Role of Water/Methanol Clustering Dynamics on Thermosensitivity of Poly(N-isopropylacrylamide) from Spectral and Calorimetric Insights

Sun, Shengtong; Wu, Peiyi

doi:10.1021/ma1016693

Cited by 93 publications

(86 citation statements)

References 71 publications

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“…This is in contrast to results from Sun and Wu who studied PNIPAM chains in water/methanol mixtures; at high temperature (40 °C), the chains in the mixtures had smaller radii than chains in water. However, the plateau temperature we found, which is pictured in Figure , decreases first and has a minimum at x MeOH = 0.35; then it increases slightly and decreases again at high methanol contents.…”

Section: Resultscontrasting

confidence: 99%

Temperature dependent phase behavior of PNIPAM microgels in mixed water/methanol solvents

Kojima

Tanaka

Scherzinger

et al. 2012

J Polym Sci B Polym Phys

119

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Temperature dependent phase behavior of poly(N‐isopropylacylamide) (PNIPAM) microgels in water/methanol mixtures of different composition was studied with dynamic light scattering (DLS) and small‐angle neutron scattering (SANS). Using DLS, it is possible to measure the diffusion coefficient, and thus the size of particles exactly and directly; the variation of the phase transition temperature in the different solvents is also easy to detect by this method. With SANS measurements in D2O/MeOD mixtures, some of the DLS results were confirmed. Moreover, SANS measurements give valuable information on the particle structure in different solvents. The experiments were compared with the theory of competitive hydration introduced by Tanaka et al. We found a good agreement of theory and experiment, and obtained the theoretical predictions: around the transition temperature, the composition of the bound methanol along the chains is higher than that of the outer solution, while the whole methanol composition inside the gel is lower. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2013, 51, 1100–1111

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Section: Resultscontrasting

confidence: 99%

Temperature dependent phase behavior of PNIPAM microgels in mixed water/methanol solvents

Kojima

Tanaka

Scherzinger

et al. 2012

J Polym Sci B Polym Phys

119

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“…Subsequently, Zhang and Wu found the non‐ideal behaviour of the refractive index with increasing methanol fraction and explained the formation of methanol/water complexes by suggesting that water exist predominantly in the pentagon form. This result was supported by the FTIR (Fourier transform infrared spectroscopy) measurements of Liu, Sun and Wu . In Sun and Wu's article, a fact that the interaction between PNIPAM and methanol is weakened at higher methanol fractions was confirmed.…”

Section: Introductionmentioning

confidence: 99%

“…This result was supported by the FTIR (Fourier transform infrared spectroscopy) measurements of Liu, Sun and Wu . In Sun and Wu's article, a fact that the interaction between PNIPAM and methanol is weakened at higher methanol fractions was confirmed. They also explained the collapse of PNIPAM chains with the formation of water‐methanol clusters and the subsequent reduction of hydration along PNIPAM backbone.…”

Section: Introductionmentioning

confidence: 99%

Cononsolvency of poly(N‐isopropylacrylamide) in methanol aqueous solution—insight by dielectric spectroscopy

Yang

Zhao

2017

J Polym Sci B Polym Phys

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Both water and methanol are good solvents for poly(N‐isopropylacrylamide) (PNIPAM), while PNIPAM does not dissolve in their mixed solvents, this phenomenon is called cononsolvency. Cononsolvency is closely related to many phenomena in life but so far, its mechanism is still controversial. In this work, the dielectric behavior of PNIPAM methanol aqueous solution was studied in the frequency of 40Hz–40GHz. From lower frequency to higher frequency, four relaxations were found. They are, respectively, from global chain motion, local motion of backbone, motion of side chain group, and the dipole orientation of the solvent molecule. The solvent dependence of dielectric parameters for the chain motion implied that the PNIPAM chain has undergone the coil‐globule‐coil transition. Dielectric analysis to microwave frequency showed that the volume of the bound solvent units on PNIPAM chain increases with the increasing methanol concentration, which suggested that the structure of solvation units bound on PNIPAM side chains undergo a changing process experience from water to water‐methanol cluster to the ternary methanol cluster. This work reveals the structure and dynamics of the PNIPAM chain and the solvent unit that involved in the solvation of PNIPAM, and provides some new insight into the cononsolvency phenomenon. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1227–1234

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“…Thus, additional useful information about molecular motions and conformational changes process during the phase transition can be obtained. 16,29,30 So the present contribution deals with thermal-induced behavior of PIPOZ aqueous solution via temperature-dependent IR spectroscopy and temperature-variable 1 H NMR spectra. Meanwhile, we assigned C−H and CO groups of PIPOZ solution in IR spectra in details according to the analysis of IR spectra, second-derivative spectra, 2Dcos, and PCMW.…”

Section: Introductionmentioning

confidence: 99%

Molecular Evolution of Poly(2-isopropyl-2-oxazoline) Aqueous Solution during the Liquid–Liquid Phase Separation and Phase Transition Process

Tang

2015

Langmuir

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A detailed phase transition process of poly(2-isopropyl-2-oxazoline) (PIPOZ) in aqueous solution was investigated by means of DSC, temperature-variable (1)H NMR, Raman, optical micrographs, and FT-IR spectroscopy measurements. Gradual phase separation accompanied by large dehydration degree and big conformational changes above the lower critical solution temperature (LCST) and facile reversibility were identified. Based on the two-dimensional correlation (2Dcos) and perturbation correlation moving window (PCMW) analyses, the sequence order of chemical group motions in phase transition process was elucidated. Additionally, a newly assigned CH3···O═C intermolecular hydrogen bond at 3008 cm(-1) in the PIPOZ system provides extra information on the interactions between C-H and C═O groups. The formation of cross-linking "bridging" hydrogen bonds C═O···D-O-D···O═C (1631 cm(-1)) is proposed as the key process to induce the liquid-liquid phase separation and polymer-rich phase formation of PIPOZ solution. With slow heating, more and more "bridging" hydrogen bonds were formed and D2O were expelled with an ordered and mostly all-trans conformation adopted in the PIPOZ chains. On the basis of these observations, a physical picture on the molecular evolution of PIPOZ solution during the phase transition process has been derived.

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Role of Water/Methanol Clustering Dynamics on Thermosensitivity of Poly(N-isopropylacrylamide) from Spectral and Calorimetric Insights

Cited by 93 publications

References 71 publications

Temperature dependent phase behavior of PNIPAM microgels in mixed water/methanol solvents

Temperature dependent phase behavior of PNIPAM microgels in mixed water/methanol solvents

Cononsolvency of poly(N‐isopropylacrylamide) in methanol aqueous solution—insight by dielectric spectroscopy

Molecular Evolution of Poly(2-isopropyl-2-oxazoline) Aqueous Solution during the Liquid–Liquid Phase Separation and Phase Transition Process

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