BLOCK COPOLYMER
VESICLES
UNIVERSITY OF BAYREUTHTUESDAY, JUNE 13, 2006
ADI EISENBERG
NICE TO SEE YOU AGAIN
OUTLINEINTRODUCTION (BRIEF REVIEW OF FIRST LECTURE)
SMALL MOLECULE AMPHIPHILES AND DIBLOCK COPOLYMERSMETHODS OF PREPARATIONACCESSIBLE MORPHOLOGIESTHERMO, KINETICS AND MORPHOLOGICAL CONTROL MECHANISMS
VESICLES, PREPARATION AND THERMODYNAMICSTYPES OF VESICLESTHERMODYNAMIC CURVATURE STABILIZATIONCONTROL OF INTERFACIAL COMPOSITIONINVERSIONEQUILIBRIUM CONTROL OF SIZESTRIGGERS FOR MORPHOLOGICAL AND DIMENSIONAL CHANGES
(IONS, SURFACTANTANTS, WATER…)KINETICS AND MECHANISMS OF SIZE CHANGES
VESICLES, FILLING AND NON-DESTRUCTIVE RELEASEFILLING OF ACTIVE INGREDIENTS (DOX)DIFFUSIONAL RELEASE OF CONTENTS (DOX)DIFFUSION OF PROTONS THROUGH VESICLE WALLS
CONCLUSIONS
BLOCK AND GRAFT COPOLYMERS
AB Diblock
ABA
BAB
Tapered block
Graft
Triblock
Alternating block
A sodium dodecylsulfate (SDS) micelle model (n=60) drawn to scale. After Israelachvili
Star Micelle
(PS23-b-PANa2400)
“Crew-cut” Micelle
(PS420-b-PANa46)1 :100 10:1
Morphologies of Block Copolymers in Aqueous SolutionsMorphologies of Block Copolymers in Aqueous Solutions
201
Vesicle
Morphologies of Block Copolymers in Aqueous SolutionsMorphologies of Block Copolymers in Aqueous Solutions(Continued)(Continued)
Lamella
NEXT: PREP. AND MORPH.
PREPARATIVE METHODS (1)
TEMPERATURE QUENCH AND FREEZE-DRY EQUILIBRATED SOLUTIONS
Add water to polymer solution in dioxaneAt predetermined water concentration, drop temperature to near - liquid N2
Warm under vacuum to sublime off dioxane and water.
WATER QUENCH EQUILIBRATED SOLUTION AND DIALYZE
Add water to polymer solutionAt predetermined water concentration, quench into waterDialyze
Spherical micelles
PS(200)-b-PAA(21)
Lamellae
PS(49)-b-PAA(10)
HHH
PS(410)-b-PAA(13)LCM
PS(200)-b-PAA(4)
Vesicles
PS(410)-b-PAA(13)
Rods
PS(190)-b-PAA(20)
Bicontinuous Rods
PS(190)-b-PAA(20)
Lamellae
PS(132)-b-PAA(20)
Cameron, N. S.; Corbierre, M. K.; Eisenberg, A. Can. J. Chem. 1999, 77, 1311.
THERMODYNAMICS OF FORMATIONOF CREW-CUT AGGREGATES
“MORPHOGENIC” CONTRIBUTIONS TO ΔG
1. CHAIN STRETCHING IN CORE2. REPULSION AMONG CORONA CHAINS3. INTERFACIAL ENERGY
LOW WATERCONTENT
HIGHWATERCONTENT
1. INTERFACIAL ENERGY INCREASES2. TOTAL INTERFACIAL AREA DECREASES3. CORE RADIUS INCREASES4. NUMBER OF MICELLES DECREASES5. CORE CHAINS ARE STRETCHED6. DISTANCE BETWEEN CORONA CHAINS
DECREASES7. CORONA CHAIN REPULSION INCREASES8. MORPHOLOGY CHANGES AT SOME
CRITICAL POINTS
FOR EXAMPLE: AS WATER IS ADDED
MORPHOLOGY CHANGES CAN BE INDUCED BY CHANGES IN ANY OF THE THREE
PARAMETERS BY DIFFERENT CONTROL MECHANISMS
