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Despite their immense potential, the ability to control the dispersion and microstructure of carbon nanotubes remains a hurdle for their widespread use. Stimuli-responsive polymers show conformational changes with an applied external stimulus (pH, temperature, light, etc.). The dispersion of carbon nanotubes by thermoresponsive polymers is shown to enable the macroscopic properties of aqueous suspensions to be tailored as a function of temperature. This work presents the synthesis, characterization, and use of temperature-responsive poly(N-cyclopropylacrylamide) (PNCPA) polymers containing 1, 3, and 5 mol % pyrene-bearing repeat units to tailor the dispersion state of single-walled carbon nanotubes (SWNT) in water. Turbidity measurements show that the lower critical solution temperature (LCST) of PNCPA decreases with increasing pyrene content. Viscosity measurements on aqueous SWNT suspensions stabilized with pyrene-functionalized PNCPA show highly entangled and well-dispersed nanotube microstructure above and below the LCST of the polymer, respectively. UV−vis spectra also confirm that nanotube stabilization by these polymers is dependent upon the pyrene content. Drying of these suspensions produces composites whose microstructure and electrical conductivity vary with drying temperature and pyrene content of the stabilizing polymer. This temperature-dependent dispersion behavior has significant implications for the processing of carbon nanotubes and tailoring of composite properties. Such stimuli-controlled dispersion of carbon nanotubes could have a variety of applications in nanoelectronics, sensing, and drug and gene delivery systems.

Inspired by precisely designed protein synthesis from amino acids, we demonstrate precise polyurethane synthesis from novel AB-type monomers exhibiting side chain functionalities to implement an elaborate molecular/material design, which has been difficult to address by a conventional method. To realize this idea, we designed acylazide precursor monomers having alcohol moieties, which can transform into actual AB-type monomer species having isocyanate and alcohol groups by Curtius rearrangement. Polymers from the monomers afforded self-standing films that showed very different mechanical properties from conventional polyurethanes. The detailed kinetic analysis of the Curtius rearrangement and (co)polymerization studies revealed that the polyurethane backbone structure could be flexibly programmed by the choice or combination of monomers. Moreover, the resulting polymers were further functionalized by postpolymerization modification, enabling fine-tuning of their properties. Overall, the utility of this AB-type monomer protocol to implement tailored polyurethane synthesis is thoroughly studied.

A modular strategy toward (bio)functional nanofiber meshes by electrospinning is described. In contrast to commonly established, multistep protocols or complex spinning setups, a straightforward single-step procedure is investigated to obtain polymer nanofibers with pentafluorophenyl (Pfp)-activated esters on the surface. The aim was to electrospin, for the first time, poly(pentafluorophenyl methacrylate) (PPfpMA) and PPfpMA/poly(ε-caprolactone) (PCL) blends, resulting in reactive nanofibers with fiber surfaces that can be functionalized with suitable bioactive entities. While PPfpMA fibers are brittle the spinning of PCL/PPfpMA blends leads to improved mechanical stability of the obtained fabrics. The effective introduction of surface functionalities onto the fibers was proven by both model compounds and bioactive monosaccharides. The Pfp-activated esters are enriched at the fiber surfaces and react cleanly with nucleophiles such as 2-aminoethanol, aminofluorescein, or amino-functionalized monosaccharides to generate a robust amide anchor. The attachment of functional entities releases a Pfp group that allows for monitoring of the functionalization reaction with UV/vis spectroscopy. X-ray photoelectron spectroscopy (XPS) and contact angle measurements indicate effective introduction of functionalities to the fiber surfaces, and fluorescence microscopy suggests a homogeneous distribution of amino functional fluorescence markers on the meshes. The bioavailability of the introduced carbohydrates is shown by macrophage stimulation experiments using PCL/PPfpMA fiber meshes, which are functionalized with 2-aminoethyl-α-d-mannopyranoside or β-d-galactopyranoside. Meshes functionalized with mannose specifically enhance the cytokine production of macrophages when costimulated with lipopolysaccharides compared to galactose- or aminoethanol-functionalized PCL/PPfpMA fiber mat controls.