Frank W. Mercer

Effect of Structural Features and Humidity on the Dielectric Constant of Polyimides

A series of aromatic polyimides and partially fluorinated aromatic polyimides were prepared and investigated to determine the structural features affecting their moisture absorption, dielectric constant, and dielectric constant as a function of relative humidity. The moisture absorption of polyimides is related to the total imide content of the polymer. Polyimides with a lower weight per cent of imide have a lower moisture absorption. Both dielectric constant and moisture absorption of polyimides can be reduced by incorporation of fluorine into the polymer. However, a minimum in moisture absorption (about 0.7 wt.%) and dielectric constant (about 2.7) is approached at about 20% fluorine by weight of the polymer.

Dielectric and thermal characterization of fluorinated polyimides containing heterocyclic moieties

A series of fluorinated polyinides and fluorinated polyimides containing heterocyclic moieties were prepared and investigated to determine their dielectric constants, dielectric constants as a function of relative humidity (RH) and thermal properties. Thle fluorinated polyimides containing heterocyclic moieties were prepared from diamines containing pyridine, pyridazine, oxadiazole or benzoxazole moieties. The properties of the fluorinated heterocyclic-containing polyimides were compared with those of fluorinated polyimides prepared from aromatic diamines. In most cases, the introduction of heterocyclic moieties caused an increase in dielectric constant, an increase in the dielectric constant as a function of relative humidity and a decrease in thermal stability compared with the polyimides prepared with aromatic diamines.

Polyamide Copolymers Containing Hexafluoroisopropylene Groups

Abstract New copolymers containing imide and different heterocyclic units such as oxadiazole, benzoxazole, or pyridazine, together with hexafluoroisopropylidene groups, have been synthesized by solution polycondensation of appropriate aromatic diamines with diacid chlorides incorporating preformed imide rings and hexafluoroisopropylidene bridges. In the case of oxadiazole-imide copolymers and pyridazine-imide copolymers, aromatic diamines containing preformed oxadiazole or pyridazine, respectively, have been used, while in the case of benzoxazole-imide copolymers the benzoxazole unit was formed during the polycondensation reaction between bis(o-hydroxy-amine)s and the above-mentioned diacid chlorides. Also, copolyimides containing pendant cyano groups have been prepared from aromatic diamines containing cyano substituents with the same diacid chlorides. Solubility, film-forming ability, thermal stability, and electrical insulating properties of all these compounds are discussed and compared with those of ...

Synthesis and characterization of fluorinated polyetherketones prepared from decafluorobenzophenone

Abstract A series of fluorinated polyetherketones containing perfluoroaryl moieties was prepared by solution condensation polymerization. The synthesis involves the condensation of a dialkali metal salt of a bisphenol with decafluorobenzophenone. The reaction is rapid, free of side reactions, and yields polymers with high glass transition temperatures (Tgs) and excellent thermal stability. The Tgs of the polymers ranged from 155 to 223°C as measured by differential scanning calorimetry (d.s.c.). The dynamic mechanical thermal analysis of the polymers is also described. The dielectric constants of the polymers were characterized as a function of percent relative humidity. All of the fluorinated aromatic polyetherketones were processable from solution, to yield transparent, flexible films.

Aromatic Poly(ether imide oxadiazole)s

Two oxadiazole containing aromatic diamines were synthesized. The diamines were prepared by reaction of aminophenols with 2,5-bis(4-fluorophenyl)-4l3,4-oxadiazole in a polar aprotic solvent in the presence of potassium carbonate. Reaction of the resulting 2,5-bis(4-(aminophenoxy)phenyl)-1,3,4-oxadiazoles with dianhydrides gave a series of polymeric amic acids. Thermal treatment yielded poly(imide ether oxadazole) films which displayed good thermal stability, flexibility, and glass transition temperatures ranging from 241 to 344C. The dielectric constants of the films were characterized as a function of relative humidity.

