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Dielectric Discussion group (UK) 1973-2001

(Published in IEEE Transactions on Dielectrics and Electrical Insulation, 18: 570-578)

The dieletrics discussion group (UK) and the dieletrics society platforms for dieletrics research

by Graham Williams

Emeritus Professor of Chemistry
University of Wales Swansea, SA2 8PP, United Kingdom.

Abstract

This article is a slightly amended and extended verison of a talk given by the writer at Dieletrics 2009, organized by the Dieletrics Group of the Institute of Physics (IOP), London UK and held at the University of Reading 15-17 April 2009. It gives a breif history of the Dieletrics Discussion Group (1968-1974) and the Dieletrics Society(1974-2001) in the United Kingdom and summarizes some of the major advances in studies of dynamics of polymeric materials that occured during that period and subsequently using broadband dieletric spectroscopy (BDS).

1 Introduction

IN the early 1960's Professor Mansel Davies at The Edward Davies Chemical Laboratories of the University College of Wales, Aberystwyth was conducting research into the dielectric relaxation behavior of polar liquids and solids. He was already well-known internationally for his studies of molecular structure and bonding of small molecules, using infra-red-spectroscopy, and the physical properties of hydrogen-bonded liquids and solids, using thermodynamic methods. Dielectric spectroscopy was a fairly new area for him and he realized that opportunities were very limited for scientists in the UK to gather together and discuss their research in this developing area of physical chemistry/chemical physics.

Professor Davies, seen in Figure 1 with double Nobel Laureate Linus Pauling at the Debye Centenary Meeting at Cornell University in 1984, conceived the idea of forming a Dielectrics Discussion Group, which would act as a meeting point and provide a platform for dielectrics research in the UK and beyond. As a result, a two-day Meeting was convened in the Spring of 1968 at Gregynog Hall, of the University of Wales, near Newtown, Montgomeryshire. It was organized by Mansel Davies, Alun Price and Graham Williams, all physical chemists from the University College of Wales, Aberystwyth. Fifty scientists attended, being a mix of physical chemists, theoretical chemists, physicists, electrical engineers, polymer and materials scientists, all from the UK, except Dr Brendan Scaife of Trinity College, Dublin.


Figure 1
Figure 1. Linus Pauling (left) and Mansel Davies in discussion in 1984.

The Meeting discussed dielectric relaxation behavior arising from molecular motions of dipolar molecules in the liquid and elastomeric states (now known as soft matter!) with measurements spanning a frequency range from a few Hz, through power and radiofrequencies, UHF and VHF, the microwave range and into the far infra-red.

Talks were given by David Buckingham (Bristol) and George Wyllie (Glasgow) on Dielectric Theories, by John Hasted (University College), D.A. Weyl (Unilever) and D. Rosen (Chelsea) on Aqueous Dielectrics, by Harry Block (Liverpool), Alistair M. North (Strathclyde), Kenneth J. Ivin (Belfast), Julian Swain and Graham Williams (both Aberystwyth) on Synthetic Polymers and by Mansel Davies (Aberystwyth), John Chamberlain (National Physical Lab.), Bill Pardoe (Aberystwyth) and Leslie Sutton FRS (Oxford) on Far Infra-Red Spectroscopy.

As a result of its success, it was decided at the Meeting that a continuing Dielectrics Discussion Group (DDG) would be established to meet not more frequently than once a year. A DDG Committee was formed with Dr. Leslie Sutton FRS as Chairman, Dr. Alun Price as Secretary, Prof. Mansel Davies, Dr. John Hasted and Mr. Wilson Reddish (ICI Plastics) as Committee members. A Report of the Meeting was published in Nature [1].

It was appreciated at the time that the subject of “Dielectrics” covered many sub-areas, broadly classified into those of: Polarization, Relaxation, Conduction and High-Field Phenomena. This realization was both good and not-so-good for the organization of future Meetings of the DDG. On the good side a wealth of dielectrics research was being pursued nationally and internationally, which could be discussed at such Meetings. These were conducted by scientists from many disciplines, chemistry, physics, engineering sciences, materials scientists, theoretical physicists, etc., and covered fundamental studies (e.g. of dipole relaxation behavior of liquids and solids) and applied studies (e.g. of materials used in low and high voltage transmission cables, transducers, electret microphones, semi-conducting devices, etc.). On the not-so-good side, however, was the question of how could these researchers be brought together as a single group at a Meeting when they have both overlapping and widely-diverse interests? Precisely the same problem was faced by the Gordon Research Conferences on Dielectric Phenomena and the IEEE Electrical Insulation Society Conferences on Electrical Insulation and Dielectric Phenomena (CEIDP) in the USA, which ran concurrently with the proposed DDG Meetings.

For the DDG, the solution was to run annual Meetings on chosen themes (or topics) in dielectrics research where these would change from one Meeting to the next. Each year the theme for a Meeting was chosen by the DDG Committee. The Lead Organizer, normally a member of the DDG Committee, would take on the task of formulating the detailed programme and inviting the speakers and then, together with the DDG Secretary and Treasurer, would organize the entire Meeting. This was the late 1960's and 1970's which was a flourishing period for University, Government and Industrial research in the UK, so it was possible to do all of this successfully, relying on a good response from registered members of the Group and further researchers from the UK and abroad. As will become apparent, the DDG Meetings were extremely successful over many years to come.

