Bottlebrush copolymers are comb-like macromolecules, which adopt cylindrical shape in solutions due to steric repulsion between densely grafted polymeric side chains. Cylindrical bottlebrushes can be transformed into organic nanotubes via intramolecular cross-linking of the shell layer and degradation of the inner core. Organic nanotubes with controlled nanometer dimensions can be used in many applications, such as ion transport, chemical catalysis, biosensors, selective encapsulation and separation of nanomaterials etc. Herein, we report a new method for the preparation of organic nanotubes with controlled dimensions from photo-cross-linkable core-shell bottlebrush copolymer precursors composed of an inner degradable polylactide block and an outer block containing photoactive coumarin functionalities. Upon UV irradiation at 365 nm, the peripheral coumarin functionalities undergo [2+2] cyclodimerization to form shell-cross-linked bottlebrushes. Subsequent degradation of the polylactide block provides hollow cylindrical nanoparticles held together by dimerized coumarin units in the shell layer. The length and the inner diameter of the nanotubes are determined by the length of the backbone and the polymeric side chains, respectively. Photo-cleavage of coumarin units upon 254 nm results in disintegration of nanotubes into small fragments. Amphiphilic nanotubes with a positively charged interior could potentially be used for selective encapsulation, separation, and purification of nanomaterials or biomacromolecules. 

Synthesis of photo-cross-linkable core-shell bottlebrush copolymers and their transformation into well-defined organic nanotubes

247th National Meeting (2014)

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