Lamellar crystal thickness transition of melt-crystallized isotactic polybutene-1 observed by small-angle X-ray scattering

Yamashita, Motoi; Kato, Masaru

doi:10.1107/s0021889807011570

Cited by 17 publications

(13 citation statements)

References 8 publications

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“…These crystals are encapsulated within a much larger spherulite of the tetragonal phase, which has already been reported to grow from the melt in the literature. [15][16][17][18] When the above crystallized sample was heated again, the flat-on crystals retained their shape up to 124 C; the surrounding tetragonal spherulites melted below 110 C, which is consistent with the melting temperature of the tetragonal crystals we reported in our previous work. 15 The morphology and melting behavior indicate that the flat-on crystals are in a different phase from the surrounding tetragonal crystals.…”

Section: Resultssupporting

confidence: 74%

Melt Crystallization of isotactic Polybutene-1Trigonal Form: the Effect of Side Chain Entropy on Crystal Growth Kinetics

Yamashita

Takahashi

2008

Polym J

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The morphology and crystal growth kinetics of isotactic polybutene-1 (it-PB1) trigonal phase in molten thin films have been studied with transmission electron microscopy, electron diffraction and optical microscopy. The growth rate of trigonal crystals was determined by in situ optical microscopy. It is one hundredth that of it-PB1 tetragonal crystals. The growth rate of trigonal crystals, as well as that of tetragonal crystals, shows the supercooling dependence derived from the nucleation theory. Trigonal crystals grown at 75 and 90.1 C possessed well facetted morphology, which suggests the existence of flat growth faces required for nucleation theory between 75 and 90.1 C. This is consistent with the observed temperature dependence of trigonal crystal growth rate in accordance with the nucleation theory. Lateral surface free energy of the trigonal phase determined from the observed growth kinetics is about 7 times as large as the value Hoff calculated according to Hoffman's equation, while that of the tetragonal phase is roughly in agreement with the estimation. The discrepancy between the values of andHoff for the trigonal phase can be attributed to the loss of conformational entropy of the ethyl side chains of it-PB1.KEY WORDS: Isotactic Polybutene-1 / Trigonal Phase / Melt Crystallization / Growth Rate / Self-seeding / Surface Free Energy / Isotactic polybutene-1 (it-PB1) is a semicrystalline polyolefin which exhibits outstanding mechanical properties and pronounced polymorphs that depend on its crystallization conditions.

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Section: Resultssupporting

confidence: 74%

Melt Crystallization of isotactic Polybutene-1Trigonal Form: the Effect of Side Chain Entropy on Crystal Growth Kinetics

Yamashita

Takahashi

2008

Polym J

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“…The logarithm of G 1 is plotted against crystallization temperature in figure 5. The values of the growth rate G 2 of tetragonal crystals we observed in our previous works [11,[13][14][15] are also included for comparison. It should be noted that the growth rate of trigonal crystals is one hundredth and one thousandth that of tetragonal crystals around 70 and 90°C, respectively.…”

Section: Resultsmentioning

confidence: 98%

Direct melt crystal growth of isotactic polybutene‐1 trigonal phase

Yamashita

Ueno

2007

Cryst. Res. Technol.

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The morphology, crystalline structure and crystal growth kinetics of melt-crystallized thin isotactic polybutene-1 films have been studied with transmission electron microscopy, electron diffraction and optical microscopy. It is demonstrated that a bypass of tetragonal phase crystallization and direct melt crystal growth of the trigonal phase can be achieved via self-seeding at atmospheric pressure using solution-grown trigonal crystals as nuclei. Electron microscopy and optical microscopy observations show that melt-crystallized isotactic polybutene-1 single crystals of the trigonal phase have rounded or hexagonal morphologies around 75°C. The growth rate of trigonal crystals in the melt has been obtained by in-situ optical microscopy. The growth rate of trigonal crystals in the melt is 1/100 and 1/1000 that of tetragonal crystals in the melt around 70 and 90°C, respectively.

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“…Consequently, crystal thicknesses of semi-crystalline polymers reflect the processes by which their structures are formed. We have studied the crystal growth and morphology of isotactic polybutene-1 (it-PB1) [3][4][5], and the properties of the end surface of chain-folded crystals [3,5]. it-PB1 is a semicrystalline polyolefin with ethyl side-groups, which exhibits a stable trigonal form with 3/1 helical chains and a metastable tetragonal form with 11/3 helical chains as the most common structures [6,7].…”

Section: Introductionmentioning

confidence: 99%