DOCSLIB.ORG

The Use of Conducting Polymer Sensors for Environmental Monitoring, Doctor of Philosophy Thesis, Department of Chemistry, University of Wollongong, 2001

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Use of Conducting Polymer Sensors for Environmental Monitoring, Doctor of Philosophy Thesis, Department of Chemistry, University of Wollongong, 2001 University of Wollongong Research Online University of Wollongong Thesis Collection University of Wollongong Thesis Collections 2001 The seu of conducting polymer sensors for environmental monitoring Roderick L. Shepherd University of Wollongong Recommended Citation Shepherd, Roderick L., The use of conducting polymer sensors for environmental monitoring, Doctor of Philosophy thesis, Department of Chemistry, University of Wollongong, 2001. http://ro.uow.edu.au/theses/1209 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] THE USE OF CONDUCTING POLYMER SENSORS FOR ENVIRONMENTAL MONITORING A thesis submitted in fulfilment of the requirements for the award of the degree DOCTOR OF PHILOSOPHY from UNIVERSITY OF WOLLONGONG by Roderick L. Shepherd BEnvSc(Hons) Department of Chemistry 2001 DECLARATION I, Roderick L. Shepherd, declare that this thesis, submitted in fulfilment of the requirements for the award of Doctor of Philosophy, in the Department of Chemistry, University of Wollongong, is wholly my own work unless otherwise referenced or acknowledged. The document has not been submitted for qualifications at any other academic institution. Roderick L. Shepherd 15 October 2001 II PUBLICATIONS Shepherd, R.L., Barisci, J.N., Collier, W.A., Hart, A.L., Partridge, A.C., and Wallace, G.G., Development of Conducting Polymer Coated Screen-Printed Sensors for Measurement of Volatile Compounds, Electroanalysis (In Press). Ill ACKNOWLEDGEMENTS First and foremost I must thank Professor Gordon Wallace for making this PhD an experience I will never forget, and one that I will reminisce over for the rest of my life. Through good times and bad, he was always there to help, and treated me more like a friend than a supervisor. It really made all the difference. Thanks mate, for everything, it is greatly appreciated. It has been a privilege to work under your guidance and I am sure we will continue to 'work' together in the coming years. I would also like to thank Dr Norman Barisci, for his much needed advice and assistance throughout the project. Again, I really appreciated your friendship during my time at IPRI, and for me your sense of humour in the lab always helped to keep things in perspective. Dr Ashton Partridge. The word 'Legend' springs to mind. I cannot thank you enough for the time you spent helping me out in NZ. I learned so much from you in such a short period. I think that without my trips over to Lower Hutt I would have been lost. I would also like to thank all those at Industrial Research Limited who helped make my time in NZ so enjoyable. I would also like to thank Dr Alan Hart and Wendy Collier of AgResearch, Palmerston North, NZ, for their help and advice with screen-printing. Your hospitality during my visits, and subsequent supply of electrodes is greatly appreciated. IV Thanks go to Megan Ash of Tecra Diagnostics, Sydney, for her assistance with the PMAS Listeria work and for supply of cultures over the course of the project. A wealth of much needed advice and supervision in the areas of robotics and odour plume tracking has been provided by Assoc. Prof. Andy Russell, of the Intelligent Robotics Research Centre, Monash University, Melbourne. Please accept my sincere thanks for all the time and effort you have invested in someone with little background knowledge of the area. I have thoroughly enjoyed this aspect of the work and as a consequence continue to conduct research in this area. To all at and associated with the Intelligent Polymer Research Institute, University of Wollongong, I had a fantastic time both