Constrained spreading of a molecular brush
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Engineered Molecular Fluidics NSF NIRT Grant 0609087 PIs: S.S. Sheiko 1 , K. Matyjaszewski 2 , M. Rubinstein 1 , O. Velev 3 1 University of North Carolina at Chapel Hill, 2 Carnegie Mellon University, 3 North Carolina State University Constrained spreading of a molecular brush m NS 1/2 m > NS 1/2 – un-stretched molecule (same as spreading of linear chain) 1/N NS < m < NS 1/2 – stretched backbone, un-stretched side chains NS NS/m 2 1/(NS) m < S -1/4 – saturated lower layer and appearance of the cap (NS) 1/3 < m < NS – stretched backbone and side chains (NS) 1/3 (NS/m) 1/ 2 /m 1 S -1/4 S -1/4 < m < (NS) 1/3 – fully stretched backbone and H ~ S -1/2 NS/m 3 NS 7/4 Tension energy per backbone monomer F bb /(mkT) Concept and methodology N b L m b d H Nb A H SNb kT F 2 2 2 2 3 3 3 Free energy per side chain @ constant volume HhL=Nb 3 h L d spreading disjoining backbone stretching side chain stretching N m d L As alternative to (a) closed-channel systems, we study (b) open structures, where monolayer masses, residing on a substrate, are moved and configured by an external force. Advantages • smaller volume and direct accessibility • dynamically configurable flow control • rapid heat exchange • substrate-mediated mixing, orientation, and shape of macromolecules Electric field manipulation of thin films EOF - + + + - - - - - + + + - - - - Forw ard bias reverse bias 100 μm Liquid reservoir Film spread mica N o bias Forw ard bias Forw ard bias mica mica M olecularw aterequilibrium film Liquid reservoir Film spread Thin wetting film spreading by electro-osmosis 0 5 10 15 20 25 30 35 40 0 100 200 300 400 500 600 700 800 M en is c u s D isp lace m en t ( m) T im e (sec) 25 V /cm 50 V /cm 75 V /cm 100 V /cm 200 V /cm 300 V /cm 0 50 100 150 200 250 300 0 20 40 60 80 100 120 S p e e d o f M e n is c u s ( m /se c ) E le c tric F ie ld (V/cm ) 0 100 200 300 400 0 1000 2000 3000 4000 5000 M o b ility (( m 2 /Vsec) E le c tric F ie ld (V/cm ) eof μ eof : standard electroosmotic mobility ε : permittivity ~ (80)·(8.85 × 10 -12 F/m) ζ : zeta potential of mica ~ - 80 mV η : viscosity ~ 9x10 -4 Pa·sec = 5.7 x 10 4 μm 2 / V·sec mica Dye droplet mica Nano film spread Time Film spread Manipulating of molecular fluorophore in a thin film Flow-induced molecular fractionation Reservo ir Film Flow 0 100 200 300 400 0.00 0.05 0.10 0.15 0.20 0.25 F ractio n M o lecu lar L en g th (n m ) D istance from D rop 350 m 400 m 440 m 460 m 480 m 500 m 100 200 300 400 500 40 60 80 100 120 A ve ra g e L e n g th (nm ) D istan ce F ro m D ro p , m Mike Barrett, Frank Sun, and David Shirvaniants Jairus Kleinert, Sejong Kim Katya Zhulina and Gregory Randall Molecular conformation within 2-D asymmetric mixtures 10 0 10 1 10 2 10 3 10 4 10 5 30 40 50 60 70 N B R A ,nm N A = 1240 N A = 1160 N A = 1080 N A = 1000 N A = 920 N A = 840 N A = 760 N B =11 N B =322 N B =102 N B =24 N B =1766 N B =8813 Phys. Rev. Lett. 99 , 137801 (2007) Andrey Dobrynin and Frank Sun heterogeneous substrates R A ≈ 3/4 5/4 − 1/4 Molecular visualization: - size, shape, and ordering, - diffusion, mixing, and reactions constrained unconstrained
description
Dye droplet. mica. Nano film spread. mica. d. h. Film spread. L. - PowerPoint PPT Presentation
Transcript of Constrained spreading of a molecular brush
