André M. Striegel · 2017. 2. 17. · quadruple-detector SEC. ... Base pair sequence Genetic code,...
Transcript of André M. Striegel · 2017. 2. 17. · quadruple-detector SEC. ... Base pair sequence Genetic code,...
Copolymer Characterization
by
Multi-Detector
Size-Exclusion Chromatography
André M. StriegelNational Institute of Standards & Technology
Objectives
• Introduction to macromolecular distributions.
• Determine chemical heterogeneity in copolymer using
quadruple-detector SEC.
• Examine and correct effect of n/c heterogeneity on
calculated M averages, distribution, etc.
• Extend method to “dual-absorbing” copolymers.
• Apply quintuple-detector SEC to show
physicochemical basis for conformational changes
across MMD.
Styrene Polystyrene
n can take on a range
of values
Therefore, so can M
10 20 30 40 50 60 70 80 900
20
40
60
80
100
120
Dif
fere
nti
al
We
igh
t F
rac
tio
n
Molar Mass
Molar Mass
(MM)
Short-Chain
Branching
(SCB)
Long-Chain
Branching
(LCB)
Polyelectrolyte
Charge
(+/-)
+
+
++
+
++
+
++
+
Chemical
Heterogeneity
(CH)
Chemical
Composition
Distribution
(CCD)
MM
SCB
LCB
+/-
CH
Ch
em
ica
l Co
mp
os
ition
Differential Weight Fraction
CCD
Striegel, Yau, Kirkland, & Bly, Modern Size-Exclusion Liquid Chromatography, 2nd ed. (2009)
Macromolecular distributions: Measurement and End-Use Effects
Macromolecular Representative end-use Separation method used for
Property properties affected determination
Molar mass Elongation, tensile strength, adhesion SEC, FFF, HDC, TGIC, CEC, SFC, MALDI-MS,
rheology
Long-chain branching Shear strength, tack, peel, crystallinity SEC-MALS, SEC-VISC, rheology, enzymology
Short-chain branching Haze, stress-crack resistance, crystallinity SEC-IR, SEC-NMR, TREF, CRYSTAF, enzymes
Crosslinking Gelation, vulcanization, surface roughness SEC-MALS, SEC-VISC, rheology
“Architecture” Flow modification, diffusion, encapsulation SEC-MALS-QELS-VISC
Tacticity Crystallinity, anisotropy, solubility SEC-NMR, TGIC, LCCC,
Chemical composition Morphology, miscibility, solubility GPEC, TGIC
Chemical heterogeneity Toughness, brittleness, biodegradability SEC-spectroscopy/spectrometry, LCCC, PFC
Chemical composition Mechanical properties, blending, plasticization 2D-LC (e.g., SEC-GPEC)
vs. molar mass
Block sequence Dielectric properties, reactivity, miscibility SEC-spectroscopy, 2D-LC (e.g., PFC-SEC)
Base pair sequence Genetic code, heredity, mutations Automated DNA sequencing, MALDI-MS
Polyelectrolyte charge Flocculation, transport, binding of metals SEC-conductivity
Particle size Packing, drag, friction, mixing FFF, HDC, PSDA, sieving
Striegel, Yau, Kirkland, & Bly, Modern Size-Exclusion Liquid Chromatography, 2nd ed. (2009)
Measuring
Chemical Heterogeneity
in a
Random Copolymer
Macromolecular Distributions:Measurement & End-Use Effects
• Property: Chemical Heterogeneity
0
20
40
60
80
100
120
Dif
fere
nti
al W
eig
ht
Fra
cti
on
Molar Mass
Molar Mass
(MM) MM
CHChemical
Heterogeneity
(CH)
Relative ab
un
dan
ce
Macromolecular Distributions:Measurement & End-Use Effects
• Property: Chemical Heterogeneity
• Definition: Change in average chemical
composition of a copolymer as f(M),
uncorrected for local polydispersity.
Macromolecular Distributions:Measurement & End-Use Effects
• Property: Chemical Heterogeneity
• Affects: Melting point, gas permeation,
conductivity, interfacial fracture energy
• Measured using: SEC with physico-
chemical detection methods
Measuring Chemical Heterogeneity
• Random copolymer of styrene (St) and methyl methacrylate (MMA):
Is relative ratio of St:MMA constant as a function of molar mass?
• Styrene absorbs at 260 nm, but methyl methacrylate does not.
• UV detector @ 260 nm will respond only to styrene content in polymer.
• Differential refractometer will respond to both styrene and methyl methacrylate
in polymer.
