Crystal Structure Analysis of Poly(<scp>l</scp>-lactic Acid) α Form On the basis of the 2-Dimensional Wide-Angle Synchrotron X-ray and Neutron Diffraction Measurements

Wasanasuk, Kaewkan; Tashiro, Kohji; Hanesaka, Makoto; Ohhara, Tokashi; Kurihara, Kazuo; Kuroki, Ryota; Tamada, Taro; Ozeki, Tomoji; Kanamoto, Tetsuo

doi:10.1021/ma2006624

Cited by 201 publications

(236 citation statements)

References 37 publications

(81 reference statements)

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“…63 This behavior is different from that one observed for sPS films 24,28,29,73 for which a substantial maintenance of the uniplanar orientations for solid−solid crystalline phase transitions is observed, as long as polymer chains retain their conformation.…”

Section: With Relative Intensities Intermediate Between Those Of Fullcontrasting

confidence: 74%

“…This distance is very close to the shortest distance between chain axes (of PLLA helices in the same conformation) in the α-form (b = 0.62 nm). 68,73 Polymer Packing and Molecular Origin of the a ∥ c ∥ Uniplanar Orientation. The ordered packing of the polymer helices in the cocrystalline PLLA/CPO structure of Figure 6, can allow finding the molecular origin of the a ∥ c ∥ uniplanar orientation observed for guest induced cocrystallization of amorphous PLLA films.…”

Section: With Relative Intensities Intermediate Between Those Of Fullmentioning

confidence: 99%

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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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Section: With Relative Intensities Intermediate Between Those Of Fullcontrasting

confidence: 74%

Section: With Relative Intensities Intermediate Between Those Of Fullmentioning

confidence: 99%

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

et al. 2015

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“…The NMR methodologies presented in this mini-review today are not very common in polymer science, but for sure, they role will rapidly increase in the nearest future. coordinates obtained by Wasanuk et al [54] The assigned signals correspond to the notation system given in Fig. 18.…”

Section: Discussionmentioning

confidence: 99%

“…The spinning sidebands were further employed for determination of the values of principal elements of chemical shift tensors 13 C δ ii by means of 2D PASS experiment. [53] In the next step, authors computed 13 C NMR parameters using as an input file coordinates taken from WAND neutron scattering method [54] and GIPAW methodology. In this procedure, after full optimization of position of all atoms, the second set of [44] for the detailed descriptions of the spectra.…”

Section: Nuclear Magnetic Resonance Crystallography Of Polymersmentioning

confidence: 99%

Modern solid state NMR techniques and concepts in structural studies of synthetic polymers

Kaźmierski

Pawlak

Jeziorna

et al. 2016

Polym. Adv. Technol.

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In this mini-review, we present the solid state nuclear magnetic resonance (NMR) methods which trace the new tendency in structural studies of synthetic polymers. The review is organized into three sections. In the first part, short theoretical background and introduction to very fast magic angle spinning NMR technique with sample rotation 60 kHz are shown. The second part presents method for enhancing the sensitivity of NMR experiments by application of dynamic nuclear polarization magic angle spinning technique. In the third section, the power of the NMR crystallography approach which can be used for fine refinement of polymers structure on the atomic level is discussed.

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“…What's more, nonspecific adsorption of proteins such as fibrinogen and clotting enzymes on biomaterial surfaces is recognized as the first interaction event of many undesired bio-reactions and bio-responses, followed which were platelet adhesion and activation of coagulation pathways, and then leading to thrombus formation [30]. Two kinds of proteins, bovine serum albumin (BSA) and bovine serum fibrinogen (BFG), were used as the model protein to test the protein adsorption on the surfaces of neat PLA and chain branched PLA/0.5wt%PGE under the static state.…”

Section: Blood Compatibility Of Oriented Plamentioning

confidence: 99%

Fibrillation of chain branched poly (lactic acid) with improved blood compatibility and bionic structure

Zhao

et al. 2015

Chemical Engineering Journal

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Highly-oriented poly (lactic acid) (PLA) with bionic fibrillar structure and micro-grooves was fabricated through solid hot drawing technology for further improving the mechanical properties and blood biocompatibility of PLA as blood-contacting medical devices. In order to enhance the melt strength and thus obtain high orientation degree, PLA was first chain branched with pentaerythritol polyglycidyl ether (PGE). The branching degree as high as 12.69 mol% can be obtained at 0.5wt% PGE content. The complex viscosity, elastic and viscous modulus for chain branched PLA were improved resulting from the enhancement of molecular entanglement, and consequently higher draw ratio can be achieved during the subsequent hot stretching. The stress-induced crystallization of PLA occurred during stretching, and the crystal structure of the oriented PLA can be attributed to the ' crystalline form. The tensile strength and modulus of PLA were improved dramatically by drawing.Chain branching and orientation could significantly enhance the blood compatibility of PLA by prolonging clotting time and decreasing hemolysis ratio, protein adsorption and platelet activation. Fibrous structure as well as micro-grooves can be observed for the oriented PLA which were similar to intimal layer of blood vessel, and this bionic structure was considered to be beneficial to decrease the activation and/or adhesion of platelets.

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Crystal Structure Analysis of Poly(l-lactic Acid) α Form On the basis of the 2-Dimensional Wide-Angle Synchrotron X-ray and Neutron Diffraction Measurements

Cited by 201 publications

References 37 publications

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

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

Modern solid state NMR techniques and concepts in structural studies of synthetic polymers

Fibrillation of chain branched poly (lactic acid) with improved blood compatibility and bionic structure

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