Engineered Molecular FluidicsNSF NIRT Grant 0609087
PIs: S.S. Sheiko1, K. Matyjaszewski2, M. Rubinstein1, O. Velev3
1University of North Carolina at Chapel Hill, 2Carnegie Mellon University, 3North Carolina State University
Constrained spreading of a molecular brush
mNS1/2
m > NS1/2 – un-stretched molecule (same as spreading of linear chain)
1/N
NS < m < NS1/2 – stretched backbone, un-stretched side chains
NS
NS/m21/(NS)
m < S-1/4 – saturated lower layer and appearance of the cap
(NS)1/3 < m < NS – stretched backbone and side chains
(NS)1/3
(NS/m)1/2/m1
S-1/4
S-1/4 < m < (NS)1/3 – fully stretched backbone and H ~ S-1/2
NS/m3NS7/4
Tension energy per backbone monomer Fbb/(mkT)
Concept and methodology
Nb
L
mb
d
H
NbA
H
SNb
kT
F2
2
2
2
3
33
Free energy per side chain @ constant volume HhL=Nb3
hL
d
spreading disjoining backbonestretching
side chainstretching
N
md
L
As alternative to (a) closed-channel systems, we study (b) open structures, where monolayer masses, residing on a substrate, are moved and configured by an external force.
Advantages• smaller volume and direct accessibility • dynamically configurable flow control • rapid heat exchange • substrate-mediated mixing, orientation, and shape of macromolecules
Electric field manipulation of thin films
EOF
-++ +
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-++ +----
Forward bias
reverse bias
100 μm
Liq
uid
rese
rvo
ir
Film spread
mica
No bias
Forward bias
Forward bias
mica
mica
Molecular water equilibrium film
Liquid reservoir
Film spread
Thin wetting film spreading by electro-osmosis
0 5 10 15 20 25 30 35 40
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Me
nis
cus
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pla
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men
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of
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iscu
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ec)
Electric Field (V/cm)
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Mo
bili
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2/ V
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c)
Electric Field (V/cm)
eof
μeof : standard electroosmotic mobility
ε : permittivity ~ (80)·(8.85 × 10-12 F/m)
ζ : zeta potential of mica ~ - 80 mV
η : viscosity ~ 9x10-4 Pa·sec
= 5.7 x 104 μm2/ V·sec
mica
Dye droplet
mica
Nano film spread
Time
Film spread
Manipulating of molecular fluorophore in a thin film
Flow-induced molecular fractionation
Reservoir
Film
Flow
0 100 200 300 400
0.00
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0.25
Fra
cti
on
Molecular Length (nm)
Distance from Drop 350 m 400 m 440 m 460 m 480 m 500 m
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Av
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ge
Le
ng
th (
nm
)
Distance From Drop, m
Mike Barrett, Frank Sun, and David ShirvaniantsJairus Kleinert, Sejong Kim
Katya Zhulina and Gregory Randall
Molecular conformation within 2-D asymmetric mixtures
100 101 102 103 104 105
30
40
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60
70
NB
RA ,n
m
NA = 1240
NA = 1160
NA = 1080
NA = 1000
NA = 920
NA = 840
NA = 760
NB=11 NB=322
NB=102
NB=24 NB=1766
NB=8813
Phys. Rev. Lett. 99, 137801 (2007)
Andrey Dobrynin and Frank Sun
heterogeneous substrates
RA
𝑅𝐴≈ 𝑏𝑁𝐴3/4𝑁5/4𝑁𝐵−1/4
Molecular visualization: - size, shape, and ordering, - diffusion, mixing, and reactions
constrained
unconstrained
