Molecular probe dynamics and free volume in organic glass-formers and their relationships to structural relaxation: 1-propanol

Abstract

A joint study of the rotational dynamics and free volume in amorphous 1-propanol (1-PrOH) as a prototypical monohydroxy alcohol by electron spin resonance (ESR) or positron annihilation lifetime spectroscopy (PALS), respectively, is reported. The dynamic parameters of the molecular spin probe 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and the annihilation ones of the atomic ortho-positronium (o-Ps) probe as a function of temperature are compared. A number of coincidences between various effects in the ESR and PALS responses at the corresponding characteristic ESR and PALS temperatures were found suggesting a common origin of the underlying dynamic processes that were identified using viscosity (VISC) in terms of the two-order parameter (TOP) model and broadband dielectric spectroscopy (BDS) data.

Molecular probe dynamics and free volume heterogeneities in n-propanol confined in a regular MCM-41 matrix by ESR and PALS

“…Similar changes in the Arrhenius plot of another spectraldynamic quantity, namely, correlation time in the respective motion regimes, s slow c , s fast c at the corresponding characteristic ESR temperatures, T slow,s Xi and T fast,s Xi were found. 24 Recently, a synergic approach consisting in a combination of ESR and PALS techniques was used on a series of representatives of organic compounds of various structural types in the ordinary bulk state. [24][25][26][27] They included apolar or slightly polar compounds, i.e., crystaline n-alkanes or amorphous polymers, 25 polar protic ones, i.e., mono-and polyalcohols 24,26 and polar aprotic substances 27 of small molecular, oligomeric and polymer kinds.…”

Free-Volume Evolution of 1-Propanol Confined in Variously Filled Regular Mesopores of SBA-15 Matrix

“…The confined 1-PrOH needs more energy for the transition from the glassy state to the supercooled liquid state. Similarly, the onset temperature T b2 to the plateau region, where the o-Ps lifetime is a quasi-constant [1], is shifted to a higher temperature compared to bulk state. In this plateau region confined 1-PrOH for all these pore fillings as well as 1-PrOH in bulk state have the comparable lifetimes.…”

“…Important temperatures are indicated by arrows. The basic values of the measured free-volume characteristics are in Table I, the values for the bulk 1-PrOH were taken from work [1]. From the results it follows that The glass transition temperature Tg, onset temperature of the plateau T b2 , free-volume at Tg and expansion coefficient α scl of free-volume at Tg for the supercooled liquid state for a series of the samples with different content of 1-propanol.…”

“…The glass * corresponding author; e-mail: ondrej.sausa@savba.sk transition temperature is T DSC g = 100 K [7]. Other characteristics of the bulk 1-PrOH can be found in work [1].…”

“…The aim of this work is to show the changes in the annihilation behavior of ortho-positronium (o-Ps) in 1-PrOH confined in regular mesopores of the SBA-15 matrix compared to the bulk state [1] as a function of different amounts of 1-PrOH in the pores, as well as of the temperature. As is known, the SBA-15 matrix is a hard inorganic matrix with a polar inner surface [2].…”