pH-Sensitive Fluorinated Polyimides with Grafted Acid and Base Side Chains

Wang, W. C.; Vora, Rohitkumar H.; Kang, E. T.; Neoh, K. G.; Liaw, Der‐Jang

doi:10.1021/ie020830g

Cited by 25 publications

(23 citation statements)

References 47 publications

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“…The ozone treatment time was also varied to change the density of grafting points (initiation sites) on the PAmA chains. The dependence of peroxide concentration and molecular weight of PAmA on the ozone treatment time under similar experimental conditions had been reported earlier [32]. The number-average molecular weight of PAmA decreased, while the polydispersity increased, with the ozone treatment time.…”

Section: Methodssupporting

confidence: 84%

“…The dielectric constant decreases only slightly (to about 2.0) with further decrease in porosity to about 17 % for the nanoporous PI film prepared from the PAmA-g-PEGMA copolymer with a bulk graft concentration of 2.5 and an ozone pretreatment time of 15 min for the PAmA precursor (sample g, Table 1). Further increase in ozone pretreatment time of the PAmA precursor above 15 min led to a marked decrease in the molecular weight of the PAmA backbone, [32] resulting in the deterioration of the mechanical properties of the PI film obtained. The sluggish decrease in dielectric constant with porosity for PI films with porosity above 7 % and ozone pretreatment time above 5 min for the PAmA precursor can probably be attributed to the increased irregularity and non-uniformity in pore structure and film morphology (see Fig.…”

Section: Full Papermentioning

confidence: 99%

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Nanoporous Low‐κ Polyimide Films via Poly(amic acid)s with Grafted Poly(ethylene glycol) Side Chains from a Reversible Addition–Fragmentation Chain‐Transfer‐Mediated Process

Chen

Wang

et al. 2004

Adv Funct Materials

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Thermally‐initiated living radical graft polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) with ozone‐pretreated poly[N,N′‐(1,4‐phenylene)‐3,3′,4,4′‐benzophenonetetra‐carboxylic amic acid] (PAmA) via a reversible addition–fragmentation chain‐transfer (RAFT)‐mediated process was carried out. The chemical compositions and structures of the copolymers were characterized by nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), and molecular weight measurements. The “living” character of the grafted PEGMA side chains was ascertained in the subsequent extension of the PEGMA side chains. Nanoporous low‐dielectric‐constant (low‐κ) polyimide (PI) films were prepared by thermal imidization of the PAmA graft copolymers under reduced argon pressure, followed by thermal decomposition of the side chains in air. The nanoporous PI films obtained from the RAFT‐mediated graft copolymers had well‐preserved PI backbones, porosity in the range of 5–17 %, and pore size in the range of 30–50 nm. The pores were smaller and the pore‐size distribution more uniform than those of the corresponding nanoporous PI films obtained via graft copolymers from conventional free‐radical processes. Dielectric constants approaching 2 were obtained for the nanoporous PI films prepared from the RAFT‐mediated graft copolymers.

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Section: Methodssupporting

confidence: 84%

Section: Full Papermentioning

confidence: 99%

Nanoporous Low‐κ Polyimide Films via Poly(amic acid)s with Grafted Poly(ethylene glycol) Side Chains from a Reversible Addition–Fragmentation Chain‐Transfer‐Mediated Process

Chen

Wang

et al. 2004

Adv Funct Materials

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“…The chemical structures of FPI and AAc are shown in Figure 1. The PAAc-g-FPI copolymers of different PAAc graft concentrations were synthesized by thermally-induce graft copolymerization of AAc with the ozone pre-activated FPI in NMP and under different AAc to FPI molar feed ratios and had been characterized in detail [19]. Thin films of the PAAc-g-FPI copolymer were prepared by spin casting of a 20 wt.-% NMP solution of the copolymer on polished Si (100) wafers.…”

Section: Methodsmentioning

confidence: 99%

“…[17,18] Under thermal induction, the peroxide groups undergo decomposition to initiate the free radical graft copolymerization of vinyl monomers. Since ozone treatment of the FPI is also accompanied by degradation and scission of the polymer chains, the ozone pretreatment time was fixed to 5 min under the conditions [19] that give rise to 1. (1) in which the factor 43/2 accounts for the fact that there are 43 carbon atoms and two nitrogen atoms per repeat unit of the FPI chains, while the factor 3 accounts for the fact that there are 3 carbon atoms in each AAc unit.…”

mentioning

confidence: 99%

Nanoporous Ultra‐Low‐κ Films Prepared from Fluorinated Polyimide with Grafted Poly(acrylic acid) Side Chains