RELATIVE BLOCK LENGTHS
WATER CONTENT
COPOLYMER CONCENTRATION
ADDED IONS, pH
NATURE OF COMMON SOLVENT
HOMOPOLYSTYRENE
TEMPERATURE
SURFACTANTS
POLYDISPERSITY
Phase Diagram of Fractionated PS310-b-PAA52 in Dioxane/H2O
Water Content (wt%)
0 5 10 15 20 25 30 35 40 45
Cop
olym
er C
once
ntra
tion
(wt%
)
0.1
1
10
Water Content (wt%)0 5 10 15 20 25 30 35 40 45 50
Copolymer (wt%
)
05
10
Diox
ane (
wt%
)
9095
100
S R R + V VS + R
Hongwei Shen & Adi Eisenberg, J. Phys. Chem. B 1999, 103, 9473
Now: Vesicles
TYPES OF VESICLES
small uniform vesicleslarge polydispersevesicles
entrapped vesicles
hollow concentric vesicles
onions
tube-walled vesicles
500 nm
100 nm
200 nm
PS410-b-PAA13 PS100-b-PEO30 PS200-b-PAA20
PS100-b-PEO30PS260-b-P4VPDecI70PS132-b-PAA20
Original references given in S. Burke and A. Eisenberg Macromolecular Symposia (Warsaw IUPAC meeting)
500 nm
THEMODYNAMICALLY STABLE VESICLESARE PRODUCED BY WORKING IN
LARGE REGION OF THE PHASE DIAGRAMWHERE VESICLES ARE THE ONLY
(OR THE DOMINANT)MORPHOLOGY
SIZES, WALL THICKNESS AND INTERFACE COMPOSITION CAN BE CONTROLLED
BY FINE TUNING THE DETAILEDPREPARATIVE CONDITIONS
(WATER CONTENT, SOLVENT COMPOSITION, pH, IONIC STRENGTH, ETC.)
ARE VESICLES EQUILIBRIUM STRUCTURES? WHAT ARE KINETICS AND MECHANISMS OF FORMATION AND TRANSFORMATION?CURVATURE STABILIZATION MECHANISM?PROOF OF SEGREGATION USING LABELED BLOCK COPOLYMERS IS SEGREGATION SIZE DEPENDENT? IS SEGREGATION REVERSIBLE? ARE SIZES CONTROLLABLE?ARE SIZE CHANGES REVERSIBLE?
QUESTIONS ABOUT VESICLES (1)
CAN DIFFERENT GROUPS BE ATTACHED INSIDE AND OUTSIDE?CAN VESICLES BE INVERTED?HOW FAST DO VESICLES FUSE? WHAT IS THE EQUILIBRATION MECHANISM?CAN WALL THICKNESS BE CONTROLLED?CAN VESICLES BE FILLED? CAN WALLS BE PLASTICIZED? CAN PROTONS DIFFUSE THROUGH WALLS?
QUESTIONS ABOUT VESICLES (2)
Water Content (wt%)
0 10 20 30 40
Turb
idity
0.0
0.5
1.0
1.5
2.0
Water Addition
Dioxane AdditionMicellization
Spheres to rods
Rods to Vesicles
Changes in Aggregate Morphology Are Associated With Changes in Turbidity
PS310-b-PAA52 1% w/w in dioxane
Shen, H.; Eisenberg, A. J. Phys. Chem. B. 1999, 103, 9473-9487
Time (sec)
0 200 400 600 800 1000
Turb
idity
0.8
0.9
1.0
1.1
1.2
1.3
1.4
26.4 - 27.7 wt%
26.2 - 28.8 wt%
Turbidity Increase With Time After 1% Water Jump
PS310-b-PAA52 1% w/w in dioxane
Chen, L.; Shen, H.; Eisenberg, A. J. Phys. Chem. B. 1999, 103, 9488-9497
0 sec
Chen, L.; Shen, H.; Eisenberg, A. J. Phys. Chem. B. 1999, 103, 9488-9497
Time (sec)
0 500 1000 1500 2000
Turb
idity
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
((Tca
l. - T
exp.
