Abstract
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.Graphical abstractTransmission and scattering intensity in relation to temperature and momentum transfer, respectively
Highlights
IntroductionThe ratio between the backbone and the side chain lengths determines whether the molecular brush is of spherical-like or rod-like shape [8,9,10,11]
Molecular brushes are densely grafted polymers having a rather rigid conformation due to the steric hindrance between the Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.The ratio between the backbone and the side chain lengths determines whether the molecular brush is of spherical-like or rod-like shape [8,9,10,11]
The polymer concentration was chosen at 30 g L−1, either in H2O or in D2O
Summary
The ratio between the backbone and the side chain lengths determines whether the molecular brush is of spherical-like or rod-like shape [8,9,10,11]. When the side chains are much longer than the backbone, the molecular brush has an architecture close to the one of a star-like polymer and assumes a spherical shape. On the other hand, when the backbone is significantly longer than the side chains, its architecture is close to a bottlebrush. It is of interest to study the effect of the conformational changes of stimuli-responsive side chains on the overall brush conformation. Side chains from polymers that exhibit lower critical solution temperature (LCST) behavior in aqueous solution are expected to show strong effects. LCST-type polymers are water-soluble at low temperatures and become more and more hydrophobic, as the temperature
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
