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The study was to systematically evaluate the nutritional value of annual grasses in the alpine region. Four common species of oat grass (white oat, green oat, Connor oat and Rinna oat) in the plateau region were studied, the general nutrient analysis, gas production in vitro and yield per unit area in different periods were adopted. The results showed that the fresh grass yield of the four species of oat grass reached the peak at the milk stage, and the hay yield reached its peak at the mature stage. The fresh to dry ratio, CP content and EE content of the four oat grass decreased, while the content of ADF and NDF increased with little change in energy. The content of TVFA in the 72 h fermentation broth of four oat grasses decreased with the increase of harvest time, and the content of acetic acid, propionic acid, isobutyric acid and butyric acid was the highest at heading time. The study indicates that oat grass has the highest hay yield at maturity, the highest hay quality at heading, and the highest nutrient output, digestible dry matter and organic matter yield per unit area cut at milk maturity. [ABSTRACT FROM AUTHOR]

Galvanic corrosion behaviour of copper and copper alloys in chloride solution (0.6 M NaCl) under different temperature conditions (35°C, 55°C and 80°C) was investigated by the wire beam electrode (WBE) method. It was found that the average galvanic current of the Cu and Cu-Sn alloy, which shifted from the cathode at 35°C to the anode at 80°C, increased as temperature increased during the immersion time. In contrast, the average galvanic current of Cu-Zn alloy can be ranked as 35°C > 55°C > 80°C. A sudden conversion was that the anode average current of Cu-Zn alloy at 35, 55°C changed into the cathode when the immersion time lasted untill 3 h at 80°C. The results indicate that it is feasible to study the corrosion behaviour under the different temperature environment with the WBE method. [ABSTRACT FROM AUTHOR]

A new class of organic nanotubes have been assembled from simple isophthalamide derivatives and their surface can be conveniently coated with Pt, which form new Pt nanotubes after the inside organic materials are removed with hot methanol. [ABSTRACT FROM AUTHOR]

Background: Trigger finger is a common condition in the hand, and ultrasound-guided acupotomy for trigger finger has been widely used in recent years. Purpose: This study aims to investigate the efficacy and safety of ultrasound-guided acupotomy for trigger finger. Methods: We searched for relevant studies in the Cochrane Library, China National Knowledge Infrastructure (CNKI), Embase, PubMed, Chinese Biomedical Literature Database (CBM), Wanfang Data, and other resources from their inception to January 2023. Randomized controlled trials of ultrasound-guided acupotomy for trigger finger were included. The meta-analysis was carried out using Review Manager 5.4 and Stata 15.1. Results: Overall, 15 studies with 988 patients were included. The experimental group was treated with ultrasound-guided acupotomy, and the Control group received traditional acupotomy, traditional operation or injection of medication. Meta-analysis showed that the overall clinical effectiveness (OR = 4.83; 95% CI 2.49–9.37; I2 = 73.1%; P < 0.001) in the experimental group was significantly better than that of the control group. And the Visual Analogue Scale (VAS) score (WMD = − 1; 95% CI − 1.24, − 0.76; I2 = 99%; P < 0.001), the QuinneII classification (WMD = − 0.84; 95% CI − 1.28, − 0.39; I2 = 99.1%, P < 0.001), the incidence of complications (RR = 0.26; 95% CI 0.11, 0.63; I2 = 0%, P = 0.003), and the recurrence rate (RR = 0.14; 95% CI 0.03, 0.74; I2 = 0%; P = 0.021) were significantly lower in the experimental group. Conclusion: Our systematic review and meta-analysis can prove the effectiveness and safety of ultrasound-guided acupotomy in the treatment of trigger finger, but this still needs to be verified by a clinical standard large sample test. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Along with the continuously advanced requirements for high performance rubbers such as in aircraft tires, natural rubbers show limitations in achieving high temperature creep resistance and high mechanical strength simultaneously. Meanwhile, the bi-terminal interactions of natural rubber (NR) exhibit unique reinforcement effects, which are difficult to realize in synthetic rubbers. In this article, four different types of bi-terminal polyisoprenes with distinct groups were synthesized, and they were assembled with penta-alanine molecule (5 A) to obtain high-performance rubbers by terminal hydrogen bonding reinforcement. Infrared tests indicate that the strong hydrogen bonds can be formed between two terminals and turn stronger after adding 5 A. Thus, the network of rubbers remains stable under different strains and temperatures and the activation energy of networks is elevated. As a result, this biomimetic design endows polyisoprene with high tensile strength compared with Malaysian NR and greater creep resistance. Further Mooney fitting and DMA test suggests that these confined hydrogen bonds not only increased the number of crosslinking points and entanglements of network, but also are beneficial for the segmental chain motion. In contrast to our common sense on hydrogen bonds which present large relaxation and hysteresis, this study proposes a facile method for preparing high-temperature creep-resistant rubbers by introducing confined hydrogen bonds, which represents a great advance in the structural biomimicry of NR. [Display omitted] • Four different bi-terminal polyisoprenes were synthesized. • Bi-terminal structure provided more crosslinking points and entanglements. • Two terminals and penta-alanine formed confined hydrogen bonds. • Bi-terminal interactions brought superior creep resistance relative to NR. [ABSTRACT FROM AUTHOR]

