Methods for Introducing Inorganic Polymer ... - ACS Publications

Article Cite This: J. Chem. Educ. XXXX, XXX, XXX-XXX

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Methods for Introducing Inorganic Polymer Concepts throughout the Undergraduate Curriculum Daniel T. de Lill* and Charles E. Carraher, Jr. Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, Florida 33431, United States ABSTRACT: Inorganic polymers can be introduced in a variety of undergraduate courses to discuss concepts related to polymer chemistry. Inorganic polymers such as silicates and polysiloxanes are simple materials that can be incorporated into an introductory or descriptive inorganic course. Polymers based on inorganic carbon, including diamond and graphite, can likewise be used to introduce concepts related to structure−property relationships. Diamond and graphite can be discussed in more detail in an upper-division inorganic chemistry course as well as an introduction to coordination polymers and semiconducting organic polymers. Herein, these materials are briefly discussed in terms of how they can be merged into relevant coursework.

KEYWORDS: First-Year Undergraduate/General, Second-Year Undergraduate, Upper-Division Undergraduate, Inorganic Chemistry, Polymer Chemistry, Analogies/Transfer, Physical Properties, Polymerization

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• Portland cement • agates • talc • zirconia • quartz • diamond • carboranes • carborundum • aluminosilicates A partial listing of important synthetic polymeric materials includes: • polythiazyls • polyphosphazenes • poly(boron carbonitride)s • polysiloxanes • polysilanes • poly(sulfur nitride)s • polyphosphonitriles • polycarbosilanes There is an abundance of literature on metal-containing and inorganic polymers that can assist classroom presentations.2−31 With such a diverse range of potential materials to explore in an extremely limited time frame, an instructor must carefully select the topics and materials on which to focus. First, we will describe several important inorganic and metal-containing

INTRODUCTION Introducing concepts related to polymer chemistry can easily be accomplished in a well-rounded undergraduate chemistry curriculum without the need for a separate course on the topic.1 Polymer chemistry is typically regarded as the chemistry of polymerized organic compounds, and organic chemistry provides an excellent platform to discuss such polymers. To present inorganic polymers, other coursework typically needs to be consigned for this purpose. Introductory chemistry courses can be used to discuss simple inorganic polymers but should be limited to a discussion of basic structure and properties, as the bonding in these systems requires a more advanced treatment than typically covered in these courses. An upper-division inorganic chemistry course, however, is ideally suited to introduce inorganic polymers through many of the topics typically covered in such a course. Herein, several general classes of inorganic polymers as well as some more specific examples that can be easily woven into any curriculum will be presented. Inorganic and metal-containing polymers are important in a chemistry student’s education. These materials are part of everyday life as well as cutting-edge science and engineering. Common soil is mainly composed of organic and inorganic polymeric materials. Carbon fibers and carbon nanotubes are becoming increasingly important as building materials employed in bulk as well as specialty applications. Inorganic polymers are also employed as abrasives and cutting materials, coatings, catalysts, and flame retardants. As building and construction materials, they appear as window glass, brick, stone, Portland cement, and tiles. A partial listing of important natural inorganic polymers includes: © XXXX American Chemical Society and Division of Chemical Education, Inc.

Special Issue: Polymer Concepts across the Curriculum Received: January 11, 2017 Revised: October 16, 2017

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DOI: 10.1021/acs.jchemed.7b00028 J. Chem. Educ. XXXX, XXX, XXX−XXX

Journal of Chemical Education

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Another silicon-intense class of materials are the polysiloxanes, often simply called siloxanes. The polysiloxanes were incorrectly named silicones by Kipping32 in the early 1900s, but this name continues to be widely used. Originally they were wrongly believed to have a structure similar to a ketone, hence the term silicone. Instead, these compounds are similar in shape, bonding, and construction to the silicates just discussed. In 1945, Rochow33 discovered that a silicon−copper alloy reacts with organic chlorides to form a new class of compounds called organosilanes:

polymer groups that can be introduced in the classroom, suitable for a freshmen level introductory course or a sophomore/junior descriptive inorganic chemistry course. Before beginning, it would be beneficial to discuss the differences between crystalline and amorphous solids, giving examples of each. Most materials discussed herein are crystalline, but some amorphous materials are also noted.

