Abstract：Biofilm infections pose a severe threat to global public health owing to their persistent and recalcitrant nature. The physical barrier formed by the biofilm impedes the penetration of antimicrobial agents, leading to a significantly reduced efficacy of conventional antibiotics. Herein, we developed a polymeric micelle system that responds to the biofilm microenvironment to release nitric oxide (NO), which is capable of disrupting biofilms, thereby enhancing the bactericidal efficacy of antibiotics against embedded bacteria. The hydrophobic small-molecule NO donor was first conjugated to a diblock copolymer composed of N-hydroxyethyl acrylamide and N-acryloyl morpholine to yield an amphiphilic diblock copolymer. This amphiphilic copolymer then self‑assembles into polymeric NO-releasing micelles (PNOM). Upon exposure to thiol-containing molecules in the reducing biofilm microenvironment, PNOM responsively released NO in a sustained manner over several days. In vitro studies have demonstrated that PNOM significantly potentiated the anti-biofilm efficacy of levofloxacin (Lev) against methicillin-resistant Staphylococcus aureus (MRSA). The combination of PNOM and Lev dispersed 85.3% of the biofilm biomass and eradicated 98.8% of the embedded bacteria. Moreover, in a murine model of implant-associated MRSA biofilm infection, PNOM was validated to enhance the antibiofilm efficacy of Lev in vivo, achieving a bactericidal rate of 93.9 % for MRSA biofilms and significantly alleviating inflammation. In summary, we designed a polymeric micelle system that triggers NO release in response to a thiol-rich biofilm microenvironment, thereby disrupting biofilm formation and enhancing the antibiofilm effect of antibiotics against MRSA. This approach represents a promising therapeutic strategy for treating stubborn biofilm-associated infections.Keywords：Polymeric, Micelles, Nitric Oxide, Drug-Resistant Bacteria, Biofilm Infection52|5|0Updated：2026-03-13 - Abstract：To simultaneously endow thermal conductivity, high glass transition temperature (Tg) and healing capability to glass fiber/epoxy (GFREP) composite, dynamic crosslinked epoxy resin bearing reversible β-hydroxyl ester bonds was reinforced with boron nitride nanosheets modified glass fiber cloth (GFC@BNNSs). The in-plane heat conduction paths were constructed by electrostatic self-assembly of polyacrylic acid treated GFC and polyethyleneimine decorated BNNSs. Then, the GFC@BNNSs were impregnated with the mixture of lower concentration (3-glycidyloxypropyl) trimethoxysilane grafted BN micron sheets, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate and hexahydro-4-methylphthalic anhydride, which accounted for establishing the through-plane heat transport pathways and avoiding serious deterioration of mechanical performances. The resultant GFREP composite containing less boron nitride particles (17.6 wt%) exhibited superior in-plane (3.29 W m-1 K-1) and through-plane (1.16 W m-1 K-1) thermal conductivities, as well as high Tg of 204 oC (Tg of the unfilled epoxy = 177 oC). The reversible transesterification reaction enabled closure of interlaminar cracks within the composite, achieving decent healing efficiencies estimated by means of tensile strength (71.2%), electrical breakdown strength (83.6%) and thermal conductivity (69.1%). The present work overcame the disadvantages of conventional thermally conductive composites, and provided an efficient approach to prolong the life span of thermally conductive GFREP laminate for high-temperature resistant integrated circuit application.Keywords：Thermally conductive composites;Boron nitride;High-temperature resistance;β-Hydroxyl ester bond;Healing440|41|0Updated：2023-12-04
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Excellent compatibilization effect of a dual reactive compatibilizer on the immiscible MVQ/PP blends
Abstract：Methyl vinyl silicone rubber (MVQ)/polypropylene (PP) thermoplastic vulcanizate (TPV) combines the good melt processability, recyclability and sealing performance as well as biosafety, stain and fluid resistance, and thus it is especially suitable in bio-safety areas and wearable electronic devices, etc. Nevertheless, the compatibility between MVQ and PP phases is poor. A big challenge on the compatibilization of MVQ/PP blends is that neither MVQ nor PP contains any reactive groups. In this study, a dual reactive compatibilizer composed of ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMA-co-GMA) and maleic anhydride grafted polypropylene (PP-g-MAH) was designed for the compatibilization of MVQ/PP blends. During melt