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Poly(ethylene glycol) (PEG) macromolecular brushes were synthesized directly via reversible addition-fragmentation chain transfer polymerization cyclopolymerization of diacrylate monomers bearing PEG functional groups through the formation of 11-member rings. The diacrylate monomers bearing PEG functional groups are the 1,2,3-triazole-tethered diacrylate macromolecular monomers with di erent PEG lengths synthesized via the so-called “click” chemistry. The bulky hindrance of PEG chains affected the polymerization behavior of the diacrylate macromolecular monomers, and the diacrylate monomers showed strong tendency to cyclopolymerization rather than crosslinking. NMR analysis and gel permeation chromatography profiles proved the high efficiency of cyclopolymerization without side reactions. The aqueous solutions of the obtained PEG macromolecular brushes were fluorescent under UV excitation. The fluorescence depended dramatically on the concentration of brush-like polymers due to the aggregation of cyclopolymer in water, and could be quenched by the addition of DNA.

The particle-in-cell simulations are performed to study the wake field as well as stopping power of two ion-beam pulses passing through a background plasma. The influence of plasma turbulence induced by the first pulse to the second pulse is discussed. When the density of the first pulse is much larger than the second one, the wake field in the plasma is dominated by the first pulse. In this case, the energy loss of the second pulse is completely determined by the distances between the two pulses. If the second pulse is located on the “negative area” of the wake field in plasmas, its energy loss will be greatly enhanced compared with the results of the individual-projectile. On the other side, the second pulse can be even accelerated when it is in the “positive area” of the wake field. The wake field induced by two identical pulses is also studied, and we find that the wake field can be enhanced due to the superimposed effect of the beam pulses. Otherwise, the wake field can be totally canceled out.

We performed two-dimensional particle-in-cell simulations to investigate how a magnetic field affects the wake field and stopping power of an ion-beam pulse moving in plasmas. The corresponding density of plasma electrons is investigated. At a weak magnetic field, the wakes exhibit typical V-shaped cone structures. As the magnetic field strengthens, the wakes spread and lose their typical V-shaped structures. At a sufficiently strong magnetic field, the wakes exhibit conversed V-shaped structures. Additionally, strengthening the magnetic field reduces the stopping power in regions of low and high beam density. However, the influence of the magnetic field becomes complicated in regions of moderate beam density. The stopping power increases in a weak magnetic field, but it decreases in a strong magnetic field. At high beam density and moderate magnetic field, two low-density channels of plasma electrons appear on both sides of the incident beam pulse trajectory. This is because electrons near the beam pulses will be attracted and move along with the beam pulses, while other electrons nearby are restricted by the magnetic field and cannot fill the gap.

A two-dimensional (2D) particle-in-cell simulation is carried out to study the collective effects on the wakefield and stopping power for a hydrogen ion beam pulse propagation in hydrogen plasmas. The dependence of collective effects on the beam velocity and density is obtained and discussed. For the beam velocity, it is found that the collective effects have the strongest impact on the wakefield as well as the stopping power in the case of the intermediate beam velocities, in which the stopping power is also the largest. For the beam density, it is found that at low beam densities, the collective contribution to the stopping power increase linearly with the increase of the beam density, which corresponds well to the results calculated using the dielectric theory. However, at high beam densities, our results show that after reaching a maximum value, the collective contribution to the stopping power starts to decrease significantly with the increase of the beam density. Besides, at high beam densities, the wakefield loses typical V-shaped cone structures, and the wavelength of the oscillation wakefield increases as the beam density increases.

The plasma screening effects of dense quantum plasmas on charge exchange processes of a fully stripped ion colliding with a hydrogen atom are studied by the classical trajectory Monte Carlo method. The inter-particle interactions are described by the exponential cosine-screened Coulomb potentials. It is found that in weak screening conditions, cross sections increase with the increase of the ionic charge Z. However, in strong screening conditions, the dependence of cross sections on the ionic charge is related to the incident particle energy. At high energies, cross sections show a linear increase with the increase of Z, whereas at low energies, cross sections for Z≥4 become approximately the same. The He2+ and C6+ impacting charge exchange cross sections in dense quantum plasmas are also compared with those in weakly coupled plasmas. The interactions are described by the static screened Coulomb potential. It is found that for both He2+ and C6+, the oscillatory screening effects of dense quantum plasmas a...

The plasma screening effects of dense quantum plasmas on H+ + H charge exchange and ionization cross sections are calculated by the classical trajectory Monte Carlo method. For charge exchange cross sections, it is found that the screening effects reduce cross sections slightly in weak screening conditions. However, cross sections are reduced substantially in strong screening conditions. For ionization cross sections, with the increase of screening effects, cross sections for low energies increase more rapidly than those for high energies. When the screening effects are strong enough, it is found that ionization cross sections decrease with the increase of incident H+ energy. In addition, the cross sections have been compared with those in weakly coupled plasmas. It is found that in weak screening conditions, plasma screening effects in the two plasmas are approximately the same, while in strong screening conditions, screening effects of dense quantum plasmas are stronger than those of weakly coupled plasmas.