Shape memory polymer compositions, articles of manufacture thereof, and methods of preparation and use thereof are described. The shape memory polymer compositions can hold more than one shape in memory. Suitable compositions include at least one hard segment and at least one soft segment. The Ttrans of the hard segment is preferably between -30 and 270 °C. At least one of the hard or soft segments can contain a cross-linkable group, and the segments can be linked by formation of an interpenetrating network or a semi-interpenetrating network, or by physical interactions of the blocks. Objects can be formed into a given shape at a temperature above the Ttrans of the hard segment, and cooled to a temperature below the Ttrans of the soft segment. If the object is subsequently formed into a second shape, the object can return to its original shape by heating the object above the Ttrans of the soft segment and below the Ttrans of the hard segment. The compositions can also include two soft segments which are linked via functional groups which are cleaved in response to application of light, electric field, magnetic field or ultrasound. The cleavage of these groups causes the object to return to its original shape.

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Shape memory polymers

The introduction of biodegradable implant materials as well as minimally invasive surgical procedures in medicine has substantially improved health care within the past few decades. This report describes a group of degradable thermoplastic polymers that are able to change their shape after an increase in temperature. Their shape-memory capability enables bulky implants to be placed in the body through small incisions or to perform complex mechanical deformations automatically. A smart degradable suture was created to illustrate the potential of these shape-memory thermoplastics in biomedical applications.

https://science.sciencemag.org/content/sci/296/5573/1673.full.pdf

Biodegradable, Elastic Shape Memory Polymers for Potential Biomedical Applications

Materials are said to show a shape-memory effect if they can be deformed and fixed into a temporary shape, and recover their original, permanent shape only on exposure to an external stimulus. Shape-memory polymers have received increasing attention because of their scientific and technological significance. In principle, a thermally induced shape-memory effect can be activated by an increase in temperature (also obtained by heating on exposure to an electrical current or light illumination). Several papers have described light-induced changes in the shape of polymers and gels, such as contraction, bending or volume changes. Here we report that polymers containing cinnamic groups can be deformed and fixed into pre-determined shapes--such as (but not exclusively) elongated films and tubes, arches or spirals--by ultraviolet light illumination. These new shapes are stable for long time periods, even when heated to 50 degrees C, and they can recover their original shape at ambient temperatures when exposed to ultraviolet light of a different wavelength. The ability of polymers to form different pre-determined temporary shapes and subsequently recover their original shape at ambient temperatures by remote light activation could lead to a variety of potential medical and other applications.

Light-induced shape-memory polymers

Shape-memory polymers (SMPs) have attracted significant attention from both industrial and academic researchers due to their useful and fascinating functionality. This review thoroughly examines progress in shape-memory polymers, including the very recent past, achieved by numerous groups around the world and our own research group. Considering all of the shape-memory polymers reviewed, we identify a classification scheme wherein nearly all SMPs may be associated with one of four classes in accordance with their shape fixing and recovering mechanisms and as dictated by macromolecular details. We discuss how the described shape-memory polymers show great potential for diverse applications, including in the medical arena, sensors, and actuators.

http://research.vuse.vanderbilt.edu/srdesign/2009/group8/Papers/shape%20memory%20polymers%20review%20article.pdf

Review of progress in shape-memory polymers

Shape-memory polymers

Polyurethanes having shape memory effects

Polyurethane ionomers having shape memory effects

Department of Polymer Science and Engineering, Pusan National University, Pusan 609-735, Korea(Received 22 July 1996; accepted 6 August 1996)Abstract: Following a prepolymer mixing process, polyurethane (PU) aniono-mer dispersions were prepared from polyethylene adipate glycol (PEA), iso-phorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI) and dimethylolpropionic acid (DMPA) as a potential ionic centre. E†ects of prepolymer molec-ular weight, PEA molecular weight, hard segment content, DMPA content,degree of neutralization and mixed diisocyanates have been studied in terms ofparticle size and viscosity of emulsion, and surface, mechanical and dynamicmechanical properties of the emulsion-cast Ðlms. Particle size decreased andemulsion viscosity increased with increase in prepolymer molecular weight andPEA molecular weight, DMPA content, the degree of neutralization and IPDIcontent in mixed isocyanate systems. The decrease in particle size was due toincreased chain Nexibility and/or hydrophilicity of the PU. The mechanical anddynamic mechanical properties of the PU ionomer dispersions were interpretedin terms of soft segmentEhard segment phase separations, hard segment content,chain Nexibility and coulombic forces.Key words: polyurethanes, anionomer dispersions, structureEproperty corre-lation, mechanical properties, dynamic mechanical properties.

Preparation and Properties of Water-borne Polyurethanes

A reactive hot melt adhesive (RHMA) consisting of thermoplastic polyurethane (TPU) was modified with sodium montmorillonite (Na-MMT) intercalated with poly(ethylene glycol) (PEG), and their effects on the adhesion, rheological, and mechanical properties of the RHMA were examined. The Na-MMT intercalated with PEG (Na-MMT/PEG) effectively enhanced the initial bond strength development of the RHMA, although the amounts of Na-MMT/PEG in the RHMA were less than 0.2%. The increase of the complex viscosity and pseudo-solid like behavior observed at low shear rate indicates that there are intimate interactions between the RHMA molecules and Na-MMT/PEG. The improved modulus and tensile strength of the cured RHMA film in the presence of Na-MMT/PEG demonstrates that Na-MMT/PEG effectively reinforced the RHMA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Sang Yup Lee

Papers

Polyurethanes having shape memory effects

Polyurethane ionomers having shape memory effects

Preparation and Properties of Water-borne Polyurethanes

The properties of reactive hot melt polyurethane adhesives modified with novel thermoplastic polyurethanes

Preparation and Properties of Waterborne Polyurethanes