Simple route to size-tunable degradable and electroactive nanoparticles from the self-assembly of conducting coil-rod-coil triblock copolymers

A simple route to size-tunable nanoparticles from the self-assembly of degradable and electrically conductive coil-rod-coil triblock copolymers based on an aliphatic polyester and conducting species is presented. A series of coil-rod-coil triblock copolymers consisting of a middle aniline pentamer (AP) segment and two polycaprolactone (PCL) segments were easily synthesized by a combination of a ring-opening polymerization of CL initiated by an aniline dimer (AD) giving AD-PCL and an oxidative coupling reaction between the AD-PCL and p-phenylenediamine. This strategy avoids the multistep reaction used in previous work. The electroactivity of these copolymers was investigated by UV and cyclic voltammetry. The conductivity of the copolymers was dependent on the AP content and the conductivity mechanism of the triblock copolymers is discussed. Interestingly, these triblock copolymers can undergo self-assembly in selective solvent such as CHCl₃ as indicated by NMR and transmission electron microscope (TEM) observations. Dynamic light scattering (DLS) showed that the size of the nanoparticles was dependent on the molecular weight of the copolymers and on the oxidation state of the AP. The morphology of the nanoparticles was studied by TEM and SEM. These triblock copolymers and their size-tunable nanoparticles with degradability and electroactivity offer new possibilities in biomedical applications, such as controlled drug delivery, biosensors, and cardiovascular and neural tissue engineering.