8. Step Growth Polymerization Flashcards
How does step growth and chain growth differ in propagation?
In a step growth reaction, the growing chains may react with each other to form even longer chains. In chain growth only monomers react with growing chains. Two growing chains can’t join together the way they can in a step growth polymerization.
When does functional end groups make the biggest difference for the polymer’s properties?
With low molecular weight polymers the effect will be larger than for large molecular weight polymers.
What are the 4 main ways to make polyesters?
esterification, transesterification, Hacyl chloride + alchohol, Clanhydride + alcohol
What is interfacial synthesis
Interfacial polymerization is a type of step-growth polymerization in which polymerization occurs at the interface between two immiscible phases (generally two liquids), resulting in a polymer that is constrained to the interface
Which polymerization mixture would be easiest to bring to high MW?
- A-B monomers system
- A-A and B-B monomers system
- A-A and B-B monomers system with the acid being vinyl esters
- A-A and B-B monomers system with the acid being acid chlorides
System based on A-A and B-B monomer as a general rule, although the two last options are also ok.
Which species would you expect to be the most abundant after some hours of polymerization time?
- Monomer
- Dimer
- Oligomer
- Polymer
Oligomers. In step growth the monomers are quickly used up and dimer and trimers are created. They will further react and become oligomers, but not the wanted polymers until at the of the reaction (24-72h).
What would be the main reasons for imposing a stoichiometric imbalance in an A-B system (by monofunctional reagents)?
- To decrease molecular weight
- To protect active chain ends
- To ensure one type of end groups
What are chelates?
Complexes between polydentate ligands and metalions, with several separate bindings from same ligand to same metalion
