Interfacial stereocomplexation in heterogeneous polymer powder formulations for reinforcing (laser) sintered welds

Srinivas, Varun; Bertella, Francesca; Hooy-Corstjens, Catharina S. J. van; Leeuwen, Bas van; Craenmehr, E.G.M.; Cavallo, Dario; Rastogi, Sanjay; Harings, Jules

doi:10.1016/j.addma.2020.101665

Cited by 3 publications

(5 citation statements)

References 41 publications

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“…Stereocomplexation of PDLA and PLLA is also used in additive manufacturing to improve the welding of 3D printed objects. 22,23 However, the formation of SCs is always accompanied by that of the HCs in PLLA/ PDLA blends. 24,25 Compared to the lower-molecular-weight HCs, in higher-molecular-weight PLLA/PDLA blends, the formation of the stereocomplex is kinetically less favored.…”

Section: ■ Introductionmentioning

confidence: 99%

“…PLA stereocomplex material has been demonstrated to be an effective way to promote the physical performance of PLLA- or PDLA-based materials. , For example, SC-PLA has a higher melting temperature ( T m ∼ 220–230 °C), which is 50 °C higher than that of the HCs PLLA or PDLA, higher mechanical strength and modulus, better thermal stability, and higher resistance to solvents and hydrolysis than the conventional HC PLLA or PDLA. ,, Therefore, the formation of stereocomplexation provides an avenue to prepare PLLA- or PDLA-based materials with improved physical performance. Stereocomplexation of PDLA and PLLA is also used in additive manufacturing to improve the welding of 3D printed objects. , However, the formation of SCs is always accompanied by that of the HCs in PLLA/PDLA blends. , Compared to the lower-molecular-weight HCs, in higher-molecular-weight PLLA/PDLA blends, the formation of the stereocomplex is kinetically less favored. , To overcome the challenges in molecular blending, especially in high-molar-mass PLLA/PDLA, attempts are made to make the block copolymers having a covalently linked stereocomplex. It has been proven that the covalently linked enantiomeric chains in the PLLA/PDLA block copolymers facilitate co-crystallization. , Several methods have been reported to prepare PLLA/PDLA stereo di-, tri-, and multi-block copolymers with different molecular weights, sequences, compositions, and architectures of PLLA and PDLA blocks. ,, These methods include the sequential monomer addition during the ring opening polymerization (ROP) of l - and d -lactide, , melt/solid-state polycondensation, , a combination of ROP with terminal Diels–Alder coupling, , stereo-selective polymerization of lactides by iso-selective catalysts, , a combination of ROP with click chemistry, and the esterification reaction .…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and Characterization of Well-Defined High-Molecular-Weight PDLA-b-PLLA and PDLA-b-PLLA-b-PDLA Stereo-Block Copolymers

Zhou

Romano

et al. 2023

Macromolecules

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A facile method is developed to synthesize poly(lactide) (PLA) stereo-diblock and stereo-triblock copolymers using a bismuth catalyst. The judicious choice of the catalytic system allows us to synthesize the PLA stereocomplex having a molar mass exceeding 450 kg/mol and a polydispersity of below 2. The synthesis of such a high molar mass became feasible because in the chosen catalytic system, unlike in the reported synthesis routes, the presence of water in traces does not promote chain transfer. The observations are that during polymerization, single crystals of poly(l-lactide)-b-poly(d-lactide) (PLLA-b-PDLA) and poly(d-lactide)-b-poly(l-lactide)-b-poly(d-lactide) (PDLA-b-PLLA-b-PDLA) stereo-block copolymers are formed. These platelet-like single crystals tend to aggregate, forming a globular spherical morphology equivalent to that perceived on the crystallization of the stereocomplex from solution. The adopted synthesis route provides molecular mixing of the stereo-regular PLA chains in the absence of any detectable traces of homo-crystals, which are unavoidable when the mixing is performed using a homopolymer dissolution route. The molecularly mixed stereo-regular PLAs in a polymer melt retain their molecular interaction, even after isothermal crystallization or rheological studies that follow the anticipated viscoelastic response of a polymer melt. The increasing molar masses of the PLLA/PDLA diblock and triblock copolymers show an increase in the tensile modulus and elongation to break, retrospectively indicating the brittle to ductile transformation of the polymer with increasing molar mass. Thermal and imaging experimental methods such as differential scanning calorimetry, nuclear magnetic resonance, thermogravimetric analysis, scanning electron microscopy, electron diffraction, wide-angle X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy are employed to follow the enthalpic relaxation, conformational, and structural changes.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Well-Defined High-Molecular-Weight PDLA-b-PLLA and PDLA-b-PLLA-b-PDLA Stereo-Block Copolymers

