- 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;Healing
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Published：2023-12-04 -
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 compatibilization- 11
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Published：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.
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Published：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 circuits
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Published：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 detection
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Published：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 polymers
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Published：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;Blending
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Published：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 conductivity
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Published：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 flexible
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Published：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 theranostics
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Published：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 kinetics
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Published：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 polycondensation
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Published：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 release
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Published：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 ester
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Published：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 resistance
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Published：2023-01-04 - Abstract：Achieving the linear polymers with high molecular weight via step-growth polymerization of A2 and B2 monomers is significantly limited by the requirement of strict stoichiometry of two monomers when the reactivity of A and B groups are not changed during the polymerization. Herein, a unique step-growth polymerization based on copper-catalyzed azide-alkyne cycloaddition (CuAAC) with reaction-enhanced reactivity of intermediate (RERI) mechanism was developed for the preparation of mainchain semifluorinated polymers with high molecular weight. The CuAAC polymerization of bis-alkynyl-terminated fluorinated monomers (A2) and 2,2-bis(azidomethyl)propane-1,3-diyl bis(2-methylpropanoate) (BiAz, B2) with RERI effect at different stoichiometric ratio was systematically investigated. The results indicated that the semifluorinated polymers with ultrahigh molecular weight, Mw,MALLS>106 g/mol, could be efficiently synthesized by using excess molar of BiAz monomers. The resultant high-molecular-weight semifluorinated polymers show good thermostability and high hydrophobicity. In addition, the glass transition temperature (Tg) of these mainchain semifluorinated polymers could be tuned conveniently due to the bis-alkynyl-terminated comonomers could be consumed completely when excessive BiAz monomers were used in this this step-growth polymerization.Keywords：Semifluorinated polymers;Click polymerization;Step-growth polymerization
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Published：2023-01-04 - Abstract：In recent years, flexible strain sensors have received considerable attention owing to their excellent flexibility and multifunctionality. However, it is still a great challenge for them to accurately monitor multi-model deformations with high sensitivity and linearity. In this study, the industrial insulating silk habotai was successfully converted into carbonized silk habotai (CSH) for use in strain sensors. A strain sensor created using CSH exhibited excellent sensing performance under multi-model deformations, including stretching, twist and bending. The maximum tensile strain was 434%. The gauge factors were 14.6 in the wide tensile range of 0%–400% with a high linearity of 0.959. In addition, the CSH strain sensor exhibited an extremely fast response time (110 ms) and could accurately detect bending (0°–180°) and torsional (0°–180°) strains. High durability and repeatability were observed for the multi-model strains. Finally, a new type of smart pillow was developed to accurately record head movement and breathing during sleep. The sensor may also be used for auxiliary training in table tennis. The proposed CSH strain sensor has shown great potential for applications in smart devices and human-machine interactions.Keywords：Carbonized silk habotai;Strain sensor;Smart pillow;Human motions
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Published：2023-01-04 - Abstract：Introduction of asymmetric units into conjugated polymers is an important strategy to regulate the photophysical and electronic properties of polymers, as asymmetric units can not only regulate solubility and energy levels, but also molecular stacking and orientation, thus giving much higher optoelectronic properties. However, very few studies have been reported on this field. The semiconducting properties of conjugated polymers could be regulated through regioregularity adjustment. Here, we took the asymmetric thiophene/pyridine side group DPP as core and developed the regioregular monomer T-Py-DPP through three steps: alkyl chain introduction, tin monomer coupling and NBS double bromination. The T-Py-DPP monomer was polymerized into reg-PPyTDPP-2FBT with a head-to-head structure. The regioregularity of T-Py-DPP unit endowed reg-PPyTDPP-2FBT with backbone planarity, self-assembly orientation, network-like morphology and high crystallinity in films, thus the superior bipolar transport properties. The highest hole and electron mobilities of reg-PPyTDPP-2FBT were 0.93 and 0.57 cm2·V1·s1, respectively, with 40% improvement relative to the regiorandom polymer.Keywords：Asymmetric copolymers;Regioregularity;Good orientation;Organic field-effect transistor;Enhanced performance
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Published：2023-01-04 - Abstract：Two new ratiometric hypoxia probes (Ir-C343 and Ir-GFP) are synthesized by covalently incorporating florescent internal standard molecules coumarin 343 (C343) and green fluorescent protein (GFP) into bis[1-(9,9-dimethyl-9H-fluoren-2-yl)-isoquinoline] (succinylacetone) Ir(III) (Ir-fliq), respectively. After connecting with internal standard molecules, the Ir-fliq moiety still exhibit high sensitivity to oxygen concentration, while the fluorescence intensity of the internal standard remains relatively constant under different oxygen concentrations. As a result, a ratiometric response is realized that is only related to oxygen concentration. In addition, Ir-GFP shows more promising applications in the ratiometric hypoxia imaging of cells due to its long excitation wavelength, good water solubility, high biocompatibility, and low relative fluorescence intensity compared with the phosphorescent emitter Ir-fliq.Keywords：Hypoxia probe;Ratiometric probe;Hypoxic response;Cell imaging
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Published：2023-01-04 - Abstract：Thermoplastic polyimides (PIs) with shape memory potential have received growing attention in recent years. In this work, high-performance thermoplastic PIs were fabricated by introducing PIs with chain rigidity (r-PI) into PI with chain flexibility (f-PI). The influences of molecular chain entanglement and π-π interactions on their thermomechanical and shape memory properties were investigated. The degree of molecular chain entanglement was quantitively characterized based on dynamic mechanical analysis (DMA). The π-π interactions were investigated in detail by X-ray diffraction (XRD) and UV-Vis spectroscopy. It was found that the entanglement density increased and π-π interactions became stronger with the introduction of r-PI into f-PI, leading to the improvement of shape recovery. Moreover, a broad and increased glass transition temperature (Tg) was achieved, endowing multiple shape memory properties of the PIs. The synergistic effects of increased entanglement density and enhanced π-π interactions were beneficial to regulating interchain interactions and thereby achieving high performance shape memory performance of the PIs.Keywords：Shape memory polyimide;Molecular chain entanglement;π-π stacking
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Published：2023-01-04
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