Polymer ClassificationsLouisiana State University 高分子分类路易斯那州立大学

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1、1Polymer Classifications: Foreword.This presentation is to be used with Chapter 2 of the Virtual Book. Students can complete their virtual book thusly:1.Make simple sketches and write ideas during the class when this material is presented.2.Improve that by making better sketches and editing a downlo

2、aded copy of Chapter2. 2Linear polymers can be represented by a simple sequence such as: A-A-A-A-A .Polystyrene Styrene monomerCHCH2nNylonTwo monomers make one repeating unit.*There many different kinds of nylon.H2N-(CH2)6-NH2Nylon monomerHOOCCOOHNylon 6,63Polydispersity is the term we use to descri

3、be the fact that not all macromolecules in a given sample have the same “repeat number” x.size#size#sizePolydisperseMonodispersePaucidisperseEven in a pure sample, not all molecules will be the same. Nature often does better than people do. #4AdditionCondensationExamplePolystyreneNylonEmpirical form

4、ulaNo change from monomer.Changes as byproduct (often water) is given off.How growsOne monomer at a timeMonomer + dimer, hexamer + octadecamer, etc. PolydispersityCan be paucidisperse“Most probable”Molecular weightWide range: can be very highLow (except biopolymers)SynonymChain growth polymerization

5、Step growth polymerizationChain growthStep growth5Addition: one monomer at a timeAlso called chain growth.Condensation: anything goes! Also called step growth. 6The molecular weight of condensation (step growth) polymers is limited to fairly low values. Condensations: usually 50,000 g/molAddition: c

6、an be quite high (e.g., 46 x 106 for polystyrene)Convert that to tons/mol Nature makes huge polycondensates, but they are usually made in chain growth fashion! Why?7There are such things as inorganic polymers. -P=N-RRxOthers: POSS, poly(phthalocyanines), many colloids (colloids are close relatives o

7、f polymers)R used to be a secret. Not sure if it still is. 8Cascade polymers are also known as dendrimers. This remains one of the hottest areas of macromolecular science. Co-invented at LSU, it is still practiced here. (McCarley, Warner, Daly, Russo)Tomalia DowNewkome LSUTomalia: now at MMINewkome:

8、 now at U. AkronFuture Nobelists?The poly(phenylene) dendrimer at left has actually been crystallized (Mullen). 9The arborol dendrimer below was made by Newkome at LSU.and we still make this one at LSU. 10Copolymers can be used to tailor functionality or generate new phases and behaviors. BlockBlock

9、 copolymer, example: Poly(styrene)-block-poly(butadiene)RandomRandom copolymer, example: Poly(styrene-ran-butadiene)GraftGraft copolymer, example: Poly(styrene)-graft-poly(butadiene)11Some chemists really care about nomenclature.Type Connective Example unspecified -co- poly(A-co-B) statistical -stat

10、- poly(A-stat-B) random -ran- poly(A-ran-B) alternating -alt- poly(A-alt-B) periodic -per- poly(A-per-B-per-C) block -block- polyA-block-polyB graft -graft- polyA-graft-polyB From the Chemistry at U. Missouri Rolla websiteJames TraynhamLSU, 200312Star polymers have the ability to act a little bit li

11、ke spheres and you can get higher Ms. f = 4Each “arm” of this star is a “random coil”. Star rods would be fun.What does that mean?A lot of the magic of polymers is just size.Suppose each of the 4 “arms” is polydisperse. Are such molecules more or less polydisperse than their linear counterparts?13Le

12、tter polymers are synthetically challenging and useful for testing theories.In Hartford, Hereford and Hampshire, Hs Hardly Happen*In Knoxville, Tennessee (home of Jimmy Mays) they do. Matters in polyolefinsmakes for better processing? Regular letter polymers help manufacturers defend billion dollar

13、patents. *Adapted from the musical, “My Fair Lady”From the Mays website14Combs, brushes and ladders give you ways to stiffen a polymer. Think “bottle brush”15Rodlike polymers are used for very high strength, liquid crystals, photonics, efficient viscosification and control of phase relations. SNSN*n

14、 Rodlike because of helixUsed in stealth bomber?Maybe. Rodlike because of linear backbone16Polyelectrolytes: strange things happen when you try to separate charges by a few Angstroms. Strong polyelectrolytes (e.g., salts of strong polyacids or polybases)Sodium polystyrene sulfonate: fully charged, y

15、et behavior depends on added saltWeak polyelectrolytes (e.g., weak polyacids or polybases)Poly(acrylic acid)Behavior depends on added salt and pHOne of the hottest areas of fundamental polymer research involves polyelectrolytes. Concentration of charge along a backbone, with charged groups closely s

16、eparated, produces some weird distortions in the moleculesand in the surrounding solution. Opposites may repel!CH3SO3NaMonomer: CH2=CH-COOHMonomer: Do they still tell you about Angstroms? 17You are made of biopolymers.R group varies one unit to the nextNHROn H18Proteins can do almost anything.Protei

17、ns are the most amazing molecules on Earth, large or small. They have 4 levels of structure, which can confer enormously high function. In particular, they make excellent catalystsyou are all “burning” fuel nowat 37oC.efficiently compared to most human-designed combustion devices! Its the proteins t

18、hat do this. They also give structure and strength and resilience. They can change their shapethe original “smart molecule”. 19The 4 levels of structure Primary: the sequence of the amino acids Secondary: helix, coil or random sheet (and a few others) Tertiary: folding of the unit, including S-S- br

