Daniel Whelligan gained his first degree (1st class) in Natural Sciences from the University of Cambridge (Churchill College) in 2000. After graduation, he spent the summer at Université Bordeaux I, France carrying out organic synthesis in the group of Professor Stephane Quideau. He then moved to the University of Durham for his PhD with Dr Patrick Steel on the use of silenes (Si=C) in novel organic synthetic methods. In 2004, he secured an Alexander von Humboldt Postdoctoral Research Fellowship to work on the use of paracyclophanes in asymmetric catalysis with Professor Carsten Bolm at RWTH Aachen University, Germany. From 2006-7, he took time to travel around the world including a 3 month postdoctoral research placement with Professor Mark von Itzstein at the Institute for Glycomics, Griffith University, Australia. On return to the UK, Daniel worked from 2007-10 at the Institute of Cancer Research (ICR) as a Postdoctoral Training Fellow in Medicinal Chemistry in the group of Dr Swen Hoelder on the discovery of inhibitors of cancer targets. In 2011 he was appointed as Lecturer of Organic/Medicinal Chemistry at the University of Surrey.
University roles and responsibilities
- Departmental Assessments Officer
Affiliations and memberships
The Whelligan group uses organic synthesis to answer questions and solve problems in biology and alkaline fuel cell research. For biology, this includes drug discovery and the design of inhibitors and probes, using medicinal chemistry expertise, for use as investigational tools. During this research, opportunities to develop novel synthetic methods are also exploited. Major projects are described below:
Design and Discovery of Inhibitors of the DNA Repair Enzyme Aag
Collaborators: Ruan Elliott, Brendan Howlin, Lisiane Meira
The DNA repair enzyme Aag (Alkyladenine glycosylase) locates and excises alkylated or oxidatively damaged DNA bases (orange in the video, right) and thus initiates the base excision repair (BER) pathway. However, through mouse Aag knockout and overexpression studies, it has been shown that in photoreceptor, spleen, thymus, bone marrow, pancreatic β and cerebellum cells, the action of Aag in response to DNA alkylation (by MMS) leads to cell death. A small molecule inhibitor of Aag is required for use as a tool in further investigations of the biological mechanisms which mediate this cell death. Furthermore, since humans show varying levels of Aag activity and may encounter alkylating agents naturally, from the diet, pollution or as part of chemotherapy, an inhibitor may form a drug discovery lead for diseases or situations where the action of Aag may be leading to tissue degeneration.
We are engaged in Aag inhibitor discovery via two routes, both of which now follow the discovery cycle shown in Fig. 2:
- Target-based design: Using computational virtual screening, purchase and bioassay of the top 49 predicted inhibitors we have identified a 'hit' on which we are basing more effective inhibitors.
- Ligand-based design: DNA oligomers containing modified nucleotides have been shown to inhibit Aag. Based on these and their published crystal structures (Fig. 1), we have designed potential small molecule inhibitors and are engaged in their synthesis and bioassay.
For a talk to a multidisciplinary audience on this project, see the MILES Showcase Presentation.
This work is supported by a Royal Society Research Grant [RG140689].
This work was supported by the Engineering and Physical Sciences Research Council [grant number EP/I000992/1].
- Meira, L. B.; Moroski-Erkul, C. A.; Green, S. L.; Calvo, J. A.; Bronson, R. T.; Shah, D.; Samson, L. D. Proc. Natl. Acad. Sci. 2009, 106, 888.
- Calvo, J. A.; Moroski-Erkul, C. A.; Lake, A.; Eichinger, L. W.; Shah, D.; Jhun, I.; Limsirichai, P.; Bronson, R. T.; Christiani, D. C.; Meira, L. B.; Samson, L. D. PLoS Genet. 2013, 9, e1003413.
- Setser, J. W.; Lingaraju, G. M.; Davis, C. A.; Samson, L. D.; Drennan, C. L. Biochemistry 2012, 51, 382.
