Why are the plasticizing properties of various rubbers different?

The plasticizing of rubber is closely related to its chemical composition, molecular structure, molecular weight and molecular weight distribution. Natural rubber and synthetic rubber due to the structure and performance of different characteristics, generally speaking, natural rubber plasticizing is easier, synthetic rubber plasticizing is more difficult. As far as synthetic rubber is concerned, isoprene rubber, neoprene rubber is close to natural rubber, styrene butadiene rubber, butyl rubber is second, nitrile rubber is the most difficult.