Fundamental investigations of the free radical copolymerization and terpolymerization of maleic anhydride, norbornene, and norbornene tert-butyl ester: In-situ mid-infrared spectroscopic analysis

Various synthetic factors that affect the molecular weight, yield, and composition of maleic anhydride (MAH), norbornene (Nb), and tert-butyl 5-norbornene-2-carboxylate (Nb-TBE) terpolymers were investigated. Real-time monitoring via in-situ FTIR spectroscopy of co- and terpolymerizations of MAH with Nb and Nb-TBE was utilized to evaluate the observed rates of varying Nb/Nb-TBE monomer feed ratios. Pseudo-first-order kinetic analysis indicated that the observed rate of reaction (k_obs) was a strong function of the Nb/Nb-TBE ratio with a maximum of 6.68 × 10^-5 s^-1 for a 50/0/50 Nb/Nb-TBE/MAH monomer ratio and a minimum of 1.13 × 10^-5 s^-1 for a 0/50/50 Nb/Nb-TBE/MAH ratio. In addition, polymer yields were also observed to be a function of the Nb/Nb-TBE ratio and also decreased with increasing Nb-TBE. Sampling of an Nb/Nb-TBE/MAH (25/25/50 mole ratio) terpolymerization and subsequent analysis using ¹H NMR indicated that the relative rate of Nb incorporation is approximately 1.7 times faster than Nb-TBE incorporation. Also, the observed rate constant of 4.42 × 10^-5 s^-1 calculated using ¹H NMR agreed favorably with the k_obs determined via in-situ FTIR (3.83 × 10^-5 s^-1). Terpolymerizations in excess Nb-TBE and in the absence of solvent resulted in relatively high molecular weight materials (M_n > 20 000) and provided a potential avenue for control of the Nb/Nb-TBE incorporation into the resulting materials.