)/Tex
p.) (
%)
-4
-2
0
2
4
6
8
10
12
DCBADouble Exponential Fit
Single Exponential Fit
Experimental Curve
Fitting Quality
Chen, L.; Shen, H.; Eisenberg, A. J. Phys. Chem. B. 1999, 103, 9488-9497
y = y0 + a(1 – exp(–k1*t)) + b(1 – exp(–k2*t))
y = y0 + a(1 – exp(–k1*t))
Concentration of Each Species
⎥⎦
⎤⎢⎣
⎡+−
−+−
−−=
⎥⎦
⎤⎢⎣
⎡+−
−
−+−
−
−−=
⎥⎦
⎤⎢⎣
⎡+−
−
−++−
−
−+−=
21
212
122
211
121
210
21
212
122
2211
121
1210
21
212
122
2121211
121
2111210
)exp()(
)exp()(
)exp()()(
)exp()()(
)exp()(
)exp()(
mmkk
tmmmm
kktm
mmmkk
CC
mmkktm
mmmmkk
tmmmmmkk
CC
mmkktm
mmmmmmkkk
tmmmm
mmmkkkCC
ffffffrvt
bbbfbfrlt
bbfbbfbbrrt
m1 and m2 stand for:
[ ]
[ ])(4)()(21
)(4)()(21
2121212
221122112
2121212
221122111
ffbfbbbfbfbfbf
ffbfbbbfbfbfbf
kkkkkkkkkkkkkkm
kkkkkkkkkkkkkkm
++−+++++++=
++−+++−+++=
Time (sec)
0 200 400 600 800 1000 1200 1400 1600 1800 2000
C/C
r0
0.0
0.5
1.0
1.5
Vesicle
Lamella
Rod
Chen, L.; Shen, H.; Eisenberg, A. J. Phys. Chem. B. 1999, 103, 9488-9497
Concentration of Each Species
Next: Curvature stabilization mechanism
Transmission electron micrograph (TEM) of vesicles of PS300-b-PAA44
Quenched from dioxane/water (60/40) at 1 wt % polymer.
PREFERENTIAL SEGREGATION
OF CORONA CHAINS:
ARE VESICLES UNDER EQUILIBRIUM CONTROL?ARE VESICLES UNDER EQUILIBRIUM CONTROL?
WORKING HYPOTHESIS ON THERMODYNAMIC CURVATURE STABILIZATION
SHORT CHAINSTO THE INSIDE
LONG CHAINSTO THE OUTSIDE
POLYMER WITH FLUORESCENT LABEL
Bu
COOH
HCH2 CH CH2 CH CH2 CH 295 X PS295-Py-b-PAAxX = 12, 45, 74
Abs
orpt
ion
UV-vis spectrum of pyrene Emission spectrum of vesicles in solution upon irradiation at 343 nm
Wavelength (nm)360 380 400 420 440 460
Inte
nsity
(a.u
.)
Wavelength (nm)
250 300 350 400
Parent system: PS300-b-PAA44
L. Luo and A. Eisenberg, JACS 2001, 123, 1012-1013
Proof of Segregation by Block Length in Vesicles
Modified Stern-Volmer equation: φφ
11
0
0 +=− KQII
I
Spherical micelles
[Tl+]/mM0.0 0.2 0.4 0.6 0.8 1.0
1
2
3
4Vesicles
[Tl+]/mM0.0 0.2 0.4 0.6 0.8 1.0
I 0/I
1
2
3
4
PS295-Py-b-PAA74
PS295-Py-b-PAA45
PS295-Py-b-PAA12
I 0/I
PS295-Py-b-PAA12
PS295-Py-b-PAA45
PS295-Py-b-PAA74
Apparent φ and K values of the PS-b-PAA Micelles and Vesicles
micelles vesicles
system φ K(mM-1) φ K(mM-1)
PS300-b-PAA44/PS295-Py-b-PAA12
0.91±0.07*
(0.85)**
9.5±1.0(9.9)
0.065±0.003(0.065)
9.0±0.6(9.0)
PS300-b-PAA44/PS295-Py-b-PAA45
0.92±0.07(0.85)
9.2±0.9(9.7)
0.53±0.02(0.53)
8.9±0.4(8.9)
PS300-b-PAA44/PS295-Py-b-PAA74
0.91±0.07(0.85)
9.3±0.9(9.8)
0.88±0.05(0.83)
8.4±0.6(8.8)
*: value± standard error.**: the numbers in brackets were used to calculate the lines in the Figure. They were chosen to give the best fit. All the values are within the error limits.
