polb23577-sup-0001-suppinfo01

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Supporting Information for
Crystallization and Orientation of Isotactic
Poly(propylene) in Cylindrical Nanopores
Dariya K. Reida, Bridget A. Ehlingera, Lin Shaob, and Jodie L. Lutkenhausa*
a
Artie McFerrin Department of Chemical Engineering, Texas A&M University, College
Station, Texas, 77843
b
Department of Chemical & Environmental Engineering, Yale University, New Haven,
Connecticut 06511, USA
*Corresponding Author: e-mail [email protected]
Avrami Kinetics
Figure S1. Avrami Schematic
Figure S2. Relative Crystalline Fraction
Table S1. Avrami Parameters
Table S2. Values for 2θ of (hkl) reflections for the α-phase of
bulk iPP, iPP-200, iPP-40 and iPP-15
Recrystallization of iPP
Figure S3. DSC of Recrystallized iPP
Experimental
Figure S4. Experimental setup for XRD
Removal of Bulk Surface Layer
Figure S5. DSC of Plasma-Etched iPP in AAO
References
S2
S2
S3
S4
S5
S6
S6
S7
S9
S9
S9
S10
S1
Avrami Kinetics
Figure S1 schematically shows the method used to analyze the isothermal
crystallization data. The initial point of crystallization, also labeled as τ = 0 or A, is the
point when the data initially deviates from the baseline after the equilibrium isothermal
temperature has been reached. The end of crystallization or infinite crystallization, B, is
some small time after the baseline has been reached. Additionally, time-zero was defined
as the point when the isothermal temperature was initially reached during the rapid
temperature drop, see Figure 3 of paper.
Figure S1. Schematic representation of cursor placement for relative crystalline fraction
integration.
S2
Figure S2. The evolution of the relative crystalline fraction X(τ), obtained using equation
1, as a function of τ for (a) bulk-iPP, (b) iPP-200 and (c) iPP-40. Data were taken from
Figure 3 and Eqn 1.
S3
Table S1. Avrami parameters for bulk iPP and iPP infiltrated into AAO templates of
varying pore diameter crystallized at varying temperatures (Tc).
Samples
Tc
(oC)
t1/2
(min)
Range
n
k × 100
(min-n)
R2
Bulk-iPP
128
129
130
131
1.71
2.53
3.69
5.50
0.031 - 0.407
0.028 - 0.404
0.032 - 0.403
0.029 - 0.398
2.15±0.02
2.18±0.01
2.127±0.006
2.190±0.003
25.6±0.2
10.93±0.06
4.88±0.02
1.773±0.006
0.99954
0.99960
0.99982
0.99994
132
8.36
0.029 - 0.402
2.178±0.002
0.697±0.002
0.99997
133
134
135
12.49
18.76
26.68
0.031 - 0.399
0.030 - 0.401
0.030 - 0.400
2.107±0.002
2.021±0.002
1.953±0.001
0.329±0.002
0.1789±0.0006
0.1117±0.0002
0.99990
0.99993
0.99999
126
127
128
129
4.95
6.07
7.74
8.91
0.029 - 0.401
0.030 - 0.400
0.030 - 0.398
0.030 - 0.400
1.634±0.005
1.645±0.006
1.620±0.005
1.630±0.004
5.63±0.02
4.02±0.02
2.88±0.02
2.20±0.01
0.99976
0.99964
0.9996
0.99977
130
131
132
133
11.02
13.43
17.52
21.42
0.029 - 0.399
0.031 - 0.400
0.030 - 0.401
0.030 - 0.400
1.620±0.003
1.587±0.002
1.571±0.001
1.570±0.001
1.585±0.007
1.228±0.004
0.851±0.002
0.613±0.001
0.99982
0.99992
0.99993
0.99995
132
7.28
133
10.88
0.028 - 0.048
0.052 - 0.398
0.030 - 0.099
0.102 - 0.401
0.029 - 0.095
1.62±0.01
1.502±0.006
1.72±0.01
1.437±0.005
1.536±0.009
3.503±0.005
3.83±0.03
1.80±0.01
2.47±0.02
1.36±0.01
0.99991
0.99947
0.99963
0.99948
0.99954
135
15.03
136
17.41
0.097 - 0.399
0.030 - 0.400
1.376±0.004
1.432±0.003
1.75±0.01
1.254±0.006
0.99951
0.99974
iPP-200
iPP-40
Table S1 lists the Avrami parameters for the full range of crystallization temperatures.
