ISSN:
0022-3832
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
The cationic polymerization of butadiene with several Friedel-Crafts catalysts has been described. Aluminum chloride and chlorosulfonic acid are active catalysts at -75°. The rate of polymerization at -75° is much faster than at the higher temperatures. Except for boron trifluoride etherate, which catalyzes the polymerization at -30°, the other catalysts (sulfuric acid, fuming sulfuric acid, stannic chloride, and boron trifluoride hydrate) produce appreciable amounts of polymer only at 0° or higher.The effect of variables, such as catalyst concentration, catalyst solvent, dilution, reaction time, etc., differs with each individual catalyst. In some cases, results were not conclusive due to lack of reproducibility. It was found that the presence of moisture is mainly responsible for this lack of reproducibility. Traces of water promote the polymerization with stannic chloride or boron trifluoride etherate, but inhibit the polymerization when an ethyl bromide solution of aluminum chloride is used as catalyst.Rubberlike polyhutadienes can be obtained with all catalysts except sulfuric and fuming sulfuric acids. However, the physical properties of these polymers show that the molecular weight is very low and that the polymer is not suitable as a rubber. Polymers ranging from viscous liquids to hard, brittle solids have also been obtained. In general, the solubility of the polymers is low. Approximately 60% of the butadiene enters the polymer chain by 1,4 addition.The copolymerization of butadiene and styrene at -75° with an ethyl bromide solution of aluminum chloride has also been studied. At conversions between 20 and 30% a soluble, rubberlike copolymer having a low molecular weight is formed. An insoluble, brittle polymer is obtained a t higher conversions.The soluble, cationic copolymer has a characteristic ultraviolet absorption curve which is different from that of GR-S. It has a styrene content of approximately 50% by weight which demonstrates that the styrene is more active in cationic copolymerization than is butadiene.
Zusätzliches Material:
16 Tab.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1951.120060409
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