Supramolecular polymer-based gel fracturing fluid with a double network applied in ultra-deep hydraulic fracturing

A gel based on polyacrylamide,exhibiting delayed crosslinking characteristics,emerges as the preferred solution for mitigating degradation under conditions of high temperature and extended shear in ultralong wellbores.High viscosity/viscoelasticity of the fracturing fluid was required to maintain excellent proppant suspension properties before gelling.Taking into account both the cost and the potential damage to reservoirs,polymers with lower concentrations and molecular weights are generally preferred.In this work,the supramolecular action was integrated into the polymer,resulting in significant increases in the viscosity and viscoelasticity of the synthesized supramolecular polymer system.The double network gel,which is formed by the combination of the supramolecular polymer system and a small quantity of Zr-crosslinker,effectively resists temperature while minimizing permeability damage to the reservoir.The results indicate that the supramolecular polymer system with a molecular weight of(268—380)×10^(4)g/mol can achieve the same viscosity and viscoelasticity at 0.4 wt%due to the supramolecular interaction between polymers,compared to the 0.6 wt%traditional polymer(hydrolyzed polyacrylamide,molecular weight of 1078×10^(4)g/mol).The supramolecular polymer system possessed excellent proppant suspension properties with a 0.55 cm/min sedimentation rate at 0.4 wt%,whereas the0.6 wt%traditional polymer had a rate of 0.57 cm/min.In comparison to the traditional gel with a Zrcrosslinker concentration of 0.6 wt%and an elastic modulus of 7.77 Pa,the double network gel with a higher elastic modulus(9.00 Pa)could be formed only at 0.1 wt%Zr-crosslinker,which greatly reduced the amount of residue of the fluid after gel-breaking.The viscosity of the double network gel was66 m Pa s after 2 h shearing,whereas the traditional gel only reached 27 m Pa s.

A New Three-dimensional Supramolecular Polymer Built from Non-covalent Bonding Interactions

A new complex, [Ni2（L）4（H2O）8]（1, L1 = 4-（1H-imidazol-4-yl）benzoic acid）, has been hydrothermally prepared and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and PXRD. Complex 1 crystallizes in monoclinic, space group P21/c with α = 22.281（2）, b = 7.3959（7）, c = 24.978（3） ？, β = 90.876（10）, V = 4115.6（7） ？3, Z = 8, C20H22N4O8Ni, Mr = 505.13, Dc = 1.630 g/cm3, μ = 1.001 mm-1, S = 1.080, F（000） = 2096, the final R = 0.452 and wR = 0.1152 for 9380 observed reflections （I 〉 2σ（I））. The result of X-ray diffraction analysis revealed three different kinds of Ni（II） centre mononuclear molecules in the asymmetric unit. The independent mononuclear units are bridged to form a three-dimensional supramolecular polymer by extensive hydrogen bonds and C–H… non-covalent bonding interactions.

Synthesis, Crystal Structure and Property of a Series of Supramolecular Polymers Based on Novel 3,5-Dimethyl- 2,6-bis(3-(pyrid-2-yl)-1,2,4-triazolyl)pyridine Ligand

Solvothermal reactions of 3,5-dimethyl-2,6-bis（3-（pyrid-2-yl）-1,2,4-triazolyl） pyridine （L）, 1,4-benzendicarboxylic acid （H2bdc）, and transitional metal cations of M11 （M = Mn, Co, Cd） in the presence of oxalic acid （H2ox） afford three novel supramolecular polymers （CPs）, namely, {[M2（ox）（L）2][bdc][M2（Hox）2（OH）（H2O）4]·3H2O}n （M = Mn for 1, Co for 2, Cd for 3）. Single-crystal X-ray diffraction analysis reveals that complexes 1-3 are isostructural and the 3D supramolecular structure was connected through non-covalent interactions. With the help of H2ox, the L ligands cheated with center atoms forming a butterfly [M2（ox）（L）2]2＋ building block. The bdc2- ligand linked with the unprecedented [M2（Hox）2（OH）2（H2O）4] units through strong O-H...O hydrogen bonds forming a zigzag chain, which are further connected through π-π interactions between L and bdc2- ligands to form a 3D supramolecular structure. Moreover, elemental analyses, IR, thermogravimetric, PXRD and luminescence have been investigated.