Laibin Luo & Adi Eisenberg, Langmuir 2001, 17, 6804
Segregation in PS300-b-PAA44 copolymer vesicles
PS30 0-b- PAA44
φ = 0.91
φ = 0.065
PS295-Py-b-PAA12
PS3 0 0-b- PAA4 4 PS3 0 0-b- PAA4 4
φ = 0.91
φ = 0.88
PS295-Py-b-PAA7 4
PS3 0 0-b- PAA4 4
PS295-Py-b-PAA4 5
φ = 0.92
φ = 0.53
Size-dependent segregation of hydrophilic block in PS-b-PAA diblock copolymer vesicles
Vesicle Size (nm)0 200 400 600 800 1000 1200
Que
nchi
ng P
erce
ntag
e
0.0
0.2
0.4
0.6
0.8
1.0PS310-b-PAA28/PS295-Py-b-PAA74
PS300-b-PAA44/PS295-Py-b-PAA74
PS310-b-PAA28/PS295-Py-b-PAA12
PS300-b-PAA44/PS295-Py-b-PAA12
Is Size Dependent Segregation Reversible?
[Tl+]0.0 0.2 0.4 0.6 0.8 1.0
I 0/I
1.00
1.05
1.10
1.15
1.20
1.25
1.30
1.35
1.40PS300-b-PAA44/PS295-Py-b-PAA12
66.7%
50.0%
39.4%
28.6%
24.5%
increasing water contentdecreasing water content
Run
#
1
2
3
4
5
6
7
8
9
Reversibility of chromophore segregation in response to change in vesicle size induced by increasing or decreasing
water contents for PS300-b-PAA44 with 5% PS295-Py-b-PAA12 in 44.4/55.6 THF/Dioxane mixture
Experiment# (direction)
Water content /%
Vesicle size /nmφ (accessibility) /%
Polymer concentration /%Experiment# (direction)
Water content /%
Vesicle size /nm
φ (accessibility) /%Polymer concentration /%
1
24.591±3
4.82±0.06
7.55
228.6
100±49.73±0.09
7.14
339.4
120±513.8±0.2
6.06
450.0
151±619.8±0.2
5.00
566.7
201±325.9±0.3
3.339
24.5
91±24.95±0.04
1.22
8
28.6
99±59.87±0.06
1.43
7
39.4
120±413.9±0.2
1.97
6
50.0
150±620.2±0.2
2.50
Next: different interfaces in and out and inversion possibility
CAN DIFFERENT GROUPS BE ATTACHED INSIDE AND OUTSIDE?
GOAL: PAA insideP(4-VP) outside
POLYMERS USED:
PS300-b-PAA11 (SHORT PAA FOR INSIDE)
PS310-b-P(4-VP)33 (LONG P(4-VP) FOR OUTSIDE)
PS295-Py-b-PAA12 (LABELED SHORT PAA)
PS300-b-PAA44* (FOR ζ COMPARISON)
PREP: DMF, adjust pH to 3, add water to 50%, quench, dialyze* dioxane, add water to 40%, quench, dialyze
BLOCK COPOLYMERS RESULTING MORPHOLOGIES
PS310-b-P(4-VP)33 60% VESICLES; D=88±12nm; Wall=26±2nm
PS300-b-PAA11 35%PS295-Py-b-PAA12 5%
PS300-b-PAA11 LCMs
PS310-b-P(4-VP)33 VESICLES; D=102±14nm; Wall=26±2nm
PS310-b-P(4-VP)33 60% VESICLES; D=90±12nm; Wall=26±2nm
PS300-b-PAA11 40%
PS300-b-PAA44 VESICLES; D=98±7nm; Wall=26±3nm
OUTSIDE OF VESICLES STUDIED BY pH DEPENDENCE OF ζ-POTENTIAL
-60
-40
-20
0
20
40
pH2 3 4 5 7 8 9 106
ζpotential / m
V
EXTERIOR OF MIXED VESICLES SAME AS THAT OF PS310-b-P(4-VP)33 VESICLES
PS300-b-PAA44
PS310-b-P(4-VP)33
PS310-b-P(4-VP)33/PS300-b-PAA11
PAA26-b-PS890-b-P4VP40
O O
Nn
R
Hm x l
NH
F. Liu AND A. Eisenberg, Angewandte Chemie Int. Ed. 2003
.
The charges are on the chains, counterions are not shown
F. Liu and A Eisenberg, JACS 2003
HCl
NaOH
PAA-b-PS-b-P4VP
in DMF/THF
H2O
H2O
PAA-b-PS-b-P4VP
PAA -b-PS-b-P4VP
Vesicles with P4VP outside
Vesicles with PAA outside
PREPARATION OF THE TWO TYPES OF VESICLES
NEXT:INVERSION
Vesicles with PAA Outside
Vesicles with both PAAand P4VP outside
Vesicles withP4VP outside
2 h 6 h
INVERSION OF VESICLES, SCHEMATIC
Critical water content…..
log C0
-6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5
CW
C (w
t%)
2.0
2.5
3.0
3.5
4.0
DMF
DMF/THF (85/15, wt/wt)
DMF/THF (85/15 w/w),[HCl]/[4VP]:5.6)
Figure 7. Critical water content vs logarithm of the polymer concentration in various solvents or solvent mixtures
Critical water content…..
log C0
-6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5
CW
C (w
t%)
2.0
2.5
3.0
3.5
4.0
DMF
DMF/THF (85/15, wt/wt)
DMF/THF (85/15 w/w),[HCl]/[4VP]:5.6)
Critical water content vs logarithm of the polymer concentration in various solvents or solvent mixtures.
