Introduction To Polymer Science PDF

EL PT INTRODUCTION TO POLYMER SCIENCE PROF. DIBAKAR DHARA DEPARTMENT OF CHEMISTRY, IIT KHARAGPUR Module 01: Introduction N Lecture 01: Importance of Polymer Science and Brief Historical Background Importance of Polymer Science EL The Ages of Hum...

EL PT INTRODUCTION TO POLYMER SCIENCE PROF. DIBAKAR DHARA DEPARTMENT OF CHEMISTRY, IIT KHARAGPUR Module 01: Introduction N Lecture 01: Importance of Polymer Science and Brief Historical Background Importance of Polymer Science EL The Ages of Human Kind Human Civilization has been marked by several ages, all based on materials: PT  Stone age  Age of Elements (Silicon, Uranium, Lithium, Indium, Gallium etc)  Bronze age  Iron age (Steel, Aluminum) N  Polymer Materials age (Carbon based materials) “I am inclined to think that the development EL of Polymerization is, perhaps, the biggest thing that chemistry has done, where it has the biggest effect on everyday life” Lord Alexander Todd (1907-1997) PT President of the Royal Society of London N Nobel Laureate in Chemistry, 1957 Polymers are the materials of choice  One of biggest success stories in new materials development over the last century EL  Increasingly replaced conventional materials like wood, metals, stone or ceramics in several applications  Especially in new material applications, polymers are now very often the materials of choice PT  Polymers are everywhere  Plastics  Rubbers  Paints and surface coatings  Resins  Adhesives  Synthetic fibers N  Specialty applications Polymers are everywhere: visible to invisible EL PT https://in.pinterest.com/ N Why polymers are so popular Desired properties in a material EL  High strength: load-bearing capability  Resiliency: comfort-giving property  Transparency: ability to see-through the material  Lower cost PT None of the non-polymeric materials like metals, glass, ceramics and natural substances like wood can satisfy all these characteristics, whereas polymers have all these properties plus...... N Other beneficial properties of polymers EL  Durable: stable against hydrolysis and electrochemical corrosion  Lighter weight: excellent strength - weight ratio  Design flexibility: low-cost and low-energy processing, with high freedom of design and styling  Thermal and electrical insulator  Provides many options PT  Feedstock flexibility  Petroleum fractions  Natural gas Petrochemical industry  Coal  Agricultural and forest products and biomass as alternative N Origin of Polymer Properties What are Polymers? EL Large molecules (macromolecules) – consist of many repeating structural units PTCH2=CH2 Monomers …– CH2 – CH2 – CH2 – CH2 – CH2 – CH2 –... Mainly based on organic compounds Polymer N  Short Molecules Long Molecules High MW help in providing EL superior properties like high tensile strength, impact resistant, toughness, melt viscosity, high melting temperature, etc. PT Too short to entangle Completely entangled Can separate easily Molecules can not easily move Behave independently independently Bowl of Rice Bowl of Noodles N  Brief History of Science of Polymers (Macromolecules) EL  Polymer science was born in the great industrial laboratories of the world.  Polymers have existed in natural form since life began – such as DNA, RNA, proteins, polysaccharides – plays crucial roles in plant and animal life. PT  From ancient times these naturally occurring polymers were exploited as materials for clothing, decoration, shelter, tools, printing materials, etc.  Origin of today’s polymer industry - in the nineteenth century when important discoveries were made concerning the modification of some natural polymers. N Before 1907 – only modified natural materials EL In 1907, first fully synthetic polymer “Bakelite” was invented by Leo H Baekeland from reaction of phenol and formaldehyde. Commercial production: 1910 PT N http://plastiquarian.com The Dawn of the Chemical Industry: The Manufacture of Bakelite EL  Leo Baekeland was trying to invent a substitute for Shellac, then wholly supplied by India to the world  In the process he made the first man made polymeric material, beginning the age of plastics PT  Heat resistant and insulating  He founded a company called Bakelite Corporation in 1910 to manufacture the product Leo H Baekeland (1863-1944) N US Patent # 942,699; December 7, 1909  The Concept of “Macromolecules” EL  Polymer industry was running well without proper understanding of the nature of polymers.  