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SILICATES AND POLYSILOXANES Silicon is the most abundant element in the earth’s crust. It is normally not found in elemental form but rather combined with other elements, most often oxygen. Most of these silicates are present as polymers based on the condensation of the orthosilicate anion, SiO44−. Table 1 contains some of these common silicates, including their basic geometric units and examples of each.

CH3Cl + Si(Cu) → (CH3)2 SiCl 2 + Cu

These compounds react with water to form dihydroxylsilanes: (CH3)2 SiCl 2 + H 2O → (CH3)2 Si(OH)2 + HCl

This is followed by the formation of dimers, trimers, ..., oligomers, and finally polysiloxanes, where “n” is the number or repeat siloxane units, resulting in its polymeric nature:

Table 1. Comparison of Some Common Polymeric Silicates Basic Geometric Unit

General Silicate Formulaa

Tetrahedron

SiO44−

Dimer cluster Trimeric ring Tetrameric ring Hexameric ring Linear chain

Si2O76− Si3O96− Si4O128− Si6O1812− Si4O128−

Double-stranded ladder Parquet (layered)

Si4O116− Si4O104−

Network

SiO2

a

−(Si(CH3)2 −O−)n −

Examplesa Granite olivine(Mg,Fe)2SiO4; topaz AkermaniteCa2MgSi2O7 Wollastonite Neptunite BerylAl2Be3Si6O18 DioposideCaMg(SiO3)2; chrysotile Hornblende

Because of the toxicity of HCl, the chlorine groups can be replaced by acetate groups, leading to the familiar vinegar smell of many silicon caulks and sealants. Branching and cross-linking are introduced through the use of methyltrichlorosilane. Modern caulks and sealants are made using the tetrafunctional tetraethoxysilane group to introduce cross-linking into the resin. Most commercially available polysiloxanes are based on dimethylsiloxane units. Polysiloxanes are characterized by a combination of mechanical, chemical, and electrical properties unique to this class of polymers. One remarkable trait is that they have the widest range of application temperatures of any commercial polymer. In fact, the first footprints made on the moon were made by these compounds. This low-temperature flexibility is a result of a very low glass transition temperature (Tg) of about −120 °C, a consequence of the fact that the methyl groups radiating off the Si−O backbone are free to rotate as a result of the longer Si−O bonds and wider Si−O−Si angle compared with hydrocarbon-based polymers. Viscosity, a measure of resistance to flow, can be discussed here to introduce and easily visualize basic structure−property relationships. As the linear polysiloxane chain increases in length, the viscosity increases. While the viscosity increases with chain length, other physical properties such as density and surface tension remain approximately constant for chain lengths greater than ∼25 monomers. Before this polymer length is achieved, the shorter-chain polysiloxanes (2−30 units) do have interesting applications. These liquid linear polysiloxane chains have a low attraction between chains and films composed of the chains. This chain slickness results in the flow control of coating materials. Thus, they assist coating materials, including paints, to flow across the surface to fill voids, crevices, and corners. Their good thermal conductivity and fluidicity at low temperatures allow their use as low-temperature heat exchangers and in low-temperature baths and thermostats. Furthermore, polysiloxanes within this mass range can be made into porous films used in apparatuses that permit divers to “breathe” underwater for short periods of time because of their permeability to oxygen but not to water. As the chain length continues to increase (∼50−400 monomers), highly viscous polysiloxane fluids result that are good lubricants for most metal to nonmetal contacts and are

TalcMg3Si4O10(OH)2; mica; kaolinite Quartz; feldspar (orthoclase) KAlSi3O8

The formulas are, for the most part, simplified.

