3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)3.012 Fund of Mat Sci: Structure – Lecture 23GLASSESImage removed for copyright reasons.A photonic fiber made from polymeric and chalcogenide glasses (Prof. Fink)3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Homework for Fri Dec 2• Study: Chapter 2 of Allen-Thomas (2.5 excluded)3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Last time: 1. Pair correlation functions2. Bernal’s model of hard spheres, Voronoipolyhedra3. Polymers: homo and co-polymers, tacticity, glass transition, termoplastics-elastomers-thermosets, addition or condensation polymerization, chain or step growthFigure by MIT OCW.Rate of coolingFastSlowαgΤgα1ΤVXL(T)V (T)3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Glass transition temperatureTable removed for copyright reasons. See page 39, Table 2.2 in in Allen, S. M., and E.L. Thomas. The Structure of Materials. New York, NY: J. Wiley & Sons, 1999.See Allen and Thomas, p. 39, table 2.2.3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Classification: mechanical• Thermoplastics: (linear, or at most contain branches). Melting temperature, and a glass temperature. Recyclables.• Elastomers: low degree of cross-linking (rubbers)• Thermosets: high-degree of cross-linking, structural rigidity3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Classification: structurexxFlexible CoilRigid RodCyclic (Closed Linear)PolyrotaxaneInterpenetratingNetworksDensely Cross-LinkedLightly Cross-LinkedRegular Star-BranchedRegular Comb-BranchedRandom Long BranchesRandom Short BranchesRegular DendronsControlled Hyperbranched(Comb-burstTM)Random HyperbranchedDendrimers(StarburstR)LINEAR CROSS-LINKED BRANCHED DENDRITIC(I) (II) (III) (IV)1930's- 1940's- 1960's-1980's-Figure by MIT OCW.3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Random walks: size of polymers3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Mean Square Displacements3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Mean Square Displacements3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Packing Fraction in Polymeric Glasses3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Solvent quality factor202020201010101010101010Poor SolventGood SolventSolvent InSolvent OutLocal Picture Global PictureSolvent quality factorα2 = < r2 >θ< r2 >θ − Solvent Figure by MIT OCW.3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Theta condition• In a good solvent the chain will expand –interaction between the polymer and the solvent is favored, and solvent-monomer contacts are maximized (and monomer-monomer contacts are minimized).• In a poor solvent the chain will contract, to reduce interactions with the solvent. In practice, difficult to study (polymer will precipitate away).•At the theta condition α=1Self-avoiding random walk3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Prof N. Thomas 3.063RWSARWFigure by MIT OCW.Figure by MIT OCW.3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Diffusion: Rouse chain• Low molecular weight linear polymers:• An elastic string of Brownian particles in a viscous medium: diffusion=1/NFigure by MIT OCW.Large molecular weight: Reptation3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Figure by MIT OCW.3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)MonomerRepeating UnitPolymer NameUsesCH2 = CH2CH2 = CH _ CH3CF2 = CF2CH2 = CHClCH2 = CH _ CH2 _ CH _ CH2 = CHC = N=CH2 = C _ CH3COCH3=OCH2 = CHOCCH3=O_ CH2_ CH2_ _ CF2_ CF2_ C = N=_ CH2_ CH _ Cl_ CH2_ CH_ CH3_ CH2_ CH _ COCH3=OCH3CH2COCCH3=OCH2CHPolyethylenePoly(vinyl chloride)PolypropylenePolystyrenePoly(tetrafluoroethylene)TeflonPoly(acrylonitrile)Orlon , AcrilanPoly(methyl methacrylate)Plexiglas , LucitePoly(vinyl acetate)Film, toys, bottles, plastic bags"squeeze" bottles, pipe, siding,flooringMolded caps, margarine tubs,indoor/outdoor carpeting, upholsteryPackaging, toys, clear cups,egg cartons, hot drink cupsNonsticking surfaces, liners,cable insulationRugs, blankets, yarn, apparel,simulated furLighting fixtures, signs,solar panels, skylightsLatex paints, adhesivesRR RR RFigure by MIT OCW.3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)MonomerCopolymer Name UsesCH2 = CH ClCH2 = CClCl+Vinyl chloride Vinylidene chlorideCH2 = CH CH2 = CHC = N+Styrene AcrylonitrileCH2 = CH Styrene=CH2 = CHCH = CH2CH2 = CHC = CH2 CH3CH2 = CHC = NAcrylonitrile=CH2 = CCH3CH3+++1, 3-butadieneSaranSANABSButyl rubberFilm for wrapping food.Dishwasher-safe objects, vaccum cleaner parts.Bumpers, crash helmets, telephones, luggage.Inner tubes, balls, inflatable sporting goods.Isobutylene IsopreneFigure by MIT OCW.3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Network models: Continuous random network• Monofunctional (dimers), bifunctional(linear chains), trifunctional or more (networks)Images removed for copyright reasons. See page 65, Figure 2.20 in Allen, S. M., and E.L. Thomas. The Structure of Materials. New York, NY: J. Wiley & Sons, 1999.3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Oxide glasses• Zachariasen constraints:– Each oxygen linked to not more than 2 cations– Functionality of central cation small– Oxygen polyhedra share corners– At least three corners of each polyhedron shared3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Quartz and silicaFigure by MIT OCW.Figure by MIT OCW.3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Network modifiersDiagram of the effect of the lead-to-phosophorus ratio on phosphate glass removed for copyright reasons.See page 71, Figure 2.25 in Allen, S. M., and E. L. Thomas. The Structure of Materials. New York, NY: J. Wiley & Sons, 1999.3.012 Fundamentals of Materials Science: Bonding - Nicola Marzari (MIT, Fall 2005)Chalcogenide glassesDiagram of the schematic bonding pattern of a chalcogenide network glass removed for copyright reasons.See page 72, Figure
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