[babycakes]

how come, when polymers are formed from monomers, they form in a regular pattern rather than reguarly? its really hard to explain what i mean so ill try and draw something to *delete me*



     H     CH3    H   CH3   H    CH3  
H - C -  C  -  C - C  -  C - C - H       poly(propene) (sorry not a brill picture!)
     H      H     H     H     H     H


why do the CH3s go every other one rather than randomly
would it ever happen where they were random or does it always happen like this?

hope this makes sence
its not homework or anything im just interested!!
thankyou very much!!

[Borek]

You mean something like that?

[babycakes]

yeha thats a much better picture than mine!! thx!
still not sure why the ch3s always come of every other carbon tho

[HP]

Polypropilene is synthesyzed by coordination polymerization of propylene using Cigler-Natta catalys. These catalyzes are mixed organotitanium/organoaluminium compounds which coordinate with the double bonds propylene which allows it to polymerize stereoregulary...This is not like the free radical polymerization alkenes(for example methyl methacrylate to organic glass) when the obtained polymer is random. With coordination polymerization propylene the obtaine polypropilene is much stereoregular ...

[Paradoxtom]

more here: http://www.chemie.fu-berlin.de/chemistry/kunststoffe/takt.htm

[HP]

Nice ilustration of what i mean Paradoxtom
The Ziegler-Natta catalyzes first generation for olefin polymerization. The next methalocene catalyzes like the Kaminsky catalyst provide the drawn stereoregularity in polymer chain..
http://en.wikipedia.org/wiki/Kaminsky_catalyst

[babycakes]

ok most of that went straight over my head but thankyou anyways!
in that picture why are there no ch3s on the top row?

[Paradoxtom]

its only a sample