Tunable near‐infrared optical properties based on poly(methyl methacrylate)–oxide waveguide materials

In this study, two classes of low‐loss optical planar waveguides were prepared from trialkoxysilane‐capped poly(methyl methacrylate) (PMMA)–silica and PMMA–titania hybrid materials, respectively. The prepared hybrid films had very uniform structure and surface planarity. The incorporation of the silica or titania segments into the acrylic polymer matrix reduced the intermolecular interaction and thus induced an increase in anharmonicity of the C‐H bond in the acrylic segment. Therefore, the third harmonic stretching vibration absorption of the C‐H bond was red‐shifted and resulted in a tuning of near‐infrared (NIR) optical absorption. The optical loss of the studied waveguides was reduced from 0.65 dB/cm of the PMMA waveguide to 0.26 and 0.28 dB/cm with increasing the silica and titania content in the hybrid materials, respectively. The reduction of the C‐H number density and shifting of the NIR absorption spectra accounted for the relationship between the optical loss and the inorganic oxide content. The increased anharmonicity through the incorporation of the inorganic moiety in the hybrid materials provides another approach for tuning the NIR optical properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1224–1228, 2005     

Synthesis and characterization of organic-inorganic hybrid thin films from poly(acrylic) and monodispersed colloidal silica

Hybrid thin films containing nano-sized inorganic domain were synthesized from poly(acrylic) and monodispersed colloidal silica with coupling agent. The 3-(trimethoxysilyl)propyl methacrylate (MSMA) was bonded with colloidal silica first, and then polymerized with acrylic monomer to form a precursor solution. Then, the precursor was spin coated and cured to form the hybrid films. The silica content in the hybrid thin films was varied from 0 to 50 wt%. The experimental results showed that the coverage area of silica particle by the MSMA decreased with increasing silica content and resulted in the aggregation of silica particle in the hybrid films. Thus, the silica domain in the hybrid films was varied from 20 to 35 nm by the different mole ratios of MSMA to silica. The results of scanning electron microscope, transmission electron microscope, and elemental analysis support the above results. The prepared hybrid films from the crosslinked acrylic polymer moiety showed much better film uniformity, thermal stability and mechanical properties than the poly(methyl methacrylate) (PMMA) based hybrid materials. Large pin-holes were found in the PMMA-silica hybrid films probably due to the significant difference on thermal properties between the two moieties or the evaporation of solvent. The refractive index decreased linearly with increasing the silica fraction in the hybrid films. Excellent optical transparence was obtained in the prepared hybrid films. These results show that the hybrid thin films have potential applications as passive films for optical devices.     

Synthesis and properties of new polyimide-silica hybrid films through both intrachain and interchain bonding

In this study, the new polymer-silica hybrid materials were prepared based on the organo-soluble polyimides of 4,4′-hexafluoroisopropylidenediphthalic anhydride (6FDA) and four diamines. 3-Aminopropyl trimethoxysilane (APrTEOS) and γ-glycidyloxypropyltrimethoxysilanes (GOTMS) were used to increase the intrachain chemical bonding and interchain hydrogen bonding between the polyimide and silica moieties, respectively. The chemical interaction would significantly affect the morphologies and properties of the prepared films. Highly homogeneous hybrid thin films were obtained according to the studies of atomic force microscopy and TEM. The silica size observed by the TEM picture was smaller than 5 nm. The thermal properties of the organo-soluble polyimides were significantly enhanced by hybridizing only 6.30-7.99 wt% of silica. The intrachain chemical bonding could effectively enhance the coefficient of thermal expansion in comparison with the interchain interaction. Low dielectric constants in the range of 2.85-3.73 were obtained for the prepared hybrid films. The refractive indices of the prepared materials could be tuned through the polyimide structure or the silica content. The optical losses of the planar waveguides based on the prepared polyimides and their hybrids at 1310 nm were in the range of 0.5-2.7 dB/cm, which were mostly due to the higher harmonics of the aromatic C-H vibration and the extrinsic loss. The prepared polyimide-silica hybrid materials could have potential applications for microelectronics or optical communications.     

Organic and polymer planar optical waveguides

Single-mode and multi-mode planar optical waveguides with low loss were fabricated by spin-coating thin films of poly(vinyl alcohol) (PVAl) and 4-dihexylamino-4′-nitro-stilbene (DHANS) doped poly(methylmethacrylate) (PMMA) onto glass substrates, and characterised by theoretical analysis and optical guided-mode measurements. The optical constants of the waveguides were determined with good accuracy by measuring the coupling synchronised angles and fitting them, via a recursion method, into the waveguide dispersion equations. The number of the guided modes observed in these thin films can be controlled by tailoring the film thickness.     