working and socialising with you. The experience would have been much less rich without the amazing group of people at IPRI, which is more like a family than a research team. I have to take this opportunity to thank Prof. Leon Kane-Maguire, who through his incredible passion for science and life in general continues to inspire all of those around him. To my parents, Linette, and Peter, thankyou both for all your support over the years, and in particular during my PhD. I couldn't have done this without you. Finally, I have to thank my kelpie, Buster, for keeping things in focus during the last few months in the lab. V DEDICATION This thesis is dedicated to my mother, Linette, whose determination and optimism in times of incredible personal hardship inspired me to keep going. VI TABLE OF CONTENTS Chapter 1 Properties of Conducting Polymers and Application to Environmental Monitoring 1 1.1 Conducting Polymers (CPs) 2 1.2 Preparation of CPs 4 1.3 Factors Influencing CP Formation 5 1.3.1 Chemical Polymerisation 5 1.3.2 Electrochemical Polymerisation 6 1.4 CPs for Chemical Sensing 6 1.4.1 General CP Properties 7 1.4.1.1 Ion Exchange 7 1.4.1.2 Incorporation of Biological Components 8 1.4.1.3 Flexible Substrate Range 9 1.4.2 General Application Areas 9 1.5 Environmental Monitoring with CPs 10 1.5.1 Solution Based Sensors 11 1.5.1.1 Amperometric Sensors 12 1.5.1.2 Potentiometric Sensors 13 1.5.1.3 Voltammetric Sensors 18 1.5.1.4 Resistometric Sensors 19 1.5.1.5 Optical Sensors 20 1.5.1.6 Other Applications 22 1.5.1.7 Water Soluble CPs 23 1.5.2 Gas Sensors 24 1.5.2.1 Detection Mechanism 24 1.5.2.2 Resistometric Gas Sensors 28 1.5.2.3 CP Mass Sensors 35 1.5.2.4 Optical Sensors 37 1.5.2.5 CP Electronic Noses 38 1.6 Thesis Outline 42 Chapter 2 Development of Conducting Polymer Coated Screen-Printed Sensors for Measurement of Volatiles 44 2.1 INTRODUCTION 45 2.1.1 Aims and Approach 46 2.2 EXPERIMENTAL 48 2.2.1 Chemicals and Materials 48 2.2.2 Instruments 48 2.2.3 Screen-printing 49 2.2.4 Polymer Deposition 50 2.2.4.1 Direct Growth on Screen-printed Polymer Substrates 50 2.2.4.2 PPy/Cl Coated Melinex 50 2.2.4.3 Silicon Sensor Fabrication 51 2.2.5 Vapour Generation 51 VII 2.2.6 Resistance Measurement 52 2.3 RESULTS AND DISCUSSION 53 2.3.1 Polypyrrole Deposition 53 2.3.1.1 Melinex 53 2.3.1.2 Effect of Current Density 57 2.3.1.3 Other Polymer Substrates 57 2.3.1.4 PPy/Cl Modified Melinex 60 2.3.1.5 Optimisation of PPy/Tiron Growth Time 63 2.3.1.6 Silicon Sensors 69 2.3.1.7 Estimate of Film Thickness 71 2.3.2 Characterisation 73 2.3.2.1 Scanning Electron Microscopy 73 2.3.2.2 Atomic Force Microscopy 74 2.3.2.3 Cyclic Voltammetry 79 2.3.3 Sensor Responses 81 2.3.3.1 Responses to Methanol 81 2.3.3.2 Linearity of Response and Limit of Detection 85 2.3.3.3 Discrimination of Vapours 92 2.4 CONCLUSIONS 95 Chapter 3 Anion Exchange Modification of PPy/Cl Vapour Deposited Gas Sensors 97 3.1 INTRODUCTION 98 3.1.1 Aims and Approach 102 3.2 EXPERIMENTAL 102 3.2.1 Preparation of PPy/Cl sensors 102 3.2.2 Cyclic Voltammetry 102 3.2.3 Soaking 103 3.2.4 Chronoamperometry 103 3.2.5 Potentiometry 103 3.2.6 Pulsed Potential 104 3.2.7 X-ray Photoelectron Spectroscopy 104 3.2.8 Responses to Vapours 104 3.3 RESULTS AND DISCUSSION 105 3.3.1 Ion Exchange by Soaking 105 3.3.1.1 Potentiometry 106 3.3.1.2 Effect on PPy/Cl Gas Responses 108 3.3.2 Cyclic Voltammetry 111 3.3.3 Chronoamperometry 116 3.3.4 Pulse Potential Anion Exchange 118 3.3.4.1 Effect on Sensor Resistance 118 3.3.4.2 Effect of Electrolyte Concentration 120 3.3.4.3 Effect on Methanol Vapour Responses 120 3.3.4.4 Effect on Vapour Discrimination 123 3.3.5 X-ray Photoelectron Spectroscopy 126 3.4 CONCLUSIONS 129 VIII Chapter 4 Approaches to Reducing the Humidity Response of PPy Gas Sensors 131 4.1 INTRODUCTION 132 4.1.1 Aims and Approach 134 4.2 EXPERIMENTAL 136 4.2.1 Chemicals and Materials 136 4.2.2 Vapour Diffusion 137 4.2.3 Fabrication of PPy/Cl Tube