Synthesis and structure–property relationships of novel thiazole‐containing poly(amide imide)s with high refractive indices and low birefringences

The primary objective of this study was to investigate the structure–property relationships in high‐performance polymers with high refractive indices and low birefringences. A series of novel poly(amide imide)s (PAIs) were synthesized from a thiazole‐containing diimide–diacid monomer and various aromatic diamines. The influence of the pendant phenyl substituents on the optical properties of these PAIs was studied by comparison with the analogous polymers containing methyl groups. The PAIs exhibited excellent solubility and good thermal stability. The optical transmittances of the PAI films at 450 nm were higher than 75%. The combination of the thiazole units, thioether linkages and pendant phenyl rings provided the PAIs with high average refractive indices of 1.7361–1.7536 and low birefringences of 0.0066–0.0097 at 632.8 nm. © 2014 Society of Chemical Industry     

Synthesis and characterization of highly refractive polyimides derived from 2,7-bis(4′-aminophenylenesulfanyl)thianthrene-5,5,10,10-tetraoxide and aromatic dianhydrides

New polyimides (PIs) containing thioether and sulfonyl groups in their main chains have been developed. These PIs were synthesized by a two-step polycondensation procedure from several dianhydrides such as 4,4′-[p-thiobis(phenylenesulfanyl)] diphthalic anhydride (3SDEA), 4,4′-oxydiphthalic anhydride (ODPA), 4,4′-[sulfonylbis(phenylenesulfanyl)] diphthalic anhydride (pDPSDA) and a new sulfonyl and sulfur-containing aromatic diamine, 2,7-bis(4′-aminophenylenesulfanyl)thianthrene-5,5,10,10-tetraoxide (APTTT). All of the PIs show good thermal and optical properties such as optical transparency higher than 80% at 450 nm for a thickness of ca. 10 μm, glass transition temperatures higher than 250 °C, thermal decomposition temperatures (T_10%) in the range of 504-514 °C. Because of the two sulfonyl groups at each monomer unit in the polymer main chain, all of the PIs show good transparency maintaining relatively high refractive index.     

Moderately high refractive index,low optical dispersion polymers with pendant diamondoids

Soluble, colorless polymers containing pendant diamondoid moieties (adamantane and diamantane) were synthesized and characterized. The materials exhibited an unusual combination of moderately high refractive index with low optical dispersion. These properties may make the polymers valuable as specialty optical plastics. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and characterization of novel ZnS/sulfur-containing polymer nanocomposite optical materials with high refractive index and high nanophase contents

A series of novel transparent bulk ZnS-polymer nanocomposites with high refractive index were successfully prepared via in-situ bulk polymerization in the presence of 2-mercaptoethanol (ME)-capped ZnS NPs. The polymerization mechanism combined the step-growth and free radical polymerization of different monomers of episulfide, m-xylylene diisocyanante (XDI), 2-hydroxyethyl methacrylate (HEMA) and N,N-dimethylacrylamide (DMAA). The high refractive index of episulfide compounds, including ESGMES, ESDGEBA and MPS, were synthesized and used as monomers in polymerization systems. The cured nanocomposites with 30 wt% nanoparticles show high refractive index and good transparency. The refractive index of the nanocomposites could be continuously regulated in the range from 1.59 to 1.65 by the content of ZnS NPs and the pencil hardness is round about 5H. The content of ME-ZnS NPs can affect the thermal stability, mechanical and optical properties of the resulting nanocomposites, and the relationship between them were studied by TGA, DMA, pencil hardness test, Charpy impact test.     

