Organic hybrid materials consisting of an all-conjugated polythiophene backbone and well-defined poly(ethylene glycol) (PEG) grafted chains have been prepared by anodic polymerization of chemically synthesized macromonomers. The latter consist of a pentathiophene sequence in which the central ring bears a PEG chain with M_w = 1000 or 2000 at the 3-position. The influence of the polymerization potential, the length of the PEG branches and the dopant agent on the structure and properties of the graft copolymers has been examined. The chemical structure of the grafted materials has been corroborated by FTIR and X-ray photoelectron spectroscopies. Scanning electron microscopy and atomic force microscopy studies reveal that the morphology and topography of these materials are influenced by the above mentioned factors, even though homogeneous films showing a compact distribution of nanoaggregates, very flat surfaces (i.e. roughness < 15 Å) and nanometric thickness (i.e. 100–500 nm) were obtained in all cases. Cyclic voltammetry assays have been used to determine the presence of charged species, the electroactivity, the electrostability and the formation of cross-links. The electrochemical stability of the copolymer with grafted PEG chains of M_w = 1000 has been found to increase with the number of consecutive oxidation–reduction cycles (self-electrostabilizing behavior). Finally, a preliminary investigation into the applicability of these hybrid materials as active surfaces for the selective adsorption of proteins is presented.

The properties, microscopic organization and behavior as the cellular matrix of an all-conjugated polythiophene backbone (PTh) and well-defined poly(ethylene glycol) (PEG) grafted chains have been investigated using different experimental techniques and molecular dynamic simulations. UV-vis spectroscopy has been used to determine the optical band gap, which has been found to vary between 2.25 and 2.9 eV depending on the length of the PEG chains and the chemical nature of the dopant anion, and to detect polaron → bipolaron transitions between band gap states. The two graft copolymers have been found to be excellent cellular matrices, their behavior being remarkably better than that found for other biocompatible polythiophene derivatives [e.g. poly(3,4-ethylenedioxythiophene)]. This is fully consistent with the hydrophilicity of the copolymers, which increases with the molecular weight of the PEG chains, and the molecular organization predicted by atomistic molecular dynamics simulations. Graft copolymers tethered to the surface tend to form biphasic structures in solvated environments (i.e. extended PTh and PEG fragments are perpendicular and parallel to the surface, respectively) while they collapse onto the surface in desolvated environments. Furthermore, the electrochemical activity and the maximum of current density are remarkably higher for samples coated with cells than for uncoated samples, suggesting multiple biotechnological applications in which the transmission with cells is carried out at the electrochemical level.

Amphiphilic copolymers consisting of an all conjugated polythiophene backbone and sparsely attached oligo-ε-caprolactone side chains have been prepared by anodic electropolymerization of hydroxymethyl-3,4-ethylenedioxythiophene (HMeEDOT) with a thiophene-ended oligo-ε-caprolactone macromonomer (Th-PCL), obtained by ring opening polymerization of ε-caprolactone with thiophene methanol. The random copolymers, obtained starting from two different molar ratios of the co-monomers in the feed (HMeEDOT : Th-PCL of 80 : 20 and 60 : 40), and the homopolymer (PHMeEDOT) were synthesized by using three different working electrodes. After structural characterization by FTIR, the electrochemical, morphological and surface properties of the obtained copolymers were examined, and the results evidenced a dependence on both the working electrode and the composition in the feed. In order to evaluate the opportunities in the copolymers's further bioapplications, biodegradability, cytotoxicity and cell proliferation investigations were carried out. By combining the results of electrochemical characterization with those of biocompatibility and dopamine sensing capability tests, it was concluded that a co-monomer feed ratio of 80 : 20 could be the optimal choice for the potential use of these amphiphilic copolymers in sensing devices. All in all, this study shows the benefit of a designed “hairy-rod” conjugated polymeric architecture which, via their side chain nature (biocompatible/biodegradable, hydrophobic, oligomeric) and their grafting density, enabled the synthesis of a material for targeted application.

Development of smart functionalized materials for tissue engineering has attracted significant attention in recent years. In this work we have functionalized a free-standing film of isotactic polypropylene (i-PP), a synthetic polymer that is typically used for biomedical applications (e.g. fabrication of implants), for engineering a 3D all-polymer flexible interface that enhances cell proliferation by a factor of ca. three. A hierarchical construction process consisting of three steps was engineered as follows: (1) functionalization of i-PP by applying a plasma treatment, resulting in i-PP_f; (2) i-PP_f surface coating with a layer of polyhydroxymethy-3,4-ethylenedioxythiophene nanoparticles (PHMeEDOT NPs) by in situ chemical oxidative polymerization of HMeEDOT; and (3) deposition on the previously activated and PHMeEDOT NPs coated i-PP film (i-PP_f/NP) of a graft conjugated copolymer, having a poly(3,4-ethylenedioxythiophene) (PEDOT) backbone, and randomly distributed short poly(ε-caprolactone) (PCL) side chains (PEDOT-g-PCL), as a coating layer of ∼9 μm in thickness. The properties of the resulting bioplatform, which can be defined as a robust macroscopic composite coated with a “molecular composite”, were investigated in detail, and both adhesion and proliferation of two human cell lines have been evaluated, as well. The results demonstrate that the incorporation of the PEDOT-g-PCL layer significantly improves cell attachment and cell growth not only when compared to i-PP but also with respect to the same platform coated with only PEDOT, constructed in a similar manner, as a control.

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.

Given that copolymers of complex topology and composition are at the forefront of multifunctional materials research, this work reports an amphiphilic random, heterografted copolymer of (A-g-B)_m-ran-(A-g-C)_n type, 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 a hierarchical fashion, having π-conjugated polythiophene (PTh) as the main chain and polar units, polyethylene glycol (PEG) and oligo-ε-caprolactone as side chains. The properties of the new copolymer, 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 solution and film states. By electronic microscopy techniques, two types of supramolecular structures were evidenced: (a) porous spherical particles and (b) rod-like structures. When deposited on carbon electrodes, the copolymer presented a good electroactivity and electrostability. Copolymer's biocompatibility studies, performed by using Cos-1 and Vero cell lines, demonstrated an excellent adhesion when compared with a bare steel electrode while a slight decrease of proliferation was registered, more pronounced for Vero cells, in spite of cell normal growth and morphology. Thanks to its excellent capability for electrochemically interfacing with aqueous electrolytes, the voltammetric oxidation of the NADH coenzyme at the PTh-g-(PEG-r-PCL) film-modified carbon electrode revealed that it can be used as a selective biosensor of this biomolecule, as well.