Synthesis and characterization of a positive‐working,aqueous‐base‐developable photosensitive polyimide precursor

A positive‐working, aqueous‐base‐developable photosensitive polyimide precursor based on poly(amic ester)‐bearing phenolic hydroxyl groups and a diazonaphthoquinone photosensitive compound was developed. The poly(amic ester) was prepared from a direct polymerization of 2,2′‐bis‐(3‐amino‐4‐hydroxyphenyl)hexafluoropropane and bis(n‐butyl)ester of pyromellitic acid in the presence of phenylphosphonic dichloride as an activator. Subsequently, the thermal imidization of the poly(amic ester) precursor at 300°C produced the corresponding polyimide. The inherent viscosity of the precursor polymer was 0.23 dL/g. The cyclized polyimide showed a glass‐transition temperature at 356°C and a 5% weight loss at 474°C in nitrogen. The structures of the precursor polymer and the fully cyclized polymer were characterized by Fourier transform infrared spectroscopy and ¹H‐NMR. The photosensitive polyimide precursor containing 25 wt % diazonaphthoquinone photoactive compound showed a sensitivity of 150 mJ/cm² and a contrast of 1.65 in a 3 μm film with 1.25 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 10 μm was obtained from this composition. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 352–358, 2002     

A positive‐working photosensitive polyimide based on thermal cross‐linking and acidolytic cleavage

A novel positive‐working photosensitive polyimide (PSPI) based on a poly(hydroxyimide) (PHI), a crosslinking agent having vinyl ether groups, and a photoacid generator (PAG) was prepared. The PHI as a base resin of the three‐component PSPI was synthesized from 4,4′‐oxydiphthalic anhydride and 2,2′‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane through ring‐opening polymerization and subsequent thermal cyclization. 2,2′‐bis(4‐(2‐(vinyloxy)ethoxy)phenyl)propane (BPA‐DEVE) was used as a vinylether compound and diphenyliodonium 5‐hydroxynaphthalene‐1‐sulfonate was used as a PAG. The phenolic hydroxyl groups of the PHI and the vinyl ether groups of BPA‐DEVE are thermally crosslinked with acetal structures during prebake step, and the crosslinked PHI becomes completely insoluble in an aqueous basic solution. Upon exposure to UV light (365 nm) and subsequent postexposure bake (PEB), a strong acid generated from the PAG cleaves the crosslinked structures, and the exposed area is effectively solubilized in the alkaline developer. The dissolution behavior of the PSPI containing each 11.5 wt % of BPA‐DEVE and of the PAG was studied after UV exposure (365 nm) and PEB. It was found that the difference in dissolution rates between exposed and unexposed areas was enough to get high resolution. A fine positive pattern with a resolution of 5 μm in a 3.7‐μm‐thick film was obtained from the three‐component PSPI. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel positive‐type photosensitive polyimide with low dielectric constant

A novel positive‐type photosensitive polyimide (PSPI) with a low dielectric constant was developed. The PSPI system was composed of soluble block PI (Bco‐PI) with a hydroxy group and diazonaphthoquinone as a photoreactive compound. The base Bco‐PI was prepared by a direct one‐pot polycondensation of 2,2‐bis(3‐amino‐4‐hydroxy‐phenylhexafluoropropane), 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane, and cyclohexanetetracarboxylic dianhydride in the presence of a γ‐valerolactone and pyridine catalyst system using N‐methyl‐2‐pyrrolidone as the solvent. The film of Bco‐PI was colorless and transparent, both important factors for a PSPI. Photosensitive soluble block PI (Bco‐PI), containing 20 wt % ester of 2,3,4‐trihydroxybenzophenone with 1,2‐naphthoquinone‐(2)‐diazide‐5‐sulfonic acid (NT200), showed a sensitivity of 350 mJ/cm² and a contrast of 1.20 when it was exposed to UV light, followed by development with 5% tetramethylammonium hydroxide aqueous solution at room temperature. The estimated optical dielectric constants of the PIs with and without NT200 were 2.68 and 2.75, respectively. These values were significantly lower than those of conventional aromatic PIs, such as Kapton film (50EN). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 15–21, 2005     

Synthesis and characterization of novel negative-working aqueous base developable photosensitive polyimide precursors

