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Shape memory polymers
| Details |
Inventors: Langer, Robert S.; Lendlein, Andreas;
Assignee: MnemoScience GmbH (Aachen, DE)
Primary Examiner: Gorr; Rachel
Assistant Examiner:
Attorney, Agent or Firm: Holland & Knight LLP
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 T.sub.trans of the hard segment is preferably between -30 and 270.degree. C. At least one of the hard or soft segments can contain a crosslinkable 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 T.sub.trans of the hard segment, and cooled to a temperature below the T.sub.trans 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 T.sub.trans of the soft segment and below the T.sub.trans 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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DETAILED DESCRIPTION OF THE INVENTION Shape memory polymer compositions, articles of manufacture thereof, and methods of preparation and use thereof are provided.
The shape memory polymers can include at least one hard segment and at least one soft segment, or can include at least one kind of soft segment wherein at least one kind of the soft segments are crosslinked, without the presence of a hard segment.
In a preferred embodiment, the polymers can hold two or more shapes in memory.
Definitions A polymer is a shape memory polymer if the original shape of the polymer is recovered by heating it above a shape recovering temperature (defined as the T.
sub.
trans of a soft segment) even if the original molded shape of the polymer is destroyed mechanically at a lower temperature than the shape recovering temperature, or if the memorized shape is recoverable by application of another stimulus.
As used herein, the term "segment" refers to a block or sequence of polymer forming part of the shape memory polymer.
As used herein, the terms hard segment and soft segment are relative terms, relating to the T.
sub.
trans of the segments.
The hard segment(s) has a higher T.
sub.
trans than the soft segment(s).
The ratio by weight of the hard segment:soft segments is between about 5:95 and 95:5, preferably between 20:80 and 80:20.
As used herein, the term "biodegradable" refers to materials that are bioresorbable and/or degrade and/or break down by mechanical degradation upon interaction with a physiological environment into components that are metabolizable or excretable, over a period of time from minutes to three years, preferably less than one year, while maintaining the requisite structural integrity.
As used herein in reference to polymers, the term "degrade" refers to cleavage of the polymer chain, such that the molecular weight stays approximately constant at the oligomer level and particles of polymer remain following degradation.
The term "completely degrade" refers to cleavage of the polymer at the molecular level such that there is essentially complete mass loss
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Manufacturing Materials 
