Grafting Of N-isopropylacrylamide Research Articles

Plasma-induced customizable poly(ester-urethane) surface for cell culture platforms

This work aims to study the bio-interfacial properties of poly(ester-urethane) composite scaffolds based on poly (3-hydroxybutyrate) [PHB] and modified by surface plasma-radiation-induced graft polymerization of N-isopropylacrylamide (NIPAAm). The delivering power of the Argon radio-frequency plasma was increased from 5−20 W. The yields over the polyurethane surface, grafting density, topographical dimensions, architecture, surface energy, and wettability were surveyed in the established plasma regimes. Successful grafting of NIPAAm was verified by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis. Characterization using atomic force microscopy revealed that the surface of the scaffolds is more uniform in lower plasma delivering powers. The results show a high grafting density surface with a low degree of grafting (3–9 %). The contact angles decreased, and the surface energy rose with increasing delivering power. The surface area, total pore volumes are similar between the samples. The porosity percentage and the average pore diameter hinted at a decrease in the treated composite as compared to the pristine scaffold. Although all the composites showed to be non-toxic and highly viable (>98 %) for human dermal fibroblasts, the results showed better attachment, spreading, and growth of fibroblasts on scaffolds with moderate hydrophilicity (5 W). The in vivo experiments revealed that the plasma-treated scaffolds diminished the inflammatory infiltrate, which means an improved acceptance as compared with untreated PHB polyurethane.

Nano-modification of polyamide thin film composite reverse osmosis membranes by radiation grafting

Radiation synthesis of reverse osmosis membranes were carried out by grafting of N-Isopropyl acrylamide (NIPAM) and ZnO nanoparticles incorporation onto polyamide thin film composite reverse osmosis membranes PA(TFC). The effect of monomer concentration, radiation time and concentration of ZnO nanoparticles on the grafting percent were investigated. The properties of the prepared grafted reverse osmosis membranes were characterized by using different analytical tools such as contact angles goniometer, Fourier transform IR (FTIR), X-ray diffraction (XRD), Field Emission-Scanning Electron Microscope (FESEM). The performance of the reverse osmosis process of the neat and the modified PA(TFC) membranes in terms of water flux and salt rejection (%) was investigated. The chlorine and biofouling resistance properties of the neat and the modified PA(TFC) membrane were evaluated. It is found that, the performance of the modified ZnO NPs/P(NIPAM)-g-PA(TFC) membrane is much better than the neat PA(TFC) membrane.

Adsorption Studies of PVA Based Thermosensitive Polymers in Heavy Metal Removal

Thermosensitive copolymers were synthesized by grafting of N-isopropyl acrylamide (NIPAM) monomer onto crosslinked poly(vinyl alcohol) (PVA) and characterized by FTIR, XRD, elemental and SEM-EDS analysis. Also, the swelling capacities, water release values and cloud points of the copolymers were determined. The removal of Cu(II), Ni(II) and Cd(II) ions was studied by using of the copolymers as solid phase extractor. Dodecyltrimethylammonium chloride (DTAC) was the extractant to complex with ions in the process. The copolymer adsorbs the metal–extractant complexes above its lower critical solution temperature (LCST) by hydrophobic interaction. Increasing the time and initial metal ion concentration caused an increase in the adsorption capacities, and the copolymer displayed S-type adsorption in Giles’s classification. The experimental data followed pseudo-second-order model, and the dominated adsorption mechanism was external mass diffusion. In addition, adsorption/desorption cycles presented the usability of the synthesized copolymer as sorbent for environmentally friendly processes.

Functionalization of poly(ester‐urethane) surface by radiation‐induced grafting of N‐isopropylacrylamide using conventional and reversible addition–fragmentation chain transfer‐mediated methods

AbstractThe functionalization of poly(ester‐urethane) (PUR) surface was conducted using radiation‐induced grafting. A thermosensitive layer constructed from N‐isopropylacrylamide (NIPAAm) was introduced onto a polyurethane film and characterized using attenuated total reflection Fourier transform infrared and X‐ray photoelectron spectroscopies and contact angle measurements. Size exclusion chromatography was used to analyse the PUR‐graft‐PNIPAAm copolymers and homopolymers formed in solution. Additionally, reversible addition–fragmentation chain transfer (RAFT) polymerization was performed in order to obtain PNIPAAm‐grafted surfaces with well‐defined properties. Atomic force microscopy was used to evaluate the surfaces synthesized via conventional and RAFT‐mediated grafting methods. The results of various techniques confirmed the successful grafting of NIPAAm from PUR film. © 2015 Society of Chemical Industry

Microwave-induced synthesis of alginate–graft-poly(N-isopropylacrylamide) and drug release properties of dual pH- and temperature-responsive beads

