Non-crosslinked Polymers Research Articles

Polyphosphazene membranes. IV. Polymer morphology and proton conductivity in sulfonated poly[bis(3-methylphenoxy)phosphazene] films

The microstructure of sulfonated poly[bis(3-methylphenoxy)phosphazene] was studied using wide- and small-angle X-ray diffraction. A reflection peak, attributed to the presence of ionic clusters, was observed in the small-angle X-ray diffraction patterns of hydrated and dry polymers with an ion-exchange capacity (IEC) ≥0.6 mmol/g. The Bragg spacing from the ionic cluster structure was about 30 Å for the nonhydrated polymer and 50 to 90 Å for fully hydrated films. The effects of IEC, cation form of the polymer, temperature, and polymer water content on the cluster structure were investigated. The specific proton conductivity of water-swollen, sulfonated poly[bis(3-methylphenoxy)phosphazene] films at 25°C increased with increasing IEC, with a maximum conductivity of 0.1 S/cm at a polymer ion-exchange capacity of 1.6 mmol/g. The water-content percolation threshold for conductivity was between 17.5 and 25 vol %, and decreased with polymer IEC. The temperature dependence of proton conductivity for 1.2 mmol/g IEC poly[bis(3-methylphenoxy)phosphazene] membranes exhibited Arrhenius behavior with an apparent activation energy of 27.8 and 36.7 kJ/mol for crosslinked and noncrosslinked polymers, respectively. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 49–59, 2001

DNA sequencing by capillary electrophoresis

Capillary electrophoresis has been under development for DNA sequencing since 1990. This development has traveled down two parallel tracks. The first track studied the details of DNA separation by gel electrophoresis. Early work stressed rapid separations at high electric fields, which reached the extreme of a 3.5 min sequencing run at 1200 V/cm. While fast separations are useful in clinical resequencing applications for mutation detection, long read-length is important in genomic sequencing. Unfortunately, sequence read-length degrades as electric field and sequencing speed increases; this tradeoff between read-length and sequencing speed appears to be a fundamental result of the physics of DNA separations in a polymer. The longest sequence sequencing read-lengths have been obtained at modest electric fields, high temperature, and with low concentration noncrosslinked polymers. In parallel with our understanding of DNA separations, the second track of DNA sequencing development considered the design of large-scale capillary instruments, wherein hundreds of DNA samples can be sequenced in parallel. Real-world application of these very high throughput capillary electrophoresis systems will require significant investment in sample preparation technology.

A constitutive model for nonlinear viscoelastic behavior of polymers

AbstractA new constitutive model for the nonlinear behavior of noncrosslinked polymers with infinitesimal strains is derived. It generalizes a model of adaptive links for the viscoelastic behavior of crosslinked polymers. According to the model, a viscoelastic medium is treated as a set of elastic springs that replace each other. The springs model chemical links between polymer molecules, which arise and collapse because of the micro‐Brownian motion, a law for replacing the springs determines the stress relaxation in a viscoelastic medium. Unlike crosslinked polymers, noncrosslinked polymers demonstrate steady‐state creep flow after some transition period. To describe both the transition process and the steady creep, the model distinguishes two different types of adaptive links. Links of the first type are ruptured under loading, whereas links of the second type replace one another. Both these processes (destruction and replacement) are treated as kinetic, and equations of chemical kinetics are introduced for their description. The nonlinearity of the model arises because of a dependence of rates of kinetic processes on the stress intensity. The constitutive equations derived are testified by comparing theoretical results with data for polypropylene fibers. For the verification we use data presented by three independent sources. The results demonstrate good agreement between experimental observations and their theoretical predictions. Finally, the effect of molecular weight of polymers on parameters of the model is studied.

Hydrophilic poly-ylids derived from 4,4′-bipyridyl: synthesis, structure and membrane-forming characteristics

Interfacial polycondensation of 1,1′-diamino-4,4′-bipyridinium di-iodide, [H 2 N- + NC 5 H 4 -C 5 H 4 N + -NH 2 ]I 2 , with aromatic di- or tri-acyl chlorides, affords a novel class of hydrophilic polymers. These materials are isoelectronic with polyesters but contain ylid linkages [N − -N − -CO] in place of ester bonds [C-O-CO]. Non-crosslinked polymers of this type are insoluble in conventional organic solvents but dissolve readily in proton-donor solvents such as formic and trifluoroacetic acids. Single-crystal X-ray studies of the model oligomer C 6 H 5 CO-N − - + NC 5 H 4 -C 5 H 4 N + -N − -COC 6 H 5 reveal an essentially rigid-rod structure and, in keeping with this, the poly-ylids derived from terephthaloyl chloride and naphthalene-2,6-diacyl chloride exhibit lyotropic liquid crystallinity. Interfacial syntheses of poly-ylids on ultrafiltration membranes afford supported membranes with nodular morphology and useful nanofiltration properties.