blending, a copolymer compatibilizer at the MVQ/PP interface can be formed because of the in-situ reaction between EMA-co-GMA and PP-g-MAH. The thermodynamic predict of its compatibilization effect through calculating the spreading coefficient of the in-situ formed copolymer indicates that it can well compatibilize MVQ/PP blends. The experimental results show that under the GMA/MAH molar ratio of 0.5/1, the interface thickness largely increase from 102nm for non-compatibilized blend to 406nm, and the average size of MVQ dispersed phase largely decreases from 2.3μm to 0.36μm, the Tg of the two phases shifts toward each other, the mixing torque and mechanical properties of the blend are increased, all indicating its good compatibilization effect. This study provides a good compatibilizing method for immiscible MVQ/PP blends with no reactive groups in both components for the preparation of high performance MVQ/PP TPVs.Keywords：Methyl vinyl silicone rubber (MVQ), Polypropylene (PP), Immiscible polymer blends, Reactive compatibilization11|1|0Updated：2023-01-04 - Abstract：The active layer of all polymer solar cells (all-PSCs) is composed of a blend of a p-type conjugated polymer (p-CP) as donor and an n-type conjugated polymer (n-CP) as acceptor. All-PSCs possess the advantages of light weight, thin active layer, mechanical flexibility, low cost solution processing and high stability, but the power conversion efficiency (PCE) of the all-PSCs was limited by the poor photovoltaic performance of the n-CP acceptors before 2016. Since the report of the strategy of polymerized small molecule acceptors (PSMAs) in 2017, the photovoltaic performance of the PSMA-based n-CPs improved rapidly, benefitted from the development of the A-DA’D-A type small molecule acceptors (SMAs). PCE of the all-PSCs based on the PSMA acceptors reached 17%~18% recently. In this review article, we will introduce the development history of the n-CPs, especially the recent research progress of the PSMAs. Particularly, the structure-property relationship of the PSMAs is introduced and discussed. Finally, current challenges and prospects of the n-CP acceptors are analyzed and discussed.Keywords：n-type conjugated polymers;All-polymer solar cells;polymer acceptors;polymerized small molecule acceptors.12|1|6Updated：2023-01-04
- Abstract：Since the first report of diketopyrrolopyrrole (DPP)-based conjugated polymers for organic thin-film transistors (OTFTs), these polymers have attracted great attention as representative semiconductors in high-performance OTFTs. Through unremitting efforts in molecular-structure regulation and device optimization, significant mobilities exceeding 10 cm2V–1s–1 have been achieved in OTFTs, greatly promoting the applied development of organic circuits. In this review, we summarize our progress in molecular design, synthesis and solution-processing of DPP-based conjugated polymers for OTFT devices and circuits, focusing on the role of design strategies, synthesis methods and processing techniques. Furthermore, the remaining issues and future outlook in the field are briefly discussed.Keywords：Diketopyrrolopyrrole, Polymer semiconductors, Organic thin-film transistor, Organic circuits26|2|1Updated：2023-01-04
- Abstract：Precisely optimizing the morphology of functional hybrid polymeric systems is crucial to improve its photophysical property and further extend their optoelectronic applications. The physic-chemical property of polymeric matrix in electrospinning (ES) processing is a key factor to dominate the condensed structure of these hybrid microstructures and further improve its functionality. Herein, we set a flexible polyethylene oxide (PEO) as the matrix to obtain a series of polydiarylfluorenes (including PHDPF, PODPF and PNDPF) electrospun hybrid microfibers with a robust deep-blue emission. Significantly different from the rough morphology of their poly(N-vinylcarbazole) (PVK) ES hybrid fibers, polydiarylfluorenes/PEO ES fibers showed a smooth morphology and small size with a diameter of 1~2 μm. And there is a relatively weak phase separation under rapid solvent evaporation during the ES processing, associated with the hydrogen-bonded-assisted network of PEO in ES fibers. These relative “homogeneous” ES fibers present efficient deep-blue emission (PLQY>50%), due to weak interchain aggregation. More interestingly, low fraction of planar (β) conformation appears in the uniform PODPF/PEO ES fibers, induced by the external traction force in ES processing. Meanwhile, PNDPF/PEO ES fibers present a highest sensitivity than those of other ES fibers, associated with the smallest diameter and large surface area. Finally, compared to PODPF/PVK fibers and PODPF/PEO amorphous ES fibers, PODPF/PEO ES fibers obtained from DCE solution exhibit an excellent quenching behavior toward a saturated DNT vapor, mainly due to the synergistic effect of small size, weak separation, β-conformation formation and high deep-blue emission efficiency.Keywords：matrix effect, electrospun fibers, polydiarylfluorenes, planar conformation, explosive detection4|0|0Updated：2023-01-04
