The Contribution of IUPAC to Polymer Science ... - ACS Publications

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The Contribution of IUPAC to Polymer Science Education Chin Han Chan,† Christopher M. Fellows,*,‡ Michael Hess,§ Roger C. Hiorns,∥ Voravee P. Hoven,⊥ Gregory T. Russell,# Cláudio G. dos Santos,∇ Adriana Šturcová,○ and Patrick Theato*,◆ †

Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia School of Science and Technology, University of New England, Armidale, NSW 2351, Australia § Department of Physics, University of North Texas, Denton, Texas 76203, United States ∥ CNRS/Univ Pau & Pays Adour, Institut des Science Analytiques et Physico-Chimie pour l'Environnement et les Materiaux, UMR 5254, 64000 Pau, France ⊥ Department of Chemistry, Faculty of Science, Chulalongkorn University, Phayathai Road, Pathumwan, Bangkok 10330, Thailand # Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand ∇ Departamento de Química − ICEB, Universidade Federal de Ouro Preto, 35400-000 Ouro Preto-MG, Brasil ○ Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovskeho nam. 2, 162 06 Prague 6, Czech Republic ◆ Institute for Technical and Macromolecular Chemistry, University of Hamburg, Bundesstrasse 45, D-20146 Hamburg, Germany ‡

ABSTRACT: Polymer education relies on generally agreed terminology and nomenclature rules. The Polymer Division of the International Union of Pure and Applied Chemistry (IUPAC) generates and recommends such rules for naming processes and materials in polymer science. It is the goal of IUPAC that these recommendations be applied in polymer science curricula worldwide. For this purpose, a large amount of material has been provided by the Polymer Division of IUPAC, and in this paper these resources are described from the personal perspective of the authors. A discussion of terminology is then provided, including a detailed discussion of the term “dispersity” (Mw/Mn) and the rationale behind the recommended IUPAC names of different polymerization mechanisms. This is followed by a commentary on polymer nomenclature with examples. Finally, exemplary applications of resources provided by the Polymer Division of IUPAC for educational purposes around the world are presented. KEYWORDS: Second-Year Undergraduate, Graduate Education/Research, Polymer Chemistry, Internet/Web-Based Learning, Polymerization, Nomenclature/Units/Symbols

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will first give a broad background on the main publicly available

INTRODUCTION

Polymer science is a crucial subdiscipline of chemistry, and education in it is thus a critical part of any chemical education. This article describes some of the activities of the International Union of Pure and Applied Chemistry (IUPAC) and resources it provides that are useful in education, with particular attention given to the work of the Polymer Division (Division IV).1 IUPAC generates and recommends rules for naming processes and materials in chemistry that are followed globally by courts of law, governmental bodies, industries, and institutes for research and education. The goals of the IUPAC Polymer Division are to facilitate international scientific exchange, to cooperate with other international organizations, and to promote macromolecular and polymer science and technology at the international level. Specifically for the promotion of education, the IUPAC Polymer Division has set up a Subcommittee on Polymer Education (SPEd).2 This article © XXXX American Chemical Society and Division of Chemical Education, Inc.

resources provided by IUPAC and then detail some selected teaching examples of the educational use of polymer terminology, discuss the benefits to be gained through the art of correctly naming polymers, give examples of educational courses run with the support of the IUPAC Polymer Division, and finally describe some of the benefits of IUPAC specifically for polymer science education in selected emerging economies. Special Issue: Polymer Concepts across the Curriculum Received: October 24, 2016 Revised: June 16, 2017

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DOI: 10.1021/acs.jchemed.6b00800 J. Chem. Educ. XXXX, XXX, XXX−XXX

Journal of Chemical Education

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Figure 1. Interactive net around the term “macrocycle” from the Gold Book (online version):11 (a) first level; (b) second level; (c) third level. Reprinted with permission from ref 11. Copyright 2005−2017 International Union of Pure and Applied Chemistry.

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(linear) polymer consisting of two or more “blocks”, whereas how to name such a macromolecule is the domain of nomenclature. Both areas are important in polymer chemistry, a discipline that straddles physical chemistry (where terminology concerns predominate over nomenclature) and synthetic chemistry (vice versa).

IUPAC RESOURCES

IUPAC Polymer Division

From the very beginning of a new scientific field, care has to be taken with regard to terminology and nomenclature. Even if there is no agreed-upon interpretation of the discoveries in a new field, it is vitally important that the scientists exploring these unknown territories have a common language to talk about them. This was the situation in the field of polymer science at the time of Staudinger’s seminal 1920 paper in which the principles of polymer science structure were first defined.3 This publication formed the basis of modern fibers and plastics technologies by introducing the concept of giant molecules, socalled macromoleculesa concept that even laid the foundations for understanding biochemistry and genetics. Nevertheless, the very existence of macromolecules was a hotly disputed question during the 1920s.4 While polymer science was initially seen as part of organic chemistry, it became clear in the 1940s and 1950s that it had developed into a part of chemistry that could stand on its own feet next to the classical subdisciplines of organic, inorganic, physical, and analytical chemistry. In 1952, a group of prominent polymer scientists first gathered under the auspices of IUPAC to recommend names and naming rules for the substances and processes with which they were dealing.5 This report would be the first of many recommendations made over the following decades.6 Within one year of the formal founding of the Polymer Division in 1967, the Commission on Macromolecular Nomenclature had been formed, a body that since 2005 has been known as the Subcommittee on Polymer Terminology (SPT).7 Nomenclature and terminology are related terms, but as understood by IUPAC they have distinct meanings. For example, “block copolymer” is the term for a

IUPAC Documents

IUPAC documents are usually published in the journal Pure and Applied Chemistry as either Recommendations or Technical Reports. Recommendations are strictly formalized definitions established after intense discussions among international specialists and undergo a strict process of approval, including a public review. These definitions contain only the absolutely necessary information and may read like legal documents. As such, they serve as reliable source of information for decisions in patent cases and provide unequivocal definitions for journalism, industry, and education.8 Technical Reports provide critically reviewed information about specific experimentally observable matters: tested and approved methods of characterization of polymers, for example, or rate constants of polymerization.9 In polymer science, terminology and nomenclature recommendations are typically published by the SPT in close cooperation with the Nomenclature and Graphical Representation Division of IUPAC, while most Technical Reports are released by the Polymer Division’s Subcommittee on Structure and Properties of Commercial Polymers (SPCP). SPT is responsible for universally recognizable definitions of terms for polymer science and does the work of generating the rules that allow unique descriptions of each polymer. The latter of these two activities is done on behalf of IUPAC’s Chemical Nomenclature and Structure Representation Division (Division VIII). All of SPT’s recommendations on nomenclature are B