The first decade of the 21st century saw an increasing interest in the development of devices and biomaterials for delivery of bioactive substances that can be controlled by external stimuli. This study deals with the production of novel pH and temperature responsive beads for colon-specific delivery of indomethacine (IM). For this purpose, N-isopropylacrylamide (NIPAAm) was grafted onto sodium alginate (NaAlg) with microwave radiation in aqueous solution. The graft copolymer (NaAlg-g-PNIPAAm) was characterized by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), elemental analysis, differential scanning calorimetry (DSC), and thermogravimetric analysis. A series of pH- and temperature-responsive NaAlg-g-PNIPAAm beads were prepared as drug delivery matrices of indomethacine cross-linked by glutaraldehyde (GA) in the hydrochloric acid catalyst. Preparation condition of the beads was optimized by considering the percentage entrapment efficiency, particle size, swelling capacity of beads, and their release data. Effects of variables such as graft yield, drug/polymer ratio, exposure time to GA, and concentration of GA on the release of IM were investigated and discussed at two different pH values (1.2 and 7.4) and temperatures (25°C and 37°C). It was observed that IM release from the beads decreased when the grafting of NIPAAm, drug/polymer ratio (d/p), and extent of cross-linking were increased. The results also showed that NaAlg-g-PIPAAm beads were positive pH and temperature responsive. The release of IM from grafted beads was slower for the pH 1.2 solution than that of the pH 7.4 buffer solution, whereas the release rate was higher at 37°C than at 25°C.

Cu(II) immobilization in AAc/NIPAAm-based polymer systems synthesized using ionizing radiation

Polymer systems based on the pH-responsive monomer acrylic acid (AAc) and the thermosensitive monomer N-isopropylacrylamide (NIPAAm) were synthesized using gamma radiation. Three systems were synthesized: a comb-type hydrogel structure (grafting of NIPAAm onto crosslinked PAAc), a binary graft of both monomers onto a polypropylene (PP) film synthesized by a one-step method and a binary graft prepared by a two-step method. The binary graft systems were characterized by swelling behavior and the reversibility of water uptake. The three systems were compared with respect to their Cu(II) adsorption quantity, reversibility and time response. The binary graft system synthesized in one step exhibited the best adsorption response. The comb-type hydrogel required 150 h to reach its maximum swelling percentage, and the binary graft systems on polypropylene (PP) prepared by the one- and two-step irradiation-based methods required 10 and 30 min, respectively. The optimum pH range for Cu(II) immobilization was 5–6 in the binary graft system synthesized in one step. The maximum adsorption capacity for Cu(II) in the (PP-g-(AAc/NIPAAm)) (45% graft) was found to be 337 mg g −1, and the adsorption followed the Freundlich model.

Grafting of N-isopropyl Acrylamide onto Bacterial Polyhydroxybutrate/Hydroxyvalerate Copolymers

This work deals with the grafting of N-isopropyl acrylamide (IPA) onto poly (3-hydroxybutyrate-3-hydroxyvalerate), (PHBV) (5.4 mole % 3-hydroxyvalerate), using benzoyl peroxide as free radical initiators. The effect of N-isopropyl acrylamide and initiator concentrations and reaction time on the degree of grafting has been investigated. The maximum degree of grafting was 82%. The grafted products were characterized by FTIR, 1HNMR, DSC, wide-angle X-ray diffraction and TGA analysis. The DSC results showed that the cold crystallization temperature from the glassy state increased with increasing the extent of grafting, while the Tg and Tm are not affected significantly. TGA analysis revealed that grafting of the host PHBV polymer did not affect much its onset decomposition temperature. The Grafted products swell in aqueous solution and the swelling is controlled by the extent of grafting, temperature, and pH. The biodegradability of PHBV and its graft copolymers solution-cast films was investigated in active soil. The results indicated that the introduction of the hydrophilic PVP and PIPA graft chains enhanced the biodegradability of PHBV.

Surface functionalization of polypropylene devices with hemocompatible DMAAm and NIPAAm grafts for norfloxacin sustained release

To improve the hemocompatibility and elution of antimicrobial agents for medical devices, N,N′-dimethylacrylamide (DMAAm) and N-isopropylacrylamide (NIPAAm) were sequentially grafted onto polypropylene (PP) films. Various (PP-g-DMAAm)-g-NIPAAm grafts were prepared using different time periods of irradiation while keeping the radiation dose constant. The hydrogel layer that formed on the surface of the PP was temperature-responsive (shifted from 32°C for NIPAAm to 37°C for the copolymer). The (PP-g-DMAAm)-g-NIPAAm films adsorbed serum albumin but not fibrinogen and had significantly lower hemolytic and thrombogenic activity. The DMAAm promoted the loading of norfloxacin (13.3 μg cm—2) when the hydrogel layer was swollen; as the NIPAAm shrank, a sustained delivery (∼6 h) occurred at body temperature. These functionalized PP films have potential as hemo- and cyto-compatible materials for medical devices and drug delivery products.

