Miscibility of poly (styrene‐co‐methylmethacrylate)s differing in composition

Kohl, P. R.; Seifert, Andreas M.; Hellmann, G. P.

doi:10.1002/polb.1990.090280809

Cited by 32 publications

(19 citation statements)

References 37 publications

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“…This analysis assumes that the copolymer blends segregate to form distinct layers. Although miscibility windows have not been measured for PS‐ r ‐PVP copolymers, the Flory–Huggins model predicts a minimum Δ f of 0.11 for demixing, with χ PS–PVP = 0.11 24, 25. Furthermore, self‐consistent field calculations by Gersappe and Balazs26 indicated that blends of random copolymers would segregate at such an interface.…”

Section: Resultsmentioning

confidence: 99%

Effects of composition drift on the effectiveness of random copolymer reinforcement at polymer–polymer interfaces

Benkoski

Fredrickson

Krämer

2001

J Polym Sci B Polym Phys

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Random copolymer layers are surprisingly effective at reinforcing polymerpolymer interfaces. One hypothesis is that composition drift during synthesis can account for the higher than expected toughening. To test this hypothesis, we polymerized a series of poly(d-styrene-r-2-vinylpyridine) (dPS f -r-PVP 1Ϫf ) copolymers with various fractions (f ) of deuterated styrene to only 10% completion to avoid composition drift. The fracture energies (G c ) of polystyrene/dPS-r-PVP/poly(2-vinylpyridine) interfaces with relatively thick layers of dPS-r-PVP were measured. G c decreased relative to interfaces reinforced with composition-drifted dPS-r-PVP. Conversely, G c increased when two or more copolymers were blended together. In such samples, the copolymers form distinct layers with multiple interfaces characterized by the difference in f (⌬f ) between adjacent layers. We find that G c is governed by ⌬f max , the largest difference in adjacent compositions, and, therefore, by the width of the narrowest interface (w min ). G c increases strongly as w min increases from 3 to 5 nm. Remarkably, these w min values are about half the entanglement spacing in bulk polystyrene.

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Section: Resultsmentioning

confidence: 99%

Effects of composition drift on the effectiveness of random copolymer reinforcement at polymer–polymer interfaces

Benkoski

Fredrickson

Krämer

2001

J Polym Sci B Polym Phys

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“…The chosen PS-PMMA systems fulfill these conditions to a large extent. First of all, the two polymers are virtually immiscible with an interaction parameterXSIMMA (450 K) = 0.26 [43]. This corresponds to an expected interphase thickness dlnterphase = 2 nm (cf.…”

Section: Ps-pmma Samples As Calibration Systemsmentioning

confidence: 99%

Determination of domain sizes in heterogeneous polymers by solid‐state NMR

1993

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Advanced solid-state NMR techniques exploiting 'H spin diffusion are described,which rely on selecting 'H magnetization of one of the components on the basis of 'H chemical shift or mobility differences under multiple-pulse irradiation. To monitor the progression of 'H spin diffusion, the higher resolution of I3C CP MAS spectra is exploited for NMR detection. For evaluation ofthe data,full quasi-analytical solutions ofthe diffusion equation as well as initial-rate approximations are derived, applied, and discussed. In order to obtain quantitative results, the 'H spin-diffusion constant has to be determined. To this end, the domain sizes in poly(styrene)-poly(methy1 methacrylate) systems including symmetrical diblock copolymers have been measured. The comparison of the NMR results with SAXS and TEM data yields the spin-diffusion coefficient for PS and PMMA.The resulting value ofD=0.8 nm2/ms is expected to be typical for rigid organic systems.The domain sizes investigated range from approximately 1 nm to ca. 100 nm. Bestimmung der DomanengroJen in heterogenen Polymeren mittels Festkorper-NMREs werden moderne Festkorper-NMR-Methoden beschrieben, die 'H-Spindiffusion ausnutzen und 'H-Magnetisierung einer der Komponenten des Systems auf Grund unterschiedlicher chemischer 'H-Verschiebung oder von Mobilitatsunterschieden bei Multipuls-Einstrahlung selektieren.Um die zeitliche Entwicklung der 'H-Spindiffusion zu ermitteln,wird fur den NMR-Nachweis die hohere Auflosung der "C-CP-MAS-Spektren ausgenutzt. Zur Auswertung der Ergebnisse werden vollstandige quasi-analytische Losungen der Diffusionsgleichung sowie Naherungen fur kurze Zeiten abgeleitet, angewendet und diskutiert. Um quantitative Ergebnisse zu erhalten, mu6 die 'H-Spindiffusionskonstante bestimmt werden. Zu diesem Zweck wurden die DomanengroRen in Poly(styren)-Poly(methylmethacry1at)-Systemen, einschliefllich symmetrischer Diblockcopolymere, gemessen. Ein Vergleich der NMR-Ergebnisse mit Rontgenkleinwinkelund elektronenmikroskopischen Daten ergibt als Wert des Spindiffusionskoeffizienten fur PS und PMMA D=0.8 nm2/ms, der als typisch fur starre organische Systeme angenommen werden darf. Die untersuchten DomanengroIJen liegen im Bereich von etwa 1 nm bis 100 nm.

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“…iii) Toluene is a nonselective solvent, i.e., its interaction parameters with PS and PMMA are practically equal so that approximately XAS = XBS = ,~(,aS = X;3S =" Zs (= 2.5 nm -3) [23]. Blocks and chains of the same chemistry may be assumed to behave interactionally almost equally, so that approximately ZAB = Z,A;3 = ZaB = Za~ -Z (= 0.14 nm -~ [23] and XAa = XBfl --0.…”

Section: Theorymentioning

confidence: 99%

Interface stabilization and micelle formation in blends with a block copolymer

Löwenhaupt

Hellmann

1990

Colloid & Polymer Sci

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The phase separation behavior of ternary blends of two homopolymers, PMMA and PS, and a block copolymer of styrene and methylmethacrylate, P(S-b-MMA), was studied. The homopolymers were of equal chain length and were kept at equal amounts. Two copolymers were used with blocks of equal length, which exceeded or equaled that of the homopolymer chains. Varied was the copolymer content f. Films were cast from toluene, which is a nonselective solvent. The morphologies of the cast films were compared with the structure of the critical fluctuations in solution, which were calculated in mean field approximation. The axis of blend compositions f can be divided into parts of dominating macrophase and microphase separation. Above a transition concentration fo, all copolymer chains are found in phase interfaces. Below fo, part of them form micelles within the homopolymer phases.

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Miscibility of poly (styrene‐co‐methylmethacrylate)s differing in composition

Cited by 32 publications

References 37 publications

Effects of composition drift on the effectiveness of random copolymer reinforcement at polymer–polymer interfaces

Effects of composition drift on the effectiveness of random copolymer reinforcement at polymer–polymer interfaces

Determination of domain sizes in heterogeneous polymers by solid‐state NMR

Interface stabilization and micelle formation in blends with a block copolymer

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