Polymerization-induced thermal self-assembly (PITSA)

Polymerization-induced self-assembly (PISA) is a versatile technique to achieve a wide range of polymeric nanoparticle morphologies. Most previous examples of self-assembled soft nanoparticle synthesis by PISA rely on a growing solvophobic polymer block that leads to changes in nanoparticle architecture during polymerization in a selective solvent. However, synthesis of block copolymers with a growing stimuli-responsive block to form various nanoparticle shapes has yet to be reported. This new concept using thermoresponsive polymers is termed polymerization-induced thermal self-assembly (PITSA). A reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide from a hydrophilic chain transfer agent composed of N,N-dimethylacrylamide and acrylic acid was carried out in water above the known lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAm). After reaching a certain chain length, the growing PNIPAm self-assembled, as induced by the LCST, into block copolymer aggregates within which dispersion polymerization continued. To characterize the nanoparticles at ambient temperatures without their dissolution, the particles were crosslinked immediately following polymerization at elevated temperatures via the reaction of the acid groups with a diamine in the presence of a carbodiimide. Size exclusion chromatography was used to evaluate the unimer molecular weight distributions and reaction kinetics. Dynamic light scattering and transmission electron microscopy provided insight into the size and morphologies of the nanoparticles. The resulting block copolymers formed polymeric nanoparticles with a range of morphologies (e.g., micelles, worms, and vesicles), which were a function of the PNIPAm block length.

The effect of ligand, solvent and Cu(0) source on the efficient polymerization of polyether acrylates and methacrylates in aqueous and organic media

The synthesis of well-defined telechelic polyacrylates and polymethacrylates in organic and aqueous media via Cu(0)-mediated reversible-deactivation radical polymerization is thoroughly investigated.

Cu(0)-mediated living radical polymerisation in dimethyl lactamide (DML); an unusual green solvent with limited environmental impact

The synthesis of poly-acrylates, methacrylates and styrene derivatives by SET-LRP is reported in a user and environmentally friendly “green” solvent, dimethyl lactamide (DML).

Hydrosilylation as an efficient tool for polymer synthesis and modification with methacrylates

Hydrosilylation is a well-established reaction for the preparation of organo-silicon compounds, in which vinyl groups react with silanes (Si–H) usually catalysed by late transition metal complexes, most often Pt(ii) complexes.

Photo-induced living radical polymerization of acrylates utilizing a discrete copper(ii)–formate complex

A photo-polymerization protocol, utilizing a pre-formed and well-characterized Cu(ii) formate complex, [Cu(Me₆-Tren)(O₂CH)](ClO₄), mediated by UV light is described.

Aqueous SET-LRP catalyzed with “in situ” generated Cu(0) demonstrates surface mediated activation and bimolecular termination

Ultrafast, inversely temperature dependent aqueous SET-LRP with “in situ” generated Cu(0) yields quantitative chain-ends demonstrating surface mediated activation and termination.

Synthesis of well-defined α,ω-telechelic multiblock copolymers in aqueous medium: in situ generation of α,ω-diols

The synthesis of well-defined α,ω-dihydroxyl telechelic multiblock copolymers by sequential in situ chain extensions via aqueous Cu(0) mediated living radical polymerization (SET-LRP) is reported.

Templated polymerizations on solid supports mediated by complementary nucleoside interactions

The preparation of immobilized poly(methacryloyl nucleosides) and their abilities for template polymerizations is discussed.

Conjugation of polymers to proteins through an inhibitor-derived peptide: taking up the inhibitor “berth”

A hexapeptide derived from an enzyme inhibitor was used to conjugate a hydrophilic polymer to the inhibitor “berth” in the enzyme, affording the enzyme resistance to the inhibitor.

Surface immobilization of a protease through an inhibitor-derived affinity ligand: a bioactive surface with defensive properties against an inhibitor

Surface immobilization of a protease through its inhibitor-derived peptide was shown to be advantageous in retaining the enzymatic activity of the protease and protecting the protease from being inhibited by its inhibitor.

Sequence-controlled multi-block copolymerization of acrylamides via aqueous SET-LRP at 0 °C

Aqueous single electron transfer living radical polymerization (SET-LRP) has been employed to synthesize multi-block homopolymers and copolymers of a range of acrylamide monomers including N-isopropylacrylamide (NIPAM), 2-hydroxyethyl acrylamide (HEAA), N,N-dimethyl acrylamide (DMA) and N,N-diethylacrylamide (DEA).

Copper(ii) gluconate (a non-toxic food supplement/dietary aid) as a precursor catalyst for effective photo-induced living radical polymerisation of acrylates

Copper gluconate, is employed as a precursor catalyst for the photo-induced living radical polymerisation of acrylates.

Positionable vertical microfluidic cell based on electromigration in a theta pipet

A microscale vertical fluidic cell system has been implemented, based on a simple theta pipet pulled to a sharp point (ca. 10-20 μm diameter for the studies herein) and positioned with a high degree of control on a surface. The dual channel arrangement allows an electric field to be generated between an electrode in each compartment of the pipet that can be used to control the electromigration of charged species between the two compartments, across a thin liquid meniscus in contact with the substrate of interest. By visualizing the interfacial region using laser scanning confocal microscopy, the adsorption of fluorescently-labeled materials on surfaces is monitored quantitatively in real time, exemplified through studies of the adsorption of anionic microparticles (1.1 μm diameter) on positively and negatively charged substrate surfaces of poly-L-lysine (PLL) and poly-L-glutamic acid (PGA), respectively, on glass. These studies highlight significant electrostatic effects on adsorption rates and also that the adsorption of these particles is dominated by the three phase meniscus/solid/air boundary. The technique is easily modified to the case of a submerged substrate, resulting in a much larger deposition area. Finite element method modeling is used to calculate local electric field strengths that are used to understand surface deposition patterns. To demonstrate the applicability of the technique to live biological substrates, the delivery of fluorescent particles directly to the surface of a single root hair cell of Zea mays is demonstrated. The mobile pipet allows deposition to be directed to specific regions of the cell, allowing discrete sites to be labeled with particles. Finally, the technique is used to study the uptake of fluorescent polymer molecules to single root hair cells, with quantitative analysis of the adsorption rates of vinyl-sulfonic acid copolymers, with varying rhodamine B content.

Synthesis and Aggregation of Double Hydrophilic Diblock Glycopolymers via Aqueous SET-LRP

A chemically unprotected mannose-containing acrylate (ManA) monomer was synthesized and polymerized by Cu(0)-mediated radical polymerization in water (SET-LRP). One-pot block copolymerization was achieved upon addition of a solution of N-isopropylacrylamide (NIPAm) or diethylene glycol ethyl ether acrylate (DEGEEA) forming thermoresponsive double hydrophilic diblock glycopolymers which revealed self-assembly properties in aqueous solution forming well-defined, sugar-decorated nanoparticles.

Absolut “copper catalyzation perfected”; robust living polymerization of NIPAM: Guinness is good for SET-LRP

The controlled polymerization of N-isopropyl acrylamide (NIPAM) is reported in a range of international beers, wine, ciders and spirits utilizing Cu(0)-mediated living radical polymerization (SET-LRP).