Sensors 137 4.2.4 Response of PPy/Cl Tube sensors 138 4.3 RESULTS AND DISCUSSION 139 4.3.1 Silicone Coating 139 4.3.2 Diffusion Tube Sampling 145 4.3.3 Estimating Methanol Concentration 151 4.3.4 Solvent Discrimination in Solution 152 4.3.5 PPy/Cl Tube Sensor 154 4.3.5.1 Sensor Fabrication 155 4.3.5.2 Methanol Responses 156 4.3.6 T.I.T. Sensor 159 4.4 CONCLUSIONS 162 Chapter 5 Preliminary Investigations into the use of Vapour Deposited PPy Gas Sensors for Autonomous Robotic Plume Tracking 164 5.1 INTRODUCTION 165 5.1.1 Aims and Approach 166 5.2 EXPERIMENTAL 166 5.3 RESULTS AND DISCUSSION 168 5.3.1 Static Responses 168 5.3.1.1 Wind Velocity 169 5.3.1.2 Ammonia Concentration 170 5.3.2 Ammonia Plume Tracking 171 5.4 CONCLUSIONS " 174 Chapter 6 Factors Influencing the Electrochemistry of Polymethoxyaniline sulfonate (PMAS) and the Effect on Listeria Detection 176 6.1 INTRODUCTION 177 6.1.1 Aims and Approach 178 6.2 EXPERIMENTAL 179 6.2.1 Chemicals and Materials 179 6.2.2 Instruments and Apparatus 179 6.2.3 Post-GPC Processing 180 6.3 RESULTS AND DISCUSSION 180 6.3.1 PMAS Electrochemical Stability 181 6.3.2 GPC Characterisation of PMAS 184 6.3.3 Characterisation of Fractions 187 IX " 6.33.1 GPC 187 6.3.3.2 UV-visible Spectroscopy 189 6.3.3.3 Estimation of Fraction Concentration 195 6.3.3.4 Cyclic Voltammetry 196 6.3.3.5 Differential Pulse Voltammetry 199 6.3.4 Electrochemical Properties of the Monomer 203 6.3.5 Effect of MAS on PMAS Response 205 6.3.6 Dialysis of PMAS 207 6.3.6.1 Effect of Monomer on PMAS Response Stability 208 6.3.6.2 Stability of Dialysed PMAS over Time 211 6.3.7 Listeria Detection 213 6.3.7.1 MAS 213 6.3.7.2 Dialysed PMAS 215 6.3.7.3 PMAS Fractions 217 6.3.8 Effect of KC1 Concentration on Dialysed PMAS Response 221 6.3.8.1 Listeria Detection at Elevated KC1 Concentrations 224 6.4 CONCLUSIONS 225 Chapter 7 Conclusions and Future Work 228 7.1 General Conclusions 229 7.2 Chapter 2 229 7.3 Chapter 3 231 7.4 Chapter 4 233
Load more

Recommended publications
  • 1 Synthesis and Functionality of Substituted Polyacetylenes Jianzhao Liu, Jacky W
    1 1 Synthesis and Functionality of Substituted Polyacetylenes Jianzhao Liu, Jacky W. Y. Lam, and Ben Zhong Tang 1.1 Introduction Polyacetylene (PA) is the archetypal conjugated polymer. The seminal discovery of the metallic conductivity of its doped form has triggered a huge surge of interest in conductive polymers and has spawned an exciting area of research on synthetic metals.1) As a result of rapid advances in the area, we are now on the threshold of a ‘‘plastic-electronics era’’ that previously could only be imagined in science fiction. Structurally, PA is a linear polyene chain [−(HC=CH)n−]. The existence of two hydrogen atoms in its repeat unit offers ample opportunity to decorate the backbone with pendants: replacement of hydrogen in each repeat unit by one or two substituents yields mono- (1) and disubstituted PAs (2), respectively (Scheme 1.1). The pendant and backbone can interact with each other: for example, the former perturbs the electronic conjugation of the latter, while the latter in- fluences the molecular alignment of the former. Proper structural design may tune the backbone–pendant interplay into harmony and synergy, generating new substituted PAs with novel functionalities. While PA is electrically conductive, introduction of such pendant as mesogen, chromophore, photosensitive double bond, or naturally occurring building block may endow it with such new func- tional properties as electro-optic activity, photonic responsiveness, and biologic compatibility. Considerable efforts have been devoted to the synthesis of the substituted PAs and study of their properties [1–9]. Attachment of polar groups to the polyene backbone enables the integration of functional pendants into the PA chain through various functional-group transformations, which was, however, a difficult task at the early stage of PA chemistry.
