Cross-linking of Polymer of Intrinsic Microporosity (PIM-1) via nitrene reaction and its effect on gas transport property

Polymer of Intrinsic Microporosity (i.e. PIM-1) has been crosslinked thermally via nitrene reaction using polyethylene glycol biazide (PEG-biazide) as a crosslinker. The crosslinking temperature was optimized using TGA coupled with FT-IR spectroscopy. The dense membranes containing different ratios of PIM-1 to PEG-biazide were cast from chloroform solution. Crosslinking of PIM-1 renders it insoluble even in excellent solvents for the uncrosslinked polymer. The resulting crosslinked membranes were characterized by FT-IR spectroscopy, TGA and gel content analysis. The influence of crosslinker content on the gas transport properties of PIM-1, its density and fractional free volume (FFV) were investigated. Compared to the pure PIM-1 membrane, the crosslinked PIM-1 membranes showed better gas separation performance especially for CO₂/N₂, CO₂/CH₄ and propylene/propane (C₃H₆/C₃H₈) gas pairs and as well as suppressed penetrant-induced plasticization under high CO₂ pressure.     

Gas Separation with Polymer Membranes

Gas-selective polymer membranes have long been used in industrial applications. Studies of polymers with well-defined flexible phenyl ether segments such as 1 should contribute to the understanding of the selection mechanism and thus ultimately lead to the synthesis of optimized membrane materials. Various different bridging groups X were used in the studies.     

High Gas Permeability in Aged Superglassy Membranes with Nanosized UiO-66−NH2/cPIM-1 Network Fillers

Superglassy membranes synthesised by polymers of intrinsic microporosity (PIMs) suffer from physical aging and show poor gas permeance over time, especially thin membranes, due to the fast rearrangement of nonequilibrium polymer chains. Herein, we constructed a novel PIM-1 thin film nanocomposite membrane (TFN) using nanosized UiO-66−NH₂ (≈10 nm)/carboxylated PIM-1 (cPIM-1) as the composite filler. Unlike conventional fillers, which interact with the polymer only via the surface, the UiO-66−NH₂/cPIM-1 forms a stable three-dimensional (3D) network intertwining with the polymer chains, being very effective to impede chain relaxation, and thus physical aging. Nanosizing of UiO-66−NH₂ was achieved by regulating the nucleation kinetics using carbon quantum dots (CQD) during the synthesis. This led to increased surface area, and hence more functional groups to bond with cPIM-1 (via hydrogen bonding between −NH₂ and −COOH groups), which also improved interfacial compatibility between the 3D network and polymer chains avoiding defect formation. As a result, the novel TFN showed significantly improved performance in gas separation along with reduced aging (i.e. ≈6 % loss in CO₂ permeability over 63 days); the aged membranes had a CO₂ permeance of 2504 GPU and ideal selectivity values of 37.2 and 23.8 for CO₂/N₂ and CO₂/CH₄, respectively.     

Polymers with Intrinsic Microporosity as Solid Ion Conductors for Solid-State Lithium Batteries

Solid-state electrolytes (SSEs) with high ionic conductivity and superior stability are considered to be a key technology for the safe operation of solid-state lithium batteries. However, current SSEs are incapable of meeting the requirements for practical solid-state lithium batteries. Here we report a general strategy for achieving high-performance SSEs by engineering polymers of intrinsic microporosity (PIMs). Taking advantage of the interconnected ion pathways generated from the ionizable groups, high ionic conductivity (1.06×10⁻³ S cm⁻¹ at 25 °C) is achieved for the PIMs-based SSEs. The mechanically strong (50.0 MPa) and non-flammable SSEs combine the two superiorities of outstanding Li⁺ conductivity and electrochemical stability, which can restrain the dendrite growth and prevent Li symmetric batteries from short-circuiting even after more than 2200 h cycling. Benefiting from the rational design of SSEs, PIMs-based SSEs Li-metal batteries can achieve good cycling performance and superior feasibility in a series of withstand abuse tests including bending, cutting, and penetration. Moreover, the PIMs-based SSEs endow high specific capacity (11307 mAh g⁻¹) and long-term discharge/charge stability (247 cycles) for solid-state Li−O₂ batteries. The PIMs-based SSEs present a powerful strategy for enabling safe operation of high-energy solid-state batteries.     

