Delayed Absorption Superabsorbent Polymer for Strength Development in Concrete.

Superabsorbent polymers (SAPs) are used as internal curing agents in cementitious materials, which reduce autogenous shrinkage in concrete as they have a low water-to-cement ratios and improve the freeze-thaw resistance. However, the compressive strength of concrete may also be reduced due to additional voids in the hydrated cement matrix. In this study, we fabricated a delayed absorption type of SAP (I-SAP) composed of cross-linked modified acrylate and studied its absorption characteristics and effect on compressive strength after 28 days.

Effects of a New Type of Shrinkage-Reducing Agent on Concrete Properties.

Shrinkage-reducing agents have been developed to mitigate shrinkage and to control cracks in concrete. This study aims to evaluate the impact of a newly developed shrinkage-reducing agent (N-SRA) on concrete properties and to compare its properties with a conventional shrinkage-reducing agent (C-SRA). The hydration rate, compressive strength, splitting tensile strength, shrinkage, occurrence of cracking, and freezing and thawing were investigated.

Enantioselective Construction of Octahydroquinolines via Trienamine-Mediated Diels-Alder Reactions.

A trienamine-mediated asymmetric Diels-Alder reaction using a 5-nitro-2,3-dihydro-4-pyridone derivative as a dienophile in the presence of a secondary amine organocatalyst derived from cis-hydroxyproline was discovered. The reaction provides optically active octahydroquinolines through an endo-selective [4 + 2] cyclization pathway. The following stereoselective denitration, isomerization, and/or hydrogenation generated divergent stereoisomers of decahydroquinolines, which are useful synthons for the total synthesis of Lycopodium alkaloids.

Electron Spin Resonance Study of Molecular Orientation and Dynamics of Phenyl Imino and Nitronyl Nitroxide Radicals in Organic 1D Nanochannels of Tris( o-phenylenedioxy)cyclotriphosphazene.

Imino and nitronyl nitroxide (IN and NN, respectively) radicals such as phenyliminonitroxide (PhIN) and phenylnitronylnitroxide (PhNN), respectively, were dispersed in the organic 1D nanochannels of tris( o-phenylenedioxy)cyclotriphosphazene (TPP). Electron spin resonance (ESR) measurements were conducted on these inclusion compounds (ICs) in the temperature range 4.2-300 K.

ESR study of molecular orientation and dynamics of nitronyl nitroxide radicals in CLPOT 1D nanochannels.

New inclusion compounds (ICs) were prepared using the organic 1D nanochannels of 2,4,6-tris(4-chlorophenoxy)-1,3,5-triazine (CLPOT) as a nanosized template and nitronyl nitroxide (NN) radicals such as phenylnitronylnitroxide (PhNN) and p-nitrophenylnitronylnitroxide (p-NPNN). ESR measurements below 255 K for the CLPOT ICs diluted with spacer molecules gave rigid limit spectra similar to that for PhNN molecules in a glassy ethanol matrix at low temperature, which suggests isolation of the radical molecules. ESR measurements for them in the range of 290-400 K gave a modulated quintet ESR signal, which suggested uniaxial rotational diffusion of NN radicals in the nanochannels approximately around the principal y-axis of the g-tensors.