Crystal Structure Of Polymer Research Articles

Polyvinylidene fluoride phase design by two-dimensional boron nitride enables enhanced performance and stability for seawater desalination

The instability of polyvinylidene fluoride (PVDF) membranes in membrane distillation (MD) for seawater desalination is still a problem, despite the tremendous effort expended to resolve this issue. Here, a simple and feasible approach for improving desalination performance through the incorporation of two-dimensional boron nitride nanosheets (BNNSs) in polyvinylidene fluoride-co-hexafluoropropene (PVDF-co-HFP) electrospun nanofiber membrane (BNs-PH) is proposed as well as demonstrate its origin for fundamental understanding. The BNs-PH membrane exhibits a stable water vapor flux (18 LMH) and superior salt rejection (99.99%), even after operation for 280 h (commercial PVDF: steep decay within 28 h; neat PH: wetting within 4 h). From structural/chemical analyses, the BNNSs play a crucial role in forming favorable phases of the PH polymer crystal structure, inducing a superhydrophobic surface with greater nanoporosity and higher heterogeneity as well as enhanced mechanical properties (increase of UTS: 13.4%; modulus: 1.2%) for long-term operation. Theoretical modeling results of an air-gap MD system are consistent with our experimental results. The approach introduced in this study can be applied to other desalination systems to boost various water treatment applications.

Fabrication of Large Single Crystals for Platinum-Based Linear Polymers with Controlled-Release and Photoactuator Performance.

Preparation of large single crystals of linear polymers for X-ray analysis is very challenging. Herein, we employ a coordination-driven self-assembly strategy to secure the appropriate head-to-tail alignment of anthracene moieties, and for the first time obtained large-sized Pt-based linear polymer crystals through a [4+4] cycloaddition of anthracene in a single-crystal to single-crystal fashion. Using X-ray diffraction to determine the polymer crystal structure, we found that both the polymerisation and depolymerisation steps proceed via a stable intermediate. Taking advantage of the temperature-dependent slow depolymerization, the Pt-based linear polymer showed potential as a sustained release anticancer drug platform. Utilizing the reversible contraction effect of unit-cell volume upon irradiation or heating, the stimuli-responsive crystals were hybridized with polyvinylidene fluoride to obtain a "smart material" with outstanding photoactuator performance.

Fabrication of Large Single Crystals for Platinum‐Based Linear Polymers with Controlled‐Release and Photoactuator Performance

AbstractPreparation of large single crystals of linear polymers for X‐ray analysis is very challenging. Herein, we employ a coordination‐driven self‐assembly strategy to secure the appropriate head‐to‐tail alignment of anthracene moieties, and for the first time obtained large‐sized Pt‐based linear polymer crystals through a [4+4] cycloaddition of anthracene in a single‐crystal to single‐crystal fashion. Using X‐ray diffraction to determine the polymer crystal structure, we found that both the polymerisation and depolymerisation steps proceed via a stable intermediate. Taking advantage of the temperature‐dependent slow depolymerization, the Pt‐based linear polymer showed potential as a sustained release anticancer drug platform. Utilizing the reversible contraction effect of unit‐cell volume upon irradiation or heating, the stimuli‐responsive crystals were hybridized with polyvinylidene fluoride to obtain a “smart material” with outstanding photoactuator performance.

Erratum to: Crystal Structure and Luminescent Property of a New Two-Dimensional Polymer Based on 1,4-Bis(4-(Imidazole-1-YL)Benzyl)Piperazine

In the original article there was a mistake in the information of the corresponding author. The correct spelling of the names of the authors and their order is: C. Zhang, J.-Q. Tao, and J. Wang*.

Probing the interior lamellar periodicity and nano-assembly of polymer spherulites via combinatory etching methodology

Physical and chemical degradative effects of etching agents on polymer spherulites have been explored thoroughly to understand the etching mechanism as well as to perceive the polymer crystal structure and assembly. Interior lamellae of an aromatic polyester, poly(trimethylene terephthalate) (PTT), crystallized into a well-defined periodic-birefringent spherulitic structure, are subjected to sequence-assorted etching agents of basic methylamine (MA) vapor, acidic permanganate (KMnO4) reagent, inorganic acids mixture (H2SO4:H3PO4), and organic dichloroacetic acid (DCA). The chemistry involved in reactions between the selected etchants with the polymer spherulites was probed and their synergistic effects on exposing the interior 3D assembly were assessed. The exposed circumferential alignment of rod-like polycrystals interconnected by nanofibrils signifies the hidden interfaces between the lamellae that are assembled in a periodic grating structure to form banded PTT spherulites.

