Thermodynamic interactions in model polyolefin blends obtained by small-angle neutron scattering

Balsara, Nitash P.; Fetters, L. J.; Hadjichristidis, N.; Lohse, David J.; Han, C. C.; Graessley, William W.; Krishnamoorti, Ramanan

doi:10.1021/ma00049a009

Cited by 187 publications

(293 citation statements)

References 16 publications

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“…40 Their measured densities gave consistent results with an equal degree deuteration according to the chemical formula C4D2.8H5.2. 41 The blend and the diblock systems are symmetric with respect to their molecular weight and composition. Size exclusion chromatography (SEC) was not conducted on the first block of the diblock.…”

Section: Methodsmentioning

confidence: 99%

Abnormal Pressure Dependence of the Phase Boundaries in PEE−PDMS and PEP−PDMS Binary Homopolymer Blends and Diblock Copolymers

et al. 2001

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Both polymer blends and diblock copolymers have been investigated with small-angle neutron scattering (SANS) in varying temperature and pressure fields. Four samples were studied: a polymer blend of near critical composition and the corresponding symmetric diblock copolymer of poly-(ethylethylene) (PEE) and poly(dimethylsiloxane) (PDMS) and two further symmetric diblock copolymers of poly(ethylenepropylene) (PEP) and PDMS differing in their molecular mass. From the SANS results the phase transition temperatures, the Flory-Huggins interaction parameter, the Ginzburg number, and the sizes of the chain were determined. As the transition temperature and the Flory-Huggins parameter are independently determined from the SANS data, the Clausius-Clapeyron equation offers a cross-check of the theoretical background used for SANS analysis. The resulting parameters showed for all samples qualitatively similar behavior. In particular, a quite unusual decrease of the phase boundaries in low increasing pressure regimes was observed. Analysis based on the Clausius-Clapeyron equation shows that the reason for this pressure-induced decrease of the phase boundary is a dominating increase of the entropic Flory-Huggins parameter. The Ginzburg parameter was found constant with pressure. The size of the diblock copolymer chains changes with temperature and pressure. Beyond the chain stretching observed near the ordering temperatures (T ODT) for both decreasing temperature and applied pressure, a discontinuous decrease of the chain size was consistently found at the TODT. The chain size vs temperature was found to follow a scaling behavior with slightly different exponents in the disordered and the ordered regimes consistent with former simulation calculations.

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Section: Methodsmentioning

confidence: 99%

Abnormal Pressure Dependence of the Phase Boundaries in PEE−PDMS and PEP−PDMS Binary Homopolymer Blends and Diblock Copolymers

et al. 2001

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“…While the mixture of H-and D-latex beads in solution is likely to be ideal, because it is random in the latex suspension just before the gel point, the melts of H-and D-chains are usually not ideal: a monomeric (Flory-Huggins) interaction parameter χ between H and D monomers has to be introduced [55][56][57] . Eq.…”

Section: Iii1 Structural Evolution During Annealing Of Pure H-d-matrmentioning

confidence: 99%

Modeling of Intermediate Structures and Chain Conformation in Silica–Latex Nanocomposites Observed by SANS During Annealing

et al. 2012

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Abstract:The evolution of the polymer structure during nanocomposite formation and annealing of silica-latex nanocomposites is studied using contrast-variation small angle neutron scattering.The experimental system is made of silica nanoparticles (R si ≈ 8 nm) and a mixture of purpose-synthesized hydrogenated and deuterated nanolatex (R latex ≈ 12.5 nm). The progressive disappearance of the latex beads by chain interdiffusion and release in the nanocomposites is analyzed quantitatively with a model for the scattered intensity of hairy latex beads and an RPA description of the free chains. In silica-free matrices and nanocomposites of low silica content (7%v), the annealing procedure over weeks at up to T g + 85 K results in a molecular dispersion of chains, the radius of gyration of which is reported.At higher silica content (20%v), chain interdiffusion seems to be slowed down on time-scales of weeks, reaching a molecular dispersion only at the strongest annealing. Chain radii of gyration are found to be unaffected by the presence of the silica filler. Tables: 5 2 Figures: 7

