Carbonyl addition elimination mechanism

This is a step growth polymerisation mechanism. This method is important for the preparation of condensation polymers. Here addition and elimination at the carbonyl double bond of carboxylic acids or it's derivative occurs.

Step growth polymerisation mechanism.

The species in the bracket is at metastable equilibrium and it can either return to it's original state by eliminating Y or it can proceed to its final state by eliminating X. Example of this reaction is interfacial condensation.

Interfacial condensation

The reaction of acid halide with a glycol or a diamine can be proceed rapidly to high molecular weight polymers, if carried at the interface between two liquids, each containing one of the reactants.

Typically an aqueous phase containing glycol or diamine and an acid acceptor is layered at room temperature over the organic phase containing acid chloride. The polymer formed at the interface can be pulled off as a continuous film or filament.

The polymers formed by interfacial condensation are polyureas, polyphenyl esters, polyamides, polyurethanes etc. Those polymers which are unstable at higher temperature are formed by interfacial condensation.

Comments

Polylactic acid/PLA.

Polylactic acid/PLA. Polylactic acid is a biodegradable thermoplastic polymer . Polylactic acid is obtained from lactic acid monomer. Polylactic acid. Polylactic acid is stable to UV radiation. Polylactic acid has good resistance to moisture. Polylactic acid has good elasticity. Polylactic acid is an aliphatic polyester . It can be used as a food packaging polymer. Polylactic acid is suitable for textile fibre applications such as shirts, carpets, sportswear etc. Polylactic acid is used in implants and medical devices (screws, sutures etc). Polylactic acid is suitable for use in floor mats. Uses of Polylactic acid. Questions on Polylactic acid/PLA; Q1) What is Polylactic acid? Ans) Polylactic acid is a biodegradable thermoplastic polymer. Q2) What is the monomer of Polylactic acid? Ans) Polylactic acid is obtained from lactic acid monomer. Q3) Write some properties of Polylactic acid? Ans) Some properties of Polylactic acid are given below; ...

Determination of molecular weight by osmotic pressure method

Determination of molecular weight by osmotic pressure method. Osmotic pressure method is also called membrane osmometry. This method is widely used to determine the number average molecular weight of polymers. This method is based on the phenomenon of osmosis. If a pure solvent is separated from a solution through a semipermeable membrane, due to concentration (chemical potential) difference between the solvent and solution, the solvent will flow into the solution through semipermeable membrane. The pressure applied on the solution to completely stop the flow of solvent into it through semipermeable membrane is called osmotic pressure. The theory of osmotic pressure also applies to a solution of polymers. Ordinary solution obeys Van't Hoff equation i.e π=cRT/M Where π is osmotic pressure, c is concentration in mass per unit volume, R is gas constant, T is temperature and M is molar mass. The polymer solution are non ideal. Taking into account their deviation and us...

Determination of molecular weight of polymers by viscosity method.

Determination of molecular weight of polymers by viscosity method. It is a simple method for determining the molecular weight of polymers. Addition of polymers in the solvent increases the viscosity of the solvent, due to introduction of inhomogeneities by the polymers. If η₀ is the viscosity of the solvent and η is the viscosity of the solution at the same temperature, then the relative viscosity is given by Relative viscosity. Specific viscosity: It is defined as the relative increase in viscosity and is given as Specific viscosity. Reduced viscosity: It is defined as the relative increase in viscosity per unit concentration (C) of polymer and is given as Reduced viscosity. Intrinsic viscosity: The reduced viscosity is dependent on concentration (C). If a graph is plotted between reduced viscosity vs concentration then the extraplotation value when C=0 is called intrinsic viscosity. Intrinsic viscosity. Graph of reduced vi...

Polymers

Search This Blog