The Interaction of Creep and Physical Aging in a Semicrystalline Thermoplastic Matrix Composite above Tg

The second generation of polymer matrix composites are based on ther moplastic resins—crystalline and amorphous. For these non-crosslinked polymers, long- term creep at elevated temperatures has been suggested to be a possible detrimental effect. t-T superposition is the standard technique used to predict long-term properties. We have examined creep above the nominal Tg in both the viscoelastic and viscoplastic load range for AS4/Jl[poly(bis 4,4' dicyclohexylmethane) n-dodecanediamide], uniaxial composites. Surprisingly, long-term creep does not appear to be a problem; within reasonable load ranges it is compensated by shrinkage due to physical aging, resulting in negative creep under some circumstances. Simple t-T superposition is invalid for long-term predictions. Physical aging occurs above the nominal T g due to a double or distributed Tg.

Investigation of microdisperse crosslinked copolymers by hydrodynamic and gel permeation chromatography

The previously developed method for separating microparticles on columns used in gel permeation chromatography and the method of their detection have been employed for studying the structure of microdisperse crosslinked copolymers of the type elastomeric core-rigid shell. The fractions of the crosslinked and non-crosslinked polymers in the latex particles of poly(butyl acrylate) and in a copolymer prepared by grafting methyl methacrylate to crosslinked poly(butyl acrylate) by the emulsion polymerization method have been determined. The degree of grafting of MMA to the crosslinked poly(butyl acrylate) particles has been found.

Linear addition polymers and telechelic prepolymers from primary amines and diglycidylether of bisphenol A. Part 11. Non-crosslinked epoxide-amine addition polymers

Linear addition polymers and telechelic prepolymers from primary amines and diglycidylether of bisphenol A. Part 11. Non-crosslinked epoxide-amine addition polymers

Liquid-phase polymer-based retention — the separation of metals by ultrafiltration on polychelatogens

The importance of trace-element analysis in geological, biological, environmental and industrial processes has been increasingly recognized. Although modern instrumental methods of analysis have been applied, preliminary enrichment techniques are required to separate the components to be determined from the interfering constituents of the sample1,2. For the separation of inorganic ions contained in natural waters, industrial fluids or dissolved solid materials, solvent extraction, sorption, ion exchange, precipitation and other methods have been used. However, techniques based on a two-phase distribution or on heterogeneous reactions often cause problems because, in contrast with homogeneous reactions, diffusion controlled processes must be used. Until now, no simple, rapid method has been available for the preconcentration and separation of metals in the homogeneous aqueous phase. Here we demonstrate a technique for the enrichment and separation of metals in aqueous solution using soluble non-crosslinked polymers with chelating groups (polychelatogens)3,4 called liquid-phase polymer-based retention (LPR).

Hydrogenation of cyclohexene by molecular hydrogen catalysed by linear polymers highly loaded with rhodium complexes

Abstract Three non-crosslinked polymers are used as supports for rhodium complexes, viz ., . The two polystyrenes are flexible, whereas the poly(iminomethylene) has a rigid rod configuration. Rhodium is anchored by addition of either [RhCl(C 2 H 4 ) 2 ] 2 or [RhCl(1,5-cyclooctadiene)] 2 . These systems are investigated for catalytic activity in the hydrogenation of cyclohexene with moleclar hydrogen. For comparison, rhodium complexes of PPh 3 and of PCy 2 Ph are studied under the same conditions, i.e. , in THF at 30 °C and a constant hydrogen pressure of 1 atm. The polymer catalysts are more stable than the corresponding monomers and they have a higher activity. The latter is ascribed to a diminished tendency to dimerize. In contrast to the monomers, the polymer systems are also active in the hydrogenation of 1,5-cyclooctadiene.

Longitudinal deformation and rupture of linear flexible-chain polymers

The main patterns of the deformation-strength behaviour of linear polymers on uniaxial extension are generalized. The boundaries of the transition of non-crosslinked polymers have been determined in isothermal conditions from the fluid to the highly elastic and leathery states on application of an axial load. The relationship between the parameters of longitudinal and low-amplitude deformation has been established. The influence of the molecular parameters and liquid media on the character of the deformation and rupture of non-crosslinked linear polymers has been investigated.

Relaxation nature and regularities of breakdown of crosslinked and non-crosslinked polymers in the high-elastic state

A study was made of the durability and strength of crosslinked and non-crosslinked elastomers with varying degrees of crosslinking. A power law is observed for durability and strength with exponents showing a slight dependence on the number of chemical crosslinks in 1 cm 3 polymer N. The activation energy of durability is independent of N and coincides with the activation energy of relaxation λ-transitions but strength and relaxation characteristics show a marked dependence on the degree of crosslinking passing through a maximum, which is explained by the effect chemical network on non-temperature factors of durability and relaxation times and therefore on dimensions of micro-ranges of supermolecular microstructure. Results confirm a unique relaxation type process of visco-elasticity and fracture.

