Polymerisation-induced self-assembly (PISA) enables the rational design and efficient synthesis of a wide range of diblock copolymer nano-objects (spheres, worms, or vesicles) at high copolymer concentrations. Briefly, a soluble precursor block is chain-extended via reversible addition-fragmentation chain transfer (RAFT) polymerisation using a monomer that forms an insoluble block in the chosen solvent. As this second block grows, it eventually undergoes phase separation that drives the in situ self-assembly, see Figure 1. Small-angle X-ray scattering (SAXS) is a powerful tool for characterising diblock copolymer nano-objects during PISA in terms of their size and morphology, providing fundamental insight into structure-property relationships. Here we report in situ SAXS measurements recorded during the synthesis of diblock copolymer nano-objects prepared by RAFT aqueous dispersion polymerisation. This powerful technique enables us to monitor the evolution of structure. For such experiments, we use a bespoke stirrable SAXS cell, see Figure 1. Poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) [PGMA-PHPMA] is a well explored amphiphilic diblock copolymer that can form spheres, worms or vesicles as well as exhibiting thermoresponsive behaviour. The onset of nucleation, particle growth and progressive morphological transitions (i.e. sphere-to-worm, worm-to-vesicle) can be observed by SAXS. Detailed analysis of the scattering patterns provide new insights for growth mechanisms during PISA syntheses. Moreover, the reaction solution volume within the SAXS cell is approximately 2 mL, which allows post mortem characterisation of the final block copolymer using 1H NMR spectroscopy, GPC, TEM and DLS.

In situ SAXS studies during RAFT aqueous dispersion polymerisation

2019 Fall National Meeting

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