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published in Pure and Applied Chemistry, where they can be downloaded for free. Most of the recommendations up to the year 2008 have been brought together in the Compendium of Polymer Terminology and Nomenclature, the so-called Purple Book.10 Up to the present time, several different “color books” have been published by IUPAC. The first “color book” was initiated by Victor Goldhence the name “Gold Book”, which was accordingly published with a golden cover. The online version of this reference covers about 7000 terms from general chemistry.11 It features useful interactive schemes showing networks of related terms and different levels of complexity. Figure 1 shows an example for the term “macrocycle”, and the reader is invited to explore these interactive link maps online. Subsequent “color books” dealing with different aspects of chemistry in more detail have been named by their cover colors: as well as the Purple Book, there are the Blue Book (organic chemistry),12 the Green Book (physical chemistry),13 the Red Book (inorganic chemistry),14 the Orange Book (analytical chemistry),15 the Silver Book (clinical laboratory sciences),16 and the White Book (biochemical nomenclature).17 The synthesis of ever more complicated polymers has required the continuing creation of different nomenclature systems,18 which are discussed in The Art of Naming Polymers (vide infra). Recommendations have been issued for structurebased nomenclature for irregular single-strand organic polymer systems,19 structure-based nomenclature of regular singlestrand polymers,20 nomenclature of macromolecular rings,21 and nomenclature of nonlinear polymers.22 A glossary of class names of polymers based on chemical structure and architecture23 and, more recently, recommendations for abbreviations (collecting the abundant recommended abbreviations of polymer names and advising how to form a concise abbreviation)24 have also been published Structure-based nomenclature obviously requires a detailed knowledge of the structure of the polymer, which cannot always be determined. In such cases it is possible to name the polymer starting from the real or hypothetical monomer(s), i.e., sourcebased nomenclature.25 A number of commonly used sourcebased names of polymers are now no longer recommended, such as polyethylene (correct source-based name: polyethene) and polypropylene (correct source-based name: polypropene). (It should be noted that in structure-based nomenclature, the historical polyethylene is the preferred name.10,20) While they are no longer recommended, IUPAC recognizes that for practical reasons some of these outdated names may be kept. With basic nomenclature covered, the focus of the Polymer Division’s activities has shifted to updating nomenclature to deal with more complex structures such as stars, lactic acids, and compounds carrying dyes and medically active materials, all while maintaining a parallel and strong focus on terminology. In the latter area, significant documents include glossaries of basic terms in polymer science,26 terms related to thermal properties and thermomechanical properties of polymers,27 terms of relevance to crystalline polymers,28 and recommendations concerning the definition of terms related to individual macromolecules, macromolecular assemblies, and amorphous bulk polymers.8 Then there is the only document with recommendations that deal with low-molar-mass substances, Def initions of Basic Terms Relating to Low-Molar-Mass and Polymer Liquid Crystals.29 Clearly, all of these published IUPAC documents can be of direct use to educators and students.

Some practical examples are discussed in Polymer Terminology: Selected Teaching Examples (vide infra). It is an ongoing problem that researchers and publications do not always follow the IUPAC recommendations. Therefore, the IUPAC Polymer Division is publishing a series of so-called “Brief Guides” to provide authors with concise and definitive information to allow rapid access to the most relevant recommendations.30 An important recent development for education in polymer science has been linking IUPAC to the modern world’s preeminent source of knowledge: Wikipedia. The IUPAC Polymer Division is supporting Wikipedia by adding inserts (or “transclusions”) that provide the correct IUPAC definitions for Wikipedia (English) entries and by otherwise referencing IUPAC definitions within Wikipedia. This is by no means meant to overrule Wikipedia but rather to provide readers with the standardized, internationally accepted definition without further comment or criticism of what is written in the main Wikipedia article. An example is provided by the Wikipedia article on anionic addition polymerization.31 SPT is also active in generating new Wikipedia pages. A Wikipedia page that is essentially a wiki-style version of A Brief Guide to Polymer Nomenclature, which was published in July 2012,30 receives around 8000 visits per year.32 Subcommittee on Polymer Education Web Site

The educational Web site of the Polymer Division Educational Subcommittee (SPEd)33 begins with a link to A Brief Guide to Polymer Nomenclature30 and has numerous links to videos that explore polymer concepts or interview award-winning polymer scientists. Especially noteworthy are the winning videos of the contest “A World without Polymers” held during the International Year of Chemistry 2011. In the near future, it is intended that all of the IUPAC resources listed above along with new material will be available through the SPEd Web site.

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POLYMER TERMINOLOGY: SELECTED TEACHING EXAMPLES Science is highly specialized knowledge, and as such it requires highly specialized vocabulary. This means a considerable portion of science education must be devoted to teaching the “language” of the (sub)discipline at hand. For example, a first lecture to first-year students on thermodynamics is traditionally dominated by the peculiar language of that odd trade, with definitions of systems (open, closed, and isolated), surroundings, work, heat, energy, and so on. It is no different in polymer chemistry courses, which usually begin with the etymology of the word “polymer”,34 leading on to monomer, oligomer, (constitutional) repeat(ing) unit, and more. For most students this lecture will introduce no new concepts. Rather, it will be about establishing a specialized and well-demarcated language. This illustrates the importance of terminologywhy it needs to exist and why it needs to be clearly defined. The addressing of terminology issues has always been regarded as an absolutely essential and vital task of the Polymer Division of IUPAC. What is the importance of terminology? Generally speaking it is twofold: first, to avoid confusion, especially that created by the occurrence of different terms for the same thing, and second, to promote precision in understanding. A simple but very important example is provided by the words “polymer” and “macromolecule”. The roots of these words are “many parts” and “large molecule”, respectively. The former is preferred in chemical circles, the latter in biology. For these C