Oxidation resistance is strongly necessary for the use of crosslinked ultrahigh molecular weight polyethylene (UHMWPE) in artificial joints. The hybrid antioxidant strategy emerged as a promising alternative to the single rival that relies on vitamin E (VE). The goal of this study was to investigate the universality of the antioxidant synergy between VE and sugar alcohol (SA). Three types of SA, including D-sorbitol, maltitol and erythritol, were employed to cooperate with VE. Compared to the use of VE alone, these hybrid antioxidants generally enabled the corresponding UHMWPE composites with prolonged oxidation induction time (OIT) and increased crosslink density. The correlation between OIT and crosslink density of VE/SA-stabilized UHMWPE composites showed low attenuation. The applicability of the hybrid antioxidants to protect UHMWPE against oxidation was further demonstrated using the in vitro clinically relevant accelerated aging. Among the used SA, D-sorbitol exhibited the strongest ability to enhance the synergetic efficiency. The possible mechanism was revealed from the following aspects: the number of secondary hydroxyls per molecular mass and the molecular polarity determined via polarity parameter calculation. These findings provide significant insights for fabricating UHMWPE bearing materials with superior comprehensive performance and extended service longevity. [Display omitted] • The universality of the synergy between Vitamin E (VE) and sugar alcohols (SAs) to stabilize UHMWPE is demonstrated. • Compared with using VE alone, the combination of VE and SA enables UHMWPE with longer OIT and higher crosslink density. • D-sorbitol exhibits the strongest ability to enhance the synergetic efficiency among the used SA. • The influence of SA structure on the synergic antioxidant effects is revealed. [ABSTRACT FROM AUTHOR]

Abstract: This Letter reports the synthesis of three dicationic and two hexacationic receptors in which two porphyrin units are connected with an aryl amide linker. 1H NMR and X-ray crystal structure analysis for model compounds show that in aqueous or DMSO medium the receptors could adopt preorganized U-styled conformation due to intramolecular hydrogen bonding-induced rigidity of the amide linker. 1H NMR, UV–vis and fluorescent investigations revealed that the ionic receptors efficiently complex C60C in aqueous medium with cooperative intermolecular electrostatic and donor–acceptor interactions as driving forces. A 1:1 binding stoichiometry has been established for the complexes and the related association constants have been evaluated. [Copyright &y& Elsevier]

Abstract: The self-assembly of a novel series of hydrogen bonding-mediated homodimers in chloroform-d has been described. Six anthranilamide-based monomers have been prepared, in which two self-binding formamido, trifluoroacetamido, acetamido, butyl or methyl ureido units are introduced at the two ends of the backbones. Quantitative 1H NMR investigations in chloroform-d revealed that the formamido and ureido units are more efficient than acetamido to induce the formation of stable homodimers. The association constants of all the new homodimers have been determined by 1H NMR dilution method. Multiply hydrogen bonding-driven binding patterns have been proposed for the homodimers. It is also found that ureido-derived homodimers do not adopt common linear binding pattern observed for simple urea derivatives. [Copyright &y& Elsevier]

It is still a great challenge to mimic the structure and function of natural rubber by introducing polar components into synthetic polyisoprene. In order to explore the function of phosphate groups on the mechanical properties of polyisoprene rubber, a terminally functionalized compound (PIP-P) containing phosphate groups was synthesized and further vulcanized to prepare the model compound V-PIP-P. Through analyzing the test results, it was found that these phosphate groups formed polar aggregates in non-polar polyisoprene rubber matrix, serving as an additional dynamic cross-linking sites, which increases the cross-linking density and improves mechanical properties. The influence of the phosphate groups on the strain-induced crystallization (SIC) was further investigated via synchrotron wide-angle X-ray diffraction (WAXD) experiment. These phosphate group aggregates not only reduced the onset strain of SIC, but also slowed down the molecular chain mobility, which hinder the crystal lateral growth. The above results help us to gain a deeper understanding for the function of phosphate groups in the formation of "naturally occurring network" and guide the molecular design of next generation polyisoprene rubber. [ABSTRACT FROM AUTHOR]

Bilactam derivatives with different side groups were synthesized and the twisting angle tuning effect induced by the intramolecular hydrogen bond on the charge transport through their single-molecule junctions was investigated. Molecules with strong intramolecular hydrogen bonds exhibited twice higher conductance because of the reduced dihedral twisting, which was reversible with the addition of hydrogen bond destroying solvent. Our findings reveal that the presence of intramolecular hydrogen bonds promotes the planarization of the molecular structure without additional transmission channels, offering a new strategy for controlling molecular switches via tuning the molecular twisting. [ABSTRACT FROM AUTHOR]

