A New Route to the Formation of Nanoporous Capsules Using Block Copolymer Thin Films & Colloids

Project Title: A New Route to the Formation of Nanoporous Capsules using Block Copolymer Thin Films & Colloids Pavlina Mantzana

Affiliation: University of Leeds Department: Institute of Particle Science and Engineering (IPSE) School of Process, Environmental and Materials Engineering (SPEME) Address: Houldsworth building, LS2 9JT, United Kingdom Tel: +44 (0)113 3432392, Fax: +44 (0)113 3432377, E-mail: [email protected] or [email protected] Supervisor(s): Prof. Simon Biggs (University of Leeds) and Prof. Ian Hamley (University of Reading) Project sponsor(s): Nanomanufacturing Institute (NMi), Leeds

Objective Nanosciences and nanotechnologies represent a revolutionary approach in the way of thinking and producing, as they follow the traditional approach and production processes, from “big” to “small”. Nanotechnology is truly multidisciplinary and it opens the way towards new production routes, new structures and towards more efficient, better performing and intelligent materials. The properties of nanomaterials fundamentally differ from those of the macroscale ones, brought about by the size reduction and by new properties only apparent at the nanoscale. Nanotechnology, alongside the growth in research on soft materials brought about the new era of “soft nanotechnology”. Exploitation of the self- organisation of soft materials can be used to create a myriad of nanostructures for a number of diverse applications. The objective of this project is the preparation of such nanostructures and more precisely the preparation of novel nanocapsules.

Project progress To achieve the above objective, spherical colloidal particles, such as weakly cross-linked melamine formaldehyde (MF) nanoparticles, are sequentially coated with block copolymer micelles, via the so- called layer-by-layer approach (LbL). Different coating sequences allow the design of coatings with different properties. Diblock copolymers of PDMA96-PDEA26 and PDEA50-PMAA50, with varied properties (Figures 1, 2 & 3), are used to create these complex multilayers on MF particles. The corona of the outermost micelle layer can be cross-linked with the bifunctional agent 1,2-bis(2- iodoethoxy)ethane (BIEE) and the core MF dissolved. In a variation to this approach, alternative coatings can also be produced by replacing one or more layers with polymer coated Au nanoparticles (Figure 4), which can provide us with a range of different properties of what is a hollow particle. The irreversibility observed between the uncoated and the coated with PDMA Au at different pH is notable (Figures 5 & 6). The production of these novel hollow capsules can then be investigated, the morphology of which is studied experimentally via the use of a range of analytical techniques and instrumentation such as Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), ζ-potential and UV-VIS. Figures 7 and 8 show some ζ–

NMi website-updated details potential results and SEM images of the coated MF particles and of the formed capsules respectively (see legend). This novel type of hollow capsules can have a variety of potential applications; in the field of drug delivery, as well as in separation media (chromatography columns with well defined, adsorbent beads), coatings, catalysis, even in photonics and a range of other technologies that rely on such particles.

CH CH CH CH 3 3 3 3 C CH C C C CH2 2 CH2 CH2 96 26 COO COO COO 50 COO 50

C2H4 C2H4 C2H4 C2H4

N N N N

C H C H C H C H CH3 CH3 2 5 2 5 CH3 CH3 2 5 2 5 (A) (B) Figure 1: Molecular structures of the diblock copolymers (A) PDMA-PDEA and (B) PDEA-PMAA

u i 10 d

y 4 Spherical surface micelles Hexagonally

o Random orientation packed orientation

d micelles

m y Silica Mica

0 n H 3( 4 5 6 7 8 9 10 11 12 pH Figure 2: Reversible micellisation of PDMA-PDEA Figure 3: AFM images of PDMA93-PDEA25 at diblocks in aqueous solution pH9 500nm

Figure 4: TEM Au nanoparticles coated with polymer

pH 4 pH 6 pH 9 Au max absorbance vs time 0.5 540 0.45

e 538 (

) 0.4 536 m pH 6 0.35 n

e pH 5.5 0.3 c 532 n a 530 pH 4 0.25 b r 0.2 o 528 s pH 9 b 526 0.15 A 524 0.1 522 0.05 0 20 40 60 80 100 120 0 Time (min) 300 400 500 600 700 800 Figure 5: Au stability FigureNMi 6: Coated website-updated Au stability details absorbance vs time plots at different pH At 1hr as a function of pH (pH4, pH6, pH9) 50 40 30

l 20 a i t

n 10 e t o

p 0 - a t

e -10 0 1 2 3 4 5 6 z -20 Layer Number -30 -40

Figure 7: ζ-potential versus layer number Zeta potential measurements, after deposition and absorption of each of the micellar layers, confirming charge reversal of the particle surface

(A) (B)

(C) (D)

(E) (F) Figure 8: SEM images of (A) 5 layer coated MF particles, (B) 5 layer coated MF particles and cross-linked with BIEE, (C) 5 layer coated MF particles and dissolved in 0.1M HCl, (D) 5 layer coated MF particles, cross-linked and dissolved in 0.1M HCl, (E) & (F) 1 layer coated MF particles, cross-linked and dissolved, where it is clearly visible that some of the particles have “burst”

NMi website-updated details