Shape-memory Polymers

Lendlein, Andreas; Kelch, Steffen; Kratz, Karl; Schulte, J.

doi:10.1016/b0-08-043152-6/02033-7

Cited by 52 publications

(45 citation statements)

References 22 publications

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“…T sw is the temperature at the maximum recovery rate v r , which is the ratio of R r to the temperature interval of recovery, as can be obtained from the Equation 3. [26] v r R r DT r 3 PDMABu82 (b), PDMAHe71 (c)). …”

Section: Structure-property Relationship Between Comonomer Content mentioning

confidence: 99%

Amorphous, Elastic AB Copolymer Networks from Acrylates and Poly[(L‐lactide)‐ran‐glycolide]dimethacrylates

et al. 2008

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Shape-memory polymers (SMP) are dual shape materials, which can fix a temporary shape besides their original shape. The process of deformation under application of an external stress above a transition temperature (T trans ) and fixation by cooling below T trans is called programming. The original, permanent shape can be recovered by application of heat. [1][2][3][4][5] Heating could be realized directly by an increase in environmental temperature or indirectly by exposing to alternating magnetic fields [6,7] or illuminating with IR-light. [8] Shapememory polymers have a high innovation potential as biomaterial, especially for minimally invasive surgery. One basic concept in the development of biodegradable polymer systems with shape-memory properties is based on covalently crosslinked polymer networks, [9][10][11][12] containing switching segments from semi-crystalline poly(e-caprolactone) [10,11,13] or poly[(e-caprolactone)-co-glycolide]. [12] The latter ones enable an accelerated hydrolytic degradation because of the presence of easily hydrolizable ester bonds in the form of glycolate ester bonds. [12,14] Another approach is the development of AB copolymer photoset networks, which are obtained from poly(e-caprolactone)dimethacrylate with n-butylacrylate or cyclohexylmethacrylate by UV-crosslinking. [10,11] These polymer networks showed excellent shape-memory properties and as tested so far good tissue-compatibility, in cell culture and in vivo tests. [15][16][17][18][19] Amorphous polymer networks were developed based on poly[(L-lactide)-ran-glycolide)] chain segments. [20,21] This material is transparent and has a shape-memory capability, but its mechanical properties have to be further improved. Polymer networks from poly[(L-lactide)-ran-glycolide)]dimethacrylates (DM) tend to be brittle below the glass transition temperature T g of 55°C and are difficult to handle in the course of the network synthesis and extraction without destroying the samples. The incorporation of a second amorphous phase with a low glass transition temperature (T g,l ) into these materials, which keeps the material elastic, is a potential strategy to effectively improve the elastic properties of poly[(L-lactide)-ran-glycolide]-segment based networks. Formation of an amorphous mixed phase is supposed to allow an adjustment of the switching temperature for the shape-memory effect to a temperature range between roomand body temperature.In a first approach, to obtain dilactide-based amorphous polymer networks with increased toughness and elasticity at room temperature, multi-phase polymer networks were synthesized from amorphous and degradable ABA triblock macrodimethacrylates based on poly(rac-lactide)-b-poly(propylene oxide)-b-poly(rac-lactide). Atactic poly(propylene oxide) (PPG) with a number average molecular weight M n of 4000 g mol -1 and a low T g of -73°C formed the B-block while the molecular weight of A-blocks from poly(rac-lactide) was varied. Variation in this block length resulted in networks with a T g varying between 11°C ...

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Section: Structure-property Relationship Between Comonomer Content mentioning

confidence: 99%

Amorphous, Elastic AB Copolymer Networks from Acrylates and Poly[(L‐lactide)‐ran‐glycolide]dimethacrylates

et al. 2008

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“…Thermally activated shape memory polymers (SMP) are an emerging class of active materials that respond to a specific temperature event by generating a shape change (Nakayama, 1991;Otsuka and Wayman, 1998;Monkman, 2000;Lendlein and Kelch, 2002;Lendlein et al, 2005). Compared to shape memory alloys, SMPs are inexpensive to manufacture, malleable and damage tolerant, and can undergo large shape changes in excess of 100% strain.…”

