Academic literature on the topic 'Poly(N-isopropylacrylamide) [PNIPAM]'
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Journal articles on the topic "Poly(N-isopropylacrylamide) [PNIPAM]"
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Tao, Xiang Dong, Ran Zhan, and Qian Duan. "Synthesis and Property Study of Modified Poly(N-isopropylacrylamide) Containing Eu(III)." Advanced Materials Research 239-242 (May 2011): 2553–57. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.2553.
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Poly(N-isopropylacrylamide)(PNIPAM) with terminal aromatic groups were synthesized by atom transfer radical polymerization (ATRP), using N-isopropylacrylamide as monomer and phenyl 2-chloropropionate, (4’-phenyl)phenyl 2-chloropropionate and (2’,6’-diphenyl)phenyl 2-chloropropionate as initators. Then novel functional complexes of poly(N-isopropylacrylamide) and Eu(III) (PNIPAM-Eu(III)) with thermosensitive and fluorescent properties were synthesized and characterized by X-ray photoelectron spectroscopy (XPS), and fluorescence spectroscopy. Eu(III) was bonded to nitrogen and oxygen atoms in the polymer chain of PNIPAM and formed the complexes of PNIPAM-Eu(III). The lower critical solution temperatures (LCSTs) of PNIPAM-Eu(III) were slightly greater compared with that of PNIPAM. Europium(III) complexes had excellent fluorescence performance, the fluorescence spectrum present characteristic emission of Europium(III) at 613 nm.
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Winnik, Françoise M., Alexander Adronov, and Hiromi Kitano. "Pyrene-labeled amphiphilic poly-(N-isopropylacrylamides) prepared by using a lipophilic radical initiator: synthesis, solution properties in water, and interactions with liposomes." Canadian Journal of Chemistry 73, no. 11 (November 1, 1995): 2030–40. http://dx.doi.org/10.1139/v95-251.
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Fluorescently labeled amphiphilic poly-(N-isopropylacrylamides) (PNIPAM) substituted with a N-[4-(1-pyrenyl)butyl]-N-n-octadecyl group at the chain end were prepared by free-radical polymerization in dioxane of N-isopropylacrylamide (NIPAM) using 4,4′-azobis{4-cyano-N,N-[4-(1-pyrenyl)butyl]-n-octadecyl}pentanamide as the initiator. The solution properties of the polymers in water were studied as a function of polymer concentration and temperature. Quasi-elastic light-scattering measurements and fluorescence experiments monitoring the pyrene excimer and pyrene monomer emissions revealed the presence of multimolecular polymeric micelles below the lower critical solution temperature (LCST) of PNIPAM. These underwent partial, reversible reorganization as they were heated above the LCST. The interactions of the pyrene-labeled amphiphilic PNIPAM with dimyristoylphosphatidylcholine (DMPC) liposomes have been examined in water at 25 °C. From fluorescence experiments it was established that the polymeric micelles are disrupted irreversibly upon contact with the liposomes. The anchoring of the polymer chains occurs by insertion of their hydrophobic tail within the phospholipidic bilayer, as evidenced from a large decrease of the pyrene excimer emission relative to pyrene monomer emission. The copolymers remained anchored within the bilayer as the temperature of the copolymer–liposome suspension was raised above the LCST of PNIPAM. Keywords: liposome, poly-(N-isopropylacrylamide), fluorescence, micelles.
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Babelyte, Migle, Laura Peciulyte, Vesta Navikaite-Snipaitiene, Joana Bendoraitiene, Volodymyr Samaryk, and Ramune Rutkaite. "Synthesis and Characterization of Thermoresponsive Chitosan-graft-poly(N-isopropylacrylamide) Copolymers." Polymers 15, no. 15 (July 25, 2023): 3154. http://dx.doi.org/10.3390/polym15153154.
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Thermoresponsive chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAAm) copolymers of different composition were synthesized by free-radical polymerization of chitosan (CS) and N-isopropylacrylamide (NIPAAm) in aqueous solution using potassium persulfate (PPS) as an initiator. By changing the molar ratio of CS:NIPAAm from 1:0.25 to 1:10 graft copolymers with a CS backbone and different amounts of PNIPAM side chains were prepared. The chemical structure of the obtained CS-g-PNIPAAm copolymers was confirmed by FTIR and 1H NMR spectroscopy. 1H NMR spectra were also used to calculate the content of attached PNIPAAm side chains. Moreover, the lower critical solution temperature (LCST) behavior of synthesized copolymers was assessed by cloud point, differential scanning calorimetry and particle size measurements. The aqueous solutions of copolymers containing ≥12 molar percent of PNIPAAm side chains demonstrated LCST behavior with the phase separation at around 29.0–32.7 °C. The intensity of thermoresponsiveness depended on the composition of copolymers and increased with increasing content of poly(N-isopropylacrylamide) moieties. The synthesized thermoresponsive chitosan-graft-poly(N-isopropylacrylamide) copolymers could be potentially applied in drug delivery systems or tissue engineering.
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Lima, Luiz H., Yael Morales, and Thiago Cabral. "Ocular Biocompatibility of Poly-N-Isopropylacrylamide (pNIPAM)." Journal of Ophthalmology 2016 (2016): 1–6. http://dx.doi.org/10.1155/2016/5356371.
