			Home About us Contact

Spherulite Morphology (spherulite + morphology)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Crystallization and Ring-Banded Spherulite Morphology of Poly(ethylene oxide)- block -Poly(, -caprolactone) Diblock Copolymer

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2004
Shichun Jiang
Abstract Summary: The crystallization behavior of crystalline-crystalline diblock copolymer containing poly(ethylene oxide) (PEO) and poly(, -caprolactone) (PCL), in which the weight fraction of PCL is 0.815, has been studied via differential scanning calorimeter (DSC), wide-angle X-ray diffraction (WAXD), and polarized optical microscopy (POM). DSC and WAXD indicated that both PEO and PCL blocks crystallize in the block copolymer. POM revealed a ring-banded spherulite morphology for the PEO- b -PCL diblock copolymer. DSC heating curve for the PEO- b -PCL block copolymer. [source]

A Defect-Free Ring Polymer: Size-Controlled Cyclic Poly(tetrahydrofuran) Consisting Exclusively of the Monomer Unit,

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2008
Yasuyuki Tezuka
Abstract A series of size-controlled, cyclic poly(tetrahydrofuran)s ( of 4,400,8,600) that consist exclusively of the monomer, i.e., oxytetramethylene, unit (I) have been prepared in high yield through the metathesis polymer cyclization of a telechelic precursor having allyl groups, 1, in the presence of a Grubbs catalyst, and the subsequent hydrogenation of the linking, i.e., 2-butenoxy, unit in the presence of an Adams' catalyst (PtO2). A remarkable topology effect has subsequently been observed upon the isothermal crystallization of these two model polymers, showing distinctive spherulite growth rates and spherulite morphologies in comparison with the relevant linear poly(tetrahydrofuran) counterpart that has ethoxy end groups (II). [source]

Crystallization and morphology of cholesterol end-capped poly(ethylene glycol)

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007
Yuan-Jin Qiu
Abstract Crystallization and morphology of polyethylene glycol with molecular weight Mn = 2000 (PEG2000) capped with cholesterol at one end (CS-PEG2000) and at both ends (CS-PEG2000-CS) were investigated. It is found that the bulky cholesteryl end group can retard crystallization rate and decrease crystallinity of PEG, especially for CS-PEG2000-CS. Isothermal crystallization kinetics shows that the Avrami exponent of CS-PEG2000 decreases as crystallization temperature (Tc). The Avrami exponent of CS-PEG2000-CS increases slightly with Tc, but it is lower than that of CS-PEG2000. Compared to the perfect spherulite morphology of PEG2000, CS-PEG2000 exhibits irregular and leaf-like spherulite morphology, while only needle-like crystals are observed in CS-PEG2000-CS. The linear growth rate of CS-PEG2000 shows a stronger dependence on Tc than PEG2000. The cholesterol end group alters not only the free energy of the folding surface, but also the temperature range of crystallization regime. The small angle X-ray scattering (SAXS) results show that lamellar structures are formed in all these three samples. By comparing the long periods obtained from SAXS with the theoretically calculated values, we find that the PEG chains are extended in PEG2000 and CS-PEG2000, but they are once-folded in CS-PEG2000-CS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2464,2471, 2007 [source]

Crystallization and Ring-Banded Spherulite Morphology of Poly(ethylene oxide)- block -Poly(, -caprolactone) Diblock Copolymer

Miscibility and Physical Properties of Poly(3-hydroxybutyrate -co- 3-hydroxyhexanoate)/Poly(ethylene oxide) Binary Blends

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 12 2009
Fang Yu
Abstract In order to improve some inferior physical properties of bacterial poly(3-hydroxybutyrate -co- 3-hydroxyhexanoate) [P(3HB -co- 3HHx)] by blending with PEO, the miscibility, spherulite morphology, crystallization behavior and mechanical properties of P(3HB -co- 3HHx)/PEO binary biodegradable polymer blends were investigated. A good miscibility between P(3HB -co- 3HHx) with a 3HHx unit content of 11 mol-% and PEO in the amorphous state was found when the PEO weight fraction was 10,wt.-%, while the miscibility decreased dramatically when the PEO weight fraction exceeded 20,wt.-%. Strongly depending on the blend composition, the mechanical properties of P(3HB -co- 3HHx) was found to be significantly improved by blending with PEO with a weight fraction of ,5,17.5,wt.-%. [source]