A molecular brush with thermoresponsive poly(2-ethyl-2-oxazoline) side chains: a structural investigation

Autor: Clemens Sachse, Florian Jung, Lester C. Barnsley, Chia-Hsin Ko, Kaltrina Shehu, Rainer Jordan, Christine M. Papadakis, Jia-Jhen Kang
Rok vydání: 2020
Předmět:
Zdroj: Colloid & polymer science 299, 193–203 (2021). doi:10.1007/s00396-020-04704-6
ISSN: 1435-1536
0303-402X
DOI: 10.1007/s00396-020-04704-6
Popis: The thermoresponsive behavior of a poly(2-oxazoline)-based molecular brush is investigated in aqueous solution. The molecular brush under study, PiPOx100-g-PEtOx17, has a poly(2-isopropenyl-2-oxazoline) (PiPOx) backbone grafted with thermoresponsive poly(2-ethyl-2-oxazoline) (PEtOx) side chains. Since the backbone degree of polymerization is only a factor of ~ 6 higher than the ones of the side chains, it features an architecture between a star-like polymer and a comb-like polymer. Its aqueous solution exhibits lower critical solution temperature (LCST) behavior with a cloud point temperature Tcp = 40.5 °C at 30 g L−1. The temperature-dependent structural evolution is disclosed using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). An increase of the molecular brush size is found upon heating from room temperature to Tcp, which is attributed to the extension of the backbone resulting from the dehydration and collapse of the side chains. Above Tcp, the size decreases again, which indicates the collapse of the whole molecular brush. Large aggregates are found to be present in the solution in the temperature range 25–50 °C. These become more compact, as the temperature is increased across Tcp.
Databáze: OpenAIRE
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