Polyimide Blends Research Articles

Stable Low Voltage Organic Light-Emitting Diode Using Insulating Polymer/Conducting Polymer Blends

Organic light-emitting diodes (OLEDs) utilizing the blend of doped polyaniline (PANI-DBSA) and aromatic polyimide (PMDA-ODA PI) as a hole transport layer (HTL) were successfully fabricated. Tris(8-hydroxyquinolinato aluminum) (Alq3), indium-tin oxide (ITO), and aluminum (Al) were used as a lumophore, transparent anode, and stable cathode, respectively. The charge injection of the OLEDs with the softbaked and imidized HTL was started at ca. 4 Vdc and 3 Vdc, whereas the turn-on voltage was ca. 5 Vdc for the OLED with the imidized film as a HTL. The electroluminescent (EL) spectra of both OLEDs were almost the same as those of photoluminescence (PL) of the HTL/Alq3 films with marginal shift toward higher energy.

Phase Separation Behaviors Of Polyimide Blends

ABSTRACTWe investigated phase behaviors of polyimide blends such as polyethermide(PEI)/polystyrene(PS), PEI/polyamideimide(PAI), PEI/polyethyleneoxide(PEO), and PAI/PEO systems. Our sample systems exhibited lower critical solution temperature(LCST) phase behaviors. In the PEI/PS system, phase transition occurred near or above the glass transition temperature(Tg) of PS and the critical temperature of the system increased with decreasing molecular weight of PS. For PEI/PAI and PEI/PEO systems, the critical temperature of PEI/PAI system is higher than that of PEI/PEO system. Phase transition temperatures of PAI/PEO systems appeared near or below the melting point of PEO.

Transport properties of crosslinkable polyimide blends

The use of polymeric membranes for separation of chemically aggressive media, or at elevated temperatures, has been limited by membrane availability. While a number of polymers are both resistant to chemical dissolution and thermally stable to over 300°C, none has been shown to be simultaneously capable of the selective transport of gases at high rates. The research reported here analyzes the influence of solid-state crosslinking of polyimides to achieve this unique combination of properties. Polyimide blends consisting of an inert polymer base with a diacetylene-functionalized additive were prepared and the properties evaluated before and after crosslinking by thermal annealing. Crosslinking rendered the resultant polymers insoluble in what were previously solvents, but had no measurable influence on gas permeabilities or selectivities. The permeability/permselectivity of these new crosslinked polyimide blends are competitive with the best known polymers. Moreover, the combined ease of processing and resultant stability are unmatched.

Ternary fluoro‐containing polyimide blends and fluoro‐containing polyimide/polyester blends

Two ternary miscible fluoro-polyimide blends have been identified. They are 6FDA-3,3′-6F-diamine/6FDA-4,4′- F - diamine/BTDA - 4,4′ - 6FDA blend and 6FDA - 3,3′ - 6F - diamine/6FDA - 4,4′ - 6F - diamine/ODPA - PMDA - 4,4′-6F-diamine blend (6FDA is 2,2′-bis(3,4′-dicarboxy- phenyl)hexafluoro propane dianhydride, 6F-diamine is 2,2′-bis(3-aminophenyl) hexafluoro propane). Their miscibility probably arises from the fact that their diamine parts have hexafluoro isopropylidene groups, their dianhydride parts have similar bond angle, space, rigidity and length. Several 6FDA-polyimides and PCTG 5445 (glycol-modified polycyclohexanedimethanolterephthalate) form- ing miscible blends have also been discovered. These surprising results suggest that hexafluoro-isopropylidene-group containing polyimides are quite intermolecular active and the 1,4-cyclohexane dimethanol component in PCTG 5445 may also offer unique miscibility capability. © 1997 John Wiley & Sons, Ltd.

Spontaneous Molecular Orientation of Polyimides Induced by Thermal Imidization. 3. Component Chain Orientation in Binary Polyimide Blends

The degrees of uniaxial and in-plane molecular orientation for homopolyimides (PI) and PI/PI binary blends were estimated from the absorption dichroism of perylenetetracarboxydiimide (PEDI) bound t...

