Nonisothermal crystallization behavior of the poly(ethylene glycol) block in poly(<scp>L</scp>‐lactide)–poly(ethylene glycol) diblock copolymers: Effect of the poly(<scp>L</scp>‐lactide) block length

Yang, Junliang; Zhao, Ting; Cui, Jijun; Liu, Leijing; Zhou, Yuanyuan; Li, Gao; Zhou, Enle; Chen, Xuesi

doi:10.1002/polb.20886

Cited by 59 publications

(67 citation statements)

References 44 publications

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“…This makes the crystallizable block copolymers representative systems having confined crystallization behavior, especially in the strong segregation regime [52]. Confined crystallization has been widely observed in the diblock copolymers having double crystalline blocks, such as PEO-b-PCL [112][113][114][115][116], PLLA-b-PEO [117][118][119][120][121][122], PLLA-b-PCL [123][124][125], poly(p-dioxanone) (PPDX)-b-PCL [126][127][128], polyolefin-based block copolymers [129][130][131][132][133][134][135], and so on. The confined crystallization kinetics and crystalline morphology of such block copolymers have been extensively studied.…”

Section: Crystalline Morphology Of Polymer Segments Confined In Blockmentioning

confidence: 99%

Crystalline and Spherulitic Morphology of Polymers Crystallized in Confined Systems

Xie

Bao

et al. 2017

Crystals

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Due to the effects of microphase separation and physical dimensions, confinement widely exists in the multi-component polymer systems (e.g., polymer blends, copolymers) and the polymers having nanoscale dimensions, such as thin films and nanofibers. Semicrystalline polymers usually show different crystallization kinetics, crystalline structure and morphology from the bulk when they are confined in the nanoscale environments; this may dramatically influence the physical performances of the resulting materials. Therefore, investigations on the crystalline and spherulitic morphology of semicrystalline polymers in confined systems are essential from both scientific and technological viewpoints; significant progresses have been achieved in this field in recent years. In this article, we will review the recent research progresses on the crystalline and spherulitic morphology of polymers crystallized in the nanoscale confined environments. According to the types of confined systems, crystalline, spherulitic morphology and morphological evolution of semicrystalline polymers in the ultrathin films, miscible polymer blends and block copolymers will be summarized and reviewed.

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Section: Crystalline Morphology Of Polymer Segments Confined In Blockmentioning

confidence: 99%

Crystalline and Spherulitic Morphology of Polymers Crystallized in Confined Systems

Xie

Bao

et al. 2017

Crystals

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“…For the PLLA block, 2 at 14. C. 26 They prove that both blocks are able to crystallize. Moreover, the PEG block is melt completely and presents as the melting solvent when the temperature is above 60 C.…”

Section: Waxd Analysismentioning

confidence: 99%

“…According to our previous report, 26 the crystal of PLLA block is -phase (pseudo-orthorhombic) and the crystal of PEG block is monoclinic crystal form. For the PLLA block, 2 at 14.…”

Section: Waxd Analysismentioning

confidence: 99%

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Isothermal Crystallization Behavior of the Poly(L-lactide) Block in Poly(L-lactide)-Poly(ethylene glycol) Diblock Copolymers: Influence of the PEG Block as a Diluted Solvent

Yang

Zhao

Liu

et al. 2006

Polym J

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ABSTRACT:Isothermal crystallization kinetics and morphology of the poly(L-lactide) block in poly(L-lactide)-poly(ethylene glycol) diblock copolymers were studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM), respectively. The results were compared with that of the PLLA homopolymer. The introduction of the PEG block accelerated the crystallization rate of the PLLA block and promoted to form ring-banded spherulites. The analysis of isothermal crystallization kinetics has shown that the PLLA homopolymer accorded with the Avrami equation. But the PLLA block of the diblock copolymers deviated from the Avrami equation, which resulted from increasing of the crystallization rate and occurring of the second crystallization process. The equilibrium melting temperature (T o m ) of the PLLA block fell with its molecular weight decreasing. The conditions to obtain more regular ring-banded spherulites were below: the sample was the PLLA block of LA 5 EG 5 ; the crystallization temperature was about from 95 C to 100 C, which almost corresponded to regime II. Poly(L-lactide)(PLLA) is possessed of many predominant properties, such as biodegradability, biocompatibility, innocuity, tissue absorbability and so on. Therefore, it is widely used in medical area 1-4 as an important biomaterial. But it also has some flaws. For example, bad watersolubility, friability etc. Moreover, the properties are not able to meet the demand for expandedness of its application area. In order to improve its property, the synthesis of PLLA-based block copolymer is one of the most important ways. Poly(ethylene glycol) (PEG) is the simplest polyether. It has good biocompatibility, blood-compatibility, hydrophilicity and flexibility. 5,6 Hydrophilic PEG is introduced to form block copolymer which hopes to improve hydrophilicity, biocompatibility and other properties.7-10 Therefore, PLLA-PEG block copolymers have attracted many researchers' attention and have been studied on their properties and application. 11-15Although crystallization process of block copolymer that have double-crystallizable blocks is more complex than other block copolymer systems, the studies on crystallization process and morphology also attracted many people's attention in recent years owing to their important meaning in practical application. [16][17][18][19] As a double-crystallizable block copolymer, it is out of question that the properties and application of PLLA-PEG block copolymers have intimate relations with their crystallization process, crystallinity and crystallization morphology. Therefore, studying them is the indispensable contents. Fujiwara conducted detailed investigation on the crystallizationinduced morphological change, macromolecular selforganization process and crystalline structure. [20][21][22] Lee reported that PLLA and PEG blocks were phase separated, and the crystallization behavior of one block was markedly affected by the presence of the other block. 23 Luo thought that the crystallization morphology was deeply depen...

