Synthesis and characterization of a new network polymer electrolyte containing polyether in the main chains and side chains

A new network polymer electrolyte matrix with polyether in the side chains and main chains was synthesized by the azo-macroinitiator method and urethane reaction. The macroinitiator, polymer and network polymer were confirmed by Fourier-transform infrared (FT-IR) spectroscopy and ¹H NMR. FT-IR was also used to study the environment of lithium ions doped in these network polymer electrolytes. Three important groups are considered: N-H, carbonyl, and ether groups. The thermal properties of the polymer electrolytes were measured by differential scanning calorimetry and thermogravimetric analysis. The T_g value of this polymer is less than that of a general comb-like polymer. Added lithium ions interact with the oxygen atoms on ether groups, causing the T_g of the polymer electrolyte to increase. Moreover, the interaction between lithium ions and ether groups decreases the decomposition temperature of the polymer. The conductivity measured by AC impedance reached a maximum of 10⁻⁴ S cm⁻¹. A plot of conductivity vs. temperature fit the Vogel-Tamman-Fulcher equation, indicating that ionic mobility in this network polymer electrolyte is coupled to segmental chain movements.     

Photophysics of a polyether containing tetramethylanthracene units

PESA is a rigid rod polymer incorporating anthrylene units in its backbone. The photophysics of PESA in solution are representative of the isolated anthracene chromophore. In the solid state, strong interchain excimer emission is observed. Solid PESA undergoes efficient photocrosslinking which we assign to interchain anthracene dimer formation. Competitive quenching of photocrosslinking by diphenyliodonium hexafluorophosphate suggests that localized singlet excitation energy can migrate among chains until trapped by excimer formation. The excimer state is intermediate in photocrosslinking. © 1993 John Wiley & Sons, Inc.     

Sequence-specific fragmentation of deprotonated peptides containing H or alkyl side chains

The [M - H]- ions of a variety of di- to pentapeptides containing H or alkyl side chains have been prepared by electrospray ionization and low-energy collision-induced dissociation (CID) of the deprotonated species carried out in the interface region between the atmospheric pressure source and the quadrupole mass analyzer. Using the nomenclature applied to the fragmentation of protonated peptides, deprotonated dipeptides fragment to give a2 ions (CO2 loss) and y1 ions, where the y1 ion has two fewer hydrogens than the y"1 ions formed from protonated peptides. Deprotonated tri- and tetrapeptides fragment to give primarily y1, c1, and "b2 ions, where the "b2 ion has two fewer hydrogens than the b2 ion observed for protonated peptides. More minor yields of y2, c2, and a2 ions also are observed. The a ion formed by loss of CO2 from the [M - H]- ion shows loss of the N-terminal residue for tripeptides and sequential loss of two amino acid residues from the N-terminus for tetrapeptides. The formation of c(n) ions and the sequential loss of N-terminus residues from the [M - H - CO2]- ion serves to sequence the peptide from the N-terminus, whereas the formation of y(n) ions serves to sequence the peptide from the C-terminus. It is concluded that low-energy CID of deprotonated peptides provides as much (or more) sequence information as does CID of protonated peptides, at least for those peptides containing H or alkyl side chains. Mechanistic aspects of the fragmentation reactions observed are discussed.     

Modification effects of amphiphilic comb-like polysiloxane containing polyether side chains on the PVDF membranes prepared via phase inversion process

