The effect of dimethylsulfoxide on the dissociation process of physical complexes of polyacrylonitrile in N,N‐dimethylformamide

Abstract

The physical properties and gelation behavior of polyacrylonitrile (PAN) solutions were investigated in mixed solvents of N,N‐dimethylformamide (DMF) and dimethylsulfoxide (DMSO). For the individual solubility parameters, DMSO had the polar term closer to PAN than DMF. Small‐angle X‐ray scattering profiles and Fourier transform infrared spectra of 20 wt% PAN solutions confirmed that the internal structure and intermolecular complexes between nitrile groups were broken up by the DMSO molecules. The slope of Cole–Cole plot, a measure of the solution heterogeneity, increased with the mole fraction of DMSO (XDMSO) via three distinct zones. The homogenization was particularly noticeable in Zone 1 (0.0 < XDMSO < 0.4) and Zone 3 (0.7 < XDMSO < 1.0). The Huggins constant and UV‐visible absorption at 268 nm of dilute solutions decreased sharply above XDMSO of 0.7 in Zone 3. This indicated a marked increase of PAN solubility by dissociating the intramolecular complexes between nitrile groups. In Zone 1, the storage modulus of 20 wt% PAN solutions decreased but loss modulus remained almost constant with XDMSO at lower frequency below 1 rad s−1, indicating the weakening of the true entanglement points of the intermolecular complexes. The mechanism indicated that the intermolecular complexes between nitrile groups were dissociated by DMSO earlier than the intramolecular ones. © 2017 Society of Chemical Industry

Rheological Investigation of Relaxation Behavior of Polycarbonate/Acrylonitrile-Butadiene-Styrene Blends

“…The logarithmic plot of storage modulus (G′) versus loss modulus (G″), that is, the so-called modified Cole-Cole plot, is depicted in Figure 8 and the initial slopes at the various blend ratios and measurement temperatures are listed in Table 3 . A slope of 2 in the plot represents an isotropic and homogeneous system without any internal structure or specific intermolecular interactions [ 22 , 23 , 24 , 25 , 26 ]. As the content of ABS increases, the slopes of the curves decreased.…”

“…Hence, a knowledge of the rheological properties of materials is significantly essential for determining processing parameters. In addition, rheology can be applied to both the processing conditions and analysis the chain motion of polymer blends because bulky and systematic responses can be obtained by involving microscopic chain deformation at given controllable processing conditions such as shear rate, strain, temperature and time [ 21 , 22 , 23 , 24 , 25 , 26 ].…”

Malleable Hydrogel Embedded with Micellar Cargo‐Expellers as a Prompt Transdermal Patch

“…Owing to the inherent heterogeneity of the PHEMA/PVA gel, it shows a lower initial storage‐modulus ( G ′) slope (0.86) than that of the PVA gel (1.15) (generally, the G ′ curve of an ideal homogeneous system has a slope of 2) (Figure 3f). [ 61,62 ] It should be noted that the G ′ of the H0‐gel exceeds that of the H43‐gel through crossover at about 10 rad s −1 , and the gap widens with increasing frequency. This result suggests that while the neat PVA gel prefers to store energy to some extent, the embedded PHEMA gel promptly consumes external stress; this energy‐absorbing behavior is strongly correlated with molecular relaxation (Figure 3f).…”