Vitrimers usually exhibit reprocessability and recyclability due to the reversible crosslinking bonds, thus these materials are expected to be applied as sustainable materials. However, the vitrimer elastomers are susceptible to creep because of their inherent exchange nature, which limits their practical application. The key to improve the creep resistance at service temperature relies on controlling and regulating the intrinsic dynamic properties. Therefore, an in-depth study of the effect of molecular variables on dynamic properties was useful for the design and application of vitrimers. exchangeable units distribution is one of the major molecular variables to tune the dynamics, but it has hardly been studied. Herein, vitrimer elastomers with different uneven degrees of exchangeable units distribution (n) was prepared to study the quantitative relationship between exchangeable units distribution and dynamic behaviors. Due to the uneven exchangeable units distribution, the crosslink-rich and crosslink-poor regions existed simultaneously in networks. The relaxation time of resulting networks increased and then decreased with n due to the combined effects, and samples with moderate uneven distribution showed the longest relaxation time. At the same time, the relaxation times for all samples were short enough to reprocess at elevated temperatures. What is more, the activation energy (E a) and topology freezing transition temperature (T v), two important intrinsic parameters for controlling the dynamics, increased linearly with n values. In the meantime, the creep strains and creep rates decreased with n, revealing improved creep resistance. This work provides a strategy to control the dynamics by adjusting the exchangeable units distribution thus enhancing creep resistance. And the proposed strategy and resulting quantitative models might be applied to other vitrimers, which could be utilized to prepare desired vitrimers with exact network designs for various applications. [Display omitted] • Vitrimers with uniform and uneven distribution of exchangeable units were prepared by crosslinking random and taper polymers. • The dynamics were tuned with the exchangeable units distribution, thus improving creep resistance under service condition. • E a and T v values increased linearly with uneven degrees of exchangeable units distribution. [ABSTRACT FROM AUTHOR]

Inhomogeneous network construction is a useful strategy to solve the trade-off between mechanical strength and creep in vitrimer rubbers. But it is still lack of tools to tune the mechanical properties and network dynamics of this new system. In this paper, uneven distribution of functional groups was realized by sequential coordination polymerization of myrcene and isoprene and epoxidation. The following epoxidation and curing generated VMI-x samples with inhomogeneous network. Polyisoprene was used to prepare control samples called VPI-x with homogeneous network. Different lengths of dicarboxylic acid crosslinkers (SA = succinic acid, HA = heptanedioic acid, DA = decanedioic acid) were used to probe their effects on dynamic behaviors, mechanical properties and recyclability. Morphological test and nanomechanical mapping confirmed the inhomogeneous feature of VMI-x samples. For both inhomogeneous and homogeneous samples, SA and DA crosslinkers brought higher tensile strength and modulus, earlier SIC phenomenon and higher orientation percentage of amorphous molecular chains than those of HA, which are ascribed to extra permanent cross-linking existing in SA samples and transition entanglements existing in DA samples. However, the constrain effect of SA crosslinker is too strong in inhomogeneous network to sacrifice the extensibility, which is much smaller than those of HA and DA. SA and DA samples also present restricted segmental motion and superior creep resistant properties compared to HA samples according to the results of broadband dielectric spectroscopy and DMA test. Differently, at high temperature above 130 °C, the stress relaxation, topology freezing transition temperature (Tv) and recycling efficiency of strength are dominated by the crosslinker length monotonically, probably due to the disentanglement of DA crosslinkers. Compared to homogeneous network, inhomogeneous ones showed obvious enhanced mechanical properties, lower hysteresis, quicker segmental relaxation, lower creep and quicker network relaxation. This work demonstrates that crosslinker lengths could tune the vast aspects of vitrimer elastomers and is a non-negligible factor to determine their properties, especially for those with inhomogeneous networks. [Display omitted] • Inhomogeneous vitrimer elastomers were built by varying crosslinker length. • The mechanical properties and creep resistance can be finely tuned. • Stress relaxation and recyclability are related to crosslinker length monotonically. [ABSTRACT FROM AUTHOR]

The branching structures in natural rubber (NR) were believed to be critical for its superior mechanical properties. However, it is challenging to unravel the branching structure-function relationship of NR due to the complexity of the system. Herein, polyisoprene-(polyisoprene-g-polylactide) (PI-PLA) as model compound containing branching structure was designed and synthesized, which can improve the modulus, strength and viscoelasticity activation energy compared to those of the pristine polyisoprene (PI). The reason is that the branching structure contributes to the entanglement between polyisoprene chains. In order to probe the effect of branching structure on noncovalently crosslinked system, the polyisoprene block of PI-PLA was epoxidized and mixed with Fe3+ ions to introduce coordination bonds. Compared with the linear counterpart, the branching structure obviously enhanced activation energy of coordinated polyisoprenes, remarkably improving the mechanical properies of elastomer. [ABSTRACT FROM AUTHOR]

Two conjugated polymers (PuIDTBD and PuIDTQ) with unsymmetric side chains have been prepared for polymer solar cells using two other polymers (PIDTBD and PIDTQ) with symmetric side chains as control compounds. The combination of methyl and 4-hexylphenyl side chains on the same bridged carbon can ensure good solubility, decrease π-π stacking distances, and bring proper miscibility with PC71BM simultaneously. Therefore, the corresponding polymer solar cells (PSCs) based on donor polymers with unsymmetric side chains exhibited enhanced short-circuit current density (JSC) and power conversion efficiency (PCE) compared with those of control polymers. The PIDTBD and PIDTQ based devices possessed low PCE of 2.13% and 1.48%, while PCEs of devices based on PuIDTBD and PuIDTQ were improved to 3.93% and 4.12%, respectively. The results demonstrate that unsymmetric side chain engineering of conjugated polymers is an effective approach to achieve high performance PSCs. [ABSTRACT FROM AUTHOR]