Most silicates can be divided by structure into groups such as network, layer, or chain motifs. These secondary building units (SBUs) are simply constructed by polymerization of the SiO44− tetrahedron (the primary building unit, PBU). Here, the assembly of Si and O into a tetrahedral geometry can be demonstrated, followed by how these tetrahedra combine to form 1-D chains, 2-D layers, and 3-D networks (the SBUs; Figure 1). In lower-division courses, this is sufficient to understand the fundamentals of these materials. In upperdivision courses, this can be used as an introduction to zeolites and aluminophosphate materials.

Figure 1. Polyhedral depiction of the SiO44− tetrahedral primary building unit (PBU) in silicate compounds and examples of how these PBUs can produce intricate secondary building units (SBUs) ranging from 0-dimensional clusters to 1-D chains and 2-D sheets. B



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employed as mold release agents for glass, plastic, and rubber parts. Fluids formed from mixing polysiloxanes with polytetrafluoroethylene or molybdenum disulfide are used as highperformance greases. Polysiloxanes are used as dielectric fluids (liquids) in a variety of electrical applications including transformers and capacitors, as toners in photocopiers, as hydraulic fluids in vacuum and hydraulic pumps, and in inertial guidance systems. Brake fluids are also made from such polysiloxanes. Chain lengths of about 700 to 6000 are highly viscous fluids that are often employed as damping fluids for weighing meters at truck stops and as liquid springs in shock absorbers. These longer-chain fluids are also used as impact modifiers for thermoplastic resins and as stationary phases in gas chromatography. Even longer chains are so viscous that they appear solid, and when cross-linked they form solid thermosets and elastomers. These solid polysiloxanes can then be used as sealants, O-rings, thermostripping, caulk, dampening, and window gaskets. Weatherstripping on cooling units, trucks, and automobiles is also often made of these polysiloxanes. Biomaterials are routinely made from related polysiloxanederived materials. Artificial skin has been fabricated from a bilayer made from a cross-linked mixture of bovine hide, collagen, and chondroitin sulfate derived from shark cartilage with a thin top layer of polysiloxanes. The polysiloxane top layer acts as a moisture- and oxygen-permeable support that protects the lower layer from the “outer world”. Ears and nose parts are also often made from polysiloxane-intense materials.

Though the most familiar form of crystalline carbon is diamond, the most common form is the much softer and flexible graphite.38−40 Graphite occurs as two-dimensional sheets of hexagonally fused benzene rings composed of sp2hybridized carbon. The bonds holding the fused hexagons together are “ordinary” covalent bonds. The sheets, however, are held together by weaker π−π interactions, which can be explained to reinforce concepts such as dipoles and polarizability. While the bonds between carbon atoms in the sheet are extremely strong, the intrasheet interactions are significantly weaker. This allows the sheets to easily slip past one another, and this “slipperiness” of the layers accounts for graphite’s use as a good lubricant for clocks, door locks, and hand-held tools and as the “lead” in lead pencils. Unlike diamond, graphite conducts electricity because of the delocalization of the pz electrons. Since it does not easily burn, it is commonly used to form electrode contact points. Dry cells and some types of alkali storage batteries also employ graphite because of this and other properties. Aside from decent electrical conduction, graphite also conducts heat well and is chemically inert, so crucibles for melting metals are often coated with graphite. With good stability toward strong acids, it is used to coat acid tanks. Because of its ability to slow neutrons, it is made into carbon rods used in nuclear reactors to regulate the nuclear reaction. Carbon Nanotubes