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However, as it has become possible to synthesize a richer variety of macromolecules and more knowledge has been gained on the structure of synthetic and biological macromolecules, adjustment of terminology has been required. This is why the work of the IUPAC Polymer Division Subcommittee on Polymer Terminology will never be done: changes in knowledge require the refinement of old terms and the coining of new ones. SPT is also needed because science is a human endeavor. In the exuberance of discovery, scientists create new terms in much the same way as a child invents wordswhile there is logic, it is raw and has rough edges. It is not uncommon for different scientists to make discoveries (approximately) simultaneously: if they do so independently of each other, then it is natural for them to propose different terms for the same thing. Sooner or later, SPT will be required to step in and resolve the situation.

reasons, it is legitimate to wonder whether there are nuances to the meaning of each or whether they have precisely the same meaning. One misinterpretation would be to assume that “polymer” connotes an artificial substance whereas “macromolecule” refers to a product of nature. While such a distinction might once have been worthy of consideration, in the age of chemical biology it has no plausibility: many “biological macromolecules” may now be synthesized in the laboratory, and these horizons are ever-expanding. Alternatively, it might be supposed that the term “macromolecule” refers to large molecules with the intramolecular variety that is characteristic of most large biological molecules, e.g., proteins, whereas “polymer” might be reserved for the more constitutionally uniform molecules that are characteristic of synthesis. Again, this suggestion does not stand up to scrutiny. For example, commercial paints are often made from four monomers, so why should they be termed differently to DNA, which is also a quaterpolymer, consisting of four types of residue? Most copolymers cannot be regarded as having constitutional uniformity. Even the most well defined synthetic homopolymers that are experimentally realizable have end groups and defects. On the flip side, even highly structurally variegated biological macromolecules can still be regarded as consisting of “many parts”, molecular subunits that share common features. Given all of this, IUPAC has recommended that “macromolecule” and “polymer molecule” be regarded as interchangeable and defined as follows:10,26 Molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. The key concepts in this definition are that of high molar mass (defined relatively rather than absolutely) and that of repetition of some smaller building block (again defined relatively rather than absolutely), so that the diversity of amino acid residues possible in a protein can be considered as repetitions of the same moiety. IUPAC further recommends that “polymer” be defined to mean “substance composed of macromolecules”, noting that10,26 Conventionally, the word polymer used as a noun is ambiguous; it is commonly employed to refer to both polymer substances and polymer molecules. Henceforth, macromolecule is used for individual molecules and polymer is used to denote a substance composed of macromolecules. Polymer may also be employed unambiguously as an adjective, according to accepted usage, e.g., polymer blend, polymer molecule. (Of course, most chemists continue to write “polymer” when really they mean “polymer molecule”, but this is more out of expedience than any rebellion against the arguments above.) Several things should be clear from this discussion. One is how confusion may be avoided by clear and authoritative definitions of terminology. Another is how precise understanding is aided by deep consideration of terminologyin a ̈ sense there does appear to be a distinction between a naive “macromolecule” and a “polymer molecule”, but on deeper reflection it can be understood that the mooted difference is not logical. Clearly, understanding of polymer chemistry is enhanced by this process. Finally, it can be seen that terminology must evolve as scientific knowledge expands. In the time of Staudinger, it was reasonable to distinguish between synthetic macromolecules and biological macromolecules.

Basic Classification of Polymerization Reactions

The terms “addition polymerization” and “condensation polymerization” made sense when they were first proposed by Carothers.35 Indeed, they still make some sense, which is why they are still encountered frequently. However, they stopped being rigorous in 1937, when the first polyurethanes were made in Germany.36 It is obvious that the polymerization paradigm is the same for polyurethanes as for the previously discovered polyesters and polyamides, but no small molecule is eliminated in the reaction between an alcohol and an isocyanate. For this reason the term “condensation polymerization” becomes untenable for this class of reactions. Having come this far, it is also appropriate to express discomfort with the term “addition polymerization”. Clearly it is an extension of the use of the term “addition” in organic chemistry, but why should a reaction between an alcohol and an acid, for example, not be regarded as “addition”? After all, this process “adds” two molecules together to form a larger molecule, just as does addition of a radical to an olefin, and we did not specifically call it “addition across a double bond polymerization”. For these reasons, the terms “chain-growth polymerization” and “step-growth polymerization” came into vogue as replacements for “addition polymerization” and “condensation polymerization”, respectively.37 The majority of textbooks use these revised terms, which implies that they are rigorous. However, it is easy to poke holes in them, and unencumbered undergraduates frequently do. The first is that the word “growth” is thoroughly superfluous, for it is implicit in the term “polymerization”by definition a polymerization process must involve molecular “growth”! Of course, redundancy is more an ugliness than a sin, but it is best avoided lest a novice wonders whether there is an obscure layer of meaning to the word “growth”. Second, “chain polymerization” and “step polymerization” are unsatisfactory for the simple reason that a chain reaction mechanism is defined (including by IUPAC!11) to consist of a series of elementary steps. So why should a polymerization mechanism that consists of reaction “steps” be considered different from a “step polymerization”? It makes little sense. To remove this confusion and imprecision, IUPAC has recommended the following terms and definitions:38 • Chain polymerization: chain reaction in which the growth of a polymer chain proceeds exclusively by the reaction or reactions between a monomer or monomers and a reactive site or reactive sites on the polymer chain D



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chemical compound. However, one of the major paradigm shifts for macromolecular chemistry is that this idyllic outcome is impossible for all practical methods of synthetic polymerization. As a consequence, any general course on polymer science will introduce the topic of molar mass distributions. Here students will encounter the notions of average size and width of distribution. After all, if one of the defining characteristics of polymers is that they consist of molecules with a distribution of sizes, it is necessary to explain how polymer scientists characterize this feature of their materials. Thus, students learn that

with regeneration of the reactive site or reactive sites at the end of each growth step. • Polycondensation: polymerization in which the growth of polymer chains proceeds by condensation reactions between molecules of all degrees of polymerization. • Polyaddition: polymerization in which the growth of polymer chains proceeds by addition reactions between molecules of all degrees of polymerization. Thus, polyamides and polyesters are produced by polycondensation, while polyurethanes are produced by polyaddition. On the other hand, radical, anionic, and cationic polymerization are all classified as chain polymerizations. In the recommendations the following was also noted:38 Propagation in chain polymerization often occurs without the formation of small molecules. However, cases exist where, at each propagation step, a low-molar-mass byproduct is formed ... When a low-molar-mass byproduct is formed, the adjective condensative is recommended to give the term “condensative chain polymerization”. These recommendations are summarized in Table 1.

