Morphological changes of the polylactic acid microstructure under the action of supercritical carbon dioxide

Bogorodskii, S. E.; Zarkhina, T. S.; Кузнецов, Е. В.; Минаева, С. А.; Попов, В. К.; Соловьева, А. Б.; Timashev, P. S.

doi:10.1134/s1990793114070057

Cited by 8 publications

(3 citation statements)

References 12 publications

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“…As a result, the polymer transformed into a liquid-like (plasticized) state and was ready for further foaming at the depressurization stage. Consequently, carbon dioxide plays a dual role as a plasticizing agent at the preliminary stage of the process and a foaming agent during the main stage (described in detail elsewhere [ 36 ]).…”

Section: Methodsmentioning

confidence: 99%

Wide-Ranging Multitool Study of Structure and Porosity of PLGA Scaffolds for Tissue Engineering

et al. 2021

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In this study, the nanoscale transformation of the polylactic-co-glycolic acid (PLGA) internal structure, before and after its supercritical carbon dioxide (sc-CO2) swelling and plasticization, followed by foaming after a CO2 pressure drop, was studied by small-angle X-ray scattering (SAXS) for the first time. A comparative analysis of the internal structure data and porosity measurements for PLGA scaffolds, produced by sc-CO2 processing, on a scale ranging from 0.02 to 1000 μm, was performed by SAXS, helium pycnometry (HP), mercury intrusion porosimetry (MIP) and both “lab-source” and synchrotron X-ray microtomography (micro-CT). This approach opens up possibilities for the wide-scale evaluation, computer modeling, and prediction of the physical and mechanical properties of PLGA scaffolds, as well as their biodegradation behavior in the body. Hence, this study targets optimizing the process parameters of PLGA scaffold fabrication for specific biomedical applications.

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Section: Methodsmentioning

confidence: 99%

Wide-Ranging Multitool Study of Structure and Porosity of PLGA Scaffolds for Tissue Engineering

et al. 2021

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“…Highly porous bioresorbable polymer matrices are of particular interest as a material platform for creating scaffolds required in regenerative medicine and tissue engineering [ 1 , 2 , 3 ]. Among the various methods for synthesizing these materials, one of the frequently applied techniques is the depressurization-assisted foaming of pre-plasticized raw polymers in the atmosphere of a supercritical or subcritical plasticizing-foaming agent [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Over the past three decades, a large number of experimental studies on the impact of plasticization and depressurization modes on structural and functional properties of the synthesized polymer matrices as scaffold prototypes have been carried out [ 6 , 7 , 13 ].…”

Section: Introductionmentioning

confidence: 99%

Depressurization-Induced Nucleation in the “Polylactide-Carbon Dioxide” System: Self-Similarity of the Bubble Embryos Expansion

2021

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Self-similar expansion of bubble embryos in a plasticized polymer under quasi-isothermal depressurization is examined using the experimental data on expansion rates of embryos in the CO2-plasticized d,l-polylactide and modeling the results. The CO2 initial pressure varied from 5 to 14 MPa, and the depressurization rate was 5 × 10−3 MPa/s. The constant temperature in experiments was in a range from 310 to 338 K. The initial rate of embryos expansion varied from ≈0.1 to ≈10 µm/s, with a decrease in the current external pressure. While modeling, a non-linear behavior of CO2 isotherms near the critical point was taken into account. The modeled data agree satisfactorily with the experimental results. The effect of a remarkable increase in the expansion rate at a decreasing external pressure is interpreted in terms of competing effects, including a decrease in the internal pressure, an increase in the polymer viscosity, and an increase in the embryo radius at the time of embryo formation. The vanishing probability of finding the steadily expanding embryos for external pressures around the CO2 critical pressure is interpreted in terms of a joint influence of the quasi-adiabatic cooling and high compressibility of CO2 in the embryos.

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“…There are a huge variety of different conventional techniques enabling the fabrication of such scaffolds from aliphatic polyesters, including solvent casting and particulate leaching [8], phase separation [9,10], freeze-drying [11], electrospinning [12] and many others [13]. Gas [14,15] and supercritical fluid polymer foaming [16,17] methodology, mainly based on the use of carbon dioxide, has unambiguous advantages over mentioned above techniques due to its "solvent free" nature, providing the absence of harmful organic solvent residues [18,19] and retention of the bioactivity of the active and/or thermally labile components in the pharmaceutical formulations and bioactive scaffolds, since all processes can be performed at near ambient (around 40 • C) temperature [20,21].…”

Section: Introductionmentioning

confidence: 99%

Extreme Foaming Modes for SCF-Plasticized Polylactides: Quasi-Adiabatic and Quasi-Isothermal Foam Expansion

et al. 2020

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The experimental evidence on depressurization foaming of the amorphous D,L-polylactide, which is plasticized by subcritical (initial pressures below the critical value) or supercritical (initial pressures above the critical value) carbon dioxide at a temperature above the critical value, relates to two extreme cases: a slow quasi-isothermal foam expansion, and a rapid quasi-adiabatic expansion. Under certain conditions, the quasi-isothermal mode is characterized by the non-monotonic dependencies of the foam volume on the external pressure that are associated with the expansion-to-shrinkage transition. The quasi-adiabatic and quasi-isothermal expansions are characterized by a significant increase in the degree of foam expansion under conditions where the CO2 initial pressure approaches the critical value. The observed features are interpreted in terms of the energy balance in the foam volume and the phenomenological model based on the equation of the foam state. The expansion-to-shrinkage condition is based on the relationship between the average bubble radius and the pressure derivative of the surface tension for the plasticized polylactide. The maximum expansion ratio of the rapidly foamed polylactide in the vicinity of the critical point is interpreted in terms of the maximum decrement of the specific internal energy of the foaming agent (carbon dioxide) in the course of depressurization.

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Morphological changes of the polylactic acid microstructure under the action of supercritical carbon dioxide

Cited by 8 publications

References 12 publications

Wide-Ranging Multitool Study of Structure and Porosity of PLGA Scaffolds for Tissue Engineering

Wide-Ranging Multitool Study of Structure and Porosity of PLGA Scaffolds for Tissue Engineering

Depressurization-Induced Nucleation in the “Polylactide-Carbon Dioxide” System: Self-Similarity of the Bubble Embryos Expansion

Extreme Foaming Modes for SCF-Plasticized Polylactides: Quasi-Adiabatic and Quasi-Isothermal Foam Expansion

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