Article
Polymer Science
Hideto Tsuji, Kazumasa Iguchi, Yuki Arakawa
Summary: The research studied the effects of different molecular weights of crystalline blocks but similar overall molecular weights on the crystallization behavior, structure, morphology, and thermal properties of PLLA-b-PDLLA/PDLA-b-PDLLA blends. It was found that the incorporated long amorphous PDLLA blocks facilitated unique SC crystallization in the blends with different crystalline block fractions.
Article
Engineering, Environmental
Weishuo Chen, Channa Zhong, Shuangcheng Li, Die Wen, Dongdong Zhou, Jun Shao, Shuiliang Chen, Haoqing Hou, Sheng Xiang
Summary: The blends of poly(D-lactic acid) and poly(L-lactic acid) (PDLA/PLLA) exhibit higher crystallization rate and mechanical strength than individual PDLA or PLLA due to the formation of stereocomplex crystals (SC). SC serves as an effective nucleating agent for PLA homochiral crystals (HC). However, the morphology of SC in asymmetric blends and its effect on the crystallization behavior of HC remains unclear. In this study, PDLA/PLLA blends with different weight ratios were prepared using different methods to obtain SC with different morphologies. The results showed that SC morphology influenced the formation of HC, with fibrous and banded SC inhibiting HC formation, spherical SC enhancing HC formation, and network structure SC significantly accelerating the crystallization rate of HC.
JOURNAL OF POLYMERS AND THE ENVIRONMENT
(2023)
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
Qianjin Zhu, Kaixin Chang, Liyan Qi, Xinyi Li, Woming Gao, Qinwei Gao
Summary: In this study, PLLA films were surface-modified using different solutions, leading to changes in their structure and properties. The modification with PDLA weakened the crystal structure of the films, while modification with PDLAG increased the stereocomplex (SC) structure and decreased the homogeneous crystal (HC) structure.
Article
Polymer Science
Yangzhe Hou, Han Jia, Yamin Pan, Chuntai Liu, Changyu Shen, Xianhu Liu
Summary: This study successfully prepared brand-new porous PLA films with enhanced flexibility and heat resistance using blade coating and thermally induced phase separation methods. The resulting blend films showed improved mechanical properties and high porosity, making them suitable for microfiltration, packaging, and modified applications.
Article
Biochemistry & Molecular Biology
Wei-Wei Chang, Jinye Niu, Hui Peng, Weifeng Rong
Summary: In this study, selective formation of stereocomplex (sc) crystallization and suppression of homocrystallization (hc) in high-molecular-weight (HMW) PLLA/PDLA blends were achieved by adding C70 as a nucleator. Fourier-transformed infrared spectroscopy analysis revealed improved intermolecular interactions and inhibited molecular chain diffusion and mobility, leading to accelerated sc crystallization. The addition of C70 also resulted in a higher thermal stability compared to the neat PLLA/PDLA blend.
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
(2023)
Article
Polymer Science
Suyang Dai, Ziming Dai, Ni Jiang, Zhenbo Ning, Zhihua Gan
Summary: In this study, poly(L-lactide) (PLLA) was toughened by crosslinked polyurethane (CPU) through reactive blending. The resulting material exhibited significant increase in elongation at break, enhanced toughness, and shape memory capacity, showing great potential for applications in biodegradable green composites.
Article
Thermodynamics
Rui Zhang, Fanfan Du, Katalee Jariyavidyanont, Evgeny Zhuravlev, Christoph Schick, Rene Androsch
Summary: By analyzing different grades of PDLLA using fast scanning calorimetry, it is found that the glass transition dynamics of PDLLA and PLLA are essentially the same, suggesting that stereoisomerism does not influence the glass transition dynamics.
THERMOCHIMICA ACTA
(2022)
Article
Biochemistry & Molecular Biology
Wenjun He, Lin Ye, Phil Coates, Fin Caton-Rose, Xiaowen Zhao
Summary: The addition of poly(lactide-co-caprolactone) (PLCL) segments into poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA) chains resulted in the development of a fully biodegradable and flexible PLLA/D-PLCL block polymer with long-chain branches and a stereocomplex (SC) crystalline structure. The PLLA/D-PLCL films showed increased complex viscosity/storage modulus, lower tan delta values in the terminal region, and strain-hardening behavior compared to neat PLLA. Through biaxial drawing, the uniformity and non-preferred orientation of the PLLA/D-PLCL films were improved. By introducing PDLA, the phase structure transformed from a sea-island structure to a co-continuous network structure, leading to enhanced tensile strength and elongation at break.
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
(2023)
Article
Polymer Science
Amit Kumar Pandey, Hideaki Takagi, Noriyuki Igarashi, Nobutaka Shimizu, Shinichi Sakurai
Summary: The addition of SFN was found to enhance the formation and crystallizability of SC crystals in the PLLA/PDLA (50/50) blend, while suppressing HC crystallization. This finding is significant for the performance and applications of the material.
