Oxyalkylene polymers with alkylsulfonylmethyl side chains: Gas barrier properties

Gas barrier properties of alkylsulfonylmethyl-substituted poly(oxyalkylene)s are discussed. Oxygen permeability coefficients of three methylsulfonylmethyl-substituted poly(oxyalkylene)s, poly[oxy(methylsulfonylmethyl)ethylene] (MSE), poly[oxy(methylsulfonylmethyl)ethylene-co-oxyethylene] (MSEE), and poly[oxy-2,2-bis (methylsulfonylmethyl)trimethylene oxide] (MST) were measured. MSEE, which has the most flexible backbone of the three polymers, had an oxygen permeability coefficient at 30°C of 0.0036 × 10⁻¹³ cm³(STP)·cm/cm²·s·Pa higher than that of MSE, 0.0014 × 10⁻¹³ cm³(STP)·cm/cm²·s·Pa, because the former polymer's T_g was near room temperature. MST with two polar groups per repeat unit and the highest T_g showed the highest oxygen permeability, 0.013 × 10⁻¹³ cm³(STP) · cm/cm²·s·Pa, among the three polymers, probably because steric hindrance between the side chains made the chain packing inefficient. As the side chain length of poly[oxy(alkylsulfonylmethyl)ethylene] increased, T_g and density decreased and the oxygen permeability coefficients increased. The oxygen permeability coefficient of MSE at high humidity (84% relative humidity) was seven times higher than when it was dry because absorbed water lowered its T_g. At 100% relative humidity MSE equilibrated to a T_g of 15°C after 2 weeks. A 50/50 blend of MSE/MST had oxygen barrier properties better than the individual polymers (O₂ permeability coefficient is 0.0007 × 10⁻¹³ cm³(STP)·cm/cm² ·s·Pa), lower than most commercial high barrier polymers. At 100% relative humidity, it equilibrated to a T_g of 42°C, well above room temperature. These are polymer systems with high gas barrier properties under both dry and wet conditions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 75–83, 1998     

Thermophysical properties of azomethine ether main-chain liquid crystalline polymers at pressures to 200 MPa

This article reports on an experimental investigation of the equation of state and the transition behavior of main-chain thermotropic liquid crystalline polymers over a wide temperature range, and at pressures to 200 MPa. The materials studied were a series of azomethine ether polymers. A varying number n (= 4, 7, 8, 9, 10 and 11) of methylene spacer units in the backbone provided systematic variation of the structure. Experimental techniques used included high-pressure dilatometry (PVT measurements) to 200 MPa, high-pressure differential thermal analysis, also to 200 MPa, and conventional (atmospheric-pressure) differential scanning calorimetry (DSC). The equation of state of the materials can be well represented by the Tait equation in distinct regions, separated by a glass transition, T_g(P), a first-order transition to a nematic state, T_k-n(P), and a first-order transition to an isotropic melt state T_c(P). The atmospheric pressure values of T_k-n and T_c decreased with increasing number of spacer units and showed a clear odd-even effect. T_g and T_k-n both increased with pressure. The pressure dependence of T_c could not be observed due to the onset of degradation in the same temperature region. On isobaric cooling at 3°C/min, the crystallization from the nematic state occurred a few tens of degrees below T_k-n. This supercooling was independent of pressure for some materials, while for others it increased with increasing pressure. The values of the enthalpy and entropy associated with the first-order transition into the nematic state were lower than those of typical isotropic polymers at their melting transitions. The transition enthalpy did not have any systematic variation with increasing number of spacer units. Values of the transition enthalpy calculated from the Ciapeyron equation did not always agree with the values measured by DSC. This may be due to the two-phase nature of the low-temperature state. At the transition to the isotropic state, the transition enthalpy at P = 0 decreased with n and showed an odd-even effect. © 1994 John Wiley & Sons, Inc.     

Flame temperatures from Raman scattering

Pure rotational, as well as vibrational Raman scattering has been observed from stable diatomic molecules in high-temperature flames. Accurate (rotational) flame temperatures may be determined from the rotational line intensities. For a hydrogen diffusion flame in air T_rot(N₂) = 1880 ± 21K, T_rot(H₂) = 1890 ± 80 K, T_vib(N₂) = 1995 ± 130 K, and T_vib(H₂) =1900 ± 150 K.     

