Effect of nucleation and plasticization on the stereocomplex formation between enantiomeric poly(lactic acid)s

Saeidlou, Sajjad; Huneault, Michel A.; Li, Hongbo; Park, Chul

doi:10.1016/j.polymer.2013.08.031

Cited by 49 publications

(34 citation statements)

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“…The melting temperature of sc crystallites at lower temperature, which corresponds to the crystallites formed in isothermal crystallization, is used to determine T m 0 . As shown in Table 1, the obtained T m 0 s of sc crystallites vary from 252 to 275°C, which agrees with that of racemic blend with high optical purity (263°C) reported by Tsuji and Ikada, 53 but larger than that of the asymmetric PLLA/PDLA blend reported by Saeidlou et al 54 It has been found that T m 0 of homocrystallites increases with MW. 39 However, less perfect sc crystallites would be formed in racemic blends with increasing MW, due to the suppressed stereocomplexation.…”

Section: ■ Experimental Sectionsupporting

confidence: 87%

Competitive Stereocomplexation, Homocrystallization, and Polymorphic Crystalline Transition in Poly(l-lactic acid)/Poly(d-lactic acid) Racemic Blends: Molecular Weight Effects

et al. 2015

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Competitive crystallization kinetics, polymorphic crystalline structure, and transition of poly(l-lactic acid)/poly(d-lactic acid) (PLLA/PDLA) racemic blends with a wide range of molecular weights (MWs) were symmetrically investigated. Stereocomplex (sc) crystallites are exclusively formed in the low-MW racemic blends. However, stereocomplexation is remarkably depressed, and homocrystallization becomes prevailing with increasing MWs of PLLA and PDLA. Suppressed stereocomplexation in high-MW (HMW) racemic blends is proposed to be due to the low chain diffusion ability and restricted intermolecular crystal nucleation/growth. Equilibrium melting point of sc crystallites first increases and then decreases as MW increases. Crystallinity and relative fraction of sc crystallites in racemic blends enhance with crystallization temperature (Tc), and the sc crystallites are merely formed at Tc > 170 °C because of their higher thermodynamic stability. In situ wide-angle X-ray diffraction (WAXD) analysis reveals that the stereocomplexation and homocrystallization are successive rather than completely simultaneous, and the stereocomplexation is preceding homocrystallization in isothermal crystallization of HMW racemic blends. Both initial crystalline structure of homocrystallites (hc) and MW influence the heating-induced hc-to-sc transition of HMW racemic blend drastically; the hc-to-sc transition becomes easier with decreasing Tc and MW. After crystallization at the same temperature, sc crystallites show smaller long period than their hc counterparts.

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Section: ■ Experimental Sectionsupporting

confidence: 87%

Competitive Stereocomplexation, Homocrystallization, and Polymorphic Crystalline Transition in Poly(l-lactic acid)/Poly(d-lactic acid) Racemic Blends: Molecular Weight Effects

et al. 2015

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“…It is known that nucleation and plasticization have a significant effect on PLA homocrystallization . In a previous study on the stereocomplex formation for melt mixed PLLA/PDLA blends it was shown that these modification techniques are also helpful for acceleration of stereocomplex formation even at elevated temperatures, with nucleation having a major contribution . Therefore, the second objective of this work was to probe the effect of a nucleating agent on stereocomplex formation through rheological measurements.…”

Section: Introductionsupporting

confidence: 65%

Poly(lactic acid) stereocomplex formation: Application to PLA rheological property modification

Saeidlou

Huneault

et al. 2014

J of Applied Polymer Sci

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Poly(lactic acid) (PLA) stereocomplex formation in isothermal conditions in the absence and presence of a nucleating agent was studied from a rheological point of view due to sensitivity of viscoelastic properties to structural changes during this process. PDLA was melt blended in low concentrations with PLLA to produce a stereocomplex. Amorphous samples were prepared and crystallization was carried out in a rheometer at high temperatures to simulate melt processing conditions. Stereocomplexation was explored over time by measuring rheological parameters in small deformation oscillatory shear mode at a low frequency using parallel plate geometry. Kinetic data obtained by this means was compared to data from calorimetric studies, showing a different trend depending on the characterization method. Moreover, after the completion of crystallization, final crystalline structure was probed over a wide range of frequencies to investigate the rheological modification role of PDLA on PLLA major component. Differences in rheological characteristics of asymmetric PLLA/PDLA blends as compared to neat PLLA were associated to the structural changes happening because of the formation of the stereocomplex. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41073.

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“…Different strategies have been employed to enhance the crystallization kinetics of PLA including chain branching [12][13][14][15], iso-/non-iso-thermal treatment under plasticizing gas environments at elevated pressures [8,12,16,17], polymer blending [18][19][20][21][22], incorporation of inorganic/organic fillers or nucleating agents [8,21,[23][24][25][26][27][28][29][30], and strain-induced crystallization [31][32][33]. Among these, adding inorganic/organic fillers or nucleating agents has been considered one of the most common and effective approaches.…”

Section: Introductionmentioning

confidence: 99%

Non-isothermal crystallization behaviors of poly(lactic acid)/cellulose nanofiber composites in the presence of CO2

Ding

Chu

Mark

et al. 2015

European Polymer Journal

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Effect of nucleation and plasticization on the stereocomplex formation between enantiomeric poly(lactic acid)s

Cited by 49 publications

References 50 publications

Competitive Stereocomplexation, Homocrystallization, and Polymorphic Crystalline Transition in Poly(l-lactic acid)/Poly(d-lactic acid) Racemic Blends: Molecular Weight Effects

Competitive Stereocomplexation, Homocrystallization, and Polymorphic Crystalline Transition in Poly(l-lactic acid)/Poly(d-lactic acid) Racemic Blends: Molecular Weight Effects

Poly(lactic acid) stereocomplex formation: Application to PLA rheological property modification

Non-isothermal crystallization behaviors of poly(lactic acid)/cellulose nanofiber composites in the presence of CO2

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