Polymers Reactions and Polymers Production (3 rd cycle)

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1 MEQ, MQ, DEQuim, DQuim 2 nd semester 2017/2018, IST-UL Science and Technology of Polymers (2 nd cycle) Polymers Reactions and Polymers Production (3 rd cycle) Lecture 1

2 Block 1 Fundamentals of Macromolecular Chemistry: Definitions, nomenclature, polymer classifications. Macromolecular structure and characterization. Polymer solutions. Average molecular weight and molecular weight distributions: definitions and methods of determination. Lectures 1 to 6

3 INTRODUCTION

4 Statistical data

5 (annual sales volume net)

9 Fundamentals of Macromolecular Chemistry

Polymers Poly many mers parts (greek) A polymer is a long-chain molecule composed of a large number of repeating units (monomer residues) of

n = number of repeating units in a polymer chain = degree of polymerization (DP) M W (Polymer) =DP M W (Repeating Unit) Polymers: macromolecules of

Secondary bondings (Van der Waals) According to IUPAC, polymers are named by poly(monomer) Example: Polystyrene (PS) Repeating unit (RU): styrene,

10 Polymers Poly many mers parts (greek) A polymer is a long-chain molecule composed of a large number of repeating units (monomer residues) of identical structure. n = number of repeating units in a polymer chain = degree of polymerization (DP) M W (Polymer) =DP M W (Repeating Unit) Polymers: macromolecules of relative molecular weight of at least 1000 or a DP of at least 100 The repeating units are covalently bonded to each other. Secondary bondings (Van der Waals) According to IUPAC, polymers are named by poly(monomer) Example: Polystyrene (PS) Repeating unit (RU): styrene, C 8 H 8 Structure of polyethylene (PE) (crystalline region) Thermal and mechanical properties depend on n: DP or n > 1000 Mw (styrene) = 104 average Mw of PS = brittle solid that does not soften until it is heated to ca. 100ºC DP or n=7 viscous liquid at RT Note: when n<10 oligomers (oligo = some )

11 Polymers Poly many mers parts (greek) Some polymers are derived from the mutual reaction of two or more monomers that are chemically similar but not identical. Example: Nylon 6,6 The RU consists of two structural units, residues of both monomers employed

12 Questions What is the degree of polymerization of a sample of polyethylene which has a molar mass of g/mol? (R: 3570 mers/mol)

13 Typical properties of polymers (Appendix): - Insulators - Amorphous or semi-crystalline - Low density - Varied strength and ductility - Tend to degrade or melt at higher temperatures (e.g. T>200ºC) - Corrosion resistant - Tend to be flammable

14 History 1. Natural polymers Natural rubber (isoprene) Polysaccharides (cellulose, cotton, starch) Proteins (wool, silk) 2. Synthetic polymers (commodities) PE, PP, PS, PVC, PET 3. Engineering Polymers PMMA, PC, PU, POM, PPO, 4. Functional polymers 5. Biopolymers Naturally Occurring Polymers

Milestones in polymer industry Prior to the early 1920's, chemists doubted the existence of molecules

.. Polymers were thought to be aggregates of small molecules linked by secondary forces (Van der Waals)

covalently bonded (high molecular weight molecules) Notion of Mw and its determination by viscometry

15 Milestones in polymer industry Prior to the early 1920's, chemists doubted the existence of molecules having molecular weights greater than a few thousand... Polymers were thought to be aggregates of small molecules linked by secondary forces (Van der Waals) Celluloid Staudinger ( ) proposed that in many macromolecules the repeating units were covalently bonded (high molecular weight molecules) Notion of Mw and its determination by viscometry Bakelite (phenol-formaldehyde resin) the 1st fully synthetic polymer Carothers (1931): 1 st polycondensation reactions (polyesters, polyamides) leading to high Mw polymers

16 from Introduction to Physical Polymer Science, 4th Ed., L.H. Sperling, John Wiley & Sons, Inc., 2006

17 Milestones in polymer industry Development of high performance engineering plastics that could compete with more traditional materials, such as metals in automotive and aerospace applications

18 Polymers classification by: Natural or synthetic Polymerization mechanism (condensation, addition) Polymer structure: Chemical structure: - Homopolymers or copolymers; - Characteristic interunit linkage: polyolefins, unsaturated polyolefins, vinyl resins, acrylic resins, styrenic resins, polyesters, polyamides, polycarbonates, polyurethanes, polyureas, Chain topology: linear, branched, cross-linked, ladder Stereoregularity: syndiotatic, isotatic, atatic Thermoplastics, thermosets, elastomers, fibers Inorganic backbone or organic backbone Amorphous or crystalline

Types of polymers Thermoplastics 85% Thermosets 56% 15% Elastomers 11% Fibers 18% 90% Commodities: HDPE, LDPE/LLDPE, PP, PVC, PS, PET

melamine-formaldehyde, ) Unsaturated poliesters Epoxides Polyurethanes Chemically cross-linked (isoprene, butadiene, isobutylene, )

and non-cellulosic Polyester (PET); Polyamides (PA 6,6); Acrylic (PAN), Polyolefinic (PP) ) one of the monomers must be trifunctional or

