Although shape-memory metal alloys have wide use in medicine and other areas, improved properties, particularly easy shaping, high shape stability, and adjustable transition temperature, are realizable only by polymer systems. In this paper, a polymer system of shape-memory polymer networks based on oligo-(-caprolactone) dimethacrylate as crosslinker and n-butyl acrylate as comonomer was introduced. The influence of two structural parameters, the molecular weight of oligo(-caprolactone) dimethacrylate and the weight content of n-butyl acrylate, on macroscopic properties of polymer networks such as thermal and mechanical properties has been investigated. Tensile tests above and below melting temperature showed a decrease in the elastic modulus with increasing comonomer weight content. The crystallization behavior of the new materials has been investigated, and key parameters for the programming procedure of the temporary shape have been evaluated. Shape-memory properties have been quantified by thermocyclic experiments. All samples reached uniform deformation properties with recovery rates above 99% after 3 cycles. Whereas strain recovery increased with increasing n-butyl acrylate content, strain fixity decreased, reflecting the decreasing degree of crystallinity of the material.

Surfactants responsive to pH, [1] temperature, [2] CO 2 , [3] and light [4] are well known. Here we report for the first time ionic liquid surfactants that are magneto-responsive, thus offering the potential to perturb liquid emulsions simply by the application of an external magnetic field. Although ionic liquids (ILs) containing transition metal complexes have been known for some time, [5] it had always been assumed that the metallic centers were isolated, lacking long-range interactions and communication necessary to be magnetically active. [6] Only recently have ionic liquids containing magneto-active metal complex anions, such as 1-methyl-3-butylimidazolium tetrachloroferrate ([bmim]FeCl 4 ), [7] been reported. [7,8] These magnetic ionic liquids (mag-ILs) are especially interesting as they are molecular liquids, rather than typical magnetic fluids (ferrofluids) which comprise magnetic colloidal particles (! 10 nm) dispersed in a carrier fluid. The nanoparticle-free mag-ILs are themselves paramagnetic. As such they contain high effective concentrations of metal centers and allow physico-chemical properties (hydrophobicity, electrical conductivity, melting point, etc.) to be controlled by external magnetic fields. Furthermore, because mag-ILs and magnetic ionic liquid surfactants (MILSs) are non-volatile they offer advantages over conventional ferrofluids which often employ flammable organic solvents.[**] P.B. thanks HEFCE and the University of Bristol, School of Chemistry for a DTA, PhD scholarship. A.B. and A.M.S. credit funding by ERA NanoSciE + . We also achnowledge STFC for the allocation of beam time, travel, and consumables grants at ILL, and the Krüss Surface Science Centre, Bristol, for facilities for surface tension measurements.Supporting information for this article is available on the WWW under http://dx.

Although shape-memory metal alloys have wide use in medicine and other areas, improved properties, particularly easy shaping, high shape stability, and adjustable transition temperature, are realizable only by polymer systems. In this paper, a polymer system of shape-memory polymer networks based on oligo-( -caprolactone) dimethacrylate as crosslinker and n-butyl acrylate as comonomer was introduced. The influence of two structural parameters, the molecular weight of oligo( -caprolactone) dimethacrylate and the weight content of n-butyl acrylate, on macroscopic properties of polymer networks such as thermal and mechanical properties has been investigated. Tensile tests above and below melting temperature showed a decrease in the elastic modulus with increasing comonomer weight content. The crystallization behavior of the new materials has been investigated, and key parameters for the programming procedure of the temporary shape have been evaluated. Shape-memory properties have been quantified by thermocyclic experiments. All samples reached uniform deformation properties with recovery rates above 99% after 3 cycles. Whereas strain recovery increased with increasing n-butyl acrylate content, strain fixity decreased, reflecting the decreasing degree of crystallinity of the material.M etallic alloys with shape-memory properties like NiTi alloys are already used in different areas, e.g., biomedical applications (1). § However, their mechanical properties can be adjusted only within a limited range, and they are not degradable.Here, we report an AB-polymer network showing shapememory properties. The advantage of this polymer system is its versatility. Several macroscopic properties such as transition temperature and mechanical properties can be varied in a wide range by only small changes in their chemical structure and composition.Shape-memory polymers are characterized by two features, triggering segments having a thermal transition T trans within the temperature range of interest and crosslinks determining the permanent shape. Depending on the kind of crosslinks, shapememory polymers can be thermoplastic elastomers or thermosets. By using this technology, shape-memory polymers potentially can be tailored for specific applications.For this polymer system, oligo( -caprolactone) has been selected as a crystallizable triggering segment that can fix a temporary shape by physical crosslinks. These segments were incorporated covalently into the thermosets. Therefore, oligo( -caprolactone) diols were functionalized with polymerizable methacrylate endgroups. The molecular weight of this macromonomeric crosslinker represents a first parameter on the molecular level to adjust crystallinity and mechanical properties of the polymer networks. For that purpose, especially for temperatures below the transition temperature, an additional monomer is introduced representing a second parameter. As comonomer, n-butyl acrylate, has been selected. Because of the low glass transition temperature of poly(n-butyl acrylate) [T g ϭ Ϫ55°C (2)...

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