Graft Copolymerization Of N-isopropylacrylamide Research Articles

Preparation and properties of thermosensitive molecularly imprinted polymer based on konjac glucomannan and its controlled recognition and delivery of 5-fluorouracil

Biocompatible thermosensitive molecularly imprinted polymers (MIPs) based on konjac glucomannan was prepared by graft copolymerization of N-isopropyl acrylamide, a thermosensitive monomer, with konjac glucomannan, a natural polysaccharide. The products were characterized by various means. The MIPs possessed switchable thermal regulation on the recognition and delivery of 5-fluorouracil (5-Fu), an anticancer drug. The results of adsorption experiments showed that the MIPs had excellent adsorption capacity at a temperature below the lower critical solution temperature, and the MIPs could specifically recognize and adsorb 5-Fu with good selectivity, repeatability, and stability. The adsorption isotherms of MIPs were fitted by six isothermal models and the dual-site Langmuir- Freundlich model presented the best fit. In addition, the in vitro release properties of 5-Fu from the thermosensitive MIPs were evaluated in phosphate buffer solution and the cumulative release of 5-Fu at 25 °C was higher than that at 38 °C. The release curves were fitted by zero-order, first-order, and Higuchi kinetic equations, respectively, and the results showed that the release of 5-Fu complied with the Fick's law. Compared with non-molecularly imprinted polymers, the MIPs could release 5-Fu continuously for a certain period with a good controlled release effect, indicating that they possess great prospects as drug delivery materials.

The mechanism of adhesion and graft polymerization of a PNIPAAm thermoresponsive hydrogel to polypropylene meshes.

In this study, a commercial and fully flexible monofilament mesh has been used for the deposition of a thermosensitive hydrogel, generated by graft copolymerization of N-isopropylacrylamide (NIPAAm) and N,N'-methylene bis(acrylamide) (MBA) monomers. The mechanism of adhesion and graft copolymerization have been elucidated combining micro- and standard spectroscopy techniques such as Raman spectroscopy, FTIR spectroscopy and XPS, before and after the activation of the polypropylene (PP) fibre surface by using oxygen-plasma. The good covalent interactions among NIPAAm monomers and PP fibres, and the hydrogel chain growth in such flexible bidimensional structures, were demonstrated. Additionally, the thermoresponsive properties of PNIPAAm were obtained (VPTT behaviour). The bilayer system is stable below and above a low critical solution temperature (LCST) of 33.2 °C.

Chemical modification of PET surface and subsequent graft copolymerization with poly(N-isopropylacrylamide)

Thermo-sensitivity has been introduced onto poly(ethylene terephthalate) (PET) surfaces by graft copolymerization of N-isopropylacrylamide (NiPAAm). The PET surface was first photo-oxidized in the presence of H2O2, to have enriched concentration of COOH groups which were later reacted with allylamine (AlAm) to introduce vinyl end groups at the surface. These groups were used as active sites for thermally initiated graft copolymerization of NiPAAm. The influence of solvent, monomer concentration and time on grafting has been investigated. Spectroscopic analysis confirmed the presence of (AlAm) linked to treated surfaces as well as poly(NiPAAm) grown from them. The thickness of grafted layer can be adjusted between 10 and 18μm via grafting degree by controlling of grafting reaction parameters. Imaging in water environment revealed the reversible modification of surface morphology below and above the lower critical solution temperature (LCST) of PNiPAAm. The grafted surfaces were analyzed by colorimetric assay, ATR-FTIR, Raman, and XPS spectroscopies and Thermogravimetric analysis (TGA), and Differential scanning calorimetry (DSC).

Synthesis of dual stimuli-responsive amphiphilic particles through controlled semi-batch emulsion polymerization

The synthesis and property of dual stimuli-responsive amphiphilic particle consisting of a hydrophobic component, a pH-sensitive poly(ethyleneimine) (PEI) and a temperature-sensitive poly(N-isopropyl acrylamide) (PNIPAm) have been investigated. This novel type of multicomponent polymer (MCP) particles were prepared through a one-pot controlled semi-batch emulsion polymerization which involved an initial formation of PNIPAm/PEI core-shell nanogel particle via a graft copolymerization of N-isopropyl acrylamide from PEI, followed by the seeded emulsion polymerization of methyl methacrylate or styrene. Properties of these MCP particles including particle composition, size, size distribution, surface charge and morphology were systematically examined. The structure of hydrophobic monomer was found to strongly influence the morphology of resultant MCP particles. The multilayered polystyrene/PNIPAm/PEI particles exhibited unique property of temperature-tunable surface charge. This property was demonstrated through studies of intracellular uptake of FITC-label PS/PNIPAm/PEI nanoparticles into HeLa cells at 27 and 37 °C. The results provide some insights into the design of future stimulus-responsive nanoparticle-based therapeutics.

