Abstract
Nature as the ultimate inspiration can direct, gate, and selectively transport species across channels to fulfil a specific targeted function. Harnessing such precision over local structure and functionality at the nanoscale is expected to lead to indispensable developments in synthetic channels for application in catalysis, filtration and sensing, and in drug delivery. By combining mesoporous materials with localised charge-switchable poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes, precisely controlling pore filling and exploring the possibility of incorporating two different responsive polymers, we hope to approach the precision control of natural systems in the absence of an external force. Here, we report a simple one-step approach to prepare a mesoporous silica thin film with ~8 nm pores functionalised with a photoiniferter by combining sol–gel chemistry and evaporation-induced self-assembly (EISA). We show that surface-initiated photoiniferter-mediated polymerisation (SI-PIMP) allows the incorporation of a high polymer content up to geometrical pore blocking by the simple application of UV light in the presence of a monomer and solvent, proceeding in a controlled manner in pore sizes below 10 nm, with the potential to tune the material properties through the formation of surface-grafted block copolymers.
Highlights
The high degree of control exercised in biological channels to regulate key processes including ionic flow and molecular transport across cell membranes is the ultimate inspiration and key motivator for the material scientist to mimic in synthetic materials [1,2]
The impact of a sacrificial iniferter was examined by the addition of benzyl diethyldithiocarbamate (BDC), a structural mimic of N,N-(diethylamino) dithiocarbamoyl-benzyl(trimethoxy)silane) (SBDC), which were synthesised according to a previous literature protocol [29]
The polymerisable films have an average thickness of 232 nm and porosity of 21% from ellipsometry; and are characterised by a low specific surface area of approximately 4.9 m2 /g according to BET measurements taken from substrate-supported films
Summary
The high degree of control exercised in biological channels to regulate key processes including ionic flow and molecular transport across cell membranes is the ultimate inspiration and key motivator for the material scientist to mimic in synthetic materials [1,2]. Surface-initiated atom transfer radical polymerisation (SI-ATRP) remains the most widely investigated technique due to its wide range of polymerisable monomers with controllable molecular weight and narrow dispersities, chemical tolerance, and mild polymerisation conditions [3,18] While several techniques such as initiators for continuous activator regeneration (ICAR) [3] and activators (re)generated by electron transfer (A(R)GET) [10] have been implemented to reduce the concentration of the copper catalyst that contaminates the final material, ATRP systems are more onerous, requiring numerous components to mediate a controlled polymerisation. This could severely limit the pore size that can be functionalised in terms of the control achievable and the polymer content.
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