Aryl-group substituted polysiloxanes with high-optical transmission,thermal stability,and refractive index

Polysiloxanes are an important class of polymers for optoelectronic applications. Novel polysiloxanes with high-refractive index (RI) based on phenanthrenyl-substituted monomers are prepared by a polycondensation reaction starting from various substituted dialkoxysilanes as monomers. The substitution patterns on the Si atom are systematically changed to vary the properties of the linear polymers as well as the final cured material. The two monomers with polycyclic aromatic side groups 9-phenanthrenylmethyldimethoxysilane and 9-phenanthrenylphenyldimethoxysilane are synthesized and fully characterized, including their single crystal X-ray structures. Linear polysiloxanes with variations in hydride, methyl, vinyl, phenyl, and phenanthrenyl side group content are prepared by acid- and base-catalyzed polycondensation reactions. Both Si H and Si vinyl substituted polymers with molecular weights up to 30 kDa and adjustable RI's from 1.52 to 1.63 are obtained and the thermally cured by Pt-catalyzed hydrosilylation reactions. Polysiloxane resins are obtained with high-RI's, optical transmittance above 95% and thermal stabilities up to 420°C. Long-term thermal stability tests show transmittance values above 85% even after 60 days of thermal treatment at 180°C.     

Synthesis and properties of cross‐linkable high molecular weight fluorinated copolyimides

A series of novel high molecular weight fluorinated co‐polyimides (Co‐PIs) containing styryl side chain based on 1,3‐bis(2‐trifluoromethyl‐4‐aminophenoxy)‐5‐(2,3,4,5‐tetrafluorophenoxy)benzene (6FTFPB) were successfully synthesized. The weight‐average molecular weights (M_ws) and polydispersities of the co‐polyimides were in the range 8.93–10.81 × 10⁴ and 1.33–1.82, respectively. The co‐polyimide film showed excellent solubility in organic solvents, high tensile properties (tensile strength exceeded 91 MPa), excellent optical transparency (cutoff wavelength at 332–339 nm and light transparencies above 89% at a wavelength of 550 nm), and high thermal stability (5% thermal weight‐loss temperature up to 510 °C). The casting and spinning films could be cross‐linked by thermal curing. The cured films show better combination property (including excellent resistance to solvents) than that of co‐polyimides. For instance, the glass transition temperature of Co‐PI‐1 (the molar weight ratio of 6FTFPB was 30%) increased from 217 to 271 °C, the tensile strength enhanced from 94 to 96 MPa, the 5% thermal weight‐loss temperature improved from 514 to 525 °C. Moreover, after cured, Co‐PI‐1 film also has a coefficient of thermal expansion (CTE) value of 60.3 ppm °C^?1, low root mean square surface roughness (R_q) at 4.130 nm and low dielectric constant of 2.60. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 349–359     

Novel thermal curing reaction of oxetane resins with polyfunctional phenols

The thermal curing reaction of polyfunctional oxetanes (oxetane resins) such as tris[4‐(3‐ethyloxetane‐3‐yl)methoxyphenyl]methane (TEOMP) and 1,3,5‐tris(3‐ethyl‐3‐oxetanylmethoxy)benzene with certain polyfunctional phenols was performed in bulk with quaternary onium salts as catalysts. The reaction proceeded smoothly at 180–220 °C and produced insoluble gel products, and the rate of gel production increased with the reaction temperature. The rate of the addition reaction of TEOMP with 3,3′,5,5′‐tetrachlorobisphenol A was also measured by IR spectroscopy, and the rate of reaction was proportional to the product of the oxetane concentration and the catalyst concentration in the film state. Furthermore, the glass‐transition temperatures and 5 and 10 wt % weight‐loss temperatures of the resulting gel products were confirmed with differential scanning calorimetry and thermogravimetric analysis, and the glass‐transition temperatures and 5 wt % weight‐loss temperatures were 127–162 °C and 323–351 °C, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2028–2037, 2005     

Preparation of high molecular weight polybenzoxazine prepolymers containing siloxane unites and properties of their thermosets