Article
Thermodynamics
Yi Li, Lijia Zhao, Changyu Han, Liguang Xiao, Yancun Yu, Guangbin Zhou, Mingzhi Xu
Summary: The study shows that the addition of low-Mw PVAc can accelerate the crystallization of PLLA/PDLA components, while high-Mw PVAc can inhibit crystallization; blending with PVAc enhances the formation of SCs, with the best effect seen with low-Mw PVAc; only SCs are obtained in blends with 30% low-Mw PVAc, improving the thermomechanical properties.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2022)
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
Polymer Science
Zhaolei Li, Xinxin Ye, Chunfeng Meng, Haijun Zhou, Weijie Guo, Shangtao Chen, Jianming Zhang, Chao Yan, Alain Dufresne
Summary: Introducing a crosslinkable epoxy resin (EP) into poly(l-lactic acid)/poly(d-lactic acid) racemic blends was found to inhibit homo-crystals and promote stereocomplexation, although it delayed lamellar thickening of the stereocomplex crystals during heating due to constrained chain diffusion caused by the uniformly dispersed EP network. This approach shows promise for gaining deeper insights into poly(lactic acid) stereocomplexation.
POLYMER INTERNATIONAL
(2021)
Article
Biochemistry & Molecular Biology
Yi Wu, Kesong Yu, Xiaoli Zhang, Junji Hou, Jingbo Chen
Summary: The addition of a small amount of poly(D-lactic acid) improves the EMI shielding performance of poly(lactic acid)/carbon nanotubes composites. Furthermore, lightweight and environmentally friendly composites with excellent EMI shielding performance can be prepared using a green supercritical CO2 foaming method.
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
(2022)
Article
Polymer Science
Hideto Tsuji, Masato Yamasaki, Yuki Arakawa
Summary: In this study, new enantiomeric stereo periodical copolymers of lactic acids were synthesized and a novel type of stereocomplex (SC) formation between these enantiomeric SPCPs was reported. The melting temperatures of SC crystallites of the blend were found to be between the alpha- and beta-forms of the homocrystallites, which is different from the results observed for enantiomeric poly(lactic acid) homopolymers. The findings suggest the possibility of widening the physical properties and biodegradation behavior of PLA-based materials through the synthesis and stereocomplexation of various types of SPCPs with different stereosequences.
Article
Polymer Science
Selvaraj Nagarajan, Eamor M. Woo, Chi-Hsuan Su, Cheng-En Yang
Summary: Investigations reveal that PBA can self-aggregate into unique periodic structures, which correlate with its special photonic properties. The interior lamellae are arc-shaped, with a structure in SEM that matches the optical inter-band spacing. A 3D assembly mechanism for PBA crystals is proposed, showing potential applications.
MACROMOLECULAR RAPID COMMUNICATIONS
(2021)
Article
Polymer Science
Selvaraj Nagarajan
Summary: The self-assembly structures of lamellae in optical ring bands have a critical impact on their optical and physical arrangements. Two different types of dendritic banded spherulites have been identified, and the optical ring patterns of these spherulites are mainly differentiated by the fractal orientation of crystal branches in the ridge region. The 3D-lamellar assembly mechanisms proposed provide an explanation for the growth of dendritic ring-banded spherulites at different temperatures.
MACROMOLECULAR RAPID COMMUNICATIONS
(2021)
Review
Polymer Science
Eamor M. Woo, Selvaraj Nagarajan, Chi-Hsuan Su, Cheng-En Yang
Summary: This study examines the crystal assembly in the family of aliphatic polyesters through crystallization and self-aggregation, which forms periodic structures viewed as circular ring bands in optical birefringence patterns. The periodic packing shares similarities with grating architectures in interiors and banding on top surfaces. Interestingly, the grating structures in ring-banded polyesters can cause optical light interference into colors. The study also explores the unique periodic morphology and architectures of two polyesters, serving as ideal models for discussions on their photonics with periodic gratings.
JOURNAL OF POLYMER RESEARCH
(2022)
Article
Polymer Science
Kuan-Ying Huang, Eamor M. Woo, Selvaraj Nagarajan
Summary: Amorphous PVPh was added to semicrystalline PPDO to form a unique dendritic/ringed structure with periodic ring bands. The structure consisted of feather-like lamellae dividing into multiple branches following the Fibonacci sequence. The periodic ring bands were responsible for the formation of the unique dendritic/ringed PPDO structure.
Article
Engineering, Chemical
Yu-Zhe Huang, Eamor M. Woo, Selvaraj Nagarajan
Summary: The morphologies and arrangements of biodegradable polyesters, poly(p-dioxanone) (PPDO) blended with poly(ethylene succinate) (PESu), were studied. Three different types of nuclei were found in the PPDO/PESu blend system, and a novel technique was used to dissect the interior 3D structures of PPDO. The detailed 3D-assembly provides insights into the complexed architectures of this polymer.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2022)
Article
Polymer Science
Selvaraj Nagarajan, Hsiao-Hua Li, Eamor M. Woo, Wei-Tsung Chuang, Yi Wei Tsai
Summary: This study investigates the formation of sector-face dendritic aggregates during the crystallization process of Poly(ethylene succinate) (PESu). Through microscopic techniques and X-ray analysis, the unique characteristics of these two faces are confirmed.
