• Polymer(Korea)
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• v.33 no.4
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• pp.313-318
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• 2009

Copolyimides were synthesized from bis (3-aminophenyl) sulfone (APS) and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) containing a fluorine substituent ($-CF_3$) with different mole ratios of 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA) containing a sulfone group (-$SO_2$-). The PI films were obtained from poly (amic acid) (PAA) by solution casting through thermal imidization on a glass plate. Wide-angle X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), universal tensile machine (UTM) measurements, and UV-Vis spectrometry were used to assess thermo-mechanical properties, morphology, and optical transparency. Thermal properties and optical transparency decreased with increasing DSDA mole fraction. In contrast, mechanical properties increased with increasing DSDA mole fraction. As compared to conventional PI films, however, the PI copolymer films in this work were found to exhibit better optical transparency.

• Polymer(Korea)
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• v.38 no.6
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• pp.774-781
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• 2014

Acetylenic or phenylethynyl end-capped polyisoimide oligomers ($M_w$ 2500 g/mol, 5000 g/mol) based upon 4,4'-diamino diphenyl ether (4,4'-ODA)/4,4'-oxydiphthalic anhydride (ODPA) and 4,4'-ODA/3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA) were synthesized by using 4-ethynylaniline (4-EA) or 4-phenylethynyl phthalic anhydride (4-PEPA) as an end capper. The incorporation of ethynyl groups were confirmed by FTIR spectroscopy. The isomerization temperature was influenced by molecular weight as well as the backbone structure of polyisoimides oligomers. Thus, polyisoimide oligomers with molecular weight of 2500 g/mol was found to be imidized at temperature $10^{\circ}C$ lower than that for the oligomers with molecular weight of 5000 g/mol. The crosslinking reaction of ethynyl groups occurred at a higher temperature than that for the isoimide/imide isomerization reaction. These two reactions were totally or partially overlapped on the DSC thermograms for the polyisoimide oligomer end-capped with 4-EA. Kinetics of thermal imidization and crosslinking reactions for the 4,4'-ODA/ODPA polyisoimide oligomers end-capped with 4-PEPA were investigated by performing dynamic DSC experiments at heating rate of $10^{\circ}C/min$. The activation energy and pre-exponential factors were 141 kJ/mol and $1.45{\times}10^{13}min^{-1}$ for the imidization reaction and 177 kJ/mol and $2.90{\times}10^{13}min^{-1}$ for the crosslinking reaction, respectively.

• Polymer(Korea)
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• v.36 no.3
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• pp.275-280
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• 2012

Poly(amic acid)s were successfully synthesized from 1,4-bis(4-aminophenoxy)benzene (1,4-APB) or 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP) with pyromellitic dianhydride (PMDA), 3,3'-4,4'-benzopenonetetracarboxylic dianhydride (BPDA) and $p$-phenylenediamine ($p$-PDA) and then they were effectively converted into polyimide films by thermal imidization. The chemical structure and thermo-mechanical properties of polyimide films were examined using Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analyzer (TGA), thermo-mechanical analyzer, dynamic mechanical analyzer (DMA) and universal tensile machine (UTM). The moisture absorption, thermal and mechanical properties of polyimide films decreased with increasing the amount of 1,4-APB and HFBAPP. The polyimide films using HFBAPP showed lower properties than that of 1,4-APB at the same ratio, but it displayed better thermal properties and lower moisture absorption at the similar coefficient of thermal expansion (CTE) with a copper. On the basis of our finding, it is concluded that 4-component polyimide films could be utilized for base films for flexible copper clad laminates (FCCL) of flexible printed circuit boards.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.623-626
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• 2011

Various poly(amic acid)s were synthesized from PMDA/BPDA/p-PDA/ODA with different mole ratios and effectively converted into 4-component polyimide films by thermal imidization. The chemical structures and thermo-mechanical properties of polyimide films were examined using Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analyzer (TGA), thermo-mechanical analyzer (TMA), dynamic mechanical analyzer (DMA) and universal tensile machine (UTM). The tensile strength, modulus, and thermal properties of polyimides films increased with the amount of rigid PMDA and p-PDA, while the elongation and moisture absorption of polyimide films increased with the amount of flexible BPDA and ODA. One of 4-component polyimide films exhibited a similar coefficient of thermal expansion (CTE) value to that of copper when it was composed of PMDA : BPDA : p-PDA : ODA with the ratio of 5 : 5 : 4 : 6. Thus, this polyimide film could be useful for a base film for flexible copper clad laminates (FCCL) of flexible printed circuit boards.

