Data from: pH-Dependent friction of Polyacrylamide hydrogels
Data files
Sep 12, 2023 version files 402.77 KB
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2023_Chau_TribLetters_Data.zip
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README.md
Abstract
Polyacrylamide hydrogels are widely used in biomedical applications due to their tunable mechanical properties and charge neutrality. Our recent tribological investigations of polyacrylamide gels have revealed tunable and pH-dependent friction behavior. To determine the origins of this pH-responsiveness, we prepared polyacrylamide hydrogels with two different initiating chemistries: a reduction-oxidation (redox)-initiated system using ammonium persulfate (APS) and N,N,N’N’-tetramethylethylenediamine (TEMED) and a UV-initiated system with 2-hydroxy-4’-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959). Hydrogel swelling, mechanical properties, and tribological behavior were investigated in response to solution pH (ranging from ~ 0.34 to 13.5). For polyacrylamide hydrogels in sliding contact with glass hemispherical probes, friction coefficients decreased from µ = 0.07 ± 0.02 to µ = 0.002 ± 0.002 (redox-initiated) and from µ = 0.05 ± 0.03 to µ = 0.003 ± 0.003 (UV-initiated) with increasing solution pH. With hemispherical polytetrafluoroethylene (PTFE) probes, friction coefficients of redox-initiated hydrogels similarly decreased from µ = 0.06 ± 0.01 to µ = 0.002 ± 0.001 with increasing pH. Raman spectroscopy measurements demonstrated hydrolysis and the conversion of amide groups to carboxylic acid in basic conditions. We therefore propose that the mechanism for pH-responsive friction in polyacrylamide hydrogels may be credited to hydrolysis-driven swelling through the conversion of side chain amide groups into carboxylic groups and/or crosslinker degradation. Our results could assist in the rational design of hydrogel-based tribological pairs for biomedical applications from acidic to alkaline conditions.
README
Data from peer-reviewed article:
Title: pH-Dependent Friction of Polyacrylamide Hydrogels
Journal: Tribology Letters
Authors: Allison L. Chau, Conor D. Pugsley, Madeleine E. Miyamoto, Yongkui Tang, Claus D. Eisenbach, Thomas E. Mates, Craig J. Hawker, Megan T. Valentine, and Angela A. Pitenis
Corresponding author: Angela Pitenis, apitenis@ucsb.edu
File List
A) Fig_2a.csv
B) Fig_2b.csv
C) Fig_3a.csv
D) Fig_3b.csv
E) Fig_5_FigS4.csv
F) Fig_S1.txt
G) Fig_S2.csv
H) Fig_S3.csv
I) Fig_S5a.csv
J) Fig_S5b.csv
K) Fig_S5c.csv
L) Fig_S5d.csv
M) Fig_S5e.csv
N) Fig_S5f.csv
O) Fig_S5gcsv
P) Fig_S5h.csv
Q) Fig_S6.csv
R) Fig_S7a.csv
S) Fig_S7b.csv
T) Friction_Irgacure.csv
U) Friction_TEMED_APS.csv
V) Modulus_Irgacure.csv
W) Modulus_TEMED_APS.csv
X) Swelling_Irgacure.csv
Y) Swelling_TEMED_APS.csv
Z) Volume_change_TEMED_APS.csv
FIGURE 2: friction and reduced elastic modulus data
A) Fig_2a.csv: friction coefficient vs. solution pH
- row 1: x and y axis, corresponding to solution pH (x) and friction coefficient average (y) and friction coefficient standard deviation (+/- y)
- row 2: initiating system (redox [TEMED + APS] or UV initiated [Irgacure]) and probe material (glass or PTFE)
- row 3 and beyond: data
- dataset 1: redox (TEMED + APS) hydrogels with glass probe - columns A + B + C
- dataset 2: redox (TEMED + APS) hydrogels with PTFE probe - columns A + D + E
- dataset 3: UV initiated (Irgacure) hydrogels with glass probe - columns A + F + G
- cells with n/a: data was not gathered for those conditions (pH = 2, pH = 10)
- Notes: data from Friction_Irgacure.csv and Friction_TEMED_APS.csv
B) Fig_2b.csv: reduced elastic modulus vs. solution pH
- row 1: x and y axis, corresponding to solution pH (x) and reduced elastic modulus average (y) and reduced elastic modulus standard deviation (+/- y)
- row 2: units for corresponding axes
- row 3: initiating system (redox [TEMED + APS] or UV initiated [Irgacure])
- row 4 and beyond: data
- dataset 1: redox (TEMED + APS) hydrogels with glass probe - columns A + B + C
- dataset 2: UV initiated (Irgacure) hydrogels with glass probe - columns A + D + E
- cells with n/a: data was not gathered for those conditions (UV initiated gels, pH = 13.5)
- Notes: data from Modulus_Irgacure.csv and Modulus_TEMED_APS.csv
FIGURE 3: swelling data
C) Fig_3a.csv: water content vs. solution pH
- row 1: x and y axis, corresponding to solution pH (x) and water content average (y) and water content standard deviation (+/- y)
- row 2: initiating system (redox [TEMED + APS] or UV initiated [Irgacure])
- row 3 and beyond: data
- dataset 1: redox (TEMED + APS) hydrogels - columns A + B + C
- dataset 2: UV initiated (Irgacure) hydrogels - columns A + D + E
- cells with n/a: data was not gathered for those conditions (UV initiated gels, pH = 13.5)
- Notes: data from Swelling_Irgacure.csv and Swelling_TEMED_APS.csv
D) Fig_3b.csv: volume change vs. solution pH
- row 1: x and y axis, corresponding to solution pH (x) and volume change average (y) and volume change standard deviation (+/- y)
- row 2: initiating system (redox [TEMED + APS])
- row 3 and beyond: data
- dataset 1: redox (TEMED + APS) hydrogels - columns A + B + C
- Notes: data from Volume_change_TEMED_APS.csv
FIGURE 5: Raman spectroscopy data (same data as shown in Figure S4)
E) Fig_5_FigS4.csv: Raman spectroscopy normalized intensity vs. wavenumber
- row 1: x and y axis, corresponding to wavenumber (x) and normalized intensity (y)
- row 2: units for corresponding axes
