Date of Award
Program or Major
Doctor of Philosophy
A new method of measuring the efficiencies of free radical grafting reactions is presented. This technique utilized the compositional analysis capability of dual detector (UV and RI) gel permeation chromatography in which the mixture of polymer resulting from the graft copolymerization reaction is also subjected to separation by molecular size. Samples of the reaction mass drawn from a reactor are diluted with GPC carrier solvent and injected directly into the chromatograph without any other preparative step. Grafting efficiency, graft ratio, molecular weight distributions, and the frequency of graft chains along the backbone polymer are simultaneously determined. This simple technique overcomes the need to separate or purify the polymer mixture prior to analysis, as required for most other methods.
Graft site initiation occurs by primary radical and/or polymeric radical attack on the backbone polymer. Graft site can be generated by either chain transfer reaction or double bond addition mechanism. The controlling mechanism is determined by the structure of the backbone and the activity of the free radicals. The efficiency of incorporation of monomer into the graft chains depends upon the graft site initiation mechanism, the mode of polymer chain termination (recombination or disproportionation) and chain transfer reactions. A series of kinetic studies of different grafting systems results in a series of uniquely different expressions describing the graft efficiency, $\phi$. The dependency of $\phi$ upon monomer, initiator and backbone concentrations is different from case to case. A complete kinetic model is also established, which is capable of predicting reaction rate, graft efficiency, graft frequency, graft ratio, and molecular weight averages and distributions. Simulations are provided to compare predicted results with experimental data for each system.
Huang, Nai-jen, "Fundamental studies of grafting reactions in free radical copolymerization" (1994). Doctoral Dissertations. 1785.