Mechanism of polymerization pdf

The transition metal ion ti in this example is connected to the end of the growing chain and simultaneously coordinates the incoming monomer at a vacant orbital site. Show full abstract the polymerization mechanisms with activated monomer in most cases. Addition and condensation polymerization processes. In the polymerization of styrene, methyl methacrylate, the acrylates including acrylic acid, vinyl acetate, methylvinyl ketone, vinyl. The polymerization is initiated by the formation of radicalic monomer. Mechanisms of polymerization an overview sciencedirect.

Many of these addition reactions are known to proceed in a stepwise fashion by way of reactive intermediates, and this is the mechanism followed by most polymerizations. In addition polymerization monomers only join at the active site of the chain. The initiation mechanism is explained by an autoxidation to an active ketohydroperoxide form. Free radical polymerization consists of three fundamental steps, initiation, propagation, and termination. But in condensation polymerization, any molecule can react with any other. In the following paragraphs the chain mechanism of the bulk free radical. The distinct initiation, propagation, and termination steps of chaingrowth polymerization are meaningless in stepgrowth polymerization. The use of stable carbenium cations results in a new type of polymerization of nbenzoyl lactams with a. A ionic mechanism are two type i cationic mechanism ii anionic mechanism. The second condensation polymerization you will carry out is a reaction between phenol and formaldehyde to produce a polymer known as bakelite see mechanism at the top of the next page. The difference of isotope effects on c2 was assigned to differences in the mechanism of the propagation step in cui mediated and freeradical polymerization.

Let us do a comparative analysis of the two types of polymerization to understand them better. Bakelund performed this synthesis at the beginning of the twentieth century, producing the first synthetic polymer. Polymers can be formed by a variety of reaction pathways. In this unit we will look at those formed by the process of free radical polymerization. A difunctional monomer or equal molar amounts of two different difunctional monomers are necessary at least to form a linear high molecular weight polymer. Two general mechanisms have been proposed and for simplicity here we simply. Every polymerization reaction proceeds through three steps.

To clarify whether atom transfer radical polymerization can be extended to free radical ringopening polymerization, the polymerization of 5,6benzo2methylene1,3dioxepane bmdo was carried. Mechanism and kinetics of free radical chain polymeriza. A general diagram illustrating this assembly of linear macromolecules, which supports the name chain growth polymers, is presented here. The mechanism of polymerization involves addition of a proton acid to aziridine to produce the corresponding aziridinium ion 6.

Emulsion polymerization requires the use of watersoluble initiators and surfactants. Termination to form dead polymer occurs primarily by two mechanisms. Emulsion polymerization is a unique process for radical chain polymerization. The copolymerization proceeds at approximately the same rate as. If an alkylating agent is used as initiator, the alkylated monomer will transfer a proton to a monomer thus producing the same initiating species equation 2.