2 DDG, THE EARLY YEARS 1968–1972

The enthusiasm and great efforts made by the DDG Committee in those early years established the DDG as a prime meeting point and a platform for dielectrics research. Dr. Sutton was Chairman of the DDG (and then The Dielectrics Society) from 1968 to 1986. His gentle, firm leadership was much appreciated by the Group. On his retirement from the Chairmanship of the Society, a dinner was held for Dr. Sutton in New College, Oxford in June 1986 to express appreciation for his services to the DDG and the Dielectrics Society. Outstanding work was done in those early years by Dr. Alun Price, as DDG Secretary, which ensured both the smooth organization of the Meetings and the financial stability of the Group.

Proceeding on the basis of choosing a different theme for each Meeting, those for 1968–1972 were as follows (attendances are in parentheses) [2]: 1968 Inaugural meeting of the DDG, Gregynog Hall (50); 1969, High Field Phenomena and Impurity Effects, New College, Oxford (75); 1970, Heterogeneous Systems and Biomaterials, Aberystwyth (123); 1971, Polarization and Conduction, theory and experiments, Bedford College (120); 1972, Non-linear Dielectrics and Ferroelectrics, Cambridge (94).

While the topics varied considerably, the lists of participants reveal that a fair number came faithfully to each Meeting, showing that a “family” of dielectrics scientists was being established, which was one of the initial aims of Mansel Davies. Also the number of participants was encouraging, rising from 50 to the low 100's, which reflected both the increased awareness of the Group and increased participation from researchers in Continental Europe. However, the majority of participants in this period were from the UK, which reflected the considerable activities in dielectrics research in University, Industry and Government laboratories in the UK. Regrettably, over the years and up to the present time, and in contrast to activities internationally, those activities in the UK have decreased considerably.

The 1970 Meeting at the UCW, Aberystwyth attracted 123 participants, including three great dielectrics researchers – Professors Charles Smyth, Robert H. Cole and Herbert Frohlich (Figure 2). The Dielectrics Discussion Group had arrived!


Figure 2
Figure 2. Charles Phelps Smyth, Professor of Chemistry at Princeton University and brother of Henry DeWolf Smyth of the 1945 Smyth Report “Atomic Energy for Military Purposes”, was, in the 1930's, one of the first to study systematically the dielectric properties of dipolar liquids and solids and made major contributions to the subject during his 50+ years career. Photograph of Professor Smyth reproduced courtesy of the Department of Rare Books and Special Collections, Princeton University Library. Robert H. Cole, Professor of Chemistry at Brown University, was trained as a physicist but practiced as a physical chemist – becoming Head of Chemistry at Brown. He was the only person to obtain a Ph.D. with Nobel Laureate J.H. van Vleck at Harvard for experimental rather than theoretical work. In a 50+ year career he was distinguished for his many experimental and theoretical contributions to the dielectric behavior of liquids, glasses and polar gases - incorporating both phenomenological (Cole-Cole, Davidson-Cole) and molecular (time-correlation function) representations of dielectric relaxation behavior - and for his book “Underwater Explosions” that resulted from the war-years he spent at the Woods-Hole Facility. Photograph reproduced with the permission of Professor John Berberian. Herbert Frölich, Professor of Theoretical Physics at Liverpool University was distinguished for his book “Theory of Dielectrics” and for his contributions to dielectric relaxation theory, theory of dielectric breakdown, polaron theory, biodielectrics and superconductivity. Photograph reproduced with the permission of The University of Liverpool.

3 THE DDG 1973–1974 AND THE DIELECTRICS SOCIETY 1974–2001

3.1 THE ANNUAL MEETINGS

There followed a series of DDG Meetings until 1974, when it became The Dielectrics Society (DS), a registered charity with the same Committee structure and purpose as the DDG. Meetings held annually from 1973 to 2001 are listed below [2]. Professor James Calderwood of Salford University, the DS Treasurer at the time, did much to guide the Committee through the requirements that led to charitable status.