Synthesis and evaluation of novel aromatic acrylic monomers for optically clear adhesive with high refractive index

Conventional optical polymers have low refractive index; (RI <1.5) which limit their usage in the field of optoelectronics. Therefore, two types of aromatic monomers with high RI value were developed; that is, ionic monomer (PA.HEMA.NEt3.H⁺) with RI = 1.5150 and monomer (PA.BA.GMA) with RI = 1.5403. The monomers were then individually combined with a newly synthesized oligomer based on phthalic anhydride epoxy acrylate; that is, (EA.PA) with RI = 1.5567. The structures of the synthesized monomers and oligomer were confirmed by NMR and FTIR spectroscopy and the chemical titration of the structure end groups. Different combinations of the monomers with oligomer EA.PA were examined to develop a UV-curing adhesive with appropriate viscosity. According to TGA and DMTA test results, the composition containing oligomer EA.PA showed improved thermal degradation stability and high glass transition temperature. The lap shear adhesion test showed positive effect of oligomer EA.PA and PA.BA.GMA with an adhesion strength of up to 1.2 MPa. The RI value of the composition containing PA.BA.GMA and oligomer EA.PA was measured as 1.55 which is qualified for the most applications in optoelectronic. The improvement in RI value may be well attributed to the presence of aromatic rings in the polymer chain backbone. The high degree of aromaticity is in favor with the improved thermal stability in adhesive composition.     

Synthesis and characterization of organo-soluble thioether-bridged polyphenylquinoxalines with ultra-high refractive indices and low birefringences

Two aromatic tetraketones, 4,4′-thiobis[(p-phenyleneoxy)benzil] (STK, 1) and 4,4′-thiobis[(p-phenylenesulfanyl)benzil] (3STK, 2) were synthesized by the nitro nucleophilic substituent reactions of 4-nitrobenzil and corresponding diol compounds. The two tetraketones were polymerized with three aromatic tetraamines, including 3,3′-diaminobenzidine (a), 3,3′,4,4′-tetraaminodiphenylether (b) and 3,3′,4,4′-tetraaminodiphenylsulfone (c), respectively to afford six thioether-bridged polyphenylquinoxalines (PPQs) - PPQ-1a-1c and PPQ-2a-2c. The obtained PPQs exhibited good solubility not only in conventional m-cresol and chloroform, but in the aprotic solvent - N-methyl-2-pyrrolidinone (NMP). PPQ-1c and 2c containing sulfone units were even soluble in tetrahydrofuran at room temperature with a solid content of 15 wt%. Flexible and tough PPQ films cast from their NMP solution showed good thermal stabilities, including glass transition temperatures in the range of 215-248 °C and 5% weight loss temperatures exceeding 500 °C in nitrogen. The PPQ films at a thickness of ∼10 μm exhibited moderate optical transparency at 450 nm. The best optical transmittance around 80% was achieved by PPQ-1c and 2c containing electron-withdrawing sulfone moieties. The synergic effects of flexible thioether linkages and highly conjugated quinoxaline rings in the present PPQs endowed them with ultra-high refractive indices up to 1.7953 at 632.8 nm and birefringences close to zero.     

高折射率脂环型环氧有机硅预聚体的合成

以高含氢硅油(甲基氢硅油)为原料,在Lamoreaux催化剂作用下,先与N-烯丙基咔唑进行硅氢加成反应,再与4-乙烯基环氧环己烷反应,合成了折射率达1.577的脂环型环氧有机硅预聚体(Ep-Cz-SiO)。Ep-Cz-SiO的结构由¹H NMR和IR表征,并确定了分子中咔唑基团的含量。咔唑基团的引入显著提高了环氧有机硅预聚体的折射率。热重分析表明,所制备的带有咔唑基团的脂环族环氧有机硅预聚体的热稳定性高于含氢硅油原料。     

The effect of solvent quality on the chain morphology in solutions of poly(9,9′-dioctylfluorene)

The thermodynamics of the alpha (α) phase to beta (β) phase transition was investigated in solution of poly(9,9′-dioctylfluorene) in a variety of solvents with UV-vis absorption spectroscopy, differential scanning calorimetry, fluorescence spectroscopy, atomic force microscopy, and near-field scanning optical microscopy. The results show that the solvent quality has a strong affect on the α- to β-conformational change. The trend in enthalpies and transition temperatures indicates that the transition results from an increase in intramolecular interactions upon chain collapse at lower temperatures. This transition leads to subsequent gelation and/or aggregation that stabilizes the β-phase at higher temperatures and leads to a large hysteresis in the transition temperature. The enthalpy for the transition from an aggregated β-phase to a fully solvated α-phase is found to be 21.04 kJ mol⁻¹ of monomer for toluene solutions. Differences between the measured heat and those previously reported are discussed.     

