Effect of miscible polymer diluents on the development of lamellar morphology in poly(oxymethylene) blends

Yeh, Fengji; Hsiao, Benjamin S.; Chu, Benjamin; Sauer, Bryan B.; Flexman, Edmund A.

doi:10.1002/(sici)1099-0488(19991101)37:21<3115::aid-polb20>3.0.co;2-i

Cited by 29 publications

(7 citation statements)

References 17 publications

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“…Comparing the changes in the estimated thicknesses during crystallization, a slight decrease in the long period and a more pronounced decrease in crystalline lamellae thickness were observed, while the amorphous layer thickness increased. This behavior was also reported for copolymers of PHB and 3‐hydroxyhexanoate 58 and for poly(oxymethylene) containing 20% of poly(vinyl phenol), which is a miscible diluent 64 . The increase of the amorphous layer during crystallization could be related to the exclusion of TEC from the crystalline regions toward the amorphous fraction.…”

Section: Resultssupporting

confidence: 64%

Plasticization of poly(3‐hydroxybutyrate) with triethyl citrate: Thermal and mechanical properties, morphology, and kinetics of crystallization

Umemura

Felisberti

2020

J of Applied Polymer Sci

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Poly(3-hydroxybutyrate) (PHB), is one important biopolymer and a promising alternative to petroleum-based plastics. In this article, formulations of PHB and triethyl citrate (TEC) as plasticizer were prepared by melt extrusion. The effect of TEC on the mechanical, thermal, and morphological properties of PHB was investigated by tensile tests, impact resistance, dynamic-mechanical analysis, differential scanning calorimetry, polarized optical microscopy, and small-and wide-angle X-ray scattering. TEC acted as an efficient plasticizer for PHB, imparting gradual changes in the properties as the mass fraction of TEC increased. A reduction in the elastic modulus, an increase in the intensity of β relaxation indicated a higher capacity of mechanical energy dissipation for the formulations containing higher mass fractions of TEC. TEC reduced its glass transition and melting temperatures, contributing to the increase of the processing window of the temperature and minimizing thermal degradation of PHB. TEC had a strong influence on the kinetics of crystallization, the morphology of the spherulites, and the crystalline structural parameters, such as long period, crystalline lamella, and interlamellar amorphous region thicknesses. Our study clarifies how the morphology of the PHB crystalline phase evolves in the presence of the plasticizer and with the time of crystallization.

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Section: Resultssupporting

confidence: 64%

Plasticization of poly(3‐hydroxybutyrate) with triethyl citrate: Thermal and mechanical properties, morphology, and kinetics of crystallization

Umemura

Felisberti

2020

J of Applied Polymer Sci

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“…In other words, a large number of noncrystallizable components such as graft or crosslinked copolymer species formed by the interchange reactions between the two polymers were excluded from the lamellar stacks and resided in interfibrillar regions, interspherulitic regions, or both. When a crystalline polymer is blended with a noncrystallizable component, three different morphologies can occur, assuming that the noncrystallizable component is rejected from the crystal: (1) it can be trapped within the lamellar stacks (interlamellar); (2) it can be excluded from the lamellar stacks and reside within the spherulite (interfibrillar); and (3) it can be totally excluded from the spherulite region (interspherulitic) 32, 33. The first morphology is considered as the inclusion model, while the other two are considered as exclusion models.…”

Section: Resultsmentioning

confidence: 99%

Morphology development and crystallization behavior of poly(ethylene terephthalate)/phenoxy blend

Kim

Lee

Choi

et al. 2007

J Polym Sci B Polym Phys

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The morphological development and crystallization behavior of a poly(ethylene terephthalate)/poly(hydroxyl ether of bisphenol A) (phenoxy) blend were studied with time‐resolved light scattering, optical microscopy, differential scanning calorimetry, and small‐angle X‐ray scattering (SAXS). During annealing at 280 °C, liquid–liquid phase separation via spinodal decomposition proceeded in the melt‐extruded specimen. After the formation of a domain structure, the blend slowly underwent phase homogenization by the interchange reactions between the two polymers. Specimens annealed for various times (ts) at 280 °C were subjected to a temperature drop and the effects of liquid‐phase changes on crystallization were then investigated. The shifts in the position of the cold‐crystallization peaks indicated that the crystallization rate is associated with the composition change of the separated phases as well as the change of the sequence distribution in polymer chains during annealing. The morphological parameters at the lamellar level were determined by a correlation function analysis on the SAXS data. The crystal thickness (lc) increased with ts, whereas the amorphous layer thickness (la) showed little dependence on ts. Observation of a constant la value revealed that a large number of noncrystallizable species formed by the interchange reactions between the two polymers were excluded from the lamellar stacks and resided in the interfibrillar regions, interspherulitic regions, or both. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 223–232, 2008

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“…[5] Later, however, it was observed that molecularly dispersed drugs reside predominantly in the amorphous parts of PEG. [49][50][51][52] Note that the term 'solid solution' refers to systems with crystalline carriers.…”

Section: Solid Solutionsmentioning

confidence: 99%

Review: physical chemistry of solid dispersions

2009

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Objectives With poorly soluble drug candidates emerging in the drug discovery pipeline, the importance of the solid dispersion formulation approach is increasing. This strategy includes complete removal of drug crystallinity, and molecular dispersion of the poorly soluble compound in a hydrophilic polymeric carrier. The potential of this technique to increase oral absorption and hence bioavailability is enormous. Nevertheless, some issues have to be considered regarding thermodynamic instability, as well in supersaturated solutions that are formed upon dissolution as in the solid state. Key findings After a brief discussion on the historical background of solid dispersions and their current role in formulation, an overview will be given on the physical chemistry and stability of glass solutions as they form supersaturated solutions, and during their shelf life. Conclusions Thorough understanding of these aspects will elicit conscious evaluation of carrier properties and eventually facilitate rational excipient selection. Thus, full exploitation of the solid dispersion strategy may provide an appropriate answer to drug attrition due to low aqueous solubility in later stages of development.

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Effect of miscible polymer diluents on the development of lamellar morphology in poly(oxymethylene) blends

Cited by 29 publications

References 17 publications

Plasticization of poly(3‐hydroxybutyrate) with triethyl citrate: Thermal and mechanical properties, morphology, and kinetics of crystallization

Plasticization of poly(3‐hydroxybutyrate) with triethyl citrate: Thermal and mechanical properties, morphology, and kinetics of crystallization

Morphology development and crystallization behavior of poly(ethylene terephthalate)/phenoxy blend

Review: physical chemistry of solid dispersions

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