Preface

Human scientific knowledge has advanced to different borders. One of these limits is shown around us and every day we observe it; in fact it takes part of ourselves. Life, life functions and malfunctions are outside of the descriptions or predictions of any scientific model.

Present physical models were able to predict the existence of subatomic particles or astronomical structures beyond the borders of the explored universe long before we designed and constructed devices required for their observation. But they cannot describe or predict health or illnesses that constitute our every experience. Life is chemistry. Biochemical reactions include biopolymers and macromolecules as reactants. The reactions induce conformational movements, but current chemical models do not include quantification of any conformational, allosteric or structural reaction-driven changes.

Up until the 1980s, chemists did not have at their disposal dense reactive gels that could mimic the intracellular matrix (ICM) of living cells, which constitutive polymeric chains may participate as reactants in chemical or electrochemical reactions. From them, a plethora of different materials has emerged, giving electroactive films in liquid electrolytes, including conducting polymers, redox polymers, fullerenes, carbon nanotubes, graphenes, phthalocyanines and so on.

In this book the electrochemistry of conducting polymers as reactive gels that mimic, in its simplest expression (reactive chains, reaction-driven conformational movements, ions and water), the composition of the ICM in living cells is described.

Electrochemical reactions (oxidation or reduction) from the different families of conducting polymers (Chapter 4) drive conformational movements of the constitutive polymeric chains and structural macroscopic changes of the film, such as conformational relaxation, swelling, shrinking and conformational compaction from different energetic states of trapped ions. Chapter 6 describes how these reaction-driven structural changes that mimic biochemical reactions are identified, controlled and quantified.

Such reactive gels can be used as material models of the ICM to obtain the empirical kinetics of the reaction. The new aspect, from a chemical kinetic point of view, is the possibility of repeating the full, selected kinetic procedure using different shrunken or conformationally packed initial states. Surprising results have been attained, such as the activation energy (E_a), the reaction coefficient (k) and the reaction order being the three of them, which are functions of the initial energetic state of packed conformations. The kinetic magnitudes include conformational and structural quantitative information: the chemical kinetics become structural chemical kinetics (Chapter 7).

The electrochemically stimulated conformational relaxation (ESCR) model and the consequential structural chemical kinetic (SCK) model here presented describe the obtained empirical results. Variation of the chain conformational energy during a reaction reaches a quantitative magnitude. The final structural equations for E_a, k and the reaction orders are adapted to those biochemical reactions taking place in the absence of electric fields, like enzymatic reactions, and allosteric and folding/misfolding effects.

The faradaic ionic exchange shifts the gel composition by several orders of magnitude, as functional reactions do in organs. The values of any composition-dependent properties of the material (volume, color, charge storage, ionic storage, ionic conductivity and so on) will change under the control of the driving current through several orders of magnitude. Chapter 5 is devoted to these composition-dependent properties, each mimicking a biological function. Each of these biomimetic properties allows the development of a biomimetic device that works in a way driven by the reaction of the device’s constitutive material, as biological organs do. In this regard, Chapter 8 describes artificial muscles, smart membranes, artificial glands, decontaminating systems, artificial chemical synapses, chemo-ionic-conformational memories, smart surfaces, electrochromic devices, organic batteries, biosensors and mechanical sensors. However, the reaction shifts the value of each of the composition-dependent properties simultaneously. This fact opens an unexplored and unexpected scientific and technological world of multi-tool devices, where several tools work simultaneously in a physically uniform device driven by the same reaction. Chapter 9 is devoted to the exploration of sensing motors, inspired by haptic muscles. Haptic muscles and the brain give rise to proprioception. Based on electrochemical, polymeric and mechanical basic principles, a theoretical model is presented describing artificial proprioception and the attained experimental results.

A short review of some of the basic electrochemical cells and methods is given (Chapter 2). Chapter 3 is devoted to the complex mechanism of the electrochemical synthesis of conducting polymers whose control allows the synthesis of tailored materials and may help new researchers to understand the new concepts and principles presented here.

Some final consideration and remarks related to reactions and structures, materials and biological structural processes are collected in the final chapter. Challenges in the quantification and prediction of biological reactions and functions are presented, while the door is left open for a quantitative description of electro-chemo-conformational memories and brain memory.

Toribio Fernández Otero