For over a century, scientists believed that the polymers consisted of PT physically-associated aggregates of small molecules like micelles of surfactants.  In 1920, Hermann Staudinger, then professor of organic chemistry at the Eigenössische Technische Hochschule in Zurich, first conceived that polymers are made of very large molecules containing large N sequence of simple chemical units linked together by covalent bonds.  Hermann Staudinger: Father of Macromolecular Chemistry  He propounded the revolutionary concept, that macromolecules can be formed EL by linking of a large number of small molecules by means of covalent bonds  Through sheer intuition and imagination, he proposed that polymers were composed of large number of repeating units linked together by covalent bonds ("Über Polymerisation”; Ber. Dtsch. Chem. Ges., 53, 107, 1920). At that time he had no experimental evidence for his hypothesis. Hermann Staudinger 2020: The Year of Polymers – 100 Years of Macromolecular Chemistry (1881-1965) PT  The scientific community was very reluctant to admit the existence of extremely large compounds with molecular weights exceeding 5000. Instead, micelle-type aggregates, as observed for soap molecules, were considered to account for the unusual properties of such materials. Moreover, some scientists were convinced that the size of a molecule could never exceed the size of the unit cell, as measured by X-ray crystallography. N  Staudinger persevered in spite of being criticized by the scientific community. Hermann Staudinger: Father of Macromolecular Chemistry  Staudinger, following the scientific tradition of classical organic chemistry, presented sound experimental evidence to support the existence of high molecular EL weight polymers  Staudinger's hydrogenation experiments on natural rubber showed that hydrogenated rubber was very similar to normal unsaturated rubber.  During the late 1920s, Staudinger provided additional evidence based on viscometry to confirm that molecular weights remained unchanged during chemical PT modification of polymers.  Despite the impressive experimental evidence, Staudinger continued to encounter very strong opposition from eminent scientists of the period, notable amongst them, Emil Fischer and Heinrich Wieland, both were Nobel prize winners  By the end of the 1920s and during the 1930s, Staudinger's macromolecular concept found increasing acceptance by other chemists especially due to work of Herman Mark and Wallace H. Carothers. Staudinger was finally awarded Nobel N Prize in 1953. Pillars of Macromolecular Chemistry Developed EL fundamental understanding, both theoretical and experimental, in the physical chemistry of macromolecules Herman F Mark Wallace H Carothers PT (1895-1992) (1896-1937) Paul J Flory X Ray Crystallography of (1910-1985) Confirmed the existence of Macromolecules to molecules of extremely high 1974 Nobel Prize show that a molecule molecular weight, but led as in Chemistry could be larger than its well to the development of unit cell (1926-28) nylon, the first totally synthetic N fiber used in consumer products. Development of industrial polymers EL PT Acknowledgement: Dr. Gerhard Maier N Development of industrial polymers EL PT Acknowledgement: Dr. Gerhard Maier 2020 onwards - the Second Century of Polymer Science N N PT EL  EL PT INTRODUCTION TO POLYMER SCIENCE PROF. DIBAKAR DHARA DEPARTMENT OF CHEMISTRY, IIT KHARAGPUR Module 01: Introduction N Lecture 02: Definitions/Terminologies, Classifications Content of Lecture 2  Some definitions/terminologies related to polymers EL  Classification of polymers PT N SOME DEFINITIONS / TERMINOLOGIES EL  Monomers, Oligomers and Polymers  Macromonomer and Telechelic Polymers/Oligomers  Repeating and Structural Unit, Degree of Polymerization (DP) PT  Different skeletal structures N  ORIGIN OF THE TERM “POLYMER” Polymer (Greek poly “many” + meros “parts”) EL  Faraday in 1826 was puzzled by the fact that ethylene and butene differed in their gas density, but had the same elemental composition.  The word “polymer” was introduced by the Swedish chemist J. J. Berzelius. He considered, for example, butene to be a polymer of ethylene and benzene of acetylene.  Staudinger adopted this definition of Berzelius. For Staudinger, polystyrene was a PT polymer of styrene. However, he objected to the use of this term for products of polycondensation.  