- row 3: solution (0.5 M HCl, DI water, or 0.5 M NaOH) or hydrogel type (polyacrylamide-co-acrylic acid [P(AAm-co-AA)]) with AA concentration (1, 5, 6, 9, or 12 wt)
- row 4 and beyond: data
- dataset 1: redox (TEMED + APS) hydrogels in 0.5 M HCl - columns A + B
- dataset 2: redox (TEMED + APS) hydrogels in DI water - columns C + D
- dataset 3: redox (TEMED + APS) hydrogels in 0.5 M NaOH - columns E + F
- dataset 4: P(AAm-co-AA) hydrogel with 1 wt AA in DI water - columns G + H
- dataset 5: P(AAm-co-AA) hydrogel with 5 wt AA in DI water - columns I + J
- dataset 6: P(AAm-co-AA) hydrogel with 6 wt AA in DI water - columns K + L
- dataset 7: P(AAm-co-AA) hydrogel with 9 wt AA in DI water - columns M + N
- dataset 8: P(AAm-co-AA) hydrogel with 12 wt AA in DI water - columns O + P
FIGURE S1: surface topography map information
F) Fig_S1.txt --> surface topography map information
- information about how the surface topography map was processed as well as the sample identifier (internal use)
FIGURE S2: x-ray photoelectron spectroscopy data
G) Fig_S2.csv --> x-ray photoelectron spectroscopy counts vs. binding energy
- row 1: x and y axis, corresponding to binding energy (x) and counts per second (y)
- row 2: units for corresponding axes
- row 3: sample (acrylamide [AAm] powder, ammonium persulfate [APS] powder, bisacrylamide [MBAm] powder, or polyacrylamide [PAAm] hydrogel)
- row 4 and beyond: data
- dataset 1: AAm powder - columns A + B
- dataset 2: APS powder - columns C + D
- dataset 3: MBAm powder - columns E + F
- dataset 4: PAAm hydrogel (argon etched for 105 s) - columns G + H
FIGURE S3: Raman spectroscopy data
H) Fig_S3.csv --> Raman spectroscopy normalized intensity vs. wavenumber
- row 1: x and y axis, corresponding to wavenumber (x) and normalized intensity (y)
- row 2: units for corresponding axes
- row 3: solution (0.5 M HCl, DI water, or 0.5 M NaOH) or hydrogel type (polyacrylamide-co-acrylic acid [P(AAm-co-AA)]) with AA concentration (1, 5, 6, 9, or 12 wt)
- row 4 and beyond: data
- dataset 1: redox (TEMED + APS) hydrogels in 0.5 M HCl for three gels - columns A (x) + B (y for gel 1) + C (y for gel 2) + D (y for gel 3)
- dataset 2: redox (TEMED + APS) hydrogels in DI water for three gels - columns E (x) + F (y for gel 1) + G (y for gel 2) + H (y for gel 3)
- dataset 3: redox (TEMED + APS) hydrogels in 0.5 M NaOH for three gels - columns I (x) + J (y for gel 1) + K (y for gel 2) + L (y for gel 3)
- dataset 4: P(AAm-co-AA) hydrogel with 1 wt AA in DI water for three gels - columns M (x) + N (y for gel 1) + O (y for gel 2) + P (y for gel 3)
- dataset 5: P(AAm-co-AA) hydrogel with 5 wt AA in DI water for three gels - columns Q (x) + R (y for gel 1) + S (y for gel 2) + T (y for gel 3)
- dataset 6: P(AAm-co-AA) hydrogel with 6 wt AA in DI water for three gels - columns U (x) + V (y for gel 1) + W (y for gel 2) + X (y for gel 3)
- dataset 7: P(AAm-co-AA) hydrogel with 9 wt AA in DI water for three gels - columns Y (x) + Z (y for gel 1) + AA (y for gel 2) + AB (y for gel 3)
- dataset 8: P(AAm-co-AA) hydrogel with 12 wt AA in DI water for three gels - columns AC (x) + AD (y for gel 1) + AE (y for gel 2) + AF (y for gel 3)
FIGURE S5: Raman band deconvolution data
I) Fig_S5a.csv --> Raman band deconvolution curve fitting - PAAm gels at pH = 0.34
- row 1: x and y axis, corresponding to wavenumber (x) and normalized intensity (y)
- row 2: units for corresponding axes
- row 3: data indentifier (peak number, cumulative fit, or measurement)
- row 4 and beyond: data
- dataset 1: peak fit 1 - columns A + B
- dataset 2: peak fit 2 - columns C + D
- dataset 3: peak fit 3 - columns E + F
- dataset 4: peak fit 4 - columns G + H
- dataset 5: peak fit 5 - columns I + J
- dataset 6: peak fit 6 - columns K + L
- dataset 7: peak fit 7 - columns M + N
- dataset 8: peak fit 8 - columns O + P
- dataset 9: cumulative peak fit - columns Q + R
- dataset 10: measurement - columns S + T
J) Fig_S5b.csv --> Raman band deconvolution curve fitting - PAAm gels at pH = 7
- row 1: x and y axis, corresponding to wavenumber (x) and normalized intensity (y)
- row 2: units for corresponding axes
- row 3: data indentifier (peak number, cumulative fit, or measurement)
- row 4 and beyond: data
- dataset 1: peak fit 1 - columns A + B
- dataset 2: peak fit 2 - columns C + D
- dataset 3: peak fit 3 - columns E + F
- dataset 4: peak fit 4 - columns G + H
- dataset 5: peak fit 5 - columns I + J
- dataset 6: peak fit 6 - columns K + L
- dataset 9: cumulative peak fit - columns M + N
- dataset 10: measurement - columns O + P
K) Fig_S5c.csv --> Raman band deconvolution curve fitting - P(AAm-co-AA) gel with 1 wt AA
- dataset 1: peak fit 1 - columns A + B
- dataset 2: peak fit 2 - columns C + D
- dataset 3: peak fit 3 - columns E + F
- dataset 4: peak fit 4 - columns G + H
- dataset 5: peak fit 5 - columns I + J
- dataset 6: peak fit 6 - columns K + L
- dataset 7: peak fit 7 - columns M + N
- dataset 8: peak fit 8 - columns O + P
- dataset 9: cumulative peak fit - columns Q + R
- dataset 10: measurement - columns S + T
L) Fig_S5d.csv --> Raman band deconvolution curve fitting - P(AAm-co-AA) gel with 5 wt AA
- dataset 1: peak fit 1 - columns A + B
- dataset 2: peak fit 2 - columns C + D
- dataset 3: peak fit 3 - columns E + F
- dataset 4: peak fit 4 - columns G + H
- dataset 5: peak fit 5 - columns I + J
- dataset 6: peak fit 6 - columns K + L
- dataset 7: peak fit 7 - columns M + N
- dataset 8: peak fit 8 - columns O + P
- dataset 9: cumulative peak fit - columns Q + R
- dataset 10: measurement - columns S + T
M) Fig_S5e.csv --> Raman band deconvolution curve fitting - P(AAm-co-AA) gel with 6 wt AA