Fabrication and characterization of planar and channel polymer waveguides. II. Poly(p‐phenylene benzobisthiazole) (PBZT) films

Solutions of poly(p‐phenylene benzobisthiazole) (PBZT) in methane sulfonic acid (MSA) were prepared and studied. Solutions with concentrations less than 0.04 wt % PBZT were characterized by dilute solution viscometry. Planar PBZT waveguides were spin‐coated from a 0.5 wt % PBZT solution onto oxidized silicon wafers. The optical attentuation of the resulting polymer waveguides was measured and found to depend on both the thickness of the oxide layer on the silicon substrate and also the wavelength of the incident light. The lowest optical loss recorded for PBZT in this investigation was 4.81 ± 1.39 dB/cm at 834 nm. This work thus demonstrates the successful fabrication of PBZT into thin‐film planar waveguides. The PBZT films prepared here also show improved optical characteristics over PBZT films prepared previously by either extrusion or spin coating. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1448–1456, 2000     

Synthesis and characterization of polyimide/oligomeric methylsilsesquioxane hybrid films

In this study, polyimide/silsesquioxane hybrid materials were synthesized from aminoalkoxysilane‐capped poly(pyromellitic dianhydride‐co‐4,4′‐oxydianiline) (PMDA‐ODA) and oligomeric methylsilsesquioxane (O‐MSSQ) precursors. The O‐MSSQ moiety was used to obtain well characterized nano‐inorganic cage and network structures in the hybrid materials. The effects of molecular structures and composition on the morphologies and properties of the prepared hybrid materials were studied. The phase separation of the prepared hybrid materials could be controlled by varying the molecular weight of the polyimide moiety, the Si? OH end group content of the O‐MSSQ or the coupling agent. Homogeneous and transparent hybrid thin films were obtained from the low molecular weight polyimide moiety with a coupling agent, 3‐aminopropyltrimethoxysilane (APrTMS). However, microphase separation occurred if the molecular weight of the polyimide moiety was enhanced or was prepared without a coupling agent, as evidenced by atomic force microscopy (AFM), field emission scanning electron microscopy (FE‐SEM), and electron spectroscopy for chemical analysis (ESCA). The high Si? OH content of the O‐MSSQ could enhance the bonding density between the organic and inorganic moiety and thus retard phase separation. The thermal and mechanical properties of the prepared hybrid materials were largely improved compared with the parent polyimide, PMDA‐ODA, and were demonstrated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and thermal‐stress analysis. The hybrid materials showed adjustable refractive index and dielectric constant by varying the O‐MSSQ content. The birefringence of the PMDA‐ODA was reduced by incorporating the O‐MSSQ moiety. This work revealed that the polyimide/O‐MSSQ hybrid materials could have potential applications as optical films or low dielectric constant materials. Copyright © 2004 Society of Chemical Industry     

ZrO2-SiO2二元系统平面光波导薄膜的制备与性能表征

应用溶胶-凝胶技术,以TEOS与ZrOCl2·8H2O为先驱体,研制了用于有源光波导基质材料的ZrO2-SiO2二元系统薄膜,探明了ZrO2-SiO2二元系统薄膜折射率、厚度与薄膜组分、匀胶速度、陈化时间、热处理温度的内在关系,实现薄膜厚度和薄膜折射率在一定范围内的连续可调,为研制一类新型的光通信窗口有源光波导材料提供了基质材料.     

Physical and Gas Transport Properties of Novel Hyperbranched Polyimide – Silica Hybrid Membranes

Summary Physical and gas transport properties of novel hyperbranched polyimide – silica hybrid membranes were investigated. Hyperbranched polyamic acid as a precursor was prepared by polycondensation of a triamine monomer, 1,3,5-tris(4-aminophenoxy)benzene (TAPOB), and a dianhydride monomer, 4,4-(hexafluoro-isopropylidene)diphthalic anhydride (6FDA), and subsequently modified the end groups by 3-aminopropyltrimethoxysilane (APTrMOS). The hyperbranched polyimide – silica hybrid membranes were prepared using the polyamic acid, water, and tetramethoxysilane (TMOS) via a sol-gel technique. 5 % weight-loss temperature and glass transition temperature of the hyperbranched polyimide – silica hybrid membranes determined by TG-DTA measurement considerably increased with increasing silica content, indicating effective cross-linking at polymer – silica interface mediated by APTrMOS moiety. CO₂, O₂, and N₂ permeability coefficients of the hybrid membranes increased with increasing silica content. It was pointed out that the increased gas permeabilities are mainly attributed to increase in the gas solubilities. On the contrary, CH₄ permeability of the hybrid membranes decreased with increasing silica content because of decrease in the CH₄ diffusivity and, as a result, CO₂/CH₄ selectivity of the hybrid membranes remarkably increased. It was concluded that the 6FDA-TAPOB hyperbranched polyimide – silica hybrid membranes have high thermal stability and excellent gas selectivity, and are expected to apply to a high-performance gas separation membrane.     

