Massipolümerisatsiooni

Massipolümerisatsiooni, also known as bulk polymerization, is a method of polymerization where monomers are polymerized in the absence of any solvent or diluent. This means the reaction mixture consists solely of monomers, initiators (if applicable), and any other additives. The monomer itself acts as the reaction medium.

This technique offers several advantages. It results in a high-purity polymer because there is no solvent to remove afterwards, simplifying the purification process and potentially leading to polymers with excellent optical clarity. Furthermore, the high concentration of monomers can lead to faster polymerization rates. Massipolümerisatsiooni can also yield a high yield of polymer product.

However, the method also presents significant challenges, primarily related to heat transfer and viscosity. As the polymerization proceeds, the viscosity of the reaction mixture increases dramatically, making mixing and heat dissipation difficult. The heat generated by the exothermic polymerization reaction can accumulate, leading to a phenomenon known as the "gel effect" or "Trommsdorff effect," where the reaction rate accelerates uncontrollably, potentially causing dangerous thermal runaway. This heat buildup can also lead to the formation of undesirable side reactions and broadened molecular weight distributions.

Despite these difficulties, massipolümerisatsiooni is employed for producing certain polymers like polymethyl methacrylate (PMMA), polystyrene, and polyvinyl chloride (PVC) when careful control of temperature and mixing can be maintained, often through specialized reactor designs or by controlling the conversion rate.