Shape memory properties of poly(d,l-lactide)/hydroxyapatite composites

Zheng, Xiaotong; Zhou, Shaobing; Li, Xiaohong; Weng, Jie

doi:10.1016/j.biomaterials.2006.03.043

Cited by 224 publications

(154 citation statements)

References 36 publications

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“…80 to 98% upon filling. This was attributed to H-bonding between the matrix and nanoparticles creating net points in an additional physical network-like structure [10,11]. Accordingly, a more efficient network should be configured.…”

Section: Molecular Structure 211 T G -Based Systemsmentioning

confidence: 99%

Biodegradable polyester-based shape memory polymers: Concepts of (supra)molecular architecturing

Karger‐Kocsis

Kéki

2014

Express Polym. Lett.

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Shape memory (SM) biodegradable polymers (SMPs) and related composites are emerging smart materials in different applications. SMPs may adopt one (dual-shape), two (triple-shape) or several (multishape) stable temporary shapes and recover their permanent shape (or other temporary shapes in case of multi-shape versions) upon the action of an external stimulus. The external stimulus may be temperature, pH, water, light irradiation, redox condition etc. In most cases, however, the SMPs are thermally activated. The 'switching' or transformation temperature (T trans ), enabling the material to return to its permanent shape, is either linked with the glass transition (T g ) or with the melting temperature (T m ).Thus, SMPs are often subdivided based on their switch types into T g -or T m -based SMPs. As reversible 'switches' other mechanisms such as liquid crystallization and related transitions, supermolecular assembly/disassembly, irradiation-induced reversible network formation, formation and disruption of a percolation network, may also serve [1]. The permanent shape is guaranteed by physical or chemical network structures. The latter may be both on molecular and supramolecular levels. Linkages of these networks are termed net points. The temporary shape is created by mechanical deformation above T trans . In some cases the deformation temperature may be below Abstract. Shape memory polymers (SMPs) are capable of memorizing one or more temporary shapes and recovering to the permanent shape upon an external stimulus that is usually heat. Biodegradable polymers are an emerging family within the SMPs. This minireview delivers an overlook on actual concepts of molecular and supramolecular architectures which are followed to tailor the shape memory (SM) properties of biodegradable polyesters. Because the underlying switching mechanisms of SM actions is either related to the glass transition (T g ) or melting temperatures (T m ), the related SMPs are classified as T g -or T m -activated ones. For fixing of the permanent shape various physical and chemical networks serve, which were also introduced and discussed. Beside of the structure developments in one-way, also those in two-way SM polyesters were considered. Adjustment of the switching temperature to that of the human body, acceleration of the shape recovery, enhancement of the recovery stress, controlled degradation, and recycling aspects were concluded as main targets for the future development of SM systems with biodegradable polyesters.

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Section: Molecular Structure 211 T G -Based Systemsmentioning

confidence: 99%

Biodegradable polyester-based shape memory polymers: Concepts of (supra)molecular architecturing

Karger‐Kocsis

Kéki

2014

Express Polym. Lett.

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“…Existing biocompatible SMP networks contain either untethered polymer chains resulting in plastic deformations and broad transitions or excessive chain-chain interactions requiring extra energy to overcome. Consequently, they require harsh temperatures to fix temporary shape (<0°C) (3,(6)(7)(8) or trigger shape recovery (>70°C) that is often slow and incomplete (9)(10)(11). Moreover, few existing SMPs possess tunable biofunctionalizability and adequate mechanical strength at body temperature (12).…”