The branching structure formed by α terminal of natural rubber (NR) was believed to be critical for its superior mechanical properties. However, it is challenging to unravel and mimic the relationship between the terminal structures and properties of NR due to the complexity of the system. Herein we synthesized a model compound containing phosphate groups at the end of the polyisoprene rubber to explore the role of α-terminal. After a series of tests, it is found that the phosphate groups formed branching points with or without iron ions. TEM test showed that sizes of aggregates formed by phosphate groups changed to be smaller after addition of FeCl 3. Water contact angle test verify the formation of branching structures. Rheology test showed that branching structures increased their storage modulus G' compared to linear polymer. The effects of phosphate groups aggregations on the chain dynamics were also investigated. Dielectric relaxation analysis indicated that the branching structure formed by phosphate groups confined the chain movement. All the above results help us to get a deeper understanding on the structural formation and function about α-terminal groups of NR. Image 1 • A model compound containing phosphate groups at the end of the polyisoprene chain was synthesized. • The branching structure formed by phosphate groups was confirmed. • The effects of branching structure on storage modulus and chain dynamics were investigated. [ABSTRACT FROM AUTHOR]

Abstract Asymmetrical side chains were widely used in conjugated molecules, but related stereoisomeric phenomenan is rarely investigated. Herein, two stereoisomers based on ladder-type acceptor IDT-BT-R with asymmetrical side chains were synthesized and their properties were studied. Compared to cis -IDT-BT-R, trans -IDT-BT-R with centrosymmetrical structure showed stronger crystallinity and more ordered molecular packing. As a result, trans -IDT-BT-R based photovoltaic devices exhibited higher charge transport properties and superior power conversion efficiency (PCE) up to 9.43%. Graphical abstract Two stereoisomers of ladder-type acceptor molecules were obtained and their aggregation behaviors and photovoltaic performance were investigated. Image 1 Highlights • Two stereoisomers with asymmetrical side chains based on IDT-BT-R were successfully synthesized. • Centrosymmetric trans -IDT-BT-R showed enhanced crystallinity and denser intermolecular packing. • OSCs based on trans -IDT-BT-R showed high PCE of 9.43%. [ABSTRACT FROM AUTHOR]

Abstract Four acceptor1-acceptor2-donor-acceptor2-acceptor1 (A1-A2-D-A2-A1) structural electron acceptors with different end-chains were designed and synthesized which all possessed indacenodithiophene (IDT) core, benzothiadiazole (BT) bridge as acceptor2, and rhodanine (R) end groups as acceptor1. The non-fullerene acceptor attached with ethyl group is called IDT-BT-R2 and used as control compound. And the other three of them are attached with methoxymethyl, trifluoroethyl and 1-piperidino groups generating IDT-BT-RO, IDT-BT-RF3 and IDT-BT-RN, respectively. The influence of end-chains on their optoelectronic properties were compared between four non-fullerene acceptors. Compared with IDT-BT-R2, the molecule IDT-BT-RF3 show red-shifted light absorption and lower LUMO level because of the electron withdrawing property of fluorine atoms. OSCs based on IDT-BT-RF3 display more efficient charge separation and lower degree of monomolecular recombination, allowing OSCs to show higher short-circuit current (J sc) than the system of IDT-BT-R2. OSCs based on IDT-BT-RO also show more efficient charge separation and less monomolecular recombination. Due to the elevated LUMO level of the acceptor IDT-BT-RN, organic solar cells (OSCs) utilizing this material as acceptor display high open-circuit voltage (V oc) of 1.10 eV and low energy loss of 0.49 eV when maintaining a relatively high power conversion efficiency (PCE) of 7.09%. We demonstrated that the end-chain engineering could finely tune the light absorption properties and energy levels of novel non-fullerene acceptors and eventually improved OSCs performance can be harvested. Graphical abstract Image 1 Highlights • Heteroatoms were incorporated into end-chains to generate novel electron acceptors. • Fluorine or oxygen atoms containing end-chains lead more efficient charge separation and less charge recombination. • OSCs based on IDT-BT-RN showed high V oc of 1.10 eV, PCE of 7.09% and low energy loss of 0.49 eV. [ABSTRACT FROM AUTHOR]

Natural rubber is one of most famous self‐reinforced rubbers thanks to the phenomenon of strain‐induced crystallization. It is usually used in a vulcanized form to enhance the mechanical strength but this results in recycling issues. Herein a thermoplastic analogue of vulcanized natural rubber is obtained as a structural mimic. Terminally functionalized polyisoprene rubber B‐4A‐PIP was prepared by using tetra‐analine as physical crosslinking units. The strong binding of tetra‐analine groups gave B‐4A‐PIP a high tensile strength (15 MPa) and breaking strain of 890 %, which is much higher than those of undecorated copolymer B‐OH‐PIP. B‐4A‐PIP has a similar onset strain of crystallization and crystallization index to vulcanized natural rubber. Randomly functionalized polyisoprene R‐4A‐PIP showed a much lower mechanical strength and SIC properties although R‐4A‐PIP and B‐4A‐PIP possessed similar molecular weights and amounts of tetra‐analine groups. Terminal functionalization: Tetrapeptide grafting polyisoprenes were prepared with different sequences of polar groups. The terminal polar block promoted the toughness and stain‐induced crystallization behavior of thermoplastic polyisoprene; these properties were comparable to vulcanized natural rubber. [ABSTRACT FROM AUTHOR]

