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Boosting PLA melt strength by controlling the chirality of co-monomer incorporation.

ABSTRACT: Bio-based and degradable polymers such as poly(lactic acid) (PLA) have become prominent. In spite of encouraging features, PLA has a low melt strength and melt elasticity, resulting in processing and application limitations that diminish its substitution potential vis-a-vis classic plastics. Here, we demonstrate a large increase in zero shear viscosity, melt elasticity, elongational viscosity and melt strength by random co-polymerization of lactide with small amounts, viz. 0.4-10 mol%, of diethylglycolide of opposite chiral nature. These enantiomerically pure monomers can be synthesized using one-step zeolite catalysis. Screening of the ester linkages in the final PLA chains by the ethyl side groups is suggested to create an expanding effect on the polymer coils in molten state by weakening of chain-chain interactions. This effect is suspected to increase the radius of gyration, enabling more chain entanglements and consequently increasing the melt strength. A stronger melt could enable access to more cost-competitive and sustainable PLA-based biomaterials with a broader application window. Amongst others, blow molding of bottles, film blowing, fiber spinning and foaming could be facilitated by PLA materials exhibiting a higher melt strength.

SUBMITTER: Narmon AS

PROVIDER: S-EPMC8179584 | biostudies-literature | 2021 Mar

REPOSITORIES: biostudies-literature

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Boosting PLA melt strength by controlling the chirality of co-monomer incorporation.

Narmon An Sofie AS Dewaele Annelies A Bruyninckx Kevin K Sels Bert F BF Van Puyvelde Peter P Dusselier Michiel M

Chemical science 20210310 15

Bio-based and degradable polymers such as poly(lactic acid) (PLA) have become prominent. In spite of encouraging features, PLA has a low melt strength and melt elasticity, resulting in processing and application limitations that diminish its substitution potential <i>vis-a-vis</i> classic plastics. Here, we demonstrate a large increase in zero shear viscosity, melt elasticity, elongational viscosity and melt strength by random co-polymerization of lactide with small amounts, <i>viz.</i> 0.4-10 m ...[more]

PMID: 34163778

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Project description:Fabrication of well-ordered and bio-mimetic scaffolds is one of the most important research lines in tissue engineering. Different techniques have been utilized to achieve this goal, however, each method has its own disadvantages. Recently, melt electrowriting (MEW) as a technique for fabrication of well-organized scaffolds has attracted the researchers' attention due to simultaneous use of principles of additive manufacturing and electrohydrodynamic phenomena. In previous research studies, polycaprolactone (PCL) has been mostly used in MEW process. PCL is a biocompatible polymer with characteristics that make it easy to fabricate well-arranged structures using MEW device. However, the mechanical properties of PCL are not favorable for applications like bone tissue engineering. Furthermore, it is of vital importance to demonstrate the capability of MEW technique for processing a broad range of polymers. To address aforementioned problems, in this study, three ten-layered box-structured well-ordered scaffolds, including neat PLA, neat PCL, and PLA/PCL composite are fabricated using an MEW device. Printing of the composite PLA/PCL scaffold using the MEW device is conducted in this study for the first time. The MEW device used in this study is a commercial fused deposition modeling (FDM) 3D printer which with some changes in its setup and configuration becomes prepared for being used as an MEW device. Since in most of previous studies, a setup has been designed and built for MEW process, the use of the FDM device can be considered as one of the novelties of this research. The printing parameters are adjusted in a way that scaffolds with nearly equal pore sizes in the range of 140 µm to 150 µm are fabricated. However, PCL fibers are mostly narrower (diameters in the range of 5 µm to 15 µm) than PLA fibers with diameters between 15 and 25 µm. Unlike the MEW process of PCL, accurate positioning of PLA fibers is difficult which can be due to higher viscosity of PLA melt compared to PCL melt. The printed composite PLA/PCL scaffold possesses a well-ordered box structure with improved mechanical properties and cell-scaffold interactions compared to both neat PLA and PCL scaffolds. Besides, the composite scaffold exhibits a higher swelling ratio than the neat PCL scaffold which can be related to the presence of less hydrophobic PLA fibers. This scaffold demonstrates an anisotropic behavior during uniaxial tensile test in which its Young's modulus, ultimate tensile stress, and strain to failure all depend on the direction of the applied tensile force. This anisotropy makes the composite PLA/PCL scaffold an exciting candidate for applications in heart tissue engineering. The results of in-vitro cell viability test using L929 mouse murine fibroblast and human umbilical vein endothelial (HUVEC) cells demonstrate that all of the printed scaffolds are biocompatible. In particular, the composite scaffold presents the highest cell viability value among the fabricated scaffolds. All in all, the composite PLA/PCL scaffold shows that it can be a promising substitution for neat PCL scaffold used in previous MEW studies.

Dataset Information

Boosting PLA melt strength by controlling the chirality of co-monomer incorporation.

Publications

Boosting PLA melt strength by controlling the chirality of co-monomer incorporation.

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