• Polymer(Korea)
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• v.38 no.6
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• pp.752-759
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• 2014

Crosslinked polyimides (PIs) were synthesized by reacting 4,4'-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) and 2,2'-bis(trifluoromethyl)benzidine (TFDB) with various ratios of the cross-linkable, end-capping agent cis-1,2,3,6-tetrahydrophthalic anhydride (CDBA) via ring-opening metathesis polymerization. Residual stress behaviors were investigated in-situ during thermal imidization of the crosslinked PI precursors using a thin film stress analyzer (TFSA) by wafer bending method. The thermal properties were investigated via differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and thermogravimetric analysis (TGA). The optical properties were measured by ultraviolet-visible spectrophotometer (UV-vis) and spectrophotometry. All properties were interpreted with respect to their morphology of crosslinked networks. With increasing the amounts of the end-capping agent, the residual stress decreased from 27.9 to -1.3 MPa, exhibited ultra-low stress and high thermal properties. The minimized residual stress and enhanced thermal properties of the crosslinked PI makes them potential candidates for versatile high-density multi-layer structure applications.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.305-312
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• 2005

Poly(urethane-imide)s were prepared by reaction between crosslinkable endgroup containing soluble polyimide (PI) by chemical imidization and acrylate end-capped polyurethane (PU). Poly (amic acid) was prepared from 2,2'-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 4,4'-oxydianiline (ODA) and then end-capped with maleic anhydride (MA). The PU prepolymers were prepared by the reaction of polycaprolactone diol, tolylene 2,4-diisocyanate and end-capped with hydroxyl ethyl acrylate. The effect of PU content on the residual stress behavior, morphology and thermal property was studied. The poly(urethane-imide)s were characterized by thin film stress analyzer (TFSA), XRD, TGA and DMTA. Low residual stress and slope in cooling curve were achieved by higher PU content. Compared to typical polyurethane, these polymers exhibited better thermal stability due to the presence of the imide groups. Finally the residual stress of poly(urethane-imide)s was strongly affected by the morphological structure.

• Journal of Adhesion and Interface
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• v.10 no.2
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• pp.98-105
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• 2009

Poly(amic acid) was synthesized from the reaction of p-PDA/ODA and PMDA/BPDA and silane oligomer containing epoxy group was also synthesized from the reaction of tetramethylorthosilicate (TMOS) and glycidol. After hybridizing poly (amic acid) and silane oligomer, they were effectively converted into polyimide/silica hybrid films by thermal imidization process. As the silica contents in hybrid films increased, CTE values decreased from 17 ppm/K to 10 ppm/K and the tensile modulus increased, in spite of decreasing tensile strength. In addition, the peel test showed that the adhesion strength of hybrid film was enhanced from $0.43kg_f/cm$ to $1.02kg_f/cm$. Therefore, it could be concluded that the polyimide/silica hybrid film is effective to enhance adhesion strength for FCCL films.

• Polymer(Korea)
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• v.26 no.6
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• pp.701-709
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• 2002

To synthesize a new positive photosensitive polyimide precursor, parts of carboxylic acid groups in poly (amic acid) were esterified with 4,5-dimethoxy-2-nitrobenzyl bromide in the presence of K$_2$CO$_3$/HMPA followed by the chemical imidization of residual carboxylic acid units. The chemical structure of resulting polymer was characterized by $^1$H-NMR, UV/vis and FT-IR spectroscopic methods, and its thermal properties were examined by DSC and TGA. Upon UV irradiation, 4,5-dimethoxy-2-nitrobenzyl moiety underwent the photodegradation. As a result, the polymer became soluble in alkaline developer due to the formation of carboxylic acid moiety, which was used to make a micron-sized positive pattern. Sensitivity curves were obtained from the gel fraction experiments with respect to the various 4,5-dimethoxy-2-nitrobenzyl ester contents. From those curves, the sensitivity was ranged iron 4000 to 6000 mJ/㎠, and the contrast was measured to be from 3.1 to 4.9.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.2
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• pp.23-30
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• 1999

The relationships between morphological structures and residual stress behaviors of polyimide thin films depending on isomeric diamines were investigated. For this study, Poly(phenylene biphenyltetracarboximide) (BPDA-PDA) and poly(oxydiphenylene biphenyltetracarboximide) (BPDA-ODA) films were prepared from their isomeric diamines: 1,3-phenylene diamine (1,3-PDA) 1,4-phenylene diamine (1.4-PDA), 3,4'-oxydiphenylene diamine (3,4'-ODA), and 4,4'-oxydiphenylene diamine (4,4'-ODA), respectively. For those films, residual stresses were detected in-situ during thermal imidization of the isomeric polyimide as a function of processing temperature over the range of 25~$400^{\circ}C$ using. Thin Film Stress Analyzer (TFSA). In comparison, residual stress of BPDA-1.4PDA having better in-plain orientation and chain order was the lowest value of 7MPa whereas those of BPDA-1,3-PDA, BPDA-3,4'-ODA, and BPDA-4,4'-ODA were in the range of 40-50MPa. Conclusively, the effect of morphological nature (chain rigidity, chain order, orientation) and chain mobility relating to the g1ass transition behavior on the residual stress of isomeric polyimide thin films wart analyzed.

• Polymer(Korea)
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• v.31 no.2
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• pp.130-135
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• 2007

To enhance the thermo-mechanical properties of polyimide films which have potential application for the FCCL, we have synthesized the poly (amic acid) s composed of 4-components PMDA/BTDA and PDA/ODA as monomer system, u4 then they were effectively converted into 4-component polyimide films by thermal imidization process. It has been found that CTE values in the range of $100\sim200^{\circ}C$ decreased with the amount of PDA, which also caused 36% and 59% increases in tensile modulus and strength respectively. And also, peel test results on 3-layered copper clad laminate using 4-component polyimide films showed excellent adhesion strength above 1.8 kgf/cm. On the basis of obtained results it can be concluded that 4-component polyimide films may be applied for the high performance FCCL base films.