Novel Functional Graphene and its Thermodynamic Interfacial Localization in

Biphasic Polyolefin Systems for Advanced Lightweight Applications

Antimo Grazianoa, Christian Garciad, Shaffiq Jafferc, Jimi Tjonga, Mohini Sain,a,b,*

aCentre for Biocomposites and Biomaterials Processing, Faculty of Forestry, University

of Toronto, 33 Willcocks Street, Toronto, M5S 3BS, Canada

bDepartment of Mechanical and Industrial Engineering, University of Toronto, 5 King’s

College Road, Toronto, M5S 3G8, Canada

cTOTAL American Services Inc., 82 South Street, Hopkinton, MA, 01748, USA

dBahen Centre for Information Technology, University of Toronto, 40 St. George Street,

Toronto, M5S 2E4, Canada

*Corresponding author:

Professor Mohini Sain

Email: m.sain@utoronto.ca

MANUSCRIPT NUMBER: CSTE_2019_1854_R2

SUPPORTING INFORMATION

CHARACTERIZATION AND TESTING

Fourier Transform Infrared Spectroscopy (FTIR)

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FTIR spectrums were obtained by using an FTIR Tensor 27 Spectrometer (Bruker).

Each sample, in powder form, was mixed with Potassium Bromide and pressed into

pellets. Spectra were recorded in a wavelength range of 400 – 4000 cm-1, at a resolution

of 4 cm-1, over 32 scans.

Thermal Gravimetric Analysis (TGA)

TGA was carried out using a Thermal Gravimetric Analyzer, TA instrument TGA Q500,

USA, under nitrogen atmosphere. About 5 – 8 mg of each sample was subjected to

degradation process from room temperature to 500° C, with a heating rate of 10 °C/min.

This technique was also used to determine the weight percentage of grafted MAPP onto

RFGO. In addition, the MAPP grafting density could be calculated through equation 1:

[1]

Grafted amount (mmolg

)= 1000×∆W(1000−∆W )×M (1)

where ΔW is the difference between % weight loss of RFGO and % weight loss of MR,

while M is the molecular weight of MAPP.

X-Ray Diffractions (XRD)

X-ray patterns were registered using an X-ray diffractometer PANalytical PW3710,

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using Cu Kα radiation, with current intensity of 30 mA and generator voltage of 40 kV.

Data were taken at scan speed of 0.5 °2θ/min, step size of 0.02 °2θ and 2.5 sec time

per step. The °2θ range considered was 5 - 30. The interlayer distance (d) was

calculated using Bragg’s law (equation 2):

d ¿λ

2sin (θ) (2)

where λ is the X-ray wavelength (typically 0.154 nm), and θ the scattering angle.

Atomic Force Microscopy (AFM)

The lateral dimension of modified GO was obtained using an AFM Hitachi 5100N, in

tapping mode, under ambient conditions. Sample preparation was performed by

dispersing MAPP-RFGO in ethanol and then dropping this solution on a wafer surface.

RESULTS AND DISCUSSION

FTIR, TGA, XRD and AFM were carried out to analyze the effectiveness of GO

modification in partially restoring the graphene structure, while functionalizing it with

amino groups, as well as the successfulness of the grafting of MAPP onto RFGO. As

seen from figure S1, the FTIR spectrum of GO indicated the typical oxygen moieties,

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which are O-H (3400), C=O (1720 cm-1), C=C (1630 cm-1), C-O (1220 cm-1) and C-O-C

(1050 cm-1).[2]

Figure S1. FTIR spectrums of GO (red), RFGO (blue) and MAPP-RFGO (black)

After modification, some amino groups appeared in the RFGO spectrum, being C-N

(1564 and 1085 cm-1) and N-H (1460 cm-1). This proved the effectiveness of GO

functionalization.[3] Moreover, the peaks at 1720, 1220, and 1050 cm-1 almost

completely disappeared, indicating that the hydrazine monohydrate effectively removed

most of the carbonyl, carboxyl and epoxy groups, partially restoring the graphene

structure. When analyzing the MAPP-RFGO spectrum, strong bands between 2800 and

3000 cm-1 could be seen, representing CH2 stretching vibrations, typical of PP.[4]

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Together with this, the appearance of imide groups (1400 and 1600 cm-1) demonstrated

that the covalent grafting process, through the reaction between the anhydride of MAPP

and the amino functionalities of RFGO, was successful.

According to the TGA curves (figure S2), GO underwent two main degradations, the first

being related to the moisture content removal, while the second (the major mass loss)

regarding the decomposition of oxygen related moieties, such as carbonyl, carboxyl and

epoxy groups.[5]

Figure S2. TGA curves of GO (red), RFGO (blue), MAPP (green) and MAPP-RFGO

(black)

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On the other hand, RFGO had a much slighter weight loss, which proved that the GO

modification was successful in removing most of the oxygen containing functionalities,

thus partially restoring the graphene structure. By comparing the TGA curve of MAPP-

RFGO with the one of MAPP, the weight loss of the former is smaller than the one of

the latter, demonstrating effective grafting of MAPP onto RFGO.[6] Additionally,

considering that MAPP completely degraded at about 470 °C, it is worth noticing that,

above this temperature, MAPP-RFGO had roughly 20% of its weight left, which is the

amount of RFGO in MAPP-RFGO. This is another way to confirm that MAPP was

successfully grafted onto RFGO. Next, since MAPP is completely degraded at 500 °C,

while the weight of RFGO and MR remain the same, even at higher temperatures, the

weight concentration of grafted MAPP onto RFGO could be calculated,[1] and its value

was found to be 58%. Lastly, by using equation 1 and following the work done by Zabihi

and coworkers,[7] the grafting density of MAPP onto RFGO was estimated (0.35

mmol/g).

Figure S3 shows the XRD patterns of GO, RFGO and MAPP-RFGO. GO was

characterized by a peak at 2θ = 10.4°, corresponding to an interlayer distance (d) of

0.85 nm.[8]

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Figure S3. XRD patterns of GO (blue), RFGO (red) and MAPP-RFGO (black)

Conversely, in the case of RFGO, a peek was seen at 2θ = 25.2°, meaning that d=0.36

nm, which is very similar to the one of pure graphene (0.34 nm).[9] This confirmed,

along with the FTIR and TGA results, the partial reconstruction of graphitic structure, via

functionalization and reduction of GO. Lastly, in the MAPP-RFGO pattern, the peaks

corresponding to the crystalline planes of PP appeared, indicating the grafting of MAPP

onto RFGO.[10]

Figure S4 illustrates the AFM image and height profile of MAPP-RFGO. Its thickness

was around 8 nm, which is considerably higher than the one of single layer GO (~1 nm).

[11]

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Figure S4. AFM image of MAPP-RFGO (A) and its height profile (B)

It is believed that the functionalization of GO with EDA, to obtain RFGO, increased the

thickness to about 3.5 nm, due to the presence of amino functionalities on both edges of

the GO main lattice, as reported elsewhere.[12] Therefore, when grafting MAPP onto

RFGO, lengthier functional groups were covalently attached, on both sides of RFGO,

making the thickness of MAPP-RFGO reasonably rise to 8 nm.[13]

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