General problems of structural changes which occur at storage of two‐phase crystalline polymers with a metastable structure at room conditions are considered on the example of a vinylidene fluoride ‐ hexafluoropropylene copolymer. The physical aging occurs in flexible‐chain crystalline polymers (polyethylene, fluoropolymers under consideration, etc.), where, due to low glass transition temperatures, the liquid‐like dynamics of amorphous phase chains is realized at room temperature through cooperative micro‐Brownian motions with short relaxation times. Taking into account that covalent‐bound sections of the chains of the amorphous phase can enter the crystallites, the noted mobility may initiate changes in the size of the latter. Such a possibility is proved by the example of the noted copolymer. At low‐temperature crystallization of a vinylidene fluoride ‐ hexafluoropropylene copolymer from a solution the formed α‐phase crystals have little perfection. The size of the crystals increases when the films are stored in room conditions. Because of the crystal polymorphism, at the same time a certain fraction of γ‐phase crystals which are present in initial films undergo a polymorphic transformation γ → α. These processes lead to an increase in crystallinity. Moreover, during such processes additional structuring is observed, which is reduced to the displacement of various kinds of intra‐chain defects into the amorphous phase (and especially into the surface). Since the copolymers under study are ferroelectrics, they were studied by piezo force microscopy. It was found that despite the crystallization predominantly in nonpolar α‐phase, piezo force microscopy revealed a domain structure, which formation mechanism is discussed. The structural changes at physical aging of the films affect the character of the noted domain structure. Thus, it is suggested that the mechanism of the described structural changes is realized through the developed cooperative mobility of the chains in the amorphous phase, which characterizes the processes of rotational diffusion.
Dielectric response of vinylidene fluoride‐hexafluoropropylene copolymer, crystallized in different polymorph modifications, to a high‐voltage electric field was studied. Polarization switching at high electric fields below coercive was detected. It was found that crystallization of the copolymer predominantly in nonpolar α‐phase is accompanied by more intensive growth of electric displacement at polarization. For the sample with higher content of polar γ‐phase, the value of high‐voltage conductivity “anomalously” decreased with increasing field at fields above coercive. The data on the field dependences of the remnant polarization showed that this should be attributed to an increase of the effective capture cross section of deep traps of γ‐phase polar planes for impurity and injected carriers. X‐ray diffraction has revealed the field‐induced transition of a part of the chains of the amorphous phase to the crystal.
This paper reviews opportunities for using electron microscopy in various gas atmospheres for the analysis and morpho physiological modification of biological structures. The approaches that allow varying the gaseous phase content, as well as temperature, humidity, and pressure, are considered. The applicability of both kinetic and dynamic approaches to the tissue and bioinorganic structure manipulations is pointed out. The possibility of simulation of the beam induced formation and disintegration of abiogenetic molecular structures is also mentioned as a particular case of the electron beam influence and treatment of the precursor medium in an artificial atmosphere.
In this projecting work we propose a mass spectrometric patch-clamp equipment with the capillary performing both a local potential registration at the cell membrane and the analyte suction simultaneously. This paper provides a current literature analysis comparing the possibilities of the novel approach proposed with the known methods, such as scanning patch-clamp, scanning ion conductance microscopy, patch clamp based on scanning probe microscopy technology, quantitative subcellular secondary ion mass spectrometry or "ion microscopy", live single-cell mass spectrometry, in situ cell-by-cell imaging, single-cell video-mass spectrometry, etc. We also consider the ways to improve the informativeness of these methods and particularly emphasize the trend at the increasing of the analysis complexity. We propose here the way to improve the efficiency of the cell trapping to the capillary during MS-path-clamp, as well as to provide laser surface ionization using laser trapping and tweezing of cells with the laser beam transmitted through the capillary as a waveguide. It is also possible to combine the above system with the microcolumn separation system or capillary electrophoresis as an optional direction of further development of the complex of analytical techniques emerging from the MS variation of patch-clamp.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.