Diffusion‐controlled vinyl polymerization. IV. Comparison of theory and experiment

Abstract

SynopsisBulk polymerization data of methyl methacrylate, ethyl methacrylate, ethyl acrylate, n-propyl acrylate, vinyl acetate, and styrene were compared with the predictions of the theory proposed in the earlier parts of this series (1-111). This theory of polymerization kinetics uses the concepts of free volume and chain entanglements to describe the relationship between chain mobility and chain length dependent termination reactions. Excellent agreement was found between the predictions of the theory and the polymerization rate and molecular weight data of the six polymerization systems studied. Emphasis was placed on the ability to explain the development of higher order molecular weight averages (mw, mz, etc.) because they provide the most crucial tests for such a model. No changes were required in the model as it was applied to the different polymerization systems for a variety of reaction conditions. The theory offers a unified understanding of the diverse polymerization behavior displayed by such systems. METHOD OF ANALYSISThis section deals with the general computational procedures and set of equations used for modeling vinyl polymerizations with the proposed theory. Only an outline is given below because the details of the theory have already been discussed.

Pulsed NMR Investigation on the Polymerization of Methyl Methacrylate

“…The critical molecular weight that gives rise to the entanglement effect has been reported to be about 10,000. 24 From Figures 4 and 7, the molecular weight where the T 2 , component begins to appear is higher than the critical molecular weight. It could be possible to conclude that the component of T 2 , corresponds to regions containing entanglements of polymer chains in the reaction mixture.…”

“…As the temperature is raised, the molecular weight becomes lower. Soh 24 pointed out that in the bulk polymerization of MMA, the entanglement of polymer chains occurs as the polymer concentration and/or the mo- Polymer yield (%) Figure 6. Relationship between F, and polymer yield:…”

Pulsed NMR Study of the Curing Process of Epoxy Resin

“…Soh et al pointed out that the entanglement of a linear polymer chain, like polyisoprene, also occurred without cross linking as the polymer concentration and/or molecular weight increased. [26][27][28][29] They also explained the occurrence of an entanglement of a polymer chain whose molecular weight was more than ca. 10 4 , large enough to cause a transient network structure.…”

The RAFT Process as a Kinetic Tool: Accessing Fundamental Parameters of Free Radical Polymerization

“…While, initially, the termination reaction may appear to be a simple bimolecular reaction between two highly reactive radical species, the scientific community has produced many reviews that focus solely on FRP termination processes and the variety of methods that allow for its quantification [37]. The termination process is inherently complex to characterize because it is a multistep diffusion-controlled event that requires translational diffusion of the center of masses of large macroradicals and subsequent segmental rearrangement of their chain ends before chemical reaction can occur (see Scheme 4.2) [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. Additionally, so-called reaction diffusion, which means the approach of two radical sites via chain growth toward each other, was shown to contribute to the termination rate [56,57].…”