Complex Crystal Formation of Poly(<scp>l</scp>-lactide) with Solvent Molecules

Marubayashi, Hironori; Asai, Shigeo; Sumita, Masao

doi:10.1021/ma202324g

Cited by 136 publications

(183 citation statements)

References 71 publications

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“…Figure 3 displayed the WAXD patterns in the range of 2θ=5~35 o for the neat PLA and the PLA/MWNTs composites. The samples before drawing exhibited a diffraction peak at 2θ = 16.7°, which belonged to α crystal form of PLA as reported previously [23]. It can be seen that the diffraction peak position of oriented PLA and PLA/MWNTs composites with different draw ratio had no change, however, there were significant differences in intensity.…”

Section: Crystallization Propertysupporting

confidence: 78%

Structure and blood compatibility of highly oriented PLA/MWNTs composites produced by solid hot drawing

Zhao

et al. 2013

J Biomater Appl

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Citation: Li Z, Zhao X, Ye L, Coates PD, Caton-Rose F and Martyn MT (2014) Structure and blood compatibility of highly oriented PLA/MWNTs composites produced by solid hot drawing. Journal of Biomaterials Applications. 28(7): 978-989. composites were fabricated through solid hot drawing technology in an effort to improve the mechanical properties and blood biocompatibility of PLA as blood-contacting medical devices. It was found that proper MWNTs content and drawing orientation can improve the tensile strength and modulus of PLA dramatically. With the increase of draw ratio, the cold crystallization peak became smaller, and the glass transition and the melting peak of PLA moved to high temperature, while the crystallinity increased, and the grain size decreased, indicating of the stress-induced crystallization of PLA during drawing. MWNTs showed a nucleation effect on PLA, leading to the rise of the melting temperature, increase of crystallinity, and reduction of spherulite size for the composites. Moreover, the intensity of (002) diffraction of MWNTs increased with draw ratio, indicating that MWNTs were preferentially aligned and oriented during drawing. Microstructure observation demonstrated that PLA matrix had an ordered fibrillar bundle structure, and MWNTs in the composite tended to align parallel to the drawing direction. In addition, the dispersion of MWNTs in PLA was also improved by orientation. Introduction of MWNTs and drawing orientation could significantly enhance the blood compatibility of PLA by prolonging kinetic clotting time, reducing hemolysis ratio, and platelet activation.

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Section: Crystallization Propertysupporting

confidence: 78%

Structure and blood compatibility of highly oriented PLA/MWNTs composites produced by solid hot drawing

Zhao

et al. 2013

J Biomater Appl

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“…The pattern of the film crystallized by liquid DMF (Figure 3A) is similar to that one of the film crystallized by CPO ( Figure 1D) with only small shifts of the diffraction angles, consistent with the orthorhombic unit cell with a = 1.55 nm, b = 1.23 nm, and c = 2.86 nm. 61 Photographic patterns analogous to those of Figure 2A (see Supporting Information) clearly indicates that a high degree of a ∥ c ∥ uniplanar orientation ( f 020 ≈ 0.9) can be achieved by cocrystallization with DMF.…”

Section: ■ Results and Discussionmentioning

confidence: 79%

Poly(l-lactic acid): Uniplanar Orientation in Cocrystalline Films and Structure of the Cocrystalline Form with Cyclopentanone

