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.     

Investigations for obtaining semi-interpenetrating polymer networks based on monomers of different reactivity toward radicals

Classically, the one-step synthesis of interpenetrating polymer networks (IPNs) and related materials requires noninterfering polymerization modes to achieve distinct networks, held together by only physical entanglements. For the combination of (meth) acrylic and allylic monomers, both polymerizable by free radicals, a new in situ sequential synthesis for obtaining semi-IPNs is proposed. Using specific initiators that decompose at two different temperatures, refractive index measurements, Fourier transform infrared spectroscopy, and dynamic mechanical analysis have shown that neat species are formed and that the two monomers do not copolymerize. © 1993 John Wiley & Sons, Inc.     

Hybrid organic-inorganic materials using zirconium based NBBs and vinyl trimethoxysilane: Effect of pre-hydrolysis of silane

Various Nano Building Blocks (NBBs) such as polyhedral silsesquioxanes (POSS), functionalized metal oxide particles and transition metal oxoclusters have been already developed and used to improve thermal and mechanical properties of organic polymers. The NBBs ideal for the preparation of hybrid materials and nanocomposites are monodispersed, well-defined objects capped with polymerisable functions suitable for copolymerisation with organic monomers.In this study zirconium oxoclusters (ZrNBB) were obtained as a crystalline precipitate by reaction between zirconium propoxide and vinylacetic acid. They were post-functionalised by copolymerisation with vinyl trimethoxysilane in different molar ratios. The hybrid samples were prepared both with the organosilane pre-hydrolysis step and without adding water. Hybrid materials were obtained through the radical polymerization process by adding benzoyl peroxide (BPO). Silane pre-hydrolysis prevents bulk samples from being obtained.The polymerization process was studied using differential scanning calorimetry (DSC), and the shear storage modulus (G′) and loss modulus (G″) of hybrid polymers were investigated by dynamic mechanical spectroscopy (DMS). Multinuclear liquid- and solid-state NMR analyses and Fourier transform infrared (FTIR) spectroscopy were used to characterize the reagents and hybrid materials, and to study the influence of the synthesis conditions on condensation and polymerization.     

Transparent multiphasic polystyrene/epoxy blends

Blends of polystyrene (PS) with an epoxy monomer (DGEBA) and a tertiary amine (BDMA), were initially miscible at 120°C but phase‐separated at very low conversions in the course of polymerization. Although there was a significant difference between the refractive indices of polystyrene and the DGEBA/BDMA solution, the refractive index of the epoxy network increased in the course of polymerization, attaining a value close to that of PS at complete conversion. A sharp decrease of the light transmittance was observed at the cloud‐point, observed at very low conversions. However, the continuous increase of the refractive index of the epoxy phase with conversion produced an approximate matching of both refractive indices, leading to transparent materials at complete conversion. Morphologies generated by reaction‐induced phase separation depended on the molar mass distribution of polystyrene and its mass fraction in the blend. For a PS with a high value of the mass‐average molar mass (M_w), it was possible to generate a dispersion of PS particles in the epoxy matrix (blends containing 5 wt% PS), phase‐inverted morphologies (blends containing 15 wt% PS) and double‐phase morphologies (blends with 10 wt% PS). Therefore, PS/DGEBA/BDMA blends could be used to obtain transparent epoxy coatings toughened by polystyrene particles or transparent polystyrene parts reinforced by a dispersion of epoxy particles.     

Synthesis of highly refractive and transparent poly(arylene sulfide sulfone) based on 4,6-dichloropyrimidine and 3,6-dichloropyridazine

A highly refractive and transparent poly(arylene sulfide sulfone) (PASS) containing pyrimidine (or pyridazine) unit has been developed. The polymer was prepared by a polycondensation reaction of 4,4′-dimercaptodiphenyl sulfone (DMDPS) and 4,6-dichloropyrimidine (DCPM) (or 3,6-dichloropyridazine (DCPD)). They showed good thermal stabilities such as a relatively high glass transition temperature of 193–202 °C and a 5% weight loss temperature (T_5%) of 370–372 °C. The optical transmittance of the polymer at 450 nm is higher than 81%. The heterocycles unit and plural –S– linkages provides the polymer with a high refractive index of 1.737–1.743 at 633 nm and a low birefringence of 0.003–0.004.     

