The development of actuators with remote control is important for the construction of devices for soft robotics. The present paper describes a responsive hydrogel of nontoxic, biocompatible, and biodegradable polymer carboxymethyl hydroxypropyl guar with dynamic covalent cross-links and embedded cobalt ferrite nanoparticles. The nanoparticles significantly enhance the mechanical properties of the gel, acting as additional multifunctional non-covalent linkages between the polymer chains. High magnetization of the cobalt ferrite nanoparticles provides to the gel a strong responsiveness to the magnetic field, even at rather small content of nanoparticles. It is demonstrated that labile cross-links in the polymer matrix impart to the hydrogel the ability of self-healing and reshaping as well as a fast response to the magnetic field. In addition, the gel shows pronounced pH sensitivity due to pH-cleavable cross-links. The possibility to use the multiresponsive gel as a magnetic-field-triggered actuator is demonstrated.

The investigation of the mechanical properties of polymer track-etched membranes (TMs) has attracted significant attention in connection with the extended region of their possible applications. In the present work, the mechanical stress fields around the pores of an elongated polyethylene terephthalate TM and around the 0.3 mm holes in model polymer specimens were studied in polarized light and with the finite element method. A break-up experiment showed the controlling role of stress field interaction in the forming of a microcrack system and the generation of a main crack with rupture of the TM (or model pattern). This interaction depended on the relative distance between the pores (holes) and their orientation. The results of the calculations of the pore distribution function over the surface of the TM via the net method and wavelet analysis are presented. The fractal character of pore distribution was established. The geometric characteristics of the TM pore system as initial defects are inherited by obtaining TM-based composites.

An energy criterion is proposed for the level of agglomeration (coalescence) of nanowires fixed at the base on a rigid substrate and immersed in a continuous medium (air, liquid), which excludes capillary phenomena. This criterion, based on the competition between the elastic energy of a bent nanowire and its surface formation energy, can also be applied to the attachment of nanowires to a surface and (in a modified form) to the coalescence of details of micro- and nanomachines. Nanowires for surface-enhanced Raman scattering, obtained by template synthesis based on track membranes, with subsequent removal of polymer, are considered as a specific example.

It is shown that the empirical Williams–Landel–Ferry (WLF) and Vogel–Fulcher–Tammann (VFT) equations, as well as the semiempirical equations of other researchers, for the viscosity η in the glass transition region are, in fact, hyperbolic functions of temperature with corresponding relationships between their parameters. The hyperbolic dependence can be derived from the mathematically common expansion of lnη into a Taylor series in a small temperature parameter near the glass transition temperature, provided that the temperature range satisfies approximately (T − T_g)/T_g ≲ 0.1–0.15). The applicability of the principle of corresponding states for glasses of similar composition follows from this expansion. A new two-parameter equation in the form of a second-degree polynomial is proposed for ln(η) in the glass transition region. This equation contains physically significant parameters and adequately describes the available experimental data for individual glass-forming substances. The temperature range over which the proposed series expansion up to the third (quadratic in the small parameter) term is valid can be determined only experimentally, because the coefficients of the series depend on the nature of the glass. For the specific experimental data we used, the sharp temperature dependence of the viscosity in the glass transition region makes the quadratic polynomial applicable over almost the entire temperature range studied.