Didaktisch-methodischer Ermöglichungsrahmen

Sauter, Werner; Sauter, Simon

doi:10.1007/978-3-642-41418-3_3

Cited by 6 publications

(8 citation statements)

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“…The concept of high deformation capability with simultaneous high recovery ratio was investigated by cyclic, thermomechanical tensile tests (see Experimental part). [8] Fixation of the temporary shape of the sample was performed in the stress-controlled conditions to achieve high shape fixity. Compared to programming under strain-controlled conditions, the stress-controlled programming results in a higher degree of chain orientation causing crystallization-induced elongation, and in this way an increase of χ c .…”

Section: Shape-memory Propertiesmentioning

confidence: 99%

“…[4,6] In contrast, shape-memory polymers (SMPs) based on covalent networks have shown high shape recovery ratios but exhibit a limited elastic deformation capacity. [2,[7][8][9][10] Furthermore, many applications for biomedical devices require large shape changes as the devices need to be inserted through small incisions or in a minimally invasive way by the usage of catheters, and subsequently need to recover their original, application relevant shape. Thus far, only a few examples of covalently crosslinked SMP with high recoverable strains have been reported.…”

Section: Introductionmentioning

confidence: 99%

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Poly(carbonate‐urea‐urethane) networks exhibiting high‐strain shape‐memory effect

Mazurek-Budzyńska

Razzaq

Tomczyk

et al. 2016

Polymers for Advanced Techs

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A challenge in the design of shape‐memory polymers (SMPs) is to achieve high deformability with a simultaneous high shape recovery ratio. Here we explored, whether SMPs featuring large deformation capability and high shape recovery ratios can be created as polymer networks providing two kinds of netpoints based on covalent bonds and physical interactions. As a model system, we selected poly(carbonate‐urea‐urethane)s (PCUUs) synthesized by a precursor route, based on oligo(alkylene carbonate) diols, isophorone diisocyanate (IPDI), and water vapor. The PCUU networks exhibited a one‐way shape‐memory effect (1W‐SME) with programmed strains up to εprog = 1000% whereby they provided excellent shape fixity (92–97%) and shape recovery (≥99%) ratios. The switching temperatures (Tsw) varied between 36 and 65 °C and increased with the increasing molecular weight of the oligo(alkylene carbonate) diol and length of the hydrocarbon chain between the carbonate linkages. Tsw was also influenced by the strain applied during programming (εprog). Poly(carbonate‐urethane)s have been reported to have good biocompatibility and biostability, which in the combination of high‐strain capacity and high Young's modulus makes the obtained PCUUs interesting candidate materials suitable for medical devices such as medical sutures or vascular stents. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Shape-memory Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Poly(carbonate‐urea‐urethane) networks exhibiting high‐strain shape‐memory effect

Mazurek-Budzyńska

Razzaq

Tomczyk

et al. 2016

Polymers for Advanced Techs

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“…[ 29 ] Each PLGA-PU system was together with the applied processing and programming method. [ 17,18 ] This processing method is called shapememory creation procedure, [ 16 ] where the samples are heated above the transition temperature T trans of the switching segments and deformed to the desired elongation ε m . Next the sample is cooled to a temperature T low , which is below T trans , while keeping either the deformation strain or stress constant, whereby the temporary shape is fi xed by solidifi cation of the domains associated to T trans .…”

Section: Preparation Of Atomistic Packing Models For Poly[( Rac -Lamentioning

confidence: 99%

“…The entropy-driven recovery of the memorized permanent shape is triggered by heating the sample again to T high under stress free conditions. [ 18 ] The SME can be quantifi ed by cyclic, thermomechanical tensile tests, which allow recording the complete strain-temperaturestress behavior of test specimen. [ 16 ] Characteristic values for the quantifi cation of the SME are the shape fi xity ratio ( R f ), which is the ability of a polymer for temporarily fi xation of the deformed shape and the shape recovery ratio ( R r ) describing how well the original shape is recovered.…”

Section: Preparation Of Atomistic Packing Models For Poly[( Rac -Lamentioning

confidence: 99%

Atomistic Simulation of the Shape‐Memory Effect in Dry and Water Swollen Poly[(rac‐lactide)‐co‐glycolide] and Copolyester Urethanes Thereof

Ghobadi

Heuchel

Kratz

et al. 2013

Macro Chemistry & Physics

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An atomistic molecular dynamics simulation approach is applied to model the influence of urethane linker units as well as the addition of water molecules on the simulated shape‐memory properties of poly[(rac‐lactide)‐co‐glycolide] (PLGA) and PLGA‐based copolyester urethanes comprising different urethane linkers. The shape‐memory performance of these amorphous packing models is explored in a simulated heating–deformation–cooling–heating procedure. Depending on the type of incorporated urethane linker, the mechanical properties of the dry copolyester urethanes are found to be significantly improved compared with PLGA, which can be attributed to the number of intermolecular hydrogen bonds between the urethane units. Good shape‐memory properties are observed for all the modeled systems. In the dry state, the shape fixation is found to be improved by implementation of urethane units. After swelling of the copolymer models with water, which results in a reduction of their glass transition temperatures, the relaxation kinetics during unloading and shape recovery are found to be substantially accelerated.

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“…[4,5] In case of materials containing physical netpoints, the network structure has a non-permanent but reversible character. [6,7] These netpoints may be formed by crystalline domains or supramolecular interactions. Therefore, the network structure of physically crosslinked materials may be sensitive to solvents, heat, or high mechanical stresses.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced synthesis of polyester networks from methacrylate functionalized precursors: analysis of side reactions

Friess

Lendlein

Wischke

2014

Polymers for Advanced Techs

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*Polyester networks can be prepared by ultraviolet (UV)-light-induced radical polymerization of methacrylate functionalized oligo(ε-caprolactone)s. The properties and functions of the obtained materials depend on defined network structures and may be altered, if crosslinking would occur by side reactions in other positions than the methacrylate endgroups. In order to explore whether and to which extent such side reactions occur, network synthesis as well as related model reactions were performed in the absence of photoinitiator. Hereby precursor structures (linear and four-arm star-shaped) and reaction conditions (in solution and in the melt) were varied. Unspecific side reactions were found only upon extensive UV irradiation for 60 min (26 mW cm -2 ) with minor but detectable alterations of physicochemical properties of the networks. The analysis of model reactions suggested minor photolytic cleavage of ester bonds during polymer network synthesis. However, the effect of these side reactions on network properties and functions appeared to be less relevant than an incomplete precursor integration because of a too short UV irradiation for crosslinking.

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Didaktisch-methodischer Ermöglichungsrahmen

Cited by 6 publications

References 0 publications

Poly(carbonate‐urea‐urethane) networks exhibiting high‐strain shape‐memory effect

Poly(carbonate‐urea‐urethane) networks exhibiting high‐strain shape‐memory effect

Atomistic Simulation of the Shape‐Memory Effect in Dry and Water Swollen Poly[(rac‐lactide)‐co‐glycolide] and Copolyester Urethanes Thereof

Photoinduced synthesis of polyester networks from methacrylate functionalized precursors: analysis of side reactions

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