Studies on syntheses and properties of episulfide‐type optical resins with high refractive index

A series of novel high refractive index episulfide‐type optical resins were prepared by ring‐opening copolymerization of bis(β‐epithiopropylthioethyl) sulfide (BEPTES) with episulfide derivative of diglydicyl ether of bisphenol A (ESDGEBA) and 2,4‐tolylene diisocyanate (TDI), respectively, in the presence of triethylamine as a curing catalyst. The episulfide monomers, BEPTES and ESDGEBA, were synthesized from their corresponding epoxy compounds, respectively. The cured transparent resins exhibit high refractive index (n_d > 1.63) and relatively low dispersion. The refractive index (n_d) and Abbe's number (ν_d) of the BEPTES/ESDGEBA curing system increased linearly with the weight content of BEPTES monomer in the range from 1.633 and 34.0 for the copolymer with 10 wt % of BEPTES to 1.697 and 38.1 for the homopolymer of pure BEPTES. For the BEPTES/TDI curing system, the refractive index and Abbe's number varied linearly with the molar ratio of BEPTES to TDI from 1.652 and 28.7 to 1.669 and 34.6. High glass‐transition temperatures (T_g > 130°C) of the cured BEPTES/TDI resins were observed, which indicate that the cured BEPTES/TDI resins possess a good heat resistance. The optical, physical, and thermal properties of the episulfide‐type cured optical resins were also discussed in this study. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2426–2430, 2003     

High refractive index hyperbranched polymers with different naphthalene contents prepared through thiol-yne click reaction using di-substituted asymmetric bulky alkynes

In the present study, different aromatic moieties, naphthalene and benzene, were introduced into alkynes to constitute 1,3,5-tris(naphthylethynyl)benzene as B₃ monomer. This monomer could be reacted with different ratios of hexane-1,6-dithiol (A₂ monomer) via mono-selective Thiol-Yne reaction (TYR) to form hyperbranched polymers PI. TYR yielded in both, model reactions and polymerizations, mono-adducts with high regioselectivity and proved the absence of any bis-adducts. Polymers of very high molecular weights of up to 625,000 g/mol could be achieved without any sign of gel formation. All the polymers exhibit high transparency in the visible wavelength range and also show high refractive indices of up to 1.745 at 589.7 nm due to the high incorporation of naphthalene and phenyl groups. Besides, all polymers prove excellent solubility and processability together with excellent thermal properties.     

高折光指数含硅环氧树脂的合成与性能研究

将二苯基二氯硅烷经过氢化铝锂还原为二苯基硅烷,再与4-乙烯基环氧环己烷进行硅氢加成后合成了1种新型含硅环氧树脂二[2-(3,4-环氧环己基)乙基]二苯基硅烷(EODPS)。该树脂的折光指数达到1.567,并具有较好的透明度。采用甲基六氢苯酐和乙酰丙酮铝-二苯基硅醇组合物分别对EODPS进行固化。通过红外光谱,DSC分析表征了EODPS的结构,研究了其固化活性,并对固化后产物的热稳定性、力学性能和吸水性进行了测试,且与脂环族环氧树脂CEL-2021P性能进行了比较。结果表明,与CEL-2021P相比,EODPS具有更高的热稳定性和更低的吸水率,可用于LED封装。     

The research on syntheses and properties of novel epoxy/polymercaptan curing optical resins with high refractive indices