Radiothermoluminescence. I. Radiothermoluminescence for investigation of thermal and radiation-induced crosslinking of rubber mixtures

Phase heterogeneity of vulcanizates based on cis-polybutadiene (cis-Europrene) and SBR (Europrene 1500) blends obtained by radiation, thermal, two-stage radiation-thermal, and two-stage thermal-radiation processes was investigated by the radiothermoluminescence method. Unvulcanized blends of these polymers are found to be heterogeneous, exhibiting two glass transition temperatures T_g, which coincide with the values for the initial components. Following vulcanization, the difference between the two T_g values for a polyblend decreases. The decrease is more distinct for polyblends crosslinked at high temperatures. When the vulcanization temperature exceeds 140°C and the crosslink density (or 1/M_c) exceeds 5 × 10^?5–1 × 10^?4 mole/cm³, the glass temperature ranges of the crosslinked blend are practically superimposed. Such crosslinked mixtures should be considered pseudohomogeneous in phase.     

Challenge and Solution of Characterizing Glass Transition Temperature for Conjugated Polymers by Differential Scanning Calorimetry

Thermomechanical properties of polymers highly depend on their glass transition temperature (T _g). Differential scanning calorimetry (DSC) is commonly used to measure T _g of polymers. However, many conjugated polymers (CPs), especially donor–acceptor CPs (D–A CPs), do not show a clear glass transition when measured by conventional DSC using simple heat and cool scan. In this work, we discuss the origin of the difficulty for measuring T _g in such type of polymers. The changes in specific heat capacity (Δc _p) at T _g were accurately probed for a series of CPs by DSC. The results showed a significant decrease in Δc _p from flexible polymer (0.28 J g^?1 K^?1 for polystyrene) to rigid CPs (10^?3 J g^?1 K^?1 for a naphthalene diimide‐based D–A CP). When a conjugation breaker unit (flexible unit) is added to the D–A CPs, we observed restoration of the Δc _p at T _g by a factor of 10, confirming that backbone rigidity reduces the Δc _p. Additionally, an increase in the crystalline fraction of the CPs further reduces Δc _p. We conclude that the difficulties of determining T _g for CPs using DSC are mainly due to rigid backbone and semicrystalline nature. We also demonstrate that physical aging can be used on DSC to help locate and confirm the glass transition for D‐A CPs with weak transition signals. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1635–1644     

Molecular weight dependence of crystal pattern transitions of poly(ethylene oxide)

Crystal patterns in ultrathin films of six poly(ethylene oxide) fractions with molecular weights from 25000 to 932000 g/mol were characterized within crystallization temperature range from 20 ℃ to 60 ℃.Labyrinthine,dendritic and faceted crystal patterns were observed in different temperature ranges,and then labyrinthine-to-dendritic and dendritic-tofaceted transition temperatures T L-D and T D-F were quantitatively identified.Their molecular weight dependences are T L-D(M w) = T L-D(∞) K L-D /M w,where T L-D(∞) = 38.2 ℃ and K L-D = 253000 ℃.g/mol and T D-F(M w) = T D-F(∞) K D-F /M w,where T D-F(∞) = 54.7 ℃ and K D-F = 27000 ℃.g/mol.Quasi two-dimensional blob models were proposed to provide empirical explanations of the molecular weight dependences.The labyrinthine-to-dendritic transition is attributed to a molecular diffusion process change from a local-diffusion to diffusion-limited-aggregation(DLA) and a polymer chain with M w ≈ 253000 g/mol within a blob can join crystals independently.The dendritic-to-faceted transition is attributed to a turnover of the pattern formation mechanism from DLA to crystallization control,and a polymer chain with a M w ≈ 27000 g/mol as an independent blob crosses to a depletion zone to join crystals.These molecular weight dependences reveal a macromolecular effect on the crystal pattern formation and selection of crystalline polymers.     

New amorphous perfluoro polymers: perfluorodioxolane polymers for use as plastic optical fibers and gas separation membranes

To address the need for perfluoro polymers with higher T_g, we have prepared and characterized various perfluorodioxolane monomers via direct fluorination of the hydrocarbon precursors. These monomers were readily polymerized in bulk or in solution initiated by perfluorodibenzoyl peroxide. The polymers obtained have relatively high T_g(~160°C) and exhibited low material dispersion. These polymers are completely amorphous and soluble in fluorinated solvents. The polymers are also chemically and thermally stable (T_g > 300°C). Thus, these perfluorodioxolane polymers may be used as plastic optical fiber material where high T_g is required, such as in automobile and aircraft application. These perfluorodioxolane polymers were also investigated for use as gas separation membrane. Among these polymers, the copolymer of perfluoro (2‐methylene‐1,3‐dioxolane) and perfluoro (2‐methylene‐4,5‐dimethyl dioxolane) showed superior gas separation performance compared with the commercial perfluoro polymers for a number of gas pair, including CO₂/CH₄, H_e/CH₄, H₂/CH₄, and N₂/CH₄. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis, characterization and single crystal structures of one-dimensional coordination polymers formed with [Ni(L)]·2ClO4 and polycarboxylate ligands