Tc = 134 oC was omitted from the data set of the 40 nm sample due to error in the
S4
measurement. For both bulk and confined samples the Avrami exponent, n, remained
largely unaffected by the crystallization temperature. However, t1/2 generally increased
and k decreased with increasing crystallization temperature, both are generally observed
trends.
Table S2. Values for 2θ of (hkl) reflections for the α-phase of bulk iPP, iPP-200, iPP-40
and iPP-15.
o (1)
d-spacing
2θ (o)
2θ (o)
2θ (o)
2θ (o)
(nm)1
Bulk-iPP
iPP-200
iPP-40
iPP-15
(h k l)α
2θ ( )
(110)
14.14
0.626
14.19
14.01
14.19
13.98
(040)
16.92
0.524
17.06
16.78
16.90
16.81
(130)
18.55
0.478
18.67
18.30
18.54
18.59
(111)
21.31
0.417
21.14
---
21.13
---
(131)/(041)
21.86
0.406
21.88
---
21.98
---
(150)/(060)
25.35
0.351
25.66
---
---
---
(200)
27.18
0.328
---
26.95
27.00
26.86
(220)
28.51
0.313
28.35
---
---
---
S5
Recrystallization of iPP
Figure S3. Heating and cooling thermograms of as-purchased (bulk) and recrystallized
iPP. Scan rate = 10 C min-1. Second scan shown.
As-purchased iPP was recrystallized from p-xylene to remove any remaining catalyst
and other impurities. The polymer was first brought to a boil in a ~ 1 wt% solution and
heated for 10 min once the polymer had dissolved, then allowed to cool to room
temperature. The resulting solution was filtered using Whatman Grade 1 filter paper and
rinsed with methanol. The isolated powder was dried overnight under vacuum at 80 oC to
remove residual solvent. Differential scanning calorimetry scans of the sample before and
after recrystallization reveal stark differences, Figure S3. Firstly, the exothermic peak
maximum shifted from ~ 123.5 oC to 120.6 oC following recrystallization. The shift was
attributed to the removal of impurities from the as-purchased material. Secondly, a
secondary peak appeared at ~ 147.5 oC of the endotherm, this peak may be due to low
molecular weight chains melting.
S6
Experimental
Sample Preparation. Isotactic polypropylene (iPP) was purchased from Sigma
Aldrich. The molecular weight and dispersity were determined to be Mw ~ 243,000 g mol1
and
2.18,
respectively
using
gel
permeation
chromatography.
Following
recrystallization from p-xylene to remove any remaining catalyst and impurities, the
molecular weight and dispersity were 241,000 g mol-1 and 2.19, respectively. Resultant
iPP powder was hot pressed into sheets at 166 oC with a load of 4 metric tons.
Anodic aluminum oxide (AAO) templates were fabricated from aluminum foil (99.999
%, Sigma Aldrich) using a two-step electrochemical oxidation method.2 Anodization of
aluminum in 0.3 M sulfuric acid solution at 25 V or in 0.3 M oxalic acid solution at 40 V
resulted in self-ordered pores of 15 or 40 nm diameter, respectively.
An AAO template was placed directly on top of an iPP sheet, sandwiched between two
glass slides, and fastened with binder clips. Infiltration of iPP into the AAO template was
conducted under vacuum at 200 oC for 20-24 hours. The samples were then immediately
quenched on a steel plate. Samples used for the X-day diffraction studies with cradle
were annealed for an additional 30 minutes.
