Accelerated Acid-Assisted Degradability and Tunable Properties of 1,1-Diphenylethylene Copolymers

The thermal and mechanical properties of alternating copolymers of vinyl monomers and 1,1-diphenylethylene (DPE) and the chemical degradation of these copolymers by superacid in a low-temperature environment are reported. The DPE alternating copolymers were prepared by the anionic copolymerization with styrene (S-DPE), 4-tert-butylstyrene (tbS-DPE), butadiene (B-DPE), and isoprene (I-DPE); and the selective and complete hydrogenation of B-DPE copolymer producing poly(butane-alt-diphenylethylene) (Bt-DPE) and poly(butane-alt-dicyclohexylethylene) (Bt-DCHE). As the comonomer choice for the DPE copolymers shifts from diene to bulky styrenic ones, the glass transition temperatures of the DPE copolymers increase from 101 to 195 °C. The viscoelastic and tensile properties of the diene and DPE copolymers are comparable to those of polystyrene (PS). The study of chemical degradation of the DPE copolymers by triflic acid for upcycling, i.e., increasing product values, was conducted at 20 and 35 °C, in low-energy environments. The degradation of the S-DPE and tbS-DPE copolymers proceeded at least 2 orders of magnitude faster than that of PS in terms of molecular weight decrease. We attribute the accelerated degradation of those styrenic and DPE copolymers to the increased stability of the activated α-carbon of the DPE group in the chains. The major products of S-DPE and tbS-DPE copolymers are benzene, benzene/indane derivatives, and DPE monomer, which are generic chemicals widely used in the chemical industry. In contrast, B-DPE and Bt-DPE copolymers are relatively inert with triflic acid compared to the other DPE copolymers. This work demonstrates that incorporating DPE into vinyl polymers as a comonomer enables the adjustment of the thermal and mechanical properties of those copolymers and their chemical upcyclability.