Band 3, Heft 2 - Special Issue: Polymer Science

Radical polymerization is transformed into what is known as reversible addition–fragmentation chain transfer (RAFT) polymerization by the addition of a RAFT agent. RAFT polymerization enables the preparation of polymers with predictable molar mass, narrow chain length distribution, high end-group integrity and provides the ability to construct macromolecules with the intricate architectures and composition demanded by modern applications in medicine, electronics and nanotechnology. This paper provides a background to understanding the mechanism of RAFT polymerization and how this technique has evolved.

Reversible-Deactivation Radical Polymerisation (RDRP) is one of the most exciting developments in chemistry over the past few decades, but it is rarely mentioned when polymerisation mechanisms are introduced in the final years of secondary education or first years of tertiary education. We propose that this is unfortunate, as RDRP is simpler than conventional Radical Polymerisation both conceptually and in terms of setting quantitative problems, and that it illustrates several other important features of chemistry as a human endeavour: How essential mechanistic unities are hidden by the details of how we write a chemical reaction, how a ‘bug’ in one stage of development of a process can become a ‘feature’ in a later stage, and how exciting changes can occur quite suddenly in fields thought to be mature and uninteresting.

Ring-opening polymerization is defined by IUPAC (Penczek, S., Moad, G. (2008). Glossary of the terms related to kinetics, thermodynamics, and mechanisms of polymerization. (IUPAC Recommendations 2008), Pure and Applied Chemistry , 80(10), 2163–2193) as (cit.) “Ring-opening polymerization (ROP): Polymerization in which a cyclic monomer yields a monomeric unit that is either acyclic or contains fewer rings than the cyclic monomer”. The large part of the resulting polymerizations is living/controlled; practically all belong to chain polymerizations. After the introduction, providing basic information on chain polymerizations, the paper presents the concise overview of major classes of monomers used in ROP, including cyclic ethers, esters, carbonates, and siloxanes as well as cyclic nitrogen, phosphorus, and sulfur containing monomers. There are discussed also thermodynamics, kinetic polymerizability, and major mechanisms of ROP. Special attention is concentrated on polymers prepared by ROP on industrial scale.

We present an overview for the basic fundamental of thermal analysis, which is applicable for educational purposes, especially for lecturers at the universities, who may refer to the articles as the references to “teach” or to “lecture” to final year project students or young researchers who are working on their postgraduate projects. Description of basic instrumentation [ i.e. differential scanning calorimetry (DSC) and thermogravimetry (TGA)] covers from what we should know about the instrument, calibration, baseline and samples’ signal. We also provide the step-by-step guides for the estimation of the glass transition temperature after DSC as well as examples and exercises are included, which are applicable for teaching activities. Glass transition temperature is an important property for commercial application of a polymeric material, e.g. packaging, automotive, etc. TGA is also highlighted where the analysis gives important thermal degradation information of a material to avoid sample decomposition during the DSC measurement. The step-by-step guides of the estimation of the activation energy after TGA based on Hoffman’s Arrhenius-like relationship are also provided.

Polymers, macromolecules in nature and bio-polymers like proteins and antibodies are present in our every-day life and play an important role in our economy. They are obviously present as plastic products (e.g., containers, clothing, car tires) or components, e.g., as expedients in pharmaceutical formulations, additives in food and feed, stabilizers in cosmetics, used in construction materials, ceramics and are key in microchip production. Size-exclusion chromatography is the most important characterization technique for macromolecules. This review covers applications, instrumental setup, step-by-step guides for performing experiments and covers theoretical background as well as troubleshooting and tips and tricks.

In this publication, we present the basic to characterize the electrical properties of electrolytes that are widely used in ion-rechargeable batteries using electrochemical impedance spectroscopy (EIS). This simplified yet insightful background provided may be used for educational purposes, especially for beginners or young researchers for both undergraduate and postgraduate students. We start with introduction of electrolytes and electrochemical impedance spectroscopy (EIS) instrumentation, following with the step-by-step guidelines using three different procedures to estimate the bulk resistance ( R b ) of the electrolytes, which is inversely proportional to the conductivity ( σ DC ) of the materials Rb∝1/σDC$\left({R}_{\mathrm{b}}\propto 1/{\sigma }_{\mathrm{DC}}\right)$. Several examples and exercises on estimation of quantity R b are supplemented for educational purposes. Comparison was made on estimation of R b using manual graphical procedures, mathematical regression procedures using commercial graphical software and equivalent circuit fitting procedures using exclusive EIS software. The results suggest that the manual graphical technique may serves as a useful approach for beginners before venturing to exclusive software. Besides, the instructors may use the procedures to coach the users to extract reliable and reproducible data before data interpretation. Lastly, the phenomenological approach on dielectric relaxation for solid polymer electrolytes [poly(ethylene oxide) (PEO) + lithium salt] and non-solid polymer electrolytes [poly(methyl acrylate) (PMA) + lithium salt], in the classic sense will be addressed in terms of impedance ( Z *), permittivity ( ε *), tangent loss (tan δ ), modulus ( M *) and conductivity ( σ *) spectra in Part 2.