  • 1973 Interfacial phenomena and related topics, Oxford
  • 1974 Electrets and related high field polarization, Swansea
  • 1975 Motions in molecules and biomolecules, London
  • 1976 Solid dielectrics - imperfections and impurities, Oxford
  • 1977 Anisotropic dielectrics, Cambridge
  • 1978 Electron and photon induced effects in dielectrics, Oxford
  • 1979 Molecular dynamics of polymeric systems, Cambridge
  • 1980 Dielectric relaxation, science and engineering, Aussois, France.
  • 1981 High field phenomena in dielectrics, Oxford
  • 1982 Dielectrics of liquids, biological systems, Cambridge
  • 1983 The physics of dielectrics solids, Canterbury
  • 1984 Piezo-dielectrics, interfacial and ionic conduction, Reading
  • 1985 Bioelectronics and biosensors, Bangor
  • 1986 Polymers, thin film electronics, Sussex
  • 1987 Dielectric properties of ordered systems, ferroelectrics, Cambridge
  • 1988 A Celebration of Dielectrics, 21st. Ann. Conf., Oxford
  • 1989 Molecular Electronics, Bangor
  • 1990 Adv. in breakdown and high field phenomena, Canterbury
  • 1991 Relaxation, charge injection, transport, Canterbury
  • 1992 Application of dielectrics workshop, ferroelectrics, Imperial College
  • 1993 Dielectric relaxation, advances in theory instruments, Canterbury
  • 1994 Technological Applications of Dielectrics, Canterbury
  • 1995 Impedance Spectroscopy, Electrodes Interfaces, Canterbury
  • 1996 Smart Dielectrics, Electro-responsive materials, Canterbury
  • 1997 Charges in Solid Dielectrics, Canterbury
  • 1998 Anisotropic Dielectrics and Ferroelectrics, Canterbury
  • 1999 Dielectrics at High Frequencies, Canterbury
  • 2000 Developments in Dielectrics Research, Canterbury
  • 2001 Field Effects in Dielectrics, Toulouse

3.2 ORGANISATION, EXAMPLES OF DIVERSITY AND FURTHER DEVELOPMENTS

One can see from the above, and in detail in the Dielectrics Society Archive [2], many of the Meetings in this period were held in the attractive and convenient venues of Oxford and Cambridge Colleges. Then, in the early 1990's, a new venue was established at the University of Kent at Canterbury. Dr Sutton remained Chairman to 1986, a remarkable tenure of 18 years, and was followed by Professors T. John Lewis (Bangor University), Graham Williams (Swansea University), Harry Block (Cranfield University) and Robert Hill (King's College, London). Professor Gary Stevens (Surrey University) was the first Chairman of the IOP Dielectrics Group and, with Prof. Hill, coordinated the transition from the Dielectrics Society into the Dielectrics Group of the IOP in 2001. The Archive [2] is comprehensive, providing details of all 34 Meetings from 1968 to 2001 and is a unique record of progress made in dielectrics research over the past forty years.

Each Meeting attracted between 70–100 participants; their scope and composition became increasingly international with time and attracted leading researchers in the dielectrics sciences. Details of the lectures and Posters presented at the Meetings are given in the Archive [2] together with Extended Abstracts, often totaling as much as 60 pages for a Meeting. While it is not possible to describe here details of these three-day Meetings, we consider just two examples, the Meetings in 1981 and 1996, in order to illustrate their variety and diversity of topics.

3.2.1 HIGH FIELD PHENOMENA IN DIELECTRICS; 1981, OXFORD

The Meeting included a strong theme on the practical effects of high E-fields on liquids (e.g. alkanes) and solids (e.g. insulators), leading to electrical discharges, electrical treeing and dielectric breakdown. Further themes were molecular in nature, being concerned with non-linear optical and dielectric polarizabilities and with electrical/electro-optical phenomena observed for ultra-thin (LB) films or with practical devices derived from electrically-charged films (van Turnhout) or suspensions (Block). The details of the 19 lectures, the Posters and their Extended-Abstracts (totaling 59 pages) are given in the Dielectrics Society Archive [2].

Electrical discharges, Conduction, Dielectric Breakdown; in polymers (Hirsch, Adamec, Davies, Blythe); in liquids (Forster, Felici, Watson); electrical treeing (Cooper, Coelho, Coletti) Langmuir/multilayer films (Roberts, Taylor, Hasted) Non-linear dielectric polarization effects (Buckingham, Anitoff,) Electrorheology (Block), Electroactive Devices (van Turnhout); Electro-optics (Jennings).

3.2.2 SMART DIELECTRICS; 1996, KENT

The late 1980's had seen large, well-funded initiatives in the UK (through the Engineering and Physical Research Council -EPSRC) and globally in the general area of “Molecular Electronics”. In timely fashion, this had been the subject of the 1989 Dielectrics Society Meeting in Bangor. The Smart Dielectrics Meeting in 1996, for which the writer was the Lead Organizer, reported on some of the advances being made using designer materials having electro-responsive and electro-optical properties.

The programme concerned electro- and photo-active materials, mainly organic, in the form of polar dielectrics, polyelectrolytes, organic semi- and photo-conductors, photo- refractive polymer films, organic ferroelectric films, liquid crystalline polymer films, piezo- and pyro-electric polymer films, electroluminescent polymers, electro-rheological fluids and non-linear optical polymer films, which were described by leading international scientists. The physicochemical functions of the materials were demonstrated and interpreted in terms of fundamental molecular properties. The details of the 22 talks, the 38 Posters and their Extended-Abstracts (totalling 74 pages) are given in the Dielectrics Society Archive [2]. Photoactive/electroactive polymers (Bassler, Wendorff, Bradley);Liquid Crystals (Kremer, Wubbenhorst, Vij); Ferroelectrics (Whatmore, Sakabe, Millar, Davies); Non-linear optics (King, Rohlfing, Bloor); Charge storage (Lewiner, Hampton, Felici); Electrorheology (Block, Khusid, Henning).