CWC vs POLYMERCONCENTRATION
Extrapolation to 30% water gives a CMC of 10-60
Next: control of wall thickness
Diameter (Wall-thickness)in Dioxane/THF (3/1)
Diameter (Wall-thickness)in Dioxane
292±118 (42±5)340±149 (42±3)
424±149 (38±4)
301±118 (33±4)
116±19 (28±2)
94±16 (24±2)
96±17 (27±3)
Micelles (20±2)
269±111 (39±4)177±85 (22±2)
9.77PAA47-b-PS434
104±22 (20±2)
202±106 (36±4)11.32PAA47-b-PS368
147±76 (34±3)11.66PAA47-b-PS356
108±23 (28±3)13.27PAA47-b-PS307
100±19 (27±3)14.59PAA47-b-PS275
75±9 (23±2)15.93PAA47-b-PS248
Micelles (20±2)19.26PAA47-b-PS197
370±127 (39±4)9.49PAA34-b-PS324
134±60 (22±3)12.45PAA34-b-PS239
86±14 (19±4)15.31PAA34-b-PS188
% PAA Block
Sizes and Wall-thicknesses of Vesicles Prepared from VariousPAA-b-PS block Lengths in Two Solvent Systems
y = 0.1014x - 1.9141R2 = 0.9876
20
25
30
35
40
45
50
240 290 340 390 440
DP of Styrene block
Wal
l-thi
ckne
ss (n
m)
Relation between the poly(styrene) block length and the wall-thicknessin vesicles made from the PAA47-b-PSn block copolymers series
Relation between the square root of the poly(styrene) block length and the wall-thickness in vesicles made from the
PAA47-b-PSn block copolymers series
Wall-thickness (nm)
y = 0.2665x + 9.6846R2 = 0.9851
15
16
17
18
19
20
21
20 25 30 35 40 45
(DP
of S
tyre
ne b
lock
)1/2
(nm
)1/2
y = 0.2665x + 9.6846R2 = 0.9851
y = 9.7445x + 22.758R2 = 0.9876
200
250
300
350
400
450
20 25 30 35 40 4515
16
17
18
19
20
21
22
23
24
25
Relationship between Average Vesicles wallRelationship between Average Vesicles wall--thickness (d) and the thickness (d) and the Degree of Polymerization of Styrene block (Degree of Polymerization of Styrene block (DPDPStyreneStyrene) or (DP) or (DPStyreneStyrene))1/21/2
for PAAfor PAA4747--bb--PSPSnn
Average Wall-thickness (d±σ, nm)
DP
of S
tyre
ne B
lock
Bloc
kSt
yren
eof
DP
Next: Size control
y = 0.0045x2 - 1.8875x + 272.17R2 = 0.9728
50
100
150
200
250
300
350
400
450
500
230 280 330 380 430
DP Styrene
Ves
icle
Dia
met
er (n
m)
Average Vesicle Diameter of PAA47-b-PSn Block Copolymers as a Function of DPStyrene
0
20
40
60
80
100
120
140
160
50 100 150 200 250 300 350 400 450
♦ PAA47-b-PSn in Dioxane
▲ PAA47-b-PSn in Dioxane/THF (3/1)
● PAA34-b-PSn in Dioxane
■ PAA34-b-PSn in Dioxane/THF (3/1)
Average Vesicles Diameter (D, nm)
Size
Sta
ndar
d D
evia
tion
(σ)
PolydispersityPolydispersity vs. Vesicle Sizesvs. Vesicle Sizes
The size change of PS300-b-PAA44 diblock copolymer vesicles with changing water content and organic solvent
composition
THF (%)0 10 20 30 40 50 60 70
Wat
er (%
)
0
10
20
30
40
50
60
70
80
Rods + Vesicles
119 119 100
100121
120
149
150151
120
201 150 119
91
102
100
100100 100
90
919191
8988
Reversibility of vesicle sizes in response toincreasing or decreasing water contents for PS300-b-PAA44 vesicles in
THF/Dioxane (44.4/55.6) solvent mixture
H2O
20.0 24.5 (91) 28.6 (100) 50.0 (151)
H2O
H2O H2O
H2O
66.7 (201)
200 nmWater content / % (size / nm)
39.4 (119)T
HF/
DIO
X
TH
F/D
IOX
TH
F/D
IOX
TH
F/D
IOX
TH
F/D
IOX
20.0 24.5 (91) 39.4 (119) 50.0 (151)28.6 (99)
Laibin Luo & Adi Eisenberg, Langmuir 2001, 17, 6804; 2002, 18, 1952.