Amphiphilic comb-like polysiloxane (ACPS) containing polyether side chains was used as the modification reagent in the preparation of hydrophilic porous poly (vinylidene fluoride) (PVDF) membranes via a phase inversion process. The effects of ACPS on morphology, crystallinity, mechanical properties, reservation of ACPS in the phase inversion process, chemical structure, hydrophilicity and filterability performance of porous PVDF membranes were discussed. It was found that the addition of ACPS would result in the delayed demixing which yields “sponge-like” sublayers and longer crystallization time during the membrane formation process. It was revealed that O/F ratios of the bulk membrane were almost the same as those of the corresponding casting solutions which obviously indicated the high reservation of ACPS in the membrane formation process. The fact that the O/F ratios in the membrane surface layers were much higher than those in the bulk membrane proved the enrichment of ACPS on the surface. The filterability experiments and water contact angle testing proved the hydrophilicity of the blend membranes. Through a schematic model, the mechanism relating the membrane structure and performance was interpreted. From the observed results, it can be concluded that ACPS acts as a potential candidate material for preparing PVDF membranes with extraordinary hydrophilicity and filterability. __________ Translated from Acta Polymerica Sinica, 2007, 12: 1168–1175     

Polypeptide chains containing D-gamma-hydroxyvaline

Life has an unexplained and distinct l-homochirality. Proteins typically incorporate only l-amino acids into their sequences. In the present study, d-Val and d-gamma-hydroxyvaline (d-Hyv; V) have been found within ribosomally expressed polypeptide chains. Four conopeptides were initially isolated, gld-V/gld-V'from the venom of Conus gladiator and mus-V/mus-V' from the venom of Conus mus. Their complete sequences (gld-V/gld-V' = Ala-Hyp-Ala-Asn-Ser-d-Hyv-Trp-Ser and mus-V/mus-V' = Ser-Hyp-Ala-Asn-Ser-d-Hyv-Trp-Ser) were determined by a combination of nano/pico-NMR and MS/MS methods. The amino acid triad that contains the gamma-hydroxylated residue, Ser-d-Hyv-Trp, is a novel structural motif that is stabilized by specific interactions between the d-amino acid and its neighboring l-counterparts. These interactions inhibit lactonization, a peptide backbone scission process that would normally be initiated by gamma-hydroxylated residues. Conopeptides possessing the Ser-d-Hyv-Trp motif have been termed gamma-hydroxyconophans. We have also isolated analogous conopeptides (gld-V and mus-V) containing d-Val instead of d-Hyv; these are termed conophans. gamma-Hydroxyconophans and conophans are particularly atypical because (i) they are not constrained as most conopeptides, (ii) they are extremely short in length, (iii) they have a high content of hydroxylated residues, and (iv) their sequences have no close match with other peptides in sequence databases. Their modifications appear to be part of a novel hyperhydroxylation mechanism found within the venom of cone snails that enhances neuronal targeting. The finding of d-Val and d-Hyv within this family of peptides suggests the existence of a corresponding d-stereospecific enzyme capable of d-Val oxidation.     

Deformation behavior of polymer networks containing or interacting with a solvent

General formalism to describe both equilibrium and nonequilibrium states of polymer networks containing a solvent or interacting with the solvent medium is proposed. Two classes of problems have been formulated. It is necessary to determine the stress-strain state of an inhomogeneously swollen material in one case and that of a statically loaded material occurring in thermodynamic equilibrium with the solvent in the other case. The state of the swollen material is characterized in terms of the global mechanical stress tensor and the solvent chemical potential. In the case of incompressible material and liquid, an osmotic stress tensor is introduced. A method for deriving physical expressions for the mechanical stress tensor, the chemical potential, and the osmotic stress tensor is proposed on the basis of the known free energy relations that follow from different theories of rubber elasticity. The efficacy of the general formalism is demonstrated using particular examples in which the deformation behavior and the equilibrium swelling of mechanically loaded polymer networks are considered.     