- dataset 1: peak fit 1 - columns A + B
- dataset 2: peak fit 2 - columns C + D
- dataset 3: peak fit 3 - columns E + F
- dataset 4: peak fit 4 - columns G + H
- dataset 5: peak fit 5 - columns I + J
- dataset 6: peak fit 6 - columns K + L
- dataset 7: peak fit 7 - columns M + N
- dataset 8: peak fit 8 - columns O + P
- dataset 9: cumulative peak fit - columns Q + R
- dataset 10: measurement - columns S + T
N) Fig_S5f.csv --> Raman band deconvolution curve fitting - P(AAm-co-AA) gel with 9 wt AA
- dataset 1: peak fit 1 - columns A + B
- dataset 2: peak fit 2 - columns C + D
- dataset 3: peak fit 3 - columns E + F
- dataset 4: peak fit 4 - columns G + H
- dataset 5: peak fit 5 - columns I + J
- dataset 6: peak fit 6 - columns K + L
- dataset 7: peak fit 7 - columns M + N
- dataset 8: peak fit 8 - columns O + P
- dataset 9: cumulative peak fit - columns Q + R
- dataset 10: measurement - columns S + T
O) Fig_S5g.csv --> Raman band deconvolution curve fitting - P(AAm-co-AA) gel with 12 wt AA
- dataset 1: peak fit 1 - columns A + B
- dataset 2: peak fit 2 - columns C + D
- dataset 3: peak fit 3 - columns E + F
- dataset 4: peak fit 4 - columns G + H
- dataset 5: peak fit 5 - columns I + J
- dataset 6: peak fit 6 - columns K + L
- dataset 7: peak fit 7 - columns M + N
- dataset 8: peak fit 8 - columns O + P
- dataset 9: cumulative peak fit - columns Q + R
- dataset 10: measurement - columns S + T
P) Fig_S5h.csv --> Raman band deconvolution curve fitting - PAAm gels at pH = 13.5
- dataset 1: peak fit 1 - columns A + B
- dataset 2: peak fit 2 - columns C + D
- dataset 3: peak fit 3 - columns E + F
- dataset 4: peak fit 4 - columns G + H
- dataset 5: peak fit 5 - columns I + J
- dataset 6: peak fit 6 - columns K + L
- dataset 7: peak fit 7 - columns M + N
- dataset 8: peak fit 8 - columns O + P
- dataset 9: peak fit 9 - columns Q + R
- dataset 10: cumulative peak fit - columns S + T
- dataset 11: measurement - columns U + V
FIGURE S6: Raman linear calibration curve data
Q) Fig_S6.csv --> Raman linear calibration curve data
- Table 1: ratio of peaks vs. acrylic acid mol percent (A1-A9, E1-E9)
- Column A: hydrogel sample (polyacrylamide [PAAm] or poly(acrylamide-co-acrylic acid) [P(AAm-co-AA)] and solution (DI water, HCl, or NaOH)
- Column B: acrylic acid (AA) mol% average
- Column C: acrylic acid (AA) mol% standard deviation
- Column D: ratio of peak areas (peak at 1555 cm^-1/peaks at 1670 cm^-1 and 1716 cm^-1) average
- Column E: ratio of peak areas (peak at 1555 cm^-1/peaks at 1670 cm^-1 and 1716 cm^-1) standard deviation
- cells with n/a: no standard deviation for those conditions (P(AAm-co-AA) gels)
- Table 2: ratio of peaks vs. ratio of acrylic acid/amide (G1-G9, J1-J9)
- Column A: ratio of acrylic acid mol/amide mol average
- Column B: ratio of acrylic acid mol/amide mol standard deviation
- Column C: ratio of peak areas (peak at 1555 cm^-1/peaks at 1617 cm^-1) average
- Column D: ratio of peak areas (peak at 1555 cm^-1/peaks at 1617 cm^-1) standard deviation
- cells with n/a: no standard deviation for those conditions (P(AAm-co-AA) gels)
FIGURE S7: switchable friction data
R) Fig_S7a.csv --> friction coefficient vs. solution pH - switchable friction data
- Table 1: raw data for hydrogel with TEMED + APS initiating system (A2-A7, K2-K7)
- Column A: sample identifer (internal use)
- Column B: solution pH (pH = 0.35, 7, or 10)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
- Table 2: raw data for hydrogel with Irgacure initiating system (A9-A14, K9-K14)
- Column A: sample identifer (internal use)
- Column B: solution pH (pH = 0.35, 7, or 10)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
- Table 3: data for Figure S7a (A19-A23, E19-E23)
- Column A: solution pH
- Column B + C: friction coefficient average and standard deviation for the hydrogel with TEMED + APS initiating system
- Column D + E: friction coefficient average and standard deviation for the hydrogel with Irgacure initiating system
S) Fig_S7b.csv --> reduced elastic modulus vs. solution pH - TEMED + APS initiated gels
- Table 1: elastic modulus for PAAm sample in pH = 0.35 (0.5 M HCl) (B2-B24, J2-J24)
- Column B: sample identifier (internal use)
- Column C: position
- Column D: cycle number
- Column E: maximum force reached during analysis
- Column F: maximum contact pressure reached during analysis
- Column G: maximum contact radius reached during analysis
- Column H: estimated reduced elastic modulus using the Hertz model
- Column I + J: averages and standard deviation of reduced elastic modulus per position
- cells with n/a: no cycle data at the specified position
- Table 2: elastic modulus for PAAm sample in pH = 7 (DI water) (L2-L24, T2-T24)
- Column L: sample identifier (internal use)
- Column M: position
- Column N: cycle number
- Column O: maximum force reached during analysis
- Column P: maximum contact pressure reached during analysis
- Column Q: maximum contact radius reached during analysis
- Column R: estimated reduced elastic modulus using the Hertz model
- Column S + T: averages and standard deviation of reduced elastic modulus per position
- Table 3: elastic modulus for PAAm sample in pH = 10.01 (0.001 M NaOH) (V2-V24, AD2-AD24)
- Column V: sample identifier (internal use)
- Column W: position
- Column X: cycle number
- Column Y: maximum force reached during analysis
- Column Z: maximum contact pressure reached during analysis
- Column AA: maximum contact radius reached during analysis
- Column AB: estimated reduced elastic modulus using the Hertz model
