Deuteration Effects and Solubility Parameter Ordering in Blends of Saturated Hydrocarbon Polymers

Self Cite

The thermodynamic interactions between poly(4-tert-butyl styrene) [P(4tBS)] and 1,4-polyisoprene (PI; both hydrogenous) were obtained as functions of the temperature, PI molecular weight, and blend composition through the examination of miscible ternary blends of these two components with a common miscible labeled polymer [90% 1,2-deuterated polybutadiene (dPBD)] with small-angle neutron scattering. The thermodynamic interaction parameters between P(4tBS) and dPBD and between P(4tBS) and PI increased with increasing temperature and were consistent with lower critical solution temperature behavior. Although the binary blends of P(4tBS) and dPBD exhibited phase separation at elevated temperatures, the thermodynamic interaction parameters between P(4tBS) and PI remained large and negative and independent of the PI molecular weight. Finally, the thermodynamic interactions for PI and P(4tBS) depended strongly on the ratio of PI to P(4tBS) and were also sensitive to the amount of dPBD present in the ternary blend.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermodynamic interactions in blends of poly(4‐tert‐butyl styrene) and polyisoprene by small‐angle neutron scattering

Yurekli

Krishnamoorti

2004

Self Cite

“…Small changes in the covalent structure of a monomer can change the qualitative appearance of the phase diagram, as demonstrated a decade ago by the work of Graessley and coworkers 1–5. The mixing behavior of the melts of polymeric hydrocarbons is sensitive to structural changes as subtle as the substitution of deuterium for ordinary hydrogen 6–8. The introduction of long branches can affect the value of the Flory–Huggins χ parameter, as shown by measurements of blends of star and linear polystyrene (PS) 9.…”

Section: Introductionmentioning

confidence: 99%

Some mechanisms for subtle influences of stereochemical composition on the physical properties of macromolecules

Mattice¹,

Helfer²,

Rane³

et al. 2005

Coarse‐grained chains can be designed so that they successfully capture subtle effects arising from the local covalent structure of real chains. Constraining the conformations of the coarse‐grained chains with an appropriate rotational isomeric state model can achieve this objective. This claim has been documented by simulations of the dependence of the mixing behavior of polypropylene melts on the stereochemical composition of the chains; atactic polypropylene and isotactic polypropylene are miscible, but the replacement of either component with syndiotactic polypropylene can lead to immiscibility. This has also been documented by a comparison of simulations and infrared–visible sum frequency generation spectroscopy studies of the surface structures of atactic polystyrene and random copolymers of ethylene and propylene. The success of this method when the stereochemical composition is defined by side chains as small as CH3 suggests that it should also be applicable to other problems in which the influence of the stereochemical composition is less subtle because the stereochemistry is defined by larger side chains. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1271‐1282, 2005

“…Thermodynamic interactions in polyolefin blends have been shown to originate from induced‐dipole forces, but they differ in subtle, important ways, depending on the component structures 13, 14. SANS was used to determine interactions of blends, including solubility data,13, 14 light scattering was used to determine phase boundaries, and PVT measurements were used to establish cohesive energy data 13. However, isotope and microstructure interactions have been shown to contribute to χ, the interaction parameter, in that the mixtures of deuterated and protonated polymers are nonideal, having small repulsive thermodynamic interactions 7.…”

Section: Introductionmentioning

confidence: 99%

Characterization of polyolefin melts using the polymer reference interaction site model integral equation theory with a single‐site united atom model

Freischmidt

Shanks

Moad

et al. 2001

A general approach, based on the polymer reference interaction site model (PRISM) integral equation theory, suitable for characterizing arbitrarily complex polyolefin melts is described. We tested the method by calculating the melt structures of linear polyethylene (PE) and isotactic polypropylene (iPP) and the spinodal decomposition temperatures for PE/iPP blends. The computational expense of the PRISM calculation was reduced with a single‐site united atom model in which the polyolefin CH, CH2, and CH3 groups were approximated as chemically equivalent sites with spherically symmetric energetic interactions. The site–site interactions were defined by a potential function comprising a hard core with an attractive Lennard–Jones term. These energetic parameters were optimized with a central composite design strategy that enabled a simultaneous fit of experimental melt density and structure factor data. Values were obtained for PE and iPP individually and for common universal parameters that could potentially be used for all polyolefins. The rotational isomeric state–metropolis Monte Carlo (RMMC) technique was used to generate sets of conformers at specified temperatures covering the melt‐temperature range of the polymers. The characteristic ratio was used to assess the quality of the conformers and the RMMC method. Values of 9.68 for PE and 9.27 for iPP were obtained. The single‐chain structure factors calculated by the RMMC method were used to calculate the total structure factor for each melt. These were validated against published X‐ray diffraction results. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1803–1814, 2001