Radiation grafting of NIPAAm and acryloxysuccinimide onto PP films and sequent crosslinking with polylysine

N-isopropylacrylamide (NIPAAm) and N-acryloxysuccinimide (NAS) were grafted from their binary mixtures in tetrahydrofurane (THF) and toluene solutions onto polypropylene (PP) films by the pre-irradiation oxidative method in air. Effects of pre-irradiation dose, dose rate, and monomer concentrations (NAS/NIPAAm) were studied. The grafted copolymers exhibited the lower critical solution temperature (LCST) at around 31 °C. Based on its thermo-reversible behavior, this system has been used for immunoassay, drug delivery, separation processes and immobilization of enzymes. N-acryloxysuccinimide (NAS) has been used as an active ester to bind proteins through amide bond formation with lysine, and because of this property, the grafted copolymer has been crosslinked with polylysine. Techniques used to characterize the films included differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared (FTIR-ATR) and elemental analysis. Results on thermo-sensitivity are presented. This new system could find applications in vesicle immobilizations.

Preparation of a Thermosensitive Highly Regioselective Cellulose/N-Isopropylacrylamide Copolymer through Atom Transfer Radical Polymerization

Regioselective copolymerization of N-isopropylacrylamide (NIPAM) onto cellulose was achieved by atom transfer radical polymerization (ATRP) using a regioselectively modified 6- O-bromoisobutyryl-2,3-di- O-methyl cellulose macroinitiator. Varying the ratio of NIPAM to macroinitiator to ligand to transition metal in a Cu(I)Br/ N, N, N', N'', N'''-pentamethyldiethylenetriamine (PMDETA) catalyst system affected graft yield and degree of polymerization. ATRP proceeded to completion without any trace of the macroinitiator, and a degree of polymerization (DP) of polyNIPAM up to 46.3 was obtained. Increasing the DP of the NIPAM component increased both the thermal decomposition temperature and the glass transition temperature of the copolymer. The grafting of NIPAM also affected the solubility properties of the methylcellulose. The 6- O-polyNIPAM-2,3-di- O-methyl cellulose formed a stable suspension in water at room temperature and underwent a hydrophillic-to-hydrophobic transition and copolymer precipitation when the temperature was raised above 30 degrees C.

Radiation synthesis of a thermo-pH responsive binary graft copolymer (PP-g-DMAEMA)-g-NIPAAm by a two step method

(PP-g-DMAEMA)-g-NIPAAm was synthesized using gamma radiation from a 60Co source. Graft polymerization of N,N’-dimethylaminoethylmethacrylate (DMAEMA) onto polypropylene (PP) was accomplished in about 100 percent yield by the mutual irradiation technique at a dose of 10 kGy. Grafting of N-isopropylacrylamide (NIPAAm) onto PP-g-DMAEMA was carried out by the pre-irradiation method with doses from 20 to 100 kGy. The influence of temperature, reaction time, and monomer concentration on grafting yield was studied. Grafting processes were confirmed by infrared spectroscopy (FTIR-ATR). (PP-g-DMAEMA)-g-NIPAAm films were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The lower critical solution temperature (LCST) and critical pH point of the films were obtained by water contact angle and percent swelling measurements. The LCST was also determined by DSC. We report here hare a new binary graft copolymer which shows two LCST values, synthesized in two steps.

Swelling Characteristics of pH- and Thermo-Sensitive Crosslinked Poly(Vinyl Alcohol) Grafts

Grafting of N-isopropylacrylamide, NIPAAm, onto partially and fully hydrolyzed poly(vinyl alcohol–g-maleic anhydride), PVA–MA, was carried out in presence of ammonium persulfate as initiator. The crosslinked PVA–MA–NIPAAm copolymers were prepared in presence of different weight percentages of methylene bisacrylamide, MBA, as crosslinker and N,N,N,N′-tetramethylethylenediamine, TMEA, as accelerator. Crosslinked PVA–MA–NIPAAm copolymers were prepared at two different temperatures 5 and 55 °C. The structural features of these grafts were confirmed by 1H NMR analysis. Solution behaviors of both PVA–MA and PVA–MA–NIPAAm were evaluated from viscosity measurements. The swelling ratios of the crosslinked polymers were measured at different temperatures and pH values. The phase transition of the crosslinked gels was measured from DSC analysis. Crosslinked PVA–MA–NIPAAm grafts show different pH and temperature sensitivity. The swelling behaviors of PVA–MA–NIPAAm were referred to formation of hydrogen bonding between amide and carboxylic groups and also to hydrophobic aggregation of NIPAAm grafts.

