The design of functional 3D macroporous monoliths has become a necessity for a wide range of applications. The traditional post-modification strategies of porous materials are efficient but often consist of tedious multi-step processes. This work describes a straightforward macromolecular surfactant-assisted method for producing chemically functionalized macroporous polyHIPEs with interconnected structures. Accordingly, high internal phase emulsion-templated polymerizations were implemented in the presence of SG1-terminated amphiphilic copolymers prepared by nitroxide-mediated radical polymerization (NMP). The latter served as both stabilizers and functionalizing agents upon thermal activation of its terminal alkoxyamine and covalent anchoring of the released radical copolymer onto the walls of the scaffold. The effect of the polymerization temperature on the functionalization and openness of the final porous materials was explored. As a result, a range of open-cell styrene and acrylate-based polyHIPEs chemically grafted with PEO were obtained. Moreover, polyHIPEs were also decorated with alkyne-bearing PEO and subsequently modified via CuAAc click chemistry in order to demonstrate the potential of this macromolecular surfactant-assisted functionalization method.

A high internal phase emulsion composed of ionic liquids and CO2 serves as a template for producing unprecedented macroporous poly(ionic liquid) gels.

The synthesis of a series of poly(ethylene oxide)-b-polystyrene copolymers with different block lengths was performed by radical addition fragmentation chain transfer. These amphiphilic copolymers were tested as stabilizers for water-in-oil medium internal phase emulsion (MIPE) templating polymerization and the formation of polyMIPEs with controlled morphology. Aside from the structure of the emulsion stabilizer, several parameters susceptible to influence the size of the cavities and the interconnectivity of the porous monoliths were probed including the choice of the comonomers, treatment of the emulsion by ultrasound, the use of controlled radical polymerization method for the network formation as well as interfacial initiation. Interconnected cellular monoliths were produced. The polymerization of the ultrasonicated water-in-ethylhexylacrylate/divinylbenzene MIPE notably led to near-mesoporous open-cell material. Mechanical properties and specific surface areas of the polyMIPEs were also investigated and discussed.

This work investigates key parameters of a straightforward macromolecular surfactant-assisted functionalization strategy of porous polymers produced by high internal phase emulsion (HIPE) polymerization. For that purpose, a series of well-defined amphiphilic poly(ethylene oxide)-b-poly(styrene) (PEO-b-PS) copolymers with various compositions and molar masses were synthesized by radical addition fragmentation chain transfer (RAFT) polymerization and used as macromolecular surfactants for the emulsion-templated polymerization of styrene/divinylbenzene (S/DVB). The morphology of the resulting foams, referred to as polyHIPEs, was found dependent on the PS block length and concentration of the block copolymer surfactant in the emulsion. Moreover, we determined the lowest PS block length required for preserving the anchoring of the copolymer at the surface by physical entanglement within the S/DVB cross-linked matrix leading to a PEO-coated porous material. The functionalization of the porous monoliths with PEO was evidenced by sessile drop shape analyses and water uptake experiments. The chemical anchoring of the PEO-b-PS at the surface of polyHIPEs was also explored by interfacial initiation of the RIPE polymerization from a PEO-b-PS-RAFT macroinitiator leading to porous structures with permanent PEO coatings. In this case, copolymerizing DVB with acrylate instead of styrene improved the interconnectivity of the porous monoliths.

Controlled radical polymerization produces poly(N-vinylamide)s with thermally induced multistep assembly.

Recent years have witnessed an increasing development of “smart” or “stimuliresponsive” polymers. 1-3 The behavior and properties of such materials can drastically change when small modifications occur in their environment. Numerous stimuli have been investigated including temperature, light, pH, redox, etc. For example, the water solubility of polymers like poly(acid acrylic) (PAA) or poly(vinyl pyridine) (PVP) can be modulated by pH adjustment. 4 Other polymers exhibit a phase transition at a certain temperature leading to a sharp modification of their solubility. Poly(N-isopropylacrylamide) (PNIPAM) 5 and poly(oligo(ethylene glycol)methacrylate) (POEGMA) 6, 7 are typical examples of such thermoresponsive polymers. Interestingly, the stimuli responsive polymer sequences can be integrated in more complex macromolecular architectures like block copolymers. In this case, a change in the temperature or pH can trigger the reversible self-assembly of the copolymer into micelles or vesicles. At high copolymer concentration in water, reversible gelation phenomena can also occur. These materials can be considered as real “adaptive systems” and are exploited in more and more applications, notably for the development of drug delivery systems (DDS). In this work, we focused on the synthesis of novel thermo-responsive copolymers based on poly(N-vinylcaprolactam) (PNVCL). 8-11 The latter is considered as a biocompatible and exhibits a lower critical solution temperature (LCST) in water that is close to the physiological temperature, which is of particular interest for the development in the biomedical field. Although N-vinylamides, like NVCL, can easily be polymerized radically, their growing radicals are quite reactive which makes the control of their polymerization and the insertion of well-defined poly(N-vinylamide)s segments into complex architectures difficult. For this reason, we developed a controlled radical polymerization (CRP) technique, called Organometallic-Mediated Radical Polymerization (OMRP), 12,13 which is very efficient for non-conjugated monomers (see section A). 8, 14-16 This tool notably permitted us to prepare singleand doublethermo-responsive diblock and triblock copolymers that follow a multistep assembly behavior in water upon temperature changes (see section B). 9-11 Based on this technology, we also designed thermoand redoxresponsive nanogels which are promising drug delivery carriers (see section C). 11

The thermally-induced gelation and gel properties of concentrated aqueous solutions of double thermoresponsive poly(N-vinylamide)-based di- and triblock copolymers are studied by rheology. The copolymers under investigation, prepared by cobalt-mediated radical polymerization and coupling reactions, are composed of poly(vinylcaprolactam) (PNVCL) blocks and of a statistical poly(vinylcaprolactam-stat-vinylpyrrolidone) segment with a cloud point temperature (TCP) higher than that of PNVCL. Heating the di- and triblock solutions beyond the first phase transition temperature favors gel formation while heating above the second TCP leads to opaque gels without macroscopic demixing. Moduli of the triblock hydrogels are systematically higher than those of the corresponding diblocks, even above the second transition. Rheological data suggest distinct micellar structures for each copolymer architecture: densely packed micelles of diblocks and 3-D networks of bridged micelles for triblocks. Strain sweep experiments also emphasize the positive effect of the micelle bridging on the elasticity and stability of the hydrogels. The formation and properties of the obtained gels are also shown to depend on the copolymer concentration, block length, and composition. Addition of salt also allows us to tune the phase transition temperatures of these double thermoresponsive hydrogels.