The formation of high surface concentrations of hydroxyl groups in the plasma polymerization of allyl alcohol

Abstract

Plasma polymers (PPs) of allyl alcohol (AA) were prepared under a range of different monomer flow rate conditions. The resultant PPs were analysed by X-ray photoelectron spectroscopy (X.p.s.) and high resolution monochromated X.p.s., with the help of trifluoroacetic anhydride (TFAA) labelling of hydroxyl groups, and time-of-flight secondary ion mass spectrometry (TOF s.i.m.s.). Emphasis was put on obtaining PPs with good hydroxyl retention, and on exploring the structure of these materials. Selected PPs were heated in argon to investigate the functional group mobility, and the level of crosslinking in these materials was evaluated by a simple washing test in distilled water. The u.v. stability was assessed on exposure to a ‘black lamp’. The observed behaviour of the PPs is explained by the presence of trapped residual free-radical centres in these materials. The results reported have important implications for the use of PPs as coating materials, particularly in applications where these materials may be subjected to natural sunlight. To increase the amount of surface functionality in these polymers, the post-plasma polymerization grafting of the AA was investigated. In order to assess the importance of the double bond in the monomer, various PPs of 1-propanol were also prepared and labelled.