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  • 1
    Electronic Resource
    Electronic Resource
    Dynamic light-scattering studies of internal motions in DNA. III. Evidence for titratable joints associated with bound polycations (1981)
    New York : Wiley-Blackwell
    Biopolymers 20 (1981), S. 209-230 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dynamic light-scattering techniques are employed to study the internal Brownian motions of a commercial calf thymus DNA, clean and contaminated φ29 DNAs, and a clean φ29 DNA with bound spermidine as a function of pH. The Rouse-Zimm model parameters of both calf thymus and contaminated φ29 DNAs differ substantially from those of clean φ29 DNA in the neutral-pH region. However, this difference is largely removed by adding 0.01M EDTA (which has no effect on clean φ29 DNA) to the calf thymus DNA sample. These findings imply the existence in that preparation of polycation contaminants, presumably basic proteins, that can substantially alter the local mechanical properties of the DNA near their binding sites. The internal motion parameters kBT/f and b of both calf thymus and contaminated φ29 DNAs are found to exhibit pronounced characteristic variations between pH 8.5 and 10.5, over which range there is essentially no detectable titration to a resolution of about 1% of the base pairs. These variations, which are not observed for clean φ29 DNA, are qualitatively similar to those previously reported for a φ29 DNA with 21 single-strand breaks per chain. This indicates the formation of titratable joints associated with bound polycation contaminants. These basic ligands presumably facilitate local denaturation by stabilizing the titration of one or more protons on base-ring nitrogens near their binding sites. Spermidine binding up to 85-87% of neutralization of the total DNA charge has only a relatively minor effect on the internal motion parameters at neutral pH in 0.01M NaCl. However on raising the pH to 10.2, the internal motion parameter kBT/f undergoes a marked decrease similar to that observed for both calf thymus and contaminated φ29 DNAs and also φ29 DNA with single-strand breaks. This indicates that spermidine, too, is capable of inducing titratable joints. Evidence is presented that the titratable joints associated with bound polycations on the calf thymus DNA may serve primarily as torsion joints, as was found previously for the titratable joints associated with single-strand breaks.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1981.360200115
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  • 2
    Electronic Resource
    Electronic Resource
    Interfacial polycondensation and characterization of polyphosphates and polyphosphonates (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1157-1165 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of four bisphenol A-based polyphosphates and phosphonates was accomplished. The polymerization involved a condensation between bisphenol A and a phosphorodichloridate. The heterophasic polycondensation technique was used with the aid of a phase transfer catalyst to yield molecular weights in the range of 20,000-40,000. The polymers were characterized by FT-IR, FT-NMR, and DSC. Systematic studies on the interfacial polymerization indicated that a more concentrated organic phase and a slight excess of diol favored the production of high molecular weight polymers. An optimum concentration of 5-10 mol % was observed for three different phase transfer catalysts. Kinetic studies showed that the polymerization was complete within the first 10 min. The degree of agitation was shown to be important, as the overhead mechanical stirrer was not as effective as the blender. In addition, crosslinking with pentaerythritol yielded significant increases in the molecular weights of these polymers.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290809
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamic light-scattering studies of internal motions in DNA. I. Applicability of the rouse-zimm model (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 425-461 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The intermediate scattering function G(K,t) for any polymer model obeying a linear separable Langevin equation can be expressed in terms of the eigenvalues and eigenvectors of its normal coordinate transformation. An algorithm for the extract numerical evaluation of G(K,t) for linear Rouse-Zimm chains in the presence of hydrodynamic interaction has been developed. The computed G(K,t)2 were fit to C(t) = A exp(-t/τA) + B, and apparent diffusion coefficients calculated according to Dapp ≡ 1/(2τAK2). G(K,t)2 was surprisingly well-fit by single-exponential decays, especially at both small and large values of Kb, where K is the scattering vector and b the root-mean-squared subunit extension. Plots of Dapp vs K2 in-variably showed a sigmoidal rise from D0 at K2 = O up to a constant plateau value at large K2b2.Analytical expression for G(K,t), exact in the limit of short times, were obtained for circular Rouse-Zimm chains with and without hydrodynamic interaction, and also for free-draining linear chains, and in addition for the independent-segment-mean-force (ISMF) model. The predicted behaviors for G(K,t) at large Kb (or KRG) was found in all cases to be single-exponential with 1/τ ∝ K2 at large Kb, in agreement with the computational results. A simple procedure for estamating all parameter of the Rouse-Zimm model from a plot of Dapp vs K2 is proposed.Experimental data for both native and pH-denatured calf-thymus DNA in 1.0M Nacl with and without EDTA clearly plateau behavior of Dapp at large values of K, in harmony with the present Rouse-Zimm and ISMF theories, and in sharp contrast to previous predictions based on the Rouse-Zimm model.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170211
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  • 4
    Electronic Resource
    Electronic Resource
    Concentration-dependent diffusion of dye in reactive dyeing systems (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 1743-1749 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The physical model of the reactive dyeing system proposed by Sada et al. is extended in this communication to the case with a conentration-dependent diffusion coefficient of dye. The present model with an exponential concentration dependence of the diffusion coefficient is shown to predict the observed data better than did the previous one with a constant diffusion coefficient. Effects of the concentration dependence of the diffusion coefficient, dye reaction rate, degree of mixing, and volume ratio of fiber substrate to the dyebath on the rate of fractional fiber fixation and the dye concentration in the dyebath are investigated parametrically. It has been found that the effect of the volume ratio of the fiber substrate to the dyebath on the fractional fiber fixation is not of the same order of magnitude as those of the other three factors.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070441007
