Final answer:
The viscosity of Carbomer 407 decreases more significantly in ethanol than in water due to ethanol's lower polarity, which leads to more disruption of electrostatic forces between carboxylate ions and a weaker interaction with polymer chains allowing them to move past each other more easily.
Step-by-step explanation:
When Carbomer 407, a polymer formed from the polymerization of acrylic acid, is introduced to a higher pH environment, the carboxylic acid groups ionize to form carboxylate ions. These ions have strong electrostatic repulsion, leading to an increase in the viscosity of the solution due to their linear molecular structure.
However, when water and ethanol are added to this high pH solution, there is a decrease in viscosity, with a more pronounced effect in the presence of ethanol. This phenomenon occurs because ethanol is a less polar solvent than water, and it disrupts the electrostatic forces between carboxylate ions more effectively.
Ethanol's ability to form hydrogen bonds is different compared to water, resulting in less intermolecular interaction with the carboxylate ions. Viscosity decreases as ethanol disrupts the network more than water, which is also due to the structure of the carbomer and the length of the polymer chains.
Moreover, ethanol has the ability to solvate the polymer chains, providing a medium where the coiled polymer chains can more easily move past each other. Since the carbomer polymer has a higher molecular weight and long chains, in a less polar solvent like ethanol, the polymer chains find it easier to slip past one another, contributing to a decrease in viscosity.
This effect is further enhanced by ethanol's lower dielectric constant, which makes ionic charges less shielded and therefore weakens electrostatic interactions between carboxylate groups.