    [Show full text]
  • Electronic Polymers
    Electronic Polymers Insulators Semiconductors Metals Superconductors σ <10-7 10−7< σ <102 σ >102 σ >>1020 σ ranges 10-20 to 1020 Requires doping (oxidation or reduction) for conductivity Electrical Properties Electric conductivity of inorganic (I) and organic (O) compounds, I O measured in S/cm. Triniobium germanide (Nb3Ge) and poly(thiazyl) (SN)n are superconducting materials at very low temperatures near 20 zero kelvin. The conductivities for conducting (C), semi-conducting S Nb3Ge, (SN)n 10 (SC) and insulating (I) compounds are given for 20oC (= 293.16 K = 68oF). Cu = Copper, Hg = mercury, Ge = germanium, Si = silicon, 1015 AgBr = silver bromide, G = glass, S = sulfur, (SiO2)n= quartz, TTF = tetrathiafulvalene, TCNQ = 7,7,8,8 tetracyanoquinodimethane, NBR C 1010 = nitrile rubber (a copolymer from acrylonitrile and butadiene), DNA = deoxyribonucleic acid, PVC = polyvinyl chloride, PE = polyethylene, PTFE = polytetrafluoroethylene. Cu 105 TTF/TCNQ Hg 1 Siemens = 1 Ohm-1 (SN)n 1 Ge 1040 change in material property ! SC dP Si 10-5 AgBr Material Conductivity (S/cm) NBR -10 G 10 -7 DNA Insulators σ < 10 PVC 10-15 Semiconductors 10−7 < σ < 102 I S (SiO ) PE 2 n Metals σ > 102 10-20 PTFE Superconductors σ >> 1020 n = # carriers/cm3 Figure by MIT OCW. σ = nμq μ= mobility (cm2/V•sec) q = charge Types of Charge • Usual carriers: electrons, holes, ions(cations & anions) • New for conducting polymers – solitons, polarons, bipolarons Ji = σijEj where Ji is the current, σij is the conductivity and Ej is the applied field Battery Application – Li-polymer vs Pb. – Weight: 1/10th – volume: 1/3rd – power density: 10x – processable into any shape; dry, no toxic fumes etc.
