Application Compendium - Agilent Technologies
Application Compendium - Agilent Technologies
Application Compendium - Agilent Technologies
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log Mp<br />
5<br />
4.6<br />
4.2<br />
3.8<br />
0.5<br />
15% Water / 15% ACN /<br />
70% Water<br />
17% Water / 17% ACN /<br />
66% THF<br />
1.5 2.5 3.5 4.5<br />
min<br />
Figure 5b. Critical point diagrams for PMMA.<br />
19% Water / 17% ACN /<br />
64% THF<br />
Under the critical conditions for PMMA, chromatography of<br />
PS resulted in elution based on adsorption mode.<br />
Chromatograms of two polystyrene narrow standards eluting<br />
under polymethyl methacrylate critical conditions are shown<br />
in Figure 6.<br />
0<br />
Polystyrene Mp 580 g/mol<br />
Polystyrene Mp 1260 g/mol<br />
2 4 6 8<br />
min<br />
Figure 6. Chromatograms of polystyrene standards under polymethyl<br />
methacrylate critical conditions.<br />
Under the critical conditions for PS, PMMA resulted in elution<br />
based on SEC.<br />
Figure 7 shows chromatograms of a series of polymethyl<br />
methacrylate narrow standards and a SEC calibration curve<br />
obtained under the polystyrene critical conditions.<br />
5.5<br />
10<br />
4<br />
molecular weight<br />
/ gmol -1<br />
1.0E6<br />
1.0E5<br />
1.0E4<br />
1.0E3<br />
1.0<br />
1.4 1.8 2.2 2.6<br />
min<br />
Figure 7. PMMA standards and SEC calibration curve run under PS critical<br />
conditions.<br />
The poly(styrene-b-methyl methacrylate) sample was<br />
analyzed under the critical conditions for polystyrene.<br />
Using these conditions, the elution is controlled purely by<br />
the molecular weight of the methyl methacrylate block of<br />
copolymer, the polystyrene block is ‘chromatographically<br />
invisible’.<br />
Figure 8 shows the molecular weight distributions of the<br />
polystyrene block by conventional GPC using polystyrene<br />
standards before introduction of the methyl methacrylate<br />
and growth of the PMMA block, and the PMMA block under<br />
critical conditions for polystyrene using PMMA standards.<br />
dw/dlogM<br />
6.0<br />
4.8<br />
3.6<br />
2.4<br />
1.2<br />
0.0<br />
3.5<br />
PMMA block<br />
by NMR = 30,300 g/mol<br />
by SEC (PS LCCC)<br />
= 29,400 g/mol<br />
PMMA block<br />
(SEC under PS LCCC,<br />
PMMA standards)<br />
3.9 4.3 4.7 5.1<br />
min<br />
PS block<br />
(Normal SEC,<br />
PS standards)<br />
Figure 8. Molecular weight distributions of the styrene block before<br />
reaction with PMMA, and the PMMA block under critical conditions for<br />
polystyrene.<br />
3.0<br />
5.5