Ethoxyvinylarenes as Versatile Intermediates for Heterocycle Synthesis
Azaindoles (4) find widespread use in drug discovery yet methods which permit access to all possible regioisomers are limited and their purchase is costly. Whelligan et al previously published a two-step synthesis of all regioisomers from chloro- or bromo-aminoarenes which involves Suzuki coupling with ethoxyvinylborolane 2, to give an ethoxyvinylarene 3, followed by acid-mediated cyclisation.3 We are now investigating the versatility of the ethoxyvinylarenes 3 in terms of producing substituted azaindoles or tricycles in one step.
- Popowycz, F.; Mérour, J.-Y.; Joseph, B. Tetrahedron 2007, 63, 8689.
- Popowycz, F.; Routier, S.; Joseph, B.; Mérour, J.-Y. Tetrahedron 2007, 63, 1031.
- Whelligan, D. K.; Thomson, D. W.; Taylor, D.; Hoelder, S. J. Org. Chem. 2009, 75, 11.
The Mechanism of Action of Mycolactone, Causative Agent of Buruli Ulcer
Collaborator: Rachel Simmonds
Buruli ulcer is a slow-growing, necrotising skin disease found predominantly in patients in rural areas of developing countries, particularly in Western Africa. It can cover >15% of a patient's body and cause permanent disability. It is caused by the microbial pathogen Mycobacterium ulcerans which secretes mycolactone A/B, the sole cytopathic toxin known to date. Importantly, no acute inflammatory response is mediated to the infection and this has been found to be partly due to the immunosuppressive activity of mycolactone A/B. As part of ongoing mechanistic studies in the Simmonds group, we intend to attach synthetic tags to mycolactone A/B to facilitate 'pull-down' of its protein targets from human cell lines and visualisation of its in-cell localisation using fluorescence.
We are also investigating improved methods for the isolation and purification of mycolactone A/B and mycolactone F (a fatty acid chain analogue) from cultures of M. ulcerans and M. marinum (a fish pathogen), respectively.
- Hall, B.; Hill, K.; McKenna, M.; Ogbechi, J.; High, S.; Willis, A. E.; Simmonds, R. E. PLoS Pathog. 2014, 10(4), e1004061.
- Hall, B.; Simmonds, R. Biochem. Soc. Trans. 2014, 42, 177-183.
- Hong, H.; Stinear, T.; Porter, J.; Demangel, C.; Leadlay, P. F. ChemBioChem 2007, 8, 2043.
- Simmonds, R. E.; Lali, F. V.; Smallie, T.; Small, P. L. C.; Foxwell, B. M. J. Immunol. 2009, 182, 2194-2202.
Alkaline Fuel Cells and Electrolysers: Design and Synthesis of Novel Membrane Head Groups
Collaborator: John Varcoe
Hydrogen fuel cells that use proton exchange membranes as their 'salt bridge' are well established but the alternative, alkaline anion exchange membranes (AAEMs), offer advantages including the use of cheaper, non-platinum metals as the electrocatalysts (anode and cathode). The same is true for electrolysers (figure right) which can be used to generate hydrogen from water. We aim to overcome the two main disadvantages of AAEMs compared to proton exchange membranes: 1. the lower conductivity of hydroxide ions and, 2. chemical instabilities of the membranes in the presence of hydroxide. To this end, we design and synthesise small organic molecules for radiation grafting into membranes and conversion into cationic head groups. This provides novel AAEMs with improved properties.
- Varcoe, J. R.; Slade, R. C. T.; Wright, G. L.; Chen, Y.J. Phys. Chem. B 2006, 110, 21041.
- Varcoe, J. R.; Atanassov, P.; Dekel, D. R.; Herring, A. M.; Hickner, M. A.; Kohl, P. A.; Kucernak, A. R.; Mustain, W. E.; Nijmeijer, K.; Scott, K.; Xu, T.; Zhuang, L.Energy Environ. Sci. 2014, 7, 3135.
- Ong, A. L.; Whelligan, D. K.; Fox, M. L.; Varcoe, J. R.Phys. Chem. Chem. Phys. 2013, 15(43), 18827.
