Polymer Chemistry 고분자화학 Course Overview

담당 교수: 윤영수 E-mail: promars0soo@gmail.com ysyun@kangwon.ac.kr Phone: 033-570-6540 Office: 3E320 TEXT BOOK: “CONTEMPORARY POLYMER CHEMISTRY” 3rd edition (Harry R. Allcock, Frederick W. Lampe, James E. Mark)

CONTEMPORARY POLYMER CHEMISTRY Harry R. Allcock Frederick W. Lampe James E. Mark

Goal This course is designed to provide an introduction to polymer chemistry, including the synthesis, analysis, and physicochemical properties of macromolecules. Additional lectures will be on examples of polymer applications in industrial fields in order to understand polymers. (본 강의는 고분자 화학에 대한 개론으로 합성법, 분석법 및 물리화학적 특징들을 제공한다. 또한, 실제 응용 사례들을 접함으로써 고분자에 대한 전반적인 이해를 하도록 한다.)

“Polymers are Everywhere”

1. DEFINITIONS 1.1 Monomers A monomer is any substance that can be converted into a polymer. Polymerization Monomers Small molecules Polymer One large molecule (Ethylene) (Polyethylene) (Amino acid) (Polypeptides)

1.2 Dimers and Trimers 1.3 Oligomers Monomer + Monomer = Dimer Dimer + Monomer = Trimer …Tetramer, Pentamer, ,,, 1.3 Oligomers Low-molecular weight polymerization products -Dimers, trimers, tetramers, pentamers, and so on – cyclic or linear Glycolic acid (monomer) Dimer Trimer

Example of Oligomers Benzene (cyclic trimer) Acetylene (monomer) Polyacetylene Trioxane (cyclic trimer) Formaldehyde (monomer) Polyformaldehyde

1.3 Polymers - The term polymer is used to describe high-molecular-weight substances. Polymer: large molecules made up of simple repeating units Greek poly, meaning many, and mer, meaning unit Synonymous Term: Macromolecules - However, this is a very broad definition, and in practice it is convenient to divide polymers into subcategories according to their molecular weight and structure. - Generally, low polymers = MW 10,000 ~ 20,000 High polymers = MW 20,000 ~ several million

2. CLASSIFICATION OF POLYMERS

Representation of polymer types

2.1 Linear Polymers - A long chain of skeletal atoms to which are attached the substituent groups. - Linear polymers are usually soluble in some solvent, and in the solid state at normal temperatures they exist as flexible materials, or glasslike thermoplastics. EX) Polyethylene, Poly(vinyl chloride, PVC), Poly(methyl methacrylate, PMMA), Polyacrylonitrile, Nylon

2.2 Branched Polymers - Consisting of side chains or branches in the main chain - They are often soluble in the same solvents as the corresponding linear polymer However, they can sometimes be distinguished from linear polymers by their lower tendency to crystallize or by their different solution viscosity or light scattering

2.3 Crosslinked Polymers - This polymer is one in which chemical linkages exist between the chains. Such materials are usually swelled by “solvents” but do not dissolve. Actually, the amount by which the polymer is swelled by a liquid depends on the density of crosslinking. Degree of crosslinking is high enough, the material may be a rigid, high-melting, unswellable solid. crosslinking crosslinking

2.4 Star Polymers Star polymers have arms radiating from a common core. The number of arms may from three to six or more. Such polymers are prepared either by growing the arms by polymerization from a multifunctional core, or by linking preformed polymer molecules to a core through reactive end groups on the polymer. Tri-star polymer

2.5 Dendrimeric Polymers Preparation method Core-first: they are accessible through the reactions of a multifunctional core with a ti- (or higher) functional monomer. The growth of the molecule is usually carried out in successive layers or “generations” moving further and further from the core. 2. Arms-first: each highly branched arm is synthesized first, and several of these are then linked in a final step to the core. 1st generation 2nd generation 3rd generation

2.6 Cyclolinear Polymers - A special type of linear polymer formed by the linking together of ring systems. The properties resemble those of conventional linear polymers, except that the solubility of the cyclolinear species is often low. The tendency for crystallization may be very high.