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Several materials form nanotubes, such as boron−nitrogen, tungsten(IV) sulfides, titanium(IV) oxides, gallium nitrides, and various silicon compounds, but the focus here will be on those based on carbon.41−44 Such nanotubes are called carbon nanotubes (CNTs), and they can be formed in nature through combustion of organic matter. It has been found that certain ancient steel products may have possessed carbon nanotubes derived from the exposure of the processed steel to carbon sources. Thus, the “Damascus steel” used in making very strong weapons is believed to have profited from the presence of carbon nanotubes. While CNTs have existed since antiquity, they were not studied until quite recently. In 1952,45 Radushkevich and Lukyanovich published pictures of tubes of carbon. This discovery was largely unnoticed. In 1991, Iijima reported the first observation that CNTs could be produced as side products in fullerene synthesis.46 It is often accepted that this observation prompted the current interest in carbon nanotubes. CNTs are allotropes of carbon with diameters of about 1/ 50,000 that of a human hair. The following has been suggested:44 [C]arbon nanotubes will be one of the most important 21st century materials because of the exceptional properties and abundance of the feedstock, carbon. CNTs are generally classified into two groups. Multi-walled carbon nanotubes, MWCNTs, are comprised of 2 to 30 concentric graphitic layers with diameters ranging from 10 to 50 nm [and] lengths that can exceed 10 micrometers. Single-walled carbon nanotubes, SWCNTs have diameters ranging from 1.0 to 1.4 nm, with lengths that can reach several micrometers. To visualize CNTs, imagine a single sheet of fused benzene rings that has been rolled up to form a rod that is capped at each end with half of a fullerene molecule (Figure 2). If only one sheet is rolled, it is a single-walled CNT (SWCNT);

INORGANIC CARBON POLYMERS As carbon forms the basis for most synthetic polymers, it also forms the foundation for a number of important inorganic polymers. Here we will briefly describe the basic structures and properties of some of these. The discussion of these compounds can be extended to include advanced concepts like band theory and its relationship to conductivity (structure−property relationships), as will be presented later. Diamond

Elemental carbon exists in many different forms (allotropes), including the two best known: diamond and graphite.34−37 Graphite is the thermodynamically stable allotrope of carbon, while diamond is the kinetically stable phase. Given time (eons) or exposure to extreme temperatures, the kinetically stable diamond will eventually convert to the thermodynamically stable graphite. Natural diamonds form when concentrations of pure carbon are subjected to great pressures and heat by the earth’s mantle. They are particularly known as the hardest known natural material with the highest bulk thermal conductivity. The diamond structure consists of a three-dimensional lattice of tetrahedrally arranged sp3-hybridzed carbon atoms arranged as a face-centered cubic crystal. As a result of its rigid structure, diamonds are generally highly pure with few contaminants. They are highly optically dispersive, so only a little impurity causes a relatively large color change. Introducing small amounts of boron causes them to become semiconducting, leading to their use in the production of transistors. While the largest gem-quality diamonds are mainly found in nature, most diamonds are artificially made. These are small, often the size of a grain of sand. Commercially, because of their high strength, they are employed in cutting, shaping, grinding, boring, and polishing. C



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multiwalled CNTs (MWCNT) are produced when several sheets are rolled to produce concentric tubes.

Figure 3. Simplified way of depicting how an organic metal center or cluster can be combined with an organic “linker” moiety to produce one-, two-, or three-dimensional network solids.

Figure 2. Depiction of a single layer of graphite (graphene, left) and how it can be folded to produce a carbon nanotube (here, zigzag conformation, middle). Top-down views (right) of a single-walled CNT versus a multiwalled CNT.

