NMR Investigations of Temperature-Induced Phase Transition in Aqueous Polymer Solutions

2011 ◽  
Vol 305 (1) ◽  
pp. 18-25 ◽  
Author(s):  
Jiří Spěváček
Keyword(s):  
Phase Transition ◽  
Polymer Solutions ◽  
Aqueous Polymer

Novel porphyrin-labelled poly(N-isopropylacrylamides): syntheses from bromoalkyl-containing prepolymers and physicochemical properties

2000 ◽  
Vol 04 (06) ◽  
pp. 579-587 ◽  
Author(s):  
YURI S. AVLASEVICH ◽  
TIMOUR A. CHEVTCHOUK ◽  
VALERY N. KNYUKSHTO ◽  
OLEG G. KULINKOVICH ◽  
KONSTANTIN N. SOLOVYOV
Keyword(s):  
Phase Transition ◽  
Phase Separation ◽  
Physicochemical Properties ◽  
Absorption Spectra ◽  
Polymer Solutions ◽  
Soret Band ◽  
Water Soluble ◽  
Absorption Bands ◽  
Aqueous Polymer ◽  
Peak Intensity

Novel water-soluble tetraarylporphyrin-labelled polymers have been synthesized by the reaction of bromoalkyl-containing poly(N-isopropylacrylamides) with 5-(4-pyridyl)-10,15,20-tri(4-methoxyphenyl) porphyrin. Corresponding Zn -porphyrin-containing polymers have also been prepared. Phase transition diagrams show that aqueous polymer solutions exhibit phase separation upon heating. Absorption spectra of the porphyrin-labelled polymers have been recorded in water and organic solvents. It is found that the absorption bands in aqueous polymer solutions are broadened and shifted bathochromically, the peak intensity of the Soret band in the polymer spectra being strongly lowered in water. Fluorescence properties of the polymers are briefly reported.

Heat Transfer in Internal Flows of Non-Linear Fluids: A Review

2006 ◽  
Author(s):  
Dennis A. Siginer ◽  
Mario F. Letelier
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Heat Transfer Enhancement ◽  
Polymer Solutions ◽  
Single Mode ◽  
Secondary Flows ◽  
Transfer Enhancement ◽  
Experimental Heat ◽  
Aqueous Polymer ◽  
Non Linear

A survey of the developments in heat transfer studies of non-linear inelastic as well as elastic fluids in tubes is given. Experimental findings concerning heat transfer enhancement characteristics of viscoelastic aqueous polymer solutions are very significant. Specifically, it is reported that heat transfer results for viscoelastic aqueous polymer solutions are drastically higher than those found for water in laminar flow in rectangular ducts. A number of investigators suggested that the high experimental heat transfer values were due to secondary flows resulting from the elasticity of the fluids. In this context recent results concerning the fully developed thermal field in constant pressure gradient driven laminar flow of a class of viscoelastic fluids characterized by single mode, non-affine constitutive equations in straight pipes of arbitrary contour ∂D is reviewed. Heat transfer enhancement due to shear-thinning is identified together with the enhancement due to the inherent elasticity of the fluid. The latter is the result of secondary flows in the cross-section. Increasingly large enhancements are computed with increasing elasticity of the fluid as compared to its Newtonian counterpart. Large enhancements are possible even with dilute fluids. Isotherms for the temperature field are presented and discussed for several non-circular contours such as the ellipse and the equilateral triangle together with heat transfer behavior in terms of the Nusselt number Nu.

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