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Texture Induced by Molecular Weight Dispersity: Polymorphism within Poly(L-lactic acid) spherulites

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Chinese Journal of Polymer Science 2020年第12期38卷 1365-1373页

作者： Da-Peng Hu Min Chen Yu-Hui Yang Han-Ying Li Ministry of Education Key Laboratory of Macromolecular Synthesis and Funtinalizatin Department of Polymer Science and EngineeringZhejing UniversityHangzhou 310027 China

Poly(L-lactic acid)(PLLA)has drawn much attention due to its excellent medical and pharmaceutical applications for *** a semi-crystalline polymer,morphology and crystal structure of PLLA greatly determine its ***,w e demonstrate,for PLLA films,a nonconventional texture featuring two types of spherulites emerging in pairs to form a distinct nested structure where a small spherulite(〜10μm)is embedded in a large one(100μm to 300μm).In addition to the size,the molecular weight and polymorph are different in the large and small *** a-form and relatively low molecular weight are identified in the large spherulites,while meta-stable a'-form and relatively high molecular weight in the small *** differences suggest that the polydisperse PLLA polymers fractionate during film formation and the high-molecular-weight fraction crystallizes into the small spherulites with meta-stable structure because of its complicated polymer entanglement and high *** contrast,the rest of polymers crystallize into the large spherulites with the thermodynamically stable ***,this texture exhibits accelerated PLLA degradation initiated from the small spherulites,which is distinct from the typical PLLA *** provided by this work may lead to new texture-properties relationship associated with polydispersity of molecular weight.

关键词： PLLA spherulite Polymorphs Molecular weight

Supersaturation-driven self-assembly formation of ceftriaxone sodium spherulites:From amorphous form to spherulites

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Particuology 2024年第7期90卷 10-19页

作者： Shankun Liang Yuchao Niu Xueyan Hu Wu Xiao Xuehua Ruan Gaohong He Xiaobin Jiang State Key Laboratory of Fine Chemicals Frontiers Science Center for Smart MaterialsSchool of Chemical EngineeringDalian University of TechnologyDalian116024China School of Chemical Engineering at Panjin Dalian University of TechnologyPanjin124221China

Drug particles with spherical morphology possess amazing advantages in terms of particle flowability,mechanical properties,drug solubility,and *** growth mechanism of drug spherulite is of great importance for the preparation and regulation of ***,ceftriaxone sodium spherulites were fabricated by the antisolvent crystallization method using dropwise addition of ceftriaxone sodium solution to *** observation of the whole crystallization process combined with electron microscopy technique revealed the spherical growth process from amorphous form to *** the supersaturation of the crystallization system was adjusted,the ceftriaxone sodium crystals transformed from amorphous form to *** the process of antisolvent crystallization with acetone as antisolvent,when the theoretical supersaturation degree S was higher than 2.62,the crystallization system tended to appear amorphous form;when S was between 2.57 and 2.62,the amorphous form transformed into clustered spherulites;when S was less than 2.57,the surface of spherulites will be covered with flaky crystal,which transformed into urchin-like *** the understanding of the spherical growth mechanism,the ceftriaxone sodium spherulites prepared in this research with modified supersaturation control had a low residue of antisolvent acetone,and the flowability was significantly improved.

关键词： spherulite Ceftriaxone sodium Antisolvent crystallization Supersaturation Online observation

Pattern and origin of spherulites in a rhyolite dike swarm, northeastern Cheongsong, Korea

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Global Geology 2006年第1期9卷 60-79页

作者： Sang Koo Hwang Chang Oh Choo Department of Earth and Environmental Sciences Andong National University Andong 760-749 Korea epartment of Geology Kyungpook National University Daegu 702-701 Korea

Several NNW-trending Cretaceous rhyolite dikes in the northeastern Cheongsong area of southern Korea contain spherulitic fabrics and are locally quarried as an ornamental stone. The dikes, part of the Cheongsong dike swarm, contain a variety of spherulites which are characterized by radial array of acicular intergrowths from fibrous quartz and alkali feldspars. They are classified as some simple, multiple and compound spherulite types from flower-like patterns, and the types are different each other in spatial distribution within the dikes. The various radial fabrics suggest that they crystallized under the different cooling mechanisms and processes in rapidly cooling dikes. Spheroids lacking a flower-like pattern may be precipitated after compositional segregation in a supercooled magma. Simple acicular spherulites could be crystallized by devitrification of true glass which cooled rapidly below the transformation temperature, whereas layered multiple spherulites could result from a crystallization of supercooled magma at relatively rapid cooling rates above the transformation temperature. Acicular multiple spherulites could be produced from a combination of the above three mechanisms operating at slower cooling rates.