- Column AC + AD: averages and standard deviation of reduced elastic modulus per position
- cells with n/a: no cycle data at the specified position
- Table 4: data for Figure S7a (A28-A33, C28-C33)
- Column A: solution pH
- Column B + C: elastic modulus average and standard deviation for the hydrogel with TEMED + APS initiating system
Compilation of raw friction coefficient data
T) Friction_Irgacure.csv
- Table 1: raw data for hydrogel with UV (Irgacure) initiating system at pH = 0.34 (0.5 M HCl) with glass probe (A1-A9, K1-K9)
- Column A: hydrogel type (polyacrylamide)
- Column B: sample identifier (internal use)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
- Table 2: raw data for hydrogel with UV (Irgacure) initiating system at pH = 2 (0.01 M HCl) with glass probe (A12-A19, K12-K19)
- Column A: hydrogel type (polyacrylamide)
- Column B: sample identifier (internal use)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
- Table 3: raw data for hydrogel with UV (Irgacure) initiating system at pH = 7 (DI water) with glass probe (A22-A29, K22-K29)
- Column A: hydrogel type (polyacrylamide)
- Column B: sample identifier (internal use)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
- Table 4: raw data for hydrogel with UV (Irgacure) initiating system at pH = 10 (0.001 M NaOH) with glass probe (A32-A39, K32-K39)
- Column A: hydrogel type (polyacrylamide)
- Column B: sample identifier (internal use)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
U) Friction_TEMED_APS.csv
- Table 1: raw data for hydrogel with TEMED + APS initiating system at pH = 0.34 (0.5 M HCl) with glass probe (A2-A10, K2-K10)
- Column A: hydrogel type (polyacrylamide)
- Column B: sample identifier (internal use)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
- Table 2: raw data for hydrogel with TEMED + APS initiating system at pH = 2 (0.01 M HCl) with glass probe (A12-A19, K12-K19)
- Column A: hydrogel type (polyacrylamide)
- Column B: sample identifier (internal use)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
- Table 3: raw data for hydrogel with TEMED + APS initiating system at pH = 7 (DI water) with glass probe (A21-A28, K21-K28)
- Column A: hydrogel type (polyacrylamide)
- Column B: sample identifier (internal use)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
- Table 4: raw data for hydrogel with TEMED + APS initiating system at pH = 10 (0.001 M NaOH) with glass probe (A30-A37, K30-K37)
- Column A: hydrogel type (polyacrylamide)
- Column B: sample identifier (internal use)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
- Table 5: raw data for hydrogel with TEMED + APS initiating system at pH = 13.5 (0.5 M NaOH) with glass probe (A39-A46, K39-K46)
- Column A: hydrogel type (polyacrylamide)
- Column B: sample identifier (internal use)
- Column C + D: normal force average and standard deviation
- Column E + F: friction force average and standard deviation
- Column G + H: kinetic friction coefficient average and standard deviation
- Column I: cycle # where analysis begins (internal use)
- Column J: number of cycles analyzed
- Column K: range of x position analyzed on the friction force loop (internal use)
- Table 6: raw data for hydrogel with TEMED + APS initiating system at pH = 0.34 (0.5 M HCl) with PTFE probe (N2-N10, Y2-Y10)
- Column N: hydrogel type (polyacrylamide)
- Column O: sample identifier (internal use)
- Column P: date/attempt (internal use)
- Column Q + R: normal force average and standard deviation
- Column S + T: friction force average and standard deviation
- Column U + V: kinetic friction coefficient average and standard deviation
- Column W: cycle # where analysis begins (internal use)
- Column X: number of cycles analyzed
- Column Y: range of x position analyzed on the friction force loop (internal use)
- Table 7: raw data for hydrogel with TEMED + APS initiating system at pH = 7 (DI water) with PTFE probe (N12-N19, Y12-Y19)
- Column N: hydrogel type (polyacrylamide)
- Column O: sample identifier (internal use)
- Column P: date/attempt (internal use)
- Column Q + R: normal force average and standard deviation
- Column S + T: friction force average and standard deviation
- Column U + V: kinetic friction coefficient average and standard deviation
- Column W: cycle # where analysis begins (internal use)
- Column X: number of cycles analyzed
- Column Y: range of x position analyzed on the friction force loop (internal use)
- Table 8: raw data for hydrogel with TEMED + APS initiating system at pH = 13.5 (0.5 M NaOH) with PTFE probe (N21-N28, Y21-Y28)
- Column N: hydrogel type (polyacrylamide)
- Column O: sample identifier (internal use)
- Column P: date/attempt (internal use)
- Column Q + R: normal force average and standard deviation
- Column S + T: friction force average and standard deviation
- Column U + V: kinetic friction coefficient average and standard deviation
- Column W: cycle # where analysis begins (internal use)
- Column X: number of cycles analyzed
- Column Y: range of x position analyzed on the friction force loop (internal use)
Compilation of raw elastic modulus data
V) Modulus_Irgacure.csv
- Table 1: raw data for hydrogel sample 1 with Irgacure initiating system at pH = 0.34 (0.5 M HCl) (A2-A24, I2-I24)
- Column A: hydrogel type (polyacrylamide)
- Column B: position
- Column C: cycle number
- Column D: maximum force reached during analysis
- Column E: maximum contact pressure reached during analysis
- Column F: maximum contact radius reached during analysis
