Chinese Journal of Polymer Science Vol. 26, No. 3, (2008), 1−9 Chinese Journal of Polymer Science ©2008 World Scientific CHEMICAL MORPHOLOGY IN GRAFTING ACRYLAMIDE TO POLYETHYLENE * S. Termnak, K. Sintasanai, T. Amornsakchai, T. Nipithakul and D. Triampo ** R3/1 Department of Chemistry and Rubber Center of Excellence, Faculty of Science, Mahidol University, Salaya Campus, Phuttamonthon Sai 4 Rd., Nakhon Pathom 73170, Thailand Abstract The paper demonstrates the use of scanning force microscopy (SFM)/chemical force microscopy (CFM) to study the growth of grafted polyacrylamide (PAM) chains onto polyethylene (PE)-film with varying grafting time. Results from the CFM reveal reduced interaction between the probe and areas with grafted-PAM on the surface. The topography and the friction trace-minus-retrace (TMR) images are complementary to one another resulting from the reduced interaction of the probe that has specificity to chemical domains. Keywords: Chemical force microscopy (CFM); Grafted polyacrylamide; PE-film. INTRODUCTION In the advancement of polymer materials, it has been essential to modify and tailor-made the properties of a polymer for specific applications. Surface grafting is a method of modification in which only the surface is modified without changing the properties of the bulk. In this way, one reduces the cost of modifying the entire piece of a product when only the surface requires specific function. At the same time, one can also utilize the desirable properties of the bulk. Several surface modification methods can be found in the literature: plasma treatment, chromic acid treatment, and surface grafting [1−14] . Some of the advantages of surface grafting are that it is relatively easy and has controllable grafting process that would yield high density of grafted chains. Because grafting of the surface may only be a small portion, difficult for detection, some of the questionable proof of grafting is yet to be investigated. In this work, we demonstrate the use of chemical force microscopy (CFM) in studying the surface grafting process of polyacrylamide (PAM) onto polyethylene (PE)-film. CFM is a type of scanning force microscopy (SFM). Ordinary SFM can differentiate the surface chemical properties by sensing the difference in interactions between a sample and a probe tip. Chemical modification of a probe surface can enhance differentiation of the different chemical domains on a sample surface [15, 16] . Probe modifications are mainly carried out using self- assembled monolayers (SAMs) or organosilane with various functional terminal groups. This provides chemical function specificity on the probe surface. The grafting of PAM onto PE-film is to be investigated because PE is a type of polyolefin that has one of the world largest volume consumption and is of the simplest in terms of composition [17] . However, PE has difficulty in terms of adhesion with applications such as, printing, coating, composites, etc. PE surfaces are inert and nonpolar as a result of their long aliphatic chains of hydrocarbon consisting of only carbon and hydrogen [18] . For this reason, there have been several attempts in modifying the PE surfaces so they would be more polar and have better adhesion. PAM is grafted onto PE to improve PE’s adhesion properties. Because PAM has amide * This work was financially supported by the NSTDA for Science and Technology Scholars funding and the MTEC Young Research Group funding MT-NS-45-POL-14-06-G. ** Corresponding author: D. Triampo, E-mail: scdar@mahidol.ac.th Received March 29, 2007; Revised May 21, 2007; Accepted June 5, 2007