The reactivity ratios for the bulk free‐radical copolymerization of n‐butyl acrylate (BA)/n‐butyl methacrylate (BMA) are estimated at 80 °C. By performing a series of low conversion runs including replicate runs, the reactivity ratios are estimated as rBA = 0.460 and rBMA = 2.008. Runs to high conversions are then conducted at three different feed compositions (fBMA = 0.2, 0.5, and 0.8) to validate the reactivity ratios. The composition data from the high conversion experiments show good agreement with the estimated reactivity ratios in the integrated form of the Mayo–Lewis model. The molecular weight, gel content, and glass transition temperature of BA/BMA copolymers are also determined.
Two imaging modalities based on molecular and elemental spectroscopy were used to characterize a painting by Cosimo Tura. Visible‐to‐near‐infrared (400–1680 nm) reflectance imaging spectroscopy (RIS) and X‐ray fluorescence (XRF) imaging spectroscopy were employed to identify pigments and determine their spatial distribution with higher confidence than from either technique alone. For example, Mary’s red robe was modeled through the distribution of an insect‐derived red lake (RIS map) and lead white (XRF lead map), rather than a layer of red lake on vermilion. The RIS image cube was also used to isolate the preparatory design by mapping the reflectance spectra associated with it. In conjunction with results from an earlier RIS study (1650–2500 nm) to map and identify the binding media, a more thorough understanding was gained of the materials and techniques used in the painting. 相似文献
The mixture of ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, bmimBF4) and water (2.5%, molar fraction) under isothermal conditions at 80 degrees C was investigated by FTIR spectroscopy and two-dimensional correlation infrared spectroscopy (2D-IR) methods. Three regions were focused: the OH stretching band of water (3755-3300 cm (-1)), the stretching band of CH on the imidazole ring (3300-3020 cm (-1)), and the BF stretching band of anions (1310-1260 cm (-1)). During this process, water was gradually evaporated as time passed, which produced influences on the interactions among cations, anions, and water molecules. In the FTIR analysis, we found an interesting "V"-shaped changing trend in peak areas of the C-H on the imidazole ring and the B-F stretching band; the inflection of the system was 913 s, gained through the "moving window" method. A two-step variation was accordingly found during this process. Hydrogen bonds formed by water molecules with cations or water molecules with anions were destroyed by the reduction of water, making a fall in the former period of "V" process, while electrostatic interactions newly formed between anions and cations leading to a rise during the latter period of this course. In this paper, various conformations formed among cations, anions, and water molecules were clearly assigned, and we managed to trace the whole dynamic mechanism of this isothermal process by 2D-IR techniques. 相似文献
A highly stable second-order nonlinear optical multilayer film was constructed on insulating substrates using the electric-field-induced layer-by-layer assembly technique. The substrates used in this method could be arbitrary. In another, the substrates could be modified with polyanion solution by spin coating as cladding layer. Then, the nonlinear optical multilayer films were assembled on the cladding layer directly by the electric-field-induced layer-by-layer assembly technique. The resulting cross-linked multilayer films fabricated by this method displayed high optical transparency, good thermal stability, and excellent nonlinear optical properties which can be made into waveguide devices directly. 相似文献