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Foamed polyimides have been developed in order to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the nanometer range, thus the term “nanofoam.” The polyimide foams are prepared from block copolymers consisting of thermally stable and thermally labile blocks, the latter being the dispersed phase. Foam...
Nanomechanics has been slow in entering nanotechnology because of extreme conditions resulting from scaling. This is an issue in particular for polymers, although widely used in macroscale applications. Highly repetitive nanoscale deformation cycling in combination with excellent shape retention and thermal stability is demonstrated. While generic principles described are pertinent to a range of applications,...
We report the controlled synthesis of micrometre-sized thermally labile PMMA particles. This was achieved by a combination of dispersion polymerization and chain transfer techniques. The dispersion polymerization allows for the synthesis of spherical micrometre-size particles of PMMA, whereas the use of cobalt chain transfer agents results in vinylidene end-functionalized PMMA. Furthermore, the...
In order to produce polyimide films in situ on silicon substrates, while minimizing the thermally induced residual stresses on cooling from the cure temperature, we have prepared various polyimide-polydimethylsiloxane based block copolymers derived from pyromellitic dianhydride (PMDA) and p,p -oxydianiline (ODA) via the poly(amic-alkyl ester) precursor route. This approach allows more synthetic flexibility...
Novel imide-aryl ether phenylquinoxaline copolymers were prepared and their morphology and thermal properties investigated. A key feature of these copolymers is the incorporation of an aryl ether phenylquinoxaline linkage into a semi-rigid polyimide backbone based in pyromellitic dianhydride (PMDA) with 4,4 -oxydianiline (ODA) and either 2,3-bis-[(3-aminophenoxy)phenyl]quinoxaline or 2,3-bis-[(4-aminophenoxy)phenyl]quinoxaline...
We have developed a new technology, based on chemically induced phase separation, that allows for the synthesis of porous epoxies with a closed cell morphology and a narrow pore size distribution in the micrometre range. The potential of this technique for the synthesis of new types of porous thermosets is enlightened by the comparison with the current state of the art on technologies for the preparation...
A new route has been developed for the synthesis of thermally stable polymer foams with high glass transition temperatures. Compositionally asymmetric microphase-separated block copolymers were prepared where the minor component, poly(α-methylstyrene), is thermally labile and the major component, polyimide, is thermally stable. The minor component can unzip, to its monomer upon heating, and the...
A new route for the synthesis of high glass transition temperature, thermally stable polymer foams with pore sizes in the nanometre regime has been developed, using compositionally asymmetric microphase-separated block copolymers where the minor component (poly(α-methylstyrene)) is thermally labile and the major component (polyimide) is thermally stable. The minor component can unzip to its monomer...
A means of generating high temperature polymer foams which leads to pore sizes in the nanometre regime has been developed. Foams were prepared by casting block copolymers comprising a thermally stable block and a thermally labile material, such that the morphology consists of a matrix of the thermally stable material with the thermally labile material as the dispersed phase. Upon thermal treatment,...
A means of generating high temperature polymer foams which leads to pore sizes in the nanometre regime has been developed. Foams were prepared by casting block copolymers comprising a thermally stable block and a thermally labile material, such that the morphology provides a matrix of the thermally stable material with the thermally labile material as the dispersed phase. Upon a thermal treatment...
New routes for the synthesis of high T g thermally stable polymer foams with pore sizes in the nanometre regime have been developed. Foams were prepared by casting well-defined microphase-separated block copolymers comprising a thermally stable block and a thermally labile material. At properly designed volume fractions, the morphology provides a matrix of the thermally stable material with...
Transmission electron microscopy (TEM) has been used to determine the porosity of polymer nanofoams produced by thermal decomposition of the thermally labile component of different copolymers. The results are compared with those obtainable by i.r. spectroscopy and density gradient methods, showing quantitative agreement for small pore sizes. TEM permits much higher spatial resolution than i.r. spectroscopy...
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