    [Show full text]
  • Synthetic and Mechanistic Studies of Poly(Vinyl Chloride) and Some Other Chlorinated Polymers XIANLONG GE College of William &A
    Synthetic and Mechanistic Studies of Poly(vinyl chloride) and Some Other Chlorinated Polymers XIANLONG GE College of William & Mary, Department of Applied Science, 2003 Field: Polymer Science, Degree: Ph.D. Advisor: William H. Starnes, Jr., Professor of Chemistry Abstract Poly(1,2-dichloroethylene) (PDCE) is an unknown polymer that should be a superb engineering thermoplastic for use in a variety of high-performance applications. This thesis discusses approaches to its synthesis and describes the preparation and some of the properties of a number of new polymers that contain chlorine. Other major topics addressed here are (a) the involvement of an excited cation diradical intermediate in the thermal degradation of poly(vinyl chloride) (PVC) and (b) the mechanism of the thermal stabilization of PVC by “plasticizer thiols”. Unlike vinyl chloride, 1,2-dchloroethylene (DCE) undergoes dimerization under free-radical conditions. Chain transfer to DCE by β-Cl elimination was shown to be the major reason for its nonpolymerization. The dimeric radical rearranges by a 1,2-Cl shift, but apparently to only a very minor extent. During the chlorination of alkyl chlorides with molecular chlorine, a bridged intermediate is involved, and for this reason, vicinal chlorides were found to be the major products. The yields of geminal chlorides increased significantly in the presence of solvents that form complexes with chlorine atoms, but such solvents also decreased the reactivity of the chlorination. Thus the chlorination of PVC in the presence of complexing solvents was not a useful method for the synthesis of PDCE Polyacetylene (PA) was prepared by the methods of both Shirakawa and Luttinger.
    [Show full text]
  • Polyacetylene: Myth and Reality
    materials Review Polyacetylene: Myth and Reality Bruce S. Hudson Department of Chemistry, Syracuse University, Syracuse, NY 13244-4100, USA; [email protected]; Tel.: +1-315-443-5805 Received: 31 December 2017; Accepted: 31 January 2018; Published: 6 February 2018 Abstract: Polyacetylene, the simplest and oldest of potentially conducting polymers, has never been made in a form that permits rigorous determination of its structure. Trans polyacetylene in its fully extended form will have a potential energy surface with two equivalent minima. It has been assumed that this results in bond length alternation. It is, rather, very likely that the zero-point energy is above the Peierls barrier. The experimental studies that purport to show bond alternation are reviewed and shown to be compromised by serious experimental inconsistencies or by the presence, for which there is considerable evidence, of finite chain polyenes. In this view, addition of dopants results in conductivity by facilitation of charge transport between finite polyenes. The double minimum potential that necessarily occurs for polyacetylene, if viewed as the result of elongation of finite 1 1 chains, originates from admixture of the 1 Ag ground electronic state with the 2 Ag excited electronic singlet state. This excitation is diradical (two electron) in character. The polyacetylene limit is an 1 equal admixture of these two Ag states making theory intractable for long chains. A method is outlined for preparation of high molecular weight polyacetylene with fully extended chains that are prevented from reacting with neighboring chains. Keywords: polyacetylene; double-minimum potential; Peierls barrier; zero-point level; cross-linking 1. Introduction/Background History Polyacetylene is selected for review because of its relative simplicity; the small periodic repeat permits polyacetylene to be treated by sophisticated computational methods.
    [Show full text]
  • Introduction to Polymer Solar Cells (Pscs)
    2132-15 Winter College on Optics and Energy 8 - 19 February 2010 Introduction to Polymer Solar Cells (PSCs) K.S. Narayan Jawaharlal Nehru Centre for Advanced Scientific Research India K.S. Narayan Jawaharlal Nehru Centre for Advanced Scientific Research Bangalore,India [email protected] •Salubrious Weather < 22 °C > • Science and Technology Hub (S. Asia’s Si‐Valley) •Central Location to Historic and Natural Sites •Well connected • Culturally Vibrant•Verdant Environment, Academically Stimulating JAWAHARLAL NEHRU CENTRE FOR ADVANCED SCIENTIFIC RESEARCH An autonomous institution of Department of Science and Technology, established in 1989 Lecture 1 • Conducting Polymers, Semiconducting Polymers • Excitons in Semiconducting polymers • Diodes • Charge Separation… Bulk Hetrojunctions Kinetics‐rates‐branching factors Gaussian Model for Transport Lecture 2 • Jsc‐ Voc – Fill Factor Problems and Losses Bulk limiting factors Interfaces Mobility – Transport Symmetry – Aging‐degradation Lecture 3 • General Directions and Present Strategies • Recent Results from my laboratory Polymers: Structural variety … n Polyethylene H n Polypropylene CH3 n Polyvinyl chloride PVC Cl Polystyrene – Styrofoam, thermocole n Polyvinyl acetate - Fevicol n OAc • Insulators • Semiconductors • Conductors Pattern – Colours ‐ …… Conjugated Polymers n Polyacetylene n Polyphenylene vinylene S n Polythiophene Polypyrrole N n H N N N N n Polyaniline The 4 orbitals of a carbon atom in the form which allows it to couple to other atoms. When two atoms are brought together the wavefunctions which are in the plane overlap and couple. The attraction (stabilisation) introduced by the overlap. Polyacetylene • Despite the expectation of metallic behaviour, pristine polyacetylene was an insulator. Bond alternation due to Peierls distortion leads to the formation of a band gap between the valence and conduction band.