The above examples give an indication of the scientific scope and breadth of the Dielectrics Society Meetings. The efforts made by the organizers (Committee, Lead Scientists, Secretary and Treasurer) were quite exceptional for such a small independent DDG and Dielectrics Society. These were made in their own time and, essentially, at their own expense. Despite the large amount of skilled work involved for each Meeting, little credit is normally given towards the research profiles of individuals, or their Institutions, for organizing such Research Meetings. However, the organizers worked to support and promote the scientific aims of the Society and, in doing so, found their satisfaction both in the successes of the Meetings and being an essential part of a continuing, evolving “family of scientists” concerned with dielectric phenomena. In the present days, where the Research Councils and Research Assessment Exercises of the Funding Councils require so much from individual researchers in Chemistry, Physics, Biological Sciences and Engineering Sciences, it seems increasingly difficult for small groups to give the time and effort to organize Meetings of the scope of the Annual DDG and the Dielectrics Society Meetings shown above without the active involvement and participation of the major Scientific Societies.

During my period as Chairman of the Society (1992–1995) we decided to have a small Meeting of past and present Officers of the DDG and the Dielectrics Society to appraise how the Society had approached the scientific-scope and organization of previous Meetings, and to see what we should to do in the future. This Special Meeting was organized by Professor John Fothergill in the summer of 1993 at Leicester University; a photograph taken at the time is shown in Figure 3.


Figure 3
Figure 3. The Special Meeting of The Dielectrics Society, Leicester University 1993. Photograph reproduced with the permission of Professor John Fothergill. Back Row David Bloor (Durham), Robert Hill (King's College), George Chantry (National Physical Lab.), Geoff Davies (Leeds), Friedrich Kremer (Mainz & Leipzig), John Fothergill (Leicester), Harry Block (Cranfield), T.J. Lewis (Bangor), Cyril Smith (Salford). Middle Row Tony Blythe (ICI/BICC), Len Dissado (Leicester), Gary Stevens (Surrey), Alun Price (Aberystwyth), James Calderwood (Salford), Elizabeth Carter (National Physical Lab.) Front Row Arnold Lynch (ex Post Office Research, Dollis Hill), Graham Williams (Swansea), Mansel Davies (Aberystwyth), Wilson Reddish (ICI Plastics, Welwyn).

We were delighted that Professor Mansel Davies was present and I am sure he was pleased to see how the Society had developed since his DDG initiative at Gregynog Hall in 1968. Sadly, he passed away in January 1995 [3] five months after Linus Pauling (whose Obituary he had written). The Mansel Davies Award of the Dielectrics Society, now of the IOP Dielectrics Group, honors his contributions to the DDG and the Society, and is given “for the best presentation by an early career researcher” at a Meeting.

In the photograph, Figure 3, are those who had been, or became, Chairmen - T. John Lewis, Graham Williams, Harry Block, Robert Hill, Gary Stevens, John Fothergill; Secretaries - Alun Price, Cyril Smith, Tony Blythe or Treasurers - James Calderwood, Robert Hill, of the DDG or the Dielectrics Society. Not present is the late Professor Andrew Jonscher (Chelsea) who made great contributions to the workings of the Society.

Professor Friedrich Kremer, formerly of the Max Planck Institute for Polymer Research, Mainz, now Professor of Experimental Physics at the University of Leipzig, is also in the photograph. During the past 25 years or so he has made outstanding contributions to the development of experimental techniques for Broadband Dielectric Spectroscopy (BDS) and to dielectric studies of the molecular dynamics of polymers, ferroelectric liquid crystals, ultra-thin polymer films and materials in confining environments [4]. In 1995 he was awarded the Karl Heinz Beckurts Prize in Germany for the promotion of Science and the Economy, which recognized his contributions to the development of modem commercially available dielectric instrumentations.

3.3 THE DDG, DS AND COMPLEMENTARY ORGANIZATIONS

In the years from 1968 to 2001, the DDG and its successor, The Dielectrics Society, worked in parallel with complementary organizations in advancing the dielectric sciences. The “Pocono Conferences”, which met in the late 1940's and early 1950's at resort hotels in the Pocono mountains of Pennsylvania, were concerned with both practical and fundamental aspects of electrical insulation and dielectric phenomena of liquid, solid and gaseous dielectrics. In 1963 the IEEE (USA) was formed and in that year established the IEEE Professional Technical Group (PTG) on Electrical Insulation, which became in 1964 the IEEE Group on Electrical Insulation, which initiated the IEEE Transactions on Electrical Insulation. This Journal continued until the end of 1993 when it was replaced by the IEEE Transactions on Dielectrics and Electrical Insulation. These became leading research Journals for the dielectrics sciences and owed much in their successful development to the outstanding contributions made by Dr. Arend van Roggen who was the Editor from 1977 to end of 2001. In 1984 the IEEE Group on Electrical Insulation became the Dielectrics and Electrical Insulation Society (DEIS), whose history up to 1990 has been outlined by Professor John Tanaka [5]. The history of the related Electrical Insulation Conference (EIC) (USA), which was formed in 1958 as the only applications-oriented conference sponsored by the DEIS, has been outlined by Thomas Castaldi and John Tanaka [6].