Diameter (nm)
80 150 200 300 400 600 800 1500100 1000
Num
ber
of v
esic
les
0
2
4
6
8
10
12
14
SIZE DISTRIBUTIONS OF PS310-b-PAA28 VESICLES(FROM TEM)
D = 90±3nm; σ/D = 0.03Prepared in DMF/THF (79.6/20.4 w/w)
D = 1010±340nm; σ/D = 0.34Prepared in DMF/THF (38.8/61.2 w/w)
TOTAL INTERFACIAL AREA VS. VESICLE SIZE
d
2R(=D)
( )( )[ ]
( )
( )[ ]
( )[ ]
( )[ ]( )[ ]
( )[ ]( )[ ]
322
22
3
22
22
33
33
33
33
22
2
2
33223
3
π4*π
34
π34
π34
π34π
34
)π4π4
π4
dRddRdRdRV
dRdRRV
dRRdRR
V
dRR
V
dRR
dRR
dRRdR
R
+−++
=
−−−+
=
−+−−
=
−−=
−−=
−−=
−+=
−=
=
Wall Total
3Wall Total
wallTotal
wallTotal
R
Area SurfaceTotal
Vesicles of Number
Wall of Volume
SurfaceTotal SurfaceInside
SurfaceOutside
1. For Radius (R) >> Wall thickness (d),
2. For R ∼ d,
Assume
WHY DO VESICLE SIZES INCREASE WITH INCREASING WATER CONTENT?
dVA TOTALWALL2
=
322
22
33223
dRddRdRdRVA TOTALWALL+−++
=
),1(10 336 cmmVTOTALWALL == −
Total Surface Area vs. Vesicle Size
nmd 27=
d
2R(=D)
Vesicle Radius (/nm)
50 70 200 300 500 700100 1000
Surf
ace
Are
a (/m
2 )
100
200
300
σ/D
0
5
10
15
20
25
30
35
40
II- Effect of HCl
Polymer + acid
Water content (% w/w)0 10 20 30 40
Tur
bidi
ty
0
1
2
3
HCl = 63.8 uM HCl = 640.9 uM HC =1272.1 uM
HCl = 0
Polymer only
In the presence of acid we observe:
no shift in CWC (ca. 10.5% w/w)
after vesicle formation(ca. 11.5 % w/w) turbidity ↑i.e. bigger vesicles form
0.5% solutions of PS310-b-PAA36 in dioxane
In the absence of additives, poly(acrylic acid) is slightly ionizedThe electrostatic repulsion between chains
is reduced by adding
Salt, shields the charges
Acid,protonates the
carboxyl groupsWhen repulsion among chains
decreases Aggregation number increases
Larger vesicles form
or
Why does NaCl or HCl cause larger vesicles to form?
50
150
250
350
450
10 20 30 40Water Content (% w/w)
Avg
. Ves
icle
Dia
met
er (n
m)
Effect of additives on vesicle size
HCl = 64 μM
polymer only
NaOH =16 μM
NaCl = 2.7 mM
PS310-b-PAA36
III- Effect of NaOH
Water content (% w/w)
0 10 20 30 40
Tur
bidi
ty
0
1
2
3
NaOH = 0NaOH = 16.4 uMNaOH = 33.4 uMNaOH = 66.6 uMNaOH = 333.5 uM
Polymer + NaOH
Polymer onlyIn the presence of base we observe that:
for NaOH > 16.4 uM, no self-assembly
for NaOH = 16.4 uM, CWC shifts(10.5 → 12.5 % water)
after vesicle formation, - turbidity ↓i.e. smaller vesicles form- turbidity increases ONLY slightly with water content
0.5% solutions of PS310-b-PAA36 in dioxane
Why does NaOH cause smaller vesicles to form?
