A thermoresponsive dynamic polymer brush fabricated by the segregation of amphiphilic diblock copolymers

Abstract

A highly dense polymer brush was previously fabricated by the spontaneous segregation of amphiphilic diblock copolymers in an elastomer matrix into water and a hydrophobic polymer interface and named a 'dynamic polymer brush'. We fabricated a lower critical solution temperature (LCST)-type thermoresponsive dynamic polymer brush by mixing polyisoprene-b-poly[tri(ethylene glycol)methyl ether methacrylate] (PI-b-PME3MA) into a polystyrene-b-polyisoprene-b-polystyrene (SIS) elastomer. The LCST of PME3MA in water is 52 °C. The structure of the polymer brush was determined at several different temperatures using neutron reflectivity. With increasing temperature, the brush thickness of the LCST-type thermoresponsive dynamic polymer brush decreases, similar to the conventional fixed brush with the LCST-type thermoresponse. However, the graft density of the dynamic polymer brush surprisingly increases with increasing temperature. The change of the brush density of the conventional fixed polymer brush is not allowed. However, we observed for the first time that dynamic polymer brushes uniquely respond to increasing temperature with increasing brush densities.

Adhesion Force Analysis of Dynamic Polymer Brushes

“…However, dynamic PEG brush surfaces appearing on the PDMS elastomers with ED25 and ED21 showed a transitional change of works of adhesion at a certain pressure (dashed lines). In previous work, dynamic polymer brushes showed responses to the environmental change by changing the brush structure and graft density . Grafting density is always constant for fixed brush systems but variable for dynamic polymer brush systems, so the response of grafting density is unique to dynamic polymer brush.…”

“…Polymer brushes fabricated by this method are not fixed on the surface and are able to respond to environmental change. For example, using 2-[2-(2-methoxyethoxy)­ethoxy]­ethyl methacrylate (PME3MA) as a hydrophilic block, dynamic polymer brushes responded to temperature and changed not only the brush structure but also the graft density …”

New insights into the solid–liquid interface exploiting neutron reflectivity

“…An interesting application of this is in the capture of Uranium on PE brushes. [68,69] The polymers are generally bound to the surface through covalent interactions, however Tanoue et al [70] have investigated a di-block co-polymer bound to the surface by adsorption chemistry of one block, with the other block allowed to penetrate and create the crosslinking. The brush attains a surprisingly high surface density, with the hydration energy of the hydrophilic block supporting the extension of the brush during swelling.…”

Surface segregation of polydimethylsiloxane-polyether block copolymers in coatings driven by molecular architecture

“…By use of a thermoresponsive hydrophilic analogue, brush thickness and density could be directed further. [50] In a similar approach, Grunlan [51][52][53][54] and co-workers imparted silicone surfaces with anti-fouling properties by making use of a siloxane-tethered PEO chain. Chemical crosslinking of the amphiphilic chain in turn provided improved stability of the functional layer.…”