Full Characterization of Polymers Using the ACQUITY Advanced Polymer Chromatography (APC) System with Multi-Detection
1
[ APPLICATION NOTE ]
WATERS SOLUTIONS
ACQUITY Advanced Polymer
Chromatography™ (APC) System
KEYWORDS
Size Exclusion Chromatography, SEC, Ultra
High-Performance Liquid Chromatography,
UHPLC, GPC, polystyrene, PS1478
and PS706a, polyvinylchloride,
PVC, polycarbonate
APPLICATION BENEFITS
The ACQUITY™ APC™ System employs high
efficiency separation columns and a low
dispersion flow path, resulting in:
■
High resolution analysis
■
Shorter analysis times
■
Reduced solvent consumption
■
Reduced sample concentration
Full Characterization of Polymers Using the ACQUITY Advanced Polymer
Chromatography (APC) System with Multi-Detection
Larry Meeker1 and John Stenson2
1
Waters Corporation, Houston, TX, USA; 2 Malvern Panalytical, Houston, TX, USA
INTRODUCTION
In recent years, new developments in the area of Size Exclusion
Chromatography (SEC) have resulted in the introduction of Ultra High-
Performance Liquid Chromatography (UHPLC) for polymer applications.
Waters™ ACQUITY Advanced Polymer Chromatography (APC) is a
breakthrough technology that is able to provide SEC analyses of polymeric
materials with enhanced resolution and speed than conventional SEC.
The APC System employs Refractive Index (RI) and Ultraviolet PDA (UV)
to generate relative molecular weight information versus conventional
calibration techniques that use elution volume/retention times.
Similar improvements have been made to advanced GPC/SEC technologies
such as viscometers and light scattering detectors to make them
compatible with APC. Malvern Panalytical recently introduced a version
of the OMNISEC REVEAL advanced detector unit that through a collaboration
with Waters has been optimized for integrated use under APC conditions.
In this application note, the analyses of several polymers by ACQUITY APC
combined with the OMNISEC REVEAL are presented and discussed.
Figure 1. ACQUITY APC System with OMNISEC REVEAL.
2
Full Characterization of Polymers Using the ACQUITY Advanced Polymer Chromatography (APC) System with Multi-Detection
[ APPLICATION NOTE ]
[ APPLICATION NOT
EXPERIMENTAL
Sample description
Two NIST polystyrene (PS) standards, PS1478
and PS706a, a broad polyvinylchloride (PVC)
and a broad polycarbonate (PC)
LC conditions
LC system:
ACQUITY APC
Detection:
OMNISEC REVEAL with
RI, LS (RALS 90° angle,
LALS 7° angle), and
IV detectors
Vials:
Waters vials with
pre-slit septa
Column
ACQUITY APC XT,
150 mm, 900 Å, 450 Å,
and 200 Å, in series
Column temp.:
35 °C
Sample temp.:
35 °C
Injection volume:
20 µL
Flow rate:
1.0 mL/min
Mobile phase:
THF (unstabilized)
Data management
ACQUITY APC operation: Standalone
ACQUITY Console Software
OMNISEC operation, data collection,
and processing: Malvern Panalytical
OMNISEC software
RESULTS AND DISCUSSION
NIST POLYSTYRENE STANDARDS
A chromatogram for the NIST PS1478 polystyrene narrow molecular weight
standard is shown in Figure 2. Also shown in Figure 2 is the Log molecular
weight, Log intrinsic viscosity (IV), and Log hydrodynamic radius (Rh).
Figure 3 shows the chromatogram for the NIST PS706a polystyrene broad
molecular weight standard. Also shown in Figure 3 is the Log Mw, Log IV,
and Log Rh.
Both chromatograms demonstrated excellent detector response with
low sample loadings.
Figure 2. RI, RALS, and DP chromatograms obtained from a PS1478 NIST standard.
10 µL injection volume, 2.5 mg/mL concentration. Log Mw, IV, and Rh are also shown.
Figure 3. RI, RALS, LALS, and DP chromatograms obtained for a PS706a NIST standard.
5 µL injection volume, 2 mg/mL concentration. Log Mw, IV, and Rh are also shown.
3
Full Characterization of Polymers Using the ACQUITY Advanced Polymer Chromatography (APC) System with Multi-Detection
[ APPLICATION NOTE ]
Table 1 shows the quantitative results obtained
from the OMNISEC-REVEAL. The absolute
molecular weights were calculated directly
from Right Angle Light Scattering (RALS) and
Low Angle Light Scattering (LALS). In addition,
the viscometer provides the ability to calculate
the size and structural information about the
polymers. The values of molecular weight,
dispersity (Mw/Mn), intrinsic viscosity (IV),
hydrodynamic radius (Rh), and the
Mark-Houwink plot, and log K parameters were
all consistent with the values expected. The
calculated values of PS706a and PS1478 matched
the NIST certified Mw values of 285±0.23K g/mol
and 37.4±0.26K g/mol respectively, illustrating
excellent precision and accuracy.
Table 1. Molecular weight, size, and structure results for PS1478 and PS706a.
