Stereocomplex formation between enantiomeric poly(lactides)

Ikada, Yoshito; Jamshidi, K.; Tsuji, Hideto; Hyon, Suong Hyu

doi:10.1021/ma00170a034

Cited by 1,339 publications

(1,194 citation statements)

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(3 reference statements)

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“…3.47a reports diffractograms of selected samples. The two crystalline reflection peaks at 2θ = 16.5° and 19° are typical of the α-form of P(L)LA having a pseudo-orthorhombic unit cell [127] and their intensity increased with the progress of degradation. Fig.…”

Section: Hydrolytic Degradation Experimentsmentioning

confidence: 99%

“…This issue has been overcome by combining gas foaming with the salt leaching procedure [117,124] or by trimming off the non-porous skin from the scaffold after its fabrication [125,126]. ScCO 2 foaming of biodegradable polymers has been mainly applied to poly-α-hydroxacids, though some publications also report the use of PCL [127,128]. Given their morphology and their mechanical performances, these scaffolds can be employed for TE of hard tissues, such as bone and cartilage.…”

Section: Gas Foamingmentioning

confidence: 99%

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Porous Polymeric Bioresorbable Scaffolds for Tissue Engineering

Gualandi

2011

Springer Theses

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and some lactide copolymers) and of non-commercial polyesters (i.e. poly-ω-pentadecalactone and some of its copolymers) were explored and discussed.Two techniques were employed to fabricate scaffolds: supercritical carbon dioxide (scCO 2 ) foaming and electrospinning (ES). The former is a powerful technology that enables to produce 3D microporous foams by avoiding the use of solvents that can be toxic to mammalian cells. The scCO 2 process, which is II commonly applied to amorphous polymers, was successfully modified to foam a highly crystalline poly(ω-pentadecalactone-co-ε-caprolactone) copolymer and the effect of process parameters on scaffold morphology and thermo-mechanical properties was investigated.In the course of the present research activity, sub-micrometric fibrous nonwoven meshes were produced using ES technology. Electrospun materials are considered highly promising scaffolds because they resemble the 3D organization of native extra cellular matrix. A careful control of process parameters allowed to fabricate defect-free fibres with diameters ranging from hundreds of nanometers to several microns, having either smooth or porous surface. Moreover, versatility of ES technology enabled to produce electrospun scaffolds from different polyesters as well as "composite" non-woven meshes by concomitantly electrospinning different fibres in terms of both fibre morphology and polymer material. The 3D-architecture of the electrospun scaffolds fabricated in this research was controlled in terms of mutual fibre orientation by properly modifying the instrumental apparatus. This aspect is particularly interesting since the micro/nano-architecture of the scaffold is known to affect cell behaviour.Since last generation scaffolds are expected to induce specific cell response, the present research activity also explored the possibility to produce electrospun scaffolds bioactive towards cells. Bio-functionalized substrates were obtained by loading polymer fibres with growth factors (i.e. biomolecules that elicit specific cell behaviour) and it was demonstrated that, despite the high voltages applied during electrospinning, the growth factor retains its biological activity once

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Section: Hydrolytic Degradation Experimentsmentioning

confidence: 99%

Section: Gas Foamingmentioning

confidence: 99%

Porous Polymeric Bioresorbable Scaffolds for Tissue Engineering

Gualandi

2011

Springer Theses

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“…However the application has been restricted due to the insufficient thermal resistance in comparison to the other synthetic polymers used for the textile fibers. One of the way to solve this problem is to utilize the stereocomplex crystal (SC) which forms in the equal blend of poly(L-lactic acid) (PLLA) and poly(Dlactic) (PDLA), first reported by Ikada et al 1 . It has been known that SC has a melting point about 235°C higher than that of the homo-chiral crystal (HC) of PLLA.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Take-Up Velocity on the Higher-Order Structure of the Melt-Electrospun PLLA/PDLA Blend Fibers

et al. 2015

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The higher-order structure and the formations of SC and HC of the PLLA/PDLA blend melt-electrospun fibers collected on a rotating target were investigated. The diameter of the fiber decreased and the orientation factor increased with increasing take-up velocity. The formation of SC was promoted with decreasing fiber diameter and with increasing take-up velocity. The fiber collected on the fixed target was amorphous and did not show the molecular orientation to any particular directions indicating that the stretching of the fiber by the electrostatic force did not give much molecular orientation to the fiber. On the other hand, the stretching of the fiber by applying the mechanical taking-up gave a significant degree of the molecular orientation to the fiber direction. The crystalline orientation of HC of the annealed fiber was higher than that of SC.

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“…15,16 In addition, poly (L-lactic acid) and poly(D-lactic acid) could form a 1/1 stereocomplex, and the crystalline structure of the stereocomplex was quite different from that of poly(L-lactic acid) or poly(D-lactic acid). [17][18][19][20] It was reported that multiblock copolymers of poly(L-lactic acid) and poly(D-lactic acid) formed the stereocomplex more easily without first forming the single-polymer crystals. 21 However, PLA with short L-and D-block sequences exhibited relatively a low melting temperature.…”

Section: Introductionmentioning

confidence: 99%

NMR analysis and chemical shift calculations of poly(lactic acid) dimer model compounds with different tacticities

Suganuma

Horiuchi

Matsuda

et al. 2012

Polym J

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In this work, poly(lactic acid) (PLA) dimer model compounds with different tacticities were synthesized and studied in detail by 1 H and 13 C nuclear magnetic resonance (NMR) in three solvents, deuterated chloroform (CDCl 3 )/CCl 4 (20/80 v/v), CDCl 3 and dimethyl sulfoxide -d 6 . All of the peaks in the 1 H and 13 C NMR spectra were assigned with the help of two-dimensional NMR. Although the solvents were different, the tacticity splitting of the dimers showed no significant difference among the solvents. The chemical shifts were calculated and compared with experimental shifts to understand the origin of the tacticity splitting in PLA. Thus, a conformational energy calculation was first performed to determine the energetically stable states in isotactic and syndiotactic dimers by several quantum chemical calculation methods. The 1 H and 13 C chemical shifts were then calculated for each conformation of the model compounds by considering both the conformational energies of the predominant conformation and the chemical shift of each conformation. The observed tacticity splitting of the chemical shifts between isotactic and syndiotactic 1 H and 13 C NMR peaks of the dimers was reproduced particularly well, using the combination of Becke's three parameter hybrid method for conformational energy calculations and Hartree-Fock for chemical shift calculations.

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Stereocomplex formation between enantiomeric poly(lactides)

Cited by 1,339 publications

References 3 publications

Porous Polymeric Bioresorbable Scaffolds for Tissue Engineering

Porous Polymeric Bioresorbable Scaffolds for Tissue Engineering

Effect of the Take-Up Velocity on the Higher-Order Structure of the Melt-Electrospun PLLA/PDLA Blend Fibers

NMR analysis and chemical shift calculations of poly(lactic acid) dimer model compounds with different tacticities

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