Lesson 1 Introduction to Polymer PDF

# Lesson 1: Introduction to Polymer ## Presented by: - Ts Dr Siti Noor Hidayah Mustapha ## Outline Lesson 1: Introduction to Polymer 1. Definition and nomenclature 2. Classification of polymers 3. Copolymer and copolymerization 4. Molecular structure of polymer 5. Inter and intra-molecular att...

# Lesson 1: Introduction to Polymer ## Presented by: - Ts Dr Siti Noor Hidayah Mustapha ## Outline Lesson 1: Introduction to Polymer 1. Definition and nomenclature 2. Classification of polymers 3. Copolymer and copolymerization 4. Molecular structure of polymer 5. Inter and intra-molecular attraction of polymer 6. Molecular weight and molecular weight distribution ## What is Polymer? - Polymers is a macromolecules made up of smaller units called monomers or repeating units that covalently bonded together. ## What is Monomer? - Monomer can be molecule or a distinct segment of molecular chain consisting of either molecular unit or group of molecular units that has the same kind and number of atoms. ## What is Polymerization? - Polymerization is the process of joining together small molecules or monomers by covalent bonds to form large molecule, with or without the formation of other products. ## Nomenclature of Polymer - Single polymer commonly has lot of possible names: - Common name (not standard) - Trade name (not standard) - ACS name (standard) - IUPAC name (standard) - The standard name of polymer is proposed by American Chemical Society (ACS) and International Union of Pure and Applied Chemistry (IUPAC) - The non-standard name which is common name and trade name is given based on the historical model or popular name of the polymer. It might also any random catchy, snappy-sound names given by specific industry people (the chemist, engineer, or purchasing agents). ## Example | Common Name | ACS Name | IUPAC Name | |-------------------------|------------------------------------------------------------------|---------------------------------------------------------------------------------| | Poly (ethylene terephthalate) or (PET) | Poly(oxy-1,2-ethanediyloxycarbonyl-1,4-phenylenecarbonyl) | Poly(ethyl benzene-1,4-dicarboxylate) | | Nylon | poly[amino(1-oxo-1,6-hexanediyl)] | poly[amino(1-oxohexan-1,6-diyl)] | ## Classification of Polymer - Classification of polymer is based on : - Type of Monomer - Chain Structure - Property ## Classification based on Types of Monomer ### Hydrocarbon Polymers - Polymers with carbon (C) and hydrogen (H) in the chain. - **Example:** - Polypropylene (PP) (a diagram of a polypropylene molecule is included here.) ### Non-hydrocarbon Polymers - Polymers which contained other atoms besides carbon (C) and hydrogen (H) - **Example:** - Poly(methyl methacrylate) (PMMA) (a diagram of a poly(methyl methacrylate) molecule is included here.) ## Classification based on Type of Monomer Arrangement ### Homopolymers - Polymer is made by linking only one type of small molecule, or monomer together. - **Example:** (A diagram of a homopolymer chain is included here) ### Copolymers / Heteropolymer - Polymer that is consist of two different types of monomers in the same polymer chain. - **Example:** (A diagram of a copolymer chain is included here) ## Classification based on Chain Structure ### Linear - Polymer consisting of a single continuous chain of repeating units - The chain can closely pack - High melting point - High density - Normally thermoplastic - **Example:** - High density polyethylene (HDPE) (A diagram of an HDPE molecule is included here.) ### Branch - Also call non-linear polymer - A polymer that includes side chains of repeating units connecting to the main chain. - Have irregular/different size of side chain - Loosely packed - Lower density - Low melting point and boiling point - Normally thermoplastic - **Example:** - Low density polyethylene (LDPE) (A diagram of an LDPE molecule is included here.) ### Crosslinked - Some polymers have crosslinks between polymer chain creating 3-dimentsional networks. - A high-density crosslinking restrict the motion of the chains and leads to a rigid materials. - Mostly are thermosetting polymer - Permanently hard when heated as covalent crosslink forms and resist the vibrational and rotational chain at high temperature - Harder and stronger than thermoplastics - **Example:** (A diagram of a crosslinked polymer chain is included here.) - The same thermoplastic polymer, it can also classify separately based on their density and molecular weight in which it related to its chain structure (linear or branching) - The mechanical and thermal properties of polymer also depends significantly on its chain structure. ## Example - High density polyethylene (HDPE) - Low density polyethylene (LDPE) - Linear low density polyethylene (LLDPE) - Ultra high molecular weight polyethylene (UHMWPE) - Ultra low molecular weight polyethylene (ULMWPE or PE-WAX) - High molecular weight polyethylene (HMWPE) - High density cross-linked polyethylene (HDXLPE) - Cross-linked polyethylene (PEX or XLPE) - Medium density polyethylene (MDPE) - Very low density polyethylene (VLDPE) ## Classification based on Property ### Thermoset - Crosslinked - Rigid - Harden when heated - **Example:** - Epoxies - Phenolics - Polyimides ### Thermoplastic - Uncross-linked - Heat reversible. - Melt when heated and harden when cooled - **Example:** - Acrylics - Nylon - Polyethylene - Poly(vinyl chloride) ### Elastomer - Flexible to rigid - Combination of plastic and rubber property. - **Example:** - Epoxidized natural rubber (ENR) - Synthetic rubbers – Nitrile-butadiene rubbers (NBR), styrene-butadiene rubber (SBR) - Polydimethylsiloxane (PDMS) ## Copolymer / Heteropolymer - Polymer that is consist of two different types of monomers in the same polymer chain. - **Copolymerization** - Refers to methods used to chemically synthesize a copolymer. - **Commercially relevant copolymers:** - Acrylonitrile butadiene styrene (ABS) - Styrene-butadiene rubber (SBR) - Nitrile-butadiene rubber (NBR) - Styrene acrylonitrile - Styrene-isoprene-styrene (ISI) - Ethylene-vinyl acetate ## Types of Copolymer ### Alternating copolymer - The different monomers arranged in alternate positions along the backbone of the polymer. - **Example**: (A diagram of an alternating polymer chain is included here.) ### Block copolymer - A group of monomer types occur together along the polymer backbone. - **Example**: (A diagram of a block copolymer chain is included here.) ### Random copolymer - The monomers segments are arranged in random along the polymer backbone. - **Example**: (A diagram of a random copolymer chain is included here.) ### Graft copolymer - A copolymer in which a chain of one polymer is attached to the chain of a different polymer type. - **Example**: (A diagram of a graft copolymer chain is included here) ## How to produce specific co-polymer structure? - Mainly depending on: - monomers types (reactivity, hydrophobicity, hydrophilicity) - Polymerization process and techniques - Polymerization conditions (temperature, initiator, materials selection etc) ## Molecular Structure of Polymer - Polymer structure are strongly influence the properties of polymer. - **Details of polymer structure:** - Overall chemical composition – types of monomer and length of polymer chain - Sequence of the monomer units (applicable for copolymer) - Stereochemistry or tacticity of the polymer chain - Geometric isomerization (normally applicable for diene type of polymers) ## Isomers - Isomers are compounds with the same molecular formula but a different arrangement of the atoms in space. | Isomer Type | Description | |--------------------|-------------------------------------------------------------------------------------------------------| | Structural Isomers | Atoms that are arranged in a completely different order. The process by which one molecule is transformed into another molecule which has exact the same atoms. | | Geometric Isomers | When there is a carbon-carbon double bond in a molecule. Stereochemistry referring to 3D arrangement of atoms and molecules. It includes the cis (same) and trans (opposite) | | Stereoisomers | When 2 or more molecules have identical molecular formula and the same structural formula. However, they differ in their 2D and 3D spatial arrangements of their bonds | ## Structural Isomers - **Example:** -C3OH8- (A diagram of structural isomers is included here.) - Atoms that are arranged in a completely different order. ## Geometric Isomer - The process by which one molecule is transformed into another molecule which has exact the same atoms - **Example:** (A diagram of cis-but-2-ene and trans-but-2-ene molecules is included here.) ## Stereoisomers / Tacticity - Tacticity is the stereochemical arrangement of the units in the main chain of polymer | Stereoisomer Type | Description | |--------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------| | Stereo-regular | Allow chain folding and form a crystalline (ordered chain arrangement) polymer. | | Stereo-irregular | No chain folding and form an amorphous (random ordered of chain) polymer. | ### Isotactic - Functional groups arranged on the same side of the main carbon skeleton - **Example:** (A diagram of an Isotactic polymer chain is included here.) ### Syndiotactic - Functional groups arranged in the alternate fashion of the main carbon skeleton - **Example:** (A diagram of a Syndiotactic polymer chain is included here.) ### Atactic - Functional groups arranged in a random manner around the main carbon skeleton - **Example:** (A diagram of an Atactic polymer chain is included here.) ## Inter and Intra-Molecular Attraction in Polymer - Polymerization (in forming macromolecule polymer) is covalent bond - sharing electron - non-metal atoms - stronger bond than ionic bond - **Interchain binding:** - Hydrogen bond - van der Waals forces - entanglement - **Example:** (A diagram of a covalent bond in a molecule is included here.) ## Hydrogen bond - One of the strongest dipole interaction. - Attraction of some oxygen atoms to hydrogen atoms - The stronger forces typically result in higher tensile strength and higher crystalline melting points. - **Example:** (A diagram of hydrogen bonds in a water