Tuneable swelling of thermo- and pH-responsive copolymer films

Abstract

We report on thermo-and pH-responsive copolymer films consisting of N-isopropylacrylamide (NIPAAm) and different carboxyalkylacrylamides exhibiting switchable swelling states over a wide range of temperatures and pH-values. The copolymers were covalently grafted as brush-like films onto solid substrates. Analysis by quartz crystal microbalance with dissipation monitoring revealed the phase transition behaviour to be sensitively controlled by the balance of polar and non-polar interactions, which could be dissected into the local level of comonomer structure as well as the more global level of copolymer chain composition. Remarkably, the phase transition was determined to be in general lower than in solution, which originated from the higher local polymer concentration of the swollen surface-grafted copolymer layer as explained by the general phase behaviour based on classical theory of polymers in solutions. The different swelling profiles of the environmentally responsive copolymer films are expected to offer valuable options for the design of switchable interfaces as, for instance, applicable for the modulation of model biosystems.

Light‐Triggered Multifunctionality at Surfaces Mediated by Photolabile Protecting Groups

“…[ 103 ] Depending on their chemical composition and functionality, polymer brushes allow tailoring of surface properties such as wettability, biocompatibility, cell, bacteria, or protein resistance, adhesion, or lubrication. [103][104][105][106][107][108][109] When PRPGs are attached to polymer brushes, the physicochemical properties of the surface can be changed upon light exposure. [110][111][112][113] Reported examples are based on PRPGs attached to ionizable side groups along the brush chain.…”

Protein adsorption on and swelling of polyelectrolyte brushes: A simultaneous ellipsometry-quartz crystal microbalance study

“…[24][25][26][27] With the help of QCM-D, for example, the grafting of polystyrene brushes as well as temperature and pH-sensitive swelling of copolymer films was monitored. 28,29 As another example, adsorption of the enzyme tyrosinase to polyelectrolyte surface layers and its remaining activity in the immobilized state were observed. 30 By combining spectroscopic ellipsometry ͑SE͒ and QCM-D it is possible to derive the solvent-content of very thin adsorbed surface layers, leading to a further insight into swelling and adsorption mechanisms.…”

Preparation and analysis of switchable copolymers for biomedical application

“…When the material surface to be coated contains hydroxyl groups (e.g., glass, silicon, titanium alloys), the silyl-hydroxyl reaction can be used. This was demonstrated by Kaufmann et al (2010) for NiPAAm-based carboxyalkylacrylamide copolymers that bind to the substrate upon heat treatment at 170 °C. On an amine-modified surface, a randomly distributed copolymer of NiPAAm and 10% acrylic acid was immobilised as reported by Lee and von Recum (2010).…”

“…As expected, reduced amplitude of the wettability switching occurs upon comonomer addition. Kaufmann et al (2010) combine both options (i.e., to increase or to decrease the phase transition temperature) in a single molecular architecture and propose a copolymer of NiPAAm and carboxyalkylacrylamides. The introduction of hydrophilic units into NiPAAm-based copolymers was investigated by Nitschke et al (2007).…”

“…Another approach to a dual-responsive material that combines thermo-sensitivity with pH sensitivity was proposed by Kaufmann et al (2010). Copolymers of NiPAAm and carboxyalkylacrylamides with molar fractions up to 10 mol% were synthesised.…”