Surface-Active and Stimuli-Responsive Polymer−Si(100) Hybrids from Surface-Initiated Atom Transfer Radical Polymerization for Control of Cell Adhesion

A simple two-step method was developed for the covalent immobilization of atom-transfer radical polymerization (ATRP) initiators on the hydrogen-terminated Si(100) (Si-H) surface. Well-defined functional polymer-Si hybrids, consisting of covalently tethered brushes of poly(ethylene glycol) monomethacrylate (PEGMA) polymer, N-isopropylacrylamide (NIPAAm) polymer, and NIPAAm-PEGMA copolymers and block copolymers on Si-H surfaces, were prepared via surface-initiated ATRP. Kinetics study revealed that the chain growth from the silicon surface was consistent with a "controlled" process. Surface cultures of the cell line 3T3-Swiss albino on the hybrids were evaluated. The PEGMA graft-polymerized silicon [Si-g-P(PEGMA)] surface is very effective in preventing cell attachment and growth. At 37 degrees C [above the lower critical solution temperature (LCST, approximately 32 degrees C) of NIPAAm], the seeded cells adhered, spread, and proliferated on the NIPAAm graft polymerized silicon [Si-g-P(NIPAAm)] surface. Below the LCST, the cells detached from the Si-g-P(NIPAAm) surface spontaneously. Incorporation of PEGMA units into the NIPAAm chains of the Si-g-P(NIPAAm) surface via copolymerization resulted in more rapid cell detachment during the temperature transition. The "active" chain ends on the Si-g-P(PEGMA) and Si-g-P(NIPAAm) hybrids were also used as the macroinitiators for the synthesis of diblock copolymer brushes. Thus, not only are the hybrids potentially useful as stimuli-responsive adhesion modifiers for cells in silicon-based biomedical microdevices but also the active chain ends on the hybrid surfaces offer opportunities for further surface functionalization and molecular design.

Radiation grafting of NIPAAm on PVDF nuclear track membranes

Polymer surface modifications are obtained by the application of radiation treatments and other physico-chemical methods: fragment fission (ff) or ion implantation, etching and grafting procedure. Poly vinylidene fluoride (PVDF) foils were irradiated during different times to produce pores of different diameters through the foils. In this way, nuclear track membranes (NTM) were produced with different track diameters and track numbers. Active sites were formed using a γ-ray Co-60 source and then contacted with N-isopropylacrylamide (NIPAAm) to obtain a graft copolymer that responds to environmental conditions. The present work shows the grafting yield as a function of: γ-dose, NIPAAm concentration, pore diameter, track density, etc.

Graft copolymerization ofN-isopropylacrylamide onto poly(vinyl chloride)

Poly(vinyl chloride) (PVC) was dehydrochlorinated in alkali solution and then grafted with N-isopropylacrylamide (NIPAM) using benzoyl peroxide as an initiator under a nitrogen atmosphere. The results show that grafting of NIPAM onto dehydrochlorinated PVC (DHPVC) by means of chemical initiation is easily performed. The influence of various reaction conditions such as NIPAM concentration, reaction time, initiator concentration, and PVC content on the grafting copolymerization was investigated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1234–1241, 1999

Photografting of N-isopropylacrylamide on cellulose and temperature-responsive character of the resulting grafted celluloses

Photografting (λ > 300 nm) of N-isopropylacrylamide (NIPAAm) on cellulose was investigated at 50°C in water solvent. Fibrous dissolving pulp from softwoods was used as the cellulose sample. Oxidation and swelling treatments of the cellulose sample with aqueous solutions of periodic acid and sodium hydroxide, respectively, were useful for enhancing an ability of the sample to initiate the photografting, where about 80% of NIPAAm monomer used could be introduced into the cellulose sample as grafted chains. The oxidized cellulose sample was also proven to have a high activity for the ceric-salt-initiated grafting of NIPAAm, though a maximum percent grafting was observed at a certain concentration of ceric salt and the value was lower than the percent grafting of the photografting system under the same grafting conditions. The resultant NIPAAm-grafted cellulose samples exhibited a temperature-responsive character, where they swelled and shrank in water at temperatures lower and higher around 30°C, respectively. It was found that the extent of the character is not influenced by the grafting initiation systems, but largely affected by the swelling treatment of cellulose before grafting. That is, the character was smaller for the grafted cellulose samples prepared using swollen sample than those prepared using unswollen sample.