Parameters
Samples
PS1478
PS706a
Retention volume (mL)
4.47
3.28
Mn (g/mol)
35,790
11,600
Mw (g/mol)
37,360
286,700
Mz (g/mol)
39,120
479,300
Mw/Mn
1.044
2.57
IVw (dL/g)
0.2322
0.9394
Rhw (nm)
5.144
15.34
Rgw (nm)
N/A
15.42
M-H a
0.7239
0.6534
M-H log K (dL/g)
-3.943
-3.534
POLYCARBONATE AND POLYVINYLCHLORIDE
Samples of polycarbonate (PC) and polyvinylchloride (PVC) were dissolved in the mobile phase and injected into the
ACQUITY APC-OMNISEC REVEAL system. Figure 4 shows the chromatogram obtained for PC, and Figure 5 that for PVC.
As with the NIST samples, both chromatograms show excellent detector response with low sample loadings.
Figure 4. Representative
RI, RALS, LALS, and DP
chromatograms with molecular
weight, IV, and Rh distributions
of polycarbonate (PC).
10-µL injection volume,
3 mg/mL concentration.
Log Mw, IV, and Rh are
also shown.
Figure 5. Representative
RI, RALS, LALS, and DP
chromatograms with
molecular weight, IV,
and Rh distributions of
polyvinylchloride (PVC).
10-µL injection volume,
3 mg/mL concentration.
Log Mw, IV, and Rh are
also shown.
4
Full Characterization of Polymers Using the ACQUITY Advanced Polymer Chromatography (APC) System with Multi-Detection
[ APPLICATION NOTE ]
Table 2 shows the results obtained for PC and
PVC by the ACQUITY APC-OMNISEC REVEAL
system. The quantitative data obtained align
with the expected results obtained previously
using traditional GPC.
An overlay of the Mw distributions for duplicate
injections of PC, PVC, and PS706a is shown in
Figure 6. Figure 6 also demonstrates that the
three samples (PC, PVC, and PS) have very
different molecular weight distribution plots,
with the PS sample shifted toward the high
Mw region and PC toward the low Mw region.
The results in Table 1 and 2 show the average
values for IV and Rh for the different polymers.
These values can be used to make broad
structural comparisons between samples, but
to get a complete picture of the structure it is
necessary to use a Mark-Houwink plot to look at
the IV distribution across the entire Mw range.
The Mark-Houwink plot in Figure 7 shows
the structural comparison between the three
different samples, PC, PVC, and PS706a. This
plot shows the Log Mw plotted against the Log
IV and allows structural differences between the
samples to be clearly identified. PS is lowest on
the plot indicating it has a lower IV than PC and
PVC at comparable Mws. A lower IV is indicative
of a higher molecular density and suggests
a more compact configuration. PC has the
highest IV value indicating it has the most
open configuration.
PVC has a density falling between PC and PS.
In addition to this the IV of PVC deviates from a
linear behavior, with decreasing IV values in the
high Mw region. This indicates the presence of
branching at higher molecular weights. It would
have not been possible to obtain this insight
into the polymer’s architecture without the
use of a viscometer.
Parameters
Samples
PC
PVC
Retention Volume (mL)
4.34
3.87
Mn (g/mol)
12,220
39,750
Mw (g/mol)
23,060
84,460
Mz (g/mol)
33,650
268,600
Mw/Mn
1.886
2.124
IVw (dL/g)
0.4545
0.7351
Rhw (nm)
5.272
9.283
Rgw (nm)
N/C
N/C
M-H a
0.667
0.7063
M-H log K (dL/g)
-3.323
-3.566
Table 2. Molecular weight, size, and structure results for PC and PVC samples.
Figure 6. Overlay of duplicate molecular weight distributions of PC, PVC, and PS.
Figure 7. Mark-Houwink plots of PC, PVC, and PS overlaid and compared to show
structural differences.
Molecular weight (Da)
PC
PVC
PS
Region of
branching in
PVC
Increasing molecular density
Molecular weight (Da)
[ APPLICATION NOTE ]
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©2020 Waters Corporation. Produced in the U.S.A. February 2020 720006483EN AG-PDF
CONCLUSIONS
The combination of the ACQUITY APC System with the OMNISEC REVEAL
multi-detector system provides high quality, high-resolution and rapid
sample analysis. The presence of the highly sensitive LS and RI detectors
and the viscometer in the OMNISEC REVEAL system allowed for the
calculation of absolute molecular weight, hydrodynamic radius, and
structure of the materials. Two NIST polystyrene standards were correctly
characterized using the system as well as PC and PVC samples. A structural
comparison was performed using the Mark-Houwink plot with differences
between samples observed and regions of branching within PVC identified.
A comparison of the polymer characteristics was performed which would
not have been possible using only a conventional calibration system.
Accurate molecular weights and structural information can only be attained
using a multi-detection platform, such as ACQUITY APC and OMNISEC
REVEAL. The unique combination of ACQUITY APC separations with
Malvern Panalytical’s advanced detectors offers greater resolving power
with full sample characterization.
Acknowledgements
The authors gratefully acknowledge Malvern Panalytical for providing
the data presented in this application note.
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