Jeffrey William Labadie

High temperature polymer foams

Abstract A means of generating high temperature polymer foams with pore sizes in the nanometre range has been developed. Foams were prepared by casting block copolymers comprising a thermally stable block as the matrix and a thermally labile material as the dispersed phase. Upon thermal treatment the thermally unstable block underwent thermolysis, leaving pores with a size and shape dictated by the initial copolymer morphology. Nanopore foam formation is shown for triblock copolymers composed of a poly(phenylquinoxaline) (PPQ) matrix with either poly(propylene oxide) (PO) or poly(methyl methacrylate) (PMMA) as the thermally labile coblocks. Upon decomposition of these blocks, a 10–20% reduction in density was observed, consistent with the initial PO or PMMA composition, and the resulting PPQ foams showed dielectric constants of about 2.4, substantially lower than that of PPQ (2.8). Small-angle X-ray scattering and transmission electron microscopy showed pore sizes of approximately 100 A.

High-temperature polyimide nanofoams for microelectronic applications

Abstract 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 formation is effected by thermolysis of the thermally labile block, leaving pores of the size and shape corresponding to the initial copolymer morphology. Nanofoams prepared from a number of polyimides as matrix materials were investigated as well as from a number of thermally labile polymers. The foams were characterized by a variety of experiments including TEM, SAXS, WAXD, DMTA, density measurements, refractive index measurements and dielectric constant measurements. Thin film foams, with high thermal stability and low dielectric constants approaching 2.0, can be prepared using the copolymer/nanofoam approach.

High temperature nanofoams derived from rigid and semi-rigid polyimides

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 the thermally unstable block undergoes thermolysis, leaving pores where the size and shape are dictated by the initial copolymer morphology. Multiblock and triblock copolymers, comprising rigid, semi-rigid and flexible polyimide matrices with either poly(propylene oxide) or poly(methyl methacrylate) as the thermally labile coblocks, were prepared. The copolymer synthesis was carried out through the poly(amic alkyl ester) precursor to the polyimide since this precursor is stable and allows for isolation and characterization prior to imidization. Microphase-separated morphologies were observed for all copolymers irrespective of block type or length by both dynamic mechanical and small-angle X-ray scattering techniques. Upon decomposition of the propylene oxide or methyl methacrylate coblock, reductions in the film thickness and the total integrated scattering were found for those copolymers derived from rigid and semi-rigid polyimide matrices, thus indicating a collapse of the foam as it was being formed. Conversely, copolymers based on the flexible polyimide produced stable foams upon decomposition of the labile coblocks.

Polyimide Nanofoams For Low Dielectric Applications

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 formation is effected by thermolysis of the thermally labile block leaving pores the size and shape corresponding to the initial copolymer morphology. Nanofoams prepared from a number of polyimides as matrix materials, were investigated as well as a number of thermally labile polymers. The foams were characterized by a variety of experiments including, TEM, SAXS, WAXD, DMTA, density measurements, refractive index measurements and dielectric constant measurements. Thin film foams, with high thermal stability and dielectric constants approaching 2.0, can be prepared using the copolymer/nanofoam approach.

Imide-aryl ether benzoxazole random copolymers

Abstract Novel imide-aryl ether benzoxazole copolymers were prepared and their morphology and mechanical properties investigated. A key feature of these copolymers is the incorporation of a benzoxazole moiety by the use of 2,2′-bis[4-(3-aminophenoxy)phenyl]-6,6′-bibenzoxazole or 2,2′-bis[4-(4-aminophenoxy)-phenyl]-6,6′-bibenzoxazole as co-diamines in polyimide syntheses. The preparation of these diamines involved the nucleophilic aromatic substitution of 2,2′-bis(4-fluorophenyl)-6,6′-bibenzoxazole with either 3- or 4-aminophenol in the presence of K 2 CO 3 . The diamines were co-reacted with various compositions of pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) to synthesize the desired poly(amic acids). Films were cast and cured (350°C) to effect the imide formation, affording films with elongations between 40 and 110% and moduli in the 2000–2750 MPa range. The copolymers exhibited good dimensional ( T g in excess of 300°C) and thermal stability. Wide-angle X-ray diffraction measurements on the copolymers showed that the ordered morphology characteristic of PMDA/ODA polyimide was retained. Improvements in the auto-adhesion were observed, particularly in those copolymers which displayed a T g .

Imide-aryl ether phenylquinoxaline random copolymers

Abstract Novel imide-aryl ether phenylquinoxaline copolymers were prepared and their morphology and mechanical properties investigated. A key feature of these copolymers is the incorporation of an aryl ether phenylquinoxaline linkage into a semi-rigid polyimide backbone based on 4,4′-oxydianiline (ODA) and pyromellic dianhydride (PMDA) by the use of either 1,4-bis[6-(3-aminophenoxyl)-3-phenyl-2-quinoxalinyl] benzene or 1,4-bis[6-(4-aminophenyoxyl)-3-phenyl-2-quinoxalinyl]benzene as co-diamines. These monomers were prepared by a novel nucleophilic aromatic substitution reaction of 1,4-(6-fluoro-3-phenyl-2-quinoxalinyl) benzene with 4- or 3-aminophenol in the presence of K2CO3. These diamines were used as co-monomers with PMDA and ODA to synthesize poly(amic-acids). Films were cast and cured (350°C) to effect imidization, affording films which showed high elongations and moduli. The copolymers with high phenylquinoxaline compositions displayed Tg values in the 300°C range. The thermal stability of the copolymers was comparable to that of the parent polyimide with decomposition temperatures between 470 and 530°C. The morphology of the copolymers was investigated by dynamic mechanical, wide angle X-ray diffraction (WAXD) and swelling measurements.

Thiophene-based poly(arylene ether)s: 5. Imide-arylene ether statistical copolymers

Abstract Imide-aryl ether thiophene copolymers were prepared and their thermal and mechanical properties were investigated. A key feature of these copolymers is the incorporation of the 2,5-thiophene moiety using 5,5′-bis[(3-aminophenoxy)thienyl-2] Ketone or 5,5′-bis[(4-aminophenoxy)thienyl-2] ketone as diamines in polyimide syntheses. The preparation of these thiophene diamines involved the nucleophilic aromatic substitution of bis(5-chlorothienyl-2) ketone with either 3- or 4-aminophenol in N -methyl-2-pyrrolidinone using potassium carbonate. These diamines were reacted with various compositions of pyromellitic dianhydride and 4,4′-oxydianiline to synthesize the desired poly(amic acid)s. Films were cast and cured (300°C) to effect the imide formation, and the resulting films showed tough ductile mechanical properties with high glass transition temperatures that decreased with increasing thiophene diamine content.

Thermoplastic toughened styrenic thermosets: synthesis, properties and consequences of radical based cure chemistry

A novel thermosetting resin based on vinylic end groups was prepared and its network formation investigated. 2,2-Bis(4-vinylbenzyloxyphenyl)hexafluoropropane was prepared by the condensation of vinylbenzyl chloride with Bisphenol-AF in the presence of K2CO3. This distyrenic monomer was cured thermally to produce a highly crosslinked network with <0.5% sol fraction. The networks prepared by this reactive monomer were brittle. However, their fracture toughness could be modified with the incorporation of vinylbenzyl end-capped perfluoroalkylene aryl ether oligomers. The thermoplastic component phase separated into discrete composite particles in the continuous network phase. The thermoplastic modified network showed improved fracture toughness without sacrificing the modulus or good dielectric characteristics.