Through molecular designing, three poly(amic esters) (PAEs) have been synthesized from pyromellitic dianhydride (PMDA), 2,2′-bis-(3-amino-4-hydroxyphenyl) hexafluoropropane (BisAPAF), 4,4′-diaminodiphenyl ether (4,4′-ODA) and 2-hydroxyethyl methacrylate (HEMA). Due to the introduction of photosensitive acrylate groups and aqueous base soluble phenolic hydroxyl groups in the backbone, these poly(amic esters) can be used as the precursors of negative-working, aqueous base developable photosensitive polyimides (PSPIs). These poly(amic esters) were prepared by direct polymerization by using phenyl phosphonic dichloride (PPD) as an activator. The inherent viscosities of these polymers were 0.20 (dL/g). Their structures were characterized by Fourier transform infrared spectroscopy (FTIR) and ¹H NMR. In order to improve the photolithographic performance of these PSPIs, different photosensitizers, photoinitiators and a crosslinker have been added in the PSPI formulations. Among them, the Michler's ketone (MK)/tribromomethyl phenyl sulfone (TBPS) system gave the best results. Using a 2.38 wt% aqueous TMAH solution as a developer, patterns with a resolution of 10 μm were obtained from these PSPI formulations. In addition, the effects of the molecular structure of the precursors and the concentration of developer on the photosensitivity of the PSPI formulations were also discussed.     

A novel positive photosensitive polybenzoxazole based on a tetrahydropyranyl (THP) protected polyhydroxyamide

Summary A new positive working, aqueous base developable photosensitive polybenzoxazole (PBO) precursor composition based on a partially tetrahydropyranyl (THP) protected PBO precursor and a Bisphenol A based 1,2-naphthoquinone diazide-4-sulfonate (DNQ-4) photosensitive compound has been developed. The polymer was prepared from a low temperature polymerization of 2 , 2'-bis-(3-amino-4-hydroxyphenyl) hexafluoropropane (BisAPAF) and isophthaloyl chloride (IC), followed by reacting with 3,4-Dihydro-2H-pyran in the presence of p-toluenesulfonic acid monohydrate as a catalyst. The photosensitive PBO precursor containing 20wt % DNQ-4 photosensitive compound showed a sensitivity of 221 mJ/cm² and a contrast of 1.44 in a 3 m film with a 0.6wt % tetramethylammonium hydroxide (TMAH) developer. A pattern with a resolution of 10 m was obtained from this composition. The novel PBO precursor photosensitive composition showed a significant improvement in dark film loss after development, which can and could be used to make a thick film resist.     

A novel positive‐type photosensitive polyimide having excellent transparency based on soluble block copolyimide with hydroxyl group and diazonaphthoquintone

A novel positive‐type photosensitive polyimide having excellent transparency based on soluble block copolyimide (Bco‐PI) with hydroxyl group and diazonaphthoquinone (DNQ) as a photoreactive compound was developed. The base Bco‐PI A was prepared by a direct one‐pot polycondensation of cyclohexanetetracarboxylic dianhydride (H‐PMDA), 2,2‐bis(3‐amino‐4‐hydroxyphenylhexafluoropropane) (Bis‐AP‐AF), and bis(4‐(3‐aminophenoxy)phenyl)sulfone (m‐BAPS) in the presence of a γ‐valerolactone and pyridine catalyst system by using dipolar aprotic solvent such as N‐methyl‐2‐pyrrolidone (NMP).The wholly aromatic polyimides have strong absorptions in the visible regions, because of their change–transfer complex formation. On the other hand, alicyclic dianhydride, H‐PMDA, contributed to the resulting Bco‐PI film with colorlessness and transparency, which are the important factors for a photosensitive polyimide. Photosensitive Bco‐PI, containing 20 wt % 1,2‐naphthoqiunonediazide‐5‐sulfonic acid p‐cresol ester (PC5), showed a sensitivity of 250 mJ/cm² and a contrast of 2.56 when it was exposed to UV light, followed by development with 5% tetramethylammonium hydroxide (TMAH) aqueous solution at room temperature. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1619–1624, 2005     

A novel positive‐type photosensitive polyimide based on soluble block copolyimide showing low dielectric constant with a low‐temperature curing process