Self-Accelerating Diels–Alder Reaction for Preparing Polymers of Intrinsic Microporosity

It is a formidable challenge in polycondensation to simultaneously construct multiple covalent bonds to prepare double-stranded polymers of intrinsic microporosity (PIMs) with fused multicyclic linkages. To the best of our knowledge, this is the first study to develop a self-accelerating Diels–Alder reaction for successfully preparing double-stranded PIMs with fused multicyclic backbone structures. A self-accelerating Diels–Alder reaction was developed based on the [4+2] cycloaddition of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD) and ortho-quinone compounds. In this reaction, the cycloaddition of ortho-quinone with the first alkyne of DIBOD activates the second alkyne, which reacts with ortho-quinone at a rate constant 192 times larger than that of the original alkyne. Using this self-accelerating reaction to polymerize DIBOD and spirocyclic/cyclic difunctional ortho-quinone monomers, a novel stoichiometric imbalance-promoted step-growth polymerization method was developed to prepare PIMs. The resultant PIMs possess intrinsic ultramicropores with pore sizes between 0.45 to 0.7 nm, high specific surface areas above 646 m² g⁻¹, and good H₂ separation performance.     

Mechanically Strong and Flexible Hydrolyzed Polymers of Intrinsic Microporosity (PIM‐1) Membranes

A systematic strategy to molecularly design flexible tough hydrolyzed polymers of intrinsic microporosity (hPIM‐1) films from the PIM‐1 polymer is explored in this study. Flexible films can be fabricated from N‐methyl‐2‐pyrrolidone (NMP) by appropriate hydrolysis conditions. The optimal weight ratio of NaOH/H₂O/EtOH in the base‐catalyzed reaction is 0.5/2/2. Because of the highly polar carboxylic acid groups, the resultant hPIM‐1 has a lower water contact angle. The hPIM‐1 has one‐half fractional free volume compared to PIM‐1 which is in good agreement with permeability. Moreover, hPIM‐1 follows as the same dual‐mode sorption model as PIM‐1. To the best of our knowledge, this is the first ever reported flexible hPIM‐1 film in the literature. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 344–354     

Preparation and Properties of Nanoporous Triblock Copolymer Membranes

“ Unplug those pores!” could be a slogan common to cosmetologists and polymer chemists. Membranes with nanochannels can be obtained by first forming a film by casting a solution of a triblock and homopolymer mixture, then selectively cross-linking domains in the film by photolysis, and finally forming nanochannels through removal of the homopolymer by solvent extraction. Such membranes are not liquid permeable but have gas-permeability constants about six orders of magnitude higher than that of low-density polyethylene films.     

Chiral Polymers of Intrinsic Microporosity: Selective Membrane Permeation of Enantiomers

Following its resolution by diastereomeric complexation, 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethyl‐1,1′‐spirobisindane (TTSBI) was used to synthesize a chiral ladder polymer, (+)‐ PIM‐CN . (+)‐ PIM‐COOH was also synthesized by the acid hydrolysis of (+)‐ PIM‐CN . Following characterization, both (+)‐ PIM‐CN and (+)‐ PIM‐COOH were solvent cast directly into semipermeable membranes and evaluated for their ability to enable the selective permeation of a range of racemates, including mandelic acid (Man), Fmoc‐phenylalanine, 1,1′‐bi‐2‐naphthol (binol), and TTSBI. High ee values were observed for a number of analytes, and both materials exhibited high permeation rates. A selective diffusion–permeation mechanism was consistent with the results obtained with these materials. Their high permeability, processability, and ease of chemical modification offer considerable potential for liquid‐phase membrane separations and related separation applications.     