More crystal field theory in action: the metal-4-picoline (pic)-sulfate [M(pic)x]SO4 complexes (M= Fe, Co, Ni, Cu, Zn, and Cd).

Seven crystal structures of five first-row (Fe, Co, Ni, Cu, and Zn) and one second-row (Cd) transition metal-4-picoline (pic)-sulfate complexes of the form [M(pic)x]SO4 are reported. These complexes are catena-poly[[tetrakis(4-methylpyridine-κN)metal(II)]-μ-sulfato-κ2O:O'], [M(SO4)(C6H7N)4]n, where the metal/M is iron, cobalt, nickel, and cadmium, di-μ-sulfato-κ4O:O-bis[tris(4-methylpyridine-κN)copper(II)], [Cu2(SO4)2(C6H7N)6], catena-poly[[bis(4-methylpyridine-κN)zinc(II)]-μ-sulfato-κ2O:O'], [Zn(SO4)(C6H7N)2]n, and catena-poly[[tris(4-methylpyridine-κN)zinc(II)]-μ-sulfato-κ2O:O'], [Zn(SO4)(C6H7N)3]n. The Fe, Co, Ni, and Cd compounds are isomorphous, displaying polymeric crystal structures with infinite chains of MII ions adopting an octahedral N4O2 coordination environment that involves four picoline ligands and two bridging sulfate anions. The Cu compound features a dimeric crystal structure, with the CuII ions possessing square-pyramidal N3O2 coordination environments that contain three picoline ligands and two bridging sulfate anions. Zinc crystallizes in two forms, one exhibiting a polymeric crystal structure with infinite chains of ZnII ions adopting a tetrahedral N2O2 coordination containing two picoline ligands and two bridging sulfate anions, and the other exhibiting a polymeric crystal structure with infinite chains of ZnII ions adopting a trigonal bipyramidal N3O2 coordination containing three picoline ligands and two bridging sulfate anions. The structures are compared with the analogous pyridine complexes, and the observed coordination environments are examined in relation to crystal field theory.

Evidence for Crystalline Structure in Dynamically-Compressed Polyethylene up to 200 GPa

We investigated the high-pressure behavior of polyethylene (CH2) by probing dynamically-compressed samples with X-ray diffraction. At pressures up to 200 GPa, comparable to those present inside icy giant planets (Uranus, Neptune), shock-compressed polyethylene retains a polymer crystal structure, from which we infer the presence of significant covalent bonding. The A2/m structure which we observe has previously been seen at significantly lower pressures, and the equation of state measured agrees with our findings. This result appears to contrast with recent data from shock-compressed polystyrene (CH) at higher temperatures, which demonstrated demixing and recrystallization into a diamond lattice, implying the breaking of the original chemical bonds. As such chemical processes have significant implications for the structure and energy transfer within ice giants, our results highlight the need for a deeper understanding of the chemistry of high pressure hydrocarbons, and the importance of better constraining planetary temperature profiles.

Composition-Morphology Correlation in PTB7-Th/PC71BM Blend Films for Organic Solar Cells.

From a morphological perspective, the understanding of the influence of the [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) content on the morphology of the active layer is not complete in organic solar cells (OSCs) with bulk heterojunction (BHJ) configuration based on the low-bandgap polymer poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2- b;4,5- b']dithiophene-2,6-diyl- alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4- b]thiophene-)-2-carboxylate-2-6-diyl] (PTB7-Th). In this work, we obtain the highest power conversion efficiency (PCE) of 10.5% for BHJ organic solar cells (OSCs) with a PTB7-Th/PC71BM weight ratio of 1:1.5. To understand the differences in PCEs caused by the PC71BM content, we investigate the morphology of PTB7-Th/PC71BM blend films in detail by determining the domain sizes, the polymer crystal structure, optical properties, and vertical composition as a function of the PC71BM concentration. The surface morphology is examined with atomic force microscopy, and the inner film morphology is probed with grazing incidence small-angle X-ray scattering. The PTB7-Th crystal structure is characterized with grazing incidence wide-angle X-ray scattering and UV/vis spectroscopy. X-ray reflectivity is employed to yield information about the film vertical composition. The results show that in PTB7-Th/PC71BM blend films, the increase of PC71BM content leads to an enhanced microphase separation and a decreased polymer crystallinity. Moreover, a high PC71BM concentration is found to decrease the polymer domain sizes and crystal sizes and to promote polymer conjugation length and formation of fullerene-rich and/or polymer-rich layers. The differences in photovoltaic performance are well explained by these findings.

