We report on submicron-sized solid and hollow hydrogen-bonded polymer nanoparticles spontaneously assembled in solutions at neutral pH. Those assemblies were mediated by nuclei of a phase-separating temperature-responsive polymer in aqueous solution, followed by stabilization of the emerged polymer nuclei by a hydrogen-bonding molecule. The feasibility of such an approach was demonstrated via the pair of a well-known temperature-responsive polymer poly(N-isopropylacrylamide) (PNIPAM) and tannic acid (TA). The use of temperature as a trigger for nanoparticle formation complements the acidity trigger that was earlier used to induce spontaneous assembly of hydrogen-bonded nanocapsules composed of poly(2-succinyloxyethyl methacrylate) and poly(N-vinylpyrrolidone) (PVP). In the TA/PNIPAM system, the morphology was controlled by the ratio of components as well as solution pH. Due to the weak charge of TA molecules at pH 7, the assemblies of TA/PNIPAM were nanocapsules rather than solid particles, and an increase in solution pH from 5 to 7 triggered transformation of solid nanoparticles to nanocapsules. Importantly, TA/PNIPAM nanocapsules exhibited label-free fluorescence and could be easily visualized using confocal laser scanning microscopy. Both solid nanoparticles and nanocapsules are easy to make, below 100 nm in size, and made of non-toxic, biocompatible components. These particles can be used as individual nanocarriers in biomedical and imaging applications or serve as building blocks in functional surface-mediated or bulk assemblies.

One-step assembly of hydrogen-bonded nanoparticles and nanocapsules mediated by phase separation of poly(N-isopropylacrylamide)

254th National Meeting (2017)

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