Lignin synthesis has been debated for quite some time, it is uncertain whether the polymerization is simply chemically and kinetically controlled or if other entities, such as enzymes and proteins, are involved. If lignin synthesis is only chemically controlled, then some of the polymer growing branches will eventually react together. When two growing chains, already linked at a branching point, react together, a closed loop is created. The purpose of this study is to look for these closed loops. As lignin structure is complicated and the amount of branching points not too elevated, a model is needed to simplify the problem.
The most employed model for lignin is dehydrogenation polymer, obtained from radical oxidation of coniferyl alcohol. In order to have a chance of detecting the closed loops in the model polymer it is necessary to increase the number of branching points. The idea to achieve this goal came from star polymers, where a multibranched polymerization center is used to start the growth of polymeric chains in multiple directions. The intoduction of a multibranched polymerization center in the dehydrogenation polymer should provide the necessary amount of branching points and increase the chances of closed loops detection.
Three new, three-branched model compounds were synthesized, to act as polymerization centers. The synthesis of these compound had never been tried before. Two of the model compounds were synthesized and characterized, but the reaction yield for one of them was too low to proceed with the study. the synthesis of the third model compound was abandoned. Coniferyl alcohol polymerization tests have been run with one of the model compound and with two model compounds precursors. This research is at a too early stage for the detection of closed loops, but some encouraging results have been obtained in that direction.
