  We study the dynamics of solutions of infinitely thin needles up to densities
deep in the semidilute regime by Brownian dynamics simulations. For high
densities, these solutions become strongly entangled and the motion of a needle
is essentially restricted to a one-dimensional sliding in a confining tube
composed of neighboring needles. From the density-dependent behavior of the
orientational and translational diffusion, we extract the long-time transport
coefficients and the geometry of the confining tube. The sliding motion within
the tube becomes visible in the non-Gaussian parameter of the translational
motion as an extended plateau at intermediate times and in the intermediate
scattering function as an algebraic decay. This transient dynamic arrest is
also corroborated by the local exponent of the mean-square displacements
perpendicular to the needle axis. Moreover, the probability distribution of the
displacements perpendicular to the needle becomes strongly non-Gaussian, rather
it displays an exponential distribution for large displacements. On the other
hand, based on the analysis of higher-order correlations of the orientation we
find that the rotational motion becomes diffusive again for strong confinement.
At coarse-grained time and length scales, the spatiotemporal dynamics of the
needle for the high entanglement is captured by a single freely diffusing
phantom needle with long-time transport coefficients obtained from the needle
in solution. The time-dependent dynamics of the phantom needle is also assessed
analytically in terms of spheroidal wave functions. The dynamic behavior of the
needle in solution is found to be identical to needle Lorentz systems, where a
tracer needle explores a quenched disordered array of other needles.