Two Three-dimensional Supramolecular Polymer Built from Mixed N-Donor and Carboxylate Ligands

Two new complexes, [Mn（L）（mmbda）（H_2O）]（1） and [Co（L）（btc）（H_2O）]·H_2O（2）, were synthesized by reacting the corresponding metal（Ⅱ） salts with rigid ligand 1,4-di（1Himidazol-4-yl）benzene（L） and two different carboxylic acids of 5-methylisophthalic acid（H_2mmbda） and 1,2,4-benzenetricarboxylic acid（H_3btc）, respectively. The structures of the complexes were characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and PXRD. Complex 1 crystallizes in triclinic, space group P1 with a = 6.9436（4）, b = 9.7306（6）, c = 15.5302（10） ？, α = 73.7430（10）, β = 85.1010（10）, γ = 70.0360（10）o, V = 946.75（10） ？~3, Z = 2, C_（21）H_（20）N_4O_5 Mn, M_r = 463.33, D_c = 1.618 g/cm^3, μ = 0.742-1, S = 1.002, F（000） = 474, the final R = 0.0285 and wR = 0.0600 for 4328 observed reflections（I 〉 2σ（I））. Complex 2 crystallizes in monoclinic, space group P2_1/n with a = 12.5216（12）, b = 7.3312（8）, c = 22.510（2） ？, β = 93.104（2）o, V = 2063.3（4） ？~3, Z = 4, C_（21）H_（18）N_4O_8Co, M_r = 513.31, D_c = 1.646 g/cm^3, μ = 0.892^（-1） mm, S = 1.096, F（000） = 1044, the final R = 0.0673 and wR = 0.1780 for 3594 observed reflections（I 〉 2σ（I））. Both of complexes are one-dimensional（1D） chain structures and rich hydrogen bonds extend such 1D chains to form three-dimensional（3D） supramolecular polymers.

Supramolecular Polymer Intertwined Free-Standing Bifunctional Membrane Catalysts for All-Temperature Flexible Zn-Air Batteries

Rational construction of flexible free-standing electrocatalysts featuring long-lasting durability,high efficiency,and wide temperature tolerance under harsh practical operations are fundamentally significant for commercial zinc-air batteries.Here,3D flexible free-standing bifunctional membrane electrocatalysts composed of covalently cross-linked supramolecular polymer networks with nitrogen-deficient carbon nitride nanotubes are fabricated(referred to as PEMAC@NDCN)by a facile self-templated approach.PEMAC@NDCN demonstrates the lowest reversible oxygen bifunctional activity of 0.61 V with exceptional long-lasting durability,which outperforms those of commercial Pt/C and RuO_(2).Theoretical calculations and control experi-ments reveal the boosted electron transfer,electrolyte mass/ion transports,and abundant active surface site preferences.Moreover,the constructed alkaline Zn-air battery with PEMAC@NDCN air-cathode reveals superb power density,capacity,and discharge-charge cycling stability(over 2160 cycles)compared to the reference Pt/C+RuO_(2).Solid-state Zn-air batteries enable a high power density of 211 mW cm^(−2),energy density of 1056 Wh kg^(−1),stable charge-discharge cycling of 2580 cycles for 50 mA cm^(−2),and wide temperature tolerance from−40 to 70℃with retention of 86%capacity compared to room-temperature counterparts,illustrating prospects over harsh operations.

