Oxidation of Stereo‐regular Poly(styrene‐co‐4‐methylstyrene) by Cobalt(II) Acetate Tetrahydrate/Sodium Bromide Catalyst

Chemical modification on the stereo‐regular poly(styrene‐co‐4‐methylstyrene) (sPS‐PMS) was attempted in this study. Metallocene copolymerization of styrene (St) and 4‐methylstyrene (MSt) was performed by using η⁵‐pentamethylcyclopentadienyl‐titanium(IV)tributoxide (Cp*Ti(OBu)₃)/methylaluminoxane (MAO)/tri‐iso‐butylaluminum (TIBA) catalyst in the bulk state. Cobalt(II) catalyst was then applied to oxidize the benzylic methyl group on the MSt units of the resulting sPS‐PMS copolymer. Both aldehyde and carboxylic acid in the oxidized products were resolved by the FTIR and ¹H NMR. The oxidized sPS‐PMSs exhibit a low and a high‐temperature T_g and T_m corresponding to the transitions in the amorphous and the crystalline regions. Hydrogen‐bond and polar interactions between the aldehyde and carboxylic acids tend to interrupt the regular chain packing of the oxidized sPS‐PMS, resulting in the lowering of T_m with oxidation level. The oxidized sPS‐PMS showed better adhesion to glass fiber than pure sPS‐PMS copolymer as evaluated from the respective SEM fractured micrographs.