Measuring Chemical Heterogeneity
DRIDifferential refractometer
UVUltraviolet
MALSMulti-angle light scattering
VISCDifferential Viscometer
Styrene (but not MMA)
absorbs @ 260 nm
Both St & MMA
elicit DRI response
Relative Detector Response:
DRI vs. UV
20 22 24 26
0.0
0.2
0.4
0.6
0.8
1.0
UV Signal Conc. of St only
Re
lati
ve
De
tec
tor
Sig
na
l (a
rbit
rary
un
its
)
Retention volume (mL)
DRI Signal Conc. of both St and MMA
iDRI
iUV
i
PSDRI
PSUV
PMMAPS
i
PS
PMMA
i
i
S
SZ and constant
S
SF where
c
n
c
nZ
c
nF
c
nZ
St
,
,
,
,
%100)(%
Haidar Ahmad & Striegel, Anal. Bioanal. Chem., 396 (2010) 1589
5.0x104
1.0x105
1.5x105
2.0x105
2.5x105
3.0x105
3.5x105
0.5
1.0
1.5
2.0
2.5
3.0
18
20
22
24
26
28
30
Dif
fere
nti
al W
eig
ht
Fra
cti
on
(d
Wf /d
M)
Molar Mass, M (g/mol)
MMD
% Styrene
Weig
ht P
erc
en
t Sty
ren
e (%
St)
Measuring Chemical Heterogeneity
Haidar Ahmad & Striegel, Anal. Bioanal. Chem., 396 (2010) 1589
Chemical Heterogeneity
Translates Into
n/c Heterogeneity
c
nn
c
n
c
0
0lim
n: refractive index of solution
n0: refractive index of solvent
c: concentration of analyte in solution
n/c versus %PS
y = 0.0011x + 0.0852
R2 = 0.9951
0.08
0.12
0.16
0.2
0 25 50 75 100% PS
dn
/dc
(mL
/g)
dn/dc vs % PS
Linear (dn/dc vs % PS)
75% PS Block
copolymer
100% PS
100%
PMMA
Alternating
copolymers
(50% PS)
20% PS random
copolymer
25% PS Block &
Random copolymers
What Does This Mean?
• Molar mass M determined by multi-detector SEC is
influenced by chemical identity of analyte.
• This influence enters through the n/c-dependence
of the static light scattering (SLS) and differential
refractive index (DRI) detector signals:
• M averages and distribution determined from ratio
of these signals at each SEC elution slice i:
cc
nM SSLS
2
c
ncSDRI
i
i
i
i
i
i
i
i
i
c
nM
cc
n
cc
nM
S
S
2
DRI,
,SLS
What Does This Mean?
• Therefore, chemical heterogeneity translates into
n/c heterogeneity.
• In turn, heterogeneity in n/c translates into a bias
in the molar mass averages and distribution
calculated via SEC/MALS/DRI .
• (This bias will also manifest itself in SEC using
LALS, peak-position calibrant-relative calibration, or
universal calibration).
We can correct for this:
• First, correct n/c for chemical heterogeneity:
iMMA
PMMA
iSt
PSicorrected
wc
nw
c
n
c
n,,
,
y = 0.0011x + 0.0852
R2 = 0.9951
y = 0.001x + 0.087
0.08
0.12
0.16
0.2
0 25 50 75 100% PS
dn
/dc
(mL
/g)
dn/dc vs % PS
Linear fit
Predicted
n/c = [(0.191 wSt) + [0.087 (1 - wSt)]
n/c versus %PS
We can correct for this:
• First, correct n/c for chemical heterogeneity:
• Then, use this value to correct calculated M:
iMMA
PMMA
iSt
PSicorrected
wc
nw
c
n
c
n,,
,
icorrected
duncorrecteiduncorrecteicorrected
c
n
c
n
MM
,
,,
Chemical Heterogeneity Corrected MMD
5.0x104
1.0x105
1.5x105
2.0x105
2.5x105
3.0x105
3.5x105
0.5
1.0
1.5
2.0
2.5
3.0
18
20
22
24
26
28
30
Dif
fere
nti
al W
eig
ht
Fra
cti
on
(d
Wf /d
M)
Molar Mass, M (g/mol)
Uncorrected MMD
Corrected MMD
% Styrene
We
igh
t Pe
rce
nt S
tyre
ne
(%S
t)
Uncorrected Corrected
Mn (g/mol) 170,000 11,900 175,000 11,900
Mw (g/mol) 200,000 800 209,000 800
Mz (g/mol) 234,000 2,100 250,000 2,100
Mw/Mn 1.18 0.08 1.19 0.07
Error in M depends both
on M and on
n/c difference among
monomers in copolymer
Haidar Ahmad & Striegel, Anal. Bioanal. Chem., 396 (2010) 1589
22
As % composition
changes…
[(n/c)PS × wSt] +
[(n/c)PMMA × wMMA](n/c)copolymer =
(n/ c)copolymer
changes
SDRI = c (n/c)copolymer
Concentration
changes
ccnMS 2SLS )/(
Molar mass
changes
Intrinsic viscosity
changes c
sp
c
lim
0
][
Solution
conformation
changes
Chemical Heterogeneity:
Effect on Calculated Parameters
Chemical Heterogeneity Also Affects
Calculated Conformation
7x104
105
2x105
3x105
4x105
50
100
150
Intr
insic
Vis
co
sit
y,
[]
(mL
/g)
Molar Mass, M (g/mol)
Uncorrected
Corrected
0.71 0.01
0.60 0.01
105
2x105
3x105
10
15
20
25
Ra
diu
s o
f G
yra
tio
n,
RG (
nm
)
Molar Mass, M (g/mol)
Uncorrected
Corrected
0.64 0.01
0.59 0.01
Mark-Houwink Plot Conformation Plot
Polymer adopts a less extended conformation in solution than originally believed.