Hydrogen-Bonding Crosslinked Supramolecular Polymer Materials:From Design Evolution of Side-Chain Hydrogen-Bonding to Applications

Hydrogen bonds(H-bonds)are the most essential non-covalent interactions in nature,playing a crucial role in stabilizing the secondary structures of proteins.Taking inspiration from nature,researchers have developed several multiple H-bonds crosslinked supramolecular polymer materials through the incorporation of H-bond side-chain units into the polymer chains.N-acryloyl glycinamide(NAGA)is a monomer with dual amides in the side group,which facilitates the formation of multiple dense intermolecular H-bonds within poly(N-acryloyl glycinamide)(PNAGA),thereby exhibiting diverse properties dependent on concentration and meeting various requirements across different applications.Moreover,numerous attempts have been undertaken to synthesize diverse NAGA-derived units through meticulous chemical structure regulation and fabricate corresponding H-bonding crosslinked supramolecular polymer materials.Despite this,the systematic clarification of the impact of chemical structures of side moieties on intermolecular associations and material performances remains lacking.The present review will focus on the design principle for synthesizing NAGA-derived H-bond side-chain units and provide an overview of the recent advancements in multiple H-bonds crosslinked PNAGA-derived supramolecular polymer materials,which can be categorized into three groups based on the chemical structure of H-bonds units:(1)monomers with solely cooperative H-bonds;(2)monomers with synergistic H-bonds and other physical interactions;and(3)diol chain extenders with cooperative H-bonds.The significance of subtle structural variations in these NAGA-derived units,enabling the fabrication of hydrogen-bonded supramolecular polymer materials with significantly diverse performances,will be emphasized.Moreover,the extensive applications of multiple H-bonds crosslinked supramolecular polymer materials will be elucidated.

A Novel Borophosphate Coordination Polymer with Sandwich-type Supramolecular Architecture

A novel borophosphate (Hmel)3{Co2[(mel)2(HPO4)2(PO4)]·H3BO3·H2O} (mel= melamine) has been synthesized under mild solvothermal conditions. The structure of the compound exists a high ordered organic-inorganic sandwich-type supramolecular architecture via metal-coordination, hydrogen bonds and π-π stacking interactions.

A 3-D Supramolecular Network with 1-D Cation Metal-organic Coordination Polymers and Diverse Motifs from Hydrogen-bonded [M(H_2O)_4]-Carboxylates

One-pot solvothermal reaction of Iransition metal Znn salt with 4,4-bipyddyl （bpy） and 1,4-benzenediacrylic add （H2L） in the presence of Et3N generates a three-dimensional （3-D） supramolecular network with 1-D cation metal-organic coordination polymer, [Zn（H20）a（bpy）]-L 1, and structurally characterized by single-crystal X-ray diffraction, elemental analyses, IR spectroscopy, and photoluminescent property. The complex crystallizes in triclinic, space group P1 with a = 7.1291（2）, b = 7.3784（3）, c = 10.5042（3）A, α = 95.049（2）, β = 102.162（2）, 7 = 97.027（3）0, V= 532.38（3）A3, C22H24N2O8Zn, Mr = 509.82, De= 1.590 g/cm3, p（MoKa）= 1.207 ram-l, F（000） = 264, Z = 1,the finalR=O.0438and wR=O.lOll for 1589 observed reflections （I 〉 2σ（I））. In the crystal structure, the second building unit composed of [Zn（H2O）4].L constructs two distinct 2-D supramolecular sheets and a neutral 3-D architecture. The title compound 1 shows strong photoluminescence with emission maximum at 2 = 455 nm upon λex.max = 355 nm.

Syntheses and Structures of Uwo New Oxalate-bridged Transition-metal Supramolecular Polymers of [M(2-NH_2py)_2(ox)]

Two new supramoleeular polymers [ M （2-NH2 py）2 （ox） ] [ M = Co （1）, Ni （2） ; 2-NH2py = 2-aminopyridine; ox = oxalate ] were hydrothermally synthesized and characterized by elemental analyses, IR and single-crystal X-ray diffraction analyses. The isomorphic compounds 1 and 2 both possess one-dimensional zigzag chain structures, which are composed of [ M （2-NH2 py）2 ]^2＋ units bridged by tetradentate oxalate ligands to form three-dimensional supramolecular network v/a the C-H…O hydrogen bonds and π-π stacking interactions. Compound 1 displays antiferromagnetie interaction.