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Purpose. To study the safety of intravitreal injections of poly-N-isopropylacrylamide (pNIPAM) tissue adhesive in rabbit eyes. Methods. Twelve study rabbits received an intravitreal injection of 0.1 mL 50% pNIPAM in the right eye. Follow-up examinations included color fundus photography, fundus fluorescein angiography (FA), optical coherence tomography (OCT), and electroretinography (ERG). Subsequent to the last follow-up assessment, the rabbits were sacrificed and histopathological study on the scleral incision sites was performed. Results. All study animals developed mild to moderate levels of inflammatory reaction in the conjunctiva, anterior chamber, and the anterior vitreous during the first month of follow-up. After this period, the level of the inflammatory reaction progressively decreased and completely disappeared after the third month of follow-up. The lens and cornea remained clear during the entire follow-up period. OCT and FA did not show areas of retinal damage or neovascularization. Histological and ERG studies of eyes injected with pNIPAM demonstrated absence of retinal toxicity. Conclusion. Intravitreal injections of pNIPAM were nontoxic in this animal study, and pNIPAM may be safe to be used as a bioadhesive in certain retinal diseases.
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Yong, Ernest Hsin Nam, Kim Yeow Tshai, Siew Shee Lim, and Ing Kong. "Poly(N-Isopropylacrylamide) Microgel Synthesised by Emulsion Polymerization." Solid State Phenomena 307 (July 2020): 345–50. http://dx.doi.org/10.4028/www.scientific.net/ssp.307.345.
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Smart polymers have been one of the most popularly studied materials owing to their capability to alter physio-chemical behaviour upon exposure to specific external stimuli. The biocompatible thermally responsive poly (N-isopropylacrylamide), PNIPAm shows reversible transition between hydrophilic-hydrophobic characteristics at the vicinity of human physiological temperature has great potential to propel the development of smart tissue engineering scaffold and drug delivery. However, the limited availability and its high cost have dampened the extent of research on this polymer. To address these challenges, the current work demonstrates an economical lab-scale polymerization of crosslinked PNIPAm and the optimised parameters to produce mono-dispersed polymer hydrogel particles were investigated. Characterisation of the synthesized PNIPAm polymer revealed particle size polydispersity index of 0.215, indicative of distribution within the mono-dispersed range, with average hydrodynamic diameter of 346.3 nm. Zeta-potential of the synthesized PNIPAm was found to be -20.6 mV, suggesting an incipient instability in terms of colloidal coagulation. Viscosity of the synthesized PNIPAm (4 wt% concentration in methanol) was 28.6 cP. Thermal gravimetric analysis (TGA) indicated the thermal degradation of main chain PNIPAm fell in the range of 340 to 480°C.
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Yoon, Jun Hyok, Taehyoung Kim, Myungeun Seo, and Sang Youl Kim. "Synthesis and Thermo-Responsive Behavior of Poly(N-isopropylacrylamide)-b-Poly(N-vinylisobutyramide) Diblock Copolymer." Polymers 16, no. 6 (March 18, 2024): 830. http://dx.doi.org/10.3390/polym16060830.
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Thermo-responsive diblock copolymer, poly(N-isopropylacrylamide)-block-poly(N-vinylisobutyramide) was synthesized via switchable reversible addition–fragmentation chain transfer (RAFT) polymerization and its thermal transition behavior was studied. Poly(N-vinylisobutyramide) (PNVIBA), a structural isomer of poly(N-isopropylacrylamide) (PNIPAM) shows a thermo-response character but with a higher lower critical solution temperature (LCST) than PNIPAM. The chain extension of the PNVIBA block from the PNIPAM block proceeded in a controlled manner with a switchable chain transfer reagent, methyl 2-[methyl(4-pyridinyl)carbamothioylthio]propionate. In an aqueous solution, the diblock copolymer shows a thermo-responsive behavior but with a single LCST close to the LCST of PNVIBA, indicating that the interaction between the PNIPAM segment and the PNVIBA segment leads to cooperative aggregation during the self-assembly induced phase separation of the diblock copolymer in solution. Above the LCST of the PNIPAM block, the polymer chains begin to collapse, forming small aggregates, but further aggregation stumbled due to the PNVIBA segment of the diblock copolymer. However, as the temperature approached the LCST of the PNVIBA block, larger aggregates composed of clusters of small aggregates formed, resulting in an opaque solution.
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Deng, Zexing, Yi Guo, Xin Zhao, Tianming Du, Junxiong Zhu, Youlong Xie, Fashuai Wu, Yuheng Wang, and Ming Guan. "Poly(N-isopropylacrylamide) Based Electrically Conductive Hydrogels and Their Applications." Gels 8, no. 5 (May 1, 2022): 280. http://dx.doi.org/10.3390/gels8050280.
