最新刊期
卷 54 ， 期 2 ， 2023
- 摘要：Movement of large electrically charged macromolecules trapped inside spatially restrictive aqueous media is a ubiquitous phenomenon, underlying many natural living processes and technologies focused on separation science and controllable delivery of macromolecular cargos. In this broad context of general significance, we have developed a conceptual framework towards a fundamental understanding of the molecular mechanisms of how large macromolecules move around in crowded environments. Our conceptual development, based on a combination of experiments and theory, addresses the confluence of conformational fluctuations of the guest charged macromolecule being trapped and the host charged matrix (modelled using a hydrogel), structure and charge decoration of the host, long-ranged electrostatic interactions and van der Waals-type interactions in the composite system, and self-consistent coupling of the dynamics of all moving components (small electrolyte ions and large macroions) in the system. These advances are summarized in this review. Briefly, there are three components, each with tantalizing results. First, the dynamics of elasticity of the host charged gel are quantified in terms of shear modulus and bulk modulus, using dynamic light scattering measurements and modified Flory-Dusek-Patterson-Tanaka theory by accounting for electrostatics. Second, we show that a dilute solution of charged macromolecules exhibits the "ordinary-extraordinary transition" in the cooperative diffusion coefficient of the macromolecule. In the "ordinary" mode, the diffusion coefficient of a very large macromolecule can be as high as that of a small metallic ion. We attribute this strange effect to the coupling of the dynamics of the charged macromolecule and that of its dissociated counterions. The "extraordinary" mode arises from clustering of identically charged macromolecules induced by dipolar forces from ion-pairs formed by condensed counterions on the macromolecules. In the presence of added small molecular electrolyte, we find that an additional mode emerges due to the additional presence of the co-ions in the solution. Third, when the macromolecule is trapped inside the host hydrogel, we succinctly summarize the features of our discovery of a new state of polymer dynamics, namely the topologically frustrated dynamical state. In this state, which occurs at intermediate confinements arising from the host, the chain does not diffuse defying the Einstein's law of diffusion, due to the emergence of extreme metastability from freezing of chain's conformational entropy. This novel effect offers a diverse set of opportunities to controllably release macromolecular cargos using hydrogel-like host matrices as well as to build molecular machines that depend on memory associated with metastability关键词：Polyelectrolytes;Topologically frustrated dynamics;Entropic barrier;Confinement;Charged gels
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发布时间：2023-05-22
Feature Article
- 摘要：With the development of science and technology, the improvement of computer software/hardware technology has greatly enhanced the efficiency of large-scale parallel computing, enabling scientists to use a large amount of computing power to analyze the operating mechanism of high-degree-of-freedom systems in a relatively inexpensive way, and to design new material structures and properties. Wherein, as the core of the data-driven-research system of Materials Genome Engineering (MG), the Computational Materials Science has made great contribution to the development of novel polymeric materials that were driven by data. This paper reviews the research of polymeric materials based on domestic and foreign scholars borrowing from Materials Genome Initiative (MGI) ideas since the release of the MGI plan in 2011, including elastomeric materials, energy polymeric materials, optical polymeric materials, thermal conductive polymeric materials and biomedical polymeric materials. At the same time, this review puts forward the future development prospects of Computation Materials Science and the challenges it faces to provide basis and guidance for the development of polymeric disciplines.关键词：Materials genome initiative;Polymeric materials;Computational materials science;Structure-property relationship
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发布时间：2023-05-22 - 摘要：Polymers of 1,3-diene monomers have excellent properties and play an important role in rubber industry. Polymers of 1,3-diene monomers is synthesized from 1,3-butadiene, and it can be fabricated into a variety of rubber products, while isoprene rubber can replace natural rubber in some fields due to its similar chemical structure with natural rubber. The key to the polymerization of 1,3-diene monomers is the catalyst. In the past decade, iron and cobalt catalysts have received much attention due to their excellent properties such as inexpensive raw materials, abundant ligand types, simple synthesis and stable properties. Rational design and synthesis of the catalyst structures has enabled good control over the stereoselectivity, molecular weight, and thus improve their performance of the polymerization product. This paper reviews the research progress of iron and cobalt complex-catalyzed 1,3-diene polymerization in the last decade and discusses in detail the influence of catalyst structure on catalytic activity, polymer molecular weight, polymer microstructure and polymer molecular weight dispersity.关键词：Iron complexes;Cobalt complexes;1;3-Diene;Isoprene;3-Butadiene