High‐molecular‐weight polybenzoxazine prepolymers containing polydimethylsiloane unit in the main‐chain have been synthesized from α,ω‐bis(aminopropyl)polydimethylsiloxane (PDMS) (molecular weight = 248, 850, and 1622) and bisphenol‐A with formaldehyde. Moreover, another type of prepolymers was prepared using methylenedianiline (MDA) as codiamine with PDMS. The weight average molecular weight of the obtained prepolymers was estimated from size exclusion chromatography to be in the range of 8000–11,000. The chemical structures of the prepolymers were investigated by ¹H NMR and IR analyses. The prepolymers gave transparent free standing films by casting their dioxane solution. The prepolymer films after thermally cured up to 240 °C gave brown colored transparent and flexible polybenzoxazine films. Tensile test of the films revealed that the elongation at break increased with increasing the molecular weight of PDMS unit. Dynamic mechanical analysis of the thermosets showed that the T_gs were as high as 238–270 °C. The thermosets also revealed high thermal stability as evidenced by the 5% weight loss temperatures in the range of 324–384 °C from thermogravimetic analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Effect of annealing temperature on the quality of Al-doped ZnO thin films prepared by sol–gel method

The different thermal expansion coefficients and lattice mismatch between ZnO and Al may produce residual stress in Al-ZnO (AZO) thin films. Annealing processes can be applied to modulate this residual stress. In this study, three different rapid thermal annealing (RTA) temperatures (350, 450, and 600 °C) were applied to an AZO thin film, prepared using sol–gel method. The mechanical properties, optical properties, and structure of the AZO thin film were investigated experimentally. The results show that increasing the RTA temperature increased the Young’s modulus and hardness of the films. The grain size of the films also increased with increasing RTA temperature. However, the film thickness and shear stress component decreased with increasing RTA temperature. Both compressive and tensile stress decreased gradually with increasing film thickness after RTA treatment. It was demonstrated that the use of a relatively high RTA temperature can effectively relax the residual stress in AZO thin films.     

Thiourethane‐based thiol‐ene high Tg networks: Preparation,thermal, mechanical,and physical properties

Thiourethane‐based thiol‐ene (TUTE) films were prepared from diisocyanates, tetrafunctional thiols and trienes. The incorporation of thiourethane linkages into the thiol‐ene networks results in TUTE films with high glass transition temperatures. Increases of T_g were achieved by aging at room temperature and annealing the UV cured films at 85 °C. The aged/annealed film with thiol prepared from isophorone diisocyanate and cured with a 10,080‐mJ/cm² radiant exposure had the highest DMA‐based glass transition temperature (108 °C) and a tan δ peak with a full width at half maximum (FWHM) of 22 °C, indicating a very uniform matrix structure. All of the initially prepared TUTE films exhibited good physical and mechanical properties based on pencil hardness, pendulum hardness, impact, and bending tests. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5103–5111, 2007     

Preparation and properties of alkoxy(methyl)silsesquioxanes as coating agents

Polysilsesquioxanes were prepared through the acid‐catalyzed hydrolytic polycondensation of triethoxy(methyl)silane, triisopropoxy(methyl)silane, or triisobutoxy(methyl)silane and subjected to dip coating to form coating films. The film formation depended on the polarity and crystallinity of the substrate, and a correlation was found between the substrate and polysilsesquioxane solubility parameters. When the coating film was heated, thermal condensation occurred at about 500 °C between hydroxy groups or between hydroxy and alkoxy groups. The methyl group attached to silicon decomposed, and siloxane bonding formed at about 800 °C. The adhesion and hardness of the coating films were evaluated with the Japanese Industrial Standard K5400 protocol, and they increased with increases in the heating time and heat‐treatment temperature. The refractive index of the coating films decreased when the heat‐treatment temperature was increased to 500 °C because of the combustion of organic groups. In contrast, the surface electric resistance increased with the heat‐treatment temperature up to 500 °C. The dielectric constant was 2.6–2.8 and decreased with an increases in the molecular weight and the degree of crosslinking of the polysilsesquioxanes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3676–3684, 2004     

Stress behaviors and thermal properties of polyimide thin films depending on the different curing process

The effect of high boiling point solvent on the residual stress behaviors of semiflexible structure poly(4,4′‐oxydiphenylene pyromellitimide) (PMDA‐ODA) and pseudo‐rodlike poly(p‐phenylene biphenyltetracarboximide) (BPDA‐PDA) polyimide was investigated. As a solvent, a mixed solution of 20 wt % cyclohexyl‐2‐pyrrolidone (CHP; bp = 307 °C) and 80 wt % n‐methyl‐2‐pyrrolidone (NMP; bp = 202 °C) was used. The effects of solvent system and imidizing history on the morphological structure, as well as residual stress, were significantly high in the BPDA‐PDA having high chain rigidity, but relatively low in the semiflexible PMDA‐ODA with low chain rigidity. In addition, rapidly cured films prepared from PAA (NMP/CHP) showed higher residual stress and a lower degree of molecular anisotropy than slowly cured film imidized from PAA (NMP). This was induced by high chain mobility in polyimide thin films prepared from PAA (NMP/CHP) during the thermal cure process. Therefore, molecular anisotropy, depending on the solvent system and imidizing history, might be one of the important factors leading to low residual stress in polyimide thin films. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2879–2890, 2000     