Scanning Electron Microscopy (SEM). The top glass slide was detached and the
excess bulk polymer was mechanically removed with sandpaper. The top, un-infiltrated
layer of alumina was etched away using a 5 wt% sodium hydroxide solution. Then the
intermediate layer of aluminum was removed using a solution of copper (II) chloride in
hydrochloric acid at a concentration of 0.05 g ml-1. The remaining alumina was then
etched away using sodium hydroxide solution to release the nanostructures from the
S7
template. Released nanowires were imaged using a JEOL JSM-7500F scanning electron
microscope.
Differential Scanning Calorimetry (DSC). The sample was placed in 5 wt% sodium
hydroxide solution to remove the top alumina layer. A razor blade was then used to
detach the sample from the bottom slide, and excess bulk polymer was removed using an
O2-plasma etcher (Harrick Plasma PDC-32G) and/or sandpaper. The etched surface was
covered with Kapton tape and the sample was placed in a solution of copper (II) chloride
and hydrochloric acid as before to remove the aluminum layer. Thermal analysis was
performed using a TA Instruments Q200 differential scanning calorimeter. The
instrument was calibrated using the Calibration Wizard software (TA Instruments
QSeries software). The heat flow (Tzero) calibration was performed using sapphire
standards and the temperature (cell constant) was calibrated with indium at 10 oC min-1.
All DSC measurements were performed under a nitrogen atmosphere using Tzero
aluminum pans and lids. The sample weight ranged between ~ 5-15 mg, template plus
polymer, depending on whether the sample was bulk or confined polymer.
X-Ray Diffraction (XRD). The sample was removed from the bottom slide using a
razor blade. Bulk polymer was removed from the template surface as described before.
θ/2θ diffraction patterns were collected in reflection mode (Bruker-AXS D8 Advance).
Copper K-α radiation was used with a wavelength of 0.154 nm. The instrument was
operated using Commander Software and outfitted with a nickel filter. The scanning
increment and integration time were 0.03 o and 1 s respectively. Then, the orientation of
iPP infiltrated into AAO templates was investigated using a cradle. Tilt angle (Ψ) was
varied from 0
o
to 85
o
in 1
o
steps and with an integration time of 10 s. Data were
S8
collected by specifying the position of the incident and reflected beams, corresponding to
a particular (hkl) plane, and collecting the intensities of the reflected rays as the sample
stage was tilted by an angle Ψ. A schematic view of the experimental set-up for this
analysis is shown below.
Figure S4. A representation of a polymer-infiltrated AAO template investigated using
XRD. In this diagram, θ is fixed, and Ψ is allowed to vary.
Removal of the Bulk Surface Layer
Figure S5. Heating (a) and cooling (b) thermograms of iPP infiltrated into an AAO
template (200 nm pore diameter) exposed to varying durations of plasma treatment. Scan
rate 10 oC min-1. Second scan shown.
Figure S5 shows the effect of plasma etching on an AAO template (200 nm pore
diameter) infiltrated with recrystallized iPP. The sample was exposed to 0, 1, or 2 hours
of oxygen plasma, with the motivation of identifying the optimal etching duration.
S9
Without any etching, the untreated sample displayed a crystallization peak bearing a
shoulder at slightly higher temperatures, Figure S5b. After one hour of plasma treatment
the excess bulk layer was successfully removed, and the confined polymer was exposed.
This was confirmed by the appearance of a low-temperature crystallization peak in the
cooling scan and the disappearance of the previously observed shoulder. After two hours
of etching, the measured heat flow was greatly reduced, suggesting that the infiltrated
polymer had been etched away. Therefore, one hour was selected as the optimal etching
duration.
References.
1. E. Clark, In Physical Properties of Polymers Handbook; Mark, J., Ed.; Springer
New York, 2007, p 619-624.
2. H. Masuda, K. Fukuda, Science 1995, 268, 1466-1468.
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