1H NMR study of thermotropic phase transition of linear and crosslinked poly(vinyl methyl ether) in D2O

Hanyková, Lenka; Spěváček, Jiří; Ilavský, M.

doi:10.1016/s0032-3861(01)00381-0

Cited by 61 publications

(58 citation statements)

References 30 publications

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“…In addition to extensively studied poly(Nisopropylacrylamide) (PIPAm) aqueous solutions, the thermotropic phase transition was also studied by various methods (cloud point, viscometric, calorimetric, diffusion, viscoelastic, infrared and Raman measurements) for PIPMAm [1][2][3][4][5][6][7] and PVME [8][9][10][11][12][13][14][15] aqueous solutions. Recently, we have shown that 1 H NMR spectroscopy is another suitable method to follow the temperature-induced phase separation [16,17] and applied this method to D 2 O solutions of PVME and PIPMAm [18][19][20][21][22]. Both our and other cited papers have shown that LCST for PVME and PIPMAm differ by approx.…”

Section: Introductionmentioning

confidence: 94%

1H NMR study of thermotropic phase transitions in D2O solutions of poly(N-isopropylmethacrylamide)/poly(vinyl methyl ether) mixtures

Starovoytová

Spěváček

Hanyková

et al. 2004

Polymer

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Section: Introductionmentioning

confidence: 94%

1H NMR study of thermotropic phase transitions in D2O solutions of poly(N-isopropylmethacrylamide)/poly(vinyl methyl ether) mixtures

Starovoytová

Spěváček

Hanyková

et al. 2004

Polymer

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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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“…The most observable effect is a substantial decrease in the integrated intensity of all PVME bands due to the pronounced reduction in mobility. From the temperaturedependent integral intensities of the NMR signals, it is possible to calculate the fraction of phase-separated polymer units of significantly reduced mobility, p, using the following equation: 19,20,30 pðT…”

Section: ¹1mentioning

confidence: 99%

“…18,19 Above the phase separation, the fraction of PVME units involved in collapsed globule-like structures was approximately 0.85 for solutions in the concentration range 0.130 wt %.…”

mentioning

confidence: 99%

NMR and Thermodynamic Study of Phase Transition in Aqueous Solutions of Thermoresponsive Amphiphilic Polymer

Hanyková¹,

Radecki²

2012

Chemistry Letters

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1H NMR techniques combined with differential scanning calorimetry (DSC) experiments are employed to investigate the temperature-induced phase transition in aqueous poly(vinyl methyl ether) solutions. NMR data were used to construct van't Hoff plots, and changes in the enthalpy and entropy characterizing the phase transition were determined. It follows from a comparison of NMR and DSC thermodynamic parameters (¦H values) for solutions with c = 130 wt % that the size of the cooperative units (domains) undergoing the transition corresponds to the whole polymer chain.An aqueous poly(vinyl methyl ether) (PVME) solution exhibits a lower critical solution temperature (LCST) of around 308 K, above which the solution separates into two phases.1,2 On the molecular level, this phase separation is assumed to be a macroscopic manifestation of a coilglobule transition followed by aggregation, as shown for acrylamide-based polymers in water by light scattering and small neutron scattering. 37 The phase transition in PVME/water solutions has been investigated using cloud point, calorimetric, viscometric, viscoelastic, infrared, and Raman measurements.1,2,815 Maeda 9 found three distinct PVME concentration regions differing in the number of water molecules forming a complex with PVME. The phase diagram was revealed for aqueous PVME solutions from modulated-temperature differential scanning calorimetry (DSC) experiments. 14,16,17 In past decades, we applied 1 H NMR spectroscopy to investigate the structural and dynamical changes during temperature-induced phase separation in PVME/D 2 O solutions. 1823The phase separation is manifested in the NMR spectra by marked line broadening for a major part of the PVME units due to the formation of rather compact globule-like structures. 18,19 Above the phase separation, the fraction of PVME units involved in collapsed globule-like structures was approximately 0.85 for solutions in the concentration range 0.130 wt %. 19The data obtained from NMR spectroscopy were used to construct van't Hoff plots, and thermodynamic parameters of the transition in polymer solutions and hydrogels were determined. 2426 On the basis of the phenomenological model in which a macromolecule is viewed as consisting of independent cooperative units, the cooperativity of the transition can be related to a comparison of the effective (van't Hoff) enthalpy and the calorimetric enthalpy of a polymer molecule. 27,28 In the present work, our attention is focused on the thermodynamic investigation of the phase transition in aqueous solutions of PVME. The thermodynamic parameters obtained by NMR analysis using van't Hoff plots and by DSC are compared, and are used for characterization of the mesoglobules as a function of the polymer concentration. From a methodical point of view, we combined the measurements of 1 H NMR spectra (mainly integrated intensities) and calorimetric measurements.Aqueous PVME (M w = 60500 g mol ¹1, M w /M n ¥ 3) solutions were prepared in a broad polymer concentration range of c = 190 wt %. DSC mea...

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1H NMR study of thermotropic phase transition of linear and crosslinked poly(vinyl methyl ether) in D2O

Cited by 61 publications

References 30 publications

1H NMR study of thermotropic phase transitions in D2O solutions of poly(N-isopropylmethacrylamide)/poly(vinyl methyl ether) mixtures

1H NMR study of thermotropic phase transitions in D2O solutions of poly(N-isopropylmethacrylamide)/poly(vinyl methyl ether) mixtures

Structures and interactions in collapsed hydrogels of thermoresponsive interpenetrating polymer networks

NMR and Thermodynamic Study of Phase Transition in Aqueous Solutions of Thermoresponsive Amphiphilic Polymer

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