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Poly(N-isopropylacrylamide) (PNIPAM) based electrically conductive hydrogels (PNIPAM-ECHs) have been extensively studied in recent decades due to their thermal-responsive (leading to the volume change of hydrogels) and electrically conductive performance. The incorporation of conductive components into the PNIPAM hydrogel network makes it become conductive hydrogel, and as a result, the PNIPAM hydrogel could become sensitive to an electrical signal, greatly expanding its application. In addition, conductive components usually bring new stimuli-responsive properties of PNIPAM-based hydrogels, such as near-infrared light and stress/strain responsive properties. PNIPAM-ECHs display a wide range of applications in human motion detection, actuators, controlled drug release, wound dressings, etc. To summarize recent research advances and achievements related to PNIPAM-ECHs, this manuscript first reviews the design and structure of representative PNIPAM-ECHs according to their conductive components. Then, the applications of PNIPAM-ECHs have been classified and discussed. Finally, the remaining problems related to PNIPAM-ECHs have been summarized and a future research direction is proposed which is to fabricate PNIPAM-ECHs with integrated multifunctionality.
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Liu, Yan Zhi, Yan Liu, Su Rui Zhao, and Yi Jing Li. "Surface Redox Initiated Polymerization to Prepare the Poly(N-isopropylacrylamide) Coating." Advanced Materials Research 602-604 (December 2012): 1706–9. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.1706.
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A hydroxylated silicon substrate was modified with 3-aminopropyltriethoxysilane (APTES) monolayer, followed by the surface initiated graft polymerization of the N-isopropylacrylamide (NIPAm). The microstructure of poly(N-isopropylacrylamide) (PNIPAm) coating was examined by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. And the results showed that about 50 nm thickness of PNIPAm coating grafted successfully.
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Qiu, Xing-Ping, Evgeniya V. Korchagina, Jessica Rolland, and Françoise M. Winnik. "Synthesis of a poly(N-isopropylacrylamide) charm bracelet decorated with a photomobile α-cyclodextrin charm." Polym. Chem. 5, no. 11 (2014): 3656–65. http://dx.doi.org/10.1039/c3py01776a.
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Musial, Witold, Bojana Voncina, Janusz Pluta, and Vanja Kokol. "The Study of Release of Chlorhexidine from Preparations with Modified Thermosensitive Poly-N-isopropylacrylamide Microspheres." Scientific World Journal 2012 (2012): 1–8. http://dx.doi.org/10.1100/2012/243707.
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The aim of this study was to investigate and compare the release rates of chlorhexidine (CX) base entrapped in the polymeric beads of modified poly-N-isopropylacrylamides (pNIPAMs) at temperatures below and over the volume phase transition temperature (VPTT) of synthesized polymers: pNIPAM-A with terminal anionic groups resulting from potassium persulfate initiator, pNIPAM-B with cationic amidine terminal groups, and pNIPAM-C comprising anionic terminals, but with increased hydrophobicity maintained by the N-tert-butyl functional groups. The preparations, assessed in vitro below the VPTT, release an initial burst of CX at different time periods between 120 and 240 min, followed by a period of 24 h, when the rate of release remains approximately constant, approaching the zero-order kinetics; the release rates for the polymers beads are as follows: pNIPAM-C>pNIPAM-B>pNIPAM-A. The pattern of release rates at temperature over the VPTT is as follows: pNIPAM-C>pNIPAM-A>pNIPAM-B. In the presence of pNIPAM-C, the duration between the start of the release and the attained minimal inhibitory concentration (MIC) for most of the microbes, in conditions over the VPTT, increased from 60 to 90 min. The release prolongation could be ascribed to some interactions between the practically insoluble CX particle and the hydrophobic functional groups of the polymer.
Dissertations / Theses on the topic "Poly(N-isopropylacrylamide) [PNIPAM]"
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Wiberg, von Schantz Cedrik. "Ion association to poly(N-isopropylacrylamide) by diffusion and electrophoretic NMR." Thesis, KTH, Skolan för kemivetenskap (CHE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-158534.
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PNIPAM (poly(N-Isopropylacrylamide)) is a well-known thermoresponsive polymer. Dissolved in water, it shows a structural change at 32 oC, above which the polymer folds together, and a phase separation occurs. The temperature where the polymer changes structure is known as the LCST (Lower Critical Solution Temperature), and can be modified by adding certain salts to the solution [1]. The mechanism by which the ionic components of the salts affect the LCST is not yet completely understood. The purpose of this master thesis is to study this mechanism. In order to investigate the mechanism, a combination of diffusion NMR and electrophoretic NMR was used, giving the effective charge per molecule which is directly proportional to the grade of association of ions to the polymer. The salts tested were: NaCl, NaClO4, NaSO4, NaI, NaSCN and CaCl2 from which the ClO4-, SCN-, and I- ions, as well as Cl- ions from CaCl2, were found to bind to PNIPAM.
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Riquel-Loizelet, Noelline. "Assemblages supramoleculaires de type (pseudo)polyrotaxane : vers la synthèse de modèles biocompatibles de cellules musculaires." Electronic Thesis or Diss., université Paris-Saclay, 2025. http://www.theses.fr/2025UPASF004.