mentioning

confidence: 99%

High performance shape memory polymer networks based on rigid nanoparticle cores

Song

2010

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

122

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Smart materials that can respond to external stimuli are of widespread interest in biomedical science. Thermal-responsive shape memory polymers, a class of intelligent materials that can be fixed at a temporary shape below their transition temperature (T trans ) and thermally triggered to resume their original shapes on demand, hold great potential as minimally invasive self-fitting tissue scaffolds or implants. The intrinsic mechanism for shape memory behavior of polymers is the freezing and activation of the long-range motion of polymer chain segments below and above T trans , respectively. Both T trans and the extent of polymer chain participation in effective elastic deformation and recovery are determined by the network composition and structure, which are also defining factors for their mechanical properties, degradability, and bioactivities. Such complexity has made it extremely challenging to achieve the ideal combination of a T trans slightly above physiological temperature, rapid and complete recovery, and suitable mechanical and biological properties for clinical applications. Here we report a shape memory polymer network constructed from a polyhedral oligomeric silsesquioxane nanoparticle core functionalized with eight polyester arms. The cross-linked networks comprising this macromer possessed a gigapascal-storage modulus at body temperature and a T trans between 42 and 48°C. The materials could stably hold their temporary shapes for >1 year at room temperature and achieve full shape recovery ≤51°C in a matter of seconds. Their versatile structures allowed for tunable biodegradability and biofunctionalizability. These materials have tremendous promise for tissue engineering applications.nanocompsite | shape memory materials | thermal responsive materials A thermal-responsive shape memory polymer (SMP) can be imparted with a "permanent" shape above a critical transition temperature (T trans ) when it is cast in a mold. For polymers, the T trans is either glass transition temperature T g or melting temperature T m . Such a permanent shape, formed at the elastic state of the material without external stress, is retained (memorized) as the SMP cools to a temperature below its T trans . The SMP can be deformed into a desired "temporary" shape by force at T > T trans , and this strained configuration can be fixed as the temperature cools below the T trans . When a thermal stimulus above the T trans is reapplied, however, the SMP recovers to its less strained permanent shape. This unique shape memory behavior has captured the imagination of the biomedical community as scientists strive to design smart implants and tissue scaffolds that can be delivered in a minimally invasive configuration and be subsequently reverted to a preprogrammed permanent shape in vivo.Since the first demonstration of degradable SMPs for potential tissue engineering applications (1, 2), many semicrystalline and amorphous polyester and polyurethane SMP networks have been reported. Adjustment of thermomechanical properties and degrad...

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“…Since then, biodegradable SMPs have been synthesized, including network polymers formed by crosslinking oligo(ε-caprolactone) dimethyacrylate and N-butylacrylate [45], a multiblock copolymer of oligo(ε-caprolactone) and 2,2(4),4-trimethylhexanediisocyante [44], a composite of poly(D,L-lactide) and hydroxyapatite [49], and polyurethane derivatives containing polyesters [50,51]. In addition to biodegradability, other criteria attractive for SMP-based biomedical implants include reversibility in the on-off signal transition with minimal hysteresis and reinforced mechanical properties to act as mechanical actuators without buckling under stress.…”

Section: Shape-memory Gelsmentioning

confidence: 99%

Smart polymeric gels: Redefining the limits of biomedical devices

Chaterji

Kwon

Park

2007

Progress in Polymer Science

559

364

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This review describes recent progresses in the development and applications of smart polymeric gels, especially in the context of biomedical devices. The review has been organized into three separate sections: defining the basis of smart properties in polymeric gels; describing representative stimuli to which these gels respond; and illustrating a sample application area, namely, microfluidics. One of the major limitations in the use of hydrogels in stimuli-responsive applications is the diffusion rate limited transduction of signals. This can be obviated by engineering interconnected pores in the polymer structure to form capillary networks in the matrix and by downscaling the size of hydrogels to significantly decrease diffusion paths. Reducing the lag time in the induction of smart responses can be highly useful in biomedical devices, such as sensors and actuators. This review also describes molecular imprinting techniques to fabricate hydrogels for specific molecular recognition of target analytes. Additionally, it describes the significant advances in bottom-up nanofabrication strategies, involving supramolecular chemistry. Learning to assemble supramolecular structures from nature has led to the rapid prototyping of functional supramolecular devices. In essence, the barriers in the current performance potential of biomedical devices can be lowered or removed by the rapid convergence of interdisciplinary technologies.

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Shape memory properties of poly(d,l-lactide)/hydroxyapatite composites

Cited by 224 publications

References 36 publications

Biodegradable polyester-based shape memory polymers: Concepts of (supra)molecular architecturing

Biodegradable polyester-based shape memory polymers: Concepts of (supra)molecular architecturing

High performance shape memory polymer networks based on rigid nanoparticle cores

Smart polymeric gels: Redefining the limits of biomedical devices

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