Thermo- and pH-responsive behaviors of graft copolymer and blend based on chitosan andN-isopropylacrylamide

Abstract

Thermo‐ and pH‐sensitive polymers were prepared by graft polymerization or blending of chitosan and poly(N‐isopropylacrylamide) (PNIPAAm). The graft copolymer and blend were characterized by Fourier transform‐infrared, thermogravimetric analysis, X‐ray diffraction measurements, and solubility test. The maximum grafting (%) of chitosan‐g‐(N‐isopropylacrylamide) (NIPAAm) was obtained at the 0.5 M NIPAAm monomer concentration, 2 × 10−3 M of ceric ammonium nitrate initiator and 2 h of reaction time at 25°C. The percentage of grafting (%) and the efficiency of grafting (%) gradually increased with the concentration of NIPAAm up to 0.5 M, and then decreased at above 0.5 M NIPAAm concentration due to the increase in the homopolymerization of NIPAAm. Both crosslinked chitosan‐g‐NIPAAm and chitosan/PNIPAAm blend reached an equilibrium state within 30 min. The equilibrium water content of all IPN samples dropped sharply at pH > 6 and temperature > 30°C. In the buffer solutions of various pH and temperature, the chitosan/PNIPAAm blend IPN has a somewhat higher swelling than that of the chitosan‐g‐NIPAAm IPN. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1381–1391, 2000

Study on chemical, UV and gamma radiation-induced grafting of 2-hydroxyethyl methacrylate onto chitosan

“…The chitosan degradation mechanism is complex (includes the dehydration, deacetylation and chain scission) and is not well understood. However, the weight loss observed correspond to the losses observed by other authors (Kim et al, 2000;Don et al, 2002). For both copolymers its initial thermal decomposition started very near to that observed for chitosan.…”

Preparation of thermo-responsive and injectable hydrogels based on hyaluronic acid and poly(N-isopropylacrylamide) and their drug release behaviors

“…Ý 100]; where W 1 and W 2 are the weight of HA before grafting and the total weight after grafting PNIPAAm-NH 2 onto the HA main chain, respectively, as shown in our previous studiesU 29 Thermo-Optical Analysis (TOA) of PNIPAAm-Grafted HA Copolymer Solution. TOA provides a simple, rapid, and reliable experimental method to determine cloud point curves of binary polymer/solvent systems.…”

“…The synthesis and characterization was performed using similar procedures and compositions to those described in previous work. [24][25][26]29 The chain length of the PNIPAAm-NH 2 was controlled by varying the feed molar ratio of initiator to NIPAAm monomer. Briefly, NIPAAm (88.37 mmol) was dissolved in DMF (20 mL) with AESH (3.68 mmol).…”

Chitosan-Based Thermosensitive Materials

“…With this purpose cerium ammonium nitrate has been frequently employed as initiator [45], as well as a variety of thermal initiators such as azobisisobutyronitrile (AIBN) [46] and ammonium or potassium persulfate [47][48][49][50]. Cerium ion is an efficient redox agent capable of undergoing radical polymerization under soft conditions, in acidic aqueous media at low temperatures [51][52][53][54].…”

“…Due to the interesting dual-responsive behaviour of Cs-g-PNIPAm copolymers, the properties of these materials have been thoroughly studied using different techniques such as microdifferential scanning calorimetry (μDSC), dynamic light scattering (DLS), NMR, UV-Vis spectroscopy and rheological measurements, among others [46,51,52,54,[58][59][60][62][63][64][65].…”