- Ong, A. L.; Whelligan, D. K.; Murphy, S.; Varcoe, J. R. Phys. Chem. Chem. Phys. 2015, 17(18), 12135.
This work is supported by the Engineering and Physical Sciences Research Council [grant number EP/M005933/1].
Research Group and Facilities
Current PhD Students
Efi Mavrogiannaki (3rd year)
Tom Warren (2nd year)
Jacob Hiles (1st year)
Applications for PhD Studentships
Any funded PhD studentships that become available will be advertised on the University of Surrey Chemistry PhD website. Applications from self-funded or overseas government-funded students are welcome. Please email Daniel Whelligan in the first instance.
All organic synthesis is carried out in the recently refurbished Joseph Kenyon laboratory containing 24 state-of-the-art double fume cupboards, spectroscopy suite and cold room. The lab has been shortlisted for a 'Safe, Successful and Sustainable Laboratory Award 2014' and is equipped with all necessary equipment for normal and air-sensitive organic chemistry.
The Department possesses 500 and 300 MHz NMR spectrometers, a triple-quad LCMS and several GCMS, IR and UV-Vis instruments.
Lecture notes, coursework, supplementary videos and documents are available on SurreyLearn.
- Level 5 (Year 2) CHE2037 Bioorganic Chemistry and Drug Discovery
- Level 6 (Year 3) CHE3043 Topics in Organic Chemistry
- Level 6 (Year 3) CHE3049 Medicinal Chemistry II
- Level 7 (Year 4) CHEM025 Advanced Topics in Organic Chemistry
- Level 7 (Year 4) CHEM032 Advanced Medicinal Chemistry
Polymer-supported benzotriazole linked reactions
synthesised by radiation-grafting onto poly(ethylene-co-tetrafluoroethylene) (ETFE) films are reported. The relative
properties of these AEMs are compared with the benchmark radiation-grafted ETFE-g-poly(vinylbenzyltrimethylammonium)
AEM. Two AEMs containing heterocyclic-QA head groups were down-selected with higher relative stabilities in aqueous KOH
(1 mol dm-3) at 80°C (compared to the benchmark): these 100 ¼m thick (fully hydrated) ETFE-g-poly(vinylbenzyl-Nmethylpiperidinium)-
and ETFE-g-poly(vinylbenzyl-N-methylpyrrolidinium)-based AEMs had as-synthesised ion-exchange
capacities (IEC) of 1.64 and 1.66 mmol g-1, respectively, which reduced to 1.36 mmol dm-3 (ca. 17 ? 18% loss of IEC) after
alkali ageing (the benchmark AEM showed 30% loss of IEC under the same conditions). These down-selected AEMs exhibited
as-synthesised Cl- ion conductivities of 49 and 52 mS cm-1, respectively, at 90°C in a 95% relative humidity atmosphere, while
the OH- forms exhibited conductivities of 138 and 159 mS cm-1, respectively, at 80°C in a 95% relative humidity atmosphere.
The ETFE-g-poly(vinylbenzyl-N-methylpyrrolidinium)-based AEM produced the highest performances when tested as
catalyst coated membranes in H2/O2 alkaline polymer electrolyte fuel cells at 60°C with PtRu/C anodes, Pt/C cathodes, and
a polysulfone ionomer: the 100 ¼m thick variant (synthesised from 50 ¼m thick ETFE) yielded peak power densities of 800
and 630 mW cm-2 (with and without 0.1 MPa back pressurisation, respectively), while a 52 ¼m thick variant (synthesised
from 25 ¼m thick ETFE) yielded 980 and 800 mW cm-2 under the same conditions. From these results, we make the
recommendation that developers of AEMs, especially pendent benzyl-QA types, should consider the benzyl-Nmethylpyrrolidinium
head-group as an improvement to the current de facto benchmark benzyltrimethylammonium headgroup.
