User:Kcliu/polyelectrolyte complex formation

Polyelectrolyte Complex (PEC) Formation is the processes of forming electrolytes to create polyelectrolytes. It is the formation between strong ionic groups with opposite charges that have high molecular weights in an aqueous solution.

Aggregation

Aggregation is the polymerization between electrolytes that forms polyelectrolytes. Electrolyte cations and anions,electrolytes with positive charge and negative charge, interact with each other when they are in a liquid solution. The reason is that there is always a strong Coulomb force acting between oppositely charged strong electrolyte ions. The level of the aggregation between ions is determined by the molarity of the solutions that are involved. Therefore, adding salt in the solution changes the concentration of the solution and therefore makes the compounds behave differently during formation. The level of aggregation is high when the solution is deionized. Furthermore, the aggregation level is the lowest in a salt-free solution and it is extremely low in pure water. If the ionic strength of the complex is high, a secondary congregation, another step of the reaction, may be caused. The polyelectrolyte complex that is formed after a secondary congregation is the final product of the PEC formation.

Stability and Efficiency

The stability of the polymer compounds is determined by the molecular weight and the charge density of polyions. PEC can also take place in a biological body to lead cell aggregation or hemolysis,the breaking down of red blood cells, by contacting cells, tissues, and organs. It can also help when doing gene transfection. Besides the molecular weight, the pH and the ionic strength of the medium can also determine the efficiency of PEC formation. High molecular weight, high pH value and high ionic strength can make the PEC formation more effective.

Formation process

Usually, polyelectrolyte complex formation is prepared by directly adding the right volume of polycation aqueous solution into strongly stirred polyanion solution according to cationic charges to anionic charges. To make sure that the ratio of the cations to anions is accurate, the solution must be slowly added from one to the other and the one that is added to must be constantly stirred while and after the two solutions are mixed. A set of titration could be used to make sure the ratio is correct. Also, a PEC formation usually takes place under room temperature.

Classification

There are three types of Polyelectrolyte Complex Formation, soluble, colloidally stable, and coacervate complex. Soluble PEC usually contains polyions that have significantly different molecular weight and weak ionic group. Colloidally stable PEC formation happens between strong polyelectrolyte which has high aggregation force. At last, Coacervate complex formation happens between polyelectrolyte that has moderate strength.

Today's Research

Being both polymers and electrolytes, these macro compounds have the properties of polyionic compounds. In today’s reality, PECs are produced for industrial applications such as coatings, binders, and flocculants for water purification.

External links

• [1]Royal Institute of Technology (KTH)