Sul-containing fluorinated polyimides for optical waveguide device

Novel sul-containing fluorinated polyimides have been synthesized by the reaction of 2,2′-bis-(trifluoromethyl)-4,4′-diaminodiphenyl sulfide (TFDAS) with 1,4-bis-(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA), 2,2′-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4,4′-oxydiphthalicanhydride (ODPA) or 3,4,3′,4′-biphenyl-tetracarboxylic acid dianhydride (s-BPDA). The fluorinated polyimides, prepared by a one-step polycondensation procedure, have good solubility in many solvents, such as N-methyl-2-pyrrolidinone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), cyclohexanone, tetrahydrofuran (THF) and m-cresol. The molecular weights (M_n's) and polydispersities (M_n/M_w's) of polyimides were in the range of 1.24 × 10⁵ to 3.21 × 10⁵ and 1.59–2.20, respectively. The polymers exhibit excellent thermal stabilities, with glass-transition temperatures (T_g) at 221–275 °C and the 5% weight-loss temperature are above 531 °C. After crosslinking, these polymers show higher thermal stability. The films of polymers have high optical transparency. The novel sul-containing fluorinated polyimides also have low absorption at both 1310 and 1550 nm wavelength windows. Rib-type optical waveguide device was fabricated using the fluorinated polyimides and the near-field mode pattern of the waveguide was demonstrated.     

主链含有机硅结构单元的光敏聚酰亚胺的研究

提出了一类主链上含有机硅结构单元的光敏聚酰亚胺（ＰＳＰＩ）。其合成过程是首先制备聚酰胺酸预聚体，接着在二环己基碳二酰亚胺存在下，使之转变为聚硅氧酰亚胺，然后引入光敏基团。通过ＩＲ、ＤＳＣ、元素分析、ＵＶ、介电分析方法对聚酰亚胺的结构、感光特性、热性能、电性能、粘附性、吸湿性能等进行了表征。对结构与性能之间的关系进行了初步探讨。     

Photosensitive peptide hydrogels as smart materials for applications

Photosensitive supramolecular peptide hydrogels with the gelators forming by the integration of photosensitive moieties and peptides have been briefly summarized the hydrogelation capabilities, the expressing manner serving as smart materials, and practical applications.     

Polyimides for electronics applications

A variety of options exists for lithographically defining polyimides for microelectronics applications. The two investigated here, photosensitive polyimide and wet etching of low-stress polyimides, offer lower cost, higher throughput solutions compared with dry etch processes. Via sizes of less than 25 μm and film thicknesses of greater than 14 μm are difficult to process using these techniques: however, for applications such as interlayer dielectrics for high-density packaging or solder masks for flip chip die attachment, these limitations may not be insurmountable. Photosensitive polyimide can be patterned with fewer steps, but the overall quality of the film in terms of surface planarity and residual stress is not as good as wet etching of conventional polyimide.     

A mechanism for the electron beam lithography of solvent-soluble photosensitive polyimides

Solvent-soluble and intrinsically photosensitive polyimides were prepared, and their electron beam reaction was investigated. Negative tone patterns were formed by the electron beam irradiation of PI(BTDA/DEDPM) and PI(BEDA/DEDPM). The mechanism for the pattern formation of PI(BTDA/DEDPM) was determined from transient absorption measurements, changes in the molecular weights, and IR spectrum measurements to be crosslinking via hydrogen abstraction by the triplet excited state benzophenone moiety. For the case of PI(BEDA/DEDPM), the pattern was formed by insolubilization due to chemical change in the polymer. These reactions are found to be so inhomogeneous that insolubilization of the polymer occurs at an early stage of gelation.     

Photosensitive polyimides consisting of simple mixtures of 4-substituted diazonaphthoquinones and polyamic acids

Polyimide resists that can be developed with a basic aqueous solution were produced by simple mixtures of conventional polyamic acids and naphthoquinone diazides in which sulfonate groups are substituted at the 4-position. The diazonaphthoquinones bearing electron-withdrawing groups gave negative tone resists. On the other hand, those bearing electron-donating groups gave positive tone resists. The difference in the resist behaviors depending on the photoactive structure was explained by crosslinking caused by photogenerated sulfonic acids. The thermal stability of polyimides prepared from the resists was almost the same as that of conventional polyimides.     