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发布时间：2023-05-22
Review
- 摘要：Low molecular weight polylactide with UV resistance was synthesized through ring-opening polymerization of lactide (LA) using aloe-emodin (AE) derived from renewable resources as initiator. The molecular structure, optical properties and thermal properties of the synthesized PLA were systematically studied. The research results show that the alcoholic hydroxyl group in the AE molecular structure initiates the ring-opening polymerization of LA to form the polylactide PLA-En capped by the En group (the structure after the reaction of the alcoholic hydroxyl group in the AE structure), the relative number average molecular weight (Mn) of PLA-En can be tuned (0.29×104-2.93×104 g/mol) by adjusting the molar ratio n (20-200) between AE and LA; the introduction of En groups can endow PLA-En with similar light absorption and fluorescence emission characteristics to AE, and is hardly affected by molecular weight. At the same time, the thermal stability of obtained polylactide is improved. The thermal decomposition temperature of PLA-En is more than 15 ℃ higher than that of PLA-Cn (Cn is the structure after the reaction of the alcohol hydroxyl group in the CA structure) with similar molecular weight initiated by hexadecanol (CA), but the melting point is not much different. The increase in thermal decomposition temperature endows PLA-En with a wider melt processing temperature window than PLA-Cn, the former exceeds 100 ℃ and the latter does not exceed 90 ℃. 3 mass% of PLA-En (n=20, Mn = 0.29×104 g/mol) was introduced into commercial polylactide PLA (Mn = 6.28×104 g/mol), which could endow PLA with UV light blocking properties, but does not affect the transparency and mechanical properties of PLA. The results of this study lay a good foundation to introduce PLA-En into the PLA matrix material and develop a transparent PLA material with UV light protective ability.关键词：Aloe-emodin;Low molecular weight;Polylactide;UV resistance;Additive
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发布时间：2023-05-22 - 摘要：Luminescent polymers are suitable for the fabrication of solution-processed large-scale display and lighting devices due to their superior film-forming ability, and can effectively improve the device performances while endowed with thermally activated delayed fluorescence (TADF) characteristic. In this work, four polymers with carbazole/acridine backbone donor and terpyridine pendant acceptor, named PCzABTPy1‒PCzABTPy50, are synthesized by using the cross coupling copolymerization of two carbazole derivative monomers and a acridine derivative TADF monomer (ABTPy) containing terpyridine group, and managing the TADF monomer feed molar ratio of 1%, 5%, 10% and 50%. The polymers with low content of TADF unit show dual emissions peaked at 420 and 488 nm in dilute solution, whereas all polymers only display a single emissive peak ranging from 470 nm to 508 nm in neat film. Their TADF features are confirmed by the transient photoluminescence decay spectra, in which a short-lifetime prompt component (12‒15 ns) and a long-lifetime delayed component (1.3‒4.8 μs) are clearly detected. The non-doped and solution-processed organic light-emitting diodes (OLEDs) using the polymer neat films as emissive layers all show blue emissions with emissive wavelength from 452 nm to 484 nm. The OLED based on PCZABTPy10 achieves excellent performances with the maximum external quantum efficiency (EQE) of up to 9.4% and the low turn-on voltage of 3.0 V. Moreover, the EQE still remains 7.4% at the luminance of 1000 cd/m2.关键词：Thermally activated delayed fluorescence;Conjugated polymer;Terpyridine;Blue emission;Electroluminescence
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发布时间：2023-05-22 - 摘要：Silicone rubber (SR) is a widely used elastomer material. However, due to the complicated network structure, it is difficult to realize the rational design of SR. In this study, we attempt to build the correlation between the microscopic and macroscopic mechanical properties of SR from the perspective of single-chain elasticity. First, the single-chain elasticities (including entropic and enthalpic elasticities) of the main component chains (siloxane chain) and cross-linking chains (carbon-carbon chain) in methyl vinyl SR are obtained by single-molecule atomic force microscopy. Subsequently, the theoretical single-chain elasticities of the above two polymer chains are obtained by quantum mechanical calculations. The theoretical results are consistent with the experimental results, indicating that the inherent elasticities of the two polymer chains in the quasi-undisturbed environment have been obtained. Next, the inherent elasticities of the two polymer chains are integrated into the traditional statistical model of rubber. Finally, it is found that the mechanical properties of three different SRs over the entire deformation range can be perfectly described by the new model (called TCQMG model) with adjustable parameters. In addition, the effects of multiple parameters on the mechanical properties of SR are analyzed by the TCQMG model. This model will help bridge the gap between the single-molecule mechanics and macroscopic properties of SR elastomer materials, and can provide theoretical guidance for the rational design of new SRs. Considering the similarity in cross-linking network structure between SR and other elastomers, it is expected that the TCQMG model can be used as a general model to describe the macroscopic properties of these elastomers.关键词：Silicone rubber;Single-molecule atomic force microscopy;Statistical model;Cross-linking network
