Nanofluidics derived from low‐dimensional nanosheets and protein nanochannels are crucial for advanced catalysis, sensing, and separation. However, polymer nanofluidics is halted by complicated ...preparation and miniaturized sizes. This work reports the bottom‐up synthesis of modular nanofluidics by confined growth of ultrathin metal–organic frameworks (MOFs) in a polymer membrane consisting of zwitterionic dopamine nanoparticles (ZNPs). The confined growth of the MOFs on the ZNPs reduces the chain entanglement between the ZNPs, leading to stiff interfacial channels enhancing the nanofluidic transport of water molecules through the membrane. As such, the water permeability and solute selectivity of MOF@ZNPM are one magnitude improved, leading to a record‐high performance among all polymer nanofiltration membranes. Both the experimental work and the molecular dynamics simulations confirm that the water transport is shifted from high‐friction‐resistance conventional viscous flow to ultrafast nanofluidic flow as a result of rigid and continuous nanochannels in MOF@ZNPM.
A rigid‐scaffold‐reinforced polymeric nanoparticles’ interfacial channel strategy is proposed for fabricating nanofluidic membranes that exhibit water permeance and dye/salt selectivity that are 1–2 orders of magnitude higher than conventional polymeric membranes. The unprecedented separation performance is due to the paradigm shift of water transport from conventional viscous flow to ultrafast nanofluidic flow in the membrane nanofluidics.
The failure criterion of rocks is a critical factor involved in reliability design and stability analysis of geotechnical engineering. In order to accurately evaluate the triaxial compressive ...strength of rocks under different confining pressures, a nonlinear empirical strength criterion based on Mohr-Coulomb criterion was proposed in this paper. Through the analysis of triaxial test strength of 11 types of rock materials, the feasibility and validity of proposed criterion was discussed. For a further verification, six typical strength criteria were selected, and the prediction results of each criterion and test results were statistically analyzed. The comparative comparison results show that the prediction results obtained by applying this new criterion to 97 conventional triaxial compression tests of 11 different rock materials are highly consistent with the experimental data. Statistical analysis was executed to assess the application of the new criterion and other classical criteria in predicting the failure behavior of rock. This proposed empirical criterion provides a new reference and method for the determination of triaxial compressive strength of rock materials.
By controlling the feed ratio of CMS/styrene and the polymerization time, a series of hyperbranched copolystyrenes（HBCPS） were synthesized with comparable weight-averaged molecular weights（Mw） but ...different degree of branching（DB） through atom transfer radical self-condensing vinyl copolymerization（ATR-SCVCP） with Cu Br/2,2？-bipyridyl as the catalyst. The resulting HBCPS samples were used to investigate the effect of branching architecture on their glass transition behavior. With the DB increased, the glass transition temperatures（Tg） of HBCPS samples measured by DMA and DSC both decreased. Their spin-lattice relaxation times（1H T1r） of protons displayed the same downtrend with increasing DB. Besides, a correlation between the Tgs and the DB was well established by all-atom molecular dynamics（MD） simulations. The values of MD-determined Tgs are little higher than the corresponding experimental ones. However, the dependence of Tgs on DB is in good agreement with the experimental results, i.e., Tg decreases both in experiments and simulations with increasing DB.
We present results of molecular dynamics simulations for coarse-grained polymers confined in nanopores in a wide temperature range to investigate the factors that affect the glass transition. We ...focus on the influences of interaction strength, confinement size and the mobility of boundary on the static and dynamic properties of confined polymers, and further study their influences on the glass transition temperature Tg and the fragility Df, which quantifies how rapidly relaxation times vary with temperature T. For the immobile nanopore boundary (i.e. the hard wall confinement model), strong attractive interaction between wall and polymer induces slow polymer dynamics near the wall, while the weak interaction gives rise to a relatively enhanced monomer mobility. The mobile nanopore boundary (i.e. the soft wall confinement model) has a great influence on the shift of Tg and Df: it accelerates the structural relaxation of nearby monomers and leads to a lower Tg and a larger Df. The soft confinement effect is more obvious for nanopores with strong interaction than those with weak interaction. In addition, smaller confinement size leads to lower Tg of confined polymers, except for those confined in hard nanopores with strong attractive interaction. Our analysis demonstrates the change of Tg of confined polymers is mainly controlled by the surface effects originated from the polymer–wall interaction and the mobility of nanopore boundary.
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•The hard nanopore with strong attractive interaction slows polymer dynamics near the wall.•The hard nanopore with weak attractive interaction accelerates polymer dynamics near the wall.•The soft nanopore boundary induces enhanced polymer dynamics.
Quantum spin-dependent transport in a ferromagnetic(FM)/DNA/ferromagnetic(FM) device is theoretically investigated based on the lattice Green function method and the Landauer-Büttiker theory. The ...effect of a transverse electric field on magnetoresistance (MR) of the device is investigated. It is predicted that either the direction or strength of the transverse electric field can change the MR of the device. We suggest a possible application of modulating MR of the FM/DNA/FM device by a transverse electric field.
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