Polymer frequency, effect

Figure 7. Tubular plug-flow addition polymer reactor effect of the frequency factor (ka) of the initiator on the molecular weight-conversion relationship at constant activation energy (Ea). Each point along the curves represents an optimum initiator feed concentration-reactor jacket temperature combination and their values are all different, (Ea = 32.921 Kcal/mol In ka = 35,000 In sec ...

We hypothesized that this polymerization proceeds by a single-site catalyst under different morphological conditions and variable monomer concentrations, i.e. polymerization in the crystalline polymer and in the amorphous polymer state. The frequency factor of the polymerization in the crystalline polymer should be lower than that in the amorphous polymer. The effect of monomer concentration on the polymerization rate is shown in Figure 17.14 using toluene as a solvent. The reaction rate is proportional to the monomer concentration. From these results, the polymerization reaction can be described by the following equations ... 

Our first attempt to apply electro-optics in the investigation of the adsorption of neutral polyacrylamide on kaolinite particles was in 1988 [4,5]. Several electro-optical parameters were used to follow the adsorption of polymer on colloid particles—the amplitude of the electro-optical effect, the critical frequency of relaxation of the low- and high-frequency effects, the electro-optical decay time after the switching off of the electric field. Variations in these parameters with concentration of the added polymer give information on the particle electric polarizability, the thickness of the adsorbed polymer layer, the size of aggregates that appear in the suspension due to flocculation [4-10], etc. 

It is the frequency effect of viscoelastic material that makes the static measurement of polymer properties less valuable than normally perceived. More work needs to be done in characterizing the typical polymers used in CMP for their frequency responses, which will allow a more accurate positioning of their behavior. Although the glass transition point is often used as a characteristic metric for these polymers, perhaps the shoulder of the curve (marking the actual transition from the viscoelastic to the glassy solid region) would be more useful. 

Of the relevant time scales that drive the frequency effects of the polymer pads, many of them have their origin in the physical structure of the polishing pad. The largest scale of these is represented by the groove. But the basic nature of many of the typical polymer pads includes a somewhat random interruption of the polymer material in the form of pores. The pores have three major impacts (a) they modulate the abrasive surface presented to the wafer (b) they break up the homogenous nature of the pad material itself, causing modification of the physical properties of the material and (c) they provide microreservoirs for both slurry distribution and byproduct... 

R.A. Wallace, Correlation between ion exchange membrane conductivity and the frequency effect, J. Appl. Polym. Sci., 1973,17, 309-313. 

To validate the extended Cole-Cole equation, Li et al. measured the frequency effect using a JNC JC-BPOIM polymer-stabilized BPLC. The employed IPS cell has 10 pm electrode width and 10 pm electrode gap, and 7.5 pm cell gap. Results are plotted in Figure 14.8, where the VT curves gradually shift to the right side and V increases as frequency increases. At 5 kHz, the transmittance at 60 V ns is only -10% of that of the peak transmittance. These results indicate that frequency has a tremendous impact on the electro-optic properties of this BPLC cell. 

F. Peng, Y. Chen, J. Yuan, et al.. Low temperature and high frequency effects of polymer-stabilized blue phase liquid crystals with a large dielectric anisotropy, J. Mater. Chem. C. 2, 3597-3601 (2014). DOI 10.1039/c4tc00115j... 

In these spectra only the carbonyl bands associated with PCL are shown and each spectrum has been expanded to full scale (obviously, the relative absolute absorbances of the carbonyl bands associated with PC and PCL will vary according to composition). In common with the results obtained in the PCL-PVC system, the amorphous carbonyl band of PCL is observed to shift to lower frequencies as the concentration of PC is increased. This is interpreted as evidence for specific chemical interactions occurring between the two components of the blend and suggests compatibility of the polymers. In effect, the amorphous PCL may be considered to be a macromolecular plasticizer for PC. 

Forced-vibration instruments drive specimens at specific frequencies and determine the response, usually over a range of temperatures. Storage and loss moduli or related parameters are determined. Series of modulus-temperature curves can be generated by making measurements at several different fi equencies. Because thermal and mechanical transitions are functions of frequency as well as temperature, data from such curves can be used to calculate activation energies of transitions. In addition, frequencies can be chosen to represent or approximate polymer processing effects and use conditions. 

From the low-frequency region of the transition zone where the corresponding relaxation spectrum has a slope of — on the logarithmic scales, as in Fig. 12-4, the monomeric friction coefficient fb can be calculated by equation 1 of Chapter 12. If the cross-linking process is not accompanied by side reactions which significantly alter the chemical nature of the polymer, the effects on fo and the position... 

Since molecular theories of viscoelasticity are available only to describe the behavior of isolated polymer molecules at infinite dilution, efforts have been made over the years for measurements at progressively lower concentrations and it has been finally possible to extrapolate data to zero concentration. The behavior of linear flexible macromolecules is well described by the Rouse-Zimm theory based on a bead-spring model, except at high frequencies . Effects of branching can be taken into account, at least for starshaped molecules. At low and intermediate frequencies, the molec-... 

Here, the author considers that the introduction of low-vibrational frequency (LVF) ligands as a linker part in the polymer chains would result in the preparation of a lanthanide coordination polymer with strong luminescence properties. Strongly liuninescent lanthanide complexes composed of LVF hfa and bidentate phosphine oxide ligands have been described in former chapters. The author also proposes that the introduction of aromatic aryl groups in the linker part of lanthanide coordination polymer is effective for the construction of thermostable luminophores with intermolecular interactions, such as CH/F, n-n, and CWn interactions. 

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