|V.S.D.Voet at rug.nl|
Tailor-made poly(vinylidene fluoride) containing block copolymers for the design of novel magnetoelectric polymer-nanocomposites
Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, offer the ability to couple to either the electric or magnetic polarization. Natural single-phase magnetoelectric compounds are rare, and their magnetoelectric response is usually relatively weak at low temperatures, limiting their ability in practical devices. In contrast, multiferroic composites which incorporate both ferroelectric and ferromagnetic phases, yield giant magnetoelectric coupling response above room temperature. From application viewpoint, microwave devices, sensors, transducers and novel memory media are among the suggested technical implementations of these magnetoelectric composites.
The volume fraction of the two phases as well as the quality of interfacial adhesion between the two phases play an important role in determining the extend of the magnetoelectric response. An elegant way to freely tune the mentioned parameters is the use of the self-assembly of ferroelectric poly(vinylidene fluoride) (PVDF) containing block copolymers. Parameters such as the degree of polymerization, the Flory-Huggins interaction parameter and the composition of the block copolymers can be used to tailor the morphology. Subsequently, the obtained block copolymer nanostructure can function as a template for a non-polymeric phases. For example, incorporating ferromagnetic materials inside a certain morphology will lead to magnetoelectric polymer-nanocomposites in various shapes and tunable sizes. We expect strongly improved magnetoelectric responses from these novel materials as compared to current magnetoelectric composites.
In order to explore the morphologies arising from block copolymer self-assembly, the synthesis routes towards PVDF containing block copolymers have been studied recently.
PVDF macroinitiators have been synthesized via a chain transfer emulsion polymerization and alternatively via a functional benzoyl peroxide initiated polymerization. Reasonably narrow polydispersities were obtained. The macroinitiators were used to initiate the atom transfer radical polymerization (ATRP) of styrene (S), 4-vinyl pyridine (4VP) and tert-butyl methacrylate (tBMA) to form PVDF-b-PS, PVDF-b-P4VP and PVDF-b-tBMA copolymers.
Currently, the microphase separation into ordered nanostructures is studied extensively.
|Laatst gewijzigd:||01 juli 2015 10:53|