2.6 Ladder Polymers Two skeletal strands are linked together in a regular sequence by crosslinking units. In practice, aromatic rings may constitute the linking units. Ladder polymers have a more rigid molecular structure than do conventional linear polymers and they are often much less soluble. R: polymer chain

2.7 Cyclomatrix Polymers Many polymer systems are known in which ring system are linked together to form a three-dimensional matrix of connecting units. Since 3D network of bonds is formed in these systems, the polymers are highly insoluble, rigid, very high melting, and usually stable at elevated temperatures. Silicon resins

2.8 Copolymers A polymer is made from two or more different monomers. It should be noted that the sequence of monomer units along a copolymer chain can vary according to the method and mechanism of synthesis.

A – B – A – A – A – B – A – B – B – A – A – B – A 2.8.1 Random copolymers In random copolymers, no definite sequence of monomer units exists. Poly (A-ran-B) A – B – A – A – A – B – A – B – B – A – A – B – A 2.8.2 Alternating copolymers A regular alternating sequence of two monomer units Poly (A-alt-B) A – B – A – B – A – B – A – B – A – B – A – B

A – A – A – A – B – B – B – B - A – A – A – A 2.8.3 Block copolymers Combination of one block of monomers and another block of monomers They are often formed by ionic polymerization process. Ex) AB diblock copolymers A – A – A – A – A – B – B – B – B – B Ex) ABA triblock copolymers A – A – A – A – B – B – B – B - A – A – A – A 2.8.4 Terpolymer A terpolymer contains three different monomer units. These can be sequenced randomly or in blocks.

A – A – A – A – A – A – A – A – A – A – A – A 2.8.5 Graft Copolymers Two preparation methods 1) Monomer B can be polymerized from sites along the length of polymer A. 2) Two preformed polymers derived from A and B can be induced to react with each other to form a graft structure. – B – B – B – B – B – B – B – B – B – B – B – B A – A – A – A – A – A – A – A – A – A – A – A

2.8.6 Telechelic Polymers A telechelic polymers is one that bears reactive functional groups at one or both of its chain ends. These are frequently produced by living polymerization processes.

2.9 Average Molecular Weights and Distributions A sample of a synthetic polymer has no single, fixed molecular weight. Instead, there is a distribution of different molecular weights in the same sample of material.

1) Number-average molecular weight Ni: Number of molecules of molecular weight Mi Xi: Number fraction or mole fraction of molecular weight Mi *It can be obtained from the study of the osmotic pressure of polymer solutions. 2) Weight-average molecular weight vi: Weight of molecules of molecular weight Mi Wi: Weight fraction of molecules with molecular weight Mi *It can be obtained from light-scattering or ultracentrifugation experiments, GPC

3) Polydispersity index (PDI, fraction MW/Mn) The fraction is a measure of the molecular weight distribution. For most polymers Mw/Mn: 1.5 – 2.5 For monodisperse polymer: Mw/Mn = Mz/Mw = 1 Mw > 1 Polydisperse Mn Mw = 1 Monodisperse Mn

2.10 Polymer Morphology 2.10.1 Thermoplastics 2.10.2 Elastomers Linear or branched polymers which can be melted upon the application of heat. (Largest proportion of the polymers used in industry.) 2.10.2 Elastomers A flexible polymer that is in the temperature range between its glass transition temperature and its liquefaction temperature. Crosslinked rubbery polymers that can be stretched easily to high extensions and which rapidly recover their original dimensions when the applied stress is released. Low crosslink density

2.10.3 Plasticizers 2.10.4 Thermosetting Resin 2.10.5 Polymer blends Only when this rigid polymer is softened by the addition of low-volatility liquids, such as phthalate esters, can it be used as flexible-film or tygon tubing. 2.10.4 Thermosetting Resin Rigid materials and network polymers in which chain motion is greatly restricted by a high degree of crosslinking. 2.10.5 Polymer blends Two or more polymers are mixed together mechanically. Many polymer blends display properties that are different from those of the individual polymers. Polymer blends can be of two main types, miscible or immiscible.

Comparison of the thermal behavior of amorphous, crystalline, and liquid crystalline polymers

Summary Definition of Polymer - High molecular weight polymers - Average molecular weight and distribution Classification of Polymers - Linear, branched, crosslinked, dendrimeric, star, ladder polymers - Copolymers: random, alternating, block copolymers - Grafting polymers and Telechelic Polymers Polymer morphology - Thermosetting resin, Elastomers, Thermoplastics, Polymer blends