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“…Therefore the crystallized morphology formed by high-T m blocks is a kind of spatial confinement for the subsequent crystallization of low-T m blocks, which will be qualitatively different from the confinement imposed by amorphous or glassy microdomains observed in crystallineamorphous diblock copolymers. [9][10][11] There are some studies so far on the morphology formation of double crystalline block copolymers with different T m values, [12][13][14][15][16][17][18][19][20][21][22][23][24] where they are mainly focused on the characteristic morphology finally formed in the system.…”

mentioning

confidence: 99%

Composition Dependence of Crystallization Behavior Observed in Crystalline-Crystalline Diblock Copolymers

Ikeda

Ohguma

Nojima

2008

Polym J

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The crystallization behavior of poly("-caprolactone) (PCL) blocks starting from a solid morphology formed in advance by the crystallization of polyethylene (PE) blocks (PE-crystallized morphology) in PCL-b-PE diblock copolymers has been investigated by a time-resolved synchrotron small-angle X-ray scattering (SR-SAXS) method as a function of composition (or volume fraction of PE blocks PE in the system). The PE-crystallized morphology and the crystallized state of PCL blocks (i.e., melting temperature and crystallinity of PCL blocks) were examined by static SAXS and differential scanning calorimetry methods, respectively. When PCL-b-PE with PE 0:58 was quenched from a microphase-separated melt into low temperatures T c (30 C T c 45 C), the PE block crystallized first to yield the PE lamellar morphology, an alternating structure consisting of thin PE crystals and amorphous PE + PCL layers, followed by the crystallization of PCL blocks starting from this PE lamellar morphology, where two different crystallization behaviors of PCL blocks were observed depending on T c ; at higher T c (! 40 C) the Avrami index was ca. 3, indicating a heterogeneous crystallization in 3D space. However, it was smaller ($ 2) at lower T c ( 38 C), suggesting a confined crystallization within the PE lamellar morphology. The temperature at which the crystallization mechanism changed was almost independent of PE in these copolymers. The late stage of PCL crystallization (or post-Avrami process) was not significantly dependent on PE and similar to that of crystalline homopolymers. For PCL-b-PE with PE ! 0:73, the PE block crystallized on the basis of molten microdomains to yield the PE-crystallized microdomain, and eventually PCL crystallization was confined within this microdomain for every T c at early and late stages. These results were consistent with our previous conclusions derived from the investigation of resulting morphology.KEY WORDS: Crystalline-Crystalline Diblock Copolymer / Composition / Crystallization Behavior / Synchrotron SAXS / Crystalline-crystalline diblock copolymers show a complicated morphology formation according to the melting temperature T m of constituent blocks when they are quenched from a microphase-separated melt into low temperatures.1 If T m values of two blocks are close enough, we have a simultaneous crystallization of both blocks to result in a complicated morphology formation.2-8 If T m of one block is enough higher than that of the other, we have a two-step crystallization; high-T m blocks crystallize first to form a crystallized morphology and subsequently low-T m blocks start to crystallize from this morphology. Therefore the crystallized morphology formed by high-T m blocks is a kind of spatial confinement for the subsequent crystallization of low-T m blocks, which will be qualitatively different from the confinement imposed by amorphous or glassy microdomains observed in crystallineamorphous diblock copolymers. [9][10][11] There are some studies so far on the morphology formation of double crystall...

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Nonisothermal crystallization behavior of the poly(ethylene glycol) block in poly(L‐lactide)–poly(ethylene glycol) diblock copolymers: Effect of the poly(L‐lactide) block length

Cited by 59 publications

References 44 publications

Crystalline and Spherulitic Morphology of Polymers Crystallized in Confined Systems

Crystalline and Spherulitic Morphology of Polymers Crystallized in Confined Systems

Isothermal Crystallization Behavior of the Poly(L-lactide) Block in Poly(L-lactide)-Poly(ethylene glycol) Diblock Copolymers: Influence of the PEG Block as a Diluted Solvent

Composition Dependence of Crystallization Behavior Observed in Crystalline-Crystalline Diblock Copolymers

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