Rheological properties of the liquid crystalline poly(γ-benzyl α, L-glutamate) gels in benzyl alcohol

We have determined the degree of stiffness of a poly(γ-benzyl α, L-glutamate) (PBLG) chain in benzyl alcohol by measuring the intrinsic viscosities of dilute Solutions with differing molecular weights. Viscoelastic properties in oscillatory shear flow have been studied and the dependence of the loss and storage moduli on temperature, composition, and frequency are reported. We have also studied the transient shear stress relaxation behavior of the PBLG gel at different temperatures and concentrations. A comparison has been made between these gels and a classical poly(dimethyl siloxane) (PDMS) network, as well as, typical glassy polymers. Shear creep and recovery measurements have been made for this system. Some extensional step strain experiments using lubricated squeezing have been investigated. Tensile experiments have been made to determine stress-strain relationship during elongation. Preliminary experiments using the impulse approach to viscoelasticity further indicate the high elastic contribution in the gel.     

Study of solution properties of poly(α-methyl styrene) in various solvents by dilute-solution viscometry

The values of Mark–Houwink–Sakurada constants were determined for poly(α-methyl styrene) (PαMs) of high and low molecular weights in a variety of solvents by a new approach, which requires only polydisperse samples. The results are in accord with those reported in the literature. In addition, the present work reports the values of the Flory interaction parameter for PαMs in 13 solvents of distinct solvent power at various temperatures. Three refined methods pertaining to both polar and nonpolar solvents were applied to estimate the solubility parameter (δ₂) of PαMs resulting in δ₂ = 18.75 ± 0.15 (J/mL)^1/2 at 30°C. Finally, the scatter data of the Huggins coefficient over a range of expansion factors varying from 0.7 to 2.6 seem to conform better to a newly proposed empirical equation than to the contemporary model after Imai. © 1993 John Wiley & Sons, Inc.     

Studies of linear polymer dimensions of poly(4-chlorostyrene) in various solvents around the θ temperatures by intrinsic viscosity

Intrinsic viscosities of poly(4-chlorostyrene) solutions in isopropyl-benzene and n-propylbenzene at temperatures above and below the theta (θ) temperatures of these solvents were measured using a capillary viscometer. The viscosity measurements were performed on three poly(4-chlorostyrene) samples having molecular weights (M?;_v) 1.75 × 10⁶, 6.5 × 10⁵ and 2.7 × 10⁵. A smooth and continuous contraction below the θ temperatures was observed for both solvents. The temperature dependence of [/eta] can be represented by a master curve in a plot of α³/eta|/tau|M^1/2 (g^1/2 mol^?1/2) versus |/tau|M^1/2 (g^1/2 mol^?1/2), where α/eta = [/eta(T)]/[/eta(θ)]^1/3 is the expansion factor and /tau = (T - θ)/T is the reduced temperature. A universal plot of reduced viscosity size (α/eta) versus reduced blob parameter (N/N_c) shows the achievement of collapsed state for T<θ. The prediction of thermal blob theory is also verified for T > θ. The temperature dependence of intrinsic viscosity, both below and above the θ temperature, exhibits similar behaviour to the temperature dependence of dipole moments for both of these solvents.     

γ-Ray assisted synthesis of silver nanoparticles in chitosan solution and the antibacterial properties

In the present study, chitosan had been utilized as a “green” stabilizing agent for the synthesis of spherical silver nanoparticles in the range of 5–30 nm depending on the percentage of chitosan used (0.1, 0.5, 1.0 and 2.0 wt%) under γ-irradiation. X-ray diffractometer identified the nanoparticles as pure silver having face-centered cubic phase. Ultraviolet–visible spectra exhibited the influence of γ-irradiation total absorbed dose and chitosan concentration on the yield of silver nanoparticles. The antibacterial properties of the silver nanoparticles were tested against Methicillin-resistant Staphylococcus aureus (MRSA) (gram-positive) and Aeromonas hydrophila (gram-negative) bacteria. This work provides a simple and “green” method for the synthesis of highly stable silver nanoparticles in aqueous solution with good antibacterial property.     

