Analysis of the linear methods of determining copolymerization reactivity ratios, 9. Penultimate systems with r2 = 0

The copolymerization equation considering the penultimate unit effect, the so called penultimate model, takes a simplified shape in the case of r2 = 0 (monomer 2, M2, does not homopolymerize). For this case a method analogous to the conventional KT(Kelen‐Tüdős)‐transformation for estimation of r1 and r1′ is proposed. The new method was verified by literature data for the system styrene/fumarodinitrile, polymerized with benzoyl peroxide at 70°C, yielding r1 = 0,062 and r1′ = 0,812. Classification of copolymerization curves by means of the classical copolymerization model permits to distinguish between three curve‐types: r1 < 2 (alternation with respect to M2), r1 = 2 (linear diagram with slope 0,5) and r1 > 2 (non alternating system). The penultimate model permits to generate further curve‐types of “S”‐shape with r1 > 2 and r1′ > 2 or r1 > 2 and r1′ < 2 (r1 = r1′ for classically behaving systems and r1 ≠ r1′ for non‐classically behaving systems).