⎛ sn ⎞2 M ⎟ = w −1 ⎜ Mn ⎝ Mn ⎠

where sn is the standard deviation of the number-average molar mass distribution, Mn is the arithmetic mean of the numberaverage molar mass distribution, and Mw is the arithmetic mean of the weight-average molar mass distribution. While statisticians generally use s to quantify the width of a distribution, it makes more sense in polymer science to use sn/Mn (i.e., the standard deviation relative to the mean) since Mn can vary by orders of magnitude from sample to sample. The above general result establishes that there is a very simple relationship between sn/Mn and Mw/Mn, and thus the latter quantity finds common currency among polymer scientists for quantifying the width of molar mass distributions. Mw/Mn (defined as the dispersity, symbol Đ) is traditionally termed the “polydispersity index” and is a concept that is central to any polymer science curriculum. Students also learn the terms “monodisperse” and “polydisperse” for polymers of uniform and nonuniform size, respectively. Teaching this terminology never fails to elicit from at least one student the puzzled question “If all the molecules are the same size, why is it termed “disperse”?” Indeed, “monodisperse” is a selfcontradiction, and by the same logic “polydisperse” is tautologous. From this it follows that “polydispersity” is illogical, and it is also obvious that Mw/Mn is not an “index” as the term is used in mathematics. In other words, all of these popularly used terms are actually impediments to understanding. For these reasons, SPT became involved and unhesitatingly recommended the abandonment of the traditional terminology, to be replaced by the following: • Uniform polymer: polymer composed of molecules uniform with respect to relative molecular mass and constitution.26,40 • Nonuniform polymer: polymer comprising molecules nonuniform with respect to relative molecular mass or constitution or both.26,40 • Dispersity: ratio of Mw to Mn for a homopolymer or an alternating copolymer of sufficiently large molar mass, such that the effects of the distinct structures of the endgroups of the constituent macromolecules can be neglected ... Dispersity is a measure of the dispersion (or spread) of a molar-mass distribution.40 These terms supersede “monodisperse (polymer)”, “polydisperse (polymer)”, and “polydispersity index”, respectively. It should be clear how these new terms promote understanding of the important underlying concepts. It should be noted that there are more and more scientists who do use IUPAC recommendations, and over the last 10 years or so we have

Table 1. Summary of Recommended Terms for Polymerizations10 Stoichiometry

Growth Mechanism Monomer molecules reacting with active polymer chains Monomer, oligomer, and polymer molecules of all sizes reacting together

With Low-MolarMass Byproducts

Without LowMolar-Mass Byproducts

Chain reaction

Condensative chain polymerization

Chain polymerization

(Usually) nonchain reaction

Polycondensation

Polyaddition

Reaction Type

(1)

One criticism that might be leveled at these recommendations is that polycondensation and polyaddition both produce polymer chains. Of course this is not what is denoted by the adjective “chain” in “chain polymerization”, but nevertheless, there is some potential for confusion. However, this ambiguity stems from the multiple meanings of “chain” not only in chemistry but in English usage generally,39 and as such it may be tolerable. It must be admitted that uptake of the above recommendations has been limited. One reason for this is the limited popularization of these recommendations to date, and another is likely to be simply the tenacity of habits, because there is no obvious reason to prefer “step(-growth) polymerization” over “polycondensation” and “polyaddition” in the teaching of polymer chemistry. In fact, given the other mechanisms in organic chemistry to which students are exposed early on, the latter terms should make more immediate sense to students than the former terms. It should be clear how deeper and more precise understanding of polymerization mechanisms is promoted by employment of the above terminology. Therefore, it is to be hoped that their use spreads across the polymer curriculum at all levels. Dispersity

There is much to be said for the use of semiquantitative terms (such as “extremely”, “high”, “low”, etc.) because polymers are not like small molecules and contain many variants in a single batch: no two samples are the same. Synthetic small-molecule chemistry strives for product purity100% yield of a single E



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observed a general trend in the literature toward the use of correct IUPAC nomenclature. In part this is a recognition of the power of search engines; a correctly named polymer is more likely to be found. Indeed, the term “dispersity” is now being used quite widely in research papers, even though it has been only seven years since it was proposed and recommended.40 The next step is for it to find its way into textbooks. It should be evident from this discussion how IUPAC pays heed to historical usage as far as possible rather than proposing completely new terms that are disconnected from past practice. For example, we note how in the previous subsection, the words “chain”, “condensation”, and “addition” were retained. This makes the transition to new terminology easier because radical change is not imposed.

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Figure 2. QR code for A Brief Guide to Polymer Nomenclature.

THE ART OF NAMING POLYMERS: NOMENCLATURE RULES BY TEACHING EXAMPLES While performing polymer science can be extremely exciting, correctly naming polymers can seem a rather dry topic. However, nomenclature does have enormous impact through consumer and intellectual property protection and in commercial, educational, and scientific domains. In education, polymer nomenclature facilitates understanding of the structures and properties of polymers. This is not a simple task, as the literature often uses traditional names that might say nothing about the polymer structure. SPT is therefore working on two fronts: first, to make clear recommendations that can be easily used by educators and researchers, and second, to make these recommendations accessible. The former is part of the every day work of SPT, with exchanges between its members ensuring the crafting of easily comprehensible and well-defined terms, resulting in their free publication in the journal Pure and Applied Chemistry. The latter work, that of ensuring wide distribution and usage of SPT’s recommendations, is mostly done by transposing existing paper-based documents into electronic form. For example, the “color books” are all now downloadable as PDF files. It is also planned to release the Purple Book as a fully searchable HTML document.10−15 However, other projects also exist on the basis that many of the aforementioned documents, while clearly written, are not easily accessible to the nonspecialist. They are often quite long and dense and generally require a strong working knowledge of polymer science. In order to help teachers and students who do not have this, and especially those who have only a basic knowledge of English, SPT decided to develop a series of Brief Guides that would allow easy access to the main points all within an easily accessible document. The first of these, A Brief Guide to Polymer Nomenclature,30 summarizes the main points required to understand and use IUPAC nomenclature for most of the polymers described in the literature. It can be downloaded directly or called up on a smartphone by scanning the QR code shown in Figure 2. It was widely disseminated in numerous journals and appears to have had an impact on nomenclature in the community. It is now widely used as part of university courses. It should be noted that it carries hyperlinks back to the main source documents. Typically, SPT members introduce the importance of nomenclature in lectures by showing how each name must be explicit and unique. An example is provided by the chemical names “polychlorostyrene” and “poly(chlorostyrene)”, where the former refers to a small multisubstituted molecule and the latter a chlorinated polymer. Basic terms are also introduced,

