The heteronucleobase (adenine and uracil)-functionalized poly(ε-caprolactone) (A-PCL-U) possessing supramolecular structure has been successfully synthesized through the combination of ring-opening polymerization and Michael addition reaction. Attachment of multiple hydrogen-bonding units to chain ends of PCL results in phase separation and substantial increase in the viscosity. The association constant (K a) between adenine and uracil groups of A-PCL-U calculated from NMR measurement is 18.9 M−1. XRD and DSC analyses indicate that the crystalline structure of the A-PCL-U is changed to some extent due to phase segregation as compared to the PCL homopolymer. The AFM micrograph demonstrates that phase segregation is formed from the hard nucleobase chain ends and the soft poly(ε-caprolactone) chains of the supramolecular complex.

Complementary nucleobase-functionalized polymeric micelles, a combination of adenine-thymine (A-U) base pairs and a blend of hydrophilic-hydrophobic polymer pairs, can be used to construct 3D supramolecular polymer networks; these micelles exhibit excellent self-assembly ability in aqueous solution, rapid pH-responsiveness, high drug loading capacity, and triggerable drug release. In this study, a multi-uracil functionalized poly(ε-caprolactone) (U-PCL) and adenine end-capped difunctional oligomeric poly(ethylene glycol) (BA-PEG) are successfully developed and show high affinity and specific recognition in solution owing to dynamically reversible A-U-induced formation of physical cross-links. The U-PCL/BA-PEG blend system produces supramolecular micelles that can be readily adjusted to provide the desired critical micellization concentration, particle size, and stability. Importantly, in vitro release studies show that doxorubicin (DOX)-loaded micelles exhibit excellent DOX-encapsulated stability under physiological conditions. When the pH value of the solution is reduced from 7.4 to 5.0, DOX-loaded micelles can be rapidly triggered to release encapsulated DOX, suggesting these polymeric micelles represent promising candidate pH-responsive nanocarriers for controlled-release drug delivery and pharmaceutical applications.

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A new supramolecular material, N-(6-(3-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)yl)propanamido)pyridin-2-yl)undec-10-enamide (U-DPy) possesses an extremely high association constant (K a >10 7 M 21 ), which is able to dimerize through a self-complementary sextuple hydrogenbonding array. As the end groups of an oligomer, U-DPy forms a self-assembling polymer system. These new mono-and difunctional telechelic supramolecular polymers have highly prominent properties, leading to a substantial increase in viscosity, thermal stability and unique morphology changes in the solid state. More surprisingly, they can self-organize into lamellar crystallization and a spherical structure. In addition, upon increasing the concentration in the solution state, the size of the resulting spherical structure is gradually increased. These spherical structures are constructed from supramolecular polymers with a high degree of polymerization.

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