1. Experimental Techniques in Characterizing Polymer Adsorption
Matthew Herbert

2. Overview Background Theory Experimental Techniques
Adsorption vs. absorption
Applications
Theory
Common conformations
Adsorption Isotherm
Experimental Techniques
Infrared Spectroscopy (IR)
Forward Recoil Spectrometry (FRES)
Neutron Scattering (NS)
Quartz Crystal Microbalance (QCM)

3. Adsorption vs. Absorption
Adsorption: Physical adherence or bonding of ions and molecules onto the surface of another phase
Physiosorption
Chemisorption
Absorption: The incorporation of a substance in one state into another of a different state.
adsorbate
adsorbate
adsorbate
adsorbate
adsorbate
adsorbent
adsorbent
adsorbent
adsorbent
G. Glockner. Polymer Characterization by Liquid Chromatography. Journal of Chromatography Library – Volume 34. p74-92

4. Applications Friction and Lubrication
Mineral processing, petroleum, paper industry
Stabilization or flocculation of colloidal dispersions
Inks, cosmetics, processed food
Biomedical Applications
Protein interaction (enamel, nacre), drug delivery, etc.
Colloid and Surface Chemistry Laboratory.

5. Overview Background Theory Experimental Techniques
Adsorption vs. absorption
Applications
Theory
Common conformations
Adsorption Isotherm
Experimental Techniques
Infrared Spectroscopy (IR)
Forward Recoil Spectrometry (FRES)
Neutron Scattering (NS)
Quartz Crystal Microbalance (QCM)

6. Conformations
Polymer adsorption occurs when there is a favorable adsorption energy of the polymer over that for a solvent molecule.
Xs = (Us-Up)/kT
Xs = dimensionless energy parameter
Us = adsorption energy of solvent segment
Up = adsorption energy of polymer segment
Homopolymers (a)
Each segment is equally attracted to interface
End-functionalized homopolymers (b)
Special end-functional group that grafts to interface
Diblock copolymers (c)
Specific block group in chain is attracted to interface
G. Glockner. Polymer Characterization by Liquid Chromatography. Journal of Chromatography Library – Volume 34. p74-92
Karim, A., Kumar, S. Polymer Surfaces, Interfaces and Thin Films. P

7. Adsorption Isotherm
Functional relationship between adsorbate and adsorbent in the adsorption process.
Described in terms of surface excess (amount of adsorbed polymer per interfacial area) vs. bulk volume fraction of adsorbing species (bulk solution concentration)
Γ = adsorbed amount
Encyclopedia of polymer science:

8. Overview Background Theory Experimental Techniques
Adsorption vs. absorption
Applications
Theory
Common conformations
Adsorption Isotherm
Experimental Techniques
Infrared Spectroscopy (IR)
Forward Recoil Spectrometry (FRES)
Neutron Scattering (NS)
Quartz Crystal Microbalance (QCM)

9. Infrared Spectroscopy
3 basic components
Radiation source
Monochromator or interferometer (FTIR)
Detector
Measuring absorption of incident IR radiation as a function of…
Change in frequency of monochromatic beam wrt time (IR)
All frequencies examined simultaneously (FTIR)
A=εbc
Beers-Lambert Law:
Absorption = molecular absortivity (ε) x path length of source beam (b) x sample concentration (c)
Infrared Spectroscopy.

10. Infrared Spectroscopy
1. Adsorption mechanism
2. Relative adsorbed concentration with respect to a calibration curve of known polymer concentration
Γ = amount adsorbed
∆C = change in concentration
V = known volume of adsorbate
A = surface area of adsorbent
ν = wavenumber
λ = wavelength
C. Blachier et al., Journal of Colloid and Interfac Science 336 (2009)
Infrared Spectroscopy.

11. Forward Recoil Spectrometry (Elastic Recoil Detection)
Measures loss of energy between incident He ions and recoiled nuclei
Edet = detected energy
Q = total number of incident ions
N(x) = H and D concentration at given depth
σ(E1,θ) = scattering cross section evaluated at E1
E1 = energy before recoil collision
Ω = detector solid angle
δEdet = energy width of a channel
dEdet/dx = effectivestopping cross section of H or D
K = kinematic factor for forward scattering
t = depth
Energy detected = K(incident energy – energy lost on inward path) – energy lost on outward path – energy lost passing through filter
R.J. Composto et al., Materials Science and Engineering R 38 (2002)
M.H. Rafailovich et al., Hyperfine Interactions 62 (1990) 45-53
Karim, A., Kumar, S. Polymer Surfaces, Interfaces and Thin Films. P

12. J. Genzer et al., Polymer 40 (1999) 4223-4228
Neutron Scattering
Q = scattering vector (change in neutron momentum)
Nj = neutron refractive index of medium j
Nd = atomic number density
B = coherent scattering length
P(z) = scattering length density
λ = neutron wavelength
J. Genzer et al., Polymer 40 (1999)
D.G. Bucknall et al., “Neutron Reflection Studies of Polymer-polymer Interfaces”. Polymers and Surfaces: A Versatile Combination

13. Quartz crystal microbalance
Measures change in oscillating frequency of a quartz crystal disk as a function of mass.
Cf = crystal calibration constant
fq = resonant frequency of quartz
pq = quartz density
vq = quartz volume
mf = foreign mass
J.C. Munro et al., Macromolecules 2004, 37,

14. Extended List of Techniques
What adsorption information can this technique provide?
Infrared Spectroscopy
Adsorption mechanism, concentration of adsorbed polymer (with respect to known calibration curve)
Forward Recoil Spectroscopy
Depth vs. concentration profile of hydrogen and deuterium (labelling polymer with deuterium required for contrast)
Neutron Scattering
Depth vs. concentration profile (labelling polymer with deuterium provides contrast)
Quartz Crystal Microbalance
Adsorbed mass (∆f) , viscoelastic properties (∆D)
Nuclear Reaction Analysis
Depth vs. concentration profile
Electron Spin Resonance
Surface coverage information
Rutherford Backscattering Spectrometry
concentration vs. depth profile for heavier elements
Secondary Ion Mass Spectrometry
surface composition
Ellipsometry
layer thickness, composition, surface roughness

15. Thank you Questions?