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This work examines the small-scale deformation and thermally induced recovery behavior of shape memory polymer networks as a function of crosslinking structure. Copolymer shape memory materials based on diethylene glycol dimethacrylate and polyethylene glycol dimethacrylate with a molecular weight of 550 crosslinkers and a tert-butyl acrylate linear chain monomer were synthesized with varying weight...
Main chain bile acid polymers obtained via entropy-driven ring-opening metathesis are biodegradable polymers with excellent shape memory properties. X-ray scattering was used to study the conformational changes implicated in the shape memory effect of these polymers. Strain induced orientation and ordering was observed upon the drawing of the polymer films. A correlation between ordering and the shape...
This paper describes a shape memory behavior of graft copolymers poly(methyl methacrylate)-graft-poly(ethylene glycol) (PMMA-g-PEG). In shape memory test, the sample was deformed from its original shape to a temporary shape above glass transition temperature (T g ), cooled below T g to fix the temporary shape, and subsequently heated above T g for spontaneous recovery to the...
Shape-memory polymers (SMPs) are active smart materials with tunable stiffness changes at specific, tailored temperatures. The use of thermoset SMPs has been limited in commodity applications because a variety of common low-cost plastics processing techniques are not possible with network polymers. In this study of thermoset SMPs, beyond adjusting the glass transition temperature (T g ) between...
Shape memory semi-interpenetrating polymer networks (semi-IPNs) composed of crystalline poly (ethylene oxide) (PEO) and crosslinked poly (methyl methacrylate) (x-PMMA) have been investigated. The selected compositions show shape memory property with a reasonable fast recovery (recovery time ∼1 min) and shape recovery ratio of 99%. Effects of composition (x-PMMA/PEO = 80/20…60/40) and crosslinker (triethyleneglycol...
Shape-memory polymers (SMPs) are a class of mechanically functional “smart” materials defined by their ability to change shape upon exposure to an environmental stimulus. The shape-memory effect has traditionally been activated by thermal mechanisms via heating the polymer above a transition temperature to increase chain mobility and initiate shape recovery. This study proposes a unique approach to...
Polymers capable of reversible “two-way” shape memory behaviour are of great interest for applications where reversible actuation is demanded, and semicrystalline crosslinked systems have been indicated as an interesting solution towards this end. In this work we have explored the two-way shape memory response of semicrystalline poly(ε-caprolactone)-based polymer networks, prepared with various macromolecular...
In this paper, we report on the shape memory behavior of a family of hardblock-free multiblock thermoplastic polyurethanes (TPUs) consisting of poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG). Due to high molecular weight (M n > 200 kDa), high degrees of entanglement were achieved. Instead of conventional “hard” blocks, entanglements served as the physical crosslinks in this...
A framework for understanding the structure (shape memory and thermomechanical)–property relationships in shape memory polymers (which could be reasonably modeled as comprising of a soft phase and a hard phase) using indentation is developed. A finite element model is developed to predict the complete stress–strain–temperature characteristics of shape memory polymers under uniaxial and indentation...
In this work we have explored the shape memory capabilities of a novel type of covalently cross-linked semi-crystalline polymers, prepared by exploiting the mild sol–gel chemistry, starting from alkoxysilane-terminated poly(ε-caprolactone) (PCL), and using silica-based domains as cross-link points. By adopting PCL precursors with different molecular weights, semi-crystalline networks with well defined...
The formation of polymer networks polymerized with the Copper (I) – catalyzed azide – alkyne cycloaddition (CuAAC) click reaction is described along with their accompanying utilization as shape memory polymers. Due to the click nature of the reaction and the synthetic accessibility of azide and alkyne functional-monomers, the polymer architecture was readily controlled through monomer design to manipulate...
The rapidly expanding field of shape memory polymers (SMPs) is driven by a growing number of potential applications, such as biomaterials, optics, and electronics. The basic concept involves polymers that can be trapped in a thermodynamically-unfavorable shape, then triggered by an external stimulus to return to their original shape, doing useful work in the process. Part of the attraction of using...
This paper describes an unconventional, yet simple method to program sheets of shape memory polymer into a variety of two dimensional (2D) structures. The final shape is “encoded” by physically cutting an initial design out of a pre-strained film. The orientation of the initial cut-out relative to the direction of strain and the subsequent relaxation of strain via heating defines the final shape....
This study presents a comprehensive morphological, physical, and shape memory characterization of biocompatible shape memory polymer (SMP) blend foams composed of thermoplastic polyurethane (TPU) and polylactic acid (PLA). The TPU/PLA blend compositions studied were 80/20, 65/35, and 50/50 in weight percentage. The influence of blend composition and processing conditions on the pore morphology of...
Thermally stimulated novel shape memory polymer blend of ethylene octene copolymer (EOC) and ethylene propylene diene terpolymer (EPDM) has been developed. This novel polyolefinic blends possess superior shape memory behaviour in presence of heat. Shape memory behaviour study at 60 °C of the blends shows that the blends containing higher fraction of EPDM exhibits superior shape memory behaviour in...
Shape memory polymers (SMPs) have been intensively studied for a wide range of potential applications, including biomedical devices, morphing structures, and 4D printing. For amorphous polymers, the glass transition temperature measured by dynamic mechanical analysis (DMA) is an important consideration in designing SMPs. However, typical DMA curves are cooling- and heating-rate dependent and the cooling...
Biodegradable shape memory polymers are attractive materials for the design of biomedical scaffolds as they allow deploying implants remotely with minimal intervention, whilst allowing degradation and tissue repair. However, shape memory properties are difficult to design from common degradable polymers, without chemical modifications. Here were developed readily tunable processable shape memory polymer...
A novel shape memory polymer is presented based on polybenzoxazine and poly(ε-caprolactone) (PCL). Polybenzoxazines with unbound and covalently incorporated PCL were prepared applying hydroxyl and tosyl terminated PCLs, respectively. Thermo-responsive and shape memory behavior with high shape fixity and recovery were demonstrated for samples containing a high ratio of covalently bonded PCL in a crosslinked...
Polystyrene (PS) was blended with shape memory polyurethanes (SMPU). Styrene blocks were grafted onto PU chains during SMPU synthesis to yield a modified SMPU with a higher affinity towards PS. Furthermore, blends containing a compatibilizer, poly (styrene-co-maleic anhydride) (SMA), were also prepared by melt mixing the components. The non-compatibilized blends display phase separated structures...
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