关键词： spherulite rhyolite dike swarm Korea

Unusual Spherulitic Morphology of Poly(propylene fumarate)

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Chinese Journal of Polymer Science 2021年第4期39卷 493-500,I0007页

作者： Xiao-Yu Meng Yi Li Shu-Fang Yao Xue-Wei Wei Hai-Mu Ye Department of Materials Science and Engineering College of New Energy and MaterialsChina University of PetroleumBeijing 102249China

spherulites are the most common crystalline morphology and thus the visual expression of crystal structures for *** diversified patterns have provided intuitive morphology probes for various crystallization behaviors,while the correlations between them are still needed to be *** this work,the complicated spherulitic morphology of poly(propylene fumarate)(PPF),which is sensitive to crystallization temperature,is *** melt,respectively,crystallizes into rough spherulites,regularly banded spherulites,and spherulites containing both two kinds of morphology at low,high,and mediate *** systematically assaying,it is clear that the growth axis along the radial direction changes from a-axis to b-axis as the crystallization temperature increases,which leads to the formation of unique crystallization-temperature-dependent *** on detailed characterization of Fourier transform infrared spectroscopy,the packing state of the specific hydrogen bonds of"C=C-H…O=C-C=C"in PPF crystal lattices is determined,and furthermore,the mechanism for temperature-dependent selection of growth axes for PPF spherulites in melt is reasonably speculated.

关键词： spherulite Crystallization Growth axis Hydrogen bond

Initiation, Development and Stabilization of Cavities during Tensile Deformation of Semicrystalline Polymers

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Chinese Journal of Polymer Science 2018年第10期36卷 1195-1199页

作者： Ying Lu Yong-Feng Men State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022 China University of Science and Technology of China Hefei 230026 China

By using polybutene-1 as a typical example, we illustrate the initiation, development and stabilization of cavities in the sample during tensile deformation. Samples with the same crystallinity, long spacing and crystalline lamellar thickness but very different sizes of spherulites were prepared via changing the melt history. Dimension of cavities during stretching the samples was determined by in situ ultra small angle X-ray scattering techniques. It turned out that the size of the cavities was bigger in the sample with larger spherulites than the one with smaller spherulites. The results show clear evidence of initiating cavities within crystalline phase at the grain-boundary of crystalline blocks, growing of cavities passing through parallel stacked lamellar crystals and amorphous layers and finally stablized by tilted lamellae at both ends of the plate-like cavities within the spherulites.

关键词： Cavitation Deformation Polymer Polubutene-1 spherulite

CRYSTALLIZATION CHARACTERISTICS OF β-PHASE CRYSTALS IN COPOLYMERS OF POLYPROPYLENE WITH LOW ETHYLENE CONTENT

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Chinese Journal of Polymer Science 2001年第3期19卷 317-322页

作者： Wen-tao Hao Yi-yong He Xiao-lie Luo De-zhu Ma Department of Polymer Science and Engineering University of Science and Technology of China Hefei 230026 China 中国科学技术大学安徽合肥

Polypropylene copolymers (CPP) containing β-nucleating agent were investigated by differential scanningcalorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing light microscopy (PLM). The results show thathigh content of β-phase crystals can also be formed for CPPs. Like PP homopolymers, the CPPs also have a most favorabletemperature near 132℃ for β-phase crystal growth. The crystallization rate of CPPs containing β-nucleating agent (β-CPP) ismuch greater than that of PP homopolymer containing β-nucleating agent (β-PP homopolymer). The observation ofspherulite morphology of β-CPP and β-PP homopolymer shows that the spherulites of β-CPP are more imperfect than thoseof β-PP homopolymer.

