Study on the Conformation of Comb-Like Polymers (CLPs) Confined to a Solid Surface

摘要

Naonometer-thick lubricants, such as perfluoropolyether (PFPE) ZDOL, have been used to protect magnetic media surface from wear damage in hard disk drives (HDD) for several decades. PFPE’s salient weaknesses like high cost, environmental concerns, and notable thickness have challenged their future usage in this fast developing industry. In order to identify a good substitute of PFPEs to alleviate those negative effects, as well as decrease the magnetic spacing, the nanofilm conformation of a novel lubricant, called comb-like polymers (CLPs), confined to the silicon wafer surface has been investigated via studying the molecular weight dependence of the monolayer thickness in this thesis. CLP nanofilm was fabricated through dipcoating process. Saturated bonded thickness of CLPs was determined by spectroscopicudellipsometry (SE) and taken as monolayer thickness. Experimental results showed that the monolayer thicknesses of PFPE ZDOL 2000 and PFPE ZDOL 4000 were 1.02±0.11 nm and 1.59±0.21 nm, respectively. The corresponding molecular weight exponent “n” of ZDOL wasud0.64±0.06, which indicates a slightly stretched random coil conformation. The monolayer thicknesses of four different CLPs, commercially known as PF-636, PF-6320, PF-656 and PF-6520, were 0.48±0.02 nm, 0.69±0.05 nm, 0.64±0.04 nm, and 0.80±0.06 nm, respectively, whichudare significantly lower than that of Zdol. The “n” values of PF-63X and PF-65X were 0.33±0.04, and 0.20±0.01, respectively, which indicates a flatter conformation than ZDOL. The difference between PFPEs and CLPs has been attributed to the different rigidity of ZDOL and CLPudmolecules caused by different chemical structure of their backbones and side groups. Our experimental results suggest that the CLP chains are more rigid and tend to lie flatter on the silicon wafer surface and it will potentially reduce magnetic spacing and increase the areal density. The experimental results also indicated that the rigidity of the CLP chains result in faster solution adsorption. Though more reliability tests are required to determine the feasibility of CLPs as a media lubricant, the current studies suggest that CLPs have great potential as nanometer-thick lubricant.