Wang

Vora

Kang³

et al. 2003

Advanced Materials

113

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ExperimentalMaterials: The PLED configuration used in this work was ITO/ PEDOT:MPS(50 nm)/polyfluorene:plystyrene(PS)(80 nm)/Ca(30 nm)/ Ag(250 nm). The ITO glass substrate was a product of Samsung Corning Co. and had a sheet resistance of 10 X/square. MPS used as a PE-DOT modifier was purchased from Dow Corning Co. PEDOT/polystyrenesulfonate (Bayer Co. Ltd.) was used as a HTL, and polyfluorene-based green copolymer (Green K2, Dow Chemical Co.):PS (1:1) blend was used as an LEP. A Ca and Ag double layer was used as a cathode for the devices.Device Fabrication: ITO glass substrates were cleaned with acetone and isopropyl alcohol in an ultrasonic bath for 15 min, respectively, and were dried at 120 C for 2 h before use. The ITO glass substrates were exposed to ultraviolet(UV)/ozone for 15 min and were spin coated with an aqueous PEDOT:MPS solution. The PEDOT:MPS solution was prepared by dissolving MPS in PEDOT solution at concentrations of 0, 0.1, 0.2, and 0.5 wt.-%. The mixed solution was stirred for 60 min to hydrolyze MPS. The hydrolyzed PEDOT:MPS solution was spin-coated on a UV/ozone-treated ITO substrate at a spin speed of 2000 rpm (rpm = revolutions per minute) to get a 500 nm thick HTL layer. After that, the PEDOT:MPS coated substrate was baked at 200 C for 10 min to remove residual solvent. The I±V±L characteristics and lifetime of PEDOT:MPS devices were measured with spin-coated devices. Spin coating of the LEP dissolved in toluene was carried out at a spin speed of 3000 rpm and 80 nm LEP thin film was obtained. The substrates were baked at 90 C for 60 min before cathode deposition. For LITI devices, LEP was spin coated on a poly(ethyleneterephthalate) donor film with a light to heat conversion layer at a thickness of 80 nm. The transfer of the LEP to the HTL layer was performed with a Nd:YAG laser with a total power of 8 W. The LEP-coated donor film was placed on the HTL-coated substrates and was closely adhered to the substrates using vacuum chuck to remove the gap between the donor film and the substrates. The donor film was then exposed to the Nd:YAG laser beam and the exposed LEP was transferred to the substrates. After LITI transfer, the donor film was peeled off and the substrate was baked at 90 C for 60 min. After baking, Ca was deposited at a rate of 0.5 s ±1 followed by Ag evaporation at a rate of 5 s ±1 in a high vacuum chamber (» 10 ±7 torr) as a cathode for devices. The thickness of Ca and Ag was 30 nm and 230 nm, respectively. After cathode deposition, the devices were encapsulated with a metal can and barium oxide.Measurements: I±V±L characteristics of the devices were measured with a PR 650 spectrophotometer and lifetime results were obtained at a constant current mode at a brightness of 500 cd m ±2 . The indium diffusion in PEDOT:MPS devices was analyzed with XPS. The XPS measurements of the coated samples were carried out in ultra-high vacuum chamber ESCALAB 250(VG scientific) with a monochromated Al Ka source was used for analysis; etching of the samples was performed with Ar ion sputter...

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“…The dependence of peroxide concentration and molecular weight of PAA on the ozone treatment time under similar experimental conditions had been reported earlier. 37 The number average molecular weight of PAA decreased, while the polydispersity increased, with the ozone treatment time. In this case, the molecular weights (M n 's) of PAA before and after ozonepretreatment for 5 min are 81,300 and 65,600, respectively.…”

Section: Graft Copolymerizationmentioning

confidence: 97%

Low‐κ nanocomposite films based on polyimides with grafted polyhedral oligomeric silsesquioxane

Chen

Nie

et al. 2005

J of Applied Polymer Sci

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Nanocomposites of polyimides (PI) with covalently grafted polyhedral oligomeric silsesquioxane (R7R′Si8O12 or POSS) units were prepared by thermally‐initiated free‐radical graft polymerization of methacrylcyclopentyl‐POSS (MA‐POSS) with the ozone‐pretreated poly[N,N′‐(1,4‐phenylene)‐3,3′,4,4′‐benzophenonetetra‐carboxylic amic acid] (PAA), followed by thermal imidization. The chemical composition and structure of the PI with grafted methacrylcyclopentyl‐POSS side chains (PI‐g‐PMA‐POSS copolymers) were characterized by nuclear magnetic resonance (NMR), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). The POSS molecules in each grafted PMA side chain of the amorphous PI films retained the nanoporous crystalline structure, and formed an aggregate of crystallites. The PI‐g‐PMA‐POSS nanocomposite films had both lower and tunable dielectric constants, in comparison with that of the pristine PI films. Dielectric constants (κ's) of about 3.0–2.2 were obtained. The present approach offers a convenient way for preparing low‐κ materials based on existing PI's. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

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pH-Sensitive Fluorinated Polyimides with Grafted Acid and Base Side Chains

Cited by 25 publications

References 47 publications

Nanoporous Low‐κ Polyimide Films via Poly(amic acid)s with Grafted Poly(ethylene glycol) Side Chains from a Reversible Addition–Fragmentation Chain‐Transfer‐Mediated Process

Nanoporous Low‐κ Polyimide Films via Poly(amic acid)s with Grafted Poly(ethylene glycol) Side Chains from a Reversible Addition–Fragmentation Chain‐Transfer‐Mediated Process

Nanoporous Ultra‐Low‐κ Films Prepared from Fluorinated Polyimide with Grafted Poly(acrylic acid) Side Chains

Low‐κ nanocomposite films based on polyimides with grafted polyhedral oligomeric silsesquioxane

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