Abstract
Spherical particles from shape-memory polymers (SMP) can be stretched to ellipsoids with high aspect ratio (AR) and temporarily stabilized. They can switch back to low AR upon thermal stimulation. Here, the creation of an alternative shape-switching capability of particles from low to high AR is introduced, where a SMP matrix from polyvinyl alcohol (PVA) is used to create crosslinked high AR particles and to program the embedded micrometer-sized particles from a second SMP (oligo(ε-caprolactone) micronetworks, MN) with a low switching temperature Tsw. This programming proceeds through shape-recovery of the PVA matrix, from which the MN are harvested by PVA matrix dissolution. The use of a dissolvable SMP matrix may be a general strategy to efficiently create systems with complex moving capabilities.
Highlights
Spherical particles from shape-memory polymers (SMP) can be stretched to ellipsoids with high aspect ratio (AR) and temporarily stabilized
The aspect ratio (AR; AR = lÁsÀ1; l: longest axis; s: shortest axis) of the particles can serve as a quantitative measure of switching efficiency, as it should be decreased to unity when switching is quantitative
While some previous work illustrated a temperature- or solvent-induced shape-memory effect (SME) of covalently crosslinked polyvinyl alcohol (PVA) or PVA composites,[26,27,28] which, may not or at least not dissolve in water, here the use of water soluble PVA was essentially required for later isolation of particulate inclusions from PVA phantoms
Summary
The relevance of the network architecture for the switching function of those microobjects. Realizing the opposite movement from spheres to ellipsoids, i.e., an alternative switching direction (aSME) towards an increased AR, sets higher conceptual challenges. Such phenomena are known for colloidal particles from amphiphilic polymers based on photoinduced isomerization or selective. Instead of being crosslinked to MN in spherical shape after templating as performed in literature[14] and shown, upper pannel (denoted as SME), an alternative switching feature towards higher AR (denoted as aSME) should be realized by first programming the PVA with embedded MP to an elongated temporary shape with subsequent UV-induced MN synthesis. Particles isolated by PVA dissolution should be evaluated for their micronetwork structure and shapeswitching ability
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