Synthesis and optical properties of polyimides

Polyimides are important industrial materials because of their excellent properties. They are extensively used in the electronics industry and have great potential in the field of optical communications. In this article, we discuss the effect of the polyimide structure and the processing conditions on the optical properties. Both commercially available fluorinated polyimides and polyimides synthesized in our laboratory were used in this study. The relationship between the extent of fluorination and the refractive index was studied, and it was found that fluorination reduced the refractive index as expected. Studies conducted on the structure–property relationship revealed that with the use of more rigid monomers for the polyimides, the polyimides could be modified to show a large birefringence. The extent of birefringence depended on the composition of the polymer. In addition, the processing conditions directly controlled the residual stress in the polymer films. The residual stress was an important factor in inducing light scattering, which resulted in higher optical loss. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4832–4838, 2000     

New organo-soluble polyimides for optical,microelectronic and fiber applications

A novel class of organo-soluble polyimides has been developed based on monomers containing twisted-biphenyl structures. Thus, 2, 2'-disubstituted-4, 4'-diaminobiphenyls and 2, 2'-disubstituted-4, 4', 5, 5'-biphenyltetracarboxylic dianhydrides have been prepared and polymerized in refluxing phenolic solvents. The polyimides, some of which are soluble in ketone and ether solvents, can be readily solution cast into colorless thin films. The rigid polymer chains align parallel to the substrate surface (in-plane orientation) during the casting process, which results in anisotropy in the film properties. The anisotropy in the refractive index has been used in the development of compensation layers for liquid crystal displays. The polymers have also been dry jet-wet spun from phenolic solutions to afford fibers that display tensile strengths of 3.5 GPa and moduli of 130 GPa.     

Chain orientation and anisotropies in optical and dielectric properties in thin films of stiff polyimides

Thin films of poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA), prepared by thermal imidization of the precursor poly(amic acid) on substrates, have been investigated by optical waveguide, ultraviolet-visible (UV-VIS), infrared (IR), and dielectric spectroscopies. The polyimide films exhibit an extraordinarily large anisotropy in the refractive indices with the in-plane index n_∥ = 1.806 and the out-of-plane index n_⊥ = 1.589 at 1064 nm wavelength. No discernible effect of the film thickness on this optical anisotropy is found between films of ca. 2.1 and ca. 7.8 μm thickness. This large birefringence is attributed to the preferential orientation of the biphenyltetracarboximide moieties with their planes parallel to the film surface, coupled with the strong preference of BPDA-PDA chains to align along the film plane. The frequency dispersion of the in-plane refractive index n_∥ is consistent with the results calculated by the Lorentz–Lorenz equation from the UV-visible spectrum exhibiting several absorption bands in the 170–500 nm region. The contribution from the IR absorption in the range 7000–400 cm,^?1 computed by the Spitzer-Kleinmann dispersion relations from the measured spectra, adds ca. 0.046 to the in-plane refractive index n_∥. Tilt-angle–dependent polarized IR results indicate nearly the same increase for the out-of-plane index n_⊥. Application of the Maxwell relation then leads to the out-of-plane dielectric constant ε^⊥ ? 2.7 at 1.2 × 10¹³ Hz, as compared with the measured value of ca. 3.0 at 10⁶ Hz. Assuming this small difference to remain the same for the in-plane dielectric constants ε_∥, we obtain a very large anisotropy in the dielectric properties of these polyimide films with the estimated in-plane dielectric constant ε_∥ ? 3.4 at 1.2 × 10¹³ Hz, and ε_∥ ? 3.7 at 10⁶ Hz. © 1992 John Wiley & Sons, Inc.     

Synthesis and properties of nonlinear optical side chain soluble polyimides for photonics applications

Aromatic polyimides with side chain nonlinear optical chromophores have been investigated through a facile two-step synthetic route. First, various poly(hydroxy imide)s have been synthesized by direct thermal imidization of diaminophenol dihydrochloride salt and aromatic dianhydride monomers. The resulting polyimides bearing phenolic hydroxy groups were found to react easily with the terminal hydroxy group on the chromophores via the Mitsunobu condensation to give corresponding polyimides with high optical nonlinearities and good solubility in common organic solvents. Detailed physical properties showed that these polyimides have a molecular weight (M_w) of 31,000 and high glass transition temperature above 220°C, ensuring a long-term alignment stability at elevated temperature. The electrooptic coefficients, r₃₃, of the electrically poled polymer films were in the range 1.8–7.6 pm/V at 1.3 μm. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 301–307, 1998     

Synthesis and characterization of novel perfluorinated polyimides with 3D‐controlled structures for photonic applications