NaOH deprotonates poly(acrylic acid)
Electrostatic repulsion among chains ↑
For NaOH >16.4 uM,
the high ion contentdecreases solubility
For NaOH = 16.4 uM,chain repulsion is high aggregation number ↓smaller vesicles form
Next: fission and fusion mechanisms and fusion kinetics
MECHANISM OF VESICLE FUSION
COALESCENCE AND FORMATION OF CENTER WALL
DESTABILIZATION OF CENTER WALL
ASYMMETRIC DETACHMENTOF CENTER WALL
RETRACTION OF CENTERWALL INTO OUTER WALL
FORMATION OF UNIFORM OUTER WALL
CONTACT AND ADHESION
MECHANISM OF VESICLE FISSION
ELONGATION
INTERNAL WAIST FORMATION
NARROWING OFEXTERNAL WAIST
SPHERICAL VESICLE
COMPLETE SEPARATION
• System: 1.0 wt % PS310-b-PAA52 in dioxane/water (11.5%)
2.0 mM 5.1 mM 11.0 mM9.2 mM 17.1 mM
[SDS] increases
Susan E. Burke and Adi Eisenberg Langmuir 2001, 17, 8341.
Effect of SDS on Morphology
• System: 1.0 wt % PS310-b-PAA52 in dioxane/water in the presence of SDS
rods
rods and vesicles
vesicles
spheres + rods
spheres
Susan E. Burke and Adi Eisenberg Langmuir 2001, 17, 8341.
MORPHOLOGICAL PHASE DIAGRAM
Effect of SDS on Morphological Transitions
• System: 1.0 wt % PS310-b-PAA52 in dioxane/water
Susan E. Burke and Adi Eisenberg Langmuir 2001, 17, 8341.
15 to 16 wt.% H2O for PS310-b-PAA36 in Dioxane
0.95
0.97
0.99
1.01
1.03
1.05
60 70 80 90 100 110 120 130 140Time (sec.)
Turb
idity
R2 = 0.98
y = yo + A(1-e-tb)
A = 0.061 +/- 0.001yo = 0.969 +/- 0.001
b = 0.066 +/- 0.002
22 to 23 wt.% H2O for PS310-b-PAA36 in Dioxane
1.29
1.30
1.31
1.32
1.33
1.34
1.35
1.36
1.37
60 80 100 120 140 160 180
Time (sec.)
Turb
idity
Experimental Smoothed Calculated
y = yo + A(1-e-tb)
R2 = 0.93
A = 0.044 +/- 0.001yo = 1.296 +/- 0.001
b = 0.040 +/- 0.003
TWO EXAMPLES OF KINETIC RUNS OF VESICLE SIZE CHANGES
An example of change in turbidity as a function of time upon 5wt% water jumps
0.5 wt.% PS310-b-PAA36 in Dioxane
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 25 50 75 100 125 150Time (sec.)
Turb
idity
17.5 wt.% 22.5 wt.% 27.5 wt.% 32.5 wt.%
T = A (1-e-bt)
Effect of the magnitude of the water jump
0.5wt.% of PS310-PAA36 in Dioxane R2 = 0.90
R2 = 0.9171
R2 = 0.9084
0102030405060708090
15 20 25 30 35Water Content (wt.%)
Avg
.Rel
axat
ion
time
(sec
.)
1w t % jumps 2w t% jumps5w t% jumps 7w t% jumpsLi (1 % j ) Li (2 % j )
PS300-b-PAA11
PS310-b-PAA28 PS300-b-PAA75
Terreau, O.; Luo, L.; Eisenberg, A. Langmuir 2003, 19, 5601-5607
Length Segregation of Corona Chains Decreases Vesicle Sizes
0
100200
300400
500600
700
1 1.5 2 2.5PAA Chain Polydispersity
Aver
age
Vesi
cle
Dia
met
er
(nm
)
Dynamic Light ScatteringTansmission Electron Microscopy
Terreau, O.; Luo, L.; Eisenberg, A. Langmuir 2003, 19, 5601-5607
Effect of Corona Block Polydispersity on Sizes of Vesicles Made from Polystyrene-b-Poly(acrylic acid)
Solvent content, number average molecular weight, and polymer concentration were kept constant.
n
Next: filling and release
What’s DXR• DXR.HCl: doxorubicin hydrochloride
• Anti-cancer drug• Molecular weight = 580 (g/mol) • Water soluble (50 mg/ml)
Active Loading into Vesicles
pH = 6.3
pH = 2.5
Use vesicles as model carriers for DoxorubicinInduce loading by creating a transmembrane pH gradient
vs.