A soluble block copolyimide (Bco‐PI) was prepared by direct one‐pot polycondensation of 2,2‐bis‐(3‐amino‐4‐hydroxyphenyl)hexafluoropropane, 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane, and cyclohexane‐tetracarboxylic dianhydride in the presence of γ‐valerolactone and a pyridine catalyst system using γ‐butyrolactone as the solvent. The thermal transmission temperature (T_g) of Bco‐PI was 282°C. By having the curing process occur at 250°C, which was below the T_g, colorless and transparent films could be obtained. The film showed excellent optical characteristics. Such properties could not be attained by the conventional high‐temperature thermal imidization process of poly(amic acid). The hydroxy groups in the polyimide backbone gave the Bco‐PI the potential to become alkaline. To the Bco‐PI was added 15 wt % ester of 2,3,4‐trihydroxybenzophenone with 1,2‐naphthoquinone‐(2) diazide‐5‐sulfonic acid (NT200) as the photoreactive compound. The system worked as a positive‐type photosensitive polyimide (PSPI). The sensitivity and contrast of the PSPI system were 220 mJ/cm² and 1.27, respectively, when exposed to UV light, followed by development with a 5% tetramethylammonium hydroxide (TMAH) aqueous solution at room temperature. After curing at 250°C for 1 h, the average refractive index of Bco‐PI with and without NT200 was 1.5543 and 1.5563, and the optically estimated dielectric constant of the polyimides was 2.66 and 2.67, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4240–4246, 2006     

Positive‐working aqueous base developable photosensitive polybenzoxazole precursor/organoclay nanocomposites

Positive‐working aqueous base developable photosensitive polybenzoxazole (PBO) precursor/organoclay nanocomposites have been prepared through the addition of an organoclay to a PBO precursor. The organoclay was formed by a cation exchange reaction between a Na⁺‐montmorillonite clay and an ammonium salt of dodecylamine. The PBO precursor used in this study was a polyhydroxyamide that was prepared from a low‐temperature polymerization of 2′2′‐bis(3‐amino‐4‐hydroxyphenyl) hexafluoropropane and 4,4′‐oxydibenzoyl chloride with an inherent viscosity of 0.3 dL/g. The photosensitive resin/clay formulations were prepared from the precursor with 2,3,4‐tris(1‐oxo‐2‐diazonaphthoquinone‐5‐sulfonyloxy)‐benzophenone photosensitive compound and 3–5 wt % organoclay. The PBO precursor/clay was subsequently thermally cured to PBO/clay at 350°C. Both X‐ray diffraction and transmission electron microscope analyses showed that the organoclay was dispersed in the PBO matrix in a nanometer scale. The thermal expansion coefficient of PBO/clay film, which contained 5 wt % organoclay, was decreased 33% compared to the pure PBO film. The PBO/clay nanocomposite films also displayed higher thermal stability, glass transition temperature, and water resistance than the pure PBO film. The photosensitive PBO precursor/clay nanocomposite showed a line/space pattern with a resolution of 5 μm and its sensitivity and contrast were not affected by the organoclay. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2350–2356, 2005     

Positive‐tone,aqueous‐developable,polynorbornene dielectric: Lithographic,and dissolution properties

A positive‐tone, aqueous base soluble, polynorbornene (PNB) dielectric formulation has been developed. The photolithographic solubility switching mechanism is based on diazonaphthoquinone (DNQ) inhibition of PNB resin functionalized with pendent fluoroalcohol and carboxylic acid substituents. The optical contrast (at 365 nm) was found to be 2.3. The maximum height‐to‐width aspect ratio of developed line and space features was 3 : 2. The sensitivity, D₁₀₀, of a formulation containing 20 pphr of DNQ photoactive compound (PAC) was calculated to be 408 mJ cm^?2. The effects of the PAC molecule structure on miscibility and dissolution of the photosensitive films in aqueous base developer were studied. The effect of the monomer composition of the PNB polymer on the dissolution rate of the formulated PNB resin was evaluated. A unique dissolution and swelling behavior was observed. The effect is attributed to a copolymer synthesized with two monomers each of which is susceptible to deprotonation in aqueous base. FTIR measurements showed that the pure PNBFA has a small percentage of free hydroxyl groups, which did not change appreciably by the addition of PAC to the mixture. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of negative‐type polyamic acid ester with 1‐methacryloyloxy‐2‐propanoate group