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发布时间：2023-05-22 - 摘要：Poly(ethylene-co-octene)/multi-walled carbon nanotubes/carbon fibre (POE/MWCNTs/CF, 90:5:5, W/W/W) composites were prepared by melt-mixing, and the composites were then foamed in a batch process using supercritical carbon dioxide foaming method. The cell structure was analyzed for the microcellular samples prepared at foaming temperatures of 55, 60 and 65 ℃, and its effect was emphasized on the compression properties of the microcellular samples and the piezoresistive response (sensitivity and linear response range) of the assembled sensors. It was demonstrated that the microcellular sample foamed at 55 ℃ exhibited a relatively uniform cell structure, a narrower cell diameter distribution (mainly in the range of 10‒30 μm), and moderately thick and highly continuous cell walls, which endowed the microcellular sample with higher resilience, compression strength, compression modulus and electrical conductivity. The sensor assembled with this microcellular disk had a wider linear response range (0‒30% compression strain) and higher sensitivity (strain factor of 1.67), which were analyzed based on the cell structure. The sensor exhibited faster piezoresistive response and recovery performance and good repeatability, and showed higher stability and durability in the 1000 cycles of cyclic compression/release test with 30% strain. Moreover, the sensor could monitor typical human motions, such as finger pressing, elbow bending, squatting, and foot stepping, which corresponded to a wider compressive strain range . The results demonstrate that the microcellular conductive composites with more uniform cell structure and moderately thick and highly continuous cell walls foamed by supercritical fluid foaming method have good sensing performance.关键词：Poly(ethylene-co-octene)/multi-walled carbon nanotubes/carbon fibre composite;Supercritical carbon dioxide foaming;Microcellular structure;Resilience;Sensing performance
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发布时间：2023-05-22 - 摘要：Three copolymers (random, block and gradient copolymers) (PBA-r-PMMA, PBA-b-PMMA, PBA-g-PMMA) with different MMA/BA sequences and two terpolymers were prepared by RAFT polymerization. Their molecular weights and molar ratios of PMMA/PBA for the terpolymers were almost the same as those of the first three copolymers. Spherical nanoparticles NP-(PBA-g-PMMA) and NP-(PBA-r-PMMA) were obtained by co-assembly and crosslinking of the two terpolymers. The glass transition behaviors for these five materials were characterized using DSC. The results showed that NP-(PBA-g-PMMA) and PBA-g-PMMA had a wide temperature ranges of glass transition (~130 ℃), which confirmed that the nanoparticles of grafted gradient copolymer and gradient copolymer were successfully synthesized. The five materials were further characterized using the DMA analysis and the tensile testing at different temperatures. The results showed that more and more chain segments gradually changed from plastic to rubber during the heating process for NP-(PBA-g-PMMA) and PBA-g-PMMA, and their mechanical properties showed a gradual change rather than the sudden change of random or block copolymer, due to the wide Tg of gradient copolymers. At high temperatures, the mechanical properties of gradient copolymer were better than those of random copolymer. For NP-(PBA-g-PMMA) and NP-(PBA-r-PMMA) , they showed a similar situation due to the properties of the grafted copolymers, but their strengths and moduli were higher than those of the corresponding pure copolymers, and their elongations at break were lower, which could be ascribed to the reinforcing effect of inorganic cores.关键词：Gradient copolymer;Polymer grafted nanoparticles;Silicon dioxide;Glass transition temperature
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发布时间：2023-05-22 -
Fabrication and Stimuli-responsiveness of Phenylboronic Acid-containing Polymer Brush Micropattern 增强出版
摘要：The smart biointerface with the capability to dynamically control the interaction between the biomolecules and material interface has attracted much attention. Here, a responsive smart biointerface was created based on the boronic acid-containing polymer brush micropattern. With 3-methacrylamidophenylboronic acid as monomer, micropatterned poly(3-methacrylamidophenylboronic acid) (PMAPBA) brushes were fabricated through combining the digital mirror device (DMD)-based light modulation technique and surface-initiated photoinduced atom transfer radical polymerization (Photo-ATRP). A series of methods such as optical microscopy, X-ray photoelectron spectroscopy, and time of flight-secondary ion mass spectrometry were applied to characterize the geometric shape, chemical composition and distribution of the resulting brush structure. The pH-responsiveness of micropatterned PMAPBA brushes was investigated with fluorescein isothiocyanate stained immunoglobulin G (IgG), and the result from laser confocal microscope revealed that the increase in the pH of the solution will hinder the immobilization of IgG protein on the PMAPBA brushes, which was attributable to the negatively charged hydrophilic ions produced by the ionization of phenylboronic acid. Besides, the catechol-boronate interaction between phenylboronic acid moieties and the secondary hydroxyls on the dextran could promote the immobilization of dextran on the PMAPBA brushes under neutral and alkaline conditions. In addition, the sugar-responsiveness of PMAPBA brushes enabled dynamic modulation of IgG adsorption behavior. The PMAPBA brushes micropatterned surface with dual stimuli-responsive could provide a novel route for the preparation of dynamic bioactive surfaces and controlled drug release systems.关键词：Phenylboronic acid;Polymer brush micropattern;pH-Responsiveness;Sugar-responsiveness- 153
