Solution polymerization
Encyclopedia
Solution polymerization is a method of industrial polymerization
. In this procedure, a monomer
is dissolved in a non-reactive solvent
that contains a catalyst.
The reaction results in a polymer which is also soluble in the chosen solvent. Heat
released by the reaction is absorbed by the solvent, and so the reaction rate
is reduced. Moreover the viscosity
of the reaction mixture is reduced, not allowing autoacceleration
at high monomer concentration
s. Once the maximum or desired conversion is reached, excess solvent has to be removed in order to obtain the pure polymer. Hence, solution polymerisation is mainly used for applications where the presence of a solvent is desired anyway, as is the case for varnish
and adhesives. It is not useful for the production of dry polymers because of the difficulty of complete solvent removal.
This process is one of two used in the production of sodium polyacrylate
, a superabsorbent polymer
used in disposable diapers.
Notable polymers produced using this method are polyacrylonitrile
(PAN) and polyacrylic acid
(PAA).
Polymerization
In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
. In this procedure, a monomer
Monomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...
is dissolved in a non-reactive solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
that contains a catalyst.
The reaction results in a polymer which is also soluble in the chosen solvent. Heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
released by the reaction is absorbed by the solvent, and so the reaction rate
Reaction rate
The reaction rate or speed of reaction for a reactant or product in a particular reaction is intuitively defined as how fast or slow a reaction takes place...
is reduced. Moreover the viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
of the reaction mixture is reduced, not allowing autoacceleration
Autoacceleration
Autoacceleration is a dangerous reaction behavior that can occur in free radical polymerization systems. It is due to the localized increases in viscosity of the polymerizing system that slow termination reactions...
at high monomer concentration
Concentration
In chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...
s. Once the maximum or desired conversion is reached, excess solvent has to be removed in order to obtain the pure polymer. Hence, solution polymerisation is mainly used for applications where the presence of a solvent is desired anyway, as is the case for varnish
Varnish
Varnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss...
and adhesives. It is not useful for the production of dry polymers because of the difficulty of complete solvent removal.
This process is one of two used in the production of sodium polyacrylate
Sodium polyacrylate
Sodium polyacrylate, also known as waterlock, is a polymer with the chemical formula [-CH2-CH-]n widely used in consumer products. It has the ability to absorb as much as 200 to 300 times its mass in water. Acrylate polymers generally are considered to possess an anionic charge...
, a superabsorbent polymer
Superabsorbent polymer
Superabsorbent polymers are polymers that can absorb and retain extremely large amounts of a liquid relative to their own mass....
used in disposable diapers.
Notable polymers produced using this method are polyacrylonitrile
Polyacrylonitrile
Polyacrylonitrile is a synthetic, semicrystalline organic polymer resin, with the linear formula n. Though it is thermoplastic, it does not melt under normal conditions. It degrades before melting. It melts above 300 degrees Celsius only if the heating rates are 50 degrees per minute or above...
(PAN) and polyacrylic acid
Polyacrylic acid
Poly or PAA or Carbomer is a type of anionic polymer. The monomer of poly is acrylic acid. In a water solution at neutral pH, many of the side chains of PAA will lose their protons and acquire a negative charge. This makes PAA a polyelectrolyte.Dry PAA is a white solid...
(PAA).