Work began with testing the reproducibility of the previously published method of synthesising the ethoxyvinyl(amino)arenes. This was done successfully, although a change in ligand (SPhos to RuPhos) proved beneficial, with seven different analogues being synthesised in yields ranging from 36% to 98%. This same reaction was attempted with halo-hydroxypyridines, with a novel route to furopyridines in mind, but with no success. The synthesis of non-commercially available halo-hydroxypyridines themselves also proved to be challenging with no material being isolated.
Various methods were tested for the bromo-cyclisation of ethoxyvinyl(amino)arenes to 3-bromopyrrolopyridines. A two-step method using acid cyclisation followed by bromination was entirely successful. Two-step, one-pot and one-step methods both appeared to promote polymerisation/oligermisation. Success was achieved with a one-step method employing an acid additive but only on selected ethoxyvinyl(amino)arene isomers and with varying yields.
The work was extended to the attempted synthesis of anti-malarial precursors using the bromo-pyrrolopyridine isomers as building blocks and converting them to alkyl-linked glutarimides. This led to the successful and novel synthesis of the reactants vinyl glutarimide and glutarimylethylborolane. However, successful conditions for their palladium catalysed cross coupling with the bromides were not found.
anion-exchange membranes with high performance and stability, Energy & Environmental Science 10 pp. 2154-2167 Royal Society of Chemistry
the polymer-bound positively-charged head-groups that enable anion conduction. The effect of the backbone polymer
chemistry, of the precursor film, on RG-AEM stability has been studied to a lesser extent and not for RG-AEMs made from
pre-irradiation grafting of polymer films in air (peroxidation). The mechanical strength of polymer films is generally
weakened by exposure to high radiation doses (e.g. from a high-energy e?-beam) and this is mediated by chemical
degradation of the main chains: fluorinated films mechanically weaken at lower absorbed doses compared to nonfluorinated
films. This study systematically compares the performance difference between RG-AEMs synthesised from a
non-fluorinated polymer film (low-density polyethylene ? LDPE) and a partially-fluorinated polymer film (poly(ethylene-cotetrafluoroethylene)
? ETFE) using the peroxidation method (pre-irradiation in air using an e?-beam). Both the LDPE and
ETFE precursor films used were 25 ¼m in thickness, which led to RG-AEMs of hydrated thicknesses in the range 52 ? 60 ¼m.
The RG-AEMs (designated LDPE-AEM and ETFE-AEM, respectively) all contained identical covalently-bound
benzyltrimethylammonium (BTMA) cationic head-groups. An LDPE-AEM achieved a OH? anion conductivity of 145 mS cm-1
at 80 °C in a 95% relative humidity environment and a chloride Cl? anion conductivity of 76 mS cm-1 at 80 °C when fully
hydrated. Alkali stability testing showed that the LDPE-AEM mechanically weakened to a much lower extent when treated
in aqueous alkaline solution compared to the ETFE-AEM. This LDPE-AEM outperformed the ETFE-AEM in H2/O2 anionexchange
membrane fuel cell (AEMFC) tests due to high anion conductivity and enhanced in situ water transport (due to the
lower density of the LDPE precursor): a maximum power density of 1.45 W cm-2 at 80 °C was achieved with an LDPE-AEM
alongside a Pt-based anode and cathode (cf. 1.21 mW cm-2 for the benchmark ETFE-AEM). The development of more
mechanically robust RG-AEMs has, for the first time, led to the ability to routinely test them in fuel cells at 80 °C (cf. 60 °C
was the prior maximum temperature that could be routinely used with ETFE-based RG-AEMs). This development facilitates
the application of non-Pt catalysts: 931 mW cm-2 was obtained with the use of a Ag/C cathode at 80 °C and a Ag loading of
0.8 mg cm-2 (only 711 mW cm-2 was obtained at 60 °C). This first report on the synthesis of large batch size LDPE-based RGAEMs,
using the commercially amenable peroxidation-type radiation-grafting process, concludes that the resulting LDPEAEMs
are superior to ETFE-AEMs (for the intended applications).
onto ETFE: the synthesis of the most alkali stable radiationgrafted
anion-exchange membrane to date, JOURNAL OF MATERIALS CHEMISTRY A 6 (3) pp. 823-827 The Royal Society of Chemistry
anion-exchange membrane (AEM) containing a butylspacer
between the benzene and the methylpyrrolidinium groups
(C4-AEM) had double the ex-situ alkali stability at 80 °C compared
to a methylene benchmark (C1-AEM). H2/O2 fuel cells containing
the C4-AEM still achieved a peak power density of > 1 W cm-2.
