Electroactive and bioactive films of random copolymers containing terthiophene, carboxyl and Schiff base functionalities in the main chain

A new bis-thienyl type monomer with preformed azomethine linkages (AzbT) was chemically synthesized and, subsequently, electro-copolymerized with 2,2' : 5', 2 ''-terthiophene (Th-3). AzbT : Th-3 mixtures with different molar ratios (i.e. 50 : 50, 60 : 40 and 80 : 20) were considered, the resulting thin films being made of random insoluble copolymers, P(AzbT-co-Th-3)s. The content of AzbT in P(AzbT-co-Th-3) s was found to increase with the AzbT : Th-3 molar ratio in the electropolymerization medium. Furthermore, characterization of the different copolymers suggests the existence of several concomitant processes in the reaction medium. Thus, depending on the composition of the reaction medium, AzbT worked as a co-monomer and/or as a dopant for the growing polymer chains. The morphology of the films evolved from a porous multi-level surface to a more compact and flat globular structure with increasing AzbT content. On the other hand, the electrochemical and optical properties were also influenced by the AzbT : Th-3 ratio. Cytotoxicity and cell adhesion and proliferation tests, which were performed using human osteosarcoma and monkey kidney epithelial cell lines (MG-63 and Vero, respectively), revealed that P(AzbT-co-Th-3) matrices can be potentially applied as bioactive substrates. This behaviour was especially relevant for the 80 : 20 copolymer, which exhibits optical and electrochemical properties in the range of polythiophene derivatives, suggesting that it is a promising functional biomaterial.Peer ReviewedPostprint (author’s final draft

An amphiphilic, heterografted polythiophene copolymer containing biocompatible/biodegradable side chains for use as an (electro)active surface in biomedical applications

Given that the copolymers of complex topology and composition are at the forefront of multifunctional materials research, this work reports aboutan amphiphilic random, heterografted copolymer of (A-g-B)m-ran-(A-g-C)ntype, which was designed to work as an efficient and biocompatible electronic interface. The copolymer (henceforth denoted as PTh-g-(PEG-r-PCL) for simplification) was synthesized in hierarchical fashion, having ¿-conjugated polythiophene (PTh) as main chain and polarunits, polyethylene glycol (PEG) and oligo-¿-caprolactone as side chains. Theproperties of the newcopolymer,in solution and in solid state,were evaluated. The applied investigations showed that, due to its amphiphilic character and incompatibility of the side chains, PTh-g-(PEG-r-PCL) experiences microphase separation in solutionand film states. By electronicmicroscopy techniques were evidenced two types of supramolecular structures: (a) porous spherical particles and (b) rod-like structures. When deposited on carbon electrodes,the copolymerpresented a good electroactivity and electrostability.Copolymer's biocompatibility studies, performed by using Cos-1 and Vero cell lines,demonstrated an excellent adhesion when comparing with bare steel electrode while a slight decrease of proliferation was registered, more pronounced for Vero cells, in spite of cells normal growth and morphology. Thanks to its excellent capability for electrochemically interfacing with aqueous electrolytes, the voltammetric oxidation ofNADH coenzyme at PTh-g-(PEG-r-PCL) film-modified carbon electrode revealed that it can be used as selective biosensor of this biomolecule, as well.Preprin

Amphiphilic polypyrrole-poly(Schiff base) copolymers with poly(ethylene glycol) side chains: synthesis, properties and applications