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En s'inspirant du vivant, le biomimétisme invite à développer de nouvelles familles de matériaux, pour des applications variées. Dans ce contexte, des assemblages supramoléculaires de type (pseudo)polyrotaxanes, semblables à des colliers de perles, pourraient permettre d'obtenir des matériaux innovants stimulables, par exemple des matériaux capables de mimer le mouvement d'un muscle sous l'effet d'un stimulus. L'objectif de cette thèse a été de synthétiser des (pseudo)polyrotaxanes biocompatibles et thermostimulables, à partir de γ-cyclodextrine (γ-CD) et de copolymères à blocs, constitués de poly(N-isopropylacrylamide) (PNIPAM) et de poly(oxyde d'éthylène) (POE), afin d'obtenir des matériaux dont les propriétés mécaniques pourraient être modifiées de manière réversible en réponse à un stimulus extérieur. Le PNIPAM a été choisi pour son caractère thermosensible, tandis que le POE, a lui été choisi pour son affinité particulière avec les cyclodextrines, facilitant ainsi leur enfilage. Au cours de ces travaux de thèse, la formation d'assemblages supramoléculaires avec des CDs a d'abord été étudiée en présence d'homopolymères de PNIPAM et de POE (de longueurs variables et d'extrémités variables), puis avec des copolymères diblocs, puis triblocs (ABA ou BAB), synthétisés selon différentes voies (couplage, ATRP, RAFT). La caractérisation des édifices a été réalisée en mobilisant diverses techniques d'analyse : RMN 1H, MALDI-TOF, DRX, CES et TGA. Les résultats ont montré que les γ-CDs s'enfilaient majoritairement sur le bloc de POE qu'il soit situé au centre ou aux extrémités des différents copolymères avec un nombre de CDs que l'on peut contrôler, en fonction de la stœchiométrie (γ-CDs) : (polymère) adoptée avant la complexation, la longueur des chaines, la température. Plusieurs architectures ont été proposées pour ces assemblagesInspired by the living world, biomimicry encourages the development of new families of materials for a wide range of applications. In this context, (pseudo)polyrotaxane-type supramolecular assemblies, like strings of pearls, could make it possible to obtain innovative stimulable materials, for example materials capable of mimicking the movement of a muscle under the effect of a stimulus. The aim of this thesis was to synthesize biocompatible, thermostimulable (pseudo)polyrotaxanes from γ-cyclodextrin (γ-CD) and block copolymers, consisting of poly(N-isopropylacrylamide) (PNIPAM) and poly(ethylene oxide) (POE), in order to obtain materials whose mechanical properties could be reversibly modified in response to an external stimulus. PNIPAM was chosen for its thermosensitive properties, while POE was chosen for its particular affinity with cyclodextrins, making them easier to thread. During this thesis work, the formation of supramolecular assemblies with CDs was first studied in the presence of homopolymers of PNIPAM and POE (of variable lengths and variable ends), then with diblock, then triblock copolymers (ABA or BAB), synthesized by different routes (coupling, ATRP, RAFT). Characterization of the edifices was carried out by mobilizing various analytical techniques: 1H NMR, MALDI-TOF, DRX, CES and TGA. The results showed that γ-CDs threaded predominantly onto the POE block whether located in the center or at the ends of the various copolymers with a number of CDs that could be controlled, depending on the (γ-CDs):(polymer) stoichiometry adopted prior to complexation, chain length, temperature. Several architectures have been proposed for these assemblies
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Vialar, Pierre. "Propriétés mécaniques et nanotribologiques de monocouches auto-assemblées de microgels de poly(NIPAM) cationique en milieux aqueux." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0225/document.
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Le but de cette thèse est de faire évoluer les connaissances et la compréhension des systèmes lubrifiants en milieux aqueux, synthétiques comme biologiques. Pour cela, nous élaborons des systèmes de monocouches auto-assemblées de microgels thermosensibles de pNIPAM cationiques afin d’en étudier les propriétés mécaniques et nanotribologiques. Nous mettons au point plusieurs synthèses de microgels afin d’étudier l’effet de l’élasticité sur le comportement tribologique. Nous regardons également l’effet de la nature du greffage des microgels en sur-face, en élaborant une méthode de couplage chimique novatrice, pour comparer les propriétés de monocouches physi- et chimisorbées. Nous étudions les propriétés mécaniques en mi-lieux aqueux des couches des différents microgels en fonction de la température, de la nature du greffage et du sel en présence, à l’aide d’une Microbalance à Cristal de Quartz avec mesure de Dissipation (QCM-D). Le coeur de notre étude est réalisé à l’aide d’un Appareil de Forces de Surface (SFA) modifié pour permettre des mesures tribologiques, dont les résultats seront traités en deux parties. La première consiste à caractériser les forces normales de surface lors-que l’on comprime deux surfaces décorées de microgels. La seconde est constituée de l’ana-lyse de ces surfaces sous compression et cisaillement. Nous explorons les propriétés lubrifiantes du système et observons l’apparition une force de normale dépendant de la vitesse de cisaillement, et dont nous cherchons l’origine. Nous avons ainsi découvert un mécanisme propre au substrat souple, décoré de particules discrètes avec un contact répulsif sans friction à longue portéeThe aim of this project is to advance the knowledge and understanding of lubricating systems, whether synthetic or biological, in aqueous media. For this purpose, we develop self-assem-bled monolayer 2D-arrays of cationic pNIPAM thermosensitive microgels in order to study their mechanical and nanotribological properties. We establish several synthetic routes to modulate the microgel rigidity and study its effect on the tribological behaviour. We also look at the effect of the grafting nature of microgels on the substrate, by developing an innovative chemical coupling method, to compare the properties of physisorbed and chemisorbed mon-olayers. We probe the mechanical properties of the microgel layers in aqueous environment while varying the temperature, the nature of the grafting and the salts added to the system, primarily by using a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D). The core of our study is performed using a modified Surface Forces Apparatus (SFA) which allows for tribological measurements, the results of which will be treated in two parts. First, we char-acterise the normal surface forces when compressing two surfaces decorated with the micro-gel layers. Second, we study the behaviour of these surfaces under compression and shear. We explore their lubricant properties and observe the appearance of a shear-induced velocity-dependent lift force, whose origin we seek to determine. We thus discovered a mechanism specific to a compliant substrate, decorated with discrete particles presenting a repulsive con-tact without friction at long range
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Hervé, Mélanie. "Polymères greffés thermoassociatifs : de l'organisation en solution aux propriétés macroscopiques." Paris 6, 2002. http://www.theses.fr/2002PA066180.
