Can anyone please help me distinguish these two?
As network solid is defined here:
http://en.wikipedia.org/wiki/Network_covalent_bonding , wouldn't polyethlene fall under that description too?
Thanks!
A networked solid is one which doesn't have isolated molecular forms but is instead a network of atoms which are all covalently bonded together. The common examples given are things like graphite and diamond. I'm sure you already knew this.
I suppose, at first glance, there might appear to be some similarities between polymers, like polyethylene, and networked compounds like diamond. They both are covalently bonded networks of something, you can't have isolated diamond or polyethylene molecules, etc.
However, in my opinion, these are fundamentally different substances for at least two reasons. First, the moieties being held together in diamond are atoms, whereas those covalently bonded together in polymers are molecules (e.g., whatever monomer was used in the polymerization). The definition for networked solids seems to indicate that the monomers need to be atoms. Secondly, in molecular solids, like polyethylene, the bonds holding the molecules into their solid form are due to Van Der Waal's interactions. In networked solids, such as diamond, the bonds making it a solid are covalent. This is probably what gives rise to the huge disparity in melting points between something like polyethylene, which I can melt with a cigarette lighter, and diamond, which I could probably only melt if I put it on the surface of the sun.
Hope that helps.
