Combined Continuous Wave and Pulsed Plasma Modes: For More Stable Interfaces with Higher Functionality on Metal and Semiconductor Surfaces

Abstract

A novel approach to producing improved bio‐interfaces by combining continuous wave (CW) and pulsed plasma polymerization (PP) modes is reported. This approach has enabled the generation of stable interfaces with a higher density of primary amine functionality on metal, ceramic and semiconductor surfaces. Heptylamine (HA) was used as the amine‐precursor. In this new design, a thin CW PPHA layer is introduced to provide strong cross‐linking and attachment to the metal or semiconductor surfaces and to provide a good foundation for better bonding a pulsed PPHA layer with high retention of functional groups. The combined mode provides the pulsed mode advantage of a 3‐fold higher density of primary amines, while retaining much of the markedly higher stability in aqueous solutions of the continuous mode.

Practical Amine Functionalization of Multi‐Walled Carbon Nanotubes for Effective Interfacial Bonding

“…The NH 2 /C ratio for HAPP‐CW + P is the highest (about 3.5%) of the three modes, because the combined mode possesses the advantages of CW and pulsed modes. This further supports our previous work, using the CW + P mode on metal and semiconductor surfaces 33. In the CW plasma polymerization, the precursor undergoes a high level of fragmentation leading to a highly cross‐linked plasma polymer film,41–44 which provides a good foundation for better bonding of a pulsed HAPP layer with a higher level of retention of amino groups due to the reduction of the fragmentation of the monomer during the pulsed plasma polymerization.…”

“…The sample was then dried at room temperature. Due to its lower toxicity, HA (CH 3 (CH 2 ) 6 NH 2 , 99% purity, Sigma–Aldrich) was used as the monomer based on our previous work 33, 34. Epon 862 epoxy resin and Epikure W aromatic amine curing agent (mixing ratio 100/26.4) used in this work were purchased from Hexion Specialty Chemicals, Inc. Neat epoxy, untreated MWCNT/epoxy, and plasma treated MWCNT/epoxy composites were prepared.…”

“…This effective surface functionalization enables good dispersion of the MWCNTs in solvents and strong interfacial bonding with polymers (Figure 1). Three different plasma modes were tested – continuous wave (CW), pulsed (P), and combined (CW + P) – because the combined mode had previously been shown to give a more stable and higher level of functional groups on metal and semiconductor surfaces 33. The practicality of the plasma treatments was improved by either replacing ammonia gas with the safer and non‐toxic nitrogen mixed with a small amount of hydrogen or, for the polymerization route, by replacing the more toxic and unstable allylamine with heptylamine (HA).…”

Controlling cell growth on titanium by surface functionalization of heptylamine using a novel combined plasma polymerization mode

“…Based on our previous work, heptylamine was used as the monomer due to its lower toxicity and because a more stable monomer pressure was achieved in comparison with allylamine 4. In addition a sufficient level of amino functional groups for the intended biological application was also achieved 4, 5. The stability of the primary amine levels was quantified by derivatization with trifluoromethyl benzaldehyde (TFBA), followed by X‐ray photoelectron spectroscopy (XPS).…”

Surface wetting processing on BNNT films by selective plasma modes

“…The CA of the 5CW+10P treated BNNT films increased to 42.8° after 100 h aging in air, while the CA of the 10CW treated films jumped back to 81.5°. This is because the CW mode plasma treatment creates a strong cross-linking on BNNTs and this structure serves as a base for the further P mode treatment, which gives rise to better bonding of functional groups during P mode treatment [48,49].…”