ABSTRACT:A new class of functional macroporous monoliths from polymerized high internal phase emulsion (polyHIPE) with tunable surface functional groups was developed by direct polypeptide surface grafting. In the first step, amino-functional polyHIPEs were obtained by the addition of 4-vinylbenzyl or 4-vinylbenzylphtalimide to the styrenic emulsion and thermal radical polymerization. The obtained monoliths present the expected open-cell morphology and a high surface area. The incorporated amino group was successfully utilized to initiate the ring opening polymerization of benzyl-L-glutamate N-carboxyanhydride (BLG NCA) and benzyloxycarbonyl-L-lysine (Lys(Z)) NCA, which resulted in a dense homogeneous coating of polypeptides throughout the internal polyHIPE surfaces as confirmed by SEM and FTIR analysis. The amount of polypeptide grafted to the polyHIPE surfaces could be modulated by varying the initial ratio of amino acid NCA to amino-functional polyHIPE. Subsequent removal of the polypeptide protecting groups yielded highly functional polyHIPE-g-poly(glutamic acid) and polyHIPE-g-poly(lysine). Both type of polypeptide-grafted monoliths responded to pH by changes in their hydrohilicity. The possibility to use the high density of function (-COOH or -NH2) for secondary reaction was demonstrated by the successful bioconjugation of enhanced green fluorescent protein (eGFP) and fluorescein isocyanate (FITC) on the polymer 3D-scaffold surface. The amount of eGFP and FITC conjugated to the polypeptide grafted polyHIPE was significantly higher than to the amino-functional polyHIPE signifying the advantage of polypeptide grafting to achieve highly functional polyHIPEs. INTRODUCTIONMacroporous polymeric monoliths combining high surface area with excellent flow and mass transport properties are ideally suited for a variety of applications including column filtration/separation, supported organic chemistry and as media for tissue engineering and 3D cell culture.i-viii A material that has received increased attention as a microcellular polymer monolith is prepared from concentred high internal phase emulsions (HIPE) containing more than 74% internal phase volume. If the continuous phase contains one or more monomeric species and polymerization is initiated, highly porous materials referred to as polyHIPEs are produced once the dispersed phase droplets are removed. Initially developed by Unilever ix , polyHIPE preparation traditionally involves the formation of a stable concentred water-in-oil emulsion using hydrophobic monomers as part of the continuous phase and an aqueous phase as the dispersed phase.x,xi The preparation of the so-called "reverse" polyHIPE by polymerization of an oilin-water HIPE was also developed during the last decade.

Amino-functional macroporous monoliths from polymerized high internal phase emulsion (polyHIPE) were surface modified with initiators for atom transfer radical polymerization (ATRP). The ATRP initiator groups on the polyHIPE surface were successfully used to initiate activator regeneration by electron transfer (ARGET) ATRP of (meth)acrylic monomers, such as methyl methacrylate (MMA) or tert-butyl acrylate (tBA) resulting in a dense coating of polymers on the polyHIPE surface. Addition of sacrificial initiator permitted control of the amount of polymer grafted onto the monolith surface. Subsequent removal of the tertbutyl protecting groups yielded highly functional polyHIPE-g-poly(acrylic acid). The versatility to use the high density of carboxylic acid groups for secondary reactions was demonstrated by the successful conjugation of enhanced green fluorescent protein (eGFP) and coral derived red fluorescent protein (DsRed) using EDC/sulfo-NHS chemistry, on the polymer 3D-scaffold surface. The materials and methodologies presented here are simple and robust, thus, opening new possibilities for the bioconjugation of highly porous polyHIPE for bioseparation applications.

Steady-state and time-resolved fluorescence spectroscopy of the homopolymers and di-and triblock copolymers of 2-naphthylethylisocyanide (7), 9-anthrylethylisocyanide (lo), and 2-phenanthrylethylisocyanide (11) exhibit emission from the isolated chromophores, i.e., naphthyl, anthryl, or phenanthryl, upon excitation at 284 or 354 nm. The absence of excimer emission in the fluorescence spectra of all these homopolymers is indicative of a rigid polymeric backbone. Fluorescence quenching in diblock copolymers containing a dimethylaniline donor block and a naphthalene or anthracene acceptor block takes place through directional energy migration to the acceptor-quencher interface. The migrating excited state is then quenched at the interface either by photoinduced electron transfer in the anthracene4imethylaniline diblock copolymer or by exciplex formation in the naphthalene-dimethylaniline diblock copolymer. Upon incorporation of an intervening block derived from pentamethylphenylethylisocyanide 8, exciplex formation is suppressed in the related triblock copolymer. Transient absorption spectra of this family of di-and triblock copolymers reveal the formation of radical ion pairs, with a lifetime of 1.1 ps in the anthracene4imethylaniline diblock copolymer.

Polymerization of 1-vinylpyrene in acetonitrile was achieved electrochemically at a conducting Sn02 electrode by application of anodic potentials and photoelectrochemically at a n-GaAs semiconductor electrode under visible light irradiation. Both polymers exhibited characteristic excimer emission (Xmal 480 nm) in both films and THF solutions similar to poly(vinylpyrene) synthesized by using Ziegler-Natta catalyst. The lifetime of the excimer emission was ~110 ns. The mechanism of photodegradation of poly(vinylpyrene) was elucidated by using ESR techniques.

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