97/03738 New polymer membranes prepared from polysulfone and polyimide blends for separation of industrial gas mixtures

97/03738 New polymer membranes prepared from polysulfone and polyimide blends for separation of industrial gas mixtures

Ternary fluoro-containing polyimide blends and fluoro-containing polyimide/polyester blends

Two ternary miscible fluoro-polyimide blends have been identified. They are 6FDA-3,3′-6F-diamine/6FDA-4,4′- F - diamine/BTDA - 4,4′ - 6FDA blend and 6FDA - 3,3′ - 6F - diamine/6FDA - 4,4′ - 6F - diamine/ODPA - PMDA - 4,4′-6F-diamine blend (6FDA is 2,2′-bis(3,4′-dicarboxy- phenyl)hexafluoro propane dianhydride, 6F-diamine is 2,2′-bis(3-aminophenyl) hexafluoro propane). Their miscibility probably arises from the fact that their diamine parts have hexafluoro isopropylidene groups, their dianhydride parts have similar bond angle, space, rigidity and length. Several 6FDA-polyimides and PCTG 5445 (glycol-modified polycyclohexanedimethanolterephthalate) form- ing miscible blends have also been discovered. These surprising results suggest that hexafluoro-isopropylidene-group containing polyimides are quite intermolecular active and the 1,4-cyclohexane dimethanol component in PCTG 5445 may also offer unique miscibility capability. © 1997 John Wiley & Sons, Ltd.

Blends of thermoplastic polyimide with epoxy resin: Part II Mechanical studies

Bifunctional epoxy resins have been modified with thermoplastic polyimide in order to improve their toughness. The effects of polyimide content, curing conditions, curing agents, and types of polyimide on the fracture properties have been examined. Relationships between the microstructure of the cured resins and their mechanical properties have also been investigated.

Study on the β relaxation mechanism of thermosetting polyimide/thermoplastic polyimide blends

The thermosetting polyimide PMR-15 and its blends with thermoplastic polyimides have been studied by dynamic mechanical analysis. The results obtained indicate that the level of β relaxations in PMR-15 are increased with an increase in cross-linking density. This phenomenon is interpreted as a change of chemical structure during the cross-linking process. Addition of thermoplastic polyimide makes the magnitude of β relaxations increase when PMR-15 is the major component. This might be due to the strong intermolecular charge-transfer interaction between PI and PI or PMR-15 and PMR-15 molecular chains being partly replaced by the weak intermolecular interaction between PI and PMR-15 in PMR-15/PI blends, resulting in some phenylene rings or imide groups in PIs and PMR-15 chains being able to participate in β relaxation. However, this increment in β relaxation magnitude can be reduced by heat treatment of the sample, as a result of phase separation. Hence, it is concluded that the β relaxation magnitude is determined by the number of groups which can participate in relaxation per unit length, i.e. the magnitude of β relaxation increases with decreasing interaction between the molecular chains.

Miscibility of fluoro-containing polyimide blends

Experimental results confirm the general rules for miscible polyimide pairs containing the hexafluoroisopropylidene group if (1) the dianhydride composition is the same in each pair and (2) the diamine is changed from the 3,3′ (meta-substituted) 6F-diamine to the 4,4′ (para-substituted) 6F-diamine. These rules are also applicable to end-capped polyimide pairs. This conclusion is supported with the calculations of χ values based on the Flory-Huggins theory. We also discover two interesting polyimide alloys: 6FDA-PMDA-3,3′-6F-diamine/6FDA-PMDA 4,4′-6F-diamine forms fully miscible blends, while 6FDA-3,3′-6F-diamine/BTDA-4,4′-6F-diamine forms partially miscible blends (6FDA = hexafluorodianhydride, PMDA = pyromellitic dianhydride, BTDA = benzophenonetetracarboxylic dianhydride). These surprising results confirm that the rigidity, bond angle, space and the length of the dianhydride can significantly affect the molecular packing and miscibility tendency of polyimide blends.