Polymer networks in dentistry

Polymer networks applied in clinical dentistry can be divided into two groups: (i) hard, solid two-and threedimensional crosslinked structures formed during photo-curing of dental polymeric filling compositions, and (ii) soft, hydrogel-type of networks based on polymeric ionic complexes, used for the tightening of microchannels in teeth. The first group is based on crosslinked di- and trifunctional monomers, and on solid poly(acrylic acid) - inorganic glasses (“glass - ionomer cements”) This group has found wide clinical applications, in spite of many disadvantages such as susceptibility towards hydrolytic, mechanical. bio- and enzymatic degradations, and contents of toxic, allergenic and mutagenic components. The second group, the soft-hydrogel type of networks, has been investigated and developed at our institute in order to tighten channels in teeth. The microchannels, with a diameter of 30–200Å in enamel and 1–3 μm in dentine, are filled with a loose, native bio-hydrogel of protein origin. Hydrogels have the ability to swell in water of biological fluids present in the oral cavity, and can retain a significant fraction of fluid within the structure. Decreasing pH below 5.5 causes a slow dissolution of the hydroxyapatite crystals in the walls of the microchannels with a consequent widening of their lumens. Metabolites and toxins from microorganisms, which are always present in the oral cavity, can penetrate into these enlarged channels and cause inflammatory reactions in the underlying pulp tissue. In order to decrease fluid flow and inhibit penetration of microorganisms, but still allow diffusion of ions and water, we have developed and tested polymeric hydrogels based on poly(acrylic acid) and metal salts, and chitosan, which can be formed directly in the micro-channels of dental hard tissues.     

Damping elastomer with broad temperature range based on irregular networks containing hyperbranched polyester and dangling chains

Elastomer is one of the important materials for vibration and noise reduction. However, its narrow effective damping temperature range (tanδ ≥ 0.3) remains to be a major issue that hinders its application as a damping material. Herein, we precisely design and synthesize a polyurethane structure where specific dangling chains with both electron‐donating group and electron‐absorbing group were introduced into prepolymers, generating more hydrogen bonding interaction with the main chain to hinder microphase separation. At the same time, hyperbranched polyester as a cross‐linking agent increases its free volume effectively. The synergy effect of enhancement of hydrogen bonding, decrease of microphase separation, and increase of free volume results in a higher damping polyurethane elastomer with a great wider effective damping temperature range up to 175°C (−60°C‐115°C), which provides a new idea for the preparation of damping elastomer.     

Molybdenum nitride fibers or tubes via ammonolysis of polysulfide precursor

Millimeter-sized molybdenum nitride (MoN), in the forms of fiber-like prisms or hollow tubes, has been successfully synthesized via thermal ammonolysis of molybdenum polysulfide precursor. The initial morphology of the precursor is well preserved in the final product. This method could be expanded to preparation of other fiber-like nonmetal ceramics without addition of template. The polysulfide precursor (abbreviated to PS), hydrothermally prepared at 30°C (PS1) or 150°C (PS2), was characterized by various methods for better comprehension of the sulfide-nitride topotactic conversion model.     

Anion,cation and ion-pair recognition by bis-urea based receptors containing a polyether bridge

Two bis-urea type receptors were synthesized containing a polyether bridge and two 4-nitrophenyl groups as chromogenic units, R1 and R2. Molecular recognition studies of receptors towards different tetraalkylammonium and alkali metal salts were carried out in DMSO by UV-Vis and ¹H-NMR spectroscopy. The receptors were found to have high affinity for diverse anions and ion-pairs, showing the highest affinities towards the tetramethylammonium and sodium salts. The cation binding ability of the receptors was evidenced by means ¹H NMR, mass spectrometric ESI⁺ studies and the crystal structures of some precursors. Additionally, the molecular modelling at the DFT level of the tetramethylammonium acetate complexes illustrates the potential ion-pair binding ability of the receptors: the anion is recognized through strong hydrogen bonds from the NH─ groups from the two urea sites, while the cation is bound by a combination of cation─π, C-H···O and C-H···π interactions.     

