353 



INTKUACTIOX OF 1>( )LVM KUS AND M KCl I A M( ' A L WAVES 



It does come near tlie point of niinnnuni interaction tor tlie wliole sys- 

 {vn\. In any ease, as discussed Ix'toic, the a\'era^(' temperature coefficient 

 of fji/i in the poor solvent is very low compared to th(> jiood so1v(Mi1. The 

 \alues of Mb iii't' roughly ^ to ^ those in benzene. 



GENERAL THEORY OF SINGLE CHAIN MECHANICS; KTIIN AM) KIHKWOOD 



As noted before, much of the present undei-standing of stress-strain 

 properties of polymer chains, in dilute solutions, liciuitls or solids, has 

 come from W. Kuhn's long intei(\st in this sul).iect. Many supplementary 

 contributions have been stimulated by Kuhn's work, and new points of 

 view have been introduced by others. For instance, I'ecently new and 

 different proposals have V)een made about the flow birefringence and 

 non-Xewtonian viscosity of solutions of deformable spheres. These 

 ideas could be tested on suitable microgel solutions. 



Recently, moreo\-er, an especially significant general theory of visco- 

 elastic beha\-iour of pol>'mer in solution has been constructed by Kii'k- 

 wood.'' It explicitly considers the hydrodynamic conditions leading to 

 the rigidity now observed for high-frequency shear waves. It formulates 

 definitely the configurational changes of isolated chains in solution when 

 strained in shear. As this theory is advanced to forms where simpler 

 calculations can be made, it may answer many of the cjuestions raised 

 by the new experiments on single chain properties. 



14.0 0.8 



13.0 0.7 



12.0 0.6 



9.0 0.3 



0.1 



ZbY 30 35 40 45 50 55 



visible ^temperature in degrees centigrade 

 turbidity; 



^ 5 



If) o 



(0 yj 



Fig. 30 — Temperature dependence of absolute viscosity, 17.S , inherent viscosity, 

 (nnr/c, and shear stiffness, mb of, 1 per cent snhitinn nf jiolyst yrene in eyclohexane 

 down through turbidity point. 