Haidar Ahmad & Striegel, Anal. Bioanal. Chem., 396 (2010) 1589
Determining
Chemical Heterogeneity
in Copolymers:
The “Dual-Absorption” Case
“Dual-Absorption” Copolymers
• In previous case, only one monomer in copolymer absorbed at a given UV wavelength.
• What is both monomers absorb at the same wavelength, however?
• Also, what can adding QELS detection tell us about the copolymer?
• How does chemical heterogeneity affect solution structure?
• What is the underlying physicochemical basis?
Poly(AM-co-DMAM)
H2C CH CH2 CH
C O
NH2
C O
N
( () )x 1-x
Poly(acrylamide-co-N,N-dimethyl acrylamide)
Homopolymer Absorptivities
Absorptivity = 84 ± 1 mL ∙ mg-1 ∙ cm-1 Absorptivity = 1913 ± 1 mL ∙ mg-1 ∙ cm-1
@ 240 nm
Polyacrylamide
(PAM)
Poly(N,N-dimethyl acrylamide)
(PDMAM)
CH2 CH
C O
N
( )n
H2C CH
C O
NH2
( )n
SEC/MALS/DLS/VISC/UV/DRI
© Wyatt Technology Corporation 2005 - All Rights Reserved
What’s Next…
• Remainder of day
– hands-on experience with hardware and software
– batch lab experiment, real data!
• Summary session bring questions!
Solvent
Reservoir
Pump Injector Thermostatted
SEC columns MALS/DLS
DRI VISC
Fluid connection
Electronic connection
UV
Wt% DMAM at each SEC slice i
%
c
n
c
nSaaZ
aZc
nS
DMAM
PDMAMPAM
r,iR,CopolymePAMPDMAMPDMAM
PAMPDMAM
PAM
r,iR,Copolyme
i 100%
iDRI
iUV
iCopolymerRS
SS
,
,
,,
PDMAM
PDMAMPDMAMR
PDMAM
PDMAM
PDMAMDRI
PDMAMUV
PDMAMa
c
n
Sa
c
n
S
SZ
,
,
,
where
a = absoptivity of constituent
homopolymers
Rowland & Striegel, Anal. Chem., 84 (2012) 4812
Chemical Heterogeneity of
P(AM-co-DMAM)
Rowland & Striegel, Anal. Chem., 84 (2012) 4812
104
105
106
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Molar Mass, M (g mol-1)
Dif
fere
nti
al
We
igh
t F
rac
tio
n
72
74
76
78
80
82
84
86
88
90
92%
N,N
-dim
eth
yla
cry
lam
ide
Polymer Size(s)
• Radius of gyration (a.k.a. rms radius): From MALS + DRI
• Hydrodynamic (a.k.a. Stokes) radius: DLS (a.k.a. QELS) + DRI
• Viscometric radius: MALS + VISC + DRI
2/1
2)(1
1
i
c miG Rrn
R
Ts
BH
D
TkR
6
3/1
10
3
AN
MR
RG and RH Conformation Plots
Rigid Rod
Random Coil
Hard Sphere
0.60 ≥ α ≥ 0.50
α = 1
α = 0.33
105
106
1
10
100
Rad
ius (
nm
)
Molar Mass (g mol-1)
RH
RG
slope = 0.58
= 0.56
df = 1.8
Rowland & Striegel, Anal. Chem., 84 (2012) 4812
ρ ( ≡ RG /RH) Parameter
105
106
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
R
G/R
H
Molar Mass, M (g/mol)
Linear Random CoilTransition to More
Extended Coil
PDMAM
homopolymer
Rowland & Striegel, Anal. Chem., 84 (2012) 4812
Mark-Houwink & Conformation Plots
Rigid Rod
Random
Coil
Hard
Sphere
0.80 ≥ a ≥ 0.50
a = 2
a = 0
105
106
1
10
100
10
100
1000
Rad
ius (
nm
)
Molar Mass (g mol-1)
