Browsing by Author "Nair, CPR"

Now showing 1 - 5 of 5
  • Item
    Chitosan-Comb-graft-Polyethylene Glycol Monomethacrylate-Synthesis, Characterization, and Evaluation as a Biomaterial for Hemodialysis Applications
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2009) Radhakumary, C; Nair, PD; Nair, CPR; Mathew, S
    Chitosan was reacted with "Polyethylene glycol monomethacrylate" (PEGm) using a redox initiation method. Different compositions were prepared by varying the relative amount of PEGm in the feed. A maximum of 88% yield with 320% grafting could be achieved. The graft copolymerization was confirmed by FTIR, thermal, and XRD studies. Higher graft % could be achieved as the monomer used is a macro monomer of PEG and the resultant graft is a comb-like polymer. Grafting with PEGm did not affect the thermal stability of chitosan film significantly, however, it resulted in a marginal increase in the tensile strength of the films in the dry state. The products showed much improved swelling at pH 7.4 and pH 1.98 compared to the virgin chitosan. The preliminary biocompatibility evaluation showed that the materials are blood compatible and non-cytotoxic. Though the permeability to low molecular weight solutes like creatinine and glucose was equal to or better than commercial cellulose membranes, the copolymer films expressed comparatively less permeability to these solutes initially, due to the crystalline domains of PEO grafts that impede the transport. On exposure in the medium, this effect is nullified culminating in better permeability. The crystallization of PEG grafts was very helpful in preventing the permeation of the high molecular weight solute albumin, the leakage of which above a certain limit is dangerous to the patient. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2873-2886, 2009
  • Item
    Chitosan-graft-poly(vinyl acetate) for hemodialysis applications
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2012) Radhakumary, C; Nair, PD; Nair, CPR; Mathew, S
    Chitosan was graft copolymerized with vinyl acetate using ceric ammonium nitrate as the initiator. The chitosan-g-poly(vinyl acetate) (chitosan-g-PVAc) membranes were found to be blood compatible, noncytotoxic, and biodegradable. The physicochemical characterization of the membranes revealed that the membranes possess the synergistic effect of the natural-synthetic hybrids of chitosan and PVAc with excellent mechanical stability and tunable hydrophilic/hydrophobic characteristics. The permeation characteristics of chitosan-g-PVAc membranes for four different solutes creatinine, urea, glucose, and albumin was studied in vitro at 37 degrees C for assessment of the suitability of them as hemodialysis membranes. The studies showed that the membranes exhibit higher permeability to creatinine, urea, and glucose compared with the commercial cellulose membrane and are impermeable to the essential nutrient albumin. Hence, the need for the development of biocompatible, mechanically strong dialysis membranes could be addressed with the modification of chitosan through grafting with PVAc. Potential applications like artificial kidney, artificial pancreas, and so forth, are envisaged from these membranes. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
  • Item
    Graft copolymerization of 2-hydroxy ethyl methacrylate onto chitosan with cerium (IV) ion. I. Synthesis and characterization
    (JOURNAL OF MACROMOLECULAR SCIENCE-PURE AND APPLIED CHEMISTRY, 2003) Radhakumary, C; Divya, G; Nair, PD; Mathew, S; Nair, CPR
    Graft copolymerization of 2-Hydroxy ethyl methacrylate (HEMA) on to chitosan was studied using cerium (IV) as the initiator. Optimization of the grafting was worked out by varying the reaction time and monomer concentration. Under controlled conditions, up to 685% grafting with a grafting yield of 92.4% was achieved. FTIR, thermal and XRD techniques were used to confirm the formation of the grafted copolymer. Grafting caused a marginal decrease in the mechanical strength in the dry conditions and a significant decrease under wet conditions for the resultant polymer. The products showed significantly improved swelling at pH 7.4 and pH 1.98 compared to the original chitosan. Grafted polymer showed enhanced Tg and decomposition temperature. The grafting also resulted in improved hydrophilicity as is evident from the contact angle studies of the films.
  • Item
    HEMA-grafted chitosan for dialysis membrane applications
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2006) Radhakumary, C; Nair, PD; Mathew, S; Nair, CPR
    Chitosan was graft copolymerized with HEMA (2-Hydroxyethylmethacrylate) for the development of blood-compatible dialysis membranes. The permeation characteristics of HEMA-grafted chitosan films for four different solutes creatinine, urea, glucose, and albumin was studied in vitro at 37 C for assessment of the suitability as dialysis membranes. The grafted film CH-12.5 composition (425% grafting) showed very high permeation to creatinine by reaching the equilibrium within 45 min. The compositions CH-7.5 and CH-12.5 showed excellent permeation to glucose when compared to virgin chitosan films. In the case of urea permeation, all the grafted compositions exhibited higher percent permeation than the virgin chitosan films. The copolymer films CH-7.5 and CH-12.5 showed enhanced permeability for the high molecular weight solute, albumin. The other grafted copolymer compositions followed almost the same trend as that of chitosan for the low molecular weight solutes as well as the high molecular weight solute. The copolymer films were also found to be highly blood compatible, noncytotoxic, and biodegradable. Hence, the need for developing blood-compatible chitosan membranes with desirable permeability properties is achieved by the graft copolymerization of HEMA onto chitosan. (c) 2006 Wiley Periodicals, Inc.
  • Item
    Synthesis, characterization, and properties of poly(vinyl acetate)- and poly(vinyl alcohol)-grafted chitosan
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2007) Radhakumary, C; Nair, PD; Mathew, S; Nair, CPR
    Graft copolymers of chitosan and vinyl acetate were synthesized by free radical technique using cerium (IV) as the initiator. Under controlled conditions, as much as 92% grafting with a grafting yield of 30-40% could be achieved. Chitosan-g-poly(vinyl alcohol) copolymers were derived by the alkaline hydrolysis of the chitosan-g-poly(vinyl acetate) precursor. Thermogravimetric, FTIR, and X-ray diffraction analyses of chitosan and the copolymers confirmed the grafting reaction between chitosan and vinyl acetate and also the subsequent hydrolysis. Both the copolymers possessed very good film-forming properties. Grafting resulted in a significant increase in mechanical strength of both the copolymers in the dry condition. Chitosan-g-poly (vinyl acetate) (CH-PVAc) proved more hydrophobic than did pure chitosan, whereas chitosan-g-poly(vinyl alcohol) (CH-PVOH) exhibited enhanced hydrophilicity as evident from their swelling characteristics and contact angle measurements. The enhanced swelling of CH-PVOH was ascribed to the presence of the pendant poly(vinyl alcohol) group. At pH 1.98, the CH-PVAc copolymer films showed greater stability than do pure chitosan films, which is highly beneficial for specific biomedical applications. Both the copolymers showed lower glass transition temperature than do pure chitosan. Grafting did not affect the overall thermal stability, and the differential thermogram substantiated the grafting. The investigations indicate that the synthetic-natural hybrid copolymers having desirable mechanical properties and tailored hydrophilic/hydrophobic characteristics are realizable. These polymers could be exploited for varied biomedical applications. (c) 2007 Wiley Periodicals, Inc.