X-ray analysis of α-, β-, and γ-phase Ag–Hg alloy films produced on polymer substrates by casting polyacrylamide–AgNO3 aqueous solution in Hg atmosphere

It is reported that, by dropping Hg metal on the wet α-phase Ag–Hg alloy film formed on the cast polyacrylamide–AgNO₃ aqueous solution, the α phase of fcc structure can be converted into other phases that contain more Hg. The X-ray analysis of these phases reveals that they are the β phase of hexagonal structure and the γ phase of bcc structure. It is also shown that the lattice constant of the α phase can be controlled to some extent by pH of the aqueous solution of PAAm from which the alloy film is formed.     

Rheological properties of concentrated cellulose solutions in N-methylmorpholine-N-oxide

Conclusions -- Rheological properties of concentrated solutions of cellulose in N-mcthylmorpholine-N-oxide on varying the concentration of cellulose in the solution from 10 to 28% by wt. have been studied.-- It has been found that on increasing the cellulose content of the solution, the viscoelastic properties of the solution qualitatively change.-- In spinning highly concentrated solutions (cellulose content greater than 20%) an abrupt impairment takes place in stability of jet formation; this is connected with a change in supermolecular structure and elastic properties of the solution.Translated from Khimicheskie Volokna, No. 6, pp. 32–34, November–December, 1990.     

Practical evaluation of the [η]–M relationship. II. Estimation of Kθ values of polymer solutions

A method is proposed for the prediction of the intrinsic viscosity of θ solutions, based upon the constitution of the dissolved polymer. The method makes use of additive values for constitutional groups to calculate a quantity that represents the specific chain stiffness per main chain atom.     

The properties of polymer blends of the β-modification of polypropylene and an elastomer

Blends of β-polypropylene with elastomers have been prepared under laboratory and processing technological conditions. As a result of the elastomer addition the temperature interval favourable for the formation of the β-modification became narrower. Blends have spherulitic structure like pure β-PP. The elastomer has negligible effects on the size of spherulites and on the rate of crystallization. Optical microscopy and DMA measurements revealed that the blends were two-phase systems in the solid state. The mechanical properties of the blends are close to those of β-PP in the investigated composition range. Increasing elastomer content reduced the strength characteristics but considerably improved cold impact resistance, the most beneficial combination containing about 8–12% of elastomer. A mathematical relationship has been proposed describing the relationship between impact strength and elastomer content. The dependence of the structural characteristics and macroscopic properties of elastomer-modified β-PP blends on the composition and on the temperature is similar to that of the identical β-PP blends.     

Thermal analysis of polyethylene prepared by γ-ray-induced polymerization in various solvents

Thermal properties of polyethylenes prepared by γ-ray-induced polymerization in various solvents were examined by differential scanning calorimetry. The solvents used were ethyl and n-butyl alcohols, tert-butyl alcohol containing 25 vol% of water, 2,2,4-trimethylpentane, 2,2,5-trimethylhexane, and cyclohexane. The dependence of the profiles of the heating curves for the produced polymers on polymerization temperature varies with the solvent type. This difference was discussed in terms of the degree of undercooling in various solvents during polymerization. In all solvent systems, the melting point and heat of fusion of the polymers decrease continuously with polymerization temperature. This decrease is caused by an increase in branches with reaction temperature. The melting point and heat of fusion are 100–124°C and 30–44 cal/g, respectively, and no superheating is observed. These facts suggest that folded chain crystals are commonly formed in these systems.     

An efficient Synthesis of Acetylenic γ- and δ-Hydroxy Ketones, γ- and δ-keto acids,and γ- diketones via addition of 1-alkinyllithium compounds to γ- and δ-lactones

2-Hydroxy-6-alkyn-5-ones 3 , 1-hydroxy-5-alkyn-4-ones 4 , and 1-hydroxy-6-alkyn-5-ones 5 are conveniently obtained in excellent yields through a highly selective monoaddition of an 1-alkynyllithium compound 2 to γ-valerolactone (1a) , γ-butyrolactone (1b) or δ-valerolactone (1c) . They are oxidized by pyridinium dichromate or Jones reagent to the corresponding acetylenic 1,4-diketones 6 , 4-oxo carboxylic acids 7 , and 5-oxo carboxylic acids 8 , respectively.     

