Viscoelastic and dielectric behaviour of thin films made from siloxane-containing poly(oxadiazole-imide)s

Low Dielectric Poly(imide siloxane) Films Enabled by a Well-Defined Disiloxane-Linked Alkyl Diamine

This paper presents an efficient pathway to achieve the dielectric constant as low as 2.48 @ 25 °C, 1 MHz for nonporous poly(imide siloxane) films with mechanical and thermal robustness. A symmetric disiloxane-linked alkyl diamine, bis(aminopropyl)tetramethyldisiloxane (BATMS) with a well-defined molecular formula NH2CH2CH2CH2Si(CH3)2OSi(CH3)2CH2CH2CH2NH2, has been used to controllably reduce the dielectric constant of the polymer films by adjusting the loading of BATMS. The thermal stability of all the polymer films remains robust with T 5 and T 10 no less than 458 and 472 °C, respectively, while the glass-transition temperature decreases with increasing incorporation of flexible disiloxane-alkyl segments into a polymer backbone. There exists a consistent regularity between the thermal, optical, and dielectric properties with the loading amount of BATMS in the polymer films, inferring that the disiloxane-alkyl segments are homogeneously distributed in the polymer backbone. Charge-transfer complex inhibition of polymer films by disiloxane segments has been revealed by an enlarged d-spacing in wide-angle X-ray diffraction spectra and a blue shift in film fluorescence emission spectra. The combined low dielectric constant, robust mechanical and thermal stability, and improved hydrophobicity make the series of BATMS-resulting poly(imide siloxane) films promising candidates for sophisticated flexible microelectronic application.

Thermal and oxidative behavior of a tetraphenylsilane-containing phthalonitrile polymer

Phthalonitrile polymers have potential for high-temperature applications in polymer matrix composites as electronic encapsulation compounds. To investigate the effect of inclusion of an organosilicon moiety, a tetraphenylsilane-containing phthalonitrile monomer was synthesized in high yields. The monomer possessed a high melting point of 222–223°C, while no hydrolytic sensitivity was observed. Cured polymers exhibited glass transitions in the range of 290–325°C and coefficients of thermal expansion of 73–77 µm/(m °C). In thermogravimetric analysis (TGA), 5 wt% loss was observed at 482–497°C and 519–526°C, under air and nitrogen, respectively. Infrared (IR)-TGA of evolved gases revealed multiple degradations in both nitrogen and air. The material possessed good thermo-oxidative stability (TOS) when aged in air at 250°C. After aging for 5000 h, oxidative degradation was characterized using Fourier transform IR microscopy, energy dispersive spectroscopy, optical microscopy, and Knoop hardness testing. Four zones were identified in aged samples. The cleavage of Si-phenyl bonds and the formation of Si–O phases and carbonyl groups were observed.

Thermal rearrangement of ortho-allyloxypolyimide membranes and the effect of the degree of functionalization

Aromatic polyimides containing different ratios of ortho-hydroxy to ortho-allyloxy units were prepared and thermally rearranged.

Phosphine oxide based polyimides: structure–property relationships

The PI flame retardance has been influenced by the variation of flexible segments leading to a reduction of THR.

Dielectric and gas transport properties of highly fluorinated polyimides blends

The physicochemical properties of highly fluorinated polyimide blends were studied in order to highlight the advantages of employing a high content of fluorine atoms to tailor the properties of polyimide materials. Thus, dynamo-mechanical analysis was used to evidence the physical phenomena taking place during heating. The trend of storage modulus, loss modulus and loss factor tangent with temperature during and after the α relaxation was explored. The dielectric spectroscopy was carried out to investigate the dielectric behaviour at different temperatures and frequencies and to evaluate the values of dielectric constant, dielectric loss and electrical resistance. The dielectric spectroscopy data were corroborated with the dynamo-mechanical analysis to highlight the sub-glass transitions encountered in these blend films. Dielectric loss diagrams showed sub-glass transitions in the form of γ and β relaxations mainly due to the segmental mobility of the polymer chain components. The gas separation performance of some of the investigated blends was assesed, and their ability to achieve simultaneously higher gas permeability and higher selectivity was demonstrated.

