Lab synthetic methods are usually separated into two groups, first group is step-growth polymerization and second is chain-growth polymerization.
The essential modification between the two is that in chain growth polymerization, monomers are added to the chain one at a time only, such as in polyethylene, whereas in step-growth polymerization chains of monomers might mix with one another directly, such as in polyester.
Though, the latest methods such as plasma polymerization do not fit neatly into either category.
Synthetic polymerization reactions may be carried out with or without a catalyst. Laboratory synthesis of biopolymers, especially of proteins, is an area of intensive research.