Two new one-dimensional coordination polymers {[Ni(L)(maleate)] · H₂O} _n (1) and {[Ni(L)(H₂btc)] · 2DMF} _n (L = cyclam, btc = 1,2,4,5-benzenetetracarboxylate, DMF = N,N-dimethylformamide) (2) have been synthesized and structurally characterized by single crystal X-ray diffraction. In the structures (1) and (2), the carboxylate groups of bridging ligands are coordinated to nickel(II) cyclams resulting in the formation of one-dimensional coordination polymers. In addition to the Ni–O bonds, it is observed that the hydrogen bonding interactions between the pre-organized N–H groups of the cyclams and bridging anions support the formation of coordination polymers in both complexes.     

Glass transition temperatures of several fluorine-containing polymers

The glass transition temperatures T_g of several fluorine-containing polymers were determined by use of the differential scanning calorimeter. Values between ?3 and 230°C were obtained. In polymers of α-olefins, T_g increases with the fluorine content of the backbone and the length of the n-perfluoroalkyl branch. In styrene polymers T_g also is higher if the backbone contains fluorine but nearly the same T_g's are found for polymers with phenyl and pentafluorophenyl groups. Saturated polymers of perfluoro-α,ω-dienes have lower T_g's than polyperfluoro-α-olefins. The T_g's of chloroperfluoropolymers are higher than those of perfluoropolymers. Polyperfluoropentadiene-1,3 has the lowest T_g of the polymers examined. Polyperfluoropentadiene-1,3 forms by 1,4-addition.     

The glass-to-gel transition in solvent-swollen polystyrene networks

Glass transition temperatures have been determined for polystyrenes crosslinked with 1–10% divinylbenzene and swollen with toluene, chloroform, N,N-dimethylformamide, and tetrahydrofuran to as high as 0.7 weight fraction solvent. The T_g′s depend approximately on the weight fractions and the T_g′s of the components according to the empirical equation 1nT_g = m₁ 1nT_g1 + m₂ 1nT_g2 of Pochan. The T_g′s of the networks swollen with toluene also fit approximately a quasithermodynamic equation of Karasz based on the T_g′s and the ΔC_p′s at T_g of the components.     

CORRELATION BETWEEN GLASS TRANSITION OF POLYMERS AND ENERGY OF ROTATIONAL ISOMERIZATION OF MOLECULAR CHAINS

It has been shown that the free volume fraction at T_g is not a universal parameter for linear polymers of different molecular structure. The reason is that the volume expansion at T_g is partially contributed from the change of the numbers of conformations of isolated molecular chains due to internal rotation. In this paper, glassy transformation was connected with internal rotation of isolated molecular chains, and the relationship between free volume fraction of polymers at T_g and energy e of rotational isomerization of isolated molecular chains was formulated, e=-k·T_g·In (△α·T_g/1-△α. T_g). The values of calculated from the above formula are in good agreement with those published in the literatures. Thus, the method described in this paper can be used to estimate a parameter for the flexibility of isolated molecular chains.7     

Self‐Assembly,Spectroscopic and Electrochemical Studies of Nickel(II)‐4,8‐Diazaundecanediamide Complex

The self‐assembly of NiCl₂·6H₂O with a diaminodiamide ligand 4,8‐diazaundecanediamide (L‐2,3,2) gave a [Ni(C₉H₂₀N₄O₂)(Cl)(H₂O)] Cl·2H₂O ( 1 ). The structure of 1 was characterized by single‐crystal X‐ray diffraction analysis. Structural data for 1 indicate that the Ni(II) is coordinated to two tertiary N atoms, two O atoms, one water and one chloride in a distorted octahedral geometry. Crystal data for 1: orthorhombic, space group P 21nb, a = 9.5796(3) Å, b = 12.3463(4) Å, c = 14.6305(5) Å, Z = 4. Through NH···Cl–Ni (H···Cl 2.42 Å, N···Cl 3.24 Å, NH···Cl 158°) and OH···Cl–Ni contacts (H···Cl 2.36 Å, O···Cl 3.08 Å, OH···Cl 143°), each cationic moiety [Ni(C₉H₂₀N₄O₂) (Cl)(H₂O)]⁺ in 1 is linked to neighboring ones, producing a charged hydrogen‐bonded 1D chainlike structure. Thermogrametric analysis of compound 1 is consistent with the crystallographic observations. The electronic absorption spectrum of Ni(L‐2,3,2)²⁺ in aqueous solution shows four absorption bands, which are assigned to the ³A_2g → ³T_2g, ³T_2g → ¹Eg, ³T_2g → ³T_1g, and ³A_2g → ³T_1g transitions of triplet‐ground state, distorted octahedral nickel(II) complex. The cyclic volammetric measurement shows that Ni²⁺ is more easily reduced than Ni(L‐2,3,2)²⁺ in aqueous solution.     