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  • 5
    Electronic Resource
    Electronic Resource
    Epoxy resins. I. The stability of the epoxy-trimethoxyboroxine system (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 3355-3374 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The useful life of a material depends on its environmental exposure. The diglycidyl ether of bisphenol A (DGEBA) cured with trimethoxyboroxine (TMB) was evaluated under various aging conditions. For isothermal aging, the main factor controlling weight loss appeared to be related to the diffusion of the degradation products (Eact = 22.1 kcal/mole). Chemical decomposition kinetic parameters were obtained using vacuum thermogravimetric analysis (TGA) on powder samples. The thermal decomposition activation energy and the reaction order of cured DGEBA were 37.5 kcal/mole and 1.05, respectively. The hydrolytic aging of this material was also kinetically analyzed, and it was concluded that the weight change was controlled by both water diffusion into the sample and diffusion of hydrolysis products from the sample. During hydrolytic aging below the glass transition temperature, the specimens gained weight up to 0.05 g based on 1-g unaged cured resin and then leveled off. At higher temperatures, the specimens initially gained weight and then began to lose weight, reaching a constant weight gain. The activation energies for water diffusion into the cured resin are 19.5 kcal/mole at temperatures above Tg and 21.5 kcal/mole at temperatures below Tg. The main hydrolysis product was boric acid from reaction of the boroxine ring with water. The time-temperature superposition principle was used for the weight loss study on isothermal and isothermal hydrolytic aging. The scale factor in this approach was found to be the ratio of the diffusion coefficient at the temperature of interest to that at a reference temperature.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070231120
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  • 6
    Electronic Resource
    Electronic Resource
    Properties of UV-curable polyurethane acrylates: Effect of reactive diluent (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 647-666 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Several families of UV-cured polyurethane acrylates were synthesized, and the effects of reactive diluent type and content on their physical properties were investigated. Increasing reactive diluent content promoted the development of a second, high glass transition temperature phase in all the materials, thereby leading to increased strength and modulus. Changes in the extensibility of the samples upon addition of reactive diluent were inversely related to the effect of the diluent on the crosslink density. The effects of using different reactive diluents (di-, tri-, and tetraethylene glycol diacrylate and N-vinyl pyrrolidone) on the physical properties of the samples were attributed to differences in the softening point (Tg) of the homopolymer reactive diluents and the relative compatibility of the reactive diluents with the urethane acrylate segments.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070300215
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  • 7
    Electronic Resource
    Electronic Resource
    Epoxy resins. III. Application of fourier transform IR to degradation studies of epoxy systems (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 3121-3148 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three cured epoxy resins were investigated under various degradation conditions by Fourier transform infrared (FTIR) spectroscopy for measurement. The epoxy resins were the diglyadyl ethers of bisphenol A (DGEBA), phenolphthalein (DGEPP), and 9,9-bis(4-hydroxyphenyl)fluorene (DGEBF). The thermal stability order of functional groups that incurred DGEBA was total methyl group ∼ total benzene ring 〉 methylene 〉 p-phenylene 〉 ether linkage 〉 isopropylidene. The oxidative thermal and photodegradation processes were found to be related to the classical autocatalytical oxidation of aliphatic hydrocarbon segments. The Wieland rearrangement, Norrish-type reaction, Claisen rearrangement, and other possible degradation mechanisms were suggested by the data.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170171006
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  • 8
    Electronic Resource
    Electronic Resource
    Epoxy resins. II. The preparation, characterization, and curing of epoxy resins and their copolymers (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 3095-3119 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A polymer with high aromatic ring content in the chain backbone usually has high heat and flame resistance. Three diglycidyl ethers of epoxy resins were prepared from bisphenol A (DGEBA), phenolphthalein (DGEPP), and 9,9-bis(4-hydroxyphenyl)fluorene (DGEBF) in a study of the relation between the cured polymer structure and properties. The epoxy resin prepared from phenolphthalein was separated by liquid chromatography and three fractions were obtained. The fractions had a basic structure of 3,3-disubstituted phthalide and differed only in molecular weight. The DGEPP resin changed color from yellow to red after mixing with trimethoxyboroxine (TMB), the curing agent, and to orange after completing the curing cycle. To prepare a highly crosslinked material with good thermal stability, TMB with three active Lewis sites in a molecule was used as the curing agent. The reactivity of the three different resins toward TMB, measured by differential scanning calorimetry (DSC), was DGEBA 〉 DGEBF 〉 DGEPP. For the same curing conditions the order of crosslink density was DGEBA 〉 DGEPP 〉 DGEBF. To modify the flammability of DGEBA, the conventional epoxy resin, it was copolymerized with DGEPP and DGEBF, the higher-performance epoxy resins. The glass transition temperatures of poly(DGEBA-co-DGEPP) and poly(DGEBA-co-DGEBF) systems deviated from this relationship. The DGEBF copolymers showed an increased char residue (40 wt % at 700°C) at 20 mole % of DGEBF. This deviation may be due to the lower crosslinking density of this system.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170171005
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