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Application of
Controlled/“Living” Radical
Polymerisation Techniques in the
Preparation of Polymer Hybrid Materials
A thesis submitted in fulfilment of the
requirements for the degree of
Doctor of Philosophy
By
Jessica C. Tom
School of Chemistry
The University of Sydney
2014
“I have not failed. I have just found 10,000 things that do not work.”
Thomas Edison
1847-1931
i
Abstract
It has been well documented that polymer composite or hybrid materials often
display superior properties than the indiv idual components, finding diverse
applications in advanced technologies including biomedical devices and controlled
drug delivery systems to materials chemistry. In recent years, research efforts to
prepare polymer hybrid materials have focussed on the application of
controlled/“living” radical polymerisation techniques to covalently link synthetic
polymers to various substrates via a strong covalent bond using either a grafting-to
or grafting-from approach. The current strategies employed to prepare polymer
hybrid materials suffer significant drawbacks that prevent widespread commercial
use including the formation of heterogeneous products resulting from often
laborious chemical modifications and limited molecular weight due to unavoidable
bimolecular termination, thereby delaying the development and implementation of
more advanced materials to fulfil the demands of modern technology. In this thesis,
we report the preparation of novel polymeric hybrid materials based on cellulose, a
naturally occurring polymer via physical blending to form supramolecular
conjugates which we call cellulose–polymer hybrid materials. We demonstrate
through the incorporation of a variety of synthetic polymers and block copolymers
prepared via reversible addition–fragmentation chain transfer (RAFT)
polymerisation that it is possible to incorporate functional polymers with cellulose
using cooperative hydrogen bonding rather than the covalent methods traditionally
used. We also show that polymers such as polystyrene that are typically
incompatible with natural polymers can be incorporated successfully by the
addition of another block bearing polar moieties. We expect the simplicity of this
approach combined with the versatility of modern polymerisation techniques will
prove a more cost-effective approach to prepare biopolymer-based materials with
tuneable properties and improved functionality, making industrial production more
viable. We also report the preparation of inorganic-organic hybrid materials using a
silica nanoparticle template bearing a bromo ester initiating group for the
preparation of core–shell materials with precisely tuneable properties using
ii
Abstract
surface-initiated single-electron transfer living radical polymerisation (SET-LRP). The
precise control over core–shell structures is generally hindered by the polymer
length that can be synthesised by controlled methods such as atom transfer living
radical polymerisation. Detailed studies using a variety of monomers including
methyl acrylate and tert-butyl acrylate are presented to demonstrate the versatility
and limitations of SET-LRP to produce ultrahigh molecular weight polymer grafts
from a spherical substrate. We show that SET-LRP is an effective technique to
prepare well-defined core–shell materials with tuneable properties. The process we
propose is based on the use of copper wire, which offers polymers with lower
concentrations of copper contaminants and is easily removed and recycled, with
fast polymerisation kinetics and low reaction temperatures, making it the process of
choice for both academia and industry.
iii
Statement of Contributions
The chain transfer agents used in this work were supplied and synthesised by Algi
Serelis of the DuluxGroup.5 0, RPAA1F00T, PApA5o00,l yPDmMAeErA9s3, (PAA
PDMAEA96 and PDMAEA350) used to investigate the effect of polymer chain length
on the miscibility of cellulose–polymer blend materials were sourced from Wei Zhao
of the Key Centre for Polymers and Colloids, the University of Sydney, as specified in
the Experimental Section (Chapter 2). Initial characterisation of the cellulose hybrid
materials by differential scanning calorimetry and thermal gravimetric analysis was
performed by Nasim Shah Mohammadi in accordance with the experimental
requirements for the completion of Masters by Research.
The initiator bearing an ethoxysilane moiety, {[(2-bromo-2-
methylpropionyl)oxy]propyl}triethoxysilane (BPE), was prepared and coupled to a
silica solid-support by Dr. John Moraes (Key Centre for Polymers and Colloids,
University of Sydney) in collaboration with A/Prof. Kohji Ohno (Institute for
Chemical Research, Kyoto University) for the purpose of investigating the efficacy of
single-electron transfer living radical polymerisation to prepare well-defined
inorganic-organic core–shell particles with precisely tuneable properties based on
synthetic polymer and shell thickness. Hexamethylated tris(2-aminoethyl)amine
(Me6TREN) was provided by Cheuk Ka Poon (Key Centre for Polymers and Colloids,
University of Sydney).
Training in specimen preparation techniques and operation of specialised
equipment was overseen by staff at the University of Sydney. Microscopy training
was supervised by the technical staff of the Australian Centre for Microscopy and
Microanalysis (ACMM): Steve Moody (SEM operation and sample preparation),
Shaun Bulcock (TEM operation) and Naveena Gokoolspardah (TEM sample
preparation). Spectroscopy training was provided by the Vibrational Spectroscopy
Facility staff, Dr. Elizabeth Carter, Dr. Joonsup Lee and Dr. Lauren Clements. Dr.
Hank De Bruyn of the Thermophysical Properties Facility provided technical support
and training for both DSC and TGA.
iv
Declaration
This dissertation is submitted in partial fulfilment for the degree of Doctor of
Philoso apt htyhe School of Chemistry, University of Sydney in the field of Polymer
Chemistry. Except where otherwise stated, all experimental work reported in this
thesis was performed by the author in the Key Centre for Polymers and Colloids in
the School sotfr yC hate mthie University of Sydney between March 2011 and
March 2014. Where collaborations have been necessary, the collaborators
contribution has been made clear and referenced in the usual manner throughout
the text. Furthermore, no peaertn osfu bthmisit twedo rkfo rh aasn yb other
degree at this or any o ther institution.
