Environmental etch performance, and scratch and mar of automotive clearcoats

Environmental etch damage to automotive coatings, and scratch and mar of these coatings are an important element of customer satisfaction as well as a significant warranty repair consideration for automotive companies. The conditions that result in environmental etch are examined and a laboratory test proposed. Data from this test are compared to automotive hoods exposed in Florida. The performance of various crosslinking chemistries is discussed and the requirements for improved environmental etch are outlined. Scratch and mar performance of these systems is also reviewed. We have found that coatings respond to physical stress by elastic recovery, by plastic flow and by brittle fracture. Classifying types of damage in this way is important for understanding the chemistry needed for improved scratch and mar of coatings.     

The influence of monomer types on the colloidal stability in the miniemulsion copolymerization involving alkoxysilane monomer

Unlike conventional emulsion polymerization, monomer droplet nucleation becomes dominant in miniemulsion polymerization, offering the miniemulsion polymerization a great advantage over conventional emulsion polymerization when incorporating alkoxysilane monomer, which can easily undergo premature hydrolysis and condensation reactions, into polymer latex. The extensive premature hydrolysis and condensation can lead to the issue of the colloidal instability. In this article, the influence of monomer types on the colloidal stability in the miniemulsion co-(or ter-)polymerization was investigated when incorporating alkoxysilane monomer into styrene or acrylate latex. In the cases of butyl acrylate (BA)/γ-methacryoxypropytrimethoxysilane (MPMS), BA/methyl methyacrlate (MMA)/MPMS, and BA/styrene (St)/MPMS miniemulsion polymerization, nearly no coagulum was observed. The obtained latex had a long shelf life. However, the coagulum was formed in the late stage of MMA/MPMS and St/MPMS miniemulsion copolymerization. The shelf life of the corresponding latex was short. The selection of the main monomer, which can fast consume alkoxysilane comonomer, was critical to obtain the stable latex. In this way, the alkoxysilane groups were completely buried in particles thus the coagulation caused by condensation reactions derived from the alkoxysilane hydrolysis among particles was suppressed.     

Synthesis and properties of an alkoxysilane dye containing three electronic donor groups for nonlinear optical applications

In order to obtain an efficient hybrid inorganic–organic nonlinear optical (NLO) materials, an azo-dye containing three electronic donor groups 2,5-dimethyl-4-(4′-nitrophenylazo)phenol (DMNPAP) was synthesized and reacted with 3-isocyanatopropyl triethoxysilane (ICTES) to give an alkoxysilane dye (ICTES–DMNPAP). Molecular structural characterizations for DMNPAP and ICTES–DMNPAP were investigated by elemental analysis, ¹H NMR, FTIR, UV–visible spectra and differential scanning calorimetry (DSC). The alkoxysilane dye could be hydrolyzed and polymerized in the presence of water, and then transparent hybrid films could be fabricated by spin coating on the indium–tin-oxide (ITO) glass substrates. Compared with the dye 4-nitro-4′-hydroxy-azobenzene (NHA) containing only one hydroxyl as donor group, DMNPAP exhibited larger β_CTμ_g value measured by solvatochromic method, and second harmonic generation (SHG) measurement of the hybrid films was in agreement with the result.     

Crosslinking of PET through solid state functionalization with alkoxysilane derivatives

A new way for crosslinking poly(ethylene terephthalate) (PET) films and fibers is described using solid state functionalization of the PET end groups (alcohol and acid) with two reagents, respectively, 3-isocyanatopropyltriethoxysilane (IPTESI) or/and 3-glycidoxypropyltrimethoxysilane (GOPTMSI). This functionalization is then followed by hydrolysis-condensation reactions of PET-alkoxysilane end groups leading to the PET crosslinking.First of all, the functionalization reactions were investigated on model compounds by ¹H NMR spectroscopy in a range of temperature 80-160 °C. Furthermore, the diffusion of reagents in solid PET, depending on the initial degree of PET crystallinity, was characterized in the same temperature range through the variation of sample mass. On the other hand, this method allowed us to determine the diffusion coefficients and the solubility of the reagents in solid PET at different temperatures and initial crystallinity degrees.End groups functionalized PET films and fibers by alkoxysilane were then crosslinked by immersion of the samples in hot water. The crosslinking density was characterized by measuring the insoluble fraction of PET in good solvent constituted by a mixture of trifluoroacetic acid and dichloromethane (50/50 vol.). An insoluble fraction close to 70% was obtained by the functionalization treatment of amorphous PET film (8% crystallinity) by a mixture of GOPTMSI + IPTESI (50/50 M) at 155 °C for 1 h followed by hydrolysis-condensation reactions at 80 °C for 72 h. Thermomechanical and thermal properties of films and fibers were observed and found to be considerably enhanced in comparison to the untreated samples. The tensile properties of these partially crosslinked samples were maintained up to 320 °C.     

Ammonolysis of (3-chloropropyl)trimethoxysilane

Technological parameters of the ammonolysis of (3-chloropropyl)trimethoxysilane to (3-aminopropyl)trimethoxysilane have been determined. Influence of temperature, reaction time and the molar ratio of ammonia to (3-chloropropyl)trimethoxysilane has been examined. Influence of the parameters has been described using the following factors describing the process: the degree of conversion of (3-chloropropyl)trimethoxysilane and the selectivity of transformation to (3-aminopropyl)trimethoxysilane in relation to consumed (3-chloropropyl)trimethoxysilane.     