- Column G: estimated reduced elastic modulus using the Hertz model
- Column I + J: averages and standard deviation of reduced elastic modulus per position
- Table 2: raw data for hydrogel sample 2 with Irgacure initiating system at pH = 0.34 (0.5 M HCl) (K2-K24, S2-S24)
- Column K: hydrogel type (polyacrylamide)
- Column L: position
- Column M: cycle number
- Column N: maximum force reached during analysis
- Column O: maximum contact pressure reached during analysis
- Column P: maximum contact radius reached during analysis
- Column Q: estimated reduced elastic modulus using the Hertz model
- Column R + S: averages and standard deviation of reduced elastic modulus per position
- Table 3: raw data for hydrogel sample 3 with Irgacure initiating system at pH = 0.34 (0.5 M HCl) (U2-U24, AC2-AC24)
- Column U: hydrogel type (polyacrylamide)
- Column V: position
- Column W: cycle number
- Column X: maximum force reached during analysis
- Column Y: maximum contact pressure reached during analysis
- Column Z: maximum contact radius reached during analysis
- Column AA: estimated reduced elastic modulus using the Hertz model
- Column AB + AC: averages and standard deviation of reduced elastic modulus per position
- Table 4: raw data for hydrogel sample 1 with Irgacure initiating system at pH = 2 (0.01 M HCl) (A27-A49, I27-I49)
- Column A: hydrogel type (polyacrylamide)
- Column B: position
- Column C: cycle number
- Column D: maximum force reached during analysis
- Column E: maximum contact pressure reached during analysis
- Column F: maximum contact radius reached during analysis
- Column G: estimated reduced elastic modulus using the Hertz model
- Column I + J: averages and standard deviation of reduced elastic modulus per position
- Table 5: raw data for hydrogel sample 2 with Irgacure initiating system at pH = 2 (0.01 M HCl) (K27-K49, S27-S49)
- Column K: hydrogel type (polyacrylamide)
- Column L: position
- Column M: cycle number
- Column N: maximum force reached during analysis
- Column O: maximum contact pressure reached during analysis
- Column P: maximum contact radius reached during analysis
- Column Q: estimated reduced elastic modulus using the Hertz model
- Column R + S: averages and standard deviation of reduced elastic modulus per position
- Table 6: raw data for hydrogel sample 3 with Irgacure initiating system at pH = 2 (0.01 M HCl) (U27-U49, AC27-AC49)
- Column U: hydrogel type (polyacrylamide)
- Column V: position
- Column W: cycle number
- Column X: maximum force reached during analysis
- Column Y: maximum contact pressure reached during analysis
- Column Z: maximum contact radius reached during analysis
- Column AA: estimated reduced elastic modulus using the Hertz model
- Column AB + AC: averages and standard deviation of reduced elastic modulus per position
- Table 7: raw data for hydrogel sample 1 with Irgacure initiating system at pH = 7 (DI water) (A52-A74, I52-I74)
- Column A: hydrogel type (polyacrylamide)
- Column B: position
- Column C: cycle number
- Column D: maximum force reached during analysis
- Column E: maximum contact pressure reached during analysis
- Column F: maximum contact radius reached during analysis
- Column G: estimated reduced elastic modulus using the Hertz model
- Column I + J: averages and standard deviation of reduced elastic modulus per position
- Table 8: raw data for hydrogel sample 2 with Irgacure initiating system at pH = 7 (DI water) (K52-K74, S52-S74)
- Column K: hydrogel type (polyacrylamide)
- Column L: position
- Column M: cycle number
- Column N: maximum force reached during analysis
- Column O: maximum contact pressure reached during analysis
- Column P: maximum contact radius reached during analysis
- Column Q: estimated reduced elastic modulus using the Hertz model
- Column R + S: averages and standard deviation of reduced elastic modulus per position
- Table 9: raw data for hydrogel sample 3 with Irgacure initiating system at pH = 7 (DI water) (U52-U74, AC52-AC74)
- Column U: hydrogel type (polyacrylamide)
- Column V: position
- Column W: cycle number
- Column X: maximum force reached during analysis
- Column Y: maximum contact pressure reached during analysis
- Column Z: maximum contact radius reached during analysis
- Column AA: estimated reduced elastic modulus using the Hertz model
- Column AB + AC: averages and standard deviation of reduced elastic modulus per position
- Table 10: raw data for hydrogel sample 1 with Irgacure initiating system at pH = 10 (0.001 M NaOH) (A77-A99, I77-I99)
- Column A: hydrogel type (polyacrylamide)
- Column B: position
- Column C: cycle number
- Column D: maximum force reached during analysis
- Column E: maximum contact pressure reached during analysis
- Column F: maximum contact radius reached during analysis
- Column G: estimated reduced elastic modulus using the Hertz model
- Column I + J: averages and standard deviation of reduced elastic modulus per position
- Table 11: raw data for hydrogel sample 2 with Irgacure initiating system at pH = 10 (0.001 M NaOH) (K77-K99, S77-S99)
- Column K: hydrogel type (polyacrylamide)
- Column L: position
- Column M: cycle number
- Column N: maximum force reached during analysis
- Column O: maximum contact pressure reached during analysis
- Column P: maximum contact radius reached during analysis
- Column Q: estimated reduced elastic modulus using the Hertz model
- Column R + S: averages and standard deviation of reduced elastic modulus per position
- Table 12: raw data for hydrogel sample 3 with Irgacure initiating system at pH = 10 (0.001 M NaOH) (U77-U99, AC77-AC99)
