Shape-memory properties of magnetically active triple-shape nanocomposites based on a grafted polymer network with two crystallizable switching segments

Abstract

Shape-memory polymers (SMP) and composites thereof belong to the class of actively moving polymers, which have the capability of storing one (dualshape) [1][2][3][4][5][6], two (triple-shape) [7][8][9][10][11][12][13] or multiple (multiple-shape) [14] stable temporary shapes and recover their original or other temporary shapes when exposed to an external stimulus. The field of SMP research has developed rapidly over the last years [6,[15][16][17][18][19][20][21][22][23][24][25] and it has become apparent that these functional polymers are motivating novel applications. Thermo-sensitive SMP contain physical or chemical network-points, which determine their original shape, while each temporary shape is fixed by switching domains associated to a thermal transition temperature T trans , that can be a glass transition (T g ) or a melting transition (T m ) [16,17]. The process for programming of a temporary shape is called 'shapememory creation procedure' (SMCP) and can be realized e.g. by deforming the material to an extension of ! m at T > T trans and cooling to T < T trans while keeping the deformation, which then is fixed temporarily by solidification of the related set of switching domains [26]. The recovery of the original shape is named shape-memory effect (SME), which is typically induced by increasing the environmental temperature (T env ) [3,5,27,28] Abstract. Thermo-sensitive shape-memory polymers (SMP), which are capable of memorizing two or more different shapes, have generated significant research and technological interest. A triple-shape effect (TSE) of SMP can be activated e.g. by increasing the environmental temperature (T env ), whereby two switching temperatures (T sw ) have to be exceeded to enable the subsequent shape changes from shape (A) to shape (B) and finally the original shape (C). In this work, we explored the thermally and magnetically initiated shape-memory properties of triple-shape nanocomposites with various compositions and particle contents using different shape-memory creation procedures (SMCP). The nanocomposites were prepared by the incorporation of magnetite nanoparticles into a multiphase polymer network matrix with grafted polymer network architecture containing crystallizable poly(ethylene glycol) (PEG) side chains and poly(!-caprolactone) (PCL) crosslinks named CLEGC. Excellent triple-shape properties were achieved for nanocomposites with high PEG weight fraction when two-step programming procedures were applied. In contrast, single-step programming resulted in dual-shape properties for all investigated materials as here the temporary shape (A) was predominantly fixed by PCL crystallites.

Biodegradable polyester-based shape memory polymers: Concepts of (supra)molecular architecturing

“…Polyhedral silsesquioxane (POSS) containing PCL with acrylate end groups were also synthesized and photocrosslinked. Narendra Kumar et al [23] elaborated a synthesis route for producing thermally and magnetically activated triple-shape memory polymers using methacrylate end functionalized crystallizable PCL (T m = 55°C) and polyethylene glycol (PEG) (T m = 38°C). The copolymer was cured by peroxide in presence and absence of silica coated magnetite nanoparticles.…”

Electrically conductive epoxy nanocomposites containing carbonaceous fillers and in-situ generated silver nanoparticles

“…They have been widely applied as smart textiles and apparels [11], intelligent medical devices [12], heat shrinkable packages for electronics [13], high performance water-vapor permeability materials [14], self-deployable structures [15], and microsystems [16]. SMPs can recover their original (or permanent) shapes under appropriate external stimuli, such as heating [1,8,16,17], cooling [18], light [19,20], electric field [21][22][23][24][25][26], magnetic field [27][28][29], water [30], pH, specific ions or enzyme [31]. However, the demand to avoid external heaters has led to a new generation of electrically conducting SMPs filled with conductive nanoparticles, such as carbon nanotubes [21,22], carbon particles [23,26], conductive fiber [24] and nickel zinc ferrite ferromagnetic particles.…”

Shape memory epoxy nanocomposites with carbonaceous fillers and in‐situ generated silver nanoparticles

“…They can be utilized in intelligent medical devices, smart textiles and apparels , high performance water–vapor permeability materials , heat shrinkable packages for electronics , self‐deployable structures and micro‐systems . As mentioned before, different external stimuli can be applied to SMPs to activate the shape recovery effect: heating , cooling , light , electric field , magnetic field , water , pH, ions or enzymes . Recently, the demand to eliminate external heaters led to the development of novel electrically conductive SMPs filled with conductive nanofillers, such as CNTs , carbon particles , conductive fiber and nickel zinc ferrite ferromagnetic particles.…”