ΔpH ≈ 4 ΔpH = 0
pH = 2.5
pH = 2.5pH = 6.3
pH = 2.5
“Active” vs. “Passive” Loading
As a function of the wall permeability (addition of dioxane as a plasticizer)
Solvent content in the PS200-rich phase as a function of the water content (dotted lines extrapolate the cwc). The insert shows the plot against the water increment beyond the cwc.
pH = 2.5
pH = 2.5
Active vs. Passive Loading
Vesicles prepared from PS310-b-PAA36
Common solvent: dioxane
Loading Efficiency
0
20
40
60
80
100
120
0 20 40 60 80Dioxane content (% w/w)
% m
oles
load
pH = 2.5
pH = 6.3
Loading Mechanism
= XNH2
= XNH+3
+: neutral form is permeable
: protonated form is NOT permeable
pH = 6.3pH = 2.5
+
Release of DOX from PS310-b-PAA36 vesicles
Lim Soo, P.; Choucair, A.; Eisenberg, A.; In Press
Time (seconds)1/2
0 200 400 600 800 1000 1200 1400 1600
Q (m
oles
/ cm
2 )/ 1
x 10
-9)
0
2
4
6
8
100% dioxane/ 100% water25% dioxane/ 75% water50% dioxane/ 50% water
360 380 400 420 440 460 480 5000
1
2
3
4
5
63.00
4.00 4.60
7.40
6.00
7.00
8.00
9.0010.00
W avelength (nm )
Inte
nsity
(CPS
) X 1
0-6
5 .00
A
Excitation spectra of 8-hydroxypyrene-1,3,6-trisulphonate (HPTS)
3 4 5 6 7 8 9 10
0
100
200
300
pH
I 403
/I 454
0
1
2
3
4I454 /I403
B
Calibration profiles of HPTScurves were taken as I454/I403 or I403/I454 vs. pH.
400 420 440 460 480
Wavelength (nm)
0 h 1 h
144 h
7%
B
76 h
365 h
1056 h
400 420 440 460 480
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
Inte
nsity
(a.u
.)
Wavelength (nm)
0%
A400 420 440 460 480
Wavelength (nm)
0 h
1 h
20 h43 & 70 h
28%
D400 420 440 460 480
Wavelength (nm)
0 h
1/4 h 3, 6, 23 h
E
40%
400 420 440 460 480
Wavelength (nm)
0 h
1 h
3 h
5 h
19 h
46 h92 h
140 h 265, 338 h
14%
C
Time evolution of fluorescence excitation spectra from vesicle solutions with added HPTS
at different dioxane contents;
A: 0 wt%; B: 7 wt%; C: 14 wt%; D: 28 wt%; E: 40 wt%;
0 5 10 15 20
0
2
4
6
8
[H+ ]x
107
t1/2
0 3 6 9 12 15 180.0
0.3
0.6
0.9
1.2
[H+ ] x
107
t1/2
0%
7%
14%
28%
40% 7%
Plots of proton concentration [H+] against the square root of diffusion time t.
5 10 15 20 25 30 35 40 45
0
1
2
3
4lo
g[D
*(Φ)/
D*(
7%)]
dioxane content in solution (%)
Plot of log[D*(Φ)/D*(7%)] against dioxane content.
Vesicles – Summary (1)
Many types of vesicles can be prepared (equilibrium)
Sizes can be thermodynamically and reversibly controlled by
Water content, ion content, solvent composition, molecular weight distribution of corona block, relative block length, polydispersity, etc
Part of a morphological continuum spheres rods vesicles
Kinetics and mechanisms of transitions are known
Vesicle curvature stabilized by chain segregation: Longer chains outside, shorter chains inside.
Segregation is size dependent and reversible.
Vesicles – Summary (2)Interface compositions can be controlled by using diblock
mixtures,
for example: PS-b-PAA with PS-b-PVP.
Vesicles with opposite interfaces from ABC triblocks
(PAA-b-PS-b-PVP)
Triggered inversion is possible.
Wall thickness is controllable
(Small molecules inside vesicles)
(Active loading is possible. Release occurs by diffusion)
(Wall permeability can be controlled (by 100x))
F. LIUN. DUXIN
“PARTING IS SUCH SWEET SORROW”