- Column U: hydrogel type (polyacrylamide)
- Column V: position
- Column W: cycle number
- Column X: maximum force reached during analysis
- Column Y: maximum contact pressure reached during analysis
- Column Z: maximum contact radius reached during analysis
- Column AA: estimated reduced elastic modulus using the Hertz model
- Column AB + AC: averages and standard deviation of reduced elastic modulus per position
- Column AD + AE: averages and standard deviations of the three hydrogel samples at their specified solution pH
W) Modulus_TEMED_APS.csv
- Table 1: raw data for hydrogel sample 1 with TEMED + APS initiating system at pH = 0.34 (0.5 M HCl) (A2-A24, I2-I24)
- Column A: hydrogel type (polyacrylamide)
- Column B: position
- Column C: cycle number
- Column D: maximum force reached during analysis
- Column E: maximum contact pressure reached during analysis
- Column F: maximum contact radius reached during analysis
- Column G: estimated reduced elastic modulus using the Hertz model
- Column I + J: averages and standard deviation of reduced elastic modulus per position
- Table 2: raw data for hydrogel sample 2 with TEMED + APS initiating system at pH = 0.34 (0.5 M HCl) (K2-K24, S2-S24)
- Column K: hydrogel type (polyacrylamide)
- Column L: position
- Column M: cycle number
- Column N: maximum force reached during analysis
- Column O: maximum contact pressure reached during analysis
- Column P: maximum contact radius reached during analysis
- Column Q: estimated reduced elastic modulus using the Hertz model
- Column R + S: averages and standard deviation of reduced elastic modulus per position
- Table 3: raw data for hydrogel sample 3 with TEMED + APS initiating system at pH = 0.34 (0.5 M HCl) (U2-U24, AC2-AC24)
- Column U: hydrogel type (polyacrylamide)
- Column V: position
- Column W: cycle number
- Column X: maximum force reached during analysis
- Column Y: maximum contact pressure reached during analysis
- Column Z: maximum contact radius reached during analysis
- Column AA: estimated reduced elastic modulus using the Hertz model
- Column AB + AC: averages and standard deviation of reduced elastic modulus per position
- Table 4: raw data for hydrogel sample 1 with TEMED + APS initiating system at pH = 2 (0.01 M HCl) (A27-A46, I27-I46)
- Column A: hydrogel type (polyacrylamide)
- Column B: position
- Column C: cycle number
- Column D: maximum force reached during analysis
- Column E: maximum contact pressure reached during analysis
- Column F: maximum contact radius reached during analysis
- Column G: estimated reduced elastic modulus using the Hertz model
- Column I + J: averages and standard deviation of reduced elastic modulus per position
- Table 5: raw data for hydrogel sample 2 with TEMED + APS initiating system at pH = 2 (0.01 M HCl) (K27-K46, S27-S46)
- Column K: hydrogel type (polyacrylamide)
- Column L: position
- Column M: cycle number
- Column N: maximum force reached during analysis
- Column O: maximum contact pressure reached during analysis
- Column P: maximum contact radius reached during analysis
- Column Q: estimated reduced elastic modulus using the Hertz model
- Column R + S: averages and standard deviation of reduced elastic modulus per position
- Table 6: raw data for hydrogel sample 3 with TEMED + APS initiating system at pH = 2 (0.01 M HCl) (U27-U46, AC27-AC46)
- Column U: hydrogel type (polyacrylamide)
- Column V: position
- Column W: cycle number
- Column X: maximum force reached during analysis
- Column Y: maximum contact pressure reached during analysis
- Column Z: maximum contact radius reached during analysis
- Column AA: estimated reduced elastic modulus using the Hertz model
- Column AB + AC: averages and standard deviation of reduced elastic modulus per position
- cells with n/a: no cycle data at the specified position
- Table 7: raw data for hydrogel sample 1 with TEMED + APS initiating system at pH = 7 (DI water) (A49-A71, I49-I71)
- Column A: hydrogel type (polyacrylamide)
- Column B: position
- Column C: cycle number
- Column D: maximum force reached during analysis
- Column E: maximum contact pressure reached during analysis
- Column F: maximum contact radius reached during analysis
- Column G: estimated reduced elastic modulus using the Hertz model
- Column I + J: averages and standard deviation of reduced elastic modulus per position
- cells with n/a: no cycle data at the specified position
- Table 8: raw data for hydrogel sample 2 with TEMED + APS initiating system at pH = 7 (DI water) (K49-K71, S49-S71)
- Column K: hydrogel type (polyacrylamide)
- Column L: position
- Column M: cycle number
- Column N: maximum force reached during analysis
- Column O: maximum contact pressure reached during analysis
- Column P: maximum contact radius reached during analysis
- Column Q: estimated reduced elastic modulus using the Hertz model
- Column R + S: averages and standard deviation of reduced elastic modulus per position
- Table 9: raw data for hydrogel sample 3 with TEMED + APS initiating system at pH = 7 (DI water) (U49-U71, AC49-AC71)
- Column U: hydrogel type (polyacrylamide)
- Column V: position
- Column W: cycle number
- Column X: maximum force reached during analysis
- Column Y: maximum contact pressure reached during analysis
- Column Z: maximum contact radius reached during analysis
- Column AA: estimated reduced elastic modulus using the Hertz model
- Column AB + AC: averages and standard deviation of reduced elastic modulus per position