Humidity properties of Schiff base polymers

Abstract The synthesized Schiff base polymers were investigated for humidity and chloroform response characteristics. The crystal structure of polymers were analyzed using X-ray diffraction (X-RD) method. We used the QCM (quartz crystal microbalance) method for the analyses of the water steam adsorption and desorption ratio of polymers. The experimental results showed that Schiff base polymers were very sensitive to humidity and chloroform at room temperature and it was possible to use it as a sensing element in moisture sensor applications.

Rheology, crystal structure, and nanomechanical properties in large-scale additive manufacturing of polyphenylene sulfide/carbon fiber composites

Extrusion based high-throughput Additive Manufacturing (AM) provides a rapid and versatile approach for producing complex structures by using a variety of polymer materials. An underexplored aspect of this technique is concerned with the formation of interfaces between successively deposited layers. This is particularly important for large-scale additive manufacturing of semi-crystalline polymers because of the highly non-isothermal conditions involved, which influence both nucleation and crystal growth. The objective of this work is to investigate the microstructure and the corresponding viscoelastic properties of carbon fiber (CF) reinforced polyphenylene sulfide (PPS) resulting from extrusion-based high-throughput AM process. Questions on development of morphology focus on polymer crystal structure and carbon fiber orientation in the vicinity of the interface between successive layers. This study attempts to establish a fundamental understanding of the role of the AM has in transferring a set of intrinsic material properties to the macroscopic properties of the final AM structure.

Lead(II) coordination polymers with imidazole-4- and pyrazole-3-carboxylate isomeric linkers: Structural diversity and luminescence properties

Using 1H-imidazole-4-carboxylic acid (4imCOOH) and 1H-pyrazole-3-carboxylic acid (3pyrCOOH) coordination polymers [Pb(4imCOO)2(H2O)]n (1) and [Pb2(3pyrCOO)4]n (2) were constructed. Obtained polymers were characterized via FT-IR, X-ray, PL and TG methods. The coordination polyhedron around Pb(II) in 1 is described as distorted pentagonal pyramid with hemidirected coordination sphere (based on DFT calculations). Compound 2 consists of two crystallographically independent Pb(II) centres: Pb1 forms distorted monocapped pentagonal pyramid polyhedron (CN = 7, hemidirected), whereas the coordination polyhedron of Pb2 is distorted monocapped pentagonal pyramid (CN = 7) or tricapped octahedron (CN = 9, including secondary bonds) with holodirected geometry (confirmed by DFT calculations). Crystal structure of polymer 1 demonstrates a 1D structural motif with 2C1 topology while polymer 2 is a 2D compound with cpf topology. Polymer 1 presents blue-green emission at 485 nm at RT in the solid state, whereas polymer 2 exhibits two emission centres with maximum at 449 nm (blue fluorescence) and at 532 nm (green-yellow fluorescence), respectively.

Directing the Aggregation of Native Polythiophene during in Situ Polymerization.

The performance of semiconducting polymers strongly depends on their intra- and intermolecular electronic interactions. Therefore, the morphology and particularly crystallinity and crystal structure play a crucial role in enabling a sufficient overlap between the orbitals of neighboring polymers. A new solution-based in situ polymerization for the fabrication of native polythiophene thin films is presented, which exploits the film formation process to influence the polymer crystal structure in the resulting thin films. The synthesis of the insoluble polythiophene is based on an oxidative reaction in which the oxidizing agent, iron(III) p-toluenesulfonate (FeTos), initially oxidizes the monomers to enable the polymer chain growth and secondly the final polymers, thereby chemically doping the polythiophene. To exploit the fact that the doped polythiophene has a different crystal packing structure compared to the undoped polythiophene, we investigate the structural effect of this inherent doping process by varying the amounts of FeTos in the reaction mixture, creating polythiophene thin films with different degrees of doping. The structural investigation performed by means of grazing incidence wide-angle X-ray scattering (GIWAXS) suggests that the strongly doped polymer chains aggregate in a π-stacked manner in the film formation process. Moreover, this π-stacking can be maintained after the removal of the dopant molecules. GIWAXS measurements, molecular dynamics simulations, and spectroscopic analysis suggest the presence of polythiophene in a novel and stable crystal structure with an enhanced intermolecular interaction.

