The synthesis of high molecular weight star-shaped polymers comprising poly(1,3-cyclohexadiene) arms coupled to a divinylbenzene (DVB) core is reported. In-situ FTIR spectroscopy was used to verify first-order polymerization kinetics for 1,3-cyclohexadiene at 40 °C in cyclohexane with a 10 wt % monomer concentration using a tetramethylethylenediamine (TMEDA) to n-butyllithium (n-BuLi) ratio of 5/4. The propagation rate constant was determined to be 0.31 L mol-1 s-1. The degree of 1,2-addition (70%) vs 1,4-addition (30%) for 1,3-cyclohexadiene was determined using 1H NMR spectroscopy. The molecular weights of the preformed arms were 10 000 and 5000 g/mol, and the ratio of DVB to n-BuLi was systematically varied from 6:1 to 24:1. Gel permeation chromatography coupled with light scattering detection was utilized to detect the formation of star-shaped polymers and the presence of star-star coupling. In-situ spectroscopy and obvious color changes indicated that the addition of DVB to poly(1,3-cyclohexadienyllithium) was rapid. The molecular weight distribution (Mw/Mn) of the star polymers ranged from 1.4 to 1.9. The polymeric materials were thermally stable to 330 °C under a nitrogen environment. The refractive indices of both the homopolymers and star polymers were 1.572 at 600 nm and remained relatively constant from 1600 to 550 nm. The Tg of the high molecular weight star-shaped polymers was 150 °C.
ASJC Scopus subject areas
- Materials Chemistry