Electromagnetic shielder compatible ZnO transparent conducting oxides hybridized with various sizes of Ag metal nanoparticles

In this paper, the effect of different sizes of Ag-nanoparticles dispersed in ZnO matrix using sol–gel method has been focused. Low-temperature crystallized ZnO thin films was achieved by sol–gel process, using zinc acetate dihydrate and 2-methoxyethanol as starting precursor and solvent, respectively. Various sizes of Ag-nanoparticles could be prepared by the spontaneous reduction method with changing the preparation temperatures and mole concentrations of Ag 2-ethylhexanoate in dimethyl sulfoxide solvent. The crystallographic structure of the Ag–ZnO hybrid film was analyzed by X-ray diffraction. Ag-nanoparticle size and optical property of Ag–ZnO hybrid films were measured by UV–vis spectrophotometer.     

CO2 laser-assisted preparation of transparent Eu2Ti2O7 thin films

We present a laser-assisted preparation of transparent europium-titanate Eu₂Ti₂O₇ thin films with tailored structural and optical properties. We have evaluated the effects of the irradiation time on the structural and the optical properties of the films. This approach allows the preparation of nanocrystalline crack-free films and micro patterns. The amorphous thin films were prepared by a sol-gel method. The films were annealed by a CO₂ laser beam for various time intervals. The laser irradiation induced a crystallization process that resulted in the formation of Eu₂Ti₂O₇ nanocrystals. The nanocrystals regularly grew with increasing irradiation time reaching the size from 25?nm to 45?nm. A film of a thickness 480?nm exhibited an optical transmission of 91.9% that is close to the maximal theoretical limit. The film's refractive index at 632?nm was 2.26. A micrometric pattern was prepared by a direct laser writing followed by a wet chemical etching. Feasibility of the demonstrated approach, together with the high film's quality, and europium-titanate chemical resistivity open up many opportunities for advanced applications. The approach can be used for a preparation of protective coatings and integrated photonic devices such as planar optical waveguides and couplers.     

硅溶胶/苯乙烯-丙烯酸酯共聚物无机-有机杂化水分散液的制备和表征

A stable silica sol with 3-5 nm in diameter, which can form homogeneous film without crack, was prepared and characterized. Then, the inorganic-organic hybrid aqueous dispersion composed of such a silica sol and an emulsion of styrene （St） and acrylate （Ac） copolymer was prepared and the hybrid effect between the silica sol and poly（St-co-Ac） was observed by Fourier transform infra-red （FT-IR） spectroscope. The toughness of the film prepared by this kind of hybrid aqueous dispersion was excellent, as it was enhanced appreciably by commixing with a small amount of poly（St-co-Ac） emulsion. Some amino-polysiloxane modified hybrid aqueous dispersions were also prepared and the properties of the modified dispersions and their films were investigated. The experimental results showed that the film prepared with such an amino-polysiloxane modified hybrid dispersion exhibited excellent hydrophobicity and low surface energy after heat treatment for 1.5 h, during which the formation of the graft copolymer was observed. The surface energy of this film decreases as a result of the enrichment of siloxane segments on the film surface.     

Photosensitive polyimide/silica hybrid optical materials: Synthesis, properties, and patterning

In conventional ionic salt photosensitive polyimides, large volume shrinkage during imidization would be occurred due to eliminating pendant photosensitive moieties, such as 2-methyl acrylic acid 2-dimethylamino-ethyl ester (MDAE). In this study, the volume shrinkage of photosensitive poly(4,4′-(hexafluoroisopropylidenediphthalic anhydride)-co-oxydianiline) (6FDA-ODA)/MDAE was largely reduced by photocrosslinking MDAE with a coupling agent and the silica domain in the hybrid materials. The used coupling agents were 3-methacryloxypropyl trimethoxysilane (MPTMS) or (4-vinylphenethyl)trimethoxysilane (VPTMS). The coupling agent and the silica domain are designed primarily for reducing the volume shrinkage and enhancing the thermal properties, respectively. The retention of MDAE in the prepared hybrid films is supported by X-ray photoelectron spectroscopy (XPS) and thickness variation during curing process. The silica domain in the hybrid materials from TEM analysis was in the range of 10-50 nm, which was formed by the coupling agent and tetramethoxysilane. The silica domain significantly enhanced the thermal properties of the prepared hybrid films in comparison with parent fluorinated polyimide, including the glass transition temperature and coefficient of thermal expansion. The prepared hybrid materials also exhibited reduced refractive index and optical loss by increasing the silica. The SEM diagram suggested the prepared photosensitive hybrid materials could obtain lithographical patterns with a good resolution. These results indicate that the newly prepared photosensitive polyimide/silica hybrid materials may have potential applications for optical devices.     

