S/AA copolymers

Fig. 3.1. 3 Evolution of AA contents in S/AA copolymer samples from FRRPP (using DEE as solvent) and solution polymerization systems (using cyclohexane, CHX, as solvent) for PS portion of copolymer products (Replotted with permission from Caneba et al., 2003)

Table 4.1.3 Results of solubility and emulsification of S/AA copolymer products

Fig. 4.1.9 Formulas for deuterated pyridine (a) and S/AA copolymer (b). In (b), 1 refers to the carbon element in carboxyl group and 2-7 stands for the carbon elements in benzene ring, which is linked to the backbone of copolymer chain

Proton and C-NMR plots for pyridine and a typical S/AA copolymer are shown inFigs.4.1.6. 1.8. 

Figure 7.9 Expanded C-NMR spectra of carboxyl carbon on S-AA copolymer. Peak (A) SAS, (B) AAS, (C) AAA, (D) AAA. Reprinted with permission from S. Wong and G.W. Poehlein, Journal of Applied Polymer Science, 1993, 49, 6, 991. 1993 John Wiley and Sons [105])

All the GPC results in Tables 4.1.1 and 4.1.2 show unimodal peaks. This could indicate relative absence of random S/AA copolymer species. Also, molecular weights from the RI detector measurements are consistently larger than those from UV detector measurements. This indicates the disproportionate presence of AA in 

Spectroscopic studies of aqueous solutions are of particular interest if they provide information about the microenvironment of the copolymer. In the case of S/AA copolymer, the water band at about 3420 cm" cannot be subtracted completely. This behavior indicates that some solvent molecules 

Wong and Poehlein [53] concluded that the sequence distribution of styrene-acrylic copolymers can be measured by C-NMR of the carboxyl carbon and the Cj carbon of phenyl in S-AA copolymers. Low-conversion copolymer composition data obtained by NMR at different initial monomer ratios were used with the Kelen-Todos plot method to determine the reactivity ratios of ra = 0.13 and rs = 0.38. The resonance peaks split by triads were assigned and confirmed by comparing experimental triad values with those calculated from the Alfrey-Mayo statistics-kinetics model. 

UV is only rarely used as a technique to analyse copolymer composition, because it is hard to find diaractenstic, undisturbed peals in the UV spectra of copolymers. Wojtczak and witala [66] used UV to analyse methylated S-(meth)acrylic acid (S-(M)AA) copolymers made in both emulsion and in bulk and concluded that there is a larger difference in microstmcture between bulk and emulsirxi S-AA copolymers than diere is betweai S-MAA copolym. Shashidnar et al. [67] compared the compositional analysis of S-(meA)acrylate copolymers and found agreement between IR and UV measurements. 

A question posed by Wong and Poehlein [105] regarding the monomer system of styrene acrylic acid is whether sequence distribution information can be determined in NMR spectra. In this work, H- and C-NMR spectra of S-AA copolymers were examined to determine the resonances that are sensitive to the copolymer microstructure. The compositions of the copolymers were measured by NMR and the reactivity ratios calculated. The triad sequences were assigned by experiments and the Alfrey-Mayo statistics-kinetics model. 

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