Responsive plasma polymerized ultrathin nanocomposite films

The plasma polymerization of NIPAAM and titanium isopropoxide monomers into responsive ultrathin films with responsive optical properties using plasma enhanced chemical vapor deposition is reported. The composite ultrathin films possess a large window for potential changes in their refractive index from 1.60 to 1.95. We demonstrated that these polymer films exhibit fast (transition time below 2 s), large, reversible, and repeatable changes to their thickness and refractive index as a function of periodic environmental humidity changes.     

Transparent red -emitting silicone resin for color conversion and encapsulation of NUV light-emitting diodes

Herein, a novel transparent phenyl vinyl silicone resin nanocomposite containing exfoliated fluorescent Eu-containing hydrotalcite-like compound (EFHSN) is developed to serve as a dual role of color conversion and encapsulation material. Excited by near-NUV light, the EFHSN emits a strong characteristic red light (614 nm). Meanwhile, the EFHSN shows not only excellent transparency (T > 95%) in the UV-Vis region and high refractive index (1.46) but also superior thermal stability, which could meet the need of commercial encapsulation materials and optical application. Therefore, the EFHSN is expected to be used in InGaN-based NUV light-emitting diodes and flexible optoelectronic device.     

Synthesis and cross-linking of bifunctional monomers containing carbazole moieties

New bifunctional carbazolyl-containing monomers were synthesized and their cationic photo-initiated polymerization investigated. The monomers containing two reactive groups such as epoxy, oxetanyl and vinyloxyethyl, were prepared from commercially available 9-(2,3-epoxypropyl)carbazole. The kinetics of UV curing of the monomers was monitored by real-time FT-IR technique. The type of functionality was found to have a considerable influence on the photo-curing rate, but has not an evident effect on the final reactive group conversion. The cross-linked systems were found to have low glass transition temperatures ranging from 7 to 10 °C. Electron photoemission spectroscopy revealed ionization potentials of 5.75–5.8 eV for the thin cross-linked layers of the monomers.     

五价有机铋的合成及其在聚氨酯中的应用

合成了7种无毒的新型有机铋催化剂，采用核磁共振仪、质谱仪（MS）和红外光谱仪（FTIR）等对其进行表征，确认了其化学组成，并将其应用于聚氨酯涂膜材料制备，研究催化剂结构和添加量等对涂膜的固化时间、抗腐蚀性能和拉伸性能等的影响。结果表明，五价有机铋催化剂性能明显好于三价铋，0.3 %（质量分数，下同）的铋金属催化剂即可将聚氨酯涂膜的固化时间缩短至其四分之一，耐溶剂性能提高30 %，拉伸强度增加33 %，断裂伸长率降低35 %；铋分子中芳基的平面性对其活性影响很大，含有氧桥二苯结构配体的催化剂由于平面性好，显示出了较好的催化性能。     

Comprehensive study of metal on the characteristic properties of epoxy resins

A series of different type of epoxy resins containing metal(s) have been prepared by the using cobalt acrylate (CoA₂), nickel acrylate(NiA₂),bismuth acrylate (BiA₃) during resinification. The values of epoxide equivalent weight, chlorine content increases whereas hydroxyl content, refractive index decreases in the presence of metal acrylate(s). The influence of complex formation of metal acrylate with ether linkage of epoxy resins were investigated by spectroscopy. Epoxy resins containing cobalt acrylate which was cured by p‐acetylbenzilidinetriphenylarsoniumylide (p‐ABTAY) shows better conducting properties in comparison to NiA₂ and BiA₃ containing epoxy resins. The dispersion of metal(s) in epoxy resins matrix was confirmed by scanning electron microscope (SEM). The glass transition temperature of epoxy resins containing CoA₂ is lower than that of blank epoxy resins and epoxy resins containing bismuth and nickel acrylate. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of trifluoromethyl substituted styrene polymers and copolymers with methacrylates: Effects of trifluoromethyl substituent on styrene