Natural rubber is one of most famous self‐reinforced rubbers thanks to the phenomenon of strain‐induced crystallization. It is usually used in a vulcanized form to enhance the mechanical strength but this results in recycling issues. Herein a thermoplastic analogue of vulcanized natural rubber is obtained as a structural mimic. Terminally functionalized polyisoprene rubber B‐4A‐PIP was prepared by using tetra‐analine as physical crosslinking units. The strong binding of tetra‐analine groups gave B‐4A‐PIP a high tensile strength (15 MPa) and breaking strain of 890 %, which is much higher than those of undecorated copolymer B‐OH‐PIP. B‐4A‐PIP has a similar onset strain of crystallization and crystallization index to vulcanized natural rubber. Randomly functionalized polyisoprene R‐4A‐PIP showed a much lower mechanical strength and SIC properties although R‐4A‐PIP and B‐4A‐PIP possessed similar molecular weights and amounts of tetra‐analine groups. [ABSTRACT FROM AUTHOR]

A novel method for the synthesis of a thiophene analogue of isoindigo (TIIG) is described. The reaction involves a palladium-catalyzed C-H activation/oxidative cyclization sequence. This new methodology has potential for diversifying the isoindigo family. The thin-film transistors (TFTs) prepared from a TIIG-based copolymer (PIDTT-TIIG) with indacenodithieno[3,2-b]thiophene (IDTT) exhibit unipolar charge-transport properties with hole mobilities of 0.17 cm² V-1 s-1. [ABSTRACT FROM AUTHOR]

A novel ladder-type donor pyran-bridged indacenodithiophene (IDTP) is developed by introducing two oxygen atoms into indacenodithiophene unit. IDTP possesses a twisted backbone and leads to facially asymmetric arrangement of side chains, resulting in enhanced local π-π stacking of according polymer poly[(5,5,11,11-tetrakis(4-octylphenyl)-5,11-dihydrothieno[2′,3′:5,6]pyrano[3,4-g]thieno[3,2-c]isochromene)- alt-4,7-(5-fluoro-2,1,3-benzothiadiazole)] (PIDTP)-FBT, which shows extended absorption range. Moreover, oxygen atoms render deeper highest occupied molecular orbital (HOMO) levels of poly[indacenodithiophene- alt-4,7-(5-fluoro-2,1,3-benzothiadiazole)] (PIDTP)-FBT compared with PIDT-FBT, therefore bringing a higher open-circuit voltage ( Voc). [ABSTRACT FROM AUTHOR]

Vitrimer elastomers bring huge chance to solve the recycling problem of conventional rubbers. However, their application is extremely limited by their lack of creep resistance. Although the crosslinking density can significantly affect the relaxation behavior of dynamic covalent networks, but limited by the tradeoff between mechanical strength and creep resistant properties. Here, we introduce inhomogeneous dynamic covalent network with regions of different crosslinking densities, in which the low crosslinking density mainly contribute to the creep resistance and the high crosslinking density contribute to the mechanical strength. In detail, block copolymers with polymyrcene and polyisoprene blocks and its control sample polyisoprene were prepared and epoxidized. The polymyrcene block is a double bond-rich block compared to polyisoprene block, which will become an epoxy group-rich block after epoxidation and a high cross-link density phase region after crosslinking with a dicarboxylic acid agent. Therefore, the cross-linked block copolymer will have an inhomogeneous dynamic covalent network, which were confirmed by the Multi-quantum (MQ) NMR tests, AFM images and tanδ measurement. And the heterogeneous structure becomes more obvious with the increased length of polymyrcene block. WAXD results show that cross-linked block copolymers have lower strain-induced crystallization onset strain and higher crystallinity, making them far stronger and tougher. In addition, block copolymer samples demonstrate lower creep and lower permanent set due to slow relaxation of the low crosslinking density regions. The recycling efficiencies of mechanical strength of block copolymer samples were higher than that of homopolymer. This work provides a useful approach for improving the mechanical properties and dimensional stability of vitrimer elastomers simultaneously. [Display omitted] • Vitrimer elastomers with inhomogeneous network were built from molecular level. • The extent of inhomogeneity could be tuned by the length of myrcene block. • Strength, creep resistance and recyclability of inhomogeneous samples were improved. [ABSTRACT FROM AUTHOR]

