“…In order to confirm the response of the TEMPO to the matrix glass transition of the end functionalized PI, the same probe was incorporated in a non functionalized PI of the same microstructure and MW (not shown). In agreement with earlier results 31 and data on natural rubber , we found the same T 50G − T g proximity for both polymers. 4 (a) Extreme outer peak separation 2 Ã zz vs temperature for PI-1,4-S doped with TEMPO (▪)and K-TEMPO (·).…”
Endfunctionalized polyisoprenes (PI) and polystyrenes (PS) with
either one sulfonate or
ammonium end group and α,ω-macrozwitterionic PI and PS have been
synthesized and investigated by
CW-EPR using the spin probe technique. From the extrema separation
of the temperature dependent
spectra a characteristic temperature, T‘50G, is
introduced which can be employed as a measure for the
temperature dependence of the chain end association in these telechelic
ionomers. In this way it is shown
that the mobility of an ionic 2,2,6,6-tetramethylpiperidine-N-oxyl
derivative is dramatically restricted
when compared to the corresponding nonionic probe. For PI the
reduction in probe mobility corresponds
to temperature shifts as high as 140 K relative to the dynamics of the
polymer, indicating the presence
of highly immobilized ion multiplets. As shown by the temperature
dependent data, the method is
sensitive to additional immobilization of the ionic domains induced by
bulky substituents adjacent to the
ionic chain ends. Comparison of the EPR results with structural
data from SAXS measurements reveals
that the main factors governing the dynamics of multiplets are the
chemical type of ionic end group and
the nature of the polymer backbone. Analysis of the EPR data for
telechelic PS shows that in high-T
g
polymers the dynamics of the ionic aggregates occurs at comparable time
scales as the dynamics of the
polymer backbone.
“…In order to confirm the response of the TEMPO to the matrix glass transition of the end functionalized PI, the same probe was incorporated in a non functionalized PI of the same microstructure and MW (not shown). In agreement with earlier results 31 and data on natural rubber , we found the same T 50G − T g proximity for both polymers. 4 (a) Extreme outer peak separation 2 Ã zz vs temperature for PI-1,4-S doped with TEMPO (▪)and K-TEMPO (·).…”
Endfunctionalized polyisoprenes (PI) and polystyrenes (PS) with
either one sulfonate or
ammonium end group and α,ω-macrozwitterionic PI and PS have been
synthesized and investigated by
CW-EPR using the spin probe technique. From the extrema separation
of the temperature dependent
spectra a characteristic temperature, T‘50G, is
introduced which can be employed as a measure for the
temperature dependence of the chain end association in these telechelic
ionomers. In this way it is shown
that the mobility of an ionic 2,2,6,6-tetramethylpiperidine-N-oxyl
derivative is dramatically restricted
when compared to the corresponding nonionic probe. For PI the
reduction in probe mobility corresponds
to temperature shifts as high as 140 K relative to the dynamics of the
polymer, indicating the presence
of highly immobilized ion multiplets. As shown by the temperature
dependent data, the method is
sensitive to additional immobilization of the ionic domains induced by
bulky substituents adjacent to the
ionic chain ends. Comparison of the EPR results with structural
data from SAXS measurements reveals
that the main factors governing the dynamics of multiplets are the
chemical type of ionic end group and
the nature of the polymer backbone. Analysis of the EPR data for
telechelic PS shows that in high-T
g
polymers the dynamics of the ionic aggregates occurs at comparable time
scales as the dynamics of the
polymer backbone.
“…The effects of the molecular size of the spin probe on the correlation times and activation energies of probes in natural rubber have been quantitatively discussed by Tórmálá and Weber. 19 The TgQQ behavior of Tempol in PS has been reported,20 with Tbog = 250 K as compared to T50G = 390 K for BzONO in pure PS. Tempol may be "seeing" a subglass transition or it may be responding to a larger available volume as a result of thermal expansion in the glassy state.…”
“…On the other hand, it is important to elucidate the effect of the probe structure on its reorientation dynamics in the given polymer. Detailed examination has shown [12] that the main factor determining the dynamics of the probe is its volume [12] and not its mass [11]. Therefore, probe motion can be described in terms of the flee-volume model of the particle mobility in condensed media [13,14].…”
A general version of the Kusumoto-Bullock free volume model for reorientation dynamics of spin probe in solid polymers is described. Its application enables one to obtain simultaneously the size parameter of a segment and the kinetic-energy parameter of segmental mobility. These data, along with theoretical knowledge of the conformational microstructure and conformational dynamics, allow a discussion of molecular mobility in terms of concrete conformation-segmental motion mechanisms. Participation of one-barrier transitions of the type PptqQ-+ Pp'g+-q'Q, and two-barrier transition of the type gauche-migration, creation and annihilation of kink sequence was observed for linear polyethylene. In agreement with the conformational microstructure, it was found for isotactic polypropyIene that Schatzki's crankshaft motions of four-member segments might be involved.
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