Crystallization and Melting Behavior of Poly (<scp>l</scp>-lactic Acid)

Kawai, Tadakazu; Rahman, Nelly; Matsuba, Go; Nishida, Koji; Kanaya, Toshiji; Nakano, Mitsuru; Okamoto, Hiroyuki; Kawada, Jumpei; Usuki, Arimitsu; Honma, Nobutaka; Nakajima, Katsuyoshi; Matsuda, Minoru

doi:10.1021/ma070082c

Cited by 569 publications

(675 citation statements)

References 38 publications

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“…As shown in Figure 6, neat PLLA shows three main characteristic diffraction peaks at around 14.86°, 16.70°, and 19.04°, corresponding to (010), (200), and (203), respectively. 32,33 In the case of the nanocomposites, the diffraction peaks shift slightly to the lower angle as compared with those of neat PLLA, indicating that the corresponding interplanar spacings increase with the addition of MWNTs. The related values of interplanar spacing for neat PLLA and its nanocomposites are summarized in Table 3, which increase slightly with the addition of MWNTs.…”

Section: Resultsmentioning

confidence: 96%

Effect of Functionalization of Multiwalled Nanotubes on the Crystallization and Hydrolytic Degradation of Biodegradable Poly(l-lactide)

2008

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Biodegradable poly(L-lactide) (PLLA)/multiwalled carbon nanotubes (MWNTs) nanocomposites were prepared via solution blending using two kinds of MWNTs, i.e., pristine multiwalled carbon nanotubes (p-MWNTs) and carboxyl-functionalized multiwalled carbon nanotubes (f-MWNTs). Various techniques were used to investigate the functionalization of MWNTs on the morphology, crystallization, and hydrolytic degradation of PLLA in the nanocomposites. Both MWNTs show fine dispersion in the PLLA matrix; however, the dispersion of f-MWNTs is better than that of p-MWNTs. The incorporation of MWNTs accelerates the crystallization of PLLA in the nanocomposites due to the heterogeneous nucleation effect; furthermore, the crystallization rate of PLLA is faster in the PLLA/f-MWNTs nanocomposite than in the PLLA/p-MWNTs nanocomposite. The exciting aspect of this research is that the hydrolytic degradation of PLLA is enhanced after nanocomposites preparation.

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Section: Resultsmentioning

confidence: 96%

Effect of Functionalization of Multiwalled Nanotubes on the Crystallization and Hydrolytic Degradation of Biodegradable Poly(l-lactide)

2008

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“…those constituted by the PEG and HD lateral groups) and furthermore with a similar crystallization temperature. Phase separation and crystalline morphology studies of block copolymers are currently receiving much attention [28][29][30][31][32], and even microstructures that can be formed from the melt, from solution and for both thin and bulk samples have been extensively reviewed [33,34]. Ringed spherulites with an interspacing close to 9 µm could also be detected in the specimens (Figure 2d) although at a lower ratio.…”

Section: Spherulitic Morphologies Of Poly(mepegca-co-hdca)mentioning

confidence: 99%

Nanospheres and nanocapsules of amphiphilic copolymers constituted by methoxypolyethylene glycol cyanoacrylate and hexadecyl cyanoacrylate units

Valente¹,

Valle²,

Casas³

et al. 2013

Express Polym. Lett.

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Nanospheres and nanocapsules of an amphiphilic copolymer having methylated polyethylene glycol and hexadecyl lateral groups were prepared by the solvent displacement method and using confined impinging jet mixers. Degradation, thermal properties and crystalline structure were investigated. Interestingly, pegylated chains hydrolyzed through ester bond cleavage, whereas the more hydrophobic hexadecyl ester groups were resistant to degradation in aqueous media. The copolymer crystallized from the melt, giving rise to spherulites with a negative birefringence and domains corresponding to crystallization of the different lateral groups. Size distribution and morphology of nanoparticles were mainly evaluated by electron microscopy. Nanocapsules were characterized by a stable membrane with a thickness close to 5 nm that allowed efficient encapsulation of a triglyceride oil. Triclosan was selected as an example of a hydrophobic drug to be loaded in both nanospheres and nanocapsules. The release behavior of these dosage forms was clearly different. Thus, the Burst effect was practically suppressed when using nanocapsules; in addition, these showed a sustained, controlled release over a greater time period. Antimicrobial activity of triclosan loaded nanospheres and nanocapsules was evaluated using Gram-negative and Gram-positive bacteria. The former were highly sensitive to the released triclosan whereas the latter strongly depended on the number of particles in the culture medium