Zhou

Romano

et al. 2023

Macromolecules

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“…Ruiz et al found enhanced nucleation density and rate, spherulitic growth, and crystallization rate when using 5–10 wt % cyclic PLLA solution blended in linear PLLA thanks to the synergistic effect of nucleation and plasticization . Polylactide stereocomplexes are also used to enhance and reinforce the interface between the filaments of PLLA and PDLA codeposited during the fuse deposition modeled welds and laser sintering of the polymer powder . Most of the above strategies are postpolymerization treatments, which lead to additional steps in the production or processing workflow, contributing to increasing the production costs of PLA.…”

Section: Introductionmentioning

confidence: 99%

“…27 Polylactide stereocomplexes are also used to enhance and reinforce the interface between the filaments of PLLA and PDLA codeposited during the fuse deposition modeled welds 28 and laser sintering of the polymer powder. 29 additional steps in the production or processing workflow, contributing to increasing the production costs of PLA.…”

Section: ■ Introductionmentioning

confidence: 99%

Synthesis and Characterization of High-Molecular-Weight PLAs with a Well-Controlled Particle Morphology

Li,

Rastogi,

Romano

2023

Ind. Eng. Chem. Res.

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The synthesis of high-/ultrahigh-molecular-weight poly(L-lactide) (PLLA) having a controlled morphology remains a challenge because of the low crystallization rate of the material and the absence of a proper nucleation site during polymer synthesis. Using three different polymerization routes, the synthesis of highand ultrahigh-molecular-weight PLLA (weight-average molecular weight up to 1.1 million g/mol) having a well-defined particle morphology is reported. A comparative study on the evolution of the structure, morphology, and crystallization behavior of PLLA, influenced by different nucleating agents during polymerization, is addressed. The structure and the morphology of the resulting polymers, crystallization kinetics, and thermal properties of the PLAs are investigated systematically by GPC, SEM, TEM, NMR, DSC, and XRD. In the presence of PDLA, with the formation of the PLLA/PDLA stereocomplex crystal, spherical particles having a flakelike micromorphology are formed. The flakelike structures are proven to be single crystals of the stereocomplex PLLA and PDLA. The nascent reactor powder, having single crystals, could be compressed below the melting point and can be drawn into uniaxial objects in the solid state without melting. The solid-state deformation circumvents the entropic relaxation that is detrimental to chain orientation and restricts thermal degradation experienced during melt processing. Moreover, the proposed routes for controlling the nascent reactor particle morphology open the path to PLA synthesis in a continuous process, avoiding any postpolymerization treatment of the synthesized polymer.

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“…Poly(lactic acid) (PLA) is of great interest in materials research and industry − since it is biodegradable and biocompatible, exhibits low toxicity, and can be produced from renewable carbon sources (Scheme a). Owing to the chirality of lactic acid, PLA can form enantiomers, namely, poly( l -lactic acid) (PLLA) and poly( d -lactic acid) (PDLA) (Scheme b).…”

Section: Introductionmentioning

confidence: 99%

Insights into Stereocomplexation of Poly(lactic acid) Materials: Evolution of Interaction between Enantiomeric Chains and Its Role in Conformational Transformation in Racemic Blends

Zhang

Fan

Guo

et al. 2022

ACS Appl. Polym. Mater.

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Enantiomers alternately packed stereocomplex crystals (SC) compete with homochiral enantiomer-packed homocrystals (HC) during the crystallization of poly(lactic acid) (PLA) racemic blends. However, an intensive understanding of the structural evolution of enantiomeric chains in racemic blends remains challenging because of the narrow time window required for structural evolution. Here, we report the initial conformation evolution and concomitant interaction between the enantiomeric chains in the racemic melt over a wide temperature range using commercial fast-scan chip calorimetry. The results showed that, after cooling the racemic melt at 3,000 K/s, 10 3 helices always emerged first. The interaction between the enantiomeric chains appeared gradually and triggered the transformation of 10 3 helices into 3 1 helices. A comprehensive understanding of the role of the interaction between the enantiomeric chains during the conformation transformation not only provides a physical basis for studying the competition between SC and HC of PLA but also lays a theoretical foundation for the preparation of biodegradable engineering plastics.

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Interfacial stereocomplexation in heterogeneous polymer powder formulations for reinforcing (laser) sintered welds

Cited by 3 publications

References 41 publications

Synthesis and Characterization of Well-Defined High-Molecular-Weight PDLA-b-PLLA and PDLA-b-PLLA-b-PDLA Stereo-Block Copolymers

Synthesis and Characterization of Well-Defined High-Molecular-Weight PDLA-b-PLLA and PDLA-b-PLLA-b-PDLA Stereo-Block Copolymers

Synthesis and Characterization of High-Molecular-Weight PLAs with a Well-Controlled Particle Morphology

Insights into Stereocomplexation of Poly(lactic acid) Materials: Evolution of Interaction between Enantiomeric Chains and Its Role in Conformational Transformation in Racemic Blends

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