ABSTRACT. A series of 4-chloro-2-[(arylmethylidene)amino]phenols (1-11) including methoxy group were synthesized using appropriate synthetic route. The structures of the Schiff bases were characterized by FT-IR, UV-Vis, ESI-MS, 1 H and 13 C-NMR spectroscopic techniques and analytical methods. A relation is observed between melting points and existence of intramolecular hydrogen bonding. IR spectra of the compounds including and not including hydrogen bonding were compared. The compounds 2 and 4 show the characteristic UV bands attributed to the NH-forms. According to the 1 H-NMR spectral data the compound 2 has the strongest intramolecular hydrogen bonding and the compound 6 shows two isomeric structure. On the other hand, antibacterial and antifungal activities of the compounds were investigated. Most of the compounds show selective activity toward S. epidermidis and C. albicans. KEY WORDS KEY WORDS KEY WORDS
In this study, synthesis and polymerization of epoxidized methacrylated castor oil (EMETCO) is demonstrated. EMETCO is synthesized in two steps. Castor oil (CO) is methacrylated with methacryloyl chloride at the first step. Then the methacrylated castor oil (METCO) is epoxidized by Prilezhaev reaction. Structure of EMETCO is determined by 1H NMR and IR techniques. EMETCO was copolymerized with acrylic acid (AA), styrene (ST), and methacrylic acid (MA). Thermal and mechanical properties of the synthesized polymers are evaluated. Among the polymers synthesized EMETCO‐ST‐MA polymer gives the highest storage modulus at 2.25 GPa. On the other hand, EMETCO‐AA copolymer exhibited the lowest storage modulus at 350 MPa. Moreover, EMETCO‐ST copolymer shows the lowest 5% weight loss temperature while EMETCO‐MA exhibited the highest 5% weight loss temperature at 280 °C. Practical Applications: Epoxidized Methacrylated Castor Oil is a bio‐based epoxy acrylate monomer. The low viscosity and two different functional groups make this material suitable for many polymerization reactions and applications. This compound would be used as a replacement materials for many industrial monomers such as styrene, acrylated epoxidized soybean oil, or prepolymers in the future. EMETCO is a castor oil based epoxy acrylate monomer. It is a hybrid material that contains different types of polymerizable groups. Synthesis of the monomer is not complicated and completed in two steps. Methacrylation of castor oil occurs at the first step and epoxidation follows that reaction. The resultant compounds is a transparent oil.
Background The inherent colour change in maxillofacial silicone elastomers becomes perceptible 6–12 months after fabrication. Determining the factors that accelerate the degradation of the prosthesis can help the clinicians increase its life span. Therefore, the aim of the study was to investigate the effect of time passage, processing temperature, and molding-stone colour on the colour change of maxillofacial silicone elastomers after darkroom storage for 6000 h. Methods A total of ten study molds, each incorporating ten specimen gaps were fabricated using five different colors of dental stones. The gaps were filled with coloured Cosmesil M511 maxillofacial silicone elastomer. Five of the study molds, one of each stone color, were processed at room temperature (25 °C) for 24 h while the remainder were vulcanized at 100 °C for 1 h. Two stainless-steel molds were also fabricated to obtain a total of twenty control-group specimens of the same dimensions that were processed under the same conditions as the study molds. Colour measurements of the vulcanized silicone samples were performed using a Konica Minolta spectrophotometer. Initial measurements were obtained after the blocks were removed from the molds and the final measurements were recorded 6000 h after storage in the dark at 25 °C and 40% relative humidity. The CIEDE2000 colour-difference formula was used to measure the changes in the colour. One-way and two-way ANOVA, and an independent-sample t-test were used for statistical assessments. Results For every group, the colour change exceeded the perceptible thresholds. Thus, either the vulcanization temperature or the colour of the molding stone has a significant effect on the colour change over time. Those samples vulcanized in green and white molding stones at 100 °C exhibited a significantly higher ∆L*, ∆a*, and ∆b* values relative to the samples vulcanized at room temperature. Conclusion The molding-stone colour and vulcanization temperature both affect the degree of colour change after storage in a dark environment. The L*, a*, and b* values for the maxillofacial silicone elastomers are influenced by the direction of the increase or decrease according to the selected colour. This effect varies as the temperature increases.
BackgroundColour degradation is a major problem in maxillofacial silicone elastomers. Recent studies have focused on colour stability and the mechanical properties of the silicone elastomers. A colour match is also essential for the acceptance of the prosthesis by the patient. The aim of this study is to assess the colour degradation of the silicone elastomer after being moulded in different colours of dental stones at two different vulcanization temperatures.MethodsFive different colours of dental stones were used to fabricate a total of 120 silicone blocks using a Cosmesil M511 maxillofacial silicone elastomer. Vulcanization was completed at two different temperatures (25 and 100° Celsius). Colour measurements were obtained with a Conica Minolta spectrophotometer. The CIEDE2000 formula was used to calculate the colour differences (∆E00). Two-way ANOVA, one-way ANOVA with Bonferroni corrected post-hoc p values and independent samples t-test were used for the statistical analyses.ResultsHigh temperature vulcanization causes lightening of the maxillofacial silicone elastomers without regard to the dental stone colour (p = 0.001). Specimens moulded in green stone lightened least at room temperature (p = 0.999). Compared to the control group, at high temperature, all specimens moulded in coloured dental stones darkened significantly (p < 0.001 for white, blue and yellow; p = 0.006 for green; p = 0.045 for reddish-brown). In the high temperature group, the shift to a green chroma was significant in the white, yellow and green dental stones groups (p = 0.001, p = 0.002, p < 0.001, respectively). The mean b* of the high temperature control group was higher than that of the room temperature control group (p < 0.001). The only ∆E00 score lower than the perceptibility threshold for dental materials (∆E00 = 1.30) was between the room temperature control group and the room temperature green dental stone group (∆E00 = 0.96).ConclusionsGreen and blue dental stones cause less colour degradation in silicone elastomers. Reddish-brown dental stones cause the most colour degradation in silicone elastomers. At 100 °C, the colour of the silicone elastomer lightens and yellows even if the elastomer is vulcanized in a stainless steel mould. White, yellow and reddish-brown dental stones make the silicone elastomer appear more yellow even if the elastomer is vulcanized at room temperature.
A series of N‐(5‐chloro‐2‐hydroxyphenyl)‐(3/4/5‐substituted)‐salicylaldimines (I–XI) were synthesized using appropriate synthetic route. Their structures were characterized by FT‐IR, UV‐Visible, ESI‐MS, 1H and 13C NMR spectroscopic techniques and analytical methods. The crystal structure of N‐(5‐chloro‐2‐hydroxyphenyl)‐5‐bromosalicylaldimine (V) was determined by X‐ray diffraction at room temperature. Relationship between the melting points and the structures of the compounds was examined. Antimicrobial activity of the compounds was evaluated against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis. Antifungal activities were reported for Candida albicans. Schiff bases showed considerable antimicrobial activity against S. aureus, S. epidermidis and C. albicans. N‐(5‐Chloro‐2‐hydroxyphenyl)‐3‐hydroxy‐salicylaldimine (II) has the broadest and highest antimicrobial activity according to the others.
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