NMR Studies of the Structure and Dynamics of Polymer Gels Based onN-Isopropylacrylamide (NiPAAm) and Methacrylic Acid (MAA)

Díez-Peña, Eva; Quijada‐Garrido, Isabel; Barrales‐Rienda, J. M.; Wilhelm, Manfred; Spiess, Hans Wolfgang

doi:10.1002/1521-3935(20020201)203:3<491::aid-macp491>3.0.co;2-1

Cited by 67 publications

(54 citation statements)

References 22 publications

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“…Assuming that the exchange between free and bound water is associated with diffusion process of water molecules through mesoglobules, the direct correlation between the rate of exchange process (slow or fast) and the size of phase-separated mesoglobules was shown for concentrated and semidiluted PVME/D 2 O solutions [49]. Two separate signals of water were also found in PVME and PNIPAm hydrogels [50][51][52] and in homo-and copolymer [53]. On the other hand, a decrease in the temperature dependence of spin-spin relaxation time (T 2 ) of water observed in the transition region for PNIPAm microgels by Sierra-Martin et al [54,55] indicates a fast exchange between bound and free water.…”

Section: Characterization Of Ipn Hydrogel Samplesmentioning

confidence: 99%

Structures and interactions in collapsed hydrogels of thermoresponsive interpenetrating polymer networks

et al. 2014

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Temperature-induced collapse of hydrogels of interpenetrating polymer networks (IPNs) poly(Nvi nyl cap ro lac t am) / po ly( N -i sop ro pyl ac ryla mide ) (PVCL/PNIPAm) and poly(N-isopropylmethacrylamide) (PNIPMAm)/PNIPAm, where both components are thermoresponsive, was studied by combination of 1 H nuclear magnetic resonance (NMR) spectroscopy, small-angle neutron scattering (SANS), differential scanning calorimetry (DSC), and dynamic mechanical measurements. Behavior of studied hydrogels (one or two transitions) was found to depend on the ratio of both IPN components. For hydrogels of IPNs containing around 50 mol% of PNIPAm monomer units, separate transitions were revealed for both components. From SANS curves, it follows that compact three-dimensional multi-chain globules are formed in PNIPMAm/PNIPAm and PVCL/PNIPAm IPN hydrogels at temperatures above the phase transition, with a gyration radius of 14-28 nm. A certain portion of spatially restricted bound water (HDO) was established for all the studied IPNs at temperature above the volume phase transition from measurements of 1 H NMR spectra, spin-spin relaxation times (T 2 ), and diffusion coefficients (D) of HDO. Slow exchange regime between bound and free water was revealed. Spin-spin relaxation times (T 2 ) and diffusion coefficients (D) as obtained for the bound HDO are up to 2 orders of magnitude smaller in comparison with "free" HDO. Higher content of bound water as found for collapsed hydrogels of IPN PVCL/PNIPAm in comparison with PNIPMAm/PNIPAm hydrogels is in accordance with swelling experiments and lower values of the shear mechanical modulus; this shows the decisive role of bound water in this respect.

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Section: Characterization Of Ipn Hydrogel Samplesmentioning

confidence: 99%

Structures and interactions in collapsed hydrogels of thermoresponsive interpenetrating polymer networks

et al. 2014

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“…To deeply investigate if the polymer with higher LCST collapses at the same time that the polymer with lower transition temperature, several mixtures were analysed by 1 H NMR in D 2 O at different temperatures. 1 H NMR spectroscopy can be used to study the thermoreversible transition, [17,51] since a broadening of the NMR signals is observed at temperature above the LCST. As an example, Figure 5 shows the results obtained for sample 1G in a 0.1 M NaCl/D 2 O solution, where the signals corresponding to the polymer disappears above the LCST as consequence of the polymer collapse.…”

Section: Thermal Behaviour In Aqueous Solution Of Mixtures Of P(meo 2mentioning

confidence: 99%

Thermoresponsive Behavior of Mixtures of Epoxy Functionalized Oligo(ethylene glycol) Methacrylate Copolymers

París

Liras

Quijada‐Garrido

2011

Macro Chemistry & Physics

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Thermoresponsive random copolymers based on 2‐(2‐methoxyethoxy)ethyl methacrylate (MEO2MA) and oligo(ethylene glycol) methyl ether methacrylate (OEG8‐9MA) are synthesized by atom transfer radical polymerization (ATRP). In a second step, they are used as macroinitiators for the ATRP of glycidyl methacrylate (GMA), introducing a short end‐block with epoxy functionalities that allows the connection of the thermoresponsive polymers to a variety of molecules, surfaces, or particles. The resulting epoxy functionalized terpolymers exhibit lower critical solution temperatures (LCST), which can be adjusted by changing the feed monomer ratio of MEO2MA and OEG8‐9MA. Binary blends show one or two cloud points depending on the blend composition. A model for the polymer collapse in one mixed particle or in two different particles as function of composition is proposed. magnified image

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“…A new signal with smaller chemical shift which appears in the phase transition region and at temperatures above the phase transition we previously observed in concentrated poly(vinyl methyl ether) (PVME)/D 2 O solutions and similarly as in that case also for IPN hydrogels we assigned this signal to molecules of bound water. Two separate signals of water were found also in PVME and PNIPAm hydrogels and in homo‐ and copolymer microgels of NIPAm and N,N ‐diethylacrylamide in water/methanol mixtures . Figure shows that difference of chemical shifts between signals of “free” and bound water increases with increasing temperature reaching 0.06 ppm and 0.04 ppm for PNIPMAm/PNIPAm and PVCL/PNIPAm IPN hydrogels, respectively.…”

Section: Resultsmentioning

confidence: 87%

Phase Transition in Hydrogels of Thermoresponsive Interpenetrating Polymer Networks

Spěváček

Hanyková

2016

Macromolecular Symposia

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Summary We compared behavior of hydrogels of two types of thermoresponsive interpenetrating polymer networks (IPN), PNIPMAm/PNIPAm and PVCL/PNIPAm, during their phase transition. One or two transitions, depending on the ratio of both IPN components, were found by NMR and DSC. SANS results showed that compact multi‐chain globules with gyration radius ∼20 nm are formed in collapsed IPN hydrogels. A certain portion of spatially restricted bound water (HDO) was established for all studied IPNs in the phase transition region and at temperatures above the phase transition by NMR methods. Fraction of bound water slowly decreases with time. The separate signal of bound water in NMR spectra appears already in pretransition region at temperatures when polymer segments just begin to form collapsed structures. Higher content of bound water as found for collapsed PVCL/PNIPAm hydrogels in comparison with PNIPMAm/PNIPAm hydrogels is in accord with swelling experiments and lower values of the shear mechanical modulus, and shows the decisive role of bound water in this respect.

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NMR Studies of the Structure and Dynamics of Polymer Gels Based onN-Isopropylacrylamide (NiPAAm) and Methacrylic Acid (MAA)

Cited by 67 publications

References 22 publications

Structures and interactions in collapsed hydrogels of thermoresponsive interpenetrating polymer networks

Structures and interactions in collapsed hydrogels of thermoresponsive interpenetrating polymer networks

Thermoresponsive Behavior of Mixtures of Epoxy Functionalized Oligo(ethylene glycol) Methacrylate Copolymers

Phase Transition in Hydrogels of Thermoresponsive Interpenetrating Polymer Networks

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