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In fact polyurethane polymerizes with addition polymerization (because its polymerization produces no small molecules), but its reaction mechanism corresponds to a step-growth polymerization. The distinction between "addition polymerization" and "condensation polymerization" was introduced by Wallace Carothers in 1929, and refers to the type of ...
This is true for step-growth polymerization of linear polymers. For chain-growth polymerization or for branched polymers, the Đ can be much higher. In practice the average length of the polymer chain is limited by such things as the purity of the reactants, the absence of any side reactions (i.e. high yield), and the viscosity of the medium.
The Flory–Stockmayer Theory allows for the prediction of when gelation occurs using percent conversion of initial monomer and is not confined to cases of stoichiometric balance. Additionally, the Flory–Stockmayer Theory can be used to predict whether gelation is possible through analyzing the limiting reagent of the step-growth polymerization.
Step-growth polymers increase in molecular weight at a very slow rate at lower conversions and reach moderately high molecular weights only at very high conversion (i.e., >95%). Solid state polymerization to afford polyamides (e.g., nylons) is an example of step-growth polymerization. [8]
Acid Chloride Preparative Route for Nylon-6,10, which is often used in the nylon rope trick. The nylon rope trick is a scientific demonstration that illustrates some of the fundamental chemical principles of step-growth polymerization and provides students and other observers with a hands-on demonstration of the preparation of a synthetic polymer.
Polymerization occurs where the two phases meet, at the interface. Interfacial polymerization is a type of step-growth polymerization in which polymerization occurs at the interface between two immiscible phases (generally two liquids), resulting in a polymer that is constrained to the interface.
In conventional covalent polymerization, two models based on step-growth and chain-growth mechanisms are operative. Nowadays, a similar subdivision is acceptable for supramolecular polymerization; isodesmic also known as equal-K model (step-growth mechanism) and cooperative or nucleation-elongation model (chain-growth mechanism).
Random graph theory of gelation is a mathematical theory for sol–gel processes.The theory is a collection of results that generalise the Flory–Stockmayer theory, and allow identification of the gel point, gel fraction, size distribution of polymers, molar mass distribution and other characteristics for a set of many polymerising monomers carrying arbitrary numbers and types of reactive ...