et al. 2015

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Guest molecules, like cyclopentanone (CPO), N,Ndimethylformamide (DMF) tetrahydrofuran (THF) and 1,3−dioxolane (DOL), which are able to cocrystallize with poly(L-lactic acid) (PLLA), can also generate high degree of crystalline phase orientation, by simple sorption in amorphous unoriented PLLA films. This crystalline phase orientation is defined as a ∥ c ∥ (a-parallel, c-parallel) because the ac plane of most crystallites is preferentially parallel to the film plane. This crystalline phase orientation, which is achieved without stretching even for high thickness films, is unprecedented for PLLA and can be maintained after suitable guest exchange procedures. The reported results confirm the recent hypothesis that cocrystallization with lowmolecular-mass guest molecules could be a common route for getting uniplanar orientations of polymer crystalline phases, even in the absence of stretching. Wide angle X-ray diffraction analyses of unoriented and oriented PLLA samples have allowed proposing the structure of the cocrystalline form of PLLA with CPO. In particular, four PLLA chains exhibiting the 10/7 helical conformation and 16 CPO guest molecules are packed according the space group P2 1 2 1 2 1 in an orthorhombic lattice with a = 1.61 nm, b = 1.26 nm, and c = 2.90 nm. The presence in PLLA cocrystalline structures of dense bc layers with close-packed polymer helices allows an easy rationalization of the observed uniplanar orientation. ■ INTRODUCTIONPolymeric cocrystalline forms, i.e. structures were a polymeric host and a low-molecular-mass guest are cocrystallized, although early recognized in literature, have been ignored for many decades. 1−15 Only in the last 2 decades have a few polymeric cocrystalline forms received attention in material science, mainly due to their ability to produce nanoporouscrystalline forms, 16−21 as a consequence of guest removal. 16,22,23 In the past decade, it has been also found that cocrystallization with suitable guest molecules of two commercial polymers: syndiotactic polystyrene (s-PS) and poly(2,6-dimethyl-1,4-phenylene ether) (PPO), can lead without any stretching procedure to high thickness f ilms (up to 200− 300 μm) with high degrees of different kinds of uniplanar orientations of the crystalline phases, i.e., with high degrees of parallelism of well-defined crystal planes with respect to the film plane. 24−34 In particular, for s-PS films, three different kinds of uniplanar orientations can be achieved by simple procedures involving cocrystallization in the presence of suitable guest molecules (solution crystallization, 24−26 solventinduced crystallization in amorphous samples, 27−30 or solventinduced recrystallizations of suitable crystalline films 31 ). The three observed uniplanar orientations correspond to the three simplest orientations of a high planar-density layer (formed by close-packed alternated enantiomorphous s-PS helices) with respect to the film plane. 32,33 As for PPO, two different kinds of uniplanar orientations have been recently obtained by cocrystallizat...

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“…1,2) Whereas PLLA forms α-crystals in film without special treatments, it can also form some other crystal forms under some sample preparation conditions. Marubayashi et al 3,4) reported that PLLA forms complex crystals with some solvents including N,N-dimethylformamide (DMF), and designated these crystals as "ε-crystal". Guenet, Daniel and their coworkers [5][6][7][8] reported that syndiotactic polystyrene also form complex crystals with some solvents such as 1,2-dichloroethan and 1-chloropropane, and gels in these solvents.…”

Section: Introductionmentioning

confidence: 99%

Flow Temperature of Poly(Lactic Acid) Gel in Solvents with Different Solubility

Matsuda

Fukui

Iwase

et al. 2018

J. Soc. Rheol., Jpn

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Poly(L-lactid acid) (PLLA) forms complex crystals (ε-crystal) with some solvents including N,N-dimethylformamide (DMF), and can be easily gelled in such solvents. The solvent of these gels can be exchanged to some other solvents which do not form ε-crystal with PLLA. The flow temperatures of PLLA gels after exchanging DMF to various solvents were investigated to clarify the relation between the exchangeability and the solubility of solvents to PLLA. After changing the ε-crystals to α-crystals (crystal form of PLLA in films without special treatments) by immersing the gels into 1-propanol, the flow temperatures of PLLA gels could be expected by Hansen solubility parameters. The results suggest that the exchangeability of the solvent of the PLLA gel is determined both by the solubility to PLLA and the ability of the new solvent to induce the change from ε-crystals to α-crystals.

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Complex Crystal Formation of Poly(l-lactide) with Solvent Molecules

Cited by 136 publications

References 71 publications

Structure and blood compatibility of highly oriented PLA/MWNTs composites produced by solid hot drawing

Structure and blood compatibility of highly oriented PLA/MWNTs composites produced by solid hot drawing

Poly(l-lactic acid): Uniplanar Orientation in Cocrystalline Films and Structure of the Cocrystalline Form with Cyclopentanone

Flow Temperature of Poly(Lactic Acid) Gel in Solvents with Different Solubility

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