Poly(dimethyltin glutarate) as a prospective material for high dielectric applications

Poly(dimethyltin glutarate) is presented as the first organometallic polymer, a high dielectric constant, and low dielectric loss material. Theoretical results correspond well in terms of the dielectric constant. More importantly, the dielectric constant can be tuned depending on the solvent a film of the polymer is cast from. The breakdown strength is increased through blending with a second organometallic polymer.

Properties of some azo-copolyimide thin films used in the formation of photoinduced surface relief gratings

The patterning of the free standing azo-copolyimide films under different irradiation conditions led to the uniform surface relief gratings.

Copolyimides containing perylene and hexafluoroisopropylidene moieties

Three poly(ether-peryleneimide)s were prepared by one-step solution polycondensation reaction at high temperature of an aromatic diamine containing an oxadiazole ring and/or diphenylether units with a mixture of perylenetetracarboxylic dianhydride and hexafluoroisopropylidene-diphthalic dianhydride. The structure of the polymers was confirmed by Fourier transform-infrared analysis. These polymers possess good solubility in N-methylpyrrolidinone and can be processed into thin and tough flexible films. They are highly thermostable, up to 465°C, and display glass transition in the range of 227–266°C. The dielectric constant values of these polyimides at 25°C and in the frequency domain of 1 Hz to 100 kHz are in the range of 2.29–2.96. The photoluminescence spectra of those poly(ether-peryleneimide)s consist of the emission of perylenediimide chromophore and conjugated segments containing five-imide rings, without the emission from oxadiazole chromophore.

Preparation and characterization of poly(imide siloxane) block copolymers based on diphenylthioether dianhydride isomer mixtures

A series of poly(imide siloxane) block copolymers were prepared based on diphenylthioether dianhydride isomer mixtures (m-TDPA), 4,4′-oxydianiline (ODA) and bis(γ-aminopropyl)polydimethylsiloxane (APPS). The ODA and m-TDPA composed the hard segment, while the APPS and m-TDPA composed the soft segment. The hard segment length was kept constant, while the soft segment lengths were varied with varying the APPS contents. The copolymers had inherent viscosities range from 0.37 to 0.51 dL g−1, and their weight-average molecular weights and number-average molecular weights were in the range of 45 000–52 600 and 21 300–27 000, respectively. All copolymers were readily soluble in many organic solvents, and could afford flexible films via solution casting. The cast films exhibited mechanical properties with tensile strengths at break of 26.7–86.2 MPa, elongations at break of 9.9–112.2%, and tensile moduli of 0.12–2.15 GPa, depending on the soft segment length. The films also exhibited low water uptakes in the range of 0.18–0.68 wt.%. Furthermore, the copolymers showed high glass transition temperatures derived from the hard segments in the range of 196–225 °C, and good thermal stability with almost no weight loss up to 350 °C under nitrogen atmosphere and 335 °C under air atmosphere.

Copoly(1,3,4-oxadiazole-naphthylimide)s containing siloxane units in the main chain: synthesis and properties

This study was concerned with the synthesis and properties of new soluble copolyimides containing naphthalene, oxadiazole and tetramethyldisiloxane units. These copolyimides were prepared by two-step polycondensation reaction in solution of aromatic diamines containing preformed oxadiazole ring with a mixture 1 : 1 of naphthalene tetracarboxylic dianhydride and tetramethyldisiloxane- [1,3-bis(4′-phthalic anhydride)]. The structure of these polymers was confirmed by Fourier transform infrared and 1 H-NMR spectroscopy. The solubility, thermal stability and glass transition temperature of these copolyimides were measured and compared with those of related polyimides which do not contain siloxane groups. All these polymers emitted an intense blue color light upon irradiation with UV light. These copoly(oxadiazole-naphthylimide)s could be considered promising candidates for organo-soluble high-performance polymers for use in novel technological applications.