Robert S. Moore

Long‐Transient Effects in Lasers with Inserted Liquid Samples

Buildup and decay transients were observed when polar or nonpolar liquid cells were placed within the resonator of a helium—neon laser operating in the red at 6328 A. Similar but smaller effects were also observed with two solids. Time constants were the order of a few seconds for all materials, which suggests a thermal phenomenon, but general heating effects were ruled out by the strong localization of the phenomenon. Transverse motion of the cell by about one beam width caused new transients similar to the initial ones.It is believed that the effects are caused by absorption of the red light in the material, producing a local heating in the vicinity of the beam and a lens effect arising from the transverse gradient of refractive index. Absorptions of 10−3 to 10−4 parts per centimeter are sufficient to produce the effects, and are believed to be reasonable values for the materials studied. One of the most important applications may in fact be for the measurement of small absorbancies.The experiments are ...

Dynamic Mechanical Properties of Concentrated Polystyrene Solutions at 40 MHz

Measurements of dynamic shear impedance at 40 MHz and room temperature are reported for two polystyrene‐solvent systems as a function of concentration. These measurements were made by an ultrasonic reflectance technique. The polymers had sharp molecular‐weight distributions, Mw/Mn∼1.08, and molecular weights of 2.39×105 and 2.67×105. The concentrations ranged from about 1% to 20% and 3% to 30% in di‐n‐butyl phthalate, DBP (a near theta‐solvent) and in toluene (a good solvent) for the two polymers, respectively. Results are reported in terms of the in‐phase, G′, and out‐of‐phase, G″—ωηs, components of the dynamic shear modulus of the polymer and in terms of the reduced dynamic viscosity (η′—ηs)/(η—ηs), where η′ is the dynamic viscosity, ηs is the solvent viscosity, and η is the steady‐flow solution viscosity. Results on the polystyrene—toluene system indicate that the system undergoes a change from Zimm‐like to Rouse‐like behavior with increasing concentration and, hence, with reduced frequency. No evide...

Photographic Light Scattering and Photomicroscopy of Deformed Ringed Spherulites

Polyethylene films were studied by photographic light scattering and photomicroscopy at successive increments of strain, usually 5%. Photomicrographs were taken at times sufficiently long after sample deformation so that the light scattering patterns were constant with respect to intensity and shape. Analysis of such scattering patterns and photomicrographs indicated that upon spherulite deformation, the ring spacing (hence the twist‐distance) increased in the direction of tensile strain and decreased at right angles to the strain direction, as noted in earlier experiments on samples subjected to tensile stress. At about 30% strain the wide‐angle parallel polarizer scattering pattern (polarization and strain directions horizontal) split into a set of 4 arcs nearly parallel to the meridian. With increasing strain (analyzer and strain directions vertical) the arcs of the 4‐arc wide‐angle crossed polarizer scattering pattern, originally at 45° to the polarizer and analyzer axes, occurred nearer the meridian ...

Dynamic Mechanical Properties of Polystyrene Solutions from 23 to 300 MHz

Measurements of dynamic shear impedance at five frequencies from 23 to 300 MHz and at 25°C are reported for a monodisperse polystyrene as a function of concentration. The concentrations ranged from 3% to 20% polymer in di‐n‐butyl phthalate, a near‐theta solvent, and covered the region from the start of coil overlap to well beyond entanglement. Results are reported in terms of the in‐phase, G′−ν1Gs′, and quadrature, G″−υ1ωηs′, components of the dynamic shear modulus of the polymer, where Gs′ is the solvent contribution to the in‐phase modulus, ω is the angular frequency, ηs′ is the dynamic solvent viscosity, and υ1 is the volume fraction of solvent. The use of dynamic values for the solvent follows from observation of relaxation and non‐Newtonian behavior in the solvent beyond 100 MHz. The usual reduced variables method, even in this modified form, could not be successfully applied to superimpose data at different concentrations, indicating the need for further modification to account for finite concentrat...

Dynamic Mechanical Properties of Chlorinated Biphenyls and Polystyrene—Chlorinated Biphenyl Solutions at 40 MHz

Measurements of dynamic shear impedance at 40 MHz and 25°C were carried out on solutions of monodisperse polystyrenes of molecular weight 2.67×105 and 2.39×105 in chlorinated biphenyl solvents (Aroclors). Measurements were also obtained on solutions of monodisperse polystyrenes of molecular weight 2.03×103 and 1.8×106 in di‐n‐butyl phthalate (DBP). In addition, measurements were obtained on one binary mixture of Aroclors and on five pure Aroclor solvents. These covered a range of 106 in steady‐flow viscosity. The dynamic measurements were made by an ultrasonic reflectance technique employing pulse super‐position or by a phase‐amplitude balancing method. Results for the polystyrene—Aroclor system indicate that the effect of a solvent slightly better thermodynamically than DBP is observed as an increase in the in‐phase modulus, whereas little effect is observed in the magnitude of the polymer contribution to the out‐of‐phase modulus (G″—ωηs), where ω is the angular frequency, ηs is the solvent viscosity, an...

Detection of Vitrons in Pentachlorobiphenyl at 40 MHz and the High‐Frequency Mechanical Properties of Chlorinated Biphenyls

Measurements of the in‐phase and quadrature components of the dynamic shear impedance were carried out on pentachlorobiphenyl (Aroclor 1254) at 40 MHz from 293° to 318°K using an ultrasonic reflectance technique. The minimum in a plot of the high‐frequency limiting shear modulus G∞′ as a function of temperature predicted by Miles and attributed to the formation and breakup of vitrons, i.e., clusters, was not observed. This result is considered in light of other evidence for cluster formation. These measurements were compared with data of other workers at low frequencies for other homologs of the Aroclor series using a modified reduced variables procedure based on G∞′. Excellent superposition was found using this method. Data for the Aroclor series were also compared using a procedure based on the semiempirical equation developed by Lamb as well as in terms of the theories of Peterlin, Reinhold, and Thurston for high‐frequency response. From the latter, estimates of h* ≥ 0.3,φ / f = 0, and 30 ≤ Z < 100 wer...

Rheo‐Optical Properties of ABS Polymers and their Component Materials

This paper reports results of studies of birefringence (Δ) in ABS systems and in two component materials, measurements which reveal information about the orientation and response of these materials to deformation. Continuous measurements of (Δ) at strain rates (e) from 8.5×10−5 to 3.3×10−3 sec−1 were carried out with a He–Ne laser light source on polystyrene (PS), poly(styrene‐acrylonitrile) (SAN), and two clear ABS polymers. Measurements at constant e were related to mechanical response of the materials in creep, and two tests for the invariance of the stress optical coefficient were developed. These were achieved through comparison of computer‐generated plots of appropriate rheo‐optic functions with rheological counterparts derived from previous creep measurements via the convolution procedure of Hopkins and Hamming. Such comparisons indicated nearly identical constant time dependences for the respective logarithmic plots of (Δ/e) and (stress/e) vs time (t) for the PS and SAN polymers. Comparison of...