Poly chemistry 4

• Polydispersity index: 𝑃𝐷𝐼 = 𝑀𝑤𝑀𝑛.
• Radical polymerization is insensitive to contamination and water.
• Living polymerization is also referred to as “controlled radical polymerization”.
• Typical polymers made from chain-growth polymerization include polyethylene, polypropylene, polystyrene, and polyvinylchloride.
• Polymers from step - growth polymerization usually have a hetero-atom in their backbone.
• The “grass” mechanism in living polymerization means all polymers grow at a similar rate.
• Dibenzoyl peroxide (DBP) and Azoisobutyronitrile (AIBN) are other radical initiators used in radical chain growth.
• In step - growth polymerization both ends are still reactive.
• X stabilizes the radicals in polyethylene, very harsh conditions are necessary: 1700 atm, 75 ° C.
• Once the polymer is long enough, the initiator is not needed in radical chain growth.
• In chain-growth polymerization, the extent of reaction is represented as 𝑁0 minus 𝑁, where 𝑁0 is the number of molecules originally present in the system and 𝑁 is the number of molecules present in the system at any time t.
• Ph = phenyl = is a radical initiator used in radical chain growth.
• The general structure of a monomer is represented as:
• In kinetics, the rate determining step is the slowest step that limits the overall reaction rate.
• The “popcorn” mechanism in living polymerization allows for big jumps in molecular weight.
• In chain growth polymerization, typical polymers made include polyethylene, polypropylene, poly styrene, and polyvinylchloride.
• Radical chain growth involves three steps: initiation, propagation, and termination.
• In radical chain growth, the monomer is ethylene, the simplest monomer.
• The general structure of a vinyl monomer is: double bond, some pendant group, poly methylmethacrylate.
• Radical chain growth takes place in three steps: initiation, propagation, and termination.
• Several possibilities exist for the radical initiators used in radical chain growth.
• Atom Transfer Radical Polymerization (ATRP) involves adding monomers to a dormant state, where the initiator is a Brush polymer or Star-shaped polymers.
• The propagation step in ATRP involves 𝑅 𝑀 𝑛 ̇ + 𝑀 𝑘 𝑝 𝑅 𝑀 𝑛 + 1 ̇.
• For ATRP, the initiator is the special part and involves Cu.
• Steady state approximation in ATRP assumes initiation and termination proceed at same rate, 𝑟 𝑖 = 𝑟 𝑡 2 𝑘 𝑑 𝑓 [𝐼].
• Initiator efficiency of 𝑅 ̇ to propagate chains is 0.
• Rate determining step 1 in ATRP involves 2-step initiation with 2 initiators per monomer.
• The termination step in ATRP involves 𝑟 𝑡 = 2 𝑘 𝑡 𝑅 𝑀 𝑛 ̇ 𝑅 𝑀 𝑚 ̇ 𝑘 𝑡.
• The dithioester in RAFT is typically present in large excess because the RAFT agent is present in large excess.
• The main product of RAFT is the dithioester, which is the desired product.
• In the propagation step of RAFT, 𝑃 𝑛 + 𝑀 → 𝑃 𝑛 + 1 ̇.
• Molecular weight distribution in RAFT is controlled by the number of polymer chains, with a typical number of polymer chains being 𝑀 𝑤 # of polymer chains.
• RAFT also involves a pre-equilibrium state, where 𝑅 ̇ + 𝑀 → 𝑃 𝑚 ̇ 1.
• The product of RAFT is a dithioester, which allows radicals to delocalize and can initiate other radical reactions, useful for block-copolymers.
• In the termination step of RAFT, 𝑃 𝑚 + 𝑀 → 𝑃 𝑚 + 1 ̇.
• Controlled radical polymerization techniques such as Atom Transfer Radical Polymerization (ATRP) and Reversible addition fragmentation transfer (RAFT) result in a linear increase in the degree of polymerization with the conversion, low polydispersity index (PDI ≤ 1.3), high level of end functionalization, possibility of the synthesis of block copolymers, and typical fr.
• The RAFT mechanism involves three steps: initiation, propagation, and termination.
• In the initiation step of RAFT, 𝑃 ̇ + 𝑀 → 𝑃 1 ̇.
• Reverse addition fragmentation transfer (RAFT) involves an initiator and a RAFT agent.
• In the re-initiation step of RAFT, 𝑃 𝑚 ̇ 1 → 𝑃 𝑚 ̇.