Spin crossover polymer composites, polymers and related soft materials

Abstract

We review the synthesis, properties and applications of spin crossover polymer composites, polymers and some related 'soft' materials. These materials have received recently much attention because they provide an efficient way for the processing of spin crossover complexes in various shapes at various size scales and can give rise also to unique physical properties. First, we discuss in detail the state of the art of the elaboration of spin crossover polymer composites, using either inorganic complex precursors in solution or pre-formed spin crossover powder. A particular attention is paid on the influence of the polymer matrix on the spin crossover properties and on the use of 'active' polymers for development of synergies between the properties of the matrix and the load. Polymer composite devices for applications in the fields of artificial muscles, energy harvesting and thermochromic sensors are also highlighted. Then, more recent works, in which organic polymeric chains are used as ligands for the transition metal ions are presented. Finally, we overview various related 'soft' spin crossover compounds including spin crossover dendrimers, gels, liquid crystals and Langmuir Blodgett films with particular emphasis on compounds with supramolecular interactions of alkyl chains.

Fe(II) Spin Crossover/Polymer Hybrid Materials: Investigation of the SCO Behavior via Temperature-Dependent Raman Spectroscopy, Physicochemical Characterization and Migration Release Study

“…The incorporation of SCO complexes into polymers [ 16 , 17 ] has been investigated for several reasons, including convenience for physical characterizations (e.g., photophysical measurements) [ 18 ] and competitiveness toward potential technological applications [ 14 ]. In addition, the need for the integration and processing of SCO compounds in different shapes and sizes (micro- and nanoscale) has motivated their incorporation into different types of polymer matrices by using spray coating, electrospinning and 3D printing or even by chemical reaction of the SCO system with polymers [ 19 , 20 ].…”

Co-Processing of [Fe(NH2trz)3](2ns)2 and UHMWPE into Materials Combining Spin Crossover and High Mechanical Strength

“…Cellulose was also employed as the matrix for sheets of 15 mm width comprising Htrz/trz complexes [33]. Composites of polypyrrole comprising an iron(II) complex with Htrz/trz ligand sphere were obtained upon in situ polymerization of pyrrole, and the materials thus obtained were further processed to films by sintering under pressure [33]. The conductivity of those materials changed at the spin crossover temperature of the incorporated complex, which is assumed to be a consequence of the thermally induced volume change associated with the spin crossover [32].…”

“…Electrospinning was applied for the preparation of fibers of polystyrene with a Rtrz complex (about 3 µm fiber diameter) and of poly(lactic acid) with Htrz/trz of NH2trz complexes [33]. Fibers consisting of a blend of a complex with Rtrz and ultra- There are a number of reports on the processing of spin-crossover coordination polymers, in particular [Fe(NH 2 trz) 3 ]X 2 , a prerequisite to obtaining materials that can be useful in technological applications.…”

“…Manufacture of continuous objects was achieved by their incorporation in silica monoliths prepared by a sol-gel process or by growth of spin-crossover nanoparticles in cylindrical pores of preformed silica monoliths [32,33]. There are several reports of freestanding films prepared by solution casting, such as of polymers based on vinylidene fluoride containing an iron(II) complex with Htrz, trz and NH 2 trz, of poly(methyl methacrylate) or polystyrene and Rtrz complexes, of poly(oxetane) and a complex with hydroyethylsubstituted 1,2,4-triazole, and of poly(vinyl pyrrolidone) and NH 2 trz complexes [32].…”

“…In addition, preformed films of Nafion can be impregnated with solutions of Htrz or NH 2 trz and iron(II) ions to yield films with spin-crossover properties [32]. Further, films of natural polymers based on cellulose were impregnated with solutions of iron(II) complexes and Htrz/trz or NH 2 trz ligand sphere [33]. Cellulose was also employed as the matrix for sheets of 15 mm width comprising Htrz/trz complexes [33].…”