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James, Hodari-Sadiki L. "Thermo-Responsive Polymers for Cell-Based Therapeutic Applications." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416231680.
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Alghunaim, Abdullah. "Immobilization of Poly(N-Isopropylacrylamide) on Hydroxylated Surfaces Using Cross-linked Organosilane Networks." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1467858917.
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Patel, Nikul Girishkumar. "A Spin-Coated Thermoresponsive Substrate for Rapid Cell Sheet Detachment and Its Applications in Cardiac Tissue Engineering." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1386671454.
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Pullela, Srinivasa. "DYNAMICS OF INTELLIGENT POLY(N-ISOPROPYLACRYLAMIDE) MICROGELS." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-464.
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This dissertation investigates the self assembly and automatic oscillation of intelligent
poly (N-isopropylacrylamide) [PNIPAM] microgel particles. The equilibrium phase
diagram as a function of temperature and concentration was constructed for the charged
PNIPAM spheres. The PNIPAM microgel particles display rhythmic size oscillations
when covalently coupled to a nonlinear chemical reaction, the Belousov-Zhabotinsky
(BZ) reaction. The nonequilibrium dynamics of PNIPAM microgels in the presence of
BZ reaction was studied by the systematic variation of substrate concentrations and
temperature. In addition, the BZ chemical reaction was modeled to reveal the existence
of upper temperature limits for nonlinear chemical systems.
The experiments employ environment sensitive PNIPAM particles that are sensitive to
temperature, pH, and ionic strength. The PNIPAM particles have been demonstrated
here to behave as hard spheres at low pH values and soft spheres at high pH. This is
done by measuring the freezing and melting boundary of fluid-crystal coexistence region
with a new technique which is simpler and quicker compared to the traditional
sedimentation method.
A novel method was developed to achieve size uniformity of PNIPAM gel particles with
covalently-bound tris(bipyridyl)ruthenium(II) via the coordination chemistry between a
ruthenium complex and the monodispersed PNIPAM gel particles bearing bipyridine
ligands. The correlation between the dynamic behavior of BZ reaction induced mechanical oscillations of PNIPAM particles and substrate concentrations was presented
in a ternary phase diagram. In particular, the dependence of oscillation frequency and
induction time on the substrate concentrations was studied. The temperature dependency
of the induction time and oscillatory frequency of the BZ reaction in this polymerimmobilized
catalyst system were compared to the bulk BZ reaction with the catalyst in
the solution phase. Prolonged induction times were observed for the immobilized
catalyst, compared with free catalyst, while little difference was observed on the
oscillation frequency.
A theoretical improvement has been achieved by incorporating the temperature
dependence in the BZ Oregonator model. Bifurcation has been calculated in the phase
space spanned by initial reagents concentration ratio, stoichiometric factor and
temperature. The existence of upper temperature limits has been demonstrated.
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Allen, Ainsley Larue. "Covalent Layer-by-Layer Synthesis of Responsive Porous Filters." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9153.
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Poly(N-isopropylacrylamide) (PNIPAM), a temperature responsive polymer, undergoes a phase change at a lower critical solution temperature (LCST) in aqueous solutions. For PNIPAM this temperature is 32 °C in water. Below the LCST, the polymer is readily solvated by water. As the temperature of the solution increases, the polymer undergoes a phase transition so that above the LCST it is no longer water soluble. The LCST of PNIPAM may be changed by the addition of salt solutions from the Hofmeister series which will follow the Hofmeister effect for salting-in and salting-out the polymer.
Temperature responsive polymers may be grafted to a surface in a variety of methods to create responsive thin films that exhibit a change in wettability. The surface wettability is directly related to the polymers ability to be solvated in its coil conformation. When PNIPAM is grafted to a surface, the surface becomes alternatively hydrophobic and hydrophilic in response to both temperature and the anions in the Hofmeister series which take the surface either above or below the LCST of PNIPAM.