Synthesis and structure of a praseodymium (III) complex with carboxylate ligand: A thermal and spectroscopic study

One Pr(III) lanthanide ion complex was initially synthesized and characterized by TGA-DSC in air atmosphere, as well as characterized by CHN elemental analysis, defining the stoichiometric ratio as Pr(DMBz)3. The gaseous products evolved during the thermal decomposition were also monitored in N2 atmosphere employing TGA/FT-IR system. A crystal structure is obtained by state-of-the-art powder X-rays diffraction methods measured in conventional laboratory equipment and refined by the Rietveld method, which defined it as a monoclinic system of the space group P21/c with a polymeric crystal structure, [Pr(DMBz)3]n. FT-IR theoretical spectrum and time-dependent density functional theory (TD-DFT) were calculated from TGA-DSC and crystalline system data. The experimental and theoretical FT-IR spectra present a high correlation degree when the main stretching bands are compared, while the energy transfer (HOMO – LUMO) in their neighborhoods suggests the main contributions of the light-emitting states.

Coordination polymers based on zinc(ii) and manganese(ii) with 1,4-cyclohexanedicarboxylic acid

Three new metal-organic coordination polymers were obtained namely, [Mn3(chdc)3-(NMP)2(DMF)2] (1, chdc2– is trans-1,4-cyclohexanedicarboxylate, NMP is N-methylpyrrolidone, DMF is N,N-dimethylformamide), [Zn3(chdc)3(NMP)2]•2NMP (2), and [Zn3(chdc)3(ur)-(DMF)0.5]•DMF (3, ur is the urotropine). The crystal structures of polymers 1, 2, and 3 were determined by single-crystal X-ray crystallography. All three compounds were found to contain a trinuclear secondary building unit {M3(OOC)6}. Coordination polymers 1 and 2 have a layered structure, while polymer 3 has a three-dimensional coordination framework with isolated pores formed due to the presence of urotropine bridging molecules. Compounds 1 and 3 were characterized by IR spectroscopy, thermogravimetric and elemental analysis data, powder X-ray diffraction. Compound 3 was also characterized by UV-Vis diffuse reflectance spectrum.

First-row transition metal-pyridine (py)-sulfate [(py)xM](SO4) complexes (M = Ni, Cu and Zn): crystal field theory in action.

The crystal structures of three first-row transition metal-pyridine-sulfate complexes, namely catena-poly[[tetrakis(pyridine-κN)nickel(II)]-μ-sulfato-κ2O:O'], [Ni(SO4)(C5H5N)4]n, (1), di-μ-sulfato-κ4O:O-bis[tris(pyridine-κN)copper(II)], [Cu2(SO4)2(C5H5N)6], (2), and catena-poly[[tetrakis(pyridine-κN)zinc(II)]-μ-sulfato-κ2O:O'-[bis(pyridine-κN)zinc(II)]-μ-sulfato-κ2O:O'], [Zn2(SO4)2(C5H5N)6]n, (3), are reported. Ni compound (1) displays a polymeric crystal structure, with infinite chains of NiII atoms adopting an octahedral N4O2 coordination environment that involves four pyridine ligands and two bridging sulfate ligands. Cu compound (2) features a dimeric molecular structure, with the CuII atoms possessing square-pyramidal N3O2 coordination environments that contain three pyridine ligands and two bridging sulfate ligands. Zn compound (3) exhibits a polymeric crystal structure of infinite chains, with two alternating zinc coordination environments, i.e. octahedral N4O2 coordination involving four pyridine ligands and two bridging sulfate ligands, and tetrahedral N2O2 coordination containing two pyridine ligands and two bridging sulfate ligands. The observed coordination environments are consistent with those predicted by crystal field theory.

Crystalline structure of an ammonia borane–polyethylene oxide cocrystal: a material investigated for its hydrogen storage potential

Rare polymer crystal structure formed by ammonia borane in polyethylene oxide exhibiting a snake-like chain through the crystal.