Development of poly(N-isopropylacrylamide)/alginate copolymer hydrogel-grafted fabrics embedding of berberine nanosuspension for the infected wound treatment

In the present study, a novel hydrogel-grafted fabrics embedding of berberine nanosuspension was developed for the treatment of infected wound. Hydrogel-grafted fabric was prepared by graft copolymerization of N-isopropylacrylamide and alginate using ceric ammonium nitrate as initiator. Berberine nanosuspension was prepared and embedded in the hydrogel-grafted fabrics to achieve sustained drug release. The prepared hydrogel-grafted fabrics embedding of berberine nanosuspension was characterized by FT-IR spectroscopy, scanning electron microscopy, and swelling degree studies. Fourier transform infrared spectroscopy revealed that berberine was embedded into the matrix of hydrogel-grafted fabrics, rather than on the surface. Scanning electron microscopy showed that a thin hydrogel layer was formed on the surface of nonwoven fibers. The swelling study showed that hydrogel-grafted fabric had water absorbing characteristic with reversible temperature sensitivity. The drug release study demonstrated that hydrogel-grafted fabrics can be used as a sustained drug delivery system of hydrophobic compounds. The berberine nanosuspension embedded hydrogel-grafted fabric was further investigated in an animal infected wound model and was found to be a very promising wound healing dressing for the treatment and healing of infected wounds.

Drug release studies of N-isopropyl acrylamide/acrylic acid grafted polypropylene nonwoven fabric

Radiation-induced graft copolymerization of N-isopropyl acrylamide (NIPAAm) and acrylic acid (AA) mixture was carried out on polypropylene (PP) nonwoven fabric to develop a thermosensitive material. The immobilization and release behaviour of 4-acetamidophenol onto the modified PP nonwoven fabric were studied. The effect of degree of grafting and temperature on the drug release behaviour was investigated. At 32 °C temperature, a small amount of drug was released, and a relatively large amount of drug still remained in the polymer matrix. However, when the release temperature was 40 °C (above the LCST of 37.5 °C), the drug release was greatly accelerated due to temperature induced structure changes of the grafted copolymer chains. It was also observed that the drug release was higher for samples with higher degree of grafting. At higher graft levels, the grafted chains are longer and form the hydrogel network which leads to the more efficient entrapment of the drug within the network on the surface and consequently, more drug tends to diffuse out as compared to the low graft levels. The resulting grafted membranes exhibited temperature-triggered drug release behavior, and have enormous potential for use as drug carriers.

Synthesis of novel thermoresponsive micelles by graft copolymerization of N-isopropylacrylamide on poly(ε-caprolactone-co-α-bromo-ε-caprolactone) as macroinitiator via ATRP

α-Bromo-e-caprolactone (α-BrCL) was synthesized from α-bromocyclohexanone by using 3-chloroperoxybenzoic acid. α-BrCL was then used as a comonomer in the ring-opening polymerization of e-caprolactone (CL) initiated with aluminum isopropoxide to synthesize poly(CL-co-α-BrCL) copolymer. This copolymer was used as the macroinitiator in the atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm) for the synthesis of stimuli-responsive and biodegradable PCL-g-PNIPAAm copolymer. A core-shell type nano-structure was formed with a hydrophilic outer shell and a hydrophobic inner core from these copolymers, which exhibited a phase transition temperature around 31 °C. The copolymers were characterized by 1H-NMR and FT-IR spectroscopies. Number-average molecular weight of the poly(CL-co-α-BrCL) and PCL-g-PNIPAAm copolymers was calculated from corresponding 1H-NMR spectra to be 5770 and 6810 gmol−1, respectively. Thermal stability of the copolymer was investigated by thermogravimetric analysis (TGA) and crystallization behavior was studied by differential scanning calorimetry (DSC). Transmission electron microscopy (TEM) showed that the self-assemble micelle aggregates had well defined spherical shape. From the fluorescence spectra, fluorescence intensity of pyrene in the copolymer micelles increased and red-shifted as the copolymer concentration increases, indicating the formation of self-assemble polymeric micelles in water. The critical micelle concentration was found to be 3.2 × 10−3 mg/mL. TEM results showed that micelles have spherical shapes with a diameter of about 70 nm. The obtained micelles can be desirable for potential applications in biomedical fields, such as drug delivery systems.