本征导电聚合物的智能性

在化学掺杂或电化学掺杂过程中，性质发生可逆性变化的本征导电聚合物是一种潜在的智能材料，可望实现或部分实现传感、处理和执竽功能，适于制成电机执行器、智能窗、化学分离与释放体系、传感器和非线性光学器件等。     

Photodielectric Polymers for Holographic Use

The use of polymeric materials as “thick” recording media for holographic applications is discussed. These materials offer some interesting applications owing to their high diffraction efficiency, high storage density, excellent angular and spectral discrimination, as well as in situ real-time recording. The present state of art is outlined, as are prospects for the future.     

Direct Insertion Polymerization of Ionic Monomers: Rapid Production of Anion Exchange Membranes

The limited number of methods to directly polymerize ionic monomers currently hinders rapid diversification and production of ionic polymeric materials, namely anion exchange membranes (AEMs) which are essential components in emerging alkaline fuel cell and electrolyzer technologies. Herein, we report a direct coordination-insertion polymerization of cationic monomers, providing the first direct synthesis of aliphatic polymers with high ion incorporations and allowing facile access to a broad range of materials. We demonstrate the utility of this method by rapidly generating a library of solution processable ionic polymers for use as AEMs. We investigate these materials to study the influence of cation identity on hydroxide conductivity and stability. We found that AEMs with piperidinium cations exhibited the highest performance, with high alkaline stability, hydroxide conductivity of 87 mS cm⁻¹ at 80 °C, and a peak power density of 730 mW cm⁻² when integrated into a fuel cell device.     

An Interfacial Layer Based on Polymers of Intrinsic Microporosity to Suppress Dendrite Growth on Li Metal Anodes

The performance and safety of lithium (Li) metal batteries can be compromised owing to the formation of Li dendrites. Here, the use of a polymer of intrinsic microporosity (PIM) is reported as a feasible and robust interfacial layer that inhibits dendrite growth. The PIM demonstrates excellent film-forming ability, electrochemical stability, strong adhesion to a copper metal electrode, and outstanding mechanical flexibility so that it relieves the stress of structural changes produced by reversible lithiation. Importantly, the porous structure of the PIM, which guides Li flux to obtain uniform deposition, and its strong mechanical strength combine to suppress dendrite growth. Hence, the electrochemical performance of the anode is significantly enhanced, promising excellent performance and extended cycle lifetime for Li metal batteries.     

Layered Zeolite for Assembly of Two-Dimensional Separation Membranes for Hydrogen Purification

Membrane separation is an energy-efficient and environmentally friendly process. Two-dimensional (2D) molecular sieving membranes featuring unique nanopores and low transport resistance have the potential to achieve highly permeable and selective mixture separation with low energy consumption. High-aspect-ratio zeolite nanosheets with intrinsic molecular-sieving pores perpendicular to the layers are desirable building blocks for fabricating high-performance 2D zeolite membrane. However, a wider application of 2D zeolitic membranes is restricted by the limited number of recognized zeolite nanosheets. Herein, we report a swollen layered zeolite, ECNU-28, with SZR topology and eight-member ring (8-MR, 3.0 Å×4.8 Å) pores normal to the nanosheets. It can be easily exfoliated to construct 2D membrane, which shows a high hydrogen selectivity up to 130 from natural gas and is promising for hydrogen purification and greenhouse gas capture.     

聚合物/无机纳米粒子复合膜在气体分离中的研究进展

由于聚合物膜具有可高度设计、机械性能好、易于加工 等优点,是理想的气体分离材料。然而,聚合物膜在气体选择性和渗透性方面存在平衡限制,在聚合物中引入纳米粒子,是提高气体分离性能的一种有效手段。本文基于聚合物/无机纳米粒子复合膜在气体分离领域的研究现状,重点阐述了零维纳米粒子（二氧化硅、二氧化钛）、一维纳米粒子（碳纳米管）、二维纳米粒子（氧化石墨烯、二维过渡金属氧化物）、三维纳米粒子（金属有机框架、沸石）对气体分离性能的影响,并展望了聚合物复合分离膜的发展趋势,为未来高效分离膜的研发提供了参考。     

Azide‐based Cross‐Linking of Polymers of Intrinsic Microporosity (PIMs) for Condensable Gas Separation

