Experimental procedure solution polymerization

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). 

Obviously, more experimental data for wider ranges of temperatures and monomer concentrations are required to arrive at a better understanding of the mechanism of free-radical polymerization in partially and fully ionized systems. Acryhc acid is no perfect monomer for kinetic studies in wide ranges of experimental conditions. As in the case of PLP-SEC studies into kp of non-ionized monomers, methacrylic acid is a better choice also for investigations into ionized systems within extended temperature and monomer concentration ranges. For MAA, kp values were measured at monomer concentrations, Cmaa, between 5 and 40 wt.-% and at temperatures from 6 to 80 °C over the entire range of MAA ionization, between a = 0 and a = The experimental procedure is similar to the one used in the experiments on aqueous solutions of AA at different degrees of ionic dissodation. ... 

A variation of the previous experimental procedure is the use of base-catalyzed TEOS polymerization instead of acid. These membranes were ionized in alkali metal hydroxide solutions before TEOS was added (Mauritz, 2000). The final material is a Nanon/alkali metal silicate with a weight uptake decreasing with increasing pH in the external solution. 

A pyrrolidone solution of py-K/C02 was prepared from 2-pyrrolidone, KOH, and CO2 by the technique of Barnes. Details of the experimental procedure are described in Reference 7. Polymerizations were carried out in dry polyethylene bottles, under nitrogen, by mixing and heating an appropriate portion of the reaction mixture with a preweighed amount of the onium salt, of crown ether. Following polymerization and water wash, the crown ether, if used, was removed by chloroform extraction from the polder. 

The majority of publications deal with the application of catalytic chain transfer (GGT) in bulk or solution, but examples in the patent literature do apply GGT to emulsion and suspension. These patents report only limited data and full details of the experimental procedures are not revealed. Molecular weight data for the final products are given, but information on coagulation, conversion, and particle size are often not provided. The use of GoBF in MMA emulsion polymerization has been reported outside the patent literature but efficient CCT was not achieved, suggesting the process may be sensitive to at least some of the reaction components. 

The ultracentrifuge has been used extensively, especially for the study of biopolymers, and can be used in several different experimental modes to yield information about polymeric solutes. Of the possible procedures, we shall consider only sedimentation velocity and sedimentation equilibrium. We shall discuss these in turn, beginning with an examination of the forces which operate on a particle setting under stationary-state conditions. 

To my knowledge, this approach has not found further use. This could be due to the complicated procedure in which chemical treatment is applied to form pre-jelled silica. The solution is highly viscous presenting a severe experimental problem. It is also not easy to regulate the degree of polymerization of the silica. 

The diffusion of small molecules in polymeric solids has been a subject in which relatively little interest has been shown by the polymer chemist, in contrast to its counterpart, i.e., the diffusion of macromolecules in dilute solutions. However, during the past ten years there has been a great accumulation of important data on this subject, both experimental and theoretical, and it has become apparent that in many cases diffusion in polymers exhibits features which cannot be expected from classical theories and that such departures are related to the molecular structure characteristic of polymeric solids and gels. Also there have been a number of important contributions to the procedures by which diffusion coefficients of given systems can be determined accurately from experiment. It is impossible, and apparently beyond the author s ability, to treat all these recent investigations in the limited space allowed. So, in this article, the author wishes to discuss some selected topics with which he has a relatively greater acquaintance but which he feels are of fundamental importance for understanding the current situation in this field of polymer research. Thus the present paper is a kind of personal note, rather than a balanced review of diverse aspects of recent diffusion studies. 

This catalyst was prepared and used for polymerization in the following manner. A 0.1 M solution of TiCl in toluene was made up and stored in the dry box. The desired amount of ir-allyl nickel iodide was weighed out, dissolved in 1.0 ml toluene, and placed in a Fisher-Porter tube. In all polymerizations, [Ni] = 3x10 M and the Ni/Ti ratio was - 1. To the ir-allyl nickel iodide solution was added an appropriate amount of the stock solution of TiCl, and the mixture was agitated at ambient temperature for 20 minutes. Almost immediately upon addition of the TiCl solution, a brown precipitate formed. After 20 minutes, the solvent (toluene) was added, and the tube was sealed and removed to the bench, where butadiene was transferred into the tube to give the desired monomer concentration. The tube was placed in an oil bath at the polymerization temperature, and the rest of the reaction and work-up was carried out as described in the general procedure detailed previously. Typical experimental details are given below ... 

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