The synthesis of responsive nanocomposite grafts was successfully applied to glass slides and three-dimensional surfaces, porous glass frits which were capable of controlling the passive flow rate. The nanocomposite graft was assembled in a covalent layer-by-layer approach to create more chemically robust surfaces, and also to incorporate nanoparticles into the graft for increased surface roughness and therefore improve wettability response. Because of a much greater inherent roughness to a glass frit, characterization of the polymers and nanoparticles was performed before they were covalently bound to the surface. The final product, a functionalized frit with a PNIPAM/SiO2 nanocomposite graft, was analyzed by observing changes in the passive permeation rate of the frit between water and salt solutions. These changes in flow were indicative of the surface bound PNIPAM changing between its hydrophilic and hydrophobic conformation in response to water and concentrations of kosmotropic salts such as sodium sulfate and sodium citrate. In addition to the solute response, the frit was also determined to be responsive to temperature and concentration. Water exhibited a passive flow rate 1000 times faster than a kosmotropic salt but had a similar flow rate to that a chaotropic salt. By measuring the flow rate of 0.5 M Na2SO4 at ~7 °C in a cold room and at room temperature it was observed that sodium sulfate in the cold room passed through the frit at a rate 100 times faster than at room temperature. Because of the hysteresis of PNIPAM documented in literature, washing procedures were kept consistent between experiments to achieve more reproducible results.
It was concluded that the frits were temperature responsive and had relative standard deviations below 25 percent for flow rates on a single frit. However, standard deviations of flow rates between frits were higher. This was likely due to a combination of factors, such as the frits’ pore size range of 10 μm resulting in the possibility of varied degrees of functionalization of each frit.
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Ciocoiu, Oana Nicoleta. "Grafting of sodium alginate with poly (N-isopropylacrylamide) chains. Study of the thermothickening behavior." Thesis, 2010. http://nemertes.lis.upatras.gr/jspui/handle/10889/3213.
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Designing new materials with improved or tailored properties is one of the main goals of the chemists. Two common ways are mainly used to get a material with improved or new properties: blending or chemical synthesis. Chemical synthesis is an unlimited method to get new substances with well-defined properties even it is often time consuming and not seldom costly.A rheology study has shown a considerable increase in viscosity of 1% aqueous solutions, 40 and 120 times at 550C, for the graft copolymers with a composition 67 and 80% in PNIPAM respectively as temperature increases above 350C. This behaviour is also related with a critical concentration that has been found around 0.6% for the same copolymers.
Fluorescence measurements have shown that this behavior is related with the hydrophobic character and aggregation of PNIPAM chains by increasing temperature over 350C.
A dynamic light scattering study in dilute aqueous solutions by varying temperature could provide more information on the kind of the transition taking place and the nature of the particles formed as temperature increases.Ο σχεδιασμός νέων υλικών με βελτιωμένες ιδιότητες είναι ένας από τους κύριους στόχους των χημικών. Δύο είναι οι πιο συνηθισμένοι τρόποι που χρησιμοποιούνται κυρίως για τη παραλαβή ενός υλικού με βελτιωμένες ή νέες ιδιότητες: ανάμειξη ή χημική σύνθεση. Χημική σύνθεση είναι η μέθοδος όπου λαμβάνονται νέα υλικά με καθορισμένες ιδιότητες αλλά έχει ως μειονέκτημα το κόστος και είναι συχνά χρονοβόρα.Μετρήσεις ρεολογίας έδειξαν μια αξιοσημείωτη αύξηση στο ιξώδες του 1% υδατικού διαλύματος, από 40 μέχρι 120 φορές στους 550C, για συστάσεις του εμβολιασμένου συμπολυμερούς σε PNIPAM 67 εως 80% αντίστοιχα, καθώς η θερμοκρασία αυξάνεται πάνω από τους 350C. Επιπλέον αυτή η συμπεριφορά σχετίζεται με μια κρίσιμη συγκέντρωση που βρέθηκε ίση με 0,6% για τα ίδια συμπολυμερή. Μετρήσεις φθορισμού έδειξαν ότι αυτή η συμπεριφορά σχετίζεται άμεσα με τον υδρόφοβο χαρακτήρα του PNIPAM καθώς η θερμοκρασία αυξάνεται πάνω από τους 350C. Μετρήσεις με δυναμική σκέδαση φωτός σε αραιά υδατικά διαλύματα σε διάφορες θερμοκρασίες μπορούν να δώσουν επιπλέον πληροφορίες για τη μετάπτωση που λαμβάνει χώρα και τη φύση των σωματιδίων όσο η θερμοκρασία αυξάνεται.
Book chapters on the topic "Poly(N-isopropylacrylamide) [PNIPAM]"
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Bergbreiter, David, and Chunmei Li. "Dye-Labeled PNIPAM [Poly(N-isopropylacrylamide)]-Supported Acylation Catalysts." In Catalysis of Organic Reactions. CRC Press, 2002. http://dx.doi.org/10.1201/9780203911013.ch45.
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"Thermally Responsive Materials." In Stimuli-Responsive Materials: From Molecules to Nature Mimicking Materials Design, 55–93. The Royal Society of Chemistry, 2016. http://dx.doi.org/10.1039/bk9781849736565-00055.
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This chapter focuses on thermally responsive polymers and their building blocks. Starting from polymeric assemblies in solutions, going into solids with stimuli-responsive transitions, a comprehensive summary of existing monomers capable of thermal responses is provided. The attractiveness of temperature-responsive homo- and copolymers is primarily driven by the ability of macromolecular segments to undergo conformational changes at a designated temperature. The earliest reports of the thermal phase transitions in poly(N-isopropylacrylamide) (PNIPAM) go back to the late 1960s, and this still continues to be an important and advantageous area in controlled drug delivery, bioseparation, enzyme activity, filtration, and mediating surface/interfacial properties. The last section of this chapter focuses in the thermally responsive peptides, their stimuli-responsiveness, selected applications, and examining the general principles governing the role of entropic contributions to stimuli-responsiveness.