such as recognizing, as discussed above, that the two words “macromolecule” and “polymer” do not mean the same thing. It is clarified that when naming polymers, minor irregularities such as chain defects, variations in chain length, and alternations in the head-to-tail repeating units can be ignored. The three types of polymer nomenclature, namely, structurebased,10,20 source-based,10,22 and traditional, are introduced, and then each is discussed using a variety of examples, ranging from polyethene to complex block and graft copolymers. As might be expected, the first nomenclature is used when the structure of the polymer is known and the second when the source monomers are known, while the last is allowed although not encouraged, unless confusion would arise. Thus, for example, polymerization of isobutylene (IUPAC name: 2methylpropene) leads to a polymer with the traditional name polyisobutylene, while its source-based name would be poly(2methylpropene). In structure-based nomenclature, poly(1,1dimethylethane-1,2-diyl) would be the correct name. A general problem often encountered in the literature is the correct placing of brackets. Therefore, their use in the order {[(...)]} is recommended. In source-based nomenclature, IUPAC recommendations or well-established traditional names are used. The use of italic structural qualifiers, such as -alt-, is then established.41 For example, for polystyrene-blockpoly(4-chlorostyrene) (Figure 3), the name can be easily

Figure 3. Polystyrene-block-poly(4-chlorostyrene).

constructed around the connector -block-, with brackets (in this case parentheses) being used where locants (in this case “4-”) are employed. The use of the italic letters to distinguish structural features (i.e., that it is a block copolymer) should be noted. The description of the use of structure-based nomenclature is performed using an example inviting the student to understand the notion of the preferred constitutional repeating unit (CRU). It is determined by drawing a large enough part of the polymer chain to show the structural repetition, identifying all possible repeating structures, and then deciding which one F



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to fundamental polymer research, relies heavily on the inclusion of IUPAC resources. Apart from being a research institution, the IMC AS CR also provides training of scientists at the beginning of their careers. Graduates at the M.Sc. or Ph.D. level who come from economically disadvantaged countries can enroll in a 10-month program organized under the auspices of UNESCO and IUPAC.42 The full title of the program is “UNESCO/IUPAC Postgraduate Course in Polymer Science”, and English is the language of instruction. The program consists mainly of problem-based learning where the course participants take part in an individual research project under the supervision of senior researchers of the institute. The participants not only come from various countries but can also have different scientific backgrounds, often outside of polymer science, and be newcomers into the field. Their supervised research is thus accompanied by a series of lectures, seminars, and laboratory demonstrations. The lectures are given by senior scientists of the institute and are concerned with the main aspects of polymer science: polymer chemistry, polymer physics, the application of polymers, and the spectroscopic and scattering methods used for polymer characterization. It is important that the young scientists learn to use the correct language of polymer science in a clear and precise way. In the lectures, the course participants are continually referred to the IUPAC Compendium of Polymer Terminology and Nomenclature.10 For example, Chapter 3 of the Purple Book, which is concerned with the definitions related to individual macromolecules, their assemblies, and dilute polymer solutions,8 is referenced in introductory lectures on molecular weight and dimensions of polymers and their assemblies, on properties and main characteristics of polymer solutions, and in a lecture on polymer networks. In addition to Chapter 3, the lecture on polymer networks also refers to Chapter 11, which is a result of collaboration between the Inorganic Chemistry Division and the Polymer Division.43 Furthermore, Chapters 6 and 9 of the Purple Book are the basis of lectures on the morphology of polymers and on polymer blends, respectively.28,44 The course participants are given a chance to learn about new classes of polymers and new polymer processes and polymeric materials in lectures about applications of macromolecules for drug delivery and controlled release of drugs, about biodegradable and bioanalogous polymers, and about polymer systems for optoelectronic applications. Very new concepts are introduced when the young scientists are taught about the integration of biological and nonbiological systems, and some of the terminology of these new areas of macromolecular science is addressed.45 However, new recommendations will be required as these directions of polymer research continue to expand.

of these structures concurs with the rules of seniority described by Kahovec et al.20 A commonly used example, taken from the Brief Guide,30 is given in below. Determining a Constitutional Repeating Unit (CRU)

The following italicized content is reprinted with permission from ref 30. The online version of ref 30 includes hyperlinks. Structure-based nomenclature uses that of the preferred constitutional repeating unit (CRU). It can be determined as follows: (i) a large enough part of the polymer chain is drawn to show the structural repetition, e.g.,

(ii) the smallest repeating portion is a CRU, so all such possibilities are identif ied. In this case:

(iii) the next step is to identif y the subunits that make up each of these structures, i.e., the largest divalent groups that can be named using IUPAC nomenclature of organic compounds; (iv) using the shortest path from the most senior subunit to the next senior, the correct order of the subunits is determined by identifying the order of seniority of Constitutional Repeating Units. (v) the preferred CRU is chosen as that with the lowest possible locant(s) for substituents:

In the above example, the oxy subunits in the CRUs are heteroatom chains. From Figure 5, oxy subunits are senior to the acyclic carbon chain subunits, the largest of which are bromosubstituted −CH2−CH2− subunits. 1-Bromoethane-1,2-diyl is chosen in preference to 2-bromoethane-1,2-diyl as the former has a lower locant for the bromo-substituent. The preferred CRU is therefore oxy(1-bromoethane-1,2-diyl) and the polymer is thus named poly[oxy(1-bromoethane-1,2-diyl)]. Note the enclosing marks around the subunit carrying the substituent. Polymers that are not made up of regular repetitions of a single CRU are called irregular polymers. For these, each constitutional unit (CU) is separated by a slash, e.g., poly(but-1-ene-1,4-diyl/1vinylethane-1,2-diyl). Interestingly, questions from students first encountering polymer nomenclature do not usually concern the polymers with which they are working but rather the implications of polymer irregularities for nomenclature and how a range of structures (macromolecules) in one sample (the polymer batch) can be named. This most likely derives from the fact that students will have learned organic nomenclature first, where samples are assumed to consist of just one type of molecule. Therefore, it is critical to stress that polymers, unlike small molecules, really do have an enormous number of variations within each batch and that there are unavoidable limits to the precision with which a material can be described.

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VALUE OF IUPAC RESOURCES FOR TEACHING POLYMER SCIENCE IN DEVELOPING/EMERGING COUNTRIES Two examples of polymer science education in developing/ emerging countries are given below. Rather than giving an exhaustive picture, these are intended to be exemplary statements illustrating ongoing transitions in polymer education in developing/emerging countries worldwide. Focus is laid on the use of IUPAC resources in the polymer science curricula. For a more extensive overview of polymer education in other countries, the reader is referred to the recent special issue of Macromolecular Symposia reporting on polymer education.46

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EXAMPLE OF A COURSE IN POLYMER SCIENCE THAT USES IUPAC RESOURCES Polymer science education at the Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic (IMC AS CR), which is one of the world’s largest institutions devoted G



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Polymer Science Education in Malaysia

addition, there is a consensus that the introduction of instruments should be as basic as possible to nurture the assembly process and fabrication capability. This provides the opportunity for learning and troubleshooting to the graduates later. Advanced instruments that look like a black box to the undergraduates should be avoided in the first course on polymer science.47 Fortunately, there is a strong bond between industry, government, and universities to cope with systematic teaching aspects and the demands of the polymer industry, which in Malaysia is predominantly the rubber industry. Concerning the contribution of IUPAC to polymer science education in Malaysia, undergraduates in science degree programs learn IUPAC-recommended nomenclature for organic compounds in the elementary organic chemistry course. However, compliance with IUPAC recommendations for polymer nomenclature is not yet emphasized during the teaching process in most public universities. The public awareness of IUPAC recommendations in science education and polymer education has been increasing in both academia and industry in recent years, especially since Institut Kimia Malaysia (IKM) became one of the IUPAC National Adhering Organizations in 2009.48 Through the involvement of Malaysian representatives in various IUPAC divisions, including the Polymer Division and its subcommittees, Malaysia is becoming more active in promoting and enhancing chemistry education and public appreciation of chemistry using the platform and from the perspective of IUPAC. IKM has been organizing IUPAC-endorsed conferences, including two conferences related to polymers and materials: the Fourth Federation of Asian Polymer SocietiesInternational Polymer Congress in 2015 and the 25th POLYCHAR 2017 World Forum on Advanced Materials in 2017. These two conferences provide a platform especially for young scientists to present their research findings and to meet with distinguished scientists from all over the world. The role and contribution of IUPAC in chemistry/ polymer education and public appreciation of chemistry/ polymers are always disseminated through the conferences. On top of that, the IKM magazine published quarterly for all of its membersChemistry in Malaysiahas been reproducing selected IUPAC recommendations. A recent example is the reprinting of A Brief Guide to Polymer Nomenclature30 in the IKM magazine.50 In summary, the impact of IUPAC resources on teaching polymer science in Malaysia has not yet been realized. Neither academic polymer education (preuniversity, undergraduate, and postgraduate studies) nor the current practice of local industries in Malaysia complies fully with IUPAC recommendations yet. Nonetheless, public awareness of the IUPAC recommendations is escalating, and this is a positive and encouraging development.

Generally, the polymer syllabi of the science degrees offered by the public universities in Malaysia have to comply with requirements of the Ministry of Education, the Malaysian Qualifications Agency (MQA) standards, and university regulations. The role of the university is to deliver basic and strong fundamental knowledge to the undergraduates, hoping that these graduates will be armed with their strong fundamental skill acquired in the university before they begin work in industry.47 At present, there are 20 public universities in Malaysia, including five research universities that focus on research and development, four comprehensive universities that concentrate on specific fields related to its establishment, and 11 focused universities that offer a variety of courses and fields of study.48 Only 13 out of these 20 public universities offer undergraduate science degree programs specifically including polymer chemistry or polymer technology. The learning modules (embracing topics on basic concepts, synthesis, characterization, and processing for polymer sciences) are usually taught in the second or third year of a three- or four-year science degree program. While there is normally a small component of laboratory practical work included in the course,49 this component may not be compulsory for these science degree programs.47 A final-year research project and industrial attachment for 3−6 months provide extended exposure and training opportunities to the undergraduates before they graduate and serve in industry, although industrial attachment is not compulsory in some universities. Only three public universities offer degree programs in the fields of polymer engineering and technology: (1) Universiti Sains Malaysia (USM) offers a B.Eng. in Polymer Engineering; (2) Universiti Malaysia Perlis (UniMAP) offers a B.Eng. in Polymer Engineering; and (3) Universiti Teknologi MARA (UiTM) offers a B.Sc. in Polymer Technology. These degree programs are focused on polymer-specific courses. The courses offered are mainly related to introduction to polymers, plastics, and elastomeric materials; polymer synthesis; polymer structure and properties; polymer thermodynamics; polymer testing and characterization; polymer blends; plastic, rubber, and latex processing; polymer engineering products; polymer composites; polymers in electronic applications; polymer adhesives and coatings; environmentally friendly polymers; and so on. UniMAP is the only public university that offers an M.Sc. in Polymer Engineering by coursework, whereas Universiti Pendidikan Sultan Idris (UPSI), another public university, offers polymer-related courses in the framework of an M.Sc. in Advanced Materials. Most of the universities that offer materials and polymer science programs are equipped with high-technology polymer characterization instruments, such as TGA, DSC, DMA, GPC, SEM, TEM, FT-IR, and so on for research purposes as well as for undergraduate and postgraduate teaching in the relevant areas of polymer science and engineering. As part of continuous improvement in polymer science education in Malaysia, it is recommended that subjects such as polymer physics, polymer processing, and latex technology be included in the core syllabus of degree programs. The practical experiments in polymer sciences should be designed to impart skills in handling simple laboratory apparatus such as viscometers, dilatometers, osmometers, and so on. Statistical techniques in data handing and analysis (reproducibility, repeatability, precision, and accuracy) will be important. In