Examples of cation exchange in new ionic oxovanadium(IV) complexes with anions of cyclobutane-1,1-dicarboxylic acid

The results on the synthesis and study of the crystal structures of compounds based on anionic fragments {VO(Cbdc)2}2– formed by oxovanadium(IV) (vanadyl, VO2+) and two chelate-bound anions of cyclobutane-1,1-dicarboxylic acid (H2Cbdc = C4H6(COOH)2) are presented. The use of ammonium cation NH4+ as a counterion in the synthesis leads to the formation of the mononuclear complex (NH4)2[VO(Сbdc)2(H2O)] · 2H2O (I). In the case of K+ cation, compound [K4(VO)2(Сbdc)4(H2O)4] n (II) with the 3D polymeric crystal structure is formed. The reaction of compound II with Mg(NO3)2 · 6H2O in an aqueous solution involves the partial substitution of K+ by Mg2+ cations to form 1D polymeric compound {[KMg0.5(VO)(Сbdc)2(H2O)6.5] · 3H2O} n (III), while a similar reaction of compound I does not afford the product of substitution of NH4+ by Mg2+ cations (CIF files CCDC 1551021–1551023 for compounds I–III, respectively).

Catena-Poly[[trimethyltin(IV)]-μ-3,4-difluorobenzeneseleninato-κ2O:O′

The title compound, [Sn(CH3)3(C6H3F2O2Se)]n, was prepared by treatment of 3,4-difluorobenzeneseleninic acid and trimethyltin chloride with sodium ethoxide in methanol. In the polymeric crystal structure, infinite chains, with the SnIVatom in a trigonal–bipyramidal C3O2coordination environment involving methyl ligands and the bridging 3,4-difluorobenzeneseleninate anion, are present. The chains extend parallel to [010] and are linked through slipped π–π interactions and weak C—H...O hydrogen bonds into a three-dimensional network.

Influence of Pyrazine/Piperazine Based Guest Molecules in the Crystal Structures of Uranyl Thiophene Dicarboxylate Coordination Polymers: Structural Diversities and Photocatalytic Activities for the Degradation of Organic Dye

The reaction of uranyl acetate dihydrate with 2,5-thiophenedicarboxylic acid (H2TDC) as the main ligand and pyrazine (PYZ); piperazine (PZ); 1,4 pyridyl piperazine (PYPZ); 1,4-di(pyridin-4-yl) piperazine (DPYZ); 1,2 pyrimidyl piperazine (PMPZ) as auxiliary ligand leads to the formation of five new compounds [UO2(TDC)(H2O)]·(PYZ)0.5·H2O, (I); [(UO2)2(TDC)3]·(HPZ)·4(H2O), (II); [UO2(TDC)2(H2O)]·(H2DPYZ)·H2O, (III); [UO2(TDC)3]·(H2DPYZ), (IV); [(UO2)2(TDC)3(H2O)]·(H2PMPZ).H2O, (V). They were analyzed by IR, UV–vis, thermogravimetric analysis, X-ray diffraction analysis, powder X-ray diffraction, and fluorescence spectroscopy. Depending on the countercation, uranyl thiophene dicarboxylate is shown to crystallize as 2D layer in (I, IV), 2D layer with twofold interpenetrated (6,3) nets in (II), 1D chains in (III), and 2D layer without 2-fold interpenetrated (6,3) nets in (V). The coligand DPYZ in structures of (III and IV) had not been added to the reaction but has been formed by the N-arylation of the PYPZ lig...

Frozen "Tofu" Effect: Engineered Pores of Hydrophilic Nanoporous Materials.

Frozen tofu is a famous Asian food made by freezing soft bean curds, which are naturally porous to store flavor and nutrients. When the narrow pores of the soft bean curd are saturated with water and then frozen, pore widths expand to generate a completely new porous structure—frozen tofu has visibly wider pores than the initial bean curd. Intriguingly, this principle can be generalized and applied to manipulate micro/nanopores of functional porous materials. In this work, we will manipulate the pore size of nanoporous polymeric photonic crystals based on the phase change between water and ice. Wet-drying and freeze-drying methods were applied to shrink or expand the pore size intentionally. This principle is validated by directly observing the optical reflection peak shift of the material. Owing to the change in pore size, the reflection peak of the polymeric photonic crystal structure can be permanently, and intentionally, tuned. This simple but elegant mechanism is promising for the development of smart materials/devices for applications ranging from oil/water membrane separations, health monitoring, and medical diagnostics to environmental monitoring, anticounterfeiting, and smart windows.