A molecular dynamics simulation study on polymer networks of end-linked flexible or rigid chains

The differences in formation and structural properties of polymer networks consisting of end-linked flexible or rigid chains were studied by molecular dynamics simulation. Networks were formed from monodisperse, linear, short, flexible or rigid chains with functional end groups and a stoichiometric ratio of trifunctional cross-linkers. The rigid chains had a rodlike shape defined by an angle potential, while the flexible chains had no angle potential. In order to understand the influence of chain rigidity, all parameters of precursor chains (length, reactivity, bond potential, nonbonding potential) were the same, with the exception of the angle potential. The system density rho, corresponding to the concentration of monomer in solvent, was varied from 0.01 to 0.11. Different network structures resulting from the different processes of network formation were observed. Simulations showed that the flexible chains created an inhomogeneous network on a large scale via microgel cluster formation, in agreement with experimental observations, whereas the rigid chains rapidly created a homogeneous network in the entire system volume without first generating microgel clusters, with the additional difference that they gave rise to mutually interpenetrating networks at the local scale.     

Open metal-organic framework containing cuprate chains

A three-dimensional Cu(II) metal-organic framework, copper hydroxide p-pyridinecarboxylate hydrate, [Cu(OH)(C5H4NCO2).H2O], was synthesized by hydrothermally reacting copper nitrate with p-pyridinecarboxylic acid. The crystals were suitable for single-crystal X-ray diffraction analysis, which showed that the Cu(II) centers adopt a slightly distorted square pyramidal geometry. They coordinate to both the pyridyl and carboxylate functionalities of the pyridinecarboxylate bridging ligands. Infinite copper oxide chains run through the structure and are connected by p-pyridinecarboxylate (p-PyC) ligands. Crystal data: monoclinic, space group P2(1)/n, a = 3.5521(2) A, b = 15.8665(11) A, c = 12.9977(9) A, beta = 95.285(2) degrees , and Z = 4. Thermogravimetric analysis (TGA) revealed that the guest H2O molecules in the channels may be removed, and the material is stable to ca. 245 degrees C. Magnetic measurements indicated the material has one-dimensional (1D) antiferromagnetic ordering within the Cu2+ chains with a Néel temperature of ca. 51 K. Data fitting to the Bonner-Fisher model yielded a coupling constant, J, of -7.3 cm(-1) and g factor of 2.15. The Curie tail below 20 K is due to a small amount of paramagnetic impurities, calculated to be approximately 0.2% in concentration. Further characterization of crystallinity and morphology are discussed, including powder X-ray diffraction (PXRD), elemental analysis, and optical microscopy.     

Model networks of end-linked polydimethylsiloxane chains

Summary Elastomeric networks of high extensibility were prepared by end-linking mixtures of vinyl-terminated polydimethylsiloxane chains having molecular weights of approximately 600 and 11,000 g mol^–1, with silanes chosen to give junction functionalities ranging from 3 to 8. The resulting bimodal networks were studied in elongation, at 25 °C, to their rupture points, and in swelling equilibrium in benzene at room temperature. The elongation moduli [f ^*] were found to be in satisfactory agreement with previous results obtained by end-linking hydroxyl-terminated polydimethylsiloxane chains. Values of [f ^*] at low and moderate deformations gave relatively low values of the ratio of elasticity constants 2C ₂/2C ₁, which is a measure of the extent to which the elongation changes from approximately affine to nonaffine as the elongation increases. The low values obtained for this ratio are presumably due to diminished interpenetration of configurational domains in the case of very short chains. In spite of its small magnitude, 2C ₂/2C ₁ does show some decrease with increase in , as predicted by the recent molecular theory of rubberlike elasticity developed by Flory. The swelling equilibrium results were also found to be in satisfactory agreement with theory. The elongation moduli increased significantly at high elongations, and the values of the elongation at which the upturn was first discernible were very nearly independent of , This is consistent with the interpretation of this anomalous behaviour in terms of limited chain extensibility. The maximum extensibility generally decreased somewhat with increase in and this caused a decrease in both the ultimate strength and the toughness of the elastomer, as measured by the energy required for rupture.     