The well-known Conferences on Electrical Insulation and Dielectric Phenomena (CEIDP) were initiated in 1920 by the National Academy of Sciences (USA) and the National Research Council (USA) and came under the IEEE EIS in 1980. The CEIDP published their Annual Reports, which contained Abstracts of the papers presented at the CEIDP Conferences, together with issues of The Digest of the Literature on Dielectrics. The former were converted to collections of critical reviews when the CEIDP joined the IEEE and these first-appeared in 1984 as vol. 19 of the IEEE Transactions on Electrical Insulation. In 1955 the CEIDP created the J.B. Whitehead Memorial Lectureship in recognition of research contributions made by individuals to the dielectrics sciences. Several members of the Dielectrics Society have been awarded this Lectureship and include: Professors T. John Lewis, James. H. Calderwood, Graham Williams, Andrew Jonscher, Len Dissado and Friedrich Kremer.

Biennial Gordon Research Conferences on Dielectric Phenomena in New England were initiated in 1965 by John D. Hoffman of the National Bureau of Standards, Washington DC and continued to 1994. These, together with regular International Conferences on Dielectrics and Ferroelectrics, provided further “platforms for research” in the dielectrics sciences.

In 1991 The Dielectrics Society (Chairman, Professor Robert Hill) was incorporated into the Institute of Physics (London, UK), as its new Dielectrics Group, with Professor Gary Stevens as Chairman. The Dielectrics Group, through its Meetings, continues to provide a platform in the UK for dielectrics research across a broad range of topics. In 2006 three of its members published a paper that analyzed trends in international research activities and publishing the dielectrics sciences [26].

The activities of the IEEE, DDG, Dielectrics Society and IOP Dielectrics Group helped to bring together physicists, chemists, electrical engineers, materials scientists, polymer scientists, etc., from academia and industrial and government research laboratories to create, as I have written, an “international family” of scientists and engineers whose interactions advanced and promoted dielectric research in the UK, Europe, the USA and globally. Scientists at these Meetings, who had interests in quite different aspects of dielectric phenomena, found they used complementary experimental techniques and complementary methods of analyses. This led to new ideas for research, to research collaborations and, importantly, to long-term friendships, which have been of great benefit to the dielectrics sciences.

4 SOME OF THE ADVANCES IN DIELECTRICS SCIENCES DURING 1968–2001 AND BEYOND

So what were some of the advances in the dielectrics sciences during the period 1968–2001 of the DDS and the Dielectrics Society?

The writer is not qualified to describe those made in high-field dielectric polarization, conduction and breakdown phenomena or non-linear dielectric phenomena in materials and their associated applications in technology. The following comments apply only to his specialist-areas, i.e. to studies of the low-field (linear) dielectric relaxation and ionic conduction behavior of synthetic polymers, low molar mass glass-formers and liquid crystals using Broadband Dielectric Spectroscopy (BDS) in the range 10-4 to 1012 Hz.

In the 1950's and early 1960's most studies of the linear polarization, relaxation and conduction behavior of materials in this vast frequency range were made by means of point-by-point, hand-balanced measurements of the dielectric impedance or propagation-factor at given frequencies. The measured quantities for a material (e.g. capacitance, resistance) were converted to its intrinsic dielectric properties (e.g. complex permittivity) using hand-operated calculating machines. Having obtained these desired quantities, the researcher would return to the hand-operated instruments to make further (lengthy) measurements. Analyses and detailed processing of data were done at the end of a sequence of measurements. While the data were extremely accurate (more so than those obtained from most modern automated instrumentation), this was an extremely laborious process and held-back the development and applications of Broadband Dielectric Spectroscopy for decades, while newer techniques, such as multi-nuclear NMR, ESR relaxation and quasi-elastic laser light-scattering, went ahead with modern semi-automatic equipment. Throughout this period Mansel Davies felt that BDS would only advance to rival/compete/complement with modern spectroscopic/scattering/relaxation techniques when fast, automatic dielectric instrumentation became commercially-available.

His wish has been achieved in brilliant fashion. We now have commercial instrumentation that measures permittivity and loss quickly and accurately over the unrivalled working-range 10-2 Hz to 1010 Hz, and even this can be extended readily, down or up, by two decades [4], [7], [8]. In addition, since fast, on-line processing of data is now standard, decisions can be made immediately following a frequency scan to decide on the next set of measurements, which gives momentum to the study of a material over wide ranges of frequency, temperature and applied pressure. Comprehensive studies of a material that took days or weeks to complete in the mid-1960's may now take only a few hours. The speed of acquisition of broadband dielectric spectra in the range 1 Hz to 1010 Hz using modern equipment (low frequency response analyzers, higher frequency network analyzers) also make it possible to monitor systems that change physically or chemically (or both) with time. Thus bulk thermo-polymerization reactions [9] and photo-chemical reactions [10] and crystallization processes [11] for polymer systems can be monitored in real-time by BDS. In parallel with developments in BDS measuring-techniques, new methods for theoretical analyses of dielectric data for materials that use phenomenological and molecular approaches to rationalize dielectric relaxation behavior have been introduced. Prominent among these are (i) the wide use of the KWW (stretched-exponential) function [12], [13], [14], [15] for the primary dielectric relaxation in amorphous polymers (similarly-applied to relaxation data from NMR, EPR, fluorescence depolarization and quasi-elastic light- and neutron- scattering studies of polymers) and (ii) the Cole-Glarum “field free” time-correlation function (TCF) approach to multiple dipole relaxations [16] whose TCFs can be modeled for polymer systems by physical theories and by “molecular dynamics” computer simulations [17], [18].