Isomerization of aromatic azo chromophores in poly(ethyl acrylate) networks and photomechanical effect

The photochemical and thermal cis-trans isomerization of azo chromophores which were either dissolved, a pendant group or part of a crosslink in rubbery poly(ethyl acrylate) networks has been investigated. The thermal relaxation behaviour of the azo compound in the networks depends on the crosslinking density and can be described by a WLF-equation with the same parameters as found for non-crosslinked polymers. For stretched polymer films with azo-aromatic crosslinks, a photomechanical effect, i.e., a reversible contraction and expansion was observed, which is mainly ascribed to conformational change of the azo chromophore.

The effect of thermal history and strain rate on the mechanical properties of diethylenetriamine‐cured bisphenol‐A‐diglycidyl ether epoxies

AbstractThe tensile mechanical properties of diethylenetriamine (DETA)‐cured bisphenol‐A‐diglycidyl ether (DGEBA) epoxies prepared from 9, 11 and 13 phr DETA are reported as a function of thermal history, strain‐rate and test temperature. These epoxies exhibit macroscopic yield stresses and >10% ultimate elongations. The mechanical properties of these epoxies exhibit a free‐volume dependence as a function of thermal history. Annealing below Tg causes an increase in the macroscopic yield stress and a decrease in the ultimate elongation, whereas quenching from above Tg lowers the yield stress and increases the elongation. These mechanical property modifications are shown to be reversible with reversible thermal–anneal cycles. The activation volumes associated with Eyring's theory for stress‐activated viscous flow for the DGEBA‐DETA epoxies are within the range of values (9–12 nm3) reported for noncrosslinked polymers. These observations suggest that the DGEBA‐DETA epoxies are not as highly crosslinked as would be expected from normal addition reactions of epoxide groups with primary and secondary amines. The formation of lower crosslink density networks is discussed in terms of potential chemical reactions.

Complex Formation of Crosslinked Poly(4-vinylpyridine) Resins with Copper(II)

Abstract Poly(4-vinylpyridine) was crosslinked with 1,4-dibromobutane, The obtained resin (DBQP) formed a stable complex with Cu2+, and the adsorption capacity of DBQP varied with the degree of crosslinking. The complex, formation of DBQP with Cu2+ was studied by examining the adsorption equilibrium and the spectroscopic measurement. The resin complex seems to be formed via no step-by-step mechanism, and the stability constant was appreciably large in comparison with those of non-crosslinked polymers and of a monomeric analogue. In the highfy crosslinked resins, the ligand-field is relatively weak and the stability of the Cu2+ complex is decreased.

Aminolysis of n‐butyl methacrylate–styrene copolymer with Di‐ and trifunctional amines

AbstractAminolysis of a random copolymer of styrene and n‐butyl methacrylate (2.54:1.00 mole ratio) with 6‐aminohexanol has been studied. Kinetics were determined by covalently dyeing the functional polymer and spectrally measuring dye content. In the presence of 1,4‐diaza[2,2,2]bicyclooctane (DABCO), an activation energy of 22.2 ± 1.0 kcal/mole was calculated from the temperature dependence of the overall rate of reaction. The rate is independent of solvent polarity. The rate at 189°C is 2.1‐fold slower than that of poly(n‐butyl methacrylate). The phenyl group of the styryl moiety inhibits the reaction, apparently via a steric effect. This aminolysis technique affords noncrosslinked (similar M̄n and M̄w) functional polymers. By a similar process an aminediol and an alcohol which contained a secondary and a primary amino group also yielded noncrosslinked functionalized polymers.

Characterization of polybutadiene type polymers by reaction gas chromatography

Various polybutadiene homo and compolymers, both crosslinked and non-crosslinked forms have been investigated by pyrolysis-gas chromatography and ozonolysisgas chromatography. It was found that the amount of vinylcyclohexene in the pyrolysis products and succinic aldehyde in the ozonolysis products characterizes the polybutadiene chain in the sample. The results obtained when pyrolyzing cis vs. trans forms or crosslinked vs. non-crosslinked polymers were similar in case of 1,4-polybutadiene but differ in case of 1,2-polybutadiene.

Approximations in Linear Viscoelasticity Theory: Delta Function Approximations

The relationships between certain approximations that have been proposed recently in connection with the linear viscoelastic behavior of noncrosslinked amorphous polymers are discussed. The approximations reviewed here are applicable with slight modifications to other types of linear response, for example, dielectric behavior.