New amphiphilic poly(ethylene glycol) (PEG)-grafted random intrinsically conducting copolymers which combine three different functionalities have been engineered, prepared and characterized. Specifically, these “rod-coil” type copolymers bear conducting polypyrrole (PPy) and poly(Schiff base) (PSB) sequences randomly distributed in their backbones; hydrophilic grafted side chains consisting of well-defined PEG chains are attached to the PSB units. Basically, the synthesis of the copolymers is conducted sequentially by employing the “macromonomer” technique via electrochemical co-polymerization of a bis (pyrrole) benzoic Schiff base-containing PEG macromonomer with pyrrole monomers. After investigation of the chemical and electrochemical properties of the synthesized copolymers, their advantages of multi-functionality in terms of biomedical applications have been demonstrated. More specifically, the conjugated PPy and PSB sequences enabled the grafted copolymers to exhibit great ability to catalyse the oxidation of serotonin, an important neurotransmitter found in blood platelets and in the central nervous systems of animals and humans. On the other hand, the enhanced biocompatibility in comparison with bare PPy is due to the presence of PEG side chains, while bacteriostatic activity against both Gram-negative and Gram-positive bacteria is imparted by the synergistic combination of the polycationic character of the PPy main chain with the benzoic Schiff base functional groups and with the bent-shaped architecture of the facially amphiphilic PSB sequences, respectively. Accordingly, these grafted copolymers are promising materials for developing implantable electrodes for serotonin detection which present the abovementioned characteristics.Peer ReviewedPostprint (published version

Synthesis and self-assembly of fluorene-vinylene alternating copolymers in “Hairy-Rod” architecture: side chain – mediated tuning of conformation, microstructure and photophysical properties

<p>In the present work, we demonstrate that the side chain choice, as a tunable parameter, is an effective strategy to drive molecular ordering, packing motifs and overall microstructure of a conjugated polymer. By applying Wittig polycondensation novel ‘rod-coil’ structures, in ‘hairy-rod’ architecture, based on fluorenylene vinylene copolymers with well-defined oligomeric side chains were synthesized using ‘T’-shaped or ‘Cross’-shaped <i>p</i>-terphenyl macromonomers. The overall character of the copolymers was systematically varied by attaching of hydrophilic PEG 2000, hydrophobic polar oligo-ε-caprolactone or hydrophobic and non-polar oligostyrene side chains. Self-assembling of the copolymers by simple direct dissolution method was achieved in various solvents by modifying their selectivity in relation to the side chain or main chain. The morphology investigations demonstrated that unique nanofeatures obtained in each case (helical foldamers, vesicles, disks, or helical turns) depend on the nature, number, and position of the side chains which influence the photophysical properties. The ‘hairy-rod’ topology is also responsible for the self-assembly of the materials in molten state, as thermal analysis revealed, and the propensity of the new synthesized conjugated main chain for helical folding was evidenced, as well.</p

Thiophene &alpha;-Chain-End-Functionalized Oligo(2-methyl-2-oxazoline) as Precursor Amphiphilic Macromonomer for Grafted Conjugated Oligomers/Polymers and as a Multifunctional Material with Relevant Properties for Biomedical Applications

Because the combination of &pi;-conjugated polymers with biocompatible synthetic counterparts leads to the development of bio-relevant functional materials, this paper reports a new oligo(2-methyl-2-oxazoline) (OMeOx)-containing thiophene macromonomer, denoted Th-OMeOx. It can be used as a reactive precursor for synthesis of a polymerizable 2,2&rsquo;-3-OMeOx-substituted bithiophene by Suzuki coupling. Also a grafted polythiophene amphiphile with OMeOx side chains was synthesized by its self-acid-assisted polymerization (SAAP) in bulk. The results showed that Th-OMeOx is not only a reactive intermediate but also a versatile functional material in itself. This is due to the presence of 2-bromo-substituted thiophene and &omega;-hydroxyl functional end-groups, and due to the multiple functionalities encoded in its structure (photosensitivity, water self-dispersibility, self-assembling capacity). Thus, analysis of its behavior in solvents of different selectivities revealed that Th-OMeOx forms self-assembled structures (micelles or vesicles) by &ldquo;direct dissolution&rdquo;.Unexpectedly, by exciting the Th-OMeOx micelles formed in water with &lambda;abs of the OMeOx repeating units, the intensity of fluorescence emission varied in a concentration-dependent manner.These self-assembled structures showed excitation-dependent luminescence as well. Attributed to the clusteroluminescence phenomenon due to the aggregation and through space interactions of electron-rich groups in non-conjugated, non-aromatic OMeOx, this behavior certifies that polypeptides mimic the character of Th-OMeOx as a non-conventional intrinsic luminescent material