The advances in knowledge of the molecular dynamics of amorphous, crystalline and liquid crystalline polymers gained from their dielectric behavior and subsequent theoretical analyses, can be judged by comparing the contents of the research text “Anelastic and Dielectric Effects in Polymeric Solids” in 1967 by McCrum, Read and Williams, [19] with those in the recent texts [4], [7], [8]. The studies cover, inter alia, the behavior of amorphous homopolymers, random and block copolymers, polymers in confined spaces, ultra-thin polymer films, liquid crystalline polymers, semi-conducting and photoconducting polymers, polymer blends and mixtures, polyelectrolytes – their multiple dielectric relaxations, temperature and pressure and volume effects – together with piezo-, pyro- and ferro-electric properties, non-linear optical properties of “poled” films, real-time dielectric monitoring of bulk thermo- polymerization, diffusion-control of polymerization leading to glass or elastomer formation, real-time dielectric monitoring of polymer crystallization from the bulk revealing the constrained and normal amorphous phases. Future studies may be concerned with novel polymers such as amorphous “gradient A-B copolymers” [20] whose chemical composition along the chain varies systematically from AAAAA at one end to BBBBB at the other, which results in an extremely broad primary relaxation (dielectrically and mechanically), and hence an extremely broad glass-transition range for these materials– which offers many interesting practical applications.

Also many new BDS studies, in real-time, of systems undergoing chemical or physical changes (or both) are likely to be made. Until now such studies have only monitored changes in the low frequency relaxation behavior (6 Hz) of a reacting or crystallizing system. Network-analyzers operate at higher frequencies so can be used to monitor changes in dynamics where dielectric relaxation times of the molecules undergoing chemical or physical changes (or both) with time are in the range 10-7 to 10-10 sec e.g. photoisomerizable and photochromic molecules in solution. The advances in measurement techniques for the studies of dielectric relaxation processes in materials apply equally to “broadband conductance spectroscopy” (“BCS”) of systems exhibiting intrinsic ionic conduction (e.g. electrolytes, polyelectrolytes). As a general rule, in such systems the real conductivity is approximately constant at low frequencies, with value σ0, then increases as a power law, fm, with m

Two further major developments have occurred, which provide meeting points and platforms for dielectrics research. The first International Discussion Meeting on Relaxations in Complex Systems, organized by Kia Ngai and his Committee, took place in Crete in June 1990. This Meeting covered large areas of research with polymers, glass-forming liquids and ionics, as studied by relaxation (dielectric, NMR, dynamic mechanical), dynamic scattering (X-ray, laser light, neutron) and thermodynamic (volume, enthalpy, specific heat) techniques, which were interpreted using a variety of phenomenological and molecular theories for the different dynamical processes, and by computer simulations of chain dynamics using “Molecular Dynamics” and “Monte Carlo” methods. A large proportion of the works presented at the Meeting published in J. Non-Crystalline Solids (JNCS), (1278 pages) [23a] was concerned with new dielectric studies of materials. There followed regular Meetings, of increasing size, which have been published [23b–e] in JNCS. The one held in Lille in 2005, attracted over 600 participants as did the latest Meeting in Rome in 2009. A large proportion of the papers presented at these Meetings were concerned with new experimental and theoretical studies of materials using Broadband Dielectric Spectroscopy.

The International Dielectrics Society (IDS) was formed and held its first Meeting in Jerusalem in the Spring of 2001. Attended by more than 130 participants from 25 countries, it covered many aspects of Broadband Dielectric Spectroscopy, including the behavior of polymers, glasses, biological systems and new applications to practical systems. The papers from the Meeting were published (409 pages) in JNCS [24a] Since that time the IDS has held Meetings every two years, successively in Leipzig, Delft [24b], Poznan and Lyon, with a further Meeting that took place in Madrid in 2010. Papers from each Meeting have been published as Special Issues of JNCS. Also the IDS held a Dielectrics Workshop within the Lille Meeting of the 2005 International Discussion Meetings on Relaxations in Complex Systems - see under “Tutorials” on the homepage of the IDS. Tutorials were given by G. Williams (BDS studies of solids), F. Kremer (molecular dynamics in geometrical confinement), R. Richert (dielectric modulus studies), Y. Feldman (BDS of complex systems), B. Roling (conductance spectroscopy of ionics), J.C. Dyre (theories of dielectric relaxation and conduction) and H. Morgan (Electrokinetics). The majority of these can be viewed as Powerpoint Presentations on the IDS website.

I have gone into some detail above to show how BDS studies of materials have undergone a renaissance in recent years through the International Dielectrics Society, the International Discussion Meetings on Relaxations in Complex Systems and the Dielectrics Group of the IOP.