- Table 10: raw data for hydrogel sample 1 with TEMED + APS initiating system at pH = 10 (0.001 M NaOH) (A75-A94, I75-I94)
- Column A: hydrogel type (polyacrylamide)
- Column B: position
- Column C: cycle number
- Column D: maximum force reached during analysis
- Column E: maximum contact pressure reached during analysis
- Column F: maximum contact radius reached during analysis
- Column G: estimated reduced elastic modulus using the Hertz model
- Column I + J: averages and standard deviation of reduced elastic modulus per position
- Table 11: raw data for hydrogel sample 2 with TEMED + APS initiating system at pH = 10 (0.001 M NaOH) (K75-K94, S75-S94)
- Column K: hydrogel type (polyacrylamide)
- Column L: position
- Column M: cycle number
- Column N: maximum force reached during analysis
- Column O: maximum contact pressure reached during analysis
- Column P: maximum contact radius reached during analysis
- Column Q: estimated reduced elastic modulus using the Hertz model
- Column R + S: averages and standard deviation of reduced elastic modulus per position
- cells with n/a: no cycle data at the specified position
- Table 12: raw data for hydrogel sample 3 with TEMED + APS initiating system at pH = 10 (0.001 M NaOH) (U75-U94, AC75-AC94)
- Column U: hydrogel type (polyacrylamide)
- Column V: position
- Column W: cycle number
- Column X: maximum force reached during analysis
- Column Y: maximum contact pressure reached during analysis
- Column Z: maximum contact radius reached during analysis
- Column AA: estimated reduced elastic modulus using the Hertz model
- Column AB + AC: averages and standard deviation of reduced elastic modulus per position
- Table 13: raw data for hydrogel sample 1 with TEMED + APS initiating system at pH = 13.5 (0.5 M NaOH) (A97-A119, I97-I119)
- Column A: hydrogel type (polyacrylamide)
- Column B: position
- Column C: cycle number
- Column D: maximum force reached during analysis
- Column E: maximum contact pressure reached during analysis
- Column F: maximum contact radius reached during analysis
- Column G: estimated reduced elastic modulus using the Hertz model
- Column I + J: averages and standard deviation of reduced elastic modulus per position
- Table 14: raw data for hydrogel sample 2 with TEMED + APS initiating system at pH = 13.5 (0.5 M NaOH) (K97-K119, S97-S119)
- Column K: hydrogel type (polyacrylamide)
- Column L: position
- Column M: cycle number
- Column N: maximum force reached during analysis
- Column O: maximum contact pressure reached during analysis
- Column P: maximum contact radius reached during analysis
- Column Q: estimated reduced elastic modulus using the Hertz model
- Column R + S: averages and standard deviation of reduced elastic modulus per position
- Table 12: raw data for hydrogel sample 3 with TEMED + APS initiating system at pH = 13.5 (0.5 M NaOH) (U97-U119, AC97-AC119)
- Column U: hydrogel type (polyacrylamide)
- Column V: position
- Column W: cycle number
- Column X: maximum force reached during analysis
- Column Y: maximum contact pressure reached during analysis
- Column Z: maximum contact radius reached during analysis
- Column AA: estimated reduced elastic modulus using the Hertz model
- Column AB + AC: averages and standard deviation of reduced elastic modulus per position
- Column AD + AE: averages and standard deviations of the three hydrogel samples at their specified solution pH
Compilation of raw swelling data
X) Swelling_Irgacure.csv
- Table 1: raw data for hydrogels with Irgacure initiating system at pH = 0.34 (0.5 M HCl) (A2-A7, L2-L7)
- Column A: hydrogel type (polyacrylamide)
- Column B: acrylic acid mol% (0%)
- Column C: acrylamide mol% (100%)
- Column D: sample identifier (internal use)
- Column E: swollen mass (g)
- Column F: dried mass (g)
- Column G: q = swollen mass/dried mass ratio
- Column H: Q = ((swollen mass - dried mass)/swollen mass)*100
- Column I + J: q average and standard deviation of the three samples after 2 weeks of drying
- Column K + L: Q average and standard deviation of the three samples after 2 weeks of drying
- Table 2: raw data for hydrogels with Irgacure initiating system at pH = 2 (0.01 M HCl) (A9-A14, L9-L14)
- Column A: hydrogel type (polyacrylamide)
- Column B: acrylic acid mol% (0%)
- Column C: acrylamide mol% (100%)
- Column D: sample identifier (internal use)
- Column E: swollen mass (g)
- Column F: dried mass (g)
- Column G: q = swollen mass/dried mass ratio
- Column H: Q = ((swollen mass - dried mass)/swollen mass)*100
- Column I + J: q average and standard deviation of the three samples after 2 weeks of drying
- Column K + L: Q average and standard deviation of the three samples after 2 weeks of drying
- Table 3: raw data for hydrogels with Irgacure initiating system at pH = 7 (DI water) (A17-A22, L17-L22)
- Column A: hydrogel type (polyacrylamide)
- Column B: acrylic acid mol% (0%)
- Column C: acrylamide mol% (100%)
- Column D: sample identifier (internal use)
- Column E: swollen mass (g)
- Column F: dried mass (g)
- Column G: q = swollen mass/dried mass ratio
- Column H: Q = ((swollen mass - dried mass)/swollen mass)*100
- Column I + J: q average and standard deviation of the three samples after 2 weeks of drying
- Column K + L: Q average and standard deviation of the three samples after 2 weeks of drying
- Table 4: raw data for hydrogels with Irgacure initiating system at pH = 10 (0.001 M NaOH) (A25-A30, L25-L30)
- Column A: hydrogel type (polyacrylamide)
- Column B: acrylic acid mol% (0%)
- Column C: acrylamide mol% (100%)
- Column D: sample identifier (internal use)