Physical properties of a new iron(III) complex, [3-pmH · 3-pm][Fe(NCS)4(3-pm)2]

The iron(III) compound of formula [3-pmH · 3-pm][Fe(NCS)₄(3-pm)₂] (3-pm = 3-(hydroxymethyl)pyridine) has been prepared by reaction between iron(III) thiocyanate and 3-(hydroxymethyl)pyridine in ethanol. The characterization was based on elemental analysis, infrared spectra and magnetic measurements. Single crystal X-ray diffraction methods show the monoclinic P2(1)/c space group with unit cell parameters: a = 12.295(3) Å, b = 15.854(3) Å, c = 16.880(3) Å, β = 100.12(3)° and Z = 4. The asymmetric unit of the title compound consists of [3-pmH · 3-pm]⁺ and [Fe(NCS)₄(3-pm)₂]^? held together by ionic interaction and a hydrogen bond interaction (O(68)–H(68) ··· O(78)). The central metal ion is octahedrally coordinated by six nitrogens, four from NCS^? form the equatorial plane and two from two 3-(hydroxymethyl)pyridines occupy axial positions. Magnetic susceptibility data in the temperature range 1.8–300 K show that iron(III) is high-spin S = 5/2(⁵ T _2g). Structural parameters and IR spectra of similar complexes are compared and discussed.     

Synthesis,structure, cytotoxic activities,and DNA-binding of 1-D copper(II) and zinc(II) coordination polymers

Two 1-D coordination polymers have been synthesized and identified as [Zn(ox)(en)] _n (H₂O)_{2 n} (1) and [Cu₂(dmeo)(N₃)₂] _n (2), where en represents diaminoethane, ox and dmeo stand for dianions of oxalic acid and N,N′-bis[2-(dimethylamino)ethyl]oxamide, respectively. Polymer 1 was characterized by elemental analysis, molar conductance measurement, IR and electronic spectra, and single-crystal X-ray diffraction. Polymer 1 consists of 1-D chains bridged by oxalate. The Zn^II can be described as a distorted octahedral environment and the Zn^II···Zn^II separation through the μ-oxalato-bridge is 5.5420(9)?Å. Hydrogen bonds assemble the coordination polymers to a 3-D supermolecular structure. The crystal structure of 2 has been reported previously. However, the bioactivities were not studied. The DNA-binding properties and cytotoxic activities of the two coordination polymers are investigated. The results suggest that the two polymers interact with HS-DNA in groove binding with binding affinity following the order of 1?>?2, which is consistent with their anticancer activities.     

Crosslinked liquid crystal polymers from liquid crystal monomers: Synthesis and mechanical properties

Difunctional acrylates and methacrylate monomers have been made which are high order smectic liquid crystal (or crystalline) at room temperature. This report discusses materials with the following structure: F–S–M–S–F, where F is a functional group, acrylate or methacrylate (A or M); S is a spacer (CH₂)_n(n), and M is a mesogen—in this case 4,4′-dioxybiphenyl (B). They are codified as BnA or BnM where n is the number of methylenes in the spacer. High conversion with high T_g can be obtained when polymerizing in the smectic state because the reactive end groups are concentrated in a small volume and can react well with little or no diffusion. B2A, B3A, B6A, B11A, and B3M were polymerized in the smectic state and compared to polymers made at temperatures where the monomers were isotropic. High conversion was obtained below final T_g—even then, probably because the polymers were ordered. All the polymers were studied by WAXD and dynamic mechanical spectroscopy. Solid-state NMR on B3A showed that there was very high conversion of the double bonds at all temperatures. B3A photopolymerized in the smectic state (60–76°C) produced a crystalline polymer with T_g = 185°C (1 Hz). When photopolymerized at 85°C, above the isotropization temperature (T_i), a poorly organized polymer was obtained with a T_g of 155°C (1 Hz). Monomers with an odd number of methylene groups as spacers were crystalline after polymerization. With an even number of methylene groups, they lost most of their crystallinity on polymerization below T_i, but retained a low order smectic structure. Similar structures were obtained with all the monomers when they were polymerized above T_i. There was little effect of polymerization temperature on T_g when the spacers had an even number of methylene groups. © 1993 John Wiley & Sons, Inc.     

