A simulation method to analyze chemo-mechanical behavior of swelling-induced shape-memory polymer in response to solvent
(1137–1146)Journal of Applied Polymer  Science 123 #2 (2012)
Lu of the Harbin Institute of Technology, China, considered that the  equilibrium is reached between the mechanical load and the chemical potential of polymer network and solvent, the SMP polymer usually swells with a field of inhomogeneous and anisotropic deformation is equivalent to a hyperelastic field.  We implement this theory in the free-energy function equation, and analyze examples of swelling-induced deformation and shape recovery behavior.  (RDC 10/12/2011).

 Impact of shape-memory programming on mechanically-driven recovery in polymers
(4947-4954) Polymer 52 #21 (2011)
Yakacki et al develop a unique approach to mechanically drive recovery in SMP networks using external forces to facilitate shape change in a material with stored strain. SMP networks were synthesized from tert-butyl acrylate and poly(ethylene glycol) dimethacrylate in three network compositions. Networks were tailored to maintain a constant glass transition temperature (about 52 °C) with increasing crosslinking density, shown by rubbery modulus values of 1.2, 3.1, and 8.2 MPa.  Hollow SMP cylinders were axially elongated (programmed) to stored strain levels of approximately 25%. A second set of samples was machined to match the programmed dimensions of the SMP sample set. Compression testing revealed that the compressive strength and energy required for deformation for the programmed SMP samples were on average 62% and 52% of the as-machined samples’ values, respectively.  The ratios between programmed and as-machined samples’ compressive properties were independent of both crosslinking density and temperature up to the onset of glass transition.  Lastly, an interference-fit test model was used to demonstrate that mechanically-driven SMPs could immediately create and maintain a stronger fixation force compared to as-machined samples and thermally-driven SMP samples.  .

Optimization of the shape memory effect in shape memory polymers
(3574–3581) Journal of Polymer Science Part A: Polymer  Chemistry 49 #16 (2011)
Sun et al ofShenyang Jianzhu University and Nanyang Technological University, China, altered a number of its properties, such as the recovery temperature, shape fixity ratio, maximum recovery stress, and final recovery stress (and even a right combination of some of them, e.g., the maximum recovery stress and final recovery stress), simply by means of selecting the programming temperature to achieve optimized performance.  (RDC 7/14/2011)

Stability and deterioration of a shape memory polymer fabric composite under thermomechanical stress
(1470-1477) Polymer Degradation and Stability 96 #8 (2011)
Ahmad et al of the University of Bolton and the University of West of Scotland, United Kingdom. studied the effect of  fibres and fabrics on shape memory polymers (SMPs).  However incorporation of fibres and fabrics in SMPs is often accompanied with the deterioration of thermomechanical properties and shape memory effect. Up to 100% extension, the SMPCs showed good shape memory effect with excellent shape recovery ratio, recovery stress and mechanical properties; while beyond that the recovery ratio and recovery stress of the composites deteriorated rapidly due to the significant delamination and debonding of fibres and fabrics from the SMP resin and accumulation of broken fibres.  (RDC 6/23/2011)

Macromolecular Orientation in Glassy Starch Materials That Exhibit Shape Memory Behavior
(9854–9858) Macromolecules 43 #23 (2010)
Chambre  et al, France, explore the molecular mechanisms involved in residual stress in relation with shape memory effects in glassy amorphous starch.  A local molecular orientation was shown by WAXS and IR dichroism. Results clearly demonstrate that the residual stress observed in the temporary shape is due to local molecular orientation in amorphous starch resulting from the flow of matter induced by the deformation process. The molecular orientation disappears when the sample relaxes and recovers its initial shape. (RDC 2/26/2011)

Significant Impact of Thermo-Mechanical Conditions on Polymer Triple-Shape Memory Effect
(175–180) Macromolecules 44 #1 (2011)
Li and Xie of General Motors, Michigan explored the polymer triple-shape memory effect which refers to the capability of a polymer to memorize two temporary shapes and subsequently recover them, all in one shape memory cycle.  In this study, Nafion is used as a model material.  The choice of the programming and recovery heating methods in constructing triple-shape cycles was found to have a profound impact on the triple-shape properties.  (RDC 1/19/2011)

In vivotissue responses to thermal-responsive shape memory polymer nanocomposites
(985-991)  Biomaterials 32  #4 (2011)
Filion et al of the University of Massachusetts  developed a class of biodegradable POSS-SMP nanocomposites exhibiting stable temporary shape fixing and facile shape recovery within a narrow window of physiological temperatures.  The materials were covalently crosslinked from star-branched building blocks consisting a bioinert polyhedral oligomeric silsesquioxane (POSS) core and 8 degradable poly(d,l-lactide) arms.  These minimally immunogenic and biodegradable shape memory polymers  are promising candidates for scaffold-assisted tissue repair where both facile surgical delivery and controlled degradation of the scaffold are desired for achieving optimal short-term and long-term clinical outcomes.  (RDC 11/29/2010)

A biomimic shape memory polymer based self-healing particulate composite  
(6021-6029) Polymer 51 #25 (2010)
Nji and Guoqiang of Louisiana State University a shape memory composite was tested consisting of 6 vol%  copolyester in the polystyrene matrix and tested for repeated crack healing.  Over 65% of the peak bending load can be repeatedly recovered and the structural-length scale damage (notch) is healed at molecular-length scale.  (RDC 11/18/2010)

Radiation crosslinked shape-memory polymers 
(3551-3559) Polymer 51 #15 (2010)
Voit, Ware and Gall of the University of Texas at Dallas  developed a novel manufacturing process, Mnemosynation.   The customizable mechanical properties of traditional SMPs are coupled with traditional plastic processing techniques to enable a new generation of mass producible plastic products with thermosetting shape-memory properties: of low residual strains, tunable recoverable force and adjustable Tg. (RDC 12/22/2010)

Photopolymerized thiol-ene systems as shape memory polymers 
(4383-4389) Polymer 51 #19 (2010)
Nair et al the University of Colorado show that thiol-ene based shape memory polymer systems have comparable thermomechanical properties with some advantages due to the thiol-ene polymerization mechanism which results in the formation of a homogeneous polymer network with low shrinkage stress and negligible oxygen inhibition.  The resulting thiol-ene shape memory polymer systems are tough and flexible as compared to the acrylic counterparts.  The polymers evaluated in this study were engineered to have a glass transition temperature between 30 and 40 °C, exhibited free strain recovery of greater than 96% and constrained stress recovery of 100%. The thiol-ene polymers exhibited excellent shape fixity and a rapid and distinct shape memory actuation response.  (RDC 12/19/2010)

Synthesis and optical properties of organic–inorganic hybrid gels containing fluorescent molecules 
(5095-5099) Polymer 51 #22 (2010)
The shape memory effect of the copolymer was evaluated by dynamical mechanical analysis, shape recovery ability, and shape recovery speed. Having the properties of the good shape fixity and the large shape recovery, the functionalized polynorbornene copolymer is expected to use as a potential shape memory material