Siloxane-modified polyimides

One of the major goals of this endeavor was to solubilize the normally intractable polyimides by the incorporation of siloxane segments, and, optionally, by solution imidization. Solubilities of a series of siloxane-modified polyimide copolymers were evaluated in a variety of solvents as indicated in Table I. Copolymer solubility was found to be a function of the siloxane oligomer concentration... 

Values of the upper glass transition temperatures of the siloxane modified polyimides were found to be a function of both the level of incorporated siloxane as well as the siloxane molecular weight (Table II). The upper transition temperature of the solution... 

Segmented polyimide-polydimethylsiloxane copolymers have been successfully synthesized both in laboratory and industrial quantities to produce multiphase siloxane-modified polyimides. The siloxane detracts somewhat from the otherwise excellent thermo oxidative stability of the polyimide, but it does produce a number of important properties. These include multiphase behavior, improved adhesion to many substrates, improvements in fire resistance and enhanced gas and liquid separation membranes, where one wishes not only to maximize the contribution of the siloxane to permeability, but also to utilize the imide to re-... 

As mentioned earlier, siloxanes impart a number of beneficial properties to polymeric systems into which they are incorporated, including enhanced solubility, resistance to degradation in aggressive oxygen environments, impact resistance and modified surface properties. These particular advantages render polysiloxane-modified polyimides attractive for aerospace, microelectronic and other high performance applications (40-43). 

DTA has been used to determine the Tg of polymers including polystyrene [3], polyimides [4], copolyarylene ethers [5], bis(trichlorophenolate)dipyridine [6], nitroazobenzene substituted polymethacrylates [7] and polycarbonates [8], polydimethyl siloxane modified silica xerogels [9], and linear polydicyclopentadiene [10]. 

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