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An ultra-thin, graphene oxide (GO) based, anticancer drug carrier was developed using Reversible Addition Fragmentation chain Transfer (RAFT) mediated emulsion polymerisation. Short chain macro-RAFT copolymer, BuPATTC-(BA4-stat-AA9-stat-StS5), was used to disperse the GO in water. Subsequent free radical emulsion polymerisation produced an aqueous suspension of partially polymer-coated GO (PPC-GO). The polymer coating was unevenly distributed, forming a patchy and extremely rough surface on the GO substrate. The use of macro-RAFT copolymers greatly improved the overall colloidal stability of the GO. Furthermore, particle morphologies were found to be controllable by adjusting the amount of monomer starve fed into the polymerisation. PPC-GO was demonstrated to be an effective carrier for the anti-cancer drug doxorubicin (Dox), storing equivalent to its own original weight in Dox. A releasing mechanism using L-ascorbic acid (L-AA) as an agent was reported. Dox release can be triggered by chemical reduction using L-AA, which weakens the hydrogen bonds between Dox and GO. After release of the Dox, the remaining PPC- reduced GO (PPC-rGO) was found to be stable in aqueous suspension.

We demonstrate a scalable continuous feed method for the synthesis of polymer Janus nanoparticles with different composition and with different aspect ratios between lobes, including with one hard cross-linked polystyrene lobe and one soft film-forming poly(methyl methacrylate-co-butyl acrylate) (P(MMA-co-BA)) lobe, through reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization. Snowman shaped particles of size around 40 nm are synthesized through a continuous monomer feeding method, which enables kilogram-scale synthesis of diverse polymer Janus nanoparticles, with a solids content greater than 30%. The Janus nanoparticles with the soft P(MMA-co-BA) lobes spontaneously self-assemble around solid particles in an aqueous phase, forming a thin (5 -100 nm) polymer film that completely encapsulates the solid particles. The process is achieved at room temperature and under mild conditions. The film-forming Janus nanoparticles show excellent encapsulation ability for a variety of solid particles, such as organic and inorganic pigments, carbon nanotubes and calcite, without requiring polymerization to be conducted in the presence of the solid particles. When the Janus nanoparticles were used to encapsulate calcite particles in low sheen paints, the encapsulation provided superior stain resistance to the formed paint film.

Diffusion of active cytotoxic agents throughout an entire solid tumour is a particular challenge to successful drug delivery. Here we show the simple and robust generation of non-toxic, 10-15 nm superparamagnetic iron oxide nanoparticles (SPIONs) that have been sterically stabilized by either 100% anionic or 100% cationic or 100% neutral end-functionalized steric stabilizers or by novel combinations of cationic and neutral end-functionalized polymer. When these nanoparticles were co-administered with various anti-cancer drugs, a significant increase in the diffusion and effectiveness of the cytotoxin in a 3-dimensional model of a solid tumour was shown for specific combinations of surface functionality and cytotoxin. The critical determinant of enhanced cytotoxin diffusion and effectiveness was the end functionality of the steric stabilizers and not the core composition (either iron oxide, silica or gold). We provide evidence that SPIONs stabilized with heterogeneous steric stabilizers enhance nuclear uptake of doxorubicin across multiple cell layers.

We report the thermoresponsive behavior in aqueous solution of amphiphilic diblock co-oligomers of ethylene glycol (EG) and styrene (S) obtained by reversible addition fragmentation chain transfer (RAFT) polymerization (mPEG16-b-PS2, mPEG16-b-PS4 and mPEG16-b-PS6). The block co-oligomers were obtained from the polymerization of styrene mediated by a PEG macro-RAFT agent, mPEG-PBTC. The precise control offered by RAFT polymerization over the length of the short hydrophobic chain permits tuning of the thermoresponsive behavior for all the studied methoxy poly(ethylene glycol)-block-polystyrene copolymers. mPEG16-b-PS2 was shown to self-assemble into micelles at temperatures below the lower critical solution temperature (LCST) of the block co-oligomer, whilst no such critical temperature was observed for solutions of self-assembled mPEG16-b-PS4 and mPEG16-b-PS6. mPEG16-b-PS4 self-assembles into relatively mobile spherical particles which evolve into prolate spheroids with increasing temperature, whilst mPEG16-b-PS6 forms particle clusters, which have lower mobility than the mPEG16-b-PS4 particles. This work is the first study on the aggregation behavior of such short chain lengths of mPEG-b-PS as a function of temperature, and shows how tuning the PS oligomer length permits control of the thermoresponsive behavior of mPEG-b-PS assemblies in water.

Matrix methods are used to obtain general solutions for the Smith-Ewart case II mechanism for emulsion polymerizations; this relates to systems for which bimolecular termination is considered to be more important than free radical exit from the particles. These solutions are compared with simplified forms of the general solutions derived from case I, wherein exit is assumed to be more significant than termination. In neither case is resort made to the steady state approximation. There appears to be general agreement between theory and the results for the seeded emulsion polymerization of vinyl acetate, although discrepancies were apparent when very stringent comparisons were made.

A procedure is presented for the quantitative analysis of kinetic data obtained for Interval III of emulsion polymerizations. The commencement of polymerization directly in Interval III allows the rate coefficients for the entry of free radicals into, and the exit (desorption) of free radicals from, the latex particles to be determined from the early stages of the polymerization, when text-decoration:overlinen⩽½(when termination is essentially instantaneous). The results obtained for styrene are in agreement with those derived from direct entry into Interval II and from relaxation studies; those from Interval III are less prone to uncertaintly arising from particle size changes. For text-decoration:overlinen > ½, the dependence of the termination rate coefficient on the ratio of monomer to polymer in the latex particles is also obtained. The methods used to determine all rate coefficients obviate any assumptions as to the efficiency of capture of aqueous free radicals or the values of the rate coefficient for propagation or of monomer concentration within the particles.

Using matrix methods, complete time-dependent solutions are derived for the Smith–Ewart equations describing polymerization in emulsion systems with a constant number of polymerizing loci, where the mechanisms of free radical entry, exit and termination all operate simultaneously. The results, which are valid for any system where the average number of free radicals per particle is < ∼ 0.6, reduce to previous, more restricted, solutions under the appropriate limits.

The kinetics of the seeded emulsion polymerization of styrene, with the swollen radii of the seed ranging from 44 to 79 nm, have been measured dilatometrically. The conversion against time curves displayed an increase in the instantaneous rate of polymerization, followed by an apparent steady state domain. These measurements permitted for the first time the direct evaluation of the kinetic parameters that govern both the entry of free radicals into the latex particles and the first-order loss of free radicals from the particles. The latter rate coefficient was found to vary with the inverse square of the swollen particle radius, as expected for the diffusion controlled exit of free radicals from the particles. The magnitudes of the observed entry rate coefficients, when coupled with their dependence upon the initiator concentration, suggest that free radical capture by the seed particles was relatively inefficient. The capture efficiency increased significantly, however, with decreasing initiator concentration if the number of seed latex particles was held constant. The results obtained show clearly that the average number of free radicals per particle can be < 1/2 for styrene emulsion polymerizations under suitable conditions (e.g., low initiator concentrations and/or small particle sizes). Thus styrene can follow Smith—Ewart case 1 kinetics.The validity of the interpretation of the data is strongly supported by the excellent agreement with literature values obtained for various kinetic parameters.A background initiation process that causes the emulsion polymerization of styrene to proceed in the absence of added initiator was detected. This appears to be the emulsion polymerization analogue of the thermally induced bulk polymerization of styrene.