Helical Carbon and Graphite Films Prepared from Helical Poly(3,4‐ethylenedioxythiophene) Films Synthesized by Electrochemical Polymerization in Chiral Nematic Liquid Crystals

Helical carbon and graphite films from helical poly(3,4‐ethylenedioxythiophene) (H‐PEDOT) films synthesized through electrochemical polymerization in a chiral nematic liquid‐crystal (N*‐LC) field are prepared. The microscope investigations showed that the H‐PEDOT film synthesized in the N*‐LC has large domains of one‐handed spiral morphology consisting of fibril bundles. The H‐PEDOT films exhibited distinct Cotton effects in circular dichroism spectra. The highly twisted N*‐LC with a helical pitch of smaller than 1 μm produced the H‐PEDOT film with a highly ordered morphology. The spiral morphologies with left‐ and right‐handed screws were observed for the carbon films prepared from the H‐PEDOT films at 800 °C and were well correlated with the textures and helical pitches of the N*‐LCs. The spiral morphologies of the precursors were also retained even in the graphite films prepared from the helical carbon films at 2600 °C.     

Photochemical synthesis of new polymer structures. II. Photocycloaddition of olefins to polyvinylbenzophenone and poly(styrene-co-vinylbenzophenone)

The photocycloaddition of simple olefins to poly(4-vinylbenzophenone) (PVB) and poly(styreneco-4-vinylbenzophenone) (PS-VB) was studied in benzene solution and in the solid polymer. In solution oxetane yields of 61–82% were obtained with di-, tri-, and tetrasubstituted olefins, which are visualized as capable of giving a radical on a 3° carbon atom in the biradical preceding ring closure to form the oxetane. Photocycloaddition of isobutene to PVB and PS-VB occurs in solid polymer films to more than 90% conversion of the polymer ketone. Quantum yields of oxetane formation are 0.013 ± 0.003 on irradiation at 366 nm, independent of film thickness between 1.9 and 10.6 μm and of temperature between 23 and 65°C. The absence of a pronounced effect of the polymer glass transition on the efficiency of the cycloaddition in PVB suggests that large-scale molecular motion is not required by this solid-state photoreaction. Crosslinking by photochemical cycloaddition was demonstrated in mixed films of PVB and squalene, a polyfunctional olefin.     

Ultraviolet–ultraviolet dual‐cure process based on acrylate oxetane monomers

A dual‐cure process consisting of two subsequent ultraviolet‐initiated radical and cationic polymerizations was investigated. The process was studied with two acrylate oxetane monomers, one of them having a spacer between the two polymerizable moieties. It was shown by Fourier transform infrared (FTIR) that the first (radical) step was performed successfully for both systems. As for the second (cationic) step, only the monomer with the spacer was able to polymerize, allowing the crosslinking of the polyacrylic chains generated by the first step. The efficiency of the process was confirmed by differential scanning calorimetry because the glass‐transition temperatures of the cured films were ?16 and + 34 °C after the first and second steps, respectively. The dual cure of this system was further analyzed by real‐time FTIR, which showed that 86% of the acrylate and 80% of the oxetane moieties were converted after 20 and 50 s of light exposure, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 469–475, 2003     

Effects of humidity,imidization history,and thickness on water sorption behavior of poly(p-phenylene biphenyltetracarboximide) films

Poly(p-phenylene biphenyltetracarboximide) films with various thicknesses were prepared from the poly(amic acid) precursor by thermal imidization at 230–400°C for 1–10 h under a nitrogen atmosphere. The water sorption in the films was measured at 25°C over 22–100% relative humidity using a Cahn microbalance as a function of film thickness and thermal imidization history. The water diffusion in all the films followed nearly Fickian process despite the morphological heterogeneity due to the ordered and less ordered phases. The diffusion coefficient and water uptake varied in 0.85 × 10^?10 ? 7.50 × 10^?10 cm²/s and 0.12–2.4 wt %, respectively, depending upon humidity, film thickness, and imidization history. Both diffusion coefficient and water uptake increased with increasing humidity, but decreased as imidization temperature and time increased. With increasing film thickness, the diffusion coefficient increased whereas the water uptake decreased. The water sorption behavior was interpreted with the consideration of morphological variations, such as polymer chain order, in-plane orientation, and intermolecular packing order due to the film thickness and imidization history. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of poly(epoxy‐imide) crosslinked networks