Stimuli-Responsive Polymeric Membranes through Graft Copolymerization of N-Isopropylacrylamide onto Polycarbonate Track Etched Membranes for Biomedical Applications

Stimuli-responsive polymeric membranes have attracted the attention of researchers all around the world owing to their potential applications in the fields of controlled drug delivery, bioseperation, water treatment, and chemical sensors. N-isopropylacrylamide (NIPAAM) is well known for its novel thermo-sensitive behavior in aqueous media, was successfully grafted on the surface and in the pores of polycarbonate track etched membrane (PCTE).The influence of reaction parameters such as monomer concentration, reaction time, reaction temperature and concentration of the initiator on the grafting yield was investigated in detail. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of these parameters. Maximum percentage of grafting (92%) was obtained at benzoyl peroxide concentration = 0.08M, NIPAAM concentration = 6 v/v, and reaction temperature at 600°C in a reaction time of 5h. The microstructure and morphology of the PCTE-g-NIPAAM membranes were characterized through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) studies. Water Contact Angle Measurement was used to study the hydrophilic behavior of the grafted membranes. These grafted membranes were investigated for their swelling behavior. The thermo-sensitive behavior of the PCTE-g-NIPAAM membranes was studied. The diffusion coefficient of the model drug salicylic acid through pristine PCTE and the PCTE-g-NIPAAM membranes was determined

KOPOLIMERISASI CANGKOK (GRAFT COPOLYMERIZATION) N-ISOPROPILAKRILAMIDA PADA FILM SELULOSA YANG DIINDUKSI OLEH SINAR ULTRAVIOLET DAN KARAKTERISASINYA

Graft Copolymerization of N-Isopropylacrylamide on Cellulose Film Induced by UV-Irradiation and its Characterization. The effect of monomer and initiator concentrations, graft polymerization temperature, polymerization system and organic solvents on photografting of N-isopropylacrylamide on regenerated cellulose films (thickness = 20 µm) in UV irradiation were investigated. The higher percentage of grafting was afforded for the system with the higher monomer and initiator concentration. The photografting initiated even in the system at 30 °C by using a longer irradiation time. It was found that the maximum percentage of grafting was attained at 2.5 (%Vol) of methanol/acetone in the mixed solvent. The resulting NIPAAm-grafted cellulose films were characterized by attenuated total-reflection IR spectroscopy, showed a peak at 1640 and 1550 cm -1 due to the amide groups of the NIPAAm-grafted chains. According to scanning electron microscopy characterization, the grafted chains was found to distribute inside the film sample even in the grafted films with lower percentage of grafting. The grafted samples showing a temperatureresponsive character swelling and shrinking in water at 5 °C and 50 °C, respectively.

Synthesis and characterization of thermosensitive graft copolymer of N-isopropylacrylamide with biodegradable carboxymethylchitosan

A novel thermosensitive and hydrogel was designed and synthesized by graft copolymerization of N-isopropylacrylamide (NIPAAm) with biodegradable carboxymethylchitosan (CMCS). The influence of the content of CMCS grafted on the properties of the resulted hydrogels was examined. The morphology of the hydrogels was observed by scanning electron microscopy (SEM), their thermal property was characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and deswelling/swelling kinetics upon external temperature changes. In comparison with the conventional PNIPAAm hydrogels, the resulted hydrogels have improved thermosensitive properties, including enlarged water content at room temperature and faster deswelling/swelling rate upon heating. The strategy described here presents a potential alternative to the traditional synthesis techniques for thermosensitive hydrogels.

Graft copolymerization of N-isopropylacrylamide with 3-(methacryloxy)propyl trimethoxysilane on ultrafine silica and its application in chromatography separation

Thermosensitive core-shell particles were synthesized through graft copolymerization of N-isopropylacrylamide with [ 3-(methacryloxy) propyl]trimethoxysilane (MPT) coupled on the surface of ultrafine silica beads. The copolymerization was carried out using polyvinyl alcohol as a surfactant, water and cyclohexanol as mixed solvent, and 2,2′-azobis(isobutyronitrile) as an initiator. The effect of surfactant concentration and the composition of the mixed solvent on the graft rate were investigated. The structure of modified silica was confirmed by infrared spectra. Differential scanning calorimetry (DSC) has revealed the thermosensitivity of the particles. The thermosensitive particles were used as packing materials of high performance liquid chromatography (HPLC) columns for separating naphthalene derivatives. Satisfactory separation was obtained by controlling the temperature of the column. In contrast, the packing material of silica-MPT has no such separation efficiency due to the lack of thermosensitivity. The effect of the composition of the mobile phase on the separating efficiency was also investigated. The temperature-controlled separation was effective only when the water content was higher than 90% (v/v) in the water-methanol mobile phase. The mechanism for the temperature-controlled separation is attributed to a polarity change of poly(N-isopropylacrylamide) which undergoes volume phase transition on the silica surface as the temperature increases.

