Narrow Results

We have prepared three C₆₀ polymers under high-temperature and high-pressure conditions, and confirmed them to be orthorhombic (1D), tetragonal and rhombohedral (2D) polymer by XRD method, respectively. The ¹³C MAS NMR spectra of both orthorhombic and rhombohedral polymer have been measured and two resonance peaks observed. One resonance at 73 ppm resulted from the sp³ carbons with an intermolecular bonding, the other at 145 ppm is from the inequivalent sp² carbons on the C₆₀ molecule. For 1D polymer, the fine structure of the main peak at 145 ppm has been analyzed. By simulation of the ¹³C MAS NMR peak shape of the inequivalent carbons, we propose that there exist nine inequivalent carbons on a C₆₀ molecule in the orthorhombic (1D) polymer.

Dynamic Monte Carlo simulations are performed for lattice self-avoiding tail-like polymer chains with one end attached to a non-interacting and impenetrable flat surface. The configurational entropy S_TL of the tail-like chain is determined by the scanning method. The entropy S_TL is smaller than that of the free chain without surface S_F. The entropy drop ΔS=S_F-S_TL increases linearly with lnn for short chains and increases linearly with n for long chains. However, the average entropy drop per bead ΔS/n decreases with n, indicating that the average effect of the surface on one chain bead decreases with the increase in chain length.

The purpose of this study is to obtain some information about the viscoelastic properties of the material and to see the effect of the addition of plasticizer on these properties. In particular, we try to study the loss of plasticizer, caused by ageing under conditions of utilization, on the properties of material at the neighborhood of vitreous transition.

Using a viscoelastimeter, the study of a polyamide-11 (PA11) at the neighborhood of its temperature of vitreous transition Tv has shown that the increase of the plasticizer rate clearly improves the properties of the material by decreasing its Tv temperature. The comparison of the curves giving the modulus of elasticity E' of the various samples showed that the mechanical properties of the material improve with the increase of the concentration of plasticizer, but ageing reduces this improvement by causing the loss of plasticizer, thus, the temperature range of utilization of material is reduced.

The translocation of polymer chain through an interacting pore under chemical potential difference Δμ is simulated using Monte Carlo technique. Three translocation modes, dependent on the polymer–pore interaction ε and Δμ, are discovered. The translocation process is found to be an nonequilibrium process, which influences the dependence of translocation time τ on ε and Δμ. It is found that τ decreases in a power law relation with the increase of Δμ, and the exponent is dependent on the interaction.

Diffusion of polymer in narrow periodical channels, patterned alternately into part $\alpha$ and part $\beta$ with the same length $l_p/2$, was studied by using Monte Carlo simulation. The interaction between polymer and channel $\alpha$ is purely repulsive, while that between polymer and channel $\beta$ is attractive. Results show that the diffusion of polymer is remarkably affected by the periodicity of channel, and the diffusion constant $D$ changes periodically with the polymer length $N$. At the peaks of $D$, the projected length of polymer along the channel is an even multiple of $l_p/2$, and the diffusion of polymer in periodical channel is nearly the same as that of polymer in homogeneous channel. While at the valleys of $D$, the projected length of polymer is an odd multiple of $l_p/2$, and polymer is in a trapped state for a long time and it rapidly jumps to other trapped regions during the diffusion process. The physical mechanisms are discussed from the view of polymer–channel interaction energy landscape.

Materials having nanoscale structures have shown potentials for applications in microelectronics, biomedicine and energy storage. A continuing challenge is the capability of fabricating multi-function nanodevices with controlled nanostructures and excellent performances. Measurement platforms, which provide accurate and detailed information on internal structures, surface morphologies, mechanical properties and electrochemical properties are a key to this challenge. In this review, we, in particular, highlight the crucial role of measurement techniques in quantifying these nanostructures and their properties.

The measurement of patients’ dosages of radiation caused by medical diagnostics continues to be challenging. A Cantor sequence photonic crystal structure using porous silicon doped with a polymer of polyvinyl alcohol, carbol fuchsin and crystal violet (DPV) is proposed. The influence rules of geometrical and optical parameters such as the radiation doses, number of periods, porosity of porous layers, incident angle and thickness of layers are investigated using MATLAB based on the transfer matrix method. The transmittance of the Cantor sequence of a defective photonic crystal sensor under different conditions is investigated to select the optimum conditions. The proposed system recorded the accepted sensitivity of 0.265nm/Gy, FoM of 6.5Gy${}^{-1}$, Q of 12,701, RS of $6\times 10^{-3}$ and LoD of $8\times 10^{-3}$ for gamma radiation. The suggested detector has simple design, accurate monitoring efficiency and immense potential for gamma radiation sensing.

In this work, the structure, dielectric and optical properties of PVDF/zirconia-based polymer nanocomposites were investigated. The morphology and structure of the nanocomposites were analyzed by XRD, SEM, FT-IR, UV and EDS analyses. It was determined that the forbidden gap for the PVDF/1%ZrO₂-based nanocomposite is 4.7eV, for PVDF/5%ZrO₂-4.5eV, and for PVDF/10%ZrO₂-4.2eV. It is shown that the dielectric permittivity of the nanocomposites increases sharply up to 3% of ZrO₂ nanoparticles in the polymer and then decreases slightly with an increase in the concentration of nanoparticles. An increase in the permittivity indicates an increase in polarization processes in nanocomposites at a 3% conentration of ZrO₂ nanoparticles in the PVDF matrix. It has been established that the dielectric loss tangent at low frequencies starts to decrease, and at high frequencies, it increases. The increase in the dielectric loss tangent at high frequencies is explained by an increase in relaxation processes and energy dissipation in these systems.