• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.950-953
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• 2000

Aligning capabilities of nematic liquid crystal(NLC) using an in-situ photo-alignment method with obliquely polarized UV exposure on a polyimide (PI) surface for homeotropic alignment were studied. The high angle for NLC can be measured by obliquely UV exposure of 30°on the PI surface for 10∼20 min. The pretilt angle of NLC generated using the in-situ photo-alignment was higher than that of a conventional photo-alignment method. Finally, we suggest that the control of pretilt angle in NLC with obliquely polarized UV exposure during imidization of the polymer for homeotropic alignment is promising method to generate high pretilt angle.

• Electrical & Electronic Materials
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• v.9 no.1
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• pp.59-66
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• 1996

Polyimides containing cyclobutane ring in main chain is known to be thermally stable and able to be developed in organic solvents after photolysis with 254 nm UV light. This type of polyimides can be used as promising positive photoresist in VLSI fabrication process. In the current VLSI process, photoresist films are formed by spin coating. The film thickness is more than several hundred nano meters. It seems that there is room for improvement of film coating process by introducing Langmuir Blodgett technique. Thereby ultra thin film photoresist can be formed, and higher density of integration in VLSI be achieved. In the present work, depositing procedure of LB films of this polyimide was investigated. LB film thickness was measured by ellipsometry to evaluate deposited film status. Chemical imidization procedure was studied to avoid several problems in thermal imidization. The pattern of submicron dimension has successfully formed on LB film of 8nm thick, which found showing good contrast.

• Proceedings of the Materials Research Society of Korea Conference
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• 2001.05a
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• pp.125-125
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• 2001

• Proceedings of the Korean Fiber Society Conference
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• 2001.04a
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• pp.43-46
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• 2001

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.139.1-139
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• 1998

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.979-984
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• 1999

Aromatic soluble polyimides were synthesized from 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and various dianhydrides such as pyromelltic dianhydride(PMDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride(BTDA), and 4,4'-(hexafluoroisopropylidene)-bis(phthalic anhydride)(6FDA). Polyimides prepared by thermal imidization were insoluble in common organic solvents (acetone, MNP, DMAc, DMSO, THF, and DMF) but those prepared by chemical imidization were soluble. The difference of solubility was explained by esterification between hydroxyl group and $CH_3COO^-$ from acetic anhydride used as a dehydration agent in chemical imidization. Glass transition temperatures of polyimides by thermal method were higher than those by chemical method. All of the polyimides are stable up to $300^{\circ}C$ regardless of the sample preparation. The x-ray diffraction patterns showed that all polyimides were amorphrous.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.179-187
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• 1992

Poly(styrene-co-maliec anhydride) was reacted with aromatic amines such as aniline, p-toluidine, and p-chloroaniline in 10% (w/w) DMF solution to convert maleic anhydride units into maleimides. Optimum reaction conditions for cyclodehydration step of imide ring formation were : (a) reaction temp. of $80^{\circ}C$ (b) mole ratios of cyclodehydration agents : anhydride units in SMA/acetic anhydride/sodium acetate/triethyl amine= 1.0/2.0/0.2/1.1. $T_g$of SMI(imide modified SMA) was increased with increasing degree of imidization, but $T_g$leveled off in the early stage of imide content. And $T_g$of SMI was increased with the following order of amines used for imidization reagents : aniline < p-toluidine < p-chloroaniline.

• Polymer(Korea)
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• v.30 no.2
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• pp.158-161
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• 2006

Recently the application of plastic optical fiber (POF) in automotives and planes demands the heat-resistant and high refractive index con materials. We synthesized polyglutarimides (PGIs) via imidization of PMMA with primary amines under high pressure and high temperature and investigated thermal and optical properties by varying the molar ratio of amines and the type of amines (ethyl amine vs. isopropyl mine). The degree of imidization was calculated based on the peak intensity in $^1H$ NMR and FTIR. We found that the glass transition temperature $(T_g)$ of PGIs increased over $30^{\circ}C$ compared to the traditional core materials in POF, PMMA, and they are stable up to $300\sim400^{\circ}C$. PGIs anthesized with ethyl mine show the better heat resistance than those with isopropyl amines. Additionally, they show the comparable transparency and higher refractive index than PMMA. It implies that they can be utilized as the excellent photo-efficient and heat-resistant core materials in POF.

• Journal of Adhesion and Interface
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• v.5 no.1
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• pp.29-35
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• 2004

We have prepared polyster/nanQhybridized polyimide films in the range of 1~9 wt% of organophilic synthetic layered silicate (STN). Firstly, poly(amic acid)/STN nanocomposite solutions were prepared via solution blending method in DMAc or THF/MeOH solution, and then cast on the polyester film followed by imidization reaction, thermal and chemical method repestively. XRD and TEM experiment showed that the STN was fully exfoliated through the polyimide matrix. Surface morphologies of nanohybridized polyimide films were characterized by AFM and thermal, mechanical properties were also confirmed by TGA, DMA and UTM each. And also, the water vapor permeabilities highly depended on the content of STN. The sample from chemical imidization route and THF/MeOH solvent system showed better water vapor barrier properties than thermal one and DMAc system.

• Applied Chemistry for Engineering
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• v.5 no.5
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• pp.756-763
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• 1994

Using 2,2-Bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 2,2-bis-[4-(4-aminophenoxy)phenyl] hexafluoropropane and 4,4-diaminodiphenyl ether, the homopolyamic acids, copolyamic acids and blend of homopolyamic acids were prepared and converted to polyimide(PI)s by thermal imidization. In results, it has been found that a exchange reaction of polyamic acids can be occurred during thermal imidization. With measurement of mechanical properties, it was suggested that PI/PI molecular composite can be obtained by copolymerization or physical blending of homopolyamic acids.