Poly(epoxy imide)s were prepared by a reaction between a hydroxyl‐group‐containing soluble copolyimide and commercial epoxy resins at 220 °C for 2 h. Poly(epoxy imide) thin films exhibited higher thermal stability and lower dielectric constants than a commercial flip‐chip package material (U300). The thermal stabilities of the poly(epoxy imide)s were 1.4–2.0 times higher than that of U300. The thermal stability increased with increasing crosslink density and with decreasing bulky CF₃ groups (which were easily decomposable). The dielectric constants of the poly(epoxy imide)s were 1.1–1.3 times lower than that of U300, and this is highly desirable for the microelectronic packaging industry. The dielectric constant dramatically decreased when bulky CF₃ groups were added and when the functionalities of epoxy resins decreased. The residual stresses, slopes in the cooling curves, and glass‐transition temperatures of the poly(epoxy imide)s were measured with a thin‐film stress analyzer. Low residual stresses and slopes in the cooling curves were achieved with a higher crosslink density. However, in the presence of bulky CF₃ groups, the copolyimide backbone structure did not affect the residual stress values. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4293–4302, 2004     

High thermal conductivity of polymerizable liquid‐crystal acrylic film having a twisted molecular orientation

The aligned films, the homogeneous film, the 90°‐twisted film and the 180°‐twisted film, have been prepared by immobilizing the polymerizable liquid crystals under the UV irradiation. The relation between the thermal conductivity and the aligned molecular direction of the films was investigated. It is indicated that the additional thermal transmission effect, which the increase of the thermal conductivity may be induced, would exist in the twisted films. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1419–1425, 2006     

Thermal stability of porous it‐PMMA thin film obtained by the extraction of st‐PMAA from it‐PMMA/st‐PMAA stereocomplex with layer‐by‐layer assembly on a substrate

The functionality of porous isotactic (it) poly(methyl methacrylate) (PMMA) thin films, which were previously developed by the selective extraction of syndiotactic (st) poly(methacrylic acid) (PMAA) from the it‐PMMA/st‐PMAA stereocomplex thin film on a substrate using the layer‐by‐layer assembly method was investigated after thermal treatment (70, 80, and 90 °C) in water for 4 h. Quartz crystal microbalance analysis and infrared spectra measurements revealed that the st‐PMAA incorporation ability of the porous it‐PMMA thin film decreased in order at 80 and 90 °C, while there was no decrease observed at 70 °C. X‐ray diffraction analysis also supported the thermal stability of the porosity at 70 °C, whereas two it‐PMMA crystalline peaks (2θ = 9° and 14°) were generated during heating at 90 °C. The loss of the functionality of the it‐PMMA thin film was thus shown to be due to crystallization, which was caused by the increase in polymer‐chain mobility during the heating process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3265–3270, 2010     

Preparation and characterization of organic–inorganic hybrids and coating films from 3‐methacryloxypropylpolysilsesquioxane

3‐Methacryloxypropylpolysilsesquioxane (MA‐PS) was prepared by acid‐ or base‐catalyzed hydrolytic polycondensation of 3‐methacryloxypropyltrimethoxysilane (MAS). MA‐PS coating film was prepared by dip‐coating on organic, metal and inorganic substrates, including poly(ethylene terephthalate), aluminum, stainless steel, and glass. The coating films on poly(ethylene terephthalate) and glass showed high adhesive strength. The hardness of coating films increased with increasing heat treatment temperature, whereas they decreased with increasing H₂O/MAS molar ratio. The refractive index of coating films increased with increasing heat treatment temperature. In addition, flat and transparent free‐standing films (0.24–0.27 mm thickness) were prepared from MA‐PS that were crack‐free after heat treatment at 1000 °C. Copyright © 2001 John Wiley & Sons, Ltd.     

