Triarm Polycaprolactone Interface for Spatially Controlled Functionalization of Carbon Nanotube Fibers.

Abstract

Carbon nanotube fibers (CNTF) with exceptional strength, electrical, and thermal conductivities possess the potential for deployment in electrochemical and analytical applications. For such applications, CNTF are typically encapsulated using polymeric interface membranes such as polyvinyl chloride (PVC) for accommodating functional elements or recognition molecules. These membranes typically assemble stochastically on CNTF surfaces owing to the nonuniform interfacial interaction energies between the characteristic groups of the polymers and the CNTF surface. This stochastic assembly of encapsulating membranes subsequently inhibits the homogeneous distribution of recognition molecules on the CNTF surface, which influences the analytical performances. Herein, a triarm polycaprolactone (3-PCL) block copolymer is designed to homogenize the interfacial energies between the polymeric membranes and the CNTF surface. The 3-PCL interface is hypothesized to enable spatially controlled assembly of polymeric membranes on the CNTF surface and subsequently a homogeneous distribution of recognition molecules. As an illustration, the CNTF with a 3-PCL interface is demonstrated as an ion-selective microelectrode (ISE) for selective and sensitive detection of ammonium ions (NH4+) via homogeneous incorporation of a NH4+-specific ionophores within an encapsulating PVC membrane on the CNTF surface. An LOD and linear response range of 1 × 10-7 M and 1 × 10-7 to 1.0 × 10-1 M, respectively, were achieved. These values are an order higher as compared to ionophores incorporated within the PVC membrane on the CNTF surface without the 3-PCL interface. Further, a linear two-arm polymer (2-PCL) was evaluated as an interface for validation of significantly higher and stable analytical responses that could be achieved using the 3-PCL interface. Thus, the 3-PCL possesses the potential to be an ideal interface for incorporation of functional materials and recognition elements within polymeric membranes on the CNTF surface for the development of high-performance electrochemical and analytical devices.

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