Recently, increased efforts have been made with regard to the preparation of IEMs and understanding the relationships between membrane properties and RED cell power performance. The work in this thesis has focused on the development of RED-focused IEMs by radiation induced grafting polymerisation (RIG). The RIG technique has been used to chemically modify commercially available polymer films to produce a large sample of IEMs targeted for application in RED. The IEM properties were experimentally determined and used as part of a literature recognised mathematical model to estimate the gross power densities that can theoretically be obtained by each IEM in a working RED cell.
The results obtained for RIG IEMs contradicts the earlier notion that IEM permselectivity is of less significance than area resistance and indicate that a minimum permselectivity (H 90%) is required for RED IEMs. A trade-off relationship between the two properties is observed, rationalised by Donnan exclusion factors surrounding IEM water content. Chemical crosslinking was implemented into RIG methods to control excessive gravimetric water uptake (WU%). Linear tertiary diamine head-groups were used to produce crosslinked anion-exchange membranes (AEMs), with tetramethylhexanediamine (TMHDA) head-group yielding theoretical gross power densities of 3.42 W m-2 for single IEM RED model calculations and 1.89 W m-2 for AEM/CEM pair calculations (paired with literature SPEEK 65 CEM). Crosslinked CEMs were produced via chemical crosslinking by divinylbenzene (DVB) and bis(vinylphenyl)ethane (BVPE) was implemented into the RIG method, which resulted in cation-exchange membranes (CEMs) yielding theoretical gross power densities of 5.55 and 5.99 W m-2 respectively, for single IEM RED model calculations and 2.81 and 2.71 W m-2 for AEM/CEM pair calculations (paired with commercial Neospeta® AFN AEM).
Anion-exchange membranes made from meta-vinylbenzyl chloride
exhibit an alkali stability enhancement, ACS Applied Energy Materials 1 (5) pp. 1883-1887 American Chemical Society
common in alkali membrane fuel cells and water electrolysers but
they suffer from degradation under alkaline conditions. Radiationgrafted
anion-exchange membranes exhibit an alkali stability enhancement
when made using non-commercial meta-only vinylbenzyl
chloride (VBC) monomer, compared to the use of commercially
available para-only or meta/para-mixed VBC isomers. We hypothesize
a mechanism on why the use of meta-VBC eliminates AEM
degradation via chain scission.
In previous work, to discover an inhibitor, a published X-ray co-crystal structure of AAG was used in a virtual screen of two million compounds for potential binding activity. Of the top 49 virtual hits, one real hit triazole-thione-based inhibitor (UNIS00021) with an IC50 of ~60 µM was identified in a biochemical assay. In this thesis, efforts to design and synthesise analogues of UNIS00021 with improved potency against AAG are described.
Successful divergent syntheses were developed which provided access to: 1. analogues varying at the alkyl group of the amide (six different amides); 2. analogues with a free amine in place of the amide and with variation of the length of the alkyl linkage group (five different amines); and 3. analogues bearing a C5-methyl group instead of thiol/thione at the core (one cyclohexylamide triazole). Work was also begun on the synthesis of analogues varying the N4-CH2-aryl group but was not completed due to time constraints.
Two main types of microplate biochemical assay were investigated for assessment of the candidate inhibitors? potencies against AAG using: 1. a surface-bound fluorescein-conjugated substrate DNA-oligomer; and 2. a free substrate oligomer and LCMS. Despite much experimentation, these assays continued to show inconsistent and irreproducible inhibition curves so it was not possible to make conclusions about the candidate inhibitors? potencies.