- Abstract：The development of donor-acceptor (D-A) type conjugated polymers depends largely on the design of novel A building blocks. Herein, we report a novel A building block based on the cyano-substituted organoboron unit (SBN-3). Compared with the most common fluorine-substituted B←N unit, SBN-3 displays a significantly downshifted LUMO energy level because of the strong electron-withdrawing ability of cyano groups. In addition, due to the greater impact of cyano substitution on LUMO than on HOMO, SBN-3 exhibits a reduced band gap, near-infrared absorption and fluorescence properties. The D-A type conjugated polymers based on the cyano-substituted B←N unit with thiophene-based units show narrow optical band gaps of ca. 1.3 eV as well as distinctive electronic structures, i.e., delocalized LUMOs and localized HOMOs. This work thus provides not only an effective approach to design strong A units but also a new electron-deficient building block for D-A type conjugated polymers.Keywords：cyano-substituted;B←N unit;Building block;narrow band gap;D-A type conjugated polymers4|2|1Updated：2023-01-04
- Abstract：A series of thermoplastic polyimide resins with a low coefficient of thermal expansion (CTE) was prepared by blending a rigid resin system 3,3',4,4'-Biphenyltetracarboxylic dianhydride(BPDA)/p-phenylenediamine(PDA) with a flexible resin system 4,4'-[isopropylidenebis(p-phenyleneoxy)]diphthalic anhydride (BPADA)/PDA. The effects of the blending ratio on the macromolecular coil size, free volume, and CTE of the mixed system were studied. The mixing is carried out in the prepolymer polyamide acid (PAA) stage, which makes the two systems more compatible and is conducive to the formation of a semi-interpenetrating network structure between the rigid molecular chains and flexible molecular chains. The flexible structure of the BPADA/PDA system is used to ensure the melt processing performance. The rigid characteristics of the BPDA/PDA system can inhibit the movement of molecular chains and reduce the free volume fraction, thereby reducing the CTE value. When the rigid system content reaches 30%, the CTE can be reduced to 38 ppm/K. This method provides a new approach for studying low CTE thermoplastic polyimide resins.Keywords：Coefficient of thermal expansion (CTE);Thermoplastic polyimide;Melt processing property;Blending10|1|0Updated：2023-01-04
- Abstract：Molecular doping is one of the most important tools to manipulate the electrical properties of conjugated polymers for application in organic optoelectronics. The polymer crystallinity and distribution position of the dopant crucially determine electrical conductivity of the doped polymer. However, in solution-mixed doping, the interplay between polymer and dopant leads to highly structural disorder of polymer and random arrangement of dopant. Here, we propose a strategy to ensure the dopant induced polarons have high charge dissociation and transport by letting the conjugated polymers aggregate in the marginal solvent solution by cooling it from higher temperature to room temperature. We select poly(3-hexylthiophene-2,5-diyl) (P3HT) solution doped by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) as a model system. The P3HT crystallizes in the marginal solvent, such as 1,1,2-trichloroethane (TCE) driven by the favor π-π interaction between planar polymer backbone. The dopant F4TCNQ enters the alkyl side chain region not the π-π stacking region and thus guarantees high crystallinity and the π-π interaction of P3HT. This distribution of F4TCNQ which away from the polymer backbone to ensure higher charge dissociation and transport. Finally, we obtained a high conductivity value of 23 S/cm by doping P3HT with 20% F4TCNQ by using the marginal solvent, which is higher than doping P3HT with a disordered coil conformation in chlorobenzene (CB) of 7 S/cm, which the dopants enter both the alkyl side chain region and the π-π stacking region.Keywords：Solvent;Crystalline;Dopant location;Doping efficiency;Electrical conductivity26|4|1Updated：2023-01-04