molecule is included here.) ## Van der Waals Forces - Weak force, weaker than chemical bonds. - Molecules can be thought of as being surrounded by a cloud of negative electrons. But the electrons are mobile, and at any one instant, they might find themselves toward one end of the molecule, making that end slightly negative (d-). The other end will be momentarily short of electrons and so becomes (d+). - Basically, temporary fluctuating dipoles are present in all molecules, and the forces due to these dipoles are the basis for van der Waals attraction. ## Chain Entanglement - Polymer molecules are long chains, which can become entangled with one another, much like bowl of spaghetti. - Along with intermolecular forces, chain entanglement is an important factor contributing to the physical properties of polymer. - The difficulty in untangling their chains makes polymers, and the plastic made from them strong and resilient. ## Molecular Weight and Molecular Weight Distribution - A polymer's molecular weight is the sum of the atomic weights of individual atoms that comprise a molecule. It indicates the average length of the bulk resin's polymer chains. - All polymer molecule consist of long chains which do not all have the same exact molecular weight per chain. Average molecular weight is calculated. - There are 3 different ways to calculate the molecular weight of polymer: - Number-average molecular weight, Mn - Weight-average molecular weight, Mw - Viscosity-average molecular weight, Mv ## Number-average molecular weight, Mn - Basically, its measuring chain length - $M_n = \frac{\sum_{i=1}^{\infty} M_iN_i}{\sum_{i=1}^{\infty}N_i}$ or $M_n = \frac{\sum_{i=1}^{N}N_iM_i}{\sum_{i=1}^{N}N_i} = \frac{\sum_{i=1}^N W_i}{\sum_{i=1}^N W_i/M_i} = \frac{1}{\sum_{i=1}^N W_i/M_i}$ - $M_n = \sum_{i=1}^N x_iM_i$ - Where $N_i$ the number of molecules having a molecular weight $M_i$, and $w_i$ is the weight fraction of all molecules having a molecular weight $M_i$. - **Example:** - Consider a polymer sample comprising of 5 moles of polymer molecules having a molecular weight of 40.0 g/mol and 15 moles of polymer molecules having molecular weight of 30.0 g/mol. - What is the molecular weight, Mn of the polymer? ## Weight-average molecular weight - Basically, its measuring the statistical size of polymer - Mass of particles is calculated by the sum of all molecular weights multiplied by their weight fractions - $M_w = \frac{\sum_{i=1}^{\infty} N_i(M_i)^2}{\sum_{i=1}^{\infty}N_iM_i}$ - $M_w = \sum_{i=1}^N w_iM_i$ - Where $M_i$ is molecular weight of oligomer n, and $N_i$ is number of molecules of that molecular weight. - **Example:** - Calculate the Mw for a polymer sample comprising of 9 moles of polymer molecules having molecular weight of 30.0 g/mol and 5 moles of polymer molecules having molecular weight of 50.0 g/mol ## Viscosity-average molecular weight - The average molecular weight is related to viscosity of polymer under specific conditions. - In the case solution viscosity, the weight dependence of the viscosity can be described by well-known empirical Mark-Houwink (1940) relation: - $M_n = \left[\frac{\sum_{i=1}^N N_iM_i^{\alpha+1}}{\sum_{i=1}^N N_iM_i}\right]^{1/a} = \left[\frac{\sum_{i=1}^N W_i M_i^{\alpha}}{\sum_{i=1}^N W_i}\right]^{1/a} = \left[\sum_{i=1}^N W_iM_i^{\alpha} \right]^{1/a}$ - Where [n] is the intrinsic viscosity, and a, Kn are the Mark-Houwink parameters. These two quantities have been measured for many polymers. - Two very common techniques for measuring the molecular weight of polymers are: - high-pressure liquid chromatography (HPLC) - size exclusion chromatography (SEC) - gel permeation chromatography (GPC). - These techniques are based on forcing a polymer solution through a matrix of cross-linked polymer particles at high pressure of up to several hundred bars. ## Molecular weight distribution - The viscosity average is usually larger than the mass average but smaller than the number average, $M_w < M_v < M_n$. - **Example:** (A diagram of molecular weight distribution is included here.) ## Polydispersity index (PDI) - It is the ratio of $M_w$/$M_n$ - Also known as molar-mass dispersity index - It is the indication of how broad a range of molecular weights of the polymer - **Example:** (A diagram of PDI comparison is included here.) ## Implication of molecular weight - Increasing molecular weight increase the mechanical properties, melting point of polymer material. ## Implication of molecular weight distribution | Distribution | Description | |-------------|---------------------------------------------------------------------------------------------------------------| | Broad | Tensile decrease, impact decrease, elongation, creep & stiffness decrease, processing useful in process such as extrusion, high melt strength | | Narrow | Tensile increase, impact increase, elongation, creep & stiffness increase, processing useful in process such as injection molding due to materials able to melt over a narrow range of temperature | - **Example:** (A diagram of molecular weight distribution for a CSTR and batch/plug flow is included here.)