On a personal note, I write this article 50 years on from the year I completed my Ph.D. at Aberystwyth under the direction of Professor Mansel Davies – the year in which I published my first papers on dielectric relaxation (one experimental, one theoretical) [25a, b]. Although he was my supervisor, he told me to write up these papers and publish them in my own name, which was a remarkable, generous gesture to a young student. It is fitting that this article concerning the history of the DDG and Dielectrics Society should end with an appreciation of Professor Davies. He is remembered as an outstanding physical chemist, polymath and generous human being. His scientific vision and enthusiasm were a source of inspiration for his students and colleagues alike and, with his exceptional knowledge and personality, he bridged the “two cultures” of C.P. Snow with ease.

ACKNOWLEDGMENTS

The original version appeared as a “Feature Article” in the November 2009 Newsletter of the Dielectrics Group of the IOP. The author wishes to thank the IOP for their help in preparing the earlier Feature Article in the IOP Newsletter and Professors Fothergill and Berberian, Princeton University and Liverpool University for permissions to reproduce the photographs. The author thanks Professor John Fothergill for reading the paper and his helpful comments. The author wishes to thank Dr Enis Tuncer, Official Historian of the IEEE Dielectrics and Electrical Insulation Society for suggesting publishing the present version in the IEEE Transactions on Dielectrics and Electrical Insulation and for providing information concerning the history of the IEEE DEIS. His help in preparing this paper in the format appropriate for the Transactions is greatly appreciated by the author.

REFERENCES

[1]    Report of the first Meeting of the Dielectrics Discussion Group 26-27 March 1968. Nature, Vol. 218, May 4th issue, 1968.

[2]    The Dielectrics Group is indebted to the present Chairman, Professor John Fothergill, for placing the Archives of the Dielectrics Discussion Group and the Dielectrics Society on the website of the IOP Dielectrics Group (see in “Group Archive” and “Dielectrics Society Archive”).

[3]    An appreciation of the life of Professor Mansel Davies is given by the writer in Physics World, 1995, April Issue, p.63; see also the website of the IOP, London, UK, under Dielectrics Group, “Mansel Davies Award”.

[4]    See for example “Broadband Dielectric Spectroscopy”, F. Kremer and A. Schonhals (Eds.) Springer Verlag, Berlin, Germany, 729pp, 2003.

[5]    J. Tanaka, “History of the Dielectrics and Electrical Insulation Society”, IEEE Trans. Electr. Insul., Vol.25, pp. 3-16, 1990.

[6]    T.E. Castaldi and and J. Tanaka, “History of the Electrical Insulation Conference”, Feature Article, IEEE Electrical Insulation Magazine, Vol. 19, No.4, pp. 20-32, 2003.

[7]    J.P. Runt and J.J. Fitzgerald, (Eds.), “Dielectric Spectroscopy of Polymeric Materials”, Amer. Chem. Soc. Series, 461 pp, 1997.

[8]    E. Riande and R. Diaz-Calleja, “Electrical Properties of Polymers”, Marcel Dekker, New York, USA, 630pp, 2004.

[9]    G. Williams, I.K. Smith, P.A. Holmes and S. Varma, “Real-time dielectric studies of polymerizing systems”, J. Phys. Condens. Matter, Vol. 11, pp. A57-A74, 1999.

[10]    J. Fournier, G. Williams and P.A. Holmes, “Dielectric properties during free-radical bulk polymerization visible light-induced polymerization of bisphenol-A bis(2-hydoxyethyl ether dimethacrylate”, Macromolecules, Vol. 30, pp. 2042-2051, 1997.

[11]    R Lund, A. Alegria, L. Goitandia, J. Colmonero, M.A. Gonzalez and P. Lindner, “Dynamical and Structural Aspects of the cold crystallization of poly(dimethylsiloxane)”, Macromolecules, Vol. 41, pp. 1364-1376, 2008.

[12]    R. Kohlrausch, “Theorie des elektrischen Ruckstandes in der Leidener Flasche”, Pogg. Ann. Phys. Chem., Vol. 91, pp. 179, 1854

[13]    F. Kohlrausch, “Ueber die elastische Nachwirkung bei der torsio”, Pogg. Ann. Phys. Chem., Vol. 119, p.337, 1863.

[14]    G. Williams and D.C. Watts, “Non Symmetrical dielectric relaxation behavior arising from a simple empirical relaxation function”, Trans. Faraday Soc., Vol. 66, pp. 80-85, 1970.

[15]    M. Cardona, R.V. Chamberlain and W. Marx, “The history of the stretched exponential function”, Ann. Phys. (Leipzig), Vol. 16, pp. 842, 2007.

[16]    (a) G. Williams, “The use of the dipole correlation function in dielectric relaxation” Chem. Rev., Vol. 72, p. 55, 1972; (b) G. Williams, “Theory of dielectric properties”, as in [7], Chapter1, pp. 3-54.

[17]    RH. Boyd and G.D. Smith, Polymer Dynamics and Relaxation, Cambridge UP, Cambridge, 2007.

[18]    W. Paul and G.D. Smith, “Structure and dynamics of amorphous polymers: computer simulations compared to experiment and theory”, Rep. Progr. Phys., Vol. 67, pp. 1117-1185, 2004.

