Molecular Design And Preparation Of Single Pyrene-Capped Polymer

In order to realize the synthesis of various polymers capped with single pyrene group through conventional free radical polymerization (FRP), a new type of pyene-containing free radical initiator (Py-FRI) has been first designed and synthesized with 4,4’-Azobis(4-cyanopentanoic acid) (ACVA) and 1-pyrenemethylamine as the starting chemicals. After being systematically characterized, Py-FRI was used as the initiator of FRP to synthesize single pyrene-capped polystyrene (PyPS), single pyrene-capped polymethyl methacrylate (PyMMA), and pyrene-capped polyvinylimidazole (PyPVI).1) In the FRP of styrene, we have realized the controllable synthesis of PyPS with different number-average molecular weight by adjusting the ratio of monomer, initior, and chain-transfer agent (1-dodecanethiol, DDT). In detail, three PyPS with number-average molecular weight of around 20,000,10,000, and 5,000 have been synthesized by using the Py-FRI/styrene molar ratio of 0.33%,0.56%, and 1.33%, and the DDT/styrene weight ratio of 0.1%,0.2%, and 0.6%, respectively. The average pyrene content in these three PyPS was determined to be 1.04～1.14 pyrene groups per one polystyrene chain.2) In the FRP of methyl methacrylate, we have realized the controllable synthesis of PyPMMA with different number-average molecular weight by adjusting the ratio of monomer and initior as well as polymerization temperature. In detail, four PyPMMA with number-average molecular weight of around 40,000,20,000,10,000, and 5,000 have been synthesized by using the Py-FRI/methyl methacrylate molar ratio of 0.33%, 0.67%,1.33%, and 4% under the polymerization temperature of 95℃, respectively. The average pyrene content in these four PyPMMA was determined to be 0.97～1.10 pyrene groups per one polymethyl methacrylate chain.3) In the FRP of N-vinylimidazole, three PyPVI with different number-average molecular weight have been synthesized by varying the molar usage of DDT. Due to the limitation of experimental techniques, the discussion on average pyene content in resultant PyPVI is absent. More experiments are still under way.The performed work clearly suggests that FRP, as an alternative technique to anionic polymerization, living free radical polymerization, etc, is feasible for synthesis of single functional group, such as pyrenyl group, capped various polymers. The key point is to molecularly design and synthesize the initior containing the respective functional groups. Considering that pyrene-containing polymer, especially single pyrene capped polymer is a good dispersant of cabon nanomaterials, the polymer synthesized in this work may find one important application as dispersant in the preparion of graphene by liquid-phase exfolication of natural graphite.