commonly synthesized by hydrothermal or solvothermal means,49−52 where the reagents are combined into a Teflonlined autoclave and heated under autogenous pressure. The microwave synthesis of CPs is becoming more common, but it is difficult to obtain single crystals using this method. More traditional crystallization methods, such as slow evaporation and solvent layering, have also been successful in producing CPs. CPs are widely studied not only because of their large structural diversity but also because they have remarkable properties compared with other kinds of solid-state compounds. If a CP has permanent porosity, it is typically called a metal−organic framework (MOF). MOFs possess some of the highest surface areas ever recorded, which coupled with their porosity leads to applications in molecular storage and separations, catalysis, and sensing, among others.53−68 The ability to fine-tune the pore structure and functionality are paving the way for MOFs to be used in a diverse number of potential applications, making them useful materials to introduce to an undergraduate inorganic chemistry course that has students with a broad range of scientific interests. A lecture on CPs toward the end of a semester can be used to reinforce concepts that were introduced earlier. Hard−soft acid−base (HSAB) considerations, the chelate effect, coordination geometries, molecular symmetry, and bonding complexities can all be reviewed as they pertain specifically to CP systems. Thus, discussing these compounds can serve as a platform not only to introduce new concepts such as diffraction or crystallization techniques but also to review selected topics from earlier in the course. One example that may be used is a lanthanide adipate framework templated with 4,4′-bipyridine, commonly denoted as GWMOF-6 (Figure 4).69−71 The self-assembly of this framework can be rationalized using both HSAB concepts and the chelate effect. The harder nature of the anionic adipate ions leads to a preferential bonding interaction with lanthanide ions compared with the relatively softer (but technically a hard/ borderline) base 4,4′-bipyridine. Additionally, the adipate ions provide a larger entropic drive for the self-assembly process through the ability to chelate with the lanthanide ions, whereas bipyridine can only potentially participate in monodentate binding. This compound can also be used to introduce students to the basic properties and chemistry of the lanthanide series as

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ADVANCED INORGANIC POLYMER CONCEPTS The polymers discussed thus far provide a descriptive means to include inorganic polymers across the entire range of the chemistry curriculum. For an upper-division or advanced inorganic chemistry course, there are several ways that polymeric compounds can be introduced in a manner to strengthen the overall course, especially regarding structure− property relationships. Both coordination polymers and semiconducting organic polymers can be discussed toward the end of a course to tie in many various concepts that were likely presented earlier. Furthermore, the descriptive discussion of inorganic carbon polymers can be extended to include electrical conductivity and band theory. Coordination Polymers and Metal−Organic Frameworks

The concept of network inorganic solids can be extended to include coordination polymers and metal−organic frameworks (collectively, CPs).47,48 CPs are the result of using multifunctional organic moieties to connect metal centers or clusters into one-, two-, or three-dimensional compounds (Figure 3). Their assembly can be visualized using Tinker Toys and the like as an analogy. The scientific literature devoted to CPs has increased exponentially over the past decade, and there are extensive research efforts devoted to the study and development of these compounds. Students should be cautious not to confuse coordination complexes with coordination polymers, and a CP should not be referred to as a “complex”.48 Complexes are discrete, zero-dimensional molecular species, whereas CPs are better classified as a type of extended network solid. Often, a primary goal of synthesizing new CPs is to obtain a product suitable for single-crystal X-ray diffraction for structural determination. There are many ways to synthesize CP compounds, and the synthesis of CPs can be used to discuss crystallization methods in general. Producing single crystals has been likened more to an art form rather than a science, but certainly there is science involved, and the instructor may choose to include basic to advanced crystallization theory here, including thermodynamics and/or kinetics of crystallization as well as basic X-ray diffraction theory and techniques. CPs are D



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parameters and mathematics to analyze structural topology. This ability to target specific SBUs with tailored pores is arguably one reason for the current fascination with these materials, as targeted design leads to targeted functionality. MOF-5 is an ideal compound to demonstrate this, especially as it pertains to gas storage, separations, or even catalysis. One specific example here is the isoreticular MOF-5 system, where the major difference is the functionality of the terephthalate linker and/or its length by adding phenyl groups. While the crystal classes and overall topologies of these compounds remain cubic, the free volume of the unit cell dramatically increases with increasing linker length. The relationship between porosity and gas storage ability can be investigated here, including how gas storage begins to decrease as a certain size limit is achieved because of finite areas (MOF walls, SBU metal cluster) for which the gases to interact.73,74 Semiconducting Polymers