19 Types of polymers Thermoplastics 85% Thermosets 56% 15% Elastomers 11% Fibers 18% 90% Commodities: HDPE, LDPE/LLDPE, PP, PVC, PS, PET Engineering: PA, PC, PMMA, POM, PU, Speciality: Kevlar, Kapton, PEEK, Phenolics (phenol-formaldehyde) 90% Amino-based (urea-formaldehyde, melamine-formaldehyde, ) Unsaturated poliesters Epoxides Polyurethanes Chemically cross-linked (isoprene, butadiene, isobutylene, ) Physicaly cross-linked / thermoplastic elastomers (ABS, SAN, SBS, ) 50% Natural (cellulosic cotton, wool, silk ) 70% Synthetic (cellulosic and non-cellulosic Polyester (PET); Polyamides (PA 6,6); Acrylic (PAN), Polyolefinic (PP) ) one of the monomers must be trifunctional or greater. Insoluble; rigid, breakable, higher termal and mechanical resistance Inorganic polymers Silicones, polysilanes Polyphosphazenes Polygermanes, polystannanes

20 Adhesives and sealants Hot melts (thermoplastics); Contact (termoplastics + ); Structural (thermosets) Paints and coatings Solvent-less o Non-reactive: hot-melt; Reactive: photoresists Solvent-based o Non-reactive: lacquers, inks (latex/emulsions) o Reactive: varnishes, inks (pigments, solvents) Biological polymers Polysaccharides (cellulose, starch / amylopectin, chitin / chitosan,...) Lignin Proteins (wool, silk,...) Phosphoric acid polyesters (nucleic acids,...) Aliphatic polyesters (poly-b-d-hydroxy-butyrate, suberin,...) Polyprenes (natural rubber (polyisoprene-cis),...)

21 The ultimate mechanical properties of any polymer result from a balance of: Molecular weight or molecular weight distribution Chemical structure The structure and molecular weight condition the intermolecular forces: Hydrogen bonds Van der Waals forces permanent dipole - permanent dipole (Keesom forces) permanent dipole - induced dipole (Debye forces) instantaneous dipole - Induced dipole (London forces) Ion-dipole forces

22 Kevlar : Absence of aliphatic units in the main chain: high thermooxidative stability; highly crystalline material, forming a stronger fiber than that of steel on an equal weight basis

23 Number of carbon atoms in the chain matters PE chains are long enough to connect individual stems together within a lamellar crystallite by chain folding Comparison of paraffin wax and polyethylene structure and morphology:

24 Polymers structure

25 Polymers structure Primary Relates to the chemical structure (atomic composition) of the monomers. Results from the covalent bonds between RUs: Homopolymers/Copolymers Chain topology: linear, cyclo-linear, branched, crosslinked (macromolecular networks), Natural Macromolecules Secondary Relates to the size (M w ) and shape (conformation and configuration) of an isolated single macromolecule (single polymer chain). Results from the spatial arrangement of the main chain segments, dictated by stereochemistry (most stable conformation) or H bonding. Tertiary Aggregation of polymer chains Results from 3D structure of the chain dictated by intramolecular forces and H bonds between distant segments of the chain Quaternary Results from the interaction between different chains

26 Chemical structure Homopolymers Only one type of RU It should be noted that some polymers, such as nylon 6,6 and PET have RUs composed of more than one structural unit these are still considered homopolymers! Copolymers Composed of two or more RUs. Called terpolymer if there are 3 RUs. Different sequences depending on the monomers reactivity: Random (statistical) Alternating (regular) NH nylon 6,6 (polyamide 6,6). CH 2 6 NH C O O CH 2 C. 4 Block (regular) Ex. of ABA-triblock: PS-block-polybutadiene-block-PS (SBS) Graft (regular) by polymerizing a monomer in the presence of a fully formed polymer of other monomer (e.g. elastomeric SBR, and high impact polymers: high-impact PS and ABS)

27 Some common homopolymers and their typical applications

28 Some common homopolymers and their typical applications

29 Some common homopolymers and their typical applications

30 Questions A copolymer consists of 35 wt% acrylonitrile and 65 wt% styrene. Determine the mole fraction of the two components of this copolymer. (R: 0.51 and 0.49)

31 Skeletal structure (chain topology) Depends on the functionality of the monomers (mono, bi or multifunctional) Linear: chain with two ends (the sequence of linkages between bifunctional monomers is necessarily linear) Branched: side chains of significant length bonded to the main chain (reaction between polyfunctional molecules) Network polymers: 3D structure in which each chain is connected to all others by a sequence of junction points and other chains; characterized by their cross-linking density (number of junction points per unit volume): Loose networks: low cross-linking density (e.g. vulcanization (i.e. sulphur cross-linking) of natural rubber) flexible elastomer (elementary chain, i.e. portion of chain in between 2 branching points, is more than 5 monomeric units) Cross-linked: high cross-linking density rigid plastic

