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ENHANCEMENT OF POLYMERIZATION RATES FOR RIGID ROD-LIKE MOLECULES BY SHEARING

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Title ENHANCEMENT OF POLYMERIZATION RATES FOR RIGID ROD-LIKE MOLECULES BY SHEARING
 
Creator AGARWAL, US
KHAKHAR, DV
 
Subject terephthalamide)
polyamides
 
Description RIGID, rod-like polymers are of considerable technological importance in the production of high-strength and high-modulus fibres1. Polymerization reactions generally require near-parallel orientation of such molecules, and because of the slow rotational diffusion of the reacting species2, the rate of polymerization is found to decrease significantly in the later stages of the reaction; this ultimately limits the molecular weight of the polymer. It is known, however, that rod-like molecules can be readily oriented in solution by means of imposed flow fields. Here we examine the effect of a shear flow on the polymerization reaction between p-phenylene diamine and terephthaloyl chloride, where the product, poly(p-phenylene terephthalamide), has a rigid, rod-like structure1. We find that once the molecular weight of the reactants exceeds a critical value, shearing of the reaction mixture induces a pronounced orientation of the molecules, accompanied by a significant increase in the polymerization rate. The technological implications are clear: exposure of polymerizing mixtures of rod-like molecules to high shear rates can result in a dramatic enhancement in the molecular weight of the resulting polymer.
 
Publisher MACMILLAN MAGAZINES LTD
 
Date 2011-08-17T12:15:27Z
2011-12-26T12:55:32Z
2011-12-27T05:41:00Z
2011-08-17T12:15:27Z
2011-12-26T12:55:32Z
2011-12-27T05:41:00Z
1992
 
Type Article
 
Identifier NATURE, 360(6399), 53-55
0028-0836
http://dx.doi.org/10.1038/360053a0
http://dspace.library.iitb.ac.in/xmlui/handle/10054/9863
http://hdl.handle.net/10054/9863
 
Language en