- Column E: swollen mass (g)
- Column F: dried mass (g)
- Column G: q = swollen mass/dried mass ratio
- Column H: Q = ((swollen mass - dried mass)/swollen mass)*100
- Column I + J: q average and standard deviation of the three samples after 2 weeks of drying
- Column K + L: Q average and standard deviation of the three samples after 2 weeks of drying
Y) Swelling_TEMED_APS.csv
- Table 1: raw data for hydrogels with TEMED + APS initiating system at pH = 2 (0.01 M HCl) (A1-A6, L1-L6)
- Column A: hydrogel type (polyacrylamide)
- Column B: acrylic acid mol% (0%)
- Column C: acrylamide mol% (100%)
- Column D: sample identifier (internal use)
- Column E: swollen mass (g)
- Column F: dried mass (g)
- Column G: q = swollen mass/dried mass ratio
- Column H: Q = ((swollen mass - dried mass)/swollen mass)*100
- Column I + J: q average and standard deviation of the three samples after 2 weeks of drying
- Column K + L: Q average and standard deviation of the three samples after 2 weeks of drying
- Table 2: raw data for hydrogels with TEMED + APS initiating system at pH = 10 (0.001 M NaOH) (A10-A15, L10-L15)
- Column A: hydrogel type (polyacrylamide)
- Column B: acrylic acid mol% (0%)
- Column C: acrylamide mol% (100%)
- Column D: sample identifier (internal use)
- Column E: swollen mass (g)
- Column F: dried mass (g)
- Column G: q = swollen mass/dried mass ratio
- Column H: Q = ((swollen mass - dried mass)/swollen mass)*100
- Column I + J: q average and standard deviation of the three samples after 2 weeks of drying
- Column K + L: Q average and standard deviation of the three samples after 2 weeks of drying
- Table 3: raw data for hydrogels with TEMED + APS initiating system at pH = 0.34 (0.5 M HCl), pH = 7 (DI water), and pH = 13.5 (0.5 M NaOH)
- Column A: solution pH (pH = 0.34 [0.5 M HCl], pH = 7 [DI water], or pH = 13.5 [0.5 M NaOH])
- Column B: sample identifier (internal use)
- Column C: swollen mass (mg)
- Column D: dried mass (mg)
- Column E: Q = ((swollen mass - dried mass)/swollen mass)*100
- Column F + G: Q average and standard deviation of the three samples at the specified pH
Z) Volume_change_TEMED_APS.csv
- Column A: solution pH (pH = 0.3 [0.5 M HCl], pH = 7 [DI water], pH = 13.5 [0.5 M NaOH])
- Column B: sample identifier (internal use)
- Column C: hydrogel diameter (mm) after polymerization before swelling (triplicate measurements per sample)
- Column D: hp = hydrogel height (mm) after polymerization before swelling (triplicate measurements per sample)
- Column E: mp = hydrogel mass (g) after polymerization before swelling
- Column F: hydrogel diameter (mm) after swelling for 14 days in specified solution (triplicate measurements per sample)
- Column G: hs = hydrogel height (mm) after swelling for 14 days in specified solution (triplicate measurements per sample)
- Column H: ms = hydrogel mass (g) after swelling for 14 days in specified solution
- Column I: Vp = hydrogel volume (mm^3) after polymerization before swelling (assuming V = pi*r^2*h)
- Column J: Vs = hydrogel volume (mm^3) after swelling for 14 days in specified solution (assuming V = pi*r^2*h)
- Column K: volume change = ((Vs-Vp)/Vp)*100
- Column L: Q = (hs/hp)^3
- Column M: mass change = ((ms-mp)/mp)*100
- Column N + O: volume change average and standard deviation of the three samples at the specified pH
- cells with n/a: mass data was only collected once per sample
#############################################################################################
MATLAB CODES
MATLAB Codes: all codes are under MIT license- please cite the code if a significant portion has been used
A) Tribometer_Indent_Analysis_v5 --> uses natsortfiles function
B) Compiling_Friction_Data_v7 --> uses natsortfiles function
ANALYZING TRIBOMETER DATA
A) Tribometer_Indent_Analysis_v5: opens microtribometer indentation data from Excel files and fits the data with the Hertz contact mechanics model using the lsqcurvefit function
B) Compiling_Friction_Data_v7: opens microtribometer friction data from Excel files and calculates the friction coefficient from the specified x-range in the friction force loop over a specified number of cycles
FUNCTIONS TO DOWNLOAD
- Author: Stephen Cobeldick
- Download from: https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort
- Citation: Stephen23 (2023). Natural-Order Filename Sort (https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort), MATLAB Central File Exchange. Retrieved 2021.
- Function of codes: reads and sorts through the files to analyze
- Functions: A) natsortfiles B) natsort
- Notes: natsortfiles calls natsort
Methods
Microindentations and sliding experiments were conducted with a custom-built linear reciprocating tribometer. Data was analyzed and processed with the following Matlab codes (Tribometer_Indent_Analysis_v5 and Compiling_Friction_Data_v7).
Raman spectroscopy was conducted with a confocal Raman microscope (Horiba Jobin Yvon T640000) with an excitation wavelength of 488 nm and laser power of 400 mW. A 50x objective lens was used to focus the laser light 10 µm below the sample surface. Spectra data was obtained with a resolution of 0.66 cm-1.
X-ray photoelectron spectroscopy was conducted with a Thermo Scientific ESCALABTM Xi+. A monochromatic Al/Kα x-ray radiation with a pass energy of 100 eV, dwell time of 50 ms, and spot size of 650 µm was used. Spectra were obtained after 105 s of etching using a 6 kV Ar1000+ cluster ion source.
Usage notes
All data is in .csv or .txt format and can be opened with any open-source software.