Internal motions of linear chains and spherical microgels in dilute solution

Abstract

It is well known that for a flexible polymer chain in dilute solution, two different types of motions mainly contribute: the translation motion of the centres of mass of individual polymer chains; and the internal modes generated from the motions of segments with respect to the centre of mass of the chain. During the past two decades, with the advances in light scattering instrumentation and sophisticated methods of data analysis, both types of motions can be distinguished in experiments and utilized for testing molecular theories of polymer chain dynamics in dilute solution. In this article, we first review some previous experiments, in particular the dynamical properties of polystyrene (PS) and polyisoprene (PIP) chains in good and theta (Q) solvents, and then our own results, including a comparative study of the internal motions of poly(N-isopropylacryl-amide) (PNIPAM) linear chains and spherical microgels under good solvent conditions. The final part of this article deals with how the solvent quality (the solution temperature) affects the internal mobility of PNIPAM linear chains and microgels.

Effects of Culture Substrate Made of Poly(N-isopropylacrylamide-co-acrylic acid) Microgels on Osteogenic Differentiation of Mesenchymal Stem Cells

“…Especially, some thermally sensitive polymers and their derivatives with a switchable/reversible hydrophilic-hydrophobic transition are widely explored as cell culture substrates [18,19]. Among them, poly( N -isopropylacrylamide) (PNIPAM), with a lower critical solution temperature (LCST ~ 32 °C), is the mostly studied system [20,21]; namely, at temperatures higher than ~32 °C, PNIPAM becomes insoluble in water. Therefore, the substrate will facilitate or resist cell adhesion when the temperature is above or below its LCST.…”

Characterization of the Local Volume Probed by the Side-Chain Ends of Poly(oligo(ethylene glycol) 1-Pyrenemethyl ether methacrylate) Bottle Brushes in Solution Using Pyrene Excimer Fluorescence

“…Both r EE and R G are expected to scale as n ν , where n is the number of bonds of the chain and ν is the Flory exponent equal to 0.5 for a linear chain in the bulk or in a theta solvent or 0.6 for a chain in a good solvent . Experimentally however, it is usually not r EE that is determined but the radius of gyration ( R G ) using scattering techniques. , Experimental techniques that probe the ends of a linear chain must enhance the chain end signal to facilitate its detection, typically by labeling the two chain ends with fluorescent dyes such as a pair of fluorescence resonance energy transfer (FRET) donor and acceptor dyes − or two pyrene labels. − The dyes are selected for their ability to report on either r EE directly for a FRET pair or the local concentration of the chain ends within the macromolecular volume for the pyrene labels. r EE can then be derived from the analysis of the pyrene fluorescence.…”

“…Assuming that the pyrenyl terminal of each EG n side chain could probe a spherical volume, whose diameter was defined by the r EE,SC (= n 0.5 × l , with n being the number of chemical bonds of length l ) of the side chain, yielded a predicted value for [Py] loc which was found to correlate strongly with ⟨ k ⟩, as had been observed for the Py x -G­( N ) dendrons. , The strong correlation between ⟨ k ⟩ obtained from PEF measurements and [Py] loc suggests that PEF provides an experimental means to probe the internal density of macromolecules in general and the conformation adopted by the EG y side chains of PEG y MA samples in solution in particular. This application of PEF to probe the conformation of macromolecules and specific parts of a macromolecule in solution represents an important development in the use of PEF, which should nicely complement scattering experiments. ,,,− …”

Microgel particles: The structure‐property relationships and their biomedical applications

“…Above the LCST, the microgels expel water and collapse. Upon lowering the temperature below this the microgel particles swell, increasing their size by more than an order of magnitude, making them the basis of a responsive system . This volume phase transitions in response to temperature has been studied thoroughly employing methods including static and dynamic light scattering, differential scanning calorimetry, and rheology .…”

“…Upon lowering the temperature below this the microgel particles swell, increasing their size by more than an order of magnitude, making them the basis of a responsive system . This volume phase transitions in response to temperature has been studied thoroughly employing methods including static and dynamic light scattering, differential scanning calorimetry, and rheology . When comonomers like acrylic acid (AA) or methacrylic acid (MAA) are incorporated into the microgels, the resulting microgels add a similar responsiveness to both pH and ionic strength .…”