Shape memory effects of poly(L-lactide) and its copolymer with poly(ε-caprolactone)

Lu, Xi Li; Cai, Wei; Gao, Zhiyong; Tang, Wen

doi:10.1007/s00289-006-0680-6

Cited by 57 publications

(44 citation statements)

References 16 publications

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“…They can ensure, however, only moderate R f and R r data. Variation of the molecular weight (M W ), that affects both entanglement and crystallization, yielded limited success [9]. Incorporation of hydroxyapatite nanoparticles up to 50 wt% into poly(D,L-lactide) (PDLLA) resulted in improved R r .…”

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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“…Completely amorphous, degradable polymers can be cross-linked in order to create networks that fix and recover a temporary shape around the glass transition temperature, as was shown initially shown by Alteheld et al 11 Alternately, if the chains are semicrystalline, linear polymers can exhibit T g -based shape memory using the crystalline physical cross-links as anchoring points to bring the material back to its original form. This has been shown for various copolyesters 12,13 as well as lactidebased polymers with inorganic nanofillers physically mixed in 14 or chemically attached along the backbone. 15 Naturally derived polymers have also been shown to exhibit shape memory properties such as poly(3-hydroxyalkanoates)s. When copolymerized with 3-hydroxyvalerate by the microorganism Pseudomonas sp.…”

Section: Introductionmentioning

confidence: 99%

PLGA−POSS End-Linked Networks with Tailored Degradation and Shape Memory Behavior

et al. 2009

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Biodegradable PLGA oligomers were synthesized to feature a hybrid organic-inorganic moiety, POSS, incorporated at the center of each chain by using it as the ring-opening initiator. After end-capping with vinyl groups, the macromers were photocured into networks with POSS content ranging from 10 to 41 wt %. Increasing POSS inclusion increased the crystallinity of the network while decreasing the degradation rate due to its hydrophobic and nonhydrolyzable properties. It was found that co-curing PLGA oligomers with and without POSS in the backbone could be utilized to create networks with a reduced POSS loading level, at a given cross-link density, allowing tuned crystallinity. Hydrolytic degradation of the co-cured networks was slower than for the PLGA homonetwork but still led to complete degradation after 14 weeks in PBS buffer at 37°C. The networks exhibited versatile shape memory properties, exploiting the combination of covalent cross-linking and the glass transition, POSS-phase melting temperature, or both as the shape-switching trigger. Using the glass transition was found to yield the best shape fixing, while the best recovery percentages (∼100%) were achieved when the melting transition was used. One network, with 24 wt % POSS, was able to be fixed in a temporary shape by POSS crystallization and to largely preserve this shape during degradation. After 4 weeks and 60% mass loss, 50% of the initial deformation still remained while the PLGA network (shape fixed through T g ) had recovered fully. Our findings are expected to impact future design of biodegradable polymers with shape memory, having revealed the precise tuning of properties possible through controlled placement of a crystallizable and hydrophobic moiety in the polymer network chain.

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“…Biocompatible polymers with hydrolyzable chemical bonds are being used to produce safe, non-toxic fluorescent microspheres for material penetration studies. The selection of polymeric materials depends on both biocompatibility and processability, with tailored fluorescent properties depending on specific applications [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Enhanced mechanical and photoluminescence effect of poly(l-lactide) reinforced with functionalized multiwalled carbon nanotubes

et al. 2012

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The poly(L-lactide) (PLLA) biocompatible and biodegradable polymer was reinforced with functionalized Multiwalled carbon nanotubes (MWCNTs) to overcome on insufficient mechanical properties of this polymer for high load bearing applications. To fully realize the potential of MWCNTs for this purpose, they have to be homogeneously dispersed in polymer matrix and have efficient load transfer across the MWCNTs/polymer interface. The pristine MWCNTs (pMWCNTs) were functionalized, at first, by Friedel-Crafts acylation, which introduced the aromatic amine groups on the sidewall of MWCNTs (MWCNT-NH 2 ) without shortening or cutting of pMWCNTs. And then, the PLLA chains covalently grafted from the sidewall of MWCNT-NH 2 by in situ ring-opening polymerization of L-lactide oligomers using stannous octanoate as the initiating system. The Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy spectra revealed that the PLLA chains grafted form the sidewall of MWCNTs strongly. The surface morphology of pristine and PLLA-grafted MWCNTs (MWCNT-g-PLLAs) was characterized by scanning electron microscopy and transmission electron microscopy. The tensile test of prepared composites of PLLA with various concentrations of MWCNT-g-PLLAs show a significant increment in tensile strength and elongation at failure of composites with increasing the concentration of MWCNT-g-PLLAs in composites. Also, it is found that the MWCNT-g-PLLAs increased the photoluminescence effect of PLLA and widened the luminescence region of PLLA.

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Shape memory effects of poly(L-lactide) and its copolymer with poly(ε-caprolactone)

Cited by 57 publications

References 16 publications

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

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

PLGA−POSS End-Linked Networks with Tailored Degradation and Shape Memory Behavior

Enhanced mechanical and photoluminescence effect of poly(l-lactide) reinforced with functionalized multiwalled carbon nanotubes

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