Experimental procedure solution polymers

As field desorption (FD) refers to an experimental procedure in which a solution of the sample is deposited on the emitter wire situated at the tip of the FD insertion probe, it is suited for handling lubricants as well as polymer/additive dissolutions (without precipitation of the polymer or separation of the additive components). Field desorption is especially appropriate for analysis of thermally labile and high-MW samples. Considering that FD has a reputation of being difficult to operate and time consuming, and in view of recent competition with laser desorption methods, this is probably the reason that FD applications of polymer/additive dissolutions are not frequently being considered by experimentalists. 

Adsorption is determined by the depletion method using a Dohrmann DC 80 carbon analyzer. The mineral is contacted with the polymer solution and agitated with a mechanical tumbler for 24 hours, a time which has been verified to be sufficient for adsorption to be complete (9). A more detailed description of experimental procedures is given elsewhere (10). All the data reported in this study are taken in the plateau region of the adsorption isotherm. 

We have prepared two linear soluble polyurethanes P(LAGA-MDI) and P(LAGA-HMDI) by solution polymerization of LAGA with MDI and HMDI respectively in dimethyiacet-amide as a solvent using dibutyltin dilaurate as a catalyst at 75°C over 24 hours According to the procedure used in the preparation of the isosorbide polyurethanes as described in the experimental section. Both polymers have been isolated in quantitative yield in their lactone form by precipitation from chloroform (15). 

One of the major innovations in combinatorial and medicinal chemistry in recent years aiming at efficient diversity-oriented synthesis has been the implementation of polymer reagents in polymer-assisted solution phase (PASP) synthesis. This contribution will present—following an introduction to the field—a concept of advanced polymer reagents based on reactive intermediates and active reactants that should extend the scope PASP synthesis significantly. Experimental procedures describing preparation and use of the novel polymer reagents are included. 

In a comparison study of the values of flow birefringence An and the viscosity t of a polymer solution it is often possible to simplify the experimental procedure so as to avoid the determinations of the characteristic values of [n] and [tj] by determining the quantity An/g (i - tjq) at finite solution concentration instead of the ratio [n]/[7j]. Here is the viscosity of the solvent and the value of g(rj - t o) - At characterizes the effective shearing stress in solution introduced by the dissolved polymer. Many experimental data show that for a flexible-chain polymer in the absence of the macroform effect the ratio An/At, which may be called the shear optical coefficient , is independent of solution concentration, and, also, over a wide range of molecular weights, of chain length ... 

The polymer is deposited as a uniform annular coating in a glass capillary column. A solute is injected into an inert carrier gas that flows through the column. The elution curve of the sample is then used with a model to determine the solute activity and diffusivity in the stationary phase. A detailed description of the equipment and the experimental procedure is given by Pawlisch (361. It is of value to present the model used to describe the process. The description provided by Pawlisch (361, given below, indicates how the model was developed. 

Several comments can be made about the nature of these approximate results. Note that Eqs. (6.23) and (6.24) give power-law region for both viscosity and normal stresses most experimental data for polymer solutions and melts do in fact exhibit a prominent power law region which extends over about three decades of shear rates. The values of the exponents — 2/3 for viscosity and 4/3 for the normal stress function - are not unreasonable values. In the power-law region it is often observed that the exponent for 6 is about twice that for tj. We must, however, note that comparison of Eqs. (6.21) and (6.22) with Eqs. (6.8) and (6.9) and a similar comparison of the power-law results shown in Table 2 indicate that the approximate procedure does not agree very well with the exact calculations. 

Process parameters. Within the experimental procedure a number of parameters can be varied. In a series of preliminary experiments, a suitable standard value was chosen for the temperature (20°C), the pressure build-up rate (2 bar/min), the stirrer rate, the initial relative concentration of the polymer solution and the relative liquid phase expansion. As the solubility of PPE in toluene increases with increasing temperature a relative concentration has been introduced which is defined as the ratio of the polymer concentration in the initial solution and the saturation concentration at the process temperature. All parameters were varied separately around this standard value, as is indicated in Table 1, to determine their individual effect on the particles size and shape. 

Details concerning the experimental apparatus and the experimental procedure will be presented elsewhere [ 18] The polystyrene solutions used in the experiment were taken from the same batches as those used by Zhang et al. [22] for measuring the mass-diffusion coefficient and the Soret coefficient of these polymer solutions. 

Interestingly, the identical experimental procedure was Independently developed, under the name of "solute exclusion" (SE) technique, in the studies of water swollen cellulosic materials (ref. 15-18) (See Fig. 2). Though this technique proved to be effective in elucidating the porous structure of swollen pulps and related materials, it suffered from a lengthy experimental procedure for obtaining a solute exclusion curve through a series of accurate concentration measurements of polymer solutions. 

A technique for the preparation of Eudragit RL-100 acrylic resin microcapsules was developed, which was based on the principle of solvent evaporation. Diclofenac sodium was used as a model drug for encapsulation. A solution of drug and Eudragit dissolved in acetone-isopropyl alcohol was sprayed in liquid paraffin. The microcapsules obtained were unifonu and free flowing particles. The release rate was more sustained by increasing the polymer coneentration. The experimental procedure provided a rapid and eonvenient method for the preparation of Eudragit microcapsules. 8 refs. 

Based on this approach, the apparent viscosity of the polymer solution, uapp corrected if the apparent viscosity of the corresponding hypothetical Newtonian fluid flowing in the same capillary with the same total pressure drop is known. There are two procedures to determine the apparent viscosity of such a Newtonian fluid. The direct experimental procedure is to measure the apparent viscosity of the appropriate Newtonian fluid in the high-shear capillary viscometer. This experimental calibration technique was employed by Graham and co-workers (20). Although this experimental technique is direct, in practice it is difficult to perform. It is difficult to find a Newtonian fluid with the identical rheological properties as exhibited by the polymer solution at low-shear rates. 

Statistical-mechanical treatments of polymer adsorption at a planar surface have been pursued extensively using both analytical and Monte Carlo techniques. These procedures place polymer chain configurations in a one-to-one correspondence with random walk configurations on a lattice. While the analytical methods are limited to massless segments, and the Monte Carlo techniques are restricted to relatively short chains because of computational limitations, both provide results capable of experimental verification. The restriction to dilute solutions and non-interacting adsorbed molecules has been circumvented in recent theoretical treatments of concentrated pol3nner solutions. 

Polymer flow tests consisted of sequentially injecting 300-ppm polymer, 600-ppm polymer, and brine. Solutions were prepared and used in a manner that minimized chemical degradation. Each flood sequence was continued until both effluent polymer concentration and resistance factor stabilized. In some cases, polymer injection was terminated before fluid of injection concentration was produced. Details of the experimental procedure are included in Appendix A. The resistance factor at a given stage of the polymer flood was determined as the ratio of the flowing pressure drop at that stage to the initial brine pressure drop at the same rate. Figs. 1 and 2 exhibit the extremes of concentration response observed with these cores. Core 55 rapidly attained a produced concentration equal to the injected concentration, while Core 42 reached a maximum produced concentration of about 96 percent of injected. 

The experimental procedures have been described in detail elsewhere 1119,120]. In brief. FT-IRS was u.sed to detennine -AWab of polymer solvent couples in very dilute solutions (ca. 0.02 mol dm ), using the method of Fowkes (12 ]. XPS measurements were made on thin films of the candidate polymers by ex-... 

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