Cross‐linked polymers of intrinsic microporosity (PIM)s for gas separation membranes, were prepared by a nitrene reaction from a representative PIM in the presence of two different diazide cross‐linkers. The reaction temperature was optimized using TGA. The homogenous membranes were cast from THF solutions of different ratios of PIM to azides. The resulting cross‐linked structures of the PIMs membranes were formed at 175 °C after 7.5 h and confirmed by TGA, XPS, FT‐IR spectroscopy and gel content analysis. These resulting cross‐linked polymeric membranes showed excellent gas separation performance and can be used for O₂/N₂ and CO₂/N₂ gas pairs, as well as for condensable gases, such as CO₂/CH₄, propylene/propane separation. Most importantly, and differently from typical gas separation membranes derived from glassy polymers, the crosslinked PIMs showed no obvious CO₂ plasticization up to 20 atm pressure of pure CO₂ and CO₂/CH₄ mixtures.

     

Intrinsic field theory of chemical reactions

An intrinsic principle of least action is presented for the intrinsic dynamism of chemical reactions. Then, as the stationary trajectory, a meta-IRC (intrinsic reaction coordinate) draws a geodesic curve in a rigged Riemannian space. This establishes a geodesic law for the intrinsic dynamism. Moreover, a diagrammatic perturbation theory is formulated for the intrinsic dynamism, and a dynamical interaction between a chemically reacting system and a background system is investigated. Then, the structural stability of the system is discussed using a new concept of the dynamical potential field. An example is given in order to elucidate the present theory.Dedicated to Prof. Hermann Hartmann on the occasion of his 65th birthday.     

从GPC和特性粘数计算高聚物各种平均相对分子质量的新方法

聚合物相对分子质量表征问题可以从ＧＰＣ数据和特性粘数较可靠地迅速解决，同时求出其烽均、粘均、重均，动力学平均相对分子质量及相对分子质量－特性粘数关联参数。为些须对以往方法作较大的改进，其关键是用迭代法进行特性粘数与相对分子质量的关联。方法经用聚甲基丙烯酸甲酯验证后用于聚碳酸亚乙酯（ＰＥＣ）和聚碳酸亚丙酯（ＰＰＣ）分别得到关系式。     

成膜溶剂对聚4-甲基戊烯-1膜的形态结构和透过行为的影响——Ⅱ.膜的气体透过行为

以聚4-甲基戊烯-1(PMP)为膜材质,分别以环己烷、三氯乙烯、四氯乙烯及环已烷/三氯乙烯为溶剂,研究了这些溶液浇铸膜对O_2、N_2、H_2及CO_2等气体的透过行为。结果表明,气体的透过主要发生在PMP的无定形区域,但也在PMP的晶区进行。PMP的Ⅵ型结晶比Ⅰ型结晶具有较低的气体透过活化能。     

富羧酸基团的共轭微孔聚合物:结构单元对孔隙和气体吸附性能的影响

Polar groups in the skeletons of conjugated microporous polymers (CMPs) play an important role in determining their porosity and gas sorption performance. Understanding the effect of the polar group on the properties of CMPs is essential for further advances in this field. To address this fundamental issue, we used benzene, the simplest aromatic system, as a monomer for the construction of two novel CMPs with multi-carboxylic acid groups in their skeletons (CMP-COOH@1 and CMP-COOH@2). We then explored the profound effect the amount of free carboxylic acid in each polymer had on their porosity, isosteric heat, gas adsorption, and gas selectivity. CMP-COOH@1 and CMP-COOH@2 showed Brunauer-Emmett-Teller (BET) surface areas of 835 and 765 m²·g^-1, respectively, displaying high potential for carbon dioxide storage applications. CMP-COOH@1 and CMP-COOH@2 exhibited CO₂ capture capabilities of 2.17 and 2.63 mmol·g^-1 (at 273 K and 1.05 × 10⁵ Pa), respectively, which were higher than those of their counterpart polymers, CMP-1 and CMP-2, which showed CO₂ capture capabilities of 1.66 and 2.28 mmol·g^-1, respectively. Our results revealed that increasing the number of carboxylic acid groups in polymers could improve their adsorption capacity and selectivity.