Studies on β-alkoxypropionitriles as solvents for extractive distillation

Five solvents of the β-alkoxypropionitrile series have been studied by gas-chromatographyin order to examine their potential usefulness as solvents for extractive distillation. Four isomers of C₄-olefin and a diene were used as solutes for the determination of activity coefficients at infinite dilution at 30°C. Relative volatilities were calculated for these solvents and compared with those for other commercial solvents used currently. Relative volatilities of seven C₄-hydrocarbons in two solvents were also studied and compared with the existing literature data for β-methoxypropionitrile containing 5% antisolvent. The present g.c. studies show that besides the well-studied β-methoxypropionitrile, the second member of the series, β-ethoxypropionitrile, also has the potential for use as a selective solvent.     

Studies on β-alkoxypropionitriles as solvents for extractive distillation

Five solvents of the β-alkoxypropionitrile series have been studied by gas-chromatography in order to examine their potential usefulness as solvents for extractive distillation. Four isomers of C₄-olefin and a diene were used as solutes for the determination of activity coefficients at infinite dilution at 30°C. Relative volatilities were calculated for these solvents and compared with those for other commercial solvents used currently. Relative volatilities of seven C₄-hydrocarbons in two solvents were also studied and compared with the existing literature data for β-methoxypropionitrile containing 5% antisolvent. The present g.c. studies show that besides the well-studied β-methoxypropionitrile, the second member of the series, β-ethoxypropionitrile, also has the potential for use as a selective solvent.     

Miscibility,morphology and tensile properties of vinyl chloride polymer and poly(ε‐caprolactone) blends

The miscibility, morphology and tensile properties of three blend systems of poly(ε‐caprolactone) (PCL) with poly(vinyl chloride) (PVC) and with two chlorinated PVCs (CPVCs) with different chlorine contents (63 wt% and 67 wt% of Cl) have been studied. Based on the shifts of single glass transition temperature, the Gordon–Taylor K parameter is calculated as a measurement of interaction strength between PCL and (C)PVCs. Higher K values are found for blends of (C)PVCs with higher chlorine content, together with the interaction χ parameters estimated from the melting point depression results. The morphology observed with polarized light microscopy shows that spherulites exist in blends rich in PCL (≥50 wt%) only. Wide angle X‐ray diffraction studies indicate that the crystal structure of PCL is independent of the Cl content of (C)PVCs. The tensile properties of various blends exhibit a minimum as the PCL content increases. The elongation at break increases with increasing PCL content. © 2000 Society of Chemical Industry     

Morphology and properties of polyurethane/poly(methyl methacrylate) interpenetrating polymer networks by Co60–γ ray

PU/PMMA IPNs were first synthesized using Co⁶⁰–γ radiation. The morphology, glass transition behavior, and mechanical properties of the formed IPNs have been studied by TEM, DSC, and electron tensile testing machine. The TEM micrographs and the results of DSC showed that Co⁶⁰–γ radiation was effective for obtaining small volume sizes of phase domains in IPNs. The structure with two continuous phases occurs in the content range of 40% to 70% PU. The ability of interpenetration enhanced with increasing the content of the crosslinking agents. The mechanical properties of IPNs reflected very good synergistic behavior.     

Synthesis of γ‐Fluoro‐α, β‐unsaturated Carboxylic Esters from Saturated α‐Fluoro Aldehydes

γ‐Fluoro‐α, β‐unsaturated carboxylic esters 7a, 7b and 7d and 4‐fluoro‐4‐phenylbut‐3‐enoic ester ( 8 ) are obtained by two alternative pathways from 2‐fluoro aldehydes 5a—d , either by Horner—Wadsworth—Emmons reaction or by Wittig reaction. The aldehydes 5a—d are prepared by Swern oxidation of the corresponding fluorohydrins 4a—d . These are available from α‐olefins by bromofluorination, bromineby‐acetate replacement and subsequent hydrolysis.