Electroless Copper Plating on Liquid Crystal Polymer Films Using Dimethylamine Borane as Reducing Agent

Dimethylamine borane (DMAB) was used in electroless copper plating on liquid crystal polymer (LCP) films. An orthogonal test was applied to optimize the plating condition. With Cu film resistivity as the evaluation index, the optimum plating condition is: 10 g/L of CuSO₄ ? 5H₂O, 14 g/L of EDTA‐2Na, 6 g/L of DMAB, 9.5 of pH value and 50 °C. As pH value increases, the Cu film resistivity decreases and the depo‐ sition rate increases. As temperature increases, the Cu film resistivity decreases first and then increases with a minimum at 50 °C while the deposition rate increases first and then decreases with a maximum at 50 °C. The decreased Cu film resistivity can be attributed to the occurrence of CuO. The adhesive strength of copper layer to LCP film is constant at pH values lower than 8.5 and decreases slightly with the increase in pH value. As temperature increases, the adhesive strength decreases slightly. The decreased adhesive strength with both pH and temperature may be a result of an increased corrosion attack from the bath to the surface of LCP films. Low Cu film resistivity and high deposition rate as well as high adhesive strength can be obtained using DMAB reducing agent.     

Copolymerization of fluorene‐based main‐chain benzoxazine and their high performance thermosets

A series of fluorene‐based benzoxazine copolymers were synthesized from the mixture of 9,9‐bis(4‐hydroxyphenyl)fluorene and bisphenol A, and 4,4′‐diaminodiphenyloxide and paraformaldehyde. And the cured polybenzoxazine films derived from these copolymers were also obtained. Fourier transform infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonances confirmed the structure of these benzoxazines. Their molecular weight was estimated by gel permeation chromatography. The curing behavior of the precursors was monitored by FTIR and differential scanning calorimetry. Dynamic mechanical analysis and thermogravimetric analysis were performed to study the thermal properties of the cured polymers. The cured polybenzoxazines exhibit excellent heat resistance with glass transition temperatures (T_g) of 286–317°C, good thermal stability along with the values of 5% weight loss temperatures (T₅) over 340°C, and high char yield over 50% at 800°C. The mechanical properties of the cured polymers were also measured by bending tests. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of Perfluorinated Oxetane and Surface Properties of Its Cationic UV Cured Coating as a Reactive Additive

Perfluorinated oxetane(F-OXE) was synthesized via the ring-opening reaction of epoxy-functionalized oxetane with 2-(perfluorooctyl)ethanol under base-catalysis, and characterized by FTIR and ¹H NMR spectroscopy. The synthesized F-OXE was mixed with a commercial cationic UV curable resin, UVR6110, as a reactive additive at different mass fractions, and UV-irradiation cured in the presence of triphenylsulphonium hexafluoroantimonate as a cationic photoinitiator. The surface property study of cured films indicated that both hydrophobicity and oleophobicity were effectively enhanced by the addition of a small amount of F-OXE. The contact angles of water and 1-bromonaphthalene on the surface of the cured film with 1.0%(mass fraction) F-OXE loading increased from 72° to 106° and from 0° to 76°, respectively, compared with those on the surface of the film without F-OXE addition. The surface tension of UVR6110-F-OXE cured film decreased greatly from 55.6 mN/m of referenced film to 22.9 mN/m. The results from X-ray photoelectron spectroscopy analysis confirm the migration and aggregation effect of perfluoroalkyl group to the surface of cured film. For 1%(mass fraction) addition of F-OXE, the relative content of fluorine greatly increased from 0.70%(mass fraction) in the interior of the cured film to 36.73%(mass fraction) at the surface of the cured film, whereas those of carbon and oxygen decreased from 73.29% to 40.96% and from 26.00% to 22.30%, respectively.     

Effect of Polymerizable Photoinitiators on the UV‐polymerization behaviors of photosensitive polysiloxane

In this contribution, three polymerizable benzophenone photoinitiators containing maleimide group including 4‐maleimidebenzophenone (MBP), 4‐chlorine‐4′‐maleimide benzophenone (CMBP), and 4‐maleimide‐4′‐[(4‐maleimide)thiophenyl]benzophenone (MMTBP) were designed and synthesized to enhance the polymerization degree of photosensitive polysiloxane containing methacryloxy active groups (MAPSO). The polymerization behaviors of the MAPSO cured by different photoinitiators were investigated using Fourier transform infrared (FTIR). It was noted that the MAPSO initiated by MMTBP showed a high carbon–carbon double bond conversion above 80% because of the existence of thiophenyl group which could generate more radicals from the photolysis reaction at the C? S bond. In addition, the thermal stability of the UV‐cured MAPSO were studied by thermogravimetric analysis (TGA), the result showed that the initial 5% mass loss (T _5%) and residual weight percent at 800 °C in nitrogen of the UV‐cured MAPSO initiated by MMTBP systems was 200 °C and 33.8%. Thus, this work provides a new perspective and efficient strategy to improve the polymerization degree of UV‐curable polysiloxanes with carbon–carbon double bonds. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1696–1705