Miscibility and crystallization behavior of thermosetting polyimide/thermoplastic polyimide blends

AbstractCompatibility, morphology, crystalline structure and mechanical properties of the blends of a thermosetting polyimide with thermoplastic polyimides consisting of dianhydrides of different lengths have been studied by the use of dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and small angle X‐ray scattering (SAXS) techniques. The results of our research show that the blends change from compatible to semi‐compatible when the difference between the length of the dianhydrides of the two components increases. Addition of a thermoplastic polyimide inhibits the crystallization of the thermosetting component. However, this effect decreases with increasing length of the dianhydrides and the distribution of the molecules of the thermoplastic polyimide component changes from interlamellar to interfibrillar. Impact strength and morphology of the fractured surfaces indicate that among the semi‐interpenetrating polymer networks (semi‐IPN) obtained the toughening effect of the partially compatible one is the best. The results are discussed in terms of charge transfer interaction between imide group and p‐phenylene group.

Miscibility and phase properties of poly(aryl ether ketone)s with three high temperature all-aromatic thermoplastic polyimides

Several semicrystalline poly(aryl ether ketone)s (PEK, PEEK and different isomers of PEKK) were melt-blended at T > 400°C with three high temperature thermoplastic polyimides. The compatibility and crystallization properties of the blends were studied by differential scanning calorimetry (d.s.c.). Blends of a semicrystalline New-Thermoplastic PolyImide (N-TPI) showed some surprising differences in the fastquenched amorphous samples. Its compatibility could be approximately ranked in the order PEKK > PEK ⪢ PEEK, where PEEK was completely incompatible. For the case of PEK/N-TPI, extensive d.s.c. data on amorphous fast-quenched films blended at different temperatures between 400 and 455°C were used to construct a phase diagram showing an upper critical temperature of 440°C. Two other wholly aromatic non-crystalline polyimides, LARC-IA and LARC-ITPI, were also studied. These are difficult to process in their neat form due to high melt viscosity. In the case of LARC-IA, the addition of miscible or semi-miscible lower viscosity polymer such as PEKK lowers the melt viscosity dramatically. LARC-ITPI was completely incompatible in all cases. N-TPI and LARC-IA were also melt blended with different isomers of PEKK including PEKK(50T/50I), (60T/401), (80T/20I) and (100T/0I), which have melting temperatures of 320, 310, 355 and 390°C, respectively, and equivalent glass transition temperatures of ∼160°C; T/I refers to the ratio of 1,4 and 1,3 ketone linkages, respectively. Surprising differences were seen in the miscibility of the different PEKK isomers. PEKK(60T/40I) was the only PEKK miscible with N-TPI and LARC-IA at essentially all compositions. Tentative structure-property relationships for blend compatibility and the nature of the interactions leading to miscibility are discussed.

Preparation of New Polybenzothiazole–Polyimide Blends through Polymerization Blending of Polyamic Acids in Precursor Polyamide Solution for Polybenzothiazole

Preparation of New Polybenzothiazole–Polyimide Blends through Polymerization Blending of Polyamic Acids in Precursor Polyamide Solution for Polybenzothiazole

Nanostructured polymers: a molecular interpretation of nanoscale reinforcement in polyurethane/polyimide blends

A series of segmented poly(ether-urethane-urea)/polyimide blends were characterized using small angle x-ray scattering (SAXS), tensile testing, dynamic mechanical analysis (DMA), and Fourier-Transform Infrared (FTIR) Spectroscopy. The SAXS revealed a dependence of the domain size, interdomain distance, and degree of phase mixing on polyimide concentration. The reduction in domain size was accompanied by an increase in interdomain distance and phase mixing. The FTIR studies showed that PI chains dispersed in the PU were stabilized by the formation of hydrogen bonding. In addition, free urea carbonyl absorption bands appeared as a function of PI concentration implying an interference with the formation of hard domains in the PU. The PU/PI blends showed large improvements in tensile properties at low concentrations (1–5 wt. % PI). The enhancement in mechanical properties is attributed to synergism between the molecularly dispersed nanosize rigid segments and the formation of hydrogen bonding.