Jessica C . Tom
8 July, 2 014
v
Acknowledgements
I cannot proceed to thank everybody responsible for getting me through this long
and arduous academic course without first thanking my supervisor Professor
Sébastien Perrier. Firstly, for inviting me to continue my research in the area of
polymeric asfctiern cecompleting Honours, but also for his support and
understanding throughout this very trying project. I must also acknowledge the
support and encouragement afforded by Dr. Chiara Neto. Her unwavering
confidence in me was upliftindgo a bnedt tmero tainvadt etod bmeeli etvoe in my
own abi lities.
I could never have completed this degree without the assistance and
friendship afforded by the transient members of the Key Centre for Polymers and
Colloids, to whom I am greatly ind Mebotnead Saenmds aforirleavr er grateful.
provided guidance, support and understanding, having just gone through the
experience of working with a difficult material. John Moraes provided guidance and
technical support happily, not to mention levity and entertainment. Ming Koh for
his support and friendship, providing endless laughs, mismatched coffee breaks and
unexpected gossip. I don’t believe a single person could have survived without Eh
Hau Pan, our fabulous lab manager, who knew all the ins and outs of the Chemistry
School, had everything we needed on hand, and was exceptionally kind and
encouraging. To Rob Chapman, Sabrina Dehn, Guillaume Gody, Maarten Danial,
Raphael Barbey, Isidro Cobo, Andrew Telford, Manuel Ghezzi and Naatasha Isahak
for their friendship, encouragement, faith and lab expertise. Special thanks must be
given to Raph for painstakingly reading my cellulose chapter so thoroughly and Naat
for listening to all my woes over coffee. Andrew Dolan for boosting confidence
through encouragement and the provisions of “Friday” night drinks for us poor
underpaid and underappreciated Ph.D. students. To A/Prof. Brian Hawkett, for
always presenting a friendly smile in the wee hours of the morning and his
postdoctoral fellows who willingly bestowed helpful suggestions and insight, not to
mention unwavering encouragement, support and reassurance that this will one
day end.
vi
Acknowledgements
To Dr. Christopher Waldron and Dr. Athina Anastasaki, the University of
Warwick, for their willingness to exchange ideas regarding the experimental set-up,
sensitivity and nuisances of SET-LRP with vigour and enthusiasm. Your contributions
were invaluable.
I would also like to acknowledge the funding received from the Australian
Government (Australian Postgraduate Award) for the duration of my candidature,
and the University of Sydney (Postgraduate Research Support Scheme) for providing
additional financial support for conference attendance. This proved invaluable for
furthering my understanding within related fields and networking opportunities.
Finally, I must thank my family and friends for their ongoing support and
encouragement throughout my Ph.D. In particular, to Diran Fabricatorian for always
being there, his faith in my abilities, helping me relax and rejuvenate, be it through
rock climbing or trying out a new trendy café. To Jack Mac, who would always listen
to my concerns with understanding, hugs and of course more coffee. Derrick
Roberts, whose faith in me never faulted. Alice Poppleton, Chas Haschek and Alex
Luke for their reassurance, encouragement, understanding and patience afforded to
me over the many years. And finally to Lisa Cameron, who was my ultimate
inspiration. She could always lift my spirits, guide me through trying times, and offer
the encouragement and confidence I needed to continue. But to ensure no person
goes without acknowledgement (and to save paper) I must express my gratitude to
anyone who ever lifted my spirits, made me laugh, saw the best in me and believed
in me – I truly thank you.
vii
Contents
Abstract ................................................................................................................... ii
Statement of Contributions.................................................................................... iv
Declaration .............................................................................................................. v
Acknowledgements ................................................................................................ vi
Contents ............................................................................................................... viii
List of Figures ........................................................................................................ xi
List of Schemes ................................................................................................... xvii
List of Tables ....................................................................................................... xix
List of Abbreviations ............................................................................................ xxi
1 General Introduction ........................................................................................... 1
1.1 Preamble ...................................................................................................................... 2
1.2 Overview of Dissertation .......................................................................................... 4
1.3 References .................................................................................................................... 5
2 Preparation of Cellulose-Based Hybrid Materials with Synthetic Polymers
Prepared via Reversible Addition–Fragmentation Chain Transfer Polymerisation
................................................................................................................................. 6
2.1 Introduction ................................................................................................................ 7
2.2 Experimental ............................................................................................................. 14
2.2.1 Materials ................................................................................................................ 14
2.2.2 Equipment ............................................................................................................ 15
2.2.3 Preparation of Synthetic Polymers by RAFT Polymerisation ...................... 18
2.2.4 Dissolution of Cellulose and Preparation of Cellulose–Polymer Blends .... 24
2.3 Results and Discussion ............................................................................................ 25
2.3.1 Blending Cellulose with Hydrophobic Polymers ............................................ 27
2.3.2 Blending Cellulose with Hydrophilic Polymers .............................................. 32
2.3.3 Effect of Chain Length on the Properties of the Cellulose Matrix ............. 47
2.3.4 Block Copolymers ............................................................................................... 54
viii