In the Part 2 of this article, we present the phenomenological response of the dielectric relaxation for polymer electrolytes monitored by electrochemical impedance spectroscopy (EIS) in terms of electrochemical point of view, such as impedance ( Z *), permittivity ( ε *), loss tangent (tan δ ), modulus ( M *) and conductivity ( σ *) spectra. It is noteworthy to note that all the electrochemical aspects mentioned are of interest for conduction and seen as closely related to each other indirectly or directly. Two different systems; solid polymer electrolyte (SPE) [poly(ethylene oxide) (PEO) + lithium perchlorate (LiClO 4 )] and non-SPE [poly(methyl acrylate) (PMA) + LiClO 4 ] were employed for discussion. EIS is a powerful technique to characterize the electrical properties of polymer electrolytes. The results suggest that impedance and modulus are of interest for decoupling of dielectric and electric properties by evaluating the short-range and long-range mobility of the charged entities, respectively. One is able to identify the conduction mechanism of the polymer electrolytes easily if the responses are well understood. The objective of this article to introduce a simplified yet an insightful background and technique that is easy to be followed and useful for educational purposes especially for beginners or young researchers for both undergraduates and postgraduates.

Optically active macromolecules, having a preferred- or single-handed helical conformation, play important roles in polymeric materials and in life. This article presents how helical polymers can be assessed from a view of chirality. These assessments, based on optical rotation (OR) and circular dichroism (CD) spectral measurements with associated information, include theoretical spectral calculations as well as chromatographic resolution. Specific applied examples are discussed for poly(9,9-dioctylfluorene-2,7-diyl) and derivatives, stereoregular polyolefins bearing centers of chirality in the side chain, isotactic poly(triphenylmethyl methacrylate), and π-stacked poly(dibenzofulvene). For more convincing establishment of a helix, it is important to correlate chiroptical properties with related information such as molar-mass effects, temperature effects, and chemical transformation effects on the properties. Helices of the polyolefins and poly(TrMA) were confirmed considering these aspects. In addition, comparison of chiroptical properties between the polymer in question and a monomeric unit model compound generally helps to confirm a helix. There are no general, reliable methods to quantify helical sense excess. On the other hand, absolute helical sense can be determined by comparing experimental and theoretical CD spectra as well as considering exciton coupling effects in CD spectra. The former method can be more generally applied for a wide range of polymers as far as a good model for calculations is designed, while the latter can be more conveniently and empirically applied for a certain class of polymer structures that are suited to exhibit exciton coupling without using computers.

The paper gives an introduction to membrane science and technology, an area of research of high significance for the development of a sustainable life for human beings. It is therefore intended to be a guide for teachers in the areas of chemistry, physics, or biology, who can incorporate the presented materials in their respective courses. The paper gives some insights into the different types of membranes, their functions, production and use in some selected areas.

Nano- and microgels are promising soft polymer materials for different application fields: stabilizers, sensors, catalysts, selective sorbents, drug delivery carriers etc. They are composed of cross-linked polymer chains swollen with a solvent. The building blocks, synthesis approaches and architecture of nano- and microgels are reviewed. The mechanisms of responsiveness to various stimuli are described, examples of applications are provided. Micro- and nanogels are good objects for learning projects and the ideas for learning projects with microgels are described.

Organic electronics has developed rapidly over the past 40 years. In 1977, a seminal discovery was reported that showed that a polymer known as polyacetylene could conduct electricity as well as metals could. This was a groundbreaking discovery that led to a Nobel Prize in Chemistry in 2000. The polymers that are used in organic electronics have now been widely studied for use in organic solar cells (OSCs), organic field effect transistors (OFETs), printable electronics, flexible electronics, antistatic coatings, actuators, and more recently in bioelectronics. In particular, the utility of organic electronics is seen in the commercial success of using organic electronic materials in organic light-emitting diodes (OLEDs) where OLED displays can be seen in mobile phones and as flat panel displays. In this paper, we provide a tutorial targeting upper secondary students describing how these special classes of polymers function, and how they can be synthesized. The paper further discusses the use of these materials in two applications: organic solar cells and organic light-emitting diodes. The paper ends with a brief discussion about hands-on activities that can be carried out in the upper secondary student science classroom.

In today’s society, with a high percentage of elderly people, floor heating to ensure constant temperature and heat jackets in winter play important roles in winter to them to live comfortable lives without compromising health – except tropical zones. Under floor heating maintains a comfortable temperature in a room without polluting the air and heat jackets allow for light clothing at comfortable temperatures. The two facilities are attributed to Joule heat generated by tunnel currents between adjacent short carbon fillers in flexible polymer matrixes under low voltage. The current between adjacent conductive fillers is due to electron transfer associated with elementary quantum mechanics. Most of undergraduate students investigating polymer physics will have learned about electron transfer in relation to the temperature dependence of the conductivity of conductive filler-insulator polymer composites as well as the phenomenon of Joule heat at high school. Despite their industrial importance, most students show little interest for investigating electric properties, since most of polymers are insulation materials. Polymer scientists have carried out qualitative analyses for tunneling current using well-known simplified equations derived from complicated mathematical process formulated by solid-state physicists. Hence this paper is focused on a teaching approach for temperature dependence on electric properties of the polymer-filler composites relating to tunnel current in terms of elementary quantum mechanics. The approach also attempts to bridge education and research by including reference to the application limit of the well-known theories to such complicated composite systems that fillers are dispersed uniformly in the polymer matrix.

The reader will find basic knowledge about the degradation of polymers, its causes, course and consequences in a broader context, as indicated through the list of the chapter titles: Introduction; Depolymerization; Initiated cleavage (degradation) of macromolecules; Thermal degradation; Photochemical degradation; Mechanochemical degradation; Oxidative degradation; Polymer burning; Kinetics of cleaving macromolecules when chain depolymerization is negligible; Degradation in polymer recycling; Protection of polymers against degradation.