As a result, small molecule inhibitors of AAG are required for ongoing studies into the biological mechanism of this cellular damage, as well as to become potential drug leads for some types of retinal degeneration, I/R-related tissue damage, or as protective agents for patients undergoing alkylative chemotherapy and showing an increased AAG activity. They could also serve the opposite effect, acting as an alkylating agent (TMZ) sensitiser in paediatric glioblastoma (GBM).
Two DNA oligomers, containing etheno-cytidine or an abasic pyrrolidine, are reported in the literature to show potent AAG inhibition in vitro. Unfortunately, their size and the charged nature of DNA chains makes them unsuitable for use as potential drug leads in vivo, as they would show low membrane permeability and face degradation by nucleases. However, the motifs present in these oligomers, together with examination of the enzyme active site, led to the conception of two types of small drug-like pyrrolidine-based inhibitor candidates termed 2-(hydroxymethyl)pyrrolidines and 4-(hydroxymethyl)pyrrolidines.
The synthetic routes to these inhibitor candidates have been studied and optimised. That to the 2-(hydroxymethyl)pyrrolidines failed at the final step of attachment of DNA base-mimicking aryl groups. However, five 4-(hydroxymethyl)pyrrolidines nucleoside mimetics were successfully synthesised, bearing imidazole and pyridine groups to represent a DNA base. These were subsequently tested in vitro against AAG in a surface-bound hairpin loop colorimetric DNA oligomer assay. The most promising candidate, (+)-395, showed an IC50 of 157 µM corresponding to a ligand efficiency of 0.37 kcal·mol-1·heavy atom-1. Due to its low molecular weight (197 g·mol-1), this inhibitor constitutes a viable starting point for a future lead optimisation programme.
In order to do that, the QSPR models were tested over a series of internal and external validation tests to explore their internal and external predictivity, prior to experimental validations which were performed later and reported in Chapter 7. The internal and external validations found out that the discrepancy in the general model (GM) which was initially thought to be a drawback to the model?s performance was actually not, as it does not compromise the model?s prediction accuracy, both internally and externally. The validation process also found that one of the structure-specific models, Ph-M (aniline-based benzoxazines) is externally predictive whilst another structure-specific model, the Ace-M (acetylenic-based polybenzoxazines) is not internally and externally predictive due to the too small training set that affects its predictivity performance.
An acetylenic-based polybenzoxazine, poly(BA-apa) and a benzylamine-based polybenzoxazine, poly(BO-ba) have been successfully synthesised in this work. Both materials have been characterised using Fourier Transform ? Infra Red Spectroscopy (FT-IR), Nuclear Magnetic Resonance (NMR) spectroscopy (both 1H and 13C) and Liquid Chromatography-Mass Spectrometry (LC-MS) to confirm their structures. These materials were analysed using Differential Scanning Calorimetry (DSC) to study their polymerisation behaviour and were later cured and taken further to Thermogravimetric Analysis (TGA) in order to investigate their thermal properties and the amount of char yield formed upon heating at 800 oC under an inert (nitrogen) atmosphere ? which then will be used for experimental validation of the QSPR models.
The study of DSC thermograms showed that both polymers exhibit a distinct polymerisation behaviour e.g. BA-apa went through two polymerisation reactions simultaneously (the oxazine ring opening polymerisation and the acetylene addition reaction) whilst BO-ba only polymerised via the ring opening reaction from the oxazine rings. It was also found that BA-apa has a lower polymerisation activation energy, consistent to its lower polymerisation temperature in comparison to the BO-ba.
TGA analysis revealed that poly(BO-ba) formed an average of 44.35 % char yield and poly(BA-apa) on the other hand formed approximately 10 % higher char which is 56.28 %. The analysis also discovered that poly(BA-apa) synthesised in this work formed 15 % less char yield than previously reported in the literature (56.28 % vs. 71 %1) due to the shorter curing schedule. The final QSPR validation which is the experimental validation found that the char yield of poly(BO-ba) was predicted very well within 5-7 % error by both GM model and Ph-M. Ace-M which was reported earlier as not internally and externally predictive, has made a nearly accurate prediction towards the char yield of poly(BA-apa), close to the literature value of 71 %. The GM model has also made a close prediction to the Ace-M model, but these predictions deviated 15-17 % from the experimental poly(BA-apa) char yield measured in this work.