Polymer Science Education in Thailand

In Thailand, polymer science has emerged as an important scientific area since the petrochemical industry was promoted as a national strategic priority during the 1970s and 1980s. Currently, the country has a limited number of academic personnel with strong backgrounds in basic science and engineering of polymers. As development has been driven by the demand of industry, most curricula were established from practical perspectives, and fundamental core topics have often been overlooked. This gives a misleading impression to society and industries that polymer science is an applied area in which understanding of fundamentals is not that important. Knowing H



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supporting projects that help to spread chemical knowledge and information, particularly to countries where English is not the official language or this information is not readily accessible. One way to reach this goal is through the translation of its documents into many languages, and the Polymer Division has encouraged several projects with this in mind, involving both printed and electronic documents. One such project was an online-accessible dictionary combining translations of terms of polymer science and their definitions that was launched in October 2012 as the Multilingual Glossary of Polymer Terminology. This electronic document used the glossary of basic terms in polymer science from the Purple Book as a starting point, from which the terms were translated into Czech, French, German, Italian, Polish, Portuguese, and Spanish. Since the project was first conceived, its dynamic nature was recognized in that new terms could always be included and new languages added to complement the original seven European languages. The page is currently under revision to include translations into languages that use non-Western characters, such as Arabic, Chinese, Japanese, Korean, Russian, Thai, and so on. It should be noted that this project relies on the volunteer work of professionals of non-English speaking countries, who carry out the translations following IUPAC approved documents recognized by the relevant official National Adhering Organizations. The essence of this project is related to major trends in global communication, evidence of which is for all to see and from which science can benefit as a whole. The trends with the greatest immediate impact on communication are the advances in mobile and smart phone technologies. It is predicted that the use of mobile Internet in the near future will exceed traditional desktop Internet use. Therefore, the development of a mobile application of the Multilingual Glossary is underway and is expected to be available in the near future.

polymer science at a basic level is sufficient for the local job market as long as the polymer-related industries are only concerned with importing technologies and exporting products. While initially successful, such a strategy becomes unsustainable in a global environment in which innovation is an inevitable element to the business success of not only big industrial firms but also small and medium enterprises evolving from “startups” and “spin-offs” relying on science and technology. Escape from the “middle income trap”51 through innovation will never be possible as long as the basic understanding of science underpinning Thailand’s industry is not strong enough. Similar to what has been described in the case of Malaysia, most Thai students and academic personnel only recognize the IUPAC contribution from the recommendations for organic compound nomenclature. Very few of them realize that there are also IUPAC recommendations for polymer nomenclature and basic terminology and definitions in polymer sciences that are an important foundation of polymer education. The Chemical Society of Thailand (CST) under the patronage of Professor Dr. Her Royal Highness Princess Chulabhorn is one of the IUPAC National Adhering Organizations. Having Thai representatives continuously participate in many research and educational activities organized by the Polymer Division and its subcommittees truly raises IUPAC recognition among academic societies but not among the public as a whole. Ever since the CST together with the Polymer Society (Thailand) (PST) and the Faculty of Science of Chiangmai University were appointed as hosts of the IUPAC World Polymer Congress 2014 (MACRO 2014) (the largest international conference of the IUPAC Polymer Division), public awareness of the contribution of IUPAC and its activities has been escalating. The conference had a high impact, especially on young scientists, who were given chances to present and share their research work, to meet and have discussions with world-renowned scientists, and most importantly to expand their collaborative research networks. With increased IUPAC visibility through the success of the MACRO 2014 organization, we confidently believe that elevating public recognition of IUPAC-endorsed polymer-related contents will no longer be a difficult task. In this respect, having IUPAC resources available in each area of polymer science and engineering definitely facilitates teaching at academic institutes as well as educating industrial personnel and society. The fact that the contents are carefully reviewed by experts in the field and endorsed by IUPAC, an internationally recognized institution, assures their correctness and reliability. Since IUPAC resources can be easily accessed online, this would pave the way to “Education 4.0”, whereby self-learning, imagination, creativity, and innovation can be promoted concurrently not only for students but also for society through active learning formats in terms of video and online tutorials. With IUPAC permission, CST and PST have a joint objective to make these resources available in the Thai language in the future.

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CONCLUSIONS AND OUTLOOK The IUPAC Polymer Division and its subcommittees, SPT, SPEd, SPCP, and Subcommittee on Modeling of Polymerization Kinetics and Processes, are multinational institutions dedicated to improving clarity of thought and communication in what can be seen as a single rather narrow field of human endeavor. However, it is a field that has wide-ranging implicationssynthetic polymers are omnipresent in everyone’s lives, and everyone is made out of natural polymers where more precise and accurate description of materials can have significant consequences in terms of economic, environmental, and health outcomes. How we talk about things is important: working together becomes impossible if we are all using the same word to mean different things, and the more precisely and accurately we define our terms, the better we can work together. The Polymer Division of IUPAC seeks to produce documents that are useful for polymer education, to make them accessible not only to English-speaking countries or developed countries but to the whole world, and to exhibit the disinterested and collegial spirit of scientific cooperation in all that we do. The immense changes in how information is generated and distributed around the world in recent decades present enormous opportunities, making it vastly easier for us to do these tasks but at the same time making it urgent that a clear voice giving rigorous and well-thought answers to polymer nomenclature and terminology questions is not drowned out by a clamor of competing authorities. The contribution of IUPAC to polymer education has only just begun.