    [Show full text]
  • The Discovery of Polyacetylene Film—The Dawning of an Era Of
    REVIEWS OF MODERN PHYSICS, VOLUME 73, JULY 2001 Nobel Lecture: The discovery of polyacetylene film—the dawning of an era of conducting polymers* Hideki Shirakawa University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan (Published 20 September 2001) The Nobel Prize in Chemistry 2000 was awarded for our discovery and development of conducting polymers, but that discovery only happened after much work on polyacetylene. In this lecture, I would like to talk about the early investigations that preceded and eventually led to the discovery of chemical doping. I do hope my talk will be of use for you, the audience, to deepen your understanding of what had happened before and how we arrived at the idea of chemical doping. I. PROLOGUE difference between lengths of double and single bonds decreases with increasing conjugation and that all bonds It has been recognized for many years that a very long tend to be equal in length in an infinitely long polyene. linear conjugated polyene might have various interesting In other words, one would expect infinitely long one- properties, especially optical, electrical, and magnetic dimensional ␲ electrons to form a half filled band, or the properties. A polyene is an even number of methyne highest-occupied (HO) and the lowest-unoccupied (LU) ␲ (vCH-) groups, covalently bonded to form a linear car- -electron bands to merge with each other, leading to bon chain bearing one ␲ electron on each carbon atom. metallic behavior (Kuhn, 1948; Bayliss, 1952). In the Therefore the chemical structure of the polyene is best 1950s, however, it became theoretically clear that a poly- represented by the formula H(CHvCH)nH, where n ene with bond alternation is energetically more stable denotes the number of repeating units.
    [Show full text]
  • The Bromine Doping of Polyacetylene C.K
    Available online at www.sciencedirect.com Physica A 321 (2003) 139–151 www.elsevier.com/locate/physa The bromine doping of polyacetylene C.K. Chiang Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8541, USA Abstract The original experiment of the bromine dopingof polyacetylene performedby Chiang andShi- rakawa is described. This simple, seminal experiment impacted physics and chemistry through the discovery of metallic conducting synthetic organic polymers and the veriÿcation and demonstra- tion of the doping concept in organic polymers. Although the molecular formula of polyacetylene is simple, this molecule exhibits complex behavior andfueling signiÿcant work not only in poly- mer science, but also in quantum physics. The soliton theories usedto describepolyacetylene’s simple but unique 1-D structure inspiredmany new quantum concepts for more complicated conducting polymers. The continuing study of model complex conducting polymers could lead to a better understanding of quantum electronic devices at the molecular level. c 2002 Elsevier Science B.V. All rights reserved. PACS: 72.82.Le; 82.35.Cd; 31.25 Keywords: Polyacetylene; Doping; Bromine; Chemistry Nobel Prize; Conducting polymer; 1-D conductor 1. Introduction The Nobel Prize in Chemistry 2000 was awarded to Alan J. Heeger, Alan G. Mac- DiarmidandHidekiShirakawa for their “Discovery andDevelopment of Conducting Polymers” [1–4]. In their Nobel lectures, the Laureates summarized over three decades of research. The ÿrst lecture given by Shirakawa, described his work on the devel- opment of polyacetylene chemistry. He ended his lecture with a story of the bromine doping of polyacetylene experiment [5]. Next, MacDiarmiddiscussedthechemistry of conducting polymers and recent development in plastic electronics [6].
