Surface modification with polymers using living radical polymerisation and click chemistry
Chen, Gaojian (2007) Surface modification with polymers using living radical polymerisation and click chemistry. PhD thesis, University of Warwick.
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Thin organic and polymer layers on solid substrates play a key role in many processes
aimed at modifying surface properties. Both "grafting to" and "grafting from"
methods have been used in this project to modify a variety of surfaces including
cellulose, resins and carbon nanotubes (CNT) with functional polymers. Living
radical polymerisation and Huisgen [2+3] cycloaddition (often termed "click"
reaction) were used to carry out these modifications.
Living radical polymerisation was first used to synthesize different α-functional
polymers and used for surface modification. For example, Living radical
polymerisations of methyl methacrylate and a fluorescent comonomer with 2-bromo-
2-methyl-propionic acid 3-azido-propyl ester and 2-bromo-2-methyl-hept-6-yn-3-one
as initiators have been successfully employed for the synthesis of fluorescently tagged
azide and alkyne terminated PMMA with molecular weight (Mn) close to that
predicted and polydispersity index (PDi) less than 1.20 and good first order kinetics
that would be expected for living radical polymerisation. Cotton and organic resin
surfaces have been functionalised with alkyne groups using simple condensation with
4-chlorocarbonyl-butyric acid prop-2-ynyl ester. The surfaces have been further
modifies using a Huisgen [2+3] cycloaddition (click) reaction of both polymeric and
small molecule azides. Different functional azides, namely mono azido-PEG and a
new fluorescent hostasol derivative have also been prepared and tested as model
substrates for cotton surface modification. This approach is shown to be very general
allowing soft and hard surfaces with different geometries to be modified. In particular
it is an excellent method to alter the nature of organic resins allowing the
incorporation of many different functionalities.
The covalent immobilization of a range of carbohydrate derivatives onto resin beads
was then carried out. Copper-catalysed Huisgen [2+3] cycloaddition was used to graft
mannose-containing azides to complementarily functionalised alkyne surfaces,
namely: a) Wang resin or b) "Rasta" particles consisting of a "clickable" alkyne
polymer loose outer shell and a Wang resin inner core. For the second approach,
Wang resin beads were first converted into immobilized ATRP initiators, and then
polymerisation of trimethylsilanyl-protected propargyl methacrylate followed by
deprotection with TBAF·3H2O afforded the desired polyalkyne clickable scaffold. An
appropriated α-mannopyranoside azide was then clicked onto it, to give a mannose
functionalized "Rasta" resin. The binding abilities of these D-mannose-modified
particles were then tested using fluorescein labelled Concanavalin A (Con A), a lectin
known for its ability of binding certain mannose-containing molecules. Our
preliminary results indicated that the novel glycohybrid materials presented in this
work are able to efficiently recognize mannose-binding model lectins such as Con A,
opening the way for their potential application in affinity chromatography, sensors
and other protein recognition/separation fields.
Other functional polymers with antibiotic or chiral properties were also grafted from
surfaces. Living radical polymerisation of poly(ethylene glycol) methyl ether
methacrylate (PEGMA) and a metronidazole monomer (MTD-MA) has been
successfully employed for the synthesis of antibiotic metronidazole containing
polymers with Mn close to that predicted, narrow polydispersity and good first order
kinetics that would be expected for living radical polymerisation. Using the
monomers PEGMA and MTD-MA, with preformed immobilized initiator on cotton,
surface initiated LRP was carried out to give cotton bearing antibiotic polymers.
Surface initiated living radical polymerisation of GMA was then successfully carried
out for the synthesis of PGMA containing bead base on Aquagel resin. The hydroxyl
groups of the PGMA moiety were then reacted with a single enantiomer (R)-(+)-1-
phenylethyl isocyanate (EtPhNCO). This demonstrates a convenient way of
immobilise enantiomer moiety onto resin surface and the resulting solid support may
be used as chiral stationary phases (CSP) for HPLC chromatography.
To modify CNTs with functional polymers not only increase the dispersability of the
CNTs, it has also enlarged the application areas of CNT’s due to the polymers' own
functional properties. MWCNTs were first converted to a solid support LRP initiator
by an esterification reaction and styrene was grafted from MWCNTs through surfaceinitiated
LRP, the PSt modified CNTs were then used to form isoporous membranes.
Similarly, Poly(amidoamine) (PAMAM) dendrons were covalently attached to
MWCNTs and dendron-MWCNT-Ag(0) hybrid materials were made afterwards
which occurred via Ag(I) coordination to the PAMAM dendron nitrogen donors,
followed by reduction with formaldehyde. Finally, noncovalent method was used to
make a thermo-sensitive water soluble CNTs. The homopolymerisations and
copolymerisation of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and
di(ethylene glycol) methyl ether methacrylate (DEGMA) using a pyrene-containing
initiator and a Cu(0)/Me6-Tren catalyst system was investigated. The pyrenefunctionalised
polymers synthesised were then used to modify CNTs and thus thermosensitive
water-dispersible CNTs were made.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||Q Science > QD Chemistry|
|Library of Congress Subject Headings (LCSH):||Surface chemistry, Addition polymerization, Ring formation (Chemistry)|
|Official Date:||September 2007|
|Institution:||University of Warwick|
|Theses Department:||Department of Chemistry|
|Sponsors:||Overseas Research Students Awards Scheme (ORSAS) ; University of Warwick|
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