A negative‐type photosensitive polyamic acid (PAA) was synthesized from cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride and 2‐(methacryloyloxy)ethyl 3,5‐diaminobenzoate in N‐methyl‐2‐pyrrolidinone. Glycidyl methacrylate was added into the PAA solution to yield a photosensitive PAA ester (PAE) by the ring‐opening esterification reaction of the carboxylic acid group in the PAA and glycidyl methacrylate. Esterification reactions were conducted with varying reaction temperatures and times. The typical PAE (PAE‐C3) with a degree of esterification of 20% was used for a photosensitivity study. We investigated the effects of the postexposure baking temperature, amount of photoinitiator, and exposure dose on the photosensitivity of PAE‐C3. Furthermore, a photolithography evaluation was conducted on PAE‐C3 in the presence of 1‐[4‐(phenylthio)phenyl]‐2‐(O‐benzoyloxime)‐1,2‐octanedione as a photoinitiator using a mercury lamp at a 365‐nm wavelength. The resolution of the film with 2.0‐μm thickness was about 8 μm. PAE‐C3 cured at 250°C for 60 min was stable up to around 310°C in a nitrogen atmosphere. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2252–2258, 2006     

Synthesis and characterization of negative‐type photosensitive polyimides based on cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride

A series of negative‐type photosensitive polyamic acids (PAAs) with various molecular weights was synthesized from cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride, 2‐(methacryloyloxy)ethyl‐3,5‐diaminobenzoate, and 2‐(methacryloyloxy)ethyl‐4‐aminobenzoate in N‐methyl‐2‐pyrrolidone. We investigated the degree of planarity, transmittance, and thermal stability for the PAAs after the photoirradiation reaction at an exposure dose of 200 mJ/cm². The films prepared from the PAA with the lowest molecular weight (PAA‐1) exhibited a higher degree of planarity and transmittance compared with those of the film prepared from the PAA with the highest molecular weight (PAA‐4). The initial decomposition temperatures of the cured PAAs with different molecular weights were similar and were stable up to around 300°C. Further, the photosensitivity and transmittance of PAA‐1 were investigated in the presence of photoinitiators at 365–400 nm with a high‐pressure mercury lamp. The resolution of the photocured film was about 50 μm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2300–2308, 2005     

Main-chain photosensitive polyamic acids using alkaline aqueous solution as developer

In order to develop photosensitive polyimides (PSPIs) imaged in alkaline aqueous solution, a photosensitive diamine and relevant polymer containing conjugated double bonds in the main chain have been synthesized. The photosensitive characteristics and thermal stability of the polymers were investigated. These polymers possess good thermal stability and sensitivity to UV irradiation, and could be used to form a PSPI resist using alkaline aqueous solution as developer. © 1999 Society of Chemical Industry     

Preparation and properties of thermally conductive photosensitive polyimide/boron nitride nanocomposites

A new thermally conductive photoresist was developed. It was based on a dispersion of boron nitride (BN) nanoflakes in a negative‐tone photosensitive polyimide (PSPI) precursor. 3‐Mercaptopropionic acid was used as the surfactant to modify the BN nanoflake surface for the dispersion of BN nanoflakes in the polymer. The thermal conductivity of the composite films increased with increasing BN fraction. The thermal conductivity of the PSPI/BN nanocomposite was up to 0.47 W m⁻¹ K⁻¹ for a mixture containing 30 wt % nanosized BN filler in the polyimide matrix. Patterns with a resolution of 30 μm were obtained from the PSPI/BN nanocomposites. The PSPI/BN nanocomposites had excellent thermal properties. Their glass‐transition temperatures were above 360°C, and the thermal decomposition temperatures were over 460°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Photosensitive polycarbonates based on reaction development patterning (RDP)