    [Show full text]
  • Magnetic Properties of Polyacetylene Composites H
    MAGNETIC PROPERTIES OF POLYACETYLENE COMPOSITES H. Thomann, L. Dalton, M. Galvin, G. Wnek, Y. Tomkiewicz To cite this version: H. Thomann, L. Dalton, M. Galvin, G. Wnek, Y. Tomkiewicz. MAGNETIC PROPERTIES OF POLYACETYLENE COMPOSITES. Journal de Physique Colloques, 1983, 44 (C3), pp.C3-313-C3- 316. 10.1051/jphyscol:1983361. jpa-00222713 HAL Id: jpa-00222713 https://hal.archives-ouvertes.fr/jpa-00222713 Submitted on 1 Jan 1983 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. JOURNAL DE PHYSIQUE Colloque C3, supplément au n°6, Tome 44, juin 1983 page C3-313 MAGNETIC PROPERTIES OF POLYACETYLENE COMPOSITES H. Thomaim*, L.R. Dalton*, M.E. Galvin**, G.E. Wnek**and Y. Tomkiewiez*** *Dept. of Chemistry, Univ. of Southern California, Los Angeles, CA 90089-0482, U.S.A. **Dept. of Materials Science and Engineering, M.I.T., Cambridge, MA 02139, U.S.A. ***IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, U.S.A. Résumé - Des composites du polyéthylène basse densité, LDPE, et du trans-polyacétylène, t-(CH)x, préparés par polymérisation de l'acé­ tylène dans des films de LDPE imprégnés de catalyseur Ziegler-Natta, ont été étudiés par double résonance (ENDOR) et échos de spins élec­ troniques (ESE) et les résultats ont été comparés avec ceux obtenus dans les mêmes conditions sur des films de trans-polyacétylène.
    [Show full text]
  • Alan J. Heeger
    380 SEMICONDUCTING AND METALLIC POLYMERS: THE FOURTH GENERATION OF POLYMERIC MATERIALS Nobel Lecture, December 8, 2000 by ALAN J. HEEGER Department of Physics, Materials Department, Institute for Polymers and Organic Solids, University of California at Santa Barbara, Santa Barbara, CA 93106, USA. I. INTRODUCTION In 1976, Alan MacDiarmid, Hideki Shirakawa and I, together with a talented group of graduate students and post-doctoral researchers discovered con­ ducting polymers and the ability to dope these polymers over the full range from insulator to metal [1,2). This was particularly exciting because it created a new field of research on the boundary between chemistry and condensed matter physics, and because it created a number of opportunities: Conducting polymers opened the way to progress in understanding the fun­ damental chemistry and physics of n:-bonded macromolecules; Conducting polymers provided an opportunity to address questions which had been of fundamental interest to quantum chemistry for decades: Is there bond alternation in long chain polyenes? What is the relative importance of the electron-elecron and the electron­ lattice interactions in n:-bonded macromolecules? Conducting polymers provided an opportunity to address fundamental issues of importance to condensed matter physics as well, including, for example, the metal-insulator transition as envisioned by Neville Mott and Philip Anderson and the instability of one-dimensional metals discovered by Ru­ dolph Peierls ( the "Peierls Instability"). Finally - and perhaps most important - conducting polymers offered the promise of achieving a new generation of polymers: Materials which exhibit the electrical and optical properties of metals or semiconductors and which retain the attractive mechanical properties and processing advantages of polymers.
    [Show full text]
  • Sensors and Sensor Arrays Based on Conjugated Polymers and Carbon Nanotubes*
    Pure Appl. Chem., Vol. 74, No. 9, pp. 1753–1772, 2002. © 2002 IUPAC Sensors and sensor arrays based on conjugated polymers and carbon nanotubes* Liming Dai‡, Prabhu Soundarrajan, and Taehyung Kim Department of Polymer Engineering, College of Polymer Science and Polymer Engineering, University of Akron, Akron, OH 44304-2909, USA Abstract: The need for cheaper, faster, and more accurate measurements has been a driving force for the development of new sensing devices. As is well known, the electrical conduc- tivity of conjugated polymers can be reliably regulated over a wide range through interac- tions with electron acceptors and donors. This, together with the fast optical dynamics (either in the ground or excited states) of most conjugated polymers, has made conjugated polymers very attractive as transducer-active materials. On the other hand, the unusual electronic, mechanical, and thermal properties of carbon nanotubes have also led to their potential use in a wide range of devices, including sensors. In particular, the ability of carbon nanotubes and their derivatives to operate as gas and glucose sensors has been recently demonstrated. This article provides a status review on the research and development of sensors and sensor arrays based on conjugated polymers and carbon nanotubes. The unique features character- istic of most reported sensing transduction modes related to conjugated polymers and carbon nanotubes are discussed, along with their pros and cons. INTRODUCTION Measurement represents one of the oldest methods used by human beings to better understand and con- trol the world. Chemical and biological sensors (or biosensors) are the evolved products of physical measurement technologies.
