Interrelation of phase and relaxation behavior in polymer blends and block copolymers with crystallizable components

Shibanov, Yu.D.; Godovsky, Yu. K.

doi:10.1007/bfb0115422

Cited by 35 publications

(5 citation statements)

References 15 publications

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“…7c). Spherulites surrounded with pores were also frequently observed by Li et al [23], Tanaka and Nishi [ 24 ] and Shibanov et al [ 25 ] during the phase separation of mixtures of crystalline and amorphous polymers. The formation process is closely related to the formation of the fingered spherulites.…”

Section: Membranes Prepared From Pllasupporting

confidence: 59%

Phase transitions during membrane formation of polylactides. I. A morphological study of membranes obtained from the system polylactide-chloroform-methanol

Witte

Esselbrugge

Dijkstra

et al. 1996

Journal of Membrane Science

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The influence of solid-liquid demixing, liquid-liquid demixing and vitrification on the morphology of polylactide membranes has been investigated. To study the effects of crystallization of polylactides on the membrane formation and morphology, polylactides of varying stereoregularity were used. The polymers applied were poly-L-lactide (PLLA) and copolymers with different molar ratios of L-lactide and I>lactide [poly-L95/D5-1actide (PLA95), poly-L80/D20-1actide (PLA80) and poly-L50/D50-1actide (PDLLA) ]. Solutions of polylactides in chloroform cast on a glass plate were immersed in methanol. From solutions containing the slowly crystallizing PLA80 or uncrystallizable PDLLA porous membranes were obtained if the phase separated system was removed from the nonsolvent bath within a few hours after immersion. After longer equilibration times in methanol the structure collapsed. The swelling in the nonsolvent methanol was too high to allow stabilization of the liquidliquid demixed structure by vitrification. Stable membranes were easily obtained with more rapidly crystallizing polymers like PLLA. Casting solutions with low PLLA concentrations gave membranes with a cellular morphology due to liquid-liquid demixing by nucleation and growth of a polymer poor phase. Crystallization only played a role in the fixation of the liquidliquid demixed structure. At increasing PLLA concentrations the demixing sequence gradually reversed to crystallization followed by liquid-liquid demixing. In these cases membranes with porous spherulites or spherulites surrounded with a cellular layer were obtained.

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Section: Membranes Prepared From Pllasupporting

confidence: 59%

Phase transitions during membrane formation of polylactides. I. A morphological study of membranes obtained from the system polylactide-chloroform-methanol

Witte

Esselbrugge

Dijkstra

et al. 1996

Journal of Membrane Science

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“…This case has been described for blends by Li et al, and Tanaka and Nishi. 39 -43 These phenomena were recentely reported by van binary polymer-solvent combinations by Schaaf et al 38,39 Shibanov concluded that in contrast to pected to play a large role in the phase separation of the solution. As has been demonstrated in deby the poorer solvent dioxane the same effect is observed.…”

Section: -8mentioning

confidence: 67%

Metastable liquid-liquid and solid-liquid phase boundaries in polymer-solvent-nonsolvent systems

Witte

Dijkstra

Berg

et al. 1997

J. Polym. Sci. B Polym. Phys.

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In general liquid–liquid demixing processes are responsible for the porous morphology of membranes obtained by immersion precipitation. For rapidly crystallizing polymers, solid–liquid demixing processes also generate porous morphologies. In this study, the interference of both phase transitions has been analyzed theoretically using the Flory–Huggins theory for ternary polymer solutions. It is demonstrated that four main thermodynamic and kinetic parameters are important for the structure formation in solution: the thermodynamic driving force for crystallization, the ratio of the molar volumes of the solvent and the nonsolvent, the polymer–solvent interaction parameter, and the rate of crystallization of the polymer compared to the rate of solvent‐nonsolvent exchange. An analysis of the relevance of each of these parameters for the membrane morphology is presented. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 763–770, 1997

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“…β-relaxation) at the lower temperature (∼−50 °C). The β transition is attributed predominantly to the motion of hydroxyl ether structural units [CH 2 −CH(OH)−CH 2 −O−] and diphenyl groups in amine-cross-linked epoxy. − The β-relaxation temperatures ( T β 's) of the phase-separated hybrid composites almost remained invariant in comparison with the control epoxy, implying that the epoxy matrix were not nearly affected by the dispersed domains. However, the T β 's of the nanocomposites are found to shift to the lower temperatures, implying that the free volume of systems were increased with POSS-triol being incorporating into the cross-linked networks, which facilitates the motion of the hydroxyether structural units and diphenyl groups.…”

Section: Resultsmentioning

confidence: 99%

Morphology and Thermomechanical Properties of Organic−Inorganic Hybrid Composites Involving Epoxy Resin and an Incompletely Condensed Polyhedral Oligomeric Silsesquioxane

2005

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Epoxy was modified by an incompletely condensed polyhedral oligomeric silsesquioxane (POSS), and the phenyltrisilanol POSS [Ph7Si7O9(OH)3, POSS-triol] was incorporated into the epoxy networks with the content of POSS up to 30 wt %. The organic−inorganic hybrid composites were prepared via in situ polymerization of epoxy monomers in the presence of POSS-triol, which started from the homogeneous solutions of POSS-triol and epoxy monomers. The nanocomposites of epoxy with POSS-triol can be prepared with the metal complex, aluminum triacetylacetonate ([Al]) being used as the catalyst for the reaction between POSS-triol and diglycidyl ether of bisphenol A (DGEBA). Otherwise, the phase separation induced by polymerization occurred, and the fine phase-separated structures were obtained, in which the spherical POSS-triol particles (0.3−0.5 μm in diameter) were dispersed in the continuous epoxy matrices. The hybrid composites with the different morphological structures displayed quite different thermomechanical properties. The phase-separated composites possessed the higher glass transition temperatures (T g's) than the nanocomposites while the nanocomposites displayed the higher storage modulus of glassy state in light of dynamic mechanical analysis (DMA). In terms of thermogravimetric analysis, the nanocomposites displayed the higher initial thermal decomposition temperatures (T d's). The improvement in thermomechanical properties has been ascribed to the nanodispersion of POSS moieties.

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Interrelation of phase and relaxation behavior in polymer blends and block copolymers with crystallizable components

Cited by 35 publications

References 15 publications

Phase transitions during membrane formation of polylactides. I. A morphological study of membranes obtained from the system polylactide-chloroform-methanol

Phase transitions during membrane formation of polylactides. I. A morphological study of membranes obtained from the system polylactide-chloroform-methanol

Metastable liquid-liquid and solid-liquid phase boundaries in polymer-solvent-nonsolvent systems

Morphology and Thermomechanical Properties of Organic−Inorganic Hybrid Composites Involving Epoxy Resin and an Incompletely Condensed Polyhedral Oligomeric Silsesquioxane

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