Voltammetric studies on poly(para phenylene) films obtained by electroreduction

Summary Voltammetric studies were carried out on poly(para phenylene) PPP thin films obtained by electroreduction of dibromobiphenyl. Both oxidation and reduction were observed in the same medium (solvent + salt) with PPP deposits on various substrates (ITO, glassy Carbon...). The difference between the oxidation and reduction thresholds agrees well with the optical bandgap 2.8–2.9 eV. At these potentials prepeaks show up which may be interpreted in terms of compensation of remnant charges of the opposite sign.     

Organic base‐catalyzed sol–gel route to prepare PMMA–silica hybrid materials

A series of sol–gel‐derived organic–inorganic hybrid materials that comprise organic poly(methyl methacrylate) (PMMA) and inorganic silica (SiO₂) was successfully prepared using aniline as an organic base catalyst to catalyze the sol–gel reactions of tetraethylorthosilicate (TEOS). Aniline was adopted not only as a catalyst but also as a dispersing agent during the preparation of the hybrid materials. The as‐prepared hybrid materials were then characterized using transmission electron microscopy, SEM/energy dispersive X‐ray spectroscopy and Fourier transform infrared spectroscopy. The characteristic temperatures (including T_d and T_g) of the hybrid materials slightly exceeded those of neat PMMA, as revealed from thermogravimetric analysis and differential scanning calorimetry evaluations. Studies of the protection against corrosion demonstrated that the hybrid coatings all improved the protection performance on cold‐rolled steel coupons relative to that of neat PMMA coatings, according to measurements of electrochemical corrosion parameters. Additionally, incorporating silica particles into the polymer may effectively reduce the gas permeability of the polymer membrane. Reducing the size of silica particles (at the same silica feeding) further improved the gas barrier property. Optical clarity studies indicated that introducing silica particles into the PMMA matrix may slightly reduce the optical clarity of the films/membranes, as determined by UV‐visible transmission spectroscopy. The contact angle of H₂O of the hybrid films increased with the amount of aniline. Copyright © 2006 Society of Chemical Industry Society of Chemical Industry     

Fabrication and properties of chemically bonded polysilsesquioxane‐polyacrylate/silica hybrid latex films with high silicon content

Polysilsesquioxane‐polyacrylate/silica hybrid latexes (PSQ‐PAS) with high silicon content were prepared by directly mixing colloidal silica with polysilsesquioxane‐polyacrylate emulsion (PSQ‐PA), which was prepared through seeded emulsion polymerization using polymethacryloxypropylsilsesquioxanes as the core and polyacrylate (PA) as the shell respectively. The chemically bonded PSQ‐PAS thin films were obtained via sol‐gel process after addition of hydrophilic cosolvent to PSQ‐PAS emulsion and subsequent drying at room temperature. The effects of silica/PSQ‐PA ratio (w/w) on the film properties of hardness, optical property and thermal stability were investigated. Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to characterize the chemical composition and morphology of the resultant hybrid particles. DLS and TEM results indicated that both PSQ and PSQ‐PA particles had narrow size distribution and their average diameters were about 200 and 350 nm, respectively. Pendulum durometer, UV–vis spectroscopy, and thermogravimetric analysis (TGA) were used to characterize the hardness, optical property and thermal stability of PSQ‐PAS latex films. The results showed that the PSQ‐PAS films hardness increased with the increasing ratio of silica/PSQ‐PA, whereas the transmittance decreased slightly. TGA curves demonstrated PSQ‐PAS films displayed excellent thermal stability, and the residual silicon weight exceeded 30%. POLYM. COMPOS., 36:389–396, 2015. © 2014 Society of Plastics Engineers     

