Two DSC Glass Transitions in Miscible Blends of Polyisoprene/Poly(4-<i>tert</i>-butylstyrene)

Zhao, Junshu; Ediger, M. D.; Sun, Ye; Yu, Lian

doi:10.1021/ma9008516

Cited by 62 publications

(61 citation statements)

References 32 publications

(78 reference statements)

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“…Extensive studies have been conducted for such miscible blends to examine the dynamics of monomeric segments being related to the glass transition. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Those studies revealed characteristic features of the miscible blends such as the broad (almost two-step) glass transition noted in thermal measurements, the broad modes of segmental motion detected with NMR, and the broad and thermo-rheologically complex relaxation processes observed with the dielectric/viscoelastic methods. These features are related to the self-concentration effect 16 and the local composition fluctuation.…”

Section: Introductionmentioning

confidence: 99%

Dynamics in miscible blends of polyisoprene and poly(p-tert-butyl styrene): thermo–rheological behavior of components

Chen

Watanabe

2011

Polym J

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For miscible blends of moderately entangled cis-polyisoprene (PI) and poly(p-tert-butyl styrene) (PtBS), viscoelastic and dielectric properties were examined over a wide range of temperature (T ) to discuss the thermo-rheological behavior of respective components. Because PI has the type-A dipole, whereas PtBS does not, the slow dielectric response of the blends was exclusively attributed to the global motion of the PI chains therein. In most of the blends examined, the viscoelastic relaxation was much slower than the dielectric relaxation, and PI and PtBS behaved as the fast and much slower components, respectively. In those blends, the PI relaxation was thermo-rheologically complex because the slow PtBS chains quenched the dynamic frictional heterogeneity in the time scale of the PI relaxation. In contrast, the viscoelastic response of PtBS was thermo-rheologically simple because the fast PI chains smeared the heterogeneity for PtBS. Nevertheless, PtBS showed no ordinary relaxation associated with the entanglement plateau but did exhibit Rouse-like relaxation slower than the entanglement-free Rouse process. This slow Rouse-like relaxation was attributed to the pseudo-constraint release mechanism for the PtBS chains activated by the global motion of the PI chains. A simple model based on this molecular picture described the G* data of the blends well.

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Section: Introductionmentioning

confidence: 99%

Dynamics in miscible blends of polyisoprene and poly(p-tert-butyl styrene): thermo–rheological behavior of components

Chen

Watanabe

2011

Polym J

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“…Not so frequently, even solid‐state NMR is being used to study the miscibility of polymer blends 11. In a DSC, the existence of a single T g between those of the constituent polymers has been accepted as a general criterion for miscibility while two T g s at the original position represents an immiscible blend 10, 12. According to Kammar et al,13 the typical domain size sensitivity of conventional DSC to phase‐separated polymeric materials is ca.…”

Section: Introductionmentioning

confidence: 99%

“…The introduction of modulated differential scanning calorimeter (MDSC) has permitted to understand the polymer miscibility in a better way compared with conventional DSC 15, 16. It is important to note that the polymer blends that are judged miscible based on conventional DSC have shown two calorimetric T g s based on heat capacity ( C p ) results obtained from MDSC 12, 17. The results of these experiments have made clear that the indication of a single T g by DSC is not a universal feature to judge the polymer miscibility 12.…”

Section: Introductionmentioning

confidence: 99%

“…It is important to note that the polymer blends that are judged miscible based on conventional DSC have shown two calorimetric T g s based on heat capacity ( C p ) results obtained from MDSC 12, 17. The results of these experiments have made clear that the indication of a single T g by DSC is not a universal feature to judge the polymer miscibility 12. The reversing signal in a MDSC provides an excellent resolution of the glass transition by separating the heat capacity from the nonreversing processes such as enthalpy relaxation and crystallization 16.…”

Section: Introductionmentioning

confidence: 99%

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Influence of poly(ether imide) on the free volume hole size and distributions in poly(ether ether ketone)

Ramani

Alam

2012

J of Applied Polymer Sci

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Blends of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) were examined for their miscibility at the nanoscopic level using positron annihilation lifetime spectroscopy (PALS) and modulated differential scanning calorimetry (MDSC). The free volume results obtained from PALS reveal that PEEK and PEI exhibit high degree of miscibility showing interlamellar segregation when the PEI content in the blend is !50%. Although the average free volume sizes of PEEK and PEI are nearly same, a clear distinction could be made from their size distribution. The free volume of PEI is found to be narrow as compared with PEEK. Also, herein, we provide the first evidence of the influence of interlamellar segregation on the free volume distribution in a polymer blend. The crystalline structure of the blend was studied by X-ray scattering and the surface morphology was examined by scanning electron microscopy (SEM). The MDSC results indicate the presence of a possible rigid amorphous fraction (RAF) and corroborate the positron lifetime and X-ray scattering results.

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“…Although immiscible blends show distinct glass transition temperatures T g , which could shift with respect to the values of the component polymers [2], the situation is complicated by the presence of two T g , also in miscible blends [3,4]. * In the case of elastomers, the advantages for blending are numerous due to an alternative of synthesizing a new elastomer, older and better-characterized rubbers can be employed, hopefully yielding an ideal complement of properties from the blended materials.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence on free volume in cured natural rubber and styrene-butadiene rubber blends

et al. 2011

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A systematic study on the evolution of free volume as a function of the temperature in vulcanized at 433 K natural rubber (NR) and styrene butadiene rubber (SBR) in 25-75, 50-50, 75-25 NR-SBR (percent content of pure NR and SBR, respectively) blends was studied by positron annihilation lifetime spectroscopy. All samples were prepared with sulfur and TBBS (n-t-butyl-2-benzothiazole sulfenamide) as accelerator. The glass transition temperatures of the samples studied were determined by differential scanning calorimetry (DSC) and from lifetime data. In general, a sigmoidal-like complex behavior of the long-lived lifetime component, linked to the nanohole free volume, as a function of the temperature was found. For SBR, the slope of the ortho-positronium lifetime against temperature curves could be well-fitted using a linear function. For blends and also for NR, two different linear functions were necessary. This last behavior is explained in terms of the supercooled process involving a reconfiguration of the elastomeric chains. In the case of blends, the state of cure of NR and SBR in each NR-SBR sample was also taken into account in the discussion of the results obtained. Besides, thermal expansion coefficients of the free volumes in the transition and glassy region of all compounds were estimated. The differences observed in the values of this parameter are discussed by taking into account the morphology and formulation of each blend, the crosslink densities, and the role of the interphases formed between both NR and SBR elastomers.

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Two DSC Glass Transitions in Miscible Blends of Polyisoprene/Poly(4-tert-butylstyrene)

Cited by 62 publications

References 32 publications

Dynamics in miscible blends of polyisoprene and poly(p-tert-butyl styrene): thermo–rheological behavior of components

Dynamics in miscible blends of polyisoprene and poly(p-tert-butyl styrene): thermo–rheological behavior of components

Influence of poly(ether imide) on the free volume hole size and distributions in poly(ether ether ketone)

Temperature dependence on free volume in cured natural rubber and styrene-butadiene rubber blends

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