On the temperature-induced coil to globule transition of poly-N-isopropylacrylamide in dilute aqueous solutions

Graziano, Giuseppe

doi:10.1016/s0141-8130(99)00122-1

Cited by 161 publications

(120 citation statements)

References 48 publications

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“…26 Poly(N-substituted acrylamides) are a family of thermoresponsive polymers displaying a LCST, and poly(N-isopropylacrylamide) (pNIPAM) is probably the most widely studied. 27 In aqueous solution, pNIPAM has a LCST at 32 °C; at this temperature it undergoes a sharp and reversible coil-to-globule phase transition from a hydrophilic to a more hydrophobic state, forcing water from the matrix. 2,5,9,19,22,[28][29][30] This phenomenon occurs due to the domination of entropic effects (displacement of water from the polymer matrix) over enthalpic effects (formation of hydrogen bonds between polymer and water molecules) as the temperature increases above the LCST.…”

Section: Introductionmentioning

confidence: 99%

Study of Water Adsorption in Poly(N-isopropylacrylamide) Thin Films Using Fluorescence Emission of 3-Hydroxyflavone Probes

et al. 2010

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. (2010) 'Study of water adsorption in PolyN-isopropylacrylamide) thin films using fluorescence emission of 3-hydroxyflavone probes'. Macromolecules, 43 (22):9488-9494. Publisher ACS PublicationsLink to publisher ' Abstract:The non-contact, measurement of water uptake in micro-scale (1-100 µm), thermoresponsive Poly(N-isopropylacrylamide) thin films is challenging. We assessed the efficacy of three different 3-Hydroxyflavone (3-HF) based fluorophores; to monitor water uptake in pNIPAM thin films close to the Lower Critical Solution Temperature (LCST) at 25 and 37 ºC. These 3-HF fluorophores undergo excited state intramolecular proton transfer, yielding emission from normal (N*) and tautomeric (T*) excited-state forms. The emission intensity ratio, log(I N* /I T* ) and N* band position are environmentally sensitive. Water adsorption in pNIPAM thin films follows a non-linear, two phase process: at low relative humidity, the adsorbed water disrupts polymerfluorophore hydrogen bonding, yielding small changes in log(I N* /I T* ) ratios, and overall intensity, at higher relative humidity, these intensity parameters (but not fluorescence lifetime) change dramatically, indicating a larger change in local polarity. These probes are thus sensitive indicators of water uptake in pNIPAM.

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Section: Introductionmentioning

confidence: 99%

Study of Water Adsorption in Poly(N-isopropylacrylamide) Thin Films Using Fluorescence Emission of 3-Hydroxyflavone Probes

et al. 2010

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“…This transition involves the breakage of intermolecular hydrogen bonds with the water molecules, which are replaced by intramolecular hydrogen bonds amongst the dehydrated amide groups. Subsequently, the PNIPAAm molecules assume a globule conformation, exposing the hydrophobic isopropyl groups to the water interface (Baysal and Karasz 2003;Graziano 2000). Therefore, when immobilized onto a solid substrate, the LCST behavior of PNIPAAm render the surface with thermo-responsive wettability (da Silva et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Poly(N‐isopropylacrylamide) surface‐grafted chitosan membranes as a new substrate for cell sheet engineering and manipulation