Vapor‐Phase Deposition of Monofunctional Alkoxysilanes for Sub‐Nanometer‐Level Biointerfacing on Silicon Oxide Surfaces

Improving the performance and lowering the analyte detection limits of optical and electronic biosensors is essential for advancing wide ranging applications in diagnostics and drug discovery. Most sensing methods require direct linkage of a recognition element and a sensor, which is commonly accomplished through an organic monolayer interface. Alkoxyorganosilanes are typically used to prepare sensor surfaces on dielectric oxides. However, many silanes lead to roughened or thick interfaces that degrade device sensitivity. Here, controlled vapor phase deposition of monoalkoxysilanes is found to lead to monolayers resistant to elevated temperatures and extreme pH conditions. The formation of high density, subnanometer monolayers is demonstrated by ellipsometry, XPS, and AFM. The uniform attachment of these monofunctional silanes to such biosensing platforms as microarrays, field effect devices, and the formation of surface enhanced Raman spectroscopy substrates is demonstrated. The advantages of using this silane deposition protocol for the above technologies are also discussed.     

Photodynamic Antimicrobial Cellulosic Material Through Covalent Linkage of Protoporphyrin IX onto Lyocell Fibers

Here, we report the preparation of porphyrin-functionalized Lyocell fibers according to an azide-alkyne click concept. First, azido-modified Lyocell fibers and alkynylated protoporphyrin building blocks were prepared through alkoxysilane chemistry and Steglich esterification, respectively. Lyocell fibers were pre-activated by swelling in organic solvents in order to increase the accessibility of hydroxyl groups in the subsequent silanization process. The azide-equipped cellulosic matrix reacted with the propargyl groups of the protoporphyrin IX derivative in a copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC), by which protoporphyrin IX was introduced onto the surface of the Lyocell fibers. The modified building blocks and the final functionalized cellulosic materials were comprehensively characterized by FTIR, NMR, UV/Vis spectroscopy and elemental analysis. Photo-bactericidal activity of modified fibers against 2?gram-positive bacteria strains, including Staphylococcus aureus and Bacillus subtilis, were investigated and compared to those of unmodified and azido-modified Lyocell fibers. The results confirmed the photo-antibacterial activity of the synthesized fibers against both bacteria strains.     

Synthesis of novel stilbene-alkoxysilane fluorescent brighteners, and their performance on cotton fiber as fluorescent brightening and ultraviolet absorbing agents

Two novel fluorescent brightening agents (compounds 3a-b shown in Figure 1) were synthesized, using a facile three-step synthetic route, from 4,4′-diamino-2,2′-disulfonic-stilbene, cyanuric chloride, and a readily cross-linkable 3-aminopropyltrimethoxy silane. The products contain hydrolytically active trimethoxysilyl, (-Si(OCH)₃), functional groups that readily hydrolyze in the presence of water, and subsequently generate a water insoluble silicon cross-linked-network (Si-O-Si) via a condensation process. The cross-linked product hydrolyzes on treatment with hot aqueous sodium hydroxide to silanols (-Si(OH)₃) to form compounds 4a-b which are readily water soluble and produce a clear fluorescent solution. The silanol forms of compounds 4a-b were used for further characterization and performance evaluation. The structures of compounds 4a-b were characterized by ¹H-NMR, Fourier-Transform infrared (FT-IR) spectroscopy and negative electrospray ionization mass (⁻ESI-MS) spectroscopy. Compounds were applied to cotton fiber as fluorescent brightening agents and their performance was evaluated by measuring the degree of whiteness, ultraviolet protection factor (UPF), fluorescence and acid fastness. Results showed that application of 0.25% (o.w.f) of compounds 4a-b impart a high degree of whiteness (CIE WI = 144, 139) as well as good ultraviolet protection factor (UPF = 29, 27) on cotton fiber exhibiting a significant increase in whiteness and UV blocking properties compared to untreated substrate (CIE WI = 81, UPF = 5). Acid fastness tests of both compounds showed a slight change in fluorescence emission intensities as a function of pH. In acidic solutions, a shift in emission maximum occurs at pH 3 from 434 to 453 nm and from 435 to 457 nm, due to the protonation of amino and sulfonic groups of stilbene fluorophore which substantially reduces the quenching process.     

Alkoxysilane layers deposited by SC CO2 process on silicon oxide for microelectronics applications

Self-assembled monolayers are studied to replace metallic films used as barrier/adhesion layers between dielectric material and copper used for interconnects in semiconductor devices. In this study, alkoxysilane layers were deposited by SC CO₂ processes on oxidized Si substrates using mainly two silanes: mercapto and aminopropyltrimethoxysilane. In order to obtain various layers, several process conditions were tuned such the process mode, static and dynamic, the temperature and the solvent. X-ray reflectometry was the main technique used to probe the structural and morphological characteristics of the films. All of these results show that the structure of the resulting organic layer depends on the molecule and on the process conditions. Aminoalkyltrimethoxysilanes lead to polycondensed layers formed with a thermally activated reaction while self-assembled monolayers are obtained with mercaptopropyltrimethoxysilane whatever the process condition.     

Film formation and mechanical properties of the alkoxysilane-functionalized poly (styrene-co-butyl acrylate) latex prepared by miniemulsion copolymerization

Alkoxysilane-functionalized poly (styrene-co-butyl acrylate) latex was prepared via miniemulsion copolymerization of γ-methacryloxypropyltrimethoxysilane (MPS), styrene and butyl acrylate using AIBN at neutral condition. The effects of initiator types, pH values, and MPS contents on the premature cross-linking of the latex particles and the mechanical properties of the films were investigated by the swelling experiments and dynamic mechanical analysis. It was found that the storage modulus of the latex films and the glass transition temperature (T_g) increased with increasing MPS content. The acidification of latex prior to film formation and annealing the latex films could improve the mechanical properties of the films.