It was Carothers in 1929 who gave a general definition of the term. He defined them as “substances” whose structures may be represented by R-R-R- where -R- are bivalent radicals which in general are not capable of independent existence” ( J. Am. Chem. Soc., 1929, 51, 2548 ) N POLYMER AND MACROMOLECULE Modern definition EL  A polymer is a substance composed of molecules which have long repetitive sequences of one or more species of atoms or groups of atoms linked to each other by primary, usually covalent bonds.  The words polymer and macromolecule are used interchangeably, but ‘macromolecule‘ strictly means the molecules of which a ‘polymer’ is composed.  Macromolecules are formed by linking together monomer molecules through chemical PT reactions, a process known as polymerization. Plastics, Rubbers (Elastomers), Fibers N POLYMER AND MACROMOLECULE EL Plastics Rubbers Silk  Very wide range of materials, properties DNA Proteins Enzymes and applications  Wide range of physical forms – solid, Collage emulsions, liquids PT Paints Cellulose n  Exhibits wide range of physical phenomenon Starch Adhesives Fibers These are all Polymers!! N Example: Polyethylene Monomer: Ethylene CH2=CH2 EL Molecular Weight = 28 g/mole Colorless, Flammable Gas at room Temperature Polymer: Polyethylene … – CH2 – CH2 – CH2 – CH2 – CH2 – CH2 –... PT Composed of hundreds to thousands of ethylene units Molecular Weight = 1,500 - 100,000 g/mole Milky white plastic solid that “melts” at 85 °C to 100 °C Polymers Consist of Large Number of Repeating Units N Macromonomer and Telechelic Polymer/Oligomer EL  Macromonomers are large monomers containing repeating units and a polymerizable group.  The term "telechelic" is proposed for polymer molecules possessing two functional terminal groups. PT N Repeat unit, Structural unit and Degree of Polymerization EL Structural units –[ PT ]n– Repeat units DP = No. of Structural Units N No. of Repeat Units = 2 × No. of Structural Units Repeat units, Structural units and Degree of Polymerization EL Structural Repeat units units –[ ]n– PT No. of Repeat Units = No. of Structural Units = DP N Find the average degree of polymerization (DP) for the following polymers with average Molecular Weight of 100,000 EL PT N Skeletal Structure  A linear polymer is represented by a chain with two ends. EL  This is true for many macromolecules, there are also many with non-linear skeletal structures Linear Cyclic (ring) Branched PT Bonded to the main chain at branch points (junction points); N characterized in terms of the number and size of the branches SKELETAL STRUCTURE Branched EL PT Dendrimers, highly branched polymers with well-defined Hyperbranched polymers, much less well-defined Brush polymers, dense linear N structure and molar mass structure and molar mass branches SKELETAL STRUCTURE Network polymers EL Three-dimensional structures PT  Each chain is connected to all others by a sequence of junction points.  These are said to be crosslinked.  Characterized by their crosslink density, or degree of crosslinking, which is related to the number of junction points per unit volume. N  Semi-interpenetrating networks and Interpenetrating networks HOMOPOLYMERS  A polymer derived from one species of monomer EL  Often used more broadly to describe polymers whose structure can be represented by multiple repetition of a single type of repeat unit which may contain one or more species of monomer unit. The latter is called a structural unit. These monomers general are not capable of polymerizing independently to form similar polymer. PT N N PT EL  EL PT INTRODUCTION TO POLYMER SCIENCE PROF. DIBAKAR DHARA DEPARTMENT OF CHEMISTRY, IIT KHARAGPUR Module 01: Introduction N Lecture 03: Classifications..cont, Nomenclature, The Big Picture, Future direction Recap of Lecture 2  Some definitions/teminologies related to polymers EL Content of Lecture 3 PT  Classification of polymers  Polymer nomenclature  The Big Picture: A bird’s eye-view of polymers  Future direction of polymer research and development N HOMOPOLYMERS EL - - - - - - --A-A-A-A-A-A-A-A-A-A-A-A- - - - - - - --[-A-]n-- PT N CATEGORIES OF COPOLYMER Arrangement of the repeat units along the polymer chain EL Statistical copolymers are copolymers in which the sequential distribution of the repeat units obeys known statistical laws (e.g. Markovian) Random copolymers are a special type of statistical copolymer in which the distribution of repeat units is truly random - - - - - - --A-A-B-A-B-A-B-B-A-A-B-A- - - - - - - PT Alternating copolymers: repeat units are arranged alternately along the polymer chain - - - - - - --A-B-A-B-A-B-A-B-A-B-A-B- - - - - - - Statistical, random and alternating copolymers generally have properties which are N intermediate to those of the corresponding homopolymers. CATEGORIES OF COPOLYMER Arrangement of the repeat units along the polymer chain EL Block copolymers are linear copolymers in which the repeat units exist only in long sequences, or blocks, of the same type. Graft copolymers are branched polymers in which the branches have a different chemical structure to that of the main chain PT N Brush copolymers CLASSIFICATION OF POLYMERS EL Basis of Classification Polymer Types Origin Synthetic, Natural, Semi-synthetic Chain Configuration Tacticity, Monomer orientation, Geometric, Line Structures Polymerization reaction product Addition and condensation Thermal Behavior Thermoplastics, Thermosets PT Crystallinity Amorphous, Semi-crystalline Application and mechanical Plastics, Fibers, Elastomers properties Volume, performance, and price Commodity, Engineering, High performance Polymerization mechanism Chain-growth and step-growth polymers N CLASSIFICATION BASED ON ORIGIN  Natural polymers: polymers from plants or animals. EL Polysaccharides: celluose, starch, cotton, Natural rubber: cis-1,4-polyisoprene Biopolymers: proteins, polynucleotides, wool, silk  Synthetic polymers: polymers that are synthesized in laboratory or in plants. Polyethylene (plastics), Nylon 6,6 (fiber), polychloroprene (rubber) PT  Semi-synthetic polymers: chemically modified natural polymers to get useful polymers Cellulose acetate (Rayon), cellulose nitrate In 1870 American inventor John Wesley Hyatt reacted cellulose nitrate with camphor at high temperature and pressure to get “celluloid” – world’s first plastic! N CLASSIFICATION BASED ON CHAIN CONFIGURATION EL  Monomer orientation Head-to-tail Head-to-head PT  Geometric or cis-trans isomerism N Poly(cis-isoprene) Poly(trans-isoprene) CLASSIFICATION BASED ON CHAIN CONFIGURATION  Stereoisomerism or tacticity EL Isotactic Syndiotactic Atactic A B A B A B A B isotactic PT A B B A A B B A syndiotactic A B A B B A A B atactic N CLASSIFICATION BASED ON POLYMERIZATION REACTION PRODUCT  Addition polymers: EL Addition reactions: two or more molecules combine to form one molecule without leaving out any small molecular by-product(s) PT N CLASSIFICATION BASED ON POLYMERIZATION REACTION PRODUCT  Addition polymers: EL Addition reactions: two or more molecules combine to form one molecule without leaving out any small molecular by-product(s) PT N CLASSIFICATION BASED ON POLYMERIZATION REACTION PRODUCT  Condensation polymers: EL Condensation reactions: two or more molecules react to form one molecule along with production of small molecular by-product(s) like water, methanol, etc. PT N CLASSIFICATION BASED ON POLYMERIZATION REACTION PRODUCT  Condensation polymers: EL PT + H2O N CLASSIFICATION BASED ON THERMAL BEHAVIOR (AND CRYSTALINIITY)  Thermoplastics : (“THERMO” = HEAT + “PLASTIC” = FORMABLE) EL  Soften with heat to a high viscosity melt, hard at room temperature, allowing them to be transformed into desired shapes that are hardened by cooling.  Can be re-melted and re-processed (recyclable)  Large, linear or branched unconnected molecules, molecules are PT entangled but not bonded to one another  Undergo no chemical reaction during molding  Constitute by far the largest proportion of the polymers in commercial production N  CLASSIFICATION BASED ON THERMAL BEHAVIOR (AND CRYSTALINIITY) EL Thermoplastic "Plastics" Crystalline Amorphous crystalline domains PT Amorphous Semi-crystalline (Tg) (Tg and Tm) amorphous domains Generally, thermoplastics do not crystallize easily upon cooling to the solid state as this requires N considerable ordering of the highly coiled and entangled chains present in the liquid state  CLASSIFICATION BASED ON THERMAL BEHAVIOR (AND CRYSTALINIITY) EL  Thermosets - THERMOSET (“THERMO” = HEAT + “SET” = HARDEN)  Begin as small molecules (low viscosity liquid)  React (“cures”) by heat, catalysis, or other chemical means to form an infinite molecular network  Network polymers in which chain motion is greatly restricted by a high degree of crosslinking - rigid materials. PT  They are permanent once formed and degrade rather than become fluid upon the application of heat. N CLASSIFICATION BASED ON THERMAL BEHAVIOR (AND CRYSTALINIITY)  Elastomers EL Thermosets  Crosslinked rubbery networks that can be stretched easily to high extensions (e.g. 3× to 10× their original dimensions), which Glassy Elastomer rapidly come back to their original dimensions when the applied stress is released.  