Diffusion-Controlled Reactions in Polymer Systems

Isothermal and non-isothermal polymerization of methyl methacrylate in presence of multiple initiators

“…In fact, it must be considered that, when the temperature is lower than the T g of the polymer, the monomer is not fully converted. The T g of the reacting system increases with increasing˛and, when it approaches the test temperature, the molecular mobility is strongly reduced and the system undergoes vitrification [11]. Under these conditions, the reaction rate is drastically reduced and the total monomer conversion strongly hampered.…”

“…When T g equals polymerization temperature, also monomer mobility is reduced thus hindering also propagation events. In these conditions, occurring at later conversion stages, monomer diffusion is hindered, and the reacting solution anneals before 100% monomer conversion due to an extreme increase of the medium viscosity [2,[9][10][11]. Finally, cage effect occurs when even the mobility of initiator radicals is hindered, thus preventing initiation events.…”

“…Finally, cage effect occurs when even the mobility of initiator radicals is hindered, thus preventing initiation events. This is detrimental to initiator efficiency, and affects monomer conversion and polymer molecular weight [11][12][13][14]. Glass and cage effects take place when polymerization is carried out at temperatures lower than the T g of the polymer, which makes the diffusional control predominant.…”

Investigation of thermally activated or photoinitiated polymerization by DSC

“…This assumption is physically often meaningless. Recently, Mita and Horie [15] discussed the influence of increasing viscosity on reaction kinetics. To summarize their results, it can be concluded that the viscosity of the system, and therefore the competition situation between chemical and diffusion control of the reaction rate, must be considered in at least two cases:…”

Diffusion-Influenced Kinetics of Reactions Involving Polymers

“…Termination in radical polymerization, crosslinking of polymer gels, and reactions involving biopolymers such as proteins and receptors are a few examples. 1,2 In spite of their practical importance, understanding of the principles behind their reaction kinetics is still in a primitive stage. This is due to the difficulty arising from the strong constraint of chain connectivity as well as of chain entanglements, leading to a deviation of the dynamics of reactive groups from the free Brownian motion.…”