# Influence of Monomer Sequence on the Cyclization Behavior of Poly(acrylonitrile-_co_-acrylamide)
## 3 Results and Discussion
### CopolymerSynthesis
In batch process, triad composition at low monomer conversion and the instantaneous number-average sequence length of AN, \(<\)N\({}_{\text{AN}}\)>\({}_{\text{n}}\), and AAM, \(<\)N\({}_{\text{AAM}}\)>\({}_{\text{n}}\) can be evaluated on the assumption of the validity of terminal model kinetics from the Equations (4) and (5) [9,45]:  
\[\text{F}_{\text{AN-AN-AN}}\ =\ \left(1-\frac{1}{1+\frac{\text{A}_{ \text{AN}}\text{AN}}{\text{I}_{\text{AAM}}}}\right)^{2}\] \[\text{F}_{\text{AN-AN-AAM}}\ =\ \text{F}_{\text{AAM-AN}}\frac{2}{1+ \frac{\text{A}_{\text{AN}}\text{AN}}{\text{I}_{\text{AAM}}}}\left(1-\frac{1}{ 1+\frac{\text{A}_{\text{AN}}\text{AN}}{\text{I}_{\text{AAM}}}}\right)\] \[\text{F}_{\text{AAM-AN-AAM}}\ =\ \left(\frac{1}{1+\frac{\text{A}_{ \text{AN}}\text{AN}}{\text{I}_{\text{AAM}}}}\right)^{2} \tag{4}\] \[\text{F}_{\text{AN-AAM-AN}}\ =\ \left(1-\frac{1}{1+\frac{\text{A}_{ \text{AN}}\text{AN}}{\text{I}_{\text{AN}}}}\right)^{2}\] \[\text{F}_{\text{AAM-AAM-AAM}}\ =\ \text{F}_{\text{AAM-AAM}}\text{-AN}\frac{2}{1+ \frac{\text{A}_{\text{AN}}\text{I}_{\text{AN}}}{\text{I}_{\text{AN}}}}\left(1- \frac{1}{1+\frac{\text{A}_{\text{AN}}\text{AAM}}{\text{I}_{\text{AN}}}}\right)\] \[\text{\langle N}_{\text{AN}}\rangle_{\text{n}}\ =\ \frac{1}{1-\frac{\text{A}_{ \text{AN}}\text{AN}}{\text{I}_{\text{AN}}}}\] \[\text{\langle N}_{\text{AAM}}\rangle_{\text{n}}\ =\ \frac{r_{\text{AN}}\text{ dA}}{1-\frac{r_{\text{AN}}\text{I}_{\text{AN}}}{\text{I}_{\text{AN}}}{\text{I}_{\text{AN}}}{ \text{I}_{\text{AN}}}^{\text{(}\text{n}-1)+1}} \tag{5}\]  
The accordance between experimental and theoretical values of copolymer composition confirms the validity of the terminal-model kinetics. The calculated values of triad composition and number-average sequence length of AN and AAM units are summarized  
Figure 2: Dependences of the molar part of AAM in the copolymer on the monomer conversion in the copolymerization of AN and AAM at 80 \({}^{\circ}\)C. (**a**) [AlBN] = [BTC] = 1 mmol/L; (**b**) [AlBN] = [BTC] = 2 mmol/L. Numbering of the curves corresponds to the numbering of the samples from Table 1.0  
in Table 1.1 Among AN centered triads, triads AN-AN-AN prevail, while among AAM-centered triads, triads AN-AAM-AN prevail in the triad composition of macromolecules. Homo-triads AAM-AAM-AAM and hetero-triads AAM-AN-AAM are unfavorable. The number-average sequence length of AN decreases with the rise of the AAM content in monomer feed, while the sequence length of AAM is about 1. Thus, the batch process suggests that AAM units are randomly distributed along macromolecules at f\({}_{\text{AAM}}\leq 7\). Different microstructures of the copolymers have been confirmed by NMR analysis of the copolymers 4-7 (Table 1) obtained at limited conversions. Figure 3 presents the typical \({}^{1}\)H NMR spectrum of copolymer 4 in DMSO-d\({}_{6}\) solution at room temperature. According to [46], the signals in the range of \(\sim\)2-3 ppm correspond to compositional triad sequences: AN-AN-AN (3.12 ppm), AN-AN-AAM (2.92 ppm), AN-AAM-AN and AAM-AN-AAM (2.75 ppm), AN-AAM-AAM (2.60 ppm), and AAM-AAM-AAM (2.31 ppm). The spectra of copolymers 5-7 are given in ESI (Figure S2a-c). \({}^{13}\)C NMR spectroscopy is used more frequently to determine polymer chain microstructure. However, the viscosity of copolymer solutions at room temperature was high enough and integration time was 20 min resulting in low intensity of the signals comparable with measurement noise due to limited capacity of the instrument (Figure S2d, ESI). Thus, for analysis of triad composition the results of \({}^{1}\)H NMR spectroscopy was used. Table 3 presents the data of triad composition of the copolymers 4-7. In all the cases, the molar part of homo-triads AAM-AAM-AAM is negligible. For copolymers 4 and 5, the molar part of hetero-triads is similar. For copolymers 6 and 7, the molar part of homo-triad AN-AN-AN is higher than for copolymers 4 and 5. Thus, it may be concluded that cyclization behavior of the copolymers 4 and 5 may differ from the copolymers 6 and 7.