[19]    N.G. McCrum, B.E. Read and G.Williams, “Anelastic and Dielectric Efects in Polymeric Solids”, Wiley 1967, Dover Publ., 617pp, 1991.

[20]    O. Kim, M.M. Mok, R.W. Sandover, D.J. Woo and J.M. Torkelson, “Uniquely broad glass transition temperatures of gradient copolymers relative to random and block copolymers containing repulsive comonomers”, Macromolecules, Vol. 39, pp. 6152-6160, 2006.

[21]    J.C. Dyre and T.B. Schroder, “Universality of ac conduction in disordered solids”, Rev. Mod. Phys., Vol. 72, pp. 873-892, 2000.

[22]    (a) I. Alig, P. Potschke, M. Abdel-Goad, I. Alig, S. Dudkin and D. Lellinger, “Rheological and dielectrical characterization of melt mixed polycarbonate-multiwalled carbon nanotube composites”, Polymer, Vol. 45, pp. 8863-8870, 2004; (b) I. Alig, D, Lellinger, S.M. Dudkin and P. Potschke, “Conductivity spectroscopy on melt processed polypropylene-multiwalled carbon nanotube composites”, Polymer, Vol. 48, pp. 10201029, 2007; (c) I. Alig, D. Lellinger, M. Engel, T. Skipa and P. Potschke, “Destruction and formation of a conductive carbon nanotube network in polymer melts; In-line experiments”, Polymer, Vol. 49, pp. 1902-1909, 2008; (d) I. Alig, T. Skipa, D. Lellinger and P. Potschke, “Destruction and formation of a carbon nanotube network in polymer melts: Rheology and conductivity spectroscopy”, Polymer, Vol. 49, pp. 3524-3532, 2008.

[23]    (a) J. Non Cryst. Solids, Vol. 131-133; 1991; (b) J. Non Cryst. Solids, Vol. 172-174, 1994; (c) J. Non Cryst. Solids, Vol. 235-237, 1998; (d) J. Non Cryst. Solids, Vol. 287, 2001; (e) J. Non Cryst. Solids, Vol. 352, 2006.

[24]    (a) J. Non Cryst. Solids, Vol.305, 2002; (b) J. Non Cryst. Solids, Vol. 351, 2005.

[25]    (a) G. Williams, “The measurement of dielectric constant and loss factor of liquids and solutions between 250 and 920 Mc/s by means of a coaxial transmission line”, J. Phys. Chem. Vol. 63, pp. 534-537, 1959; (b) G. Williams, “The evaluation of dielectric data for liquids and solutions”, J. Phys. Chem. Vol. 63, pp. 537-540, 1959.

[26]    I.J. Youngs, G.C. Stevens and AS. Vaughan, “Trends in dielectrics research: an international review from 1980 to 2004”, J. Phys. D,: Appl. Phys., Vol.39, pp 1267-1276, 2006.

Author

Graham Williams is graduate of the University of Wales, B.Sc. (1956), Ph.D. (1959), D.Sc.(1969); He worked at Basic Physics Division, National Physical Lab., Teddington (1959–1965); Polymers Division, National Bureau of Standards, Washington DC (1965–66); Chemistry Dept., University of Wales, Aberystwyth (1966–1988) (Professor (1978)); Chemistry Dept., University of Wales Swansea (1988–1998), (Prof. of Physical Chemistry, Head of Dept. 1993–1996, Emeritus Professor 1996 – to date); Leverhulme Emeritus Fellow (1998–2001). He has published over 190 papers in learned journals on (i) experimental and theoretical studies of the molecular dynamics of amorphous, crystalline, lyotropic and thermotropic liquid-crystalline polymer systems, hybrid polymer/liquid crystal materials and glass-forming liquids using dielectric, electro-optical (Kerr-effect) and dynamic mechanical relaxation techniques. Real-time dielectric studies of thermo- and photo-polymerizing systems, (ii) theoretical studies of relaxation including the introduction of the stretched-exponential (Kohlrausch-Williams-Watts) function (1970) and use of molecular time-correlation functions for dielectric, Kerr-effect and optical relaxations in polymers, glass-forming liquids and photochromic polymer films. Polarized Raman studies of photo-aligned liquid crystals (with Prof. W. Jeremy Jones). Co-author, with N.G. McCrum and B.E. Read, of the research text “Anelastic and Dielectric Effects in Polymeric Solids”, 617 pp, Wiley (1967), Dover (1991). He was a visiting lecturer to universities in Poland (1978), visiting Professor to the University of Utah, Salt Lake City (1980), The Royal Australian Chemical Institute (1983, 1985), AT&T Bell Laboratories (1984), Science University of Tokyo (1987), Max Planck Institute for Polymer Research (1991). He was Chairman of the Gordon Research Conference on Dielectric Phenomena (1970), Chairman of The Dielectrics Society (UK) (1992–1995). He was awarded the Harrison Memorial Prize (1965) and the Macromolecules and Polymers Award (1983) of The Royal Society of Chemistry (UK), the J.B. Whitehead Memorial Lecturer of the IEEE Electrical Insulation Society (1982) and the W. Prins Memorial Lecturer, Leiden University (1996).