关键词： Copolymer polypropylene β-Nucleating agent Differential scanning calorimetry Wide angle X-ray diffraction spherulite

TIME-DEPENDENT MORPHOLOGY OF POLYETHYLENE-POLYPROPYLENE BLENDS

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Chinese Journal of Polymer Science 2002年第6期20卷 497-508页

作者： Robert A. Shanks Department of Applied Chemistry CRC for Polymers RMIT University Melbourne Victoria Australia

The effect of time-temperature treatment on morphology of polyethylene-polypropylene (PE-PP) blends wasstudied to establish a relationship between thermal history, morphology and mechanical properties. Polypropylene (PP)homopolymers were used to blend with various polyethylenes (PE), including high density polyethylene (HDPE), lowdensity polyethylene (LDPE), linear low density polyethylene (LLDPE), and very and ultra low density polyethylene(VLDPE and ULDPE). The majority of the blends were prepared at a ratio of PE:PP = 80:20, while blends of PP and LLDPEwere prepared at various compositions. Thermal treatment was carried out at temperatures between the crystallizationtemperatures of PP and PEs to allow PP to crystallize first from the blends. On cooling further, PE crystallized too. A verydiffuse PP spherulite morphology in the PE matrix was formed in some partially miscible blends when PP was less than 20%by mass. Droplet-matrix structures were developed in other blends with either PP or PE as dispersed domains in a continuousmatrix, depending on the composition ratio. The scanning electron microscopy (SEM) images displayed a fibrillar structureof PP spherulite in the LLDPE-PP (80:20) and large droplets of PP in the HDPE-PP (80:20) blend, providing larger surfacearea and better bonding in the LLDPE-PP (80:20) blends. This explains why the blends with diffuse spherulite morphologyshowed greater improvement in tensile properties than droplet-matrix morphology blends after time-temperature treatment.

关键词： Polypropylene and polyethylene blends Thermal history spherulite Morphology Mechanical properties

Significant enhancement of crystallization kinetics of polylactide in its immiscible blends through an interfacial effect from comb-like grafted side chains

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Science China Chemistry 2016年第5期59卷 609-618页

作者： Yin Chen Yaqiong Zhang Feng Jiang JunyangWang Zhaohua Xu Zhigang Wang CAS Key Laboratory of Soft Matter Chemistry Hefei National Laboratory for Physical Sciences at the MicroscaleDepartment of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefei 230026China Department of Material Technology Jiangmen PolytechnicJiangmen 529090China

A significant enhancement in isothermal crystallization kinetics of biodegradable polylactide(PLA) in its immiscible blends can be accomplished through blending it with a comb-like copolymer. PLA was blended with poly(ethylene glycol) methyl ether acrylate(PEGA) and poly[poly(ethylene glycol) methyl ether acrylate](PPEGA, a comb-like copolymer), respectively. The results measured from phase contrast optical microscopy(PCOM) and differential scanning calorimetry(DSC) indicate that PLA and PEGA components are miscible, whereas PLA and PPEGA components are immiscible. The study of crystallization kinetics for PLA/PEGA and PLA/PPEGA blends by means of polarized optical microscopy(POM) and DSC indicates that both PEGA and PPEGA significantly increase the PLA spherulitic growth rates, G, although PLA/PPEGA blends are immiscible and the glass transition temperatures of PLA only have slight decreases. PPEGA component enhances nucleation for PLA crystallization as compared with PEGA component owing to the heterogeneous nucleation effect of PPEGA at the low composition of 20 wt%, while PLA crystallization-induced phase separation for PLA/PEGA blend might cause further nucleation at the high composition of 50 wt%. DSC measurement further demonstrates that isothermal crystallization kinetics can be relatively more enhanced for PLA/PPEGA blends than for PLA/PEGA blends. The "abnormal" enhancement in G for PLA in its immiscible blends can be explained by local interfacial interactions through the densely grafted PEGA side chains in the comb-like PPEGA, even though the whole blend system(PLA/PPEGA blends) represents an immiscible one.

关键词： biodegradable polymer spherulite growth rate phase separation nucleation

Structures and growth mechanisms of poly-(3-hydroxybutyrate) (PHB) crystallized from solution and thin melt film

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Science China Chemistry 2008年第9期51卷 853-858页

作者： CAO QiKun QIAO XiaoPing WANG Hui LIU JiePing Department of Chemistry Huaibei Coal Industry Teachers CollegeAnhui 235000China

The spherulitic structures and morphologies of poly-(3-hydroxybutyrate) (PHB) crystallized from a so- lution and a thin melt film were investigated in this study. The formation mechanisms of banded spherulites under different crystallization conditions are proposed. It was found that the formation of banded spherulites was caused by the rhythmic crystal growth of the spherulites and lamellar twisting growth for the polymer crystallization from a thin melt film and a solution, respectively.

关键词： rhythmic crystal growth lamellar twisting banded spherulite poly(3-hydroxybutyrate)