a = 1.07
df = 1.45
a = 0.64
df = 1.8
[]
RH
RG
slope = 0.58
= 0.56
df = 1.8 In
trinsic
Vis
cosity
, [n] (m
L g
-1)
Rowland & Striegel, Anal. Chem., 84 (2012) 4812
Rη/RG Plot
105
106
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
R/R
G
Molar Mass, M (g/mol)
Linear Random CoilTransition to More
Extended Coil
PDMAM
homopolymer
Rowland & Striegel, Anal. Chem., 84 (2012) 4812
6x104
2x105
4x105
6x105
8x105
106
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
R
Molar mass, M (g/mol)
Poly(St-ran-MMA)
Poly(St-ran-MMA)
Poly(St-alt-MMA)
Poly(St-b-MMA), 75% St
Poly(St-b-MMA), 25% St
PS
PMMA
Hard-sphere limit
Appro
xim
ate
random
coil
ra
nge
RG
R/RG of Homo- and Copolymers
Haidar Ahmad, Striegel, & Striegel, Polymer, 52 (2011) 1268
Lack of Chemical Heterogeneity in
Random S-MMA Copolymers
Random Copolymer 126k
Random Copolymer 186k
Haidar Ahmad, Striegel, & Striegel, Polymer, 52 (2011) 1268
PS PMMA
S-SS-MMA MMA-MMA
1074 cm-1
IR peak
S and MMA Homo- and Copolymers
R/R
G
R/RG
R/RG
Fraction A Fraction B Fraction C
Area under
1074 cm-1
Area under
1074 cm-1
Area under
1074 cm-1< <
Molar mass (g/mol)
Off-Line IR Analysis of SEC “Heart-Cuts”
Persistence Length, Lp
Lpr
Î1
2/1
2
GR
M
1/M
2/1)3(2
3LpL MLM
2/1
3
p
L
L
M
222
31
32/12/1
2
Lp
Lp
p
L
GML
M for ,
M
ML
L
M
R
M
Striegel, Yau, Kirkland, & Bly, Modern Size-Exclusion Liquid Chromatography, 2nd ed. (2009)
Persistence Length of Poly(AM-co-DMAM)
3.0x10-6
4.0x10-6
5.0x10-6
6.0x10-6
7.0x10-6
32
34
36
38
40
42
(M/2LPM
L) = 2.2
Lp = 12 1 nm
ML = 3120 6 g mol
-1 nm
-1
(M/R
G2)1
/2
1/M
R2 = 0.993
Poly(AM-co-DMAM)
Rowland & Striegel, Anal. Chem., 84 (2012) 4812
104
105
106
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Molar Mass, M (g mol-1)
Dif
fere
nti
al W
eig
ht
Fra
cti
on
72
74
76
78
80
82
84
86
88
90
92
% N
,N-d
imeth
yla
cry
lam
ide
Transition in Polymer Conformation
Extended Coil
(“Alt”-like)
T
r
a
n
s
i
t
i
o
n
R
e
g
i
o
n
Random Coil
(“Homo”-like)
RG ≤ Lp Lp < RG ≤ 2Lp 2Lp < RG
Lp = 12 1 nmRowland & Striegel, Anal. Chem., 84 (2012) 4812
Info From Multi-Detector SEC(Not a Comprehensive List)
MALS
QELS
VISC
DRI
UV
[]
CC
M-H plot,
R, R/RG
M aves, MMD,
Confor. plot, Lp
CH
CC: Chemical compostion, CH: Chemical heterogeneity, M-H: Mark-Houwink, RG,z/RH,z
CONCLUSIONS
• Chemical heterogeneity in copolymers results in n/c heterogeneity.
• n/c heterogeneity can affect calculated M averages, distributions, etc.
• Appropriate choice of SEC detectors allows accurate characterization of copolymers.
• Can also inform knowledge of physicochemical basis for conformational changes as f(M).
• Method has also been extended to binary blends.