Viscometry—a useful tool for studying conformational changes of poly(N-isopropylacrylamide) in solutions

Tam, Kam Chiu; Wu, Xiaowei; Pelton, Robert

doi:10.1016/0032-3861(92)91008-p

Cited by 50 publications

(42 citation statements)

References 9 publications

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“…3. As expected, a remarkable change is observed around 32°C which corresponds to the LCST of poly[NIPAM] [27,28]. Particle size for both latexes appears constant below 27°C and above 35°C.…”

Section: Effect Of Temperaturesupporting

confidence: 55%

“…Similar data have already been reported in the case of polystyrene cationic latexes bearing amidine and/or amine groups (using AEM monomer) [32,33]. The negative electrophoretic mobility observed above pH 10 is usually attributed to the presence of carboxylic groups originated from the hydrolysis of amidine groups [27].…”

Section: Effect Of Ph On the Electrophoretic Mobilitymentioning

confidence: 57%

See 1 more Smart Citation

Cationic amino-containing N -isopropyl- acrylamide-styrene copolymer particles: 2-surface and colloidal characteristics

Duracher¹,

Sauzedde²,

Elaissari³

et al. 1998

Colloid & Polymer Science

103

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In a previous paper [1], the synthesis of various polystyrenepoly[NIPAM] core-shell latexes bearing cationic amidino and/or amino charges has been described. Several colloidal properties of these cationic latexes have been characterized such as: particle size, surface charge density, electrophoretic mobility and finally colloidal stability. Due to the poly[NIPAM]-rich layer in the shell, it was found that temperature played a significant role on all these properties, a LCST around 33°C being exhibited. In addition, ionic strength was also found to affect the colloidal behavior of these latexes, the largest effect being observed with latexes having both amidino and amino surface charges. The critical coagulation concentrations (CCC) of the various latexes above and below the LCST were determined, highlighting the contribution of electrostatic and steric repulsive forces to the stability of these particles.

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Section: Effect Of Temperaturesupporting

confidence: 55%

Section: Effect Of Ph On the Electrophoretic Mobilitymentioning

confidence: 57%

Cationic amino-containing N -isopropyl- acrylamide-styrene copolymer particles: 2-surface and colloidal characteristics

Duracher¹,

Sauzedde²,

Elaissari³

et al. 1998

Colloid & Polymer Science

103

View full text Add to dashboard Cite

show abstract

“…36 The measured values of intrinsic viscosities There are several regions that can be considered within the temperature dependence of the viscosity. At first, when the temperature starts to increase, the dynamic viscosity (η) of the solution decreases according to eq 1 ( Figure 7).…”

Section: ' Results and Discussionmentioning

confidence: 99%

Poly(2-cyclopropyl-2-oxazoline): From Rate Acceleration by Cyclopropyl to Thermoresponsive Properties