We have designed and synthesized novel perfluorinated polyimides with 3D controlled structure. At first, we successfully developed the new synthetic routes to diamines with pendant bulky perfluorinated aromatic units in a multi‐step synthetic procedure. Novel perfluorinated polyimides were prepared in a two‐step reaction in N‐methyl‐2‐pyrrolidinone (NMP) solution: The first step was for the synthesis of polyamic acids (PAAs) and the second reaction was for the imidization of PAA. The polymer yield was over 89% and the inherent viscosity of PAAs was in the range of 0.24–0.36 dL/g. The thin films were prepared by spin‐coating the PAA solution in NMP onto various substrates such as a Si wafer or a KBr pellet, dried at 80 °C and further cured at 230 °C. The resultant polyimides are thermally stable over 400 °C. The refractive index and birefringence of the resultant polyimides are 1.5858–1.6452 and 0.01–0.005, respectively. The refractive index of polyimide decreases with increasing the fluorine content. The copolymerization and the ether linkages into the backbone reduce the birefringence of polyimides. Surprisingly, the pendant ether linkage is not a crucial factor in reducing the polyimide birefringence. Their birefringence is comparatively very low, compared with that of previous polyimides. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1326–1342, 2006     

Synthesis and properties of photosensitive polyimide-nanocrystalline titania optical thin films

In this study, synthesis, morphology, and properties of high refractive index photosensitive polyimide-nanocrystalline titania hybrid materials are reported. A soluble polyimide grafted with carboxylic acid or methacrylate groups (P1) was first synthesized from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,5-diaminobenzoic acid (DABA), 4-aminobenzoic acid (4ABA), and 2-hydroxyethyl methacrylate (2HEMA). The residual carboxylic acid groups could undergo an esterification reaction with titanium butoxide to provide an organic-inorganic bonding. On the other hand, the grafted methacrylate groups rendered photosensitive property for photopatterning. A homogeneous hybrid solution was obtained through the formulation on different mole ratios of titanium butoxide/carboxylic acid, water/acid content in a mixed solvent. It was followed by spin-coating, photocuring and post-baking. The titania domain size in the hybrid materials analyzed by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) was around 4-7 nm. The prepared optically transparent films had tunable refractive index (1.583 < n < 2.029), relatively good surface planarity and high thermal stability. A fine pattern with a line width of 50 μm was produced by direct lithographic process on the hybrid films. The present study demonstrates a novel approach for preparing high refractive index hybrid photosensitive materials with patternability.     

Microwave‐assisted synthesis of nanocomposites from polyimides chemically cross‐linked with functionalized carbon nanotubes for aerospace applications

Polymer‐carbon nanotube nanocomposites are extensively investigated for microelectronics and aerospace applications. In this study, novel polyimide/f‐MWCNT nanocomposites made from 2,4‐bis(4‐aminophenylamido)‐6‐chloroquinazoline, pyromellitic dianhydride and functionalized‐Multi Walled Carbon Nanotubes (f‐MWCNT) by an efficient microwave assisted method were investigated. The structure of the prepared diamine monomer was confirmed by FT‐IR, ¹H‐NMR, and ¹³C‐NMR spectral techniques. The prepared nanocomposites (T_g values from 338°C to 375°C) show improved thermal property as indicated by differential scanning calorimetry and thermogravimetric analysis. Polyimide/f‐MWCNT nanocomposites were found to have higher dielectric constant, and the limiting oxygen index values of prepared nanocomposites are in the range of 29.5 to 35.5, indicating a high flame retardancy. Additionally, the morphological studies were conducted by X‐ray diffraction and scanning electron microscopy. Overall, it is observed that chemically connected polyimide‐functionalized carbon nanotube nanocomposites could be used for aerospace and microelectronics applications that require high T_g, dielectric constant and high flame retardancy.     

Study on side-chain second-order nonlinear optical polyimides based on novel chromophore-containing diamines. I. Synthesis and characterization

Side-chain second-order nonlinear optical polyimides were prepared from four novel chromophore-containing diamines and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride by a traditional two-step process that included a solution polycondensation followed by a chemical imidization. The four diamines were 2,4-di-β-aminoethylamino-6-p-nitrophenylamino-1,3,5-triazine (M1), 4-nitro-4′-[N-(4,6-di-β-aminoethylamino)-1,3,5-triazin-2-yl]amino azobenzene (M2), 2,4-di-p-aminophenylamino-6-p-nitrophenylamino-1,3,5-triazine (M3), and 4-nitro-4′-[N-(4,6- di-4-aminophenylamino)-1,3,5-triazin-2-yl]amino azobenzene (M4). All the polyimides exhibited maximum ultraviolet-visible absorption peaks or shoulders of chromophores at wavelengths below 400 nm, and those based on M1 and M3 were transparent at wavelengths above 450 nm, whereas those based on M2 and M4 were transparent at wavelengths above 550 nm. The polyimides possessed high glass-transition temperatures (T_g's; 218–247 °C) and thermal decomposition temperatures. They were soluble in aprotic solvents such as N-methyl-2-pyrrolidone, N,N-dimethyl acetamide, N,N-dimethyl formamide, and dimethylsulfone. Some were even soluble in common low-boiling-point solvents such as tetrahydrofuran. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4330–4336, 1999     