The first project aimed to develop an in situ forming hydrogel from star poly(N-(2hydroxypropyl)methacrylamide) (PHPMA) via covalent cross-linking, catalysed by Sortase A enzyme (SrtA). The use of SrtA as a cross-linking enzyme for hydrogel-based tissue engineering has been only reported previously by Broguiere et al., Arkenberg and Lin. 1,2 Both groups employed mutant enzymes with enhanced kinetics to achieve fast gelation whereas a wild type SrtA was employed in this work. Well defined star PHPMA (Ð The second project focused on developing thermo-responsive hydrogels of the selfassembling peptide CFEFEFKFKK by doping the hydrogels with star (2-, 3-, and 4- arm) poly(N-isopropylacrylamide) (PNIPAM)/CFEFEFKFKK conjugates (C, cysteine; F, phenylalanine; E, glutamic acid; K, lysine). The work was based on a study by Maslovskis et al. who created the novel composite hydrogels containing FEFEFKFK peptide and linear PNIPAM-FEFEFKFK conjugates.3 Well-defined star PNIPAM (Ð
Reversible addition-fragmentation chain transfer (RAFT) polymerisation was employed in the synthesis of linear, block and branched forms of poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA). Linear PHPMA was synthesised according to established synthetic methods and found to yield well defined materials (12 ? 17 kg mol-1; Ð 1.02 ? 1.08). Homotelechelic PCL with terminal RAFT functionalities was employed as a macro-CTA in the synthesis of PHPMA-b-PCL-b-PHPMA triblock copolymers. After optimisation of the reaction conditions a reasonably well-defined amphiphilic polymer was obtained (Mn 29 kg mol-1; Ð 1.41) which was observed to undergo spontaneous self-assembly in water (average particle diameter 44 nm). Alternative synthetic routes utilising click methodologies (thiol-ene, hetero-Diels-Alder and copper azide-alkyne cycloaddition) were investigated but ultimately did not yield any improvements when compared to the macro-CTA grafting-from approach. Hyperbranched PHPMA was synthesised by a free-radical crosslinking copolymerisation method which utilised ethylene glycol dimethacrylate (EGDMA) as a divinyl crosslinking agent. Extensive characterisation of branching parameters was performed using a combination of triple detection size-exclusion chromatography (SEC) and 1H NMR. After optimising the reaction conditions, three hyperbranched copolymers of HPMA and acetylated-HPMA (APMA) were synthesised; surface RAFT moieties underwent additional polymerisation with HPMA to ultimately yield novel PHPMA-star-(hb-PHPMA-co¬-PAPMA) core-crosslinked amphiphilic star copolymers (Mn 139 ? 243 kg mol-1, Ð 1.07 ? 1.27).
Additionally, charge controlled nanoprecipitation of homotelechelic carboxyl terminated PCLs in a range of alkaline pH buffered solutions was performed according to a literature procedure. The lowest diameter particles were observed to form when precipitation was performed in a pH 9 aqueous phase (14 ± 1 nm), as determined by dynamic light scattering (DLS).
Overall, synthesis of PHPMA-b-PCL-b-PHPMA block copolymer at higher molecular weight and lower dispersity than previously reported materials from a homotelechelic dithiobenzoate macro-CTA was achieved. Furthermore, three novel PHPMA-star-(hb-(PHPMA-co-PAPMA)) copolymers were synthesised and the branching parameters of the hydrophobic core characterised by 1H NMR spectroscopy. Preliminary work into developing a scalable synthetic procedure for producing PCL nanoparticles was undertaken. Under optimal conditions PCL-oTHPA nanoparticles were produced with a number-average particle diameter of 14 ± 1 nm (error is ± 1 S.D.).