Question

briefly discuss the following polymer concepts use examples and structures to illustrate your answers

a) degradative chian transfer reaction

b) block copolymer

c)all possible bonding arrangements in the repeat unit of polybutadiene

d) low density polythylene

Answer 1

a) Degradative chian transfer reaction: This side reaction takes place during polymerization, if an active center is transferred from a growing macromolecule to another molecule. Degradative chian transfer process terminates the growth and gives low molecular weight polymers. These kind of reactions also decreses the rate of polymerization drastically. For example, transfer of active centers to limonene( which forms a stable free radical ) during limonene’s free-radical copolymerization with n-butyl methacrylate halts the polymer growth.

b) Block copolymer: It is a copolymer in which two monomers cluster together and form blocks of repeating units. For instance if A and B are two differnt monomer units A intially cluster together to form homomer A-A-A-A block, simialry B-B-B is another block. If they are combined together it is called Block copolymer. A-A-A-A-B-B-B-B--A-A-A-A-A-B-B-B

For example styrene butadiene styrene block copolymer .is called SBS rubber and is used as soles of shoes

c)all possible bonding arrangements in the repeat unit of polybutadiene

Three distinct modes are possible

d) low density polythylene

Its monomer is ethylene and widely used for making dispensing bottles, wash bottles, tubing, plastic bags..etc. It has a low density range of 0.917–0.930 g/cm³. other useful properties include good impact resistance, extremely flexible, meets food handling guidelines