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Polymer
| Term | Definition |
|---|---|
| Chain Transfer Agent | Stops growth of chain and transfers radical to start another chain |
| Chain Stopper | Mono functional reactant condensation polymer lowers molecular weight |
| Transesterification | Chemical reaction that turns one ester into another (ester exchange) |
| Natural Induction Time | Characterizes start of polymerization |
| Critical Micelle Concentration | The surfactant concentration above which micelles form and below which only monomers exist |
| Ideal Coploymerization | Ideal concentration of polymer = concentration in reactor |
| Asymmetric Carbon Atom | 4 different substituents on a carbon |
| Isotactic | A polymer whose substituents are all on the same side of the polymer chain |
| Solubility Parameter | Measures a material's self-cohesion; similar δ values means better solubility |
| Living Polymerization | Chains continue to grow as long as there is monomer available. No termination, radical is alive, one way to make a block polymer |
| Condensation Polymers | Polymers formed when monomers join and eliminate small molecules (like water or methanol) as byproducts. Chain stopper, functionality = 2 |
| Addition Polymers | Polymers formed when monomers add together without eliminating any byproducts. Chain transfer reactions |
| Monomer | A small molecule that can chemically bond to form a polymer chain |
| Degree of Polymerization (DP or Mₙ) | The average number of monomer units in a polymer chain |
| Number Average Molecular Weight (Mₙ) | Total weight of all polymer molecules divided by their total number |
| Weight Average Molecular Weight (Mw) | Weighted by molecular weight; larger chains contribute more |
| Polydispersity Index (PDI)` | Mw/Mn; measures molecular weight distribution |
| Step Growth Polyermization | Polymer forms by stepwise reactions between functional groups of monomers or oligomers |
| Extent of Reaction (p) | Fraction of functional groups that have reacted in step-growth polymerization |
| Carothers Equation | Related DP to the extent of reaction: Xn = 1/(1-p) |
| Initiation | Formation of an active center |
| Propagation | Monomer addition to the growing active chain end |
| Termination | Deactivation of the active chain end by combination or disproportionation |
| Chain Transfer | Transfer of the active center from a growing chain to another molecule |
| Inhibitor | Substance that destroys radicals and prevents polymerization |
| Retarder | Substance that slows polymerization without stopping initiation |
| Cationic Polymerization | Polymerization via a positively charged carbocation active center |
| Anionic Polymerization | Polymerization via a negatively charged carbanion active center |
| Living Polymerization | No termination or chain transfer; allows controlled chain length and block copolymer formation |
| Ziegler-Natta Catalyst | A metal-alkyl complex that controls polymer stereochemistry |
| Metallocene Catalyst | A single-site organometallic catalyst used for precise control of polymer microstructure |
| Stereoregularity | Ordered arrangement of side groups along the polymer chain |
| Copolymer | Polymer made from two or more different monomers |
| Reactivity Ratio (r1, r2) | The relative reactivity of a growing chain end toward each type |
| Alternating Copolymer | Monomer units alternate regularly along the chain (r1r2 < 1) |
| Random Copolymer | Monomer sequence is statistical (r1r2 = 1) |
| Block Copolymer | Long blocks of each monomer type (r1r2 >1) |
| Flory-Huggins Interaction Parameter (χ) | Quantifies polymer-solvent interactions; lower χ means better solubility |
| Theta Temperature | Temperature where polymer-solvent interactions are ideal (χ = 0.5) |
| Flory Distribution | Describes the chain-length distribution in step growth polymerization |
| Most Probable Distribution | Probability that a polymer chain has degree of polymerization x: Nx=N0(1−p)p^(x−1) |
Created by:
kcs3414