Summary Films of commercially available poly(bisphenol A carbonate) (BPA-PC) and poly[bisphenol A carbonate-co-4,4'-(3,3,5-trimethylcyclohexylidene)diphenol carbonate] (BPA-TMC-PC) containing photosensitive agent (diazonaphthoquinone (DNQ) compound) were prepared by spin-coating onto copper foil. The obtained films showed positive-tone behavior by UV irradiation and following development with ethanolamine/N-methylpyrrolidone (NMP)/H₂O mixture (1/1/1 by weight). The scanning electron microscope (SEM) photographs of the resulting images exhibited fine patterns (∼10 μm line/space resolution) with 15–16 μm film thickness. The pattern forming mechanism is based on the Reaction Development Patterning (RDP), in which the carboxylic acid resulting from photo-rearrangement of DNQ in the film attracts ethanolamine in the developer and the amine reacts with carbonate in the main chain to induce degradation of the polymer. RDP, where the main pattern forming reaction occurs during the development, is proved to be efficient for polycarbonates as well as polyimide. Received: 11 July 2001/Accepted: 1 August 2001     

Preparation and properties of UV‐curable fluorinated polyurethane acrylates

A series of UV‐curable polyurethane acrylates (PUA0, FPUA3, FPUA6, FPUA 9 FPUA12, FPUA15, where the numbers indicate the wt % of perfluoroalkyl acrylate), were prepared from a reactive oligomer [4,4 ?‐dicyclohexymethanediisocyanate(H12MDI)/ poly(tetramethylene glycol)(PTMG)/2‐hydroxyethyl methacrylate (HEMA): 2/1/2 molar ratio, prepolymer:40 wt %] and diluents [methyl methacrylate (MMA, 20 wt %)/ isobornyl acrylate (IBOA, 40–25 wt %)/heptadecafluorodecyl methacrylate (PFA, 0–15 wt), total diluents: 60 wt %]. This study examined the effect of PFA/IBOA weight ratio on the properties of the UV‐curable polyurethane acrylates for antifouling coating materials. The as‐prepared UV‐curable coating material containing a 15 wt % PFA content in diluents (MMA/IBOA/PFA) form a heterogeneous mixture, indicating that a PFA content of approximately 15 wt % was beyond the limit of the dilution capacity of diluents for the oligomer. In the wavelength range of 400–800 nm, the UV‐cured PUA0 film sample was quite transparent (transmittance%: near 100%). On the other hand, the transmittance% of the FPUA film sample decreased markedly with increasing PFA content. XPS showed that the film‐air surface of the UV‐cured polyurethane acrylate film had a higher fluorine content than the film‐glass dish interface. As the PFA content increased from 0 to 12 wt %, the surface tension of the UV‐cured urethane acrylates decreased from 26.8 to 15.6 mN/m, whereas the water/methylene iodide contact angles of the film–air surface increased from 90.1/63.6° to 120.9/87.1°. These results suggest that the UV‐curable polyurethane acrylates containing a PFA content up to 12 wt % have strong potential as fouling‐release coating materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40603.     

Enzymatic removal of 3‐monochloro‐1,2‐propanediol (3‐MCPD) and its esters from oils

3‐Monochloro‐1,2‐propanediol (3‐MCPD) is a contaminant in processed food well known for about 30 years. More recently, this compound has observed attendance due to its occurrence as fatty acid esters in edible oils and products derived from them. In this study, the first enzymatic approach to remove 3‐MCPD and its esters from aqueous and biphasic systems by converting it into glycerol is described. First, 3‐MCPD was converted in an aqueous system by an enzyme cascade consisting of a halohydrin dehalogenase from Arthrobacter sp. AD2 and an epoxide hydrolase from Agrobacterium radiobacter AD1 with complete conversion to glycerol. Next, it could also be shown, that the corresponding oleic acid monoester of 3‐monochloropropanediol‐1‐monooleic‐ester (3‐MCPD‐ester) was converted in a biphasic system in the presence of an edible oil by Candida antarctica lipase A to yield free 3‐MCPD and the corresponding fatty acid. Hence, also 3‐MCPD‐esters can be converted by an enzyme cascade into the harmless product glycerol. Practical applications: Since several reports have been recently published on the contamination of foods with 3‐MCPD and its fatty acid esters, there is a great demand to remove these compounds and an urgency to find useful methods for this. In this contribution, we present an easy enzymatic way to remove 3‐MCPD and its esters from the reaction media (i.e., plant oil) by converting it to the nontoxic glycerol. The method requires neither high temperature nor organic solvents.     

