Styrene copolymers gradient elution

Fig. 8. Copolymer separation. Gradient elution of the mixture of three poly(styrene-c -methyl acrylate) samples on a silica column (600 x 7.5 mm do = 5nm dp= 15 pm). Gradient tetrachloro-methane/methyl acetate (7-35% B in 35 min) flow rate 1 ml/min. The figures at the peaks indicate the composition of the respective copolymer in mol % methyl acrylate. Molar mass values 46.6 — 261 kg/mol 57.3 — 276 77.9 — 302. (From Ref. 381 with permission)...

Fig. 9. Copolymer separation. Gradient elution of the mixture of three poly(styrene-co-methyl methacrylate) samples on a silica column (250 x 6 mm d0 = 5nm dP = 9pm). Gradient 1,2-dichloroethane/tetrahydro-...

Fig. 10. Copolymer separation. Gradient elution of the mixture of seven poly(styrene-co-methyl methacrylate) samples on a silica column (150x4.6 mm d0 = 6 nm dP = 5 pm). Gradient iso-octane/(tetrahydrofuran +10% methanol), 10% B (0 min), 50% (8 min), 80% (10 min), 100% (11 min) flow rate 1 ml/min, reduced to 0.3 ml/min after 9.9 min. Methyl methacrylate content (wt %) indicated. Molar mass values 11.4 — 160 kg/mol 23.8 — 250 37.0 — 150 49.5 — 185 64.0 — 235 76.2 — 220 88.5 — 220. Column temperature 50 °C. (By courtesy of Elsevier Science Publ. [43])...

If the polymer absorbs at a wavelength where both solvent and precipitant are transparent, HPPLC can be performed with the help of a UV detector. Styrene-containing copolymers can be analyzed with alkane hydrocarbon/THF eluents at around 254 nm. In order to gain high sensitivity in gradient elution, we removed the stabilizer from the THF by distillation under N2 123). Caution is required with respect to peroxides. 

Mori S (1996) Characterization of styrene-acrylonitrile copolymers by size exclusion chromatography/stepwise gradient elution-liquid precipitation chromatography. Int J Polym Anal Charact 2 185-92. 

Cools, P. J. C. H., Maesen, R, BQumperman, B., van Herk, A. M., and German, A. L. Determination of the chemical composition distribution of copolymers of styrene and butadiene by gradient polymer elution chromatography. /. Chro-matogr., 736, 125, 1996. 

To extend the )plications of LC-NMR, we have further examined the compositions and blockiness of various polymer mixtures, including pBA and polybutadiene, where 1,4-butadiene, 1,2-butadiene and BA were identified by their unique H chemical shifts at tqrproximately 5.35, 4.95 and 3.98 ppm, respectively. In reverse-phase HPLC with the same solvent gradient conditions as above, homopolymer pBA and polybutadiene eluted at 21.76 and 34.20 min., respectively. TTie random copolymers of p(MMA/BA) and p(MMA/Sty) both eluted between 8 and 18 minutes. Owing to their hydrophobicity, the hi er the percentage of BA and styrene in the copolymer, the longer the retention time. Figure 5 illustrates the LC separation of pMMA, pBA, p(MMA/BA) and p(BA-b-MMA) by a reverse-phase column. A comparison of p(MMA/BA) random copolymer (retention time 13.9 min.) to p(BA-b-MMA) block copolymer (retention time 18.3 min.) with similar composition shows that the block copolymer interacted more with the C-18 stationary phase and eluted at a later time. This result demonstrated that the retention of p(MMA/BA) copolymer by reverse-phase LC is predominately influenced by die pBA portion of dre copolymer. The block copolymer, which mimics the homopolymer pBA, is mote hydrophobic and retained more on die C18 colunm than the random copolymer. The excellent LC separation permits us to quantitatively determine... 

A 30-min 99/1->93/7 chloroform/ethanol gradient was used with a silica column (A = 254nm) to characterize styrene/methyl and ethyl methacrylate copolymers [755]. That the ethanol content was critical was shown through a series of chromatograms for a 50/50 styrene/methyl methacrylate co-polymer and a 35/65 styrene/ethyl methacrylate co-polymer. For 25 pL injections of 0.1% w/v samples, the 50/50 co-polymer completely eluted with a 97/3 chloroform/ethanol mobile phase but was completely adsorbed to the silica at 99/1. Similarly, the 35/65 copolymer eluted at 95/5 chloroform/ethanol and did not elute at 98/2. Temperature effects (40-70°C) on the level of ethanol needed for elution were tabulated for these co-polymers as well. 

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