19、idges Quaternary: how the blobs assemble 20Structure = FunctionMore Structure = More FunctionS-S linkSubunit aSubunit bNormal synthetic polymerProteina-Helical secondary structureb-sheet secondary structurehttp:/www.sciencecollege.co.uk/SC/biochemicals/bsheet.gifhttp:/ sheetAlpha helixhttp:/www.bios

20、ci.ohio-state.edu/prg/protein1.gif21There are 20 common, naturally occurring amino acids. http:/www.genome.iastate.edu/edu/gene/genetic-code.html#Amino Acids 22Another type of biopolymer, nucleic acids, contains the information needed to make proteins.Borrowed fromNatural Toxins Research Center Webp

21、age:http:/ntri.tamuk.edu/cell/nucleic.htmlAn interesting sub-section of the nanotech community tries to use nucleic acids as structural materials. 23Biopolymers: Nucleic AcidsRNADNACH2OPOOHOOCH2OOHPOOOHOCH2OPOOOHOOPOOOCH2OPOOOHOOHOHNNOOHUNNNNNHNNONH2OHNNNNONH2ACGRibose sugarBaseNNNNOOPOOOHCH2OOOPOOH

22、CH2OOOPOOHCH2OOOPOOHCH2OPOOONNCH3OOHNNONHHNNNHHNNONHHCH3NNNNNHOHHNNNNHHNNOOHNNONHHOCH2OPOOOHOOCH2OPOOHOOCH2OPOOHOOOCH2OPOOHTGACACTG3553.24Nucleic acids code proteins, a molecular “build sheet”Nucleic acids are how we get (or “code”) proteins. There are 4 bases (called A,T,G,C). Three of these in a r

23、ow gives a codon which tells the cellular machinery to add a particular amino acid. Nucleic acids are much less prevalent than proteins, in the same sense that auto factories are less prevalent than automobiles. They make interesting model polymers for a variety of studiesfrom better understanding o

24、f polymer flexibility to liquid crystal behavior. You can get a list of the codons for the various amino acids at: http:/www.genome.iastate.edu/edu/gene/genetic-code.html#Amino Acids25Networks (Gels) combine the properties of liquids and solids.Keep on branching. The ultimate molecule: M = It only t

25、akes a little polymer (a few percent by weight) to turn the water to a nominal solid, and the polymers in gelatin are held by noncovalent forces. Making the network for a tire involves significantly more polymer and covalent forces are involved. High-Speed Jello VideoCLICK IT! High-Speed Jello Video

26、CLICK IT! The Gentrys Sing Keep on Branching (or something like that) CLICK FOR SONG! High-speed Jello VideoCLICK IT! Pathetic Cover of Keep on Branching by Boy Band Bay City Rollers CLICK FOR SONG! 26Thermoplastic/Thermoset is another big distinction.Macromolecular chemistry involves chemists, biol

27、ogists, physicists, and various engineers. The engineers, just like average citizens, have very little use for a molecular point of view. They tend to divide the polymer world into thermoplastic and thermoset “resins”. Thermoplastic: when you heat it, it flows (e.g., polyethylene, polystyrene) Therm

28、oset: when you heat it, it “sets up” into a solid (e.g., epoxy glue, styrene monomer)We assist the Chemical Educational Foundations You Be the Chemist Challenge program, a middle school “quiz bowl” that impacts 16,000 students in 22 states. This year, we have focused on vetting the thousands of ques

29、tions it takes to operate Challenge. To give Challenge a more “hands-on” and “real-world” flavor, the Louisiana champion, Hayden Day, studied from a new Louisiana Playbook we are designing (see sample question below and figure at left). Silica-Polypeptide Composite Particles Paul S. Russo (Louisiana

30、 State University), DMR-Award #1005707Louisiana YBTC Playbook, Problem #25. The sequence of pictures at left shows the repair of the polymeric skin of an automobile bumper which was torn during a wreck. The repair consists of pushing the parts together closely, holding them with tape on the outside

31、(red) part, and “welding” them on the inside (black) side using a soldering iron. Question 1: Is the bumper a thermoset or a thermoplastic?Question 2: Suppose instead of a torn bumper we had a gashed tire made from vulcanized rubber. Would heating a vulcanized rubber repair the tire? Question 3: Exp

32、lain how polymer welding works at a molecular level. Grad student Javoris Hollingsworth teaches 8th-grader Hayden Day, the 2012 Louisiana state champion in the Chemical Educational Foundations You Be the Chemist Challenge, about titrations. Barely visible in the background is Haydens Mom, a school t

33、eacher. Haydens father, a chemical plant technician, is looking on too. Dad studied every day with his son, and Hayden acquitted himself well in the national competition in Philadelphia in June. 28Polymers can be amorphous, crystalline, or a bit of bothcorresponding to brittle, gooey and tough (over

34、simplified!). Polymers can be solid without crystalline structures. These are called glasses. Polymers can be crystalline (amazing). Most useful polymers a little bit of bothregions in the material have crystalline inclusions and other regions are amorphous. These materials are often toughthe amorph

35、ous regions absorb shock. 29TransitionsWe deal with this later, but even from the outset you should know a little bit. Glass transition is the temperature BELOW which the amorphous regions of a sample start to act like solids.Melting transition is the temperature ABOVE which the crystalline regions of a sample start to act like fluids. Either way, these are oversimplificationsbig molecules have a number of transitions that describe the chain mobility. These molecular transitions, in turn, impact the physical propertiesfrom “feel” to “stickiness” (tack) to elongation and breakage.