Reflection of molecular structure in which the network is of low crosslink density. Glassy PT N CLASSIFICATION BASED ON APPLICATION (AND MECHANICAL BEHAVIOR)  Plastics EL  Fibers  Elastomers PT N CLASSIFICATION BASED ON VOLUME, PERFORMANCE, AND PRICE volume performance price EL Commodity PT Engineering High performance N N PT EL  EL PT INTRODUCTION TO POLYMER SCIENCE PROF. DIBAKAR DHARA DEPARTMENT OF CHEMISTRY, IIT KHARAGPUR Module 01: Introduction N Lecture 04: Classification by Polymerization Mechanism, Nomenclature Classification of Polymers EL Basis of Classification Polymer Types Origin Synthetic, Natural, Semi-synthetic Chain Configuration Tacticity, Monomer orientation, Geometric, Line Structures Polymerization reaction product Addition and condensation Thermal Behavior Thermoplastics, Thermosets PT Crystallinity Amorphous, Semi-crystalline Application and mechanical Plastics, Fibers, Elastomers properties Volume, performance, and price Commodity, Engineering, High performance Polymerization mechanism Chain-growth and step-growth polymers N Chain-growth and Step-growth Polymerization EL  Two main polymerization process  Chain growth polymerization: Polymer size increase successively, one by one monomer  Step growth polymerization: Polymer chains build up stepwise PT  Ring-opening polymerization (ROP)  Vinyl Polymerization with complex coordination catalyst (Coordination polymerization) N Chain-growth Polymerization Monomer Reacted  Initiator needed Monomer EL  Growth occurs by successive addition of monomer Terminated units to limited number of growing chains End  Product is the isolated polymer Initiator  No by-product formation  High MW even at low conversion PT N Chain-growth Polymerization Monomer Reacted  Predominantly carbon back-bone Monomer EL Terminated  Generally by addition reactions End  Shorter reaction time Initiator  Generally low to moderate reaction temperature PT N Example of Chain-growth Polymerization EL R * R * R * n R* PT N Step-growth Polymerization Monomer  Growth occurs throughout the matrix by reaction Reacted EL between monomers, oligomers, and polymers Monomer  No initiator needed (may require catalyst)  Product is the reaction mixture  Generally by-product formation  High MW only at very high conversion PT N Step-growth Polymerization Monomer  Predominantly Heteroatom in back-bone Reacted EL Monomer  Generally by condensation reactions  Longer reaction time and  Generally high reaction temperature PT N Step-growth Polymerization EL Monomer + monomer dimer Dimer + monomer trimer Dimer + dimer tetramer Trimer + monomer tetramer Trimer + dimer pentamer PT Trimer + trimer hexamer Tetramer + monomer pentamer Tetramer + dimer hexamer and so on N Examples of Step-growth Polymerization EL O n HO CO2H O C + nH2O n A-A PT nHO2C CO2H + nHOCH2CH2OH O O A-B C COCH2CH2O n + 2nH2O N  Chain-growth Step-growth  Initiator needed  No initiator needed EL  Growth occurs by successive addition of  Growth occurs throughout matrix by reaction between monomer units to limited number of monomers, oligomers, and polymers growing chains  Product is the isolated polymer  Product is the reaction mixture  No by-product formation  Generally by-product formation  High MW even at low conversion  High MW only at very high conversion PT  Generally by addition reactions  Generally by addition reactions  Predominantly carbon back-bone  Predominantly Heteroatom in back-bone  Shorter reaction time  Longer reaction time  Generally low to moderate reaction  Generally high reaction temperature temperature N Nomenclature of Polymers  Most polymers have more than one correct name plus variety of trade names which EL also are used to describe certain polymers Commonly used methods  Source-based nomenclature, prefix ‘poly’ before the name of the monomer within parentheses unless it is a simple single word PT  Poly(common name of the monomer)  Structure-based nomenclature (Non-IUPAC), the prefix ‘poly’ is followed in parentheses by words which describe the chemical structure of the repeat unit N  Poly(common name of the repeat unit) Commonly Used Nomenclature of Polymers Source-based nomenclature, prefix ‘poly’ before the name of the monomer within parentheses unless it EL is a simple single word n * * Cl Cl Poly(vinyl chloride) PT polystyrene Very common practice for polymers synthesized by chain growth polymerization N Commonly