- Abstract：Simultaneous realization of superior mechanical and antifouling properties is critical for a coating. The use of stereoscopic polysiloxanes in place of linear polysiloxanes to fabricate antifouling coatings can combine properties of organic and inorganic materials, i.e., they can exhibit both high hardness and wear resistance from inorganic components as well as the flexibility and tunability from organic components. This strategy is used to prepare a hard yet flexible antifouling coating or polymer–ceramic hybrid antifouling coatings. In this mini-review, we report the recent advances in this field. Particularly, the effects of stereoscopic polysiloxane structure on their mechanical and antifouling properties are discussed in detail.Keywords：Antifouling coating;Organic-inorganic hybrid;Sol-gel;Hard yet flexible15|3|3Updated：2023-01-04
- Abstract：Although photothermal therapy (PTT) has been developed for fighting cancers, the degradative, toxic, and metabolic nature of photothermal conversion materials (PCMs) has prevented them from being clinically implemented. Taking advantage of the surface modification strategy of mussel-inspired dopamine chemistry and its excellent photothermal conversion effect, polydopamine (Pdop) represents a versatile PTT platform, providing strategies and methods for the construction of novel Pdop-functionalized PCMs. Thanks to its adhesion and secondary reactivity, Pdop can be deposited on virtually all substrates to improve their bioavailability and biocompatibility. Pdop-based PCMs could not be only functionalized with small biomolecules via chemical bonds and/or noncovalent force but also modified with functional polymers via either the “grafting to” or “grafting from” method. This review highlights the synthetic methods, therapeutic strategies, and designs of PCMs based on Pdop in recent years to explore its scope and limitations.Keywords：Polydopamine;Photothermal therapy;Drug delivery systems;Polymers;Tumor theranostics19|11|6Updated：2023-01-04
- Abstract：The effect of freezing layer on the crystallization kinetics of poly(ε-caprolactone) (PCL) thin and ultrathin films was investigated by monitor the growth process of it on oriented polyethylene (PE) and CaF2 with and without freezing layer, respectively. It was found that the PCL films with similar thicknesses crystallize much faster on oriented PE than on CaF2 substrate. For example, the crystallization rate constant of a 102 nm thick PCL film decreases tremendously by 3 orders of magnitude from 1.1×101 on PE substrate at 50 C to 7×104 on CaF2 surface at 40 C. Moreover, the crystallization of PCL accelerates on CaF2 surface while slows down at PE surface with increasing film thickness. The ultrathin films of PCL with thickness less than 14 nm exhibits the fastest crystallization rate on oriented PE with a rate constant of about 3.5×101, which is 3 times higher than that of a ca. 50 nm thick film. This illustrates the great influence of freezing layer on the crystallization process of PCL. The freezing layer thickness of PCL on PE is estimated to be in the range of 1417 nm. Taking the radius of gyration (Rg 15.6 nm) of the used PCL material into account, the obtained results may imply the existence of a correlation between the Rg of PCL and its freezing layer thickness at PE substrate.Keywords：Poly(ε-caprolactone);Polyethylene;Interface;Freezing layer;Crystallization kinetics10|0|1Updated：2023-01-04
- Abstract：The solubility of a direct arylation polycondensation (DArP) synthesized conjugated polymer, i.e., poly(3,6-bis(furan-2-yl)-2,5-bis(4-tetradecyloctadecyl)-pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-alt-1,2-bis(3,4-difluorothien-2-yl)ethene) (PFuDPP-4FTVT), in various organic solvents was studied. The polymer is soluble in 3-methylcyclohexanone (3-MC), a green solvent from peppermint oil, besides other solvents such as anisole, cyclopentyl methyl ether (CPME) and o-dichlorobenzene (o-DCB), etc. Based on the Hansen solubility parameters (HSP) analysis, 3-MC is identified as a “marginal solvent” of PFuDPP-4FTVT. The morphology of the spin-coated films with 3-MC as the solvent strongly correlated with the solution preparation conditions. With a 3-MC solution aged for 3 h at 70 °C, n-channel organic thin-film transistors (OTFTs) with electron mobility (e) above 1 cm2·V1·s1 and current on/off ratio (Ion/Ioff) higher than 105 were fabricated by spin-coating. This is the first report on high mobility conjugated polymers for OTFTs processible with naturally occurred green solvent.Keywords：Conjugated polymers;Organic thin-film transistors;Electron mobility;Green solvent;Direct arylation polycondensation22|12|1Updated：2023-01-04
