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The automobile industry is incorporating more lightweight content in car designs to boost fuel-economy. New structural adhesives are needed to mitigate the corrosion and thermal expansion issues associated with joining dissimilar lightweight materials, but adhesive developers lack a fundamental understanding of the chemistry that occurs in the adhesive as the joint ages. In this study, we developed structural adhesive molecular models and applied classical molecular dynamics simulations and density functional theory calculations to gain molecular insights into the influence of water molecules on the properties of epoxy-based adhesives (DGEBA + Jeffamine (JD230)). The simulations were complemented by experimental synthesis and characterization. Our work underscores the impact of water molecules on the local structure of the epoxy network as well as resulting mechanical properties. Water molecules were mainly coordinated with hydroxyls, primary amines and secondary amines, but also weakly coordinated with ether linkages, which were found most probable to be labile. Simulated stress–strain data indicates that increasing the water content deteriorates the mechanical properties. The Young’s modulus decreased by ~ 30% when the water content increased to 3 wt%. This integration of molecular-level chemical insights with mechanical property simulations of the hydrated epoxy system and experimental validation holds the promise to advance lightweight joint technologies.

OBJECTIVE: Perfectionism, poor self-esteem and stress have all been described as important risk factors for eating disorders. The purpose of this study was to assess whether a stressful situation is significantly correlated to and associated with significantly higher levels of perfectionism, stress, quantifiable measures of eating disorders, and with significantly lower levels of self-esteem in a non-clinical sample. METHOD: Thirty-five female university students completed the Multidimensional Perfectionism Scale, the Rosenberg Self-Esteem Scale, the Perceived Stress Scale, and the Eating Disorder Inventory two times; once on an average university day and once on the day of an exam. Descriptive statistics and t-tests were calculated to verify whether a stressful situation was associated with a significant difference in levels of perfectionism, self-esteem, stress, and measures of eating disorders. Bivariate correlations were calculated for both the stress and non-stress situation, to observe how the dimensions of perfectionism, self-esteem, and stress were associated with measures of eating disorders. RESULTS: During the stress situation, the study participants had, on average, significantly higher levels of concern over mistakes, body dissatisfaction, drive for thinness, and perceived stress. Bivariate correlations revealed that during the stress situation perceived stress, cognitive variables and measures of eating disorders showed significant correlations with each other that were absent in the non stress situation. DISCUSSION: The results of the present study suggest that the dimensions of pathological perfectionism, low self-esteem, and perceived stress are related to an increase in dieting thoughts and dissatisfaction with body aspect in non-clinical women during a performance that could potentially challenge the perception of their self-esteem. The stressful situation can be interpreted as an experience of invalidation, which could explain the connection between cognitive constructs and behaviours related to eating disorders.

Using the power of light to drive controlled radical polymerizations has provided significant advances in synthesis of well-defined polymers. Photoinduced atom transfer radical polymerization (ATRP) systems often employ UV light to regenerate copper activator species to mediate the polymerization. Taking full advantage of long-wavelength visible light for ATRP would require developing appropriate photocatalytic systems that engage in photoinduced electron transfer processes with the ATRP components to generate activating species. Herein, we developed conjugated microporous polymers (CMP) as heterogeneous photocatalysts to exploit the power of visible light in promoting copper-catalyzed ATRP. The photocatalyst was designed by cross-linking phenothiazine (PTZ) as a photoactive core in the presence of dimethoxybenzene as a cross-linker via the Friedel–Crafts reaction. The resulting PTZ-CMP network showed photoactivity in the visible region due to the extended conjugation throughout the network because of the aromatic groups connecting the PTZ units. Therefore, photoinduced copper-catalyzed ATRP was performed with CMPs that regenerated activator species under green or red light irradiation to start the ATRP process. This resulted in efficient polymerization of acrylate and methacrylate monomers with high conversion and well-controlled molecular weight. The heterogeneous nature of the photocatalyst enabled easy separation and efficient reusability in subsequent polymerizations.

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