Order and Mobility in Polycarbonate−Poly(ethylene oxide) Blends Studied by Solid-State NMR and Other Techniques

Polyvinyl pyrrolidone/polyvinyl alcohol (PVP/PVA) and polyvinyl pyrrolidone/starch (PVP/St) blends were prepared with different compositions. The compatibility studies indicate that PVP/PVA is compatible while PVP/St is incompatible. The addition of glycerol and glutaraldehyde can improve to some extent the phase separation behavior between PVP and St. The permittivity e 0 and the dielectric loss e 00 were measured in the frequency range 0.01 Hz up to 10 MHz and temperatures from 30 up to 90 C. It is found that the blend ratio (50/50) of both investigated systems is preferable for insulation purposes in comparable with the other blends under investigation. The data of the loss electric modulus M 00 was calculated from the dielectric parameters e 0 and e 00 and analyzed into three relaxation mechanisms ascribing the cooperative motion of the main and side chains s 1 (ab), the side chain motion s 2 (b) and the segmental motion of the groups attached to the side chains s 3 (bc). The activation energy corresponds to the second relaxation process DH 2 was calculated using Arrhenius equation and found to be in the range which justifies the presumption of b-relaxation process.

Section: Introductionmentioning

confidence: 93%

Biodegradable blends based on polyvinyl pyrrolidone for insulation purposes

El-Houssiny

Ward

Mansour

et al. 2011

“…We have not attempted to model our complicated multiphase blends like other previously published works. 16,17 The single exponential T 1 values of chitosan at 3.7 ppm, and ␤-hydrogen of PHB or P(HB-co-HV) at 5.4 ppm are not exactly the same but the differences are only 20 -30%, which may be accounted for by the complex morphology in semicrystalline blends. The trends in the T 1 values of chitosan, and ␤-hydrogen are clearly the same as shown in Figures 11 and 12.…”

Section: Crampsmentioning

confidence: 99%

Miscibility and morphology of chiral semicrystalline poly‐(R)‐(3‐hydroxybutyrate)/chitosan and poly‐(R)‐(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/chitosan blends studied with DSC, ¹H T₁ and T_1ρ CRAMPS

Cheung

Wan

2002

ABSTRACT:The phase structure of poly-(R)-(3-hydroxybutyrate) (PHB)/chitosan and poly-(R)-(3-hydroxybutyrateco-3-hydroxyvalerate) (P(HB-co-HV))/chitosan blends were studied with 1 H CRAMPS (combined rotation and multiple pulse spectroscopy).1 H T 1 was measured with a modified BR24 sequence that yielded an intensity decay to zero mode rather than the traditional inversion-recovery mode.1 H T 1 was measured with a 40-kHz spin-lock pulse inserted between the initial 90°pulse and the BR24 pulse train. The chemical shift scale is referenced to the methyl group of PHB as 1.27 ppm relative to tetramethylsilane (TMS) based on 1 H liquid NMR of PHB. Single exponential T 1 decay is observed for the ␤-hydrogen of PHB or P(HB-co-HV) at 5.4 ppm and for the chitosan at 3.7 ppm. T 1 values of the blends are either faster than or intermediate to those of the plain polymers. The T 1 decay of ␤-hydrogen is bi-exponential. The slow T 1 decay component is interpreted as the crystalline phase of PHB or P(HB-co-HV). The degree of crystallinity decreases with increasing wt % of chitosan in the blend. The fast T 1 of ␤-hydrogen and the T 1 of chitosan in the blends either follow the same trend as or faster than the weight-averaged values based on the T 1 of the plain polymers. Together with the observation by differential scanning calorimeter (DSC) of a melting point depression and one effective glass transition temperature in the blends, the experimental evidence strongly suggests that chitosan is miscible with either PHB or P(HB-co-HV) at all compositions.

“…Polymer blends are a matter of active interest in recent years, mainly due to being a versatile way to develop new materials with designed properties that cannot be reached by using single polymers. The development of new useful blends however is severely limited by the incompatibility of many polymer pairs of interest due to entropic reasons 1–3. Specific interactions, as well as the dilution of repulsive interactions by less favorable ones, can produce negative heats of mixing 4–7.…”

Section: Introductionmentioning

confidence: 99%

Interactions in blends containing chitosan with functionalized polymers

Castro

Gargallo

Leiva

et al. 2005

ABSTRACT:The phase behavior of blends containing chitosan with poly(vinyl-alcohol) (PVA) and poly(2-hidroxyethyl methacrylate) (P2HEM) was analyzed. Blends were obtained by casting from acetic acid solution (HAc) and 1,1,1,3,3,3 hexafluoro-2-propanol (HF2P) and studied by DSC, FT-IR, and TGA. The phase behavior of the blends of chitosan with PVA and P2HEM, studied by DSC, shows that the systems behave as one-phase systems in HAc as well as in HF2P according to the DSC results. According to the results of FT-IR analyses of the different absorptions of the blends, relative to the pure components, they show an important shift that is considered evidence of an interaction between the components of the blends. The thermogravimetric analysis of the blends and the pure components shows that the temperature for thermal degradation of the blends is higher that that of the pure components, irrespective of the solvent casting from which the mixture was obtained. These results are interpreted as the formation of a new product that corresponds to a compatible polymer blend. The compatibilization of these systems is attributed to strong interactions, like hydrogen bonds formation between the functionalized polymers and chitosan, due to the presence of interacting functional groups in all the polymers studied.