Polymer Clasifications Louisiana State University 高分子分类路易斯安那州立大学.pptVIP

* The question also comes with a hint to Google “reptation”. Javoris Hollingsworth is the recipient of an international NSF postdoctoral fellowship, which he will use to return to China (Charles Han’s new SANS instrument). Javoris’ first visit to China was NSF-paid, too (IGERT) so now he is capitalizing on the contacts he made there. Javoris is going to be the best ambassador this country has in China! * Polymer Classifications: Foreword. This presentation is to be used with Chapter 2 of the Virtual Book. Students can complete their virtual book thusly: Make simple sketches and write ideas during the class when this material is presented. Improve that by making better sketches and editing a downloaded copy of Chapter2. * Linear polymers can be represented by a simple sequence such as: A-A-A-A-A . Polystyrene Styrene monomer Nylon Two monomers make one repeating unit.* *There many different kinds of nylon. Nylon 6,6 * Polydispersity is the term we use to describe the fact that not all macromolecules in a given sample have the same “repeat number” x. size # size # size Polydisperse Monodisperse Paucidisperse Even in a pure sample, not all molecules will be the same. Nature often does better than people do. # * Addition Condensation Example Polystyrene Nylon Empirical formula No change from monomer. Changes as byproduct (often water) is given off. How grows One monomer at a time Monomer + dimer, hexamer + octadecamer, etc. Polydispersity Can be paucidisperse “Most probable” Molecular weight Wide range: can be very high Low (except biopolymers) Synonym Chain growth polymerization Step growth polymerization Chain growth Step growth * Addition: one monomer at a time Also called chain growth. Condensation: anything goes! Also called step growth. * The molecular weight of condensation (step growth) polymers is limited to fairly low values. Condensations: usually 50,000 g/mol Addition: can be quite high (e.g., 46 x 106 for polystyren