Poly(vinylidene fluoride) (PVdF) converts easily to thermally reversible gel at room temperature in aliphatic ketones or cyclic ketones such as 3-pentanone, 3-hexanone, cyclohexanone, and g-butyrolactone, etc. Gelation of PVdF in these ketones took place through crystallization of polymers from solution. The crystallization process was investigated in detail by Fourier transform infrared (FTIR) measurements. The FTIR spectra were recorded continuously at room temperature until the solution converted to gel. It was suggested from spectral data that polymer chains packed together (i.e., crystallization took place) into the TTTGTTTG V conformation in the case of PVdF/ g-butyrolactone solution, followed immediately by gelation. On the other hand, crystallization occurred into the TGTG V conformation in the case of other ketones and gelation immediately took place. Melting temperatures T g m of PVdF gels thus prepared from these solvents were measured. T g m showed a solvent dependence.

ABSTRACT:The Flory-Huggins interaction parameter (χ 12 ) between poly(vinylidene fluoride) (PVdF) and organic solvent was estimated experimentally over wide range of temperature by an inverse gas chromatography (IGC) using many kinds of solvents such as alkane, alkene, ketone, lactone, and nitrogen-containing solvent. The thermoreversible gelation of PVdF solution was discussed from the magnitude of interaction parameter χ 12 between PVdF and solvent. The parameter χ 12 was measured for a concentrated PVdF solution by the usual IGC technique. The parameter χ 12 obtained for each PVdF/solvent system increased slowly with decreasing temperature. The present systems were divided broadly into three groups according to the magnitude of χ 12 in the vicinity of room temperature, i.e., group (a) with χ 12

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SynopsisViscoelastic properties of four linear and three very lightly crosslinked polybutadienes (microstructure about 50% trans) were studied. Of the latter, two had not reached the gel point, and their molecular weight distributions were determined by sedimentation velocity analysis; the third was crosslinked just past the gel point, with only 32% gel fraction present.Complex shear compliances were measured over a frequency range from 0.1 to 1000 cps at temperatures from -70 to 30°C. with a Fitagerald transducer and a Plazek torsion pendulum; and torsional creep measurements were made over time periods up to about three days. The creep data were converted to the corresponding dynamic viscoelastic functions at very low frequencies by conventional approximation methods. All data were reduced to 25°C. by shift factors calculated from a previously adopted equation of the WLF form. In the transition zone, the viscoelastic properties of linear samples were almost independent of molecular weight. The entanglement spacing, derived from the minimum in the loss tangent and the inflection in the storage compliance, was 130 to 160 chain atom. The maximum in the retardation spectrum attributable to motions of individual network strands was closely similar to the corresponding maxima for more highly crosslinked vulcaniaates previously studied, showing that even in the latter it is associated with entanglement network strands rather than strands between chemical crosslinks. For a linear sample with molecular weight 180,000, the retardation processes disappear at times beyond about 10 sec. a t 25°C. With crosslinking short of the gel point (i.e., branching) the slow retardation processes are enormously increased and prolonged to longer times. With further crosslinking through the gel point and beyond, the slow retardation processes decrease progressively in magnitude. Qualitatively, this behavior resembles the sharp maximum in content of highly branched and aggregated molecular species which is predicted at the gel point by crosslinking statistics; but the slow processes (or low-frequency losses) persist farther past the gel point than would be expected on this basis. The steady-state compliances of the linear samples were smaller, but for a sample crosslinked short of the gel point were much larger, than the prediction of the Rouse theory modified for molecular weight distribution.

By combining vacuum extraction in a Van Slyke chamber and separation of the extracted gases in a gas chromatograph, it is possible to determine N2 content of 1.5 ml of blood or other biological fluids in less than 10 min. The 95% confidence limits are 0.44% on either side of the mean of the triplicate analysis-or 2.4 mm Pn2 in arterial blood when breathing room air. Application of the method to the problem of arterial-alveolar N2 difference yielded the following data: 1) N2 solubility in whole blood at 37.3 C varied from 0.0125 to 0.0129; 2) N2 solubility in urine is inversely related to urine specific gravity, confirming Klocke and Rahn's data; 3) changes in arterial N2 content were reflected in arm superficial venous blood and urine N2 only after a considerable period of time, indicating that either of these will give an excellent indication of the mean Pn2 over a period of time; 4) there is no systematic difference between venous blood and urine Pn2; 5) the (a-A)N2 difference in nine normal subjects varied from 3.7 to 13.1 mm Hg. Note: (With the Technical Assistance of M. Passke) Submitted on July 24, 1962

The reduced viscosity vs. concentration relation was measured for sodium chloride solutions of sodium carboxymethylcellulose (Na‐CMC of DP ≓ 400 and DE ≓ 0.7) in a range of low concentrations (0.003 to 0.09 g./100 ml.), and the data obtained were analyzed following the procedure of Pals and Hermans. The results confirmed in many aspects findings which had previously been made in the literature, and supplied values of the necessary molecular quantities for our own sample. They indicated that our Na‐CMC molecule was relatively uncoiled even in solutions of high ionic strength. The Huggins slope constant was found to increase approximately linearly with increasing reciprocal of the ionic strength of the solution. Next, the shear dependence of reduced viscosity in dilute solutions of this polyelectrolyte was investigated by the use of a viscometric apparatus which was especially designed for accurate measurements at low shear rates. The shear rate region investigated was from about 50 to 1000 sec.−1. The measurements were made on salt‐free solutions and on solutions of constant ionic strength; in both cases only the regions of sufficiently low concentrations were treated. In the salt‐free solutions the ηsp/C vs. q (q is shear rate) curves showed an upward curvature rather than a quadratic dependence at the limit of shear rate. In this case, the initial slope of each curve increased markedly with increasing dilution. The plots of ηsp/C vs. q for solutions of constant ionic strength (ca. 0.0015 mole/l.) were approximately represented by straight lines within the concentration range investigated. The slope of the straight lines decreased regularly with increasing dilution. Some evidence that these plots have a horizontal initial tangent was observed, but this was never conclusive due to the paucity and inaccuracy of exprimental data at shear rates smaller than 100 sec.−1. The intrinsic viscosity obtained from ηsp/C vs. C curves at constant shear rates for the isoionic system was independent of q. From these findings it was realized how markedly the viscous behavior in dilute solutions of the polyelectrolyte studied was influenced by the addition of small amounts of neutral salt, not only in viscosity value itself but also in its shear rate dependence. Our data and results herein presented were concerned only with a sample of one (average) molecular weight and one degree of etherification. More data, therefore, are needed on samples of varying degrees of polymerization and etherification before a more definite understanding of the problem herein treated is possible.

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During food processing and cooking, various flavor compounds, colored substances and toxic substances are produced by the Maillard reaction. It is important to investigate the relationship between the Maillard reaction products and the actual cooking conditions. Therefore, we investigated the effects of seasonings and reaction conditions on the Maillard reaction of meat using furosine and fluorescent compounds. The addition of 1.0% NaCl decreased the reaction rate of the Maillard reaction measured by furosine in Glc -meat reaction. However, the reaction rate of meat with added sucrose did not change. Furosine content in meat with added sucrose increased rapidly when it was pan-broiled and fried, but increased slowly at the beginning when it was baked in a gas oven. The fluorescence of broiled meat showed a maximum at 333/425 nm (exc./em.) and is a useful indicator of the Maillard reaction of meat samples. The rate of increasing fluorescence in baked meat was lower than that of meat heated by other cooking methods.