Grafting of N‐moieties onto octa‐methyl polyhedral oligomeric silsesquioxane microstructures by sequential continuous wave and pulsed plasma

Abstract

A functionalization of microstructures of polyhedral oligomeric silsesquioxane (POSS) to obtain substrates contain N‐moieties, with a probable high selectivity of primary mines is demonstrated for the first time in a low pressure plasma process through a sequential continuous wave plus pulsed mode (CW + P). Selective grafting of N‐moieties was performed across octa‐methyl POSS micro‐powder by substituting hydrogen atoms of the terminal methyl groups during nitrogen/hydrogen (N2/H2) gases plasma. As opposed to wet chemical functionalization approaches, the plasma method does not require reactive chemicals and is environmentally friendly. The results demonstrate the efficiency of the treatment (N/Si) reaches 7.1% with an indication of high NH2 selectivity (NH2/N). The amount of primary amines is determined from XPS data after 4‐(trifluoromethyl) benzaldehyde (TFBA) chemical derivatization.

Plasma Modification and Synthesis of Membrane Materials—A Mechanistic Review

“…Using atmospheric-pressure plasma remains largely focused on modifying the hydrophilicity of membrane surfaces. For such purpose, carboxyl and organosilicon monomers have predominately been utilized [ 67 , 81 , 82 , 83 , 84 ]. Since vacuum cannot be the driving force, inert carrier gases such as Ar and He have been commonly used to deliver monomer precursors into the plasma chamber through a by-pass monomer chamber.…”

A “Green” Stirring Plasma Functionalization Strategy for Controllable Oxygen-Containing Functional Groups on Octa-Methyl POSS Microstructure

“…The octa-methyl POSS (>97%) for plasma functionalization were commercially provided by Hybrid Plastics Inc.,Hattiesburg, MS, USA [24]. The POSS particles that were supplied presented as agglomerates and exhibited a large particle size (25 to 100 µm).…”

“…As can be seen in Table 1, plasma functionalization was investigated under different conditions, namely different plasma modes, RF powers, and processing durations. In addition, the pre-treatment was 3 min for all samples, and the duty cycle (DC) for pulsed plasma was 10% which was calculated from ton/(ton + toff), in which ton is 0.05 ms [24]. An average 60 mg of the octa-methyl POSS was used for each treatment by the stirring plasma process.…”

“…During a CW + P oxygen plasma process, the CW plasma generates reactive oxygen species from oxygen gas with high kinetic energy which constantly bombards the surface of the POSS [28,41,42]. The pulsed plasma provides milder kinetic energy from plasma owing to a frequently repeated duration of gas discharge on-time and off-time [24,34,37]. Neutral radicals remain owing to their longer lifetime compared to ions and electrons during the off-time in pulsed plasma, which suggests the formation of functional groups from those reactive radicals [43].…”

“…Hence, the development of alternative functionalization methods for POSS materials that are efficient, tailorable, and environmentally friendly is still gaining attention [12,13,21]. Physical solutions such as thermal and plasma treatments are being proven to result in much less environmental waste compared to wet-chemical routes [22][23][24].…”