Monolayers that are bonded via a covalent Si−C bond are prepared on a silicon(100) surface by reaction of a 1-alkene with the hydrogen-terminated silicon surface. The monolayers have been analyzed by infrared spectroscopy, X-ray reflectivity, and water contact angle measurements and display a remarkably high thermal stability. The reaction also works well for ω-functionalized 1-alkenes, provided that the functional group is properly protected. After formation of the monolayer, the protecting group can be easily removed without noticeable disturbance of the monolayer integrity, and the now reactive sites at the monolayer can be used for further functionalization, as has been shown in the case of ester-protected alcohol and carboxylic acids. Functional groups that are too close to the alkene moiety interfere with monolayer formation and yield disordered monolayers.

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We report experimental results for the wetting states of a melt of polystyrene in contact with a brush of polystyrene chains end-attached to a substrate. Wettability was assessed by monitoring the stability of an ultrathin film of the molten polymer; if the film remained stable and uniform for several days, it was considered to be a case of complete wetting, whereas spontaneous breakup (initiated by hole formation) was interpreted as partial wetting. The bare (oxidized silicon) substrate without the brush is partially wet. When the grafting density is varied, two wetting/dewetting transitions are found, depending on the length P of the chains in the melt. At low grafting densities, a transition from partial to complete wetting is observed, which is driven by the swelling of the attached chains and their mixing with the melt. At a higher grafting density, there is a second wetting transition back to partial wetting which we ascribe to the poor mixing between stretched chains in the brush and free chains. The experimental results are compared with scaling relations and numerical self-consistent-field (SCF) calculations. For melts of chains that are short compared to the grafted chains, these calculations confirm the occurrence of two transitions. For much longer chains in the melt, the calculations predict that the contact angle remains finite, but its value remains very low over a certain window of grafting densities. Moreover, the calculations indicate that the zero contact angle can become metastable in this regime. This is consistent with the experimental finding that there is, also at high P, a window of grafting densities where no instabilities are found. Around the onset of instability, the films disproportionate into complicated patterns of dry surface, mesoscopic films, and droplets. These results suggest that the disjoining pressure has a double minimum structure, which is consistent with SCF calculations.

Attenuated total reflectance (ATR) and Fourier transform infrared (FTIR) spectroscopy have been applied in the characterization of sticky dough surfaces. The characterization provides insight in the chemical distribution of gluten protein, starch, water, and fat during dough kneading. ATR is especially useful for selective sampling of dough surfaces because the depth of penetration of radiation is quite shallow. For dough, it is calculated to be in the order of 0.5–4 μm in the mid‐infrared, ideal for measurements of stickiness effects, where only the dough surface is of interest. To investigate the cohesive and adhesive properties of the individual dough constituents, dough was peeled from the ATR plate to study the material that adhered to it. The infrared spectra obtained indicate that fat and gluten protein appear to be located at the outer sticky dough surfaces, rather than water and starch. In comparison with gluten, the fatty component showed relatively strong adhesive forces to the ATR plate; a high residual fraction was measured after peeling the dough. Gluten proteins display different cohesion and adhesion properties that are strongly dependent on their hydration state. This indicates that the degree of hydration of gluten proteins contributes to the sticky properties of (overkneaded) dough. When analyzing gluten protein in D2O instead of a dough matrix, more or less similar results were obtained. Significant differences in amide I and amide II intensities were measured for kneaded and stretched gluten protein in comparison to untreated, wet gluten. Besides changes in the vibrational properties of the amide groups, conformational changes in the tertiary protein structure also were observed. It appears that kneading and stretching of dough results in a major decrease in α‐helices content, accompanied by an increase of extended β‐sheet conformations.

Fourier transform infrared analysis (FTIR) was used in combination with partial least squares regression (PLS) to predict the concentration of acetone in milk. FTIR spectra were compared with results of a gas-chromatographic head space method. Principal component analysis of whole spectra (3000 to 1000 cm(-1)) suggested to reduce the spectrum of analysis for acetone to 1450 to 1200 cm(-1). A second derivative was applied to the spectra to remove baseline effects and further enhance the spectral features. Full cross-validation was used to compare the reference with predicted acetone concentrations of samples not included in model development. PLS applied to the full spectral range resulted in a complex 19-factor model with a cross-validation error of 0.22 mM. After reducing the spectrum and taking the second derivative, we obtained a model with seven factors that yielded a cross-validation error of 0.21 mM. This compares favorably with a previously reported model with 20 factors and an error of 0.25 mM. Using PLS predictions to identify cows with subclinical ketosis resulted in 95 to 100% sensitivity and 96 to 100% specificity when the threshold for subclinical ketosis was 0.4 to 1.0 mM. The corresponding positive predictive values were > or = 76% and the negative predictive values > 98% throughout an assumed range of subclinical ketosis prevalence of 10 to 30%.

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The structure and binding properties of a series of receptor molecules based on the building block diphenylglycoluril are described. These receptors bind dihydroxy-substituted aromatic guests in chloroform solution by means of hydrogen bonding and tt-tt stacking interactions. IR difference spectroscopy shows that the hydrogen bonds are formed between the OH groups of the guest molecule and the 7r-electrons of the urea carbonyl groups present in the receptor. The structure of the complexes was further investigated by comparing the complexation-induced shifts in the 'H N M R spectra with the calculated shifts for a number of geometries of the host-guest complexes. These data demonstrate that the guest molecules are clamped within the cavity of the receptor.

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