2 List of TopicsNo. ofWeeksContact HoursIntroduction to polymer chemistry, definitions and types of polymeric materials. Homo and copolymers.12Classifications of polymers: natural and synthetic polymers, linear, branched and cross-linked polymers thermoplastics and thermosets.Methods of polymerization (condensation, Free radical, Cationic and anionic)Mechanism of polymerizations.Coordination polymerization, Stereo regular polymerMechanism and kinetics of coordination polymerization.4Molecular weight and molecular weight determination.Mechanical and thermal properties of polymers.Methods of petrochemical productionChemistry of industrial fibersTechnology in manufacturing polyethylene's – Polystyrenes – PVC and natural rubber36
3 Proportion of Total Assessment GradingAssessment task (e.g. essay, test, group project, examination, speech, oral presentation, etc.)Week DueProportion of Total AssessmentMid term I6th week15%Mid term II11th weekClass discussionDuring the entire course3%Participation and attendance2%Quizzes5%Group workAssignment and presentationFrom 2nd to 14th weekFinal written Exam at the end of semester.By the end of the semester50%
4 List Recommended Textbooks and Reference Material (Journals, Reports, etc) 1. "Polymer Chemistry: The Basic Concepts", Paul C. Hiemenz.2. Polymer Synthesis: Theory and Practice: Fundamentals, Methods, Experiments By Dietrich Braun, Harald Cherdron, Matthias Rehahn, H. Ritter, B. Voit Published by Springer, 2005.
5 What is polymer Chemistry Chemistry of large molecules ( macromolecules).“Macromolecules” : molecules existed as a result of covalently linked smaller units, and possessed unique physical and chemical properties.Polymer is macromolecules, but macromolecules may not be a polymer.
6 What is polymerPolymer is compound consisting of long-chain molecules, each molecule made up of repeating units connected together.The word polymer is Greek words poly: many, and meros (reduced to mer: part.Molar mass ranges from g/g-mole.Most polymers are based on carbon and are therefore considered organic compounds.
7 Polymer Chain LengthsMany polymer properties are affected by the length of the polymer chains. For example, the melting temperature increases with increasing molecular weight.At room temp, polymers with very short chains (roughly 100 g/mol) will exist as liquids.Those with weights of 1000 g/mol are typically waxy solids and soft resins.Solid polymers range between 10,000 and several million g/mol.The molecular weight affects the polymer’s properties (examples: elastic modulus & strength).
8 Polymeric Materials, Repeating units polyethyleneethylene
16 Classification of Polymer 2. by Skeletal Structure Polymers can exist with various skeletal structures - such as:Linear polymers.2. Branched polymers.3. cross-linked polymers.4. Network polymers.5. Dendiemer PolymerSeveral important terms and concepts must be understood in order to discuss fully the characterization, structure and properties of polysaccharides (polymers in general).In strict terms, a polymer is a substance composed of molecules which have long sequences of one or more species of atoms or groups of atoms or groups of atoms linked to each other by covalent bonds.Polymers may be linear - a chain with two endsor Branched polymers - which have side chains or “branches” of significant length which are bonded to the main chain at branch point, and are characterized in terms of the number and size of branches.The other is Network Polymers which have 3-D structures in which each chain is connected to all others. Such polymers are said to be cross-linked and are characterized by their “cross-link density” or “degree of cross-linking” - related to the number of junctions.
17 Classification of Polymer by Structure: Linear structure : chain-like structure Characteristic of thermoplastic polymers.Linear
18 Branched structure that includes side branches along Polymer StructureBranched structure that includes side branches alongthe chain, also found in thermoplastic polymers.
19 Polymer StructureLoosely Cross-linked: bonding occurs between branches and other molecules at certain Connection points. As in an elastomerLoosely Cross- Linked
20 Polymer StructureTightly cross-linked or network structure - in effect, the entire mass is one gigantic macromolecule. As in a thermoset.network structure
21 Polymer StructureDendrimer Polymer: from the Greek word means tree- like polymer, dendrimer structure has:1. Symmetric around the core.2. Spherical three-dimensional morphology.Dendrimer Structure
24 Types of Polymers Polymers can be separated into plastics and rubbers. It can be classified into the following three categories:1. Thermoplastic polymers2. Thermosetting polymer plastics3. Elastomers rubbers
25 Polymer Classification Polymers are commonly classified according to thermal effect as follows:PolymersElastomersThermosetsThermoplasticsCrystallineAmorphousplasticsrubbersThe most common way to classify polymers is shown above, where they are first seperated into 3 groups Thermoplastics, Elastomers and Thermosets.Thermoplastics are then further seperated into those which are crytalline and those which are amorphous (non-crystalline).This method of classification has the advantage, in comparison to others, since it is based upon the underlying molecular structure of the polymers.
