Shape memory polymers origin

Shape memory polymers are defined by their ability to store and recover strains when subjected to a particular thermo-mechanical cycle. Shape-memory polymers can recover their original shape by being heated above their transition temperature, which are defined by different phases in the materials. In particular, the shape-... 

Under specific stimulus, shape memory materials could move from a temporary shape to their original shape. The stimulus could be light, pH, or electric or magnetic field, but the most common shmulus is heat. In this case, a shape memory polymer (SMP) possesses a switch transihon temperature. When the SMP is subject to deformation, its cross-linking structure could store internal stress if it is cooled below this switch temperature. When the polymer is heated above this temperature, it returns to its original shape. Shape memory polymer blends could be achieved using irradiahon. 

When the shape memory polymer is heated above the glass transition temperature of the hard segment, the material can be shaped. This original shape can be memorized by cooling the shape memory polymer below the glass transition temperature of the hard segment. 

Shape-memory properties can be quantified in cyclic, stimuli-specific mechanical tests [23,40]. Each cycle consists of the SMPC and the recovery of the original, permanent shape. From the data obtained, the shape fixity ratio (Rf) and the shape recovery ratio (/ r) can be determined (see, e.g., [40-42] and Chapter Characterization Methods for Shape-Memory Polymers in this volume). Rf describes the ability of the switching segment to fix a mechanical deformation, e.g., an elongation to applied during SMCP resulting in the temporary shape. Rr quantifies the ability of the material to memorize its permanent shape. Different test protocols have been developed. They differ in SMCP, which can be performed under constant strain or constant stress conditions (see Chapter Characterization Methods for Shape-Memory Polymers in this volume). The recovery process under stress-free condition enables the determination of the switching temperature Tsw for thermally-induced SMP. 

Abstract Shape-memory polymers (SMPs) are able to fix a temporary deformed shape and recover their original permanent shape upon application of an external stimulus such as heat or light. A shape-memory functionalization can be realized for polymer based materials with an appropriate morphology by application of a specific shape-memory creation procedure (SMCP). Specific characterization methods have been tailored to explore the structure-function relations of SMPs in respective applications. This paper reviews characterization methods on different length scales from the molecular to the macroscopic level. 

Herein, we unveil a unique compression system using shape memory polymer (SMP) to counter the above problems. SMPs are smart materials that can memorize the original shape so that they can recover from a temporary deformed shape upon exposure to an external stimulus, eg, heat, light, water, etc. SMPs have gained scientific significance over the last 10 years in the development of many potentially innovative products [7—11]. At present, thermally sensitive SMPs are successfully employed in many... 

Materials that show a shape-memory effect can be deformed into a temporary shape and afterwards they can recover their original shape on exposnre to an external stimulus [65,66]. Shape-memory polymers (SMPs) are stimuli-responsive smart polymers that have dual shape, which responds to application of an external stimulus. SMP is conventionally processed to receive its permanent shape. Afterward, the polymer is deformed and the intended temporary shape is fixed [67,68]. This process is called programming. These polymers basically consist of two phases, fixed points or frozen... 

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