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“…[17][18][19] The 0 phase generally occurs at lower crystallization temperatures below 120 C during melt or cold crystallization. For the present solution-grown PLLA crystals, we confirmed by FT-IR that the less ordered 0 phase is dominantly formed from all the four solutions: absorption bands at 1749, 1444, and 1382 cm À1 which are characteristic to the ordered structure 14 were not observed.…”

Section: Resultsmentioning

confidence: 99%

Formation of Porous Spherulites of Poly(L-lactide) Grown from Solutions

2009

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Porous soft materials possessing high surface to volume ratio have been attracted much attention because of their potential applications such as functional filters, catalyst, and biomedical materials. Various techniques to fabricate materials with high porosity have been developed up to the present, which utilize the layer-by-layer deposition, 1 freeze-drying, 2 electro-spinning, 3 etc. In addition, crystallization of polymers from suitable solutions is another potential technique to obtain porous materials as small particles. Very porous particles of polyamide and poly(ethylene oxide) (PEO) have been obtained via spherulitic growth in solutions. 4,5 Such characteristic feature of morphology seems to be closely related to complicated mechanisms specific to solution crystallization. We have studied the mechanism of solution crystallization especially in viscous solvents, and have revealed an unusual diffusion aspect for isotactic polystyrene/viscous solvent systems.6 Another important feature of solution crystallization is that polymer-solvent interaction plays an important role, which is responsible for the resulting crystalline morphology. For example, crystallization of PEO in a very viscous solvent results in highly swollen spherulites with solvent, while in dimethyl sulfoxide crystallites with outer polygonal contours are formed suggesting that liquid-liquid phase separation occurs during the crystallization. For many biomedical applications of the porous materials, biocompatibility and biodegradability is usually required. In this respect, poly(L-lacide) (PLLA) is one of the most promising materials for the fabrication of porous particles by the solution crystallization method. It has been shown that single crystals of PLLA are formed from very dilute solutions, and their structure has been well characterized. 8,9 On the other hand, spherulites of PLLA are generally formed from more concentrated solutions and from melt.8,10 Porous PLLA fibres can be obtained by precipitation in a non-solvent under stirring. 11In this paper, we investigate the morphology of very porous PLLA particles which are obtained by solution crystallization. We employed four solvents with different viscosities, i.e., diethyl phthalate (DEP), glycerol tri-n-propionate (TP), N,Ndimethylformamide (DMF), and dimethyl sulfoxide (DMSO). Porous spherulites exhibiting remarkable morphology of a flower-like appearance (assembled petals) are successfully obtained especially from viscous solvents (DEP and TP). EXPERIMENTAL PLLA (M w ¼ 210 kg molÀ1 ) was supplied from Mitsui Chemicals Co., which contained 98% L units. The four solvents (DEP, TP, DMF, and DMSO) were distilled under reduced pressure before use. Table I shows viscosity of the solvents at 25 C. PLLA was added to each solvent in a glass tube and heated at 150 C for 15-30 min to make an apparently homogeneous solution of which the PLLA content was 5.0 wt %. Then, the sample tube was rapidly immersed in a water bath, where the temperature was controlled at 25, 30, and 35 C, and the tempe...

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Crystallization and Melting Behavior of Poly (l-lactic Acid)

Cited by 569 publications

References 38 publications

Effect of Functionalization of Multiwalled Nanotubes on the Crystallization and Hydrolytic Degradation of Biodegradable Poly(l-lactide)

Effect of Functionalization of Multiwalled Nanotubes on the Crystallization and Hydrolytic Degradation of Biodegradable Poly(l-lactide)

Nanospheres and nanocapsules of amphiphilic copolymers constituted by methoxypolyethylene glycol cyanoacrylate and hexadecyl cyanoacrylate units

Formation of Porous Spherulites of Poly(L-lactide) Grown from Solutions

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