The Synthetic Routes of Poly(hexamethylenebiguanide)

Poly(hexamethylenebiguanide) is a synthetic polymer used in various industrial applications.
This article will discuss the synthetic routes of Poly(hexamethylenebiguanide).

Poly(hexamethylenebiguanide) synthesis can be achieved through various methods, including polycondensation, ring-opening polymerization, and polymerization of precursors.

Polycondensation:
Poly(hexamethylenebiguanide) can be synthesized through polycondensation, which involves the reaction of a bis(allylic) halide with a diamine.
The bis(allylic) halide, typically a bis(chloro) or bis(bromo) compound, is treated with an excess of diamine, such as hexamethylenediamine, at elevated temperatures to form the polymer.
The reaction Scheme 1 illustrates the basic polycondensation process:

Scheme 1: Poly(hexamethylenebiguanide) synthesis via polycondensation

The reaction proceeds through an initial condensation step, forming an intermediate dendrimer or oligomer, which is then further elongated to give the final polymer.
The reaction is typically conducted in the presence of a solvent, such as dimethylformamide (DMF), and an acid catalyst, such as para-toluenesulfonic acid (PTSA), to facilitate the reaction and remove any unwanted byproducts.

Ring-Opening Polymerization:
Another method of synthesizing Poly(hexamethylenebiguanide) is through ring-opening polymerization, typically using a metal alkoxide or a nitrogen-rich organometallic compound as the initiator.
This method involves the formation of a metallic complex, followed by the addition of a molecule of a monomer, typically a bis(allylic) halide, to the metal center to form a polymer chain.
The reaction Scheme 2 illustrates the basic process:

Scheme 2: Poly(hexamethylenebiguanide) synthesis via ring-opening polymerization

The polymerization can be carried out in the presence of a solvent, typically a polar solvent, such as N,N-dimethylacetamide (DMA), or a nonpolar solvent, such as toluene, at temperatures ranging from 100 to 200°C.
The resulting polymer can be further elongated by adding additional monomer and initiator to the reaction mixture.

Polymerization of Precursors:
Poly(hexamethylenebiguanide) can also be synthesized by polymerizing precursors, such as hexamethylenebiguanamide, which is synthesized by reacting a primary amine, such as methylamine or ethylamine, with a carboxylic acid derivative of 1,6-hexamethylene bis(allyl malonate).
The resulting bis(allyl) malonate can be reacted with a secondary amine, such as hexamethylenediamine, to form the polymer.

In conclusion, Poly(hexamethylenebiguanide) synthesis can be achieved through various methods, including polycondensation, ring-opening polymerization, and polymerization of precursors.
The synthetic routes offer a range of processing options for the manufacture of Poly(hexamethylenebiguanide), which finds extensive application in various industrial applications.