Terminally hydroxyl functionalized polyisoprene is crosslinked with carbonate bonds and guides the formation of carbonate nanophases, which accelerate the stain induced recrystallization and dissipate energy, leading to a recyclable rubber with super strength, toughness and notable transparency. [Display omitted] • Terminally hydroxyl functionalized polyisoprene is crosslinked with carbonate bonds. • The guided formation of carbonate nanophases controls the extent of transparency. • Carbonate nanophases accelerate the stain induced recrystallization and dissipate energy. • The crosslinked samples exhibit multi-time recyclability with super strength and toughness. The interplay between polymer microstructures and vulcanization method has rarely been investigated for rubbers. Herein a terminally hydroxyl functionalized polyisoprene is crosslinked by ring opening of bis(6-membered cyclic carbonate) (bCC), generating uniformly dispersed carbonate nanophase in the polyisoprene matrix. The carbonate phase not only performed as nanofillers to reinforce the rubber and accelerate the strain crystallization behavior of polyisoprene, but also imparted the recovery property and recyclability into the rubber. In contrast, the copolymer without the terminal block showed disorderly carbonate nanophase and much inferior properties. The mechanical strength and toughness could be finely tuned by the content of bCC crosslinkers, which are even superior to those of vulcanized natural rubber. In addition, the crosslinked polyisoprene exhibits notable transparency, which is not common to vulcanized rubber and could meet the requirements for transparency of rubber products in some fields. [ABSTRACT FROM AUTHOR]

In this work, a high-performance ITO-free flexible polymer solar cell (PSC) is successfully described by integrating the plasmonic effect into the ITO-free microcavity architecture. By carefully controlling the sizes of embedded Ag nanoprisms and their doping positons in the stratified device, a significant enhancement in power conversion efficiency (PCE) is shown from 8.5% (reference microcavity architecture) to 9.4% on flexible substrates. The well-manipulated plasmonic resonances introduced by the embedded Ag nanoprisms with different LSPR peaks allow the complementary light-harvesting with microcavity resonance in the regions of 400-500 nm and 600-700 nm, resulting in the substantially increased photocurrent. This result not only signifies that the spectral matching between the LSPR peaks of Ag nanoprisms and the relatively low absorption response of photoactive layer in the microcavity architecture is an effective strategy to enhance light-harvesting across its absorption region, but also demonstrates the promise of tailoring two different resonance bands in a synergistic manner at desired wavelength region to enhance the efficiency of PSCs. [ABSTRACT FROM AUTHOR]

A multi-ring, ladder-type low band-gap polymer (PIDTCPDT-DFBT) is developed to show enhanced light harvesting, charge transport, and photovoltaic performance. It possesses excellent planarity and enhanced effective conjugation length compared to the previously reported fused-ring polymers. In order to understand the effect of extended fused-ring on the electronic and optical properties of this polymer, a partially fused polymer PIDTT-T-DFBT is also synthesized for comparison. The fully rigidified polymer provides lower reorganizational energy, resulting in one order higher hole mobility than the reference polymer. The device made from PIDTCPDT-DFBT also shows a quite promising power conversion efficiency of 6.46%. Its short-circuit current (14.59 mA cm−2) is also among the highest reported for ladder-type polymers. These results show that extending conjugation length in fused-ring ladder polymers is an effective way to reduce band-gap and improve charge transport for efficient photovoltaic devices. [ABSTRACT FROM AUTHOR]

By embedding various types of colloidal silver nanoprisms into both interfacial layers, significant and general enhancement in the device performances of multiple polymer solar cell systems is demonstrated. The increased device efficiencies are due to the cooperative optical enhancement, resulting in enhanced short‐circuit current densities. These results provide a powerful, general, and tunable means to enhance light harvesting at desired wavelength bands in existing and emerging organic photovoltaic materials. [ABSTRACT FROM AUTHOR]

A synergistic approach combining new material design and interfacial engineering of devices is adopted to produce high efficiency inverted solar cells. Two new polymers, based on an indacenodithieno[3,2- b]thiophene-difluorobenzothiadiazole (PIDTT-DFBT) donor-acceptor (D-A) polymer, are produced by incorporating either an alkyl thiophene (PIDTT-DFBT-T) or alkyl thieno[3,2-b]thiophene (PIDTT-DFBT-TT) π-bridge as spacer. Although the PIDTT-DFBT-TT polymer exhibits decreased absorption at longer wavelengths and increased absorption at higher energy wavelengths, it shows higher power conversion efficiencies in devices. In contrast, the thiophene bridged PIDTT-DFBT-T shows a similar change in its absorption spectrum, but its low molecular weight leads to reduced hole mobilities and performance in photovoltaic cells. Inverted solar cells based on PIDTT-DFBT-TT are explored by modifying the electron-transporting ZnO layer with a fullerene self-assembled monolayer and the MoO3 hole-transporting layer with graphene oxide. This leads to power conversion efficiencies as high as 7.3% in inverted cells. PIDTT-DFBT-TT's characteristic strong short wavelength absorption and high efficiency suggests it is a good candidate as a wide band gap material for tandem solar cells. [ABSTRACT FROM AUTHOR]