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“…The degree of deuteration was not measured independently, but it is known that only limited isotope exchange takes place during such a process. 28 The level of exchange depends on the reaction conditions. The samples were all saturated under similar conditions and the measured densities are consistent with an equal degree deuteration.…”

Section: A Sample Preparationmentioning

confidence: 99%

Thermal composition fluctuations near the isotropic Lifshitz critical point in a ternary mixture of a homopolymer blend and diblock copolymer

Schwahn

Mortensen

Frielinghaus

et al. 2000

The Journal of Chemical Physics

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We have studied thermal composition fluctuations of a ternary symmetric homopolymer/diblock copolymer system of PEE/PDMS/PEE-PDMS ͓PEE and PDMS being poly͑ethyl ethylene͒ and poly͑dimethyl siloxane͒, respectively͔ in its disordered state with small angle neutron scattering for concentration ⌽ of diblocks up to 15%. The phase diagram shows three characteristic regimes; ͑1͒ below the Lifshitz concentration ⌽ LL Х9%; ͑2͒ in the very near vicinity of the Lifshitz concentration; and ͑3͒ above ⌽ LL . In the regime ͑1͒ of low diblock content the maximum neutron intensity is obtained at Qϭ0 and phase separation into macroscopic large domains is observed at low temperatures. With increasing diblock content the thermal fluctuations indicate a crossover from 3d-Ising to isotropic Lifshitz critical behavior with critical exponents of the susceptibility ␥ ϭ(1.62Ϯ0.01) and correlation length ϭ(0.99Ϯ0.04) appreciably larger than in the 3d-Ising case. In the structure factor this crossover is accompanied by a strong reduction of the Q 2 term leading to the dominance of the Q 4 term; the restoring force of the thermal fluctuations is strongly reduced as the Q 2 term is proportional to the surface energy. Near the Lifshitz critical temperature a further crossover was observed leading to the appreciably larger critical exponents ␥ϭ(2.44Ϯ0.08) and ϭ(1.22Ϯ0.08) and a stabilization of the disordered regime visible through a decrease of the phase boundary by nearly 10 K. This crossover is interpreted by the formation of fluctuation induced inhomogeneous diblock distribution at the interface of the thermal fluctuations. ͑2͒ In the intermediate regime between 9% and 12% diblock content the Lifshitz line was crossed twice upon increasing the temperature from low to high temperatures; at low and high temperatures the structure factor S(Q) shows diblock character ͑maximum of S(Q) at Q 0͒ while at intermediate temperature blendlike character ͑maximum of S(Q) at Qϭ0͒. At low temperatures a transition to a bicontinuous microemulsion phase is proposed. ͑3͒ At diblock content of 15% a weak order-disorder transition was observed. The data in the Lifshitz critical range and larger than the Lifshitz line could be interpreted by a recently developed theory of Kielhorn and Muthukumar who considered the effect of thermal fluctuations in ternary homopolymer/diblock copolymer samples and from which the Flory-Huggins parameter could be evaluated.

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Thermodynamic interactions in model polyolefin blends obtained by small-angle neutron scattering

Cited by 187 publications

References 16 publications

Abnormal Pressure Dependence of the Phase Boundaries in PEE−PDMS and PEP−PDMS Binary Homopolymer Blends and Diblock Copolymers

Abnormal Pressure Dependence of the Phase Boundaries in PEE−PDMS and PEP−PDMS Binary Homopolymer Blends and Diblock Copolymers

Modeling of Intermediate Structures and Chain Conformation in Silica–Latex Nanocomposites Observed by SANS During Annealing

Thermal composition fluctuations near the isotropic Lifshitz critical point in a ternary mixture of a homopolymer blend and diblock copolymer

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