Conference papers on the topic "Poly(N-isopropylacrylamide) [PNIPAM]"
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Grau-Bartual, Sandra, and Ahmed M. Al-Jumaily. "An Approach to Capture Humidity From Exhaled Air." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86507.
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Lung supportive devices (LSD) are widely used for respiratory ventilation and therapy to help provide breathing support for patients with various lung diseases including Obstructive Sleep Apnea. These devices deliver air to the patient through a nasal or facial mask, and the use of these devices normally results in dryness in the upper airways. However, the exhaled air consists of very high humidity content. The question raised, is it possible to recover some of the moisture content of this air to reuse in the inhalation process. This research focuses on developing an element which can recover the moisture from the exhaled air and the possibility of using it for re-inhalation. The main component is made up of a fibrous cotton fabric polymerized with Poly (N-isopropylacrylamide) (PNIPAM) and sewed with a resistor filament to control the temperature. The results show a viable element which is able to trap water molecules from the expiration airflow and release them into the inspiration airflow.
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Blanco, Letia, Panos S. Shiakolas, Pranesh B. Aswath, Christopher B. Alberts, Chris Grace, Kyle Godfrey, and Drew Patin. "A Thermoresponsive Hydrogel Based Controlled Drug Delivery Device." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88564.
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Thermoresponsive hydrogels exhibit the unique property of volume change as a function of change in temperature as they transition between hydrophilic and hydrophobic states. These hydrogels can be loaded with drug/protein and serve as reservoirs for drug/protein delivery applications. A hydrogel based device for controlled drug delivery is designed with a number of subsystems that are interfaced with LabVIEW for development of a functional device. The device was designed using analytical and finite element analysis procedures and fabricated. In this manuscript, the device design will be reviewed and discussed. A parametric study was performed to examine the device operation and performance as function of hydrogel heating/cooling temperature profiles. Subsequently, the device was employed in a series of experiments to examine the delivery of a protein as a function of thermal stimuli. The matrix used in this study was poly(ethylene glycol) diacrylate (PEGDA) and the drug delivery nanoparticles carriers were poly(N-isopropylacrylamide-co-acrylamide (PNIPAM) with a lower critical solution temperature (LCST) around 40°C. The protein of choice was bovine serum albumin (BSA). The results of this study illustrate that the development of a multi-drug or therapeutic delivery device is possible and that individual drugs can be delivered on demand using a closed loop control system.
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Fu, Guoguang, and Winston Soboyejo. "Modified Poly (N-Isopropylacrylamide) Hydrogels for Drug Delivery." In ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19491.
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Thermo-responsive hydrogel can change their swelling behavior and drug release characteristics in response to environmental temperature [1–5]. Poly(N-isopropylacrylamide) (PNIPA) hydrogel undergoes a phase transition when the temperatue is lower than a lower critical solution temperature (LCST) of ∼32°C in aqueous solution [8], and drug release profiles in PNIPA hydrogel can be controlled by the alternation of their solution temperatures.
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Han, Daehoon, Zhaocheng Lu, and Howon Lee. "Projection Micro-Stereolithography of Temperature Responsive Mechanically Tough Hydrogels." In ASME 2016 11th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/msec2016-8667.
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Temperature responsive hydrogel has attracted considerable attention as an outstanding material for creating a variety of reconfigurable structures. As a well-known temperature responsive hydrogel, poly(N-isopropylacrylamide) (PNIPAAm) has been widely used in various applications. Here, we report high resolution 3D micro fabrication of PNIPAAm structures using projection micro-stereolithography (PμSL). We also show the controllability of degree of swelling and transition temperature of 3D printed PNIPAAm structures by controlling process parameters of PμSL. In addition, we demonstrate improvement of mechanical properties of PNIPAAm by introducing ionic crosslinks into 3D printed PNIPAAm structures to form ionically and covalently crosslinked hybrid networks.
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Londe, Ghanashyam, Anindarupa Chunder, Lei Zhai, and Hyoung J. Cho. "A Nanostructured Thermosensitive Smart Surface With Integrated Microheater for Wettability Control." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68732.
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This paper describes the design and fabrication of a switchable thermosensitive polymer with an integrated microheater as a smart surface platform for wettabilty control. The thermoresponsive surface is synthesized on a glass substrate using the polymer poly(N-isopropylacrylamide) (PNIPAAm) which can change its wettability when subjected to change in temperature. PNIPAAm is hydrophilic when the surface temperature is less than the lower critical solution temperature (LCST) range of about 28–33 °C and is hydrophobic above the LCST range. The PNIPAAm surface is heated by spiral gold microheaters which are fabricated on the lower side of the glass substrate. The contact angle change with change in temperature is tested using a standard goniometer. Time response analysis of the surface is presented. This smart surface can be used as an active or adaptive component for microflow regulation and can be potentially integrated into large scale lab-on-chip (LOC) systems.
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Zhang, Feini, Shuqi Lai, Anthony M. Jacobi, and Paul V. Braun. "Thermo-Responsive Polymer Grafted Aluminum Surface to Actively Modulate Water Wettability." In ASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/smasis2015-9067.
