Diane M. Stoakley

Reflective and electrically conductive surface silvered polyimide films and coatings prepared via unusual single-stage self-metallization techniques

Highly reflective and/or surface conductive flexible polyimide films can be prepared by the incorporation of positive valent silver compounds into solutions of poly(amic acid)s formed from a variety of dianhydrides and diamines. Thermal curing of selected silver(I)-containing poly(amic acid)s leads to cycloimidization of the polyimide precursor with concomitant silver(I) reduction and surface aggregation of the metal yielding a reflective and/or conductive silver surface similar to that of the native metal. However, not all silver(I) precursors are effective surface metallization agents and not all poly(amic acid)s metallize with equal facility. Ligand/anion and polyimide structural effects on film metallization efficacy and on physical properties on metallized films are reviewed.

Poly(aryl ether ketones) bearing alkylated side chains

Poly(aryl ether ketones) containing pendant alkyl side chains were prepared by the nucleophilic displacement reaction of 2,2-bis(4-hydroxphenyl)tridecane, 2-2,bis(4hydroxyphenyl)nonadecane and bisphenol AF with 2,2-bis-[4-(4-fluorobenzoyl)phenyl]propane and 2,2-bis[4-(4-fluorobenzoyl)phenyl]hexa-fluoropropane in the presence of potassium carbonate in N,N-dimethylacet-amide. The polymers had inherent viscosities up to 1.04 dl g−1 in chloroform, formed creaseable films and were soluble in common organic solvents. Their dielectric constants were below 2.60 (at 10 GHz). The inclusion of the alkyl side chains lowered the T g, thermal stability and char yield of fluorinated poly(ether ketone) as expected.

Molecularly Oriented Films for Space Applications

Because of their inherent toughness and flexibility, low density, thermal stability, radiation resistance and mechanical strength, aromatic polyimides have excellent potential for use as advanced materials on large space structures. Polyimides were uniaxially and biaxially oriented to further enhance their dimensional stability, stiffness, elongation and strength. Both unoriented and oriented polymeric thin films were also cryogenically treated to temperatures below -184 °C to show their stability in cold environments. Successful stretching depended on film quality, film thickness, soak time, grip pressure, stretching rate and stretching temperature. In-plane birefringence increased with increased stretch ratios as expected. Coefficients of thermal expansion (CTEs) decreased with increased stretch ratio by as much as 31%. Tensile strengths increased by up to 85% with increasing stretch ratio. Elongations increased by as much as 95% with stretching. Significant improvements in elongation were obtained with only a 2× uniaxial orientation. Moduli did not change significantly with stretching. Mechanical properties increased more with uniaxial stretching than biaxial stretching. Cryogenic treatment increased the tensile strength of some stretched samples by a maximum of 10–20%. Properties such as modulus and CTE did not change significantly after the films had been slow cooled to cryogenic temperatures.

Chemical factors that influence the production of conductive and/or reflective silver-doped polyimide films

ABSTRACT Doping a poly(amide acid) resin with a silver containing additive (1,5-cyclooctadiene-hexafluoroacetylacetonato)-silver(I) [Ag(COD) (HFA)] resulted, after thermal cure, in either a highly reflective or highly electrically conductive polyimide film. The combination of monomers, which render films with low Tg (~210°C), and contained sulfur, produced films with surface resistance in the range 101–103 ohms. On the other hand, films with specular reflectivity (relative to a silver mirror) in the range of 65–48% were obtained using both high Tg polyimides and polyimides void of sulfur in the polyimide backbone with low Tg. Our understanding regarding the structure-property relationship on these polyimide films and also the characterization of the doped-films are discussed.

N-Methylated copoly(imide amide)s containing hexafluoroisopropylidene

Abstract A synthetic method was developed to produce N,N′ -dimethylated diamines which were then used to prepare poly(imide amide)s. Thus, N,N′ -dimethyl-4,4′-bis(4-aminophenoxy)biphenyl and N,N′ -dimethyl-2,2-bis(4-aminophenyl)hexafluoropropane were condensed at 0°C in dimethylacetamide with 2,2-bis[ N -(4-chlorocarboxyphenyl)phthalimidyl]hexafluoropropane. The yields were 76–92%, viscosities 0.28–2.26 dl g −1 , water absorptions 0.16–0.37 wt% and thermal stabilities around 460°C by thermogravimetric analysis. The addition of the methyl group caused lower molecular weights but superior thermal stability (isothermally) and decreased colour.

Effects of transition metal ions on positron annihilation characteristics in epoxies

Abstract Effects of several 3d-transition metal ions on positron annihilation characteristics in MY-720 epoxy resin have been investigated. All metal complexes were added at the mole ratio of 1 metal complex for every 10 MY-720 repeat units. In all cases, it appears that the 3d magnetic electrons are localized on their respective ions. Cr 3+ -ions make the strongest impact — both on the probability of formation of positronium atoms as well as their subsequent decay. The effects of Co 2+ and Co 3+ ions are not greatly different, indicating that the final oxidation states of Co x + -ions in the host epoxy may be the same, namely 2 + . Ni 2+ -ions are unique because their coordination geometry remains unchanged when Ni(acac) 2 is introduced in the MY-720 epoxy. In this respect, Ni(acac) 2 is similar to Co(aeac) 2 and both have comparable impacts on positron annihilation characteristics. The effects of Fe 3+ -ions are consistent with coordination symmetry change from sp 3 d 2 to d 1 sp 3 when Fe(acac) 3 is introduced in the epoxy.

New Aromatic Diacids Containing the Trifluoromethyl Group and their Polyamides

A series of new fluorinated, high-temperature polymers has been prepared from 1, 1, - bis(p-carboxyphenyl)-2, 2, 2-trifluoroethanol (3FOH). This diacid was synthesized by oxidation of 1, 1-di(p-tolyl)-2, 2, 2-trifluoroethanol, which was obtained from p-bromotoluene and ethyl trifluoroacetate. The 3FOH was also reacted with dimethyl sulphate to yield 1-methoxy-1, 1- bis(p-carboxyphenyl)-2, 2, 2-trifluoroethane (3FM), and with SOCl2 to produce 1-chloro-1, 1- bis(p-chloroformylphenyl)-2, 2, 2-trifluoroethane (3FCl). These two diacids, as the acid chlorides, were polymerized with six aromatic and four aliphatic diamines to produce polyamides which had viscosities ranging from 0.32 to 1.52 dl g−1, thermal stabilities up to 518 °C in nitrogen and glass transition temperatures from 165 °C to 337 °C. The dielectric constants of these polyamides ranged from 2.64 to 2.99. The 3FM- and 3FCl-containing polyamides were compared with the 6F (hexafluoroisopropylidene) analogues and found to be somewhat less thermally stable and had equal or lower T gs.