Swelling Kinetics and Rheological Behavior of Chitosan-PVA / Montmorillonite Hybrid Polymers

Abstract

This study involved preparation of hybrid polymer systems based on chitosan-poly(vinyl alcohol) (PVA) blends and modified Montmorillonite. These structures were characterized through microscopy and infrared spectroscopy; swelling measurements were performed to explore polymer absorbency. The behavior of polymer systems was studied through steady and oscillatory shear rheology. Results showed that more stable blend membranes were formed due to the strong interaction between chitosan and PVA. The membranes exhibited appreciable water uptake and were sensitive to saline solution with a slight shrinking.Shear viscosity was described by Cross model to characterize non-Newtonian behavior of all polymer solutions, the shear thinning increases with PVA content, while viscosity increases with chitosan extent. In oscillatory experiments, it was observed that all measured viscoelastic properties were influenced by blends composition and clay content. For all samples, results show a typical behavior of an entangled system in the case of semi-dilute macromolecular viscoelastic fluids. The dynamic moduli exhibited higher values for blends, compared with values of neat polymers, which are an indication of a good stability and a tendency of gel formation. Therefore, the prepared chitosan-PVA systems, which exhibited high swelling degrees and suitable viscoelastic properties, have promising applications in tissue engineering and membrane processes.

Effect of Side Groups on the Hydrolytic Stability of Thiolated and Disulfide Cross-linked Polyaspartamides

“…In Fig. 1(c) the broad signal at 3.00-2.55 ppm in CYS20HE80 spectrum was correlated to the 2H protons of methylene group in backbone (2) and 2H protons of CYS units in β position to amide group (4) and signal around 3.45-3.25 was related 2H protons of CYS and 2H protons of HE units in α position to amide groups (3,5). Protons at 3.75-3.55 ppm were assigned to 2H protons of HE in β position to amide group (6).…”

“…1(b) the broad signal at 3.00-2.60 ppm in CYS20DME80 spectrum was correlated to the 2H protons of methylene group in backbone (2), 6H protons of DME methyl groups (7) and 2H protons of CYS units in β position to amide group (4). Protons around 3.45-3.25 ppm was assigned to both 2H protons of CYS and DME units in α position to amide groups (3,5), while protons at 3.80-3.55 ppm related to 2H protons of DME in β position to amide group (6). The signal at 4.7 ppm was correlated 1H proton of methyne group in the backbone (1).…”

“…Protons at 3.00-2.60 ppm was assigned to 2H protons of methylene group in backbone (2), 2H protons of CYS units in β position to amide group (4) and 6H protons of DMP methyl groups (8). The 2H protons of CYS and 2H protons of DMP units in α position to amide groups (3,5) give signal at 3.45-3.22 ppm range. The peak at 4.7 ppm was correlated 1H proton of methyne group in the backbone (1).…”

“…Synthesis of polysuccinimide: Polysuccinimide was synthesized by the thermal polycondensation of aspartic acid as reported earlier [27]. The viscosity average molecular weight of the polymer was found to be 33 kDa (determined by an Anton Paar Lovis 2000 rolling ball viscometer, Mark−Houwink constants were taken from the literature [28]: K = 1.32 × 10 -1 g/cm 3 and α = 0.76). Chemical structure of the polymer was confirmed by Synthesis of thiolated polysuccinimide: 1.00 g (0.0103 mol succinimide (SI) repeating units) PSI was dissolved in 9.00 g DMF under nitrogen atmosphere in each case.…”

“…Water-soluble, biodegradable polymers including poly(amino acid)s can be potentially used to deliver nucleic acids or other bioactive compounds into targeted cells without any toxic effect of the carrier or its degradation products [1][2][3]. Poly(aspartic acid) (PASP) as an anionic poly(amino acid) can be prepared by thermal polycondensation of L-aspartic acid to polysuccinimide (PSI), followed by a ring opening reaction in alkaline medium.…”