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.

/pdf/shape-memory-polymers-21sug7mu2l.pdf

Shape memory polymers

A review of stimuli-responsive shape memory polymer composites

Many of the polymers used in composite systems and in other applications are cross-linked or thermoset polymers. How do such cross-linked polymers differ in properties from the better-understood linear or thermoplastic polymers? This review paper attempts to answer this question. The paper is written from the practical viewpoint of the experimental scientist who is using cross-linked polymers but who is not an expert on the theory of cross-linking. In spite of their intractable nature once they have been formed, and the difficulty of fabricating highly cross-linked polymers, such materials have some outstanding properties that make them ideal for many applications. The properties include (1) excellent dimensional stability and low creep rates, (2) resistance to solvents, and (3) in many cases, high heat-distortion or softening temperatures.

Cross-Linking–Effect on Physical Properties of Polymers

Preparation and applications of ion exchange membranes by radiation-induced graft copolymerization of polar monomers onto non-polar films

Experiments on the role of water in petroleum formation

Atomic radiation and polymers

A NUMBER of long-chain polymers, when subjected to high-energy radiation such as is provided in the B.E.P.O. pile at Harwell, are found to become cross-linked. Among the polymers which behave in this way may be mentioned polythene, polystyrene, ‘Terylene’, nylon and unvulcanized rubber. In other polymers, for example, methyl methacrylate, decomposition sets in after a very short irradiation period.

Effect of high-energy radiation on long-chain polymers

A method is given for improving the physical properties. particularly at high temperatures, of vinyl chloride polymers and copolymers. In this method, the polymer or copolymer is mixed with 0.05 to 7 times its weight of a finely divided inorganic solid such as carbon black (preferred), silica, or china clay, and the mixture is exposed to ionizing radiation until a total dose of 5 to 25 megarad is received. Other additives may be employed, e.g., plasticizers and antioxidants. (D. L. C.)

Irradiation of polymers

How radiation affects long-chain polymers

Dissimilar polymers are mixed, e.g. by hot rolling or by solution in a common solvent such as dimethyl formamide, and the resulting mixture irradiated by a high-energy electron beam, X-rays or gamma rays. The treatment produces chemical links between the polymers and improves compatibility and the mechanical and optical properties of the mixtures. Examples relate to the treatment of mixtures of (1) cellulose acetate and polyacrylonitrile, (2) cellulose acetate and polyvinyl acetate, and (3) polyethylene and crepe rubber. The Provisional Specification relates also to the irradiation of two dissimilar polymer masses in close contact, and to the irradiation of a single polymeric mass with high intensity radiation of low penetration to render the surface of the mass compatible with adhesives.ALSO:Dissimilar polymers are mixed, e.g. by hot rolling or by solution in a common solvent such as dimethyl formamide, and the resulting mixture irradiated by a high energy electron beam, X-rays or gamma rays. The treatment produces chemical links between the polymers and improves compatibility and the mechanical and optical properties of the mixtures. Examples relate to the treatment of mixtures of (1) cellulose acetate and polyacrylonitrile; (2) cellulose acetate and polyvinyl acetate; and (3) polyethylene and crepe rubber. The Provisional Specification relates also to the irradiation of two dissimilar polymer masses in close contact, and to the irradiation of a single polymeric mass with high intensity radiation of low penetration to render the surface of the mass compatible with adhesives.

A. Charlesby

Papers

Atomic radiation and polymers

Effect of high-energy radiation on long-chain polymers

Irradiation of polymers

How radiation affects long-chain polymers

Improvements relating to the manufacture of plastics