Rheological properties of a telechelic associative polymer in the presence of alpha- and methylated beta-cyclodextrins.
The viscosity of hydrophobic ethoxylated urethane (HEUR) solution decreased in the presence of alpha-CD or m-beta-CD; however their interactions were quite different. When the alpha-CD/hydrophobe molar ratio exceeded 5.0, the viscosity was close to that of a PEO solution of similar molecular weight. Oscillatory shear indicated that the mechanically active chains in HEUR solution decreased with the addition of alpha-CD. This agreed with the hypothesis that alpha-CD formed an inclusion complex with the hydrophobic moiety of the HEUR polymer, thereby destroying the transient hydrophobic associative network. The viscosity/temperature relationship of the alpha-CD/HEUR system (for HEUR with 70% of the PEO chains capped at both ends) did not obey the Arrhenius relationship for alpha-CD/hydrophobe molar ratio in the range 0.8-5.0. The low shear viscosity increased with increasing temperature at molar ratio of 1.0, and this was attributed to the competitive complexation of the alpha-CD/hydrophobe and the alpha-CD/PEO chain. Increasing temperature favored alpha-CD/PEO complexation. Comparison between the behavior of alpha-CD/HEUR and m-beta-CD/HEUR resulting from the different binding characteristics was discussed.
Liao
Dongsheng
D
School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798.
Dai
Sheng
S
Tam
Kam Chiu
KC
D057927:Hydrophobic and Hydrophilic Interactions; D015394:Molecular Structure; D011140:Polyurethanes / Q000737:chemistry*; D012212:Rheology; D012996:Solutions / Q000737:chemistry; D013696:Temperature; D014783:Viscosity; D047391:alpha-Cyclodextrins / Q000737:chemistry*; D047392:beta-Cyclodextrins / Q000138:chemical synthesis / Q000737:chemistry*
D011140:Polyurethanes; D012996:Solutions; D047391:alpha-Cyclodextrins; D047392:beta-Cyclodextrins