Supramolecular Architecture from the Self-assembly of One-dimensionalCoordination Polymers and Hydrogen Bonds

The novel one-dimensional coordination polymer {[Cu(L)2(H2O)]?2BF4?6H2O}∞ [1, L=1,2-bis(4-pyridinecarboxamido)ethane] was synthesized as single crystals and characterized by means of X-ray diffraction analysis, elemental analysis, IR spectroscopy and TG measurement. Structure 1 consists of looped chains. In addition, linked by hydrogen bonds, the one-dimensional chains were transformed into three-dimensional framework, which shows channels filled with anions and uncoordinated water molecules.

One-dimensional Coordination Polymers Assembled into Two Supramolecular Frameworks with High Stability

The dual ligand system of V-shaped 5-（4-carboxy-2-nitrophenoxy）-isophthalic acid（Hcn-H2ipa） and dipyridy-type molecules produces two new coordination polymers： {[Ni（cn-Hipa）（bpa）（H2O）3]·1.5H2O}n 1 and {[Cu（Hcn-ipa）（ppe）2]}n 2（bpa = 1,2-bis（4-pyridyl）ethane, and ppe = trans-1-（2-pyridyl）-2-（4-pyridyl）ethylene）. Two complexes have been characterized by single-crystal X-ray diffraction, elemental analysis, IR, and thermogravimetric analysis（TGA）. Complex 1 is of monoclinic system, space group C2 with a = 25.936（3）, b = 7.6100（10）, c = 16.558（2）, β = 105.9470（10）°, V = 3142.4（7） A3, Dc = 1.415 g/cm3, Mr = 669.23, Z = 4, F（000） = 1388, μ = 0.687 mm-1, the final R = 0.0397 and w R = 0.0967 for 12070 observed reflections with I 〉 2σ（I）. Complex 2 belongs to the triclinic system, space group P1 with a = 10.165（5）, b = 14.946（7）, c = 15.506（11） A, α = 106.461（7）, β = 102.454（8）, γ = 107.861（5）°, V = 2029（2） A3, Dc = 1.266 g/cm3, Mr = 773.20, Z = 2, F（000） = 794, μ = 0.595 mm-1, the final R = 0.0538 and w R = 0.1378 for 15488 observed reflections with I 〉 2σ（I）. Two complexes show that the 1D polymeric chains are cohered together by extensive H-bonds to complete stable supramolecular microporous frameworks.

MORPHOLOGICAL AND KINETIC STUDIES OF PHASE TRANSITIONS OF A SIDE-CHAIN LIQUID CRYSTALLINE POLYMER

The morphological changes of a side-chain liquid-crystalline polymethacrylate during isotropization and liquid-crystallization transitions were studied by means of polarizing microscopy. These transitions were found to be composed of the initiation of a new phase at local places of the old phase matrix and the growth of the new phase: domains. The kinetics of the liquid-crystallization of the polymer from an isotropic melt to a smectic mesophase was also investigated. The isothermal process of the transition can be described by the Avrami equation. The values of the Avrami exponent were found to be around 2.6. which is lower than the value usually obtained for crystallization transition of polymers, but larger than that reported for liquid-crystallization transition of main-chain polymers. These results may indicate the difference in growth geometry of new phase during transition between crystallization and liquid-crystallization in general and between liquid-crystallization of main-chain and side-chain polymers. It was found that the liquid-crystallization of the used side-chain polymethacrylate may occur at small undercoolings with high transformation rate similar to that of main-chain polymers and small-molecule liquid crystals, while the crystallization of polymers can only proceed at large undercoolings. These phenomena can be explained by the idea that the surface free energy of nucleus during liquid-crystallization transition is less than that for crystallization, and evidence was obtained from analysis of the temperature dependence of the transformation rate.

