Organically modified poly(acrylamide) (PAM)grafted mesoporous silica nanoparticles (MSNs) have been evaluated for the first time as a hybrid material for hydrogen release experiments via nanoconfinement of ammonia borane (AB). PAM was grafted from two different types of R group (isobutyric acid and phenylethyl)-containing in-built reversible additionfragmentation chain transfer (RAFT) agent-primed MSNs (PAM-COOH-MSNs and PAM-Ph-MSNs). To evaluate the suitability of these PAM-grafted MSNs as an efficient hybrid material for hydrogen release at a lower dehydrogenation temperature compared to neat AB, which was nanoconfined in PAM-grafted MSNs (AB-PAM-COOH-MSNs and AB-PAM-Ph-MSNs). The hydrogen release from AB-nanoconfined PAM-grafted MSNs was performed using temperature-programmed desorption-mass spectrometry (TPD-MS). Significantly, it was observed that AB-PAM-COOH-MSNs and AB-PAM-Ph-MSNs justified the nanoconfinement by a lower onset of hydrogen release temperature in comparison to neat AB. The possible mechanism for the lower dehydrogenation temperature of PAM-COOH-MSNs in comparison to that of PAM-Ph-MSNs was attributed to the size reduction of AB and the interaction between functional groups of polymers and MSNs with AB. Additionally, impurities such as diborane and ammonia during hydrogen release were suppressed for both PAMgrafted MSNs. Justifying the evidence for AB-PAM-COOH-MSNs in comparison to AB-PAM-Ph-MSNs, it can be proposed that organically modified poly(acrylamide)-grafted MSNs can be used as efficient nanocarriers for ammonia borane nanoconfinement and hydrogen release.
Mesoporous silica nanoparticles (MSNs) are widely studied and are an interesting material due to its application in wide range of areas, for example, in drug delivery, catalysis, in sensors, and in adsorption and separation. Specifically, MSNs contain high surface area and large pore volume, providing high drug loading capacity, tunable pore size, surface chemistry for accommodation of a variety of guest molecules, and versatile functionalization on the external and internal surface for a broad spectrum of applications. Many new strategies have been developed for the synthesis and functionalization of mesoporous silica-based materials. The functionalization of MSNs is highly important as it leads to the development of new chemical and physical properties. Thus, preparation of these organic/inorganic hybrid structures requires facile and controlled techniques to generate enhanced properties. The grafting of polymers using controlled radical polymerization (CRP) techniques has turned out to be the best suited method to synthesize these well-defined organicinorganic hybrid MSNs. Most common polymerization techniques are atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization, and nitroxide mediated polymerization (NMP). This chapter will be highlighting the state-of-the-art techniques for the synthesis of variety of MSNs, its functionalization using CRP techniques, and application of polymer functionalized MSNs.
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