Temperature dependence of the mean size of polyphenyleneoxide microvoids, as studied by Xe sorption and 129Xe NMR chemical shift analyses

Abstract

Both the Xe sorption isotherms and 129 Xe NMR spectra of poly(2,6-dimethyl-1,4-phenylene oxide), PPO, were obtained across a temperature range of -55 1C to þ 80 1C to investigate the temperature dependence of the gas sorption and the unrelaxed volume of PPO. All of the obtained sorption isotherms were analyzed based on the dual-mode sorption model, and the Langmuir saturation constant, C H 0 , which corresponds to the unrelaxed volume, was determined by curve fitting. The values of C H 0 increased linearly with decreasing temperature, and the obtained temperature was almost identical to the glass transition temperature, T g , of PPO when the C H 0 value was extrapolated to 0. The 129 Xe NMR chemical shift of 129 Xe in the PPO showed a nonlinear, low-field shift with increasing Xe pressure at temperatures below the T g . The mean volumes of individual microvoids were determined at each temperature based on the 129 Xe NMR chemical shift analysis, assuming a fast exchange of the Xe atoms between the Henry and Langmuir sorption sites. The temperature dependence of the individual microvoid volumes was similar to that of C H 0 .

Determination of glass transition temperature of polyimides from atomistic molecular dynamics simulations andmachine‐learningalgorithms

“…A commonly used method to determine T g for a polymer is to calculate its density as a function of temperature, that is, to obtain the ρ(T) curve. [15,[39][40][41][42][43] One example is shown in Figure 2 for ULTEM (i.e., 4,4'BPADA + MPD). The value of T g can be determined from the intersection of the two linear fits to ρ(T), one for the lower and the other for the higher temperature region.…”

“…A commonly used protocol to determine T g for a polymer is to calculate its density as a function of temperature, i.e., to obtain the ρ(T ) curve. [35][36][37][38][39][40] One example is shown in Fig. 2 for ULTEM (i.e., 4,4'BPADA+MPD).…”

129Xe: A Wide-Ranging NMR Probe for Multiscale Structures

“…Suzuki et al studied several other glassy polymeric systems, including poly(2,6dimethyl-1,4-phenylene oxide) (PPO) [88], PPO/PS blends [89], and tetramethyl bisphenol A polycarbonate (TMPC)/PS blends [90], using 129 Xe NMR and Xe sorption measurements. For these studies, the sorption behavior of xenon in glassy polymers was described using a dual-mode adsorption model.…”

Characterization of the microvoids of a tetramethyl polycarbonate/polystyrene blend system using Xe sorption measurements and 129Xe NMR spectroscopy

“…Most recently, we have reported the Xe sorption properties and 129 Xe NMR spectra of PPO measured at various temperatures. 10 By analyzing the 129 Xe NMR chemical shift, it was observed that the mean diameter of the microvoids in PPO increases linearly with decreasing temperature, and the extrapolated value at the glasstransition temperature was close to 4.4 Å , which is the diameter of a Xe atom. Furthermore, the characteristic cavity in a crystalline region of poly(4-methyl-1-pentene) (PMP) was investigated using gas permeation and 129 Xe NMR measurements of PMP membranes with various degrees of crystallinity.…”

“…[8][9][10][11][12][13][14][15] As the Xe atom has a very large polarizability, the 129 Xe NMR signal is sensitive and easily influenced by its environment; specifically, the induced 129 Xe NMR chemical shift is strongly altered by the Xe electron density. The NMR chemical shifts for glassy polymers exhibited a nonlinear low-field shift with an increasing amount of Xe sorption because of the fast exchange of Xe between the Henry and Langmuir sites; therefore, we calculated the NMR chemical shifts for each site using the dual-mode sorption parameters.…”