Sodium and silver phosphate glasses doped with chlorides of Fe,Mn and Zn

A number of samples of sodium and silver phosphate glasses doped with various compositions of some transition metals viz. iron, manganese and zinc chlorides alongwith undoped samples of sodium and silver phosphate glasses were synthesized and characterized by X-ray diffraction, IR spectral, electrical conductivity and differential scanning calorimetry (DSC). The glass transition temperature (T _g) and crystallization temperature (T _c) values obtained from DSC curves were found to increase with increasing concentration of the dopant Fe/Mn/Zn chlorides in both sodium and silver phosphate glasses and the following sequence is observed: T _g(–FeCl₃)>T _g(–MnCl₂)>T _g(–ZnCl₂) T _c(–FeCl₃)>T _c(–MnCl₂)>T _c(–ZnCl₂) The increase in T _g and T _c values indicate enhanced chemical durability of the doped glasses. The electrical conductivity values and the results of FTIR spectral studies have been correlated with the structural changes in the glass matrix by the addition of different transition metal cations as dopants.     

Crosslinkable maleimide copolymers for stable NLO properties

Second-order, nonlinear optical polymers based on epoxy-substituted methylvinylisocyanates and N-substituted maleimides were synthesized and characterized with spectral and thermal analysis. The photocrosslinking and thermal-crosslinking reactions of copolymers with different chromophore contents were studied. Thermally induced crosslinking during the poling process, performed at the glass-transition temperature (T_g), was prevented by T_g being decreased through the addition of a plasticizer. Electrooptic coefficients (r₃₃), measured for crosslinked and noncrosslinked systems, had similar absolute values and relaxation dynamics. This behavior was explained in terms of the similar rotational mobility of the chromophore units and the paucity of crosslinking sites. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1589–1595, 2001     

Synthesis,Structure and Magnetic Property of a Cobalt(II) Metal‐Organic Framework

The three‐dimensional (3D) porous cobalt(II) metal‐organic framework (MOF), [Co₃(L)₂(DMA)₂(MeOH)₂ · 4(DMA) · 6(MeOH)]_n ( 1 ) [L = fully deprotonated 2,7‐bis(4‐benzoic acid)‐N‐(4‐benzoic acid) carbazole, DMA = N,N‐dimethylacetamide], was synthesized by hydrothermal reaction. Based on X‐ray single‐crystal diffraction, structural analysis indicates that complex 1 crystallizes in the monoclinic C2/c space group. Complex 1 possesses a 3,6‐connected three‐dimensional (3D) topological structure with a point symbol of {4² · 6}₂{4⁴ · 6² · 8⁷ · 10²} when a trinuclear Co^II cluster was regarded as 6‐connected node and the organic ligands could be regarded as 3‐connected linkers between the 6‐connected nodes. The framework structure exhibits a one‐dimension (1D) channel with an accessible void of 4223.0 ų, amounting to 42.8 % of the total unit‐cell volume (9862.0 ų). Moreover, the magnetic properties of complex 1 were studied.     

High-pressure studies on the coacervation of copoly(<Emphasis Type="Italic">N</Emphasis>-vinylformamide–vinylacetate) and copoly(<Emphasis Type="Italic">N</Emphasis>-vinylacetylamide–vinylacetate)

The effects of pressure on the temperature-induced coacervation of copoly( N-vinylformamide–vinylacetate) and copoly( N-vinylacetylamide–vinylacetate) in aqueous solution were investigated by measuring the apparent light scattering, and the effects of the concentrations of polymer and inert salt were also studied. At lower pressures, the apparent temperature of transition, T _c, increased with an increase in the pressure, but further increases in pressure decreased T _c. In contrast, the apparent pressure of transition, P _c, monotonously increased with decreasing fixed temperature. The T– P diagram was elliptical, but the curvature was not large and extrema were not observed in the low-temperature and high-pressure range. Anions with low lyotropic numbers induced an almost linear decrease in the T _c and P _c, whereas anions with a high number increased the T _c and P _c. In both polymers, the T _c and P _c depended on the concentrations of the polymers, reflecting the association/aggregation mechanism of coacervation. This is in contrast to typical thermoresponsive polymers such as poly( N-isopropylacrylamide) and poly( N-vinylisobutyramide), which show the coil-collapse transition as a single molecular event.