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In this contribution, we reported the preparation of mesoporous silica with a reactive block copolymer as the porogenviasol-gel process. Firstly, poly(glycidyl methacrylate)-block-poly(ϵ-caprolactone)-block-poly(glycidyl methacrylate) triblock copolymer (PGMA-b-PCL-b-PGMA) was synthesized with the combination of ring-opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) polymerization. Thereafter, the triblock copolymer was functionalizedviaits reaction with 3-aminopropyltriethoxysilane (APTES) to afford a new reactive block copolymer bearing triethoxysilane moieties. The latter was employed to perform the inter-component sol-gel reactions with tetraethoxysilane (TEOS) to obtain the organic-inorganic composites with various compositions. The organic-inorganic composites were subsequently used as the precursors to obtain the mesoporous silica materialsviapyrolysis at elevated temperatures. The surface-area Brunauer-Emmett-Teller (BET) measurements indicate that the materials of mesoporous silica with adjustable porosity have been successfully obtained. [ABSTRACT FROM PUBLISHER]

Amino-terminated poly(propylene oxide) (ATPPO) was incorporated into epoxy resin to toughen thermosets. It was found that nanostructured thermosets were obtained; the nanostructures were characterized by means of atomic force microscopy and small-angle X-ray scattering. The formation of the nanostructures is interpreted on the basis of the occurrence of the reaction of terminal groups of ATPPO with diglycidyl ether of bisphenol A; this reaction is suggested to result in the formation of star-shaped block copolymers composed of poly(propylene oxide) (PPO) and epoxy blocks. Due to the presence of the star-shaped block copolymer produced in situ, the phase separation of PPO induced by the reaction was confined to the nanometer scale. The glass-transition behavior and fracture toughness of the nanostructured thermosets were investigated by means of differential scanning calorimetry, dynamic mechanical thermal analysis, and the measurement of critical stress intensity factors. The epoxy thermosets were significantly toughened by the inclusion of a small amount of ATPPO. The thermal and mechanical properties of the nanostructured thermosets are compared to the binary blends of epoxy resin containing hydroxyl-terminated poly(propylene oxide) (HTPPO) with identical molecular weight. With the identical composition, the nanostructured thermosets displayed higher fracture toughness than that of their binary blends. The difference in morphology and properties is interpreted in terms of the formation of the nanostructures. [ABSTRACT FROM AUTHOR]

A series of triaxial compression tests of frozen sandy soil are carried out under five confining pressures (1 MPa, 4 MPa, 6 MPa, 8 MPa and 10 MPa) at –6 °C. By comparing the grain size distribution curves of frozen sandy soil before and after shearing, it is found that significant particle breakage can occur during triaxial shearing. Particle breakage changes internal structure of geomaterials and has a significant effect on their stress–strain relationships. In order to accurately describe the effect of particle breakage of frozen sandy soil on the stress–strain relationships, an elastoplastic constitutive model for frozen sandy soil considering particle breakage is proposed. Based on the energy balance equation established by Indraratna and Salim, the constant critical state stress ratio (Mcr) in the energy balance equation is modified to the stress ratio (M) which changed with shear strain during the shearing process. A yield function, considering particle breakage, is proposed using the modified energy balance equation. The hardening law is determined based on the rebound test results of frozen sandy soil, and the associated flow rule is adopted in the model. Compared with experimental data, the model can well simulate the stress–strain relationships under different confining pressures for frozen sandy soil. The particle breakage characteristics of frozen sandy soil are studied. The energy balance equation considering particle breakage is modified to calculate the energy dissipation of frozen sandy soil. An elastoplastic constitutive model for frozen sandy soil considering particle breakage is proposed. [ABSTRACT FROM AUTHOR]