A novel and facile method using a printed gradation photomask combined with photoreactions for preparing polymer surfaces with gradient distribution of surface energy

grafting layer thickness and grafting chain density was developed. The gradation photomask with gradient change of photo transmittance intensity

almost in the range of 0~100% at both 254 nm and 365 nm

has been successfully prepared by direct printing black ink onto the biaxially oriented polypropylene and silica (BOPP/SiOx) hybrid film. The applications of the gradient photomask in photoinduced reactions

such as confined photocatalytic oxidation (CPO) and photografting polymerizations

have been exploited. In CPO reaction with a printed gradient photomask

the static water contact angles (CAs) of modified surfaces of BOPP and PET films exhibited the surface energy gradient properties

for example

the CAs of BOPP decreased almost linearly from about 103 (unmodified) to about 39 and PET film from about 78 (unmodified) to less than 10 respectively. In UV induced surface grafting polymerization of acrylic acid (AA)

the dry thickness of PAA brushes showed a gradient change from about several nanometers to bout 750 nm on the BOPP film substrate. While in precipitationphotografting polymerization of acrylamide (AM)

ATR-FTIR

X-ray photoelectron spectroscopy (XPS)

fluorescence microscopy and scanning electron microscopy (SEM) demonstrated the existence of the gradient grafting chain density on the polymer surfaces

i.e

the content of Nitrogen determined by XPS increased from about 0 wt% of pristine BOPP film to about 1128%. So far

this is one of the most convenient methods reported for preparation of polymer gradient surfaces

and it is a versatile facile method in preparation of a gradient surface controlled by the gradation photomask.