26 Thermoplastics Thermosetting plastics Thermoplastics: Thermoplastics soften when heated, and they become hard and rigid once again when cooled.Example: Polyethylene, PVC, Nylon Uses: Bags, ToysThermosetting plastics: Thermosetting materials do not become softy on heating.Example: Bakelite Uses: Electric switches, Telephone parts, Cooker handles
27 Effect of Branching on Properties Thermoplastic polymers always possess linear orbranched structures, or a mixture of the two- If Branches increase among the molecules, the polymer becomes:- Stronger in the solid state.- More viscous in liquid state..
28 Crystalinity and Properties •As As crystallinity is increased in a polymer: - Density increases. - Stiffness, strength, and toughness increases. - Heat resistance increases. - It becomes opaque (Not transparent).
29 THERMOPLASTICS PROPERTIES 1. Formed by addition Polymerization.2. Long chain linear polymers.3. Soften on heating and stiffen on coolingThey can be moulded into any shape.Less than 100% crystallinity, but instead amorphous.
30 THERMOSETTING PLASTICS 1. Formed by condensation Polymerization.2. Three dimensional network structure joined by strong covalent bonds3. Do not soften on heating4. Rigid materials5. At high temperature, thermoset plastics degrade rather than melt.
31 Hydrocarbon Molecules Many organic materials are hydrocarbonsMost polymers are made up of H and C.The bonds between the hydrocarbon molecules are covalent.Each carbon atom has 4 electrons that may be covalently bonded, the hydrogen atom has 1 electron for bonding.A single covalent bond exists when each of the 2 bonding atoms contributes one electron (ex: methane, CH4).
32 Saturated Hydrocarbons Each carbon has a single bond to 4 other atoms; the 4 valence electrons are bonded, the molecule is stable.The covalent bonds in each molecule are strong, but only weak hydrogen and van der Waals bonds exist between the molecules.Most of these hydrocarbons have relatively low melting and boiling points.However, boiling temperatures rise with increasing molecular weight.
33 Unsaturated Hydrocarbons Double & triple bonds are somewhat unstable : involve sharing 2 or 3 pairs of electrons, respectively. They can also form new bondsDouble bond found in ethylene - C2H4Triple bond found in acetylene - C2H2
34 IsomerismTwo compounds with same chemical formula can have different structures (atomic arrangements).for example: C8H18normal-octane2,4-dimethylhexane
35 Synthesis of PolymersThere are a number different methods of preparing polymers from suitable monomers, these are1. step-growth (or condensation) polymerization2. Chain growth (addition) polymerization
36 Synthesis of PolymersPolymerization is a process of reacting monomer molecules together in a chemical reaction to form linear chains or a three-dimensional network of polymer chains.1. Addition: repeating units and monomers are sameAddition polymerization involves the linking together of molecules, double or triple chemical bonds2. Condensation: "step-growth polymerization,Condensation: repeating units and monomers are not equal, Example: Reactions of alcohol, amine, or carboxylic acid (or other carboxyl derivative) functional groups.
37 Types of Polymerization 1. Chain-growth polymers, also known as addition polymers, are made by chain reactions
44 Addition Vs. Condensation Polymerization In addition polymerization although x may assume any value, y is confined to unitythe growing chain can react only with a monomer molecule and continue its growth
45 Addition Vs. Condensation Polymerization Polymerization reactions can generally be written asx-mer y-mer → (x +y)-merIn a reaction that leads to condensation polymers.
46 Comparison of Step-Reaction and Chain-Reaction PolymerizationStep ReactionChain ReactionGrowth occurs throughoutreaction between monomers, oligomers,and polymersDPa low to moderateMonomer consumed rapidly whilemolecular weight increases slowlyNo initiator needed; same reactionmechanism throughoutNo termination step; end groups still reactivePolymerization rate decreases steadily asfunctional groups consumedGrowth occurs by successive addition ofmonomer units to limited number ofgrowing chainsDP can be very highMonomer consumed relatively slowly, butmolecular weight increases rapidlyInitiation and propagation mechanisms differentUsually chain-terminating step involvedPolymerizaion rate increases initially asinitiator units generated; remains relativelyconstant until monomer depletedaDP, average degree of polymerization.