Selenium substitution on a ladder-typeindacenodithiophene-basedpolymer (PIDT-DFBT) is investigated in order to reduce band gap, improvecharge mobilities, and enhance the photovoltaic performance of thematerial. The new indacenodiselenophene-based polymer (PIDSe-DFBT)possessed improved absorption over its sulfur analogue in films, aswell as substantially higher charge mobilities (0.15 and 0.064 cm2/(V s) hole and electron mobility, respectively, comparedto 0.002 and 0.008 cm2/(V s) for PIDT-DFBT). The enhancedmaterial properties led to an improved power conversion efficiencyof 6.8% in photovoltaic cells, a 13% improvement over PIDT-DFBT-baseddevices. Furthermore, we examined the effect of molecular weight onthe properties of PIDSe-DFBT and found not only a strong molecularweight dependence on mobilities, but also on the absorptivity of polymerfilms, with each 15 000 g/mol increase in weight, leading toa 25% increase in the absorptivity of the material. The molecularweight dependence of the material’s properties resulted ina significant difference in photovoltaic performance with the high-molecular-weightPIDSe-DFBT providing a higher photocurrent, fill factor, and efficiencydue to its improved absorption and hole mobility. These results demonstratethe importance of achieving high molecular weight and the potentialthat selenium-containing ladder-type polymers have in the design ofhigh-performance semiconducting polymers for organic photovoltaics(OPVs). [ABSTRACT FROM AUTHOR]

Biosynthetic residues in vulcanized natural rubber (VNR) create a blend end-linking network through two kinds of terminal groups dispersed in the covalent network, leading to excellent mechanical properties, such as high tensile strength and high crack growth resistance. However, due to the complex composition of natural rubber (NR), it is not likely to rebuild the terminal structures directly. In this circumstance, this work designs the terminal structures of synthetic polyisoprene by mimicking the structure of NR at the principal level. In detail, oligopeptide groups and phosphate groups were attached at the end of polyisoprene respectively, to form similar end-linking network as found in VNR. Three terminal functionalized model polymers containing oligopeptides (4A), phosphates (P) or both oligopeptides and phosphates (PA) were synthesized and vulcanized to generate V4A, VP and VPA, respectively. The oligopeptides and phosphates interact with each other to form new blended aggregates, which makes the end-linking network integrated. Blended aggregates are captured by the CLSM and TEM. The rheological tests demonstrate that the formation of blend aggregates is the foundation of synergistic effect on shear modulus, which will disappear at high temperature or solution state. It is also found that the mechanical properties of VPA are superior to that of VP and V4A, which is attributed to the more integrated end-linking network structure. Further analysis showed that the synergistic effect between terminals makes the entanglements near the blended aggregates difficult to unwrap and become permanent entanglements, thereby increasing the crosslinking density. The more complete end-linking network endow VPA higher crystallization ability than VP and V4A. These results expand our understanding of how terminals work in NR and provide new insight into the generic design of mechanically strong elastomer. [Display omitted] • The end-linking network similar to natural rubber was constructed by terminal functionalized polyisoprene.. • The blended aggregates formed by proteins and phospholipids were captured by the CLSM.. • The effect of terminal synergy on rheological modulus, mechanical and crystallization properties was investigated.. [ABSTRACT FROM AUTHOR]

Mechanochromic fluorescence (MCF) materials show great potential in many fields. But it is still a great challenge to rationally design proper molecular structures and tune their molecular packing and MCF properties, especially for molecules with planar backbones. Herein, ladder-type molecules based on planar indeno[1,2-b]thiophene 1,1-dioxides (ITDO) backbones are designed. The moderate dipole moment originating from the donor-acceptor structure of backbone and steric sidechains leads to a loose supramolecular aggregation with dimeric structures. And the emission properties could be tuned by introducing halogen endgroups onto the backbones. As a result, ITDO-Cl and ITDO-Br showed stronger intermolecular interactions, leading to dual emission band and MCF properties. In contrast, ITDO-H and ITDO-I crystal showed single monomer emission peak without mechanochromism. [Display omitted] • Several ladder-type indeno[1,2-b]thiophene 1,1-dioxides derivatives (ITDOs) with endgroups were designed. • ITDO-Cl and ITDO-Br exhibited dual emission and mechanochromism due to the formation of supramolecular aggregation. • The luminescent properties could be tuned by changing halogen endgroups to alter dipole moment and π-π interactions. [ABSTRACT FROM AUTHOR]

Supramolecular interactions such as hydrogen bonds have seldomly considered to be strong enough to maintain dimensional stability of elastomers. Herein, the interplay between spacer length and oligopeptide binding have been used to harvest a strong and stable polyisoprene elastomer comparable to vulcanized counterpart. It is found that along the increase of spacer length from 3 to 5 and 7, the mechanical strength and thermostabilities of elastomers increased remarkably with the maintenance of high extensibility. The high apparent activation energies and obviously reduced relaxation rate could account for the observed phenomenon. This case indicates that the architecture control of polymer could coordinate with supramolecular interactions and broaden their applications. [Display omitted] • A series of tetrapeptide-decorated polyisoprenes with different spacer lengths were prepared. • The sample with longer spacer length showed superior mechanical properties and dimensional stability. • 4A-7-PIP with seven -CH 2 spacer exhibits a stress of 18.3 MPa at 870% strain and excellent creep-resistant property. [ABSTRACT FROM AUTHOR]