Osmotic pressure control in response to a specific ion signal at physiological temperature using a molecular recognition ion gating membrane.

A molecular recognition gating ion membrane was prepared by graft copolymerization of N-isopropylacrylamide and benzo[18]crown-6-acrylamide onto the pore surface of porous polyethylene film. This membrane captured Ba2+ with its crown ether receptors and generated osmotic pressure in response to Ba2+ autonomously and reversibly. However, the membrane never generated osmotic pressure in response to Ca2+. In addition, the concentration gradient of both the ion and other solute such as dextran could be used as the driving force; using a dextran concentration gradient, we can control the critical concentration and the duration time of the osmosis response.

Temperature-responsive cellulose by ceric(IV) ion-initiated graft copolymerization of N-isopropylacrylamide.

Temperature-responsive cellulose has been obtained by graft copolymerization of N-isopropylacrylamide (NIPAAm) monomer using ceric ammonium nitrate (CAN) as initiator at 25.0 +/- 0.1 degrees C in acidic medium. Kinetic and grafting parameters were evaluated at different concentrations of NIPAAm ranging from 1.25 x 10(-3) to 12.5 x 10(-3) mol dm(-3) and varying concentrations of CAN from 1.5 x 10(-3) to 9.0 x 10(-3) mol dm(-3) at constant concentration of nitric acid (2.5 x 10(-2) mol dm(-3)). The graft copolymerization of NIPAAm onto cellulose has shown a significant increasing trend below lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAAm) and shown low energy of activation (18.0 kJ mol(-1)) for graft copolymerization within the temperature range of 10-35 degrees C as determined with Arrhenius plot. The PNIPAAm-grafted cellulose has shown improved thermal stability and shown temperature-dependent degree of swelling. Variation in degree of swelling of PNIPAAm-grafted cellulose as a function of temperature has been used to determine LCST of PNIPAAm-grafted cellulose. The contact angle (theta) has shown variation on increasing the graft yield and temperature. On the basis of experimental observations, the reaction steps for graft copolymerization have been proposed and a rate expression has been derived.

Permeation of solutes with different molecular size and hydrophobicity through the poly(vinyl alcohol)-graft- N-isopropylacrylamide copolymer membrane

Thermosensitive copolymers were synthesized by graft copolymerization of N-isopropylacrylamide on poly(vinyl alcohol) (PVA-g-NIPAAm) and the copolymer membranes were prepared by evaporating solvent from their Me 2SO solution. The swelling ratio of the membrane in water increased gradually with decreasing temperature below 40°C and a considerable increase in the swelling was found below the LCST (33°C). The permeation rate of solutes through the PVA-g-NIPAAm membrane could be controlled by changing temperature. Polyethylene glycols (PEGs) with different molecular weight (400–6000) could be separated by changing temperature from 34 to 45°C. The permeation of butyl alcohols with different hydrophobicity through the slightly swollen membranes above the LCST was found to depend on not only the molecular size but also the hydrophobicity of solutes.

Preparation of poly(vinyl alcohol)‐graft‐N‐isopropylacrylamide copolymer membranes and permeation of solutes through the membranes

AbstractThermosensitive copolymers were prepared by graft copolymerization of N‐isopropylacrylamide onto poly(vinyl alcohol) in dimethyl sulfoxide (DMSO) using potassium peroxodisulfate as an initiator. The phase transition temperature was measured by differential scanning calorimetry. The copolymers exhibited almost the same transition temperature (about 33°C) as that of poly(N‐isopropylacrylamide) regardless of the composition of the copolymers. The copolymer membranes were obtained by evaporating solvent from the DMSO solution of the graft copolymers and were insolubilized by annealing the membranes at 120°C for 10 h. Permeation of the lithium ion and Methylene Blue through the membranes was investigated at various temperatures. The permeation of solutes was greatly affected by temperature, i.e., the permeation of the solutes could be controlled at temperatures below and above 33°C. © 1994 John Wiley & Sons, Inc.