A novel thioether glycidyl resin bis[3-(2,3-Epoxypropylthio)phenyl]-sulfone (BEPTPhS) with high refractive index was synthesized by condensation of bis(3-mercaptophenyl)sulfone (BMPS) with epichlorohydrin. It's structure was characterized by FTIR, MS and NMR. It was the first time that trimercaptothioethylamine (TMTEA) was used as curing agent to cure epoxy resins. Optical resins possessing high refractive index were prepared by curing diglycidyl ether of bisphenol A (DGEBA) with the mixture of TMTEA and ethylendiamine (EDA) and by curing BEPTPhS/DGEBA with TMTEA. The research on the optical properties of resins of DGEBA cured by the mixtures of TMTEA and EDA indicated that these resins possess higher refractive index (n_d>1.60), lower dispersity (ν_d>34), high impact strength (IPS>30 kJ m⁻²) and higher transmittance. The n_d, ν_d and density of these resins varied linearly with the EDA content in the curing agent mixtures. The optimum ratio of the EDA content to that of TMTEA is 20:80 (molar ratio), at this ratio the cured resin has the optimum optical properties (n_d²⁰=1.61, v_d=35.4). The cured resins of BEPTPhS/TMTEA have a high refractive index (the highest is n_d=1.67). The optical, physical and thermal properties of the cured optical resins of BEPTPhS/TMTEA were discussed in this paper.     

The relationship between refractive index and optical properties of absorbing nanoparticle

This article represents an analytical formulation for optical properties of absorbing metallic nanoparticles in visible region of electromagnetic spectrum based on Mie theory, in order to find a clear relationship between fundamental characteristics of nanoparticles with their spectral behavior and color coordinate in CIELAB color space. Calculations were performed on nanoparticles with various diameters (d = 50, 100, and 200 nm), as well as complex refractive index with different real (n = 1.5, 2.0, 2.5, and 3.0) and imaginary (k = 0.001 and 0.1) parts. Obtained results reveal that scattering phenomena in nanoparticles are strongly linked to the particle size parameter and complex index of refraction. The results indicate that the reflectance and lightness (L*) of nanoparticles increases as a result of increase in their size and real part of complex refractive index and decrease with increasing the imaginary part of complex refractive index. The CIELAB colorimetric system was used for analysis the color of nanoparticles. According to obtained results, all nanoparticles have greenish‐blue color, and undergo color change as a result of varying in their size and the complex refractive index. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 477–483, 2016     

Preparation and properties of polythiourethane/ZnS nanocomposites with high refractive index

The inorganic–organic crosslinking polythiourethane/ZnS (PTU/ZnS) nanocomposites with high refractive index and transmittance were successfully prepared. The thiol‐capped ZnS nanoparticles with a diameter of about 5 nm were fabricated into the molecular chains of PTU via the formed covalent bonds between the capped ZnS and the matrix. The investigations demonstrated the ZnS nanoparticles were uniformly dispersed in the PTU matrix even at high contents. The optical studies showed the refractive index of the highly transparent nanocomposite films linearly increased from 1.643 to 1.792 with the increase of the ZnS content. The structure, morphology, and other properties were also characterized by FTIR, NMR, AFM, XRD, DSC, TGA, etc. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

高折射率含硫环氧树脂的合成与表征

利用间接法以巯基乙醇和环氧氯丙烷 (ECH)为原料通过 3步反应得到 2 ,3 二 (2 ,3 环氧丙硫乙硫基 )丙基·2 ,3 环氧丙基硫醚型环氧树脂 (TGEBES) ,其折射率和环氧值分别达 1.5 85 0和 0 .5 3;在没有任何催化剂的条件下 ,按以三元硫醇 (BES)和ECH物质的量比为 1∶3.6、在温度为 0～ 5℃下反应 3～ 4h ,环氧化反应的产率达到84 .5 %。并利用红外光谱和核磁共振对含硫高折射率环氧树脂的结构进行了表征 ;利用高效液相色谱对TGEBES和BES的纯度进行了测定 ,结果表明TGEBES和BES纯度分别达 96 %和 97.7%以上。     

高折射率含硫环氧树脂PTETE的合成与表征

以苯硫酚、氯乙醇和环氧氯丙烷为原料,通过直接法合成高折射率苯硫基乙基-2,3环氧1丙硫醚（PTETE）环氧树脂。研究了原料配比、温度和氢氧化钠的用量等因素对产物产率的影响。得出最佳反应条件为：反应温度为0～10℃,环氧氯丙烷、MEPS与NaOH摩尔比为1．25：1：1,产率91．50％,产物的折射率1.6016。并通过FT-IR对合成的原料和产物进行表征。     