Mechanical and Morphological Phase Behavior in Miscible Polyethersulfone and Polyimide Blends

Mechanical and Morphological Phase Behavior in Miscible Polyethersulfone and Polyimide Blends

Study on structure‐property relationship of thermosetting polyimide/thermoplastic polyimide blends

The miscibility, mechanical properties and morphology of polyimide PMR-15 with the polyimide YS-30 [N(CO) 2 Ph-OPhC(Me) 2 -PhO-Ph(CO) 2 N- PhOPh] n are investigated

Studies on the thermal and curing behavior of polyimide blends

AbstractBlends of thermosetting (Thermid MC‐600 and Thermid FA‐700) and thermoplastic (UL‐TEM 1000) polyimide resins with different compositions were prepared. Curing and thermal behavior of the blends were investigated using differential scanning calorimetry and dynamic thermogravimetry in a nitrogen atmosphere. The peak exotherm temperature increased with increasing amount of thermoplastic resin, whereas the heat of polymerization decreased. The electrical characteristics of the blends were also investigated using a dielectric analyzer. Dynamic as well as isothermal scans were recorded. Ionic conductivity, permittivity, and the loss factor were measured as a function of temperature at various frequencies. These results showed the complete curing of the resins having 50% Ultem at 225°C in 1 h, whereas Thermid MC‐600 required a postcuring step to observe fully cured resins. A marginal decrease in thermal stability was observed on blending. © 1994 John Wiley & Sons, Inc.

Gas‐separation applications of miscible blends of isomeric polyimides

AbstractBlends of polyimide isomers containing hexafluoroisopropylidene in the central moiety of the diamine residue have been studied. The isomers differed by having either a meta or a para linkage between the diamine and dianhydride residues. The miscibility of these materials was investigated by studying the glass transition temperature behavior using differential scanning calorimetry. Mixtures of isomer pairs, such as 6FDA–6FmDA and 6FDA–6FpDA, exhibited one glass transition temperature. Tg, and were therefore miscible. Mixtures of nonisomer pairs exhibited two Tg's and were immiscible. The gas sorption and transport properties of the blends of the 6FDA–6FmDA and 6FDA–6FpDA isomers were characterized for a variety of gases at 35°C for pressures up to 60 atm. The permeabilities and permselectivities in the miscible blends fell between those of the pure components and were approximately logarithmic averages of the pure component properties. The miscibility of the polyimide isomers enables one to tailor the composition of the material to optimize the gas separation and mechanical properties. © 1993 John Wiley & Sons, Inc.

Thermoplastic character of polyimide blends

AbstractPolyimide blends consisting of pyromellitic dianhydride/4,4′‐oxydianiline (PMDA/ODA) and biphenyl‐tetracarboxylic dianhydride/p‐phenylene diamine (BPDA/PDA) show a distinct glass transition behavior at temperatures lower than each component does. Disruption of molecular packing by blending of polymers having dissimilar interaction sites leads to a significant increase in molecular mobility at much lower temperatures. This is examined by laminating two pieces of film cast from the blend and measuring the adhesive strength at the interface. A strong adhesion, 11.5 N/cm (6.6 lbf/in) by 180° peel test, was achieved indicating interpenetration of polyimide molecules. It was also found that the polyimide blends can be converted into highly ordered states by mechanical deformation of the blends above their glass transition temperatures (Tgs).

Study on structure‐property relationship of polyimide blends, 2. Structure and miscibility of polyimide PBPI‐E/PTI‐E blends

AbstractThe structure and miscibility of polyimide PBPI‐E/PTI‐E blends were studied by wide‐ and small‐angle X‐ray scattering and dynamic mechanical analysis, where PBPI‐E is a biphenyldianhydride‐based polyimide, and PTI‐E is a polyimide from 4,4′‐thiodiphthalic anhydride and 4,4′‐oxydianiline. The results obtained show that there exists a paracrystalline structure in the blends with high content of PBPI‐E, but this does not affect the miscibility of the blends. The blends are miscible over the entire composition range, since only one Tg was observed for each blend. Meanwhile, the segregation of PTI‐E during crystallization of PBPI‐E in the blends is interlamellar.