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Building blocks of nano-architectures

Block copolymers (BCPs) are a versatile class of materials formed by repeating chemical blocks that are simple monomers or complex polymers. New formulations have resulted in self-assembly of many novel nanostructures.

Industrial Technologies

Much like metal alloys or composite materials that combine the strengths of individual components for a superior blend, BCPs make possible a wide array of properties. EU-funded scientists working on the project AP-GAC explored the potential inherent in self-assembly of polyphosphazene-based BCPs into interesting nanostructured compounds. Polyphosphazene BCPs consist of alternating phosphorous and nitrogen atoms. They are highly tuneable and hundreds have been synthesised with various side groups bound to the phosphorous atoms since the first reported approximately 15 years ago. AP-GAC focused on preparation of BCPs consisting of only two blocks (diblock), either two different polyphosphazenes or a hybrid BCP consisting of a polyphosphazene and a polystyrene. The team successfully prepared BCPs consisting of two different polyphosphazene BCPs. Synthesis of the diblock required blocking an initiator to prevent triblock formation through bi-directional chain growth. Using their techniques, investigators delivered the first chiral polyphosphazene BCPs with chemical functionalities randomly distributed in one block. A number of interesting nanostructured architectures were created from the BCPs including chiral twisted nanostructures, vesicles, nanospheres and mesoporous films. With novel macroinitiators prepared by the project team, scientists synthesised hybrid BCPs consisting of one polyphosphazene block and one polystyrene block. Both blocks were synthesised via living polymerisation, chain growth in which the ability of a growing polymer to terminate has been removed. The team used these hybrid BCPs to create nanospheres, multi-compartmental micelles, donut-shaped micelles and cylinder networks by changing the concentration of the polymers. AP-GAC successfully achieved all research goals with demonstration of self-assembly of diblock BCPs based on polyphosphazene and created a variety of novel nanostructures. Results have been widely published. They should spur innovation both into potential applications of these novel materials as well as into additional materials to be prepared with similar techniques.

Keywords

Block copolymers, monomer, polymer, self-assembly, nanostructure, polyphosphazene, diblock, polystyrene, chiral, vesicle, mesoporous films, micelles

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