Synthesis of block copolymers by combination of photoinduced and atom transfer radical polymerization routes

Block copolymers of methyl methacrylate (MMA) and styrene (St) were obtained by the combination of two different free radical polymerization processes, namely photoinduced and atom transfer radical polymerization (ATRP) methods. In the first step, hydroxy terminated polymers were prepared by photoinitiated polymerization of MMA in the presence of N,N'-dimethylethanolamine and benzophenone as the initiating system and subsequently converted to bromine ended poly(methyl methacrylate) by the esterification of the resulting polymer with 2-bromo-propionylbromide. The functionalized polymers thus prepared were used as initiators in ATRP of St, in bulk, in conjunction with CuBr/2,2'-bipyridine as catalyst. The GPC and H-1-NMR analysis, and the kinetic studies indicate a fully controlled/"living" radical polymerization which results in the formation of block copolymers with narrow polydispersities

3,4-Ethylenedioxythiophene (EDOT) End-Group Functionalized Poly-ε-caprolactone (PCL): Self-Assembly in Organic Solvents and Its Coincidentally Observed Peculiar Behavior in Thin Film and Protonated Media

End-group functionalization of homopolymers is a valuable way to produce high-fidelity nanostructured and functional soft materials when the structures obtained have the capacity for self-assembly (SA) encoded in their structural details. Herein, an end-functionalized PCL with a π-conjugated EDOT moiety, (EDOT-PCL), designed exclusively from hydrophobic domains, as a functional “hydrophobic amphiphile”, was synthesized in the bulk ROP of ε-caprolactone. The experimental results obtained by spectroscopic methods, including NMR, UV-vis, and fluorescence, using DLS and by AFM, confirm that in solvents with extremely different polarities (chloroform and acetonitrile), EDOT-PCL presents an interaction- and structure-based bias, which is strong and selective enough to exert control over supramolecular packing, both in dispersions and in the film state. This leads to the diversity of SA structures, including spheroidal, straight, and helical rods, as well as orthorhombic single crystals, with solvent-dependent shapes and sizes, confirming that EDOT-PCL behaves as a “block-molecule”. According to the results from AFM imaging, an unexpected transformation of micelle-type nanostructures into single 2D lamellar crystals, through breakout crystallization, took place by simple acetonitrile evaporation during the formation of the film on the mica support at room temperature. Moreover, EDOT-PCL’s propensity for spontaneous oxidant-free oligomerization in acidic media was proposed as a presumptive answer for the unexpected appearance of blue color during its dissolution in CDCl3 at a high concentration. FT-IR, UV-vis, and fluorescence techniques were used to support this claim. Besides being intriguing and unforeseen, the experimental findings concerning EDOT-PCL have raised new and interesting questions that deserve to be addressed in future research

Immobilization of invertase and glucose oxidase in conducting copolymers of thiophene functionalized poly(vinyl alcohol) with pyrrole

In this study, immobilizations of invertase and glucose oxidase were achieved in conducting thiophene functionalized copolymers of vinyl alcohol with thiophene side groups and pyrrole (PVATh/PPy) via electrochemical polymerization. The kinetic parameters, V-max (maximum reaction rate) and K-m (substrate affinity), of both free and immobilized enzymes were determined. The effect of supporting electrolytes, p-toluene sulfonic acid and sodium dodecyl sulfate, on the enzyme activity and film morphologies was examined. The optimum temperature, operational and storage stabilities of immobilized enzymes were determined. PVATh/PPy copolymer was found to exhibit significantly enhanced properties compared to pristine polypyrrole. (c) 2005 Elsevier B.V. All rights reserved