Hydrogen bonding as a commonly used dynamic crosslink in elastomers suffered from inefficient stability against elevated temperature or low tensile rate. Herein, a bioinspired strategy was developed to retard the dissociation process, therefore resulting in mechanically strong and stable thermoplastic polyisoprene. Specifically, penta-alanine groups pendant on polyisoprene assemble into β-sheets and serve as crosslinkers, which usually are unstable and disassemble at moderate temperature or low tensile rate. In this work the addition of Ca2+ ions will destroy partial β-sheet structures, but at the same time coordinate with peptide aggregates and retard the dissociative process of hydrogen bonding against either the increase of temperature or stretching speed in a controlled manner. Stress relaxation test showed that the activation energies for viscous flow and relaxation time below 127 °C are obviously increased after the addition of Ca2+ ions. The mechanism study showed that the well mixing of calcium salt and peptide phase in polyisoprene matrix is critical for the formation of coordination interactions, which manipulate the dissociation of peptide aggregates. This strategy represents a feasible approach to tune the viscoelastic response of elastomers in a wide range. Image 1 • The thermostability and robustness of thermoplastic polyisoprene were improved. • The dissociation process of hydrogen bonding aggregates was retarded. • The coordination interactions between calcium ions and penta-alanines were investigated. [ABSTRACT FROM AUTHOR]

Oxidized thiophene incorporated molecules show great potential as luminescent materials. However, most works focused on thiophene-S, S-dioxides (TDO) moiety, rarely on thiophene-S-oxide (TO) incorporated molecules. Herein, TO and TDO incorporated ladder-type molecules, namely IDT2O–H and IDT4O–H, have been designed and synthesized to study their luminescent properties. Compared to IDT4O–H, IDT2O–H not only shows stronger and bathochromic fluorescence emission in solution and film states but also exhibits unusual anti-Kasha phosphorescence in film state. The experimental spectra and theoretical calculations demonstrate that the distinct energy levels and orbital features originated from their structures are crucial for the different luminescent properties of IDT2O–H and IDT4O–H. Thiophene-S-oxide and thiophene-S,S-dioxides incorporated ladder-type molecules have been designed and their luminescent features are systemically studied. Image 1 • Thiophene-S, S-dioxides (IDT4O) and thiophene-S-oxide (IDT2O) incorporated ladder-type molecules were synthesized. • IDT2O showed stronger and bathochromic photoluminescence emission in both solution and film states. • IDT2O film exhibited unusual anti-Kasha phosphorescence emission under ambient conditions. [ABSTRACT FROM AUTHOR]

Non-covalent interactions imposed by polar groups affect the properties of polyisoprene in various ways. But traditional modification method only led to randomly functionalized product which ignored the effects of sequence and location of polar groups. In this work, by using a novel polar monomer hydroxyl-myrcene (HMY), hydroxyl group terminally (BC–OH) and randomly functionalized (RC-OH) polyisoprene copolymers were successfully obtained. Due to the different hydroxyl group sequences, BC-OH and RC-OH shows different morphologies and rheological properties. Furthermore, polyhedral oligomeric silsesquioxanes (POSS) with urea bond was used as nanofiller to attach on BC-OH and RC-OH and generating BC-POSS and RC-POSS, respectively. The assembly of POSS and the formation of urea hydrogen bond will occur collaboratively. As a result, BC-POSS and RC-POSS showed distinct morphological properties and thermal stabilities. It is found that ordered urea bonds were formed in RC-POSS, while less ordered urea bonds were formed in BC-POSS. Overall, these results suggest that the tailoring of polar group sequence in polyisoprene copolymers could be a promising avenue for tuning polyisoprene performance via tuning aggregation behaviors of the polar groups. Image 1 • Terminally and randomly functionalized polyisoprene copolymers were obtained via polar monomer copolymerization. • BC-OH and RC-OH exhibit ball-like and continuous network morphologies, respectively. • POSS nanofillers with urea bonds formed spherical aggregates in BC-POSS and fibrous aggregates in RC-POSS. • Ordered urea bonds were formed in RC-POSS, while less ordered urea bonds were formed in BC-POSS. [ABSTRACT FROM AUTHOR]

Natural rubber is unique because its comprehensive mechanical performance is still unmatched by synthetic counterparts. Recyclability of vulcanized rubbers is also a major issue. As described by Y.‐X. Xu, G. Huang et al. in their Communication on page 15836 ff., a tough thermoplastic polyisoprene, inspired by natural rubber, was synthesized by introducing terminal polar groups. Tetra‐alanine is used as the crosslinking unit, which is derived from the hard segment of spider silk. [ABSTRACT FROM AUTHOR]

Die mechanischen Eigenschaften von Naturkautschuk werden durch vergleichbare synthetische Materialien noch nicht erreicht, und auch die Wiederverwertung vulkanisierter Gummiprodukte ist ein Problem. Y.‐X. Xu, G. Huang et al. berichten in ihrer Zuschrift auf S. 16062 über ein zähes thermoplastisches Polyisopren nach dem Vorbild von Naturkautschuk, das sie unter Einführung polarer Endgruppen synthetisierten. Tetraalanin, ein Motiv aus dem harten Segment der Spinnenseide, dient als vernetzende Einheit. [ABSTRACT FROM AUTHOR]