POLYMER CHEMISTRY CT 107 LECTURER: MRS N. P POLYMER CHEMISTRY CT 107 LECTURER: MRS N. P. ZINYAMA CONTACT : zinyamanp@msu.ac.zw

MODULE OUTLINE MIDLANDS STATE UNIVERSITY FACULTY OF SCIENCE AND TECHNOLOGY DEPARTMENT OF CHEMICAL TECHNOLOGY POLYMER CHEMISTRY CT 107 INTRODUCTION Polymers are an important class of materials, abound everywhere, homes, schools, offices and factories. This is due to their versatility in terms of properties, diversity, flexibility, cost and superior performance. Students will be exposed to various polymers, properties and their usage.

MODULE OUTLINE MODULE CONTENT 2.2 Polymerization reactions Definition of terms 2.2 Polymerization reactions Addition polymerization Free radical Ionic polymerization Condensation polymerization 2.3 Bonding in polymers a) Functionality of polymers b) Tacticity Structure 2.4 Polymerization techniques Bulk polymerization Solution polymerization Suspension polymerization Emulsion polymerization

MODULE OUTLINE Molecular masses of polymers Calculations of molecular masses Molar mass distribution 2.6 Characterization of polymers 2.7 Ageing of polymers 2.8 Waste disposal and recycling 2.9 New trends in polymer chemistry   References R.T. Morrison and Boyd, Organic chemistry N. L. Miller etal, Organic chemistry J.W. Nicholson, The Chemistry of Polymers, Second edition M.A. Cowd, Polymer Chemistry Internet

ASSESSEMENT ASSESSMENT Assessment Weighting Continuous assessment Assignments 5% Inclass tests 10% Practicals 25% Examinations 60%

What are polymers Polymer is a generic term used to describe a substantially long molecule, which consists of structural and repeating units strung together through chemical bonds. The term polymer covers a large, diverse group of molecules, including substances from proteins to high-strength kevlar fibres. A key feature that distinguishes polymers from other large molecules is the repetition of units of atoms in their chains. Each such basic unit or monomer is usually made of carbon, hydrogen, oxygen and/or silicon. The terms polymer and monomer were derived from the Greek roots poly (many), mono (one) and meros (part).

What are polymers The monomers, which are typically small molecules of low molecular weight, can be identical or they can have one or more substituted chemical groups. These differences between monomers can affect properties such as solubility, flexibility, or strength. To make the chain (i.e., to convert monomers to a polymer), many identical or related monomers are linked or polymerized together. Plastics are polymers (but not all polymers are plastics). Generally speaking, plastics are polymers with plastic behaviour.

Polymers Polyethylene, the simplest polymer, is shown below as a chain of repeating (-CH2-CH2-)n monomer units. Many common classes of polymers are composed of hydrocarbons. Carbon makes up the backbone of the molecule and hydrogen atoms are bonded along the backbone. There are polymers that contain only carbon and hydrogen. Polypropylene, polybutylene, and polystyrene are examples of these.

Polymers Polymers that contain primarily carbon and hydrogen are classified as organic polymers. Even though the basic makeup of many polymers is carbon and hydrogen, other elements can also be involved. Oxygen, chlorine, fluorine, nitrogen, silicon, phosphorous and sulphur are other elements that are found in the molecular makeup of polymers.

Polymers Polyvinyl chloride (PVC) contains chlorine. Nylon contains nitrogen. Teflon contains fluorine. Polyester and polycarbonates contain oxygen. There are also some polymers that, instead of having a carbon backbone, have a silicon or phosphorous backbone. These are called inorganic polymers.

Classification of polymers On the basis of repeat units Homopolymers- polymers whose repeat units are derived from only one type of monomer e.g. PVC Copolymers- polymers whose repeat structural unit are derived from two or more types of monomers eg polyesters, Bakelite

Classification of polymers Based upon source Natural polymers- polymers found in nature, in animals and plants e.g. proteins, rubber, cellulose Semi synthetic polymers- mostly derived from naturally occurring polymers by chemical modifications e.g cellulose, vulcanised rubber Synthetic polymers- a large no. Of man made polymers are extensively used in daily life e.g. fibres, PVC, PET

Classification of polymers Based on structure Linear polymers- in these the monomer units are joined together to form a long straight chain of polymer molecules. The various polymer chains are stacked over each other to form a well packed structure e.g. PE, PVC Branched chain polymers- the monomer units combine to form straight chains and branches of different length from the main chain. Crosslinked polymers- the initially formed linear polymers are joined together to form 3-D network structured giant molecules e.g. Bakelite and formaldehyde

Classification of polymers Based upon polymerisation Addition polymers- formed by the repeated addition of a large no. Of the same or different monomers possessing double or triple bonds e.g. PE, PVC Condensation polymers- formed by repeated condensation between 2 bifunctional or trifunctional monomer units usually with the elimination of small molecules like H2O and NH3 e.g. Terelyne, Bakelite, Nylon-6,6.

Classification of polymers Based upon molecular forces Elastomer- the polymers in which the intermolecular forces of attraction between the polymer chains are weakest e.g. natural rubber Fibres polymers in which the intermolecular forces of attraction are the strongest with H-Bonding and dipole dipole interactions e.g. terelyne Thermoplastics- the intermolecular forces of attraction are between those of elastomers and fibres e.g. PE, PVC They are linear, slightly branched chain polymers which become hard on heating used to mold toys, buckets Thermosetting polymers are semi solid polymers which on heating undergo permanent change in chemical composition to give hard and infusible solid mass due to extensive cross-linking of molecules e.g. Urea formaldehyde