2-Trifluoromethyl styrene (2TFMS), 2,5-bis(trifluoromethyl) styrene (25BTFMS), and 3,5-bis(trifluoromethyl) styrene (35BTFMS) were synthesized. These styrenes were readily polymerized in bulk and also in solution using AIBN as a free radical initiator. The polymerization rate of these trifluoromethyl substituted styrenes and other monomers such as styrene (St), pentafluorostyrene (PFS) and 4-trifluoromethyl-tetrafluorostyrene (TFMTFS) were measured in benzene and dioxane by monitoring the ¹H NMR spectra of the double bond hydrogen. The order of polymerization rates was TFMTFS > 35BTFMS > 25BTFMS > PFS > 2TFMS > St. T_gs of styrene polymers with CF₃ substituted on the ortho position of the phenyl ring were much higher than those of the meta and para substituted styrenes due to the steric hindrance of the bulky CF₃ group close to the polymer main chain, which resulted in a decrease in the segment mobility of the polymer chains and an increasing T_g of the polymers. The copolymers of 2TFMS with methyl methacrylate (MMA) and also 25BTFMS with trifluoroethyl methacrylate (TFEMA) were prepared. T_gs of the copolymers were in the range of 120-145 °C and the copolymers were transparent and thermally stable. The copolymer films were flexible and exhibited high transmittance as the homopolymers of MMA and TFEMA. Thus, these copolymers may be utilized as novel optical materials.     

Covalent attachment of chromophores to chlorinated copolymers for optical waveguides: Synthesis and optical characterization

Polymeric optical devices are attracting increasing interest in the field of photonics because of the very appealing performances as structures for both propagating and modulating light signals according to the properties of the employed organic materials. This paper reports the preparation and characterization of low-loss polymer waveguides fabricated from chlorinated copolymers by photochemical crosslinking. A novel monomer derived from reaction between glycidyl methacrylate (GMA) and the chromophore Disperse Red 19 (DR19) was prepared and successfully copolymerized with GMA and chlorostyrene (CS) to obtain the dye-modified copolymer. The latter was crosslinked by photoinitiated polymerization of the pendant epoxy groups, to obtain stable polymeric waveguides. It was found that the major product of the reaction between GMA and DR19 was formed through transesterification of the methacrylate with elimination of glycidol, while traces of products deriving from the epoxy ring-opening reaction were detected. The presence of the nitro substituent on DR19 favoured chain-transfer reactions during the polymerization reaction, leading to a decrease in the polymerization degree. It was also observed that the presence of grafted DR19 negatively affected the crosslinking reaction, as a lower epoxy group conversion was observed for the modified copolymer. Thermal analysis showed increased thermal stability for the copolymer containing DR19. m-line spectroscopy was used to measure the refractive index at 632.8 nm. The experimental results confirm that the new class of chlorine-based polymeric materials represent a very attractive proposal in the panorama of materials employed in the fabrication of electro-optical devices for telecommunication applications.     

Rapid and non-destructive identification of graphene oxide thickness using white light contrast spectroscopy

By white light contrast spectroscopy, we have successfully identified number of graphene oxide (GO) layers (⩽10 layers) and obtained a new refractive index of GO sheets (⩽10 layers) of n_GO = 1.2–0.24i. For few layers (⩽10 layers) GO sheets, both the contrast at ∼580 nm wavelength and the Raman intensity of G band linearly increase with the increase of the layer numbers. However, due to the laser induced heating effects and the requirement of a reference Raman spectrum in Raman spectroscopy measurements, contrast spectroscopy is non-destructive and more efficient. Simulations based on the Fresnel’s equations agree well with evolution of the contrast and G band intensity as a function of number of layers. The precise refractive index of GO obtained in this work can be widely used in further study of GO. Therefore, our experimental contrast values can be directly used as a standard to identify the thickness of GO on Si substrate with 300 nm SiO₂ capping layer, which paves a novelty way towards future fundamental research and applications of graphene-based materials.     

Synthesis and characterization of perfluorocyclobutyl (PFCB) polymers containing pendent phenylphosphine oxide

Three phenylphosphine oxide (PPO) containing trifluorovinyl aryl ether monomers were synthesized and polymerized via thermal cyclodimerization affording perfluorocyclobutyl (PFCB) polymers containing PPO pendent groups. The new polymers exhibited moderate to high glass transition temperatures (T_g=145-217 °C) and good thermal stability in nitrogen (5% weight loss, T_d>402 °C). Copolymerization with traditional PFCB forming monomers such as 4,4′-(trifluorovinyloxy)biphenyl resulted in film forming transparent thermoplastic copolymers with improved solubility and further enhanced thermal stability. Semi-fluorinated PPO containing polymers of this type may find potential application as space environment durable materials.     

