Random copolymer blends of styrene, para-fluoro styrene and ortho-fluoro styrene

Oudhuis, A. A. C. M.; Tenbrinke, G; Karasz, F. E.

doi:10.1016/0032-3861(93)90453-h

Cited by 7 publications

(6 citation statements)

References 9 publications

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“…Figure 8 presents the total heat flow for samples which have been annealed for the indicated amounts of time in the glassy state at 92 °C. The fact that both components are immiscible, as reported before, 32 is obvious from the enthalpy recovery peak(s), but only after annealing for more than 46 h. Without annealing, a single glass transition is observed. These measurements have been analyzed by the semiempirical procedure introduced by Reading.…”

Section: Figuresupporting

confidence: 70%

Temperature Modulated Calorimetry of Glassy Polymers and Polymer Blends

1998

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The theoretical modeling of the relaxation behavior of polymers in the glass transition region, advocated by Moynihan and co-workers, has been used to analyze the heat flow and the relaxation of polymer systems during isothermal modulated DSC experiments in the glass transition region. An analytic solution for the frequency dependent fictive temperature is obtained, which takes a particularly simple form in the high-frequency region. The maximal phase lag of the fictive temperature T f is π/2, where the exponent of the stretched-exponential characterizing the enthalpy relaxation, , is on the order of 0.1-0.7. The corresponding maximal phase lag in the heat flow is much smaller, on the order of 2-5 deg. It is once more iterated that, as observed long ago by Birge and Nagel, the loss heat capacity corresponds to the entropy production due to a redistribution of energy over the heat baths. The possibility of using specific-heat spectroscopy as a tool to determine miscibility in polymer blends whose constituents possess similar glass transition temperatures is discussed. Compared to conventional differential scanning calorimetry, the resolution is enhanced. However, in many cases an unambiguous conclusion still requires additional enthalpy relaxation of the blend induced by physical aging in the glassy state.

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Section: Figuresupporting

confidence: 70%

Temperature Modulated Calorimetry of Glassy Polymers and Polymer Blends

1998

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“…This method has been used successfully in the past among others to obtain interaction parameter values between styrene and o-or pfluorostyrene. 17,18 The use of appropriate random copolymer blends involving monomers with a large unfavorable exchange interaction implies that only a small incorporation of the comonomer (i.e., 4VP or 2VP in our case) can be tolerated. This in turn implies that the glass transition temperatures (T g 's) of the homopolymer (PS) and the copolymer (P(S-co-4VP), P(S-co-2VP)) will be very similar.…”

Section: Resultsmentioning

confidence: 96%

“…In our case the value of χ S,4VP ( χ S,2VP ) can be determined by studying the critical copolymer composition 1 − x for which PS and P(S x - co -4VP 1 - x ) (P(S x - co -2VP 1 - x )) are on the borderline of miscibility. This method has been used successfully in the past among others to obtain interaction parameter values between styrene and o - or p -fluorostyrene. , …”

Section: Resultsmentioning

confidence: 99%

Determination of the Flory−Huggins Interaction Parameter of Styrene and 4-Vinylpyridine Using Copolymer Blends of Poly(styrene-co-4-vinylpyridine) and Polystyrene

et al. 2000

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On the basis of the experimentally determined phase behavior in blends of polystyrene and random copolymers of styrene and 4-vinylpyridine, i.e., P(S x-co-4VP1-x)/PS, the Flory-Huggins interaction parameter is demonstrated to satisfy 0.30 < S,4VP e 0.35. This value is substantially smaller than reported before. To corroborate our results, a similar study was performed using 2-vinylpyridine leading to 0.09 < S,2VP e 0.11, in excellent agreement with the well-established value of S,2VP) 0.1.

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“…Microphase separation was characterized via enthalpy relaxation techniques first described by ten Brinke et al − This was conducted as follows for samples comprised of styrene/4-acetoxystyrene: the samples were heated at a rate of 20 °C/min to 170 °C and held at this temperature for 30 min. Next, the samples were cooled at a rate of 40 °C/min to 90 °C, where they were held for various times.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and Glass Transition Behavior of High Molecular Weight Styrene/4-Acetoxystyene and Styrene/4-Hydroxystyrene Gradient Copolymers Made via Nitroxide-Mediated Controlled Radical Polymerization

et al. 2004

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Styrene (S)/4-acetoxystyrene (AS) gradient copolymers were synthesized by moderate-temperature, nitroxide-mediated controlled radical polymerization. Hydrolysis of styrene/4-acetoxystyrene gradient copolymers produced styrene/4-hydroxystyrene (HS) gradient copolymers. Molecular weight (MW) characterization via gel permeation chromatography demonstrated that these materials were made in a “controlled” manner, while intrinsic viscosity measurements revealed that the MWs exceeded 100 000 g/mol, with apparent viscosity-average MW values ranging between 100 000 and 385 000 g/mol, making these materials the first high MW gradient copolymers ever synthesized. Characterization of the glass transition temperature, T g, revealed different behavior depending on the type of gradient copolymer produced. Using a normal thermal history for measuring T g by differential scanning calorimetry (DSC), linear gradient copolymers exhibited one T g, with a value intermediate to the T gs of polystyrene (PS) and poly(4-acetoxystyrene) (PAS) or poly(4-hydroxystyrene) (PHS). In contrast, “blocky” gradient copolymers with overall S content ≥55 mol % yielded two T gs, one near the T g of PS and the other intermediate to the T gs of PS and PAS or PHS, indicating microphase separation. When the cumulative composition of the “blocky” gradient copolymer was majority AS or HS, only one T g was resolved, with a value near the T g of PAS or PHS. For S/AS and S/HS gradient copolymers of identical chain length, overall fractional S content, and strength of gradient, physical aging at 90 °C provided resolution of a second T g via DSC, allowing comment on how manifestations of microphase separation depend on gradient structure and the strength of the comonomer repulsive interactions.

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Random copolymer blends of styrene, para-fluoro styrene and ortho-fluoro styrene

Cited by 7 publications

References 9 publications

Temperature Modulated Calorimetry of Glassy Polymers and Polymer Blends

Temperature Modulated Calorimetry of Glassy Polymers and Polymer Blends

Determination of the Flory−Huggins Interaction Parameter of Styrene and 4-Vinylpyridine Using Copolymer Blends of Poly(styrene-co-4-vinylpyridine) and Polystyrene

Synthesis and Glass Transition Behavior of High Molecular Weight Styrene/4-Acetoxystyene and Styrene/4-Hydroxystyrene Gradient Copolymers Made via Nitroxide-Mediated Controlled Radical Polymerization

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