- Abstract：Combretastatin A4 phosphate (CA4P) is a potent vascular disrupting agent with good water solubility. However, it is only effective at high doses, which decreases clinical applicability. Herein, we designed stable CA4P polymeric nanoparticles (CA4P NPs) consisting of various cholesterol derivatives, and with a drug loading efficacy of 93%. The nanoparticles released CA4P in a sustained manner and achieved a 72% inhibition rate in the murine H22 liver tumor model, which was about 2.9-fold higher than that of free CA4P (24.6%). Furthermore, the carrier components of CA4P NPs were metabolized to arginine, cholesterol, ethanol and poly(ethylene glycol) in vivo; therefore, the CA4P NPs are safe and have significant potential for clinical translation.Keywords：CA4P polymeric nanoparticle;Cholesterol derivatives;Vascular disrupting agent;Phosphate-guanidine coordination;Drug controlled release14|2|0Updated：2023-01-04
- Abstract：Coordination-insertion ring-opening polymerization (ROP) of cyclic esters is an industrial way to synthesize polyesters, which are widely applied in biomedical and environment-benign fields. However, the rate-determining transition state (TS) identified by the conventional reaction pathways (pathway A and pathway B) presented in the literature do not well describe the structure-reactivity relationship. The misidentification of the rate-determining TS might arise from the less ergodicity in the search of reaction pathways. Herein, we suggested a stride strategy based on the insight that even a partial double bond is rotatable at the catalysis temperature. As a result, we revealed a new reaction pathway, pathway C with a torsion transition state TSC2, by density functional theory (DFT). We also carried out kinetic experiments of ROP of D-lactide (D-LA), L-lactide (L-LA), ε-caprolactone (CL), and δ-valerolactone (VL), using poly(ethylene glycol) as the initiator and stannous octoate as the catalyst. The excellent linearity between the calculated free energy barriers and logarithms of the experimental kinetic constants of the two kinds of lactide and lactone monomers, was established, validating the quasi-ergodic search of reaction pathways and the scaling predicted by transition state theory. The linearity was highly predictive for the other lactide and lactone monomers, demonstrated by glycolide (GA) and trimethylene urethane (TU).Keywords：Coordination-insertion mechanism;Ring-opening polymerization;Density functional theory;Biodegradable polymer;Lactide;Lactone;Cyclic ester8|0|0Updated：2023-01-04
- Abstract：For decades, the preparation of polyisoprene rubber that can match the comprehensive properties of natural rubber (NR) has been pursued. While sacrificial bonds have been used to promote the strength and toughness of rubbers, little is known about their effects on fatigue resistance, which is important in dynamic environments. Herein, terminal block and randomly functionalized polyisoprene rubbers tethered with di-alanine, tri-alanine and tetra-alanine were prepared. The results showed that the flow activation energy, aggregates ordering and energy dissipation of the hydrogen-bonded aggregates increase with the elongation of oligopeptide length (XA, X=2, 3, 4), therefore resulting in enhanced mechanical strength and toughness of corresponding samples. Comparably, the tear strengths are barely affected by oligopeptide lengths in block samples, but promoted from dipeptide to tetrapeptide in random samples, probably due to the well dispersed oligopeptide aggregates. Most importantly, it is found that the tight binding aggregates of oligopeptides are critical for the excellent fatigue resistance, which is absent in polyisoprene and natural rubber. The loose aggregates dissociate and recombine repeatedly under cyclic loading and the tight aggregates keep the network integrated and robust. Interestingly, the largest hysteresis of PIP-4A-V with the longest oligopeptide length give the lowest heat generation, which is contrary to the traditional sacrificial bonds. Overall, the oligopeptide aggregates have repeatable energy dissipation properties and cycle life comparable to or even surpassing those of the linked proteins in NR, resulting in similar tensile strength, fracture toughness, and better fatigue resistance relative to NR. This deep insight on the role of oligopeptide aggregates is very useful for the engineering rubbers served in dynamic environments.Keywords：Polyisoprene;Hydrogen bonding;Oligopeptides;Fatigue resistance15|0|0Updated：2023-01-04
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