    [Show full text]
  • Fluoro-Alkane, -Alkenes, -Alkynes and –Aromatics
    Fluoro-alkane, -alkenes, -alkynes and –aromatics Fluoroalkanes Properties of fluoroalkanes Consider these typical bond strengths: C-C bond 88kcal/mol C-F bond 111kcal/mol C-H bond 106kcal/mol This implies that the carbon – carbon bonds are the weakest link in fluoroalkanes. 1 Features to bear in mind: (i)Bond Strengths tend to increase as the total number of fluorines increases I.e. Bond strengths F F F F F < < F C-F bond shortens (strengthens) as more F's are added 2 The C-F bond shortens (gets stronger) as more fluorines are added due to an increase in back bonding (halo effect). BDE Fluorine makes the atoms close to it bond stronger also !! ↑ shorter ↑ stronger no significant changes Some C-C bond strengthening also occurs on substitution of F for H. For example the CF3-CH2CH3 bond is ~5kcal stronger than the CF3CH2-CH3 bond. (i)-(CF2)n- is more stable than -(CH2)n- due to better chemical stability. PTFE shows resistance to oxidation and microbial attack. (Generally related to BDE’s of C-H and C-F). 3 (iii) Electron Pair Repulsions (Intramolecular) are important to PTFE. 1,3 repulsions force the F atoms out of linearity, which is in contrast to the hydrogen containing polymer analogue. 4 Boiling Points Fluorocarbons are obviously heavier than their hydrocarbon counterparts, and thus we might initially expect them to have correspondingly higher boiling points. However, the boiling points of hydrocarbons and perfluorocarbons are very similar. (B.Pts in oC) # of Carbons 1 2 3 4 5 6 FC -128 -78 -38 -1 29 57 HC -161 -88 -42 -0.5 36 69 The increase in molecular weight that increases the boiling point, therefore must be offset by the decrease in attractive intermolecular bonding forces in the fluorocarbon systems.
    [Show full text]
  • Macromolecules Volume 24, Number 13 June 24,1991 @ Copyright 1991 by the American Chemical Society
    Macromolecules Volume 24, Number 13 June 24,1991 @ Copyright 1991 by the American Chemical Society Reviews A Chemical Approach to the Orbitals of Organic Polymers Roald Hoffmann,' Christoph Janiak, and Christian Kollmar Department of Chemistry and Materials Science Center, Cornell University, Ithoca, New York 14853-1301 Received September 8,1990; Revised Manuscript Received January 8,1991 ABSTRACT The electronic structure of the prototypical unsaturated and saturated organic polymers poly- acetylene and polyethylene is elucidated by a building-up process starting from a linear carbon chain, which is then kinked and finally has one or two hydrogen atoms attached to it. In this process the common features as well as the differences between polyacetylene and polyethylene (semiconductor vs large band gap insulator, unsaturation vs saturation) emerge in a natural way. The emphasis is on bringing together the essential concepts of solid-state physics and simple ideas of chemical bonding. Some topics of special interest, such as bond alternation and solitons in polyacetylene, are also discussed, in as simple and chemical manner as poasible. Synthetic organic polymers mark our time.' The most unsaturated one, one that provides for a conjugated u common such polymer, polyethylene (l),has an extremely system consisting of p orbitals perpendicular to the plane of the backbone. This u system gives rise to interesting electronic properties? thus attracting the attention of both physicists and chemists. For instance, it provides for localized elementary
    [Show full text]