32 Linear E.g.: extra pair of electrons in the double bond of styrene 2 bonds styrene is bifunctional PS has linear structure Two condensable groups in hexamethylenediamine (-NH 2 ) and adipic acid (-COOH) makes each of these monomers bifunctional nylon 6,6 has linear structure Carbon chain linear polymers: HDPE, PP, PIB, PS, polybutadiene, polyisoprene Polymers containing halogen substituents: PVC, PTFE, polychloroprene Polymers with polar side groups: PMMA, poly-hema, polymethylacrylate, poly acrylic acid, poly methacrylic acid, poly sodium acrylate, poly cyano ethyl acrylate, poly acrylonitrile, poly vinylacetate, poly vinylbutyrate, polyvinylalcohol, poly vinylpyrrolidone, poly vinylcarbazole Heteroatoms chain polymers: Polyethers (poly oxymethylene - POM, poly ethylene oxide PEO); Polyesters (poly ethylene terephtalate PET); polyanhydride; polyamides (poly caprolactam), nylon 6,6, Kevlar,..); PC, PU, PUs, poly isocyanates, Polymers containing sulphur in the main chain: poly sulfone, Inorganic chain polymers: polymeric sulphur ( -S-S-S-S- ), polysilanes ( -Si-Si-Si- ), poly siloxanes or silicones ( -Si-O-Si-O-Si ), polyphosphazenes, T m (linear PE) is 20 C higher than T m (branched PE) the presence of polar pendant groups can considerably reduce room temperature solubility.

33 Linear Examples of some important Addition polymers (chain reaction polymerization) derived from ETHYLENE

34 Linear Stepwise structures (polycondensation reactions) and nomenclature Examples of some functional groups and their characteristic interunit linkage in polymers:

35 Cyclo-linear Polymers with alternating cyclic-linear fragments: poly phenylene oxide, poly vinyl acetal, poly vinyl butyral, Polymers with bonded rings: poly p-phenilene, poly imides, poly phenylsilsesquioxane, poly imidazo-pyrrolone, cyclization of polyacrylonitrile

36 Cross-linked Unlike linear and branched polymers, cross-linked polymers do not melt upon heating and will not dissolve, though they will swell considerably in compatible solvents. Examples: phenol-formaldehyde, unsaturated polyesters, polyurethanes, epoxys, E.g. EPOXIES exist at ordinary temperatures as low-molecular weight viscous liquids or PREPOLYMERS, such as DGEBA: The transformation of this viscous liquid into a hard, cross-linked 3D molecular network involves the reaction of the prepolymer with reagents such as amines or Lewis acids CURING reaction. 1 st ) attack of an epoxide group by the primary amine: 2 nd ) the combination of the resulting secondary amine with a secondary epoxy group to form a branch point:

37 Cross-linked The presence of these branch points ultimately leads to a cross-linked infusible and insoluble polymer with structures such as: The stoichiometry in this reaction requires 1 epoxy group per 1 active hydrogen (amine hydrogen), which means that components should be mixed in the proportion 1:1 (equivalent weigths), i.e. EEW/AHEW.

38 Loose networks H 3 C C C H H 2 C CH 2 Example: Natural rubber (poly isoprene) borracha natural H 3 C C C H. CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 C H 3 C C H H 3 C C C H C H 3 C C H 3 C C CH 2 CH 2 H C H CH 2. Heating the elastomer with sulfur and an accelerator, or with peroxides, nitro, quinones or azo compounds, depending on the polymer Vulcanization (light cross-linking) (>5 RUs between 2 branching points) Lightly cross-linked (vulcanization) long-range movement of the polymer molecules is restrained at the same time that high local segmental mobility is allowed large deformations under stress, but rapid and complete recovery of such deformation when stress is removed

39 Questions How much sulfur must be added to 100 g of polyisoprene rubber to cross-link 5% of the monomer units? Assume that all the sulfur is used and that only one sulfur atom is involved in each cross-link (S 1 ). (R: 2.4 g sulfur)

40 Ladder polymers Ladder polymers, double-chain or double-strand polymers: two parallel linear strands of molecules with a regular sequence of crosslinks. Two bonds must be broken at a cleavage site in order to disrupt the overall integrity of the molecule higher thermal and mechanical stability than linear polymers Ex: poly(imidazopyrrolone) Aromatic dianhydride (Pyromellitic dianhydride) Ortho-aromatic tetramine (1,2,4,5- tetraaminobenzene)

Chapter 13 - Polymers Introduction

Chapter 13 - Polymers Introduction I. Nomenclature A. Polymer/Macromolecule polymer - nonmetallic material consisting of large molecules composed of many repeating units - from Greek: poly (many) and meros