Synthesis and characterization of fluorinated poly(aryl ether ketone)s containing 1,4‐naphthalene moieties

The new monomer 2,2-bis[4-(4-(4-fluorobenzoyl}-1-naphthoxy)phenyl]hexafluoropropane (2) was synthesized in a two-step reaction sequence. 2,2-bis[4-(1-naphthoxy)phenyl]-hexafluoropropane (1) was prepared using the Ullmann ether synthesis reaction of 4,4-(hexafluoroisopropylidiene)diphenol with 1-bromonaphthalene. Friedel-Crafts acylation of 1 with 4-fluorobenzoyl chloride in methylene chloride containing dimethylsulfone selectively afforded 2 in 82% yield. The polycondensation of 2 with various bisphenols in DMAc in the presence of an excess of potassium carbonate as a condensation reagent was carried out at 165°C to quantitatively afford the corresponding fluorinated poly(aryl ether ketone)s containing 1,4-naphthalene moieties. Thermal analysis of the polymers showed them to have T g s ranging from 194 to 230°C and to be thermally stable in air up with initial weight losses at about 500°C. In addition, these novel polymers exhibited excellent solubility in organic solvents including NMP, DMAc, and chloroform.

Synthesis and characterization of fluorinated poly(imide-pyridazine-amide)s

Abstract New poly(imide-pyridazine-amide)s have been synthesized by the solution polycondensation of aromatic diamines containing preformed pyridazine rings with diacid chlorides which incorporate both imide and hexafluoroisopropylidene units. Solubility, thermal stability and electro-insulating properties of these compounds are discussed and compared with those of fluorinated poly(imide-amide)s which do not contain pyridazine rings, and also with those of other related heterocyclic polymers that have been previously reported.

Synthesis and properties of new alternating poly(aryl ether) copolymers containing cyano groups

Abstract A general method for the preparation of poly(aryl ether) alternating copolymers containing pendent cyano groups has been developed. We found that the activated aryl fluorides in 2-chloro-7-fluorobenzonitrile are selectively displaced by phenoxides to yield 3-chloro-2-cyanophenyl ethers as the exclusive products. Utilizing this selectivity, several new, high molecular weight, soluble poly(aryl ether amide) and poly(aryl ether ketone) alternating copolymers containing pendent cyano groups were prepared. The T g s of the copolymers ranged from 160 to 262°C. The dielectric constants of the copolymers were characterized as a function of percent relative humidity. All of the copolymers were processable from solution to yield transparent, flexible films. At elevated temperatures the cyano groups undergo crosslinking reactions yielding films with high solvent resistance.

Synthesis and properties of silicon-containing polyamides

A series of aromatic polyamides incorporating silicon together with phenylquinoxaline or with hexafluoroisopropylidene groups has been synthesized by solution polycondensation of a silicon-containing diacid chloride with aromatic diamines having phenylquinoxaline rings or hexafluoroisopropylidene groups. These polymers are easily soluble in polar aprotic solvents, such as N-methylpyrrolidinone and dimethylformamide, and in tetrahydrofurane, and can be solution-cast into thin, transparent films having low dielectric constant, in the range of 3.26 to 3.68. These polymers show high thermal stability with decomposition temperature being above 400°C and glass transition temperature in the range of 236°C to 275°C.

Studies on a Miscible Polyimide Blend

Blends of polyimides XU-218 and PEI were investigated using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis and adhesive bond testing. The thermal stability of the blends increased as the proportion of PEI increased while the α-relaxation of the blends occurred at a slower rate and was broader and more cooperative in some blends, compared with the pure polymers. Physical aging of the pure polymers and blends in the glass state revealed changes in relaxation rate and lost enthalpy that were also consistent with blends not behaving as simple mixtures. The dynamic mechanical and physical aging behaviour was attributed to an increase in density on blending which decreased the unoccupied volume and increased the constraints on molecular mobility, as well as to the presence of concentration fluctuations. The adhesive properties of the blends were also investigated and bond strength was found to vary with blend composition and test temperature.