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From: rs0thp: at :rohmhaas.com (Dr. Tom Pierce)
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Subject: Re: CCL:Polymer Chain Rigidity
To: chemistry ^%at%^ ccl.net
Date: Fri, 2 Dec 1994 09:33:45 -0500 (EST)
Cc: psubram- at -texaco.com (Palavo Subramanian)
In-Reply-To: <9412012012.AA27050.,at,.texaco.com> from "Palavo Subramanian" at Dec 1, 94 02:12:41 pm
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Previously, Palavo Subramanian wrote:
>  What is a good way to 'quantify' polymer chain rigidity ?. I am looking
> at comparing the rigidity of Polymer A as a function of temperature and
> also as a function of composition(monomer ratio in the case of a copolymer).
> Is there a good way to calculate this? Is Persistence Length a good measure
> of the rigidity?
> 
> Thanks in advance,
> --Mani--
> -- Original Sender Envelope Address: psubram*- at -*texaco.com

A good way to quantify rigidity depends on what you will experimentally
measure as 'rigid'.  The most compelling measures correlate with experiments.

Interesting measures are:
     Radius of Gyration
     Variance of Radius of Gyration
     End-to-end distances
     Variance of end-to-end distances
     Characteristic ratio (Cinfinity)
     Kuhn segment (or Persistence Length)
     
These are single chain estimates, returning to what does rigid mean,
if you are interested in packing effects then volume calculations 
might be useful.  

Note that the relationship of Radius of Gyration to End-to_end
distance will tell you "how" gaussian your chains are. 


-- 
Sincerely, Thomas Pierce - THPierce(+ at +)RohmHaas.Com  -  Computational Chemist
"These opinions are those of the writer and not the Rohm and Haas Company."