The effect of intermolecular interactions on photoluminescence of a porphyrin side-chain polymer

Photoluminescence properties and exciton decay dynamics in a porphyrin side-chain polymer, poly[porphyrin acrylate- acrylonitrile （abbreviated p[（por）A-AN]）, have been investigated by femtosecond time-resolved photoluminescence spectroscopy. All the luminescences of p[（por）A-AN] films are due to the emissive decay of the photoexcited singlet excitons in the porphyrins. The luminescence efficiencies and lifetimes are increased for samples from pure films to dilute blend films. However, they are increased as the intrachain concentration of the porphyrin sidechain groups is decreased. The intrachain rotation motions of porphyrin sidechain groups result in the initial ultrafast luminescence decays, which are much faster than those due to the interchain interactions. All the samples show no significant red-shift and broadening of the transient luminescence spectra. The interchain and intrachain nonradiative exciton relaxation processes may play an important role in the luminescence dynamics in the p[（por）A-AN] films. The possible origin of different intrachain and interchain dynamic behaviours in p[（por）A-AN] films is discussed.

MORPHOLOGICAL STUDIES OF A THERMOTROPIC SIDE-CHAIN LIQUID CRYSTALLINE POLYMER DURING MESOPHASE TRANSITIONS

The morphological features of a side-chain liquid crystalline polymer during the mesophase transitions were investigated by using the DSC technique. The polymer used was polyacrylate with mesogens of three benzene rings attached to the main chain through a flexible spacer. A special two-phase texture was observed in the transition temperature range. Similar to main-chain liquid crystalline polymers the transition process of the side-chain liquid crystalline polymer was composed of an initiation of the new phase at local places of the old phase matrix and a growth process of the new phase domains.

The New Methods for Characterization of Molecular Weight of Supramolecular Polymers

Supramolecular polymers,as a type of dynamic polymers,are subordinate to the interdisciplinary field of polymer chemistry and supramolecular chemistry,whose development has greatly promoted the prosperity of new materials.Notably,molecular weight is one of the most important parameters of supramolecular polymers,which affects the physical/chemical properties and processing applications of materials.Developing new methods for characterizing the molecular weight of supramolecular polymers is crucial for advancing the development of supramolecular polymers.In this review,we elaborate and summarize three strategies for characterizing the molecular weight of supramolecular polymers that recently reported by our research group according to the characteristics of supramolecular polymers,including(1)the molecular weight distinction corresponding to variable fluorescence colors,(2)matching different molecular weights with different fluorescence lifetime,(3)transforming supramolecular polymers into mechanically interlocked polymers or covalent polymers.Besides,we also discuss the limitations of current methods for characterizing supramolecular polymers.We hope that this review can promote the development of supramolecular polymers and significantly inspire to exploit new methods to characterizing molecular weight of supramolecular polymers.

AIE interfacial supramolecular polymers

High monomer concentration is a requisite for engendering the aggregation-induced emssion(AIE)phenomenon as well as the formation of supramolecular polymers.Therefore,this is supposed to ensure the generation of AIE supramolecular polymers,wherein the monomer soluability takes effect.Nevertheless,parts of supramolecular monomers are considered as poessessing different soluability towards the same sovlent,through which the polymerzation process is thus hard to proceed.Interfacial polymerzation gets over the soluabilty restriction,providing a facile method for propelling the reaction of thesemonomers.Herein,we had prepared M1 containing tetraphenylethene(TPE)functionalized with two terpyridine derivatives,then making M1 dissolving in CHCl3 to give solutions.Cu^(2+)solutions were fabricated through dissolving CuCl_(2)into H2O.Towards mixing those solutions,AIE interfacial supramolecular polymers(AIEISPs)displaying green fluorescence were generated at the interface of two phases on the basis of metal-coordination between terpyridine and Cu^(2+).These AIEISPs were certificated to possess the stimuli-responsiveness,for which the excessive addition of tetrabutylammonium hydroxide would cause the structure destruction owing to the stronger bonding ability with Cu^(2+)than that of terpyridine.These fabricated AIEISPs had provided a new avenue to prepare AIE supramolecular polymers.