Preparation and refractive index characterization of chalcogenide glasses with gradient refractive index

Infrared gradient refractive index (GRIN) lenses have great application value and potential in multispectral imaging systems. This study reports various chalcogenide axial GRIN glasses prepared using the hot-pressing diffusion method. It is worth noting that the S4–S60 GRIN sample has a difference in refractive index (RI) Δn of greater than 0.3 and a diffusion depth of about 5 mm, which is the deepest diffusion depth reported in chalcogenide glass to date. In addition, the linear portion in the profile of the GRIN sample has a RI difference of 0.15 and a thickness of 1.2 mm. The effects of the temperature, concentration difference, and diffusion time on the sample diffusion process are discussed. The dispersion properties of the GRIN samples were further calculated, providing a new option for correcting chromatic aberrations in optical systems. In addition, a method for the indirect nondestructive characterization of sample RI using the Raman intensity ratio is proposed, and the reliability of the method is verified by practical experiments, which is convenient for the subsequent measurement of the GRIN profile.     

Development and analysis of a high refractive index liquid phase Si3N4 slurry for mask stereolithography

Ceramic mask stereolithography additive manufacturing technology has the abilities of fast and accurate printing complex and personalized ceramic parts. However, since the ultraviolet light is strongly blocked by the ceramic particles in the slurry during exposure, the slurry with high refractive index ceramic particles has low cure depth, and serious light scattering. This investigation developed a curable silicon nitride slurry with a high refractive index liquid phase, which significantly reduced the refractive index difference between the liquid phase and the silicon nitride ceramic particles. The high refractive index acrylate monomer and solvent were chosen to increase the cure depth while ensuring the curing accuracy. Compared with the slurry whose liquid phase was pure HDDA, the addition of OPPEA and ACMO in the liquid phase showed a better refractive index increasing effect and the strongest cure depth and dimensional accuracy improvement. POE was verified as a suitable non-reactive high refractive solvent. The composition of 20 wt% OPPEA, 10 wt% ACMO, 40 wt% HDDA, and 30 wt% POE were optimized as the high refractive index liquid phase for 40 vol% solid phase silicon nitride slurry. A finite element analysis model of silicon nitride slurry was established, and the distribution of ultraviolet light intensity in silicon nitride slurry with high refractive index liquid phase was numerically simulated.     

Filled polymers with high nanoparticles concentration—Synthesis and properties

High refractive index optical compositions based on polymer matrices filled with high concentrations of ZnS nanoparticles were developed. These materials have good optical properties and processability like usual polymers, and they are suitable for factory scale use. At 25 vol % ZnS nanoparticles concentration an increase in refractive index up to 0.25 in 150 um transparent film was obtained. A process was develope for formation of polymeric compositions consisting of polymer filled with high concentrations of inorganic crystalline nanoparticles. Effects connected to high concentration of nanoparticles in the polymer were discussed. Optical properties of these materials were investigated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of carbazole‐substituted poly(dimethylsiloxane) and its improved refractive index

A series of substituted 9‐vinylcarbazole polysiloxane was synthesized followed by room temperature vulcanization to afford a crosslink network via trimethoxysilane crosslinker. Structural confirmation was made using FTIR, one and two‐dimensional ¹H‐ and ²⁹Si‐NMR spectroscopy. Quantitative estimation of the amount of substituted carbazole was made based on NMR data. These were related to the refractive index whose values were in the range of 1.4370–1.4625 at increasing carbazole content. These values are higher than uncrosslink series, attributable to the tightness of the systems. They displayed an improved thermo‐optic coefficient compared to linear unsubstituted polydimethylsiloxane (PDMS). The synergistic effect of substituted carbazole unit with the crosslink network of PDMS presents a viable choice of encapsulant for opto‐electronic devices. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41654.