Synthesis of Block Copolymers Based on the Alternating Anionic Copolymerization of Styrene and 1,3-Cyclohexadiene

Abstract

A series of poly(1,3-cyclohexadiene-alt-styrene)-containing block copolymers that exhibited predictable molecular weights and narrow molecular weight distributions were synthesized with various 1,3-cyclohexadiene contents (13-57 mol %). In situ FTIR spectroscopy in combination with the Mayo-Lewis graphical method was employed to determine the reactivity ratios for the anionic copolymerization of styrene and 1,3-cyclohexadiene. The reactivity ratios for 1,3-cyclohexadiene and styrene were 0.022 and 0.024, respectively, which indicated the formation of an alternating copolymer. The alternating copolymers served as suitable precursors for chemical modification and were either quantitatively aromatized or hydrogenated in a controlled fashion. The thermal stabilities of the modified copolymers were determined, and as expected, the hydrogenated copolymers exhibited improved thermal stability compared to that of poly(1,3-cyclohexadiene-alt-styrene)-containing block copolymers. However, the aromatized copolymers unexpectedly exhibited reduced thermal stability in both nitrogen and oxygen environments due to the introduction of labile benzylic hydrogens in the repeating unit.

Architecturally and Chemically Modified Poly(1,3‐cyclohexadiene)

“…CHD monomers together with CDMSS in ratios of 10:1 and 20:1 were introduced into PCHD anions. The cross‐over between polystyryl anion and PCHD anion is fairly rapid according to previous reports,14, 15 which provides the possibility to synthesize hyperbranched PCHD (Figure 4). The average branching number was calculated as reported 2.…”

“…The key to the CLAP method is the assumption that the substitution reaction is faster than the addition reaction. The addition of PCHD anions to styrene monomer was found to be fairly rapid even without the use of additives 14, 15. To test the relative reaction rates between the substitution and addition of PCHD anions to CDMSS, an experiment making vinyl‐functionalized PCHD oligomers was designed.…”

Thermal Degradation of Poly(1,3‐cyclohexadiene) and its Dehydrogenated Derivatives: Influence of a Controlled Microstructure

“…Long et al reported the mechanism of thermal degradations of PCHD [35] and dehydrogenated PCHD-polystyrene (PSt) copolymer. [36] However, to date, there has been no report for the thermal degradation of a soluble dehydrogenated PCHD homopolymer. In addition, there has been no information about the influence of the microstructure on the thermal degradation of PCHDs and their dehydrogenated derivatives.…”

Novel amphiphilic block copolymers derived from the selective fluorination and sulfonation of poly(styrene‐block‐1,3‐cyclohexadiene)

“…In general, the polystyrenyl anion is more stable (less susceptible to side reactions) than the polycyclohexadienyl anion, and thus PS blocks are generated first. Furthermore, the quick crossover of polystyrenyl anion to polycyclohexadienyl anion results in PCHD‐ b ‐PS copolymers with lower polydispersities as compared with the reverse addition 16, 26…”