Morphology of melt-quenched poly(ε-caprolactone)-block-polyethylene copolymers

Nojima, Shuichi; Akutsu, Yosuke; Washino, Akira; Tanimoto, Satoshi

doi:10.1016/j.polymer.2004.08.044

Cited by 61 publications

(77 citation statements)

References 30 publications

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“…In our previous studies, 25,26 we demonstrated that the peak shift observed in Figure 3a during PCL crystallization at higher T c (! 40 C) resulted from the superposition of two scattering peaks; one at higher-angle arises from the PE lamellar morphology and the other at lower-angle from the PCL lamellar morphology newly formed in the system, and the higher-angle peak is gradually replaced with the lower-angle peak as PCL blocks crystallize.…”

Section: Sr-saxs Results For the Crystallization Process Of Pcl Blocksmentioning

confidence: 59%

“…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, 12-24 where they are mainly focused on the characteristic morphology finally formed in the system.We have recently studied the crystallization behavior and resulting morphology of poly("-caprolactone)-block-polyethylene (PCL-b-PE) diblock copolymers, 25,26 where T m of PCL blocks was ca. 60 C and that of PE blocks ca.…”

mentioning

confidence: 99%

“…We have recently studied the crystallization behavior and resulting morphology of poly("-caprolactone)-block-polyethylene (PCL-b-PE) diblock copolymers, 25,26 where T m of PCL blocks was ca. 60 C and that of PE blocks ca.…”

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confidence: 99%

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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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Section: Sr-saxs Results For the Crystallization Process Of Pcl Blocksmentioning

confidence: 59%

mentioning

confidence: 99%

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

Ikeda

Ohguma

Nojima

2008

Polym J

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“…[21][22][23][24][25][26][27][28][29] During crystallization, high melting block crystallizes first creating spatial confinement for the crystallization of the low melting block resulting less crystallinity in the second block. [21][22][23][24][26][27][28][29][30][31][32][33][34] However, depending on the nature of the blocks in diblock copolymer, they may crystallize simultaneously (viz., coincident crystallization). 28,32,[35][36][37][38] Primarily, the interplay between crystallization and microphase separation plays a crucial role in dictating the final crystal morphology of the semi crystalline materials.…”

Section: Introductionmentioning

confidence: 99%

“…For example, PCL-b-PE diblock copolymer, when crystallized isothermally, PE block crystallizes first resulting lamellar morphology which confined crystallization of the PCL block. 23,24 However, block composition strongly dictates the crystallization behaviour.…”

Section: Introductionmentioning

confidence: 99%

Effect of block asymmetry on the crystallization of double crystalline diblock copolymers

Kundu

Dasmahapatra

2014

The Journal of Chemical Physics

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Monte Carlo simulation on the crystallization of double crystalline diblock copolymer unravels an intrinsic relationship between block asymmetry and crystallization behaviour.We model crystalline A-B diblock copolymer, wherein the melting temperature of A-block is higher than that of the B-block. We explore the composition dependent crystallization behaviour by varying the relative block length with weak and strong segregation strength between the blocks. In weak segregation limit, we observe that with increasing the composition of B-block, its crystallization temperature increases accompanying with higher crystallinity. In contrast, A-block crystallizes at a relatively low temperature along with the formation of thicker and larger crystallites with the increase in B-block composition. We attribute this non-intuitive crystallization trend to the dilution effect imposed by B-block.When the composition of the B-block is high enough, it acts like a "solvent" during the crystallization of A-block. A-block segments are more mobile and hence less facile to crystallize, resulting depression in crystallization temperature with the formation of thicker crystals. At strong segregation limit, crystallization and morphological development are governed by the confinement effect, rather than block asymmetry. Isothermal crystallization reveals that the crystallization follows a homogeneous nucleation mechanism with the formation of two dimensional crystals. Two-step, compared to one-step isothermal crystallization leads to the formation of thicker crystals of A-block due to the dilution effect of the B-block.

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