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发布时间：2023-05-22 - 摘要：The phase structure, crystallization and hydrogen bonding of thermal polyurethane (TPU) were controlled by annealing process. And the modulus and dielectric constant (ε') of TPU were tailored to improve the electromechanical properties of TPU. Scanning electron microscopy (SEM) and small angle X-ray (SAXS) were used to study the crystalline structure of TPU. The changes of hydrogen bonding of TPU were semi-quantitatively analyzed by infrared spectroscopy. The microphase separation structure of TPU was studied by atomic force microscope (AFM). The results show that changing annealing temperature and time results in complex aggregation structures, thus leading to very different electromechanical properties. After annealing at 80 ℃, large numbers of soft segment crystals were formed with the hard phase distributing in the continuous soft phase. Both phase separation and the destruction of hydrogen bonding were improved compared with those of 150 ℃ annealing treatment. Therefore, higher ε' and lower modulus were obtained, resulting in larger actuated strain. Besides, under the condition of low temperature annealing, a wide range of soft segment crystals were produced, which makes the molecular chains of soft segments closely arranged, resulting in a significant increase in the breakdown strength of TPU. The results show that after annealing at 80 ℃ for 6 h, the electrical breakdown strength of TPU increases from 25 kV/mm to 32 kV/mm, and the maximum actuated strain increases from 0.77% to 3.3%, increased by 4.3 times.关键词：Polyurethane;Dielectric elastomer;Crystallization;Phase separation;Actuated Strain
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发布时间：2023-05-22 - 摘要：Polyether polyurethane elastomers (PTMG-PU) with hard segment contents of 30 wt%, 37 wt% and 45 wt% were synthesized. The effects of hard segment content, immersion temperature and sample thickness on the water absorption dynamics of PTMG-PU were studied. The microphase separation structure evolution of PTMG-PU during water absorption was characterized by small Angle X-ray scattering technique. The results show that the dynamic process of water absorption of PTMG-PU between 25 and 60 ℃ can be fitted by Fick's model. The diffusion coefficient and equilibrium water absorption rate decrease gradually with the increase of hard segment content, but the time required to reach the equilibrium water absorption rate is about 22 h. In addition, the diffusion activation energy and preexponential factor of water molecules increase with the increase of hard segment content, indicating that more energy is needed to overcome the energy barrier transmitted by water molecules in PTMG-PU. Furthermore, the mechanical properties of PTMG-PU, such as tensile strength and tensile modulus, decreased significantly during the process of water absorption, which was not only due to the plasticization of water molecules with the soft phase of polyurethane elastomer, but also due to the interaction of water molecules with some hard microdomains, leading to the disintegration of some hard microdomains. This provides theoretical guidance for the design and development of high-performance PTMG-PU in high humidity environment and theoretical support for the application of PTMG-PU in practical engineering.关键词：Polyurethane elastomer;Water absorption dynamic;Mechanical property;Microphase separation structure
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发布时间：2023-05-22
Research Article
- 摘要：Knowledge of elongational properties of polymeric materials is important in different polymer processing techniques, particularly the fiber-spinning, foaming, and blow-molding techniques where the extensional flow is dominant. In this review, we summarize the methods of measuring extensional rheology for polymer melts and solutions. We start with explaining the definition and classification of different extensional flow fields in Section 1. In Section 2 we introduce different types of extensional rheometers, including Goettfert Rheotens, Münstedt Tensile Rheometer, Rheometrics Melt Extensometer, Sentmanat Extensional Rheometer, Filament Stretching Rheometer, and Capillary Breakup Extensional Rheometer. Their designing principles, operation methods, and advantages/disadvantages are described. In Section 3, we briefly introduce the different modes of extensional measurements, such as constant extensional rate, constant stress, stress relaxation and large amplitude oscillation modes. Some examples are included to elucidate the advantages of each mode. In Section 4, we give some suggestions and solutions for minimizing experimental errors and pushing the experimental limits. Finally, we highlight the importance of combining extensional rheology with other techniques in revealing more dynamic features of polymeric materials under extensional flow.关键词：Rheology;Extensional flow field;Extensional rheometer;Extensional rheology measurement
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发布时间：2023-05-22
Review (Special Topic: Techniques of Polymer Characterization)
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