Article
Polymer Science
Lidong Feng, Xinchao Bian, Gao Li, Xuesi Chen
Summary: By investigating the thermal properties, morphology, and thermal stability of PLLA/PDLA blends, a new stereoamorphous mesophase (sam-PLA) structure was discovered, and the relationship between different phases in the PLLA/PDLA blends was explored.
Article
Polymer Science
Lidong Feng, Xinchao Bian, Gao Li, Xuesi Chen
Summary: The study shows that the compatibility between PLLA and PLDLA-m decreases as the L-lactate unit content in PLDLA-m decreases, impacting the crystallization and compatibility of the blends.
Article
Chemistry, Multidisciplinary
Megha D. Deokar, Baijayantimala Garnaik, Swaminathan Sivaram
Summary: Well-defined six-arm star-branched bio-degradable block copolymers were prepared using controlled ring-opening polymerization and a sequential monomer addition method. The study found that the sequence of enchainment could be changed by reversing the order of monomer addition, resulting in different crystalline or amorphous blocks. However, disruption of the block structure was observed in one of the copolymers due to competing transesterification reactions. Differential scanning calorimetry studies showed interesting phase morphologies in these sequence-controlled block copolymers. Blending these copolymers with a commercially sourced polymer led to improved tensile toughness in the blend.
Article
Biochemistry & Molecular Biology
Fen Ma, Chenguang Jiang, Wenyuan Xie, Defeng Wu
Summary: Using polysaccharide nanocrystals, such as chitin nanocrystals, as nanofillers for biodegradable aliphatic polymers is an attractive method for developing fully degradable nanocomposites. The incorporation of chitin nanocrystals in poly(L-lactide)/poly(D-lactide) blends promotes the formation of stereocomplex crystallites and accelerates overall crystallization kinetics. The nanocomposites exhibit higher stereocomplex crystallization temperatures and lower activation energy compared to the blend. However, the presence of chitin nanocrystals reduces the fraction of stereocomplex crystallites due to the nucleation effect, despite an increased rate of homocrystallization. This study provides valuable information for the use of chitin nanocrystals as nucleators for polylactide stereocomplexes.
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
(2023)
Article
Chemistry, Applied
Yaowalak Srisuwan, Yodthong Baimark
Summary: This paper reports a study on flexible polymer blends made from PLLA-PEG-PLLA and TPS. The addition of TPS suppressed crystallizability of PLLA and PLLA-PEG-PLLA matrices, while greatly increasing the thermal stability of PLLA-PEG-PLLA. The PEG middle-blocks enhanced phase compatibility between PLLA-PEG-PLLA and TPS, resulting in ductile and flexible blend films.
CARBOHYDRATE POLYMERS
(2022)
Article
Polymer Science
Mingmei Mi, Jing Yu, Xiangyang Li, Min Zhou, Hao Xiu, Hongwei Bai
Summary: Stereocomplex-type polylactide (SC-PLA) is a promising engineering bio-plastic that enhances heat resistance and hydrolytic stability through the crystallization between poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA). By using dibenzoylhydrazide compound as a nucleating agent, the SC crystallization of PLLA/PDLA blends is promoted, leading to smaller crystal size.
Article
Polymer Science
Zirui Huang, Meiling Zhong, Haibo Yang, Enqin Xu, Dehui Ji, Paul Joseph, Ri-Chao Zhang
Summary: The isothermal crystallization of poly(l-lactide) was studied using in-situ wide angle X-ray diffraction and polarized optical microscopes equipped with a hot-stage accessory. It was found that PLLA formed spherulites at high temperature and exhibited irregular morphology at low temperature, attributed to varying crystallization rates. The change in the Avrami exponent value with temperature further supported the different trend in crystal morphology.