Artificial stepwise light harvesting system in water constructed by quadruple hydrogen bonding supramolecular polymeric nanoparticles

Stepwise energy transfer is ubiquitous in natural photosynthesis,which greatly promotes the widespread use of solar energy.Herein,we constructed a supramolecular light harvesting system based on sequential energy transfer through the hierarchical self-assembly of M,which contains a cyanostilbene core flanked by two ureidopyrimidinone motifs,endowing itself with both aggregation-induced emission behavior and quadruple hydrogen bonding ability.The monomer M can self-assemble into hydrogen bonded polymers and then form supramolecular polymeric nanoparticles in water through a mini-emulsion process.The nanoparticles were further utilized to encapsulate the relay acceptor ESY and the final acceptor NDI to form a two-step FRET system.Tunable fluorescence including a white-light emission was successfully achieved.Our work not only shows a desirable way for the fabrication of efficient two-step light harvesting systems,but also shows great potential in tunable photoluminescent nanomaterials.

Differentiated self-assembly through orthogonal noncovalent interactions towards the synthesis of two-dimensional woven supramolecular polymers

Molecular weaving is a powerful approach to make molecularly woven materials that have showed unprecedented characteristics and properties intrinsically distinct to those of non-woven materials.We here report a facile and efficient approach for the synthesis of 2D woven supramolecular polymers by differentiated self-assembly through orthogonal noncovalent interactions.Importantly,the difference in binding strength of two orthogonal noncovalent interactions can be used to control the process of molecular weaving.Consequently,single-layered 2D woven supramolecular polymers were synthesized and fully characterized by various techniques.This study demonstrates a controllable method for molecular weaving,and will significantly hasten the development of molecularly woven materials.

Pillar[5]arene based artificial light-harvesting supramolecular polymer for efficient and recyclable photocatalytic applications

Photosynthesis is the process through which living plants utilize photosynthetic pigments,such as chlorophyll,to convert CO_(2)and water into organic compounds and release O_(2)under visible light.In this study,we have successfully constructed a fluorescent supramolecular polymer(P5Py_(2)/Zn/Gen)n by employing orthogonal pillar[5]arene-based molecular recognition and metal ion coordination.Within the supramolecular polymer,the guest molecule Gen unit acts as a light-harvesting moiety,as the ACQ effect is inhibited by host-guest interactions,while the(Py)_(2)/Zn center serves as a catalytic site.By employing this orthogonal self-assembly strategy,we have enhanced the stability of both the donor and acceptor in catalyzing the reduction of p-nitrophenol to p-aminophenol.Moreover,this photocatalyst can be reused at least 5 times without significant conversion loss.These findings provide a pathway for constructing a recyclable artificial LHS that mimics the entire photosynthesis process.

Polymer donors with hydrophilic side-chains enabling efficient and thermally-stable polymer solar cells by non-halogenated solvent processing

Polymer solar cells(PSCs)with high power conversion efficiency(PCE)and environment-friendly fabrication are the main requirements enabling their production in industrial scale.While the use of non-halogenated solvent processing is inevitable for the PSC fabrication,it significantly reduces the processability of polymer donors(PDS)and small-molecule acceptors(SMAs).This often results in unoptimized blend morphology and limits the device performance.To address this issue,hydrophilic oligoethylene glycol(OEG)side-chains are introduced into a PD(2EG)to enhance the molecular compatibility between the PD and L8-BO SMA.The 2EG PD induces higher crystallinity and alleviates phase separation with the SMA compared to the reference PD(PM7)with hydrocarbon side-chains.Consequently,the 2EG-based PSCs exhibit a higher PCE(15.8%)than the PM7-based PSCs(PCE=14.4%)in the ortho-xylene based processing.Importantly,benefitted from the reduced phase separation and increased crystallinity of 2EG PDS,the 2EG-based PSCs show enhanced thermal stability(84%of initial PCE after 120 h heating)compared to that of the PM7-based PSCs(60%of initial PCE after 120 h heating).This study demonstrates the potential of OEG side-chain-incorporated materials in developing efficient,stable,and eco-friendly PSCs.