The concept of band theory is often introduced in junior/ senior-level inorganic courses. An interesting way to augment this concept is to include a discussion of semiconducting organic polymers, which could also lead into a presentation of light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs). While semiconducting polymers are not technically inorganic polymers, their use to merge and reinforce several concepts discussed in an upper-division inorganic chemistry lecture while bringing in general knowledge from other courses is quite valuable to a student’s general chemical education. One specific approach is offered here. Beginning with the structure of polyacetylene, showing both cis and trans conformations, is an easy way to introduce the semiconductivity concept. Here it is beneficial to walk the students step-by-step through the process of band formation in semiconducting polymers. A quick review of the atomic structure of carbon and how the 2s and 2p orbitals can hybridize into sp orbitals may seem too basic at this level, but with a goal of reviewing fundamental concepts, it can be beneficial to start as simple as possible. The sp2-hybridized orbital has a full valence complement once electrons from carbon and hydrogen are included, leaving one electron in a higher-energy pz orbital. If this simple molecular diagram is extended to an “infinite” number of C atoms, then band formation occurs. The students should be aware that with a half-filled pz orbital and thus a half-filled pz band, metallic conduction would be expected from these kinds of organic polymers based on sp2-hybridized carbon. If this is the case, then why are semiconducting polymers being discussed? The students are shown that the delocalization of electrons in these kinds of polymers is not complete, with some localization of electron density on individual C nuclei. Here the instructor can use Peierl’s theorem, which states that 1-D metallic conductors (like organic semiconductors) are unstable relative to their semiconducting states, and thus, there will be some way to split the half-filled pz band into a full valence band and empty conduction band with a band gap separating them. Even though metallic conductivity is theoretically expected in these systems, in reality they demonstrate semiconducting behavior. Figure 6 depicts the evolution of this process. If the concept of n- and p-doped semiconductors was discussed in band theory, it can be demonstrated that a semiconducting polymer has the capacity to likewise be doped with electron-accepting or -donating species that induce changes in both the nature and magnitude of its semi-

Figure 4. Simple depiction of the self-assembly (top) to produce GWMOF-6 (bottom; yellow polyhedra = LnO9, black lines = C, blue dots = N, hydrogen atoms omitted) using HSAB considerations and the chelate effect.

well as the use of templating agents in solid-state synthesis. Furthermore, structure−property relationships can be demonstrated: the bipyridine template acts as an energy acceptor to promote lanthanide-centered luminescence (the antenna effect). In an advanced inorganic chemistry or materials chemistry course, these materials properties can be further explored, especially pertaining to structure−property relationships. Using MOF-572 as a classic example, the formation of the MOF’s PBU and SBU can be discussed and compared to those of traditional silicate materials (Figures 1 and 5). Next, it could be illustrated that simply changing the length of the organic moiety (the “linker”) allows the size and/or shape of the resulting pore to be modified.73,74 The design of these materials is called reticular chemistry,75 which includes the geometric

Figure 5. Composition of the MOF-5 PBU (top), polyhedral representations of the PBU and SBU of MOF-5 (middle), and overall extended structure of MOF-5 (bottom). E



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Figure 6. Depiction of how organic carbon comes together to produce semiconducting organic polymers, which is useful in extending the basic concepts of band theory.

lower-division courses, a simple discussion of the structure, synthesis, and properties of several different kinds of inorganic polymers can be utilized. In particular, silicates, polysiloxanes, and inorganic carbon-based polymers are described briefly. In upper-division coursework, these fundamentals can be expanded to structure−property relationships using concepts from solid-state bonding and electrical conduction. Furthermore, coordination polymers provide an excellent means to reinforce these and other concepts.

conducting behavior. An advanced treatment of these materials that include concepts such as polarons and so forth to explain conduction in more detail is likely more appropriate for a graduate-level course or a course in materials chemistry. Similar to CPs, however, discussing the basic bonding and structure of polyacetylene and semiconducting polymers in general can be an excellent means to review concepts from earlier in the semester and to reinforce band theory as it relates to bonding and electrical conduction.