Article
Thermodynamics
Hechang Shi, Hongda Cheng, Changyu Han, Yanchun Yu, Mengdie Yu, Ye Zhang
Summary: This work investigates the effect of uniaxial stretching on the properties of neat poly(L-lactide) (PLLA) and miscible PLLA/poly(vinyl acetate) (PVAc) blends. The stretching process influences the thermal properties, crystallization behavior, miscibility, crystal structure, and mechanical properties of the materials. With an increased stretching ratio, the chains in PLLA and PLLA/PVAc blends become more oriented and exhibit enhanced crystallization, resulting in changes in thermal properties and improved toughness. The findings provide insight into the effect of stretching on miscible PLLA blends and offer practical implications for their large-scale application.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2023)
Article
Polymer Science
Adrian Korycki, Christian Garnier, Amandine Abadie, Valerie Nassiet, Charles Tarek Sultan, France Chabert
Summary: The study elaborated PEEK/PES blends with partial miscibility by melt mixing with phenolphthalein, which was confirmed by DSC and DMTA analysis. Phenolphthalein acted as a compatibilizer and plasticizer for the blends, resulting in a softened PEEK phase and improved interfacial adhesion with PES. Additionally, the storage modulus in the glassy region of the blends remained similar to pure PEEK due to the aromatic moieties in phenolphthalein.
Article
Polymer Science
Hu Qiao, Abderrahim Maazouz, Khalid Lamnawar
Summary: The present work aimed to investigate how the composition and physico-chemical properties affect the rheology, morphology, miscibility, and thermal stability of poly(lactic acid) (PLA)-poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) biopolymer blends obtained by melt mixing. The study revealed the thermo-rheological complexity of the PLA/PHBV blends in the melt, especially for PLA-rich blends, which exhibited irregularly structured morphologies due to highly mismatched viscoelastic properties. The miscibility of the blends was also affected by the lower thermal stability of PLA and PHBV. However, the melt-induced degradation process of the blends seemed to improve their miscibility and thermo-rheological simplicity to some extent.
Article
Polymer Science
Prasong Srihanam, Yaowalak Srisuwan, Theeraphol Phromsopha, Apirada Manphae, Yodthong Baimark
Summary: In this study, the phase compatibility and mechanical properties of flexible poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLLA-PEG-PLLA)/thermoplastic starch (TPS) blends were improved by adding citric acid (CA) as a compatibilizer. The crystallinity of PLLA-PEG-PLLA matrix was suppressed and the thermal stability was enhanced by CA modification of TPS. The compatibility between TPS and PLLA-PEG-PLLA phases was improved, and the blends exhibited increased tensile strength, elongation at break, and Young's modulus with higher CA content.
Article
Polymer Science
Steffen M. Weidner, Andreas Meyer, Hans R. Kricheldorf
Summary: L-lactide was polymerized in toluene using tin(II) 2-ethylhexanoate as the catalyst. The crystalline properties of the resulting polyLAs were studied under different concentrations, reaction times, and temperatures. It was found that the presence of solvent promoted cyclization, leading to the formation of cyclic polylactides. A new hypothesis for the crystal growth of cyclic polyLAs was proposed.
Article
Polymer Science
M. Margarida Cardoso, Ines N. Peca, Telma Lopes, Rui Gardner, A. Bicho
Summary: DWNPs were produced with PLGA and PLLA containing doxorubicin as a model drug. Optical and fluorescence microscopy were used to examine the inner morphology and drug distribution of the double-walled microparticles. The study showed that the double-walled nanoparticles exhibited sustained drug release and the PLLA layer acted as a rate control barrier.
Article
Materials Science, Characterization & Testing
Min Wu, Han-Xiong Huang, Li-Min Yu
Summary: In this study, immiscible poly(methyl methacrylate)/polystyrene (PMMA/PS) blends with different composition ratios were prepared using water-assisted mixing extrusion (WAME), and it was found that injecting high-pressure water can significantly refine the phase domains and improve the properties of the blends.
Article
Polymer Science
Martin Boruvka, Cenek Cermak, Lubos Behalek, Pavel Brdlik
Summary: This study focused on characterizing the properties of nanocomposite systems based on asymmetric poly(L-lactide)/Poly(D-lactide) blends with the addition of nano-hydroxyapatite (HA) and 5 wt.% PDLA loading. The results showed that increasing HA content and blending with 5 wt.% PDLA enhanced tensile modulus, crystallinity, and thermal-resistance, while in-mold annealing further improved these properties by achieving a higher degree of crystallinity. However, higher HA content and in-mold annealing resulted in decreased % elongation values at break and tensile strength, as well as caused embrittlement of the material systems.