High-refractive quinolinone-based polymers for ophthalmic devices

Seven novel high refractive index (HRI) acrylic monomers, comprising the quinolinone structural motive, have been synthesized and characterized. Cross-linked homo- as well as copolymers were prepared by photochemical bulk polymerization. The homopolymers show refractive indices at 589 nm (n ₅₈₉) ranging from 1.60 up to 1.68, glass transition temperatures (T _g) from 52 to 76 °C, and Abbe numbers (ν _Abbe) of 19 to 25. Due to these parameters, the homopolymers are not suitable to be used directly for intraocular lens (IOL) manufacture, but the quinolinone monomers may be used as high refractive index components in copolymers. Potential mixtures were calculated theoretically and one example, a copolymer with PEA and PEGPEA, was prepared and characterized. The experimentally found values were T _g?=?24 °C, n ₅₈₉?=?1.593, and ν _Abbe?=?28.3. Interestingly, the quinolinone compound which does not have any spacer between the polymerizable group and the high refractive index group appears to be the most useful one. The lightfastness of the new material fulfills the demands for IOLs. Quinolinone derivatives are promising new comonomers for high refractive index copolymers.     

Synthesis and characterization of polytriphenylamine based graft polymers for photorefractive application

Novel graft copolymers, PTPA-g-PEAs containing poly(triphenylamine) (PTPA) backbone and poly(ethyl acrylate) (PEA) branches were synthesized by the oxidative coupling polymerization of triarylamine monomers followed by grafting of ethyl acrylate via an atom transfer radical polymerization (ATRP). Photorefractive (PR) composites based on the graft copolymers showed good static PR properties and fast response time under moderate conditions. The highest diffraction efficiency (19.7% at 45 V/μm) was observed with the composite containing the graft polymer with 18 mol% of graft density and 27 wt% of PTPA. And the fastest response (8 ms at 50 V/μm) was achieved when PTPA content was 68 wt%.     

Additive and free-volume effects on the refractive index of a thiol-ene polymer network

A series of hard, transparent, thermoset polymer samples containing tetravinylsilane (TVS) and 1,3-benzenedithiol (BDT) with varying loadings of zirconium oxide clusters Zr₆(OH)₄O₄(OMc)₁₂ (ZOC) were synthesized. Resulting polymers exhibited a higher refractive index (n) than the parent polymer containing only the monomers TVS and BDT. The refractive index reached a maximum value of 1.711 at a ZOC loading of 3 wt% and then decreased as the ZOC concentration in the polymer matrix increased. The refractive index of ZOC was determined to be 1.540 using the Becke line method. Because the refractive index of ZOC is lower than that of the TVS–BDT polymer matrix, the finding that the incorporation of small quantities of ZOC can increase the refractive index of the TVS–BDT polymer composite was unexpected and is accounted for by the effects of ZOC on the packing efficiency of the composite.     

A macromolecular halogen‐free flame retardant and its effect on the properties of thermoplastic polyesters

A halogen‐free flame retardant with a macromolecular structure is presented. Its synthesis proceeds via polymerization of phosphorus‐containing acrylate monomers. The flame retardant was incorporated into poly(ethylene terephthalate) by extrusion. Samples with different concentrations (0.5, 2.5, and 5.0 wt%) as well as a 25 wt% masterbatch were prepared. All samples were transparent and colorless without any visible irregularities. Thermal investigations reveal an unchanged glass transition temperature. Tensile tests show the typical mechanical behavior of poly(ethylene terephthalate), but with an elevated Young's modulus. The burning behavior was investigated by several small‐flame tests in vertical and horizontal orientation, as well as by cone calorimetry. It is shown that samples with 2.5 wt% flame retardant pass the vertical UL94 test (V‐2, 20‐mm flame). The sample cannot be ignited in the horizontal fire test according to FMVSS 302. The oxygen index was measured to 28 vol%. Cone calorimetric measurements show that the effective heat of combustion as well as the total heat evolved is reduced.     

Novel Assemblies of Sn(II) Coordinated Polyimide Supported by a Ligand Containing N-Heterocyclic Phenantroline Unit

The purpose of this work is to investigate the possibility of the production of novel metal coordinated polyimides. This research primarily focuses on novel metal complex assemblies of Sn(II) linked to the polymer molecule by a ligand containing an N-heterocyclic phenantroline unit in the main chain. Polyimide with phenantroline units in the main chain was synthesized utilizing condensation polymerization of aromatic dianhyrides and the bis(5-aminophenantroline)dichlorotin(II) to yield metal coordinated polyimides. Characterization by thermal analysis, refractive index, and dielectric analysis revealed distinct differences between these new materials and the classical polyimides.     

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.