Optical Properties of Polyelectrolytes

Abstract

A polyelectrolyte can be defined as a macromolecule with ionizable repeat units, which can consequently display pH-dependent behavior when dissolved in aqueous solution.As the term polyelectrolyte can also be extended to encompass natural biopolymers, which contain ionizable groups such as peptides, proteins, and DNA, it is perhaps not surprising that synthetic polyelectrolytes are often used as simple models for more complex biological systems. Indeed, many of the photophyscial techniques discussed in this chapter were developed by biologists and biophysicists interested in the conformational behavior and interactions of biopolymers [1].

Polymer-Grafted 3D-Printed Material for Enzyme Immobilization—Designing a Smart Enzyme Carrier

“…In order to find an optimum between the maximum amount of enzyme immobilized, its highest residual activity, and a significant swelling-degree that can slow down the conversion, the dependence of the synthesis time on the respective parameters was investigated. As enzyme immobilization took place at the carboxylic acid group of PAA, which was responsible for its pH-sensitivity or hydrogen bond formation [22,37]; the swelling behavior of PAA with immobilized enzymes was investigated.…”

pH Dependence of Acrylate-Derivative Polyelectrolyte Properties

“…As the carboxylic acid group can only be classed as hydrophilic when the functional monomer is protonated, PMAA undergoes a rapid swelling as the pH is increased, becoming an entirely hydrophobic material with increasing anionic charge along the backbone. Extensive investigations have been carried out into its behaviour using diverse methods and techniques: pontentiometry [4,5,7,10,19], viscometry [8,11], Raman spectroscopy [20], scattering methods [21][22][23] and fluorescence probe interrogation techniques [3,[24][25][26]. The combined research has shown that PMAA undergoes a dramatic conformational change between pH 4 and 6, (corresponding to an α (degree of ionisation) between 0.1 and 0.3), whilst PAA adopts a relatively smooth swelling process in the same pH range (initiating at the same degree of ionisation).…”

“…In acidic media, due to the increased hydrophobicity, PMAA adopts a globular, contracted structure designed to minimise unfavourable interactions between the hydrophobic backbone and side chain and the aqueous solution, whilst PAA has been described as a random, statistical coil [6,7,9]. The PMAA shows significantly increased compaction due to the hydrophobic methyl backbone [8,13,22,[24][25][26][27][28][29], that has been shown to induce hypercoiling [8]. This has two net effects-increased hydrophobic density gives it both greater solubilisation potential but at the cost of reduced solubility and mobility.…”

“…The pyrene excited state emits multiple emission bands, and the relative intensity of bands 1 and 3 vary with different solvents, thus when dispersed in a solution it can give an indication of system polarity [34,35]. For example, the I 3 /I 1 ratio is known to vary between 0.55 (water) and 1.7 (n-pentane) [26]. This feature has been used in the study of many polymer systems, and commonly used by spectroscopists to study macromolecular aggregate structures such as colloids [36], microemulsions [37], micelles [38] and microgels [39,40].…”

“…This book chapter is both an update, summation of, and substantial revision to my Ph.D., work area carried out at the University of Sheffield, originally under Dr. Linda Swanson, who has published extensively on the photophysical analytical techniques described in this paper. For further reference on the application of those techniques in these systems, particularly in the study of polyelectrolytes, please see her book chapter 'Optical Properties of Polyelectrolytes' [26].…”