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Talk: Effect of Stereoisomerism on the Structure and Linear Rheology of Poly(Lactic Acid)

Bacova, Petra; Maturi, Mirko; Harmandaris, Vagelis; Molina, Sergio I.

Publisher
Zenodo
DOI
10.5281/zenodo.17290384
Repository
zenodo.org
Language
en

Abstract

Oral contribution presented at 11th International Meeting of the Hellenic Society of Rheology (HSR 2025, https://mathweb.aegean.gr/hsr2025/) which took place in Syros, Greece, from 11th to 14th of June, 2025. Abstract: In an effort to satisfy the sustainability requirements, recent studies have increasingly focused on polymers of natural origin, such as poly(lactic acid) (PLA). Due to their complex, often protein-like structures with chiral centers, bio-based polymers pose significant challenges for computational modeling as well as for systematic experimental studies. In this work we combine experimental and computational approach in order to investigate how stereoisomerism affects the local structure and the final viscoelastic behavior of low molecular weight PLA in melt. Employing atomistic molecular dynamics simulations, we show subtle yet significant differences in chain packing of the L- and D- homochiral stereoisomers with respect to the copolymer chains of PDLLA. [1] In order to reach the ultimate goal of elucidating the structure-properties-perfomance relationship, the simulation data on local and terminal dynamics are complemented by experimental characterization using differential scanning calorimetry, gel permeation chromatography and linear rheology measurements. This integrated study aims to bridge molecular-level information with macroscopic performance, and by doing so to shed light on some possible causes of controversy in the vast literature on PLA-based materials. References: [1] P. Bačová, V. Harmandaris, S.I. Molina, Computational investigation of structural properties of poly(lactic acid) and its stereoisomers: shape, size and flexibility, Macromolecules, 2025 58 (16), 8572-8580 https://pubs.acs.org/doi/full/10.1021/acs.macromol.5c00918

Full text

Effect of Stereoisomerism on the Structure and Linear Rheology of Poly(Lactic Acid) Petra Baˇ cová, Mirko Maturi, Vagelis Harmandaris, Sergio I. Molina Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Facultad de Ciencias, IMEYMAT, Campus Universitario Río San Pedro s/n., Puerto Real, Cádiz 11510, Spain PITS3D PITS3D Strategy: [1,2] * [1] https://adicork.es/index.php/sectores/; [2] Created with BioRender.com PITS3D State of the art: experiment, homopolymers Ïcrystalline ÏPLLA mostly with some % of D, pure PDLA not much known Ïsimilar LVE spectra [1] Ïcomparable Tg[1] 101 102 103 104 105 106 10-1 100101102 dynamic moduli (G’,G’’)bT (Pa) angular frequency ωαΤ (rad/s) G’, D120 G’’, D120 G’, L130 G’’, L130 [1] Othman, Norhayani, PhD thesis, 2012 PITS3D State of the art: experiment, copolymers ÏPDLLA-amorphous Ïeffect of the increasing D-content (XD) and tacticity Ï Tg=Tg,∞−52+791XD Mn 101 102 103 104 105 106 107 108 100101102103104105106107 %D dynamic moduli (G’,G’’)bT (Pa) angular frequency ωαΤ (rad/s) G’, D100 G’’, D100 G’, L50D50 G’’, L50D50 G’, L75D25 G’’, L75D25 G’, L90D10 G’’, L90D10 [1] Othman, Norhayani, PhD thesis, 2012, L.-E. Chile, P. Mehrkhodavandi, S. G. Hatzikiriakos, Macromolecules (2016) 49 (3), 909-919 [2] P. A. Klonos et al., Polymer (2024), 305, 127177 PITS3D State of the art: simulation ÏPLLA and PDLA should have the same force field, PDLLA not much data Ïsimilar to proteins: slow structural rearrangements (slow equilibration and properties such as Tgsensitive to the dihedral functions) ÏH-bonds: atomistic detail PLLA100 PDLA100 D- (R) L- (S) ɸijkl i jk l PITS3D Simulations: systems Label Mw Microstructure [g/mol] L D PLLA10 0.7 k 100%0% PLLA30 2.2 k 100%0% PLLA100 7.2 k 100%0% PLLA125 9.0 k 100%0% PLLA150 10.8 k 100%0% PLLA175 12.6 k 100%0% PDLA30 2.2 k 0%100% PDLA100 7.2 k 0%100% Copo55D 7.2 k 45%55% Copo16D 7.2 k 84%16% PITS3D Simulations: structural properties H-bond shapen-π* 3form factor 3packing length 3domain analysis 3characteristic ratio ÏPDLA slighly more flexible than PLLA Ïclear diferences in n-π* parameters between homopolymers ÏPDLLA: more spherical, more flexible, more compact, more intramolecular H-bonds Ïmore D content=more flexibility ÏGaussian character for chain longer than 100 monomers PITS3D Simulations: dynamical properties v1 Ïthe segmental and terminal dynamics of PDLA slighly faster than that of PLLA,Tgof PDLA lower than that of PLLA ÏPDLLA: combination of slower and faster segments, environmental effects Ïterminal dynamics: between Rouse and entanglement scaling PITS3D Experiments: samples Label Mw Microstructure [g/mol] L D PLLA10K 10 k 100%0% PDLLA10K 10 k 50%50% PLLA25K 25 k 100%0% PDLA25K 25 k 0%100% PDLLA25K 25 k 50%50% PLLA50K 50 k 100%0% PDLA50K 50 k 0%100% PDLLA50K 50 k 50%50% two commercial samples for 3D printing: PLA3D850, and recycled PLA (Smartfil, Smart Materials 3D) PITS3D Experiment: linear viscoelastic spectra homopolymers 10-2 10-1 100 101 102 103 104 105 106 100101102103 dynamic moduli (G’,G’’) (Pa) angular frequency ωαΤ (rad/s) PLLA, T=190° PLLA25K G’ PLLA25K G’’ PLLA50K G’ PLLA50K G’’ PDLA25K G’ PDLA25K G’’ PDLA50K G’ PDLA50K G’’ PITS3D Summary úcombination of computational and experimental methods to understand structure-property relation in PLA úlinear viscoelastic spectra complement the results from NMR and confirm GPC úlow Mw homopolymers: PDLA slower dynamics than PLLA, indications of different internal packing at monomeric level (CG potentials) úcopolymers more compact and spherical with internal H-bonds, dynamics intercorrelated PITS3D To do úquantitative Mw distributions (THF vs. DMF) úmodulated DSC for PDLA úanalysis with the Reptate software úconnecting Mw distributions with LVE spectra úremove cummulative error in G(t) data from simulation Keep calm and stay tuned! )petra.bacov[email protected] +https://polysim.eu/ +PITS3D project (Grant agreement ID: 101105208): https://cordis.europa.eu/project/id/101105208 /Petra Baˇ cová, Vagelis A. Harmandaris, Sergio I. Molina, Computational investigation of structural properties of poly(lactic acid) and its stereoisomers: shape, size and flexibility, Macromolecules, in revision