Facile and Efficient Catalyst-Free Preparation of Poly(propargyl quinolinium bromide) and Poly(propargyl acridinium bromide) and Characterizations of Their Structures and Properties

In this paper, we report facile and efficient preparation of poly(propargyl quinolinium bromide) (PPQB) and poly(propargyl acridinium bromide) (PPAB). Both PPQB and PPAB are conjugated polymers with polyacetylene as backbones. Besides, they are polyelectrolytes since the side groups of PPQB and PPAB are quaternized quinolinium and acridinium, respectively. Therefore, PPQB and PPAB are conjugated polyelectrolytes, which are promising in many important applications. PPQB was prepared by reaction of the mixture of propargyl bromide (PB) and quinoline in DMF at 60 degrees C for 100 h. PPAB was synthesized under the same conditions via the same process except that acridine was used in the place of quinoline. The preparations are very simple and efficient, which need no any catalyst or initiator. The as-prepared PPQB and PPAB were characterized by elemental analysis and GPC-MALLS. Elemental analysis confirmed that PPQB and PPAB were the respective homopolymers of propargyl quinolinium bromide (PQB) and propargyl acridinium bromide (PAB). The molecular weights of the PPQB and PPAB were measured to be 1.8x10(5) and 8.1x10(4) g/mol, respectively, indicating efficient polymerizations of the respective monomers PQB and PAB. A tentative mechanism for the polymerizations was proposed as follows: firstly, the tertiary amine group of quinoline or acridine was quaternized by PB, leading to activation of the carbon-carbon triple bonds of the resultant quaternized salt; then, the nucleophilic attack on the triple bonds by pyridine resulted in carbon anions, which initiated the anionic polymerization of the quaternized salt. Furthermore, fluorescent and conductive properties of PPQB and PPAB were studied. Fluorescent measurements revealed that both PPQB and PPAB solutions had relatively strong fluorescent emissions, and the conductivity measurements demonstrated good conductivities of PPQB and PPAB films. Compared with poly(propargyl pyridinium bromide) that we reported previously, PPQB and PPAB are much less hygroscopic when exposed to air, so that PPQB and PPAB films are stable in the air. This broadens the applications of the two polymers.