Component Dynamics in Miscible Blends of 1,4-Polyisoprene and 1,2-Polybutadiene

Abstract

The effects of blending on the rheology of the individual components in highly entangled miscible blends of 1,4-polyisoprene (PI) and 1,2-polybutadiene (1,2-PB) are investigated. Blend component contributions to the dynamic modulus, G*(<v), are recovered over the full composition range by complementing dynamic mechanical rheometry with infrared polarimetry. Distinct relaxations for each component are observed. Analysis of the modulus amplitudes of the component G* ( ) contributions reveals that the behavior of the slower relaxing component, 1,2-PB, compares well with constraint release scaling predictions. Each component is found to have a different average number of skeletal bonds between entanglements, in agreement with the predictions of an existing entanglement theory. The components appear to adopt a single reptation tube diameter and a mutual modulus shift factor, 6r(T), in each blend. Analysis of the frequency dependence of the component G*(a>) contributions indicates that each component's relaxation is governed by a distinct apparent glass transition temperature, Tt, and that at a constant T -Tg blend composition only mildly influences the component relaxation times. A mild increase in the 1,2-PB relaxation time in the blend suggests a possible increase in the 1,2-PB friction factor in the presence of PI.

Proton NMR investigation of the local dynamics of PEO in PEO/PMMA blends

“…A linear extrapolation at f Å 1.0 yields (1/T 1 ) max Å 14.1 s 01 i.e., T 1 É 70 ms at 60 MHz, a value which is much higher than that measured. This extrapolated value for the homopolymer PEO coincides with that measured for the maximum proton relaxation rate in the complex PEO-(LiClO 4 01 at 60 MHz. For this reason, the linear dependence of the maximum proton relaxation rate for PEO in PEO/PMMA blends, which is observed over the limited range of concentration 0.20°f õ 0.50, will be assumed to hold over the whole concentration range.…”

Spinodal Decomposition in Binary Blend of Poly(methyl methacrylate)/Poly(α‐methyl styrene‐co‐acrylonitrile): Analysis of Early and Late Stage Demixing

“…The design, selection, and performance of polymer blends crucially depend on the ability to predict and control their phase behavior and morphology. Many techniques have been extensively used to investigate the miscibility, molecular dynamics and phase separation kinetics of polymer blends, such as, differential scanning calorimetry (DSC), [1,2] NMR, [3][4][5][6] dielectric spectroscopy, [7][8][9][10][11][12] dynamic mechanical measurements, [13][14][15][16][17] and time-resolved light scattering. [18][19][20][21][22][23] We have recently investigated the miscibility, dielectric spectroscopy, viscoelastic properties and morphology under Summary: The phase separation kinetics of a poly(methyl methacrylate), PMMA, and poly(a-methylstyrene-co-acrylonitrile), PaMSAN, blend exhibiting a LCST-type phase diagram have been investigated as functions of temperature and demixing time for the near critical composition (PaMSAN/PMMA ¼ 25:75) using a time-resolved light scattering technique.…”

Broadband Dielectric Spectroscopy for Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) Blend

“…Many techniques have been extensively used to investigate the miscibility and molecular dynamics of polymer blends, such as, differential scanning calorimetry (DSC), 1, 2 NMR, [3][4][5][6] dielectric spectroscopy, [7][8][9][10][11][12] and mechanical measurements. [13][14][15][16][17] The dielectric relaxation spectroscopy is a powerful tool cable of providing information about the molecular dynamics and the nature of the interactions in blends by monitoring the motion of dipolar groups attached to molecular chains. The dielectric spectroscopy has been widely used in polymer relaxation analysis and has the advantage over the dynamic mechanical methods in that it covers a much wider frequency range.…”