MACROMOLECULAR CHEMISTRY AND PHYSICS
(2022)
Article
Engineering, Chemical
Baiq Firyal Salsabila Safitri, Selvaraj Nagarajan, Eamor M. Woo
Summary: In this study, a novel ring-banded spherulite with a ginger-root-like structure was formed in nonracemic mandelic acid mixtures using poly(ethylene oxide) as a morphology tailor. The formation mechanisms and assembly process of the novel crystal structure were analyzed through microscopy and X-ray characterization.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2022)
Article
Polymer Science
Selvaraj Nagarajan, Chi-Hsuan Su, Eamor M. Woo
Summary: Poly(ethylene adipate) can crystallize into either ring-banded spherulites or ringless spherulites, depending on the temperature conditions. The internal structures and polymorphism of these two morphologies differ, with the ring-banded spherulites primarily containing alpha-form crystals and the ringless spherulites containing a combination of alpha and beta crystals. Dissection analysis reveals that the interior of the banded spherulites consists of concentric-shell structures resembling cut onions. By designing optimized regularly-banded morphologies, the PEA banded spherulites demonstrate prominent photonic iridescence and the capability to structure light with circular patterns through laser interference.
Article
Chemistry, Physical
Selvaraj Nagarajan, Kuan-Ying Huang, Wei-Tsung Chuang, Jhih-Min Lin, Eamor M. Woo
Summary: Poly(p-dioxanone) (PPDO) is a bioabsorbable material commonly used in biomedical applications, with its crystal morphology dependent on temperature and polymorphism. PPDO can form ringless spherulites (RLS) and ring-banded spherulites (RBS) depending on the temperature, each with different crystal structures. The interior structure of PPDO-RBS consists of horizontal and vertical lamellae, and the growth patterns of ring bands can be customized.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Polymer Science
Hsiao-Hua Li, Selvaraj Nagarajan, Wei-Tsung Chuang, Yi-Wei Tsai, Eamor M. Woo
Summary: A unique composite dendritic spherulite is detected in a specific temperature range, and its assembly and morphology are studied using microscopy techniques and microbeam analysis. The branches in the spherulite originate from a common nucleus with different growth rates. This study provides insights into the mechanisms of crystal plate orientations and transformations.
Article
Polymer Science
Chia-I. Chang, Eamor M. Woo, Selvaraj Nagarajan
Summary: Polarized optical microscopy (POM), scanning electron microscopy (SEM), and synchrotron microbeam wide-angle X-ray diffraction (WAXD) were used to investigate the mechanisms of periodic assemblies leading to ring-banded crystal aggregates with light-grating capacity for iridescence in poly (1,4-butylene adipate) (PBA) modulated with poly (ethylene oxide) (PEO). It was found that the PBA crystal assembly forms a grating architecture with light-interference properties, similar to those found in nature.
Article
Chemistry, Physical
Selvaraj Nagarajan, Tzu-Ching Chuang, Wei-Tsung Chuang, Jhih-Min Lin, Eamor M. Woo
Summary: In an unprecedented manner, the formation mechanism of lamellar structure in ring-banded spherulites (RBSs) has been revealed using advanced synchrotron microbeam X-ray diffraction. The presence of periodically banded structure is confirmed through microscopy dissection morphology, and its sequential arrangement and orientation are demonstrated through real-time micrograph comparison. This methodology can be applied to a wide variety of polymers to analyze spherulites displaying periodic self-assembled patterns.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Multidisciplinary
Cheng-En Yang, Selvaraj Nagarajan, Widyantari Rahmayanti, Chean-Cheng Su, Eamor M. Woo
Summary: This study used different model arylate polymers to investigate their crystallization behavior, and found that they all formed periodically banded spherulites with similar characteristics. By dissecting these structures in 3D, the universal mechanisms of crystal-by-crystal self-assembly from the nano- to microscale were revealed, resulting in the formation of final periodic aggregates. Fracture analysis showed that the birefringent-banded poly(decamethylene terephthalate) (PDT) spherulites contained multi-shell spheroid bands composed of perpendicularly intersecting lamellae bundles.
Article
Biochemistry & Molecular Biology
Widyantari Rahmayanti, Selvaraj Nagarajan, Ya-Sen Sun, Eamor M. Woo
Summary: This study found that five different aryl polyesters can form ring-banded spherulites with universal characteristics during crystallization. The research explored the correlations between micro/nanocrystal assemblies, grating architectures, and structural iridescent properties. The interior lamellar assembly of arylate polyesters' banded spherulites exhibits periodic birefringence patterns similar to those found in biological structures, resulting in iridescent color.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2023)
Article
Chemistry, Multidisciplinary
Min-Han Hao, Selvaraj Nagarajan, Eamor M. Woo
Summary: This study used scanning electron microscopy and synchrotron radiation to analyze the crystal aggregates formed by poly(p-dioxanone) and poly(vinyl alcohol) during crystallization. The results showed that the periodic architectures were formed by alternating flat crystals and fibrils, with an oblique angle between the branches and the flat crystals.