Silva

López-Pérez

Elvira

et al. 2008

Biotech & Bioengineering

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The immobilization of poly(N-isopropylacrylamide) (PNIPAAm) on chitosan membranes was performed in order to render membranes with thermo-responsive surface properties. The aim was to create membranes suitable for cell culture and in which confluent cell sheets can be recovered by simply lowering the temperature. The chitosan membranes were immersed in a solution of the monomer that was polymerized via radical initiation. The composition of the polymerization reaction solvent, which was a mixture of a chitosan non-solvent (isopropanol) and a solvent (water), provided a tight control over the chitosan membranes swelling capability. The different swelling ratio, obtained at different solvent composition of the reaction mixture, drives simultaneously the monomer solubility and diffusion into the polymeric matrix, the polymerization reaction rate, as well as the eventual chain transfer to the side substituents of the pyranosyl groups of chitosan. A combined analysis of the modified membranes chemistry by proton nuclear magnetic resonance ((1)H-NMR), Fourier transform spectroscopy with attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) showed that it was possible to control the chitosan modification yield and depth in the solvent composition range between 75% and 100% of isopropanol. Plasma treatment was also applied to the original chitosan membranes in order to improve cell adhesion and proliferation. Chitosan membranes, which had been previously subjected to oxygen plasma treatment, were then modified by means of the previously described methodology. A human fetal lung fibroblast cell line was cultured until confluence on the plasma-treated thermo-responsive chitosan membranes and cell sheets were harvested lowering the temperature.

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“…The results indicated that solutions heated within the [31][32][33][34][35][36] C temperature range consisted of fluid-like particles which were able to merge and grow in size. At higher temperatures (36)(37)(38)(39)(40)(41)(42)(43)(44)(45) C) the PNIPAm mesoglobules behaved like more rigid spheres that were unable to merge by collision into larger, slower rotating globules. This study also employed FRET measurements using pyrene (Py) and naphthalene (Np) labeled PNIPAm.…”

Section: Phase Transitions At the Lcstmentioning

confidence: 99%

“…4.3) is probably the most widely known and studied. PNIPAm is a chemical isomer of poly-leucine, in that it has the polar peptide group in its side chain rather than in the hydrocarbon backbone [45]. In aqueous solution, PNIPAm has a LCST of 32 C; at this temperature it undergoes a sharp and reversible coil-to-globule phase transition from a hydrophilic to a more hydrophobic state, forcing water from the matrix [3,7,14,16,27,[46][47][48].…”

Section: Poly(n-isopropylacrylamide) Pnipammentioning

confidence: 99%

Fluorescence Analysis of Thermoresponsive Polymers

Morris

Ryder

2015

Reviews in Fluorescence 2015

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The use of microscale thin polymer films is widespread in biomedical science and engineering, with applications in areas such as tissue engineering, drug delivery, microfluidic devices, bio-adhesion mediators, and bio-actuators. Much attention is devoted to the use of functional polymers that display stimuliresponsive behavior with the intention of providing "smart" coatings. One potential example is the use of thin thermoresponsive polymer films as drug eluting coatings on medical devices, where not only does the polymer function as a drug reservoir but it also acts as a biocompatibility modulator to improve device performance.Often these thin polymer coatings have to be applied to complex geometries, which can cause problems for in-situ analysis. Another important consideration is the fact that these films have large surface area to mass ratios and thus water uptake can be significant. This is serious because coating stability, device efficacy, and long-term storage are influenced by the physiochemical properties of the polymer which are modulated by water content. Thus, there is a need for a rapid, non-contact, non-destructive, analytical method capable of analyzing thermoresponsive polymers in solution, and in-situ of the solid-state on medical devices. Fluorescence spectroscopy based methods can deal with both sample types and provide additional benefits in terms of high sensitivity and low probe concentrations, which provide for minimal sample disruption. This article gives a brief overview of the application of various fluorescence methods for the physicochemical characterization of thermoresponsive polymers such as poly (N-isopropylacrylamide), PNIPAm.

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On the temperature-induced coil to globule transition of poly-N-isopropylacrylamide in dilute aqueous solutions

Cited by 161 publications

References 48 publications

Study of Water Adsorption in Poly(N-isopropylacrylamide) Thin Films Using Fluorescence Emission of 3-Hydroxyflavone Probes

Study of Water Adsorption in Poly(N-isopropylacrylamide) Thin Films Using Fluorescence Emission of 3-Hydroxyflavone Probes

Poly(N‐isopropylacrylamide) surface‐grafted chitosan membranes as a new substrate for cell sheet engineering and manipulation

Fluorescence Analysis of Thermoresponsive Polymers

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