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INORGANIC CARBON POLYMERSEXTENDED The structures of diamond and graphite can be reviewed as already discussed, but now within the scope of bonding and electrical properties. Within diamond, all of the electrons are involved in C−C bonding in the tetrahedral 3-D network, while graphite is sp2-hybridized with delocalization of the pz electrons feasible. Indeed, the bonding in graphite is essentially the same as seen in semiconducting polymers. The difference here is that graphite is an allotrope of carbon in a crystalline 2-D hexagonal array instead of a disordered network of sp2-hybridized hydrocarbons. Despite these differences, it is the same delocalization of pz electron density that results in the ability of graphite to be an electrical conductor. The band structure of graphite also demonstrates the unique nature of this conduction, the so-called “zero-gap semiconductor”. While technically no band gap exists in graphite, there is almost no electron density at the Fermi level, and a pseudosemiconductor nature of its conductivity is induced. Graphene can also be discussed here, though with limited time to cover many topics, it can be reserved for a separate, more advanced course. Considering the single layer of graphite that results in graphene, however, can segue into how the conduction of graphite changes as it goes from a layer structure to the cylindrical structure that is seen in CNTs. Students can be shown how armchair and zigzag conformations can arise as a result of rolling up a single layer of graphite in different ways. Chiral conformations can be mentioned, as well as detailed structural analyses of CNTs if desired. In terms of electrical conductivity, CNTs are an excellent way to demonstrate the importance of structure−property relationships in chemistry. The armchair conformation of CNTs shows metallic conductivity, whereas zigzag and chiral conformations are semiconductors with generally small band gaps. The use of CPs and carbon-based electronics provides just a few ways that inorganic polymers can be utilized to blend fundamental aspects of inorganic chemistry as a means to both introduce new concepts and review earlier topics within the scope of a given course.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Daniel T. de Lill: 0000-0003-0891-7246 Charles E. Carraher Jr.: 0000-0002-8340-5964 Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Undergraduate Professional Education in Chemistry: ACS Guidelines and Evaluation Procedures for Bachelor’s Degree Programs, 2015. https://www.acs.org/content/dam/acsorg/about/ governance/committees/training/2015-acs-guidelines-for-bachelorsdegree-programs.pdf (accessed September 2017). (2) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Sheats, J.; Zeldin, M. A Half Century of Metal- and Metalloid-Containing Polymers; Wiley: Hoboken, NJ, 2003. (3) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Sheats, J.; Zeldin, M. Ferrocene Polymers; Wiley: Hoboken, NJ, 2003. (4) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Sheats, J.; Zeldin, M. Biomedical Applications of Metal-Containing Polymers; Wiley: Hoboken, NJ, 2004. (5) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Zeldin, M. Group IVAContaining Polymers; Wiley, Hoboken, NJ, 2005. (6) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Zeldin, M. Coordination Polymers; Wiley: Hoboken, NJ, 2005. (7) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Zeldin, M. Transition Metal Polymers; Wiley: Hoboken, NJ, 2005. (8) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Zeldin, M. Nanoscale Interactions of Metal-Containing Polymers; Wiley: Hoboken, NJ, 2006. (9) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Zeldin, M. BoronContaining Polymers; Wiley: Hoboken, NJ, 2007. (10) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Zeldin, M. Inorganic Supramolecular Assemblies; Wiley: Hoboken, NJ, 2009. (11) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Zeldin, M. Photophysics and Photochemistry; Wiley: Hoboken, NJ, 2010. (12) Abd-El-Aziz, A.; Carraher, C.; Pittman, C.; Zeldin, M. Inorganic and Organometallic Macromolecules: Design and Application; Springer: New York, 2008. (13) Allcock, H. R. Phosphorus-Nitrogen Compounds; Academic Press: New York, 1972. (14) Archer, R. Inorganic and Organometallic Polymers; Wiley: Hoboken, NJ, 2004.

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CONCLUSION Chemistry curricula can use inorganic polymers as a means to introduce and review basic polymer chemistry concepts. In F



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