Molecular Mobility of Amorphous Chain Segments of Ethylene−Methyl Methacrylate Copolymer Films as a Function of Temperature Estimated by Positron Annihilation, X-ray Diffraction, and ¹³C NMR

Abstract

The relationship between the morphology and the mechanical properties of copolymer ethylene-methyl methacrylate (EMMA) films with different MMA contents was investigated as a function of temperature by using positron annihilation, X-ray diffraction, and 13 C solid-state NMR. To make clear the effect of MMA side groups on the morphology and molecular mobility of EMMA as a function of temperature, the characteristics of EMMA were discussed together with those of copolymer (dimethylamino)ethyl methacrylate (EDAM) and branched polyethylene. Three kinds of transitions were confirmed by positron annihilation: the first at temperatures around -130 °C, the second around -40 °C, and the third around 50 °C. The first and the second transitions were due to the commencement of molecular motions, which can remove trapped electrons from their shallow potentials, while the third transition around 50 °C was attributed to the partial melting of unstable small crystallites. These transitions were in good agreement with the results obtained from differential scanning calorimetry (DSC) and X-ray measurements. Namely, the DSC curves of EMMA provided a peak around -25 to -30 °C corresponding to the second transition and a small peak around 43-48 °C corresponding to the third transition. Lifetime (τ 3) showed no obvious change between branched polyethylene and EMMA-I melt films. This result can be explained within the framework of the spur model of Ps formation in terms of the trapping of positrons (and may be electrons) by the polar groups, -CdO, in EMMA.

Characteristics of Ethylene−Methyl Methacrylate Copolymer and Ultrahigh Molecular Weight Polyethylene Composite Filled with Multiwall Carbon Nanotubes Prepared by Gelation/Crystallization from Solutions

“…Some properties of these polymers are listed in Table . The detailed characteristics were described elsewhere. , …”

“…The detailed characteristics were described elsewhere. 26,27 Figure 1a,b shows photo images of the MWNTs observed by SEM (JEOL 6700). Image (b) is the enlargement of image (a), which shows uniform diameter distribution of the MWNTs prepared by vapor ablating technique.…”

Molecular Dynamics Simulation of Synthetic Polymers

“…The di-block copolymers in melt state have been studied by divers researcher groups, due to great interesting from the point view of the dielectric and dynamic-mechanics behavior (Alig et al, 1992;Encinar et al, 2008;Karatasos et al, 1996;Kotaka and Adachi, 1997;Kyritsis et al, 2000;Ma et al, 2003;Moreno and Rubio, 2002;Vogt et al, 1992). Dynamic-mechanical spectroscopy is an important technique to characterize the deformation of polymeric materials applying, for example, a tension to material.…”

Dielectric and molecular dynamics study of the secondary relaxations of poly(styrene-co-methylmethacrylate) copolymers: Influence of the molecular architecture

“…In the case of block copolymers in which the two blocks have well separated T g 's, the dynamics of the low-T g blocks can be affected by the presence of a rigid phase, thus being rather different than the dynamics of the corresponding homopolymer [4][5][6][7][8][9]. In a recent work, using dielectric relaxation and dynamic mechanical spectroscopy techniques, Encinar et al [10] have studied the dynamics of the polystyrene-b-poly(t-butyl acrylate) (PS-b-PtBa) copolymers.…”