Synthesis and Optical Properties of Soluble Polyimide/Titania Hybrid Thin Films

Summary: In this study high‐refractive‐index polyimide/titania hybrid optical thin films were successfully prepared using a sol‐gel process combined with spin coating and multistep baking. The hybrid thin films were prepared from a soluble polyimide, a coupling agent, and a titania precursor. Transparent hybrid thin films can be obtained at TiO₂ content as high as 40 wt.‐%. The FE‐SEM results suggest that the TiO₂ particles in the hybrid thin films have diameters in the nanometer range. The thermal decomposition temperatures of the prepared hybrid materials are above those of the respective polyimide except for the highest TiO₂ content hybrids. The refractive indices at 633 nm of the prepared hybrid thin films increase linearly from 1.66 to 1.82 with increasing TiO₂ content. The excellent optical transparency, thermal stability, and tunable refractive index provide the potentials of the polyimide/titania hybrid thin films in optical applications.

     

Surface assisted laser desorption–ionization mass spectrometry on patterned nanoporous silica thin films

We describe the preparation and use of patterned nanocomposite silica thin films deposited on silicon for laser desorption-ionization mass spectrometry (LDI-MS) without the use of conventional matrices. Ordered nanocomposite silica thin films deposited on silicon substrates were prepared by evaporation induced self-assembly using Brij56 as the surfactant template. The films were then exposed to masked deep-UV light to selectively remove the template to yield isolated regions of ordered nanoporous silica in a field of nanostructured silica. The nanoporous regions act as isolated “wells” that allow for the mass spectral characterization of analytes by laser induced desorption–ionization MS using a commercial MALDI-TOF instrument. We demonstrate the utility of these patterned films for the mass spectral analysis of small organic molecules, such as amino acids, peptides and siderophores. No consistent background signal from the films was observed at laser intensities typically used to desorb/ionize analytes. We also show that the films remain active for over a year when stored at ambient laboratory conditions. Because these patterned nanocomposite films are straightforward to produce, readily modifiable and stable at ambient laboratory conditions, they provide a potentially useful alternative to currently available films and substrates for matrix-free LDI-MS analysis of small molecules.     

Tuning the peak position of subwavelength silica nanosphere broadband antireflection coatings

Subwavelength nanostructures are considered as promising building blocks for antireflection and light trapping applications. In this study, we demonstrate excellent broadband antireflection effect from thin films of monolayer silica nanospheres with a diameter of 100 nm prepared by Langmuir-Blodgett method on glass substrates. With a single layer of compact silica nanosphere thin film coated on both sides of a glass, we achieved maximum transmittance of 99% at 560 nm. Furthermore, the optical transmission peak of the nanosphere thin films can be tuned over the UV-visible range by changing processing parameters during Langmuir-Blodgett deposition. The tunable optical transmission peaks of the Langmuir-Blodgett films were correlated with deposition parameters such as surface pressure, surfactant concentration, ageing of suspensions and annealing effect. Such peak-tunable broadband antireflection coating has wide applications in diversified industries such as solar cells, windows, displays and lenses.     

原位交联聚乙烯醇/二氧化硅杂化功能膜的制备与性能

以正硅酸乙酯（TEOS）为前驱体,戊二醛（GA）为交联剂,利用溶胶凝胶法和原位化学交联法相结合的方法,制备了交联的聚乙烯醇/二氧化硅（PVA/SiO2）杂化功能膜。通过FTIR、SEM、溶胀和拉伸实验研究了二氧化硅和原位化学交联对杂化膜结构和性能的影响。结果表明,制备的膜是具有梯度交联结构的有机/无机杂化体系,原位化学交联对膜断面形貌影响不大。二氧化硅的引入和戊二醛原位交联都能有效地降低杂化膜的平衡溶胀度,两种因素在提高杂化膜耐水性方面具有互补作用。     

Characterization of antireflective coatings on poly(methyl methacrylate) substrate by different process parameters

The high/low refractive index organic/inorganic antireflective (AR) hybrid polymers were formed using the sol–gel process, in which TiO₂/2‐hydroxyethyl methacrylate (2‐HEMA) (high refractive index hybrid polymer) and SiO₂/2‐HEMA (low refractive index hybrid polymer) two‐layer thin films were formed on a hard coating deposited poly(methyl methacrylate) (HC‐PMMA) substrate by both spin coating and dip coating. The relationship between the process parameters and the optical properties, thickness, porosity, surface morphology, and adhesion was determined. The results show that the reflectance of the two‐layer thin films on HC‐PMMA substrate is less than 0.21% (λ = 550 nm), with good adhesion (5B) and a hardness of up to 4H. In addition, the thickness, porosity, and roughness of the films affect refractive index and the antireflection properties of the AR two‐layered thin film. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013