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Thermo-responsive wettability is studied for adaptive surface, which can potentially help to enhance the performance of thermal devices under various operation conditions. Poly(N-isopropylacrylamide) or PNIPAAm polymer brush can be grafted onto solid surfaces so that at temperatures below the lower critical solution temperature (LCST), the surface is hydrophilic, while at temperatures above LCST, it automatically becomes more hydrophobic. In this study, PNIPAAm is grafted on to aluminum alloy 6061, which is a multipurpose alloy commonly used in thermal mechanical systems. It is demonstrated by water static contact angle experiment at varies temperature that, the surface is hydrophobic at temperatures above LCST, and hydrophilic below LCST. The results are compared with bare aluminum surface at similar temperatures. Grafting PNIPAAm polymer brush on roughened aluminum surface would result in the ability to automatically switch between superhydrophobic state and superhydrophilic state in response to temperature change.
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Wu, Qinglin, Peng Tian, and Quang Cao. "Poly(N-Isopropylacrylamide-Co-Methacrylic Acid) Micro/Nanoparticles: Formulation, Size Distribution and Use for Cu++ Adsorption." In 2008 Second International Conference on Integration and Commercialization of Micro and Nanosystems. ASMEDC, 2008. http://dx.doi.org/10.1115/micronano2008-70019.
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Poly(N-isopropylacrylamide-co-methacrylic Acid (PNIPAAm-MAA) micro/nano-particles were formulated. The effect of monomer ratio, surfactant, and crosslinker contents on size/size distribution, phase transition behavior, and Cu2+ adsorption efficiency of the particles was investigated. The ionized MAA groups brought both temperature and pH sensitiveness to the PNIPAAm-MAA copolymer particles. As monomer ratio and crosslinker content increased and the amount of surfactants decreased, the particle size increased. The influence of the crosslinker content on particle size was less significant compared to the effect of monomer ratio and surfactants. When temperature increased, the particles tended to shrink and reduced their size to near or below 100nm. The Weibull distribution was successfully used to describe the diameter distribution of the nano-particles, whereas the lognormal was deemed not adequate for that purpose. The method of moments was used to predict parameters of the Weibull distribution. The Weibull parameters were recovered from diameter mean and variance, both of which were predicted from temperature. The distributions predicted from various temperatures for MAA/NIPAAm ratios of 0.05 and 0.10 showed trends similar to those in the data. Studies on chelation efficiency of the particles with Cu2+ ions showed that the amount of the Cu2+ ions adsorbed varied with temperature. Particle size played a very important role in the adsorption and nanoparticles greatly improved adsorption efficiency, compared with their micro hydrogel counterparts. The amount of adsorption increased with increase of MAA ratio in copolymers, but adsorption efficiency decreased with increased particle size. The high adsorption efficiency of metal ions by PNIPAAm-MAA polymer particles provides an effective technique for recovering metal ions (e.g., Cu2+) from wood treated with metal based preservatives.
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Spasojević, Jelena, Ivana Vukoje, Nikolina Nikolić, Julijana Tadić, Milica Milošević, Vesna Vodnik, and Aleksandra Radosavljević. "The effect of silver nanoparticle shape on the physicochemical properties of a poly(n-isopropylacrylamide) hydrogel nanocomposites." In 36th International Congress on process engineering. SMEITS, 2023. http://dx.doi.org/10.24094/ptk.023.197.
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Hydrogels have unique properties and many potential applications, particularly in medicine and biotechnology. Gel porosity and swelling properties, stability, and biocompatibility are characteristics that are widely variable and easily adjusted. Stimuli-responsive or intelligent hydrogels are a class of these materials that shows a significant response to small changes in the surrounding environment. Poly(N-isopropylacrylamide) (PNiPAAm) is the best-known thermosensitive polymer with a well-defined volume phase transition temperature (VPTT) around 32°C. On the other hand, silver nanoparticles (AgNPs) have been the subject of intense interest due to their size-dependent optical, catalytic, and electronic properties as well as remarkable antimicrobial potential. Within the last decade, scientists have demonstrated that anisotropic AgNPs can be synthesized in a controlled manner and that these materials exhibit distinctively different physicochemical properties from their spherical counterparts. A significant challenge that scientists face is establishing how these nanoparticles can be used in a wider spectrum of practical applications. Therefore, we present a simple, straightforward two-step synthesis of AgNPs/PNiPAAm hydrogel nanocomposites that includes the chemical formation of both spherical and triangular AgNPs, followed by gamma irradiation-induced PNiPAAm crosslinking in the presence of nanoparticles. The gamma irradiation technique merges sterilization and synthesis in a single technological step, optimizing the process and opening up a wide range of innovative biomedical applications. The formation of stable and uniformly distributed AgNPs in the polymer was confirmed by UV-VIS spectroscopy, while the network porous sponge-like structure was observed by SEM analysis. Physicochemical characterization was performed by examining the swelling and deswelling processes in water at 25°C and 48°C, respectively. In addition, AgNPs were shown to have an effect on VPTT values. Our main goal is to investigate how different morphologies of AgNPs affect the physicochemical properties of nanocomposite samples, considering the potential applications and the ongoing need for the widespread use of biocompatible materials.