A chemically amplified positive-working photosensitive polyimide based on a blend of poly(amic acid ethoxymethyl ester) and poly(amic acid)

We prepared a novel chemically amplified photosensitive polyimide based on a blend of poly(amic acid ethoxymethyl ester) (PAAE) and poly(amic acid); this blend produces polyimide (PI) films with improved mechanical properties after imidization with photoacid generator (PAG). PAAE and poly(amic acid) were end-capped with 5-norbornene-2,3-dicarboxylic dianhydride and 2,3-dimethyl maleic anhydride, respectively, to lower their molecular weights without compromising the properties of the resulting PI films. As a result of the blending of these PI precursors, the mechanical properties of the PI films were found to be less affected by the strong acid generated from the PAG than PI films fabricated by imidization of PAAE alone. The relatively high solubility of the blended PI precursor film in basic aqueous solutions was found to be effectively controlled by the use of a high-temperature post-exposure bake process to partially imidize the end-capped PAA. It was found that a 10-μm-thick film of the PSPI precursor system containing 13 wt% PAGs exhibits a sensitivity (D⁰) of 700 mJ/cm² when developed with 2.38 wt% aqueous tetramethyl ammonium hydroxide solution at room temperature. A fine positive pattern was fabricated in a 12 μm thick film with 1000 mJ/cm² of i-line exposure. The resultant PI film was also found to exhibit excellent mechanical and thermal properties, which are critical to its practical use as a stress buffer layer in semiconductor packaging.     

Mahua‐oil‐based resins for the high‐temperature curing of fly ash coatings

We attempted to prepare medium‐oil‐length glycerol alkyds based on Mahua oil. Fatty acids were isolated from the oil and used in the preparation of alkyds by the fusion method. The resins were characterized by IR spectroscopic analysis. The physicochemical and film properties of these resins were also studied. IR analysis of the resins revealed the formation of phthalate esters showing characteristic peaks at 1720 cm^?1. The resin was modified with melamine formaldehyde, which cured at high temperatures. Alternatively, the resin was made to air dry with ester gum, and the curing behavior was studied. The suitability of these resins for high‐temperature curing fly ash coating applications was established. Coatings were formulated with these resins and with 40% fly ash as an extender. The coatings were characterized by standard techniques, particularly for their anticorrosive and antiabrasive properties. Resistance to corrosion was evaluated in humidity and in salt‐spray conditions. We conducted a high‐stress (two‐body) abrasion test to test the abrasive wear resistance of the coatings. The Mahua‐oil‐resin‐based fly ash coatings were suitable for application in moderately corrosive and abrasive environments. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 110–120, 2003     

Synthesis and dielectric properties of polystyrene‐clay nanocomposite materials

Polystyrene‐clay nanocomposite (PsCN) materials were synthesized and their properties of crystallinity, thermal behavior, and dielectric characteristics were investigated. A polymerizable cationic surfactant, [2‐(dimethylamino)ethyl]triphenylphonium bromide, was used for the intercalation of montmorillonite (MMT). The organophilic MMT was prepared by Na⁺‐exchanged MMT and ammonium cations of a cationic surfactant in an aqueous medium. Organophilic styrene monomers were intercalated into the interlayer regions of organophilic clay hosts followed by a free‐radical polymerization. Exfoliation to 2 wt % MMT in the polystyrene (PS) matrix was achieved as revealed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal properties by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also studied. The dielectric properties of PsCNs in the form of film with clay loading from 1.0 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 25–70°C. A decreased dielectric constant and low dielectric loss were observed for PsCN materials. The dielectric response at low frequency that originated from dipole orientation was suppressed due to the intercalation of clay materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1368–1373, 2004     

Modification of negative auto‐photosensitive polyimide

This article describes the preparation of a kind of auto‐photosensitive polyimide (PSPI) that contains organo‐silicone moiety in its main chain. A group of novel auto‐photosensitive polyimides were prepared based on the aromatic diamine monomers and 3,3′,5,5′‐benzophenontetracarboxylic dianhydride (BTDA) by the method of solution polycondensation at room temperature and imidized at a high temperature. The properties of PSPIs, such as ultraviolet (UV) absorption, electric and adhesion properties, and moisture absorption, were characterized by UV analysis, a dielectric constant detector, and so on. The relationship between the structure and properties of PSPIs is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 943–947, 2000