Section: Introductionmentioning

confidence: 99%

“…The permanent shape is determined by the network of crosslinks, loosely defined here as junctions in the macromolecular network that persist through the temperature and deformation range of operation. They can be chemical bonds (thermosets), physical entanglements (thermoplastics), or small crystalline domains (phase-segregated block copolymers) (Lendlein and Kelch, 2002;Lendlein et al, 2005). The temporary shape of an SMP device can be programmed by a thermomechanical cycle, in which the undeformed device first is heated to T high 4T trans .…”

Section: Introductionmentioning

confidence: 99%

A thermoviscoelastic model for amorphous shape memory polymers: Incorporating structural and stress relaxation

Nguyen

Castro

et al. 2008

Journal of the Mechanics and Physics of Solids

382

299

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“…Shape-memory polymers have substantial innovation potential in different application areas, e.g., as intelligent implant materials in medicine (12)(13)(14) or in smart textiles (15). If polymers cannot be warmed up by heat transfer using a hot liquid or gaseous medium, noncontact triggering will be required.…”

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confidence: 99%

Initiation of shape-memory effect by inductive heating of magnetic nanoparticles in thermoplastic polymers

Mohr

Kratz

Weigel

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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586

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In shape-memory polymers, changes in shape are mostly induced by heating, and exceeding a specific switching temperature, T switch. If polymers cannot be warmed up by heat transfer using a hot liquid or gaseous medium, noncontact triggering will be required. In this article, the magnetically induced shape-memory effect of composites from magnetic nanoparticles and thermoplastic shapememory polymers is introduced. A polyetherurethane (TFX) and a biodegradable multiblock copolymer (PDC) with poly(p-dioxanone) as hard segment and poly( -caprolactone) as soft segment were investigated as matrix component. Nanoparticles consisting of an iron(III)oxide core in a silica matrix could be processed into both polymers. A homogeneous particle distribution in TFX could be shown. Compounds have suitable elastic and thermal properties for the shape-memory functionalization. Temporary shapes of TFX compounds were obtained by elongating at increased temperature and subsequent cooling under constant stress. Cold-drawing of PDC compounds at 25°C resulted in temporary fixation of the mechanical deformation by 50 -60%. The shape-memory effect of both composite systems could be induced by inductive heating in an alternating magnetic field (f ‫؍‬ 258 kHz; H ‫؍‬ 30 kA⅐m ؊1 ). The maximum temperatures achievable by inductive heating in a specific magnetic field depend on sample geometry and nanoparticle content. Shape recovery rates of composites resulting from magnetic triggering are comparable to those obtained by increasing the environmental temperature.nanocomposite ͉ shape-memory polymer ͉ stimuli-sensitive polymer S hape-memory polymers are able to recover their predefined original shape when exposed to an external stimulus. A prerequisite for the shape-memory effect is a preceding functionalization of the material to temporarily fix a mechanical deformation. Most shape-memory polymers are thermosensitive materials. The shape is actuated by exceeding a specific switching temperature, T switch (1). Thermoplastic shape-memory polymers have at least two separated phases, where the domains with the highest thermal transition (T perm ) stabilize the permanent shape by acting as physical netpoints. A second phase having another thermal transition T trans serves as switch. At temperatures above T trans the chain segments forming this phase are flexible and the material is highly elastic, whereas the flexibility of the chains below T trans is limited and enables the fixation of the temporary shape. T trans can either be a glass transition (T g ) or a melting temperature (T m ). Whereas T trans is the thermal transition of the switching segment phase, typically determined by differential scanning calorimetry (DSC), T switch is result of a thermomechanical test used to quantify the shape-memory effect.An important class of thermoplastic shape-memory polymers are polyurethanes. They often contain a hard segment from methylene bis(4-phenylisocyanate) (MDI) and 1,4-butanediol. Depending on the switching segment, T trans can be either a melting...

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Shape-memory Polymers

Cited by 52 publications

References 22 publications

Amorphous, Elastic AB Copolymer Networks from Acrylates and Poly[(L‐lactide)‐ran‐glycolide]dimethacrylates

Amorphous, Elastic AB Copolymer Networks from Acrylates and Poly[(L‐lactide)‐ran‐glycolide]dimethacrylates

A thermoviscoelastic model for amorphous shape memory polymers: Incorporating structural and stress relaxation

Initiation of shape-memory effect by inductive heating of magnetic nanoparticles in thermoplastic polymers

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