This study summarizes research on polymer grafted graphene oxide (GO) nanoparticle dispersions. The researchers synthesized two hydrogel nanocomposites: one with physically mixed GO and poly(ethylene glycol) methyl ether methacrylate (PEGMEMA), and one with GO covalently linked to PEGMEMA via reversible addition-fragmentation chain transfer (RAFT) polymerization. Rheological tests showed the covalently linked sample had higher shear modulus where lubrication dominated over reinforcement, indicating grafted polymer chains minimized lubrication effects. UV-vis spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy confirmed successful RAFT polymerization and covalent attachment of PEG

1. Polymer Grafted Graphene Oxide (GO) Nanoparticle Dispersions
Abigail A. Advincula, Joey D. Mangadlao, Rigoberto C. Advincula
Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106 USA
Reinforcement effect is
related to the interfacial
interaction of Go and
polymer, state of dispersion
of GO in the polymer matrix,
changes in the crystalline
structure and crystallinity of
polymers in the presence of
GO and the intrinsic
properties of the GO itself.
Lubrication phenomena
arise from a specific loading
of a nanofiller where
lubrication is favored due to
the sliding of the sheets,
resulting to a significant
decrease in viscosity.
Introduction
Methodology
Results
Raman Spectra & TEM
Conducting Region
Conclusions
Acknowlegments
I would like to thank Professor Rigoberto Advincula for his guidance on this
project. I would also like to thank Joey Mangadlao for his help with sample
preparation and characterization. The authors acknowledge funding from DMR-
1304214, NSF-1333651, and STC-0423914.
 Hydrogels are three-dimensional polymer
networks made up of hydrophilic cross-
linked macromolecules that are able to
absorb water when placed in an aqueous
medium.
 Hydrogels have been investigated for
possible applications ranging from
biomedical implants to drug delivery
systems.
Project Objectives
 Graphene oxide (GO) has raised interest as an
inorganic cross-linker due to its ability to
remarkably improve strength of materials and
excellent solution processability.
 Previous research in GO hydrogels has focused
on non-covalent interactions between the GO
filler and the surrounding polymeric matrix.
 We propose a GO hydrogel which covalently
attaches a polymer using reversible-addition
chain transfer (RAFT) polymerization. This
study compares a physically mixed and a
chemically linked GO & PEGMEMA system.
 Synthesis scheme of GO-RAFT, PEGMEMA-GO and PEGMEMA-GO-RAFT
 One major drawback to the use of hydrogels is that conventional polymeric
hydrogels utilizing organic cross-linkers typically exhibit poor mechanical stability.
 Inorganic cross-linkers have drawn interest in that their high surface area and large
number of functional groups allow for a strong polymer network to be established
between the inorganic cross-linkers and the polymer chains.
Results
Future Work
 We proposed a GO hydrogel which covalently attached a polymer using (RAFT)
polymerization.
 Fabrication and characterization of two samples, PEGMEMA-GO and PEGMEMA-
GO-RAFT, was completed to allow comparison of properties of a physically mixed
and a covalently linked system.
 Objective 1 focused on confirming the grafting of RAFT CTA to GO nanosheet and
the polymerization of PEGMEMA using UV-Vis, FT-IR, and TGA.
 Objective 2 focused on confirming the covalent attachment of PEGMEMA to GO
nanofillers using Raman Spectra and TEM.
 Objective 3 focused on interpreting rheological data to understand the effect of
covalent attachment on the reinforcement and lubrication effect in GO nanosheet
and PEGMEMA systems.
 Our research ultimately aims at exploring the possible architectures of GO as an
inorganic cross-linker in hopes of producing a facile and versatile filler technology for
hydrogel fabrication.
HYDROGELS
OUR APPROACH – GRAPHENE OXIDE CROSS-LINKERS
 Compare the reinforcement and lubrication effects between the PEGMEMA-GO
and the PEGMEMA-GO-RAFT using rheology data.
OBJECTIVE 1 – RAFT POLYMERIZATION ON GO NANOSHEETS
OBJECTIVE 2 – COVALENT ATTACHMENT OF POLYMER BRUSHES
OBJECTIVE 3 – DETERMINATION OF RHEOLOGICAL PROPERTIES
 Confirm covalent attachment of PEGMEMA to GO nanosheet by Raman
spectroscopy.
 Utilize transmission electron microscopy (TEM) to observe morphology of
physically mixed and covalently linked samples.
 Attach RAFT chain transfer agent (CTA) to GO nanosheets and confirm by UV-Vis,
FT-IR, and TGA.
 Attach PEGMEMA covalently by RAFT and confirm polymerization of the monomer
by techniques listed above.
OBJECTIVE 1 – RAFT POLYMERIZATION ON GO NANOSHEETS
OBJECTIVE 2 – COVALENT ATTACHMENT OF POLYMER BRUSHES
OBJECTIVE 3 – DETERMINATION OF RHEOLOGICAL PROPERTIES
 Vary conditions of PEGMEMA RAFT polymerization to control polymer’s molecular
weight, polydispersity, and composition to see alteration of GO hydrogel
nanocomposite properties.
 Vary monomer and CTA used in RAFT polymerization to investigate synthesis of
other possible architectures for GO hydrogels.
 Explore other surface-initiated polymerization techniques (e.g. ATRP) to
investigate translational capacity of polymer grafting technology to other systems.
FT-IR also confirmed successful
grafting of RAFT-CTA and RAFT
PEGMEMA.
A very pronounced C=O stretch, C-
O stretch and strong aliphatic C-H
stretch at ~2900 cm-1 evidenced
the successful polymerization of
PEGMEMA.
Thermograviometric analysis (TGA)
confirmed ~98% greater weight
loss for samples RAFT polymerized
with PEGMEMA (PEG/GO-RAFT
(2%)) than samples only modified
with CTA (GO-RAFT).
Thermograviometric Analysis
FT-IR Spectra
UV-Vis Spectra
Reinforcement vs. Lubrication EffectFabricated GO-PEGMEMA-RAFT Hydrogel Nanocomposite
Rheological tests demonstrated that where lubrication effect dominates reinforcement
(i.e. at higher GO filler content) covalently linked PEGMEMA-GO-RAFT has higher G’
compared to physically mixed PEGMEMA-GO.
The grafted polymer chains appear to minimize the lubrication effect, resulting in
higher G’.
Fabricated PEGMEMA-GO-RAFT hydrogel nanocomposite is demonstrated to be
resilient under load.
UV-Vis confirmed profile of GO-
RAFT as intermediate to that of
pure GO and RAFT-CTA.
(a) Raman spectroscopy confirmed extent of surface modification. The ID/IG ratio,
which quantifies functionalization, was found to be 0.85 for GO, 0.88 for
PEGMEMA-GO, and 0.96 for PEGMEMA-GO-RAFT.
(b) TEM sample of PEGMEMA-GO-RAFT fit reported morphologies of graphene
covalently grafted with polymers.
(c) TEM sample of PEGMEMA-GO has morphology more similar to pristine GO.
Rheology Tests
Reinforcement effect is related to the interfacial
interaction of GO and polymer, the state of
dispersion of GO in the polymer matrix, changes
in the crystallinity of polymers in the presence of
GO, and the intrinsic properties of the GO itself.
Lubrication phenomena arises from a specific
loading of a nanofiller where lubrication is
favored due to the sliding of the sheets, resulting
in a significant decrease in viscosity.
PEGMEMEA-GO PEGMEMEA-GO-RAFT