Used Nomenclature of Polymers Source-based nomenclature, prefix ‘poly’ before the name of the monomer within parentheses unless it EL is a simple single word H2 H2 Polyethylene oxide C C O n H2 H2 H2 H2 PT C C O C C n n O H2 H2 Poly(ethylene oxide) C C O n N Commonly Used Nomenclature of Polymers Source-based nomenclature, prefix ‘poly’ before the name of the monomer within parentheses unless it EL is a simple single word n H2N CH2 CH2 CH2 CH2 CH2 COOH * NH CH2 CH2 CH2 CH2 CH2 CO * n 6-Aminocaproic acid Poly(6-aminocaproic acid) PT H2 C H2C CO n * NH CH2 CH2 CH2 CH2 CH2 CO * NH n H2C C CH2 H2 Poly(ɛ-caprolactam) ɛ-caprolactam N Commonly Used Nomenclature of Polymers Source-based nomenclature, prefix ‘poly’ before the name of the monomer within parentheses unless it EL is a simple single word O * polymerization * hydrolysis * * HO O O O OH vinyl alcohol PT vinyl acetate N Poly(vinyl acetate) Poly(vinyl alcohol) Commonly Used Nomenclature of Polymers Structure-based nomenclature (Non-IUPAC), the prefix ‘poly’ is followed in parentheses EL by words which describe the chemical structure of the repeat unit O O * NH (CH2)6 NHCO (CH2)8 CO * * O CH2 CH2 O C C * n n Poly(hexamethylene sebacamide) Poly(ethylene terephthalate) PT Very common practice for polymers synthesized by step growth polymerization N IUPAC Nomenclature of Polymers Structure-based nomenclature (IUPAC), the prefix ‘poly’ is followed in parentheses by words which describe the chemical structure of the constitutional repeating unit (CRU) EL Poly(IUPAC name of CRU)  The CRU is the smallest possible repeating unit of the polymer. CRU of * H2C CH2 * is CH2 * Common Poly(propylene) PT n * IUPAC Poly(1-methylethylene) Polymethylene CH3 * Common Poly(vinyl chloride) Not common practice. Only used for newly synthesized * IUPAC Poly(1-chloroethylene) polymers and for polymers Cl N with complicated structures Nomenclature of General Class of Polymers  General name according to name of the functional group in the polymer backbone EL O * Polyesters * Vinyl Polymers * R O * Polysulfones n R O F F * R NH * Polyamides * R S * Polysulfides * n * Fluoropolymers O PT F n R R F * R O O * Polycarbonates * Si O * Polysiloxanes n * * Polyacetylenes O n * R O * Polyethers * R N H N * H Polyureas n * * Polyarylenes O n Polyurethanes N R O N * H n Nomenclature of Copolymers Repeat –[ ]n– units EL –[ ]n – alt – [ ]m – PT –[ ]n – co – [ ]m – N –[ ]n – ran – [ ]m – –[ ]n – block – [ ]m – Nomenclature of Copolymers Poly[styrene-co-(methyl methacrylate)] Poly[styrene-alt-(methyl methacrylate)] EL Polystyrene-co-poly(methyl methacrylate)] Polystyrene-alt-poly(methyl methacrylate)] Poly[styrene-stat-(methyl methacrylate)] Poly[styrene-block-(methyl methacrylate)] Polystyrene-stat-poly(methyl methacrylate)] Polystyrene-block-poly(methyl methacrylate)] Poly[styrene-ran-(methyl methacrylate)] Poly[styrene-graft-(methyl methacrylate)] PT Polystyrene-ran-poly(methyl methacrylate)] Polystyrene-graft-poly(methyl methacrylate)] ran ≡ r Polystyrene-b-poly(methyl methacrylate)] block ≡ b Poly[styrenen-co-(methyl methacrylate)m] graft ≡ g N Nomenclature of Copolymers EL O O O OCH2CH2O C C OCH2CH2OC C O Poly(ethylene terephthalate-co-ethylene isophthalate) PT O OCH2CH2O C O C n co O OCH2CH2OC C O m * N Nomenclature of Polymers: Some Other Points EL Trade name : The commercial names by manufacturer Teflon, Nylon Abbreviation name : PVC, PET Complex and Network polymer : Phenol-formaldehyde polymer PT Vinyl polymers: Polyolefins N Structure Monomer Common Name IUPAC Trade name EL Me Me Me * * Poly(isobutylene) Polyisobutylene Poly(1,1-dimethyl-ethene-1,4-dilyl) poly(1,1-dimethyl-ethene-1,2-diyl) Butyl Rubber Butyl Rubber n Me * * n Poly(chloroprene) Polychloroprene Poly(1-choloro-butene-1,4-dilyl) poly(1-chloro-1-butene-1,4-diyl) Neoprene Neoprene Cl Cl PT * * n Poly(cis-isoprene) cis-Polyisoprene Poly(cis-1-methyl-butene-1,4-dilyl) Latex cis-poly(1-methyl-1-butene-1,4-diyl) latex Nomenclature of Common Elastomers N MOLECULAR WEIGHT OF POLYMERS EL PT N N PT EL  EL PT INTRODUCTION TO POLYMER SCIENCE PROF. DIBAKAR DHARA DEPARTMENT OF CHEMISTRY, IIT KHARAGPUR Module 01: Introduction N Lecture 05: Molecular Weight, Big Picture of Polymer Science, Common Polymers Content of Lecture 5  Molecular Weight (Molar Mass) of Polymers EL  A Bird’s Eye-view of Polymer Science and Technology  Examples of Common Polymers PT N  EL MOLECULAR WEIGHT OF POLYMERS PT N Molecular Weight (Molar Mass) of Polymers  Polymer molecular