Morphological and Electronic Properties of Poly(ethylene glycol)/RAMEB Polyrotaxane and Polypyrrole Supramolecular Networks

Abstract

well their mechanical properties. The crosslinked polyrotaxanes are characterized by high mobility of the junctions, which considerably diminished the internal tension when a stimulus is applied, providing the enhancements of mechanical properties. [6][7][8][9][10][11] The blending of the CPs into the matrix, in one step reaction, leads to a more homogeneous network compounds. Recently, our efforts are being made in this directions and a versatile synthetic strategy was applied for the synthesis of such supramolecular networks by cross-linking of an insulated polyrotaxane with π-conjugated polyrotaxanes. [12] Due to controllable electrical conductivity and good thermal stability of polypyrrole (PPy), this approach has also been applied to the synthesis of composite materials based on PEGBA polyrotaxane with randomly methylated β-cyclodextrins (RAMEB). [13][14][15] Herein, we report the synthesis and characterization of a new composite material obtained by cross-linking of PEGBA/RAMEB polyrotaxane with 1,6-hexamethylene diisocyanate (HMDI). The addition of 10 wt% PPy into the PEGBA/RAMEB matrix showed improved physical, morphological as well electrical properties of the resulted cross-linked material. Moreover, the influences of the temperature and frequency on the electrical properties of the investigated PEGBA/RAMEB/PPy compound were investigated and compared with those of the pure PEGBA/RAMEB crosslinked material.The effect of 10 wt% polypyrrole (PPy) incorporation on the evolution of conductivity, dielectric constant, and dielectric loss by varying the temperature and frequency of amine-terminated poly(ethylene glycol)/randomly methylated β-cyclodextrins (PEGBA/RAMEB) polyrotaxane cross-linked with 1,6-hexamethylene diisocyanate is reported. This composite material shows an enhanced dielectric constant value of 25.6 (at 10 Hz) compared with 8.3 of the pure cross-linked PEGBA/RAMEB polyrotaxane. The values of the dielectric constant are consistent with the dielectric loss and conductivity results. The composite material shows that the direct current conductivity (σ DC ) at lower temperature is independent of frequency. In comparison, at higher temperature, σ DC is dependent on frequency, denoting that the conductivity of the composite material is a thermally activated process. Moreover, the presence of PPy significantly influences the morphology of the cross-linked PEGBA/RAMEB polyrotaxane. Addition of PPy into PEGBA/RAMEB material seems to be very attractive and should provide an opportunity to obtain desirable electronic properties.

Evaluation of the Chemical, Morphological and Dielectric Properties of Supramolecular Networks Consisting of Polyethylene Glycol Polyrotaxanes and Polystyrene/Semi‐Rotaxane with Hydroxypropyl‐β‐Cyclodextrins

“…[ 43 ] To get further information about β ‐relaxation process the frequency‐dependent ε ″ curves were analyzed by using Havriliak–Negami Equation () $$\begin{equation}\varepsilon = \varepsilon ^{\prime} - i\varepsilon ^{\prime\prime} = {\varepsilon _\infty } + \frac{{{\varepsilon _s} - {\varepsilon _\infty }}}{{{{\left[ {{{\left( {1 + i\omega {\tau _{{\rm{HN}}}}} \right)}^a}} \right]}^b}}}\end{equation}$$where ε s and ε ∞ represent the relaxed ( ω → 0) and unrelaxed ( ω →∞) values of the dielectric constant for the relaxation process, ω is the angular frequency (where ω = 2 πf ), τ HN is the HN relaxation time for the relaxation process associated with peak maxima, a and b are the broadening and skewing parameters, respectively. [ 44 ] The deconvolutions of β ‐relaxation process for all composite materials are shown in Figure . From the isochronal loss curves two dielectric peaks characteristic to the relaxation processes were identified, first peak at about −100 °C assigned to γ ‐relaxation (green lines) specific to PS chains [ 37 ] and the second one at −80 °C is the β ‐relaxation process (red lines) as consequence of the PEG segments motions in sub‐ T g temperature and also to the macrocycles sliding motion.…”