Novel chiral conjugated macromolecules for potential electrical and optical applications

Optically active 1,1′‐binaphthyl molecules have been used to construct novel chiral dendrimers and linear polymers. Efficient light harvesting effects of the dendrimers have been observed. They have shown enantioselective fluorescence responses in the presence of chiral amino alcohol quenchers. They are potentially useful as fluorescent sensors for the recognition of chiral organic compounds. Linear binaphthyl polymers have shown strong light emitting properties. Their colors of emission can be systematically tuned by incorporating linkers of various conjugation length. A very efficient light emitting diode has been prepared from the binaphthyl‐based conjugated polymers. Nonlinear optical chromophores have been organized in the chiral binaphthyl polymer chains to construct noncentrosymmetric and multipolar materials. These novel propeller‐like polymers have shown significant second‐order nonlinear optical effects.     

Polymers for electrical and optical data storage

Polymers possess great significance in data storage technology. Taking as an example electrical and optical data storage, the state of development, properties required and opportunities for application of selected polymers are discussed, namely: (i) ferroelectric polymers with low switching voltages and extremely short switching times for electric data storage; and (ii) transparent polymers with low birefringence and high thermal stability for optical data storage. In the area of electrical data storage devices/memories, ferroelectric polymers have not been able to establish themselves up to now due to their long switching time and limited thermal stability. However, recent investigations show that suitable copolymers based on PVDF/TrFE copolymers in ultra-thin layers can achieve switching times of ≤100 ns. Nevertheless, the limited thermal stability of PVDF/TrFE copolymers prevent them from being integrated into the usual manufacturing process for Si-based data storage devices (D-RAM resp. S-RAM) and thereby frustrates the desired objective of producing nonvolatile random access memories (NV-RAMs). In the area of optical data storage technology, polycarbonate (PC) has established itself due to its favorable combination of properties. Thus, audio compact disks (CDs) are manufactured exclusively of PC, while high-flow PC types of high optical purity are clearly the preferred substrate material for optical data storage disks. The increasingly stringent requirements to be met in terms of lower birefringence and better thermal stability mean that the development of suitable modified or substituted polycarbonates is required. The development work being carried out worldwide in this area is reviewed here, and new suitable substituted polycarbonates with lower birefringence and significantly increased thermal stability up to glass temperatures of 238°C are presented. In addition, we deduce structure—property relationships for the above-mentioned structurally modified polycarbonates, specifically considering rotation potentials along the polymer backbone.     

光敏性聚酰亚胺的合成及其在液晶光致取向中的运用

通过羟基聚酰亚胺与肉桂酸的接枝反应合成了具有光敏性的聚酰亚胺,并且通过红外,核磁确定了光敏性聚酰亚胺的结构,将合成的聚酰亚胺作为液晶取向层用在液晶显示器件中,证明其有良好的热稳定性。     

A new procalcitonin optical immunosensor for POCT applications

A new immunosensor for the determination of procalcitonin was developed. A sandwich assay format was implemented on a polymethylmetacrylate optical biochip, opportunely shaped in order to obtain several flow channels and potentially suitable for point of care testing applications. The sandwich format makes use of two new rat monoclonal antibodies. The capture antibody was covalently immobilised on the surface of the plastic chip, and the detection antibody was labelled with DY647 dye. Different combinations of capture and detection antibodies were investigated, and particular attention was devoted in order to avoid the non-specific adsorption. A limit of detection of 0.088 mg L⁻¹ was achieved within the working range of 0.28–50 mg L⁻¹ in buffer samples. The assay was also implemented in human serum, and 0.2 and 0.7–25 mg L⁻¹ were the attained limit of detection and working range, respectively.     

Synthesis of photosensitive polyimide for liquid crystal alignment under non-polarised UV ageing lamp irradiation and a study on the possible mechanism of alignment

ABSTRACT

A new photosensitive polyimide (PI) was successfully synthesised via esterification of PI containing hydroxyl groups with cinnamoyl chloride (CL). The cinnamate (CA) group contents of the PI was up to 90%. The PI films could induce uniform parallel alignment of liquid crystal (LC) molecules after the non-polarised ultraviolet ageing lamp exposure, which reduce the cost significantly compared with polarised ultraviolet light equipment. In addition, the PI exhibited good thermal stability. Meanwhile, the possible mechanism of PI alignment films induced by NPUVL was discussed in some detail.