et al. 2011

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There is a high potential for thermoresponsive polymers to be used in various applications, such as drug delivery systems 1À5 and separation processes, 6,7 and, therefore, these materials received significant attention over the last few years. Polymers that exhibit "lower critical solution temperature" (LCST) behavior are soluble in water below their LCST 3,7,8 due to effective hydration of the polymer based on hydrogen bonds between the polymer and the solvent. With increasing temperature, the hydrogen bonds are weakened resulting in dehydration when the LCST is reached. This entropically driven phase transition, i.e., release of water molecules, leads to a collapse of the hydrophobic polymer chains and the formation of aggregates. Therefore, the LCST can be tuned, e.g., by variation of the polymer side chains or by copolymerization with other monomers, as fully explored for the most widely studied thermo-responsive polymer, poly(N-isopropylacrylamide) [PNIPAM]. 3,6,9,10 Poly(2-oxazoline)s with methyl, ethyl, isopropyl, or n-propyl side chains are water-soluble and, except for the most hydrophilic poly(2-methyl-2-oxazoline) (pMeOx), show LCST behavior in water. 11,12 The cloud points (CP) of these poly(2-oxazoline)s increase with increasing hydrophilicity and depend on the degree of polymerization (DP) and concentration. 13À15 The CP can easily be tuned by copolymerization of various 2-oxazoline monomers, as well as by controlling the length and end groups. 16À19 Poly(2-ethyl-2-oxazoline) (pEtOx) is known to only reveal a CP when the DP is above 100, since smaller polymer chains are soluble up to 100°C. 15 Poly(2-isopropyl-2-oxazoline) (piPropOx) is an interesting thermoresponsive polymer, since its CP is close to body-temperature, making it suitable for biomedical applications. 20 However, due to its semicrystallinity the thermo-responsiveness becomes irreversible after annealing above the LCST. 21À23 Poly(2-n-propyl-2-oxazoline) (pnPropOx) is amorphous but has a lower LCST of ∼24°C. 15 In addition, the rather low T g of ∼40°C, which decreases in the presence of water, makes it difficult to handle and to store the polymer at ambient temperature. Therefore, an alternative thermo-responsive poly(2-oxazoline) with a reversible critical temperature close to body temperature is desired.Besides linear poly(2-oxazoline)s, we recently also reported comb polymers containing oligo(2-ethyl-2-oxazoline) (OEtOx) sidechains and a methacrylate (MA) backbone as thermo-responsive ABSTRACT: The synthesis and microwave-assisted living cationic ring-opening polymerization of 2-cyclopropyl-2-oxazoline is reported revealing the fastest polymerization for an aliphatic substituted 2-oxazoline to date, which is ascribed to the electron withdrawing effect of the cyclopropyl group. The poly(2-cyclopropyl-2-oxazoline) (pCPropOx) represents an alternative thermo-responsive poly(2-oxazoline) with a reversible critical temperature close to body temperature. The cloud point (CP) of the obtained pCPropOx in aqueous solution was evaluated i...

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“…The LCST can be determined by various analytical methods like optical techniques (e.g., UV-Vis spectroscopy [20–22], dynamic and static light scattering [22–27], infrared spectroscopy [28–31], Raman spectroscopy [32], fluorescence spectroscopy [33]), differential scanning calorimetry [34], or viscometry [35]. However, many of these approaches are usually limited to rather dilute suspensions, exhibiting only single light scattering.…”

Section: Introductionmentioning

confidence: 99%

Process analytical approaches for the coil-to-globule transition of poly(N-isopropylacrylamide) in a concentrated aqueous suspension

et al. 2016

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The coil-to-globule transition of poly(N-isopropylacrylamide) (PNIPAM) microgel particles suspended in water has been investigated in situ as a function of heating and cooling rate with four optical process analytical technologies (PAT), sensitive to structural changes of the polymer. Photon Density Wave (PDW) spectroscopy, Focused Beam Reflectance Measurements (FBRM), turbidity measurements, and Particle Vision Microscope (PVM) measurements are found to be powerful tools for the monitoring of the temperature-dependent transition of such thermo-responsive polymers. These in-line technologies allow for monitoring of either the reduced scattering coefficient and the absorption coefficient, the chord length distribution, the reflected intensities, or the relative backscatter index via in-process imaging, respectively. Varying heating and cooling rates result in rate-dependent lower critical solution temperatures (LCST), with different impact of cooling and heating. Particularly, the data obtained by PDW spectroscopy can be used to estimate the thermodynamic transition temperature of PNIPAM for infinitesimal heating or cooling rates. In addition, an inverse hysteresis and a reversible building of micrometer-sized agglomerates are observed for the PNIPAM transition process.Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-016-0050-7) contains supplementary material, which is available to authorized users.

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Viscometry—a useful tool for studying conformational changes of poly(N-isopropylacrylamide) in solutions

Cited by 50 publications

References 9 publications

Cationic amino-containing N -isopropyl- acrylamide-styrene copolymer particles: 2-surface and colloidal characteristics

Cationic amino-containing N -isopropyl- acrylamide-styrene copolymer particles: 2-surface and colloidal characteristics

Poly(2-cyclopropyl-2-oxazoline): From Rate Acceleration by Cyclopropyl to Thermoresponsive Properties

Process analytical approaches for the coil-to-globule transition of poly(N-isopropylacrylamide) in a concentrated aqueous suspension

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