Some complexes containing carbon chains end-capped with tungsten or ruthenium groups and tricobalt carbonyl clusters

The Pd(0)/Cu(I)-catalysed reactions between Co₃(μ₃-CBr) (CO)₉ and W(CCCCH)(CO)₃Cp gives the C₅ complex {Cp(OC)₃W}CCCCC{Co₃(CO)₉} (2). Similarly, Co₃(μ₃-CBr)(μ-dppm)(CO)₇ and W(CCCCH)(CO)₃Cp or Ru(CCCCH)(dppe)Cp* give {Cp(OC)₃W}CCCCC{Co₃(μ-dppm)(CO)₇} and {Cp*(dppe)Ru}CCCCC{Co₃(μ-dppmn)(CO)₇} (5). An attempt to prepare a C₃ analogue from Ru(CCH)(PPh₃)₂Cp and Co₃(μ₃-CBr)(CO)₉ gave instead the acyl derivative {Cp(Ph₃P)₂Ru}CCC(O)C{Co₃(CO)₈(PPh₃)} (7). The X-ray structures of 2, 5 and 7 are reported: the C₅ chains in 2 and 5 have an essentially unperturbed -CC-CC-C formulation.     

Synthesis of new liquid crystalline compounds with side chains containing hydroxy groups or chlorine atom

Catalytic hydrogenation of the oxo group in 3-hydroxy-1-(4-hydroxyphenyl)octan-1-one gave 1-(4-hydroxyphenyl)octane-1,3-diol and 1-(4-hydroxyphenyl)octan-3-ol which were converted into the corre-sponding benzyl ethers containing a hydroxy group, 1,3-diol fragment, or chlorine atom in the side chain. The products were shown to possess liquid crystalline properties.     

含手性侧链结构的1, 5-二氮环辛烷的合成

手性α-氨基醇和原氯乙酸三乙酯作用,可同时分离得到两种手性侧链：酰胺醇(2a,2b)和恶唑啉(2c,2d);分别和1,5-二氮环辛烷反应,生成带手性侧臂的1,5-二氮环辛烷化合物(1a～1d),其结构经红外、核磁、质谱和元素分析等得到了证实。     

Polymer chains in good solvent within attracting walls

It is known that a polymer chain in an ideal solvent confined within parallel attracting walls undergoes a second-order transition at the temperature T* satisfying the equation exp[-ε/(k_BT*)]=6/5; here the model consists of a chain placed on a cubic lattice, and ε (<0) is the attractive energy experienced by a chain segment contacting a wall. We then investigate the effect induced by a good solvent upon the chain behavior. A single chain is considered; within the Gaussian approximation, we assume that its partition function may be factorized in two terms, one across the wall planes and another parallel to them. For an interplanar distance L significantly smaller than the average radius of gyration the compressed chain is assumed to reach a uniform density, so that the free energy contribution due to the intrachain atomic contacts is a function of the density alone. It may be shown that the effective value of ε/(k_BT*)(=σ) is the difference between the value to be expected “in vacuo” and β/(z-2), where z is the degree of coordination of the lattice and β is the excluded-volume parameter. As a result, for large values of L we may have an attractive effect exerted by the chain on the walls whereas at small L's we invariably have a repulsion. For the cubic lattice we have a repulsion and an attraction for large L approximatively for σ < ln(6/5)+β/(z-2) and for σ > (ln(6/5)+β/(z-2), respectively, whereas we have inversion between the two regimes at some distance L for intermediate values of σ. In the limit of an infinite molecular weight the inversion translates into a thermodynamic transition. We believe the present model may explain some important features seen in polymer adhesion.     

Trimeric liquid crystals containing lateral alkyl chains

Abstract

The first twelve members of the n-alkyl 2,5-bis-(4′-cyanobiphenyloxybutyloxy)-benozates have been prepared. The compounds are nematogenic; in addition the first three members exhibit a smectic A phase. The nematic-isotropic transition temperatures decrease with little or no alternation on increasing the number of methylene groups in the lateral chain; this is analogous to the behaviour found in monomeric and polymeric mesogens possessing lateral alkyl chains.