Multilingual Polymer Glossary

The work on IUPAC recommendations and nomenclature does not end with their publication in the English language. They are further disseminated and discussed in other languages by those who prepared them. For example, scientists can benefit from the overview of the recommendations and their translations published online.52 IUPAC endorses several initiatives to improve worldwide communications in all areas of chemistry, I



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H. L.; Takami, M.; Thor, A. J. Quantities, Units and Symbols in Physical Chemistry; Royal Society of Chemistry: Cambridge, U.K., 2008; https://www.iupac.org/cms/wp-content/uploads/2015/07/GreenBook-PDF-Version-2011.pdf (accessed June 2017). (14) Connolly, N. G.; Damhus, T.; Hartshorn, R. M.; Hutton, A. T. Nomenclature of Inorganic Chemistry; Royal Society of Chemistry: Cambridge, U.K., 2005; https://www.iupac.org/fileadmin/user_ upload/databases/Red_Book_2005.pdf (accessed June 2017). (15) Inczédy, J.; Lengyel, T.; Ure, A. M. Compendium of Analytical Nomenclature: Definitive Rules 1997; Blackwell Science: Oxford, U.K., 1997; http://media.iupac.org/publications/analytical_compendium/ (accessed June 2017). (16) Férard, G.; Dybkaer, R.; Fuentes-Arderiu, X. Compendium of Terminology and Nomenclature of Properties in Clinical Laboratory Sciences: Recommendations 2016; Royal Society of Chemistry: Cambridge, U.K., 2017; http://pubs.rsc.org/en/Content/eBook/978-178262-107-2#!divbookcontent (accessed June 2017). (17) Biochemical Nomenclature and Related Documents, 2nd ed.; Liébecq, C., Ed.; Portland Press: London, 1992; http://www.chem. qmul.ac.uk/iupac/bibliog/white.html (accessed June 2017). (18) See pp 260−279 in ref 10 and: Hess, M. Nomenclature of Polymers. In Principles of Chemical Nomenclature: A Guide to IUPAC Recommendations, 2011 ed.; Leigh, G. J., Ed.; Royal Society of Chemistry: Cambridge, U.K., 2011. (19) Fox, R. B.; Bikales, N. M.; Hatada, K.; Kahovec, J. Structurebased nomenclature for irregular single-strand organic polymers (IUPAC Recommendations 1994). Pure Appl. Chem. 1994, 66 (4), 873−889. (20) Kahovec, J.; Fox, R. B.; Hatada, K. Nomenclature of regular single strand organic polymers (IUPAC Recommendations 2002). Pure Appl. Chem. 2002, 74 (10), 1921−1956. (21) Mormann, W.; Hellwich, K.-H.; et al. Structure-based nomenclature for cyclic organic macromolecules (IUPAC Recommendations 2008). Pure Appl. Chem. 2008, 80 (2), 201−232. (22) Kahovec, J.; Kratochvíl, P.; Jenkins, A. D.; Mita, I.; Papisov, I. M.; Sperling, L.; Stepto, R. F. T. Source-based nomenclature for nonlinear macromolecules and macromolecular assemblies (IUPAC Recommendations 1997). Pure Appl. Chem. 1997, 69 (12), 2511− 2521. (23) Baron, M.; Hellwich, K.-H.; Hess, M.; Horie, K.; Jenkins, A. D.; Jones, R. G.; Kahovec, J.; Kratochvil, P.; Metanomski, W. V.; Mormann, W.; Stepto, R. F. T.; Vohlidal, J.; Wilks, E. S. Glossary of class names of polymers based on chemical structure and molecular architecture (IUPAC Recommendations 2009). Pure Appl. Chem. 2009, 81 (6), 1131−1186. (24) He, J.; Chen, J.; Hellwich, K.-H.; Hess, M.; Horie, K.; Jones, R. G.; Kahovec, J.; Kitayama, T.; Kratochvíl, P.; Meille, S. V.; Mita, I.; dos Santos, C.; Vert, M.; Vohlídal, J. Abbreviations of polymer names and guidelines for abbreviating polymer names (IUPAC Recommendations 2014). Pure Appl. Chem. 2014, 86 (6), 1003−1015. (25) (a) Marechal, E.; Wilks, E. S.; et al. Generic source-based nomenclature for polymers (IUPAC Recommendations 2001). Pure Appl. Chem. 2001, 73 (9), 1511−1519. (b) Jones, R. G.; Kitayama, T.; Hellwich, K.-H.; Hess, M.; Jenkins, A. D.; Kahovec, J.; Kratochvíl, P.; Mita, I.; Mormann, W.; Ober, C. K.; Penczek, S.; Stepto, R. F. T.; Thurlow, K.; Vohlídal, J.; Wilks, E. S. Source-based nomenclature for single-strand homopolymers and copolymers (IUPAC Recommendations 2016). Pure Appl. Chem. 2016, 88 (10−11), 1073−1100. (c) Jones, R. G.; Kitayama, T.; Wilks, E. S.; Fox, R. B.; Fradet, A.; Hellwich, K.-H.; Hess, M.; Hodge, P.; Horie, K.; Kahovec, J.; Kratochvíl, P.; Kubisa, P.; Maréchal, E.; Mormann, W.; Ober, C. K.; Stepto, R. F. T.; Vert, M.; Vohlídal, J. Nomenclature and graphic representations for chemically modified polymers (IUPAC Recommendations 2014). Pure Appl. Chem. 2015, 87 (3), 307−319. (26) Jenkins, A. D.; Kratochvil, P.; Stepto, R. F. T.; Suter, U. W. Glossary of Basic Terms in Polymer Science (IUPAC Recommendations 1996). Pure Appl. Chem. 1996, 68 (12), 2287−2311. (27) Hess, M.; Allegra, G.; He, J.; Horie, K.; Kim, J.-S.; Meille, S. V.; Metanomski, V.; Moad, G.; Stepto, R. F. T.; Vert, M.; et al. Glossary of

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Voravee P. Hoven: 0000-0002-1330-6784 Gregory T. Russell: 0000-0002-6773-1428 Patrick Theato: 0000-0002-4562-9254 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This opportunity is taken to warmly thank the members of the IUPAC Polymer Division and its subcommittees for their rigorous and friendly discussions, without which this work would not have been possible.

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REFERENCES

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