Glass transition dynamics in a compatible blend by two-dimensional solid-state NMR

Abstract

Chain motion at the glass transition of one component in a compatible blend was observed by two-dimensional solid-state NMR spectroscopy. A blend of polystyrene and carbon-13-labeled poly-(2,6-dimethylphenylene oxide) at two concentrations was studied by carbon-13 spectroscopy as a function of temperature and mixing time in the vicinity of the thermal glass transition. Chain motion of the labeled polymer on a millisecond time scale commenced at temperature of approximately 10 °C below the thermal glass transition in contrast to a single-component polymeric glasses which only show such motion at temperatures above the glass transition. The motion exhibited the characteristics of rotational Brownian diffusion with an associated broad distribution of exponential correlation times. Again in contrast to single-component polymeric glasses, the distribution is considerably broader and can only be simulated by bimodal or trimodal distribution of correlation times. Each of the modes involves a distribution of exponential correlation times, and that given by a stretched exponential correlation function was employed. The relative weighting of the modes corresponded to local concentration fluctuations; calculated from a lattice model. The dynamic heterogeneity associated with these concentration fluctuations exceeds the heterogeneity generally encountered in single-component polymeric glasses.

Dynamics of PEO in Blends with PMMA: Study of the Effects of Blend Composition via Quasi-Elastic Neutron Scattering

“…[PVME] by 3-4 orders of magnitude, 15 and polystyrene and poly(2,6-dimethyl phenylene oxide) 16,17 by next to nothing. Another unique feature of the PEO/PMMA blend system is the nearly composition independent dynamics displayed by PEO.…”

Dynamic Heterogeneity in Fully Miscible Blends of Polystyrene with Oligostyrene

“…Both are considered as signatures of dynamic heterogeneities [1][2][3][4][5][6]. Theoretical models [7][8][9][10][11][12][13][14][15][16][17] have been considered in explaining these experimental features.…”

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

“…The final properties of the blend depend on the properties of the pure polymer components, miscibility and adhesion between the phases as well as the size and uniformity of the phase texture or morphology. 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.…”