weights are very large, typically ranging from a few thousand to a million EL  Unlike conventional chemicals, the molecular weight within any polymer sample is not uniform (polydisperse)  Owing to this non-uniformity, molecular weights of a polymer sample is expressed in average quantity  The numerical value assigned to the molecular weight of a polymer depends on the way in which the non-uniformity is averaged PT  number-average molecular weight Mn  weight-average molecular weight Mw  z-average molecular weight Mz  viscosity-average molecular weight Mv N Molecular Weight (Molar Mass) of Polymers  Polymer molecular weights are very large, typically ranging from a few thousand to a million EL  Unlike conventional chemicals, the molecular weight within any polymer sample is not uniform (polydisperse)  Owing to this non-uniformity, molecular weights of a polymer sample is expressed in average quantity  The numerical value assigned to the molecular weight of a polymer depends on the way in which the non-uniformity is averaged PT  number-average molecular weight Mn Some natural polymers  weight-average molecular weight Mw (proteins) - monodisperse  z-average molecular weight Mz  viscosity-average molecular weight Mv N Why molecular weights are important for polymers?  Importance of Polymer Molecular Weight  Polymers must have good properties  Polymers must have good processebility EL  Good properties are favored by high  Good processing is favored by low molecular weight molecular weight Mechanical Properties Ease of Processing PT Molecular Weight  Plastics market contains different grades of each polymer Molecular Weight  Some properties, such as refractive index and hardness at ambient temperatures, N are not much dependent on molecular weight Molecular Weight (Molar Mass) of Polymers  number-average molecular weight, Mn EL 1 M n = ∑ xi M i = xi : mole fraction of polymer i ∑ (wi / M i ) i molecules with molecular weight Mi in a sample wi : weight fraction of polymer PT  weight-average molecular weight, Mw molecules with molecular weight Mi in a sample M w = ∑ wi M i i N Molecular Weight (Molar Mass) of Polymers EL ∑ i i w M 2 ∑ i i N M 3 Ni : moles (or number) of polymer molecules with molecular weight Mz = i = i ∑ wi M i i ∑ i i N M 2 i Mi in a sample  ∑ Ni M 1/ a 1/ a (1+ a )   a PT i M v = ∑ wi M i  = i   i   ∑  i Ni M i   M z > Mw > Mv > Mn N Molecular Weight (Molar Mass) of Polymers EL Number Distribution Mass Distribution PT N Molecular Weight (Molar Mass) of Polymers Molecular Weight Distribution EL Dispersity, Đ = Mw/Mn (PDI = polydispersity) PT N Molecular Weight (Molar Mass) of Polymers MW = DP × m EL DP = No. of Structural Units m = MW of structural unit PT DP = MW / m DPn = Mn / m DPw = Mw / m MW = DP × m MW = n × 104 N Molecular Weight (Molar Mass) of Polymers EL Structural units Repeat PT units MW = DP × mavg MW = 2n × 192/2 MW = DP × mavg MW = (DP/2) × mRU MW = 2n × 96 mavg = Average MW mRU = MW of repeat unit MW = n × 192 N of structural units Example of Molecular Weight Calculation A sample of polystyrene is composed of a series of fractions of EL different-sized molecules: Calculate Mn, Mw and Mz; Dispersity Fraction Weight Molecular No. Fraction Weight A 0.03 6000 PT B 0.25 12000 C 0.30 15000 D 0.35 22000 E 0.15 33000 F 0.05 38000 N Example of Molecular Weight Calculation Weight Molecular ∑ (w / M ) EL i i Fraction Weight i 0.03 6000 0.5 × 10-5 180 1.08 × 106 0.25 12000 2.08 × 10-5 3000 3.60 × 107 0.30 15000 2.00 × 10-5 4500 6.75 × 107 PT 0.35 22000 1.59 × 10-5 7700 1.69 × 108 0.15 33000 0.45 × 10-5 4950 1.63 × 108 0.05 38000 0.13 × 10-5 1900 7.22 × 107 = 6.75 × 10-5 = 22,230 = 5.09 × 108 N Example of Molecular Weight Calculation Weight Molecular ∑ (w / M ) ∑ w M EL i i i i Fraction Weight i i 0.03 6000 0.5 × 10-5 180 1.08 × 106 0.25 12000 2.08 × 10-5 3000 3.60 × 107 0.30 15000 2.00 × 10-5 4500 6.75 × 107 PT 0.35 22000 1.59 × 10-5 7700 1.69 × 108 0.15 33000 0.45 × 10-5 4950 1.63 × 108 0.05 38000 0.13 × 10-5 1900 7.22 × 107 = 6.75 × 10-5 = 22,230 = 5.09 × 108 N Example of Molecular Weight Calculation Weight Molecular ∑ (wi / M i ) ∑ wi M i ∑w M 2 EL Fraction Weight i i i i i 0.03 6000 0.5 × 10-5 180 1.08 × 106 0.25 12000 2.08 × 10-5 3000 3.60 × 107 0.30 15000 2.00 × 10-5 4500 6.75 × 107 PT 0.35 22000 1.59 × 10-5 7700 1.69 × 108 0.15 33000 0.45 × 10-5 4950 1.63 × 108 0.05 38000 0.13 × 10-5 1900 7.22 × 107 = 6.75 × 10-5 = 22,230 = 5.09 × 108 N Example of Molecular Weight Calculation Weight Molecular ∑ (wi / M i ) ∑ wi M i ∑w M 2 EL Fraction Weight i i i i i 0.03 6000 0.5 × 10-5 180 1.08 × 106 0.25 12000 2.08 × 10-5 3000 3.60 × 107 0.30 15000 2.00 × 10-5 4500 6.75 × 107 PT 0.35 22000 1.59 × 10-5 7700 1.69 × 108 0.15 33000 0.45 × 10-5 4950 1.63 × 108 0.05 38000 0.13 × 10-5 1900 7.22 × 107 = 6.75 × 10-5 = 22,230 = 5.09 × 108 N Example of Molecular Weight Calculation EL 1 Mn = = 1/(6.75×10-5 ) = 14792 ∑ (wi / M i ) i M w = ∑ wi M i = 22230 i Mz > Mw > Mn ∑ i i PT 2 w M Mz = i = (5.09×108)/22230 = 22921 ∑ i i w M 2 i N  EL “The Big Picture” A Bird’s Eye-view of Polymer Science & Technology PT N “The Big Picture”: Life Stages and Transformation Processing, additives Waste design Final management EL Petroleum sources Natural fabrication, Product sources finishing, Powder assembly additives Waste Raw materials Intermediate POLYMERS Pellets product reuse / recycle (monomers) / biodegrade (Resins: PT In solution Polymerization compounding Processing, or in bulk pellet, Emulsi- granules or ons flakes) Renewable sources OR Application of Final product: polymers in sheets, films, N formulations etc. Life Stages and Transformation: Example EL PT N Structure-Processing-Property Relationships Properties EL Degree of crystallinity, PT Morphology Crystal structure Crystal orientation MW, MWD, Stereoregularity Composition Processing Thermal history Copolymer comp. Stress/strain history Environmental exposure N Some Common Polymers: Plastics EL  Commodity plastics: LDPE, HDPE, PP, PVC, PS  Engineering plastics: Acetal, Polyamide, Polysulphones, Polyarylate, Polyether ether ketones, Polycarbonate, etc.  Thermosetting plastics: Phenol-formaldehyde, Urea-formaldehyde, PT Unsaturated polyester, Epoxy, Melamine-formaldehyde  Specialty plastics: Biomaterials, etc. N Commodity Plastic Type Abbreviation Major Uses EL Low-density polyethylene LDPE Packaging film, wire and cable insulation, toys, flexible bottles housewares, coatings High-density Polyethylene HDPE Bottles, drums, pipe, conduit, sheet, film, wire and cable insulation Polypropylene PP Automobile and appliance parts, furniture, PT cordage, webbing, carpeting, film packaging Poly(vinyl chloride) PVC Construction, rigid pipe, flooring, wire and cable insulation, film and sheet Polystyrene PS Packaging (foam and film), foam insulation appliances, housewares N Major Engineering Plastics Type Abbreviation EL Acetal POM Polyamide Polyarylate Polybenzimidazole PBI Poltcarbonate PC PT Polyeseter Polyetheretherketone PEEK Polyetherimide PEI Polyimide PI Poly(phenylene oxide) PPO Poly(phenylene sulfide) PPS N Polysulfoned Major Thermosetting Plastics EL Type Abbreviation Typical Uses Phenol-formaldehyde PF Automobile parts, electrical and electronic equipment, utensil handles, plywood adhesives Urea-formaldehyde UF Similar to PF polymer; also treatment of textiles, coatings PT Unsaturated polyester UP Business equipment, construction, automobile parts, boat hulls, marine accessories Epoxy - Protective coatings, adhesives, electrical and electronics applications, industrial flooring highway paving materials, composites Melamine-formaldehyde MF Similar to UF polymers; decorative panels, counter N and table tops, dinnerware Fibers EL  Cellulosic : Acetate rayon, Viscose rayon  Noncellulosic : Polyester, Nylon (Nylon 6,6, Nylon 6, etc)  Acrylic : Contain at least 80% acrylonitrile (PAN 80% + PVC and others 20%) Rubber (Elastomers) PT  Natural rubber: cis-polyisoprene  Synthetic rubber: Styrene-butadiene, Polybutadiene, Ethylene-propylene (EPDM), Polychloroprene, Polyisoprene, Nitrile, Butyl, Silicone  Thermoplastic elastomer : Styrene-butadiene block copolymer (SBS) N Plastics Recycling Code As per the Society of the Plastics lndustry (SPI) EL Number Letters Plastic Recyclable? 1 PETE (PET) Poly(ethylene terephthalate) YES 2 HDPE High-density polyethylene YES 3 V (PVC) Poly(vinyl chloride) YES PT 4 LDPE Low-density polyethylene Due to the 5 PP Polypropylene mixture of compounds 6 PS Polystyrene these plastic 7 OTHER Others or mixed plastics types are hard to N recycle SUMMARY OF MODULE 1  Importance of Polymer Science EL  Brief History of Science of Polymers (Macromolecules)  Origin of Polymer Properties  Some definitions/terminologies related to polymers  Polymers, Macromolecules, Plastics, Rubbers/Elastomers PT  Classification of polymers  Mechanism of Polymerization  Nomenclature of Polymers  Molecular Weight (Molar Mass) of Polymers  A Bird’s Eye-view of Polymer Science and Technology N N PT EL