Can nucleic acid, protein and starch be considered as step growth polymers?
Yes, nucleic acid, protein and starch can be considered as step growth polymers as during their polymerisation reaction, they lead to removal of water molecule or any neutral molecule also. Thus, these are the examples of condensation polymers or step growth polymerisation.
How is the following resin intermediate prepared and which polymers is formed by this monomer unit?
Reaction between melamine and formaldehyde can be shown as
Melamine-formaldehyde polymer is formed by this monomer unit.
To have practical applications why are cross links quetioined in rubber?
Cross links in rubber required for increasing the elasticity of rubber.
Why does cis-polyisoprene posses elastic property?
cis-polyisoprene is also known as natural rubber. Its elastic property is due to the existence of weak van der Waals' interactions between their various polymer chains.
What is the structural difference between HDP and LDP? How does the structure account for different behaviour and nature, hence use of a polymer?
HDP (high density polymer) consists of linear molecule and has a high density due to close packing. It is a translucent polymer. While LDP (Iow density polymer) has highly branched structure and hence, does not pack well resulting in low density. It is a transparent material.